Ordinance 2005-14 ORDINANCE NO. 2005-14
AN ORDINANCE OF THE CITY OF WYLIE, TEXAS AMENDING
WYLIE ORDINANCE NO. 2002-05; AMENDING ENGINEERING
MANUALS FOR THE DESIGN OF STORM DRAINAGE SYSTEMS,
WATER AND SANITARY SEWER LINES AND THOROUGHFARE
STANDARDS AND STANDARD CONSTRUCTION DETAILS,
PROVIDING FOR REPEALING, SAVINGS AND SEVERABILITY
CLAUSES; AND PROVIDING FOR AN EFFECTIVE DATE OF THIS
ORDINANCE.
WHEREAS, the City Council of the City of Wylie, Texas ("City Council") has
investigated and determined that it would be advantageous and beneficial to the citizens of the
City of Wylie, Texas ("Wylie") to amend Wylie Ordinance No. 2002-OS Engineering Manuals for
the Design of Storm Drainage Systems, Water and Sanitary Sewer Lines, and Thoroughfare
Standards and Standard Construction Details (hereinafter collectively referred to as the "Design
and Construction Standards"),
NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE
CITY OF WYLIE, TEXAS:
SECTION 1.
Findin�s Incorporated. The fmdings set forth above are incorporated into the body of this
Ordinance as if fully set forth herein.
SECTION 2.
Amending Wvlie Ordinance No. 2002-05, Desi�n and Construction Standards. The
Design and Construction Standards are amended as indicated in the attached manuals.
SECTION 3.
Savin sg /Repealing Clause. All provisions of any ordinance in conflict with this Ordinance are
hereby repealed to the extent they are in conflict; but such repeal shall not abate any pending
prosecution for violation of the repealed ordinance, nor shall the repeal prevent a prosecution
Ordinance No. 2005-14
Admendment to Design Standards
from being commenced for any violation if occurring prior to the repeal of the ordinance. Any
remaining portions of said ordinances shall remain in full force and effect.
SECTION 4.
Severabilitv. Should any section, subsection, sentence, clause or phrase of this Ordinance be
declared unconstitutional or invalid by a court of competent jurisdiction, it is expressly provided
that any and all remaining portions of this Ordinance shall remain in full force and effect. Wylie
hereby declares that it would have passed this Ordinance, and each section, subsection, clause or
phrase thereof irrespective of the fact that any one or more sections, subsections, sentences,
clauses, and phrases be declared unconstitutional or invalid.
SECTION 5.
Effective Date This Ordinance sha11 become effective from and after its passage and adoption.
DULY PASSED AND APPROVED BY THE CITY COUNCIL OF THE CITY OF
WYLIE, TEXAS, on this 12�' day of Apri12005.
J HN M DY, ayor
ATTESTED AND CORRECTLY
RECORDED: ,.�`���y F ��1���'
i t
A L
C OLE EH ICH, City Secretaxy
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�i��� t P
li
Date of Publication in the Wvlie News April 20, 2005
Ordinance No. 2005-14
Admendment to Design Standards
CI TY 0� WY�I E, TEXAS
STANDARD CONSTRUCT ON DETA �S
APPROVED FOR USE
PUBLIC WORKS CIttHENCINE�ER�O, P.E.
APRIL, 2005
SECTION DESCRIPTION SHEET N0. SECTION DESCRIPTION
GENERAL NOTES GENERAL CONSTRUCTION NOTES STD-00_R WATER WATER
STREET PAVING SECTIONS STD—Ot_R WATER WATER
STREET PAVING SECTIONS DETAILS STD-02_R WATER WATER
STREET PAVING JOINTS STD-03_R WATER SEWER METER VAULT SERVI
STREET PAVING DETAILS STD-04_R SANITARY SEWER SANITARY SEWER
STREET PAVING ALLEY DRIVEWAYS STD—OS_R SANITARY SEWER SANITARY SEWER M�
STREET PAVING RADIUS STD—O6_R SANITARY SEWER SANITARY SEWER
STREET PAVING DETAILS EROSION STD-07_R EMBEDMENT TYPICAL EMBEDMENTS
STREET PAVING SIDEWALKS STD-08_R WALL THIN BRICK SCREENING
STORM SEWER STORM SEWER INLET STD-09_R WALL BRICK SCREENING R
STORM SEWER STORM SEWER INLET STD-10_R MISCELLANEOUS FRANCHISE UTILITIES
STORM SEWER STORM SEWER INLET DETAIILS STD-11_R
STORM SEWER CHANNELS CONCRETE STD-12_R
STORM SEWER CHANNELS GABIONS STD-13_R
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C8�S Media, Inc.
��je �armer�bilCe �ime� Murphy Monitor The Princeton Herald The Sachse News THE WYLIE NEWS
STATE OF TEXAS
COUNTY OF COLLIN
Before me, the undersigned authority, on this day personally appeared Chad Engbrock,
publisher of The Wylie News, a newspaper regularly published in Collin County, Texas and
having general circulation in Collin County, Texas, who being by me duly sworn, deposed and
says that the foregoing attached
City of Wylie
Ord. No. 2005-14, Ord. No. 2005-15,
Ord. No. 2005-16, Ord No. 2005-18
was published in said newspaper on the following dates, to-wit: Apri120, 2005
Chad Engbrock, Publisher
n this the da of U 2005
Subscribed and sworn befire me Y
to certify which witness my hand and seal of office.
�.�.s..�,
aN�.Y
.�oa�'�` �1�.
!r� s ,w �5
%w;'.. r �i xp. D'i -02-07 a.-
;F Notary Public in and or
The State of Texas
My commission expires O1/02/07
Murphy/Sachse/Wylie Office 110 N. Ballard P.O. Box 369 Wylie, TX 75098 972-442-5515 fax 972-442-4318
Farmersville/Princeton Office 101 S. Main P.O. Box 512 Fam�ersville, TX 75442 972-784-6397 faac 972-782-7023
ass� �e v
D cate, factory test, provide DESIGN OF STORM THE CITY OF WYLIE,
field service, and deliver DRAINAGE SYSTEMS, TEXAS, AMENDING�
to one (1) Variable Frequency WATER AND SANI- THE COMPREHENSIVE
of Drive (VFD). The VFD TARY SEWER LINES ZONING ORDINANCE
�rth shall be rated for 150 hp AND THOROUGHFARE OF THE CITY OF
�ter and operate on 460VAC, 3 STANDARDS AND WYLIE, AS HERETO- Cor
will phase, 60 Hz with drive STANDARD CON- FORE AMENDED, SO
the isolation transformers, and STRUCTION DETAILS, AS TO CHANGE THE itiln
of appurtenances needed to PROVIDING FOR ZONING ON THE bid:
ipal meet the requirements of REPEALING, SAVINGS H E R E I N A F T E R picc
E. the provided specifica- AND SEVERABILITY DESCRIBED PROPER- cell
ixas 6ons. CLAUSES; AND PRO- TY, ZONING CASE in
',11, VIDING FOR AN NUMBER 2005-07, TO be
and In case of ambiguity or EFFECTIVE DATE OF PLANNED DEVELOP- Mu
�ro- lack of clearness in stating THIS ORDINANCE. 'MENT (PD) DISTRICT
propos�l prices, the North FOR COMMERCIAL Agf
Texas Municipal Water ORDINANCE USES AND SIGN PRO- Nor
District reserves the right NO. 2005-15 GRAM; PROVIDING late
�E to adopt the most advanta- AN ORDINANCE OF FOR THE REPEAL OF 27
and
geous proposal to the THE CITI' OF WYLIE, ALL ORDINANCES IN bid;
District. The District TEXAS, AMENDING CONFLICT; PROVID- ope
reserves the right to reject THE COMPREHENSIVE ING A SEVERABII.ITY the
any and all bids, and to ZONING ORDINANCE CLAUSE; AND PROVID- all
waive any informality in OF THE CITY OF ING FOR AN EFFEC- bid
NT bids received. No bid may WYLIE, AS HERETO- TIVE DATE. vali
i be withdrawn within sixty FORE AMENDED, SO
the (60) days after the date on AS TO CHANGE THE ORDINANCE
cly which bids aze opened. ZONING ON THE NO. 2005-18
ud. H E R E I N A F T E R AN ORDINANCE OF Inc
ter NORTH TEXAS MLJNIC- DESCRIBED PROPER- THE CTTY OF WYLIE, inst
be IPAL WATER DISTRICT TY, ZONING CASE TEXAS, AMENDING rep�
NUMBER 2005-06, TO ORDINANCE NO. 2004- Wir
By s/ Dr. Joe Fanner A G R I C U L T U R A L 29, WHICH ESTAB- voli
'ng Dr. Joe Fanner (AG/28) DISTRICT FOR LISHED THE BUDGET ass�
d President, Board of SINGLE-FAMILY RESI- FOR FISCAL YEAR aPF
out Directo DENTIAL USES; PRO- 2005; REPEALING ALL hea
of 48-3t-23 VIDING FOR THE CONFLICTING ORDI- in
pa1 PEAL OF ALL ORDI- NANCES; PROVIDING foll
ORDINANCE �CES IN CONFLICT; FOR A SEVERABILITY An'
xas NO. 2005-14 pROVIDING A SEVER- CLAUSE; AND PROVID- Ell:
AN ORDINANCE OF ABILITY CLAUSE; ING FOR AN EFFEC- Ka�
THE CITY OF WYLIE, prJD pROVIDING FOR TIVE DATE. Ro�
�p TEXAS AMENDING pN EFFECTIVE DATE. for
ri_ WYLIE ORDINANCE John Mondy, Mayor 1
all NO. 2002-05; AMEND- ORDINANCE 20
to ING ENGINEERING NO.2005-16 ATTEST: doi
ri_ MANUALS FOR THE AN ORDINANCE OF Carole Ehrlich, City InG
AVISO DE ELECCI(
A los votantes registrados de la
Texas: Se da aviso por la presente que la Ciudad d�
Texas, ha ordenado una Eleccion General q�
m......�,�.,,�...
CITY OF WYLIE, TEXAS
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A MANUAL S
FOR THE DESIGN OF
STORM DRAINAGE SYSTEMS
WATER AND SANITARY SEWER
LINES
AND THOROUGHFARE STANDARDS
Ordinance 2002-OS
a-- Revised: April 12, 2005
Ordinance No. 20Q5-14
Admendment to Design Standards
COMBINED MANUAL
TABLE OF CONTENTS
PART 1: DRAINAGE SYSTEMS DESIGN MANUAL
Section I Introduction
Section II Drainage Design Theory
Section III Criteria and Design Procedures
Section IV Construction Plan Preparation
Section V Appendix
Section VI Tables
Section VII Figures
Section VIII Forms
PART 2: WATER AND SANITARY SEWER LINE DESIGN MANUAL
Section A General
Section B Water Mains
Section C Sanitary Sewers
Section D Form of Plans
Section E Data to be Included In Plans
Appendix A Sanitary Sewer Daily Flow Calculations
Title 30 TNRCC Chapter 317
PART 3: THOROUGHFARE DESIGN STANDARDS MANUAL
Section I General Requirements
Section II Street Design Standards
Section III Median and Left Tum Desi� Standards
Section IV Alley Design Standards
Section Driveway Design Standards
Section VI Sidewalk Location Design Standards
Section VII Public Right-of-Way Visibility
Section VIII Off Street Requirements
Manual Prepared By:
BIRKHOFF, HENDRICKS CONWAY, L.L.P.
CONSULTING ENGINEERS
DALLAS, TEXAS
CITY OF WYLIE, TEXAS
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MANUAL
FOR THE DESIGN OF
STORM DR.AINAGE SYSTEMS
Ordinance No. 2005-14
Admendment to Design Standards
TABLE OF CONTENTS
Pa e No.
SECTION I: INTRODUCTION
1.1 General I-1
1.2 Scope I-1
1.3 Organization of Manual I-1
SECTION II: DRAINAGE DESIGN THEORY
2.1 General II-1
2.2 Drainage Area Determination System Designation II-1
2.3 Rainfall II-1
2.4 Design Storm Frequency II-1
2.5 Determination of Design Discharge II-2
2.6 Rational Method II-2
2.7 Runoff Coefficient II-3
2.8 Time of Concentration II-3
2.9 Unit Hydrograph Method II-4
2.10 Unit Hydrograph Coefficients II-5
2.11 Flow in Gutters and Inlet Design II-6
2.12 Straight Crown Streets II-7
2.13 Parabolic Crown Streets II-$
2.14 Alley Capacity II-9
2.15 Inlet Capacity Curves II-9
2.16 Recessed Standard Curb Opening Inlets on Grade II-9
2.17 Recessed Standard Curb Opening Inlets at Low Point II-10
2.18 Combination Inlet on Grade II-10
2.19 Combination Inlet at Low Point II-12
2.20 Grate Inlet on Grade II-12
2.21 Grate Inlet at Low Point II-12
2.22 Drop Inlet at Low Point II-12
2.23 Hydraulic Design of Closed Conduits II-12
2.24 Velocity in Closed Conduits II-13
2.25 Roughness Coefficients for Closed Conduits II-13
2.26 Minor Head Losses in Closed Conduits II-13
2.27 Hydraulic Design of Open Channels II-14
2.28 Analysis of Existing Channels II-14
2.29 Design of Improv_ed Channels II-17
2.30 Concrete Box and Pipe Culverts II-17
2.31 Culverts Flowing with Inlet Control II-17
232 Culverts Flowing with Outlet Control II-18
2.33 Bridges II-20
2.34 Detention of Storm Water Flow II-21---
2.35 Manholes II-21
Pa�e No•
SECTION III: CRITERIA AND DESIGN PROCEDURES
3.1 General III-1
3.2 Rainfall III-1
3.3 Design Storm Frequency III-1
3.4 Determination of Design Discharge III-3
3.5 Runoff Coefficients and Time of Concentration III-4
3.6 Criteria for Channels, Bridges and Culverts III-4
3.7 Procedure for Determination of Desi� Discharge III-4
3.8 Flow in Gutters and Inlet Design III-5
3.9 Capacity of Straight Crown Streets III-5
3.10 Capacity of Parabolic Crown Streets III-5
3.11 Street Intersection Drainage III-5
3.12 Al1ey Capacities III-6
3 .13 Inlet Design III-6
3.14 Procedure for Sizing and Locating Inlets III-8
3.15 Hydraulic Gradient of Conduits III-8
3.16 Velocity in Closed Conduits III-9
3.17 Roughr�ess Coefficients for Conduits III-9
3.18 Minor Head Losses III-9
3.19 Procedure for Hydraulic Design of Closed Conduits III-10
3 .20 Open Channels III-10
3.21 Types of Channels III-11
3.22 Quantity of Flow III-11
3.23 Channel Alignment and Grade III-12
3.24 Roughness Coefficients for Open Channels III-12
3.25 Procedure for Calculation of Water Surface Profile for III-12
Unimproved Channels
3.26 Procedure for Hydraulic Design of Open Channels III-12
3.27 Hydraulic Design of Culverts III-13
3.28 Culvert Hydraulics III-13
3 .29 Quantity of Flow III-14
3.30 Headwalls and Entrance Conduits III-14
3.31 Culvert Discharge Velocities III-14
3.32 Procedure for Hydraulic Design of Culverts III-15
3.33 Hydraulic Design of Bridges III-15
3 .34 Quantity of Flow III-1
3.35 Procedure for Hydraulic Design of Bridges III-16
3.36 Procedure for Filling in a Flood Plain III-17
3.37 Filling in a 100 Year Floodway Fringe III-19
3.38 Detention Ponds III-21
Ordinance No. 2005-14
Admendment to Design Standards
Page No•
SECTION IV: CONSTRUCTION PLAN PREPARATION
4.1 General IV-1
4.2 Preliminary Design Phase IV-1
4.3 Final Design Phase IV-3
SECTION V: APPENDIX
5.1 Definition of Terms V-1
5.2 Abbreviation of Terms and Symbols V-5
5 .3 Bibliography V-8
SECTION TABLES VI-1
SECTION VII: FIGURES VII-1
SECTI�N VIII: FORIV�S VIII-1
I INTRODUCTION
1.1 GENERAL
Storm water runoff is that portion of the precipitation that flows over the ground surface
dur[ng and for a period after a storm. The objective of designing storm sewer systems is to
convey runoff in a functional and efficient way from places it is not wanted to the nearest
acceptable discharge point. This transfer of runoff is done in sufficient time and methods
to avoid damage and unacceptable amounts of inconvenience to the general public. Prior to
the design of a storm drainage system, an overall drainage plan shall be submitted to the
City for review. Upon written approval of the drainage plan by the City, the actual
construction plans can be designed.
This manual provides guidelines for design of storm drainage facilities in the City of
Wylie. The procedures outlined herein shall be followed for all drainage design and review
of plans submitted to the City.
1.2 SCOPE
The information included in this manual has been developed through a comprehensive
review of basic design technology as published in various sources listed in the
Bibliography and as developed through the experience of individual Engineers who have
contributed to the content.
The manual concerns itself with storm drainage conditions that are generally relative to the
City of Wylie and the immediate geographical area. Accepted engineering principles are
applied to these situations in detailed documented procedures. The documentation of the
procedures is not intended to limit initiative but rather is included as a standardized
procedure to aid in design and as a record source for the City.
1.3 ORGANIZATION OF MANUAL
This manual is divided into six basic sections. The first section is the INTRODUCTION, which is
a general discussion of the intended use of the material and an explanation of its organization.
Ordinance No. 2005-14
Admendment to Design Standards I-1
Section II: DRAINAGE DESIGN THEORY, explanation of the basic technical theory
employed by the design procedures prescribed in this manual.
Section III: CRITERIA AND DESIGN PROCEDURES, lists recommended design
criteria and outlines the design procedures followed by the City of Wylie.
Section IV: CONSTRUCTION PLAN PREPARATION, describes construction plans for
drainage facilities in the City of Wylie.
Section V: APPENDIX, contains a definition of terms, definition of symbols and
abbreviations and the Bibliography.
Section VI: TABLES, contains all the tables which are used in the design of drainage
facilities.
-d�� Section VII: FIGURES, contains all of the basic graphs, nomographs and charts for use in
design of drainage facilities.
Section VIII: FORMS, contains fortns with detailed instructions for their use.
O.rdinance No. 20Q5-14
Admendmentto Design Standards I-1
II DRAINAGE DESIGN THEORY
2.1 GENERAL
This section covers the technical theory utilized in the design procedures outlined in the
manual. It is intended as an application of basic hydraulic and hydrologic theory to specific
storm drainage situations.
2.2 DRAINAGE AREA DETERMINATION AND SYSTEM DESIGNATION
The size and shape of each drainage area and sub-area must be determined for each storm
drainage facility. This size and shape should be determined from topographic maps at scale of
1 inch 200 feet.
Where the contour interval is insufficient or physical conditions may have changed from those
shown on existing maps, it may be necessary to supplement the maps with field topographic
surveys. The actual conditions should always be verified by a reconnaissance survey. In
preparing the draina�e area maps, carefiil attention must be given to the gutter configurations
intersections. The direction of flow in the gutters should be shown on the maps and on t}
construction plans. The performance of these surveys is the responsibility of the Engineer
designing the drainage facility.
2.3 RAINFALL
FIGURE 1, which shows anticipated rainfall rates for storm durations from 5 minutes to 6
hours, has been prepared utilizing the information contained in the U. S. Department of
Commerce, Weather Bureau, HYDRO-35 (National Technical Information Service Publication
No. PB272-112, dated 3une, 1977). Interpolation of rainfall rates versus durations frorrr the
isopluvial maps contained in HYDRO-35 were used to prepare FIGURE 1 for durations less
than 60 minutes. For durations beyond 60 minutes the information shown in FIGURE 1 was
derived from Weather Bureau Technical Paper No. 40, dated May, 1961.
2.4 DESIGN STORM FREQUENCY
The individual curves shown on FIGURE 1 labeled "S Yr.", "10 Yr.", "25 Yr.", "50 I'r.", anc'
"100 Yr." are referred to as "Design Storm Frequency". The term "100-year storm" does no�
mean that a storm of that severity can be expected once in any 100-year period, but rather
II-1
that a storm of that severity has a one in one hundred chance of occumng in any jiven
calendar year.
Each storm drainage facility shall be designed to convey the runoff which results from the
100-year design storm as shown in Section III, CRITERIA AND DESIGN PROCEDURES.
2.5 DETERMINATION OF DESIGN DISCHARGE
Prior to hydraulic design of drainage facilities the amount of runoff from the particular
drainage area must be determined. The Rational, the Unit Hydrograph, and the HEC-I
Computer Program are the accepted methods, for computing volumes of storm water runoff.
Data from the Flood Insurance Study shall be used in lieu of Rational Method, Unit
Hydrograph or HEC-I for determination of drainage and floodway easement elevations and
design discharge flows, if such data is available. However, all discharge values shall be
based on full development of the drainage basin as outlined on the current zoning maps
available from the City. In the event that the Flood Insurance Study is not based on current
zoning, the study should be reanalyzed, revised and submitted to FEMA far acceptance. In
the event that the revised study indicates a water surface is less than that shown on the Flood
Insurance study the higher value shall be used if the study is not submitted to FEMA.
2.6 RATIONAL METHOD
The use of the Rational Method, introduced in 1889, is based on the following assumptions:
a) The peak rate of runoff at any point is a direct function of the average rainfall intensity
during the time of concentration to that point.
b) The frequency of the peak discharge is the same as the frequency of the average rainfall
intensity.
c) The time of concentration is the time required for the runof�' to become established and
flow from the most remote part of the drainage area to the design point.
The Rational Method is based on the direct relationship between rainfall and runoff
expressed in the following equation:
Q= C I A, where
•"Q" is the storm flow at a given point in cubic feet per second (c.f.s.).
Ordinance No. 2005-14
Admendment to Design Standards II
•"C" is a coefficient of runoff representing the ratio of runoff to rainfall.
•"I" is the average intensity of rainfall in inches per hour for a period equal to the time of
flow from the farthest point of the drainage area to the point of design and is obtained
from FIGURE 1.
•"A" is the area in acres that is tributary to the point of desi�.
The determination of the factors, runoff coefficient and time of concentration shown in this
manual have been developed through past experience in the City's system and by review of
values recommended by others. The time of concentration has been adopted from the Texas
Department of Transportation Hydraulic Design Manual, revised March 2004.
2.7 RUNOFF COEFFICIENT
The runoff coefficient "C" in the Rational Formula is dependent on the character of the soil
and the degree and type of development in the drainage area. T'he nature and condition of the
soil determine its ability to absorb precipitation. The absorption ability generally decreases
as the duration of the rainfall increases until saturation occurs. Infiltration rates in the Wylie
area generally are low due to the cohesive soils. As a drainage area develops the amount of
runoff increases generally in proportion to the amount of impervious areas such as streets,
parking areas and buildings.
2.9 TIME OF CONCENTRATION
The time of concentration is defined as the longest time that will be required for water to
flow from the upper limit of a drainage area to the point of concentration, without
interruption of flow by detention devices. This time is a combination of the inlet time, which
is the time for water to flow over the surface of the ground from the upper limit of the
drainage area to the first storm sewer inlet, and the flow time in the conduit or channel to the
point of concentration. The flow time in the conduit or channel is computed by dividing the
length of the conduit by the average velocity in the conduit. (Note: When accumulating
times, base the time of concentration on the actual calculated time of concentration at the
initial point of interception, even if it is less than the minimum time of concentration. For the
design of the storm sewer use the minimum time of concentration as shown in TABLE 1
until such time that the actual time of concentration exceeds the minimum time.
II-3
Although the basic principles of the Rational Method are applicable to all sizes of drainage
areas, natural retention of flow and other interruptions cause an attenuation of the runoff
hydrograph resulting in over-estimation of rates of flow for larger areas. For this reason, in
development of runoff rates in larger drainage areas, use of the Unit Hydrograph Method is
recommended.
2.9 UNIT HYDROGRAPH METHOD
The Unit Hydrograph Method to be used in calculation of runoff shall be in accordance with
Snyder's synthetic relationships.
The computation of runoff quantities utilizing the Unit Hydrograph Method is based on the
following equations:
0.3
tp C� (L L�
�640
qp
t P
Qp q A
S I2
RT SD L �5
Qu Q
•"t is the lag time, in hours, from the midpoint of the unit rainfall duration to the peak of
the unit hydrograph.
•"Ct" and "C are coefficients related to drainage basin characteristics. Recommended
values for these coefficients are found in TABLE 2.
•"L" is the measured stream distances in miles from the point of design to the upper limit
of the drainage area.
Ordinance No. 20Q5-14
Admendment to Design Standards II
•"L� is the measured stream distance from the point of design to the centroid of the
drainage area. This value may be obtained in the following manner:
Trace the outline of the drainage basin on a piece of cardboard and trim to shape. Suspend
the cardboard before a plumb bob by means of a pin near the edge of the cardboard and draw
a vertical line. In a similar manner, draw a second line at approximately a 90-degree angle to
the first line. The intersection of the two lines is the centroid of gravity of the area.
•"q is the peak rate of discharge of the unit hydrograph for unit rainfall duration in cubic
feet per second per square mile.
•"Q is the peak rate of discharge of the unit hydrograph in cubic feet per second.
•"A" is the area in square miles that is tributary to the point of design.
•"I" is the rainfall intensity at two hours in inches per hour for the appropriate design storm
frequency.
•"SD" is the design storm rainfall in inches for a two-hour period.
°��Li is the initial and subsequent losses, which have a recornmended constant value of
1.11 inches.
•"RT" is the total runoff in inches.
•"Q is the design storm runoff in cubic feet per second.
2.10 UNIT HYDROGRAPH COEFFICIENTS
The U. S. Army Corps of Engineers published, in August 1952, a report, which contains
observed unit hydro�aphs from records on several storms, which occurred during the period
from May 1948 throu�h May 1950 on the Turtle Creek drainage basin. Data developed in
that report, which is entitled "Definite Project Report on Dallas Floodway, Volume I-
General, Hydrologic and Economic Data, together with additional measurements made since�
that time, was used to establish the coefficients for the Wylie area.
II-5
In Section III of the manual, certain values for factors involved in a unit hydrograph analysis
are recommended. These values are not to be considered inflexible, but are intended as
guidelines when more specific data is not available. Detailed review of the development of
all these factors is not warranted,. but several should be discussed where the documentation
for the selected values might not be apparent.
The recommended rainfall intensity to be used is selected based on a duration of two hours.
The two hours are representative of the time elapsed from the beginning of the rainfall to the
peak rate of runoff. Where more definite relationships are known to exist on any particular
stream, this time should be adjusted accordingly. When using a duration of two hours,
multiply the rainfall rate (intensity) by two hours, subtract the losses, and the total runoff is
obtained.
There are two losses to be considered when arriving at the total runof£ These are termed the
"initial" and "subsequent" losses and are shown in Section III, CRITERIA AND DESIGN
PROCEDURES, as having a constant value of 1.11 inches. This is arrived at by assigning a
value of 0.75 inches as the total initial loss occumng during the first one-half hour of rainfall
and a loss of 0.24-inch per hour for the remaining one and one-half hour rainfall period,
m° calculated as follows:
Initial 0.75 inch
Subsequent Loss (1.5 hrs x 0.24 inch/hr) 0.36 inch
Total Losses 1.11 inches
As in the case of other recommended specific values, where more definite information is
available, it should be used.
2.11 FLOW IN GUTTERS AND INLET DESIGN
In the design of storm drainage facilities, the geometrics of specific types of streets are an
integral part of drainage design. Througi�out this manual references is made to certain types
and widths of streets with specific crown characteristics. The following terms are defined for
reference purposes:
MAJOR THOROUGHFARE: A street that moves traffic from one section of the city to
another section.
OMinance No. 20Q5-14
Admendment to Design Standards II
COLLECTOR STREET: This is a street that has the dual purpose of traffic movement plus
providing access to abutting properties.
RESIDENTIAL STREET: A street whose primary function is to provide local access to
abutting properties.
WIDTH OF STREET The horizontal distance between the faces of the curbs.
STRAIGHT CROWN: A constant slope from one gutter flow line across a street to the other
gutter flow line.
PARABOLIC CROWN: A pavement surface shaped in a parabola from one gutter flow line
to the other.
VERTICAL DISPLACEMENT BETWEEN GUTTER FLOW LINES Due to
topography, it will be necessary at times that the curbs on a street be placed at different
elevations.
2.12 STRAIGHT CROWN STREETS
Storm water flow in a street having a straight crown slope may be expressed as follows:
z
Q 0.56 n S' Y g 3 (Equation 1)
•"Q" is quantity of gutter flow in cubic feet per second.
•"Z" is the reciprocal of the crown slope.
•"n" is the coefficient of roughness as used in Manning's Equation; a value of 0.0175 was
used.
•"S" is the longitudinal slope of the street gutter in feet per foot.
•"Y" is the depth of flow in the gutter at the curb in feet.
II-7
This formula is an expression of Manning's Equation as referenced in Highway Research
Board Proceedings, 1946, Page 150, Equation 14.
Based on this equation, FIGURE 3 was prepared and inlet design calculations, as explained
elsewhere, were made.
2.13 PARABOLIC CROWN STREETS
FIGURES 4 and 5 show the capacity of gutters in streets with parabolic crowns. The
following formulas can be used for determining the gutter capacity or refer to the figures for
solution.
Q 1.486 ARZi3 Sli2 (Equation 2)
n
R A (Equation 3)
P
Wo
A W C 8 C X dx (Equation 4)
.u._ 2 W 2 0
•"Q" is quantity of gutter flow in cubic feet per second.
•"n" is the coefficient of roughness; a value of 0.0175 was used.
•"A" is the cross section flow area in square feet.
•"R" is the hydraulic radius in feet.
•"S" is the longitudinal slope of the street gutter in feet per foot.
•"P" is the wetted perimeter in feet.
•"W is the width of the street in feet.
•"C is the crown height of the street in feet.
Ordinance No. 20Q5-14
Admendment to Design Standards II-8
As discussed in Section III, CRITERIA AND DESIGN PROCEDURES, it may, at times, be
necessary for one curb to be at a different elevation than the opposite curb due to the
topography. Where parabolic crowns are involved, the gutter capacities will vary radically as'
one curb becomes higher or lower. The maximum vertical displacement values shown in
FIGURES 4 and 5 were developed based on a minimum depth of flow in the high gutter of
approximately two inches.
2.14 ALLEY CAPACITY
FIGURE 6, CAPACITY OF ALLEY SECTIONS, was prepared based on solution of
Manning's Equation:
Q (1.486) (AR (5 (Equation 2)
n
•"Q" is the alley capacity, flowing full in cubic feet per second.
•"n" is the coefficient of roughness; a value of 0.0175 was used.
•"A" is the cross section flow area in square feet.
•"R" is the hydraulic radius in feet.
•"S" is the longitudinal slope in feet per foot.
2.15 Il'JLET CAPACITY CURVES
The primary objective in developing the curves shown in FIGURES 8 through 22 was to
provide the Engineer with a direct method for sizing inlets that would yield answers within
acceptable accuracy limits.
2.16 RECESSED AND STANDARD CURB OPENING INLETS ON GRADE
The basic curb opening inlet capacity curves, FIGURES 8 through 12, Recessed and
Standard Curb Opening Inlets on Grade, were based upon solution of the following equation:
L Q (H1 HZ) (Equation 6)
Hz siz� JO)
•"L" is the length of inlet, in feet, required to intercept the gutter flow.
•"Q" is the gutter flow in cubic feet per second.
II-9
•"H is the depth of flow, in feet, ir1 the gutter approaching the inlet plus the inlet
depression, in feet.
•"HZ" is the inlet depression, in feet.
This is an empirical equation from "Hydraulic Manual", Texas Highway Department, dated
September 1970. The data from solution of this equation was used to plot the curves shown
on FIGURES 8 through 12.
2.17 RECESSED AND STANDARD CURB OPENING INLETS AT LOW POINT
FIGURE 13, Recessed and Standard Curb Opening Inlets at Low Point, was plotted from the
solution of the following equation:
Q= 3.087 L h (Equation 7)
•"Q" is the gutter flow in cubic feet per second.
•"L" is the length of inlet, in feet, required to intercept the gutter flow.
•"h" is the depth of flow, in feet, at the inlet opening. This is the sum of the depth of the
y flow in the gutter, y plus the depth of the inlet depression.
This equation expresses the capacity of a rectangular weir and is referenced in "The Design
of Storm Water Inlets," dated June 1956, The John Hopkins University.
The calculated inlet capacities were reduced by ten percent of the preparation of FIGURE 13
due to the tendency of inlets at low points to clog from the collection of debris at their
entrance.
2.18 COMBINATION INLET ON GRADE
FIGURES 14 through 16, Combination Inlet on Grade, were prepared based on the length of
grade in feet, L required to capture the portion of the gutter flow which crosses the
upstream side of the grade and on the length of grate in feet, L', required to capture the outer
portion of gutter flow. The figures were prepared with the solution of Equation 1 and the
following equations:
L 4v
yo 1`Z (Equation 8)
g
Ordinance No. 20Q5-14
Admendment to Design Standards II-10
L' 1.2 v tan Oo y tan 0 1 2 (Equation 9)
g
q2 L' L (g)�� yo w 3 2 (Equation 10)
4 tan Oo
2
q3 Qo 1- L (Equation 11)
Lo
Q= Q C qz q3 (Equation 12)
L Length of grate required to capture 100% of all flow over grate in feet.
v Gutter velocity in feet per second.
y Depth of gutter flow in feet.
g Gravitational acceleration (32.2 feet per second per second).
L' Length of grate required to capture the outer portion of the gutter flow in feet.
O Crown slope of pavement.
w Width of grate in feet.
q2 Carry-over flow in c.f.s. outside of the grate.
L Length of grate in feet.
q Carry-over flow in c.f.s. over the grate.
r Q Gutter flow in c.f.s.
Q Capacity of grate inlet in c.f.s.
These equations are from "The Design of Storm Water Inlets," The John Hopkins University,
June 1956.
II-11
2.19 COMBINATION INLET AT LOW POINT
FIGURE 20, Combination lnlet at a Low Point, was prepared based on the inlet having a
capacity equal to 90 percent of the quantity derived from solution of Equation 7(Paragraph
2.17) and 70 percent of the quantity derived from solution of the following Equation 13:
Q 3.087 Lh (Equation 7)
Q 0.6A 2gh (Equation 13)
•"Q" is the gutter flow in cubic feet per second.
•"A" is the net cross section area, in square free, of the grate opening.
•"g" is gravitational acceleration (32.2 feet per second per second).
•"h" is the head, in feet on the grate.
2.20 GRATE INLET ON GRADE
FIGURES 16 through 19, Grate Inlet on Grade, were prepared based on the solution of
Equations 1, 8, 9, 10, 11, and 12 as described in Paragraph 2.18, and with the assumption that
the inlet was located in a curbed gutter. Grate Inlet on Grade shall only be used with the
approval of the City Engineer.
2Z1 GRATE INLET AT LOW POINT
FIGURE 21, Grate Inlet at Low Point, was prepared on the inlet having a capacity of 50
percent of the quantity derived from solution of Equation.l3 as shown above. While this
particular inlet capacity may appear to be considerable less than would be expected, it has
been calculated based on observed clogging effects; primarily due to paper. The velocity of
the gutter flow across the same inlet on grade tends to clear the grate openings. Grate Inlet at
Low Point shall only be used with the approval of the City Engineer.
2.22 DROP INLET AT LOW POINT
FIGURE 22, Drop Inlet at Low Point, was prepared based on solution of Equation 7 as
previously referenced, using a ten percent reduction in capacity due to clogging.
2.23 HYDRAULIC DESIGN OF CLOSED CONDUITS
All closed conduits shall be hydraulically designed through the application of Manning's
Equation expressed as follows:
Q A V
Ordinance No. 20Q5-14
Admendment to Design Standards II-12
Q 1.4861 (AR C S
C nJ
R= A
P
•"Q" is the flow in cubic feet per second.
•"A" is the cross sectional area of the conduit in square feet.
•"V" is the velocity of flow in the conduit in feet per second.
•"n" is the roughness coefficient of the conduit.
•"R" is the hydraulic radius, which is the area ("A") of flow divided by the wetted
perimeter ("P").
•"S�" is the friction slope of the conduit in feet per foot.
"P" is the wetted perimeter.
2.24 VELOCITY IN CLOSED CONDUITS
Storm sewers should operate within certain velocity limits to prevent excessive deposition of
solids due to low velocities and to prevent invert erosion and undesirable outlet conditions
due to excessively high velocity. A minimum velocity of 2.5 feet per second and a maximum
velocity of 12 feet per second shall be observed.
2.25 ROUGHNESS COEFFICIENTS FOR CLOSED CONDUITS
Roughness coefficients are directly related to construction procedures. When alignment is
poor and joints have not been properly assembled, extreme head losses will occur.
Coefficients used in this manner are related to construction procedures and assume that the
pipe will be manufactured with a consistently smooth surface.
2.26 MINOR HEAD LOSSES IN CLOSED CONDUITS
The basic equation for calculation of minor head losses at manholes and bends in closed�
conduits is as follows:
II-13
h� K� V
2g
•"h�" is head loss in feet.
"K�" is coefficient of loss
•"V" is velocity in feet per second in conduit immediately downstream of point of loss.
•"g" is gravitation acceleration (32.2 feet per second per second).
The basic equations for calculation of minor head losses at wye branches (lateral connections
to main storm sewer line) and pipe size change are as follows:
h� V2 V� Where V1 VZ
2g
h� V2 V� where VZ V1
4g
•"h�" is head loss in feet
•"V2" is the downstream velocity in feet per second
•"Vt" is the upstream velocity in feet per second
•"g" is gravitational acceleration (32.2 feet per second per second)
2.27 HYDRAULIC DESIGN OF OPEN CHANNELS
Channel design involves the determination of a channel cross section required to convey a
given design flow. The two methods outlined in this manual may be used for analysis of an
existing channel or for the design of a proposed channel.
2.28 ANALYSIS OF EXISTING CHANNELS
The analysis of the carrying capacity of an existing channel is an application of Bernoulli's
energy equation, which is written:
Z dl h�l ZZ d2 h hf other losses
where
Ordinance No. 20Q5-14
Admendmentto Design Standards II
•"Z1" and "Z2" is the streambed elevation with respect to a given datum at upstream and
downstream sections, respectively.
•"d and "d2" is depth of flow at upstream and downstream sections, respectively.
•"h„1" and "h is velocity head of upstream and downstream sections, respectively.
"hf' is friction head loss.
Other losses such as eddy losses are estimated as 10 percent of �the friction head loss where
the quantity h minus h�l is positive and 50 percent thereof when it is negative. Bend
losses are disregarded as an unnecessary refinement.
Bernoulli's energy equation is illustrated in graphic form as shown below.
LJ
I-br'¢ontal Line
Fic
ryy i �12� p�
h
a�
���9Y 4 adient o
J
1
1
h 2
Water Surtace (Fiydraufic Cxadierrt
d
1
�n�l Bottom d
(Bed SIoPe S) 2
z
1
z
t�itum 2
The basic equations involved are:
Q A V
h,, V
Z
and Manning's Equation:
II-15
Q 1.486 AR2i3 S�i2
n
which is defined elsewhere in this chapter.
The friction head can be determined by using Manning's Equation in terms of the friction
slope Sf, where:
Sf Q 2
1.486 AR
thus giving the total friction head
hf L Sfl S� 1
C 2 J
using the respective properties of Sections 1 and 2 for the calculation of S fl and S�.
The velocity head h� is found by weighing the partial discharges for each subdivision of the
cross section, i.e.,
h„ VS QS
2 Q
where
•"V is velocity in subsection of the cross section.
•"A is area of the subsection of the cross section.
•"Q is discharge in the subsection of the cross section.
"V is Qs
A
When severe constrictions occur the Momentum Equation may be required in determination
of losses.
Orciinancs No. 2005-14
Admendment to Design Standards II
2.29 DESIGN OF IMPROVED CHANNELS
The hydraulic characteristics of improved channels are to be determined through the_,,,,
application of Manning's Equation as previously defined. In lieu of Manning's Equation a
HEC-2 or HEC-RAS (Water Surface Profile) computer analysis can be utilized. The City, at
its option, can require the use of a Computer Analysis in lieu of Manning's Equation. The
HEC Computer Programs are available from the U.S. Army Corps of Engineers. The
Hydrologic Engineering Center; 609 Second Street, Davis, California 95616, 916/440-2105
or can be downloaded from the Internet. User-friendly versions are available from a number
of vendors.
2.30 CONCRETE BOX AND PIPE CULVERTS
The design theory outlined herein is a modification of the method used in the hydraulic
design of concrete box and pipe culverts as discussed in Department of Commerce Hydraulic
Engineering Circular No.S entitled "Hydraulic Charts for the Selection of Highway
Culverts" dated December 1965.
The hydraulic capacity of culverts is computed using various factors and formulas.
Laboratory tests and field observations indicate culvert flow may be controlled either at the--
inlet or outlet. Inlet control involves the culvert cross sectional area, the ponding o�
headwater at the entrance and the inlet geometry. Outlet control involves the tailwate;
elevation in the outlet channel, the slope of the culvert, the roughness of the surface and
length of the culvert barrel.
2.31 CULVERTS FLOWING WITH INLET CONTROL
Inlet control means that the discharge capacity of a culvert is controlled at the culvert
entrance by the depth of the headwater and entrance geometry including the barrel shape and
cross sectional area, and the type of inlet edge. Culverts flowing with inlet control can flow
as shown on FORM "F", Case I(inlet not submerged) or as shown on FORM "F", Case II
(inlet submerged).
Nomographs for determining culvert capacity for inlet control as shown on FIGURES 25 and
26. These nomographs were developed by the Division of Hydraulic Research, Bureau of
Public Roads from analysis of laboratory research reported in National Bureau of Standards
Report No. 4444, entitled "Hydraulic Characteristics of Commonly Used Pipe Entrances", by
John L. French, and "Hydraulics of Conventional Highway Culverts", by H. G. Bossy.
II-17
Experimental data for box culverts with headwalls and wingwalls were obtained from an
unpublished report of the U. S. Geological Survey.
2.32 CULVERTS FLOWING WITH OUTLET CONTROL
Culverts flowing with outlet control can flow full as shown on FORM "F", Case III (outlet
submerged), or part full for part of the barrel, as shown on FORM "F", Case N(outlet not
submerged).
The culvert is designed so that the depth of headwater, which is the vertical distance from the
upstream culvert flow line to the elevation of the ponded water surface, does not encroach on
the allowable freeboard during the design storm.
Headwater depth, HW, can be expressed by a common equation for all outlet control
conditions:
HW H h� L �S
•"HW" is headwater depth in feet.
•"H" is the head or energy required to pass a given discharge through a culvert.
•"h is the vertical distance from the downstream culvert flow line to the elevation from
which H is measured, in feet.
•"L" is length of culvert in feet.
•"S is the culvert barrel slope in feet per foot.
The head, H, is made up of three parts including the velocity head, exit loss, H�, an entrance
loss, H and a friction loss, H f This energy is obtained from ponding of water at the
entrance and is expressed as:
H H,, H H
•"H" is head or energy in feet of water.
Ordinance No. 20Q5-14
Admendment to Design Standards II-18
•"H�" is V where V is average velocity in culvert or Q
2 A
•"H is I� V where K is entrance loss_ coefficient
Z
•"Hf' is energy required to overcome the friction of the culvert barrel and expressed as:
Hf 29.2 L V where
Ri.33 2
S
•"n" is the coefficient of roughness (See TABLE 5).
•"L" is length of culvert bazrel in feet.
•"V" is average velocity in the culvert in feet per second.
•"g" is gravitational acceleration (32.2 feet per second per second).
•"R" is hydraulic radius in feet.
Substituting into previous equation:
H= V` K V 29.2� L V
2 2g R133 28
and simplifying:
H= 1 K� 29.2„ L V' for full flow
R 133 2
S
This equation for H may be solved using FIGURES 27 and 28.
For various conditions of outlet control flow, h is calculated differently. When the elevation
of the water surface in the outlet channel is equal to ar above the elevation of the top of the
culvert opening at the outlet, h is equal to the tailwater depth or: r
h
II-19
If the tailwater elevation is below the top of the culvert opening at the outlet, h is the
greater of two values: (1) Tailwater, TW, as defined above or (2) d� D/2 where
d� critical depth. The critical depth, d�, for box culverts may be obtained from FIGURE 29
or may be calculated form the formula:
d� 0.315 Q 2i3
B
•"d�" is critical depth for box culvert in feet.
•"Q" is discharge in cubic feet per second.
•"B" is bottom width of box culvert in feet.
The critical depth for circular pipes may be obtained from FIGURE 30 or may be calculated
by trial and error. Charts developed by the Bureau of Public Roads may be used for
determining the critical depth. Try values of D, A and d� which will satisfy the equation:
__�W. Q� A3
G D
•"d�" is critical depth for pipe in feet.
•"Q" is discharge in cubic feet per second.
•"D" is diameter of pipe in feet.
•"g" is gravitational acceleration (32.2 feet per second per second).
•"A" is the cross sectional area of the trial critical depth of flow.
The equation is applicable also for trapezoidal or irregular channels, in which instances "D"
becomes the channel top width in feet.
2.33 BRIDGES
Once a design discharge and the depth of flow have been established, the size of the bridge
opening may be determined.
Ordinance No. 20Q5-14
Admendment to Design Standards II
Specific effects of columns and piers may usually be neglected in the hydraulic calculations
for determination of bridge openings. This is based on the assumption that all bents will be
placed parallel to the direction of flow. Only in extenuating circumstances would it be
desirable for bents to be placed at an oblique angle to the flow.
The basic hydraulic calculations involved in the hydraulic design involve solution of the
following:
V QA
•"V" is the average velocity through the bridge in feet per second.
•"Q" is the flow in cubic feet per second.
•"A" is the actual flow area through the bridge in square feet.
hf K V
Z
•"hf' is the head loss through the bridge in feet.
•"Kb" is a head loss coefficient.
•"V" is the average velocity through the bridge in feet per second.
•"g" is gravitational acceleration (32.2 feet per second per second).
As can be seen from the above, the loss of head through the bridge is a function of the
velocity head. The section of a head loss coefficient as recommended in Section III,
CRITERIA AND DESIGN PROCEDURES, will determine the exact hydraulic conditiflns.
2.34 DETENTION OF STORM WATER FLOW
As land changes from undeveloped to developed conditions, the peak rates of runoff and the
total volume of runoff usually increase. This increase is due to an overall increase in
impervious area as the watershed changes to a fully developed condition. Developments
shall be required to provide adequate detention so that post-development peak flows do not
exceed the peak flows calculated for the area using the rational method with the coefficient�..
for runoff appropriate for the conditions prior to development.
II-21
The criteria for the design of detention facilities are based on the concept that post-
development peak flows should not create an adverse condition when compared to pre-
development peak flows. In applying such a concept, it is necessary to consider peak flows
from a number of different design storms. By considering a range of design storms, it is
possible to design an outlet system to limit the discharge from the detention facility and
achieve zero or very little increase in flow for a range of storms. Such a design will allow the
detention system to achieve maximum effectiveness since both the more frequent and more
seve're storm events can be controlled.
A form of the Rational Method should be used to calculate inflow volumes from areas less
than 50 acres. A form of the inflow hydrographs or unit hydrograph method shall be used for
areas of 50 acres or more. No reduction in the design storm frequency shall be considered
when utilizing detention systems within the overall storm drainage design.
2.35 MANHOLES
Place manholes for cleanout and inspection purposes on all storm sewer lines as shown in the
table below.
Pi e Diameter (Inches) Maximum Distance (feet)
12 24 300
24 36 375
39 54 450
=>60 900
Ordinance No. 2005-14
Admendment to Design Standards II-22
III CRITERIA AND DESIGN PROCEDURES
3.1 GENERAL
This section contains storm drainage design criteria and demonstrates the design procedures
to be employed on drainage projects in the City of Wylie.
Applicable forms that can be used far the design of various storm drainage facilities are
contained in Section VIII of this manual and shall be part of the drainage submittal to the
City. These tables shall be reproduced in the plans.
3.2 RAINFALL
In determining the estimated runoff from a special drainage area, it is necessary to predict the
amount of rain, which can be expected. FIGURE l, RAINFALL INTENSITY AND
DUR.ATION, has been prepared to graphically illustrate anticipated rainfall intensity for
storm duration from 5 minutes to six hours for selected return frequencies and shall be used
for determining rainfall rates as required. Maximum time for design shall be 20-minutes.
3.3 DESIGN STORM FREQUENCY
Each storm draina�e facility, including street capacities, shall be designed to convey the
runoff, which results from the 100-year design storm.
Drainage design requirements for open and closed systems shall provide protection for
property during a 100-year Design Frequency Storm, with this projected flow camed in the
streets and closed drainage systems in accordance with the following:
a) RESIDENTIAL STREETS: Based on a transverse slope of a positive '/4" per foot
behind the curb, the 100-year design storm frequency shall not exceed a depth of 1-inch
over the top of curb. A maximum flow of 20 cfs will be allowed in each gutter or where
gutter capacity is exceeded plus 1-inch. Bypass from upstream inlets shall not exceed 5
cfs through residential street intersections.
b) COLLECTOR STREETS: Based on parkway slopes of a positive '/4" per foot behind
the curb, the 100-year Design Frequency flows shall not exceed a depth of'/z" over the,_
top of curb or where gutter capacity +'/z" is exceeded. A maximum flow of 20 cfs will
III-1
be allowed in each gutter or where gutter capacity +%z" is exceeded. Bypass from
upstream inlets shall not exceed 5 cfs through collector street inlets.
c) MAJOR THOROUGHFARES: Based on a transverse slope of a positive '/4" per foot
on the pavement, the 100-year Design Frequency flow shall not exceed the elevation of
the lowest top of curb. A maximum of 35 cfs will be allowed in the street or where
,gutter capacity is exceeded. Bypass from upstream inlets shall be 0 cfs through major
thoroughfare intersections.
d) ALLEYS: The 100-year Design Frequency flows shall not exceed the capacity of the
alley sections shown in FIGURE 6.
e) EXCAVATED CHANNELS: Excavated channels shall have concrete pilot channels if
deemed necessary by the City Engineer, for access or erosion control as outlined below.
All excavated channels shall have a design water surface as outlined in 3.06 and be in
accordance with FIGURE 24, Type II. Concrete lined channels shall be not less than
Type III shown in FIGURE 24.
fl MINIMLTM LOT AND FLOOR ELEVATIONS: Minimum lot and floor elevations
shall be established as follows:
i) Lots abutting a natural or excavated channel shall have a minimum elevation
for the buildable area of the lot at least at the highest elevation of the drainage
floodway easement described in (g) Easements.
ii) Any habitable structure on property abutting a natural or excavated channel
shall have a finished floor elevation at least 2-feet above the 100-year design
storm or F.I.A. floodway elevation, whichever is greater.
iii) Where lots do not abut a natural or excavated channel, minimum floor
elevations shall be a minimum of 1-foot above the street curb or edge of alley;
whichever is lower, unless otherwise approved by the City Engineer.
g) EASEMENTS: Drainage and floodway easements shall be provided for all open
channels. Drainage and floodway easements for storm sewer pipe shall be the outside
diameter of the conduit plus 10-feet with the minimum being 15 feet, and easement
Ordinance No. 2005-14
Admendment to Desigti Standards III-2
width for open or lined channels shall be at least 20 feet wider than the top of the
channel, 15 feet of which shall be on one side to serve as an access for maintenance
purposes.
h) POSITIVE OVERFLOW: The approved drainage system shall provide for positive
overflow at all Low Points. The term "Positive Overflow" means that when the inlets do
not function properly or when the design capacity of the conduit is exceeded the excess
flow can be conveyed overland along a paved course. Normally, this would mean along
a street or alley but can require the dedication of special drainage easements on private
property. Reasonable jud�nent should be used to limit the easements on private
property to a minimum. In specific cases where the chances of substantial flood
damages could occur, the City of Wylie may require special investigations and designs
by the design engineer.
i) INLET DESIGN: Inlet spacing shall be in accordance with the design criteria contained
in this manual, minimum 300 feet apart, or as required in Section 3.8, m�imum length
of inlets at one location shall not exceed 20 feet each side of street without prior
approval from the City Engineer.
j) CULVERTS AND BRIDGES: All drainage structures shall be designed to carry the
100-year Design Frequency flow. Bridges and culverts shall be designed for a water
surface elevation as outlined in 3.6. Two feet of freeboard is required for these
structures.
k) MINIMUM STREET OR ALLEY ELEVATIONS: Streets or alleys adjacent to an
open channel shall be designed with an elevation not lower than 1-foot above the
drainage and floodway easements defined in (g) above or as directed by the City
Engineer.
3.4 DETERMINATION OF DESIGN DISCHARGE
The Rational Method for computing storm water runoff is to be used for hydraulic design of
facilities serving a drainage area of less than 600 acres. For drainage areas of more than 600
acres and less than 1200 acres, the runoff shall be calculated by both the Rational Method
and the Unit Hydrograph Method with the larger of the two values being used for hydraulic�
III-3
design. For drainage areas larger than 1200 acres the runoff shall be calculated by the Unit
Hydrograph Method, or as outlined in 3.06 (1).
In lieu of the Unit Hydrograph Method a HEGl (Flood Hydrograph) Computer Analysis can
be utilized. The City at its option can require the use of HEC-1 Computer Analysis in lieu of
the unit Hydrograph Method. The HEC-1 Computer Program is available from the U.S.
Army Corps of Engineers, the Hydrologic Engineering Center, 609 Second Street, Davis,
California 95616, 916/440-2105 or can be downloaded from their Internet site. User-friendly
versions are available from a number of vendors.
3.5 RUNOFF COEFFICIENTS AND TIME OF CONCENTRATION
Runoff coefficients, as shown in TABLE 1, shall be used, based on total development under
existing land zoning regulations. Where land uses other than those listed in TABLE 1 are
planned, a coefficient shall be developed utilizing values comparable to those shown.
Times of concentration shall be computed based on the minimum inlet times shown in
TABLE 1.
3.6 CRITERIA FOR CHANNELS, BRIDGES AND CULVERTS
Discharge flows and water surface elevations shall be based on the City's design criteria for
the 100-year design storm frequency with 2-feet of freeboard. Where a unit hydrograph is
used to determine the design flows, Coefficients for "Ct" and "C should be as shown in
Table 2.
3.7 PROCEDURE FOR DETERMINATION OF DESIGN DISCHARGE
A standard form, STORM WATER RUNOFF CALCULATIONS, FORM A, is included in
the Section VIII to record the data used in various drainage area calculations. In general, this
form will be used in calculation of runoff for design of open channels, culverts and bridges.
Explanation for use of this form is included in the Section VIII.
3.8 FLOW IN GUTTERS AND INLET DESIGN
Unless there are specific agreements to the contrary prior to beginning design of the
particular storm drainage project, the City of Wylie requires a storm drain conduit to begin,
and consequently the first inlet to be located, at the point where the street gutter flows full
Ordinance No. 20Q5-14
Admendment to Design Standards III-4
based upon the appropriate desi�n storm frequency. If, in the opinion of the City Engineer,
the flow in the gutter would be excessive under these conditions, then direction will be given
to extending the storm sewer to a point where the gutter flow can be intercepted by more
reasonable inlet locations.
3.9 CAPACITY OF STRAIGHT CROWN STREETS
FIGURE 3, CAPACITY OF TRIANGULAR GUTTERS, applies to all width streets
having a straight cross slope varying from 1/8-inch per foot to %2" per foot which are the
minimum and maximum allowable slopes. Cross slopes other than '/4" per foot shall not be
used without prior approval from the City Engineer.
3.10 CAPACITY OF PARABOLIC CROWN STREETS
FIGURES 4 and 5, CAPACITY OF PARABOLIC GUTTERS, apply to streets with
parabolic crowns.
3.11 STREET INTERSECTION DRAINAGE
The use of surface drainage to convey storm water across a street intersection is subject to the
following criteria:
a) A major thoroughfare shall not be crossed with surface drainage unless approved by the
City Engineer.
b) Wherever possible, a collector street shall not be crossed with surface drainage.
c) Wherever possible, a residential street shall not be crossed with surface drainage in
excess of 5 cfs.
d) At any intersection, only one street shall be crossed with surface drainage and this shall
be the lower classified street.
3.12 ALLEY CAPACITIES
FIGURE 6 is a nomo�aph to allow determination for the storm drain capacity of various
standard alley sections. In residential areas where the standard 10-foot wide alley section
capacity is exceeded, a wider alley may be used to provide storm drain capacity.
III-5
As can be seen on FIGURE 6, the 20-foot wide alley section has the largest storm drain
capacity. Curbs shall not be added to alleys to increase the capacity unless approved by the
w,.... City Engineer. Where a particular width alley is required, such as a 12-foot width, a wider
alley, such as a 16-foot width, may be required for greater capacity. Approximate increases
in right-of-way widths will be necessary. Alley capacities are calculated to allow the entire
alley right-of-way to carry the flow, 2%2" above paving edge.
3.13 INLET DESIGN
FIGURE 7, STORM DRAIN INLETS, is a tabulation for the various types and sizes of inlets
and their prescribed uses.
The information in FIGURE 7 and the general requirements of beginning the storm drain
conduit where the street gutter capacity is reached will furnish the information necessary to
establish inlet locations.
FIGURES 8 through 21 shall be used to determine the capacity of specific inlets under
various conditions.
In using the graphs for selection of inlet sizes, care must be taken where the gutter flow
exceeds the capacity of the largest available inlet size. This is illustrated with the following
example.
Known: Major Street, Type C
Pavement Width 24 Feet
Gutter Slope 1.00%
Pavement Cross Slope 1/4-inch/1 Foot
Gutter Flow 11 cfs
Find: Length of Inlet Required (L;)
Solution: Refer to FIGURE 8
Enter Graph at cfs
Intersect Slope 1.00%
Read L,1= 16.9 Feet
DO NOT USE 14-FOOT INLET IN COMBINATION WITH 4-FOOT INLET
Enter Graph at I,i 14 Feet
Intersect Slope 1.00%
Ordinance No. 20Q5-14
Admendment to Design Standards III
Read Q 8.8 cfs
Enter Graph at Li 4
Intersect Slope 1.00%
Read Q 1.9 cfs
Therefore, �the two inlets have a total capacity of 10.7 cfs, which is less than the
gutter flow of 11 cfs.
USE TRIAL AND ERROR SOLUTION
Try 12-Foot Inlet plus 6-Foot Inlet
Enter Graph at L,i 12 Feet
Intersect Slope 1.00%
Read Q 7.3 cfs
Enter Graph at Li 6 Feet
Intersect Slope 1.00%
Read Q 3.1 cfs
The two inlets have a capacity of 10.4 cfs, which is less than the gutter flow.
Try two 10-foot Inlets
Enter Graph at Li 10 Feet
Intersect Slope 1.00%
Read Q 5.7
x 5.7 11.4 cfs capacity which is equal to the gutter flow.
Use either two 10-foot inlets or other suitable combinations; whichever will best fit the
physical conditions. Consideration should be given to alternate inlet locations or extension
of the system to alleviate the problem of multiple inlets at a single location.
Inlets shall be sized to intercept all flow in the approaching gutter. In cases where the
selection of particular size inlet would result in intercepting in excess of 90% of the gutter
flow, consideration may be given to such an inlet on a minor or secondary street.
3.14 PROCEDURE FOR SIZING AND LOCATING INLETS
In order that the design procedure for determining inlet locations and sizes may be facilitated,
a standard form, INLET DESIGN CALCULATIOI�TS, FORM B, has been included in the
Section VIII together with an explanation of how to use the form. Minimum distance�
III-7
between inlets on streets, especially major thoroughfares, shall be 300 feet or as required in
Section 3.8. Remainder to be collected offsite before flowing into street.
3.15 HYDRAULIC GRADIENT OF CONDUITS
A storm drainage conduit must have sufficient capacity to discharge a design storm with a
minimum of interruption and inconvenience to the public using streets and thoroughfares.
The size of the conduit is determined by accumulating runoff from contributing inlets and
calculating the slope of a hydraulic gradient from Manning's Equation:
S Qn Z
1.486 AR
Beginning at the upper most inlet on the system a tentative hydraulic gradient for the selected
conduit size is plotted approximately 2 feet below the gutter between each contributing inlet
to insure that the selected conduit will carry the design flow at an elevation below the gutter
profile. As the conduit size is selected and the tentative hydraulic gradient is plotted between
each inlet pickup point, a head loss due to a change in velocity and pipe size must be
incorporated in the gradient profile. (See Table 6 for VELOCITY HEAD COEFFICIENTS
FOR CLOSED CONDUITS.)
Also at each point where an inlet lateral enters the main conduit the gradient must be
sufficiently low to allow the hydraulic gradient in the inlet to be below the gutter grade.
At the discharge end of the conduit (generally a creek or stream) the hvdraulic Qradient of the
creek for the desi� storm (100-yearl must coincide with the gradient of the storm drainage
conduit and an adjustment is usually required in the tentative conduit gradient and,
necessarily, the initial pipe selection could also change. The hydraulic gradient of the creek
or stream for the design storm can be calculated by use of the HEC-2 or HEC-RAS Computer
Program.
Concrete pipe conduit shall be used to ca�ry the stormwater, a flow chart, Figure 23, based on
Manning's Equation may be used to determine the various hydraulic elements including the
pipe size, the hydraulic gradient and the velocity.
With the hydraulic gradient established, considerable latitude is available for establishment
of the conduit flow line. The inside top of the conduit must be at or below the hydraulic
Ordinance No. 20Q5-14
Admendment to Design Standards III
gradient thus allowing the conduit to be lowered where necessary. The hydraulic gradient for
the storm sewer line and associated laterals shall be plotted directly on the construction plan
profile worksheet and adjusted as necessary.
There will be hydraulic conditions that cause the conduits to flow partially full and where
this occurs, the hydraulic gradient should be shown at the inside crown (soffit) of the conduit.
This procedure will provide a means for conservatively selecting a conduit size, which will
carry the flood discharge.
3.16 VELOCITY IN CLOSED CONDUITS
TABLE 3 is a tabulation of minimum pipe grades, which will produce a velocity of not less
than 2.5 fps when flowing full. Grades less than those shown will not be allowed. Only
those pipe sizes shown in TABLE 3 should be used in designing pipe storm sewer systems.
TABLE 4 shows the maximum allowable velocities in closed conduits.
3.17 ROUGHNESS COEFFICIENTS FOR CONDUITS
Recommended values for the roughness coefficient "n" are tabulated in TABLE 5. Where�
engineering judgment indicates values other than those shown should be used, special note of
this variance should be taken and the appropriate adjustments made in the calculations.
3.18 MINOR HEAD LOSSES
The values of K� to be used are tabulated for various conditions in TABLE 6. In designing
storm sewer systems, the head losses that occur at points of turbulence shall be computed and
reflected in the profile of the hydraulic gradient.
3.19 PROCEDURE FOR HYDRAULIC DESIGN OF CLOSED CONDUITS
STORM SEWER CALCULATIONS, FORM C, has been included in the Section VIII,
together with explanation for its use to facilitate the hydraulic design of a storm sewer.
3.20 OPEN CHANNELS
Open channels are to be used to convey storm waters where closed conduits are not justified.�
Consideration must be given to such factors as relative location to streets, schools, parks and
other areas subject to frequent pedestrian use as well as basic economics.
III-9
Type II Channel Figure 24 is an improved section recommended for use where larger storm
flows are to be conveyed or where the grade creates a velocity under 2-feet per second. The
concrete flume in the channel bottom is to be used as a maintenance aid. The indicated width
of the flumes is a minimum width and as the width of the channel increases, the required
width of the flume may be increased.
Type III Channel, Figure 24, is a concrete lined section to be used for large flows in higher
valued property areas and where exposure to pedestrian traffic is limited.
Where a recommended side slope and a maximum side slope are shown on a channel section,
the Engineer shall use the recommended slope unless prior approval has been obtained from
the City of Wylie or soil conditions required a flatter slope.
The most efficient cross section of an open channel, from a hydraulic standpoint, is the one
that, with a given slope, area and roughness coefficient, will have the maximum capacity.
This cross section is the one having the smallest wetted perimeter. There are usually
practical obstacles to using cross sections of the greatest hydraulic efficiency, but the
dimensions of such sections should be considered and adhered to as closely as conditions will
allow.
Landscaping is intended to protect the channel right-of-way from erosion, as well as present
an aesthetically pleasing view. The Engineer shall include in his plans the type of grass and
placement to be furnished. Full coverage of grass must be established prior to acceptance by
the City.
Erosion and sediment control shall be included in the design and shown on the construction
plans. These controls shall meet EPA requirements.
Design water surface shall be as shown on Figure 24 and as outlined in 3.06. Floodway
easements shall be provided as shown in 3.03(g).
Special care must be taken at entrances to closed conduits, such as culverts, to provide for the
headwater requirements. These calculations and the required explanations are included in
Paragraph 3.32, PROCEDURE FOR HYDRAULIC DESIGN OF CULVERTS.
Ordinance No. 2005-14
Admendment to Design Standards III
On all channels the water surface elevations, which may be assumed as coincident with the
hydraulic gradient, shall be calculated and shown on the construction plans. One exception
to the water surface coinciding with the hydraulic gradient would be in supercritical flow,
which generally is not encountered in this geographical area. Designs utilizing supercritical
flow should be discussed with the City of Wylie in the preliminary stages of design.
Hydraulic calculations for Type I Channels Figure 24 shall be made as outlined on FORM
"D". This procedure is applicable to a stream with an irregular channel and utilizes
Bernoulli's Energy Equation to establish the water surface elevations at succeeding points
along the channel.
Hydraulic calculations for Types II and III Channels shall be made as outlined on
FORM "E".
In general, the use of existing channels in their natural condition or with a minimum of
improvement and with reasonable safety factors is encouraged.
3.21 TYPES OF CHANNELS
FIGURE 24 illustrates the classifications and geometrics of various channel types, which are
to be used wherever possible.
Type I Channel is to be used when the development of land will allow. It is intended to be
left as nearly as possible in its natural state with improvements primarily limited to those
which will allow the safe conveyance of storm waters, minimize public health hazards and
make the flood plain usable for recreation purposes. In some instances it may be desirable to
remove undergrowth.
3.22 QUANTITY OF FLOW
In the design of open channels it is usually necessary that quantities of flow be estimated for
several points along the channel. These are locations where recognized discharge points
enter the channel and the flows are calculated as previously outlined under "Determination of
Design Discharge."
3.23 CHANNEL ALIGNMENT AND GRADE
III-11
While it is recognized that channel alignments must necessarily be controlled primarily by
existing topography and right-of-way, changes in alignment should be as gradual as possible.
Whenever practicable, changes in alignment should be made in sections with flatter grades.
Normally, the grade of channels will be established by existing conditions, such as an
existing channel at one end and a storm sewer at the other end. There are times, however,
when the grade is subject to modification, especially between controlled points.
Whenever possible the grades should be sufficient to prevent sedimentation and should not
be overly steep to cause excessive erosion.
For any given discharge and cross-section of channel, there is always a slope just sufficient to
maintain flow at critical depth. This is termed critical slope and a relatively laxge change in
depth corresponds to relatively small changes in energy. Because of this instability, slopes at
or near critical values should be avoided.
Maximum allowable velocities are shown in TABLE 7. When the normal available grade
would cause velocities in excess of the maximums, plans shall include details for any special
structures required to retard this flow.
3.24 ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS
Roughness coefficients to be used in solving Manning's Equation are shown in TABLE 7,
together with maximum allowable velocities.
3.25 PROCEDURE FOR CALCULATION OF WATER SURFACE PROFILE FOR
UNIMPROVED CHANNELS
FORM "D" included in Section VIII, together with the explanation for its use, shall be used
for calculating a profile of the water surface along an unimproved channel. The HEC-2 or
HEC-RAS Computer Program is an alternate method to the use of Form "D" and may be
required by the City.
3.26 PROCEDURE FOR HYDRAULIC DESIGN OF OPEN CHANNELS
FORM "E", included in Section VIII, together with the explanation for its use, shall be used
in the design for open channels. The HEC-2 or HEGRAS Computer Program is an alternate
method to the use of Form "D" and may be required by the City.
Ordinance No. 20Q5-14
Admendment to Design Standards III
3.27 HYDRAULIC DESIGN OF CULVERTS
The function of a culvert or bridge is to pass storm water from the upstream side of a
roadway to the downstream side without submerging the roadway or causing excessive
backwater that flows upstream property.
The Engineer shall keep head losses and velocities within reasonable limits while selecting
the most economical structure. In general, this means selecting a structure that creates a
headwater condition and has a maximum velocity of flow safely below the allowed
ma�cimums.
The vertical distance between the upstream design water surface and the roadway elevation
should be maintained to provide a safety factor to protect against unusual clogging of the
culvert and to provide a margin for future modifications in surrounding physical conditions.
Tn general, a minimum of two feet shall be considered reasonable when the structure is
designed to pass a design storm frequency of 100 years calculated by Wylie's criteria.
Unusual surrounding physical conditions may be cause for an increase in this requirement.
3.28 CULVERT HYDRAULICS
In the hydraulic design of culverts an investigation shall be made of four different operating
conditions, all as shown on FORM "F". It is not necessary that the Engineer know prior to
the actual calculations which condition of operation (Case I, II, III or IV) exists. The
calculations will make this known.
Case I operation is a condition where the capacity of the culvert is controlled at the inlet with
the upstream water level at or below the top of the culvert and the downstream water level
below the top of the culvert.
Case II operation is also a condition where the capacity of the culvert is controlled at the inlet
with the upstream water level above the top of the culvert with the downstream water level
below the top of the culvert.
Case III operation is a condition where the capacity of the culvert is controlled at the outlet
with the upstream and downstream water levels above the top of the culvert.
III-13
Case IV operation is a condition where the capacity of the culvert is controlled at the outlet
with the upstream water level above the top of the culvert and the downstream water level
equal to one of two levels to be calculated.
3.29 OUANTITY OF FLOW
The quantity of flow which the structure must convey shall be calculated in accordance with
the Procedure for Determination of Design Discharge utilizing FORM "A".
3.30 HEADWALLS AND ENTRANCE CONDITIONS
Headwalls are used to protect the embankment from erosion and the culvert from
displacement. The headwalls, with or without wingwalls and aprons, shall be constructed in
accordance with the standard drawings as required by the physical conditions of the
particular installation.
In general, straight headwalls should be used where the approach velocities in the channel are
below 6 feet per second, where headwater pools are formed and where no downstream
channel protection is required. Headwalls with wingwalls and aprons should be used where
the approach velocities are from 6 to 12 feet per second and downstream channel protection
is desirable.
Special headwalls and wingwalls may be required where approach velocities are in excess of
12 to 15 feet per second. This requirement varies according to the axis of the approach
velocity with respect to the culvert entrance.
A table of culvert entrance data is shown on FORM "F". The values of the entrance
coefficient, K are a combination of the effects of entrance and approach conditions. It is
recognized that all possible conditions may not be tabulated, but an interpolation of values
should be possible from the information shown. Where the term "round" entrance edge is
used, it means a 6-inch radius on the exposed edge of the entrance.
3.31 CULVERT DISCHARGE VELOCITIES
Velocities in culverts should be limited to no more than 15 feet per second, but downstream
b conditions very likely will impose more stringent controls. Consideration must be given to
the effect of high velocities and turbulence on the channel, adjoining property and
Ordinancs No. 20Q5-14
Admendmentto Design Standards III
embanknient. TABLE 8 is a tabulation of maximum allowable velocities based on
downstream channel conditions.
3.32 PROCEDURE FOR HYDRAULIC DESIGN OF CULVERTS
FORM "F", included in the Section VIII, together with the explanation for its use, shall be
used for the hydraulic design of culverts.
3.33 HYDRAULIC DESIGN OF BRIDGES
Wherever possible the proposed bridge should be designed to span a channel section equal to
the approaching channel section. If a reduction in channel section is desired this should be
accomplished upstream of the bridge and appropriate adjustments made in the hydraulic
gradient.
Wherever possible bridges should be constructed to cross channels at a 90-degree angle,
which normally will result in the most economical construction. Wherever the bridge
structure is skewed the bents should be constructed parallel to the flow of water. Values of
Kb, head loss coefficient, normally will vary from 0.2 to 0.5 with the exact value to be
determined by an appraisal of the particular hydraulic conditions associated with the specific
project. With a minimum of constriction and change in velocity, a clear span bridge would
have a minimum coefficient. This would increase for a multispan bridge, skewed or with
piers not placed perpendicular to the flow. The Bureau of Public Roads "Hydraulic of Bridge
Waterways" should be used for determining the K coefficient.
In more complex bridge design such as long multiple spans and relief structures crossing an
irregular channel section, the procedures outlined in the Texas Highway Department
"Hydraulic Manual" or the Bureau of Public Roads "Hydraulics of Bridge Waterways",
should be utilized.
A distance of 2 feet between the maximum design water surface and the lowest point of the
bridge stringers shall be maintained.
3.34 QUANTITY OF FLOW
The quantity of flow which the structure must convey shall be calculated in accordance with
the Procedure for Determination of Design Discharge utilizing FORM "A". The HEC-1
Computer Program is an alternate method to the use of Form "A" and may be required by the
City.
III-15
3.35 PROCEDURE FOR HYDRAULIC DESIGN OF BRIDGES
FORM "G", included in the Section VIII, together with the explanation for its use, shall be
used for the hydraulic design of bridges.
The Engineer should investigate several different bridge configurations on each project to
deterrnine the most economical that can be constructed wifhin the velocity limitations and
other criteria included in this manual.
3.36 PROCEDURE FOR FILLING IN A FLOOD PLAIN
Fill and development of floodplains, which is not unreasonably damaging to the environment
is permitted where it will not create other flood problems. Following are the engineering
criteria for fill requested:
a) Alterations of the flood plain shall result in no increase in water surface elevation on
other properties. No alteration of the channel or adjacent flood plain will be permitted
which could result in any degree of increased flooding to other properties, adjacent,
upstream, or downstream. Increased flood elevation could cause inundation and damage
to areas not presently inundated by the "design flood". The "design flood" for a creek is
,�w., defined by either the 100-year flood the flood having a one percent chance of being
equaled or exceeded at least once in any given year or the maximum recorded flood,
whichever results in the highest peak flood discharges. Streams on the Federal
Insurance Rate Maps must be designed using the FIRM 100-year design or the City
design, whichever is greater.
b) Alterations of the flood plain shall not create an erosive water velocity on or off site.
The mean veloci of stream flow at the down stream end of the site after fill shall be no
�reater than the mean velocitv of the stream flow under existin� conditions.
No alteration to the flood plain will be permitted which would increase velocities of flood
waters to the extent that significant erosion of flood plain soils will occur either on the
subject property or on other property up or downstream. Soil erosion results in loss of
existing vegetation as well as augments destructive sedimentation downstream. Eventual
public costs in channel improvements and maintenance (such as removal of debris and
dredging of lakes) can be expected as a result. Staffs determination of what constitutes an
"erosive" velocity will be based on analysis of the surface material and permissible velocities
for specific cross-sections affected by the proposed alteration, using standard engineering
tables as a general guide.
Ordinance No. 20Q5-14
Admendmentto Design Standards III
c) Alterations of the flood plain shall be permitted only to the extent permitted b�qual
convevance on both sides of the natural channel. Staffs calculation of the impact of the
proposed alteration will be based on the "equal conveyance" principle in order to insure
equitable treatment for all property owners. Under equal conveyance, if the City allows
a change in the flood carrying capacity (capacity to carry a particular volume of water
per unit of time) on one side of the creek due to a proposed alteration of the flood plain,
it must also allow an equal change to the owner on the other side. The combined change
in flood carrying capacity, due to the proposed alteration plus a corresponding alteration
to the other side of the creek, may not cause either an increase in flood elevation or an
erosive velocity (Criteria 1 and 2) or violate the other criteria. Conveyance is
mathematically expressed as KD 1.486/n AR 2/3 where n= Manning's friction factor,
A= cross secfional area, and R= hydraulic radius.
d) The toe of any fill slope shall parallel the natural channel to prevent an unbalancin� of
stream flow in the altered flood plain. If the aligrunent of the proposed fill slope departs
from the contours of the natural flood plain, the flow characteristics of the floodwaters
may be altered, causing possible damaging erosion and deposition in the altered flood
plain. If the fill slope flows the natural channel, it will also tend to minimize the visual
impact of the alteration.
e) To insure maximum accessibilitv to the flood plain for maintenance and other purposes
and to lessen the probabilitv of slope erosion durinQ periods of hiQh water, maximum
slopes of filled area shall usuallv not exceed 4 to l. Vertical walls, terracin� and other
slope treatments will be considered only as a part of a landscapin� plan submission and
if no unbalancing of stream flow results. The purposes of the slope restrictions are to
maintain stability and prevent erosion of the slopes, to ease maintenance (e.g. mowing)
on the slopes themselves, and to provide accessibility to the areas below the slopes.
Being more frequently inundated and therefore subject to greater hazard of erosion, cut
slopes must be shallower than fill slopes.
fl Landscapin ,,p1an submission shall include plans for erosion control of cut and fill
slopes restoration of excavated areas and tree protection where possible in and below
fill area. Landscapin� should incorporate natural materials (earth, stone, woodl on cut or
fill slopes wherever possible. Applicant should show in plan the general nature and
extent of existing vegetation on the tract, and which areas will be preserved, altered, or
removed as a result of the proposed alterations. Locations and construction details
should be provided showing how trees will be preserved in areas which will be altered
by filling or paving within the drip line of those trees. Applicant should also submit
III-17
plans showing location, type, and size of new plant materials and other landscape
features planned for altered flood plain areas.
Erosion control plans should demonstrate how the developer intends to minimize soil erosion
and sedimentation from his site during and after the fill operation. Plans should include a
timing schedule showing anticipated starting and completion dates for each step of the
proposed operation. Area and time 'of exposed soils should be minimized, and existing
vegetation should be retained and protected wherever feasible. Disturbed areas should be
sodded or covered with mulch andlor temporary vegetation as quickly as possible. Structural
measures (e.g. drop structures, sediment ponds, etc.) should be utilized where necessary for
effective erosion control, but measures should also minimize structures and materials that
detract from the natural appearance of the flood plain.
3.37 FILLING IN A 100 YEAR FLOODWAY FRINGE
a) Definitions
i) 100 Year Flood Plain Elevation (100 Year F.P.EI.): That water surface elevation
established by applying the Manning Equation (Q 1.486/n AR 1/2 S 1/2) to the
backwater analysis of a stream (river, creek or tributary) using the 100-year storm
as the rate of flow (Q). The 100-Year F.P. Elevations are those based on the Corps
of Engineer's analysis and form the basis of the Flood Insurance Rate Map (FIRM)
as adopted by the Federal Insurance Administration, or subsequent amendments.
ii) Flood Plain: Area of land lying below the 100-year flood plain elevation.
iii) Floodwav: That central portion of the flood plain which would remain clear of
filling or other obstructions, unless modifications are made within or along the
stream bed to offset the effect of additional filling or obstructions within the
floodway.
iv) Floodwav Fringe: Area between flood plain line and the floodway line that, if
filled, would not produce a significant rise in the 100-year flood plain elevation.
v) SiQnificant Rise: A rise in the 100-year water surface elevation greater than one (1)
foot for fill on both sides of a stream or one-half (0.5) feet for fill on one side of a
stream.
vi) Floodwav Line: The inter-boundary of the floodway fringe determined by filling
within a flood plain along the entire reach of a stream in such a manner that the total
Ordinance No. 20Q5-14
Adrnendmentto Design Standards III-18
cumulative effect of the filling will not create a significant rise in the 100-year
water surface elevation.
vii) Equal Convevance Principle: An area of the cross section of a stream in its existing
condition carrying a percentage of the stream flow, will continue to carry the same
percentage of the stream flow after filling in the flood plain occurs without creating
a significant rise in the 100-year flood plain elevation.
b) Criteria for Fillin� in the 100 Year Floodwav Frin�e
i) Applies only to creeks or portions of creeks with a drainage area of five (5) square
miles, or less.
ii) Fill and development of the flood plains shall not create a"si�ificant rise" in the
100-year flood plain elevation.
iii) For fill and/or other development within the floodwav, supporting hydraulic
analysis will be required prior to or at the time of submittal of the preliminary plat
demonstrating that the proposed development will not create a"significant rise" in
the "100-year flood plain elevation".
iv) In beginning a backwater analysis for development within a flood plain, the
downstream water surface elevation will be determined as follows:
For fill on one side only of a stream, add one-half (0.5) feet to the 100-year flood
plain elevation at the downstream property line.
For fill on both sides of a stream, add one (1.0) foot to the 100-year flood plain
elevation at the downstream property line.
v) Alterations of the floodway shall not create velocities, which could produce
maximum erosive velocities in excess of those set forth in Table 7.
vi) Floodway Line shall be established in accordance with the definition in (A) above.
vii) Equal Conveyance shall be required in accordance with the definition of Equal
Conveyance Principle in (A) above.
III-19
viii) The requirements of 3.36, Paragraphs d, e and f shall apply.
ix) Final approval shall be by FEMA.
3.38 DETENTION PONDS
On-site detention shall be used to control post-development runoff. Developments shall be
required to provide adequate detention so that post-development peak flows do not exceed
the peak flows calculated for the area using the rational method with the coefficient for
runoff appropriate for the conditions prior to development. Inflow volumes shall be
calculated for the 5, 10, 25 and 100-year storm frequencies. For areas less than 50 acres a
form of the Rational Method will be acceptable, while for areas 50 acres and larger an inflow
hydrograph, unit hydrograph or HEC-1 computer model will be required. A hydraulic study
that illustrates no adverse conditions are created downstream as a result of development may
be accepted in lieu of storm water detention. City Council may waive storm water detention
requirements upon determination by the Council that such waiver is in the best interest of the
City.
The detention system shall be designed for the 100-year storm frequency, 24-hour design
storm duration and a time to empty of 48 hours. Any type of pond design shall be designed
with a freeboard of 30% the nominal�depth of the pond, but not less than 2.0 feet. The
maximum allowable headwater must be kept within the range of slope stability of the
embankment construction. All design calculations shall be a part of the construction plans.
An outlet control structure such as an orifice and weir placed at the inlet end of the outfall
pipe is to provide an integrated stage-discharge such that a wide range of storms can be
effectively controlled. Perforated riser pipes, weirs and special outlet control boxes are
acceptable. Pipe/culvert type outlet control will only be allowed with written approval from
the City. All vertical structures shall have anti-vortex and trash rack devices. Emergency
overflow structures and paved positive overflow channels shall be included with the design
of detention systems.
Whenever possible, detention ponds shall fit in the natural contour of the land, be
aesthetically pleasing and be free draining. A grading plan with 2-foot intervals shall be
placed on the construction plans. Maintenance access shall be provided for each pond. The
bottom slope shall be a minimum of 2% towards the outfall structure. Detention basins shall
Orciinance No. 2005-14
Admendment to Design Standards III
be designed with short and long term erosion control. A detention system maintenance
program shall be prepared and submitted to the City for approval before final acceptance of
the construction plans.
III-21
IV CONSTRUCTION PLANS PREPARATION
4.01 GENERAL
This section covers the preparation of drainage construction plans for the City of Wylie.
4.02 PRELIMINARY DESIGN PHASE
The preliminary design phase shall be complete in sufficient detail to allow review by the
City of Wylie. To complete this phase, ali topographic surveys should be furnished to allow
establishment of alignment, grades and right-of-way requirements. These may be
accomplished by on-the-ground field surveys, by aerial photogrametric methods, or by use of
topographic maps.
Based upon the procedures and criteria outlined in SECTION III, CRITERIA AND DESIGN
PROCEDURES, of this manual, the hydraulic design of the proposed facilities shall be
accomplished. All calculations shall be made on the a�propriate forms and submitted with
the preliminar�plans.
These plans shall show the alignment, drainage areas, size of facilities and grades.
a) Preliminary Plans
Preliminary storm drainage plans shall include a cover sheet, drainage area map, plan-
profile sheets and channel cross sections if required. The proposed improvements shall
be drawn on 22-inch by 34-inch sheets.
b) Draina�e Area Map
The scale of the drainage area map should be determined by the method to be used in
calculating the runoff as discussed in Section III. Generally, a map having a scale of
1" 200' (showing the street right-of-way) is suitable unless dealing with a large
drainage area. For large drainage areas a map having a scale of 1" 2000' is usually
sufficient. When calculating runoff ihe drainage area map shall show the boundary of
the drainage area contributing runoff into the proposed system. This boundary can
usually be determined from a map having a contour interval of 2 to 5 feet. The area
shall be further divided into sub-areas to determine flow concentration points or inlet
locations.
Ordinance No. 2005-14
Admendment to Design Standards IV-1
Direction of flow within streets, alleys, natural and manmade drainage ways and at all
system intersections shall be clearly shown on the drainage area map. Existing and
proposed drainage inlets, storm sewer pipe systems and drainage channels shall be
clearly shown and differentiated on the drainage area map. Plan-profile storm sewer or
drainage improvement sheet limits shall also be shown.
The Drainage Area Map should show enough topography to easily determine its location
within the City.
All offsite drainage within the natural drainage basin shall be shown and delineated.
Runoff calculations including inlet calculations, shall be a part of the drainage area map.
c) Plan-Profile Sheets
Inlets shall be given the same number designation as the area or sub-area contribution
runoff to the inlet. The inlet number designation shall be shown opposite the inlet.
Inlets shall be located at or immediately downstream of drainage concentration points.
At intersections, where possible, the end of the inlet shall be ten feet from the curb
radius and the inlet location shall also provide minimum interference with the use of
adjacent property. Inlet locations directly above storm sewer lines shall be avoided.
Data opposite each inlet shall include paving or storm sewer stationing at centerline of
inlet, size of inlet, type of inlet, number or designation, top of curb elevation and flow
line of inlet as shown on the typical plans. Inlet laterals leading to storm sewers, where
possible, shall enter the inlet at a 60 degree angle from the street side. Laterals shall be
four and one-half feet from top of curb to flow line of inlet unless utilities or storm sewer
depth requires otherwise. Laterals shall not enter the corners of inlets. Lateral profiles
shall be drawn showing appropriate information including the Hydraulic Gradient.
In the plan view, the storm sewer designation, size of pipe, and length of each size pipe
shall be shown adjacent to the storm sewer. The sewer plan shall be stationed at one
hundred foot intervals and each sheet shall begin and end with even or fifty foot
stationing. All storm sewer components shall be stationed.
The profile portion of the storm sewer plan-profile sheet shall show the existing ground
profile along the centerline of proposed sewer, the hydraulic gradient of the sewer, the�"'
proposed storm sewer, and utilities which intersect the alignment of the proposed storm
sewer. Also shown shall be the diameter of the proposed pipe in inches and the physical
IV-2
grade in percent. Hydraulic data for each length of storm sewer between interception
points shall be shown on the profile. This data shall consist of pipe diameter in inches,
discharge in cubic feet per second, slope of hydraulic gradient in percent, capacity of
pipe in cubic feet per second and velocity in feet per second. Also, the head loss at each
interception point shall be shown.
Elevations of the flow line of the proposed storm sewer shall be shown at one hundred
�foot intervals on the profile. Stationing and flow line elevations shall also be shown at
all pipe grade changes, pipe size changes, lateral connections, manholes and wye
connections.
4.03 FINAL DESIGN PHASE
During the final design phase the construction plans shall be placed in final form. All sheets
shall be drawn in ink on 22-inch by 34-inch sheets and shall be clearly legible when sheets
are reduced to half scale.
Review comments shall be considered, additional data incorporated and the final design and
drafting of the plans completed. All grades, elevations, pipe sizes, utility locations, items and
quantities should be checked and each plan-profile sheet shall have a bench mark shown.
Ordinance No. 20Q5-14
Admendment to Design Standards IV-3
V APPENDIX
S.OlA DEFINITION OF TERMS
An�le of Flare: Angle between direction of winwvall and centerline of culvert or storm
drain outlet.
Backwater Curve The surface curve of a stream of water:
Conduit: Any closed device for conveying flowing water.
Control: The hydraulic characteristic, which determined the stage-discharge relationship in
a conduit.
Critical Flow: The state of flow for a given discharge at which the specific energy is a
minimum with respect to the bottom of the conduit.
Entrance Head: The head required to cause flow into a conduit or other structure; it
includes both entrance loss and velocity head.
Entrance Loss: Head lost in eddies or friction at the inlet to a conduit, headwall or
structure.
Flume: Any open conduit on a prepared grade, trestle or bridge.
Freeboard: The distance between the normal operating level and the top of the side of an
open channel left to allow for wave action, floating debris, or any other condition or
emergency without overflowing structure.
Headwater: Depth of water in the channel measured form the invert of the culvert inlet.
HEGl: Computer Program to analyze a Flood Hydro�aph. This program is available
from the U. S. Army Corps of Engineers.
HEG2/HEC-RAS: Computer Prob am to analyze a Water Surface Profile. This program
is available from the U. S. Army Corps of Engineers.
Hvdraulic Gradient: A line representing the pressure head available at any given point
within the system.
Invert: The flow-line of conduit (pipe or box).
v-1
Mannin�'s Equation: The uniform flow equation used to relate velocity, hydraulic radius
and energy gradient slope.
Open Channel A channel in which water flows with a free surface.
Rational Formula: The means of relating runoff with the area being drained and the
intensity of the storm rainfall.
Soffit: The inside top of the conduit (pipe or box).
Stead Constant discharge.
Surchar�e: Height of water surface above the crown of a closed conduit at the upstream
end.
Tailwater: Total depth of flow in the downstream channel measured form the invert of the
culvert outlet.
Time of Concentration: The estimated time in minutes required for runoff to flow from the
most remote section of the drainage area to the point at which the flow is to be determined.
Total Head Line (Energy Line�: A line representing the energy in flowing water. It is
x plotted a distance above the profiles of the flow line of the conduit equal to the normal
depth plus the normal velocity head plus the pressure head for conduits flowing under
pressure.
Uniform Channel: A channel with a constant cross section and roughness coefficient.
Uniform Flow: A condition of flow in which the discharge, or quantity of water flowing
per unit of time, and the velocity are constant. Flows will be at nortnal depth and can be
computed by the Manning Equation.
Watershed: The area drained by a stream or drainage system.
S.O1B DETENTION SYSTEM DEFINITIONS
Detention Stora�e: Detention storage facilities are generally designed to control short,
high-intensity local storms, as these are the major cause of flooding on small streams (1).
Detention storage serves to attenuate the peak flow by reducing the peak outflow to a rate
less than the peak inflow, which effectively lengthens the time base of the outflow
hydrograph. The total volume of water discharged is the same; it is merely distributed over
a long period of time (2). Discharge from detention storage facilities begins immediately at
Orcfinancs No. 20Q5-14
Admendment to Design Standards V_2
the start of the storm, and the facility is usually completely drained within a day after the
storm event.
Retention Stora�e: Retention storage refers to those facilities where stormwater is
collected and stored during the flood event. The stored water is released after the flood
event by means of controlled outlet works. Alternatively, the water may be allowed to
infiltrate into the ground or evaporate. For maximum effectiveness, the water contained in
the retention storage facility must be released or lost before the next flood event occurs (2).
In some cases, it may be desirable to maintain a permanent pool within the retention area.
Such a facility is termed wet storage.
Convevance Stora�e: As stormwater enters and flows in channels, floodplains, drains, and
storm sewers, the flow is being stored in transient form and is termed conveyance storage.
Conveyance storage is generally obtained by constructing low-velocity channels with large
cross-sectional areas.
Upstream Stora�e: This storage occurs upstream of the design area to be protected. It is
intended to contain runoff, which originates upstream and beyond the area to be protected.
Within-Area Stora�e: This storage occurs in the area to be protected. It is intended to store
runoff originating in and azound the area to be protected. It is common for such storage to
be provided at the development sites.
Downstream Storaae: This is storage located downstream from the area to be protected.
The general purpose of downstream storage is to manage storm flows from the area to be
protected and to control any detrimental downstream effects from development in the
protected area.
Rainfall Storaee: Rainfall storage refers to the starage of water in the vicinity of the
rainfall occurrence or before storm water accumulates significantly (3). This storage
classification is similar to "within-area storage" as described above.
Runoff Stora�e: Runoff storage refers to the storage of larger quantities of water, that have
accumulated significantly and have begun to flow in the drainage system. This storage
classification is closely related to "upstream storage" and "downstream storage" as
described above.
Drivewav Stora�e: This storage method involves the eonstruction of .depressed section in
the driveway such that runoff from the lot and/or roof may be routed and stored there. A
V-3
properly designed outlet system will regulate the discharge of this runoff into the drainage
system (2).
Cistern/Infiltration: A cistern or tank can be located within the property area to collect
runoff from the lot and roof. If local subsurface soil properties and geologic conditions
permit, the water can be infiltrated after the storm subsides (2).
Cistern/Irri�ation: This method is identical to the "cistern/infiltration" method except that
the option is provided for the water in the cistern to be used for an irrigation water supply
or to be discharged into the storm sewer system.
Rooftop Stora�e: This storage method is most applicable to industrial, commercial, and
apartment buildings with large flat roofs. Rooftop storage is often an economical and
effective alternative. Since it is common for buildings to be designed for snow loads, it is
possible to accommodate an equivalent depth of water without significant structural
changes. A six-inch depth of water is equivalent to 31.2 pounds per square foot, less than
most snow load requirements in the northern United States and Canada (4).
Special roof drains with controlled outlet capacity are typically installed as an integral part
of the rooftop storage method. With proper installation of such drains, peak runoff from
roofs may be reduced by up to 90 percent (4).
An important consideration for the rooftop storage method would be to provide overflow
mechanisms to ensure that the structural capacity of the roof is not exceeded. An
additional consideration would be the watertightness of the rooftop.
Parkin� Lot Stora�e: Parking lots can be graded to route runoff to desired storage areas or
areas of infiltration. If the flow is routed to a storage area, outlet works such as grated
inlets or overflow weirs serve to regulate the design flow. Alternatively, the runoff may be
routed to grassed or gravel filled areas for infiltration and percolation.
On-Site Ponds: On-site ponds provide for the collected stormwater to be released in a
controlled manner by overflow weirs or orifices. When properly designed, on-site ponds
can serve the hydraulic function while providing recreational and aesthetic benefits.
Slow-Flow Draina�e Patterns: This storage method involves the design of conveyance
systems with reduced grades to provide reduced flow velocities. The desired effect is to
m y obtain temporary ponding and a form of transient storage. Slow flow drainage may be
augmented by providing controls (e.g., weirs, checks) along channels to create a system of
Ordinance No. 2005-14
Admendment to Design Standards V-4
linear reservoirs (2). Use of such controls will provide temporary storage while allowing
for a possible increase in infiltration.
Open Space Stora�e: Open spaces such as parks and recreation fields generally have a
substantial area of grass covering and provide increased infiltration opportunities. Such
open spaces produce only minimal quantities of runoff. Therefore, open spaces provide
excellent opportunities for the temporary storage of storm runoff, provided the primary use
of the open space is not altered. This is generally not a problem since recreation areas are
seldom used during storm events.
Retention Reservoirs: Retention reservoirs located in a watershed catchment generally
represent major storage facilities (2). They are most effective when located in valleys or
recessec� areas and should have the ability to regulate stream flow. Retention reservoirs
maintain a permanent pool in the form of ponds or lakes. As such, they are well suited for
water-oriented recreational features.
Detention Reservoirs: Detention reservoirs are generally located on streams and are
frequently located above the reaches where there is a continuous flow (2). Since a
permanent pool is not maintained, detention reservoirs do not provide opportunities for
water-oriented recreation. However, they may be conveniently integrated into a park and
open space plan.
Gravel Pits and Quarries: Gravel pits and quarries are located off-channel such that a side-
channel spillway is necessary to intercept and direct the peak flow fo the pit location.
Outfall from such storage facilities must generally be pumped.
5.02 ABBREVIATION OF TERMS AND SYMBOLS
A Drainage area in acres of tributary watershed. Cross-sectional area of gutter flow
in square feet. Cross-sectional area of flow through conduit in square feet.
A Sub-section area in square feet as used on unimproved channel calculations.
b Bottom width of channel i� feet.
c Runoff Coefficient for use in Rational Formula representing the estimated ratio of
runoff to rainfall which is dependent on the slope of the watershed, the land use
and the character of soil.
C Street crown height in feet.
v-5
Ct A coefficient related to drainage basin characteristics and used in Uni.
Hydrograph calculations.
C Coefficient related to drainage basin characteristics and used in HydrograpL
calculations.
c.f.s. Cubic feet per second.
d Depth of flow in feet.
d Normal depth of flow in conduit feet.
d� Critical depth of flow in conduit feet.
FL Flow line.
f.p.s. Feet per second.
g Gravitational acceleration (32.2 feet per second per second).
H Depth of flow in feet required to pass a given discharge.
h Depth of flow in feet.
HW Headwater elevation or depth above invert at storm drain entrance in feet.
h Vertical distance from downstream culvert flow line to the elevation from which
H is measured, in feet.
h f Head loss due to friction in a length of conduit in feet.
h� Head loss at junction structures, inlets, manholes, etc., due to turbulence in feet.
h� Velocity head loss in feet.
I Intensity, in inches per hour, for rainfall over an entire watershed.
Kb Head loss coefficient at bridges.
K Coefficient of entrance loss.
Ordinance No. 20Q5-14
Admendment to Design Standards
V-6
K� Coefficient for head loss at junctions, inlets and manholes.
L Length of channel in miles measured along flow line.
L� Length of stream in miles from design point to center of gravity of drairiage are�
and used in Unit Hydrograph calculations.
Li Length of curb opening inlet in feet.
I.i Initial and subsequent rainfall losses in inches and used in Unit Hydrograpl
calculations.
n Coefficient of roughness for use in Manning's Equation.
P Length in feet of contact between flowing water and the conduit measured on
cross section. (Wetted Perimeter)
Q Storm water flow in c.f.s.
QR Peak flow in c.f.s. as determined by Rational Method.
Q Peak flow in c.f.s. as determined by Unit Hydrograph Method.
q Peak rate of dischaxge of the Unit Hydrograph for unit rainfall duration of c.f.s
per square mile.
Q Peak rate of discharge of the Unit Hydrograph in c.f.s.
R Hydraulic Radius Cross section area of flow in sq. ft. (A)
Wetted perimeter in ft. (P)
RT Total runoff in inches as used in Unit Hydrograph calculations.
S Slope of street, gutter or hydraulic gradient in feet per foot or percent.
s� That particular slope in feet per foot of a given uniform conduit operating as ar�
open channel at which nornial depth and velocity equal critical depth and velocit}
for a given discharge.
SD Design storm runoff in inches for a two-hour period.
v-7
S f Friction slope in feet per foot in a conduit. This represents the rate of loss in thE
conduit due to friction.
t� Time of Concentration in minutes.
t Lag time in hours from the midpoint of the unit rainfall duration to the peak of thE
Unit Hydrograph.
TW Tailwater elevation of depth above invert a culvert outlet.
V Velocity of flow in feet per second.
v Mean velocity of flow at upstream end of inlet opening in feet per second.
v� Critical velocity of flow in a conduit in feet per second.
V2 Velocity head. A measure, in feet, of the kinetic energy in flowing water.
2g
V1 Upstream Velocity
V2 Downstream Velocity
W Street width from face of curb in feet.
WP Wetted perimeter in feet.
Reciprocal of crown slope, 1/8
8 Crown slope of pavement in feet per foot.
Y Conveyance factor calculated for unimproved channels.
5.03 BIBLIOGRAPHY
1) Chow, Ven Te, Handbook of A�plied Hydrolo�v, McGraw-Hill Book Co., New York,
1964.
2) Chow, Ven Te, Onen Channel Hvdraulics, McGraw-Hill Book Co., New York, 1959.
Ordinance No. 20�5-14
Admendment to Design Standards V-8
3) King, H. W., Handbook of Hvdraulics, McGraw-Hill Book Co., New York, 1954, 4th
Ed.
4) Corps of Engineers, "Hydrologic and Hydraulic Analysis," Civil Works Construction,
Part CXIV, Chapter 5, Supt. of Doc., Washington, D.C.
5) Corps of Engineers, Engineering Manual 1110-2-1405, "Flood Hydrograph Analysis
and Computations," Supt. of Doc., Washington, D.C.
6) U. S. Weather Bureau, Rainfall Frequencv Atlas of the United States, Technical Paper
No. 40, Supt. of Doc., Washington, D.C., May 1961.
7) Texas Highway Department, Hvdraulic Manual, Austin, Tex., September 1970.
8) Johns Hopkins University, The Desi� of Storm Water Inlets, Department of Sanitary
Engineering and Water Resources, Baltimore, Maryland, June 1956.
9) Hendrickson, John G., Jr., Hvdraulics of Culverts, American Concrete Pipe
Association, Chicago, Illinois, 1964.
10) Hydrology Handbook, A.S.C.E., New York, 1949.
11) Desi�n and Construction of Sanitary and Storm Sewers, A.S.C.E., New York, 1960.
12) American Concrete Pipe Association, Design Data, March 1969.
13) Denver Regional Council of Governments, Urban Storm Drainage Manual, March
1969.
14) State Highway Department of Georgia, Manual on Drainage Design for Hi�hwavs,
1966.
15) City of Waco, Texas, Storm Draina eg Design Manual, 1959.
16) City of Forth Worth, Texas, Storm Drainage Criteria and Design Manual, 1967.
17) Horace W. King, Chester O. Wisler, James G. Woodburn, Hydraulics, John Wiley and
Sons, New York, 1952, Sth Edition.-
18) Portland Cement Association, Handbook of Concrete Culvert Pipe Hvdraulics, 1964.
19) Highway Research Board Proceedings, 1946.
20) Department of Commerce Hydraulic Engineering Circular No. 5, Hvdraulic Charts for
the Selection of Highwav Culverts, December 1965.
V-9
21) John R. French, National Bureau of Standard Report No. 4444, Hvdraulic
Characteristics of Commonly Used Pipe Entrances.
22) H. G. Bossy, Hydraulics of Conventional Hi�hway Culverts.
23) Technical Memorandum National Weather Service, Hvdro 35, Dated June 1977.
24) Hvdraulics of Brid�e Waterwavs, Hydraulic Design Service No. 1 U. S. Department of
Transportation, Bureau of Public Roads,1970.
Ordinance No. 2D05-14
Admendment to Design Standards V-10
VI LIST OF TABLES
Table
Na• Content
1 Runoff Coefficients and Minimum Inlet Times
2 Coefficients "Ct" and "C
3 Minimum Slopes for Pipes
4 Maximum Velocities in Closed Conduits
5 Roughness Coefficients for Closed Conduits
6 Velocity Head Loss Coefficients for Closed Conduits
7 Roughness Coefficients for Open Channels
8 Culvert Discharge Velocities
vI-1
TABLE 1
COEFFICIENTS OF RUNOFF AND MINIMUM INLET TIMES
Land Use Runoff Coefficient C Minimum Inlet Time In Minutes
I
j
Residential 0.6 15
Commercial 09 10
I
Industrial 0.9 10
i
Multiple Unit Dwelling 0.8 10
Parks 0.4 15
i
Cemeteries 0.4 15
Pasture 0.4 15
Woods 0.3 15
Cultivated 0.6 20
i
Shopping Centers 0.9 10
Paved Areas 0.9 10
I
Schools 0.7 15
�i
Patio Homes 0.6 15
Churches 0.8 10
Ordinance No. 2005-14
Admendment to Design Standards VI-2
TABLE 2
COEFFICIENTS "Ct" AND "C
Approximate Approximate
Draina e Area Characteristics Value of "C Value of "C 640"
Sparsely Sewered Area
Flat Basin Slope (less than 0.50%) 0.65 350
Moderate Basin Slope (0.50% to 0.80%) 0.60 370
Steep Basin Slope (greater than 0.80%) 0.55 390
Moderately Sewered Area
I
Flat Basin Slope (less than 0.50%) 0.55 400
Moderate Basin Slope (0.50% to 0.80%) 0.50 420
Steep Basin Slope (greater than 0.80%) 0.45 440 i
I
Highly Sewered Area
Flat Basin Slope (less than 0.50%) 0.45 450
Moderate Basin Slope (0.50% to 0.80%) 0.40 470
Steep Basin Slope (greater than 0.80%) 0.35 490 i
VI-3
TABLE 3
MINIMUM SLOPES FOR PIPES
(n 0.013)
Pipe Diameter Slope Pipe Diameter Slope
(Inches (Feet/100 Feet) (Inches) (Feet/100 Feet)
51 .045
18 .180 54 .041
21 .150 60 .036
24 .120 66 .032
27 .110 72 .028
30 .090 78 .025
33 .080 84 .023
36 .070 90 .021
39 .062 96 .019
42 .056 102 .018
45 .052 108 .016
48 .048
NOTE: Minimum pipe diameter to be used in construction of storm sewers shall be 18-inches.
Ordinance No. 2005-14
Admendment to Design Standards VI
TABLE 4
MAXIMUM VELOCITIES IN CLOSED CONDUITS
T e of Conduit Maximum Veloci
Culverts 15 f. .s.
Inlet Laterals 30 f.p.s.
Storm Sewers 12 f.p.s.
Storm sewers that discharge into open channels shall be at a maximum velocity of 8-feet per second
unless channel protection is provided for the reach from the point of discharge until velocity is less
than 8-feet per second in the channel. THIS MAXIMUM VELOCITY MUST BE
MAINTAINED IN THE LAST 200-FEET OF STORM SEWER.
VI-5
TABLE 5
ROUGHNESS COEFFICIENTS FOR CLOSED CONDUITS
Recommended
Material of Construction Rou�hness Coefficient "n"
New Monolithic Concrete Conduit 0.015
Concrete Pipe Storm Sewer
Good Alignment, Smooth Joints 0.013
Fair Alignment, Ordinary Joints 0.015
Poor Alignment, Poor Joints 0.017
Concrete Pipe Culverts 0.012
Monolithic Concrete Culverts 0.012
Corrugated Pipe 0.024
Corrugated Arch Pipe 0.024
Corrugated Metal Pipe with Smooth Liner 0.015
NOTE: Reinforced concrete pipe is the accepted material for construction of storm sewers. The
use of other materials for the construction of storm sewers shall have prior approval.from
the City Engineer. For design of all pipe material an "n" of 0.013 shall be used.
Ordinancs No. 20Q5-14
Admendment to Design Standards VI-6
TABLE 6
VELOCITY HEAD LOSS COEFFICIENTS FOR CLOSED CONDUITS
MANHOLE AT CHANGE IN PIPE DII2ECTION
Descri tion An le Head Loss Coefficient K'
90 1.00
60 0.80
45 0.65
Angle 30 0.50
BEND IN PIPES
Description An le Head Loss Coefficient K'
*90 0.80
*60 0.60
**45 0.50
Angle **30 0.45
ENLARGEMENTS IN PIPE SIZES WITH CONSTANT FLOW
Ratio of Upstream Diameter Iiead Loss
Description to Downstream Diameter Coefficient K'
0.81 1.00
0.82 0.90
0.84 0.80
0.85 0.70
0.86 0.60
0.88 0.50
0.90 0.40
0.92 0.30
Only as authorized by City Engineer.
Horizontal curves are the accepted method of construction.
VI-7
TABLE 7
w,w. ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS
Maximum
Rou hness Coefficient Velocity
Channel Description Minimum Normal Maximum Ftlsec
MINOR 1VATURAL STREAMS TYPE I CHANNEL
Moderately Well Defined Channel
Grass and Weeds, Little Brush 0.025 0.030 0.033 8
Dense Weeds, Little Brush 0.030 0.035 0.040 8
Weeds, Light Brush on Banks 0.030 0.035 0.040 8�
Weeds, Heavy Brush on Banks 0.035 0.050 0.060 8
Weeds, Dense Willows on Banks 0.040 0.060 0.080 8
Irregular Channel with Pools and
Meanders
Grass and Weeds, Little Brush 0.030 0.036 0.042 8
Dense Weeds, Little Brush 0.036 0.042 0.048 8
Weeds, Light Brush on Banks 0.036 0.042 0.048 8
Weeds, Heavy Brush on Banks 0.042 0.060 0.072 8
Weeds, Dense Willows on Banks 0.048 0.072 0.096 8
Flood Plain, Pasture
Short Grass, No Brush 0.025 0.030 0.035 8
Tall Grass, No Brush 0.030 0.035 0.050 8
Flood Plain, Cultivated
No Crops 0.025 0.030 0.035 8
Mature Cro s 0.030 0.040 0.050 8
Flood Plain, Uncleared
Heavy Weeds, Light Brush 0.035 0.050 0.070 8
Medium to Dense Brush 0.070 0.100 0.160 8
Trees with Flood Sta e below Branches 0.080 0.100 0.120 8
MAJOR NATURAL STREAMS TYPE I CHANNEL
The roughness coefficient is less than that for minor stream of similar description because banks offer
less effective resistance.
Moderately Well Defined Channel 0.025 0.060 8
Irregular Channel 0.035 0.100 8
UNLINED VEGETATED CHANNELS TYPE II CHANNEL
Mowed Grass, Clay Soil 0.025 0.030 0.035 8
Mowed Grass, Sandy Soil 0.025 0.030 0.035 6
Ordinance No. 2005-14
Admendment to Design Standards VI-8
TABLE 8
CULVERT DISCHARGE VELOCITIES
Culvert Dischar es On Mazimum Allowable Velocity (f. .s.)
Earth (Sandy) 6
Earth (Clay) g
Sodded Earth g
Rock Gabions (Engineered) 12
Concrete 15
Shale (Lime Stone) 10
,r.
VI-9
VII LIST OF FIGURES
Figure No. Title
1. Rainfall Intensity and Duration
2. Time of Concentration for Surface Flow
3. Capacity of Triangular Gutters
4. Capacity of Parabolic Gutter (26' and 36' Streets)
5. Capacity of Parabolic Gutters (44' and 48' Streets)
6. Capacity of Alley Sections
7. Storm Drain Inlets
8. Recessed and Standard Curb Opening Inlet on Grade (1/4"/1' Cross Slope)
9. Recessed and Standard Curb Opening Inlet on Grade (3/8"/1' Cross Slope; 44' and 48'
Streets)
10. Recessed and Standard Curb Opening Inlet on Grade (1/2"/1' Cross Slope; 36' Street)
1 l. Recessed and Standard Curb Opening Inlet on Grade (26' Street)
12. Recessed and Standard Curb Opening Inlet on Grade (10'x 12', 16' and 20' Alleys)
13. Recessed and Standard Curb Opening Inlet at Low Point
14. Two Grade Combination Inlet on Grade
15. Four Grate Combination Inlet on Grade
16. Three Grate Inlet and Three Grate Combination Inlet on Grade
17. Two Grate Inlet on Grade
18. Four Grate Inlet on Grade
19. Six Grate Inlet on Grade
Ordinance No. 20Q5-14
Admendment to Design Standards VII
Fi�ure No. Title
20. Combination Inlet at Low Point
21. Grate Inlet at Low Point
22. Drop Inlet at Low Point
23. Capacity of Circular Pipes Flowing Full
24. Open Channel Types
25. Headwater Depth for Box Culverts with Inlet Control
26. Headwater Depth for Concrete Pipe Culverts with Inlet Control
27. Head for Concrete Box Culverts Flowing Full
28. Head for Concrete Pipe Culverts Flowing Full
29. Critical Depth of Flow for Rectangular Conduits
30. Critical Depth of Flow for Circular Conduits
r,
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VII-8
STORM DRAIN INLETS
INLET AVAIL. DESIGN
TYPE �NLET DESCRIPTION INLET WHERE USED CURVES
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EXAMPLE
Known: Solution:
Ouantity af Fiow 16.Oc.f.s. Enter Graph at 16.0 c.f,s.
Maximum Depth of Flow Desired IMersect yo 0.4�
in Gutter At Low Point (yo) 0.4� Reod Li 9.2�
Find: Use {0' Inlet
Lenqih of fniet Required (L�)
2 3 4 5 6 7 8 9 IO IS 20 30 40 50 60 70 6025
25
20 20
W 15 {5
w
z
r
w
J
10
10
9
O 9
8 8
Z
W 7
J 7
I
J 6
6
5
5
4
4 2 3 4 5 6 7 8 9 10 15 20 30 40 50 60 70 80
Q QUANTITY OF FLOW IN C. F S.
ROUGHNESS COEFFICIENT n=.Of75 RECESSED AND STANDARD
STREET CROWN TYPE CURB OPEN(NG INLET
WIDTH CAPACITY CURVES
ALL Strcight ond Parobolic AT LOW POINT
FIGURE (3
Ordinance No. 2005-14 VII-15
Admendment to Design Standards
EXAMPLE
Known Solution:
Quantity of Flow 10.0 c.f.s. Enter Graph at IO.Oc.t.s.
Gutter Slope 0.6 Intersect Slope 0.6
Find Read Percent of Flow
Intercepted 62%
Capacity of Two Grate Combination 62 of 10.0 c.f.s. 6.2 c.f.s.
Inlet as Capacity of Two Grate
Combination Inlet
Remaining Gutter Flow
10.0 c.f.s 6.2 c.f.s. 3.8 c.f.s.
s� o
�o
6
2 F
3
C'' o
P
s
1 2 3 4 5 6 7 B 9 10 15 20 30 40 50 60
QUANTITY OF FLOW IN C. F. S.
TWO GRATE COMBINATION INLET
CAPACiTY CURVES
ON GRADE
FIGURE (4
VII-16
EXAMPLE
Known: Solution:
Quontity of Flow 6.0 c.f.s. Enter Graph at 6.0 c.f.s.
Gutter Slopa I.0 Intersect Slope =1.0
Find Read Percent oi Flow
Intercepted 79
Capacity of Four Grcte Combination 79 of 6.0 c.f.s. 4.7 c.f.s.
Inlat as Capocity of Four Grate
Comb[nation Inlet
Remaining Gutter Flow
6.0 c.f.s. 4.7 c.f.s. l.3 c.f.s.
'J o
o
C� C 6 �o
N
0
Z �o
0
o
r
G Q
i
0
1 2 3 4 S 6 7 B 9 10 15 20 30 40 50 60
QUANTITY OF FLOW IN C.F.S.
FOUR GRATE COM6INATION INLET
CAPACITY CURVES
ON GRADE
FIGURE I�J
Ordinance No. 2005-14 VII-17
Admendment to Design Standards
EXAMPLE
Known: Solution:
Quantity of Flow 8.0 c.f.s. Enter Graph at 8.0 c.f.s.
Gufter Slope 0.4°!o Intersect Slope 0.4%
Find Read Percent of Fiow
Intercepted 74
Capacity of Three Grate Iniet 74% of 8.0 c.f.s. 5.9 c.f.s.
as Capacity of Three Grote fnlet
Remaining Gutter Flow
8.Oc.f.s.— 5.9 c.f.s.= 2.Ic.f.s.
°I
A 6 I
C
1'�. o c
O R
o V 0
S
T
0
0
1 2 3 4 5 6 7 8 9 IO I5 20 30 40 50 60
QUANTITY OF FLOW IN C.F.S.
THREE GRATE INLET AND
THREE GRATE COMBiNATION iNLET
CAPACiTY CURVES
ON GRADE
FIGURE I6
VII-18
EXAMPLE
Known: Solution:
Quantity of Ffow 6.0 c.f.s. Enter Graph at 6.0 c.f.s.
Gutter Slope I.0% Intersect Slope I.0%
Reod Percent of Flow
Find: Intercepted 66%
Capacity of Two Grate Inlet 66 of 6.0 c.f.s. 4.0 c.f.s.
os Capacity of Two Grate Inlet
Remaining Gutter Flow
6.0 c.f.s. 4.0 c.f.s. 2.0 c.f. s.
I
A
�o
�y
0
o�
G Q
o o
S
I 2 3 4 5 6 7 8 9 10 15 20 30 40 SO 60
QUANTITY OF FLOW lN C.F.S.
TWO GRATE INLET
CAPACITY CURVES
ON GRADE
FIGURE I�T
Ordinance No. 2005-14
Admendment to Design Standards VII
EXAMPLE
Known: Solution:
Quontity of Flow 6.0 c.f.s. Enter Graph ot 6.0 c.f.s.
Gutter 51ope 1.0 Intersect Slope I.0%
Find Read Percent of Flow
Capacity of Four Grate Inlet 1nte�rcepted 7?
77 /o of 6.0 c.f.s. 4.6 c.f.s.
os Capacity of Four Grate Inlet
Remaining Gutter F1ow
6.Oc.f.a 4.6 c.f.s.= 1.4 c.f.s.
o I
�o
6
�o
0
Z
a
o
GV
�o
o
N
��w
1 2 3 4 5 6 7 8 9 10 IS 20 30 40 50 60
pUANTITY OF FLOW IN C. F. S.
FOUR GRATE INLET
CAPACITY CURVES
ON GRADE
FIGURE IS
VII-20
EXAMPLE
Known: Solution:
Ouontity of Flow 6.0 c.f.s. Enter Graph at 6.0 c.f.s.
Gutter Slope 1.0% Intersact Slope l.0%
Read Percent of Flow
Find: intercepted 82%
Copacity of Six Grate Inlet 82 of 6.0 c.f. s, 4.9 c.f.s.
as Capocity of Six Grate Inlet
Remaining Gutter Flow
6.Oc.t.a —4.9 c.f.s. 1.1 c.t.s.
0
M
{O
6
�o
I
F�
,O
�o
5 0
0
2 3 4 5 6 7 8 9 10 13 20 30 40 50 60
OUANTITY OF FLOW IN C. F. S.
SIX GRATE INLET
CAPACITY CURVES
ON GRADE
FfGURE I9
Ordinance No. 20Q5-14
Admendment to Design Standards VII
EXAMPLE
Known: Solution:
Quantity of Flow 25.Oc.f.s. Enter Groph at 25.Or.f.s.
Maximum Depth of Flow Desired Intersect yo 0.5�
Af Low Point (yo) 0.5� Read L� 10.4�
Fi[1d: Use 12' Inlet
Length of Inlet Required (Li)
252 3 4 5 6 7 8 9 10 15 20 30 40 50 60 70 8025
20 20
w 15 15
W
Z
h
W
J
Z
i 10
O 9
9
2
8 g
z
W
7
I
J
6 6
5 5
4 2 3 4 5 6 7 8 9 10 15 20 30 40 50 60 70 80
Q— QUANTITY OF FLOW IN G F S.
ROUGHNESS COEFFICIENT n .0175
STREET CROWN TYPE COMBINATION INLET
WIDTH CAPACITY CURVES
ALL Straight and Parobofic QT LOW P01NT
FIGURE ZO
VII-22
EXAMPLE
Known: Solution:
Quanitty oi Flow 4.3 c.f.s. Enter Grcph at 4.3 c.f.s.
Maximum Depih of Flow Desired Intersect 3- Grate at 0.23�
at Low Point 0.3� Intersect 2- Grate at 0.51�
Find: Use 3
Iniet Required
0.72 3 4 5 6 7 B 9 10 150.7
0.6 0.6
0.5 0.5
0 4 0.4
F-
W
W
Z 0.3
0.3
3
0
J
O
a o.2 0.2
w
c
OJ 2 3 4 5 6 7 8 9 10 �50.1
Q— QUANTITY OF FLOW IN C. F. S.
GRATE INLET
CAPAGITY CURVES
AT LOW POINT
FI�URE Z I
Ordinance No. 20Q5-14
Admendment to Design Standards VII
EXAMPLE
Known: Solution
Ouantiry of FIaw=14.Oc.f.s. Enier Graph ot 14.0 c.f.s.
Moximum Depth ot Flow Desired Intersect y 0.6�
(y,) 0.6� Read L� I0.9�
Find: Use 12' of inlet 3�X 3�
Length of lnlet Openinq Required (L�)
251 2 3 4 5 6 7 8 9 10 IS 20 30 4025
20 20
F
W
u. 4�X4�
Z 15 15
t9
2
Z 3�X 3�
w
d
O
W 10 10
J
Z 9 9
p 8 8 2�X2�
7 7
Z
W
J 6
6
J
5 5
4 2 3 4 5 6 7 B 9 10 IS 20 30 40
Q— QUANTITY OF FLOW lN C.F. S.
Standard Drop Iniet Sizes: DROP INLET
z'xz' =a' CAPAGTY CURVES
3X3 Li=12
a'xa' =.�s' AT LOW POINT
FIGURE ZL
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CREEKS MAY REMAIN IN OPEN NATURAL CONDITION IF:
(1) TREY COFtPLY WITH THE SUBDIVISION ORDINANCE;
(2) TREE COVERAGE IS ADEQUATE TO BE ACCEPTABLE TO THE CITY
(3) UNSANITARY OR UNACCEPTABLE DRAINAGE CONDITIONS DO NOT EXIST IN
THE CREEK;
(4) APPROVED BY THE CITY
MON[MCROACNYlNT
LIYIT Of DRAIMAOt •MD [AtlYfNT
STR[fT ILOODWAY [ASCYFMT IO�MIM.
10' 111fElOARD
YIMIMUY �PL4X0 CRITERlA YINIYUM 1�
p DLlIiN r.s.
ID' 1► ST[E�EP
TNAN 3:1
UNIYPAOVED CMANNEL
TYPE I NATURAL
NOTE: TYPE I OR II ZF STEEPER THAN 3:1 SLOPE ABOVE DESICN W.S., THE NON—ENCROACK"iENT
ESMT. SHALL BE 15 FEET WIDE TO PROVIDE A STABLE ACCESS ESMT., IF ACCESS HAS NOT
OTHERWIS£ BEEN PROVIDED.
NOTE: A PARALLEL STREET IS RECOMMENDED ON AT LEAST NOTE: NO ENCROACHMENTS SHALL
ONE SIDE OF TYPE I CHANNELS IF THE DRAINAGE BE PERMITTED IN ACCESS
AND FLOODWAY ZS D£DICATED TO PUBLIC USE. EASEMENTS.
NOMEMCR W CMMf NT MOMENCR OAp1YFN'f
[4SENEN7 [�SEYfNT
10' YIN. IYIT OI OR,tIMI,YE AND iL000'YAY A M NT 10� YIM.
1'YINIYUY FIIEElOA�D
DESIiN •.5.1►L�MO CRITERIA)
I �R�� REG01tMENOEO
f .�R 1C M A% Y YAk.�+12�
1/ tTfE►ER 7MAM 4:1 {LO►! y�= I' RlCOMYfNO[D fl0►E UNL!!S
11E0U1RES 18' C3�T. A►►ROVlD /Y CITY [N�IMEER.
II CONC. ��LOT CNINN[L I� RCOYiREO IT YAY CONCRETE �IL07 CXANNEL IF 11lOUIRCD ►OR 1110310N
�E TRA►f2010�L�YEt ON OTNER iEGT10N� CONTROL OR IF MLEDCD �OR ACCLSS OY[ TO LACK
ACGE►TA6L! TO TXE CITY tNGINEER. OF A0.IRCENT �ccess EASEMEN7l.
fl�T OOTTOAI tMIM. 10'M�IDE 1I FOR ACCES!
YNLINEO CMANNELi
TYPE II UNLINED WITH 2tAI*,TLENANCE SECTION
TYPICAL
ACCESS ACClSS
lAEEY£X7 LtY1T Of OR�IM�6E AND EAiE11ENT
IO� YIN ILOODWAY lA3EVENT �0� YIN.
1' YIK FREESOIRO
DES�CN M.S.IGLAMO CRITER161
�L- IIECOYYfMOLD J�
YAX. 10�
RECOMNlNDED Y�7f1YUY
I�MIN./1'
1/ 20' 0� W10CA-
COMCRETE ILI.T IF LLlf TMAM 20'1tlIDf
TYYE III LINED
YOiE: WHEN CILlD1:7EL IS DESIGNED USI�I� PEAK
DISCHARGE FLOWS FROM THE FLOOD INSUR?�NCE
STUDY FREEBOAIL� MAY BE DELETED.
OPEN CHANNEL TYPES
FICCcc
VII-26
OPEN CHANNEL WITH PILOT PIPE
AI.TEItNATZVE TYPE II
I
1.0' MINIMUN FREEBOAR'D
I00� YE�R S TORM W A T EA S UFFOCE
I
NOTE: Bank slopes and non-encroachment easement requirements same as for Type Ii.
PIPE SIZED TO CARRY M�NIIAUM
6 YEAR STOFN.
MINIMUM SI2E IB` q
�OTF.: There are condi[ions due to the excessive capacity of the open ditch
section where a pilot pipe �.arrying less than a five-year siorm may
be used if approved by the Ci[y Engineer.
ALTERNATE OPEN
CHANNEL TYPE Ii
FIGURE 24(B)
Ordinance No. 2005-14
Admendment to Design Standards �1-27
wMOwo��
12 fFlon
ENTRANCE TYP
6 IA618 2AS2B 3AQ S
io
soo ENTR: WINGWAIL 7•
TYPE FIARE ANGLE 6
300 6
IB 30°foTS° 6
200
2A t5° to30° and
7 2B 7S° fo 90° S 4
3A
6 p 100 38
3
O
�0 2
a
W
s 60 2
SO v 1.6
W ��O W
W 2
2 4 p 30 �j o
N
O S
H Q
m 3 20/ 1.0
.9
1A t0
3 �W r
W 10 0 .e .s s
z
y e
W
a a
6 0
O s W
.7 .7
Y e 4 ,6
3 EXAMPLE
Orar o ShaiyAt lin�
Throuph Knorn Valu�s, •S
2 D ond Q/8 to Mm�ct
MW/D For Entronc•
Typ� 1. For Vaiws of
Ertfrana TrW 2 ond 3
Pmj�et Horiiontaliy
From I 10 Seol� 2 or 3.
.s
.s
1 .S 30 •3S .]S
w•�w �o. �w HEADWATER DEPTH
FOR CONCRETE BOX
CULVERT N'1TH
I N LET CONTROL
FI�URE L
VII-28
ENTRANCE TYPE
18 0 I o, 000
i68 5 6AB68
8,000
ot 6
I S 6 6, 000 6.
144 5,000 5.
4,000 ENTR. ENTRAN"CE 6 S.
132 3,000 TYPE DESCRIPTION 5 4
120 S0�9ot End With 4
2,000 4 Hecdwall q
io8 5 Bell End WitA 3 3
Headwall
96 i 6A Bell End Project- 3.
800 ��9 No Heodwall
e4 600 6 B Spiqoi End Projeet 2, 2.
S00 inq 9 No Headwall
72 400 2.
h
300 `�'�jt.•� x L5 I.S
2 y i N
Z 60 v 2 00 1.5
Z
O S4 Q
O
W 4B W IOO Z
J i K BO 2
F
v. 4 60 a i.0 i.0
S 0 p
0 40 I.0
W
36 30 i 9 9
W 3 .9
Q 33 o
o 20 W
30 .B
.e
27
IO
.7 7-
2� EXAMPLE�
6 Drow a Straiqht Llne Throuqh
21 S Known Valuas, D and 0 to Inter-
4 sect HW/D For Entianee Type I.
For Volues of Entronce Type 2 .6
3 and 3 P�ojeet Horizontally From 6
18 I to Scale 2 or 3.
2
IS
.S .S
1.0
12
HEADWATER DEPTH FOR
aoee.0 orwruc.o•os CONCRETE PIPE CULVERTS
WITH INLET CONTROL
FIGURE ZEi
Ordinance No. 20Q5-14
Admendment to Design Standards VII
s000
400o EXAMPLE
�000 Drow a 5lroiqM Line Through Known
Value of Area of Boz, Lenyth of Box,
and Ke to Interxct Pfvot Line. From
200o Pivot Line Draw a Stroght Line
Throuqh The Known Value Q to Inter
sect Head, F1 in Feet.
12X12 4
1000 S
!00 �OX10 IOOW .6
600 F. 9 X9 80 4
.e
700 aX8 6� Q F�. I.0
soo z�x� 50 0 a cr h W
w+ t� h 4+
Y� 300 O 6X6 40 Z 4 �d J �y Z
m O n
tt W �0 O 'L E z
Q SXS p
0 200 O y r
N 20 O W 3
4 X 4 O� M� S
Q a p� y��
i00 03.SX35 p Q
N i 10 O 5
o !0 ui 3x3 u O� 6
e p
O
50 4 �:z.i B
30 2Sx2.0 6 w cx�.�r�[
Q.•o__ a t0
4
40"� S j a
2X2
30
20
W
Z�
J
O
0
10
e
6 HEAD FOR
5 CONCRETE BOX CULVERTS
�LOWING FULL
n 0.012
w�aw a�uauc �o�os ��w na�
FIGURE 27
VII-30
:000
EXAMPLE
D�or a Siralqht Lln� Throuqh Known
Volw ot Diom�t�r ot Pip�, L�npth of
1000 Pipt, ond !C� to Int�n�et Pivot Lin�. .s
From Pivoi lin� Drow a SfralqM lin� i
�20 Throuqh TA� Knwn Valu� 0 to Int�r-
ioe seet H�ad H le Fat. s
soo s6 �,o�'� I.o
�00 S4
300
7Y
66 F
L00 60 Z
y
v Ss
W ♦S�o.a� _�O ti z 3
u ,,p
W 100 ,o �2 4p Y'
�o'�
i a s s
u
q 60 W !3 �OD b�� 6
G
�O SO
!7 O
O 'a 10
30 a
Z !i
1• W !0
z
J
10 I S
6
i4
HEAD FOR
4 CONCRETE PIPE CULVERTS
FLOWING FULL
n 0.012
weew o� ruuc wws �.r hu
F{GURE ZS
Ordinance No. 2005-14 VII-31
Admendment to Design Standards
EXAMPLE
Known: Solution:
Discharqe 200 c.f.s. Enter Groph at Q/B 40
Width of Conduit 5� •intersect Gritical Depth
Q/B 40 at 3.7
Find:
Critical Depth
5 6 7 8 9 10 20 30 40 50 b0 80 100 150 200 250
15 t5
10
9 9
8 8
7
W
W 6 6
Z 5 5
x 4 4
H
3 3
G
J
Q
U 2 2
F-
U
I
0.9 0.9
0.8 0.8
0.7 0.T
0.6
0.65 6 7 8 9 10 20 30 40 50 60 80 100 150 200 250
Q/8
CRITICAL DEPTH
OF FLOW FOR
RECTANGULAR CONDUITS
FIGURE Z9
VII-32
i ZQ 3000 gXAMPLE
��a Known:
108 2000 p�p� Diametsr 66��
i02 Discharp� 100 c.f.e•
Find:
96 1000 Critital Dep�h
90 Solution:
Drow a StroiqAl Line 0.90
84 Throuq� Known Vnlues
500
78 400 P�� Oiometsr and
Discharqa. Read d�/0= 0.80
o 300 0.50
o dc°66�.5=33��
66 W 200 0.70
60 a
100 0.60
W
54 O
c.i 1 a �4 c
4 B c�i S 0. SO
40
y u
i W 30
Z 42
z 20 0.40
N
W p
36
W
Q 10
0 33
w
a. 3� 5 0.30
4
27 3
24 2
21
0.20
18
d� Critical Depih of F�ow in (nches
D= Pipe Diameter in Inches
IS
CRITICAL DEPTH OF FLOW
12 FOR
CIRCULAR CONDUITS
TE%�� NNMW�Y DE►ARTY[NT
FIGURE �SO
Ordinance No. 2005-14
Admendment to Design Standards VII-33
VIII LIST OF FORMS
Form
A. Storm Water Runoff Calculations
B. Inlet Design Calculations
C. Storm Sewer Calculations
D. Water Surface Profile Calculations
E. Open Channel Calculations
F. Hydraulic Design of Culverts
G. Bridge Design Calculations
NOTE: A copy of each applicable form must be submitted with the drainage plans to the City to
review. Final plans must include these forms in the drainage plans.
VIII-1
STORM WATER RUNOFF CALCULATIONS FORM "A"
Column 1 Location of the drainage structure for which the runoff calculation is being
made or a design point on an open channel.
Columns 2� thru 6 Are to be used in calculating runoff by the Rational Method.
Column 2 Obtained from TABLE 1, or FIGURE 2
Column 3 Using the appropriate Design Storm Frequency, and the Time of Concentration
in Column 2, the Intensity is obtained from FIGURE 1.
Column 4 Size of the drainage area tributary to the point of design shown in Column 1.
Column 5 Taken from TABLE 1 and is a weighted composite value if several different
zoning districts fall within the drainage area.
Column 6 Column 3 multiplied by Columns 4 and 5.
Columns 7 thru 19 Are to be used in calculating runoff by the Unit Hydrograph Method.
Column 7 Taken from TABLE 2.
Column 8 Measured distance along the stream course from the upper-most limit of the.
drainage area to the point of design shown in Column 1.
Column 9 Measured distance along the stream course from the point of design shown in
Column 1 to the measured center of gravity of the drainage area.
Column 10 A computed value using the values shown in Columns 7, 8 and 9.
Column 11 Taken from TABLE 2.
Ordinance No. 2005-14
Admendment to Design Standards VIII
Column 12 Column 11 divided by Column 10.
Column 13 Size of the drainage area tributary to the plant of design shown in Column 1.
Column 14 Column 12 multiplied by Column 13.
Column 15 Using the appropriate Design Storm Frequency and a duration of two hours,
this value is obtained from FIGURE l.
Column 16 Obtained by multiplying the value in Column 15 times two.
Column 17 Constant value of 1.11 inches for the Ovilla geographic area.
Column 18 Result of subtracting Column 17 from Column 16.
Column 19 Column 14 multiplied by Column 18.
Column ZO The flow used for design depends on the size of the drainage area. If the si�
of the drainage area is less than 600 acres, QR should be entered. If the
drainage area is larger than 600 acres and smaller than 1200 acres, the larger of
the two flows (QR and Q�) should be entered. If the drainage area is larger
than 1200 acres, Q should be entered.
VIII-3
a��
O W ry
Q
d a
a a
II J
o d
t
a p a 00
F 6 v'
1
F `v
e
P r i
t p p
1 i
E� s�
`e a
G N
h v
n. n
O i•
c s
f i
2
a, a
6
U 6 Q d e
O
a
0
a
v� x
z F E�
O Z e
p
m E
N
r7
U 's
y
a
U
Q o�
GL
G
F� F y Z O
O Yi i
W g G U
3 &k ea
o x„
E
F�r
u
c
O 'p
0 W C
u
t
e e E u v,
z �x`
o
a
0
a
3
r M
Z
C)
m
E N
F u E
G
Q
U
O
��f I(18f10E 0.
Admendment to Design Standards
INLET DESIGN CALCULATIONS FORM "B"
Column 1 Inlet number or designation. The first inlet shown is the most upstream.
Column 2 Construction plan station of the inlet.
Column 3 Design Storm Frequency is same as the Design Storm Frequency of the storm
sewer.
Column 4 Time of concentration for each inlet is taken from TABLE l,�or FIGURE 2.
Column 5 Using the time of concentration and the Design Storm Frequency, rainfall
intensity is taken from FIGURE l.
Column 6 Runoff Coefficient is taken from TABLE 1 according to the zoning of tl�„
drainage area.
Column 7 Area drained by the specific inlet. Care should be taken to keep the drainage
area flow separate into the appropriate street gutters.
Column 8 Product of Column 5 multiplied by Columns 6 and 7.
Column 9 If there is any flow that was not fully intercepted by an upstream inlet, it should
be entered here.
Column 10 Sum of Columns 8 and 9.
Column 11 Capacity of the street gutter, in which the inlet is located, from either
FIGURES 3, 4, 5 or 6. If the total gutter flow shown in Column 10 is in excess
of the value in Column 11 the inlet should be moved upstream. If it is
substantially less than the value in Column 1 l, an investigation should be mac
to see if the inlet could be moved downstream.
VIII-5
Column 12 Street gutter slope to be used in selecting the proper size inlet.
Column 13 Crown type of the street on which the inlet is located.
Column 14 Selected size of the inlet taken from FIGURES 8 through 22.
Column 15 Inlet type taken from FIGURE 7.
Column 16 If the selected inlet does not intercept all of the gutter flow, the difference
between the two values should be entered here and in Column 9 of the inlet that
will intercept the flow.
Ordinance No. 20Q5-14 VIII-6
Admendment to Design Standards
E
u
Q o-`- ��o
i E' e
U p
ii
d 5
F
r
U r `r.
Gs7 m a+
..l X� S 1
y
C d
Q M
V F
C
C N
O
N
V
L
.�u h
W
V' 1C v
z
o
F o o��
Q Gc u
a
U q
Q o
a
V
ay
O J N
�y W C x
A
E� a W
W Q
z
�.e�-
�M ov�
Z U
x
E
N
G C
O
Y C C Q
V E
e
G
V
O
L
L
O
N
L:�
Z
�s
Z
STORM SEWER CALCULATIONS FORM "C"
Column 1 Upstream station of the section of conduit being designed. Normally, this
would be the point of a change in quantity of flow, such as an inlet, or a change
in grade.
Column 2 Downstream station of the section of conduit being designed.
Column 3 Distance in feet between the upstream and downstream stations.
Column 4 Drainage sub-area designation from which flow enters the conduit at the
upstream station.
Column 5 Area in acres of the drainage sub-area entering the conduit.
Column 6 Runoff coefficient, obtained from TABLE 1, based on the characteristics of the
subdrainage area.
Column 7 Column 5 multiplied by Column 6.
Column 8 Obtained by adding the value shown in Column 7 to the value shown
immediately above in Column 8.
Column 9 This time in minutes is transposed from Column 19 on the previous line of
calculations. The original time shall be equal to the time of concentration as
shown on TABLE 1 or FIGURE 2, whichever value has been used.
Column 10 Design Storm Frequency.
Column 11 Using the time at the upstream station shown in Column 9 and the Design
Storm Frequency shown in Column 10, this value is taken from FIGURE 1.
Ordinance No. 20Q5-14
Admendment to Design Standards VIII
Column 12 Column 8 multiplied by Column 11.
Column 13 This slope should be computed from the profile of the ground surfaa
Normally, the hydraulic gradient will have a slope approximately the same as
the proposed conduit and will be located above the inside crown of the conduit.
Column 14 Utilizing the values in Columns 12 and 13, a conduit size should be selected.
In the case of concrete pipe, FIGURE 23 may be used.
Column 15 Velocity in the selected conduit based on the values in Columns 12, 13 and 14.
Taken from FIGURE 23 for concrete pipe.
Column 16 Friction head loss is the product of Column 3 times Column 13.
Column 17 Calculation is made utilizing the values of Column 15
Vl Upstream Velocity V2 Downstream Velocity
Head gains shall be taken to zero (0) in the storm sewer design.
Column 18 Calculation is based on the values of Columns 3 and 15.
Column 19 Sum of Columns 9 and 18.
Column 20 Special desi� comments rriay be entered here.
VIII-9
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Ordinance No. 20Q
Admendment to Design Standards
WATER SURFACE PROFILE CALCULATIONS FORM "D"
Column 1 At each point where a water surface elevation is desired, a cross section must
be obtained. The sections are numbered and subdivided according to the
assigned roughness coefficient.
Column 2 Known or assumed water surface elevation at the particular section.
Column 3 Distance along the channel between sections.
Column 4 Area of snb-section calculated from plotted cross sections.
Column 5 Wetted perimeter of each sub-section exclusive of the water interfaces between
adjacent sub-sections.
Column 6 Column 4 divided by Column 5. (Hydraulic Radius)
Column 7 Column 6 raised to 2/3 power.
Column 8 Roughness coefficient for Manning's formula from TABLE 7.
Column 9 Column 4 multiplied by 1.486 and the product divided by Column 8.
Column 10 Column 9 multiplied by Column 7.
Column 11 The total flow shown in the upper left of the calculation form divided by
Column 10 and squared, which is the friction slope.
Column 12 Average friction slope between sections.
Column 13 Column 12 multiplied by Column 3.
Column 14 Flow in each individual sub-section. Varies directly with the conveyanc...
VIII-11
factor shown in Column 10. The sum of the values must equal the total flow.
Column 15 Column T4 divided by Column 4.
Column 16 Column 15 squared.
Column 17 Column 16 multiplied by Column 14.
Column 18 Sum of the values in Column 17 of a particular section divided by twice the
acceleration of gravity and multiplied by the total flow.
Column 19 Algebraic difference in velocity heads between sections.
Column 20 Eddy losses are calculated as 10 percent of the value of Column 19 when such
value is positive and 50 percent of the absolute value of Column 19 when such
value is negative.
Column 21 Sum of Column 13, Column 19 and Column 20.
Column 22 The sum of the value shown in Column 2 for the previous section and the value
in Column 21. If the elevations calculated for subsequent sections do not agree
within a reasonable limit with the assumed elevations shown in Column 2 for
that particular section, then the assumed elevations for such section must be
revised and the section properties recomputed until the desired accuracy is
obtained. An accuracy of 0.3 feet is considered a reasonable limit.
Ordinance No. 20Q5-14
Admendment to Design Standards VIII-12
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Column 1 Downstream limit of the section of channel under consideration.
Column 2 Upstream limit of the section of channel under consideration.
Column 3 Type of channel as shown in FIGURE 24 is entered here.
Column 4 Flow in the section of channel under consideration.
Column 5 Roughness coefficient of the channel cross-section taken from TABLE 7.
Column 6 Slope of the channel that is most often parallel to slope of the hydraulic
gradient.
Column 7 Square root of Column 6.
Column 8 Calculation is made using the values in Columns 4, 5 and 7.
Column 9 Assumed width of the bottom width of the channel.
Column 10 Assumed depth of flow.
Column 11 Assumed slope of the sides of the channel.
Column 12 Areas of flow that are calculated based on Columns 9, 10 and 11.
Column 13 Wetted perimeter calculated from Columns 9, 10 and 11.
Column 14 Value is calculated from Columns 12 and 13.
Column 15 Column 14 raised to 2/3 power.
Ordinance No. 2005-14
Admendment to Design Standards VIII-14
Column 16 Product of Column 13 times Column 15.
When the value of Column 16 equals the value of Column 8 the channel has been adequately sizeu.
When the value of Column 16 exceeds the value of Column 8 by more than five percent then the
channel width or depth should be decreased and another trial section analyzed.
Column 17 Calculation is based on the values of Columns 4 and 12.
Column 18 Calculation is based on Column 17.
Column 19 Remarks concerning the channel section analyzed may be entered.
NOTE: Form "E" should be used only to size open channels. Form "D" should be used to calculate
stream profile.
VIII-15
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Ordinance No. 20
Admendment to Design Standards
HYDR.AULIC DESIGN OF CULVERTS, FORM "F"
INFORMATION IN UPPER RIGHT OF SHEET:
Culvert Location: This is a word description of the physical location.
i
Length: The actual length of the culvert.
Total Discharge, QT: This is the flow computed on FORM "A".
Design Storm Frequency: Obtained from TABLE 1 and used on FORM "A".
Roughness Coefficient, n: Obtained from TABLE 5.
Maximum Velocity: Obtained from TABLE 4.
Tailwater: This is the design depth of water in the downstream channel and is
obtained in connection with the channel design perforined on FORM i
"D" or FORM "E".
D. S. Channel Width: This is the bottom width of the downstream channel obtained from tr
calculations on FORM "E". The culvert should be sized to approxima
this width whenever possible.
Entrance Description: This is a listing of the actual condition as shown in the "Culvert
Entrance Data" shown on the calculation sheet.
Roadway Elevation: The elevation of the top of curb at the upstream end of culvert.
U. S. Culvert F. L. The flow line of the culvert at the upstream end.
Difference: The difference in elevations of the roadway and the upstream flow line.
Required Freeboard: The vertical distance required for safety between the upstream design
water surface and the roadway elevation or such other requirements that
may occur because of particular physical conditions.
Allowable Headwater: This is obtained by subtracting the freeboard from the difference shown
immediately above.
D.S. Culvert F.L. The flow line elevation of the downstream end of the culvert.
Culvert Slope, So: This is the physical slope of the structure calculated as indicated.
VIII-17
Columns 1 through 10 deal with selection of trial culvert size and are explained as follows:
Column 1 Total design discharge, Q, passing through the culvert divided by the allowable
maximum velocity gives trial total area of culvert opening.
Column 2 Culvert width should be reasonably close to the channel bottom width, W,
downstream of the culvert.
Column 3 Lower range for choosing culvert depth is trial area of culvert opening, Column
1, divided by channel width, Column 2.
Column 4 Allowable headwater obtained from upper right of sheet.
Colmm� 5 Trial depth, D, of culvert corresponding to available standard sizes and
between the numerical values of Columns 3 and 4.
Columns 6, 7 and 8 are solved simultaneously based on providing a total area equivalent to the trial
area of opening in Column 1.
Column 6 Number of culvert openings.
Column 7 Inside width of one opening.
Column 8 Inside depth of one opening if culvert is box structure or diameter if culvert is
pipe.
Column 9 Column 6 multiplied by Column 7 and Column 8.
Column 10 Total discharge divided by number of openings shown in Column 6.
Columns 11 through 15 (Inlet Control) and 16 through 27 (Outlet Control) deal with Headwater
Calculations which verify hydraulics of trial culvert selected and are explained as follows:
Column 11 Obtained from upper right of sheet.
Column 12 When the allowable headwater is equal to or less than the value in Column 8,
enter Case I. When the allowable headwater is more than the value in
Column 8, enter Case II.
Ordinance No. 2005-14
Admendmentto Design Standards VIII
Column 13 Column 10 divided by Column 7.
Column 14 Obtained from FIGURE 25 for box culverts or FIGURE 26 for pipe culverts.
Column 15 Column 14 multiplied by Column 8.
Column 16 Obtained from upper part of sheet.
Column 17 Obtained from FIGURE 27 for box culverts and FIGURE 28 for pipe culverts.
Column 18 Tailwater depth from upper right of sheet.
Column 19 So, culvert slope, multiplied by culvert length, both obtained from upper right
of sheet.
Column 20 Sum of Columns 17 and 18 minus Column 19.
Column Z1 Obtained from FIGURE 27 for box culverts and FIGURE 28 for pipe culverts.
Column 22 Critical depth obtained from FIGURE 29 for box culverts and FIGURE 30 fc�
pipe culverts.
Column 23 Sum of Columns 22 and 8 divided by two.
Column 24 Tailwater depth from upper right of sheet.
Column ZS Enter the larger of the two values shown in Column 23 or Column 24.
Column 26 Previously calculated in Column 19 and may be transposed.
Column 27 The sum of Columns 21 and 25 minus Column 26.
Column 28 Enter the larger of the values from Column 15, Column 20 or Column 27. This
determines the controllir�g hydraulic conditions of the particular size culvert
investigated.
Column 29 When the Engineer is satisfied with the hydraulic investigations of various
culverts and has determined which would be the most economical selection, tY
description should be entered.
VIII-19
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Columns 1& 2 Obtained from calculations on FORM "A".
Column Assume an average velocity that is less than the maximum allowable velocity
and more than 4 feet per second. Maximum velocities are equal to those
specified for open channels.
Column 4 Total flow as shown on upper part of sheet divided by Column 3.
Column 5 Column 4 divided by Column 2.
Column 6 Selected bridge length utilizing standard span lengths.
Column 7 Calculated from bridge and channel geometrics.
Column 8 Total flow through bridge divided by Column 7.
Column 9 Selected head loss coefficient based upon specific conditions.
Column 10 Calculated utilizing values in Columns 8 and 9.
Ordinance No. 2005-14
Admendment to Design Standards VIII
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CITY OF WYLIE, TE�;.AS
MANUAI�
FOR THE DESIGN OF
WATER AND SANITARY SEWER LINES
Ordinance No. 20Q5-14
Admendment to Design Standards
TABLE OF CONTENTS
Descrintion Page No.
General 1
WaterMains 2
Sanitary 8
Formof Plans 11
Data to be Included in Plans 12
APPENDIX "A"
Sanitary Sewer Flow Calculations 14
Uwysvrdc0l \home\chol:ted\projects\manuals and daails\ciry of wylic design manual mod.doc
CITY OF WYLIE, TEXAS
MANUAL FOR THE
DESIGN OF WATER AND SANITARY SEWER LINES
SECTION A GENERAL
This manual is intended to aid and assist private engineers in the layout and design of sanitary
sewers and water lines to definite standards and to obtain uniformity in the plans. It is recognized
that each addition has its individual challenges and that no fixed rules will apply to all cases;
therefore, final acceptance of all or any part of any plans rests with the City Engineer or authorized
representative of the City of Wylie.
A. Submittal: On completion of the plan and preliminary engineering of a subdivision, it will be
to your advantage to bring or send two copies along with a contour map and preliminary water
and sewer layout to the City, whereby a check can be made as to the general layout and
availability of water and sewer. If problems arise as to the availability of water and sewer, it
may be necessary to have a meeting with the developer and discuss the problems.
B. Preliminarv Check: When the engineering plans are complete, submit three sets of legible
prints. Every attempt will be made to review plans within three weeks.
C. Final Check: When the pians are returned to you after preliminary check, the final plans must
be submitted with the marked up set. Three sets of legible prints will need to be submitted.
D. Final Approval of Plans: Before you request approval of the plans, check the following:
1) The plans must be complete and correct.
2) The approved plat must have been submitted.
3) The street grades and storm sewer plans must have been submitted and approved.
4) The plans must be signed and sealed by a Professional Engineer licensed in the State of
Texas, who is responsible for the design.
5) All fees and other monies due must be paid in full.
6) Contractor's insurance must be in correct form.
Ordinance No. 20Q5-14
Admendment to Design Standards
7) Three sets of complete engineering plans are required for City use. There should be
additional approved plans available for Contractors and Engineering Consultants use
during consiruction of the improvements. The City Representative will only recognize
those plans with the "approved" stamp.
8) Upon completion of construction and prior to acceptance of that construction by the City,
one set of mylars and one set of prints of the record drawings must be submitted to the
City.
E. Specifications are the Standard Specifications for Public Work Construction, North Central
Texas latest addition as prepared by the North Central Texas Council of Governments.
F. Special Provisions are City of Wylie Special Provisions to the Specifications.
G. Standard Details are as prepared by the City of Wylie and NCTCOG with City of Wylie
standards having precedence over NCTCOG standard details.
SECTION B WATER MAINS
In general, water mains are placed on the north and west sides of a street, as shown in the Standard
Construction Details, or otherwise as directed by the City Engineer. Where applicable, line sizes
will comply with the Water Distribution System Master Plan and shall be adequate to convey a fire
flow. Fire flow analysis will be required on lines that are questioned by City staff. Starting
pressures shall be obtained from the nearest junction node as stated in the City's Water Distribution
Master Plan computer printouts or shall be provided by the City.
A. Minimum 8-inch pipe required in residential areas.
B. Minimum 12-inch pipe required on commercial, retail and industrial areas.
C. The length of dead-end mains shall not exceed 600 feet. A Fire Hydrant will be required at the
end of the main.
D. No water main shall be located closer than 5-feet from any tree or structure.
E. Crosses shall not be used without permission from the City Engineer or authorized
representative.
F. Water Main Specifications:
1) City mains shall have a minimum diameter of 8-inches, unless a larger line size is required
by the Comprehensive Plan, Water Master Plan or to meet fire protection needs as
determined by analysis. All water lines shall meet the requirements of AWWA and
NCTCOG under the following specifications:
Line NCTCOG
Size Item AWWA Description
Standard
8" thru 12" 2.12.20 C900 DR18 PVC
Greater 2.12.5 C301 C303 Reinforced Concrete Cylinder Pipe
than
12" Pipe
2.12.20 C905 DR18 PVC
2.12.8 C151 Class 50 Ductile Iron Pipe
2) All mains supplying fire sprinkler systems outside of utility ea�ements shall be minimum
200-PSI working pressure and U.L. listed.
3) All water pipe shall be designed for a working pressure of 150-PSI unless otherwise
directed by the City Engineer or authorized representative.
G. Valves 12-inches and under shall be placed on or near street property lines not over 800 feet
apart in residential, duplex and apartment districts and not over 500 feet apart in all other
districts: and in such a manner as to require preferably two, but not more than three valves to
shut down each City block, or as may be required to prevent shutting off more than one fire
hydrant. On cross-feed mains without services, a maximum of four valves shall be used to shut
down each block. Also, valves shall be placed at or near the ends of mains in such manner that
a shut down can be made for a future main extension without causing loss of service on the
existing main. Main line valves shall be placed at all fire hydrant leads. The location of valves
larger than 12-inches will be as approved the City Engineer or authorized representative.
Valves 12-inches and under will be Gate Valves meeting requirements of AWWA C500 or
AWWA C509 (NCTCOG Item 2.13.1) with non-rising stems. Valves over 12-inches will be
Butterfly Valves meeting requirements of AWWA C504 (NCTCOG Item 2.13.4). All valves
over 14-inches shall be provided with a valve vault over the valve operator assembly to provide
ease of access for routine maintenance.
Ordinance No. 20Q5-14
Admendment to Design Standards
H. Fire H. d� rants
Section 1. Number and Locations
A sufficient number of fire hydrants shall be installed to provide hose stream protection for
every point on the exterior wall of the building with the lengths of hose normally attached to
the hydrants. There shall be sufficient hydrants to concentrate the required fire flow, as
recommended by the publication "GUIDE FOR DETERMINATION OF REQUIRED FIRE
FLOW" published by the Insurance Service Office, around any building with no hose line
exceeding the distances hereinafter established and with an adequate flow available from the
water system to meet this required flow. In addition, the following guidelines shall be met or
exceeded:
l) SINGLE FAMILY AND DUPLEX RESIDENTIAL As the property is developed, fire
hydrants shall be located at all intersecting streets and at intermediate Iocations between
intersections at a maximum spacing of 500 feet between fire hydrants as measured along
the route that fire hose is laid by a fire vehicle.
2) MTJLTIFAMILY RESIDENTIAL As the property is developed, fire hydrants shall be
located at all intersecting streets and at intermediate locations between intersections at a
maximum spacing of 400 feet as measured along the length of the centerline of the
roadway, and the front of any structure at grade shall be no further than 500 feet from a
minimum of two fire hydrants as measured along the route that a fire hose is laid by a fire
vehicle.
3) OTHER DISTRICTS As the property is developed, fire hydrants shall be located at all
intersecting streets and at intermediate locations between intersections at a maximum
spacing of 300 feet as measured along the length of the centerline of the roadway, and the
front of any building at grade shall be no farther than 300 feet from a minimum of two fire
hydrants as measured along the route that the fire hose is laid by a fire vehicle.
4) PROTECTED PROPERTIES Fire hydrants required to provide a supplemental water
supply for automatic fire protection systems shall be within 100 feet of the Fire
Department connection for such system.
5) BUILDINGS FIl2E SPRINKLED An 8-inch fire line stub-out with valve shall be
provided for all buildings to be sprinkled. A smaller stub-out can only be used with Fire
Department approval.
6) Fire hydrants shall be installed along all fire lane areas as follows:
a) Non-Residential Property or Use
Within 150 feet of the main entrance.
Within 100 feet of any Fire Deparhnent connection.
At a maximum intermediate spacing of 300 feet as measured along the length of
the fire lane.
b) Apartment Townhouse' or Cluster Residential Propertv or Use
Within 100 feet of any Fire Department connection.
At maximum intermediate spacing of 400 feet as measured along the length of the
fire lane.
7) Generally, no fire hydrant shall be located closer than 50-feet to a non-residential building
or structure unless approved by the Engineering and Fire Departments.
8) In instances where access between the fire hydrant and the building that it is intended to
serve may be blocked, extra fire hydrants shall be provided to improve the fire protection.
Railroads, divided thoroughfares, expressways and blocks that are subject to buildings
restricting movement, and other man-made or natural obstacles are considered as barriers.
Section 2. Restrictions
1) All required fire hydrants shall be of the national standard 3-way breakaway type no less
than 5'/4-inches in size and shall conform to the provisions of the latest AWWA Standard
C502 and shall be placed upon water mains of no less than 8-inches in size. Fire hydrants
shall have a bury depth of five feet.
2). Valves shall be placed on all fire hydrants leads. Valves shall be flanged by mechanical
j oint.
3) Required fire hydrants shall be installed so the breakaway point will be no less than
2-inches, and no greater than 6-inches above the grade surface.
4) Fire hydrants shall be located a minimum of 2-feet and a maximum of 6-feet behind the
curb line, based on the location of the sidewalk. The fire hydrant shall not be in the
sidewalk.
Ordinance No. 2005-14
Admendment to Design Standards
5) All required fire hydrants placed on private property shall be adequately protected by
either curb stops or concrete posts or other methods as approved by the City Engineer and
Fire Chief and shall be in easements. Maintenance of such stops or posts to be the
responsibility of the landowner on which the said fire hydrant is placed.
6) All required fire hydrants shall be installed so that the steamer connection will face the
fire lane or street, or as directed by the Fire Department.
7) Fire hydrants, when placed at intersections or access drives to parking lots, when
practical, shall be placed so that no part of the fire truck will block the intersection or
parking lot access when connections to the fire hydrant are made.
8) Fire hydrants, required by this article, and located on private property, shall be accessible
to the Fire Department at all times.
9) Fire hydrants shall be located at street or fire lane intersections, when feasible.
10) A Blue Stimsonite, Fire-Lite reflector (or approved equal) shall be placed in the center of�
the drive lane on the side of the fire hydrants.
11) In non-residential developments an 8-inch lead will be required on all fire hydrants that
are located more than 50-feet from the looped main.
12) Fire hydrant bonnet shall be painted according to the size of the main to which it is
attached. See chart below. The remainder of the hydrant above ground shall be painted
aluminum.
Water Main Size Color
4" Not Allowed
6" Not Allowed
8" Blue
10" Green
12" Larger Yellow
I. Four-inch mains used for hydrant supply in existing construction shall be replaced with new
construction and dead-ends shall be eliminated where practical. Six-inch lines shall be
connected so that not more than one hydrant will be between intersecting lines and not more
than two hydrants on an eight-inch main between intersecting lines.
J. The minimum cover to the top of the pipe must vary with the valve stem. In general, the
minimum cover below the top of the street subgrade should be as follows: 6-inch and smaller,
3.5 feet; 8-inch, 4.0 feet: 12-inch, 4.5 feet to 5 feet; 16-inch, 5.0 feet to 5.5 feet. Lines larger
than 16-inch shall have a minimum of 6 feet of cover, or sufficient cover to allow water and
sewer and other utilities to go over the large main. Increase the cover as required for water
lines to be constructed along county-type roads commonly built with a high crown about the
surrounding property, to allow for future paving grade and storm sewer changes.
K. A service with a meter box is constructed from the main to a point just behind the curb line,
usually in advance of paving. The location of the meter box is at or near the center of the front
of the lot to be served. On multiple apartments and business properties, the Owner or Architect
usually specifies the desired size and location. Minimum requirements for water service sizes
are as follows:
1) One-inch copper services are required to serve all residential lots including townhouse lots
and patio homes. Separate services shall be provided for each of the family units.
2) The size of apartment, condominium, or multi-family services will depend on the number
of units served with a minimum of one meter per building.
3) Fittings shall include mega-lugs and shall be polywrapped.
L. A domestic service connection shall not be allowed on fire hydrant leads.
M. No meter boxes will be allowed in driveways.
Ordinance No. 20Q5-'14
Admendment to Design Standards
SECTION C SANITARY SEWERS
A. Sizes and grades for sanitary sewer lines shall be based on serving the proposed development
and all upstream areas in the drainage basin at full development. The minimum size for
sanitary sewer mains shall be 8-inches. Design calculations for sizing lines shall be included in
the plans, along with drainage area map. If feasible, sewers shall be placed in streets or as
shown in the City Standard Construction Details. Sewers are usually located in the center of
residential streets. Each addition has its challenges, therefore, no fixed rules will apply to all
cases regarding the location of sanitary sewers.
B. Minimum cover shall be 3.5 feet; exceptions authorized by the City Engineer or authorized
representative shall have concrete protection. In general, the minimum depth for sewer to serve
given property with a 4-inch lateral shall be 3-feet plus 2% times the length of the house lateral
(the distance from the sewer to the center of the house). Thus, for a house 135 feet from the
sewer, the depth would be 3-feet plus 2% x 135 feet 3.0 plus 2.7 5.7 feet. The depth of the
flow line of the sewer should then be at least 5.7 feet below the elevation of the ground at the
point where the service enters the house. Profiles of the ground line 20-feet past the building
line will be required to verify that this criterion is met. On lines deeper than 12 feet, a parallel
sewer line will be required when laterals are to be attached. This requirement should be
discussed with the City Engineer.
C. Sewage flow shall be computed in accordance with Appendix "A", with the exceptions, as
required by the City Engineer. Pipes should be placed on such a grade that the velocity when
flowing full is not less than two feet or more than 6-feet per second. Minimum grades shall be
as follows:
Size 1VIinimum Slope
8" 0.35%
10" 0.26%
12" 022%
15" 0.16%
18" 0.12%
21" 0.10%
24" 0.09%
D. All grades shall be shown to the nearest 0.01 Grades shall be evenly divisible by 4, and if
practical, they should be even, such as: 0.20%, 0.40%, 0.60%, and 1.00%, etc., in order to
facilitate field computations. When the slope of a sewer changes, a manhole will be required.
No vertical curves will be allowed. Horizontal curves (pulling pipe not joints) with a minimum
200 foot Radius to match change in street direction will be allowed as approved by the City
Engineer, but will not be allowed across residential single family and duplex lots.
E. The sizes and locations of manholes, wyes, bends, tap connections, cleanouts, etc., shall be
approved by the City Engineer. In general, manholes shall be placed at all four-way
connections and three-way connections. The diameter of a manhole constructed over the center
of a sewer should vary with the size of the sewer. For 6", 8", and 10" sewers, the manhole shall
be 4.0-foot minimum diameter; for 12", 15", 18", 21 24" and 27" 5.0 foot minimum
diameter; 30" and 36" 6-foot minimum diameter. In Flood Plains, sealed manholes are to be
used to prevent the entrance of storm water. Manholes in flood plains shall be vented as
required by TNRCC. Manholes shall be placed on the ends of all lines. Drop manholes shall
be required when the inflow elevation is more than 18-inches above the outflow elevation.
Construct manholes at each end of lines that are installed by other than open cut and at each
end of aerial crossing lines. Sewer mains and water mains shall be not less than nine feet apart
as measured from outside to outside of pipe and shall meet all Texas Natural Resource
Conservation Commission requirements.
F. LATERALS: The sizes and locations of laterals shall be as approved by the City Engineer. In
general, for single family dwellings, the lateral size shall be 4" minimum; for multiple units,
apartments, local retail and commercial 6" minimum; for manufacturing and industrial, the
size should be 8" or larger as required. House laterals usually come out 10 feet downstream
from the center of the lot and shall have a 10-foot lateral separation from the water service.
Manholes will be required on 6-inch and larger laterals where they connect to the main line.
Laterals will not be attached to sewer mains that are deeper than 12 feet. A minimum of one
lateral per building shall be required. Also, a minimum of one lateral per residential lot shall be
required. Duplexes shall have two laterals.
G. Railroad, State Highway and creek crossings, etc., shall be as approved by the City Enb neer or
authorized representative. The developer is responsible for obtaining permits from the Railroad
Company and from the Texas Department of Transportation and for ensuring that construction
meets all the permit requirements.
Ordinance No. 20Q5-14
Admendment to Design Standards
H. The developer's Engineer shall furnish all line and grade stakes for construction. All property
lines and corners must be properly staked to insure correct alignment. Monuments must be set
at the corners of the property as shown in the Standard Construction Details. The City will not
be liable for improper alignment or delay of any kind caused by improper or inadequate
surveys by the developer or by interference of other utilities.
I. In order to provide access for sewer lines for cleaning, manholes shall be so located that 250
feet of sewer rod can reach any point in the line. This means that manhole spacing shall be a
maximum of 500 feet.
J. No sewer line shall be located nearer than five feet from any tree or structure.
K. No sanitary sewer in alleys unless approved by the City Engineer.
L. Sewer Lines Specifications:
1) All sewer lines shall be PVC and meet the requirement of ASTM and NCTCOG under the
following specifications:
Pi e Diameter NCTCOG Item ASTM Standard
6" thru 15" 501.17 D3034/SDR 35
D3350/PE 345434C
15" thru 48" 501.17 F679
F794
F949
F1803
D3350/PE 345434C
2) Sewer pipe shall conform to the Specifications and/or Special Provisions.
M. Lift Stations (Shall be only as approved by the City Engineer or Authorized Representative)
1) Lift station design shall be in full conformance to TNRCC Regulations, latest revision.
Letter approval from the TNRCC must be provided at time of Preliminary Engineerin�
plan submittal. Flows shall be as calculated by this manual.
2) Lift stations with peak flows under 1.4 MGD shall utilize submersible pumps as
manufactured by Flygt Corporation or approved equal.
3) The current rules can be obtained at:
www.tceq.state.tx.us
SECTION D- FORM OF PLANS
A. Plans shall be clear, legible, and neatly drawn on bordered sheets, full size shall be 22" x 34".
Initial copies submitted for review and approval shall be provided at %Z the full size on 11" x
17" sheets. Each sheet shall clearly display the Texas Professional Engineer's seal of the
Engineer under whose direction the plans were designed. A title block in the lower right-hand
corner shall be filled in to include: (1) project name; (2) Engineer's name, address, and
telephone number.
B. The plan sheet should be drawn so that the north arrow points to the top or to the right side of
the sheet. It is important that the plan show sufficient surrounding streets, lots, and property
lines so the existing water and sewer may be adequately shown and so that proper consideration
may be given to future extensions. Proposed water and sewer lines shall be stubbed out to the
addition extremities in order that future extensions may be made with a minimum of
inconvenience. Unless it would make the plan very difficult to read, both water and sewer lines
should be shown on the same sheet. The lines on the profile sheet shall be drawn in the same
direction as on the plan. Lettering shall be oriented to be read upward or from left to right.
C. On large additions or layouts requiring the use of more than six sheets (total of plan profile),
key sheets may be required on a scale of 1" 400' or 1" 1000', as designated by the City
Enb neer. They shall show the overall layout with the specific project clearly indicated with
reference to individual sheets.
D. The use of "off-standard" scales will not be permitted. A plan shall be drawn to scales of 1"
20', or 1" 40'. Plans for water and sewer that do not involve great detail should be drawn on a
scale of 1" 50'. Plans in and along creeks, heavily wooded sections, streets with numerous
utilities, or as may be required to produce a clean and legible drawing, shall be drawn on
plan-profile sheets or separate plan and profile sheets on a scale 1" 40'. If the plan is in an
extremely congested area, a scale of 1" 20' may be necessary. All profiles shall be drawn on
a vertical scale (1" 4') as required for clarity, and the horizontal scale shall be the same as for
the plan unless otherwise directed by the City Engineer.
Ordinance No. 20Q5-14
Admendment to Design Standards
SECTION E- DATA TO BE INCLUDED IN PLANS
A. Sewer Data to be Included on Plan Sheet: The plan shall show the existing and proposed water
and sewer lines and all appurtenances thereto. The plan should also have the storm sewer
system dashed in. All lines shall be numbered, lettered or otherwise designated on both plan
and profile sheets. All lines shall show sizes and direction of flow on both the plan and profile
sheets. Stationing shall be shown to the nearest 0.1 foot and each new line shall begin at 0+00
at the outlet and increase up the sewer. Station pluses at all junctions of sewers, horizontal
P.C.'s, and P.T.'s, bends, angle points, wyes, manholes, the centerlines of all cross streets and
railroads, and all crossing utilities, etc., shall be shown on both plan and profile. The degree of
angles and horizontal curve data shall be shown on the plan only. Minimum Radius for
sanitary sewer mains is 200 feet by pulling pipe not joints. Sewer laterals shall be shown at a
location most convenient to serve the property.
Sewer lat�rals will usually be near the center of the lot, either at the street or alley. If the lateral
is to be adjacent to the water service, then show the lateral 10 feet downstream. The location
shall be designated on the plans.
B. Sewer Data to be Included on the Profile Sheet: The data for the profile sheet shall be obtained
by running a line of levels along the actual route and by taking any other necessary
observations. Profiles shall show the elevations to the nearest 0.1 foot of the ground at the
centerline of the sewer, and to the right and left of the centerline of the sewer at the location of
the approximate center of the proposed houses or buildings to be served, and the approved
street or alley grade. Profiles shall also show the sewer pipe, manholes, etc. The size of the
sewer, the direction of the flow, and the grade to the nearest 0.01% shall be indicated just over
the "pipe" and the total linear footage of line, size, kind of pipe, and type of embedment or
encasement shown below the "pipe". The design flow, pipe capacity and velocity must be
shown in the profile. All of the information pertainin� to the horizontal data, station pluses,
appurtenances to be built, etc., is usually shown just above the ground line, whereas, the flow
line (invert) elevations are shown below the pipe. Elevations of crossing and parallel utilities
shall be shown. All invert elevations shall be shown to the nearest 0.01-foot. Invert elevations
shall be recorded at all junctions (all lines-in and out), at grade breaks, the ends of lines, or
other points as requested by the City Engir�eer. Benchmarks used shall also be clearly shown,
giving the descriptive locations and elevations. Elevations must be from sea level datum, not
assumed. Bench level circuits should begin at a City of Wylie Control monument and
benchmark of second order accuracy established at least every one-half mile through the
project. All existing water, sewer, gas, storm sewer, telephone, power, and other utilities
parallel to or crossing the proposed sewer or water Iine shall be adequately designated as to
size, type, and location.
C. Data to be Included for Water Plan and Profile: Indicate the location of any existing valves
required for shutdown purposes and of any tees, ends, etc., to be tied into. Indicate clearly the
sizes of the lines to be installed, and all proposed valves, fire hydrants, tees, bends, reducers,
plugs, sleeves, wet connections, tap connections, creek, railroad or highway crossings, tunnels,
meter boxes, valve vaults, and other appurtenances at each intersection or as required. Where
the pipe is to be laid around a curve, the curve data must be provided. The size and type of
services and the material, type of joint, and class of pipe may be indicated by adequate notation
in the lower left or right hand corners of the plan sheet. Water services and meter boxes shall
be indicated and shall be located at or near the center of the front of each lot. Waterline
profiles are required on lines 12-inches and larger, follow the general procedures as outlined for
sewers, except that the grades and elevations of the proposed water line usually need not be
shown closer than the nearest 0.1-foot except at P.V.I.'s where the elevation shall be shown to
the nearest 0.01-foot for field calculation purposes.
Ordinance No. 2005-14
Admendment to Design Standards
APPENDIX "A"
SANITARY SEWER DAILY FLOW CALCULATIONS
Apartment Sanitary Sewer Flow
95 gal. x.75 71.25 gal. per day per person
22 units per acre with 3 persons per unit
Calculations (71.25) (22) (3) 4,702 or 4,700 gallons per day per acre.
Office Sanitarv Sewer Flow
3100 parking spaces for 34.7 acres
One person per parking space
20 gallons per person per day
3100 89.33 persons per acre (20 gal) 1,786.7 or 1,790 gal. per day per acre.
34.7 acres
Residential Sanitarv Sewer Flow
95 gallons per person per day
4 units per acre
3.5 persons per unit
(95) (4) (3.5) 1330 gallons per acre per day
NursinQ Home Sanitarv Sewer Flow Patio Home Sanitary Sewer Flow
150 beds -heritage Manor 95 gallons per persori per day
90 gallons per day per bed 10 units per acre
90 x 150 13,500 gallons per day 3.5 persons per unit
(95) (10) (3.5) 3,325 gallons per day/acre
Add 500 gallon per acre per day for inflow and infiltration. Peaking factor shall be applied to daily
flow calculations but not to inflow and infiltration. Peak factors shall be in accordance with ASCE
Manual and Reports on Engineering Practice No. 60/WPCF Manual of Practice No. FD-5.
Generally the following factors applies:
Acres Peakin� Factor
0 65 5
70 4.9
80 4.8
85 4.78
90 4.72
100 4.66
110 4.62
120 4.50
130 4.35
140 4.25
150 4.20
CITY OF WYLIE, T��CAS
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TI�ORQUGHFARE STANDARDS
DESIGN MANUAL
Ordinance No. 20Q5-14
Admendment to Design Standards
TABLE OF CONTENTS
I. General Requirements .....1
II. Street Design Standards ................................................................................3
III. Median and Left Turn Lane Design Standards ......................................................7
IV: Alley Design Standards ................................................................................11
V. Driveway Design Standards .......................12
VI. Sidewalk and Location Design Standards ..........................................................19
VII. Public Right-of-Way Visibility .......................................................................21
VIII. Off Street Requirements ...............................................................................27
SECTION I
GENERAL REQUIREMENTS
A. INTRODUCTION
The "Thoroughfare Design Standards" are intended to implement the provisions of the Subdivision
Ordinance and to provide for the orderly, safe, healthy and uniform development of the area within
the corporate city limits and in the extraterritorial jurisdiction (ETJ) surrounding the City of Wylie.
The City of Wylie "Standard Construction Details", "Special Provisions" and the North Central
Texas Council of Governments (NCTCOG) "Standard Specifications for Public Works
Construction" are considered supplemental and are part of the Thoroughfare Design Standards. The
Thoroughfare Design Standards are to be considered as the minimum requirements for engineering
design. Adherence to the requirements of these standards and/or approval by the City of Wylie or its
authorized representatives in no way relieves the developer or his engineer for adequacy of design or
for the completeness of the plans and specifications or the suitability of the completed facilities.
Specific projects may require more stringent design standards. The City of Wylie may determine
that design requirements other than those included in these standards are necessary and will inform
the developer of such requirements before the final engineering review.
The develaper shall notify the City of Wylie, in writing, of any known deviations from the
requirements set for in the standards for thoroughfare design, construction details, or specifications.
B. THOROUGHFARE DESIGN STANDARDS
The Thoroughfare Design Standards are to be considered as the minimum requirements for
engineering design. It is not intended that these standards cover all aspects of paving construction
for any given development. The developer shall provide proper engineering design for all facilities
not covered by these standards in accordance with good engineering practice and shall utilize first
class workmanship and materials in all construction.
C. SPECIAL PROVISIONS AND STANDARD SPECIFICATIONS
The City of Wylie has adopted the most recent version of thP NCTCOG Standard Specifications for
Public Works Construction together with the Special Provisions to the Standard Specifications.
These documents set forth the minimum requirements for materials and workmanship for public
works construction.
Ordinance No. 2005-14 1
Admendment to Design Standards
D. STANDARD CONSTRUCTION DETAILS
The City of Wylie has adopted a set of standard construction details in order to promote uniformity
of development and to facilitate maintenance of various public works facilities. The standard
construction details are to be considered as the minimum requirements for materials and
workmanship for public works construction.
E. INSPECTION OF CONSTRUCTION BY CITY PERSONNEL
Inspection of construction activities shall be conducted by staff of the City of Wylie under direction
of the City Engineer or authorized representative. The City inspector shall observe and check the
construction in sufficient detail to satisfy himself that the work is proceeding in general conformance
with the standards and specifications for the project, but he will not be a guarantor of the
Contractor's performance. The City will not accept any development until City staff has approved
all construction. The developer shall be responsible for any additional expense to the City for
inspection that is necessary after normal business hours, or when the improvements will be privately
owned. The City will establish the rate for compensation and other expenses.
The developer will be responsible for furnishing the original reproducible engineering drawings
corrected to show any revised construction conditions to the City before any improvements will be
accepted. All public works improvements must accepted by the before any City Building permits
will be issued.
2
SECTION II
STREET DESIGN STANDARDS
A. DEFINITIONS
TABLE I
Pavement Median Parkway
T e R-O-W (Face to Face) (Face to Face) Width
Major Thoroughfare (Type B) 120' 6/12' (72') 22' 13'
Secondary Thoroughfare (T e C) 100' 4/12' (48') 24' 14'
Collector (T e D) 65' 38' None 13.5'
Residential Street (T e E) 50' 31' None 9.5'
Estate Residential (Type E-1) 60' 32'* None 14'
Pavement dimension for Estate Residential is Edge to Edge of Shoulder.
4 Above defined by the City of Wylie, Texas, Comprehensive Plan and most recent Major
Thoroughfare Plan.
B. MINIMUM HORIZONTAL DESIGN RADIUS
Minimum Centerline Radius is defined by the design speed of the respective street. The
design speed of each street In the City of Wylie, as defined by the Thoroughfare Plan, can be
determined from Table 2.
TABLE 2
DESIGN SPEED OF EACH TYPE OF STREET
Street Tvpe Desi�n Speed
Residential (Type E E-1) 25
Collector (Type D) 30
Secondary Thoroughfare (Type C) 40
Major Thoroughfare (Type B) 45
Ordinance No. 2005-14
Admendment to Design Standards 3
The minimum acceptable horizantal centerline radius, for each respective street's design speed,
is shown in Table 3. The cross slope is assumed to be 1/4" per foot from the inside toward the
outside.
TABLE 3
MINIMUM HORIZONTAL CENTERLINE RADIUS
R R
Y f e (e (Calculated) (Rounded for Design)
m h ftlft ft ft
25 0.170 -0.0208 0.1492 279.27 280
30 0.160 -0.0208 0.1392 431.03 440
35 0.150 -0.0208 0.1292 632.09 640
40 0.145 -0.0208 0.1242 858.83 860
45 0.142 -0.0208 0.1212 1,113.86 1,120
50 0.140 -0.0208 0.1192 1,398.21 1,400
55 0.130 -0.0208 0.1092 1,846.76 1,850
60 0.120 -0.0208 0.0992 2,419.35 2,420
(AASHTO P 177)
NTinimum centerline design radius for residential streets shall be 280-feet for curves with a
lenbth over 125 feet long.
C. MINIMUM VERTICAL ALIGNMENT
Vertical Ali�rrient is a function of Stopping Sight Distance (SSD), which is given by:
SSD 1.47PV V
30 (f g)
(Transportation and Traffic Engineering Handbook, Second Edition, Page 590)
Stopping Sight Distances are calculated for g- 0, rates of vertical curvature are derived from
AASHTO Page 307, 312 and 316 and used (K) to determine crest curve lengths per Table 4.
The maximum grade for residential streets is 10% unless otherwise approved by the City
where natural topography is such as to require steeper grades. The maximum grade for all
other streets shall be 7.50%. The minimum grade for all streets is 0.50%.
4
TABLE 4
MINIMUM ACCEPTABLE CREST CURVE GIVEN SPEED AND
DIFFERENCE IN GRADE OE ROAD
S K L-KA
MPH Ft. A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10
30 200 19 0 40 60 80 100 120 140 150 170 190
35 250 29 0 60 90 120 150 180 200 230 260 290
40 325 44 50 90 130 180 220 270 310 350 400 440
45 400 61 60 120 180 250 300 370 430 490 550 610
50 475 84 90 170 250 340 420 500 590 670 760 840
55 550 114 120 230 340 460 570 690 800 920 1030 1140
60 650 151 150 300 450 600 760 910 1060 1210 1360 1510
TABLE 5
MINIMUM ACCEPTABLE SAG CURVE GIVEN SPEED AND
DIFFERENCE IN GRADE OF ROAD
S K L-KA
MPH Ft. A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10
30 200 37 0 100 120 160 200 240 280 320 360 400
35 250 50 0 100 150 200 250 300 350 400 450 500
40 325 64 70 130 190 260 320 390 450 520 580 640
45 400 79 80 160 240 320 400 480 560 640 720 790�
50 475 96 100 200 290 390 480 580 670 770 870 960''
55 550 115 116 230 350 460 580 690 810 920 1040 1150
60 650 136 136 280 410 550 680 820 960 1090 1230 1360
Ordinancs No. 2005-14 5
Admendment to Design Standards
D. INTERSECTION CURB RADII
The radius shall be thirty (30) feet at the intersection of all Major and Secondary
Thoroughfare intersecting streets unless otherwise approved by the City Engineer or
Authorized Representative.
See Detail, page 10.
Note: At many intersections, the curb radius encroaches on the right-of-way so as to not
provide sufficient room for sidewalks, utilities, etc. within the parkway. Therefore,
right-of-way will be dedicated at the intersection of all streets such that a minimum
or nine and one-half (9.5) feet of parkway shall be maintained from the back of the
curb along the curb's radius.
E. RESIDENTIAL FRONTAGE
Residential houses shall not front a thoroughfare unless parallel access roads are provided.
Minimum distances between adjacent curbs or the thoroughfare and the access road shall be
twenty (20) feet.
F. STATE DESIGNATED ROADS
All such roads within the City of Wylie will conform to State Design Standards unless
otherwise directed by the City Engineer.
6
SECTION III
MEDIAN AND LEFT TURN LANE DESIGN STANDARDS
A. WIDTH OF MEDIAN
Median widths vary from a minimum of 4' (with left turn lanes) to a maximum of 24' (see
Table l
B. REQUIRED MEDIAN OPENING AND LEFT-TURN LANE
Median openings on divided thoroughfares shall be provided at all dedicated street
intersections and at private drives where they conform to the City's spacing requirements. A
left turn lane for the proposed drive or street shall accompany the median opening.
C. COST OF MEDIAN OPENINGS AND LEFT-TURN LANES
Median openings and left-turn lanes constructed to serve private drives and new roads shall
be paved to City standards, inspected by City Inspectors, and paid for by owners served by
the median openings and left-turn lanes. The City shall be responsible for, and pay the costs
of, the paving of inedian openings and left-turn lanes, constructed to serve existing dedicated
streets, and those that exist for drives, when a part of the Capital Improvement widening
program is undertaken by the City on an existing public street.
D. MINIMUM LEFT-TURN STORAGE, TRANSITION LENGTH, AND MEDIAN
OPENING WIDTH, LOCATION, AND SPACING REQUIREMENTS
(1) Left Turn Storaee
All left-turn storage areas shall be ten (10) feet wide with minimum storage
requirements for left-turn lanes as in Table 6.
TABLE 6
MINIMUM LEFT TURN STORA�E REQUIREMENTS
Intersectin� Thorou�hfares Minimum Storage
Major with Major 150 feet
Major with Secondary 100 feet
Major with Residential 60 feet
Major with Private Drive 60 feet
Secondary Major 100 feet
Secondary with Residential 60 feet
Secondary with Private Drive 60 feet
Note: Starage requirements listed herein are absolute minimums. Storage
requirements may increase based upon actual and projected traffic
demands.
Ordinance No. 20Q5-14
Admendment to Design Standards
(2) Transition Len tg,�h
The transition curves used in left-turn lanes shall be two 250-foot radius reverse curves,
which will require a total transition length of 100-feet.
(3) Median Openings
a) Median openings at Intersections shall be from right-of-way to right-of-way or the
intersecting street.
b) The minimum width of mi�d-block median openings shall not be less than sixty (60)
feet. See Detail, page 9.
(4) Medians Where No Left-Turn Pocket is Needed
a) If left-turn storage is provided in only one direction, (i.e., a drive cannot be installed
for the other direction}, the minimum length of inedian must be the required left-turn
storage and transition length, plus 30-feet of inedian length beyond the end of the
transition.
b) If the left turn storage is not required in either direction, but the median is simply a---
spacer between two median openings, the minimum length of the spacer must be 50-
feet. See Detail, page 10.
(5) Medians into Developments on Public Streets
Medians installed on undivided streets at entrances to subdivisions for aesthetic or any
other purpose will be a minimum of 4-feet wide and 100-feet long.
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MAJOR THOROUGHFARE
Ordinance No. 2oQ5-14 9
Admendment to Design Standards
ORNE 50' A�IN. S714EET 60' l00' JO'
60' M/N. 60' �!/N. STORAGE AS �yy5/np�+ ,t//N.
OR R.O.W. REOU/RED
TO R.O. iY.
,�p' f00' 60' M/N.
�N �np,y STORAC£ AS
R£OU/REO
TYPICAL MEDIAN DIMENSIONS WITHOUT
BACK TO BACK LEFf TURN POCKEfS
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SECTION IV
ALLEY DESIGN STANDARDS
A. ALLEI' REQUIREMENTS FOR DEVELOPMENTS
Alleys' shall be constructed in accordance with City of Wylie Subdivision Ordinance. Alleys
shall be provided in all residential areas and shall be paved with concrete in accordance with
the City's Standard Construction Details. The City Council may waive the residential alley
requirement upon determination of the Council that such a waiver is in the best interest of the
City. Alleys may be required in commercial and industrial developments. The City may
waive the commercial and industrial alley requirement upon determination of the Council, if in
its opinion adequate provisions are made for service access such as off-street loading,
unloading and parking consistent with the uses proposed.
B. ALLEY INTERSECTIONS
Alleys shall not intersect major or secondary thoroughfares with medians. Alleys which run
parallel to and share a common right-of-way line with a major thoroughfare shall turn away
from the major street not less than one subdivision lot width or a minimum of 50-feet
(whichever is greater) from the cross street intersection.
G A�.LEY WIDTHS
The minimum alley right-of-way width shall be twenty (20) feet with a minimum 12-foot
paved width. Dead-end alleys shall not be permitted without special permission from the City
Engineer or Authorized Representative. The geometry of alley construction shall conform to
the Standard Construction Details.
D. ALLEY RADIUS
Alley radii at street intersections in residential developments shall not be less than 10-feet.
Alley radii at street intersections in commercial and residential developments shall not be less
than 30-feet unless approved by the City Engineer or Authorized Representative.
Ordinance No. 20Q5-14 11
Admendment to Design Standards
SECTION V
DRIVEWAY DESIGN STANDARDS
A. DEFINITION OF DRIVEWAY TYPES
For purposes of interpreting the provisions of these Rules and Regulations, the following
definitions shall apply:
(1) A"residential" driveway provides access to a single-family residence, to a duplex, or to
a multi-family building containing five or fewer dwelling units. These drives shall
intersect residential and commercial roadways only. All access to residential property
abutting all other thoroughfares shall be off the alley or a service road. All residential
driveways shall be concrete.
(2) A"commercial" driveway provides access to an office, retail or institutional building, or
to a multiple-family building having more than five dwelling units. It is anticipated that
such buildings will have incidental truck service. Commercial drives shall access to
Major or Secondary Thoroughfares only. All Commercial driveways shall be concrete.
(3) An "industrial" driveway serves substantial numbers of truck movements to and from
loading docks of an Industrial facility, warehouse, or truck terminal. A central retail
development, such as a community or regional shopping center, may have one or more
driveways specially designed, signed, and located to provide access for trucks and such
driveways shall be considered industrial driveways. Industrial plant driveways whose
principle function is to serve administrative or employee parking lots shall be considered
commercial driveways. Industrial drives shall access to Major or Secondary
Thoroughfares only. All Industrial driveways shall be concrete.
Note: Two-way driveways shall always be designed to intersect the street at a 90
angle. One-way driveways may be designed to intersect a street at a 45 angle.
B. DRIVEWAY WIDTH
As the term is used here, the width of a driveway refers to the width of pavement at the
property line.
(1) Residential driveways onto streets shall have a minimum width of 12-feet and a'
maximum width of 24-feet. Joint access residential drives shall have no less than
nine (9) feet on any property. See Detail (a), page 15.
12
(2) CommerciaUlndustrial. Two-way operation: See Detail (b), page 15.
a) Commercial driveways shall have a minimum width of twenty-four (24) feet and a
maximum width of 30-feet.
b) Industrial driveways shall have a minimum width of 30-feet and a maximum width
of 40-feet. Joint access commerciaUindustrial drives shall have no less than Ten (10)
feet on any property, with the full drive width and access pavement to the property
built for the development at the same time.
(3) Commercial/Industrial One way operation:
a) 90-degree drives shall have a width of 18-feet for ingress and 22-feet for egress, with
the separation median width being a minimum or 4-feet and a maximum or 10-feet.
See Detail (c), page 16.
b) 45-degree drives shall have a width of 18-feet for ingress and 16-feet for egress, with
the separation median width being a minimum of 4-feet and a maximum of 10-feet.
Joint access commercial/industrial drives shall have no less than 10-feet on any
property, with the full drive width and access pavement to the property built for the
development at the same time. See Detail (d), page 16.
C. DRIVEWAY RADIUS
All driveways intersecting dedicated streets shall be built with a circular curb radius
connecting the 6-inch raised curb of the roadway to the design width pavement of the
driveway. All driveways shall provide for barrier free access. Driveway radii shall fall
entirely within the subject property so as to begin at the street curb, at the extension of the
property line.
(1) 90-DeQree Intersection (See Detail, page 15)
a) The curb radii for a residential drive shall be a minimum of 5-feet and a maximum of
10-feet.
b) The curb radii for commercial and industrial drives shall be 30-feet unless otherwise
approved by the City.
(2) 45-De�ree Intersection
The curb radii shall be 5-feet for the outside of the drive and 2'/2-feet for the median. See
Detail, page 16.
In order that the definition of the location of the edge of pavement for the thoroughfare may
be maintained, driveway radii shall always be designed to become tangent to the street curb
line. All commercial and industrial drives will have an unbroken curb length of not less than
Ordinance No. 2005-14 13
Admendment to Design Standards
20-feet from the right-of-way, or 30-feet from the roadway curb extending into the site on
each side of the drive.
12' A!lN. 10' MIN.
24' ,UA.y, N 28' AfAX.
R.O.W,
4 CONC. SIDE6YALlC
5R M/N. ✓DINT APPRQACH
8 A!lN. ON
f0 R MAX. ANY PROPER7Y
(a) DRIVEWAYS WIDTH, RADIUS, SPACING
I COMMERCGtL SEE DRNEWAY INDUSTRG4L
0 24' A.!lN. SPAClN6 AND 30� M/N.
3p' d�AX. LOCATION TABLE 40' M i. h
R.4.W.
4 CONC. SIDEWALI�,
JO/NT APPROACH
20 R MlN. l0' MIN. ON
25 R MAX. ANY PROPERJY
(b) DRiVEWAYS WiDTH, RADiUS, SPACING
14
W
Z
W
d
O
a.
1
E
i 4' MIN.
10" MAX.
21' 18'
R.Q.W. R.O.W.
4 CONC. S/DEWALK
20 R COMMERCIAL
25 R INOUSTRIAL
(c} DR{VEWAYS WIDTH, RADIUS, SPACING
BEGIN CURB FULL HEIGNT CUR
l I �nr.
N I h
R.o.w.
R.O.W. R.O.W. l
.p, �,�g 4 CONC. SI DEWALK
RB 2.5 R MlN.
SLOPING CU
(d) DRIVEWAYS WlDTH, R�DIUS, SPACING
Ordinance No. 2005-14
Admendment to Design Standards 15
D. DRIVEWAY SPACING AND LOCATION IN RELATION TO OTHER DRIVES
(1 Residential
Driveway approaches on a tract of land devoted to one use shall not occupy more
than 70% of the frontage abutting the roadway. No more than two driveway
approaches shall be permitted on any parcel of property on each street.
(2) Commercial and Industrial
The spacing and location of driveways shall be related to both existing adjacent
driveways and those shown on approved development plans. The spacing between
driveways shall depend upon the design speed of the street as shown Table 7.
Driveways shall not be permitted in the transition area of a deceleration lane or a right
turn lane.
TABLE 7
DRIVEWAY SPACING IN RELATION TO OTHER DRIVES GIVEN THE DESIGN
SPEED OF THE STREET
Desi�n Sneed (MPH) Drivewav Spacin� (Ft.1
25
65
30 90
35 100
40 120
45 150
50 200
The minimum spacing shall not be more than 10-feet less than shown above, Spacing
between driveways will be measured along the property line from the edge of one
driveway to the closest edge of the next driveway and not from centerline to c�nterline.
E. DRIVEWAY SPACING IN RELATION TO A CROSS STREET
(1) 90 De�xee Intersection Drive to_ Road
a) Driveways that intersect at 90 degrees to a residential or "secondary street" shall be
located a minimum of the drive radius from a residential street's end of curb radius.
b) A driveway that Intersects at 90 degrees to a residential or secondary street shall be
located a minimum of thirty (30) feet from a secondary or major street's end of curb
radius. (see Detail (a), page 19)
16
c) A driveway that intersects at 90 degrees to a major street shall be located a minimum
of 100-feet from any intersecting street's right-of-way or from the end of any
intersecting street's curb radius as determined by the City Engineer. If the property
length, along the street, is such that both the drive and the drive's curb radius cannot be
totally within the proposed development, the drive will be situated so as to be a joint
access drive. (see Detail (b), page 19)
(2) 4.5 deQree Intersection Drive to Road
a) If one-way angle drives are used, the radius for the driveway on a residential or
secondary may not begin less than 35-feet from an intersecting street's end of curb
radius.
b) On a major street the drive shall be located a minimum of 100-feet from any
intersecting street's right-of-way. If a property length, along the street, is such that
both the drive and drive's curb radius cannot be totally within the proposed
development, the drive will be situated so as to be a joint access drive. (see Detail
(c), page 19)
A suinmary of driveway widths, radii, and angle requirements are given in Table 8.
TABLE 8
SUMMARY OF DRIVE REQUIREMENTS
One-Way
Residential Commercial I Out Industrial
Width (ft)
Minimum 12 24 30
One-way (only)
90 18 22
45 18 16
Maximum 24 30 40
Curb Radius (ft)
45 (one-way) 5 10 10 10 10
90 5-10 30 Same Same 30
Intersection
Angles (deg.) 90 90 90 90 90
45 45 45 45 45
Ordinance No. 20Q5-14 1
Admendment to Design Standards
i
0
J6' dllN. IY'
(a) DRIVE INTERSECTING A RESIDENTIAL OR SECONDARY
I
3
0
--1
J
f00' N/N. 1�'�
(b) 90 DRIVE INTERSECTING A MAJOR
I
1 1
3
i Q
��5� I�4J 1IRL
1Gb' /4t/AR
(c) ANGLE DRIVE
18
SECTION V
SIDEWALK AND LOCATION DESIGN STANDARDS
A. DEFINITION OF SIDEWALK
A sidewalk is defined as that paved area in a roadway right-of-way between the curb lines or
the: edge of pavement or the roadway and the adjacent property lines for the use of
pedestrians. The maximum cross slope of the sidewalk shall be i/4-inch per foot. These
sidewalks shall conform to the following standards:
1) Zonin� Classification Requiring Sidewalks: Concrete sidewalks designed and located
according to City standards shall be constructed along all streets in all zoning
classifications except agricultural zoning. The Owner shall build sidewalks at the time of
site development. Should it be impractical to install the sidewalk at that time, funds for
the sidewalk construction shall be placed in escrow with the City for use at the time when
sidewalks are needed. Payment or escrow shall be made at the time of site plan or final
plat approval.
2) Residential Areas (Sin�le Family, Two Familv and Multi-Familv): Sidewalks shall be
4-feet in width and located 1-foot from the right-of-way line. Along thoroughfares with
inadequate right-of-way the sidewalk width shall be 5-feet in width and constructed
adjacent to the back of curb.
3) Non-Residential Areas: Sidewalks shall be 4-feet in width and located 1-foot from the
right-of-way line. Along thoroughfares with inadequate right-of-way the sidewalk width
shall be 5-feet in width and constructed adjacent to the back of curb.
4) Exceptions: In areas where mailboxes interfere with a clear width of 4 or 5 feet for the
sidewalk, the specified width shall be wrapped around the mailbox.
5) Waiver: The sidewalk required in non-residential areas may be waived by the City
Council either temporarily or permanently at the time of site plan or final plat approval.
Waiver may be granted based on site conditions and/or location of the tract.
6) Areas Without Screenin�ls: In areas on major and secondary roadways where either
e u screening is not required or a type of screening other than a wall is used, (e.g., a berm,
foliage, etc.) a 4-foot sidewalk will be constructed not more than 2%2-feet from the right-
of-way line as required by the Thoroughfare Plan.
Ordinance No. 20Q5-14
Admendment to Design Standards 19
7) Areas with ScreeninQ Walls: In areas where a screening wall is provided, a concrete
sidewalk shall be constructed contiguous with the screening wall. The street side of the
sidewalk shall run parallel to the street curb. The sidewalk shall be a minimum of 5-feet
wide and the measurement shall be made from the street side of the sidewalk.
8) Sidewalk on Bridges: Bridges on thoroughfares shall have a sidewalk constructed on each
side of the bridge. The sidewalk shall be a minimum of 6-feet wide with a parapet wall
provided adjacent to the curb of the thoroughfare and with a sta.ndard pedestrian bridge
rail protecting the sidewalk on the outside edge of the bridge.
9) Sidewalks Under Brid�es: When new bridges are built as a part of the construction of a
roadway or the reconstruction of a roadway and a pedestrian crossing is needed, an 8-foot
sidewalk will be built as a part of the embankment design underneath the bridge structure.
The 8-foot sidewalk shall be located generally along the toe of the embankment.
B. BARRIER-FREE RAMPS (Compliance shall be with the American Disabilitv Act)
Curbs and walks constructed at intersections or all streets and thoroughfares must comply
with the provisions of the American Disability Act and be constructed in a manner to be
easily and safely negotiated by physically challenged persons.
20
SECTION VI
PUBLIC RIGHT-OF-WAY VISIBILITY
A. STREET/DRIVE INTERSECTION VISIBILITY OBSTRUCTION TRIANGLES-
FRONTAGE PLAN/PROFILE
A landscape plan showing the plan/profile of the street on both sides of each proposed
drive/street to the proposed development with the grades, curb elevations, proposed street/drive
locations, and all Items (both natural and man-made) within the visibility triangles as
prescribed below shall be provided with all site plans, if they are not on engineering plans that
are submitted at the same time. This profile shall show no horizontal or vertical restrictions
(either existing or future) within the areas defined below.
(1) Obstruction/Interference Triangles-Defined
No fence, wall, screen, billboard, sign, structure, foliage, hedge, tree, bush, shrub, berm,
or any other item, either manmade or natural shall be erected, planted, or maintained in a
position, which will obstruct or interfere with the following minimum standards.
a) Vision at all intersections where streets intersect at or near right angles shall be clear at
elevation between 2%z-feet and 9-feet above the average gutter elevation, except
single trunk trees, within a triangular area formed by extending the two curb lines
from their point of intersection, 45-feet, and connecting these points with an
imaginary line, thereby making a triangle. If there are no curbs existing, the
triangular area shall be formed by extending the property lines from their point of
intersection 30-feet and connecting these points with an imaginary line, thereby
making a triangle. (see Detail, page 23)
b) Definitions for desirable minimum sight distance requirements for non-residential
streets, commercial driveways, and industrial driveways that intersect at or near right
angles are presented below (see Detail, page 25). The values presented are minimum
sight distances which would permit the following:
T-Upon turning left or right, an exiting vehicle could accelerate to the operating
speed of the street.
Ordinance No. 2005-14 21
Admendment to Design Standards
POINT OF iNTERSECTidN
45'
HORiZONTAL CLEAR TRIANGLE
22
The desirable minimum sight distances are based on the premise that the approaching
driver can observe the intersecting vehicle 2.5 seconds before he must apply the brakes
and travel the minimum stopping distance for his approach speed. They are, therefore,
particularly applicable to arterial streets. Actual sight distances provided at Intersections
should be much greater than these minimum values if practical. The minimum sight
distance triangle shall also apply to visibility obstructions at intersections.
Conditions for Intersection Sight Triangle-Plan/Profile:
In the plan view, the horizontal clear area at the Intersection of a proposed street/drive
shall be defined as being within a triangular area formed by:
(I) A line that is on the centerline of the proposed street/drive, beginning at the
Intersecting street's tangent curb and continuing for a distance of 15-feet back
into the proposed street/drive to the end point.
(II) A line that is parallel to and 5-feet out from the intersecting street's curb,
beginning at the centerline of the proposed street/drive and continuing for a
distance "T" as prescribed in Table 9, to the end point.
(III) A straight line that connects the end point of an:
That is on the centerline and 15-feet back into the proposed street/drive, and
the end point of a
That is a distance "T" along and 5-feet out from the existing street's curb from
the centerline or the proposed street/drive.
In the profile view, the clear window shall be defined as being within the horizontal clear
area and clear between 2.5 feet and 9 feet above the average pavement elevation.
Note: Single trunk trees within the triangles and in the median shall be allowed and
spaced so as to not cause a"picket fence" effect. Because of the large variation of
ways in which trees can be planted, the spacing will be decided upon by the City
Engineer and the developer at the time of review of the landscape plans. Any
other item that obstructs these lines so as to interfere with the above requirements
will not be allowed.
Ordinance No. 2005-14
Admendment to Design Standards 23
h
C� OR APPROACN
I�EDIAN CURB
n
TAB LE 9
MINIMUM SIGHT DISTANCE FOR
A CAR AT AN INTERSECTION
MPH T
30 110 200=310
35 i 30 250=380
40 130 325=475
45 l 65 400=565
50 190 475=6fi5
(AASHTO P 138, BRAKE REAC710N D4STANCE
STOPPING SfTE DlSTANCE)
24
TABLE 9
MINIMUM SIGHT DISTANCE FOR A CAR AT AN INTERSECTION
...a (For Level-Two Lane �treets)
M PH T
30 110 200 310
35 130 250 380
40 130 325 475
45 165 400 565
50 190 475 665
AASHTO P138, Break Reaction Distance Stopping Site Distance
The aforementioned restrictions also apply to streets that do not intersect at right angles,
except that the triangle dimensions shall not necessarily be minimum requirements. In such
cases the City Engineer shall have the authority to vary such requirements as he deems
necessary to provide safety for both vehicular and pedestrian traffic.
B. R.O.W. OBSTRUCTIONS OUTSIDE THE VISIBILITY TRIANGLES
1) Foliage of hedges, trees and shrubs in public right-of-ways which are not governed by
Zoning Ordinance of the City, or the above triangles shall be maintained such that the
minimum overhung above a sidewalk shall be 7-feet; the minimum overhang above a
street shall be 14-feet.
2) All other areas within the street right-of-ways shall be clear at elevations between 2%2-feet
and 9-feet above the average street grade,
3) Plants in the public right-of-way that will grow over 30-inches (when mature) above the
adjacent street's curb will conform to all of the above requirements, where applicable. All
landscape plans shall show the locations and type of such plants, and show each of the
prescribed triangles.
4) Ground elevations, within both triangles, will be shown by contour lines.
Note: No plantings over 30-inches above the adjacent gutter elevation are allowed in the
median for the length of the left turn stacking space unless specifically agreed upon by
the City Engineer.
Ordinance No. 20Q5-14 25
Admendment to Design Standards
C. ALLEY VISIBILITY OBSTRUCTIONS
No fence, wall, screen, billboard, sign, structure, or foliage of hedges, trees, bushes, or shrubs
shall be erected, planted or maintained in any alley right-of-way. Foliage or hedges, trees,
bushes, and shrubs planted adjacent to the alleys right-of-way which are not governed by the
above triangles or by Zoning Ordinance of the City, shall be maintained such that the
minimum overhang or encroachment shall be 14-feet above the alley surface at the edge of
the pavement.
D. EXCEPTIONS
The provisions of this manual shall not apply to, or otherwise interfere with, the following:
1) Placement and maintenance of traffic control devices under govemmental authority and
control.
2) Existing and future screening requirements Imposed by the City Council.
3) Existing and future City, State and Federal Regulations.
26
SECTION VII
OFF STREET REQUIREMENTS
A. STACHING SPACE FOR DRIVE-UP WINDOWS
The minimum stacking space for the first vehicle stop for a commercial drive-through shall
be 100-feet, and 40-feet thereafter, for any other stops.
B. PARKiNG LOT LAYOUT
1) All parking lots shall be paved with concrete unless otherwise approved by City Council.
Z) No parking area will be allowed to dead-end unless adequate turnaround space is proved.
3) Each standard 90° off-street parking space shall contain not less than 200 square feet and
measure not less than 10 feet by 20 feet, exclusive of access drives and aisles, and shall be
of usable shape and condition. One-way angled parking shall contain not less than 171
square feet and measure not less than 9.5 feet by 18 feet.
4) The width for two-way aisles shall be a minimum of 24-feet and a maximum of 45-feet.
The width for one-way aisles shall be a minimum of 20-feet (24-feet if the aisle is also a
fire lane).
5) Handicapped parking spaces shall be minimum 10-feet in width with a 5-foot minimum
walkway. The walkway can be shared by two spaces. For parallel parking the space shall
be a minimum of 24-feet by a minimum 13-feet with a 3-foot minimum walkway one end
in addition to the minimum 24-foot dimension. (see Detail, page 29)
6) Parking Overhang: No parking stall shall be situated so as to allow vehicle overhand into
public right-of-way. Curb or parking stops shall be installed so that the distance between
the face of the curb or car stop is a minimum of 2-feet from the public right-of-way.
7) Movements in Public Right-of-Way: No parking stall shall be so designed as to allow any
movement into or out of the stall, upon public right-of-way.
8) Parking lot illumination shall be designed and constructed to direct the light to the parking
lot and away from any adjoining property or street.
9) Fire lanes shall be constructed as required by Fire Department rules and regulations.
Ordinance No. 20Q5-14 2
Admendrnent to Design Standards
a a.
d d
n� SI DEWAI:K 4' d
a.
a
Q
I I 1
10' MIN. 5' M/N. 10' M/N.
HEAD-IN OR ANGLE PARKING DIMENSlONS
28