08-15-1989 (City Council) Agenda Packet DATE POSTED 8-10-89
TIME POSTED 4:00 P.M.
AGENDA
CALLED CITY COUNCIL WORK SESSION
AND MEETING
CITY OF WYLIE, TEXAS
TUESDAY, AUGUST 15, 1989
7:00 P. M. COUNCIL CONFERENCE
ROOM MUNICIPAL COMPLEX
2000 HIGHWAY 78 NORTH
CALL TO ORDER
INVOCATION
ORDER OF
BUSINESS BUSINESS
1 Presentation by Shimek, Jacobs, Finklea
on Regional Sewer System
2 Discussion on the voluntary donation
being added to the water bills
3 Report on engineering invoce from
Shimek, Jacobs, Finklea
4 Discussion on the 1989/90 Budget
5 Recess work session
6 Convenue Council into called meeting
7 Consider approval of Professional
Services for right-of-way acquisitions
for wastewater collection system
improvements
8 Recess open meeting
9 Convene Council into Executive Session
under the authority of Article 6252-17
V. A. C. S. , Section 2 paragraph "f"
regarding Real Estate
10 Reconvene open meeting
11 Adjourn
MUDDY CREEK
REGIONAL WASTEWATER SYSTEM
TO THE CITIES OF
WYLIE
SACHSE
ROWLETT
PREPARED BY
SHIMEK, JACOBS & FINKLEA
CONSULTING ENGINEERS
DALLAS,TEXAS
JUNE,1989
SHIMEK, JACOBS & FINKLEA
CONSULTING ENGINEERS
8333 Douglas Avenue, #820 Dallas, Texas 75225 (214) 361-7900
ROSS L.JACOBS,P.E.
I.C.FINKLEA,P.E. June 23, 1989
JAMES E.LAUGHLIN,P.E.
RONALD V.CONWAY,P.E.
JOHN W.BIRKHOFF,P.E.
MATT ARMSTRONG,P.E.
JOE R.CARTER,P.E.
GARY C.HENDRICKS,P.E.
STEVEN W.McCRARY,P.E.
C.L.SHIMEK,RE.
Mr. Mike Gibson, City Manager
City of Rowlett
Mr. Lloyd Henderson, City Manager
City of Sachse
Mr. Charles Norwood, City Manager
City of Wylie
Gentlemen:
Presented herein are the results of our study of a regional wastewater system to
serve the Muddy Creek basin and adjoining areas.
We find that such a system can be established for an estimated initial capital
cost of $10,970,000. It is our opinion that a Muddy Creek Regional Wastewater
System is feasible and will offer significant long term advantages.
Sincerel ,
�.,�-+-^•Aaa�, Joe R. Carter, P.E.
rk-,''''`• •••�a ..
/ *.:* 944:VA1L
C. ;11i 4 C. L. Shimek, P.E.
Enclosure ��, ,.s+41; •
'�232 ,� ',;
j+i3C��i+ +AI
I - INTRODUCTION
General
Muddy Creek flows in a southeasterly direction through southern Collin County and the extreme
northeastern part of Dallas County. It is a tributary of the East Fork of the Trinity River and
discharges to Lake Ray Hubbard. The area within, and adjacent to, the Muddy Creek drainage
basin is within the Dallas Metropolitan Area, has ample water supplies available and
transportation facilities are to be improved subsantially in the near future. It can be expected
that these ingredients will result in increasing urban development in the future.
Purpose and Scope
The purpose of this report is to present the results of a study made to develop a plan to provide a
regional system to transport and treat wastewater for the Cities of Wylie, Sachse, Rowlett and
Murphy. The City of Murphy is not one of the parties that authorized this study, but it had
previously had a study performed that indicated a regional approach was feasible. The results of
that study have, therefore, been incorporated in this report.
In carrying out this study previous planning studies that have been performed for each individual
city have been largely relied on with regard to population projections and other matters that would
affect regional system planning. Some modification was made in joint discussions with
representatives of the cities involved.
Topographic information required to determine approximate slopes available for installation of
sewers, and for determining the general location of proposed facilities,was obtained from maps
published by the U. S. Geological Survey. It is believed that these maps are sufficiently accurate
for preliminary design purposes.
Planning Areas
The planning areas, or the areas for which service will ultimately be needed, are,generally, areas
presently included in the city limits or extra-territorial jurisdiction of each of the four cities. These
areas are shown on Plates Nos. 1 c. 'd 2.
There is a total of 37,500 acres within the composite planning area,of which 18,400 acres is within
the Muddy Creek drainage basin.
I-1
Population
The four cities had a combined population of 13,464 based on the 1980 census, and an estimated
population of 35,450 in 1988 based on NCTCOG data. It is estimated that the combined
population will reach 107,800 by the year 2010. A breakdown of these figures is shown in the
following table, and graphically on Figure No. 1:
EXISTING AND PROJECTED POPULATION
City 1980 1988 2000 2010
Murphy 1,150 1,700 5,000 15,000
Wylie 3,152 8,550 16,000 24,000
Rowlett 7,522 19,550 26,500 40,000
Sachse 1,640 5,650 13,000 28,800
13,464 35,450 60,500 107,800
I-2
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POPULATION IN 1000'S
II - EXISTING FACILITIES
In order to minimize the initial investment required to construct the proposed regional system it
would be desirable to make use of existing treatment facilities to the fullest extent and defer
construction of some facilities until the existing capacity is used up and a larger population base
is available to support further improvements. It is presumed,therefore,that existing facilities will
become a part of the proposed regional system. Service to the four cities is described in the text
that follows.
Murphy
Wastewater originating in the City of Murphy is treated at a plant that was constructed, and is
operated, by the North Texas Municipal Water District. The plant has an approximate capacity
of 0.25 million gallons per day(mgd)and is virtually operating at capacity at the present time. The
location of this plant is shown on Plate No. 1.
Wylie
Through an arrangement with the North Texas Municipal Water District the wastewater treatment
plant at Wylie is currently being enlarged to provide a capacity of 2.0 mgd. NTMWD also operates
this plant. The plant location is shown on Plate No. 1.
Sachse and Rowlett
Both the Cities of Sachse and Rowlett discharge their entire wastewater flows to the City of
Garland system, and neither city has any treatment facilities. The regional plan developed
presumes that all wastewater from these cities will be diverted to the proposed Muddy Creek
Regional Wastewater System.
II-1
III - PROPOSED SYSTEM
Basis of Design
In the past a typical single family residential area with normal commercial development could be
expected to have a population density of around 7 persons per acre. Recent trends have indicated
a tendency toward higher density development. For the purpose of estimating wastewater flows
an average density of 10 persons per acre has been adopted. This appears to be a reasonably
conservative figure in that it applies to gross acreage including parks and open spaces,flood plains
and public right-of-way.
Average daily wastewater flows in this general area are equivalent to 100 to 120 gallons per capita
per day (gpcd), varying somewhat with the degree of commercial and industrial discharges. In
calculating design flows for the purpose of sizing interceptor sewers for this system an equivalent
flow of 120 gpcd has been used. The ratio of peak to average flows in a trunk or interceptor sewer
will vary somewhat with the population served. Generally, the greater the population served the
lower the peak flow will be in relation to the average flow. Peak flows for the design of this system
have been calculated by an accepted method that results in flows that vary from 3.9 times average
flow in the upper reaches of the system to 2.0 times average flow at the proposed regional plant.
Overall System
Through discussions with representatives of the cities participating in the development of a
regional wastewater plan,during which population projections and cost estimates for various stages
of construction were examined, it was decided that a system should be designed that would be
adequate to the year 2010 and that the system should be built in two phases. The overall system is
shown on Plate No. 1, accompanying this report, and Phase I Improvements are shown on Plate
No. 2.
It is proposed that the overall regional system will consist of the following elements:
1. A new regional wastewater treatment plant on Muddy Creek upstream of Lake Ray
Hubbard.
2. Muddy Creek Interceptor Sewer, extending from new plant to vicinity of existing Wylie
plant.
III-1
3. Existing Wylie Wastewater Treatment Plant.
4. Existing Murphy Wastewater Treatment Plant.
Phase I Improvements
In order to minimize the initial investment required to establish the regional system Phase I
Improvements were determined on the premise that the existing Wylie wastewater treatment plant
will continue in operation until its capacity is fully utilized, currently estimated to occur around
1997. By proceeding in this manner the construction of a substantial portion of the Muddy Creek
Interceptor Sewer can be deferred for several years. Proposed Phase I Improvements are shown
on Plate No. 2.
It is estimated that a minimum of three years will elapse in securing a waste discharge permit,
designing and constructing the proposed regional plant after the agreements required to allow the
project to proceed are executed. It appears,therefore,that the proposed plant could go in service
in 1993 if no major obstacles arise. Based on the design criteria previously cited and the population
projections included in Section I of this report the estimated combined population of the cities of
Sachse and Rowlett,who would be served by the first phase construction of the proposed regional
plant, would be 31,200 and the average wastewater flow would be approximately 3.12 mgd. It is
proposed, therefore, that the first phase regional plant have a capacity of 4.0 mgd.
The estimated cost of Phase I Improvements, in 1989 dollars, is summarized, as follows:
Muddy Creek Interceptor Sewer 1,080,000
Muddy Creek Regional Plant, 4 mgd 7,800,000*
Wylie Plant Enlargement (Exist) 1,700,000(1)
Murphy Plant (Exist) 390,000(1)
$10,970,000
ri * Includes allowances for property acquisition
(1) These figures represent outstanding debt service and are to be verified from records
III-2
Phase II -Improvements
Phase II Improvements will consist of a 4.0 mgd enlargement of the Muddy Creek Regional Plant,
and extending the Muddy Creek Interceptor Sewer to Wylie. For the purpose of assessing the
financial impact of these improvements it is proposed that the plant enlargement be accomplished
in two increments of 4 mgd each at intervals of 5 to 6 years. The estimated cost of Phase II
Improvements, in 1989 dollars, is summarized, as follows:
Around 1997
Muddy Creek Plant Enlargement, 4.0 mgd $7,000,000
Muddy Creek Interceptor Extension 1,600,000
$8,600,000
Around 2003
Muddy Creek Plant Enlargement, 4.0 mgd $7,000,000
The actual timing of additional improvements will be influenced by growth rates between now and
the year 2010. The dates shown are based on the population projections included earlier in this
report.
Proposed Muddy Creek Regional Plant
The cost estimate included for this plant is based on a plant using the activated sludge process
followed by filtration and disinfection. A schematic diagram showing the process and treatment
units is included as Figure No. 2
III-3
MUDDY CREEK REGIONAL TREATMENT PLANT
•
Influent Main Fine Activated Final Sand Disinfection, Effluent a
Lift Screens Sludge Clarifiers --r Filters -�
Station
Sludge
♦
Screenings
Sludge Sludge Cake
Digestion Dewatering
System
Return Flow
0
31
c SCHEMATIC OF INITIAL 4 MGD PLANT
N
IV - FINANCIAL
In order to evaluate the approximate effect on wastewater charges required to support the
proposed regional system a preliminary analysis of capital and operating costs has been performed.
Capital Costs
The approximate cost to construct or acquire facilities required in the regional system, in 1989
dollars, along with the approximate time the expenditures would be required is summarized, as
follows:
1993 - $10,970,000
1997 - 8,600,000
2003 - 7.000.000
$26,570,000
In estimating debt service charges it has been assumed that the project would be financed by issuing
20-year bonds bearing interest at the annual rate of 8%.
Operating and Maintenance Expense
It is estimated that operating costs at the three plants that would initially treat wastewater from the
regional system, in 1989 dollars,would be as follows:
1993
Muddy Creek Regional Plant $523,000
Wylie Plant 120,000
Murphy Plant 63.000
$706,000
Summary
Based on the population projections previously developed, and an average sewage flow of 100
gallons per capita per day,following are the estimated costs per 1,000 gallons required to construct
and operate Phase I of the system:
1993
Average annual principal and interest based on Capital Cost
of$10,970,000 and estimated population of 46,000 $0.665
Operating Expense of$706,000 0.42
$1.085
N--1
The estimated initial annual cost to each City and the elements included in the estimated cost are
shown below. The unit costs per 1,000 gallons would decline after the first year until new
improvements are required.
Murphy: Estimated 1993 Population - 2,200 Estimated Average Flow-220,000 gallons/day
Regional System charges at $1.085 per 1,000 gallons
220 x $1.085 x 365 = $87,100
Maxwell Creek Trunk Sewer-Estimated Cost $650,000
Principal and Interest at 8%, 20-yr 66,300
Total $153,400
Estimated Equivalent cost per 1,000 gallons = $1.91
Wylie: Estimated 1993 Population- 11,500 Estimated Average Flow-1,150,000 gallons/day
Regional System charges at $1.085 per 1,000 gallons
1,150 x 1.085 x 365 = $455,400
Sachse: Estimated 1993 Population- 9.500 Estimated Average Flow- 950,000 gallons/day
Regional System charges at 1.085 per 1,000 gallons
950 x 1.085 x 365 = $376,200
Estimated cost of Lift Stations, Force Main and Gravity Sewers
required to transfer Wastewater to Regional System- $2,132,000
Principal and Interest at 8%, 20-yr 217.500
Estimated Total Annual Cost $593,700
Estimated Equivalent cost per 1,000 gallons = $1.71
Rowlett: Estimated 1993 Population-22,000 Estimated Average Flow-2,280,000 gallons/day
Regional System charges at $1.085 per 1,000 gallons
2,280 x 1.085 x 365 = $903,000
Estimated cost of Lift Station, Force Main and Gravity Sewer
required to transfer Wastewater to Regional System- $2,695,000
Principal and Interest at 8%, 20-yr 275.000
Estimated Total Annual Cost $1,178,000
Estimated Equivalent cost per 1,000 gallons = $1.42
IV-2