St Andrews Manor-CS010417JI ANDES
CIVIL / ENVIRO~ENTAL ENGINEERING
April 17, 2001
Mr. Michael A. Martin, P.E.
City of Coppell
Engineering & Public Works
255 Parkway Blvd.
Coppell, Texas 75019
Re: St. Andrews Manor J00001
Please find enclosed two sets of ~ plans aad on~ ~ of your previously madlexl c~mment plans on
the above referemed project. These plans are ~ for yom faa1 review. TheminOf ~
thtou~ the plaas have been addressed ~ shown by the green responses. The font major comments are
addressed as follows:
!. A separate ! i/2" domestic water line has been designed offof Stratford Lane as're~
2. The developer, Mr. Terry Holmes, understands thnt die proposed entrance fete will have to be
permitted through the Building Inspections department.
3. The requested changes have been xnnde to the water plan sheet as requested.
4.a. There is no way to' feasiblely decrease the length of the fOrce ms/n Based'on 2*/5 mininmm grades,
the force main could only be shommed approxima~ly 300 feet. Decreasing the length of the fore'main
increases the length of the gravity line and the electrical power line, without decreasing the size or cost- of
the grinder pump. The project is less costly by insm!/linE the smaller pipe at shallow depth~ rather than
installing larger pipe at progressively deeper depths. The only way to feasiblely "shorte~"the force main ia
too elimin~ it entirely. This option is unviable. The best grade obtainable is 0.6%. Due to the limi~l~d
flows expected from this single residence, common pipe sizes of 4, 6, and 8 inchea will not produce
velocities sufficient for cleansing of the pipe.
4.b. There is no air filtration system on this unit. However, in order to alleviate the City's concerns over
odors, we have added a mix-flush valve tothe grinder pump. Odors associag~ with small units of this
type occur primarily during periods of hot weather when the pump is utilized infrequently. Bacterial scum
be~'ns to reproduce along the surface of the vault wa~r. ff leR undisturbed, this bact~al scum can
produce odors. The mix-flush valve is acmal~ not by liquid level sensors, but by time intervals
programmed into the control palaeL The mix-flush valve is typically ac~mlted oncg every 6 to 15 hours.
The mix-flush valve simply mixes the standing water for 20 to 60 seconds. This mixing destroys the
formation of the bacterial scum ami the source of the odors.
We hope we hav~ satisfactorily addressed your concerns with regard to this projec~ If not, please contact
us with your concerns or questions.
Sincerely,
_ _.~un D' Landes' P'E'
cc: Terry Holmes
File
1107 E. 1st Street · Fort Worth, Texas 76102 · Tele (817) 870-1220 · Fax(8i7) 870-1292