Riverchase(5)-CS 881220 (2) GINN, INC. CONSULTING ENGINEERS
December 20, 1988
Mr. Russell Doyle, P.E.
City of Coppell
255 Parkway Blvd.
P.O. Box 478
Coppell, TX 75019
Re: 15" Sanitary Sewer Outfall @ Riverchase
Coppell, TX
Dear Mr. Doyle:
We do not recall nor do we have any correspondence in our files
regarding Nathan D. Maier Consulting Engineers statement in
paragraph #1 of their letter. If Nathan D. Maier Consulting
Engineers could provide us a copy of their correspondence
informing our office specifically of this condition we would
appreciate it and could possibly, at that time, provide further
comment on this issue.
Regarding the TRA correspondence and your question regarding the
construction of this facility, Nathan D. Maier Consulting
Engineers would be the only ones who could provide you the basis
of their design.
On another note, on page two of Nathan D. Maier's letter, it
states that the MacArthur Blvd. connection is very similar as the
subject connection. We would suggest seeing whether or not the
Public Works Dept. has experienced a similar backing up condition
at this location and whether or not it has been a maintenance
problem to date.
Sincerely,
Kevin Peiff~r, P.E.
cc: H. Wayne Ginn, P.E.
Gabe Favre '~~ (~ ~ ~ ~
File 88305
17103 Preston Road ® Suite 100 · LB 118 · Dallas, Texas 75248 · Phone 214/248-4900
CONSULTING ENGINEERS, INC.
Novem~r 14, 1988
~ ~' ..... t~'~ ~, j/ ~'~ ~, ~',~
Mr. Russel~oyle, P.E.
Ci~ of C~pell
255 Pa~ay Blvd. . ~,.
P.O. ~ox 478 ~--~
..-¢ ;:.~- ............ .. _
CoppelI, Texas 75019 ~ ~
Re: 15-inch SanitaF Sewer OuCall at RiverchaseI;¢1/~]' ' ""
NDMNo. 87-12-151 /~/ ~EC
Dear Russell: ~~~-U~'~' ..........
This leffer is in response to a request from Shohre for additional information re¢~t~i¢~ve refer-
enced sewer. I offer the following comments:
1. ~ I have stated ~fore, I agree that this situation is not ideal. Howler, I maintain that this sy~
tern is acceptable and that our design has riffle or no room for improvement, g~en the design
constraints that were presented to us.
I am not alone in my opinion, since the ve~ capable municipal engineering fi~ hired ~ your
ci~ to prote~ its interests has approved our design aEer h~vin~ this condition specifically-
. brought to their a~ention. I have never known them to hesitate to suggest an alternative design
if they felt like one was indicated.
2. The possibility of water escaping from one of the manholes in our proje~ is ve~ remote. I say
this ~use the manholes on the TRA line are lower in elevation than oum. ~is would mean
that the TRA manholes would all ~ flooded flint, since any ba~up in our line would
precipitated ~ a backup in TRA's. Unless the TRA line is woefully undemized, I cannot imagine
this happening.
3. I will repeat my contention that once this line is fully utilized, it will develop a veloci~ at peak
flo~ that will ~ adequate to provide for cleansing. According to all the design theodes I am
aware of, 2 ~s is sufficient to achi~e cleaning veloci~.
4. I ~li~e the angle of ent~ of our line into the ouffall manhole is acceptable. I ~lculated the
difference in head Io~ entering the manhole at 90' vemus 45' downstream, and found it to
in the range of on~ 0.~ feet. ~is is tree ~cause of the ve~ Iow velocities in~ed and the
simila~ of the ~o velocities. Changing the angle of ent~ to ~ existing
line 0.22 feet along the circumference of the manhole. ~e ~li~ th~ ~ ~eates a great deal
of tu~ulen~ and head loss at these velocities is, in my opinion, unsuppodaMe ~ engineering
anal~is.
5. ~ I have pr~iously stat~, E is likely that this line ~11 need ~Hodic flushing ~r to the deve~
opment of R~emh~e. AEhough the t~es paid ~ my ~ient would seem to me to all~ for a
few s~er cleanings, Bo~ h~ agreed, in the interest ~ m~ng ~b sEuation fo~, to pr~
vide for a reasonable amount of i~e~m funding for this pu~os~
It w~ expre~ed at our last meeting that the Ma~hur ~A connexion, in contr~t to th~ one, is fine. I
would like to compare some cham~eHsti~ of each:
ThrEe NorthPark/8800 N. Central Expwy./Suite 300/Dallas, Texas 75231/(214) 739-4741
Mr. Russell Doyle, P.E.
November 14, 1988
Page 2
MacArthur Connection Subject Connection
Size of TRA Line 33" 33"
Slope of TRA Line 0.05% 0.05%.
Slope of Entry Une 0.12% 0.15%
Added Height of Entry 0.89' 0.64'
Flow LineAbove TRA's
I would suggest that these two connections are, in fact, very similar. I would further suggest that other
similar connections exist all over the metroplex, and that with proper maintenance, they provide a level
of service that is quite acceptable.
I hope this discussion will be helpful in your analysis of this situation. If I may proVide anything further,
please let know.
Sincerely,
NATHAN D. MAIER
CONSULTINg'ENGINEERS, INC.
Mike Daniel, P.E.
MD/rdp
· Trinity River Authority of Te.xas I'1
T'~~''~. ~
Central Reglon. I Wa.tewater System ~
H. Nayne GJnn ~ j~ ~ ~ ~,~
C~y Engineer
C~Ly of Coppell
P.O. Box 478
Coppe]l, Texas 750~9
Subject: Central Regional Wastewater System
Coppell Interceptor
Riverchase Point of Entry
Dear Mr. Ginn:
In response to the point of entry request dated April 21, 1987, the Authority
has reviewed the construction standards to be utilized on the point of entry at
station 130+98. The Authority approves your request based upon the information
submitted which includes the construction plans for Riverchase Development by
Nathan D. Maier dated November 1985, but is subject to the following
requirements.
1. Central Regional Wastewater System Engineering Division must be
contacted (214 263-2251 or 214 262-5186) at least 72 hours prior to
construction. If the Authority is not notified the Authority
reserves the right to request the contractor to excavate his work.
All inspections will be performed only by Authority inspectors.
City inspectors are not responsible for Trinity River Authority
property.
2. All points of entry must be constructed within one year after their
acceptance by the Authority. Any alterations to the plans
concerning the Authority's interceptors, meter stations, point of
entries or easements must also be approved by the Authority.
3. A preconstruction meeting with the contractor and the Authority
is required prior to construction.
P.O. Box 531196
Grand Prairie, Texas 75053
(214) Metro 263-2251
N]y 4, 1987
Umyn: ~nn. - ~ '-"'
. Page 2 .
4. All P.V.C. connections shall use A.C. pipe adaptors.
* 5. Connections to the interceptor shall be by sawcut or core drill
method only. Jack han~nering will not be allowed.
6. The Authority's interceptor is encased from Station 129+00 to
Station 131+00. A standard manhole does not apply here therefore a
shop drawing of the proposed manhole must be submitted prior %o
construction of the manhole.
7. The Authority recommends all incoming point of entry flow lines
should be at least above the spring line of the Authority's
interceptor, preferably above the crown. The Authority is not
responsible for overflow resulting from connections below the
recommended distance from the flow line of the Authori~y's
interceptor.
This point of entry shall serve the City of Coppell and will be metered at
Meter station 17.0E.
in addition to this, personnel from the Engineering Division must be onsite
during construction, as well as prior to any backfilling of the Authority's
facility in this area.
If you have any questions or comments please contact me.
Joan B. McNamee
Technical Services Engineer
cc: John K~rkpatrick, Engineering Technician
Janet Vick, Nathan O. Maier