Riverchase(5)-CS 881114 CONSULTING ENGINEERS, INC.
November 14, 1988
i NOV 1 4
Mr. Russell/ZJoyle, P.E.
1988
of c pei,
255 Pa)fi(way Blvd. '~'~-
P.O. ox 478
Re: 15-inch Sanitary Sewer Ouffall at Riverchase
NDM No. 87-12-151
Dear Russet:
This letter ia.~..-..~ to a request from Shohre for additional information regarding the above refer-
enced seweli,. Iollr the following comments:
· 1. AS} ~ stated before, I agree that this situation is not ideal. However, I maintain that this sys-
te~'l~ t¢;aj3t~l:f~ and that our design has little or no reom for improvement, given the design
oonetraints that were presented to u~.
I am not alone in my opinion, since the very capable municipal engineering firm hired by your
city to protect its Interests has approved our design alter having this condition specifically
brought to their attention. 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 project is very remote. I say
this because the manholes on the TRA line are lower in elevation than ours. This would mean
that the TRA manholes would all be flooded first, since any backup in our line would be
precipitated by a backup in TRA's. Unless the TRA line is woefully undersized, I cannot imagine
this happening.
3. I will repeat my contention that once this line is fully utilized, it will develop a velocity at peak
flows that will be adequate to provide for cleansing. According to all the design theories I am
aware of, 2 fps is sufficient to achieve cleaning velocity.
4. I believe the angle of entry of our line into the outfall manhole is acceptable.' I calculated the
difference in head loss entering the manhole at 90' versus 45' downstream, and found it to be
in the range of only 0.03 feet. This is true because of the very Iow velocities involved and the
:. similarity of the two velocities. Changing the angle of entry to its existing 85' moves the flow
line 0.22 feet along the circumference of the manhole. The belief that this creates a great deal
of turbulence and head loss at these velocities is, in my opinion, unsupportable by engineering
analysis.
5. As I have previously stated, it is likely that this line will need periodic flushing prior to the devel-
opment of Riverchase. Although the taxes paid by my client would seem to me to allow for a
few sewer cleanings, Bobby has agreed, in the interest of moving this situation forward, to pro-
vide for a reasonable amount of Interim funding for this purpo .s_~
it was expressed at our last meeting that the Mac, Arthur TRA connection, in contrast to this one, is fine. I
would like to compare some characteristics of each:
Three NorthPark/8800 N. Central Fxpwy./Sulte 300/Dallas, Texas 75231/(214) 739-4741
Mr. Russell Doyle, P.E.
November 14, 1988
Page 2
Mac, Arthur Connection Subiect Connection
Size of TRA Une 33" 33"
Slope of TRA Une 0.05% 0.05%
Slope of Entry Une 0.12% 0.15%
Added Height of Entry 0.89' 0.64'
Flow UneAbove 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
CONSULTIN6'ENGINEERS, INC.
Mike Daniel, P.E.
MD/rdp
255 P~W B~d.
P.O ox
~ppell, Te~ 75019
Re: 15-inch ~it~ Sewer O~all at Rive~hase
NDM No. 87-12-151
Desr Russell:
~is le~er is in r~ponse to a reque~ ~m Shohre for additional info~ation regarding the a~ve refer-
enced se~r. I offer the follo~nG ~mme~:
1. ~ I have s~t~ ~fom, I agree th~ this s~ustion is n~ ide~. However, I maintain t~ tbi~ ~-
tern is a~able and thM our d~ign h~ I~le dr no mom for improvement, given the design
co~rain~ that were presented to ~.~
~1 am not alone in my opinion, sin~ the ve~ ~pable municip~ enginee~ng fi~ hired ~ your
~)~ ci~ to prote~ ~ intems~ has ~roved our design a~er ha~ng this condition specifically
bmug~ to their aUention. I have never known them to hesitate to suggest an a~ernative design
~ ~if they fee like one w~ indicated. ..~
precipEated ~ a backup in ~A~. Unless the ~A line is woqfully undemize~l cannot imagine
3. I will repeat my conte~on ~at on~ ~is line ~ fully~lized, it will develop a v~oci~ a~ ~ak
flo~ th~ will ~ adequ~e to pr~de ~r cleansing.~Ac~ing to all the design theories I
aware of, 2 ~ is s~clent to achieve cleaning veloci~.~H ~ZL ~ ~T~
4. .~ I ~li~e the angle of ent~ of our line into the o~all manho~ ~ acceptable. I ~lculated the
~ ~ d~eren~ in head Io~ e~eHng the manhole at 90 vemus 45 d~tream, ~d found it to
in the range of on~ 0.~ ~. ~is ~ tree ~e of the vew I~ vel~i~.i~olve~ and the
t~' simila~ ~ the ~o velo~i~. Changing ~e angle of ent~ to ~ e~sting 85 mov~ the flow
line 0.22 feet along the ~mu~emnce of the manhole. ~e ~li~ th~ this cre~es a great deal
~ tu~ulen~ and head Io~ at these velocities is, in my ~inion, unsuppo~able ~ engineering
anal~is.
5. A- I h~v~ pr~ousN s~ted, ~ is likely that this line ~11 need ~Hodic flushing prior to the devel-
opment ~ R~erch~e. AEhough the t~es paid ~ my client ~uld seem to me to allow for a
~w sewer cleanings, Bob~ h~ agreed, in the intere~ ~ mo~ng this sEuation fo~ard, to p~
vide for a m~ona~e amount of interim ~nding for this pu~os~
It w~ e~re~ed ~ our ,~t meeting that the Ma~hur ~ ~nne~ion, in contrast to ~is one, is fine. ,~/~
would like to compare some cham~efisti~ of each: /
Three NorthPark/8800 N. Central Expwy./Suite 300/Dallas, Texmw 75231/(214) 739-4741
Mr. Russell Doyle, P.E.
November 14, 1988
Page 2 ,
.~~i~ MacArthur Connection Subiect Connection
ize of TRA Line 33" 33"
lope of TRA Une 0.05% 0.05%
lope of Entry Une 0.12% 0.15%
dded Height of Entry 0.89' ~ 0.64'
Flow UneAbove 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. ,~ ~,~'~!~::i0 ~¢~1~ ~.,l~,'~j..~..~'.
I hop~this discussio~will be helpful in your analysis of this situation. If I may provide anything further,
please let know. ~ ~::~r--~ ~ /,~ 4 ~
NATHAN D. MAIER
CONSULTINg'ENGINEERS, INC.
Mike Daniel, P.E.
MD/rdp
Trinity River Authority of Texas I~ I
T~
~n~l R~I~ Wastlwater System ~~
H. ~ayne 6~nn ~ I~ ~ 2 ~.~.~
Ci~ Eng~nee~
C~y of Coppe~]
P.O. Box 478
Coppe]], 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 pl&ns...for Riverchase Development by
Nathan O. Haler dated November 1985, ~ut"t~ sUI)$~t'to the following
requtr~mm~ts.
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 Pra,rie, Texas 75053
(214) Metro 263-2251
.. Wayne Ginn
, ' ....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 hammering 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 Authority's
interceptor.
This point of entry shall serve the City of Coppell and will be metered at
Meter station I?.OE.
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 Kirkpatrick, Engineering Technician
Janet Vick, Nathan D. Maier