DR8601-CS 860808ESPEY,
HUSTON &
ASSOCIATES, INC.
Engineering & Environmental Consultants
August 8, 1986
Mr. Ed Powell, City Engineer
City of Coppell
P.O. Box 478
Coppell, Texas 75019
Re: Parkwood Drainage Channel
EH&A Job
No. 8565-01
Dear Mr. Powell:
As authorized by the City of Coppell, Espey, Huston & Associates, Inc. (EH&A)
has undertaken surveying and preliminary engineering necessary to develop
alternatives and associated cost estimates for the repair of a drainage
channel located within the Parkwood Addition. This letter report outlines
our studied alternatives and cost estimates. Typical cross-sections, plan
views, profiles and preliminary cost estimates are included as attachments
to this letter report.
In addition to the alternatives identified in the attachments, we also
investigated the possibility of placing a drop structure at the point where
erosion has begun rather than the outfall into the lake. We found that
this created a need for structural lining of the channel from the drop
structure to the lake, increased the safety hazard to vehicle traffic on
the adjacent alleys and to children from the adjacent neighborhoods, and
would become a settlement trap once the lake had a normal pool elevation.
For these reasons, we discarded this alternative and concentrated on replacing
the channel at the original design depth and cross-section.
We have included cost estimates for an 8' pilot channel lining, lining of
the channel bottom, and for concrete lining of the bottom and the side slopes
to a point approximately 1' above the lO0-year flood elevation. Based on
discussions held at our last meeting, we did not include any seeding or
sodding in our estimates.
Realizing that this situation called for the most cost effective solution,
we confined our alternative outfall structures to two types, drop structures
and spillways. While both structures could be made of concrete or gabions,
the drop structure has a vertical face while a spillway has a sloping face.
Based on our experience, the most economic design has the entire elevation
change happening in one structure rather than a series of small structures.
Our recommended alternative would be the earthen channel with the 15' concrete
bottom and the concrete spillway. We also recommend that the City's Parks
Department seed or sod the slopes to obtain a vegatative cover.
333 West CampbeLl Road, Suite 400, 4th Floor · Richardson, Texas 75080 · (214) 669-9600
Mr. Ed Powell, P.E.
Page 2
_SPEY, HUSTON & ASSOCIATES, INC.
EH&A is pleased to present this report and looks forward to meeting with
you to discuss this in greater detail on August 11, 1986. After all parties
have agreed on a preferred alternative, EH&A stands ready to prepare final
construction documents.
Sincerely,
Murry ~. Bu)lio,, P.E.
Assist~ivision Manager
MAB/vn
CC:
Mr. Paul Phy
Sam Wyse
Tom Wise
Mayor Lou Duggan
Jeff Hawkins
Wayne Ginn
ALTERNATIVE 1
EARTHEN CHANNEL WITH $' CONCRETE PILOT CHANNEL
Item
No.
Description Quantity Unit P rice
EXCAVATION 86 C.Y
EMBANKMENT 2346 C.Y.
5" CONC RIPRAP 34.6 C.Y.
PIPE 30" RCP 8 L.F.
SLOPE HDWL W/BACKSPLASH 14 C.Y.
SUBTOTAL
2.00'
5.00
252.00
40.00
252.00
Amount
$ 172
11,730
8,719
320
3t520
$ 24,469
ALTERNATIVE 2
EARTHEN CHANNEL WITH CONCRETE BOTTOM
Item
No.
1
2
3
#
5
Descr.iption Quantity Unit Price
EXCAVATION 86 C.Y
EMBANKMENT 23#6 C.Y.
5" CONC RIPRAP 6t~.8 C.Y.
PIPE 30" RCP 8 L.F.
SLOPE HDWL W/BACKSPLASH 1# C.Y.
SUBTOTAL
$ 2.00
5.00
252. O0
t~O.O0
252.00
Amount
$ 172
11,730
16,330
320
3t520
$ 32,072
ALTERNATIVE 3
EARTHEN CHANNEL WITH CONCRETE LINING
· I tern
No.
1
2
3
#
Description
EXCAVATION
EMBANKMENT
5" CONC RIPRAP
PIPE 30" RCP
SUBTOTAL
Quantity · Unit
86 C.Y
23t~6 C.Y.
197 C.Y.
8 L.F.
Price
2.00
5.00
252.00
#0.00
Amount
$ 172
11,730
~9,6~4
320
$ 61,866
EHAi S-S.:Sfi/ # 8565 3 i ·
OUTFALL ALTERNATIVES
Item
No. Description
Quantity Unit Price
Amount
1. SPILLWAY STRUCTURES
GABIONS
I 18" BLANKET
2 2" GROUT
3 3 X 3 BASKET (TOE)
SUBTOTAL
208 C.Y.
17 C.Y.
60 C.Y.
135.00
8.00
135.00
$ 28,080
136
8)100
$ 36,316
CONCRETE
5"CONC RIPRAP
SUBTOTAL
112 c.Y $
252.00
28)224
28,224
2, CONCRETE DROP STRUCTURE
1 EXCAVATION (STRUCTURAL)
2 STRUCTURAL CONCRETE
3 CONC RIPRAP
SUBTOTAL
400 C.Y.
310 C.Y.
17 C.Y.
7.00
300.00
252.00
$ 2,800
93,000
4,284
$ 100,084
EHAIS-8-86/#856531