W Sandy Lk Addn-CS041012 (2)· Hal ff Associates, Inc.
ENGINEERS ARCHITECTS SCIENTISTS PLANNERS SURVEYORS
8616 Northwest Plaza Drive
Dallas, Texas 75225-4292
{214) 346-6200
Fax (214) 361-5573
MEMORANDUM
TO:
The City of Coppell
Attn: Keith Marvin P.E.
DATE: October 12, 2004
AVO: 21905
FROM:
Clint Philpott, E.I.T.
Emaih cphilpott @halff.com
PROJECT: Sandy Lake Road Addition
SUBJECT: Response to Second Submittal Review
The plans submitted today have been revised based upon the September 16 comments from the city. Attached
are the comments for reference. If you have any question, please contact me or David Littleton. My number is
214-346-6200.
Grading Plan
1. Where the additional grading out side our property is needed, we have a mutual access agreement with
the adjacent property. The agreement allows us to build the mutual access road per plans. A copy of the
agreement is included.
Drainage Area Map
1. The overall drainage area map shows the flow into the culvert along SH 121 (See Sheet C3.1A)
2. The detention volume calculation is now shown on the plans. Previously another method was used. Now
using the rational method and the amount of storage, a larger flow into the system was calculated. The
hydraulic design has been change for the increased flow in the west box culverts and the channel.
Attached is a worksheet showing, the amount of flow into each inlet and the needed open area of the
inlets. A one grate inlet has an area of 1.24 square feet. The flow into the storm system will be controlled
by the inlet capacity.
2A. We have added tables to Sheet C3.1A indicating the various flow conditions for the channel. Please note
that these tables use a longer time of concentration and do not consider detained flow.
Storm Drain Channel
1. A note has been added to C3.6 to coordinate temporary outfall at existing box culvert outlet.
Storm Drain Channel Sheet 2
1. The bottom of the channel will be grassed earth with an erosion control blanket. A note has been added
to the riprap detail on the type of control
2. The plans now show the sanitary sewer relocated outside the channel limits. This has been confirmed
with the adjacent property owner and shown on Sheet C4.1.
Storm Drain Plans
1. A profile has been made of the culvert along SH121.
Water and Waste Water Plan
1. The note requested has been added.
[] Attachments:
Copies: X File
Orifice Flow Eqn. - Q: CA(2gh)~/2
Given: C: 0.6
g (ft/s2) = 32.2
Find: Area req. ft2
SD-11 One Grate Inlet
8 Openings @ 1"x1'-10.25"
Area = 1.24 ft2
Inlet Q (cfs) h (ft) A (ft2) Size Grate
A-1 7.00 1.2 1.327 1 Grate
A-2 3.00 1.2 0.569 1 Grate
A-3 5.00 1.2 0.948 1 Grate
~,-4 6.00 1.2 1.138 1 Grate
A-5 5.00 1.2 0.948 1 Grate
A-6 5.00 1.0 1.038 1 Grate
A-7 5.00 1 1.038 1 Grate