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Keith Marvin - Fwd: RE: Freeport Parkway - Floodplain Reclamation (TNP# CPL07399)
From:Michael Garza
To:Keith Marvin
Date: 8/1/2011 8:26 AM
Subject:Fwd: RE: Freeport Parkway - Floodplain Reclamation (TNP# CPL07399)
fyi
>>> On 7/29/2011 at 5:01 PM, in message <99A53B3263DCA341B0BCC8F018D83D0105212C95@CORPEXS.TNPINC.COM>, "Niraj Acharya"
<nacharya@tnp-online.com> wrote:
Michael,
I had an opportunity to do some additional modeling based on your questions below. This is what I’ve determined:
1.) Is the approximation of 7500SF the maximum amount of land that can be reclaimed?
Yes and no. 7500sf represents the land reclaimed from the floodplain for the option that was shown. As discussed in Number 2,
below, more could be reclaimed, but would likely cause negative impacts.
2.) Would filling beyond the point blocking the proposed bridge opening cause an increase in water surface elevation? Is this the furthest
location that the retaining wall can go without increasing that water surface elevation?
The encroachment limits shown on the exhibit are maximized to avoid increases in water surface elevation (WSEL) and velocity
(i.e. avoid creating erosive conditions). Pushing the wall out further into the floodplain does not increase the WSEL. However,
there is a marked increase in channel velocities that would necessitate placing erosion protection along the channel for the entire
length of the wall (and possibly more). In addition to this erosion hazard, the price of the wall would likely increase.
3.) Do you have an approximate cost difference in option 1 vs. option 2? The homeowner would be responsible for that wall so I would
just like to get an approximate cost.
I have put together some very preliminary costs for Option 1 (earthen fill/grading) and Option 2 (wall) that were presented in the
exhibit.
Option Item Cost
Option 1 (Earthen): Excavation, fill, and grading $50,000
TOTAL: $50,000
Option 2 (Ret. 1150 sf of wall
Wall):face$40,000 to $58,000 (depending on wall type, i.e. gabions, modular block, etc.)
Excavation, fill, and grading $35,000
TOTAL: $75,000 to $93,000
I hope this adequately answers your questions. Please feel free to call/email me if you have any further questions. Have a great weekend!
Regards,
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Niraj
From: Michael Garza [mailto:mgarza@coppelltx.gov]
Sent: Wednesday, July 27, 2011 2:49 PM
To: Niraj Acharya
Cc: Kyle Dykes; Mark Holliday
Subject: Re: Freeport Parkway - Floodplain Reclamation (TNP# CPL07399)
Niraj,
A couple of question that I have and I anticipate the homeowner asking.
1.) Is the approximation of 7500SF the maximum amount of land that can be reclaimed?
2.) Would filling beyond the point blocking the proposed bridge opening cause an increase in water surface elevation? Is this the furthest
location that the retaining wall can go without increasing that water surface elevation?
3.) Do you have an approximate cost difference in option 1 vs. option 2? The homeowner would be responsible for that wall so I would
just like to get an approximate cost.
I appreciate your help.
Thanks,
Mike
Michael Garza
Engineering Dept.
City of Coppell
Office: 972-304-7019
Fax: 972-304-3570
Please consider the environment before printing this e-mail
>>> On 7/26/2011 at 5:01 PM, in message <99A53B3263DCA341B0BCC8F018D83D01051CC879@CORPEXS.TNPINC.COM>, "Niraj
Acharya" <nacharya@tnp-online.com> wrote:
Michael,
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Per your request, we have evaluated the use of a retaining wall for the purposes of floodplain reclamation on the property situated at
the northeast corner of Freeport Parkway and Cottonwood Branch.
After further analysis, our recommendation would be to construct a retaining wall along the same horizontal limits of fill previously
shown. This is due to the fact that filling beyond this point would effectively block the proposed bridge opening.
However, the analysis also indicates that if a retaining wall were to be constructed, there would no longer be a necessity for additional
channel grading below the reclamation limits. Furthermore, the proposed wall does not adversely impact water surface elevations
along the channel, or the proposed bridge design.
I have attached a revised exhibit which depicts both reclamation options. Please don’t hesitate to contact Mark Holliday or myself if you
have any questions.
Regards,
Niraj
_______________________________________
Niraj A. Acharya, PE, CFM
StormWaterGroup
TEAGUE NALL AND PERKINS, INC.
TBPE Firm No. F-230
1100 Macon Street, Fort Worth, Texas 76102
817.336.5773 (main), 817.336.2813 (fax)
nacharya@tnp-online.com
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file://C:\Documents and Settings\radloo\Local Settings\Temp\XPgrpwise\4E366341City_of...8/5/2011