SS9901-CS050713TCB I AECOM
duly 13, 2005
Mr. Rick O'Dell
City of Coppell
P.O. Box 478
Coppell, TX 75019-4409
Subject:
City of Coppell DeForest Road Lift Station Improvements
DeForest & Sandy Lake Wastewater Lift Stations
Project No. SS 99-01
Dear Mr. O'Dell:
This letter is in response to Can-Fer's proposed construction methods for the DeForest Lift Station.
Based on my conversation with you earlier today, Can-Fer plans to pour the lift station walls to a
height of 14 feet above the bottom slab of the lift station (approximate El 430.15). For this pour,
Can-Fer proposes to use the sheet piling as the form for the outside of the lift station walls. This will
result in an increased thickness for these walls; however, the additional concrete will not be reinforced.
It is Can-Fer's intent to leave the sheet piling in place, which is acceptable under the conditions
outlined in the response to RFI No. 9 (remove all shoring within 5 feet horizontally of any piping
entering or existing the lift station). Can-Fer will form the outside lift station wall for the walls above
this first pour. Thus, these walls will be constructed per the design. Under this scenario, the base lip
for the structure, which was designed to counter uplift forces, will be at approximate EL 430.15, as
opposed to at El 416.15 as designed.
The above construction methods were presented to our structural engineer, Wally Burns, for his
review. In his assessment, the increased weight of concrete will more than offset the reduced volume
of soil over the base lip to counteract uplift forces. He had no other concerns with the proposed
construction methods outlined above. Therefore, based on the information provided, Can-Fer's
proposed deviation from the structural design is acceptable. Please feet free to contact me at
972.735.3056 if you have any questions or require any additional information.
Sincerely,
Erika K. CooPer, P.E.
Projoc~neer
c:./,,Ken Griffin, P.E., City of Coppell
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