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St. Clair Auto Mall

O’Fallon, Illinois

Stormwater Detention


Auffenburg NIssan


Design Build – Contech 


Kozney Wagner and L Keeley Construction


January 2018

Technical Description:

1,794 LF of 96" Aluminium Steel Type2

The failure of a concrete detention vault that was built in 1996 necessitated the need for a new stormwater detention system. 

The contractor hired to do the work was looking for a solution that would fit the existing footprint and could be designed, fabricated, delivered, and installed in a short period of time.  

Contech engineers designed an underground detention system made from 1,794 LF of 96" Aluminized Steel Type 2 providing 120,527 CF of storage. Using large diameter pipe maximized the storage and reduced cost for the owner. The system consisted of a single header and three 598’ barrels with bulkheads. Each barrel included a 2° angle at one of the joints to ensure the system fit within the desired footprint. 

The city had review and comment authority over the design.  As such, the owner hired an engineer to review the Contech design before submittal. 

Contech designed a system which exceeded the capacity of the failed vault and fit within the existing footprint.  The new system did not require excavation outside the exiting vault and was quickly fabricated and installed without incident.  The contractor, owner, and engineer were pleased on how easy the project went.  In fact, the engineer that reviewed the Contech design has since worked with Contech on two other stormwater detention systems.

Technical Description:

1,794 LF of 96" Aluminium Steel Type2


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