​Retrofitting Stormwater Detention Basins

Overview: While much of the Cooper Creek Watershed was developed prior to stormwater detention regulations, 35% of the most densely developed portion of the Cooper Creek watershed, the 95-acre commercial/industrial area in the northeast of the Demonstration Watershed, drains through Detention basins.  At the time these detention basins were built, regulations were much more relaxed than they are today – and even today regulations for the design of stormwater detention have been written primarily to mitigate flooding, not erosive flows in local streams.  However, these existing assets can easily be retrofitted to serve that function as well.  In most cases, with only minor tweaks to the outflow structure (see diagram at top of page) these detention basins can be made to release runoff more slowly from storms that would not have caused flooding, but would have caused erosive flash flows in the creek.  Also, by holding back the water a bit longer more water soaks into the soil to be slowly released to the creek, through shallow ground water, so that aquatic wildlife can survive the dry periods between rain events.

​Objective & Time Frame: Ten detention basins have been identified within the Demonstration Watershed (seven within the most densely developed area mentioned above).  The Collaborative is working with local business owners to retrofit these basins.  We are excited to report that every business that we have approached has been open to exploring the possibility of retrofitting their detention basin (if the Collaborative can fund the retrofits with grants).  We are fortunate to have businesses in our community that are willing to be part of the solution!
​The Google Map embedded below shows the location of all ten detention basins that have been identified within the Demonstration Watershed and there retrofit status.  Our objective is to Retrofit all of the detention basin by the end of 2025.

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The dots on this map indicate the locations of detention basin retrofits within the Demonstration Watershed.  Green dots represent basins for which land owner permission and funding have been secured for retrofitting.  Yellows dot represent basins for which land owner permission has been obtained, but funding has not yet been secured for retrofitting.  Orange dots represent basins for which land owner permission has not yet been obtained for retrofitting.

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