CMA Engineering, Inc.

 

Stormwater Detention Ponds

In every type of development project, the addition of impervious cover has a significant impact on stormwater flow into adjacent streams and rivers. Increased stormwater peak flow rates can overwhelm downstream land, culverts, and bridges, as well as erode existing waterways. Part of any development project planning must include the management of peak stormwater flow. To protect life and property, regulations require that post-developed peak flow rates be reduced to less than or equal the pre-development conditions.  One way to achieve this is through on-site detention ponds.  CMA has designed many detention facilities that meet the required flow rate reduction while also reducing cost and disturbance of land. 


One method used in the HighPointe subdivision to detain stormwater was to elevate the planned roadway, Cool Spring Way, so that the embankment serves as the detention pond berm.  This design also incorporated existing floodplains, and created an inexpensive wet-weather only pond.  This single berm creates the detention pond that serves the entire HighPointe community.

HighPointe Subdivision Cool Springs Way elevated across Hollow Springs.

HighPointe Subdivision detention culverts under Cool Springs Way

Another method to detain stormwater is to design the stormwater capture volume to be located above a water quality wet pond.  For Ledge Stone, a permanent pool elevation of the wet pond was designed to have 3 feet of available volume for detention located above.  In this method, the pond can serve as an amenity to the development, as well as perform the required peak stormwater flow detention with only a slight increase in cost and land disturbance.

Ledge Stone Water Quality and Detention Pond at permanent pool elevation