Construction sites are a significant contributor of sediment pollution that impacts our streams, rivers, and lakes. Sediment is the #1 stream pollutant in Tennessee. When sediment is deposited into these waterbodies, it reduces the amount of sunlight reaching aquatic plants, clogs fish gills, smothers aquatic habitat and spawning areas, and impedes navigation. It also increases flooding as it fills in the streambed, river or lake reducing its capacity to carry or store stormwater.
How do we keep sediment from leaving construction sites?
The State of Tennessee Department of Environment and Conservation (TDEC) requires a Construction General Permit for any land disturbance over one (1) acre or smaller if part of a larger development (such as a subdivision). As part of the submittal the Owner/Contractor must provide a Stormwater Pollution Prevention Plan (SWPPP) which details how they will prevent sediment from leaving the site while under construction and permanent stormwater measures after construction is complete. The Town of Collierville Engineering Inspectors monitor these sites on a weekly basis to make sure the SWPPP is being followed and is effective.
Common Construction Best Management Practices (BMPs)
A geotextile stretched between wooden or metal stakes which provides a barrier to keep polluted waters from leaving the construction site. Sediment is captured by silt fences primarily through ponding of water and settling.
A point of entrance/exit to a construction site that is covered by rock to reduce the tracking of mud and dirt onto public roads by construction vehicles.
Permeable barriers installed around an inlet to filter runoff and remove sediment prior to entering the storm drain. Inlet protection can be constructed from silt fence, inlet filters, straw wattles, or other materials.
A temporary pond created to capture sediment from leaving the construction site. The outlet is closed to restrict sediment laden water from leaving the site. Once the pond reaches near capacity, a flocculant is mixed into the water which causes the sediment to settle to the bottom of the pond. The clean water is pumped out of the pond into the storm sewer system.