Today’s Erosion and Sediment Control Tip: #14

 


The purpose of a Construction Exit Pad is to remove sediment from vehicle tires as a vehicle exits a construction site onto a public road.  There are now some manufactured products for this practice, but the most often “go to” material is ALDOT Coarse Aggregate No. 1 (2.5 to 3.5 inch stone).  Avoid using riprap and smaller stone (i.e. No. 4 or 57 stone).  In order for an aggregate Construction Exit Pad to work as planned, make sure the Construction Exit Pad is installed properly with 8 oz. non-woven geotextile underlayment and to the right dimensions, especially the thickness (6-inch minimum).  The aggregate works to remove sediment from tires when they track “through” the aggregate and also by opening the tire treads to allow mud to drop out.  Aggregate that has been in place for a while will become interlocked or choked with soil.  When this happens the tires will ride on top of the Exit Pad instead of tracking through the aggregate.  In order to correct this there should be more stone added on top, or the exiting stone loosened. If there is a lot of soil being captured by the Exit Pad it may have to be replaced entirely to be effective.  When vehicles enter a construction site, try to keep them in areas without mud to keep soil from attaching to the tires. Soil may still find its way to the road surface and should be removed from the street to keep it out of the storm sewer system.  DO NOT wash the soil from the street into the storm sewer.

Perry L. Oakes, PE
Erosion & Sediment Control Program Coordinator


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