Real World Testing of Erosion Control Systems on Construction Sites.

Construction sites offer unique challenges for controlling erosion due to the poor fertility of the graded soil and the relatively steep slopes that are built.   The traditional method for establishing vegetation is apply the seed, lime, and fertilizer followed by a cover of straw with tackifier.  There are many other ground covers available, mostly erosion control blankets (ECBs) or hydraulically applied fiber, or hydromulch.  Testing under controlled conditions in rainfall simulators provides a measure of resistance to erosion, but provides no information on vegetation establishment.  We conducted field tests of various ground covers on actual construction sites at over a dozen locations in North Carolina to determine efficacy for grass establishment and in some cases erosion rates.  The slopes were between 3:1 and 2:1 and the soils varied widely in texture, but all were subsoil materials.   As expected, erosion rates were highly influenced by local factors, including weather, soil material, and slope length.  In general hydromulch and ECBs reduced erosion more than straw, but not in all cases.  The addition of polyacrylamide (PAM) usually reduced erosion by 50% or more compared to the ground covers alone.  The influence of the ground covers on grass establishment and growth was not as clear, with the best product in one test being the worst in another test.  Failures, as measure by achieving sufficient vegetative cover (>50%), were frequent and were likely due to lack of moisture.