COMPOST FILTER BERMS: ARE THEY THEORGANIC BMP SOLUTION?

摘要

The Texas Transportation Institute’s (TTI) Environmental Management Programconducted a study for the Texas Department of Transportation (TxDOT) to examine the waterquality from the leachate of compost filter berms and compost/wood mulch filter socks andto determine their structural integrity when used as alternative Best Management Practices(BMP) to straw bales and silt fence. The research was conducted at the TxDOT/TTIHydraulics, Sedimentation, and Erosion Control Laboratory located at the Riverside Campusof Texas A&M University. Three compost types were tested: dairy manure, biosolids and yardwaste. The berm/sock material mixture was 50:50 compost and wood chips. The objectivesof this part of the study were:? to determine the leachate constituents of unseeded and seeded compost filter berms unseeded compost filter socks? to determine the physical limitations and performance capabilities of unseeded and seeded compost filter berms unseeded compost filter socks.Each alternative was tested for two rounds consisting of three repetitions each round.Structural performance and water quality were tested on two soil types, sand and clay, usingpotable water.Results showed that the seeded compost filter berms outperformed the unseededberms in both water quality and structural integrity. Berms and socks with yard wastecompost contributed the least contaminants to the water. The dairy manure compost causeda considerable increase in the nutrient concentration in the water. The biosolid compost bermwas intermediate as far as contaminant input. However, the increase in the concentration ofthe nutrients in the water caused by these berms/socks never increased to a level so as towarrant concern. The unseeded berms had a very high structural failure rate which may havecontributed to their poor water quality performance.Recommendations of the research team (TxDOT has not reviewed the researchresults discussed in this paper) include:? Avoid placing compost filter berms in high velocity, high volume, concentrated flows,I.e., ditches, channels as they are not suitable check dam substitutes.? Because of failure potential, compost filter berms should not be used as mostdownstream BMP or last BMP before runoff enters receiving water.? Compost or wood mulch filter socks should generally be a minimum of 18' diameterwhen used as a substitute for a BMP such as silt fence.