Permeameter Testing of Sediment Control Logs and Sediment Retention of Multiple Filter Media Types

Stormwater management is necessary to protect surface waters from pollutants, and significant time and money are currently being expended in the purchase and installation of sediment control logs (SCLs) for this purpose. Application of SCLs are typically as a perimeter obstruction to flow, resulting in the detention, retention, or filtration of runoff. SCLs may also be applicable as flow barriers for slope breaks, ditch checks, and storm drain inlet sediment controls. With the variety of applications, SCLs are becoming more common on construction sites, and manufactures are developing products that incorporate novel filter media on a regular basis. The wide range of available filter media and applications can make it difficult to access which media provide the best pollutant removal for a given site. Many testing protocols exist currently, but these have traditionally been done using open channel flumes and require significant amounts of water and soil. These methods may not represent the flow or field conditions that will be present where the SCLs are used, so the results may be not applicable for specific designs.
We have used a large scale constant head permeameter and compared the testing results to open channel flume measurements to show this is a viable if not preferable alternative testing method. In this effort we have shown a non-linear relationship of the specific discharge in a variety of filter media including straw, coir, wood fiber, rock, and wood compost. The non-linear relationship suggests a non-laminar flow is occurring within the media. We have also demonstrated the height of seepage emerging from the downstream face of a sediment control log is a critical parameter to be measured if an open channel flume is used as a testing apparatus.
This study also includes sediment capture testing and found that sediment control logs are capable of removing 72% to 92% of suspended sediments by weight, mostly through sedimentation, but with as much as 15% removal through filtration depending on the media type.