Erosion and Sediment Control Tip # 28
Pipes that go through an embankment (Sediment Basin, Stormwater Detention Basin, and Drop Structures) often require seepage control to be placed on the outside of the pipe to stop what is referred to as “soil piping”. Soil Piping is the slow removal of soil particles on the outside surface of the pipe and over time creates a tunnel (or pipe) from the outlet end of the pipe to the entrance end of the pipe. Anti-seep collars have historically been used to help with this issue. However, filter diaphragms have been recognized as superior to anti-seep collars as a seepage control measure. A filter diaphragm is a designed zone of filter material (usually well-graded, clean sand) constructed around a conduit to intercept seepage and safely discharge the water to the outlet end of the pipe through a graded filter (without carrying soil particles). For you designers, check out this NRCS reference document. https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=17751.wba