Soil migration and the buildup of hydrostatic pressure are two of the leading causes of failure in hard armor, such as rock riprap and concrete block systems, along shorelines and waterways. Geotextiles act as a filter to help prevent subsurface soil migration and relieve hydrostatic pressure beneath hard armor erosion control systems. 801 and 401 meet the requirements for Class 1 and Class 3 erosion control geotextiles, respectively, as outlined in AASHTO M288.