Straw blankets now in stock. Erosion Control Blanket S31 is a short-term straw fiber erosion control blanket designed for use on mild slope and channel applications requiring erosion control for up to 12 months depending on moisture, light, and environmental conditions. The blanket is sewn together on 1.5 inch centers. The S31 meets all requirements established in the FHWA FP-03 as a Type 2C erosion control blanket for use on slopes with gradients not exceeding 3:1 (h:v) and has been tested by the National Transportation Product Evaluation Program. The S31 comes packaged in clear shrink-wrap with a yellow band and includes installation instructions