Section R655-11-6C - External Erosion ControlA. All downstream slopes of dams should be protected from erosion by placing armor or seeding with grasses. No planting of any shrubs, trees, or other woody vegetation will be allowed unless it is approved in writing by the State Engineer.B. All downstream groins of dams receiving runoff from adjacent abutments shall be protected from erosion.C. All upstream slopes on dams which impound water for significant lengths of time shall be armored. If rock riprap is used it shall be well graded, durable, and sized to withstand wave action. If the material underlying the riprap is fine grained and subject to erosion, a properly designed filter blanket must be installed. Geotextiles may be used in lieu of the filter blanket at the discretion of the State Engineer.Utah Admin. Code R655-11-6C