1502 WALL ST IMAGINE CHILDRENS MUSEUM 2022-08-25

Maintenance Standards • Monitor the spray field on a daily basis to ensure that over saturation of any portion of the field doesn't occur at any time.The presence of standing puddles of water or creation of con- centrated flows visually signify that over saturation of the field has occurred. . Monitor the vegetated spray field all the way down to the nearest surface water,or farthest spray area,to ensure that the water has not caused overland or concentrated flows,and has not created erosion around the spray nozzle(s). . Do not exceed water quality standards for turbidity. • Ecology recommends that a separate inspection log be developed, maintained and kept with the existing site logbook to aid the operator conducting inspections.This separate"Field Filtra- tion Logbook"can also aid in demonstrating compliance with permit conditions. . Inspect the spray nozzles daily,at a minimum,for leaks and plugging from sediment particles. . If erosion,concentrated flows,or over saturation of the field occurs, rotate the use of branches or spray heads or move the branches to a new field location. . Check all branches and the manifold for unintended leaks. BMP C240: Sediment Trap Purpose A sediment trap is a small temporary ponding area with a gravel outlet used to collect and store sed- iment from sites during construction.Sediment traps,along with other perimeter controls,shall be installed before any land disturbance takes place in the drainage area. Conditions of Use . Sediment traps are intended for use on sites where the tributary drainage area is less than 3 acres,with no unusual drainage features,and a projected build-out time of six months or less. The sediment trap is a temporary measure(with a design life of approximately 6 months)and shall be maintained until the tributary area is permanently protected against erosion by veget- ation and/or structures. • Sediment traps are only effective in removing sediment down to about the medium silt size fraction. Runoff with sediment of finer grades(fine silt and clay)will pass through untreated, emphasizing the need to control erosion to the maximum extent first. • Projects that are constructing permanent Flow Control BMPs,or Runoff Treatment BMPs that use ponding for treatment, may use the rough-graded or final-graded permanent BMP footprint for the temporary sediment trap.When permanent BMP footprints are used as tem- porary sediment traps,the surface area requirement of the sediment trap must be met. If the surface area requirement of the sediment trap is larger than the surface area of the per- manent BMP,then the sediment trap shall be enlarged beyond the permanent BMP footprint to comply with the surface area requirement. 2019 Stormwater Management Manual for Western Washington Volume ll-Chapter 3-Page 383