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This layer was introduced in 2018 to meet compliancy requirements of National Pollutant Discharge Elimination System (NPDES) for Washington State. The layer is updated through the record drawing data capture program and periodic updates from the Environmental and Utility Services Division. Infiltration trenches are shallow excavations with rubble or stone that create temporary subsurface storage of stormwater runoff, thereby enhancing the natural capacity of the ground to store and drain water. |