Agenda - Public Works Committee - 08/20/2024

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APPENDIX Definitions Drainage structures—Catch basins, control structures, flared ends, manholes, and structural pollution control devices. Sump catch basins and sump manholes are constructed with a sump structure for collection of sediment and debris. Drainage pipes—Storm sewer and culverts. Dry retention basins—A shallow, dry basin with an outlet at the invert of the basin. Dry retention basins are constructed to attenuate peak discharges and temporarily detain runoff to promote sedimentation. Wet detention basins—A shallow basin that maintains a permanent pool of water by using an elevated outlet control structure. Stormwater is treated through sedimentation and biological uptake of pollutants. Filtration basins—Ashallow basin or sand filter with engineered or amended soil and an under- drain system. The basin detains stormwater and allows it to infiltrate through the soil, sand or engineered media. Treated stormwater is directed to the receiving water via the under-drain system. Infiltration basins—A shallow basin in permeable soils that detain and infiltrate stormwater. There is rarely an under-drain system unless needed to provide maintenance access. Infiltration basins use the natural filtering ability of the soil to remove pollutants from stormwater runoff. If problems are identified during inspections a Work Order is prepared in accordance with the following guidelines. Replace surface soil or vegetation as needed to maintain a layer of permeable soil or a dense cover of non-woody vegetation in the base of the infiltration area. Correct any structural deficiencies that interfere with the function of the basin. Remove undesirable vegetation, such as woody vegetation. Swales, filter strips or ditches—Swales, filter strips or ditches are constructed to direct or convey stormwater runoff. They should be planted with vegetation that will maintain the structure and resist erosion. If problems are identified during inspections a Work Order shall be prepared in accordance with the following guidelines. Cleanout sediment when it blocks culverts or obstructs the pipe or flow of stormwater. Stabilize and re-seed when erosion gullies are more than one foot deep. Mow to remove vegetation that obstructs flow and to maintain desirable vegetation. These linear channels are vegetated to assist in decreasing runoff velocity and promote infiltration and physical filtration. Some may incorporate rock checks to reduce the slope of the channel.