4.5.12 Structural Detention Facility O & M Plan <br />Structural Detention Facilities are flow control devices. Structural detention facilities <br />include tanks, vaults, and oversized pipes designed to fill with stormwater during large <br />storm events and slowly release the runoff over a number of hours. There are numerous <br />components to each system; inlet pipes conveying stormwater into the detention facility, <br />detention chambers storing stormwater during storm events, and outlet drains restricting <br />the flow out of the detention chamber. <br />Underground Structural Detention Facilities shall be inspected quarterly and within 48 <br />hours after each major storm event. <br />Training and/or Written Guidance information for operating and maintaining Detention <br />Facilities shall be provided to all property owners and tenants. A copy of the 0 & M Plan <br />shall be provided to all property owners and tenants. <br />Inspection Logs shall be kept by the facility owner demonstrating the following items have <br />been inspected and are being maintained properly: <br />• Access to the detention facility shall be safe and efficient. Obstacles preventing <br />maintenance personnel and/or equipment access to the components of the facility <br />shall be removed. <br />• Debris/Sediment that is found to clog the inlet shall be removed, tested, and <br />disposed of in accordance with applicable federal and state requirements. <br />• Detention Chamber shall be cleaned out yearly or after an inch of sediment has <br />accumulated and inspected for cracks or damage. Grit and sediment that has settled <br />to the bottom of the chamber shall be removed during each cleaning. Cleaning shall <br />be done without use of detergents or surfactants. A pressure washer may be used if <br />necessary. <br />• Inlets shall be' cleared when conveyance capacity is plugged to ensure unrestricted <br />stormwater flow. <br />• Outlets shall be cleared when 50% of the conveyance capacity is plugged. <br />• Vegetation such as large shrubs or trees that are likely to interfere with detention <br />facility operation shall be identified at each inspection then removed. <br />Spill Prevention Measures shall be exercised when handling substances that contaminate <br />stormwater. Releases of pollutants shall be corrected as soon as identified. <br />Non-Chemical Pest Control measures shall be taken to prevent development of insects, <br />mosquitoes, and rodents. <br />Stormwater Management Manual 4-29 <br />Eugene 2014 <br />