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