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HomeMy WebLinkAbout008_Thriftway Stormwater Maintenance PlanINSPECTION AND MAINTENANCE FOR STORMWATER MANAGEMENT FACILITIES The Property Owner shall be responsible for the maintenance of the stormwater drainage facilities included within S. 1/2, SW 1/4, SW 1/4, SW 1/4 of Sec. 35, Certificate of Survey No. 2970. Storm Water Facilities: 1. Drainage swales slope toward retention and detention ponds to collect storm water runoff and channel it to the retention or detention pond. 2. Pipe Networks convey storm water to different discharge locations underground. 3. Outlets are points where storm water exits a pipe network. 4. Retention Ponds are storm water collection facilities that collect and temporarily store runoff and allow it to infiltrate and evaporate 5. Retention Chambers are underground facilities that collect and temporarily store runoff and allow it to infiltrate 6. Detention Chambers are unground facilities that collect and temporarily store runoff and release stormwater to existing stormwater facilities at a given flow rate 7. Drywells are underground retention facilities that use washed rock to store and infiltrate runoff Post Construction Inspection: 1. Observe that drywells, and catch basins are clear of any material or obstructions in the drainage slots. Inspect these structures to insure proper drainage following a storm event. Immediately identify and remove objects responsible for clogging if not draining properly. Semi-Annual Inspection: 1. Check retention facilities three days following a storm event exceeding ¼ inch of precipitation. Failure for water to percolate within this time period indicates clogging or poor-draining soils. Clear any clogs and replace any poor-draining soils with well- draining gravely soils. 2. Check for grass clippings, litter, and debris in drainage swales, catch basins, dry wells, culverts and retention ponds. Flush and/or vacuum drywells, underground storage chambers or storm water pipes if excessive material is observed in the facilities. Standard Maintenance: 1. Remove sediment and oil/grease from retention facilities. 2. Inspect and remove debris from drainage swales, catch basins, dry wells, and retention ponds. Use a vacuum truck to clean catch basins and dry wells. 3. Monitor health of vegetation and revegetate as necessary to maintain full vegetative cover. 4. Inspect for the following issues: differential accumulation of sediment, drain time, signs of petroleum hydrocarbon contamination (odors, oil sheen in pond water), standing water, trash and debris. Sediment accumulation: In most cases, sediment from a retention pond or underground stormwater chambers does not contain toxins at levels posing a hazardous concern. However, sediments should be tested for toxicants in compliance with current disposal requirements and if land uses in the drainage area include commercial or industrial zones, or if visual or olfactory indications of pollution are noticed. Sediments containing high levels of pollutants should be disposed of in accordance with applicable regulations and the potential sources of contamination should be investigated and contamination practices terminated. Equipment Type/Access: Ponds and underground infiltration systems will be cleaned using vacuum trucks or other equipment. All vacuum trucks will access the site through the proposed drive aisle and parking lot, as well as along Davis Lane and Baxter Lane. Special care should be taken when accessing drywells from Davis Lane and Baxter Lane to prevent damage to existing landscaping and utilities. Cost Estimate: Depending on the amount of rainfall in the given year, the cost to maintain the stormwater infrastructure will vary. It is estimated that the underground stormwater chambers and drywells will need to be have sediment removed once per year, with an estimated cost of $5,000 to do so. The property owner will be responsible for financing the maintenance of the stormwater infrastructure.