Agenda - 06-21-2022; 8-l - Orange County Southern Campus Expansion Stormwater Operations and Maintenance Plan Agreement with Town of Chapel Hill (2501 Homestead Road, Chapel Hill)

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11 o Ensure appropriate plant maintenance is occurring. o A one-time fertilizer application to establish ground cover is permissible if a soil test indicates it is necessary. No portion of the dry detention system shall be fertilized after the initial fertilization that is required to establish the vegetation. o Consult with the Town of Chapel Hill Stormwater Management Division before any aquatic herbicide is used and site specific approval is given. • If vegetation coverage is not achieved, add reinforcement planting to maintain desired vegetation density and/or split out perennials to increase plant cover. Desired vegetation coverage is 50%after 2 growing seasons and 75%after 5 growing seasons • Remediate bare soils or erosive gullies. o In perimeter areas, regrade the soil to remove the gully, plant a ground cover and water until it is established. If soil test shows that the pH has dropped, dolomitic lime shall be applied as recommended. o Within the pretreatment area, provide erosion control devices such as reinforced turf matting or riprap to avoid future problems with erosion. Filter Media Failure • If the bioretention area shows signs of clogging, identify source of sediment and work to remediate or eliminate it before proceeding with the following maintenance tasks. o Flush the underdrains and capture any sediment before it enters any downstream stream or storm drain system. o Conduct one or more test pits to determine the depth of soil contamination. o Before remediating the filter bed, remove and temporary store any plants. o Remove the accumulated sediment to the point where sediment is no longer observed in the soil media plus an additional 2 inches of soil. Either replace with new media or till 2 to 3 inches of sand into the upper 8 to 12 inches of soil. o Dispose of any removed soil in an appropriate off-site location. o Replant and mulch the area of disturbance. • If soil test shows that the pH has dropped, dolomitic lime shall be applied as recommended. • If the soil test shows that heavy metals have accumulated,the toxic soils shall be removed, disposed of properly, and replaced with new planting media. Structural Integrity • Replace or repair any cracked, separated or damaged inlet pipes, drop inlets, overflow structure, outfalls, impoundment walls or other structural elements. Functionality • If flow is bypassing the pretreatment area, regrade to route all flow to the pretreatment area. • Sediment Accumulation o Maintain stable ground cover in the drainage area. BIORETENTION PAGE 3 OF • • •