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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14 Table 1: Inspection and Maintenance Provisions for Sand Filters INSPECTIONSFREQUENCY OF MAINTENANCE ACTIVITIES Upon • If a pretreatment grass filter strip has been built,water twice a week until the completion of construction grass become established (commonly 6-8 weeks), depending on rainfall. • Maintain any grass at the perimeter of the sand filter to a height of approximately six to eight inches. • Check inlet, outlet, and conveyance system for any obstructions or clogging. Once every Remove accumulated grit, leaves, and debris and dispose off-site. quarter • Remove any trash present on the sand filter surface. • Inspect for prolonged ponding and bare or eroding areas and make adjustments as necessary. Twice during • Remove any vegetation growing on the surface of the sand filter preferably by the growing hand. season • Skim the first inch of sand media. Annually • If a sedimentation chamber is present, pump out oil and grit. Structural Integrity • Replace or repair any cracked, separated or damaged inlet pipes, outfalls, or other structural elements. • Remediate bare soils or erosive gullies by regrading the soil to remove the gully, plant ground cover and water until it is established. • If erosion has occurred within the forebay or pretreatment area, provide additional erosion protection such as reinforced turf matting or riprap. Functionality • Sediment Accumulation As Needed o Maintain stable ground cover in the drainage area. (Typical o Sweep or vacuum sediment on pavement in the contributing drainage area. Problems) o If sediment has accumulated in the pre-treatment area to a depth greater than six inches, remove the top few inches of drainage media and dispose of it in a location where it will not cause impacts to the SCM or a stream. Search for the source of the sediment in the drainage area and remedy the problem. • Filter Media Failure o If water is ponding on the surface for more than 24 hours after a storm event, check to see if the underdrain collection system is clogged and flush if necessary. It water still ponds, remove the top few inches of filter bed media and replace. If water still ponds, consult an appropriate professional. All the sand filter media may need to be replaced.