1240815MAINTENANCE MANUAL rcd 3 12 2026

Part II- Field Manuals Preventative and corrective maintenance shall be performed to maintain the function of stormwater management measures, including repair or replacement of the structure; removal of sediment, debris or trash; restoration of eroded areas; snow and ice removal; fence repair or replacement; restoration of vegetation; repair or replacement of non- vegetated linings, and removal of rodent/wildlife and repair/restoration to damaged affected areas caused by them. 1. INLETS—In parking lots and driveways, rain (and melting snow) will travel across the ground as runoff to be collected into an underground piping system, by first dropping through metal grates into concrete boxes called inlets. The inlets have specially designed grates to prevent large pieces of debris and trash from getting into the inlet and pipes. All structures should be periodically inspected for debris and clean as needed. 2. PIPES—The runoff travels underground through the pipes to a point of discharge. These pipes are usually made of reinforced concrete (RCP), high density polypropylene (HDPeP—usually black plastic), or polyvinyl chloride (PVC—usually white plastic). Most pipes are of solid wall construction to transport runoff water or to be used to temporarily detain water as part of the detention system. Other pipes may be perforated, which can be used to let water drain out through the holes into the surrounding ground or water from the ground can flow into the pipes depending on soils, ground conditions, elevations, and so forth. Pipes should be periodically inspected for debris and clean as needed. Also the pipe system should be flush periodically in order to keep the sediment from accumulating inside the pipes. 3. DISCHARGE CONTROL STRUCTURES—The pipes and basins then flow to the “heart” of the stormwater management system—the discharge control structure. Runoff water from underground pipes or directly from the basin flows into this box-like device, which may have trash racks and top grates to

ischarge control structure. Runoff water from underground pipes or directly from the basin flows into this box-like device, which may have trash racks and top grates to further eliminate any debris that may have made it all the way through the system to this point. The box (usually of precast concrete or concrete block construction) may have an additional shorter wall inside with a small opening at the bottom. The small opening in the concrete wall (often covered with a metal plate with a hole in it) is designed to slow down the rate of water leaving the developed site in order to prevent flooding downstream properties. In larger rainstorms the runoff water will flow into the basin and pipes faster than it can flow out and will begin backing up creating a temporary pond. In even larger storms the runoff water may flow over the top of the discharge control structure grates—however, this is all accounted for in the design calculations. The discharge structure should be checked for debris and maintain cleaned so it can function properly. 16