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HomeMy WebLinkAbout2016-21NMCWD/2016-21 Declaration attachment C – Stormwater 1 ATTACHMENT C STORMWATER MANAGEMENT FACILITY MAINTENANCE SCHEDULE 1. All stormwater retention, detention and treatment basins must be inspected at least once a year to determine that basin retention and treatment characteristics are adequate. A storage treatment basin will be considered inadequate if sediment has decreased the wet storage volume by 50 percent or dry storage volume by 25 percent of its original design volume. Based on this inspection, if a stormwater basin requires sediment cleanout, the basin will be restored to its original design contours and vegetated state within one year of the inspection date. 2. All grit chambers, sump catch basins, sump manholes, outlet structures, culverts, outfall structures and other stormwater facilities for which maintenance requirements are not otherwise specified herein must be inspected in the spring, summer and fall of each year. Within 30 days of the inspection date, all accumulated sediment and debris must be removed such that each stormwater facility operates as designed and permitted. Contributing drainage areas must be kept clear of litter and vegetative debris, inflow pipes and overflow spillways kept clear, inlet areas kept clean, and undesirable vegetation removed. Erosion impairing the function or integrity of the facilities, if any, will be corrected, and any structural damage impairing or threatening to impair the function of the facilities must be repaired. 3. Volume control facilities and contributing drainage areas must be inspected every three months during the operational period (between spring snowmelt and first substantial snowfall) and monitored after rainfall events of 1 inch or more to ensure that the contributing drainage area is clear of litter and debris, inflow pipes and overflow spillways are clear, inlet areas are clean, undesirable vegetation is removed and there is no erosion impairing or threatening to impair the function of a facility. If sediment has accumulated in a infiltration feature, within 30 days of inspection deposited sediments must be removed, the infiltration capacity of the underlying soils must be restored, and any surface disturbance must be stabilized. Inspection must ensure that sediment traps and forebays are trapping sediment and that more than 50 NMCWD/2016-21 Declaration attachment C – Stormwater 2 percent of the storage volume remains, the contributing drainage area is stable (i.e., no erosion is observed), and inlets and outlet/overflow spillways are in good conditions with no erosion. Maintenance techniques used must protect the infiltration capacity of the practice by limiting soil compaction to the greatest extent possible (e.g., by using low-impact earth-moving equipment). 4. In addition, the applicable requirements above, rain gardens must be kept clean of excess sediment and debris. Healthy plant growth must be maintained in rain gardens by removing dead vegetation in the spring of each year, and the top two to five inches of media must be removed and replaced every three to five years so as not to impede filtration of sediment and oils. 5. Pervious pavers and pervious concrete must be inspected at least once each year after a major storm and otherwise annually; surface openings must be vacuumed in dry weather to remove dry, encrusted sediment as necessary; and broken units that impair the structural integrity of the surface must be replaced. If water stands for an extended period, base materials must be replaced. 6. Underground storage chambers must be inspected at least once a year to ensure that adequate storage capacity remains. Capacity will be considered inadequate if sediment has decreased the storage volume by 50 percent of its original design volume. Accumulated debris and sediment will be removed, and inlet and outlet structures will be cleared of any flow impediments.