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HomeMy WebLinkAboutA. Stormwater Maintenance 08-10-2020Boulder Creek Apartments Storm Water Maintenance Plan August 2020 The owner shall maintain their components of the storm drainage system in accordance with this maintenance plan and with the applicable City of Bozeman regulations. Maintain a written account of all maintenance and repair activities, such as a log book, for future reference. Every Month, May through October 1. Grass Swales (Lawns): Mow to maintain maximum grass height of 6 inches. Do not allow mulch to discharge or accumulate within 6 feet of the flowline. 2. Storm Drain Pipe and Culverts: Trim and control vegetation near open ends of pipes, to prevent any significant restriction of flow. 3. Surface Detention/Treatment Facilities: Clean the area to keep free of leaves, grass clippings, excess vegetation and debris (paper, cardboard, plastic bags, etc.). If the basin contains water at the time of inspection, return later to clean the area. If ponded water persists over a dry period of a few days, remove cover from the outlet control structure and unclog the orifice (remove debris) to ensure unimpeded flow to the outlet pipe. If sediment sump is full to the orifice level, remove all sediment from the sump. Every Three Months, and Immediately after Major Storm or Snowmelt Events 1. Grass Swales (Lawns and Native Grasses): Walk along each swale to inspect. Clean as needed to keep free of silt, debris, excess vegetation, or any other material that impedes flow. Note areas of ponding and areas with dense weeds or sparse grass cover, and repair within 1 year (see “Repair Procedures” below). 2. Storm Water Manholes and Inlets: Inspect each inlet grate and grated manhole cover. Clean as needed to keep free of leaves, debris, excess vegetation, or any other material (paper, cardboard, plastic bags, etc.) that impedes flow. In winter, ice or snow may remain over inlet grate. If water ponds excessively and creates a problem during snowmelt events, chip ice to provide a drainage channel into the manhole or inlet. 3. Surface Detention/Treatment Facilities: From November through April, continue inspection and cleaning procedures as stated under the “monthly inspection” category above, every three months and immediately after major storm or snowmelt events. Annually 1. Storm Drain Pipe (pipe terminating in manhole or inlet): Pull inlet grates and manhole covers as needed, and inspect each end of each pipe. If observed sediment level in the sump is above the lowest (discharge) pipe flowline, clean all sediment from the pipes and the manhole or inlet sump. 2. Storm Drain Pipe or Culvert (pipe terminating in open ditch or swale): If sediment has accumulated to 3 inches or more above the pipe flowline, remove sediment from the outlet pipe and ditch to provide free drainage and re-seed or sod the area of disturbance. If soil has eroded and un-vegetated rills are visible, re-seed or sod the area. If there are recurring problem areas, repair as stated in “Repair Procedures” below. Every 5 years 1. Surface Detention/Treatment Facilities: Sediment, windblown dust and thatch will build up over time and reduce the storage capacity. Storage capacity is the basin’s airspace volume between two elevations measured in the outlet control structure: the top of the overflow riser, and the flowline elevation of the discharge pipe. Employ a land surveyor or engineer to determine the airspace volume. If it is less than the minimum volume indicated on the approved construction drawings (record drawings), remove excess material and replace landscape materials to originally constructed conditions. Repair Procedures 1. Grass Swales with Dense Weeds or Sparse Grass Cover: Re-seed or sod the area, but first determine and address the source of the problem. Expand irrigation coverage, add soil amendments, fertilize, etc., as needed to improve growth media and grass health, and to control weeds. 2. Grass Swales, Areas of Ponding: Cut sod and re-grade the area for consistent downgradient slope along the swale. Then re-seed or sod the area of disturbance. 3. Pipe Outlet Ditch, Excessive Sediment Accumulation: Cut sod, remove sediment, and re- grade the area to a consistent downgradient slope along the outlet ditch or swale. Extend the re-grading as far as needed to provide positive drainage. Then re-seed or re-sod the area of disturbance. 4. Pipe Outlet Ditch, Erosion: It is recommended to hire a Professional Engineer to address this issue. Another option is to cut sod and re-grade the area, install a permanent, non- degradable turf reinforcement mat (TRM) per the manufacturer’s recommendations, and re-seed the area of disturbance through the TRM per the manufacturer’s recommendations.