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Home My WebLink About009 BIG406MOB Storm Water Maintenance PlanJOB NO. B20-041 MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA JANUARY 2022 406.586.0277 tdhengineering.com 234 East Babcock Street Suite 3 Bozeman, MT 59715 CLIENT ENGINEER Bechtle Architects 4515 Valley Commons Drive, #201 Bozeman, MT 59718 TD&H Engineering 234 East Babcock Street, Suite 3 Bozeman, MT 59715 Engineer: Ahren Hastings, PE ON-SITE STORM WATER MAINTENANCE PLAN BIG406LLC MEDICAL OFFICE BUILDING BOZEMAN, MONTANA BIG406LLC Medical Office Building Storm Water Maintenance Plan B20-041 1 BIG406LLC MEDICAL OFFICE BUILDING – PHASE I STORM WATER MAINTENANCE PLAN PURPOSE AND INTRODUCTION This maintenance plan identifies the recommended maintenance procedures necessary for the proper function of the on-site storm water management system proposed at the BIG406LLC Medical Office Building project in Bozeman, Montana. For the purpose of this plan, the on-site storm water management system includes stormwater conveyance paths and pipes within the property, the retention/detention pond and overflow structure in the northwest corner of the property, and the drainage swale and associated existing culverts running north-to-south on the west side of the property. The maintenance responsibility for the on-site stormwater management system belongs to the landowner. The landowner may delegate routine inspection and maintenance responsibilities to the on-site facility operations management team or may hire a qualified professional entity or individual to perform certain monitoring and maintenance tasks as necessary. A log shall be kept for all required inspections and maintenance. These logs shall be made available to the City of Bozeman Public Works Department for review as requested. A sample maintenance log is included in the attached Appendix. STORM WATER MANAGEMENT SYSTEM The on-site storm water management system includes curb and gutter, drainage chases, roof drains, retention/detention pond, drainage swale, and storm culverts. These various components of storm water management infrastructure are designed to collect, convey, clean, detain, and/or infiltrate storm water runoff that is generated on the property before it leaves the site or enters local waterways. Storm water systems require proper maintenance to prevent sediment clogging, overgrown vegetation, erosion of detention ponds, obstruction of inlets, pipes, and structures, and prolonged standing water. Such issues may result in downstream pollution, unpleasant odors, unsightly areas, nuisance insects, or algae blooms, and must be mitigated. Scheduled inspections, times of inspections, locations inspected, maintenance completed, corrective actions taken, and any modifications or reconstruction performed shall be documented in the maintenance logs to be readily available upon request. Disposal of accumulated sediment must be in accordance with all applicable local, state and federal regulations. Wetlands are not anticipated to be encountered during maintenance activities for the on-site subsurface infiltration facilities. However, maintenance of off-site locations where outlet pipes or overflows discharge to protected water bodies within wetland areas may require wetland or stream bank permitting. If unsure of the regulatory status of wetland features observed at the site, consult the local authorities prior to undertaking any activities that may cause disturbance. BIG406LLC Medical Office Building Storm Water Maintenance Plan B20-041 2 STORM WATER MAINTENANCE PROCEDURES The following maintenance procedures are intended to prolong the life of installed system components and ensure their continued functionality: General Storm Water System Maintenance – 1. Parking lot areas, curbs & gutters, drainage chases, and area drains should be cleared of leaves and other debris once after primary leaf drop in the fall and once after snow melt in early spring at a minimum. This will minimize the potential for debris to enter the system which could lead to premature clogging of structures, reduced storage capacity, and/or blockage of inlets. 2. Inspect the storm drain inlets, overflow structures, and cleanouts, for sediment build-up or clogging and flush/clear as needed. Inspect for snow/ice buildup at least once weekly during winter months and clear the inlet as needed. Do not pile snow over inlets. 3. Snow storage should be performed in designated areas during winter months and should not be allowed to be piled in front of or over inlets. Piled snow around or over the inlets could block early snowmelt run-off from entering the system, possibly causing overflows and icy conditions. 4. Sanding of the parking lots and drive aisles should be done sparingly or avoided completely. Sand or other sediment on the parking lot will likely be washed into stormwater system components which can lead to buildup and reduced capacity or blockages over time. Storm Water Pond Maintenance – 1. Routine Maintenance Activities (every 3 months): a. Mow vegetation around each stormwater pond regularly throughout the spring/summer months. b. Designate a “no-mow” zone at the bottom of the ponds. This area will be trimmed once a year and protected from regularly scheduled grass mowing. Excessive mowing causes debris buildup and compaction of the soils in the bottom of the pond, reducing the pond’s infiltration ability. c. Remove trash, leaves, plant trimmings, grass clippings, pet waste and other debris from the pond area. d. Inspect pond inlets, outlets, and internal dry well grates for any obstructions that would prevent stormwater from entering or leaving the pond and remove obstructions as needed. 2. Annual Maintenance Activities (annually): BIG406LLC Medical Office Building Storm Water Maintenance Plan B20-041 3 a. At the end of each fall, cut plants in the “no-mow” zone to a height of six inches and rake and remove all clippings and leaves. b. Re-establish vegetation on eroded or barren areas of the pond. 3. Long-Term Maintenance Activities (as observed/required): a. Survey the pond elevations to determine the amount of sediment buildup, if any, in the pond. b. Excavate sediment and re-establish the pond to its initial design volume per the construction plans if sediment build-up is found to be greater than six inches or if the pond volume has decreased by more than ten percent. c. Flush sediment from outlet structures/piping and from the outfall location if build- up is observed. Remove sediment build-up from outlet structure or dry well sumps if needed. APPENDIX City of Bozeman Stormwater Basin Maintenance Guide Sample Maintenance & Inspection Log FIGURE 5 Storm Water Facilities Inspection and Maintenance Log Facility Name Begin Date End Date Date Location Facility Description Inspected by: Cause for Inspection Exceptions Noted Comments and Actions Taken Instructions: Record all inspections and maintenance for all storm water facilities on this form. Use additional log sheets and/or attach extended comments or documentation as necessary. Save all completed logs in one place and have them readily available for the City of Bozeman’s review upon request.  Location — Specify the exact location of the facility either by its name, facility ID or physical location.  Inspected by — Note all inspections and maintenance on this form, including the required independent annual inspection.  Cause for inspection — Note if the inspection is routine, pre-rainy-season, post-storm, annual, or in response to a noted problem or complaint.  Exceptions noted — Note any condition that requires correction or indicates a need for maintenance.  Comments and actions taken — Describe any maintenance performed and need for follow-up. FIGURE 1FIGURE 1 FIGURE 6