Adaptation & Resiliency Toolbox
Stormwater Maintenance Practices
What is it?
MDOT MTA holds a National Pollutant Discharge Elimination System (NPDES) General Permit for discharges from small municipal separate storm sewer systems for approximately 200 facilities including commuter bus, park and ride areas, MARC, METRO and Light Rail stations and other properties. Best Management Practices (BMPs) can be implemented by maintenance staff to improve storm drain capacity and thereby reducing the threat of water damage to various MDOT MTA assets. Simple and routine maintenance operations could lead to more stormwater attenuation capacity and reduce flooding. This measure is intended to provide additional information regarding BMP inspections and common operational practices that may be employed for existing stormwater facilities.
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Related Sections of the Toolbox:
What assets can be protected?
Maintenance Considerations
Inspection costs are minimal and limited to inspection and documentation hours. Maintenance costs can vary widely based on the level and frequency of maintenance required at each facility. It is recommended that stormwater system maintenance cost allocations be developed based on past maintenance activities, needs, and shortfalls, and that adequate fiscal year budget be allocated to satisfy maintenance requirements. In considering cost allocations for maintenance, comparison with the consequences of system failure, flooding, erosion, and roadway and facility damage due to inadequate maintenance is typically useful to illustrate the need for proper maintenance activity funding.
Supervisor/Management Staff Considerations
Supervisors/Management Staff should ensure maintenance staff have a high-level understanding of existing facilities that require routine maintenance, including but not limited to:
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Basic drainage patterns of the asset including locations of storm drain inlets, pipes and other conveyances
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Knowledge of areas near the asset that are most likely sources of sediment
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Understanding of areas that may also be environmentally sensitive; obtain any necessary permits before commencing maintenance activities (coordination with MDOT MTA Environmental Planning Division)
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Training, understanding, and compliance with MDOT MTA’s Stormwater Prevention Pollution Plan (SWPPP) developed for specific facilities
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Minor/limited approvals and permits needed
Storm Drain Cleaning and Repair
Drain inlet and culvert maintenance includes removal of accumulated sediment, trash, and natural debris to prevent flooding. Cleaning typically involves use of a backhoe or vactor truck. Inspections should be performed regularly, especially during fall and winter months, to determine if cleaning or repairs are required. Storm drain inlets, culverts, and ditches should be cleaned when sediment impairs function, or when 50 percent of the flow area is blocked. Down drains should be inspected annually.
Ditch Maintenance
Ditches should be cleaned on a regular basis; permitting may be required prior to commencing ditch cleaning activities. No changes should occur to the engineered ditch conditions. Cleaned ditches should be seeded and mulched, if appropriate, as soon as possible.
Culvert Maintenance
Culverts should only be cleaned or repaired during non-storm periods. If culvert maintenance must be done while water is flowing through the culvert, then clear water diversion should be installed. Disturbance of beds/banks adjacent to culvert should be limited to that necessary for repair/maintenance. Work areas should be fully restored upon completion with a mix of native vegetation, if appropriate.
