9.0 System Maintenance
There are three primary components to system maintenance that can maximize the capacity and function of the existing, and proposed, storm sewer systems. Schedule, equipment, and monitoring are three of the key elements to operation and maintenance of a stormwater system.
The schedule of maintenance operations is a function of unpredictable storm events and routine dry-weather maintenance activities. A standard operating procedure for municipal work crews will include a schedule identifying which storm sewer systems get maintained at which time. At a minimum, every storm sewer inlet and outfall within Town right-of-way or open space property should be cleaned, patched, sealed, or otherwise maintained once a year. Although sediment and debris removal is the most common maintenance activity, patching of exposed reinforcing steel, clearing inlet grate frames to ease removal, mastic sealing joints at asphalt/concrete, sealing pipe joints, or tightening clamps holding flared end sections can all be effective, routine maintenance activities.
The equipment used in maintenance operations can be a significant initial cost, but ultimately reduce manpower requirements. Given the Town’s variety of storm sewer inlet grates, pipe sizes, and culvert dimensions the equipment must be flexible and manage a variety of debris conditions. Fortunately, most of the Town’s stormwater infrastructure is accessible from Town right-of-way. Therefore, a vacuum truck is a likely candidate for use in maintenance operations. Whether the truck is owned, leased, or rented for the year, month, or days of stormwater infrastructure maintenance is a decision for budgeting and policy. However, the ability to lift a grate, insert a flexible nozzle of varying size, and hydro-excavate the debris and sediment from the system is an effective means of clearing the system, increasing capacity, and extending the life of the components. The material is captured in an on-board tank and disposed at an in-town stockpile for processing or an offsite dump. Other equipment can be either too large to effectively clear the inlets and pipes (i.e. backhoe, skidsteer); or too small to complete the job in an efficient manner (i.e. handheld shovels and picks).
Monitoring the system becomes a preventative maintenance activity. Observation of the storm sewer system during small rain events, fire hydrant testing, or snow melt events can identify blockages or pipe failures before large spring storms cause bigger problems. Observation of the inlet systems can become part of a staff or consultant responsibility or become a down-time task for maintenance staff. The existing system inventory completed for this master plan includes photos of every element of the system as of the Summer of 2016. The database of photos can be helpful in determining the rate of deterioration, sedimentation, or failure since that benchmark time.
Other activities can be important to a System Maintenance program, but schedule, equipment, and monitoring cover the key aspects of sustaining the existing storm sewer system. A good maintenance program increases the overall resilience of the system through knowledge of the system limitations and tendencies. When large spring storm events clog the system with hail and leaf debris, maintenance staff with experience maintaining the system over time can quickly clear choke points with effective equipment and understand the impact on the system.