While many stormwater systems are designed to be relatively passive with minimal oversight needed, harvesting and use systems require managed operation where the goal is to move water from the storage unit to a point of use so that there is sufficient storage available to receive runoff from subsequent rainfall events. The timing and management of the water storage and use operation needs to be integrated into the system design. With an actively managed operating system, regular maintenance is also important to preserve the end use water quality, maintain system safety and efficiency, and minimize costs associated with repairs and downtime.
Stormwater harvesting and use systems rely heavily on being properly operated and maintained and therefore having a formal agreement in place upfront is critical. An operation and maintenance agreement should:
In general, stormwater harvesting and use O & M plans should include the following items:
A. Site plans showing:
B. As-built drawings showing:
C. Operation and troubleshooting guidelines for system controls including:
D. Statements describing when a licensed/certified professional is needed for repair or maintenance of tanks, pumps, pipes, controls, or other components.
E. Description and schedule of inspection activities for all system components including
F. Description and schedule of maintenance activities for all system components including
G. Manufacturer’s literature for all controls, replaceable components, and prefabricated components (pumps, sensors, treatment components, prefabricated storage units, etc.).
H. Component-specific O&M plan details
I. Monitoring Plan
J. Inspection forms/maintenance logs for all regularly scheduled inspection and maintenance activities.
K. Statements outlining the roles and responsibilities of all parties participating in the operation, monitoring, and maintenance of the system, including which party must follow up on items that are outside the normal operating procedures.
Operation and maintenance plans will vary depending on the configuration and components of the harvest and use system. Operation and maintenance considerations are described by system component below. Guidelines for inspection and maintenance timeframes and activities are provided in Table 1.
Collection surfaces should be inspected to identify sources of contamination and determine maintenance needs. Source control of pollutants and large debris at collection surfaces improves the quality of harvested water and can also extend the maintenance life of downstream components by reducing sediment and associated pollutant loads delivered to conveyances .
Effluent from Stormwater BMPs
For information on the monitoring and maintenance of stormwater BMPs see the MN Stormwater Manual.
Collection systems should be kept free of debris to prevent clogging and should be inspected to identify leaks. Clogging decreases the capture efficiency of the harvest and use system and can result in flooding or damage to collection surfaces or upstream facilities. Debris that has built up in conveyances may act as a source of pollution in harvested water, increasing the burden on downstream water treatment components to meet end use water quality criteria. Leaks in the system also decrease the capture efficiency of the system and may cause damage to foundations or structures located near the collection system.
The primary function of pre-storage treatment components is to reduce sediment and adhered pollutant loads in harvested water. Since primary treatment components are designed to collect sediment, these components must be inspected and maintained to preserve sediment storage capacity and maintain functionality of the collection system .
Collection systems are often designed in a passive form using gravity, so operational needs are limited. If collection systems include pumps, then the needs would be similar for distribution systems.
Rooftop Collection Systems
Ground Surface Collection Systems
Pre-storage Treatment Components
Collection, distribution, makeup supply, and overflow systems all interact with the storage unit in some capacity. For this reason, regular inspection and monitoring of the storage system is an important diagnostic tool for monitoring system function as a whole.
Special consideration may be needed for underground systems
For additional information on inspection schedules and activities for underground systems see Section 3.5 of New York City’s Guidelines for the Design and Construction of Stormwater Management Systems.
For information on the monitoring and maintenance of stormwater ponds see the MN Stormwater Manual section on operation and maintenance of stormwater ponds.
Post-storage treatment systems generally include consumable components – filters, bulbs, chemicals – that must be periodically cleaned, replaced, or replenished to maintain the performance of the water treatment system. Maintenance considerations will vary depending on the number and kind of treatment components that are included in the system. Examples include cartridge filters, reverse osmosis filters, UV disinfection light bulbs, ozone disinfection, and chlorine disinfection. See Table 6.5 of the Texas Rainwater Harvesting Manual for additional information.
Monitoring, maintenance, and repair of pumps, pipes, and controls may require a certified or licensed professional. The O&M plan should outline the conditions under which a licensed professional is needed.
Most often a problem with the pump and pressurized distribution system is due to associated components (water level sensor, valves, pressure tank, makeup supply, or automatic bypass) and not the pump itself (Despins, 2012). Problems with associated components might be diagnosed by evaluating the water level in the tank and operation of these components (Is the tank empty when it shouldn’t be? Is the makeup supply on or off when it shouldn’t be?). Maintenance concerns will vary depending on the type of pump (e.g. submersible or non-submersible). Potential maintenance concerns for pumps include the following.
Makeup Water Supply System and Backflow Prevention
Local regulations should be consulted regarding potential cross connections when combining rainfall runoff with potable water systems. In most cases, cross connections are not allowed and an air gap must be provided between sources to limit the potential for contamination of the potable water supply.
Automated make-up supply - faulty float switches or solenoid valves can cause the makeup water supply to be activated or shut-off when the action is not required.
Overflow must be monitored periodically after rainfall events to ensure the system is capturing events it was designed to capture. Overflows that are not functioning properly may cause erosion, flooding, or damage to control systems (makeup supply, pump controls). Specific issues include the following.
Additional information can be found in Section 6.5, Overflow provision and stormwater management, Management Guidelines, Ontario Guidelines for Residential Rainwater Harvesting Systems.
Inspection and Maintenance Guidelines The General inspection and maintenance guidelines for stormwater harvest and use systems table below provides a summary of general inspection and maintenance guidelines.
General inspection and maintenance guidelines for stormwater harvest and use systems
Link to this table
|Component||Timeframe||What to look for during Inspection||Maintenance 1|
|Source Area/Collection Surface||Annually||Changes in land use or land disturbance||Implement source control BMPs as needed to help meet pre-storage water quality targets|
|Pollution hot spots|
|Damage to roofing materials||Repair as needed|
|Overhanging branches||Trim overhanging branches|
|Nests or other evidence of animal activity||Remove nests and implement additional measures to discourage animal activity|
|Monthly or as needed||General condition of pavement||Adjust street sweeping schedule as needed to maintain clean pavement|
|Collection System||Spring startup and fall||General condition of gutters, downspouts, and conveyances||Clean accumulated debris in fall prior to winter operations or seasonal shut-down, and as needed.|
|Debris clogging inlets, gutters, downspouts, and other conveyances|
|Evidence of leaks at junctions or along conveyances|
|After large storms||General condition of first flush and high-flow diverters (bypass system)||Repair as needed|
|Soil erosion or flooding along diversion flow pathways||Provide appropriate erosion control measures (rip rap, check dams, etc.)|
|Storage System||Spring start up||General condition of all storage system components||Clean, repair and replace as needed|
|Position and function of valves||Test per manufacturer’s guidelines|
|Function of operational structures and controls|
|Periodically following startup||Tank ventilation||Clean, repair and replace as needed|
|Excess soil moisture near tanks or other evidence of leaks||Repair leaks per manufacturer’s guidance|
|Growth of algae or microbes||Drain and clean tank per manufacturer’s guidelines|
|Intrusion of mosquitos or small animals||Implement appropriate pest control as needed|
|Monthly||Sediment level in tank or pond||Remove sediment when the tank sediment storage volume has reached 50% of capacity|
|Treatment Systems||Spring startup||General condition and function of all treatment system components||Conduct testing per manufacturer’s guidance
Clean and repair as needed
|Twice per year||Clogging from accumulated dirt and debris in pre-storage treatment components||Clean as needed|
|Evidence of leaks from loose fittings, joints||Repair as needed|
|3 times per year AND after each rain event that exceeds the design capacity of the collection system||Clogging of intake and filters in first flush diverters, especially during pollen season (filter clogging)||lean and replace as needed|
|Monthly or as required||Performance of water treatment system||Test water quality at point of use and at other points in the system (outlet of collection system, in-tank) as required|
|Adjust treatment parameters to meet any water quality deficiencies|
|Per manufacturer specifications and as needed||Condition of replaceable components in the treatment systems (filters, cartridges, bulbs, etc.)||Replace/repair per manufacture’s guidelines and as needed. Typical UV treatment is annual and filters are started on a quarterly basis or when differential pressure drops.|
|Distribution System||Spring startup and fall||General condition of all distribution system components||Repair/replace as needed|
|Position and function of valves||Test per manufacturer's guidelines|
|Function of operational controls|
|Presence of leaks (test)|
|Function and performance of pump||Complete all startup inspection and operations per manufacturer’s guidelines|
|Monthly||Presence of biofilms or sediment accumulation on filters||Replace/disinfect as needed|
|Per manufacturer and as needed||Function of pumps and other control equipment||Test all control components per manufacturer's guidelines or as needed to diagnose problems in the system|
|Overflow/Bypass Systems||Annual (above-ground)/ As needed (below-ground)||Clogging or damage at overflow/bypass intakes||Clean and repair as needed|
|Erosion of downstream receiving area||Stabilize erosion, repair overflow system as needed, check for failures in other upstream components|
|Proper pump control and operation||Repair and replace as needed|
1See also decommissioning and winter maintenance tasks
Throughout Minnesota, temperatures can drop below freezing (0°C) during the winter months. If stormwater harvesting systems are not fully winterized to withstand seasonal temperature fluctuations, systems should be decommissioned before the cold weather season. Winter decommissioning also provides an opportunity to preform annual inspection and maintenance. Table 2 provides a summary of winter decommissioning and maintenance tasks.
Typical winter decommission and maintenance tasks
Link to this table
|Component||Typical decommissioning and winter maintenance tasks needed prior to spring startup 1|
|Source Area/Collection Surface||
Record keeping is part of regular operation and maintenance. Record keeping is important for
Because harvesting systems can be configured differently, there is no ‘one size fits all’ form for inspections. Inspection forms and maintenance logs that are suited to the particular context should be included in the O & M plan. Example forms for spring inspection and maintenance, regular monitoring and maintenance, and inspection following storm events are included in this section.
Inspection forms should include, at a minimum, the following information:
Maintenance logs should include, at a minimum, the following information:
It may be helpful to include additional information from the O & M plan, such as replacement part type, manufacturer, or service provider contact information, on inspection and maintenance forms. Any actions required after inspection or maintenance must be brought to the attention of the system manager or party who holds responsibility per the operation and maintenance plan.
Click on these to download these sample forms