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Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices

Green Infrastructure: Stormwater and rainwater harvest and use systems can improve or maintain watershed hydrology, reduce pollutant loading to receiving waters, increase water conservation, reduce stress on existing infrastructure, and reduce energy consumption

This page provides guidance for operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices.

Supplemental information can be found on the page called Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices - supplemental information. Supplemental information includes the following.

Image of cisterns

A set of cisterns in an underground parking lot at the Minnesota Central Library to collect stormwater runoff
  • Collection surfaces
  • Collection system and pre-storage treatment components
  • Storage components
  • Post-storage treatment system components
  • Distribution components
  • Overflow and bypass systems
  • Winter decommissioning and maintenance
  • Resources for operation and maintenance
  • Additional References

Contents

Overview of typical O&M issues

Stormwater and rainwater harvest and use/reuse practices are practices like rain barrels or cisterns that capture and retain stormwater for beneficial reuse. Operation and maintenance needs vary depending on the configuration and components of the harvest and use system. While many stormwater systems are designed to be relatively passive with minimal oversight needed, harvesting and use/reuse 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.

This image shows an installed rain barrel

Installed rain barrel. Image Courtesy of Emmons & Olivier Resources, Inc.

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. A properly maintained cistern will last 20-50 years, depending on the size, design, and climate (City of Portland, 2006). The most frequently cited O&M concerns for these practices include the following.

  • Sediment or organic material buildup in the storage tank
  • Mosquito or insect breeding ground
  • Winter freezing
  • Cistern overflows or leaks
  • Erosion around the overflow discharge point

The page Environmental concerns for stormwater and rainwater harvest and use/reuse addresses some of these issues.

The sections below describe best practices to prevent or minimize these common problems.

Design phase O&M considerations

Rainwater harvesting and reuse systems store and release rainfall for future use. Rainwater that falls on a rooftop or other impervious surface is collected and conveyed into an above- or below-ground storage tank (also referred to as a cistern, rain tank, or rain barrel), where it can be used for non potable water uses and on-site stormwater disposal/infiltration. Non-potable uses may include landscape irrigation, exterior washing (e.g. vehicle, building, or sidewalk washing), or flushing of toilets and urinals. Harvesting and reuse 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.

Photo of harvest and use system Cottage Grove

Photo of tank for harvest and use system. Image courtesy City of Cottage Grove.

Designers should design these practices in ways that prevent or minimize O&M issues. Examples include the following.

  • Sizing the practice in accordance to its contributing drainage area and potential use(s)
  • Checking that the contributing drainage area (i.e. roofs) are appropriate for rainwater reuse and will not leach metals, asbestos, or other contaminants
  • Providing pretreatment, including a first flush diversion system for larger cisterns
  • Checking plumbing codes for allowable indoor uses and required water treatment
  • Consulting with a mechanical, electrical, plumbing (MEP) engineer for indoor use of harvesting systems
  • Checking site topography and storage tank location, to ensure rainwater harvesting can occur and to determine piping and pumping needs
  • Locating the tank so that it is above the groundwater table and outside of any flooding zone
  • Locating underground tanks away from underground utilities
  • Checking the integrity and stability of the soil or aggregate upon which the tank will be placed to avoid settling or shifting
  • Providing adequate hydraulic head for the intended use of the water

Designers should consult and include any local requirements regarding green infrastructure. O&M considerations often depend on whether the practice is located on public land, private land, or in the public right of way.

Designers can incorporate design solutions to facilitate maintenance activities. Examples include the following.

  • Providing adequate space around the storage tank and incorporating multiple and easy site access points to inspect around the storage tank
  • For large tanks, providing a standard size manhole or equivalent opening to inspect the inside of the storage tank.

The designer should also provide a site-specific O&M plan that includes the following.

  • Construction inspection schedule and checklists
  • Post-construction routine maintenance and cleaning schedule and checklists
  • Operating instructions for the practice (if applicable)
  • A winterization plan and schedule
  • A site plan

For more information on design criteria for stormwater and rainwater harvest and reuse practices, click here.

Construction phase O&M considerations

Proper construction methods and sequencing play a significant role in reducing O&M problems. However, unlike many other green infrastructure practices, typical harvesting and use systems are not as sensitive to the particular sequence of construction, as long as temporary or construction phase stormwater treatment is addressed (i.e., the storage component can serve both temporary or construction phase stormwater treatment needs as well as long-term harvesting needs). Some key items during the construction phase include the following.

  • Before construction begins
    • Verify that all necessary certifications, licenses, permits and approvals have been obtained, including those required by the Minnesota Plumbing Code.
    • Install any needed erosion and sediment controls in your construction site and prepare a SWPPP
    • Designate a stormwater supervisor to make sure someone is responsible for erosion and sediment control.
    • Hold a pre-construction meeting to review the construction plans and the sequencing of construction. Suggested attendees include, but are not limited to, engineers, code officials, system provider, plumbers, electricians and excavators.
  • During construction
    • Perform interim tests and inspections as required by governing agencies including pressure testing of pipe/joints and tanks if required, cross connection testing, rpz (reduced pressure zone - testing pressure between two points) testing and start up water quality testing.
    • Inspect the practice during construction to ensure that the rainwater harvesting system is built in accordance with the approved design and standards and specifications. Use a detailed inspection checklists that include sign-offs by qualified individuals at critical stages of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. Example construction phase inspection checklists are provided below.
  • After construction
    • Verify that the rainwater harvesting system was built in accordance with the approved design and standards and specifications.
    • Inspect and clean all conveyance and storage elements immediately prior to system testing. Verify that the distribution intake within storage device(s) is clear of sediment and will not entrain any sediment once flow is initiated.
    • Verify that the practice actually captures runoff. Conduct a full inundation test to inspect the inflows, piping, storage tank, and outflows.
    • Confirm that there are no leakages in the routing to the storage device or out of the storage device.
    • Use a detailed inspection checklists that include sign-offs by qualified individuals at the completion of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. Example construction phase inspection checklists are provided below.
    • Review and discuss all part warranties.
    • The design/construction team should provide the O&M team with the following information to be included in the O&M plan.
      • The “ as-built” plans of the practice
      • A list of conditions that might cause failure of the practice if not properly maintained.

More information on typical construction sequencing of rainwater harvesting practices will be found on the Construction specifications for stormwater and rainwater harvest and use/reuse page.

Post-construction phase O&M

Stormwater harvesting and use/reuse systems rely on being properly operated and maintained, especially for larger underground tanks. Proper operation and maintenance will only increase the expected lifespan of the facility. Important post-construction considerations are provided below.

  • A site-specific Operations and Maintenance Plan should be prepared by the designer prior to putting the stormwater practice into operation. This plan should provide any operating procedures related to the practices. The plan should also provide clear maintenance expectations, activities, and schedules. Include photos if possible. Be clear about who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities. The O&M plan should include an anticipated budget for O&M activities. The O&M plan should also include an example O&M inspection checklist and an example maintenance report, as well as site plan(s) and as-built drawings. Example O&M plans are provided below.
  • A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority. Example maintenance agreements are provided below.
  • Inspection and maintenance activities are distinct and can be done as separate activities or together. Inspection will typically assess the practice for any O&M issues, whereas maintenance will address the O&M issues identified by the inspection. A dedicated inspection effort on a large number of BMPs can help prioritize maintenance activities.
  • 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 perform annual inspection and maintenance. More information about winter decommissioning and maintenance tasks can be found on the Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices - supplemental information page.

The table below provides an overview and schedule of general maintenance activities. A more detailed maintenance list can be found on the General inspection and maintenance guidelines for stormwater harvest and use systems page.

Overview and schedule of general maintenance activities for Stormwater and Rainwater Harvest and Use/Reuse Practices Link to this table

  Activity Frequency Time Period Level of Effort per Visit O&M Benefit*
First Year of Operation Check operation of mechanical parts like pumps At least twice after the system becomes operational During a storm event 2-4 hours 1
Check condition of first flush and high flow diverters At least twice after storm events > 0.5 inches Within the first 6 months 1-2 hours 1
Check for clogging At least twice after storm events > 0.5 inches Within the first 6 months 1-2 hours 1
Check for erosion downstream of the high flow diverter At least twice after storm events > 0.5 inches Within the first 6 months 1 hour 1
Check for leaks At least twice after storm events > 0.5 inches Within the first 6 months 1 hour 1
Check performance of water treatment system and adjust treatment parameters After tank has filled up Within first month 2 hours 4
After First Year of Operation Inspect and clean pre screening devices and first flush diverters Quarterly Seasonally 2 hours 1
Check and clean any filters to prevent clogging 3 times per year and/or after each event that exceeds the design capacity of the collection system 1-2 hours 1
Remove leaves and debris from the gutters and downspouts Semi-annually Spring and Fall 2-4 hours 1
Clean out tank to remove sediment and algae Semi-annually Spring and Fall 4 hours 1,4
Check and repair damage to collection surface and collection tanks Annually Spring or Fall 2-4 hours 1
Check and repair erosion along the diversion pathways Annually After large storm 1-2 hours 1
Check and repair any leaks Annually Spring or Fall 2-4 hours 1
Inspect and repair mosquito screens Annually Spring or Fall 1-2 hours 1
Clear overhanging vegetation and trees over roof Annually Winter   1
Winterize or disconnect the storage system before the winter Annually Late Fall Depends on system 1
Check structural integrity of tank, pump, pipe, and electrical system and repair any damages as needed Every 3 years As convenient Depends on repairs needed 1
After 5+ Years of Operation (non-routine maintenance) After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as replacement of structural materials, conveyance equipment, or storage tanks. As needed As needed Could be significant depending on the activity 1,4

Key to Maintenance Benefits:

  1. Proper stormwater flow and infiltration
  2. Creation and maintenance of wildlife habitat
  3. Creation and maintenance of pollinator habitat
  4. Nutrient cycling and storage
  5. Aesthetics and public enjoyment
  6. Carbon sequestration
Common problems and how to troubleshoot them for Stormwater and Rainwater Harvest and Use/Reuse Practices
Symptom Possible causes Solution
Storage system overflows or high flow activator engages often Stored water is not being used up enough Increase usage of water and/or empty storage before a large storm event.
Excessive sediment build-up inside the storage tank Pretreatment is not working, first flush diversion is not working Check that the pretreatment BMPs and first flush diversion is working as intended. Check whether conditions changed in the contributing area. Install source control BMPs as needed.
Water smells foul Growth of algae or microbes inside the tank Drain and clean the tank, replace or backwash any filters
Clogging of intake and filters in the first flush diversion system Too much fine debris is accumulating. This can be particularly a problem during the spring pollen season or fall leaf-off season Clean and replace filters as needed, clean or sweep contributing areas more often.
Area around storage tank is wet or humid There may be a leak Check tank for any leaks and repair.
Erosion or scouring along the diversion pathways Overflow is activated too often or receiving area is not appropriate for the overflow Stabilize the eroded area and vegetate any bare spots. Add erosion control measures as needed (rip rap, check dams, level spreaders, etc.) Correct for drainage and flow path issues to make sure flows are evenly distributed. Make sure the flow paths are unobstructed. Make sure that the storage is being drawn down sufficiently often, and particularly before any heavy storms.
Excessive mosquitos in or around the storage unit The screens may be ripped. Check and replace the mosquito screens.

Cisterns that are used within on-site non-potable systems require daily, weekly, monthly, and periodic maintenance to keep a healthy operating system. Routine daily maintenance activities include checking for leaks, monitoring the system and responding to alarms, replacing buffers and reagents, grabbing required samples, and conducting system walkthroughs. Weekly maintenance should be performed to prevent issues from developing or worsening. These preventative tasks should be performed in accordance with the specific equipment, but should include checking chemical levels, draining condensate, inspecting screens, and collecting samples. Monthly checks should be performed to assess service levels and calibration of operational equipment, and longer-term periodic maintenance tasks should be performed to repair or replace probes, screens, and other key components of the system. More information on non-potable systems and their maintenance by the Water Research Foundation can be found in their Onsite Non-Potable Water System Guidance Manual.

Maintenance costs

Maintenance costs will vary depending on the size of the practice and the type of rainwater harvest system (cistern or rain barrel). Example costs are shown in the table below. Maintenance may be lower the first few years while parts are new, and more expensive in later years when components may need to be replaced.

Example maintenance costs for stormwater and rainwater harvest and use/reuse practices
Activity Frequency Annual Cost Reference
Inspection, Reporting & Information Management Semi-Annually $260 2009 WERF
Roof Washing, Cleaning Inflow Filters Semi-Annually $480 2009 WERF
Intermittent System Maintenance (System flush, debris/sediment removal from tank) Every 3 years $130 2009 WERF
Pump Replacement Every 3 years $198 2009 WERF
Cartridge Filter Annually $20-60 MPCA Cost-Benefit Considerations
Reverse Osmosis Filter Annually $400-1,500 MPCA Cost-Benefit Considerations
UV Light Disinfection Every 10,000 hours or 14 months $350-1,000; $80 to replace UV bulb MPCA Cost-Benefit Considerations
Ozone Disinfection As needed $700-2,600; $1,200+ for in-line monitor to test effectiveness MPCA Cost-Benefit Considerations
Chlorine Disinfection Monthly $1/month manual dose or a $600-3,000 automatic self-dosing system MPCA Cost-Benefit Considerations

Maintenance training documents and videos

Example O&M plans, checklists, reports, and maintenance agreements for stormwater and rainwater harvest and use/reuse practices
Document Link
Operation & Maintenance Plan
Construction phase inspection checklist
O&M inspection checklist
O&M example report
Maintenance Agreements

Additional detailed O&M information

More detailed information regarding specific maintenance activities are provided here. Topics discussed include the following.

  • Collection surfaces
  • Collection system and pre-storage treatment components
  • Storage components
  • Post-storage treatment system components
  • Distribution components
  • Overflow and bypass systems
  • Winter decommissioning and maintenance
  • Resources for operation and maintenance
  • Additional References

Case studies

Maintenance training documents and videos

O&M resource catalog

MPCA has compiled publicly available O&M resources related to green infrastructure. This non-exhaustive catalog is intended as a resource to practitioners.

References

  • City of Portland. 2006. Cisterns. Environmental Services.
     

Related pages

Rainwater harvest and reuse

Green Infrastructure