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.
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.
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.
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.
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.
Designers should design these practices in ways that prevent or minimize O&M issues. Examples include the following.
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.
The designer should also provide a site-specific O&M plan that includes the following.
For more information on design criteria for stormwater and rainwater harvest and reuse practices, click here.
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.
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.
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.
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
|First Year of Operation|
|Activity||Frequency||Time Period||Level of Effort||O&M Benefit|
|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|
|Activity||Frequency||Time Period||Level of Effort per Visit||O&M Benefit|
|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)|
|Activity||Frequency||Time Period||Level of Effort per Visit||O&M Benefit*|
|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:
Common problems and how to troubleshoot them for Stormwater and Rainwater Harvest and Use/Reuse Practices
Link to this table
|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 will vary depending on the size of the practice and the type of rainwater harvest system (cistern or rainbarrel). 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.
Maintenance costs for stormwater and rainwater harvest and use/reuse practices
Link to this table
|Example Maintenance Costs|
|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|
More detailed information regarding specific maintenance activities are provided here. Topics discussed include the following.
MPCA has compiled publicly available O&M resources related to green infrastructure. This non-exhaustive catalog is intended as a resource to practitioners.
Example O&M plans, checklists, reports, and maintenance agreements for stormwater and rainwater harvest and use/reuse practices
Link to this table
|Operation & Maintenance Plan|
|Construction phase inspection checklist|
|O&M inspection checklist|
|O&M example report|