Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices - supplemental information Revision as of 16:13, 7 September 2021 by Mtrojan (talk | contribs)(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff) Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices - supplemental information

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 supplemental information on operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices. For basic information on O&M for stormwater and rainwater harvest and use/reuse practices, see Operation and maintenance (O&M) of stormwater and rainwater harvest and use/reuse practices.

Operation and maintenance considerations

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 the following table: General Inspection and maintenance guidelines for stormwater harvest and use systems.

Collection surfaces

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.

Rooftops

Rooftops should be kept free and clear of debris Organic debris from trees (leaves, pollen, flowers, seeds, twigs, etc.) can degrade the quality of harvested water. Overhanging tree branches should be trimmed as needed to reduce these inputs. Animal feces can degrade water quality. Any nests should be removed and measures to discourage animal activity should be implemented as possible. Rooftops should be kept in good repair Roof material may degrade over time due to exposure to UV light, repeated freeze-thaw cycles or accumulated storm damage. This may negatively impact the quality of harvested water (TWBD, 2010).

Green space

Maintain healthy vegetation and minimize application of chemicals to protect water quality Monitor for land disturbance and provide erosion and sediment control.

Paved surfaces

Residual de-icing chemicals, sand, and salt should be cleaned from paved surfaces prior to spring startup of the system Pavement should be swept regularly (generally once per month) Any spills on the pavement should be cleaned immediately and/or contained to prevent contamination of runoff collected in the storage unit.

Collection system and pre-storage treatment components

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

Gutter and downspouts can be damaged by high winds, ice dams, or intense storms. Additional inspection is recommended following very large storms or extreme conditions. Leaves, twigs, and other organic debris should be removed from screens at a minimum in the spring and fall, but additional cleaning may be required where there is significant tree canopy.

Ground surface collection systems

Ground surface collection systems should be inspected annually for debris accumulation and erosion and repaired as needed.

Pre-storage treatment components

Sediment and debris accumulations in pretreatment storage components should be monitored periodically during the first year of operation to determine the rate of accumulation and develop an appropriate sediment removal schedule. Joints and fittings which connect collection and pre-storage treatment components should be inspected annually to look for loose fittings and leaks.

Storage 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.

• Tanks should be inspected periodically during operation to monitor for growth of microorganisms, presence of mosquitos, or formation of sludge, since these conditions can degrade water quality or may pose a health risk.
• Sediment accumulation in tanks should be monitored monthly during the first year of operation to determine the rate of accumulation and expected cleaning frequency. If possible, design your system to prevent the tank from having to be cleaned.
• If tank entry is required for inspection or repair, this work must be done by a licensed and trained contractor or otherwise qualified professional following all safety standards and regulations. Likewise, fiberglass tanks should only be repaired by authorized personnel (ARCSA, 2015). Tank systems can be designed using union disconnects and manways to access tank components. This will reduce maintenance costs and confined space entry permits.
• Water that is stored for extended periods of time in storage tank may acquire an odor, particularly if there is any organic matter, such as pollen, in the water. Tanks may need to be flushed periodically and disinfected to correct the problem (NCDENR, 2014). An alternative to disinfection which can kill the beneficial aerobic bacteria if present is to provide additional aeration to maintain a healthy tank system.
• Allow the system to overflow to other best management practices during extreme events.

Underground systems

Special consideration may be needed for underground systems

• Removal of sediment generally requires a vacuum truck.
• Repair of underground tanks should be performed only by a qualified professional.
• Tanks may crack if post-installation above ground loads are higher than load rating (equipment, vehicles) or if activities such as landscaping do not take into account the tank specification or limitations.

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.

Stormwater ponds

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 system components

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.

• Some treatment systems may require special training or certification for operation.
• Depending on the end use, it may be necessary to demonstrate compliance with water quality regulations or health codes through regular water quality monitoring at point of use.
• Some systems may use materials that require special handling and storage. In these cases Material Safety and Data Sheets (MSDS) must be available onsite.
• Any handlers of potentially hazardous material must have appropriate training (ARCSA, 2015).

Distribution components

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.

Pumps

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.

• Malfunction of dry run protection (level sensor or built-in dry run protection)
• Pump intake becoming clogged
• Microbial growth on filters at pump intakes
• Pressure tank not supplying sufficient pressure to keep the pump operating
• Pressure sensor not functioning properly
• Electrical connections

Pipes

• Maintain required coloring and labeling of pipes per plumbing codes (or other regulations).
• Pipes that are not fully winterized should be drained when the system is decommissioned for cold weather
• Inspection and repair of pipes may require a licensed technician or contractor.

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 and bypass systems

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.

• Clogging or damage at overflow/bypass intakes will cause water to short-circuit the system which may result in damage to nearby structures.
• Overactive overflow/bypass systems may be an indication of maintenance needs upstream in the system, for example, a pump failure that is preventing the storage from being drawn down or storage capacity compromised by accumulated sediment

Additional information can be found in Section 6.5, Overflow provision and stormwater management, Management Guidelines, Ontario Guidelines for Residential Rainwater Harvesting Systems.

Winter decommissioning and maintenance

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. The table below provides a summary of winter decommissioning and maintenance tasks.

Typical winter decommission and maintenance tasks for rainwater harvesting

Link to this table

Component	Typical decommissioning and winter maintenance tasks needed prior to spring startup 1
Source Area/Collection Surface	Clean residual de-icing material (sand, salt) from pavement prior to spring startup
Collection System	Drain and disconnect conveyances to prevent freeze/thaw damage
Storage System	Drain all water from above-ground outdoor storage tanks Disconnect downspouts and/or pipe upstream of the tank to prevent rainwater/snowmelt from entering the tank during winter months Disconnect electrical supply that controls equipment Shut off makeup water supply to prevent water from entering the tank
Treatment System	Drain and disconnect any pre-storage treatment devices that should be decommissioned during the winter Decommission treatment system components per manufacturer’s guidelines
Distribution System	Switch end use supply from harvested water to public water supply (if necessary) Drain all water from pumps and conveyance to prevent freeze/thaw damage Disconnect electrical supply to the pump and control equipment Complete all recommended winter maintenance for pumps and controls
Overflow/Bypass Systems	Drain and disconnect to prevent freeze/thaw damage

Resources for operation and maintenance

• Metropolitan Council. Fall 2011. Stormwater Reuse Guide, prepared by Camp Dresser & McKee, Inc. and others. St. Paul, MN.
  • Toolbox I.1b - Ground Runoff Collection, Operation & Maintenance Plans
  • Toolbox I.2 – Storage Systems, Operation & Maintenance Plans
  • Toolbox I.3 – Treatment, Operation & Maintenance Plans
  • Toolbox I.4 – Distribution, Operation & Maintenance Plans
• Despins, Christopher. September 2012. Guidelines for Residential Rainwater Harvesting Systems Handbook. Canada Mortgage and Housing Corporation (CMHC). ISBN 978-1-100-21183-1.
  • Section 1.5 - Rainwater catchment and conveyances, Management Guidelines
  • Section 2.5 - Rainwater storage and tank sizing, Management Guidelines
  • Section 3.5 - Rainwater quality and treatment, Management Guidelines
  • Section 4.5 - Makeup water system and backflow prevention, Management Guidelines
  • Section 5.5 - Pump and pressurized distribution systems, Management Guidelines
  • Section 6.5 - Overflow provision and stormwater management, Management Guidelines
• American Rainwater Catchment Systems Association (ARCSA). 2015. Rainwater Harvesting Manual, 1st Edition. Editor: Ann Audrey.
  • Section 7-4.3 – Pipes and Fittings - Operation, maintenance and repair Considerations
  • Section 10-4 – Above Ground and Underground Storage Tanks – Overview of installation and operation
  • Section 11-4 – Small-scale Storage Tanks – Overview of installation and operation
  • Section 12-4 – Large-scale Storage Tanks – Overview of installation and operation
  • Section 13-4 – Pumps and Controls – Overview of installation and operation
  • Section 14-4 – Sanitation and Water Treatment – Overview of installation and operation
  • Section 15-4.3 – Irrigating with Rainwater – Operation, maintenance and repair Considerations
• North Carolina Department of Environmental Quality (NC DEQ). April 2014. North Carolina Stormwater BMP Manual, Chapter 25, Rainwater Harvesting. Draft document.
  • Section 25.6 - Maintenance
• New York City of Environmental Protection (NYCDEP). July 2012. Guidelines for the Design and Construction of Stormwater Management Systems. Developed in conjunction with New York City Department of Buildings.
  • Section 3.5 Operations and Maintenance for Subsurface Systems

Additional References

• Despins, Christopher. September 2012. Guidelines for Residential Rainwater Harvesting Systems Handbook. Canada Mortgage and Housing Corporation (CMHC). ISBN 978-1-100-21183-1.
• North Carolina Department of Environmental Quality (NC DEQ). April 2014. North Carolina Stormwater BMP Manual, Chapter 25, Rainwater Harvesting. Draft document.