Elements of design, operation, and maintenance that address potential risks associated with stormwater harvesting and use
Link to this table

Risk Type Design Considerations O & M Considerations
Human Health Risks
Source area pollutants
  • Bypass runoff from pollutant hotspots in the source area
  • Pre-storage treatment and treatment systems
  • Source control BMPs
  • Inspection and maintenance of source area
  • Regular clean-out of accumulated sediments in storage ponds, if applicable
Hazardous spills in the source area, including sudden air releases of hazardous substances that could deposit in the collection and storage systems
  • Incorporate at least a 72-hour residence time of harvested stormwater in storage unit to contain hazardous spills in the source area prior to distribution (NRMMC et al. 2008)
  • Incorporate an emergency bypass in the collection system
  • Regular inspection of source area for hazardous spills
  • Coordination with local agencies responsible for responding to hazardous spills in the source area
  • Incorporate an emergency spill response plan in the O&M document
Metals and other chemicals from roofing materials (link to table 4 in WQ considerations)
  • Some roofs may leach chemicals at levels of concern
  • Regular inspection and cleaning of system components to prevent degradation
Bacteria, viruses
  • Source control BMPs
  • Disinfection or filtration treatment systems
  • Regular cleaning and maintenance of storage and treatment units
  • Water quality monitoring
  • Signage and/or access restriction to irrigation areas or other exposure controls
Mosquito and other vector-borne illnesses
  • Install insect screens on exposed pipe and other openings
  • See the following websites for information on mosquito control in storage ponds:
  • Regular monitoring
  • Regular mosquito control treatment of storage unit
Ecological Risks
Plant communities
  • Source control BMPs
  • Pre-storage treatment and treatment systems
  • Use of salt tolerant plant species in irrigated areas
  • Irrigation rates that optimize the saturation of soils without interfering with plant growth.
  • Avoid irrigating high-clay soils with high-salinity stormwater. Salt reduces the permeability of clay soils by increasing the stickiness of clay soils when wet and forming hard clods and crusts upon drying (See this)
  • Regular monitoring of stormwater runoff and soil quality if salt contamination of soils is a concern
Aquatic ecosystems
  • Avoid inventoried public waters and wetlands for storage of harvested stormwater
  • Install aeration systems in storage ponds to minimize algal blooms, if allowed by local code or ordinance
  • Pre-storage treatment systems
  • Regular monitoring of storage pond for adverse ecological impacts
Local hydrology
  • Design storage residence times and overflow volumes such that downstream hydrology is not adversely impacted
  • Regular inspection and maintenance of storage, overflow and distribution system components
Equipment degradation
  • Source control BMPs
  • Pre-storage treatment and treatment systems
  • Regular inspection and cleaning of system components