Green Infrastructure, CECs, and Geochemistry in Urban Stormwater Runoff used to Recharge Groundwater

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This national project is a joint effort between the USGS and EPA looking at contaminants of emerging concern (CECs) in urban stormwater runoff that is infiltrated into the subsurface or likely to be infiltrated in the future.

Phase I of the project aims to provide a broad-scale assessment of contaminants of emerging concern (CECs) and basic composition of water chemistry in urban stormwater runoff that is a source of recharge to groundwater by Green Infrastructure (GI) practices or likely will be a source of recharge to groundwater in the future to reduce stormwater volumes to surface waters or augment groundwater supply.
Phase II research will be focused on water-quality impacts to groundwater and attenuation, fate, and possible effects to human health and aquatic ecosystems from the transport of CECs in urban stormwater infiltrated to the subsurface or stored in surface-water bodies.

Masoner at OKC urban runoff site
Jason Masoner at OKC urban runoff site(Public domain.)

This project is intended to provide a characterization of contaminants of emerging concern (CECs) and basic geochemical composition in urban stormwater runoff that is or could potentially be infiltrated into groundwater by green infrastructure (GI) stormwater control measures. The project is being conducted to support part of the GI research and development effort of the U.S. Environmental Protection Agency’s (USEPA’s) Office of Research and Development’s (ORD) Safe and Sustainable Water Resources (SSWR) research program. The project is being conducted through an Inter-Agency Agreement1 (IAG) between the USEPA’s National Risk Management Research Laboratory (NRMRL) and the U.S. Geological Survey (USGS).

Stormwater runoff in urban areas contains a host of chemical constituents and/or contaminants (e.g. sediments, inorganic and organic chemicals), including CECs that flow untreated into waterbodies that are used for recreation and drinking water sources. CECs are pollutants not currently included in routine monitoring programs and have no regulatory standard but have recently been discovered in natural streams and potentially cause deleterious effects in aquatic life at environmentally relevant concentrations. GI is an emerging technology that mimics and encompasses the natural environment with engineered systems designed to enhance stormwater infiltration into the subsurface. Municipalities and water management agencies across the United States are increasingly using GI to reduce stormwater runoff and contaminant loads to receiving waterbodies. Certain types of GI such as infiltration trenches, underground infiltration galleries, recharge basins, or spreading grounds and reservoirs are designed to capture a large pulse of stormwater runoff. The stormwater captured by the GI then is rapidly infiltrated into underlying groundwater, decreasing the time for dissolved contaminants in stormwater runoff to undergo natural processes (e.g. sorption, degradation, etc.) to attenuate any contaminants present. Previous research indicate the contaminants in stormwater runoff that have the greatest potential to adversely impact groundwater include soluble salts, nutrients, certain organic contaminants (e.g. lindane, chlordane, other pesticides, 1,3-dichlorobenzene, pyrene, fluoranthene), and heavy metals.

Consumable materials used and disposed in residential, urban, commercial, industrial, and agricultural areas as well as land use characteristics (impermeable, porous, and sloped surfaces; age of development; exposure to weathering processes; and spatial location) influence the input of chemicals that include CECs (e.g. microplastics, pharmaceuticals, plasticizers, personal care products, hormones, etc.) to the stormwater. In some instances (particularly in arid locations) stormwater runoff is mixed with treated wastewater and used to recharge groundwater aquifers used as drinking water sources. During runoff events, CEC’s and other chemical constituents deposited in dust, aerosols, and/or atmospheric gases can be mobilized during storms and can contribute to contaminant loading in urban watersheds that drain stormwater to GI infiltration structures.

Phase I of this research will assess stormwater runoff for an established suite of CECs and pollutants that have the potential to enter shallow groundwater through existing or planned GI sites. Phase II research will assess possible impacts to shallow groundwater from CECs and other contaminants in stormwater runoff and will be process oriented in nature.