The U.S. Environmental Protection Agency announced in February its formula for stormwater reuse and sewer grants to states, addressing subsurface drainage treatment but not groundwater quality protection and representative aquifer monitoring in an integrated approach.
Stormwater infiltration is the EPA’s principal method of stormwater disposal to protect surface waters. Stormwater is a resource to recharge aquifers, but stormwater infiltration can impact groundwater quality as well. Many managed aquifer recharge sites use stormwater as a water source.  Greater stormwater replenishment of aquifers plans to focus on quality of the recharge impacting the receiving aquifer. 
Of significance to groundwater is that the EPA has not completed its research on stormwater infiltration impacts to groundwater  nor has it issued guidance matching infiltration methods to hydrogeologic settings. Recent reviews of stormwater disposal through underground infiltration have raised issues about impacts to groundwater quality, site-specific assessment needs, and required treatment.  
Other key points regarding stormwater infiltration effects include the following.
- An analysis of EPA data identified 1525 stormwater permittees matching groundwater-supplied community water systems, 46 percent being small communities, and potentially affecting more than 36 million people. Nearby private well owners may also be at risk.
- Assessing the continental U.S. land area for shallow underground placement of wastewaters found 60 percent with significant to moderate vulnerability to groundwater contamination , particularly in karst geology. 
- Urban, agricultural, and industrial landscapes generate stormwater pollutants of sediment, nutrients, bacteria, pesticides, metals, petroleum byproducts, and PFAS (per- and polyfluoroalkyl substances). 
- A 2018 EPA review of stormwater infiltration methods  found more research was needed before extensive use of infiltration for stormwater disposal.
Continued research matching infiltration methods with hydrogeologic settings should provide guidance to protect groundwater as a continuing safe local water source.
Click here to see the state grant formulas.
A complete article with more information on this topic will be published in an issue of Groundwater Monitoring & Remediation® later this year.
 International Groundwater Resource Assessment Center. 2020. Managed Aquifer Recharge Portal. https://ggis.un-igrac.org/view/marportal
 Flood-MAR Research Advisory Committee, State of California. 2019. Flood-MAR Research and Data Development Plan; Priority Actions to Expand Implementation of Effective and Efficient Flood-MAR Projects in California. https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Flood-Management/Flood-MAR/Flood-MAR-RDD-Plan_a_y_19.pdf?la=en&hash=F87030022485CF01BC6E9D6AE4C134818A4FCB0E
 U.S. Environmental Protection Agency. 2020. The Influence of Stormwater Management Practices and Wastewater Infiltration on Groundwater Quality: Case Studies. Prepared by Beak, D., M. Borst, Steve Acree, R. Ross, Ken Forshay, R. Ford, J. Huang, C. Su, J. Brumley, A. Chau, and C. Richardson. Washington, DC, EPA/600/R-20/143, 2020. https://cfpub.epa.gov/si/si_public_record_Report.cfm?Lab=CESER&dirEntryId=350152
 Ground Water Protection Council. 2021. GROUND WATER REPORT TO THE NATION. https://www.gwpc.org/topics/ground-water-report-to-the-nation/
 Environmental Protection Agency. 2018. The Influence of Green Infrastructure Practices on Groundwater Quality: The State of the Science, EPA/600/R-18/227, https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NRMRL&dirEntryId=342610
 National Academies of Sciences. 2019. Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges. http://nap.edu/25355.
 Pettyjohn, W.A.; M. Savoca; and D. Self. 1991. Regional Assessment of Aquifer Vulnerability and Sensitivity in the Conterminous United States. Environmental Protection Agency, Office of Research and Development, Ada, Oklahoma. EPA/600/S2-91/043. https://nepis.epa.gov › Exe › ZyPURL.cgi?Dockey=30003U3Q.TXT.
 U.S Geological Survey. 2017. Karst Hydrology Initiative & Fractured-Rock Aquifer Studies. https://water.usgs.gov/ogw/gwrp/activities/karst_hydro.html.
 U.S. Geological Survey. 2021. Runoff: Surface and Overland Water Runoff. https://www.usgs.gov/special-topic/water-science-school/science/runoff-surface-and-overland-water-runoff?qt-science_center_objects=0#qt-science_center_objects; U.S. Environmental Protection Agency. 2020. New Interim Strategy Will Address PFAS Through Certain EPA-Issued Wastewater Permits; Press Release of Nov 30, 2020. https://www.epa.gov/newsreleases/new-interim-strategy-will-address-pfas-through-certain-epa-issued-wastewater-permits; Ground Water Protection Council. 2021. GROUND WATER REPORT TO THE NATION. https://www.gwpc.org/topics/ground-water-report-to-the-nation/
 U.S. Environmental Protection Agency. 2018. The Influence of Green Infrastructure Practices on Groundwater Quality: The State of the Science, EPA/600/R-18/227, https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NRMRL&dirEntryId=342610