NGWA member Scott Andres and Regulatory Affairs Manager Chuck Job addressed stormwater pollutant impacts to groundwater used for water supply on May 14 with the National Academies of Sciences’ Highway Stormwater Committee.
The current focus of the committee is on protecting surface water from stormwater contaminants. Joining Andres and Job was Dan Yates, executive director of the Ground Water Protection Council, which is also concerned about protecting groundwater from stormwater contamination.
Yates presented the regulatory considerations of the National Pollutant Discharge Elimination System and the Underground Injection Control programs, indicating that groundwater needs protection in a “one-water” approach.
Job discussed the range of pollutants potentially affecting groundwater from stormwater infiltration and highlighted the thousands of small public water systems and residential water well systems potentially impacted.
A note was made that recent expert reviews have concluded that the impacts of infiltrated stormwater are not well understood and need to be assessed on a site-specific basis. Groundwater vulnerability site assessment tools are available and should be applied to location and design of stormwater infiltration sites to protect aquifers from contamination.
Andres concluded the presentation with examples of eight public water systems in Delaware that are impacted by increasing chloride concentration from highway runoff infiltrating through a stormwater basin and mobilizing radium from the subsurface. He noted in response to questions that:
“Increased snowfall resulting in more road salt applied causes more release of radium more quickly and in higher concentrations. Measuring with the right monitoring system helps understand groundwater flow and geochemical changes in the aquifer, otherwise incorrect assumptions may be made about whether the aquifer is impacted. Additionally, groundwater can carry the pollutants to surface water.”