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DEQ preview: Coastal Plain groundwater study finds historic drawdown, salt‑water intrusion risks
Summary
DEQ presented a draft groundwater‑supply report required by the 2024 resolution that finds the Potomac Aquifer supplies roughly 70% of withdrawals east of I‑95, total withdrawals of about 96 million gallons per day, historical drawdown and localized subsidence, and modeled limits on new large withdrawals.
DEQ on Nov. 18 previewed a draft report on groundwater supply east of Interstate 95 that the agency will deliver to the General Assembly. Brian Campbell, manager of DEQ’s Groundwater Characterization and Monitoring Program, summarized technical findings, long‑term trends and recommendations.
Key technical findings presented include:
• Total withdrawals in the Eastern Virginia Groundwater Management Area are approximately 96,000,000 gallons per day; the Potomac Aquifer accounts for about 70% of those withdrawals.
• Historical drawdown has been substantial in pumping centers such as Franklin (the presentation noted maximum historical drawdown on the order of 60 meters, roughly 200 feet) and current groundwater levels in that area reach roughly 125 feet below sea level in the Franklin region.
• Groundwater‑quality concerns include observed localized increases in chloride consistent with saltwater intrusion trends in the Potomac and Yorktown‑Eastover aquifers in areas with major withdrawals.
• Modeling of hypothetical additional withdrawals (3,000,000 gallons per day at representative locations) found that many locations would not meet permitting evaluation criteria; the best‑case modeled maximum that would pass criteria was about 360,000 gpd in a limited area of Northumberland County, with lower allowable volumes elsewhere.
Campbell said that while pressure effects from injection‑style replenishment projects could produce regional groundwater‑level gains, those gains may dissipate after injections cease and observed groundwater‑level data will be required to understand the effects of programs such as SWIFT.
Campbell told the board the Groundwater Management Act of 1992 has had positive effects but current implementation is insufficient for long‑term sustainability; the draft report will recommend statutory/regulatory clarifications and additional resources for DEQ staff and funding. Board members asked about subsidence monitoring and USGS cooperation; Campbell said monitoring instruments and data are available but some historical discontinuities exist due to past USGS funding cuts.
What happens next: DEQ will deliver the draft report to the General Assembly at the start of the upcoming session and will offer recommendations for improving the Act’s effectiveness and resourcing DEQ for longer‑term management.
