Harford County, Maryland: drinking water report. Harford County sits northeast of Baltimore with a population of about 260,000.
Harford County sits northeast of Baltimore with a population of about 260,000. The county draws water from Deer Creek Reservoir and supplemental wells, managed by the Harford County Department of Public Works. Aberdeen Proving Ground – the U.S. Army's oldest active proving ground – occupies the entire southern tip of the county along the Chesapeake Bay. For over a century, the facility has tested weapons, explosives, and chemical agents on a 72,000-acre site.
Aberdeen Proving Ground has one of the most complex environmental contamination profiles of any military installation. According to the Army's 2024 environmental status report, the facility has over 200 identified contamination areas involving chemical warfare agents, explosives residues, heavy metals, chlorinated solvents, and PFAS. The Edgewood Area of APG was the primary site for chemical weapons research and testing.
Groundwater contamination has migrated off-base in several directions. The EPA's UCMR5 data shows PFAS detections in Harford County water systems. A 2024 MDE investigation documented PFAS concentrations above 30 ppt at monitoring wells along the base's northern boundary, near residential areas in the Edgewood and Joppatowne communities.
Communities adjacent to Aberdeen Proving Ground – particularly Edgewood, Joppatowne, and the Route 40 corridor – face the highest exposure risk from military contamination. The Army has conducted some residential well testing, but coverage is not comprehensive.
Check your water for the latest data on your system. For the range of contaminants associated with APG, reverse osmosis provides the broadest household protection. Our water filter guide details systems rated for military-grade contamination. Pull your detailed report for historical trends, and visit our Maryland page for statewide context.