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.
Drinking water is one exposure route. These federal datasets also cover Harford County, MD.
The EPA places Harford County, MD in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
40% of homes in Harford County, MD were built before 1980, and 8% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Harford County, MD averages 7.2 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide
16 public water systems serving Harford County, MD have EPA lead testing on record. The reported lead sample skews toward systems that already flagged a problem, so its exceedance rate is not directly comparable with other areas. 9 water systems serving Harford County, MD carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Lead and Copper Rule Revisions | 4 |
| Revised Total Coliform Rule | 2 |
| Ground Water Rule | 2 |
| Total Trihalomethanes (TTHM) | 1 |
| Total Organic Carbon | 1 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.