New Castle County, Delaware: drinking water report. New Castle County is Delaware's most populous county, with about 570,000 residents including Wilmington…
New Castle County is Delaware's most populous county, with about 570,000 residents including Wilmington and Newark. The county draws water from a mix of sources – the Brandywine Creek and Christina River supply Wilmington, while Artesian Water Company and United Water Delaware serve suburban areas from a combination of surface water and groundwater wells. The county sits downstream of Pennsylvania's Chester County industrial and agricultural zones, inheriting whatever those upstream sources carry.
The former New Castle Air Force Base (now the New Castle Airport/Wilmington Airport) is a confirmed PFAS contamination source. According to the Delaware Department of Natural Resources and Environmental Control's 2024 PFAS investigation, monitoring wells near the airport detected PFOS at concentrations up to 190 ppt – far above the EPA's MCL of 4 ppt. Several public and private wells in the surrounding area have required treatment or shutdown.
Wilmington's aging infrastructure also poses lead risks. The city replaced 8,500 lead service lines between 2016 and 2024, but an estimated 3,000 remain. According to the 2024 Consumer Confidence Report, Wilmington's 90th percentile lead level was 9 ppb – below the action level but a concern for households with young children.
New Castle County has two distinct risk profiles – PFAS near the airport area and lead in Wilmington's older neighborhoods. Your specific risk depends on which combination applies to your address.
Check your water to see monitoring data for your system. For PFAS, reverse osmosis is the strongest household option. For lead, a certified pitcher filter handles it at lower cost. Our water filter guide covers both. Pull your detailed report for historical data, and visit our Delaware page for statewide context.