Definition

Percent of tested private wells with fecal coliform or E. coli detected

Numerator

Number of tested private wells with fecal coliform or E. coli detected

Denominator

Number of tested private wells in a specified period of time

Data Interpretation Issues

Under the PWTA, all wells are tested for the presence of a group of bacteria called total coliform (TC). When TC is detected, the sample is further tested for either fecal coliform or E. coli bacteria, depending on the testing laboratory. The presence of either fecal coliform or E. coli is strong evidence that a well has been contaminated with fecal waste, which can come from either human (septic tanks, leaking sewer lines) or animal (surface water infiltration) sources. Statewide, fecal coliform or E. coli were detected in 2.0 percent of all sampled wells. The counties in the Coastal Plain had the lowest percentage of wells in which either fecal coliform or E. coli was detected. It is believed that the sand and clay layers of the Coastal Plain better protect wells from fecal contamination than fractured rock formations in the northern part of the State.

Why Is This Important?

Coliform bacteria are organisms that are present in the environment and in the feces of all warm-blooded animals and humans. Coliform bacteria will not likely cause illness. However, their presence in drinking water indicates that disease-causing organisms (pathogens) could be in the water system. Most pathogens that contaminate water supplies come from the feces of humans or animals. Testing drinking water for all possible pathogens is complex, time-consuming, and expensive. It is relatively easy and inexpensive to test for coliform bacteria.

How Are We Doing?

Between September 2002 and December 2018, fecal coliform or E. coli was detected in 2.0 % of 111,010 private wells in sampled New Jersey. Fecal coliform or E. coli was most commonly detected in Somerset (4.3% of wells), Sussex (4.2% of wells), Passaic (3.4% of wells), Hunterdon (3.2% of wells), Warren (3.2% of wells), Mercer (2.9% of wells) and Union (2.8% of wells) Counties. Online maps showing detection of fecal coliform or E. coli are available at the county level, municipal level, and for 2 mile by 2 mile grids from NJDEP, [http://arcg.is/1CPkHyC].

What Is Being Done?

The New Jersey Private Well Testing Act (N.J.S.A. 58:12A-26 et seq.) became effective in September 2002. The PWTA requires the buyer or the seller of a property to test untreated well water prior to the sale and review the results prior the closing of title. It also requires landlords to test the private well water supplied to their tenants every five years and provide their tenants with a written copy of the results. The data generated by this program are provided to the homeowners by the laboratory performing the analyses and then sent to the New Jersey Department of Environmental Protection (NJDEP). The NJDEP notifies local health agencies when a well within their jurisdiction is tested under the PWTA. The data from the PWTA are used by NJDEP to assess the quality of the water from private wells throughout the state.