BACTERIA IN HOUSEHOLD WELLS IN
SOUTHEASTERN PENNSYLVANIA

This project was done in cooperation with the
Pennsylvania Department of Environmental Protection.


FINAL REPORT

Relation Between Selected Well-Construction Characteristics and Occurrence of Bacteria in Private Household-Supply Wells, South-Central and Southeastern Pennsylvania [PDF file]


NEED FOR THE STUDY

Bacteria are commonly detected in water from on-lot wells used for household supply in Pennsylvania. A statewide study found that about 40 percent of private water supplies from wells or springs had bacterial contamination. Typically, private on-lot wells are constructed as open holes completed in bedrock with minimal surface casing, little or no annular grout seal, and a loose-fitting well cap. It is not known if the bacterial contamination of private on-lot wells is the result of well-construction characteristics that can allow contaminants from the immediate vicinity to enter the well or if bacterial contamination within the aquifer is widespread. If sanitary well-construction practices reduce or eliminate the incidence of bacterial contamination, most bacterial sources are probably from site-specific, on-lot sources near or in the well. Alternately, if bacteria are present regardless of construction practice, systemic contamination of the aquifer may be present.

OBJECTIVE

The objective of this study is to determine if water from private household-supply wells constructed with annular grout have a lower incidence of bacterial contamination than wells completed without this sanitary well-construction feature.

APPROACH

1. Locate a set of private household-supply wells in agricultural areas that are constructed with annular grout and a second set of wells in agricultural areas that lack this sanitary construction feature.
2. Sample wells for total coliform and E. coli bacteria
3. Statistically compare the bacterial quality of ground water from the wells of different construction

Southeastern Pennsylvania was chosen as the study area because Chester and Montgomery Counties have well-construction regulations that require wells to be completed with annular grout, which provides a database of wells drilled in noncarbonate bedrock with known sanitary well construction. South Middleton Township in Cumberland County has a well-construction ordinance that requires wells to be completed with annular grout, which provides a database of wells drilled in carbonate bedrock with known sanitary construction. Wells also are being sampled in noncarbonate bedrock areas of York and Lancaster Counties (nonsanitary construction) and carbonate bedrock areas of the Cumberland Valley in Cumberland, Franklin, and Dauphin Counties (both sanitary and nonsanitary construction).

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