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Relation between selected well-construction characteristics and occurrence of bacteria in private household-supply wells, south-central and southeastern Pennsylvania

Water-Resources Investigations Report 2001-4206
Prepared in cooperation with the Pennsylvania Department of Environmental Protection Bureau of Water Supply and Wastewater Management
By: , , and 
https://doi.org/10.3133/wri014206

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Abstract

Total coliform and Escherichia coli (E. coli) bacteria were analyzed in ground water sampled from 78 private household-supply wells as part of a study by the U.S. Geological Survey in cooperation with the Pennsylvania Department of Environmental Protection to evaluate the relation between well construction characteristics and the occurrence of bacteria in ground water. Sampling was done in eight counties in south-central and southeastern Pennsylvania from September 2000 to March 2001. All samples were collected from wells in close proximity to agricultural land-use areas.

Total coliform bacteria were found in water from 62 percent (48 of 78) of the wells, and bacteria were just as likely to be found in sanitary wells (grouted/loose-fitting well cap or grouted/sanitary sealed well cap) as in nonsanitary wells (nongrouted/ loose-fitting well cap). The areas underlain by carbonate bedrock had the highest percentages of total coliform detected (about 75 percent). Nearly half of the samples collected in the areas underlain by noncarbonate bedrock also were found to have total coliform present. E. coli bacteria were found in water from 10 percent of the wells. Seventeen percent of the samples that were positive for total coliform also were positive for E. coli. The presence of E. coli bacteria was more likely in water from nonsanitary wells. Additionally, the presence of E. coli bacteria was more likely in ground water from wells underlain by carbonate bedrock. A further breakdown of the data into four groups on the basis of sanitary construction and bedrock type indicated the presence of E. coli was more likely in water from nonsanitary wells in areas underlain by carbonate bedrock.

Statistical analysis of other well-construction characteristics that might relate to occurrence of bacteria showed that the presence of total coliform bacteria was related to the depth to water-bearing zone in both sanitary and nonsanitary wells in areas underlain by carbonate bedrock. Relations also are present between the presence of total coliform bacteria and casing length in nonsanitary wells in areas underlain by noncarbonate bedrock. Bacteria were found in wells both with and without insects observed on the underside of the well cap. Because of the small number of wells sampled that had sanitary sealed caps, it is uncertain whether installation of sanitary sealed well caps would reduce the incidence of bacteria in ground water from wells or if the presence of bacteria is because of a combination of well-construction characteristics or aquifer-wide contamination of limited or broad areal extent.

Suggested Citation

Zimmerman, T.M., Zimmerman, M.L., and Lindsey, B.D., 2001, Relation between selected well-construction characteristics and occurrence of bacteria in private household-supply wells, south-central and southeastern Pennsylvania: U.S. Geological Survey Water-Resources Investigations Report 2001–4206, 22 p., https://pubs.er.usgs.gov/publication/wri014206.

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Table of Contents

  • Abstract 
  • Introduction 
  • Well-construction practices in Pennsylvania 
  • Study methods
  • Relation between selected well-construction characteristics and occurrence of bacteria n ground water
  • Summary and conclusions
  • References cited
  • Appendix: Selected well information and results of bacteria analyses for private household-supply wells in south-central and southeastern Pennsylvania
Publication type Report
Publication Subtype USGS Numbered Series
Title Relation between selected well-construction characteristics and occurrence of bacteria in private household-supply wells, south-central and southeastern Pennsylvania
Series title Water-Resources Investigations Report
Series number 2001-4206
DOI 10.3133/wri014206
Year Published 2001
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description iv, 22 p.
Country United States
State Pennsylvania
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details