A Comparison of Drinking Water Contamination in Buried Slab Wells, Other Large-Diameter Wells, and Drilled Wells

Authors

Rita M. Gergely, Iowa Department of Health

Document Type

Research

Keywords

wells, buried slab, total coliform bacteria, fecal coliform bacteria, nitrate, atrazine, Iowa

Abstract

This study presents the results of a statewide water well survey conducted by the Iowa Department of Public Health from 1993 to 1995 to determine whether there were statistically significant differences between well water contamination in buried slab wells, other large-diameter wells, and drilled wells. Wells were sampled for total coliform bacteria, fecal coliform bacteria, nitrate, and atrazine. Staff collected water samples and completed a site survey at each well, which included an interview with the occupant or owner and actual observations of the wellhead and surrounding area.

The study included 293 buried slab wells, 287 other large-diameter wells, and 445 drilled wells. Buried slab wells were significantly less likely than other large-diameter wells to be contaminated with total coliform bacteria, fecal coliform bacteria, nitrate, and atrazine. The well type (buried slab versus other large-diameter) was a more significant variable than whether the well depth was greater than 15.2 m (50 ft) for all contaminants except for total coliform bacteria. When classified by depth (less than or equal to 15.2 m (50 ft) deep or greater than 15 .2 m (50 ft deep)), buried slab wells in each depth range were significantly less likely than other large-diameter wells to be contaminated by total coliform bacteria, fecal coliform bacteria, and nitrate. The rates of contamination for total coliform bacteria, fecal coliform bacteria, and atrazine were not significantly different for buried slab wells and drilled wells. In addition, the percentage of wells with a concentration of N0₃-N greater than 20 ppm or 30 ppm was not significantly different for buried slab wells and drilled wells. However, the mean concentration of N0₃-N (nitrate expressed as nitrogen) was significantly higher for buried slab wells compared to drilled wells, as was the percentage of wells with a concentration of N0₃-N greater than or equal to 3 ppm and greater than 10 ppm.

Publication Date

July-December 2004

Journal Title

Journal of the Iowa Academy of Science

Volume

111

Issue

3-4

First Page

49

Last Page

57

Copyright

© Copyright 2005 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf

Recommended Citation

Gergely, Rita M. (2004) "A Comparison of Drinking Water Contamination in Buried Slab Wells, Other Large-Diameter Wells, and Drilled Wells," Journal of the Iowa Academy of Science: JIAS, 111(3-4), 49-57.
Available at: https://scholarworks.uni.edu/jias/vol111/iss3/3