The effects that well depth and wellhead protection have on bacterial contamination of private water wells in the Estes Park Valley, Colorado.

Over the past five years, it is estimated that 10% of residential water wells have tested positive for total coliform and 2% for E.coli bacteria in the Estes Park Valley, Colorado. Many of these water wells are shallow or hand-dug in construction. In this study, samplings of 30 private untreated water wells were tested for total coliform bacteria in the Estes Park Valley. Water wells were classified into three categories for well depth (<99 feet [30.2 m], 100-199 feet [30.5-60.7 m], and >200 feet [61 m]) and for wellhead protection (poor, fair, and good). Results indicated that 71% of the wells less than 199 feet (60.7 m) tested positive for total coliform (chi2 = 15.559, p < .0001). Also, 71% of wells classified as having poor and fair wellhead protection tested positive for total coliform (chi2 = 13.084, p = .001). This study determined that wellhead protection and well depth does play a role in bacterial contamination of water wells.