Part of a series
The most recent statewide study of Iowa’s private wells, the Iowa Statewide Rural Well Water Survey Phase 2, found that nearly half of wells had detectible levels of nitrogen, bacteria or arsenic:
- 49 percent of wells had detectable nitrate; 12 percent had levels higher than the EPA’s public drinking water standard of 10 milligrams per liter.
- 43 percent of wells had total coliform bacteria; 19 percent had enterococci, a bacteria found in feces that can cause infections in wounds or in the urinary tract; 11 percent had E. coli.
- 48 percent of wells had detectable levels of arsenic; 8 percent had arsenic levels at or higher than 0.01 milligrams per liter, which is the EPA’s drinking water standard for public water supplies.
The study was conducted by University of Iowa’s Center for Health Effects of Environmental Contamination. It was used to sample 473 private drinking water wells in 89 of Iowa’s 99 counties between May 2006 and December 2008.
THIS IOWAWATCH INVESTIGATION WAS SUPPORTED BY A GRANT FROM THE FUND FOR INVESTIGATIVE JOURNALISM
The survey also looked at agricultural contaminants like herbicides and herbicide degradates, the products that are created when the original chemical compound, called the parent compound, starts to break down. While parent compounds occasionally were found in wells, some of the degradates were found more often. They included a degradate of the herbicides alachlor and metolachlor, which were found in 27 percent and 33 percent of wells, respectively.
Because the health impact of the degradates is largely unknown, the report pointed to this as a point of concern and goal for future research, especially because some of the parent compounds are known to have negative reproductive or developmental impacts.
The statewide survey showed increased risks for shallow and older wells. Shallower wells were more susceptible to total coliform bacteria, herbicide degradates and higher nitrate concentrations than deeper wells. Older wells, defined as being constructed before 1991, were more susceptible to total coliform bacteria and herbicide degradates.
The survey also showed differences based on region, with more bacteria detections — total coliform, enterococci and E.coli — in the northwest, southwest and south-central areas of the state. Higher nitrate concentrations were common in the northwest and southwest.