DNR rule change could endanger Iowans' health

Susan Heathcote
Iowa View contributor

In a recent story entitled, “Would water monitoring changes make Iowa lakes, rivers less safe, [Aug. 15]” the Des Moines Register wrote about the Iowa Department of Natural Resources' proposed significant change to the water quality standards for E. coli bacteria.

E. coli bacteria

The new standard would reduce protections for people who swim in Iowa lakes, rivers and streams. Keeping in mind that bacteria are the leading cause of Iowa’s water impairments, the Iowa Environmental Council is concerned that the proposed changes do not adequately protect public health.

Under Iowa’s current bacteria standard, a river or lake must meet both a Geometric Mean limit and a Single Sample Maximum limit to be considered safe for swimming and other primary contact recreation uses.

Under Iowa’s current bacteria standard, a river or lake must meet both a Geometric Mean limit and a Single Sample Maximum limit to be considered safe for swimming and other primary contact recreation uses. Together these two limits ensure that the average bacteria levels during the recreational season are safe and that the water quality on individual days does not exceed a maximum threshold. However, DNR is proposing to eliminate the Single Sample Maximum limit on bacteria and rely solely on the Geometric Mean to determine if Iowa lakes and rivers are safe for swimming.

The DNR cites cost savings as one of the reasons for this change, along with concern that the current standard is “overly stringent.” There is no doubt that this change will save the DNR money since fewer waters would be identified as impaired, and DNR would no longer need to develop plans to reduce short-term spikes in bacteria as long as average water quality is good. But are these waters dependably safe for swimming? And if not, what is the risk in terms of increased illnesses?  

Will changes in DNR rules ensure protection of swimmers' health?

Let’s look at the Boone River south of Webster City, one of the rivers potentially affected by the proposed change, to see how this change might affect Iowans. This stretch of the Boone River passes through Bells Mill Park, a popular recreational area for many Iowans, including my family. Reviewing water quality data on the DNR website, I am glad to see that the average bacteria levels of water samples collected over the past three years meet Iowa’s Geometric Mean standard, and water quality is usually safe for swimming. However, this stretch of the Boone River is on the impaired waters list because seven of the samples (28 percent of samples collected) exceed the Single Sample Maximum bacteria criteria.

If the DNR change in the bacteria standard is adopted, this river segment would come off of the impaired list — despite the fact that more than one out of every four days when samples were collected, there was a spike in bacteria levels that presented a significantly increased risk of illness for anyone swimming or playing in the water at that time.

This situation illustrates why the DNR’s proposed change to rely only on a Geometric Mean standard is not acceptable. 

The EPA has studied illness rates associated with bacteria levels at public beaches. In 2012 the EPA issued new recommendations for states’ water quality standards for their recreational waters. The updated standards include both a Geometric Mean (GM) and a Statistical Threshold Value (STV), which replaces the Single Sample Maximum in previous EPA recommendations. Both the GM and STV are needed to determine if water quality is protective of recreation in the water. According to EPA, “Using the GM alone would not reflect spikes in water quality because the GM alone is not sensitive to them.” 

Susan Heathcote

The leading cause (by far) of impairments to Iowa’s lakes and rivers is high levels of E. coli bacteria. As Iowa faces a growing number of impaired waters, now is not the time to shorten Iowa’s Impaired Waters List by weakening water standards necessary to protect public health.

The Iowa Environmental Council is recommending that DNR either leave the current Single Sample Maximum E. coli bacteria standard in place, or replace it with the EPA recommended Statistical Threshold Value by adopting the 2012 EPA recommended standard. 

SUSAN HEATHCOTE is the water program director for the Iowa Environmental Council.