No clear solutions.

Here’s the rub — there’s no reasonable explanation for all this contamination. Treated urban sewage and farm manure contain low levels of E. coli. Waste from livestock farms sprayed as manure on fields is meant to stay there and fertilize fields — not flow into waterways. Some of the contamination comes from wildlife, but that’s only one small piece of the puzzle. There’s no reason E. coli should be present in our waters at these levels if there are proper systems in place to deal with the excrement of 320 million Americans and the farm animals that outnumber us — which means current systems are failing somewhere along the line.

While the country’s ecosystems are silently being flooded with poop, the situation is on track to get even worse. Earlier this year a congressional bill was introduced to further weaken regulations on dairy manure. Meanwhile climate change is increasing the frequency of critical sewage flooding events with every hurricane that hits the country.

This is not a problem that can easily be flushed away, and solving it will require communities to address the need not just for safer fecal management, but for larger sustainable choices that reduce the magnitude of the problem if they want to keep their citizens safe — and clean.

Disclaimer: This is not an absolute ranking of the most contaminated sites in America. There are many limitations to available data. Many known catastrophic manure spills and sanitation failures — such as hurricane flooding in North Carolina — do not show up in these maps, and some states just do not monitor their waters as closely as others.

Methods:

Data source:

Water-quality data downloaded from The Water Quality Portal, a cooperative service sponsored by the U.S. Geological Survey, Environmental Protection Agency and National Water Quality Monitoring Council. It serves data collected by more than 400 state, federal, tribal and local agencies.

Land cover and urban areas geospatial data provided by USGS.

Data parameters:

Quality characteristic: Escherichia coli. Other fecal organisms are sometimes evaluated by agencies, but E. coli testing has the widest and most uniform geographic coverage.

Quality measure: Number of E. coli as reported in Colony Forming Units (CFU), Most Probable Number (MPN), or number (#). Suitable data were collated under these three most widely used measures, and the top 10 percent of each of the three categories were collected separately to obtain the top 10 percent results overall.

Time period: All test results in five years — from October 2012 to October 2017. The same monitoring stations are sampled annually, but sampling occurs at different and sometimes arbitrary times of the year. To account for seasonal changes, unusual events, and other sources of stochasticity, five years of data were pooled and the highest result for each monitoring station was retained.

Limitations: Monitoring stations varied widely across states, with some states having more than 5,000 sampling sites, and others having as few as 500. However, existing monitoring stations across all states appeared to be well distributed across watersheds. Alaska, Hawaii, Illinois, and Rhode Island had the poorest monitoring coverage of all states.