A study by the Environmental Protection Agency and Lummi Indian tribe failed to find evidence that cow manure is polluting tribal shellfish beds in Portage Bay in northwest Washington.
The study suggests farmers are keeping manure out of the Nooksack River and it tributaries, which drain into the bay, said Fred Likkel, an environmental consultant and executive director of Whatcom Family Farmers.
“It shows the farm community has been working very hard for the last number of years to make sure it’s not polluting the shellfish beds,” he said.
Dairies have long been suspected of being a leading contributor to fecal coliform contaminating the Lummi shellfish beds. The Nooksack River drains nearly 800 square miles, much of it farmland, and is the primary source of freshwater for the bay.
To identify the sources of fecal coliform, the EPA analyzed the DNA in 54 water samples collected in 2016 from the bay, river, five creeks and a ditch.
The EPA reported last month that its laboratory found fecal coliform from birds in two samples, from non-cattle hoofed animals such as horses or deer in four samples, and from both birds and non-cattle hoofed animals in three samples.
The source of fecal coliform in 45 samples was undetermined. No genetic material from cattle, humans or dogs were found.
The EPA in a two-page summary said it’s possible that cattle fecal coliform was present, but at levels too low to detect or in genetic sequences that were not identified.
The Washington Department of Health in 1997 blamed dairies for fecal coliform that caused shellfish beds to close. Water quality improved and the beds reopened after dairies adopted new manure-handling rules enforced by the state Department of Agriculture.
In recent years, however, water quality has again degraded. Other potential sources of pollution include wildlife, hobby farms and failing septic tanks.
“This study really validates our position: You need to look at other sources,” Likkel said. “That doesn’t mean we can slack off and not do our job.”
Efforts to obtain further comment from the EPA and tribe were unsuccessful.
In early 2016, the EPA and the tribe set out to identify the sources of fecal coliform to help develop pollution-control strategies for the Nooksack River watershed, according to the agreement.
At first, the EPA’s Region 10 laboratory analyzed 53 water samples for genetic material from humans and hoofed mammals and found one sample with human DNA and four with animal DNA.
The laboratory later added the ability to test for material specific to cattle, birds and dogs for the other 54 samples.
The threat of lawsuits has hung over Whatcom County dairies. Seven dairies early this year agreed to pay the tribe $450,000 to compensate it for closed shellfish beds. The agreement calls for more payments later and for dairies and the tribe to collaborate on pollution-prevention plans.
Six farmer-led watershed improvement districts have hired a microbiologist to analyze fecal coliform in Scott Ditch, one of the waterways tested by the EPA. The report has yet to be completed.