DNA testing narrows source of fecal issuers

JOHN DODGE THE OLYMPIAN

THURSTON COUNTY -- At least 27 types of animals -- from humans to raccoons -- contribute to the bacterial contamination problems in Henderson Inlet.

That's one of the major findings in a 15-month, $60,000 study that used DNA testing to pinpoint pollution sources in the 45-square-mile watershed northeast of Olympia.

Test results will be used to develop a pollution control plan to protect and restore commercial shellfish growing areas in the inlet, Thurston County environmental health specialist Linda Hofstad said.

"They confirm that nonpoint pollution really comes from many locations, and that we really need to consider a variety of sources, if we are going to be successful in our efforts to improve water quality in Henderson Inlet," Hofstad said.

The picture of nonpoint pollution -- pollution that comes from multiple sources -- emerged from detailed tests of 942 water and sediment samples taken from lower Henderson Inlet from February 2000 through May 2001. Among the findings:

-Humans, dogs and birds are the most frequent contributors of fecal coliform in the urban area of the watershed.

-Birds, deer, dogs and coyotes, rodents and humans all show up at the top of the list in rural areas.

-Overall, birds, dogs and humans are the most frequent contributors of bacterial pollution.

The study did not calculate how much pollution each species adds to the marine waters, only a frequency rate of pollution, Hofstad explained. And the data only apply to Henderson Inlet.

The DNA typing study is part of a larger investigation of pollution problems that caused the closure or restricted use of 488 acres of commercial shellfish growing area in Henderson Inlet.

The loss of shellfish beds in Henderson Inlet and the Nisqually Reach forced Thurston County to form shellfish protection districts for the two areas in December.

Committees consisting of city, county and citizen representatives are being formed to develop long-term actions plans for protecting and restoring the shellfish growing areas, said Mark Swartout, county natural resource program manager.

The study reaffirmed that measures to fix leaking septic tanks and sewer lines would pay water quality dividends, Hofstad said.

And stepped-up efforts to properly dispose of dog feces in Lacey and Olympia urban areas of the watershed would also help, she said.

The Olympian Copyright 2002

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