Initial sediment test results in Kenmore show limited contamination at most sites, says DOE

A man and his dog walk on the Log Boom Park pier last July while an advisory sign states that sediment testing is planned. - Reporter file photo
A man and his dog walk on the Log Boom Park pier last July while an advisory sign states that sediment testing is planned.
— image credit: Reporter file photo

Test results from sediment samples taken from the shores of north Lake Washington last summer were released Thursday.

The Washington State Department of Ecology’s (DOE) initial view is that the majority of the 30 test sites were within an acceptable range.

“The results look encouraging,” said DOE spokesman Larry Altose. “The samples taken at Harbor Village and the North Lake Marina had elevated levels, but all the other levels were below the threshold.”

The news was met with a positive reaction from Kenmore officials.

“We’re encouraged by these findings,” said Kenmore Mayor David Baker in a release. “The city made a worthwhile investment that succeeded in giving our community information and reassurance about the lake bottom, while clarifying where to direct further environmental efforts.”

Altose said that there is no state standard for sediment contaminants, so the DOE uses the cleanup standard for dry soil as a comparison, which is 11 parts per trillion.

“That is getting down below the levels of detection,” said Altose. “We think it is a fair and formal benchmark. The concentration of sediment (in the majority of testing areas) we consider clean.”

Altose said the DOE will have to wait for the report to be completed to assess the results from the North Lake Marina and Harbor Village.

“Kenmore Industrial Park (KIP) does not seem to be the source (of contaminants) from these results,” said Altose.

Kiewit/General/Manson is using a portion of Kenmore Yard, at 6423 N.E. 175th St., as a supplemental construction site for preparation and maintenance, component construction and barge transportation to the 520 bridge.

The DOE issued a violation notice to KGM on Dec. 28 for sediment disturbance and Altose said that these results do not affect that notice. The notice states that the DOE has documented two occasions when KGM tugboats have caused visible sediment disturbances in the Kenmore Navigation Channel. KGM is now required to file a report within 30 days telling the DOE what steps they have done and will take to control such waste or pollution. The DOE will then inform KGM of the next steps.

KIP, where Kenmore Yard is located, was once the site of the 45 acre Bayside Disposal Dump and landfill. Tests have confirmed that there are no polychlorinated biphenyls (PCBs, a toxic environmental contaminant) at the site, according to officials.

In all, 30 sites were sampled and checked for various contaminants. The sediment, and not the water, was primarily sampled because the types of contaminants tested for adhere to the sediment and do not directly affect the water column. Ten water column samples were also taken.

Altose said the 10 samples did not exceed state water quality standards.

The locations tested include the Kenmore Navigation Channel, multiple sites around Kenmore Industrial Park, Harbor Village, tributary 0056 (the stream closest to Harbor Village), the North Lake Marina, Log Boom Park, Lyon Creek Park Waterfront Park in Lake Forest Park, alongside the Sammamish River and the boat launch near the Sammamish River Bridge, among others.

Eleven of the sites were close to the shore.

“They just waded out and used hand trowels to take the samples of the sediment,” said Altose.

Samples taken closest to the shore reached a depth of four inches into the sediment. That four-inch depth is known as the benthic zone. It is the ecological region in the ocean or a lake where most living organisms are found. It is also the area in which humans or dogs would come in contact.

The tests looked for a myriad of contaminants.

“There was a variety of things they were testing for, but it was primarily dioxins,” said Altose.

Specifically, the tests looked for a series of metals, chemicals, oils and dioxins that include a family of chemicals. The oils include PCBs, phthalates and chlorinated hydrocarbons.

“Phthalates are in plastics and they make (plastics) softer,” said Altose. “They are very common in our society and they do evaporate. They did appear in minute quantities.”

Other chemicals tested for include pesticides and phenols, among many others.

And although there were some results that were elevated, they were within the accepted limits.

“A few of the samples taken at other places around the lake were actually higher,” said Altose, referring to sites on the other side of Lake Washington. “You will never come to a place where there are no dioxins.”

Altose said the main channel had a “low background level of dioxins.”

As for the results at the North Lake Marina and Harbor Village, Altose said: “We don’t know where the dioxins are coming from so we need to identify the source. We have to find the source to be able to do the cleanup so that the contaminants do not come back … These reports will inform lots of decisions.”

A variety of sources primarily paid for the tests. The City of Kenmore paid $100,000, while the DOE paid $35,000. Other various entities paid much lower amounts for individual tests, such as the City of Lake Forest Park for the samples taken at Lyon Creek Park Waterfront Park and residents for testing at their docks.

The results from the Kenmore Navigation Channel are important for the City of Kenmore.

“When you want to dredge (remove sediment) the channel you have to get a permit so that you can put the (contaminated) sediment somewhere,” said Altose.

Altose said that there is a repository that can be reached by barge, which is cheaper than trucking the sediment out. Contaminated sediment would have to be trucked out to a landfill cleaning site.

“Federal funding for dredging is an important goal for the city of Kenmore for economic development of the Lakepointe/Kenmore Industrial Park and for existing water dependent Kenmore businesses,” Baker said. “These sampling results may mean the costs of disposing sediment from dredging the navigation channel will be less for taxpayers.”

The samples taken in the navigation channel reached a depth of 10 inches into the sediment.

“It looks like the city would not have a high cost to dredge the channel, but more tests would have to be done,” said Altose.


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