Tests reveal no cause for alarm re dioxins in lake bed
Friday, January 18, 2013
Background dioxins in Kenmore lake sediments similar to other Seattle-area studies
Dioxin levels in lake-bottom sediments in most areas at the northern tip of Lake Washington are consistent with background soil and sediment concentrations found in the Seattle-area, according to data released today from a joint study by the city of Kenmore (Kenmore) and the Washington Department of Ecology (Ecology).
“We’re encouraged by these findings,” said Kenmore Mayor David Baker. “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.”
“The initial data are promising, especially for the public recreational areas,” said Jeannie Summerhays, Ecology’s Northwest regional director. “We’re grateful to the city and cooperating property owners for the partnership that enabled this work to take place. In the places with higher levels, Ecology will work with property owners to determine the next steps for further evaluation, as needed.”
Kenmore and Ecology funded the evaluation of lake-bottom sediment and water samples from 30 locations at Kenmore Harbor, Log Boom Park, Kenmore Navigation Channel, the lower reach of the Sammamish River and at Lake Forest Park’s Lyon Creek Waterfront Park. The study provided follow-up to a 2011 report of dioxin in lake sediment at a private moorage in Kenmore.
The city of Lake Forest Park and several commercial lakefront property owners helped fund the study or provide access for the sampling.
All of the surface water samples show no results above the basic screening levels used by Ecology to evaluate water quality.
Sediment samples taken in areas where people and pets may have contact with the lake bottom showed dioxins below the levels Ecology uses to determine if health risks are present from contact with dioxin in soils. Dioxins in sediments at two private marinas exceeded those levels, and Ecology will pursue further investigation of those areas in cooperation with the property owners. Those sediments are in areas not readily accessible to people or pets.
One of the study’s goals was to determine potential sediment disposal options for the future maintenance dredging of the Kenmore Navigation Channel for better vessel access to waterfront businesses. The channel’s sediments contain dioxin levels similar to other areas outside the two marinas. The channel is a U.S. Army Corps of Engineers facility.
“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.”
Ecology and Kenmore plan to issue the study’s final report this spring.
The Washington Department of Health plans to conduct a health consultation for Log Boom Park and Kenmore Industrial Park this spring.
Ecology and Kenmore will host an informal open house on Jan. 23, 2013, from 5 to 7 p.m. at Kenmore City Hall to answer questions about the sampling results. Another meeting will be scheduled in the spring on the study’s final report.
The study data are available at Kenmore City Hall, Kenmore Library and online.
Additional information on Dioxin
Dioxins form in minute amounts as byproducts of burning. Exhaust from vehicles, forest fires, wood or coal burning and waste incineration can release dioxins into the air. Industrial processes that involve chlorine, such as bleaching wood pulp or manufacturing certain chemicals, can produce dioxins. Various paper and pulp products contain small amounts, at levels not considered harmful.
Dioxins can be found at low levels throughout the world. They tend to attach to small particles. In water, dioxins do not readily dissolve and tend to settle to the bottom and chemically adhere to sediment particles.
For people, the most common means of dioxin exposure is by eating something that contains it. Dioxin can enter food chain when small creatures eat tiny plants that grow in dioxin-contaminated sediments and ingest fine particles. Dioxin accumulates in the fat tissue of whatever eats it.
Studies have found increased cancer rates among people with many years of workplace dioxin exposure. Laboratory animal experiments have linked dioxin exposure to cancer. The amount of exposure in these studies was significantly higher than the levels found in the Kenmore area samples.
Most samples included sediments to a depth of 4 inches, which is the zone occupied by sediment-dwelling animals and plants. Samples from the Kenmore Navigation Channel and Northlake marina were 10 inches deep, which provides a useful screening tool to evaluate future dredged materials disposal planning.
Kenmore area sediment sampling results available on these two websites:
Background information on dioxins:
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