Source of Elevated Dioxin Levels in Oakland Bay (WA) Still Unknown

[Update 12/15/2013: Chinese ban shellfish harvested from Washington waters due to elevated levels of arsenic and paralytic shellfish poisoning toxins. Given Puget Sound's past use a convenient body of water to discharge pollutants into it's little surprise. In fact, one could say the surprise is why it took so long for contaminated shellfish to work their way into the system. See 12/13 post on the Chinese ban.]

60% of Manila clams produced in the

United States come from Oakland Bay, WA

 

The Department of Ecology has released its most recent report on the elevated levels of Dioxins discovered in 2008 testing of sediments of Oakland Bay (Shelton, WA). At that time questions of what levels of contaminants may exist below 12 inches resulted in testing and a final report, briefly summarized here. The entire text of the report on what the deeper sediment testing revealed may be found in Part 1, Part 2, and Part 3  (5mb, 5mb, 2mb respectively). In short, elevated levels of Dioxins lead to further testing and additional reports.

Harvesting clams in Oakland Bay

(sediment runoff from harvest area)



(click to enlarge)

In Oakland Bay (WA) over 60% of Manila clams in the United States are produced. Within Oakland Bay, Chapman Cove produces Kumamoto oysters described by Taylor Shellfish as having a "distinctive green tinge." In shellfish tissue samples taken for the DOH health analysis, performed after the elevated levels were discovered, the Kumamoto's were found to have the highest "ppt" (parts per trillion) of all shellfish tested. In the report, DOH felt the shellfish were safe for consumers, although they did recommend in their sediment evaluation consumers do such things as wash clams, hands, faces, brush under nails, and clean pets before allowing them inside (p. 17 and 18).

Dioxin levels in shellfish

from Oakland Bay.

 

 

According to the summary of the most recent report on possible sources, sediment samples taken from creeks feeding into the Bay indicate "these surface water inputs do not currently appear to be the source of the bay-wide dioxin levels."





Dioxin levels in Oakland Bay, Shelton Harbor,

and the "ash mound" near Shelton Creek.

(Note: The proposed Puget Sound

benchmark is 4ng/Kg.)

Within the more detailed report (10mb) it was noted that an old ash mound near Shelton Creek was found to have levels of Dioxins which, while elevated, are still below those found in the sediments of Shelton Harbor where Oakland Bay Marina is located. (Note: The City of Shelton recently amended its updated Shoreline Master Program to allow for up to 10 shellfish nurseries within existing boathouses.)

Shellfish nurseries existing and

proposed at the mouth of Shelton Creek

in Shelton Harbor.



Levels of Dioxins in the sediments of Oakland Bay, Shelton Harbor, and the Ash Mounds range from 4 times times to 8 times the statewide soil background levels of 5 ng/Kg (p. 20). The levels found near the mouth of Shelton Creek were just over 8 ng/Kg. Those in Oakland Bay were over 30 ng/Kg; Shelton Harbor 42 ng/Kg; with the two Ash Mound levels being 21 and 40 ng/Kg. The proposed benchmark for Puget Sound is 4 ng/Kg.

Just because you can't see it

doesn't mean it's not there.

Long life chemical pollutants do not

go away just because they are buried.



 

The long life of chemicals in sediments of Puget Sound, and elsewhere, is an ongoing problem for many areas. In the extreme are sediments near the ASARCO plant in Tacoma where mercury, lead, arsenic and other harmful chemicals exist within the deeper levels of sediments. 

 

In the current case, Oakland Bay was once thought to have sediments which were of little concern until sediments from deeper levels were analyzed. In that study (see opening paragraph above) it was shown that while sedimentation may slowly bury those chemicals from past historical activity, they do not go away.  More importantly, testing only the upper surficial levels does not reveal the complete picture. 

 

Geoducks harvested from depths of 3'

bring with them whatever is

contained in those sediments.

Whether "dry" harvesting (above) 

or "dive" harvesting (below).

 



Activities which expose those buried levels of sediments and cause them to re-enter the water column where they enter the food chain should be a concern for all. There, shellfish filter them out of the water column. Higher level species such as salmon consume lower level species which have absorbed them, in turn entering the food chain. These chemicals are like an Uncle who just keeps coming back and overstays his welcome.

 

Burley Lagoon, near Purdy in

south Puget Sound.

 

 

Currently Burley Lagoon is one of those areas where past industrial activity may have left remnants within deeper sediments. A letter to the Department of Ecology from the Department of Health noted elevated levels of polycholorinated byphenyl (PCB) were found in shellfish tissue samples.

"Shellfish samples exceeded screening level and will be evaluated further."

 

The likely source was the Stradley-Manning Super Fund site where transformers were stored and from which PCB's contaminated the area for years. The site was eventually cleaned and declared "safe" by EPA, but those PCB's which flowed downstream into Burley Lagoon to settle into the sediments to slowly be buried remain there, undetected and currently undisturbed.

 

In the letter to DOE, DOH performed an analysis which determined the shellfish with elevated levels of PCB were not a health risk. Not determined in that letter were whether elevated levels of PCB still exist in the deeper sediments, and if so, whether harvesting from current geoduck or future geoduck will re-introduce them into the water column. Should Taylor decide to move ahead with plans to develop its 30 + acre geoduck farm it may be wise to suggest DOE and DOH require deeper sediment testing.

 

DOE might also consider adding as a "recommendation" in its most recent report on the elevated levels of Dioxins within Oakland Bay that future sites where geoduck harvesting is occurring require sediment testing. It seems the Uncle may still be there, sleeping on the couch.