Chemical plume in groundwater extends from Navy base to city

A mile-long plume of a chemical that’s a likely carcinogen has migrated in groundwater from a contaminated site at Naval Air Station Whidbey Island to within Oak Harbor city limits.

No drinking water wells are in imminent danger since the residents in the area are all hooked up to city water, which is piped in from the Skagit River.

Still, government agencies don’t want the plume of 1,4-dioxane to continue its southward creep under the city.

“Human health is protected in the short term,” said Harry Craig, remedial project manager for the Environmental Protection Agency. “This is about environmental cleanup over the long term.”

JUST HOW far into the city the plume extends is still unknown.

Craig said scientists are asking the public for help identifying old wells that might exist south of the plume. Testing those wells will have delineate the edge of the plume.

The plume is in the northeast part of town, roughly between Maple Leaf Cemetery and the highway and possibly into the area around Northeast Sumner Drive

Doug Kelly, hydrogeologist for Island County, said it’s very likely that there are wells the county doesn’t know about in the area because records weren’t kept of their locations years ago.

Anyone who knows the location of old wells in the area should leave a message at 360-396-1030.

THE NAVY was originally scheduled to have completed a proposed plan for dealing with the 1,4-dioxane contamination a couple of months ago, but the project was pushed back because testing for perfluorinated compounds, specifically perfluorooctane sulfonate and perfluorooctanoic acid, in civilian drinking water wells on North and Central Whidbey took priority, Judy Smith of the Environmental Protection Agency said.

The plume of 1,4-dioxane — not to be confused with dioxins — spawns from Area 6, a capped landfill on the Ault Field base with adjacent areas once used as a dumping ground for liquid industrial waste, according to Craig.

In 1992, the Ault Field base was declared a Superfund site with nine areas of contamination divided into five “operable units.” A Superfund site is a polluted area designated by the federal government as requiring long-term cleanup.

AREA 6 IS the site of an ongoing cleanup effort. The description of the Area 6 pollution in the 1993 “Superfund Record of Decision” is chilling. From 1969 to 1988, many different types of hazardous waste were dumped and stored in pits, trenches and landfill in the 260-acre site at the southeast corner of the Ault Field base. That included 2.2 million gallons of liquids and sludge, between 300,000 and 700,000 gallons of acids and solvents, an estimated 100,000 to 600,000 gallons of oily sludge, and unknown quantities of oils, asbestos and other hazardous waste.

Neighboring homes had to abandon wells in the 1990s and the Navy paid for them to be connected to city water line.

The primary contaminants of concern were volatile organic chemicals present in the solvents that were dumped.

The Navy installed extraction wells to treat the groundwater beneath Area 6 through an air stripping system.

Air stripping is the process of moving air through water in an above-ground system to remove the volatile organic chemicals by evaporating them, according to the EPA’s “A Citizen’s Guide to Air Stripping.”

The treatment has worked. Maps of the chemicals in groundwater show two plumes of volatile organic chemicals have decreased dramatically over the years.

TESTING AND TREATING the water for 1,4-dioxane wasn’t part of the original treatment plan as the chemical wasn’t considered a chemical of concern in the early 1990s, but appeared on the EPA’s radar in the early 2000s. Its presence was first discovered at Area 6 in 2003. Since then, experts have been testing wells in the area to map the dimensions of the subterranean plume and the Navy has been investigating ways to treat the water for the chemical.

Craig explained that 1,4-dioxane was used to stabilize solvents. It can’t be treated with an air stripper system and is very mobile in groundwater.

The EPA considers 1,4-dioxane as being likely to cause cancer. Animal studies showed increases in tumors of the nasal cavity, liver and gall bladder. The EPA established a daily health advisory level in drinking water of 0.4 milligrams per liter for adults.

Navy officials, Craig said, are considering an advanced oxidation system — possibly using peroxide, ozone or ultraviolet light — to treat extracted water contaminated by 1,4-dioxane.

“The idea is to get in front of the plume and treat it,” said Ted Repasky, a hydrogeologist with the EPA.

THERE ARE a couple of potential wrinkles with the plan, according to Craig.

The EPA wants the water in Area 6 to also be tested for perfluorinated compounds, which are in some firefighting foam and can also leach from landfills, he said. The Navy took samples from more than 100 wells in North and Central Whidbey in the last few months and found eight with preliminary levels above the EPA’s lifetime health advisory level.

If perfluorinated compounds are present at a certain level, the EPA would like the water to be treated for them as well. The problem, if the chemicals are present, is that they can only be removed from water with granular activated carbon, which could make the treatment more complex.

IN ADDITION, Craig said the water should also be tested for bromide, a relatively benign chemical present in seawater. The potential complication is that the oxidation process which removes 1,4-dioxane from the water can turn bromide into bromate, which is more toxic.

Mike Welding, public information officer at NAS Whidbey, explained that the Navy and EPA are working together to identify the best treatment technology for the situation.

After additional water testing this year, the Navy will create a “focused feasibility study” followed by a proposed plan, which will summarize the alternatives studies and highlight the key factors that lead to the identification of the preferred alternative, Welding said.

The public will have an opportunity to review and comment on the proposed plan. The Navy will then document the decision in an amendment to the 1993 Record of Decision.