groundwater plume – Alameda Point Environmental Report

The Navy often hears calls to increase its environmental cleanup effort. Now, the community and regulators are hearing a call from the Navy to eliminate one cleanup effort altogether.

North Housing area next to Island High School where benzene plume is located.

Since 2009, several acres of the area north of Bayport that includes the Shinsei Gardens affordable housing development, former Coast Guard and military housing, the closed Island High School, and the Woodstock Child Development Center have been undergoing groundwater treatment to eliminate hot spots of benzene and naphthalene vapors. Shinsei Gardens also included special building slab engineering in its design as an extra precaution against vapor intrusion. The Navy now says that its groundwater treatment system is unnecessary and should be shut down.

In a report issued in December 2012, the Navy said the underground vapor extraction system called biosparging is not making the area any safer for human habitation. Biosparging is a form of bioremediation that uses air and oxygen injections to stimulate the growth of naturally occurring bacteria, which break down toxics. In this case, the contamination is composed of waste material discharged from an Oakland coal gasification plant and an Alameda oil refinery that operated long before the area was filled in. The contamination layer has been dubbed the Marsh Crust.

The Navy’s report points to the initial studies in the area that showed no risk from vapors. The only justification for the remediation in the first place was the limited risk of contact with water through non-potable uses, since drinking water will always be supplied by East Bay Municipal Utility District.

Now the Navy says that even non-potable uses are impractical and off the table due to high levels of minerals such as salt. With no way of coming in contact with water containing benzene and naphthalene, the Navy decided to review the data for vapor exposure and concluded there is plenty of evidence to turn off the pumps. The biosparge system was designed to run for eight years in order to reach its cleanup goals.

Biosparging system for benzene and naphthalene vapors. White tanks are charcoal vapor filters.

Biosparge manifold for injecting oxygen.

The Navy’s December 2012 Technical Memorandum is seeking to amend the original cleanup decision — known as the Record of Decision (ROD) — for this cleanup area. They will need the concurrence of the regulatory agencies: the regional Water Board, state Department of Toxic Substances Control (DTSC), and the Environmental Protection Agency (EPA). But the EPA and DTSC are not ready to agree without further testing.

According to EPA’s Chris Lichens, “The Navy’s conclusions are not based on current data, site conditions, or investigation methods. Before proceeding with a ROD Amendment,” he said, “the agencies would like the Navy to collect additional data to verify that vapor intrusion would not present a significant risk in the absence of biosparging.” Lichens added, “Along those lines, EPA and DTSC jointly prepared recommendations for additional groundwater, soil vapor, and indoor air sampling and provided those recommendations to the Navy. The Navy has not yet agreed to collect additional data, although we are still discussing it with them,” he said.

Originally published in the Alameda Sun.

One of the groundwater treatment sites

North Housing. Benzene plume extends under lawn area, street, and housing in photo.

Site 1 at the northwestern tip of Alameda Point was used as the principal disposal area for all waste generated at Naval Air Station-Alameda from 1943 to 1956. This disposal area, which was once part of the Bay, was created by sinking pontoons and barges in the Bay and backfilling with dredge soil.

Disposal of cleaning solvents and petroleum products at one unlined pit within the landfill resulted in a groundwater plume that poses a threat of leaching into San Francisco Bay today.

In the 1990s the Navy installed an underground barrier system, called a funnel and gate permeable reactive barrier, to stem the flow of contaminants into the Bay. It was not a permanent solution. In July of this year the permanent solution began with the injection of neutralizing chemicals into the plume.

Protecting marine life

San Francisco Bay at Alameda Point western shoreline where threat of solvent leaching exists.

Most cleanup activities around the base are aimed at eliminating direct health risks to humans, such as from soil or from vapors that could enter a building. In a few cases, the cleanup is focused first on direct impacts to marine life such as fish, which could in turn cause health problems for people who eat them.

The cleanup effort at the Site 1 plume is one of those cases. This effort will keep toxins — solvents, petroleum products, and metals — from ever leaching into the Bay, being ingested by fish, and then consumed by humans. The effort will also reduce unacceptable levels of vapors that are escaping directly above the plume. The future use of the site will be restricted to open space recreational.

The process

Manifold system for chemical injections — July 2012 – Manifold system of hose lines that send oxidant chemicals to individual wells that go into the underground plume contamination area. Navy photo.

The chemical injection process, called In Situ Chemical Oxidation (ISCO), is accomplished by injecting oxidants (catalyzed hydrogen-peroxide and sodium persulfate) into the plume through injection wells. “These oxidants produce short-lived reactions that directly destroy the targeted contaminants,” according to the Navy. Groundwater tests will determine if further treatments are necessary.

Tanks of chemicals for neutralizing solvent plume. Shown as work area being set up in June 2012.

Treatments will continue until either the groundwater is clean enough, or the solvent and petroleum concentration has been reduced by 75%. Once they get to 75% reduction, further injections are more or less a waste of money. From then on, the contaminant concentration is low enough that the remainder will either degrade or disperse and dilute naturally without posing a risk to fish or humans. This process is called natural attenuation and is often relied upon to finish the job when the bulk of contaminants are neutralized and treatment methods no longer yield effective results.

The groundwater plume is also contaminated with metals consisting of arsenic, copper, mercury, nickel, silver, and zinc. The metals problem will, in theory, be taken care of when the solvents and petroleum products are eliminated. This will cause the chemistry of the groundwater to change, which in turn will cause the metals to no longer remain dissolved in the water. The metals will return to their solid state and remain where they are. That’s the theory.

But to make sure it’s working, there will be a long-term groundwater monitoring program to make sure the metals aren’t moving. If problems arise in the future, the Navy will have to come back and design a new remedy. The Navy is responsible for the landfill’s contents staying in place in perpetuity.

Site 1 landfill groundwater treatment area — Map of Site 1 disposal area with arrow from left indicating plume treatment area. Map also shows outlines of individual unlined pits that were used for disposal of waste. Half of the area is now covered by runway.

The Navy opted not to remove the landfill contents because of the $93 million price tag and because the risk of contaminant releases was deemed low. A new set of environmental concerns associated with digging up and hauling away a landfill was also cited during the decision process.

The groundwater plume being treated is approximately 30 feet wide by 160 feet long, and it occurs mainly between depths of 5 and 10 feet below the ground surface.

Site 1 groundwater treatment work underway in July. San Francisco in background. Navy photo.

Delay on soil cover

All of 30-acre Site 1 will eventually be covered with soil and seeded with native grasses. Work on the soil cover was delayed when the contractor discovered that the part of the landfill once used for burning waste was larger than expected. The documentation has to go back through the review process, with a work plan for the soil cover hopefully prepared and ready to implement by 2014.