Water board wants demolition, excavation underway at Marinwood’s former dry cleaner site

by Stephanie Weldy, originally posted on April 23, 2016


The entire Marinwood Plaza shopping center, excluding the Marinwood Market, must be razed and the contaminated soil beneath it excavated and removed, state officials declared.

Work must start within six months and be finished by early next year, according to the state Regional Water Quality Control Board, which approved several elements of a proposed cleanup plan developed by Geologica, a San Francisco-based environmental consulting firm hired by the property owner, Marinwood Plaza LLC.

The cleanup order was detailed in a letter Wednesday from the state board to the property owner, who could not be reached for comment last week. The total cost of the cleanup project was unavailable.

“(The board agrees) on the need to move forward as quickly as possible with excavation of the contaminated material underneath the former dry cleaner,” said Dyan Whyte, assistant executive officer at the water board.

Soil beneath the shopping center is contaminated with PCE, or tetrachloroethylene, from the former Prosperity Cleaner dry-cleaning business.

The 18,324-square-foot center on Marinwood Avenue, just west of Highway 101, is mostly vacant with the exception of a liquor store at the south end and the 15,190-square-foot Marinwood Market — which is outside the contaminated area — at the north end.

PCE was first discovered in the neighborhood in 2007.

Soil excavation will be 25 by 30 feet and about 15 feet deep, though excavation could be more extensive depending on necessary cleanup.

By July 1, officials want six clay barriers installed in trenches along utility lines where contaminated soil vapor is believed to be traveling. The barriers are expected to limit further migration of the vapor. Soil vapor monitoring wells must be installed by March 2017 to evaluate the effectiveness of soil removal and the barriers.

Marin County Supervisor Damon Connolly said he is satisfied with the approach approved by the state board, which included certain elements of the cleanup plan, known as partial approval.

“Partial approval means the critical work of demolition of the building and excavation of the contaminated soil at the source will begin now on a firm timeline,” Connolly said.

Alex Go, owner of Savemore Discount Liquor, said Friday he had not been informed by his landlord that the building would be coming down. He is not sure what he will do with his displaced business, he said.

“I have to cut down on purchases and see if I hear of anything from the landlord for when to leave,” he said. “Then I can start planning. In the meantime, I haven’t heard anything from them, so it’s kind of hard.”

Marinwood residents had criticized an initial cleanup proposal that would have allowed toxins to naturally weaken to reduce the potential of groundwater contamination. Residents called the approach too passive, and the state water board agreed.

Under the approved plan, biodegradation, dispersion and dilution of toxins are expected to occur in groundwater both on-site and off-site once contaminated soil is removed.

The water board also asked for a feasibility study of both the natural breakdown of toxins in the soil, and an active approach, including injecting substances to oxidize and break down toxins.

The property owner and its cleanup contractor should “look at a variety of options that can be used to treat groundwater,” said Ralph Lambert, engineering geologist for the water board.

The board also ordered an off-site groundwater investigation along with possible cleanup strategies. Failure to complete such an investigation could result in fines of up to $5,000 per day, beginning July 1.

David Trotter, an attorney representing the Silveira family — which owns land that has been contaminated east of the shopping center, on the opposite side of Highway 101 — said the groundwater cleanup feasibility study is a good start, but more must be done.

Only small soil samples have been tested at the Silveira’s property, Trotter said. A more thorough investigation should be conducted at the ranch to determine what extent groundwater and soil have been affected and how they should be treated, he said.

“You have a process where you do a good remedial investigation,” Trotter said. “From that you find out what’s happening under the surface.”

Water board officials want soil vapor monitoring to be conducted between the former dry cleaner site and Casa Marinwood. Vapor monitoring and control measures must also be installed for when soil underneath the former dry cleaner building is excavated. The measures would ensure there is no threat to site workers and residents, according to the water board.

Resident Bill McNicholas said he is starting to feel better about the cleanup process. He said he is thankful Connolly persistently pushed for a speedy cleanup.

“I think everybody got a win-win to see this thing going forward,” he said. “And management is forced to act now because it’s so public, they have to stay on top of it.”

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