Olin’s proposal to clean plume to 11ppb is twice state’s public
health goal for perchlorate
Morgan Hill – The goal to clean perchlorate from South County’s groundwater proposed by the Olin Corp. is too high, say officials of the Central Coast Regional Water Board.
In January, Olin proposed to clean the 9.5 mile perchlorate plume that stretches south from Morgan Hill through San Martin and east of Gilroy to a level of 11 parts per billion. That’s nearly twice as high California’s 6ppb public health goal for the contaminant, or the level of perchlorate state scientists believe is safe for regular human consumption.
Perchlorate is a salt known to interfere with thyroid activity. When Olin announced its cleanup goal, the company contended that, based on the latest scientific evidence, 11 ppb is protective of all humans, including infants and pregnant women.
But in a letter to Olin, the regional board said that company’s approach was “inconsistent with the water board’s goal to protect groundwater as a resource and responsibility to prevent water degradation.”
The state water code demands that polluters clean groundwater to background levels unless it is technologically or financially not feasible. The cleanup level can not be higher than any published health goal. In this case, that’s 6ppb, though that number may go up when the California Department of Health Services releases a drinking water level for the contaminant, perhaps later this year.
The regional board did agree with Olin’s stance that it is too soon to announce a final cleanup goal because it’s not yet clear how much, if any, perchlorate was in the groundwater before Olin’s now closed road-flare factory opened in 1955, and the company hasn’t completed a cleanup feasibility study, due at the end of June.
More than 1,000 municipal and private wells were polluted by Olin, but most are contaminated at levels well below 6ppb. In the latest round of tests, only 31 of 863 wells were above 6ppb.
Olin engineer Rick McClure said Tuesday the company will clean the basin to a level that will not interfere with any current or potential use of the water. He said the company will continue to provide bottled water to residents whose wells test above 6ppb.
“Olin has and will continue providing alternative drinking water supplies to well owners and tenants whose perchlorate concentration exceeds the public health goal,” McClure said.
“However, cleanup of groundwater exceeding a particular clean-up level, whether it might be 24.5ppb, 11ppb, or 6ppb, can only be initiated after further studies are complete and the regional board establishes the final clean-up goal.”
