Out of 459 wells Olin said were safe, 40 may still contain
unsafe levels of perchlorate
Morgan Hill – Olin Corporation has been ordered to resume shipping bottled water to 61 households in the Morgan Hill, San Martin and Gilroy area after engineers at the Central Coast Regional Water Quality Control Board determined that 40 wells may still contain unsafe concentrations of perchlorate.
In June, Olin Corp. terminated its supply of bottled water to users of 459 wells that had been polluted by the company’s road flare plant on Tennant Avenue.
Now, after a careful review of all the laboratory data sheets associated with four consecutive quarters of data for the 459 wells, the water board has announced it is not accepting one or two quarters worth of results from 40 wells because the perchlorate readings may have been biased by the presence of naturally occurring ions in the groundwater sample.
“We’re just being conservative,” said Thea Tryon, an engineering geologist at the Central Coast Water Quality Control Board who is helping monitor the South County clean-up effort. “The quality assurance wasn’t as much as we wanted.”
Officials said there is no pattern as to where the 40 wells are located geographically. Letters were sent Friday to all households whose bottled water supply would be continued.
A letter was also sent to Olin, whose representatives did not return phone calls before press time Friday. Water board officials said they had not heard a response from Olin.
Olin is allegedly responsible for a 9.5-mile plume of perchlorate spreading south from its now defunct factory in Morgan Hill. For more than a year, the company has been ordered by the state to supply users of domestic wells in South County with bottled water if their wells tested for perchlorate at concentrations greater than 6 parts per billion (ppb) after a year of quarterly testing.
Perchlorate is a type of sodium that can affect healthy thyroid activity.
The California Office of Environmental Health Hazard Assessment has determined a concentration of 6 ppb to be a safe level of perchlorate in drinking water consumed on a daily basis.
State water officials announced Thursday they are now confident that all but the 40 wells in question are meeting the state’s health goal.
Sylvia Hamilton, chairwoman of the Perchlorate Community Advisory Group, said she is pleased with the water board’s thorough and timely review.
“I’m not surprised that this happened,” she said, referring to imperfections in Olin’s analysis. “I’m very grateful that the state board is so meticulous and professional.”
Olin contacted water board officials two weeks prior to its termination of bottled water in June.
Analytical data for the last quarter of 2006 was sent to the water board in five phases. Officials said they received the last phase of analytical data on July 18.
As to what led the water board to double check Olin’s results, board engineer Hector Hernandez said, “We were going to do this regardless – we believe it is our responsibility to confirm that compliance with the state board criteria is achieved.”
According to Hernandez, Olin must start shipment of bottled water “immediately” to the 61 households.
The added supply of bottled water may only last for one more quarter of testing.
Olin consultant Mactec collected the water samples and TestAmerica Laboratory, located in Morgan Hill, analyzed them.
According to water board officials, the way groundwater samples were collected and the laboratory equipment used to analyze the samples were correct.
Tony Burchyns covers Morgan Hill for The Times. Reach him at (408) 779-4106 ext. 201 or tb*******@mo*************.com.
