Private well owner finds high levels of chemical west of
Monterey Road
San Martin – Unsafe perchlorate contamination levels have been found on a private well west of Monterey Road, indicating the chemical’s nine-mile-plume has further dispersed from the southeast section of Tennant Avenue.
The unofficial test results, reported Dec. 4, triggered more bottled water delivery from Olin Corp. within the week and concerns that the plume of the thyroid-damaging salt could be shifting course.
Olin Corporation is allegedly responsible for an underground plume of perchlorate stretching southeast from the company’s old road-flare plant on Tennant Avenue in Morgan Hill. Perchlorate contamination was discovered in local wells in 2003 in Morgan Hill and San Martin. State water officials have ordered Olin to cleanse the soil around the factory and devise a South County cleanup plan. Previous monitoring of the chemical plume shows it traveling southeast of Monterey Road.
From 1956 to 1995 Olin and Standard Fuse operated a road-flare plant where perchlorate leaked into the ground. The chemical is used to make explosives, road flares and fireworks.
The exact location of the private well and the name of its owner were not released to the public.
A person who knows the affected well owner forwarded a request for an interview from the Gilroy Dispatch, but no calls were received by presstime.
Santa Clara Valley Water District engineering geologist Tom Mohr said the well belongs to a private property owner who drilled the well a year ago. After conducting standard tests recommended by the water district for new wells, the owner received results of nearly 9 parts per billion on Dec. 4.
The state’s public health goal for perchlorate is 6 parts per billion.
The well owner then called the Central Coast Regional Water Quality Control Board, the agency that is overseeing Olin’s cleanup order.
Olin confirmed the test results and started bottled water delivery three days after the unsafe levels of perchlorate were reported. The company must provide bottled water to residents whose wells test above 6 parts per billion for at least a year. Users of about 400 wells continue to receive bottled water.
“In this case, Olin responded very quickly,” Mohr said. “They haven’t said what they’ll do, but it sounds like they’re considering more monitoring. The options might include watching other wells.”
Mohr said the well owner lives west of Monterey Road near an area served by a pair of large wells supplying water to about 250 homes. The systems have been treated for perchlorate contamination since 2003, meaning the water is filtered, Mohr said.
“Olin’s consultants (Mactech) have already contacted us about the finding,” Mohr said. “They are trying to determine what this means.”
Rick McClure, a spokesman for Olin Corporation, did not return calls by presstime.
Hector Hernandez, an engineer with the Water Board, said all new findings above 6 parts per billion were significant.
“The well will be monitored to evaluate the concentration of perchlorate over time,” Hernandez said. “This result is one more data point to continue the evaluation of plume migration in this area.”
Hernandez said another nearby well is being tested.
Olin has relied on readings of 6 parts per billion or higher to map the migration of the perchlorate plume. It is unclear how the new reading will affect future mapping, but it could mean the company may look more to the west of Monterey Road.
“I feel we need to do a better job of characterizing the plume west of Monterey Road,” said Sylvia Hamilton, president of the San Martin Neighborhood Alliance and chairwoman of the Perchlorate Community Advisory Group. “I don’t think we’ve done enough work to be sure of its boundaries.”
The company canceled water service to hundreds of other residents in July when it reported 459 wells met the state’s public health goal. Water officials quickly declared 40 of those wells needed more testing, which Olin carried out. In October, officials reported 31 of those 40 wells met safe drinking standards, and ordered Olin to continue service to users of the remaining nine.
