A private well off Holsclaw Road south of Gilman Road in Gilroy
has tested positive for perchlorate contamination, leading water
officials to believe the poisonous groundwater plume that has
already tainted 419 wells between Morgan Hill and north Gilroy may
be trickling further south.
A private well off Holsclaw Road south of Gilman Road in Gilroy has tested positive for perchlorate contamination, leading water officials to believe the poisonous groundwater plume that has already tainted 419 wells between Morgan Hill and north Gilroy may be trickling further south.
The news is better in Morgan Hill where City Manager Ed Tewes announced at Wednesday’s council meeting, the results of monthly testing.
“All municipal wells tested nondetect in the latest monthly test,” Tewes said.
This is the second month in a row that the Condit well tested below 4 ppb; all other wells have tested nondetect for at least four months, according to Jim Ashcraft, Morgan Hill’s public works director. He has said that the time has not yet arrived to bring the three closed wells back on line because perchlorate levels in well water are so volatile, often fluxuating with each test.
The Tennant well, across the street from the Olin site was shut down permanently in April 2002. The city, with the help of the Santa Clara Valley Water District, is installing a perchlorate treatment plant on that well, expected to begin pumping and treating and providing additional water for the summer.
The Gilroy well owners, whose identity is being kept confidential by valley water, ran a test in May that revealed a 4.7 parts per billion contamination level, less than 1 part per billion above the state’s “action level” which triggers warning notices.
The information was reported to the water district earlier this week, spokesman Mike DiMarco said. It is the southernmost detection of the chemical since testing began in February. A well at Leavesley Road just east of U.S. 101 tested positive at 4 to 10 parts per billion.
“For right now I’d really consider this part of the plume,” said George Cook, an engineering geologist for the water district. “It’s following the general trend of the plume and Olin Corp. is using this information for its new (well) sampling program.”
Cook said Olin’s testing program will likely expand further south now that a detection below Leavesley has occurred.
In Morgan Hill, several private wells north of Tennant Avenue – and out of the area for which Olin has taken responsibility – have shown positive levels of perchlorate in recent months when their owners paid for tests themselves. The water district is encouraging those well owners to send copies of the test reports to its offices on Almaden Expressway.
Olin is the former Morgan Hill flare manufacturer that contaminated the groundwater table with perchlorate from its plant on Tennant at Railroad avenues. It is responsible for testing area wells and devising a clean water program for impacted water users.
The company is only testing wells south of the closed factory site for the chemical used in safety flares, jet fuel and some fertilizers.
Gilroy water officials do not believe the new detection will impact city wells, even though two city wells exist near Holsclaw and Gilman roads. All eight city wells have been tested monthly since February. To date none have shown perchlorate contamination.
“The more wells that pop up, though, sure isn’t a good thing,” said Dan Aldridge, water operations supervisor for Gilroy. “We’ll continue to monitor this monthly.”
It is possible the new detection spot is independent of the plume.
“There are a lot of sources of perchlorate and we don’t know all the former uses of the land out there,” DiMarco said.
The new detection spot is east of Llagas Creek, near the Syngenta property. Syngenta is a worldwide agribusiness company and seeds producer. It is unknown if the contaminated well is at the Syngenta site since officials from the local plant and at headquarters did not return phone calls before deadline.
Perchlorate’s health risks are still unclear and state and federal testing is under way. At some exposure levels perchlorate is known to cause thyroid problems and some tumors in humans. What is not known is the levels at which exposure becomes a danger.
The “action level” for perchlorate was lowered in 2002 by the state from 18 ppb to 4 ppb. Wells in Morgan Hill, San Martin and Gilroy have shown contamination levels from 4 ppb to 100 ppb.
Send privately secured test reports to SCVWD, Attn. Perchlorate, 5750 Almaden Expressway, San Jose, CA 95118-3686; 265-2600. More details at www.valleywater.org
