GILROY
– More than a year after it was discovered, the perchlorate
plume stretching from Morgan Hill to north Gilroy is still
bypassing the eight wells that supply 100 percent of the city’s
drinking water.
GILROY – More than a year after it was discovered, the perchlorate plume stretching from Morgan Hill to north Gilroy is still bypassing the eight wells that supply 100 percent of the city’s drinking water.
Tests done in early April revealed no detection of perchlorate in all eight city-owned and operated water wells. The results mark at least the 14th consecutive time Gilroy’s drinking water supply has come up perchlorate-free.
“Our belief is that the plume is moving in a southeasterly direction and we happen to be just enough southwest,” Water Operations Supervisor Dan Aldridge said.
While the data is welcome information, city water officials are not resting on their laurels. They say they will continue to prepare for contamination because the other leading theory, says Senior Civil Engineer Mike Goodhue, is that the plume is heading toward Gilroy’s wells, but it’s moving slowly.
As part of a multi-step plan to stave off impacts from potential perchlorate contamination, City Council approved spending $200,000 in January to upgrade electrical equipment and buy land around three existing city wells.
The improved equipment and the extra land make it possible to install ion exchange treatment tanks capable of keeping Gilroy’s drinking water clean. If perchlorate – which has been seeping into the groundwater from a former road flare manufacturing site in Morgan Hill – shows up in the Gilroy water supply, the city could install the bulky filtration system at four wells on the east side of town.
The $200,000 investment was phase one of the city’s anti-perchlorate game plan, Goodhue said. Phase two would involve the installation of the ion exchange filtering system and potentially the location of new wells.
The ion exchange equipment will cost about $1.5 million to purchase and $90,000 a month ($1.08 million a year) to maintain and operate. In addition, the city will have to spend $600,000 prepping sites – pouring the concrete and laying the pipes – for the filtration system.
It is still unclear whether the company that contaminated the groundwater basin – Olin Corporation – will have to cover Gilroy’s expenses.
Not all wells located in Gilroy have stayed perchlorate-free. Roughly half a dozen privately owned wells tested positive for perchlorate at more than 4 parts per billion.
Those well owners are eligible for bottled water delivery paid for by Olin.
One Gilroy city well – used strictly for monitoring purposes – has tested positive for perchlorate. It is located near Leavesley Road and Camino Arroyo.
Gilroy’s next perchlorate test will take place this week. Typically, results are available by the third week of the month.
