The Santa Clara Valley Water District board of directors has voted unanimously to implement a $1.7 million program aimed at protecting Silicon Valley's groundwater basins -- which hold approximately 40 percent of the region's drinking water supplies -- from contamination by a gasoline additive known as MTBE.
The program comes on the heels of a boating-management plan adopted last month by the district to control the amount of MTBE in local reservoirs.
The groundwater protection program relies on a three-pronged approach for guarding the basins against MTBE -- special investigations to fully understand and monitor the extent of MTBE contamination; tasks to increase the vigilance of the underground fuel storage tank oversight program; and external activities devoted primarily to implementing the district's legislative and legal strategies regarding MTBE.
The program culminates in two years with a long-term management plan for controlling MTBE releases before they reach groundwater basins.
MTBE is a chemical compound added to the state's gasoline supplies to reduce harmful air emissions. Human health effects from MTBE are not well understood, however all public drinking water supplies in the valley meet federal and state health standards. The primary source of MTBE in groundwater is releases from leaking underground fuel storage tank and piping systems.
There are approximately 500 sites where groundwater has been contaminated by gasoline. The district is monitoring about 400 of these sites, 75 percent of which have tested positive for the presence of MTBE at concentrations as high as 430,000 parts per billion.
The special investigations portion of the groundwater protection program includes a focused groundwater monitoring program to provide statistical sampling of how pervasively MTBE is affecting groundwater basins on a regional scale; a free well-testing program for private wells near known leaking underground fuel systems; a pilot study to investigate operating storage tanks to determine if new systems designed to meet 1998 requirements are leaking MTBE and, if so, to what extent; and an identification of public water supply wells that are vulnerable to MTBE contamination from leaking underground fuel storage tanks.
At the same time, the district will bolster its underground fuel storage tank oversight program by focusing on those sites that provide the greatest risk to the groundwater basin.
External activities include participating in various outside committees to develop and share information on MTBE impacts and groundwater protection strategies; activities to garner support for a legislative ban on MTBE; and a concerted effort to pursue regulatory and legal avenues for recovering costs and preventing damage from MTBE.
The program dovetails with the district's efforts to protect local reservoirs from MTBE contamination. In late April, the district board of directors voted to reduce the number of power boats allowed on three of the valley's 10 reservoirs, while setting restrictions on refueling of vessels. The program is a collaborative effort with Santa Clara County Parks and Recreation Department, which manages recreation at the three reservoirs through a lease agreement with the water district.
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