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Contamination forces idling of some eastside water wells

Courtesy of Ken Schmidt/City of Madera


Some of the drinking-water wells on the northeast side of Madera are being idled or abandoned because of fluctuating water levels and significant plumes of groundwater contamination by the agricultural chemical DBCP, a powerful pesticide suspected to cause sterility and cancer.

The Madera City Council recently heard a presentation on an update of the 2014 Water Master Plan by the consultant firm Akel Engineering. The engineers evaluated current operations and capacity, and made projections about future well pumping capacity, costs, and how and where to accommodate future residential populations due to well water quality issues.

Engineer Tony Akel recommended the city continue to idle or abandon existing municipal water wells in areas on the northeast side of Madera and other eastside areas.

Several eastside city wells already have been taken off line or permanently abandoned due to levels of multiple contaminates considered unsafe for drinking.

Akel said the practice of taking wells offline due to contamination in the San Joaquin Valley was not uncommon, and told the council some contaminates were present in all well water.

“The sky is not falling,” he said and there was an established method to manage contaminates through consistent monitoring of groundwater and planning for new municipal well placement.

Following a plan first outlined in a 2012 to 2014 water analysis, consultants outlined a plan to drill new municipal wells in parts of the city’s aquifer less affected by the contaminates. These are in the southwest side of Madera in different soils. The water from these wells would be pumped through a series of larger water lines and booster pump stations to provide the noncontaminated water to residents in east side areas.

According to hydrogeologist Ken Schmidt and outlined in a memo titled “City of Madera Master Plans, Geographic Trends in Groundwater Quality,” a main contaminate of concern is reportedly DBCP, a soil fumigant oil widely applied in the 1950s. It was heavily used in orchards and vineyards by farmers in the San Joaquin Valley, before the chemical was banned from use in 1977. DBCP reportedly causes sterility in humans and cancer in laboratory animals, and was noted in the Madera area groundwater sample report to the city in 1995-1997.

A 1995 article by Mark Arax, in the LA Times (, called DBCP “the culprit of the worst groundwater contamination in the United States,” and claimed more than 100 municipal water wells in the Central Valley have been shut down due to unsafe levels during that time.

The city of Fresno also was hit hard and had to close 29 wells over a 15-year period, they said. Fresno had also sued the three manufacturers, Dow Chemical, Shell Oil, and Occidential Chemical and reportedly recovered $21 million in damages and as much as $80 million for future damages, according to the LA Times article, “Banned DBCP Still Haunts San Joaquin Valley Water.”

According to toxicologists at UC Berkley school of Public Health DBCP is incredibly persistent in soils and won’t break down easily or go away. The banned chemical and other contaminates also migrate underground as the water table moves or the depth fluctuates due to pumping, according to experts, requiring frequent small test bore holes to continue to identify the areas of groundwater potentially effected.

Higher than acceptable levels of DBCP have also been found in older, shallow, 250-foot-deep residential wells in the north east side areas of Madera and also in some areas near the Madera Ranchos, according to the charts and published study. DBCP was not often the target of tests in older residential wells.

Other contaminates such as EDB (ethylene bromide), PCE, HPC and the minerals uranium, manganese and arsenic, also have been found at high levels in some areas and wells according to the Groundwater Quality memo.

Advanced filtration of municipal wells is also an option but is currently cost prohibitive, with drilling and operating new wells being more cost effective.

According to the 2014 study, the City of Madera currently has 19 deep municipal wells, 200 miles of water distribution lines, and relies on pumping groundwater for 100 per cent of it’s supply — roughly 14 million gallons of average daily usage. Total production capacity is 31 million gallons to meet peak summer time demands. Per-person usage is estimateded to be around 173 gallons per day.

According to consultants and engineers the projected the costs to the city to maintain and add new contaminate free wells and new water lines as the population increases will rise from a current $5.7 million per year to an estimated $26.8 million in FY 2016 to 2020, an amount almost five times the current cost of capital improvements and operations. Some of these costs can be recouped from new connection and development fees, they said, but the rest of the projected costs may have to be shared and absorbed by all existing water users.

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(For site location graphics, download the entire 2014 City of Madera Water Master Plan at

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