Chico Urban Area Nitrate Compliance Program

What Is the Nitrate Compliance Plan?

The Chico Urban Area Nitrate Compliance Plan (Plan) has been prepared in response to the contamination of groundwater in the Chico Urban Area by nitrate, a form of nitrogen. The discharge from individual septic systems has been cited by the Central Valley Regional Water Quality Control Board (Regional Board) as the primary source of groundwater nitrate contamination that exceeds drinking water standards set by the U.S. Environmental Protection Agency and the State Water Resources Control Board (State Board). Nitrate levels that exceed the standard have been established as a threat to the public health and is subject to regulation.

In 1990, when local corrective action was deemed by the Regional Board to be too slow and inadequate, more formalized enforcement actions were undertaken, resulting in a Prohibition Order that required the abandonment of area septic systems by July of 1995. The issue, which affects over 30,000 residents in the Chico Urban Area, had become increasingly controversial making a timely resolution difficult. The cost of sewering had emerged as a primary concern, especially for those on fixed incomes and limited ability to absorb the cost. Some doubted the adverse health effects of groundwater nitrate, the integrity of test results, or dismissed the issue as a ploy to force unincorporated residents to annex to the City of Chico. Since high nitrate levels were first discovered in 1979, few local issues have held the potential to affect such a large segment of Chico area residents. The local nitrate problem has spawned numerous studies and regulatory actions, complicated and impacted home sales, worried those on private wells, and generated hours of debate.

Unfortunately, nitrate contamination in the groundwater and soils in the Chico area has resulted with an order from the Regional Board to address and rectify the problem. A tremendous amount of human and financial resources have been spent on this project, which will require further time and capital resources.


View the Nitrate Compliance Plan Document Library.