1,2,3-Trichloropropane, also known as TCP, is an organic chemical found in some groundwater supplies. In July 2017, the State Water Resources Control Board approved the maximum contaminant level (MCL) for TCP of 5 parts per trillion (ppt), and compliance monitoring began in January 2018.

TCP has been detected in some of the groundwater supplies in our Bakersfield, Visalia, Selma, Stockton, South San Francisco, and Chico service areas. Protecting our customers’ health and safety is our highest priority, and we had been actively monitoring our groundwater supplies and designing potential treatment methods in anticipation of a regulation, so that we could more quickly and efficiently meet any new MCL ultimately set. We have completed construction of treatment facilities that will ensure our water supplies comply with the new MCL, and water serving your system continues to meet or surpass all federal and state water quality standards.

Construction of facilities is occurring in phases, so treatment at the most critical water sources needed to meet current customer demand were completed first. We will continue to install treatment at other facilities through this summer, so that additional sources of supply can be utilized.

Frequently Asked Questions

Q: What exactly is TCP?
A: TCP is a manmade chemical. The TCP contamination in our wells is believed to have come from soil fumigants. Soil fumigants in use today no longer contain TCP.

Q: How are you treating TCP?
A: The TCP in our service areas is most efficiently removed using granular-activated carbon (GAC) technology. GAC vessels, which are being installed at impacted wells, will eliminate or substantially reduce the levels of TCP to meet the new standard. In our Chico District, where only three wells had detections of TCP, we shut down the wells and are utilizing other water sources.

Q: How much will this cost?
A: While construction, operation, and maintenance of new treatment facilities are substantial, Cal Water was a plaintiff in litigation against Dow and Shell, the manufacturers of the soil fumigants that contained TCP (the parties responsible for the TCP contamination), to recover the costs for treating the contamination. We were successful in preventing our customers from bearing the costs of constructing the treatment facilities. Ongoing operations and maintenance costs will be determined in the future, based on costs at that time.

Q: Why is the MCL being set at 5 ppt, when the public health goal is 0.7 ppt?
A: The determination of whether water is safe to drink and use is made by public health experts, which have calculated the theoretical health risks of TCP at the MCL at a 1-in-142,857 cancer risk over a lifetime of exposure. Five ppt is the level that the State has established as the detection reporting limit using currently approved testing methods. A public health goal is the level of a contaminant below which there is no known or expected risk to health over a lifetime (assuming a person drinks 2 liters per day for 70 years), without regard to available treatment technology.

Q: Where does the TCP (or the waste) go after treatment?
A: TCP adheres to the surface of the carbon used in the treatment process. When the carbon is exhausted, a carbon provider will replace the old carbon with new carbon. The provider will properly dispose of or regenerate the old carbon in accordance with federal and state laws.