1,2,3-Trichloropropane

1,2,3-Trichloropropane, also known as TCP, is an unregulated organic chemical that has been in the news recently, as the State Water Resources Control Board (State) and its Division of Drinking Water has been studying it for regulation. On July 18, 2017, the State Water Resources Control Board approved the draft maximum contaminant level (MCL) for TCP of 5 parts per trillion (ppt). The Office of Administrative Law is now reviewing the proposed regulation and is expected to make a final ruling within 30 days. The MCL is expected to become effective in October 2018, with compliance monitoring to begin 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. Please know that protecting our customers’ health and safety is our highest priority. While not required to do so, we had begun actively monitoring our groundwater supplies and designing potential treatment methods in anticipation of a regulation, so that we can more quickly and efficiently meet any new MCL that is ultimately set.

We will work to ensure that all of our water supplies comply with the new MCL by the compliance deadline, expected to be in 2018, and water serving your system will continue to meet or surpass all federal and state water quality standards.

Please check back for updates as this process evolves.

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 will you treat TCP?
A: The TCP in our service areas will be most efficiently removed using granular-activated carbon (GAC) technology. GAC vessels, which will be 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 have detections of TCP, we currently intend to shut down the wells and utilize other water sources.

Q: How much will this cost?
A: While construction, operation, and maintenance of new treatment facilities are substantial, Cal Water is a plaintiff in litigation against Dow and Shell, the manufacturers of the soil fumigants that contained TCP (the parties responsible for the TCP contamination), seeking to recover the costs for treating the contamination.

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.