What is 1,2,3-Trichloropropane (TCP)?

TCP is exclusively a man-made chemical.  The primary source of TCP in groundwater is past agricultural use of soil fumigants that contained TCP as an impurity.

How much TCP is in my water?

The District first detected between 5 and 15 parts per trillion (ppt), of TCP in raw water supplied by the Country Club Well in 2008.  Testing in 2016 found 10 ppt.  Country Club Well is one of six production wells serving Seascape, Rio Del Mar, portions of Aptos and La Selva.  TCP has not been detected in any other District production wells. 

Where did the TCP come from and how long has it been there?

The most likely source of the TCP in Country Club Well was as a known impurity in the soil fumigants (nematicides) D-D and Telone.  The immediate area around Country Club Well was agricultural in the 1950s and 1960s.  We do not know how long the TCP has been in the groundwater.

Why wasn’t the TCP discovered earlier?

The District has been testing for TCP since 1989.  TCP was first detected in 2008 using an improved analytical method, capable of detecting very low levels. 

Are there any health effects to drinking water with TCP? 

The District’s water meets or exceeds all current drinking water testing requirements and regulations.  The experts at the State Water Resources Control Board, Division Drinking Water (DDW) say that some people who drink water containing TCP over many years may have an increased risk of getting cancer, based on studies of laboratory animals. 

Currently, there is no established Maximum Contaminant Level (MCL) for 1,2,3-TCP, however, in July 2016, the California State Resources Control Board Division of Drinking Water (DDW) released a draft proposed MCL for 1,2,3-TCP of 5 ppt

Once the MCL is adopted, the District will comply with it.  Country Club Well is an important source of water for the surrounding neighborhoods, supplying approximately 170,000 gallons of water per day.  The District is currently evaluating potential treatment options for the TCP.

If you have additional questions about TCP and your health, you should visit the DDW’s TCP web page.

Can an under-sink carbon filter or water filter pitcher remove the TCP? 

Although granulated activated carbon is a successful treatment option for TCP, all filter cartridges cannot remove all contaminants.  It is important to read the NSF Testing and Certification label on the cartridges.  The District recommends you seek guidance from the DDW on this issue.  You can get more information on residential water treatment devices on their website.