TCP - What Happens When You Regulate Something on Short Notice with Short Compliance Deadlines?

Oral Presentation

Prepared by A. Eaton
Eurofins Eaton Analytical (EEA), 750 Royal Oaks Drive, Monrovia, CA, 91016, United States

Contact Information:; 626-386-1125


In January of 2018 compliance monitoring began in California for 1,2,3-trichloropropane, with a California MCL of 5 ng/L (which is also the reporting limit of the approved method).  More than 4,000 systems are required to conduct quarterly monitoring and demonstrate compliance with the MCL. Any system exceeding the MCL is mandated to remove the source from service or blend sources to deliver water below the MCL. When California promulgated this regulation there were data available showing a few hundred wells statewide had problems, with many of them in the Central Valley, a known spot for pesticide use in the 40s and 50s.   California expected that overall only a few percent of additional systems would be impacted.   However monitoring it just the first quarter of 2018 indicates that the problem of TCP in drinking water in California is much more widespread than expected.  For 2018 monitoring so far indicates that nearly 9% of systems are exceeding the MCL and more than half of those either have no prior monitoring or previously did not exceed the MCL. 

These results have significant implications for both water systems and laboratories. For labs, the demand for TCP analysis ramped up over a very short period of time (<2 months from finalizing the Rule schedule to the required start of collection), giving labs little time to increase instrument capacity and creating challenges for utilities to meet the Rule requirements. Likewise with the short compliance deadline and the potential need for installation of GAC treatment or the temporary (or permanent) use of alternative sources new challenges are presented.   In the case of one City in Southern California that had to discontinue use of contaminated wells and bring in chloraminated surface water while GAC systems were being designed and installed, the result was an issue with yellow water due to iron release from pipes and a large number of complaints from residents. 

While so far California is the only state with a very low MCL for 1,2,3-TCP the State of New Jersey has also been considering a low ng/L MCL, and the CA experience is important to learn from. Hawaii has long had an MCL for 1,2,3-TCP, but at a much higher level. In spite of that, a large percentage of wells on the islands have wellhead GAC treatment, but not optimized for levels like what CA has mandated. Review of the UCMR 3 pattern of hits for 1,2,3-TCP suggests that other states could also be impacted.