Fig. 2. 1,2,3,-Trichloropropane

On December 14, 2017, the California Water Resources Control Board Division of Drinking Water (DDW) adopted a regulation promulgating a Maximum Contaminant Level (MCL) for 1,2,3-trichloropropane (1,2,3-TCP) of 0.000005 milligrams per liter (mg/L, or 5 parts per trillion or 5 ppt). This regulation required Community Water Systems (CWS) and Nontransient Noncommunity (NTNC) Water Systems to begin initial sampling of 1,2,3-TCP from their drinking water sources. Initial sampling began January 1, 2018, with the requirement of four quarterly samples to be completed during the year. The first three quarters of 1,2,3-TCP data from 2018 (Q1, Q2, and Q3) that have exceeded the MCL are compiled into the data file provided below. The dataset includes regulating agency district, water system name and number, county, population, sampling point, sample date, sample result, and facility status (e.g., Offline, Online - Not Treated, Online - Treated). This data file is a copy of the file available on the State Water Resources Control 1,2,3-TCP webpage. See the State Water Resources Control Board website for more information about the data and regulation.