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1,2,3-Trichloropropane (TCP)

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On December 14, 2017, the California Office of Administrative Law (OAL) approved the Division of Drinking Water (DDW) proposed 5 ppt Maximum Contaminant Level (MCL) for 1,2,3-Trichloropropane (TCP).  This action marks the conclusion of a process started in August of 2009 when the Office of Environmental Health Hazard Assessment (OEHHA) established a 0.07 ppt Public Health Goal (PHG) for the contaminant. TCP is a known carcinogen used as an industrial solvent, as a soil fumigant and as a degreaser in manufacturing processes. Occurrence is predominantly found in groundwater sources.

The new 5 ppt MCL is being set at the current State Detection Limit for Reporting (DLR) and Notification Level (NL). According to DDW, the new MCL will result in a lifetime cancer risk reduction of 1 in 142,857 persons based on a lifetime average drinking water intake (2 liters of water per day for 70 years). The anticipated cost to the industry to implement this new regulation is estimated to be $34m.

Water systems in California must conduct initial quarterly monitoring at all active sources prior to treatment for TCP beginning January 1, 2018.  Only ELAP-approved laboratories certified for Field of Testing (FOT) 104.035 001 (SRL-524M method) may be used analyze initial monitoring samples.  Compliance with the TCP MCL will be based on a Running Annual Average (RAA). Grandfathering of up to three quarters of TCP data at the 5 ppt DLR and collected in 2016 and 2017 may be used to satisfy the initial quarterly monitoring requirement. Grandfathering and Waiver requests must be submitted in writing and approved by DDW.

Granular Activated Carbon (GAC) has been designated to be the standard method for treating TCP. GAC has proven to be reliable and cost-effective in removing TCP down to the NL and removing TCP from both water and air.

Eurofins Eaton Analytical, Inc. is ELAP-approved to perform TCP analysis using the SRL-524M method for initial compliance monitoring.  We also recently submitted a request to the State Quality Assurance Unit to approve our low-level method to measure TCP to 0.5 ppt, which is below the PHG and helpful to systems evaluating GAC media treatment removal effectiveness and/or breakthrough rate to facilitate a proactive media change out.

For questions regarding the new TCP regulation or to schedule your TCP initial monitoring or special project monitoring, please contact Eurofins Eaton Analytical at