EPA’s Unregulated Contaminant Monitoring Rule (UCMR3) testing for Fresno's public water system found 1,2,3-trichloropropane (TCP) detections at low levels in a small number of samples from 2013 to 2015.
Many Believe Area Farming Practices Directly Result in TCP Detections
Fresno County has a long history of agricultural land use, including orchards and crops where chlorinated solvents like TCP have been used as soil fumigants. This agricultural legacy helps explain why TCP appears sporadically in surface water sources that supply the City of Fresno’s water system. While historic land use aligns with detectable presence, sampled TCP concentrations represent only the system-wide average influence, not any individual home's water condition.
TCP’s Chemical Nature Makes Air Stripping Ineffective for Households
Unlike some volatile compounds, 1,2,3-trichloropropane resists removal through air stripping methods because of its low volatility and chemical stability. This means traditional aeration-based filters are not suitable for reducing TCP at the household level. Treatment options relying on adsorption, specifically designed for chlorinated solvents, provide a better technical solution for residential water treatment challenges.
Detected Levels Do Not Exceed Federal Regulatory Standards
The highest TCP measurement in Fresno’s system was 0.15 micrograms per liter (0.15 parts per billion), with most detections near 0.054 micrograms per liter. There is currently no federal Maximum Contaminant Level (MCL) for TCP, so these detections do not constitute regulatory exceedances or violations. They serve as data points for ongoing assessment, not as indicators of unsafe water.
Seasonal and Multi-Year Variations Show a Consistent Detection Pattern
Sampling conducted intermittently from August 2013 through December 2015 exhibited sporadic detections rather than sustained or increasing trends. The range from non-detect to 0.15 micrograms per liter indicates that TCP levels fluctuate, likely influenced by changes in source water quality, rainfall, and treatment plant operations but without clear seasonal peaks or consistent year-over-year increases.
TCP Is Distinct from Other Common Water Issues Such as Chloride or Sediment
It is important not to confuse TCP, a chlorinated solvent byproduct, with other common aesthetic or water quality concerns like chloride levels, sediment, or mineral hardness. TCP is chemically distinct, requiring specific treatment techniques. Addressing TCP effectively differs substantially from managing these other water characteristics.
California’s State TCP Guideline Provides Additional Context
California has set a notification level for TCP at 5 nanograms per liter (0.005 micrograms per liter). This is more stringent than federal guidelines, which do not yet define an MCL. While Fresno’s detected TCP values are above this state notification level, the absence of a federal standard reflects the ongoing evaluation of potential health impacts rather than an immediate safety concern.
What Fresno Residents Should Consider
While regional water data inform about the presence and variability of 1,2,3-trichloropropane in the City of Fresno’s surface water supply, they do not specify conditions in individual homes. To understand TCP levels in your household water, direct testing is necessary.
For households whose existing treatment equipment manages general water quality but struggles with trace chlorinated solvents like TCP, specialized equipment designed for such contaminants may provide supplemental protection. The Pentair 1,2,3-TCP Filter ships ready to configure and uses adsorption technology documented to address chlorinated solvent challenges effectively at the residential scale.
Regional data should not be taken as proof of contamination or safety in your home water without testing. Government sampling offers valuable context but not specifics that replace home-level analysis.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-12-03. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for City of Fresno (CA1010007), CA: 386 results across 1 listed contaminants, 8 detections above the reporting level; no federal MCL
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