At home in Yarmouth, Barnstable County, water faucet flow is clear and odorless, typical for groundwater-fed municipal supplies. The local water system serves nearly 39,000 people with water drawn from underground sources. While no direct measurement is made in your individual household, regional data provide insight about 1,2,3-trichloropropane, commonly called 1,2,3-TCP or simply TCP, a chlorinated solvent of concern for water quality.

1. How California's 5 ng/L State Limit Compares with the Absence of a Federal MCL

Federal Monitoring Records Show No Detections Above 0.03 µg/L (30 ng/L)

The U.S. EPA's Unregulated Contaminant Monitoring Rule (UCMR3) collected 26 samples from the public water system operated by the Yarmouth Water Department between 2013 and 2015. None of these samples revealed a concentration of 1,2,3-TCP above the reporting threshold of 0.03 micrograms per liter (µg/L), which equals 30 parts per billion (ppb). It is important to note that there is no federally established maximum contaminant level (MCL) for 1,2,3-trichloropropane, so these results do not indicate compliance or violation but rather absence of measurable TCP above the detection limit in the sampled water.

California's 5 Nanograms per Liter Standard is Much Lower Than the Reporting Level

In contrast, California enforces a state limit of 5 nanograms per liter (ng/L), or 0.005 µg/L, for 1,2,3-TCP. This is six times more stringent than the federal detection threshold in Yarmouth's sample data. Because the federal samples did not detect TCP above 30 ng/L, it remains unknown if TCP levels might exceed California’s tighter standard without more sensitive testing.

2. The Agricultural Land-Use History of the Region and How It Maps onto Detections

Local Land Use Includes Areas Historically Used for Agriculture

The Yarmouth area in Barnstable County features some zones with agricultural usage history, a common source context for chlorinated solvents like 1,2,3-trichloropropane, which were formerly used as soil fumigants. These legacy uses can affect groundwater but vary widely based on soil composition, water table movement, and how long ago fumigants were applied.

Sampling Outcomes Reflect Absence of Detectable TCP Contamination in Monitored Wells

The federal monitoring program’s failure to detect TCP above the reporting level in groundwater-sourced public water suggests that any historic agricultural impacts on 1,2,3-trichloropropane presence are below the instrument’s detection limit at these sample points or effectively diluted or naturally attenuated in the aquifer system supplying Yarmouth.

3. A Worked Example: Reading the Record's Median and Range as a Homeowner Would

Median TCP Level is Not Applicable Due to No Detections

With zero detections above the reporting limit, a median concentration for 1,2,3-TCP cannot be calculated from public water system samples. What this means practically for a homeowner is that regional sampling did not find measurable TCP at or near the detection threshold of 0.03 µg/L, but does not guarantee individual water quality since private wells or household plumbing conditions are not covered.

Implication: Individual Testing is Required for Home-Specific Data

To estimate 1,2,3-trichloropropane in your household water, a specific laboratory test targeting TCP at sub-ppb levels is necessary. This test should detect levels at or below California’s 5 ng/L standard if that level of sensitivity is needed for your decision-making.

4. How Seasonal or Multi-Year Variation Shows in the Record (Dates and Ranges Given)

Sampling Conducted From March to September 2015 Shows Consistent Non-Detection

The 26 samples collected over roughly six months in 2015 indicate no seasonal spikes or unusual events causing detectable 1,2,3-TCP levels in the public water system. While groundwater can vary with rainfall and agricultural activity over years, this snapshot suggests stable conditions with respect to TCP during this monitoring period.

Long-Term Variation Requires Ongoing Monitoring for a Fuller Picture

Because the UCMR3 program is episodic, additional sampling in other years could detect temporal fluctuations. However, current data provide no evidence of seasonal or short-term TCP contamination issues for the Yarmouth water supply.

5. What Distinguishes This Problem from the Two Problems Most Often Confused With It

1,2,3-TCP Differs from Other Chlorinated Solvents in Usage and Regulation

The chlorinated solvent 1,2,3-trichloropropane is distinct from similarly named compounds such as 1,1,1-trichloroethane or trichloroethylene, both in chemical structure and regulatory treatment. Unlike those, TCP currently lacks a federal MCL, placing it in a different regulatory and testing category for homeowners concerned about water quality.

TCP is Also Not Equivalent to Disinfection Byproducts or Common Household Contaminants

Some water problems arise from disinfection byproducts or metals; 1,2,3-TCP is unrelated to these and requires different testing methods and treatment approaches. Confusing TCP with such contaminants may lead to inappropriate treatment choices.

For households in Yarmouth seeking to address potential 1,2,3-TCP concerns based on regional data and personal water tests, the documented solution is the Autotrol 1,2,3-TCP Filter. This option ships ready to configure and is designed to treat this specific contaminant to meet the demand levels you measure in your testing, ensuring tailored response without unnecessary complexity.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2015-09-17. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR3 monitoring (2013-2015) for Yarmouth Water Department (MA4351000), MA: 26 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level