What the Government Sampling Record Shows About 1,2,3-TCP in Thurston County
Federal monitoring of the Lacey Water Department, which supplies water to over 105,000 people via groundwater sources in Thurston County, found no detections of 1,2,3-trichloropropane (1,2,3-TCP) above the reporting level during 2014-2015. This means measurements were below 0.03 micrograms per liter (µg/L), or parts per billion (ppb), throughout sampling events. There is no federal maximum contaminant level (MCL) established for this chlorinated solvent in this region's public water system, and no health-based violations have been recorded by the EPA.
Granular Activated Carbon Contact Time: Why Bed Depth Matters More for TCP Than for Taste
Chlorinated solvents such as 1,2,3-trichloropropane are known for their persistence in groundwater. Removing these trace compounds effectively depends on sufficient contact time with granular activated carbon (GAC). A deeper carbon bed extends this contact time, allowing more thorough adsorption of the TCP molecules, which are otherwise difficult to treat compared to typical aesthetic concerns like taste or odor compounds. Therefore, systems designed to address 1,2,3-TCP prioritize bed depth over factors that only impact secondary water qualities.
The Agricultural Land-Use History of Thurston County and Its Relationship to Detected 1,2,3-TCP
1,2,3-trichloropropane originated historically as an impurity in soil fumigants used primarily from the 1950s through the 1980s. Thurston County's land use during this period included segments of agricultural activity that may have contributed to residual TCP in groundwater. However, recent federal sampling for the Lacey Water Department shows no detection above reporting levels, indicating that if legacy contamination exists, it remains at or below the detection threshold in the public supply.
A Worked Example: Interpreting the Record's Median and Range as a Homeowner Would
The sampling record reports zero detections of 1,2,3-TCP among 26 samples. This means the median concentration is less than 0.03 µg/L, and the range spans from non-detect to below the detection limit. For a homeowner, this implies the constituent is either absent or present at concentrations too low to measure by the methods used. Without individual well or tap testing, these figures do not reflect personal water conditions but can inform the general quality of the public water supply.
How Sample Depth, Well Depth, or Source Type Affects What a Resident Should Expect
The Lacey Water Department uses groundwater sources for public supply. Groundwater extraction depths vary with well locations, which affects the likelihood and concentration of 1,2,3-TCP presence. Deeper wells may encounter different geochemical conditions than shallow ones, influencing whether legacy chlorinated solvents are detected. Homeowners relying on private wells should consider that regional data for public water systems provides context but does not establish private well quality. Individual testing remains essential for precise understanding.
What 'Detected,' 'Median,' and 'Range' Mean in the Sampling Record
'Detected' refers to measurements above the reporting level—in this case, 0.03 µg/L or 0.03 ppb. 'Median' indicates the middle value among samples, which here is below detection. 'Range' shows the spread between the lowest and highest measurements, also reflecting only non-detects in this instance. Since no samples registered above detection limits, no assertions about exceedances or violations apply, and the data describe occurrences rather than confirm water safety or risk.
What You Should NOT Conclude From Area Data
Regional sampling data from the Lacey Water Department do not establish the 1,2,3-TCP concentration in any individual household's water supply. Detection absence at the public system level does not guarantee absence in private wells or household plumbing. Residents who have concerns, particularly following equipment failure, should consider laboratory testing for 1,2,3-TCP and other constituents in their own water. For addressing 1,2,3-trichloropropane specifically, technologies like the Autotrol 1,2,3-TCP Filter ship ready to configure for home use and are documented to target this chlorinated solvent effectively when present.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-06-30. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Lacey Water Department (WA5343500), WA: 26 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level