What Government Data About 1,2,3-TCP in Waipahu-Ewa-Waianae Can and Cannot Tell You
The public water supply serving Waipahu-Ewa-Waianae in Honolulu County draws from groundwater sources, with records showing that 1,2,3-trichloropropane (TCP) was detected in some monitoring samples collected between 2013 and 2015. Specifically, 4 out of 39 samples had measurable levels of TCP, with the highest reading at 0.44 micrograms per liter (µg/L), or parts per billion (ppb), and a median detection of 0.201 µg/L. These measurements stem from federal unregulated contaminant monitoring and do not indicate a violation or health-based exceedance. They represent the overall system performance rather than the condition of any individual household water supply.
Agricultural Land Use and Its Connection to 1,2,3-TCP Detections
The presence of 1,2,3-trichloropropane in groundwater commonly relates to historical agricultural practices. In Waipahu-Ewa-Waianae, land use from the mid-20th century through the 1980s included applications of soil fumigants containing TCP impurities. Such fumigants were used extensively in crop production to manage pests and soil conditions.
This agricultural footprint aligns with the localized detections of TCP in the region’s groundwater supply. Despite the discontinuation and regulation of these chemicals decades ago, TCP’s chemical stability means residues may still be present deep in the aquifer.
How TCP from Mid-Century Soil Fumigants Reached Deep Groundwater Over Decades
1,2,3-trichloropropane is a chlorinated solvent impurity historically found in soil fumigants used between the 1950s and 1980s. Its chemical properties allow it to persist in soil and then slowly migrate downward, eventually entering groundwater supplies. This slow transport explains why TCP detections appeared in wells many years after the original fumigant applications ceased.
Understanding this timeline clarifies why modern water systems in Honolulu County still monitor for TCP even though its use was phased out long ago.
Why Granular Activated Carbon Bed Depth Is Key for Effective TCP Contact Time
Addressing TCP in household water requires treatment methods that provide sufficient contact time to capture this contaminant effectively. Granular activated carbon (GAC) filters are widely used for this purpose, but TCP’s characteristics demand deeper carbon beds than those typically used for taste or odor issues.
Deeper GAC beds increase the time water remains in contact with carbon media, enhancing the likelihood that TCP molecules are adsorbed and reducing their presence in water for household use.
Household Symptoms That May Suggest but Do Not Confirm a TCP Concern
Symptoms such as unusual tastes or slight discoloration in water are generally not reliable indicators of 1,2,3-trichloropropane. Because TCP is odorless and tasteless at the concentrations detected in the area, its presence often goes unnoticed without specific laboratory testing.
If your current water treatment equipment seems overwhelmed or unable to keep pace, it may point to limitations in capacity or filter life rather than direct signs of TCP contamination.
How Plumbing Materials and Age Influence Water Quality Independently of Source Contaminants
Water quality in a household depends not only on source water but also on the materials and condition of plumbing. Older pipes might affect taste, odor, discoloration, or introduce other substances unrelated to TCP.
Distinguishing between plumbing-related issues and source water contaminants like TCP requires targeted water testing focused specifically on those chemicals.
Why TCP’s Resistance to Air Stripping Informs Treatment Choices
1,2,3-trichloropropane’s chemical properties make it notably resistant to air stripping, a technique that volatilizes contaminants by forcing air through water. This resistance means air stripping is not an effective standalone treatment for TCP in residential water supplies.
Instead, adsorptive technologies such as granular activated carbon provide a practical method that can be directly applied in household water treatment scenarios.
What You Should Not Infer from Area-Wide 1,2,3-TCP Data
While EPA sampling results for the Waipahu-Ewa-Waianae water system detect measurable TCP levels, these data do not specify the concentration in any single home’s water and do not indicate violations or safety concerns as defined by federal health standards.
To accurately assess TCP in your household water, specific testing of your supply is necessary. Should treatment enhancement be needed, equipment such as the Autotrol 1,2,3-TCP Filter, which ships ready to configure, offers a documented approach to supplement existing water treatment capabilities to address this contaminant effectively.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-01-13. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Waipahu-Ewa-Waianae (HI0000335), HI: 39 results across 1 listed contaminants, 4 detections above the reporting level; no federal MCL
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