Tetrachloroethene (PCE) is a chemical that dissolves oils and grease. Industry uses it for dry cleaning and metals degreasing. PCE is found in common consumer products. Visit the Agency for Toxic Substances and Disease Registry’s PCE summary to learn more about PCE.

Trichloroethene (TCE) is a chemical that dissolves oils and grease. It is used in dry cleaning, metals degreasing, and making adhesives and refrigerant chemicals. To learn more about TCE, Visit the Agency for Toxic Substances and Disease Registry’s TCE summary.

The United States Environmental Protection Agency (EPA) sets maximum contaminant levels (MCLs) for each chemical. An MCL is the maximum amount of a pollutant that is allowed in drinking water to protect public health. The MCLs for PCE and TCE are 5 micrograms per liter (µg/L) each.

The Idaho Department of Environmental Quality water quality standards for PCE and TCE are 5 micrograms per liter (µg/L) each. These are the same as the United States Environmental Protection Agency’s maximum contaminant levels (MCLs).

Sampling activities look at how chemicals, like PCE and TCE, are distributed in groundwater. The Portneuf Valley Aquifer is a drinking water source for people living in and around Pocatello in Bannock County. The pilot studies’ findings will help Bannock County improve the groundwater remedy to remove TCE and PCE from the groundwater in the Portneuf Valley Aquifer.

We regularly sample wells to keep track of water quality conditions and learn about changes over time due to the season or ongoing cleanup efforts. Our team samples wells within the Portneuf Valley Aquifer and around areas of known or possible groundwater contamination.

To collect samples that represent groundwater within the aquifer, we must pump about 200 gallons of water from most domestic supply wells. We can safely dispose of extracted water in vegetative and pasture areas.

Most domestic wells we sample do not have water contaminated with the chemicals that Bannock County is studying. It is safe to dump that pumped water on the ground. Water at the few properties with wells contaminated with PCE and TCE is also safe to dispose of on the property. TCE and PCE are volatile, which means that when groundwater with TCE and PCE at the relatively low concentrations observed at these properties is poured onto the ground, they transfer from the water to the air. So, dumping that water on the ground is safe.

We send letters to residents and property owners with sampling results after each annual summer sampling. CDM Smith, Bannock County’s environmental contractor, will call to make sure you received your letter.

We know where PCE and TCE concentrations are above regulatory standards, but the contaminants can move through the groundwater over time. We look at wells within or near areas of the known contamination to understand how it is moving. If TCE and PCE were not in your well before, it is still possible they will be in your well the next time we sample.

Residents with contaminated private wells may be exposed to chemicals through the following:

* Drinking, breathing, or touching well water.

* Breathing vapors that move upward through soil and into homes by a process called vapor intrusion.

* Eating fruits and vegetables watered with well water.

* Livestock and other animals drinking well water.

We evaluate the sampling results to determine if you may be at risk from any of these exposures.

Our risk assessment examined how humans and the environment could be exposed specifically to PCE and TCE, known as exposure routes. Exposure routes of concern for TCE and PCE are:

* Drinking, washing, or bathing with groundwater from a well.

* Breathing indoor air containing TCE or PCE through a process called vapor intrusion.

We compared groundwater results to United States Environmental Protection Agency’s (EPA’s) risk-based concentrations for each exposure route. The results are available in the annual offsite reports on the Documents tab.

Yes. Children are often more at risk from chemicals in the environment than adults. Our risk assessment considers this and the United States Environmental Protection Agency’s (EPA’s) 5 maximum contaminant level (MCLs) protects children.

Possibly, depending on your well. The risk from drinking well water, and using it for other household purposes, like showering and cooking, may be above the “safe” level in some of the domestic wells sampled. The offsite monitoring reports on the Documents tab include the most recent results for domestic wells. The “safe” level for PCE and TCE is less than 5 micrograms per liter (µg/L). Drinking well water from these wells above the “safe” level and using it for household purposes may be a health risk. We informed property owners and tenants if their well posed a risk.

Possibly, depending on your well. The risk from breathing vapors from contaminated groundwater may be above the “safe” exposure level in some of the domestic wells sampled. The offsite monitoring reports on the Documents tab include the most recent results for domestic wells. At wells above the “safe” exposure level, there is a possibility for negative effects, especially in sensitive populations like the elderly, children, and immunocompromised. We inform property owners and tenants if a risk of vapor intrusion exists.

No. Using well water as drinking water for pets, livestock, and fish is unlikely to pose a risk even at the highest PCE and TCE concentrations found in domestic well water from the aquifer. During the risk assessment, we looked at ecological risk screening levels for multiple mammals and fish. We determined that using domestic well water for pets, livestock, and fish is considered safe because the highest TCE and PCE concentrations were less than ecological risk screening levels.

No. Vegetables irrigated with well water are safe to eat. PCE and TCE are volatile chemicals, meaning very little will be left in the water during irrigation. The TCE and PCE left does not absorb well into the vegetables. If the vegetables do absorb TCE and PCE, the chemicals will move through the leaves into the air. Consuming vegetables irrigated with well water is considered safe.

Bannock County saves all well sampling results and notifications. If you did not receive your results or cannot find them, please email remediation@bannockcounty.gov to request sampling results for your address and the timeframe you are looking for.

No. We do not recommend acting if PCE and TCE concentrations are below standards. Regulatory standards represent the maximum allowable levels of TCE and PCE deemed safe in drinking water.

Possibly, depending on your well. We sample wells each year around areas impacted by PCE and TCE in groundwater within the Portneuf Valley Aquifer. Multiple sampling events help identify any changes in concentrations and verify risk assessment findings. Bannock County will continue to select sample wells yearly during ongoing cleanup efforts.

Bannock County will continue to tell property owners and tenants if PCE and TCE concentrations in their wells are above regulatory standards. You should not use well water with TCE or PCE above regulatory standards for drinking water. The City of Pocatello gives those properties the option to connect to City water.

No. Neither Bannock County nor the Idaho Department of Environmental Quality have the authority to shut down private wells. The County will continue to sample for PCE and TCE with the property owner’s permission. The sampling results tell property owners about water quality conditions, but the law does not require any action.

Please email remediation@bannockcounty.gov to request sampling or ask for us to stop sampling your well.

Yes. The City of Pocatello provides hookups to City water for drinking water use. Any property owner within the impacted area can connect to City water at any time.

No. A property owner will not be required to hook up to City water. Private wells with groundwater PCE and TCE concentrations above regulatory standards should use a different drinking water source or treat the water.

No reimbursement for City water hookup fees is currently available. The County will tell property owners and tenants about any changes.

You can install granular activated carbon or reverse osmosis treatment options for PCE and TCE at the top of your well. Granular activated carbon absorbs and removes TCE and PCE. Reverse osmosis is a filter- based system that removes TCE and PCE.

You are not required to install wellhead treatment. Using contaminated well water for irrigation and gardening poses a low risk.

Installing well treatment is voluntary. The property owner/tenant would be responsible for installing and paying for well treatment. No reimbursement options are currently available from Bannock County.

Property owners should give a potential buyers or renters their private well sampling results and tell them about sampling activities. Property owners should inform renters of restricted uses.