Bannock County Groundwater

Hazardous Materials

Other contamination threats to our groundwater resource in Pocatello, Chubbuck, and North Bannock County are leaking underground storage tanks, industrial or commercial sites, spills and leaks, and illegal disposal of chemicals and hazardous waste. The Department of Environmental Quality and the Southeastern District Health Department keep track and sometimes monitor known locations of contamination in Bannock County.In addition, businesses and industries that use and store hazardous chemicals or generate hazardous waste may pose a threat to our aquifer. Federal laws govern businesses and industries that use and store large quantities of chemicals or generate large volumes of hazardous waste. Large industry and business must comply with federally mandated health and safety requirements for hazardous materials and generated waste such as reporting spills and leaks, proper storage, inventory listing, spill prevention and containment, inspections, and notification and training of employees. However, below a certain volume threshold, these federal laws do not apply. It is this population of businesses and industries that are of concern because they are essentially unregulated and can legally conduct a business that involves hazardous materials in quantities that could have significant impacts on our groundwater if there were a release.The Idaho Department of Environmental Quality regularly monitors some known areas of spills or leaks and clean up is ongoing. Other remediated sites are no longer a threat to groundwater.

The Trichloroethylene (TCE) Problem in Pocatello

Municipal Wells affected by TCE Plume

TCE is a manmade chlorinated solvent used commercially as industrial degreasers, spot removers, and in dry cleaning. It is very powerful, and it only takes a very small amount of TCE to contaminate a City well (the equivalent of a teaspoon of TCE in the Lava Hot Springs swimming pools (5 parts per billion). Chronic TCE exposure can cause damage to the liver, the kidneys and the central nervous system. It may also lead to increased risk of cancer.

In the 1990s TCE was discovered in the Lower Portneuf Valley Aquifer. Officials traced its source to barrels of TCE that were dumped at the old Bannock County Landfill, which was not lined, in the 1980s. This TCE seeped through the Landfill into the groundwater. Once the TCE reached the Lower Portneuf Valley Aquifer it moved quickly northward. As seen in this picture, it got as far north as Oak Street before it was discovered.

Eight of the City of Pocatello’s 24 wells were affected, with two wells having to be replaced with new wells outside of the TCE plume.

TCE in Pocatello City Wells

This diagram shows what has happened with TCE in City wells from 1997 to 2009. It shows the amount of TCE in City drinking wells in parts per billion. The maximum contaminant level allowed by federal law is 5 parts per billion. The good news is that the levels in the wells have been dropping and since about 2000, the levels in most of the wells have remained below 2 parts per billion. The County is now working to remediate this problem at the Landfill. At the base of the landfill they have an air-stripping tower in place to remove the TCE from the ground water. It is working to keep the solvent from entering the Valley aquifer.

The Cost of Contamination

The bad news with the TCE plume is the cost to City and County taxpayers. Cleaning up contamination is a lot more costly than preventing in the first place. Bannock County has spent close to $4M cleaning up this TCE plume; The City of Pocatello has spent over $1M building new wells and water lines to replace the contaminated wells. There will continue to be ongoing costs for several more decades until all of the TCE has seeped out of the landfill and been removed with the air stripping towers at the base of the Landfill.

Leaking Underground Fuel Storage

Underground Fuel Storage Sites and Leaking Tanks

This is another problem of the past (for the most part). Old underground storage tanks at gas stations were made of steel and tended to rust and leak gasoline into the ground and then into our groundwater. All of the red dots on this map show underground storage tanks that have leaded (30% of all known underground storage tanks in the Valley). Although any one of these could have been a big problem, only one is known to have directly affected groundwater. This fuel contamination of ground water came from an underground Union Pacific Storage Tank near the rail yard.  Fortunately regulations are in place today which require new underground storage tanks to be double lined and to be better monitored to prevent accidental contamination.

Chubbuck and Fort Hall Contamination Issues

Chubbuck and Fort Hall Contamination Issues

The City of Chubbuck has discovered perchloroethylene (PCE or PERC) in its wells. This manmade chemical is a chlorinated solvent used commercially as industrial degreasers, spot removers, and in dry cleaning. Chronic PCE exposure can cause damage to the liver, the kidneys and the central nervous system. It may also lead to increased risk of cancer. The maximum contaminant level for PCE is 5.0 ppb (5.0 grams per billion grams of water).The PCE plume is shown on this map in dark blue. Unfortunately, its source is unknown, despite rigorous testing of possible contaminant sites.Fort Hall has discovered ethynlene dibromide (EDB) in their wells. EDB is a chemical used as a solvent, waterproofing agent, pesticide, anti-knock compound in leaded gasoline, and as a soil fumigant on golf courses. By 1984, EPA eliminated most of the use of EDB as a pesticide, however, it is still manufactured for other purposes.The EDB plume is shown in light blue on this map. Groundwater sampling activities conducted in the late 1990’s and again in 2004, showed that the drinking water supply beneath a sixty-three square mile area on and near the Reservation contained measurable quantities of EDB. The EDB plume in north Bannock County is presumed to originate in Bingham County on the Reservation where it was known to have been applied as a pesticide on row crops.As a result of these plumes, Fort Hall has placed all of its residents on a municipal water supply system that draws clean water; and Chubbuck has had to install an air stripper at one of its wells to remove the PCE before delivering this water to residents. Additionally, Chubbuck is now looking very carefully at where to site a future well (needed for population growth) to ensure that its water will not be contaminated with either plume.

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