Dioxins by Aimee Reynolds – Mt Department of Environmental Quality

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Dioxins by Aimee Reynolds – Mt Department of Environmental Quality
March 13, 2018 6:00 am
March 13, 2018 7:00 pm
February 20, 2018
Quarry Brewing
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124 West Broadway, Butte, 59701, United States

 THE DIOXINS PRESENTATION HAS BEEN RESCHEDULED FOR MARCH 13, 2018 – 6 pm – Quarry Brewing – 124 West Broadway

After more than 20 years of thorough environmental study and complex cleanup, the Site is reaching its final phase of soil remediation and the water treatment plant is operating successfully. Montana Pole is a former 40-acre wood treating facility that operated from 1946 until 1984. Contamination consists of wood-treating products including pentachlorophenol (PCP), related chlorinated phenols, polynuclear aromatic hydrocarbons (PAH), dioxins/furans, and petroleum compounds that spread into surrounding soils, groundwater, and the adjacent Silver Bow Creek. The Site was added to the National Priority List (NPL) in 1987. Located at 220 West Greenwood Avenue, Butte, Montana, it is in a mixed land use area. Two neighborhoods sit within a quarter of a mile.


DEQ, in coordination with the EPA, has determined that the soils in the land treatment unit have met cleanup standards for PCP and PAHs. Some dioxins remain, however, the final cleanup must ensure protectiveness of human health and the environment. DEQ has informed Butte-Silver Bow (BSB) that final remedial action steps are being designed for the soils at the Montana Pole and Treating Plant Site, with construction slated for 2015-16. Upon completion, the land treatment portion of the property may be turned over to BSB for redevelopment. The portion of the site on the north side of the highway will remain under DEQ control so that the water treatment plant can continue to operate and treat groundwater. The goal is for the final remedy to mesh with the future use plans that BSB, with input from the public, decides on. BSB recently held several workshops to solicit input from the public. Their flyer, which includes the four alternatives that were discussed, can be accessed here.

The National Priorities List (NPL) is the list of national priorities among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States and its territories. The NPL is intended primarily to guide the EPA in determinig which sites warrant further investigation (http://www.epa.gov/superfund/sites/npl/). Superfund is the federal government’s program to clean up the nation’s NPL sites.

The main reason for putting this site on the NPL was that groundwater beneath the site had become contaminated with oily wood-treating fluid that had spilled, dripped, or discharged onto the ground surface. The oily wood-treating fluid migrated downward, contaminating the soil that it passed through, and entered the groundwater. Some of this fluid made its way to the surface or groundwater and Silver Bow Creek, and some of the fluid attached to soil particles above and below the water table. A portion of this fluid dissolved in groundwater and surface water where it migrated downstream both above and below the ground surface toward potential and ecological receptors, preventing the groundwater and surface water from being used for its designated classifications, beneficial uses, and specific standards.

Silver Bow Creek is the main reason that the Site was put on the NPL. It is the main reason for cleanup as specified in the ROD. Currently, DEQ collects and analyzes samples adjacent to the site and both upstream and downstream from that point. Often, the results of the upstream sample are not much different from the results of the downstream sample, which indicates that the Site is not impacting the quality of water in Silver Bow Creek. These samples are collected once per year and test for all contaminants. Samples used to be collected much more frequently, but because we have had so many years of data that show the contaminant levels have decreased and now remain at low levels, sampling has been cut back to one time per year. If significant changes were seen that would warrant more frequent sampling, we would increase the number of times per year that samples were taken.

The term “environmental contaminant” is another name for pollution. A contaminant is a substance that is where it shouldn’t be and is at high enough levels to have a negative effect on our health or on the health of animals or plants. A contaminant is any potentially undesirable substance (physical, chemical, or biological). It usually refers to the introduction of harmful human-made substances. However, some substances that may have harmful effects at high levels, like cadmium, occur naturally in ecosystems and may also be introduced through human activities. Contaminants can be man-made substances produced by factories, such as the pesticides DDT and toxaphene. Toxic substances that don’t easily degrade or that are able to spread over a wide area are most problematic. Contaminants may be found in soils, sediment, air, water, sea animals, land animals, plants, and birds (http://www.nativeknowledge.org/db/files/aboutcon.htm).

There are three different types of contaminants in the oil wood-treating fluid that are being cleaned up at the MPTP Site: pentachlorophenol (PCP), dioxins and furans, and polycyclic aromatic hydrocarbons (PAH).

Groundwater from two buried trenches (NHRT and NCRT) is pumped to the WTP. This water is pumped through two treatment tank trains of granulated activated carbon (GAC) which absorb the contaminants (PCP, dioxon/furans, PAHs). The primary tanks absorb the majority of the contamination and the secondary tanks remove an additional small amount. When a tank’s GAC is “used up” or no longer absorbing enough PCP, the carbon is replaced. After the water exits the secondary treatment tanks, the majority of the water is then discharged to Silver Bow Creek. At times, some treated water is directed to the south portion of the site to help with the groundwater remediation and to flush contaminants beneath the Interstate to the trenches, where it can be recovered and treated in the WTP.

The nearly 10-acre LTU was designed and constructed to break down PCP in soil using natural occurring microorganisms. The break down process is enhanced by periodic tilling of the surface soil to introduce oxygen and by application of irrigation water (much like composting). The periodic irrigation also helps control blowing dust. The LTU has an underlying impermeable liner so that any water leaching from the LTU is collected in a nearby lined collection pond where it is either reused to irrigate the LTU or routed to the WTP for processing. To date, approximately 160,000 cubic yards of impacted soils have been treated on the LTU and placed back on site. The soil depth throughout the LTU is currently approximately 46″. Including the sand layer, the volume of contaminated soil that remains on the LTU is estimated at 53,000 cubic yards, assuming the sand layer is approximately 6 inches thick. After PCP and PAH data indicate that the soil meets site-specific cleanup goals, the soils will be used as backfill at the site. Dioxins are also being actively treated, but are being degraded at a much slower rate. For this reason, the treated soils will be covered and controls will be put in place to ensure that these areas are not disturbed.

Results from the 2012 sampling are shown in the table below, as are the cleanup goals that were established in the Record of Decision (ROD) for the MPTP Site.

Discharge from Water Treatment Plant
Contaminant ROD (µg/l) 2012 Levels (µg/l)
Pentachlorophenol 1.0 <.2 – 0.670
Total D PAHs 360 0.0
Dioxin TCDD 0.00001 0.000000441
Surface Water in Silver Bow Creek
Contaminant ROD (µg/l) 2012 Levels (µg/l)
Pentachlorophenol 1.0 0.670
Total D PAHs 360 0.0
Dioxin TCDD 0.00001 0.000000041 – 0.000000347
Contaminant ROD (µg/l) 2012 Levels (µg/l)
Pentachlorophenol 1.0 ND – 1,450
Total D PAHs 360 0
Dioxin TCDD 0.00003 0.000000033 – 0.0000275
Soils (those on the LTU)
Contaminant ROD (µg/l) 2012 Levels (µg/l)
Pentachlorophenol 34,000 1,300 – 77,700
B2 PAHs 4,200 0 – 0.020077a
Dioxin TCDD 0.2 0.999 – 5.99

a. From 2010 sampling


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