Agency: Homestake site
‘public health hazard’

Strong winds carry misted water through the air and toward Hwy 605 at the Homestake mining site near Milan, NM. on Wednesday. [photo by Jeff Jones / Independent]

By Kathy Helms
Diné Bureau

WINDOW ROCK — The Agency for Toxic Substances and Disease Registry has concluded that the Homestake Mining Co. mill site in Milan is a public health hazard.

The agency has extended the public comment period on its findings through July 3 after a delay in the report’s delivery.

The federal public health agency of the U.S. Department of Health and Human Services evaluates the human health effects of exposure to hazardous substances.

The Homestake mill opened in 1958 and processed uranium for approximately 30 years. It closed in 1990, leaving behind two tailings piles which have contaminated the alluvial groundwater aquifer. The larger pile covers 200 acres and is about 100 feet high; the smaller pile covers 40 acres and is 25 feet high.

Groundwater monitoring data indicate that contamination from tailings seepage has affected the San Mateo alluvial aquifer and the Upper, Middle, and Lower Chinle aquifers.

The San Mateo is the primary aquifer of concern because it is the most contaminated and it recharges the Chinle aquifers, which subdivision residents have used as a source of drinking water.

Approximately 200 people live within a mile of the tailings piles. Five residential subdivisions — Felice Acres, Broadview Acres, Murray Acres, Valle Verde, and Pleasant Valley Estates — are located between a half-mile to 2 miles from the tailings piles, with the nearest residence and drinking water well about 3,000 feet away.

Residential wells in the subdivisions were sampled for radionuclides, chemicals, and metals beginning in the mid-1970s, though only a few were sampled consistently.

Sample results indicated elevated concentrations of uranium, selenium, and molybdenum.

The state of New Mexico’s standard for uranium in groundwater was changed in June 2007 from 5,000 parts per billion to 30 ppb following a state Court of Appeals ruling. U.S. Environmental Protection Agency’s maximum contaminant level, or level considered safe for uranium in groundwater is 30 ppb and has been since 2000.

Linda Evers and her family, who live in Broadview Acres about a half-mile from the Homestake site, were included in the Homestake/Village of Milan water hookup in April 1985 which resulted from a consent decree between EPA and Homestake.

The company was required to provide an alternate water supply for well owners after contamination was found in wells downgradient from the site.

“Everybody around here is like, ‘Well, finally! That took long enough.’ When you go from 5,000 parts per billion to 30 parts per billion, and before 2000 there was no drinking water standard for uranium, it’s like, ‘Wow, really?’” Evers said

Monday evening, regarding the Agency for Toxic Substances and Disease Registry ’s public health hazard designation.
Homestake was placed on the EPA Superfund National Priorities List in September 1983 due to concerns about radon emissions from the tailings piles. Cleanup of the contaminated aquifers has been ongoing since 1977.

During sampling by EPA and the New Mexico Environment Department in September 2005, the agencies found that about two-thirds of the wells, or 22 out of 34, had uranium concentrations above the maximum contaminant level. The maximum uranium concentration detected was 849 ppb, as opposed to the 30 ppb standard.

Residents who accepted the 1985 offer for village of Milan water and used it as their sole source of water eliminated their exposure to the contaminated well water. If residents continued to use their well water, which some did, for drinking, showering, watering gardens and lawns, they were potentially exposed to the contaminants, the agency said.

The agency did not have any vegetable or soil sample results to determine what the contaminant levels were in the vegetables, and therefore doesn’t know what levels people may have been exposed to via this route.

The amount of uranium, selenium, and molybdenum ingested would depend upon how often they consumed vegetables, if they used contaminated well water to irrigate the vegetables, and if the vegetables were thoroughly cleaned prior to eating them.

Because no institutional controls have been established, residents have had the option of using the contaminated groundwater for irrigation purposes and to provide water for their livestock.

Adverse health effects in livestock would have been more likely to occur in the 1970s-1990s compared to what they are exposed to presently, because concentrations were much higher in the past, the agency said.

The Agency for Toxic Substances and Disease Registry reviewed over 30 years of sampling results and found that ongoing remediation has helped in reducing the levels of contaminants. However, sampling results from the past three years indicate that uranium and selenium concentrations are above their respective drinking water standard and will most likely be above them upon completion of the remedial actions.

Lack of consistent monitoring over the years, the considerable concentration differences in wells within the same aquifer, the unknown usage of wells during the alternate water supply period, and anomalies with the sampling data are all factors that make past exposures an indeterminate health hazard, the agency said.

Because exposure is still possible in some of the private wells, ATSDR has categorized the Homestake site as a public health hazard.