Senator Eliot Shapleigh - El Paso, Texas

Recent tests show that the arsenic plume under East Helena is wider and extends farther than it did last year; that concentrations in a few wells are the highest ever recorded; and that groundwater also is contaminated with high levels of selenium.

The underground arsenic plume now stretches from the Asarco lead smelter to monitoring wells installed in 2005, which were placed in a field west of Wylie Drive in an effort to locate the leading edge of the plume, according to information from the Environmental Protection Agency’s Denver office.

Arsenic also is being detected in monitoring wells on either side of the plume’s previous 600-foot estimated width. Those wells are near First and Main streets, and Third and Pacific streets, and previously hadn’t tested positive for the known carcinogen.

In addition, recent tests showed selenium to be present in those test wells.

The selenium at the test well at Third and Riggs streets has 10 times the federal drinking water limit, and arsenic in that well is more than 1,600 times the federal standard.

“So we no longer just have an arsenic plume; now we also have a selenium plume,” said Linda Jacobson, the EPA project manager who is monitoring the plume from Denver.

Because of the findings, Asarco is stepping up its testing of the residential wells, Jacobson said, as well as that of some of the monitoring wells.

“Asarco, without us telling them to, immediately started sampling the homes for selenium too,” Jacobson said. “They are doing monthly monitoring of the four homes on Gail Street, and another subset being done bi-monthly.”

In addition, samples taken this spring also will be tested for a wider range of non-organic compounds.

Jacobson added that no one is consuming water above the MCL, which is the federal Maximum Contaminant Level for municipal drinking water supplies.

Bob Miller, hydrologist for Asarco, said selenium has been detected on the East Helena lead smelter site, but not at these high levels off-site. He said the company is more concerned about the arsenic.

“Our strategy is we’ve looke at the primary elements, with the understanding that some of those trace elements like selenium, are being addressed as we are addressing the really important ones, like arsenic,” Miller said.

He expects that the recent spike in the off-site concentrations of arsenic and selenium in the test wells is due to work at the East Helena site. Crews have been dismantling buildings and stockpiling contaminated materials, and that may have caused additional releases.

Arsenic occurs naturally in low levels in water in the Helena area, and selenium also occurs naturally in some environments.

But both also are known byproducts of the smelting process, and EPA officials said they think the arsenic and selenium in East Helena’s underground plume are the result of Asarco’s 100 years of lead smelting operations at its plant just south of the community.

The plant closed in 2001.

Asarco knew about the arsenic plume for nearly 30 years, and readings as high as 34 ppm — about 3,000 times the MCL — were found in groundwater below the plant. But it wasn’t until 2001 that monitoring wells off-site began picking up elevated arsenic levels in the intermediate aquifer, 30 to 80 feet below East Helena.

The previous high reading was 15 ppm in October 2003 in the monitoring well at Third and Riggs Street. It typically fluctuates with lower levels during the spring testing, but last fall came up at a whopping 16.58 ppm n 1,600 times the MCL of .01 ppm for arsenic.

If a person were to drink water with arsenic present at that level, it would cause nausea and vomiting, according to Dr. David Mellard with the Agency for Toxic Substances and Disease Registry. It eventually would destroy a person’s digestive tract and could cause organ failure.

The monitoring wells are tested twice a year for a variety of dissolved metals, including lead, manganese, copper and iron.

Selenium wasn’t on the list, Jacobson said, but was inadvertently detected by EPA lab chemist Jack Sheets.

“They didn’t request to check for selenium, but when I did this analysis I thought this was way over the limit,” Sheets said.

Low doses of selenium are needed to maintain good health, and often are included in vitamins, according to the ATSDR.

The MCL for selenium is 50 parts per billion, or .05 parts per million. Dr. Mellard said that if someone were to inadvertently drink water with selenium at the 520 ppb found in the East Helena aquifer for a few months, their symptoms most likely would include deformed nails that might slough off, and brittle hair or hair loss.

“The group most at risk for drinking water containing selenium at that level would be children, particularly pre-school, elementary age and infants,” he said. They would get a higher dose because of their lower body weights.”

While the amount of selenium detected isn’t of as great a concern to Mellard as that of the arsenic, he added that “you wouldn’t want a household drilling a well into it.”

Most of the homes in East Helena are hooked into the municipal water supply system, so they’re not tapping into the plume.

However, East Helena’s public water supply wells are one to two miles down gradient from the known tip of the arsenic plume, as are the two wells that supply drinking water to the Twilight Mobile Home Park.

Fifteen residential wells are strung along Gail and Groschell streets between Wylie Drive and Cleveland Street, but they’re either used only for irrigation purposes or have been abandoned.

Jacobson said the most recent tests now show detectable levels of arsenic in two of the residential wells, but at .002 ppm they’re below the .01 ppm MCL for arsenic. They also show selenium at is 14 ppb and 16 ppb.

But what’s safe for human consumption isn’t necessarily the same for some wildlife. Kirkpatrick notes that aquatic animals are more susceptible to selenium, so the standard is lower.

With Prickly Pear Creek flowing less than a mile downgradient from the known edge of the plume, that could be troublesome.

Miller said Asarco officials don’t expect the plume to reach the creek, but they are having discussions about possibly installing additional monitoring wells farther northwest.

Another issue now facing the EPA and Asarco is that they had hoped to stop the migration of the plume by installing what’s known as a PRB — a permeable reactive barrier, which basically consists of a wall of iron filings dug into the ground. The arsenic bonds with the iron and is then held in place.

Jacobson said that can work with selenium, but that the amount of sulfate in the plume also is high, and it’s filling in the spaces on the iron filings that the selenium otherwise would take.

“That may change what strategy we may use as far as treatment of the plume. We may need more than one barrier,” Jacobson said.

Miller said they plan to install a “slurry wall” — about 40-feet deep, 1,200-feet long and 3 to 4 feet wide — at the Asarco plant site, which should keep water from flowing through the contaminated soils, which could significantly slow the off-site migration.