City shuts down second water well

August 29, 2001
By Christopher Schurtz
Las Cruces Sun-News

A second Las Cruces city well was shut down last week after New Mexico Environment Department inspectors found higher levels of the contaminant PCE in water from the well.

The well, Well 27, is one of four wells located in the Walnut and Griggs Environmental Protection Agency Superfund site that have shown traces of the contaminant perchloroethylene, or PCE.

But last week, those traces of PCE in Well 27, located near the corner of Walnut Street and Griggs Avenue, approached EPA warning levels and the well was shut down.

PCE is a chlorinated solvent used for dry cleaning and removing grease from metal. It is also believed by the EPA to cause cancer.

The first well in the Superfund site, Well 18, was shut down in 1995 after repeatedly showing high traces of PCE, well above the FDA limit. It has remained offline since.

City Manager Jim Ericson told the city council Monday night during a work session that Well 27 was shut down last week after showing traces of PCE.

"It got a high rating, but it is still below the EPA limit," Ericson said. "As a precaution, we have shut the well down."

According to City Utilities Regulatory Compliance Officer Dan Santantonio, Well 27 was found to have 4.9 micrograms per liter of PCE.

The measurement is just .1 micrograms below the EPA limit of 5 micrograms per liter. According to the agency, PCE in levels over 5 micrograms per liter can cause liver damage and lead to cancer.

Well 27 had been taken off line for repairs in February. When it was turned back on in June, state environmental tests showed PCE levels at 4.5 micrograms.

Santantonio said the well was shut off because it was unlikely PCE levels in the well were going to level off and were likely going to continue to increase.

Three other wells -- wells 21, 19 and 24 -- have shown varying traces of PCE, but none have shown a significant increase in PCE levels, Santantonio said.

All four wells with some degree of contamination have been tested every month by the New Mexico Environmental Department, at the city's request.

Water not diluted

There may also be indications those living in the Superfund site may be getting a higher concentration of PCE than city residents living outside the contaminated area.

At a public meeting in June, Olga Morales, environmental specialist for the local office of the NMED, said levels as high as 3.5 micrograms per liter were detected in tests taken earlier this year of residential tap water from houses within the Superfund site.

The dilution effect of the city's water system was not as efficient as previously thought, Morales said.

City Water Resources Director Gilbert Morales said water drawn from the wells in the Superfund site is the primary source of water to those living within the site.

In most cases, water drawn during the day essentially goes directly from the well, where it is treated with small amounts of chlorine, into city water lines and on to residential taps, Morales said.

Excess water is directed into one of several city storage tanks. The tanks are also filled during the evening to help create water pressure and to provide for water to the rest of the city for the next day.

Morales said the dynamic nature of the system allows for water to be distributed to areas around the city according to demand.

The same system, however, makes tracking water drawn from a specific well problematic because water can be drawn from varying sources throughout any given day, depending on demand.

But Morales said prior to the well being shut down, it is likely that much of the water used by residents in the area of the Superfund site came from Well 27.

Well 27 is currently being flushed for several hours in the morning, with the water from the well being directed into the storm drain that runs parallel with Amador Avenue.

Otherwise, there are no plans now to turn the well back on for use in the city's water system.

Loss of well

Morales said the city's water system will not be affected by the loss of the well, but that further well losses may pose a problem. Well 27 is an older well, Morales said, and would have been in line to be replaced in the next several years, even if it had not been shut down.

But he said it was unlikely the other three wells in the Superfund site would be shut down, unless they eventually show high traces of PCE. It is also unlikely the city will shut down wells in the area and relocate them to cleaner areas of the city.

"To do something as drastic as to eliminate four wells would be a huge expense," Morales said.

He said the EPA limit of 5 micrograms per liter is "extremely, extremely conservative" and that future plans must include a cost- benefit approach to evaluate whether the potential health risks justify the high cost of replacing wells.

The cost for replacing a single well, from installation costs to materials, is about $750,000, Santantonio said.

Santantonio said more will be known about the extent of the contamination and possible clean up costs after the contractor hired by the EPA, the Dallas-based firm CH 2M Hill, begins work on the investigation and conducts a feasibility study.

If the contractor cannot determine the party responsible for the contamination, the agency will pick up 90 percent of the cost of the clean-up, with the city picking up the rest.

The cost is far from being determined but will likely be in the millions of dollars.

One of the next steps the city may have to take is establishing a treatment plant to treat the water that contains PCE, at an estimated cost of $1 million, Santantonio said.

Because PCE breaks down quickly when exposed to air, Santantonio said the treatment system would include directing contaminated water into an exposed column before being run through a scrubber.

For those interested in treating water at their taps, Santantonio recommended reverse osmosis filters rather than charcoal filters, though both methods are apparently effective in eliminating PCE from the water.

He said charcoal filters can become a medium for microbes that may cause more health problems than PCE or other contaminants, especially if they are not changed regularly.

But he said the EPA levels are safe and filters are not needed, as he said the city is steadfastly monitoring PCE levels.

"Our responsibility is to protect the drinking water," Santantonio said. "But we all live in the city, too, and we all use the water."

No further testing

Olga Morales said no further testing is currently being conducted of residential tap water.

She said the NMED has not received any requests to test tap water in residences in the rest of the city.

No additional contamination has been found in city water during annual tests for at least 80 other contaminants, including PCE, Morales said.

The first known contamination of the city wells in the site was discovered during routine sampling of municipal wells in 1993.

One city well, Well 18, was decommissioned in 1995 because it showed levels as high as 32 micrograms of PCE per liter. The high amount found is attributable to the PCE building up in the well lines, rather than a true measure of the amount of PCE in the well, Morales said.

Four others, wells 19, 21, 24 and 27, also showed low levels of the chemical, though Well 27 levels were the highest of the four.

The contaminated plume extends in the general range from Griggs Avenue north past Hadley Avenue and from Interstate 25 east past Solano Drive.

But the actual area of the plume cannot be determined until a more detailed analysis is conducted, Santantonio said.

What is known, Santantonio said, is the actual contamination is 100 to 200 feet from the surface and only poses a health threat if drawn into city water.

The area of the plume is also continuing to spread as the chemical, which is heavier than water, follows a path of least resistance through gaps of sand and clay.

Santantonio said as water usage and pumping from the wells peaked during the summer months, a sort of vacuum effect pulled at the chemical plume, further affecting the direction of its flow.