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According to Bollmann, the plugged wells had been drilled years earlier in order to better ascertain the nature of the contaminants present in the landfill. Once the EPA's Record of Decision was issued in 1994, the goals changed, and sampling was performed to determine "whether the site was in compliance with the regulations," he says.

As for the four aquifers that lie beneath the site -- the Dawson, the Denver, the Arapahoe and the Laramie-Fox Hills -- Bollmann says they haven't been contaminated. "We have samples from the lignite bed, located on top of the Denver formation, that are clean," he says. "We have samples from the upper Denver aquifer that are clean. And with a few scattered exceptions, the samples in the unweathered Dawson are clean."

Although water samples taken from wells drilled deeper than 300 feet contain numerous chemicals, including solvents and heavy metals, those solvents are most likely the result of contamination from the labs doing the analyses, Bollmann says. The metals, he adds, are not present in levels exceeding "background concentrations."

And what, exactly, are the "background concentrations" at Lowry? At the landfill, contamination is defined as the "presence of a chemical above background concentrations." But the wells that have been designated as "background" wells are not free of pollutants, either.

Many of these "background wells" are located south of Quincy Road -- one of the areas where patrolman Bill Wilson saw tankers dumping their loads decades ago. According to the city's database, these wells also contain numerous chemicals and radionuclides -- but since they are "upgradient," or upstream of the landfill, the EPA has allowed them be used as background wells. The result? The contamination that is present in the on-site wells is downplayed.

One of the deepest wells, dubbed WW-40, descends more than a thousand feet to the Arapahoe Aquifer; it's located near the Gun Club Road entrance to the landfill. According to both Bollmann and the EPA, no contaminants were found in this well. But the database tells a different story: Arsenic, lead and mercury were among the chemicals detected when WW-40 was sampled in 1993 and again in 1994. Apparently no testing was done for radionuclides or volatile organic chemicals, which are extremely prevalent at the site. And despite the well's clean bill of health, landfill workers are drinking "commercially bottled drinking water," EPA records show.

Several other deep wells -- GW-116, GW-117 and GW-118 -- were drilled near the center of the landfill, but the database contains no sampling results for these wells. According to Bollmann, the wells were drilled not to test for contaminants, but to determine whether a fracture existed below the landfill. No such fracture was found, he says.

In 1998, landfill officials finally began testing wells again for plutonium contamination again -- but these samples were mostly taken from newly drilled wells located just outside an underground barrier wall. Even so, the database shows that these wells, which are all relatively shallow, contain plutonium and americium, albeit in low amounts.

The database reveals other puzzling trends. For example, there are 436 results in the database showing plutonium and americium levels ranging from a few hundredths of a picocurie to hundreds of picocuries. But 278 results, including nearly all of the highest readings, are dismissed as "undetected" and marked with a "U" in an adjoining column. When asked about the notation, Gwen Hooten, the EPA's current project manager at Lowry, says it represents the "detection limits" of the laboratory doing the analysis and not the actual concentration.

Detection limits are the levels of contamination that a lab detects in samples sent for analysis. Normally, laboratories provide their clients with the actual results of their analyses, as well as such qualifying information as detection limits and counting errors. So, for example, if the detection limits for plutonium were set at 50 picocuries and a sample came in that contained less than 50 picocuries of plutonium, the lab would mark a "U" on paper and report the amount as an undetectable -- a "nondetect," in cleanup lingo.

Although a layman hearing the word "nondetect" could easily think that meant a sample was uncontaminated, that might not be the case. The actual amount of the nondetect could be anywhere from 0 to 50 picocuries -- three times the EPA's safe-drinking-water standard. "The lab's not saying the concentration is zero if a 'U' is there," concedes Bollmann. "What it's saying is that it can't say with certainty the compound is present in any concentration."

Some of the wells contain results ranging from hundreds, to thousands, to a million picocuries or more for americium, arsenic, iodine and neptunium; these results are also recorded in the EPA's Record of Decision as the "maximum detected concentration." According to Hooten, however, the numbers do not reflect the actual radionuclide concentrations that exist at the site, but rather detection limits. "It was just a first run," she says. "I can't given you a specific reason for why those detection limits were chosen."

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Eileen Welsome

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