After getting an overwhelming response from private well owners, officials have stopped accepting requests to sample water in the Santa Fe area for free testing.

The state Environment Department said Friday that more than 500 requests were submitted to the agency, as well as the city of Santa Fe, Santa Fe County, Los Alamos National Laboratory, Sandia National Laboratories and Good Water Co.

By Friday, the department had taken water samples from 387 wells in an area that includes the city of Santa Fe, north to Tesuque, east to Cañoncito and Glorieta, south to Lamy, Eldorado and La Cienega, and west to the Rio Grande.

The department said it asked the other entities for their collaboration in providing free tests when it discovered previously unknown or higher-than-normal levels of contamination of arsenic, nitrate, radium and fluoride are becoming more concentrated in groundwater.

"The department believes most wells in the area probably have good quality water," a news release said. "However, because of the ongoing drought and mining of the aquifer, NMED wants to determine whether natural contaminants like arsenic, selenium, uranium, radium and fluoride are becoming more concentrated in groundwater."

Recent well water testing revealed previously unknown natural uranium contamination in the foothills area; nitrate concentrations along the Santa Fe River three times higher than past testing; radium concentrations in Glorieta not discovered in the past; and an upwelling of naturally occurring arsenic in the northwest part of the city.

"Fractured bedrock areas in the area's mountain foothills are vulnerable to septic tank pollution, including nitrate and water softener salt," the release said. "However, nitrate concentrations appear to be limited."

Samples from well testing so far have shown some wells in Glorieta have a natural high mineral content.

"Many residents served by those wells do not drink that water because of its bad taste," the department said. "Minerals from shallow bedrock in the area are dissolving into groundwater." The department will advise affected residents of options in treating the water after tests are complete.

Tests are expected to be finished in about 12 weeks from the time water is sampled.

The tests began Tuesday and were expected to continue this week. "However, because of the high volume of requests, the department will continue sampling the requests that were received as of Monday," the statement said.

The tests include field and laboratory analyses for about 50 chemical parameters, including nitrate, fluoride, heavy metals including uranium, and organic vapor such as from gasoline and degreasing solvent.

The department is taking field measurements, water samples and noting the position of domestic wells for mapping. Los Alamos National Laboratory, which will conduct the testing, will receive bottles marked with numbers that do not identify residents, their addresses or well locations, the state agency said, noting that names of well owners, addresses and phone numbers will remain confidential and won't be noted on maps.

Water supplied by public drinking water systems, such as the city of Santa Fe's water division, was not tested because those supplies are routinely analyzed pursuant to the Federal Safe Drinking Water Act.

The city recently issued to its water customers a report that summarizes the water test results from 2008. The report said city drinking water met all federal and state drinking water quality standards.