TWIN FALLS - The city of Twin Falls cannot meet federal standards for safe drinking water, even after more than a year has passed since the new standards became law.

An unacceptable amount of arsenic - a very poisonous chemical element - is present in the city's drinking water, in some cases nearly double the amount considered safe for human consumption by the Environmental Protection Agency.

The city's annual water-quality report released last week says amounts of arsenic - likely a natural geological occurrence - ranging between 1.4 and 18.1 parts per billion were discovered in water samples taken in 2006. The EPA's standard for safe drinking water is 10 parts per billion.

Although the levels are high, the city says there is no emergency, and that it is working with the Idaho Department of Environmental Quality to reduce levels.

Don Lee is a drinking-water manager in the DEQ's Boise office. "If the city is making what we consider meaningful progress toward meeting the standard, we'll work with them to avoid fines," he said.

The city and the DEQ have reached an agreement that gives Twin Falls until Jan. 11, 2011 to reduce levels to the 10-parts-per-billion standard - 10 years after the EPA announced the standard would be lowered from 50 parts per billion. The new limits for arsenic became effective in January 2006.

The city has been exploring ways to lower arsenic levels since the EPA announced the new standards in January 2001, said Gretchen Scott, a management assistant with the city. Problem is, the city's reduction plan involves diluting high-arsenic water with purer water that's disappearing at a rate of about 4 percent a year.

About 60 percent of the city's drinking water comes from Blue Lakes Springs - a source relatively free of arsenic. The city wants to blend the Blue Lakes water with high-arsenic water pumped from wells on the south end of town.

But hydrologists say the Blue Lakes Springs will continue to decline, and engineers expect the water supply to equal demand within four years unless the city finds new water sources or reduces demand.

Idaho residents consume more water than people in any other state, and that has city officials scrambling to find a new water source or purchase water rights.

Another prong in the city's plan is to reduce the amount of drinking water consumed. The city is now requiring all new subdivisions to use pressurized irrigation from canals instead of city drinking water, and ordinances are in place that restrict when residents can water lawns.

Nevertheless, arsenic levels in 2006 were actually higher than 2005 levels. Scott said it may be a while before the city has arsenic under control.

"There are lots of issues going on here, so it's not as easy as finding one solution and putting it into practice," she said.

Times-News staff writer Matt Christensen covers the environment. He welcomes comments at 735-3243 and at matt.christensen@lee.net.