Little Cottonwood Canyon's popular Tanner Flats Campground will be closed for at least a year following discovery of high lead and arsenic levels in its soil.

The Wasatch-Cache National Forest is studying alternatives to clean the campground, the site of an 1870s mining operation five miles from the mouth of Little Cottonwood Canyon.How long it will take to deal with the contaminated soil is uncertain. Forest Service officials don't know how deep the old lead smelter tailings run beneath the surface.

"Our goal is to mitigate or eradicate, and we're shooting for a one-year contract," said Pam Winn, forest engineer. "By law, we only have to mitigate to background levels, but we have decided to go further and reduce this to lower levels acceptable in residential areas. The public can expect no less of us."

Because of its mineral-rich geology, Little Cottonwood Canyon has naturally high background levels of lead and arsenic. But soil samples from Tanners Flat exceeded the acceptable level of exposure for residential areas - 500 milligrams of lead per kilogram of soil and 50 milligrams of arsenic per kilogram of soil.

The highest readings were found in one campsite, with lead concentrations of 53,000 milligrams per kilogram of soil and arsenic levels of 3,200 milligrams per kilogram. In the campground amphitheater, lead levels of 33,000 milligrams per kilogram and arsenic levels of 1,100 milligrams per kilogram were recorded in the dirt.

"As far as the lead content, our main concern is children under the age of 8 who should not be exposed to those levels for more than two weeks," said Winn. "With the arsenic, that affects everyone. Legally and morally, we have to make that campground a safe experience for people of all ages."

However, while some samples of streamside sediment showed concentrations of lead and arsenic, the water sources in the campground tested negative for contamination.

Utah Department of Environmental Quality officials first discovered the contamination of the campground in November 1995 during a routine investigation of old mining-smelter sites.

Researchers believe the high levels of lead and arsenic in the 20-acre campground came from the long-gone Jones and Pardee Smelter, one of several mining operations that sprung up following the discovery of silver at the famed Emma mine near Alta in 1865.