Samples collected from the river immediately after the Aug. 19 release exceeded the state's standards for recreational exposure to lead, said Kevin Okleberry, spills coordinator for the Utah Division of Water Quality. Lead causes developmental delays in children.
Contaminated sediment beneath the reservoir near the mouth of the canyon was removed in March, Okleberry said, but monitoring of the river will continue until the tests indicate that the sediment contains only naturally occurring concentrations of lead.
Per a settlement with state regulators that involved $145,000 in fines, the North Utah County Water Conservancy District must collect sediment samples annually until the river returns to "background," or low, lead levels. The water district also agreed to remove any additional contaminated sediment that may be discovered.
The cleanup "could take one year, or it could take 10 years," Okleberry said.
The water district has collected its first round of sediment samples, but state water-quality officials are waiting for test results, he said.
The state also collected samples of soil in American Fork, Highland and Cedar Hills from parks that had been irrigated by American Fork River water. There was some concern that the lead contamination could spread to these soils via the river water, Okleberry said.
But those samples were found to contain low levels of lead, which prompted the Utah County Health Department to lift the advisories for the river.