Leviathan treatment ponds overflow

Leviathan Mine started overflowing on Thursday, according to The Lahontan Regional Water Quality Control Board.

A combination of acid mine drainage and rainwater stored in ponds at the Leviathan Mine Superfund Site in Alpine County is spewing into Leviathan Creek.

The toxic stew is a dilute sulfuric solution with arsenic, copper, nickel, aluminum and iron.

The Regional Water Board advises that people in the area avoid human and animal contact with the waters of Leviathan and Bryant creeks and avoid fish from those waters. This is a temporary precaution until the overflow is fully evaluated.

"As a result of the wettest winter in the last ten years, acid mine drainage from ponds at Leviathan Mine began overflowing and will continue for a few days until an emergency treatment system is able to neutralize the acid mine drainage stored in one of the ponds and the treated water is discharged to Leviathan Creek," said Harold Singer, Executive Officer of the Lahontan Regional Board.

The Lahontan Water Board protects and restores water quality in California east of the Cascade and Sierra Nevada crests from the Oregon border through the Mojave Desert.

The State of California has been able to avoid pond overflows during the last six winter seasons by treating the stored acid mine drainage each summer. The ponds usually have capacity to store acid mine drainage and rainwater during wetter than normal winter until the site becomes accessible and pond water treatment is initiated in the summer. Emergency pond water treatment was planned and financed to begin by mid April this year to avoid pond overflow, as it was anticipated that pond capacity would be reached by late April 2006. However, heavy, late-season precipitation over-filled the ponds earlier than expected.

The emergency treatment operation is being conducted under approval from the U.S. Environmental Protection Agency, which has jurisdiction over operations at this Superfund site. USEPA and Lahontan Regional Water Board staffs have been monitoring stream water quality since the threat of overflow became imminent earlier this month.

The flow in Leviathan Creek is approximately 2000 gallons per minute, which includes approximately 50 gallons per minute of acid mine drainage from two sources that are not contained by the ponds. The pond overflow adds another approximately 50 gallons per minute of acid mine drainage. Leviathan Creek has been sampled prior to the pond overflow beginning and will be sampled regularly during the period of pond overflow and when treated discharges occur.

Leviathan Mine is an abandoned sulfur mine five miles east of Markleeville and six miles west of Topaz Lake, Nev. The State of California acquired the mine in 1984 to clean up water quality problems caused by historic mining. The Water Board completed a pollution abatement project at the mine in 1985, and since 1999 has continued to actively treat acidic waters discharged from the mine site.

Acid mine drainage is low pH (high acid) water containing dissolved toxic metals. Acid mine drainage is collected and stored in five lined evaporation ponds at the site. Treating the acidic water helps prevent the ponds from overflowing into Leviathan Creek, a tributary to the East Fork of the Carson River, by increasing the storage capacity in the ponds. Due to the mine's remote mountain location, normal treatment operations are limited to the summer and fall. The ponds were treated and drained this summer and fall, thereby maximizing the capacity for containing the acid mine drainage and winter/spring precipitation. However, the huge winter and spring snowfall at the site have caused the ponds to completely fill.