A cleaner Pena Blanca Lake is slowly refilling

Satisfied Coronado National Forest Service officials on Friday declared a rather dry Pena Blanca Lake bed cleaned up of toxins and ready for a refill.

The popular recreation and fishing hole was pumped out and dredged of sediment between October 2008 and July 2009. The 57-acre lake is a national Superfund or CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) site.

The “lake” is currently three ponds fed by seeps and runoff from a sparse summer monsoon season. Officials estimate it will take one to eight years for the water to fill up although Coronado engineer Eli Curriel added that “one great hurricane moving slowly could do a lot of the job in a very short time.”

The area will be reopened within the next few weeks and a public comment period will begin in October, said Nogales District Ranger Kent Ellett. The comment period is intended to scope out how to utilize 13-15 acres of new earth that is contoured above the lake. This land covers approximately 220,000 cubic yards of sediment containing methyl mercury, lead and arsenic. About 350 million to 360 million gallons of water were pumped from the lake.

The pollutants were principally from early 20th century mine tailings and possibly lead balls that were found in two drainages upstream of the lake, principally from Pena Blanca Canyon.

The contaminated sediment was deposited on the acreage in areas excavated out above the lake in addition to an old septic tank area for the old motel that had operated by the lake through the 1980s. Approximately 3 feet of soil was placed above the sediment with a red netting about 18 inches below the top to indicate erosion. Small net wrapped “waddles”�”acting as barricades to break the flow of rain water traveling down the hill to the lake�”snake across the hillsides.

A trench about 5 feet wide snakes around the acreage to catch some runoff and deposit it in the lake on the east side of the site before it can erode the soil.

Casey Fish, manager for Forest Service contractor Red J, said that the levels of contaminated sediment in the lake was less than expected, “The deepest portion was perhaps 15 feet deep.”

Earlier estimates had run as high as 60 feet of sediment in the deepest sections of the lake.

Junk and boats

Local lore had speculation running high that that remains of victims of smugglers or drug-related killing would be found, however, “all we really found was a lot of junk and about six boats,” said Fish.

Fish added that he had found bass in cages that trapped fish and other wildlife being pumped out of the lake, “at least 10 pounds.” Lab analyses of fish in 2005 found about six times the standards set for methyl mercury by the EPA and Arizona Department of Environmental Quality.

Fish said crews found “very few bullfrogs, which was a concern of the Forest Service since as an invasive species they have been wiping out (native) Chiricahua leopard frogs.”

Fungus expands

Ranger Ellett added that native amphibians of all types have continued to decline in number not just in southern Arizona but globally partially attributed to climate change but definitely to a possibly related phenomenon which is the rapid expansion of poisonous Kittred fungus.

“Within Arizona a series of schools, zoos, and research organizations have built ranariums to breed Chiricahua leopard frogs and they are being introduced to cattle ponds and waterways throughout the state,” said Ellett.

The Red J crew and local residents volunteered to build a series of netted traps that have been deposited around the lake bed to act as habitat improvement to allow fish to hide from predators as the water rises and grow to be large enough to survive or be caught by fishing enthusiasts.

Curiel said that the process of remediation had been incremental over 10 years, “Tailings were removed from Pena Blanca Canyon during 1999-2000 and sediment ponds were built in the two drainages of concern, about 6-feet deep, during the current cleanup of the lake. They overflowed for the first time after last Thursday’s rain and we’re going to go check them out. Sediment is cleaned out of these ponds and samples are being sent to a lab for analysis to see whether they contain mercury and other metals,” Curiel said.

Remediation

Arizona Parks Research and Science Manager Robert Casavant was closely observing the Pena Blanca remediation to see how well it could apply to cleaning up Patagonia Lake where drainages from mine contaminants in the Patagonia Mountains have entered sediments at the bottom of the lake. “At Patagonia, the water quality is still good and USGS (U.S. Geological Service) is doing comprehensive monitoring of the sediments,” Casavant said. “We want to see the parks department become as proactive as possible in determining how to cleanup mine contaminants from lakes and this is a great lab for us.”

USGS monitoring data was not readily available by press deadline, nor was ADEQ’s data on sediment removed from the lake.

Casavant noted that there are no monitoring wells to measure whether any contamination has entered groundwater; a departure from most cleanups, and he commented to Curiel that the process of cleaning the lake might not be permanent due to possible continuing upstream sources of contamination.

Curiel said that he felt that the Forest Service could keep those sources down and the lake clean. He said that they would visually monitor erosion of the soil covering sediments on a regular basis. Such erosion, which is difficult to predict until observing weather impacts on a remediated site, would probably be the greatest concern to maintaining a cleaned up lake. Curiel knew of no other similar projects at contaminated lakes.

Curiel added that under an agreement with EPA, “The Forest Service is the agency that will now declare this Superfund site cleaned up.”

Few tracks could be seen in the mostly dry lake bed beyond human ones coming from the south.

(Editor’s Note, Kamp of Santa Fe, is an environmental liaison for Wick Communications.)