USDA scientist predicts potential for young fish kill

June 15, 2007

By Russell Stigall

Frontiersman

MAT-SU - Spring could be a killer if Matanuska Electric Association fires up its proposed coal-fired power plant.

Large percentages of rainbow trout and mayflies could die when winter snows melt and release seven months of acidic coal plant emissions over an estimated three- to five-week period, said Mark Clark, a senior soil scientist for the U.S. Department of Agriculture. Clark bases his worst-case scenario on an evaluation of studies from the Midwest and Eastern United States.

Coal plants emit or discharge a number of acidic compounds and trace heavy metals, sulfur dioxide, nitrous oxide, mercury, selenium, arsenic and other compounds and heavy metals depending on the composition of the coal burnt and at which stage of the mining-transport-storage-combustion process, according to the World Coal Institute.

Circulating fluidized bed coal combustors, which MEA proposes, produce fewer emissions than traditional pulverized coal burners, said Tuckerman Babcock, MEA human resource manager, at a February public meeting. “By burning cooler, the bed prevents the production of much of the potential nitrous oxide in the flue gas. Add lime to the combustion process and up to 90 percent of the sulfur is trapped in solid form to be disposed of with ash and slag. The ash and slag will be shipped back to the Usibelli Coal mine for land reclamation.”

As efficient as a CFB coal plant is touted to be, MEA still expects the plant to produce some emissions. Along with several pounds mercury and 1 million-plus tons of carbon dioxide, at full power MEA's proposed circulating fluidized bed coal combustor is expected to emit 424 tons of sulfur dioxide and 393 tons of nitrous oxide each year, according to MEA's 2007 Integrated Resource Plan. If MEA burns woodchips, paper trash or other biomass, these numbers could change.

Once the coal plant is operational Mat-Su Valley fish and macro-invertebrates could be at risk when hundreds of tons of acidic emissions, deposited over Mat-Su Valley snows by seven months of brisk winter winds, flush into lakes and streams over the spring break up, Clark said. This pH shock, as Clark calls the rapid and acute jump in lake acid levels, may last for two weeks.

MEA spokesperson Lorali Carter said the co-op has not collected data through a site evaluation to comment on Clark's predictions. MEA's board of directors approved the South Palmer Gravel Pit at Mile 37 of the Glenn Highway as the preferred site for MEA's new generation plants, a coal-fired base load plant and a gas-fired peak load plant. MEA plans to do site evaluations for the preferred site and two others.

“Our generation plants will comply with all regulatory standards,” Carter said. “But that is long enough to kill everything,” Clark said.

The effects would be felt most in Valley lakes and streams cut off from deep aquifers by a layer of clay-like glacial silt, Clark said. At risk is the Meadow Lakes system, possibly including Big Lake.

First to die would be rainbow trout and snails. Then mayflies would perish, an important link in lake and stream food chains.

At a pH of about 5 - more acid than base - a fifth to three quarters of Atlantic salmon fry die, according to Canada's Department of Fisheries and Oceans Maritime Regional Habitat Status Report. However, Clark said there has been little study of Ph shock on Alaska's salmon or Dolly Varden populations.

Besides the potential destruction of trout habitat MEA member-owners will foot the bill for the co-op's acid emissions. MEA calculated into the price of its coal plant “the costs associated with emission allowances/offsets,” according to the co-op's Integrated Resource Plan. MEA based these numbers on PacifiCorp's 2004 Integrated Resource Plan.

The co-op expects to pay $997 per ton of sulfur dioxide and $2,393 per ton of nitrogen oxide. Over the 35-year life cycle of the facility these offset costs would total about $47.7 million. That's considerably less expensive when compared to the $1.4 billion MEA could pay to emit the greenhouse gas carbon dioxide, said utility consultant Mark Foster of Mark A. Foster and Associates said.

SO2 and NOx emissions from U.S. coal plants have dropped 10-fold over the last two decades, according the electric cooperative's figures. If this trend continues and MEA adopts new emission mitigation measures, the cost and impact of acid deposition could decrease.

Contact Russell Stigall at 352-2267 or russell.stigall@frontiersman.com.