A massive construction project is underway at Coronado Generating Station to meet the terms of a 2008 settlement with the EPA.
     The Salt River Project is spending approximately $550 million to fit the facility's power generating units with two new scrubbers and new burners.
     The burners are designed to lower the output of nitric-oxide and the new scrubbers will reduce the facilities output of sulfur-dioxide. The company has also agreed to install a selective catalytic reduction system (SRCS) to further lower its nitric oxide emmissions.
     Sulfur dioxide emmissions have been implicated in the production of acid rain. Nitric oxide presents various health risks in addition to a visible haze. The planned SRCS will act similarly to the catalytic converter on an automobile - both are designed to reduce nitric oxide. The SRCS, however, will use ammonia to do its chemical work. (Don't confuse nitric oxide with the gas that helps make dental work tolerable - nitrous oxide.)
     With the current retrofit, Coronado should be able to continue generating electricity for SRP's Valley customers for another 20 years.
     Construction on the two-unit power plant was started on July 25, 1974. The first unit was completed Dec. 31, 1979 and the second unit was completed Oct. 1, 1980. The two units are capable of generating 773 megawatts of electricity - enough power for 200,000 homes. The plant sends its electrical output on lines to the Valley through Globe. Household voltage is 110, SRP sends its power at 500,000 volts. The higher voltage is more efficient for long distance transmission, explained Tim Hunt, who's worked at Coronado for 33 years.
     SRP expects to have 250 construction workers on site this summer. That number is expected to rise to 500 at the peak of construction next spring.
     The work so far is "on schedule and on budget," said project manager William McClary.
     SRP is working under tight deadlines.
     The two new burners must be installed by June 2011, One of the units is already online with the new nitric-oxide lowering burners. The deadline for the first of two new scrubbers to be up and running is Jan. 1, 2012.
     These scrubbers - now being called absorbers - are not little brushes. To scrub the output of coal burners 97 percent clean of sulfur-dioxide requires new 400-foot tall stacks and a massive building filled with equipment, and pumps and fans the size of a ranch style house.
     The retrofit is an international effort. For example, the two giant fans - heavy duty variable pitch axial flow fans - for the first scrubber are manufactured in Indonesia by Howden of Denmark.
     The project is huge and it's made even more complex by having to keep the facility producing power while construction goes on. SRP's 200 workers have to keep the flames burning while 500 or so construction workers stay on their deadlines.
     Every week, four coal trains rumble down the 43 mile rail spur to the plant. Each of these trains is dragging 102 cars, each loaded with 100 tons. Every week 40,800 tons of coal from the Powder River Basin of Wyoming is delivered. Three different types of coal are used, mixed to provide the optimum blend.
     The company is adding to its already active water recycling programs with the new scrubbers but water usage is still in the millions of gallons per year. The facility now has 17, 20-inch wells.
     With the implementation of the selective catalytic reduction system the company will be introducing ammonia to the electrical generation process. The ammonia is a boon for the environment but workers will have to wear more protective clothing. The company will also be using limestone, mined locally, in the scrubber process. The result will be almost no sulfur-dioxide emissions, replaced by an output of much more inert gypsum, the primary component in drywall.