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Conditional Use Permit and Solid Waste Facility Narrative Energy Recovery Station The Elk River Energy Recovery Station is located in the northwest corner of the intersection of US Highways 169 and 10. The complete campus consists of office buildings, warehouses, transmission substations, the Elk River Energy Recovery Station (ERS) a waste to energy plant, and the Elk River Peaking Station. Under State law, the peaking station is exempt from local conditional use permits and so it is not covered by the existing conditional use permit. Elk River Energy Recovery Station is an electric power generating station burning RDF as a primary fuel, TDF or tire derived fuel, and wood or wood waste as secondary or alternate fuels. A single alternate fuel may be co-fired with the RDF or a combination of the alternate fuels may be co-fired with the RDF. None of the alternate fuels are fired without concurrently firing RDF. The RDF burned at this facility is currently produced from the Resource Processing Plant. All fuel arrives at ERS in semi trailers and is unloaded in the enclosed RDF receiving building to the east of the plant. The facility produces approximately 40 megawatts of electricity and operates 24 hours per day. The facility is maintained and operated by 41 full-time employees. The Combustors: Energy is produced through combustion of the fuel in three spreader stoker-fired excess air combustion units (combustors or boilers). The boilers are identified as emission Units 1, 2, and 3. Unit 3 is approximately twice the size of units 1 and 2. The units are 128, 128, and 268 mmBtu/hr, respectively, which equates to approximately 11.7, 11.7 and 24.4 tons of RDF per hour (a smaller feed rate-ton/hr is required when TDF is used to supplement the fuel mix). The combustors can also burn natural gas and fuel oil. Natural gas is used at start-up and as necessary to maintain proper combustion conditions; distillate fuel oil is used as a backup fuel to the natural gas. The combustion units were converted from burning coal to RDF in 1988.. Air Emissions Control eauipment: The processing plant has one baghouse to collect any particulate matter created from the two processing lines in the plant. All three of the combustion units (boilers) are connected to common emissions control equipment, which are a dry scrubber for the control of acid gasses and a baghouse for the control of Particulate Matter (PM). The dry scrubber uses lime as a reagent in the chemical removal of the acid gasses. The lime is unloaded pneumatically to the lime storage silo, which is protected by a fabric filter baghouse from emitting PM during the unloading process." Exhaust gasses are continuously monitored for Carbon Monoxide (CO), Sulfur Dioxide (SO2), Nitrogen Oxides (NOX), opacity, and oxygen (02). A number of operating parameters, including scrubber exit (baghouse inlet) temperature, and boiler feedwater flow rate, are also monitored continuously. Air emissions are governed in the state of Minnesota by the Minnesota Pollution Control Agency (MPCA) under the Title V permitting program. ERS's air permit number is 14100003. Other air emission sources on site: Hot water for internal use when boilers 1, 2, and 3 are shut down is occasionally provided by a rented fuel-oil-fired boiler. A natural gas-fired generator currently provides emergency electrical power, for use to recharge an existing battery bank. The System S:\Legal\Environmental\ERS\City of Elk River\Templates\EROUP Renewal Narrative.docx Page 2 of 3