Hog Bayou Energy Center - Executive Summary |
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Calpine Corporation has constructed a power generating facility in Mobile, Alabama. This facility, the Hog Bayou Energy Center (HBEC), is scheduled to begin operation in the first half of 2001. The HBEC will operate an aqueous ammonia storage system consisting of a 20,000-gallon storage tank and associated piping. The facility will use aqueous ammonia in a selective catalytic reduction (SCR) air pollution control system to reduce emisisons of nitrogen oxides from the operation of a combined-cycle combustion turbine genrator and heat recovery steam generator with supplemental duct burners. Ammonia will be stored at the facility as 28 percent aqueous solution in a single storage tank located at the HBEC site. Because the ammonia concentration is above the threshold concentration of 20 percent aqueous ammonia prescribed by the Risk Management Program (RMP), the HBEC is subject to the RMP regulations promulgated by the Environmental Protection Agency (EPA) and codified in the Code of Federal Regulations (CFR) as 40 CFR Part 68. As part of complying with the RMP provisions, the HBEC was required to complete a hazard assessment pertaining to accidental relases of ammonia. This involved the evaluation of a worst-case release scenario and an alternative release scenario in order to estimate offsite impacts resulting from accidental releases of aqueous ammonia from the facility. For the HBEC, the worst-case release scenario is based on a catastrophic event in which the maximum quantity of aqueous ammonia solution present in the storage tank is released. The alternative scenario evaluated for the HBEC was indentified based on discussions with facility representatives from Calpine and reflects a release during the filling of the ammonia tank from an aqueous delivery truck. The scenario assumes a release from the delivery truck's transfer hose at the HBEC's ammonia tank filling station. Since the HBEC is scheduled to commence operations in the first half of 2001, the ammonia storage system has not yet been in operation, and thus the facility has not had an accidental release of ammonia that caused injuries, property damage, or environmental damage in the past five years. Passive mitigation has been established by the HBEC to minimize the potential of accidental ammonia releases and to minimize offsite impacts in the event of an accidental release. The mitigation includes a containment dike which encloses the aqueous ammonia storage tank. |