Intermountain Generating Station - Executive Summary |
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Site Description Intermountain Generating Station is a coal-fired steam electric generating plant on about 4600 acres, and provides electricity. The site is in a rural setting. Topography of the areas off-site is generally flat and unobstructed terrain. The nearest residence or business activity is over four miles away to the South or West from the facility process unit. The nearest town is twelve miles away. The nearest water body is eight miles away. Predominate winds are from the Southwest. Process Unit Description As part of the thermal cycle, steam is recondensed by a re-circulating cooling water system. To prevent biofouling of the cooling system, gaseous chlorine is used. Chlorine is purchased in compressed liquid form and delivered and stored in one ton cylinders. At any given time, up to ten full cylinders may be in storage or use. Chlorine is delivered via vacuum extraction into a slip stream and injected into the cooling system. This process is 3/4 mile from prop erty boundaries. Accidental Release Prevention Shipments of chlorine come in only under approved purchase orders. Unloading of cylinders and process operation are performed by trained personnel familiar with the unit process and hazmat safety. Cylinders are staged horizontally on trunnions mounted on a cement floor inside a storage area. The storage area is enclosed in a chlorination room with an open east bay for loading and unloading, and open north windows. An overhead crane is used to lift and move the cylinder. Empty cylinders are moved to opposite trunnions for pickup. To prevent large releases due to system failure, only two cylinders at a time are connected to the system for use. Chlorine detection alarms are present to warn of leaks. The system and building were constructed to meet superior seismic standards. Interlocks serve to shut down the chlorination system in the event of pressure loss in the manifold that connects the cylinders in use. Chlorination must be man ually initiated. Chlorination occurs over a timed interval, and is not continuous. Components of this chlorination system meet Chlorine Institute standards. The system is covered by OSHA's Chemical Process Safety rules, and required elements of those rules are in place and implemented. These include operating and maintenance procedures. Warning annunciation occurs locally at the system and remotely in a main control room. Emergency Response Policies and Programs The facility has written environmental and safety policies requiring all employees to be familiar with rules and regulations to the extent of their work. Plant management places strong emphasis on safety and environmental policies and expects and enforces full compliance. Employees are trained in hazard chemical communication, handling, and safety. Employees also receive annual training in emergency procedures that include hazmat incidents. The facility also has an onsite hazmat team for immediate response to chemica l releases. The team members are comprised of operations personnel familiar with the systems and chemicals used on-site. A hazmat response team is present 24 hours a day, every day of the year. Policies dictate immediate response to chemical releases. All emergency communication is directed to a central control center, and response operations are coordinated by an incident commander. There is a plant-wide paging system, along with emergency radio service. Off-site resources such as a local hazmat or fire department has not been and is not expected to be called upon. The facility owns and maintains a fully stocked hazmat trailer, first aid station, ambulance, and fire emergency equipment. Three chlorine cylinder hazmat kits are available for chlorine emergencies. Other than required reporting to local, state, and federal agencies, and possible medical emergencies served by a local hospital, response actions are completely managed with on-site resources with little outside involvem ent. An emergency contingency plan is in place that describes responsibilities and actions. Evacuation procedures for employees and visitors are part of that plan. Coordination of highway control due to any off-site impact is made with the local sheriff's office, which serves as the LEPC. The site is manned and operated 24 hours per day, every day of the year. Worst-Case Release Scenario In a worst case incident, all the contents of a full one-ton cylinder would be immediately emptied to the storage area floor. Pooled liquid chlorine would then evaporate over a 10 minute period at about 200 pounds per minute. A toxic endpoint of 0.0087 mg/L would be reached at 3.0 miles from the release. These results were determined by EPA's RMP*Comp software. Assumptions include a wind speed of 3.4 mph, Stability Class F, and an ambient temperature of 77 degrees F. Mitigation measures involve an enclosure open to outside air. Position of enclosure prevents direct release of a chlorine cloud towards residences or receptors without circumnavigating a pump building or cooling towers. Offsite Consequences and Emergency Coordination Topography of the areas off-site is generally flat and unobstructed terrain. Because of the remote location of this facility, residences, farms, businesses, and other receptors are well beyond the limits of where a toxic endpoint is reached. Our offsite consequence analysis indicates none of these public receptors would be affected. There is a highway that passing along the South side of the site. In a worst case emergency, the onsite emergency coordinator will make contact with local enforcement to assist with traffic control. Onsite Visitor and Employee Protection The plant site is a gated facility with guarded entrances and roving guards. Well inside the facility is a parking lot available for employees and visitors. A separate portion of the facility includes a recreation center available for use by employees and the local community. It is fenced and gated, with full time personnel present during open hours. Access is restricted to approved visitors. Those using the facility must check in with an attendant upon entering and sign out when leaving to account for everyone on the premises. The center is closed, gated and locked during off hours. Roving guards check the center regularly. In the event of an emergency, the staff at the center will be notified by the main control room or incident commander as to evacuation or safety requirements. Coordination for the safety of visitors and employees is paramount. Contact with the local sheriff's office will be made in the event of an impact from chlorine on the highway passing by the plant. Officers will control traffic that may be affected. Personnel and visitors affected by a chlorine release will be taken to the local hospital. Accident History This system has never suffered an upset or failure that resulted in a reportable release. No evacuations or off -site impacts have occurred in the history of operation. |