City of Beacon Wastewater Treatment Facility - Executive Summary |
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The City of Beacon Wastewater Treatment Facility processes municipal wastewater and has a design capacity of 6 million gallons per day (MGD). The wastewater treatment process incorporates primary settling, activated sludge, final settling, sludge dewatering and disinfection using chlorine gas. The facility is operated such that it meets the limits established in its State Pollution Discharge Elimination System (S.P.D.E.S.) permit in the most cost effective and safe manner. The City of Beacon Wastewater Treatment facility has developed a combined EPA Risk Management/OSHA Process Safety Management Plan to cover the storage and transfer of chlorine, which is the only toxic or flammable substance listed in 40 CFR Section 68.130 used at the facility. The plant operating staff are committed to the safe handling of chlorine. The current emergency response program directs the facility personnel to contact the local fire department in the event of a chlorine leak. The facility personnel h ave received chlorine safety training from the chlorine supplier. The facility has a chlorine injection system with two injectors. The system is operated under vacuum using gaseous chlorine, and has one-one ton cylinder of chlorine on-line at a time. Another cylinder is designated as a backup, and must be manually connected to the system when the primary cylinder is empty. The facility normally stores a maximum of seven (7) one-ton cylinders at the site at any one time. The on-line cylinder and the designated backup cylinder are stored indoors on scales in a building with doors, which seal. Normally the scale room is sealed with doors that remain closed unless a chlorine cylinder is being replaced. The remaining cylinders are stored outdoors in a roofed area. During chlorine deliveries, the delivery truck backs up to the unloading area and the cylinders are transferred from the truck and moved into the storage area. The chlorinators are in a separate room. The facility ha s chlorine detectors to monitor leakage in the scale room and will have completed installation of monitors in the chlorinator room shortly after submission of this RMP. Chlorine sensors are located at six inches above floor level. The detector will alarm audibly and visually at the main control room panel and automatically start the ventilation fans and activate the emergency shutoff system for the cylinder valves. The worst-case scenario involves the unmitigated release to the atmosphere of the contents of a 2,000 pound chlorine cylinder over a period of ten (10) minutes. The cylinder discharges a dense gas release under worst case meteorological conditions of F Stability and 1.5 meters per second. The release rate and the Worst-Case Impact Area are determined using Exhibit 4-3 in the EPA's Risk Management Plan Guidance for Wastewater Treatment Plants (EPA 550-B-98-010 October 1998) and RMP*Comp. The distance to the toxic endpoint is 3.0 miles based on rural topography. Alth ough the facility is located in a valley, the rural topography assumption is appropriate for this analysis because there is the possibility of the release migrating over the surface of the river, which is best approximated as rural terrain. Such a release will impact approximately 33,000 people living within the 3 mile radius, and many other public and environmental receptors, including schools, hospitals, a prison, recreation areas, cemeteries, and a state park. The most likely release case (Alternative Case Scenario) is that one of the valves on a chlorine cylinder in the outdoor storage area may leak. Under this scenario, a steady-state leak of up to 5 pounds per minute of chlorine either as a gaseous or a two-phase release is addressed. The duration of the release is estimated to be one hour. It should be noted that the release estimate is conservative because as the release occurs the liquid in the cylinder cools causing the release rate to decrease. Eventually the cylind er will freeze up and the discharge will be stopped. It is also assumed that the cylinder discharges a dense gas release under meteorological conditions of D Stability and 3.0 meters per second at an ambient temperature of 25:C. The Alternative Case Impact Area is determined using Exhibit 4-12 in the EPA's Risk Management Plan Guidance for Wastewater Treatment Plants (EPA 550-B-98-010 October 1998) and RMP*Comp. The distance to the toxic endpoint is 0.1 miles based on rural topography. As discussed above, the rural topography assumption is appropriate for this analysis. The release is estimated to impact approximately six (6) people living within the impact radius of 0.1 mile. There are no schools, hospitals, parks, or prisons within this area. The impact radius does include a small portion of the Hudson River and the Conrail tracks. The facility has not had an accidental release of chlorine from this covered process in the five years prior to the submission of this Risk Man agement Plan (RMP). |