6th Street Pump Station - Executive Summary |
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Policy Statement It is the policy of The Water Works and Sewer Board of The City of Gadsden (GWWSB) to operate safe water and wastewater treatment plants, reducing to the greatest extent practicable any hazards associated with the necessary treatment processes and reducing any subsequent risk to the surrounding community, personnel, and environment. The policy includes working with the surrounding community and local emergency response agencies to promote a spirit of cooperation and teamwork and to orchestrate an effective contingency plan in the unlikely event of a process incident occurring at the 6th St. Pump Station (PS). It is the GWWSB's policy to adhere to all applicable federal, state, and local laws applicable to the 6th St. PS. Description of Facility and the Regulated Substance Handled The 6th St. PS is a publicly owned and operated wastewater collection and pumping station. Chlorine is used primarily for disinfecting the sewage before pumping it to West River Wastewate r Treatment Plant (WWTP). Another possible use for chlorine is for odor control. The maximum quantity of chlorine stored at the facility is 6,000 pounds (3 one-ton containers). The chlorination system consists of a vacuum regulator, chlorinator, chlorine leak detector, alarm, associated piping, valves, and other miscellaneous equipment. Chlorine Worst-case and Alternative Release Scenarios The EPA-defined worst-case scenario is the failure of one liquid chlorine container, resulting in a release of 2,000 pounds of chlorine in 10 minutes. The chlorine containers are stored in the enclosed Chlorination Building. The actual release rate is 55 percent of the total chlorine released in the enclosed building because of passive mitigation . The release rate of 0.83 kg/s is modeled using DEGADIS 2.1. Under the worst-case weather conditions prescribed by the RMP Rule, the distance to a toxic endpoint of 3 ppm is 1.60 miles, beyond which there will be enough dispersion that the hazard t o the public will no longer exist. The total population affected by this hypothetical worst-case release is estimated to be 9,630 people, based on 1990 Census Data. Realistically, the GWWSB does not anticipate that the worst-case scenario could actually happen. In the event of a total rupture of a 1-ton container of chlorine, most of the chlorine would remain in liquid form until the fire department's Hazardous Material (HAZMAT) team could neutralize the release. The GWWSB has developed an ARS for chlorine at the 6th St. PS that is a more realistic "worst-case" scenario. The ARS is the release of chlorine gas from a <-inch-diameter pipe connecting the chlorine container to the feed manifold. This scenario was selected because it is the most likely failure scenario, based on the experience of the GWWSB personnel who participated in the hazard review. It is estimated that the release would require approximately 30 minutes before a trained mechanic could repair the leak. Taking int o account passive mitigation, the estimated distance to the endpoint for the ARS is 0.20 mile. The total population within the distance to the endpoint for the alternative release is estimated to be 160 people, based on 1990 Census Data. General Accidental Release Prevention Program and Chemical-specific Prevention Steps The GWWSB has complied with the requirements of the RMP Rule, 40 CFR Part 68, for the 6th St. PS. A comprehensive review of all systems, as well as administrative, technical, and operating and maintenance procedures, has been conducted, in addition to the other required program elements of the RMP Rule. A detailed hazard review was conducted for the 6th St. PS using a "What-If" analysis. Five-year Accident History The 6th St. PS has never had a release of chlorine resulting in injuries, deaths, property or environmental damage, evacuations, or shelterings in place. The effectiveness of the facility's design, operating procedures, and training has resulted in an ex cellent safety record. Emergency Response Program The GWWSB has implemented an Emergency Response Program for the 6th St. PS, which coordinates response efforts with the Gadsden/Etowah County Emergency Management Agency (EMA), the Gadsden fire department's HAZMAT team, the police department, and the hospital. Planned Changes to Improve Safety It was observed during the hazard review that the 6th St. PS has the necessary equipment and the operating and training procedures required for the safe operation of the chlorination system. However, the following recommendations for improving the safety of the chlorination process were made: 1. Change the chlorine detector set point to 3 ppm, and inspect detectors quarterly 2. Install windsock to indicate wind direction 3. Provide copy of emergency response plan to the fire department |