Letchworth Avenue Wastewater Treatment Facility - Executive Summary |
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Accidental Release Prevention and Emergency Response Policies The Letchworth Avenue Wastewater Treatment Facility (WWTF) follows guidelines established by the Chlorine Institute, Inc. (CI) and applicable design codes and standards, to ensure adequate accidental release prevention for its chlorine disinfection facilities. The Chlorine Building was designed and constructed in accordance with CI recommendations, as well as local and state building code requirements. Chlorine piping and equipment design also complies with CI criteria, and appropriate ASTM specifications. WWTF staff follow CI procedures for operation and maintenance of the chlorination facility, and receive training in these procedures. In the event of a release from a ton container, the WWTF has a CI "Kit B" which is designed to contain most leaks from such containers. All of these measures have resulted in a successful accidental release prevention program for the WWTF's chlorination facility. The Billerica Local Emergency Planning Committee (LEPC) has included the chlorination facility at the Letchworth Avenue WWTF in its Emergency Response Plan. In case of a chlorine release, the WWTF notifies the Billerica Fire Department, which is approximately one mile away from the facility. When Fire Department personnel reach the WWTF, they make an assessment of the release and decide if it is necessary to ask for a limited or full response from the District 6 Hazardous Materials Team. The District 6 Team supports local fire departments in about 20 area communities in handling hazardous material releases. If District 6 is unable to contain the spill, they may request assistance from the chlorine supplier who has a vacuum truck available for spill cleanup. Stationary Source and Regulated Substances Handled The stationary source is the Letchworth Avenue Wastewater Treatment Facility (WWTF), a municipally owned and operated secondary wastewater treatment plant located in Billerica, MA. The only subs tance at the WWTF which falls under the 40 CFR 68 regulations is chlorine, which is used primarily for wastewater effluent disinfection. The WWTF keeps three ton containers on-line inside the Chlorine Building, and occasionally stores one ton container outside this building. Worst-Case Scenario and Alternative Release Scenario In accordance with EPA's Risk Management Program Guidance for Wastewater Treatment Plants, the worst-case scenario for the WWTF consists of the release of the entire contents of a full, one-ton container of chlorine over a ten-minute period at an outside location. This release, taking into account weather conditions of a wind speed of 1.5 meters/second, "F" stability class and an ambient temperature of 25 degrees C, results in a distance to toxic endpoint of 1.3 miles for an urban setting. No active or passive mitigation systems were considered for this scenario. For the alternative release scenario, several options were investigated. The most conservative alternative, which was reported here, was the release of liquid chlorine from a 0.9-inch diameter hole in a full ton container. The release was assumed to occur as the result of dropping a ton container from the monorail outside the Chlorine Building as the container was being carried into the building. This scenario has never occurred at the WWTF, but represents a remote possibility. Because of the outside location of this alternative, and the speed of release of liquid chlorine (one minute for the entire 2,000 pounds of chlorine), there was no consideration of active or passive mitigation measures. However, the "average" weather conditions for the alternative release scenario provided in the above guidance of 3 meters/second, "D" stability class and an ambient temperature of 25 degrees C resulted in a distance to toxic endpoint of 0.66 miles in an urban setting, or about one-half that of the worst-case scenario. General Accidental Release Prevention Program and Chemical-Specifi c Prevention Steps As described previously, the design, operation and maintenance of the chlorine disinfection facility at the WWTF has been in accordance with CI guidance documents and applicable industry standards and codes. The WWTF has contracts with equipment suppliers to ensure that highly skilled individuals maintain equipment on a regular basis, and that these same individuals instruct WWTF maintenance staff if any equipment modifications or improvements are made. The chlorine supplier also provides refresher training to operators and maintenance staff on a regular schedule. In addition, the WWTF benefits from cross-training, as several employees are knowledgeable about the operation and maintenance of the chlorination process. A sound design basis and scheduled maintenance and operator training have been key to the highly successful operation of the chlorine disinfection facility. Five-Year Accident History There have been no accidental releases of chlorine in the las t five years. Emergency Response Program The WWTF does not have its own written Emergency Response Plan, but is included in the Town of Billerica's Emergency Response Plan. In case of a chlorine release, the WWTF notifies the Billerica Fire Department, who may call upon the District 6 Hazardous Materials Team and possibly the chemical supplier, as described earlier in this summary. Planned Changes to Improve Safety Because of the safety concerns associated with the transportation and handling of elemental chlorine, the WWTF is undertaking a study in the near future to determine the feasibility and costs of replacing the current chlorine disinfection process with a sodium hypochlorite disinfection system. |