Everett Water Filtration Plant - Executive Summary |
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Source Everett Water Filtration Plant (EWFP) produces drinking water for distribution and consumption by the City of Everett and surrounding areas. The Water Filtration Plant is located at 6133 Lake Chaplin Road in Sultan, Washington, at the south end of Lake Chaplin. Drinking water is produced by introducing chlorine (Cl2) to raw water for disinfection purposes. Cl2 is the only toxic chemical regulated by the Risk Management Program (RMP) that is present at the EWFP. The chlorine system is closely monitored and controlled to prevent accidental releases to the environment. It is EWFP's policy to manage the chlorine process "using the highest standards for the protection of our people, the community, and the environment in order to ensure a safe and productive facility". Regulated Chemicals EWFP uses chlorine as a disinfectant to convert raw water to drinking water. Cl2, a gas at ambient temperatures and pressure, is delivered to EWFP in 1-ton containers and unloaded into a st orage area. The Cl2 ton containers are moved from the storage area into an enclosed room, as needed for use in the process. In the unlikely event of an accidental release, Cl2 would either be released directly into the air as a gas or evaporate into the air from liquid pools formed in low spots on the ground. The primary health affect of Cl2 gas is respiratory irritation. In sufficient concentrations, Cl2 irritates mucous membranes, the respiratory tract and the eyes. Following a release, Cl2 gas will migrate downwind and disperse to below health effect concentrations. Accidental Release Prevention and Emergency Response The toxicity of Cl2 at high concentrations makes it necessary for EWFP to observe certain safety precautions to prevent unnecessary human exposure, and reduce the threat to the personal health of employees as well as nearby members of the community. It is EWFP's policy to adhere to all applicable federal and state rules and regulations. Safety depends upon t he manner in which we handle toxic chemicals including equipment design and safe handling procedures used to operate the equipment. EWFP's release prevention program is based on four principles; inherently safe design, effective written procedures, training, and the goal of continuous improvement. The chlorine storage and handling equipment meets or exceeds design codes and standards as well as incorporating good engineering practices recommended by industry groups, such as The Chlorine Institute. As a result, EWFP's equipment incorporates inherently safe designs. Written operating procedures are prepared and reviewed annually for accuracy and safety. Operating and maintenance personnel are thoroughly trained on proper procedures and safety hazards, and are provided with regular refresher training. Equipment and procedures are frequently evaluated and updated with the goal of continuous improvement in both operation and safety. EWFP's emergency response program integrates OSHA's and EPA's preparedness planning response and training requirements. In the event of an accidental release, the emergency response plan includes notifying 911 dispatch, who will notify local responders. Plant personnel receive classroom training on implementation of the response plan in addition to participating in training exercises. Worst-case and Alternative Release Scenarios The worst-case release scenario at EWFP involves the catastrophic failure and release of the entire contents of a 1-ton liquid Cl2 ton container. Using EPA's dispersion modeling program, RMP*Comp, the maximum distance downwind from the storage tank to an endpoint concentration of 3 ppm Cl2 is 1.3 miles. This worst-case impact distance is calculated using EPA mandated assumptions which are conservative. For example, EPA requires the assumption that all of the liquid Cl2 is released as a gas within 10 minutes. Actually, only about a third of the liquid Cl2 will flash off as gas while the remaining tw o thirds either remains in the tank or spills on the ground and evaporates over a much longer time period. The worst-case analysis also requires the unrealistic assumption that the wind blows constantly at a high speed in the same direction for several hours in order for the Cl2 to migrate a long distance downwind. EWFP believes that these calculated worst-case distances overstate the distances that harmful impacts could occur. The alternative release scenarios are considered by EPA to be more representative of actual impacts attributable to an accidental release. An alternative release scenario was also developed for Cl2. The alternative release scenario was developed during detailed Process Hazard Analyses involving operating, maintenance, and engineering personnel, and outside experts. The alternative release scenario is intended to represent the largest release, that could reasonably be expected to occur. For Cl2, the alternative release is based on a liquid Cl2 ton containe r being dropped during unloading, resulting in a < inch puncture through which the entire contents of the ton container is released. Using EPA's RMP*Comp model, it is calculated that this release could exceed 3 ppm Cl2 up to 0.2 miles downwind. Five Year Accident History During the five year period between May 1994 and June 1999, the EWFP has not had a reportable release of Cl2. |