Humboldt Bay Muni Water Dist--Essex Control Center - Executive Summary |
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ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES AT THE ESSEX FACILITY The Humboldt Bay Municipal Water District (HBMWD) has the utmost commitment to the safety of its employees and the surrounding public. Toward that end, preventing accidental releases of chlorine gas to the atmosphere is essential. The HBMWD's policies and practices have emphasized safety for many years, long before the OSHA Process Safety Management standard or the EPA RMP rule existed. Plant operators are highly trained to operate and maintain the chlorination system safely, and the training is ongoing. In its nearly 40-year history of using chlorine gas for water disinfection since 1960, the facility has never had a release of chlorine that endangered the public or the environment. The HBMWD will do everything in its power to perpetuate its excellent safety record. Facility personnel conduct joint safety training exercises with the Arcata Fire Department. In the case of a release or threatened release of chlorine, the Arcata Fire Department will be called immediately to respond. The facility is staffed 24 hours a day. FACILITY DESCRIPTION AND REGULATED SUBSTANCES HANDLED The HBMWD is the regional water purveyor in the Humboldt Bay area. The Essex Control Center is the main pumping and chlorination station. One-ton containers are used to supply the chorine for disinfecting the water prior to its distribution to wholesale and retail customers. Five containers are kept in the chlorination building at the facility. The chlorine is compressed gas, liquefied by pressure. Chorine gas is piped from the on line container to the piping and vacuum regulation system to be metered into the water to achieve the proper dose for disinfection. WORST-CASE RELEASE SCENARIO The worst-case release scenario was analyzed using the EPA OCA Guidance. The facility uses chlorine in 2000-pound containers. The worst-case scenario is the failure of one container and the release and vaporization of its 2000 po unds of chlorine over a ten-minute period, as specified in the rule. The chlorine is housed in an enclosed building, so it was assumed that this building provided passive mitigation having the effect of reducing the release rate of chlorine by a factor of 0.55, as provided in the OCA Guidance. According to EPA's RMP*Comp (ver 1.06) for rural topography, the distance to the endpoint is 2.2 miles. The USGS Arcata North quadrangle map and the 1990 Census data were used along with personal judgement to estimate population and environmental receptors. The 2.2-mile-radius endpoint circle includes sparsely and densely populated areas, and the Census Tract boundaries and zip code boundaries do not allow for an accurate estimation of population within the circle. By visual inspection of the circle overlain on the quad map, it was judged that the circle included 5 to 10 percent of the population within the 95521 zip code (32,507 persons, including McKinleyville, which was still within 95521). T hus, it was estimated that the residential population within 2.2 miles of the release is approximately 2,400 persons. Other public receptors include a school, a hospital, recreation areas, and commercial and industrial areas. An environmental receptor (Azalea State Reserve) also lies within this radius. ALTERNATIVE RELEASE SCENARIO As for the worst-case scenario, the accidental release scenario was analyzed using the EPA OCA Guidance , RMP*Comp program, and passive mitigation of an enclosed building. The release is from a broken tube (pigtail) that connects the chlorine container to the rest of the chlorination piping. The pigtails are considered to be the weakest link in the system. The opening is approximately 0.25 inch in diameter, and the pressure and temperature in the container were assumed to be 90 psig and 25 C (77 F), respectively. The release rate from the enclosed building would be 5 lb/min. It was assumed that the release would occur for 60 minutes before being stopped by emergency response personnel. Using RMP*Comp, the distance to the endpoint is 0.1 mile. By visual observation in the area, it was estimated that there are one to three homes within a radius of 0.1 mile of the release. Based on the average occupancy rate of 2.5 persons per household in the Arcata Census District, the residential population is estimated to be up to approximately 8 persons. There is also the HBMWD recreational area within 0.1 mile, but no other receptors. GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL-SPECIFIC PREVENTION STEPS The accidental release prevention program is described in a document titled Process Safety Management of Chlorine at Essex Control Center. The prevention program complies with the OSHA PSM standard and the EPA RMP rule, as well as the California Accidental Release Prevention Program. Numerous prevention measures are applied to all aspects of the chlorination system. Some important examples of prevention measures include the following. 1 . Training of personnel emphasizes maintaining and operating the chlorination system in a safe manner. 2. The facility is always staffed, and the night operators inspect the chlorination system every two hours. 3. There is a chlorine leak detector and audible alarm. As a backup to on site personnel, the alarm is telemetered to the HBMWD security contractor, who will investigate unanswered alarms. 4. Established procedures are followed for the safe handling of containers while being delivered, maneuvered, and stored. 5. Only one chlorine container is on line, and one is on ready reserve to allow for the automatic switchover of the containers when the on line container is empty. The valves of the other containers are closed. 6. Pigtails are installed with the proper amount of slack and are replaced annually. 7. Each time a pigtail is connected to a container, a new lead washer is used and the valve and the connection are immediately tested for leaks. FIVE-YEAR ACCIDENT HISTORY There hav e been no releases of chlorine that have caused deaths, injuries, property or environmental damage, evacuations, or sheltering in place. EMERGENCY RESPONSE PROGRAM In the event of a release or threatened release of chlorine, facility personnel will call the Arcata Fire Department to respond to the emergency. The Arcata Fire Department conducts training and inspections at the facility. PLANNED CHANGES TO IMPROVE SAFETY No changes are being implemented as part of the risk management program. However, improving safety is an ongoing process, and changes are made from time to time. MANAGEMENT SYSTEM The HBMWD is committed to keeping its facilities safe for its employees and the potentially affected public and environment. The General Manager has the overall responsibility for the development, implementation, and integration of the risk management program elements. Under the direction of the General Manager, the Superintendent plays a key role in accomplishing these objectives. In particu lar, the Superintendent has the responsibility for implementing the risk management program at the Essex facility on a day-to-day basis. The Superintendent involves the facility supervisors and other staff to assist with the program and in accomplishing the safe operation of the facility. |