Water Reclamation Plant - Executive Summary |
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EXECUTIVE SUMMARY UPPER OCCOQUAN SEWAGE AUTHORITY (UOSA) Prevention and Emergency Response The Upper Occoquan Sewage Authority is a modern, state-of-the-art water reclamation facility that has the most stringent discharge limits in the United States. UOSA routinely meets or exceeds these limits. The Authority is dedicated to protecting the environment and the community that it serves. UOSA has an active safety and emergency-planning program. All employees receive training on hazardous chemicals and their related processes. UOSA has a detailed chemical emergency plan to deal with any release or spill. In addition, UOSA takes an active role in regional emergency planning. UOSA's safety officer is an active member of the Fairfax County Joint Emergency Planning Committee. Facility Description UOSA's primary facility is a 32 million gallons per day (mgd) water reclamation plant, located in western Fairfax County, Virginia. It serves the cities of Manassas and Manassas Park and portions of the counties of Fairfax and Prince William. The water reclamation plant is the only UOSA facility with a process covered by the Risk Management Program (RMP). UOSA has one process that falls under the Risk Management Program requirements. This process involves a covered, toxic chemical. There are no processes that involve flammable chemicals. 1. The single UOSA RMP process is dechlorination of the water reclamation plant final effluent prior to discharge. Sulfur dioxide is used to remove any residual chlorine. Sulfur dioxide is delivered, maintained and disseminated from 1-ton cylinders. Twelve (12) cylinders each containing up to 2,000 pounds of sulfur dioxide are maintained on site. Scenarios Extensive containment and remediation features are incorporated in the process area. In assessing worst case and alternative case scenarios, virtually any release in the process storage area would not escape the property and would have little or no impact on the p ublic. Therefore, the worst case and alternative case scenarios for the process involve accidents by transportation companies delivering the product. Both scenarios occur outside the normal product storage and containment area. The toxic endpoints were computed utilizing "RMP*Comp" software. The worst-case scenario for the dechlorination process involves the overturning of a delivery truck carrying ton cylinders of sulfur dioxide. This incident would occur away from the dechlorination building and the building's mitigation features would not be effective. The accident would result in cylinders being ejected from the truck and one is ruptured by impact. This results in the immediate release of the cylinder's contents of 2,000 pounds of sulfur dioxide. The toxic endpoint for this release is 1.3 miles. The alternative scenario for this process involves an accident during the unloading of full cylinders. This event occurs in the loading dock area (partially contained sally port) of the dechlorination building. A cylinder being moved from the truck to the storage room by an overhead crane is dropped and hits the edge of the concrete loading dock. The impact cracks open the cylinder and it releases its entire load of 2,000 pounds of sulfur dioxide. The release is partially contained by the building and the toxic endpoint is only 0.5 miles. Since UOSA has no flammable chemicals covered by the Risk Management Program, there are no scenarios presented involving flammable chemicals. Prevention Program (Level 3) UOSA maintains an aggressive safety and compliance program. The Authority works vigorously to comply with all applicable local, state and federal regulations. UOSA is in compliance with the provisions of the Virginia Occupational Safety & Health Process Safety Management Standard as well as the EPA Risk Management Program. In addition, UOSA engineers all chemical processes to minimize the exposure to hazardous chemicals by both employees and the pub lic. The process covered by the Risk Management Program includes significant containment features for air-borne releases. In addition, UOSA has extensive training and maintenance programs to insure that the process equipment is in excellent working order and that personnel are fully trained to operate the process in a safe manner. Finally, UOSA continues to explore alternative processes that use less hazardous chemicals. For example, UOSA's on-going expansion, scheduled for completion in late 2001, will result in sulfur dioxide being replaced by sodium bisulfite in the dechlorination process. Sodium bisulfite is not included in the Risk Management Program. Accident History UOSA has not had any chemical releases that resulted in an off-site impact to the public within the past five years. |