C. R. (Tommy) Feaster Water Treatment Plant - Executive Summary |
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INTRODUCTION The Accidental Release Prevention Risk Management Program rule (40 CFR Part 68) is similar to the Occupational Safety and Health Administration's Process Safety Management Program, which is designed to protect workers from accidental releases of hazardous substances. The Risk Management Program rule addresses over 100 chemical substances>77 of which are acutely toxic and 63 of which are flammable gases>and the accidental release of these substances. The United States Environmental Protection Agency (USEPA) estimates that over 100,000 sources are covered by the rule, including chemical manufacturers and wholesalers, certain retailers, potable water treatment systems, wastewater treatment plants, ammonia refrigeration systems, and federal facilities. The Tommy Feaster Water Treatment Plant (WTP) falls under this regulation because of the on-site storage of chlorine. The amount of chlorine stored is above the threshold limit specified by the USEPA thereby making the facilit y subject to compliance with the regulation. The Tommy Feaster WTP personnel have complied with the USEPA Risk Management Program rule and have completed an Accidental Release Prevention Program (ARPP) Plan that contains the following required information: 7 Management System 7 A hazard assessment that establishes the worst-case and alternate release scenarios and their impact on the population and the environment (40 CFR Part 68 Subpart B). 7 A prevention program that includes safety information, a hazard review, operating procedures, training, maintenance, compliance audits, and incident investigations. (40 CFR Part 68 Subpart C) 7 An emergency response plan (40 CFR Part 68 Subpart E) The following subsections discuss details of the plan that has been implemented at the Tommy Feaster WTP. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Tommy Feaster WTP facility in Lewisville, Texas has an excellent record in preventing and minimizing releases of chlorine. The emergency res ponse policies at this facility ensure that there is emergency response coverage 24 hours per day, 7 days per week. There are also adequate provisions for coordination with outside agencies, such as the Lewisville Fire Department in the event of an emergency. In the event of a release, plant staff will contact the Lewisville Fire Department, relaying information regarding the release prior to implementing plant evacuation to a location outside the plant gates, awaiting the arrival of the fire department to inform its personnel of all information about the release and to provide assurance that the plant has been totally evacuated. REGULATED SUBSTANCE The Tommy Feaster WTP uses chlorine as a disinfectant in the wastewater treatment process. The Tommy Feaster WTP regularly has a storage maximum quantity of 16 one-ton containers of chlorine at its facility that is stored outside. This is above the threshold limit (2,500 pounds) set by the USEPA. PROCESS DESCRIPTION The Tommy Fea ster WTP is located at 1400 N. Cowan, Lewisville Texas and draws its raw water supply from Lake Lewisville. Water is treated at the plant and subsequently pumped to the distribution network of pipelines, pump stations, and storage tanks. The existing chlorine feed facility at the Tommy Feaster WTP consists of (1) 6 one-ton chlorine containers, (2) two vacuum regulators mounted to an automatic switchover module with gas piping and miscellaneous valves and drip lines, (3) three flow proportionate feed chlorinators, and (4) gas piping and ejectors. On treatment plant grounds, the only area in which chlorine has a potential to generate a gaseous release is the chlorine storage area (items 1 and 2 above). Chlorine is delivered to the Tommy Feaster WTP by truck and chlorine containers are stored in the storage room located to the east of the chlorinator room, on the south side of the main building. Chlorine is removed as a gas under pressure of the liquid in the individual containers; however the majority of the chlorine feed is operated through a water injection induced vacuum, making the system extremely safe and minimizing potential pressurized leaks along the feed lines. In addition, the storage room is equipped with a scrubber, in order to neutralize possible leaks from the system. WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS The chlorine storage and process areas have associated hazards that can potentially affect on-site employees and the off-site population and environment. The U.S. EPA requires that one worst-case scenario and one alternate release scenario is reported for each regulated chemical. Worst-Case Scenario The largest potential release of chlorine would occur through a valve failure on one of the one ton cylinders located at the plant. This valve failure could potentially release all 2,000 pounds of the chlorine as a gas. Under Section 68.25(c)(1), the release time for a chemical such as chlorine is 10 minutes. Passive mitigation con trols were not applicable to the worst-case release at this plant. The EPA-approved modeling program DEGADIS+ was used to characterize the effects of the worst case scenario at the Tommy Feaster WTP facility. The distance to the toxic endpoint of 3 ppm was determined to be 1.40 miles. The estimated affected residential population is 5,623 people. Commercial/industrial areas and residential areas would be affected in the worst-case release scenario. Alternate Scenario One alternate scenario was modeled for the Tommy Feaster WTP. The release was established as a leak that would potentially develop in the packing at the chlorine container valve. A release of chlorine through the 1/4-inch diameter hole in the valve packing would occur for about 10 minutes, and is presumed to be observed or detected. The release rate of chlorine caused by leakage through this opening is calculated to be 63.4 lb/min. DEGADIS+ was also used to characterize the effects of the alternative case scenar io at the Tommy Feaster WTP. The distance to the USEPA defined toxic endpoint of 3 ppm was determined to be 1.25 miles. The estimated affected residential population is 4,158 people. GENERAL ACCIDENTAL RELEASE PRECAUTION PROGRAM The Tommy Feaster WTP carries out consistent operation and maintenance of its chlorine equipment utilizing only fully trained personnel in this area. Tommy Feaster WTP management enforces consistent operation through discipline for operational deviations. FIVE-YEAR ACCIDENT HISTORY The Tommy Feaster WTP's accident history was reviewed for a period from June, 1994, through June, 1999. During this period of time, no accidental releases of chlorine had occurred. EMERGENCY RESPONSE PROGRAM As mentioned earlier, this facility has developed an Emergency Response Program involving immediate plant evacuation once the City's Fire Department is called to implement response and repair to leaking chlorine gas. The plant is staffed 24 hours per day and 7 days p er week. Plant operators are required to make rounds for inspection and monitoring of the plant processes at least every three hours. Accordingly, plant staff will detect any releases of chlorine and the Fire Department is trained to respond to this situation. The Emergency Response Plan includes: (1) procedures to follow in the event of a chlorine emergency, (2) information about the plant evacuation plan, and (3) a detailed description of the emergency responder's plan for handling such an emergency. The Lewisville Fire Department has been designated to provide emergency responders and equipment, and will assume Incident Command upon arrival to the plant's emergency call. PLANNED CHANGES TO IMPROVE SAFETY Based on the hazard review and prevention evaluation completed for chlorine, a list of action items was developed and is being considered by Tommy Feaster WTP management to determine if implementation is to be accomplished. The most notable planned changes include the follo wing: 7 Ensure that the delivery driver follows a set procedure in the delivery of chlorine. MW will coordinate with the staff to develop a procedure for how the chlorine truck driver or vendor should perform while on plant grounds. It is anticipated that the vendor can then be subjected to this procedure at the time of the plant's next bid for chemical purchase. However, the existing vendor will likely accept these requirements voluntarily to ensure customer satisfaction. 7 Provide a sprinkler system in the storage area for fire protection. |