Forney Pump Station - 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 Forney Pump Station falls under this regulation because of the on-site storage of chlorine. The amount of chlorine stored is well above the threshold limit specified by the USEPA thereby making the facility subject to co mpliance with the regulation. The Forney Pump Station 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 Forney Pump Station. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The emergency response policies at this facility ensure that there is emergency response coverage 24 hours per day, 7 days per week. There are also a dequate provisions for coordination with outside agencies, such as the City of Dallas HAZMAT team, in the event of an emergency. In the event of a release, plant staff is receiving training to enable an on-site staff response prior to the arrival of the HAZMAT team. REGULATED SUBSTANCE The Forney Pump Station uses chlorine as a disinfectant in the water treatment process. The Forney Pump Station regularly has a storage maximum quantity of 50 tons of chlorine at its facility that is stored in two 25-ton stationary tanks. This is above the threshold limit (2,500 pounds) set by the USEPA. PROCESS DESCRIPTION The Forney Pump Station pumps water from Lake Ray Hubbard into the East Side Water Treatment Plant located at 405 Long Creek Road, in Sunnyvale, Texas. 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 Forney Pump Station consists of (1) two 25-ton tanks, (2) liquid feed piping and miscellaneous valves, (3) two evaporators, (4) gas piping and miscellaneous valves, (5) two chlorinators, and (6) one "once-through" scrubber system. On treatment plant grounds, the two areas in which chlorine has a potential to generate a gaseous release are the chlorine storage area (items 1 and 2 above) and the chlorine process areas (items 3 through 6 above). Chlorine is delivered to the Forney Pump Station by tanker truck. Chlorine is removed as a liquid under pressure of the tank. Chlorine is withdrawn from one tank at a time through a flexible metal connection. As the supply in one tank empties, the supply is manually switched to the full tank. The liquid chlorine flows by pressure to two chlorine evaporators located in the chlorine evaporator room. The chlorine gas generated by the evaporator is then transferred to the chlorinators and is fed to the east and / or west discharge header. 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 an angle valve failure on the tank located on the east side of the storage building. This valve failure could potentially release all 25 tons of the chlorine as a gas. Under Section 68.25(c)(1), the release time for a chemical such as chlorine is 10 minutes. It was assumed that the scrubber system was not functional, but that the release would be mitigated because the tanks are stored inside. The EPA-approved modeling program DEGADIS+ was used to characterize the effects of the worst case scenario at the Forney Pump Station. The distance to the toxic endpoint of 3 ppm was determined to be 3.91 miles. The estimated affect ed residential population is 11,000 people. Residential areas would be affected in the worst-case release scenario. Alternate Scenario One alternate scenario was modeled for the Forney Pump Station and did not have any active or passive mitigation. The release would occur from the tanker truck during delivery of the chlorine. It was assumed that the 1-inch fill line would break either due to equipment malfucntion or the truck drifting. The release would occur for less than 10 minutes. The distance to the USEPA defined toxic endpoint of 3 ppm was determined to be 2.86 miles. The estimated affected residential population is 3,800 people. GENERAL ACCIDENTAL RELEASE PRECAUTION PROGRAM The Forney Pump Station carries out consistent operation and maintenance of its chlorine equipment utilizing only fully trained personnel in this area. Forney Pump Station management enforces consistent operation through discipline for operational deviations. FIVE-YEAR ACCIDENT HISTORY The Forn ey Pump Station's accident history was reviewed for a period from June 1994, through June 1999. During this period of time, one accidental releases of chlorine had occurred. The quantity of the release was minimal (well below the reportable limit) and one plant mechanic was injured. The release did not reach any off-site receptors as the scrubber system had been activated. EMERGENCY RESPONSE PROGRAM As mentioned earlier, this facility has developed an Emergency Response Program in which plant employees are divided into various management and response teams. There are five in-plant contacts for an emergency, the Operations Supervisor, and the Shift Supervisors. There are also back-up personnel in the event that the primary response personnel cannot be contacted. The Emergency Response Plan includes: (1) procedures to follow in the event of a chlorine emergency, (2) information about the frequency of employee emergency response training, and (3) a detailed description of the emergency response training underway. The City of Dallas HAZMAT team has been designated to provide back-up emergency responders and equipment, and will assume Incident Command upon arrival to the plan'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 Forney Pump Station management to determine if implementation is to be accomplished. The most notable planned changes include a recommendation would be to evaluate the need for the chlorine sensors in the rooms to be connected to a back up power source, in case of the loss of electricity. The scrubbing system is currently on a back up generator in case of a power outage. In addition to this, the 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 t his 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. |