MHOC Booster 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 MHOC Booster Pump Station falls under this regulation because of the onsite storage of chlorine. The amount of chlorine stored is well above the threshold limit specified by the USEPA, thereby making the facility subjec t to compliance with the regulation. The management of the MHOC Booster Pump Station has complied with the USEPA Risk Management Program rule and has 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 MHOC Booster Pump Station. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The MHOC Booster Pump Station in Laredo, Texas has an excellent record in preventing and minimizing releases of chlorine. This MHOC is an unmanned facility operated by the staff of the Jefferson Street Water Treatment Plant, which is staffed 24 hours a day, 7 days a week. The staff will be implementing a program for onsite emergency responders. The emergency response policies at this facility ensure that adequate provisions have been implemented to coordinate activities with outside agencies, such as the Laredo Fire Department HAZMAT team, in the event of an emergency. In the event of a release, an alarm will alert the Jefferson Street Water Treatment Plant staff, who in turn will contact the Laredo Fire Department. The staff will receive training to enable an onsite staff response prior to the arrival of the Laredo Fire Department HAZMAT team. REGULATED SUBSTANCE The MHOC Booster Pump Station adds chlorine to the water to maintain a chlorine residual in the water distribution system. The MHOC Booster Pump Station regularly has a minimum of two (2) 1-ton chlorine containers located onsite. This amount trans lates into a quantity that exceeds the threshold limit of 2,500 pounds set by the USEPA. PROCESS DESCRIPTION The MHOC Booster Pump Station is located in Laredo, Texas. Chlorine is added to the water and subsequently pumped to the distribution network of pipelines, pump stations, and storage tanks. The existing chlorine facilities at the MHOC Booster Pump Station consist of a storage area and process area. One-ton chlorine containers are housed at the storage area. The process area is comprised of chlorine feed equipment, including chlorinators and rotameters as well as piping, miscellaneous valves, and vacuum regulators. The potential to generate a gaseous release of chlorine exists at the storage area as well as at the process area. WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS The chlorine storage and process areas have associated hazards that can potentially affect onsite employees and the off-site population and environment. The U.S. EPA requires that one worst-case scenari o and one alternate release scenario be reported for each regulated chemical. Worst-Case Scenario The largest potential release of chlorine would occur with the rupture of a one-ton chlorine container, releasing all 2,000 pounds of chlorine as a gas. Under Section 68.25(c)(1), the release time for a chemical such as chlorine is 10 minutes. Passive mitigation controls 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 of a chlorine release at the MHOC Booster Pump Station. The distance to the toxic endpoint of 3 ppm was determined to be 1.2 miles. The estimated affected residential population is 8,200 people. Mostly residential areas would be affected in the worst-case release scenario. Alternate Scenario One alternate scenario was modeled for the MHOC Booster Pump Station. The release was established as a leak from the packing gland on the cylinder valve. Given that a chlorine alarm is present but that the site is unmanned, a release time of 30 minutes was used. The distance to the USEPA defined toxic endpoint of 3 ppm was determined to be 0.61 miles. The estimated affected residential population is 620 people. GENERAL ACCIDENTAL RELEASE PRECAUTION PROGRAM The MHOC Booster Pump Station carries out consistent operation and maintenance of its chlorine equipment utilizing only fully trained personnel. The management enforces consistent operation through discipline for operational deviations. FIVE-YEAR ACCIDENT HISTORY The accident history for the MHOC Booster Pump Station 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 in which the Jefferson Street WTP employees will be trained in the initial response to a release. The Jefferson Street WTP is s taffed 24 hours per day and 7 days per week. The Laredo Fire Department will be contacted when the Jefferson Street WTP employees detect the leak. 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 to be implemented. The Laredo Fire Department has been designated to provide back-up emergency responders and equipment, and will assume the role of Incident Onsite Command upon arrival at the plant. 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 MHOC Booster Pump Station. The most notable planned changes include the following: 7 Ensure that the delivery driver follows a set procedure in the delivery of chlorine. The staff will develop a procedure for the chlorine truck dr iver or vendor to follow 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 Consider installing SCBAs closer to the chlorine areas. 7 Consider the need for an automatic kill switch. This switch would be useful in the case of an emergency when the chlorine supply has to be shut off immediately. A remote switch would eliminate the danger of plant personnel having to shutdown the chlorine system. Emergency shutdown procedures should be developed and implemented in the training sessions. 7 Consider installing chlorine gas detection equipment in both the process and storage areas. An audible and visual alarm should send a signal to a manned facility. 7 When the plant facilities are expanded or upgraded in the future, consideration should be given to the capability to chemically neutralize any accidental releases of chlorine. |