Jefferson Street 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 Jefferson Street Water Treatment Plant (WTP) falls under this regulation because of the on-site storage of ammonia. The amount of ammonia stored is well above the threshold limit specified by the USEPA, thereby making t he facility subject to compliance with the regulation. The Jefferson Street 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 Jefferson Street WTP. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Jefferson Street WTP facility in Laredo, Texas has an excellent record in preventing and minimizing releases of ammonia. This facility will be implementing a program for on-site emergency responders. The emergency response policies at this facility ensure that there will be emergency response coverage 24 hours per day, 7 days per week. 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, plant staff will contact the Laredo Fire Department. The staff will receive training to enable an on-site staff response prior to the arrival of the Laredo Fire Department HAZMAT team. REGULATED SUBSTANCE The Jefferson Street WTP uses ammonia in the water treatment process to minimize the formation of disinfection by-products. The Jefferson Street WTP regularly has a 10,000-gallon bulk storage tank for ammonia onsite. However, this vessel is only filled to 85% capacity based on administrative controls; only 8,500 gallons of ammonia are stored onsite. This amount translates into a quantity that exceeds the threshold limit of 10,000 pounds set by the USEPA. PROCESS DESCRIPTION The Jefferson Street WTP is located on the banks of the Rio Grande River, which serves as the source for raw water. Water is treated at the plant and subsequently pumped to the distribution network of pipelines, pump stations, and storage tanks. The existing ammonia feed facility at the Jefferson Street WTP consists of a 10,000-gallon bulk storage tank as well as piping and miscellaneous valves to deliver ammonia to three feed points: the Lower Plant Raw Water Mixing Basin, the Upper Plant Flocculation Effluent, and the Distribution System. On treatment plant grounds, the potential to generate a gaseous release of ammonia exists at the ammonia storage area as well as the three ammonia process areas. WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS The ammonia 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 be reported for each regulated chemical. Worst-Case Scenario The largest potential release of ammonia would occur through a valve failure on the 10,000-gallon tank located onsite. This valve failure could potentially release all 8,500 gallons of ammonia as a gas. Under Section 68.25(c)(1), the release time for a chemical such as ammonia is 10 minutes. Passive mitigation controls were not applicable to the worst-case release at this plant. The EPA-approved modeling program ALOHA was used to characterize the effects of the worst-case scenario of an ammonia release at the Jefferson Street WTP. The distance to the toxic endpoint of 200 ppm was determined to be 2.8 miles. The estimated affected residential population is 85,000 people. Both commercial/industrial areas and residential areas would be affected in the worst-case release scenario. Alternate Scenario One alternate scenario w as modeled for the Jefferson Street WTP. The release was established as a line break in the piping from the ammonia tank. Given that maintenance rounds are conducted every two hours, a release of ammonia from a >-inch diameter pipe could last for about 60 minutes, and is presumed to be detected because of the pungent odor. ALOHA was also used to characterize the effects of the alternative case scenario at the Jefferson Street WTP. The distance to the USEPA defined toxic endpoint of 200 ppm was determined to be 0.05 miles. The estimated affected residential population is 22 people. GENERAL ACCIDENTAL RELEASE PRECAUTION PROGRAM The Jefferson Street WTP carries out consistent operation and maintenance of its ammonia 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 Jefferson Street WTP was reviewed for a period from June 1994 through Ju ne 1999. During this period of time, no accidental releases of ammonia had occurred. EMERGENCY RESPONSE PROGRAM As mentioned earlier, this facility has developed an Emergency Response Program in which plant employees will be trained in the initial response to a release. The plant is staffed 24 hours per day and 7 days per week. Plant operators are required to make rounds for inspection and monitoring of the plant processes at least every two hours. Once a leak is detected, the Laredo Fire Department will be contacted. The Emergency Response Plan includes: (1) procedures to follow in the event of a ammonia 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 IMPRO VE SAFETY Based on the hazard review and prevention evaluation completed for ammonia, a list of action items was developed and is being considered by Jefferson Street WTP. The most notable planned changes include the following: 7 Ensure that the delivery driver follows a set procedure in the delivery of ammonia. The staff will develop a procedure for the ammonia truck driver 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 the need for an automatic kill switch on the tank. This would be useful in the case of an emergency when the tanks have to be shut off immediately. A remote switch would eliminate the danger of plant personnel having to shut the ammonia tanks off manually. Emergency shutdown procedures should be developed and imp lemented in the training sessions. 7 Consider installing ammonia gas detection equipment near the storage and process areas. 7 When the plant facilities are expanded or upgraded in the future, consider the design and construction of a containment building to encompass the ammonia storage tank. Additional consideration should be given to the capability to chemically neutralize any accidental releases of ammonia. This option should be compared with the conversion to a nongaseous ammonia compound. |