Dallas County Park Cities Municipal Utility Dist. - Executive Summary |
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EXECUTIVE SUMMARY DALLAS COUNTY PARK CITIES MUD RISK MANAGEMENT PROGRAM INTRODUCTION This document and the accompanying appendices contain all required information in order to meet 40 CFR 68 "Risk Management Program" (RMP) including an Executive Summary, RMP Data Elements, and Certification Statement (68.155 through 68.185). Supporting documentation can be found in the appendices of this plan. EXECUTIVE SUMMARY 1.0 RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Dallas County Park Cities Municipal Utility District (PCMUD) facility in Dallas, Texas has an excellent record in preventing and minimizing releases of chlorine. This facility has a thorough emergency training program for on-site emergency responders. 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 adequate provisions for coordination with outside agencies, such as with the Dallas County Fire Department, in the ev ent of an emergency. More detailed information can be found on the facility's emergency response program in Appendix D. 2.0 PROCESS DESCRIPTION AND REGULATED SUBSTANCES At this location the PCMUD treats water for the cities of Highland Park and University Park, Texas. The SIC code for the primary process at this facility is 4941. The plant is equipped for raw water intake, treating, storing, and distributing the treated water. PCMUD has one regulated substance under 40 CFR 68, chlorine, at this location. Chlorine is used as a disinfectant in the treating of water. The chlorine threshold for triggering applicability to 40 CFR 68 is 2,500 pounds. The maximum quantity of chlorine stored on-site is 20,000 pounds. Thus, 40 CFR 68 is applicable to the PCMUD water treatment facility. More detailed information on system specifics can be found in Appendix C. 3.0 WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS The chlorine storage and process areas have associated hazards that can p otentially affect on-site employees and the general public off-site if there is a release from the system. Although the alternative release scenario is more probable, the U.S. EPA requires that one worst-case and one alternative release scenario be reported for each regulated chemical. Described below are the associated hazards and the worst-case and alternative release scenarios for chlorine. The dominant characteristic of this chemical is its toxicity. It is a self-alarming chemical by its distinctive pungent and irritating odor. Because of this odor, persons exposed to chlorine vapor will not voluntarily stay in areas of even small concentrations. As a vapor, chlorine is a greenish-yellow gas under atmospheric conditions and becomes an amber liquid under pressure. Chlorine is readily absorbed into the skin and lungs and, in liquid and concentrated gas forms, can cause severe burns. The risks to persons in an accidental release of chlorine include: 1. Irritation of respir atory tract. 2. Corrosive attack of skin and other tissue. 3. Suffocation as a result of fluid in the lungs. 4. Restlessness, anxiety, and nausea. More detailed information on chlorine can be found in Appendix C. Below is a description of the release scenarios for chlorine and their off-site consequences: 7 Worst-Case Scenario. The largest potential release of chlorine will occur with a puncture in a one ton cylinder located on the north side of the plant. Therefore, the total amount of chlorine released would be 2000 pounds. Under Section 68.25(c)(1), a regulated toxic substance such as chlorine, which is normally a gas at ambient temperature and handled as a liquid under pressure, shall be considered to be released as a gas over a 10-minute period. Thus, chlorine's physical state in the worst-case release is a gas. Passive mitigation controls were not applicable to the worst-case release at this plant. EPA-approved look-up tables were used to characterize the effects of the worst case scenario at the PCMUD facility. The distance to the toxic endpoint of 3 ppm was determined to be 1.3 miles. The estimated affected residential population is 2,640 people. Commercial/industrial areas and residential areas would be affected in the worst-case release scenario. 7 Alternative Release Scenario. The worst-case release is less likely to occur than the following alternative scenario. An alternative release scenario chosen, because it was a more likely occurrence, was the U.S. EPA's default scenario. This alternative release scenario is most likely to be caused by a pig tail rupture that would result in a 0.25-inch diameter orifice. The release rate of chlorine due to leakage through this opening is calculated to be 57 lb./min. The EPA look-up tables were also used to characterize the effects of the alternative case scenario at the PCMUD facility in Dallas. The distance to the toxic endpoint of 3 ppm was determined to be 0.2 miles. The estimated affect ed residential population is 8 people. The railroad tracks to the north of the chemical process area would be affected in the alternative case release scenario. Appendix B contains more specific data on the Hazard Assessment. 4.0 GENERAL ACCIDENTAL RELEASE PRECAUTION PROGRAM The PCMUD facility carries out consistent operation and maintenance of its chlorine equipment utilizing only fully trained personnel in this area. PCMUD management enforces consistent operation through use of discipline for operational deviations. 5.0 FIVE-YEAR ACCIDENT HISTORY The review of this facility's accident history includes the following range of dates: June 22, 1994 - June 21, 1999. During this period of time, no accidental releases of chlorine have occurred. 6.0 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 5 in-plant contacts for a type of emergency found in the Emergency Response Plan (Appendix D). There are also back-up personnel in the event that the primary incident response personnel cannot be contacted. The emergency response plan includes information about the frequency of employee emergency response training as well as a detailed description of the training content. There are also specific procedures to follow in the event of a chlorine emergency. At the discretion of the Incident Commander, the Dallas County Fire Department and the LEPC will be called to provide back-up emergency responders and equipment. Additionally, PCMUD management at its discretion will contact a local emergency response firm designated in its Emergency Response Plan in the event of a chlorine emergency, when warranted by management. 7.0 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 PCMUD management to deter mine if implementation is to be accomplished. The most notable planned changes include possible installation of a scrubber system and installation of perimeter chlorine gas detectors. |