Deer Creek Intake Structure - Executive Summary |
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Executive Summary Introduction and Background The USEPA's Clean Air Act Amendments of 1990 included provisions that require facilities that use certain substances to develop a plan to reduce the likelihood of an accidental release of the substances to the atmosphere and reduce the likelihood of serious harm to the public and the environment. The plan must also include mitigation measures to reduce the potential impact on the public in the unlikely event of a release. The requirements of this plan, commonly referred to as a Risk Management Plan (RMP), are detailed and codified in 40 CFR Part 68. The Metropolitan Water District of Salt Lake City (the District) Little Cottonwood Water Treatment Plant (LCWTP) and the Deer Creek Intake Structure (DCIS) stores chlorine in quantities above the regulatory thresholds at which a RMP/PSM is required. Chlorine is used at the LCWTP to disinfect the drinking water prior to public consumption and periodically at the DCIS to control biofouling of t he pipe. The RMP/PSM consists of three compliance programs, each with progressively stricter compliance standards. Since the District is a political subdivision of the State of Utah, State and federal OSHA regulations do not expressly apply. However, the District is required by the Utah Labor Code to operate and maintain an occupational safety and health program equivalent to the program for other employers in the state. The District generally does this by looking to OSHA regulations for guidance, subject to the District's ability to independently make decisions which best meet its safety needs. Consistent with this approach the District has chosen to use the OSHA Process Safety Management (PSM) Standards as a guide. For this reason, and the fact that a worst-case release of chlorine could affect the public, the chlorination process at LCWTP and DCIS will be treated as subject to Program 3, the most stringent of the three programs. The RMP/PSM consists of three major parts. The f irst part is the Hazard Assessment, which evaluates the potential effects that a release of a regulated substance could have on the public. The second part is a Prevention Program that consists of 12 elements designed to improve the system safety and decrease the likelihood of a release. The third part is the Emergency Response Program, which develops a plan for dealing with a release in the unlikely event that one would occur. Because the RMP and PSM regulations are very similar, the Prevention Program and the Emergency Response Program for the EPA RMP also serve as a substantively equivalent OSHA PSM plan. Hazard Assessment A hazard assessment was performed to evaluate the effects that a release would have on the public. The hazard assessment includes examining the water treatment plant's 5-year accident history and hypothetical worst-case and alternative release scenario. An examination of the LCWTP and the DCIS's accident history reveals that no accidents have occurred with respe ct to the chlorine process in the last 5 years. For the worst-case and alternative release scenarios, the distance from the point of release to the "toxic endpoint," or the location at which individuals could be exposed for up to 1 hour without experiencing serious health effects, was approximated. An estimate of the population potentially affected by a release of chlorine was also determined, along with sensitive receptors such as hospitals and schools. Worst-Case Scenario The hazard assessment requires that the "toxic endpoint", or distance from the point of release to a location at which the chlorine concentration equals 3 ppm, must be determined. The regulations require the development of a worst-case release scenario based on conservative assumptions. For a 1-ton chlorine container, which is the largest size LCWTP and DCIS handles, it is required to assume that 2,000 pounds of chlorine will be released over 10 minutes. It should be noted that this is unlikely to occur since th e properties of chlorine would cause a freeze-and-thaw cycle to occur at the leak, which would slow the release. In addition, the worst-case scenario requires that conservative atmospheric conditions be assumed that result in a large area of impact. To model this scenario for both facilities, the EPA's computer program RMP*Comp was used. This program approximates the impact radius at which the chlorine concentration is equal to or exceeds the "toxic endpoint". LCWTP The radius is a distance of 1.3 miles from the chlorine storage area at the LCWTP. It should be noted that for the LCWTP, the urban setting was used which assumes that numerous obstacles, including buildings and trees will hinder the dispersion of chlorine. DCIS The radius is a distance of 3.0 miles from the chlorine storage area at the DCIS. It should be noted that for the DCIS, the rural setting was used which assumes that the terrain is open, flat and unobstructed. This assumption was used to present a more cons ervative scenario due to the confined nature of the river valley. Because the cloud from a chlorine leak would disperse relatively quickly, an individual at a "toxic endpoint" would be exposed to the exposure limit concentration for much less than the 1 hour assumed by the limit. In addition, the exposure limit concentrations result in relatively minor health effects. Therefore, an individual at the toxic endpoint would be affected less than the results of the worst-case scenario may imply. Alternative Release Scenario The RMP rule also requires that at least one alternative release scenario be evaluated for chlorine. The alternative release scenario reflects a type of release that is more likely to occur compared to the worst-case scenario. The alternative release scenario selected by the District staff was a release of chlorine through a leaking fusible plug on the chlorine cylinder. Using RMP*Comp for this scenario at both facilities, the radius of impact is approximately 0.2 mil es for LCWTP and 0.4 miles for DCIS. This alternative release scenario is considered to be more representative of the effects likely in the event of a release. Prevention Program The Prevention Program, together with the Emergency Response Program, make up the RMP/PSM. The Prevention Program consists of 12 elements designed to improve the system safety and decrease the likelihood of a release. Employee Participation The participation of the District staff in preparing the RMP/PSM program was critical to the program's successful implementation. Employee participation is valuable because it increases the safety awareness of the staff and it allows the staff's experience in operating and maintaining the processes to be incorporated into the plan. District staff participated in the development of the Prevention Program by participating in the Process Hazard Analysis that is described below. The operations and maintenance staff also participated in the development of the RMP by reviewi ng and commenting on operating and maintenance procedures and safe work practices; these personnel will continue to review and update these practices and procedures on a regular basis. All District staff received RMP/PSM awareness training that instructed staff on how the RMP/PSM requirements may impact their jobs. Staff who operate and maintain the RMP/PSM processes were trained in how to safely maintain and operate the processes. Process Safety Information The RMP regulations require that information concerning process chemicals, technology, and equipment be compiled as part of a RMP program. Emergency response planners can use such information to develop training programs and procedures, or as a general resource. The information will be supplied to contractors who will work in the chlorine areas as part of the requirements outlined in the Contractors element. |