St. Charles County Water Plant - Executive Summary |
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St. Charles County Water Plant Risk Management Plan Executive Summary The goal of the Risk Management Program (RMP) is to reduce and prevent the risk of exposure of employees, the public, and the environment to the accidental release of chemicals used in the treatment of the potable water supply. The County of St. Charles, Missouri and its employees is committed to achieving this goal through the implementation of the Risk Management Program. The benefits of this program are intended to provide a safer workplace for employees and safer environment for the community. Due to the fact that this facility is owned and operated by a local government, is not subject Occupational Safety and Health Administration (OSHA) process safety standards, and exceeds the Environmental Protection Agency's threshold of 2,500 pounds, a Program 2 level RMP has been developed to meet regulatory requirements. Procedures for implementing and maintaining the RMP Program are contained within this document. The Water Department Plant Manager along with the assistance of the County Engineer and Assistant County Engineer have the primary responsibility for the development, implementation, and integration of the RMP program. The Supervisor of Operations will have primary responsibility in the absence of the Plant Manager. This facility supplies potable water to two primary customers; the Missouri Cities Water Company and the St. Charles County public Water Supply District #2. The facility consists of well field of eight wells, a single-stage water softening treatment plant and approximately 8.0 million gallons of finished water storage. The plant has a water supply capacity of approximately 22.4 million gallons per day. The subject of the "St. Charles County Water Plant Risk Management Plan" involves the use and storage of hazardous chemicals involved in the water treatment and disinfection process. Currently, chlorine is the only chemical being stored and used in excess of the thresho ld quantity for chlorine in accordance with Section 112(r) of the Clean Air Act. Chlorine is a toxic gas which is stored as a liquid under pressure. The maximum intended inventory at any given time that the plant could store is approximately 16,000 pounds. Chlorine is irritating and corrosive to the eyes, skin, and respiratory tract and reacts violently with easily oxidized materials. Contact with evaporating chlorine or equipment releasing flashing chlorine can cause severe frostbite burns. Chlorine gas is heavier than air and will tend to travel along the ground topography filling spaces, pits, and displacing breathable air. Chlorine is also highly toxic to aquatic life. The chlorine storage area for this facility is located in separate storage building adjacent to areas of normal personnel operations. Chlorine gas is injected into water at the pre-filtration, hydrotreater, and post-filtration stages in the process to chemically disinfect along with other water treatment chemi cals prior to distribution into the public water supply system. The chlorine is delivered to the process from 2,000-pound steel cylinders via a regulated vacuum system which allows operators of the system to control the flow and rate of chlorine into the water treatment system. In accordance with CFR Part 68, Off-site Consequence Analysis (OCA) has been performed determine and document the facilities RMP program eligibility and to meet the EPA hazard assessment requirements for the applicable program. This off-site consequence analysis defines the toxic end point in all directions for worst-case and alternative release scenarios based on the applicable EPA guidance documents, modeling software, current available U.S. Census Bureau data, and available mapping tools. The quantity of the hazardous substance, release rate, release duration, wind class and speed, topography, and physical properties of the chemical are used to determine the distance to the toxic end point for the chemic al and the public/environmental receptors which may be affected. The following information summarizes the facilities worst case scenario: Scenario: "A 1-ton (2,000 lb.) container of chlorine is being unloaded with the unloading truck's boom lift when the cable connection fails. The container drops to the ground outside of the storage building and a catastrophic failure occurs upon impact release the entire contents of the container begin spilling onto the ground. As the emergency response program in initiated, a chlorine gas cloud begins to form and drift off-site with the prevailing wind direction." The EPA's RMP* Comp (Version 1.02) was utilized to model the worst case scenario utilizing the program's data elements to determine the distance to toxic end point. No passive mitigation factors were considered for the worst-case scenario analysis. Administrative controls, operating procedures, and design for the process limit the number of cylinders that can be connected to the pro cess at any given time. Thus, the worst-case scenario considers the maximum contents of one full container. Population estimates within the distance to the toxic end point (3.0 miles) were obtained by using the RTK NET Landview III program. An alternative release scenario was also developed to model a more realistic release than the worst-case scenario such as releases from joints, flanges, elbows, weld points, valves, and other vessel appurtenances. The following information summarizes and documents an "alternative release scenario" for the facility: Scenario: "A tubing or valve and yoke assembly connection fails releasing liquid chlorine into the chlorine storage room floor from a horizontal 2,000 pound cylindrical tank. The entire contents of the tank leak onto the floor of the storage room forming a pool and begin to vaporize. The release is a two-phase release occurring from a 5/16-inch diameter valve body opening." The EPA's "Off-site Consequence Analysis Guidance" docum ent was utilized to determine the alternative release scenario using the following standard assumptions: The ambient relative humidity is 50%. The ambient temperature of the surrounding air and the temperature of the chemical before the release is 77o F (25o C). The facility is located in a rural or urban area. The wind speed is 3.0 meters per second at 10.0 meters above the ground. The atmospheric stability is Class D (moderate wind speed and overcast skies). The release occurs at different elevations relative to the ground. The model determines if the extent of the liquid evaporation at the source for liquified gases. Passive building mitigation factor of 55%. The distance to the toxic endpoint (1.0 miles) for the alternative case release scenario was estimated using The EPA's Risk Management Guidance for Wastewater Treatment Plants (October 27, 1998) utilizing the program's data elements, applicable look-up tables, equations, and formulas. At atmospheric p ressure and ambient temperatures, chlorine displays a greenish-yellow color. In a gaseous state, it is approximately 2.5 times heavier than air and will tend to sink and conform to the contour of the ground in low lying areas. As the gas spreads, it will become diluted with air depending on weather conditions, wind speed, humidity, etc. As the gas becomes more diluted it will become neutrally buoyant and begin to travel with the main air streams. This effect is particularly important to the St. Charles County Water Plant because it is situated in a low lying area relative to the terrain immediately surrounding the area. It should be noted that the modeling programs and equations used to perform the worst-case and alternative release scenarios do not account for the extreme topography associated with the location of the facility. Even if there is a cross-wind, the chlorine gas may tend to follow a depression due to its density. The heavier-than-air gas behavior can also be used a s an advantage if ravines and downhill slopes lead to natural reservoirs such as a small creek or a lake. It is important to recognize that these behaviors may be a much more accurate tool for predicting the events and consequences of a release than the modeling programs. Chlorine for the facility is transported and stored in a liquid state under pressure. When a leak occurs in a container or piping system, the quick reduction in pressure that occurs will cause the liquid chlorine to vaporize when it is released into the atmosphere. The remainder of the liquid will pool and vaporize as it is warmed by environmental conditions. When chlorine changes state from a liquid or a vapor, it will expand to approximately 450 times the liquid volume. Therefore, a release of chlorine liquid poses a significantly greater risk than a chlorine gas leak from a similarly sized vessel, pipe, or leak point. It is the intention of the St. Charles County Water Plant to minimize or eliminate the risk of an accidental release of a hazardous substance by utilizing the RMP program as a managerial tool to maintain and improve its internal operations, maintenance, and training programs which already currently exist. The St. Charles County Plant has developed an emergency response program as part of the RMP Program. The purpose of this to ensure that the St. Charles County Water Plant maintains current and complete written emergency action plans (EAP's) and effective response capabilities for all RMP covered processes. The EAP combined with effective emergency response drills and training, will hopefully minimize the impact of an accidental release by ensuring that the facility has a quick, well-organized response. Currently the scope of the plan only includes releases of liquid chlorine, chlorine gas, and chlorinated water which may occur which may occur within the facilities boundaries. It has been the determined by the St. Charles County Water Plant that any major releases whic h impact off-site receptors or cannot be handled the facility response team will be coordinated by the St. Charles County Hazardous Material Response Plan - Annex N (Revision, November 1,1996) which is carried out by the St. Charles County Local Emergency Planning Commission. Other outside agencies and response teams will be called for assistance as deemed necessary. The St. Charles County Hazardous Materials Response Plan has been therefore incorporated into the St. Charles County Water Plant RMP by reference and recognized as part of the emergency action plan (EAP) for this facility. In addition, the St. Charles County Standard Operating Procedure for E.O.C. Assistance (March, 1990) is also incorporated into the RMP Plan by reference for weather and other natural disasters which could potentially cause a release of a regulated substance. The Plant Manager and the County Engineer will ensure that the emergency response team is adequately staffed and that the required equipment is supplied and maintained. The Plant Manager will coordinate with the local emergency planning committee (LEPC), local fire department, and hazardous materials teams. It is the intention of the St. Charles County Water Plant to conduct regular emergency response drills with local emergency responders in an effort to coordinate effective safe responses in the event of an actual release. Emergency evacuation procedures, guidelines, and assembly areas have been established. For minor releases, the initial assembly area will be the Control Room. For a major release and evacuation, the initial assembly point shall be at the front gate entrance to the facility. Emergency phone lists for all plant personnel are also maintained and posted at the facility. The RMP Program contains procedures for maintaining and performing the five-year accident history as required by the EPA. Currently, there are no accidental releases which have occurred within the past five years which resulted in any on-site or offsite deaths, injuries, property damage, or environmental damage, etc. from this facility. The St. Charles County Water Plant has scheduled RMP program training to be completed prior to the submittal of this document to the Environmental Protection Agency. Joint emergency response drills will be performed as soon as feasible. As a result of the process hazard analysis performed for this program, additional safety and control equipment changes, as well as procedural changes, are being reviewed and studied for implementation at the facility. These may include: 1. The purchase of additional personnel safety equipment for entry into confined space areas. 2. Additional labeling of process equipment and piping. 3. Implementation of outsider safety orientation programs. 4. Addition of engineered barriers and dikes to prevent possible release hazardous materials from exiting the building and entering storm water inlets. 5. Purchase windsock for emergency response wind direc tion monitoring. 6. Installation of automatic shut off valves and additional control/release monitoring systems. With these and other future improvements scheduled for implementation and consideration, the integrated effect of the RMP Program will have a proactive effect in reducing the risk of a release along with increasing the safety of the public and the environment. |