HENRY TATE WATER TREATMENT PLANT - Executive Summary |
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This document comprises the Risk Management Plan (RMP) for the City of Redlands (City) Water Treatment Plant located at 3050 Mill Creek Road in Redlands, California 92374 (also referred to within the City as the Henry Tate Water Treatment Plant). The City also operates one other stationary source subject to the federal RMP regulations. A separate RMP has been submitted for that Plant. The purpose of this document is to comply with the risk management planning requirements as set forth in Section 25535(d) of Article 2 of Chapter 6.95 of the California Health and Safety Code (also known as the California Accidental Release Prevention Program - CalARP) and Part 68 of Title 40 of the Code of Federal Regulations (40CFR Part 68), also known as the federal Accidental Release Prevention Requirements: Risk Management Programs or the federal RMP. The scope of the RMP includes all operations conducted at the Plant which involve the storage, handling and/or use of chlorine. ES 1.0 DESCRIPTION O F STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED The Henry Tate Water Treatment Plant is a conventional water treatment plant utilizing two reactor-type clarifiers (that provide flocculation and sedimentation) and four dual media gravity filters. The Plant's raw water source is Mill Creek. Water from the after bay of the Edison Mill Creek #1 Powerhouse travels via pipeline to the Cooley Hat where it is delivered to the influent of the Henry Tate Water Treatment Plant. The untreated or raw water entering the plant contains sand, suspended particles, and microorganisms, collectively referred to as turbidity, that must be removed before the water enters the distribution system. The basic treatment processes include a sand chamber, flocculation basins, sedimentation basins, and filters. Polymers and other chemicals are added at various points to condition and treat the water. Chlorine is added for water disinfection. Chlorine is a regulated substance subject to the federal RMP require ments. STORAGE, HANDLING AND USE OF CHLORINE The chlorine system is composed of four principal components: The chlorine container and feed system (i.e., gas transfer piping), which supplies the chlorine gas; The chlorinators and injectors, which meter the chlorine gas and mix it with feed water; The chlorine solution transfer piping, which conveys the chlorine solution to the end use points and diffuses it into the plant flow; and The chlorine residual analyzer, which measures and records residual chlorine concentrations. Chlorine Containers and Feed System The chlorine container and feed system is located in the chlorine storage room. Liquid chlorine is received in one ton containers via truck and stored in the chlorine storage room on trunnions. The trunnions are fabricated from steel and have cadmium plated steel rollers. A maximum of six full one ton containers (i.e., a maximum inventory of 12,000 pounds) may be present inside the chlorine storage room at any time. The two chlorine scales are sized to hold one standard one ton containers each (each chlorine container has a total weight of approximately 3700 pounds of which 2000 pounds is chlorine. Each of the scales has a heavy duty bushed bearing trunnion to permit cylinder rotation. The container weight is displayed on a wall mounted 18-inch diameter dial. The containers are shuttled on and off of the scale and delivery truck by a hoist. From the containers, flexible connections lead to the chlorine header. From the chlorine header, a one-inch chlorine gas line leads to the chlorinators. Automatic switchover valves are provided on the discharge piping of the chlorine ton containers. This allows an automatic switchover between the "lead" container and the ''standby' container when the lead container supplies insufficient chlorine gas pressure. For each container, one line is provided leading to a downstream chlorinator. Chlorinators and Injectors Two floor standing chlorinators are located i n the chlorinator room. The principal units included in each chlorinator are as follows: an indicating rotameter, a V-notch variable cross-section orifice for metering, a manual feed rate adjuster for the orifice, a vacuum differential regulating valve, and an automatic feed controller for the orifice. A vacuum is formed within each of the chlorinators by utility water passing through the injector. When the water moves through the injector a suction is created that opens the differential regulating valve and the vacuum relief valve. The entire unit is full of air at this point as the chlorine supply line has not yet been opened. When the chlorine feed line is opened, the vacuum relief valve closes replacing the air in the chlorinator with chlorine gas. Each of the two injectors consists of a venturi-type nozzle with vacuum gauge and a ball valve. Chlorine gas is drawn from the chlorinator through a one-inch PVC pipe into the venturi, where it mixes with utility water. The water is su pplied via a two-inch utility water line that is equipped with a plug valve and a ball check valve. The resulting chlorine solution is conveyed through separate lines to the chlorine solution distributor. Chlorine Solution Piping Upon leaving the injectors, the two chlorine solution lines lead to two rotameters. The two rotameters allow the chlorine solution to be directed to the two main feed points (the flash mix basin and the clearwell). Chlorine Residual Analyzer The two chlorine residual analyzers continually measure and record the residual chlorine content in the plant effluent (one measures the residual chlorine content of the clarified well and the other measures the residua chlorine content in the clearwell). If a level of chlorine is detected below the desired level, a low chlorine residual alarm signal is sent to the main control panel. ES 2.0 ACCIDENTAL RELEASE SCENARIOS - The RMP regulations require that at least two types of release scenarios be evaluated for their potential to impact off-site populations: the worst case release; and an alternative release (that is more credible). A number of hypothetical accidental release scenarios were postulated and evaluated for the RMP. These scenarios were categorized into worst-case release scenarios and alternative release scenarios. Each of these categories of hypothetical accidental release scenarios is discussed below. CHLORINE Worst-Case Release Scenario In this scenario, one of the one-ton containers of chlorine on site experiences a catastrophic failure due to an unknown external event. This scenario could be initiated by an external event (i.e., an airplane, missile or meteorite impacting the chlorine building where the ton containers are located). It is highly improbable that this scenario would be initiated by a seismic event. However, the possibility of this scenario being initiated by a seismic event can not be completely discarded. This scenario is considered to be extremely unlikely . In the highly unlikely case that this scenario occurs, approximately 2,000-pounds of chlorine would be released. The release of chlorine could occur outdoors or indoors. Since the release can occur outdoors (i.e., outside of the chlorine storage building) the enclosure provided by the chlorine building was not taken into account in evaluating the off-site consequences. Rather, it was assumed that the chlorine released during the catastrophic accident was released outdoors forming a cloud of chlorine vapor. The resulting vapor cloud was assumed to freely migrate off-site. Utilizing the methodology specified by USEPA, the estimated vulnerable zone for this accidental release scenario is approximately 1.3-miles. Figure ES-1 presents a graphical representation of the vulnerable zones for the worst-case release scenario for accidental releases involving chlorine. Table ES-I provides a listing of sensitive receptors located within the vulnerable zone. As shown, the only sensitive receptor s located within the vulnerable zone are recreation areas. Alternative Release Scenarios Alternative release scenarios which are considered to be more likely to occur are those which may result in the release of anywhere from less than one-pound to up to 10-pounds of chlorine. These scenarios include situations such as delivery of a leaking one-ton container of chlorine to the Plant, a pinhole leak in the chlorine transfer piping and a partial or complete failure of the chlorine transfer lines (either 100-percent vapor or chlorine dilution water) at various points in the system (either in-doors or out-doors). In order to be conservative in the estimation of the vulnerable zone, it was assumed that 10-pounds of chlorine was released during an accident involving the complete failure of a vapor transfer line from a one ton container. In such a situation, the loss of vacuum from the system would result in the automatic isolation of the one ton container at the container valve. However, i n order to be conservative, it was assumed that the material was released directly outdoors (although the full length of the vapor transfer lines is located indoors. Thus, the system enclosure provided by the chlorine building was not taken into account in evaluating the off-site consequences. Utilizing this assumption is much more conservative in nature and resulted in the estimation of the largest vulnerable zone for these types of accident scenarios. The resulting cloud of chlorine vapor was assumed to freely migrate off-site. Utilizing the methodology specified by USEPA, the estimated vulnerable zone for these types of scenarios is approximately 0.1 miles. Figure ES-2 presents a graphical representation of the vulnerable zones for the alternative-case release scenario for accidental releases involving chlorine. Table ES-1 provides a listing of sensitive receptors located within the vulnerable zone. As shown, the only sensitive receptors located within the vulnerable zone are recre ation areas. ES 3.0 FIVE YEAR ACCIDENT HISTORY During the five years preceding the submittal of this RMP, the Treatment Plant has NOT had any releases of chlorine which have resulted in: Onsite deaths, injuries, or significant property damage, or Known offsite deaths, injuries, property damage, environmental damage, evacuations, or sheltering in place. ES 4.0 ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL SPECIFIC PREVENTION STEPS The Accidental Release Prevention Program at the Treatment Plant consists of a series of programs, procedures and policies designed to minimize the risk of accidental releases involving chlorine. These programs include design and operating controls such as compliance with specified codes, the health and safety program, numerous standard operating procedures, the equipment inspection and maintenance program (including a mechanical integrity and preventive maintenance program), the management of change program, pre-start-up review, fire protection and hot work permit program, management of- and safety of- contractors, accident/incident investigation procedures, emergency response plan, RMP compliance auditing program, record keeping and a variety of training programs. Details of each of these components of the Plant's Accidental Release Prevention Program are provided in the document entitled Risk Management Plan (RMP), Volume I - Prevention Program. There are several detection and monitoring devices and alarms placed at strategic locations throughout the Plant. Table ES-2 provides a summary listing of these devices as well as their sensitivities. In addition, there are portable fire extinguishers located throughout the Plant. ES 5.0 EMERGENCY RESPONSE The City recognizes that emergency planning and emergency response are an integral component of risk management. As such, the City currently has an emergency response plan and an emergency evacuation plan in place at the Treatment Plant as part of its hazardous materials busin ess plan (HMBP). However, as a measure to improve safety, the City is currently developing a specific emergency response program for emergencies involving chlorine. ES 6.0 PLANNED CHANGES TO IMPROVE SAFETY A detailed hazard and operability study (i.e., hazards analysis) was performed on ALL operations involving chlorine in order to evaluate the potential for accidental releases. As a result of this hazards analysis a number of recommendations were made to improve the safety of the operations conducted. A summary of the recommended actions is provided in Table ES-3. Table ES-3 also presents the implementation status of the recommended actions. As shown, the City has already implemented a number of the recommendations. Table ES-3 also presents the expected date of implementation for those recommendations not yet implemented. ES 7.0 FOR MORE INFORMATION The City recognizes that some persons may be interested in obtaining more detailed information regarding risk management prevention p rogram components not discussed herein. Interested parties that have additional questions regarding the City's Risk Management Plan, are directed to contact: Mr. Stephen C. Dickey Water Superintendent City of Redlands Municipal Utilities Department, Water Division P.O. Box 3005 Redlands, California 92373 |