Blue Plains Wastewater Treatment Plant - Executive Summary |
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DISTRICT OF COLUMBIA WATER AND SEWER AUTHORITY EPA RMP EXECUTIVE SUMMARY ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The District of Columbia Water and Sewer Authority Blue Plains Facility (DC WASA) is totally committed to preventing accidental releases of toxic and flammable materials. DC WASA realizes that the TOTAL elimination of releases is a goal that must be worked towards and that in reality there is always the potential, however slight, for a release of materials. DC WASA has taken additional precautions and developed emergency response policies and procedures to minimize the effects of any material releases that might inadvertently occur. These emergency response plans include actions to be taken by DC WASA and neighboring areas and resources. It is DC WASA's goal of zero releases and therefore never require the use of the emergency response plans. However, plans will be in place and available should the need ever arise. DC WASA management has dedica ted themselves to the continued implementation of the accidental release prevention policies which is evident in the operating history of the Blue Plains Facility. DESCRIPTION OF THE FACILITY The DC WASA facility at Blue Plains is an advanced wastewater treatment plant that includes primary and secondary treatment, phosphorous removal, nitrification and denitrification, and filtration and disinfection processes along with biosolids processing. The quantity of toxic materials (chlorine and sulfur dioxide) and flammable material (methane) present in the Blue Plains facility requires the facility to comply with the EPA RMP regulation (40 CFR part 68). Chlorine is delivered to the site via 90 ton railcars. These railcars provide for the gaseous or liquid withdrawl of chlorine. During gaseous chlorine withdrawl, chlorine gas is delivered directly to the chlorinators for feeding into the system. During liquid chlorine withdrawl, chlorine liquid is fed to an evaporation unit prior to d ischarge to a chlorinator. The two major uses of chlorine at the districts wastewater treatment plant are for the control of odors at the wastewater treatment plant site and for the disinection of plant effluent (prechlorination and postchlorination). Sulfur dioxide is also delivered to the site via 90 ton railcars. These railcars provide for gaseous or liquid withdrawl of sulfur dioxide. During gaseous sulfur dioxide withdrawl, sulfur dioxide gas is delivered directly to the sulfonators for feeding into the system. During liquid sulfur dioxide withdrawl, sulfur dioxide liquid is fed to an evaporation unit prior to discharge to a sulfonator. Sulfur dioxide is used to remove the free chlorine from the treated wastewater prior to discharge into the Potomac River. Methane is a flammable gas that is naturally produced in the sludge digestion process. It is then burned in a heater to maintain a constant operating temperature in the digestors. Approximately 2 tons of methane gas is st ored in the methane storage tank onsite. Excess methane gas is burned onsite through flares. THE WORST CASE SCENARIO AND ALTERNATE CASE SCENARIO The EPA requires that DC WASA examine the worst case release scenarios for the Blue Plains Facility regardless of probability of occurrence. These worst case scenarios are extremely unlikely to occur and assume that no actions are taken to minimize the extent of the releases. The EPA has published tables that give distances related to the material release quantities. These tables are located in the EPA's OCA Guidance, the Risk Management Program Guidance for Wastewater Treatment Plants. These distances represent the area that could be impacted by the corresponding release; however not necessarily those that will be impacted. These distances are VERY conservative and assume that all conditions related to the material releases are at levels that maximize these distances. In all reality, the probability of these worst case scenarios oc curring and the corresponding impact distances effecting populations is extremely remote. The worst case scenarios as defined by the EPA are as follows: 1. TOXIC - Catastrophic Rupture of a fully loaded Sulfur Dioxide Rail Car - this scenario assumes that a fully loaded sulfur dioxide rail car suddenly ruptures instantly releasing 90 tons of sulfur dioxide to the atmosphere. The potential impact distance that is quoted from the EPA tables is a 15-mile radius from the release point. 2. FLAMMABLE - Catastrophic Rupture of a full methane gas storage tank - this scenario assumes that the methane storage tank on site fails open instantly releasing 4000 lbs. of methane gas which is then ignited creating an unconfined vapor cloud explosion and overpressure. The distance to the 1psi overpressure per the EPA tables is 0.13 miles from the point of release. Another requirement of the EPA RMP is that alternate case release scenarios for each regulated chemical must be examined. These scenario s are intended to be the more likely to occur than the worst case scenarios discussed above. This does not mean that they are going to occur, just that the probability is greater. Notice however, that the impact distances are significantly smaller than the worst case scenarios above. The alternate case scenarios are as follows: 1. Failure of Chlorine Rail Car unloading hose - this scenario assumes that the one inch unloading hose connecting the process to the chlorine rail car ruptures or uncouples during the unloading process. In this case it is assumed that the release occurs for 10 minutes before it can be isolated. The release rate of chlorine is restricted by an excess flow valve thus minimizing the total quantity released. The impact distance from the tables listed above is 0.3 miles. 2. Failure of Sulfur Dioxide Rail Car unloading hose - this scenario assumes that the one inch unloading hose connecting the process to the sulfur dioxide rail car ruptures or uncouples during the unloading process. In this case it is assumed that the release occurs for 10 minutes before it can be isolated. The impact distance from the tables listed above is 0.3 miles. 3. Loss of the methane tank water seal and the release of the digester gas from one digester through the tank seal - This scenario assumes a release occurs for a 10-minute period and the corresponding distance to the edge of a flammable gas cloud of methane is 0.1 miles. GENERAL RELEASE PREVENTION PROGRAM AND CHEMICAL SPECIFIC PREVENTION STEPS DC WASA has taken many steps to ensure that the potential for a release of materials is minimized. These actions are more of a plant culture than a regulatory requirement. All employees of DC WASA from new hires to executive management are part of the "Release Prevention Program". It is part of the employees everyday plant life that these release prevention steps are applied. In general terms, there are twelve elements to the DC WASA Blue Plains prevention progr am. They are as follows: 7 Process Safety Information - information pertaining to the process is accurate and up to date. 7 Process Hazards Analysis - formal technical hazard reviews are conducted and updated. 7 Operating Procedures - written procedures are in place and up to date. 7 Training - personnel are formally trained for the jobs they are to perform. 7 Mechanical Integrity - written procedures are in place for inspection, testing and maintenance of equipment. 7 Management of Change - procedures are in place to review and approve changes to the process. 7 Pre-Startup Review - a formal procedure is in place to review changes to the process before startup. 7 Compliance Audits - periodic reviews of the 12 elements for compliance. 7 Incident Investigation - incidents with the potential for serious consequences are reviewed by a dedicated team. 7 Employee Participation - all employees are required to participate in all of the release prevention program elements. 7 Hot Work Permit - special permits and programs are in place for all Hot Work such as welding and cutting. 7 Contractors - a formal program is in place for the selection and review of contractors. Each of these elements is focused towards eliminating releases of toxic and flammable materials from the DC WASA Blue Plains facility. FIVE YEAR ACCIDENT HISTORY To ensure that past accidents are not repeated and to learn from our mistakes, DC WASA has been compiling a history of past incidents related to the release of toxic and flammable materials. To date there has been only one incident that is documented. It involved the release of approximately 42 lbs. of chlorine gas from a process vessel that was taken out of service. As a result of this incident and subsequent investigation, maintenance and operating procedures where revised to ensure that this type of scenario does not happen again. EMERGENCY REPONSE PROGRAM As an additional layer of protection for DC WASA employees and the general public, D C WASA has in place a detailed emergency response plan. This plan is designed to assist DC WASA personnel and neighboring communities in the event an incident were to occur at the Blue Plains Facility that could impact offsite. This plan is reviewed and updated on a regular basis to ensure that the latest plant and community information is available. DC WASA has conducted a drill with local government agencies to ensure that the plan is functional both for DC WASA and the community. PLANNED CHANGES TO FACILITY TO IMPROVE SAFETY DC WASA is constantly striving to create a safer workplace for employees and to be a safer neighbor to the surrounding communities. Current safety improvement projects onsite at the Blue Plains facility consist of: 7 Reorganization of the Safety Department with the addition of a dedicated Corporate Safety Director and staff 7 Review and revision of Operating, Maintenance and Safe Work Procedures 7 Review and revision of the Emergency Response Plans 7 Conti nued training of all plant personnel 7 Ongoing technical reviews of alternate process for the removal of chlorine and sulfur dioxide and the substitution of another suitable process. |