Topeka KS - Oakland Waste Water Treatment Plant - Executive Summary |
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Executive Summary Accidental Release Prevention and Emergency Response Policies The Oakland Wastewater Treatment Plant (Oakland WWTP), located at 1115 N.E. Poplar Street in Topeka, Kansas, prevents accidental releases of digester gas by training and adhering to industry practice and applicable codes and implementing good engineering practices. Oakland WWTP construction began in the mid-1930s and currently treats an average daily flow of 14 million gallons per day (mgd). The plant has four primary digesters, three secondary digesters, a gas holder, and a gas sphere. Gas production generates energy and saves the plant money. Oakland WWTP's prevention program, safety information, hazard reviews, operating procedures, training, maintenance, compliance audits, and incident investigation procedures are continuously updated. Every employee of the Oakland WWTP is trained to be aware of the potential for digester gas releases. In an emergency, the Oakland WWTP's first consideration is the safety of personnel and the community. The second consideration is the protection of property, equipment, and the facility. The Oakland WWTP maintains emergency response procedures that allow Oakland WWTP personnel and the local fire department to respond to releases. The Oakland WWTP has a HazMat Response Team that can assist the fire department and provide operational support as required. If required, the fire department coordinates the emergency response with other local emergency response organizations per the Emergency Action and Response Plan. All employees are trained to recognize releases of digester gas and to activate the emergency response procedures immediately. The HazMat Response Team receives additional training to enable them to respond to releases of digester gas. The Oakland WWTP: Digester gas The Oakland WWTP produces digester gas when treating wastewater. The Oakland WWTP has the capacity to hold over 17,000 pounds of methane-containing digester gas (the maximum inventory is the sum of the gas in the primary and secondary digesters, gas sphere, and gas holder). Since this quantity exceeds the Risk Management Plan (RMP) thresholds, this flammable substances must be addressed in the RMP. The Oakland WWTP does not store or use any other flammables or toxics above threshold quantities that are regulated by the Environmental Protection Agency (EPA) through 40 Code of Federal Regulations (CFR) Part 68. Offsite Consequence Analysis Models and Guidance Regulation 40 CFR Part 68.25 allows for the use of publicly available techniques that account for specified modeling conditions and are recognized by industry as current practice. For the worst-case and alternative release scenarios, the Risk Management Program Guidance for Wastewater Treatment Plants, created by the United States Environmental Protection Agency (EPA) Office of Solid Waste and Emergency Response, was used. This document is an appropriate model because it is well documente d, publicly available, and recognized by the wastewater treatment industry as applicable modeling tools. Worst-Case Release Scenario For regulated flammable substances, EPA requires the worst-case release scenario to involve the release of the greatest amount of that substance (methane in digester gas) held in a single vessel. The worst-case scenario assumes that this release quantity vaporizes and that the vapor cloud explodes. Additionally, the yield factor, or percent of the total quantity that is involved in the explosion, is assumed to be 10 percent. The yield factor represents the available energy released in the explosion used to determine the explosion endpoints using a TNT-equivalent method. This worst-case release scenario analysis was based on the TNT equivalent method with a yield factor of 10 percent. The TNT equivalent method was used to determine the distance to the overpressure endpoint of 1.0 psi for vapor cloud explosions. A catastrophic failure of the gas sph ere due to corrosion, impact, or construction defects is about a 9,000 -pound release. A 9,000-pound release is the greatest amount of digester gas held in a single vessel, the 33,500 ft3 gas sphere. The distance to the endpoint is 0.17 miles. Alternative Release Scenario Since alternative release scenarios are more likely to occur than the worst-case scenarios, these scenarios are more suitable in emergency planning. According to the five-year accident history, the Oakland WWTP site has not had a digester gas release that has migrated offsite. The lower flammability limit (LFL), rather than the explosion endpoint, is the flammable endpoint definition for the alternative release scenario. The alternative release scenario considers a vapor cloud fire resulting from the dispersion of a flammable vapor cloud and subsequent explosion. This fire could flash back and present a severe heat radiation hazard. The endpoint distance is the distance the vapor cloud travels before falling b elow its LFL. The alternative release scenario assumes that the gaseous contents of one primary digester is released over a ten-minute period. With a maximum of 1,017 pounds of digester gas in the digester, the release rate is 101.7 lb/min. Given a methane LFL is 33 mg/L, the predicted distance for a release of one primary digester is 0.1 miles in an urban setting. This is a conservative estimate, and the predicted distance may overestimate an actual distance to endpoint. Accidental Release Prevention Program and Chemical-Specific Prevention Steps Oakland WWTP's prevention program consists of safety information, hazard reviews, operating procedures (Standard Operating Procedures), training, maintenance, compliance audits, and incident investigations. To prevent releases, the Oakland WWTP compiled digester gas safety information, including: Material Safety Data Sheets (MSDS); maximum intended inventory; safe upper and lower temperatures, pressures, and flows; equipment specific ations; and codes and standards used to design, build, and operate the anaerobic digester and digester gas systems. A hazard review was conducted for the digester gas systems. The hazard review team consisted of plant management, process operation and maintenance personnel, and consulting process design engineers. The team analyzed the hazards associated with the anaerobic digester and digester gas processes using the what-if technique. The hazard review team documented recommendations and set a schedule for implementation. The Oakland WWTP has adopted written Standard Operating Procedures (SOPs) that provide system descriptions, specifications, and operating procedures for the anaerobic digester and digester gas systems. The procedures address initial startup, normal operations, normal and emergency shutdown, inspections, temporary operation, restartup, and consequences of deviation. The Oakland WWTP has a training program with guidelines for conducting regular, structured p lant training for employees, including operators and maintenance personnel. Records of the training program, including content of the course, course manual, examination, and record of attendance are maintained. In-house and out-sourced maintenance personnel perform preventative maintenance, inspection, and equipment testing to ensure safe operations at the Oakland WWTP. The Oakland WWTP uses a Computerized Maintenance Management System (CMMS) to schedule, track, and document preventative and corrective maintenance activities. The CMMS infrastructure management system is a work order based system that generates work orders for preventive and corrective maintenance activities, and allows for organization and documentation of inventory, labor, materials, equipment, and contract management expenses. The compliance audit process will be performed at least once every three years to ensure that the RMP procedures and practices are adequate and being followed. To complete a compliance audit, the Oakland WWTP must demonstrate that documentation, employees' knowledge (interviews), and the physical facility (through inspection) comply with 40 CFR Part 68. The RMP incident investigation program outlines the RMP investigation process. If the digester gas incident is reportable, the employee completes an Incident Report form. An Incident Investigation Team investigates how the incident occurred and determines whether errors can be corrected by instituting safeguards for the process or whether employees need additional training. The Supervisor of Plant Operations and Maintenance - on the advice of the Incident Investigation Team - will promptly implement corrective actions. This information will be entered on the RMP Incident Report Form and Summary and signed by the Supervisor of Plant Operations and Maintenance. The Five-Year Accident History The five-year accident history must include releases from regulated processes that resulted in deaths, injuries, damage on site; or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage. In the past five years, no releases resulted in an injury related to a regulated substance at Oakland WWTP. Emergency Response Program In a release, the Oakland WWTP would use the City of Topeka, Water Pollution Control Comprehensive Safety Program Manual - Emergency Action and Response Plans. The Water Pollution Control Division has a HazMat Response Team to respond to releases or potential releases of hazardous substances for the purpose of stopping the release. This team approaches the point of release to plug, patch, or otherwise stop the release of the hazardous substance. In case of an emergency, the local fire department would be notified, followed by members of the Water Pollution Control Division Hazmat Response Team. The fire department would assume the responsibility of the Incident Command System and provide the Incident Control Commander. Members of t he Hazmat Response Team would function under the Incident Control Commander and provide the operational support. Notification procedures are outlined in the Emergency Action and Response Plan and will be initiated by the Incident Control Commander. After initial site assessment, the Control Commander would notify and coordinate emergency response with other local emergency response organizations such as the police department and the Shawnee County Department of Emergency Management if necessary. These organizations would also notify the public, if necessary. Planned Changes to Improve Safety To improve safety, the Oakland WWTP made changes based on the Hazard Review conducted for the anaerobic digester and digester gas systems. The review prompted a list of recommendations that were implemented. The most significant changes to improve safety include investigate adding: Pressure relief valves onto the preventative maintenance schedule. A fire protection system. |