Columbia Boulevard Wastewater Treatment Plant - Executive Summary |
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The Columbia Boulevard Wastewater Treatment Plant-Portland, Oregon The Columbia Boulevard Wastewater Treatment Plant (CBWTP) is a publicly owned wastewater treatment facility. It was constructed in 1952 to provide primary treatment of wastewater in the City of Portland. It was expanded to provide secondary treatment in 1974 and has the capacity to treat 100 million gallons a day (mgd). The plant has an activated sludge facility and has a reuse program for biosolids. CBWTP is owned by the City of Portland and managed by the Bureau of Environmental Services Wastewater Group (WG). The facility serves a population of over 432,000 with approximately 144,787 residential sewer and drainage customers and 12,844 commercial/industrial customers. The Bureau of Environmental Services has 450 employees and an annual budget of $153 million. The Bureau provides policy direction for regulatory programs associated with wastewater treatment and stormwater management. Programs include industria l pretreatment and source control, water quality investigations and monitoring, watershed planning, combined sewer overflow design and construction, and environmental outreach and education programs. Accident Prevention and Emergency Response The City's Bureau of Environmental Services Wastewater Group (WG) is committed to: 7 being proactive in the prevention of occupational risk and injuries/illnesses, 7 protecting human, material and organizational wastewater resources, and 7 preserving assets against detrimental loss. The WG has established a quality risk management philosophy that promotes employee involvement and accountability, and encourages a culture where safety and loss prevention is an internal value that is incorporated in every plan, decision and work activity. This philosophy extends to the health and well being of the community. New chlorination facilities were constructed in 1992 to meet revised Uniform Fire Code requirements for emergency scrubbers. This fac ility provides physical containment for any liquid or gas leak in the rail car bays and in the equipment room where the chlorinators and evaporators are located. Three scrubbers neutralize the contained chlorine. Two of the scrubbers can remove 10,000 pounds of chlorine each from the rail car bays and the third can remove 150 pounds from the equipment room. An alarm system will activate a local and remote audio alarm when the concentration of chlorine reaches 2 parts per million. The WG also has a comprehensive chlorine response plan that includes a partnership with Portland Fire Bureau and more specifically the Hazardous Materials Response Team. WG employees are highly skilled, trained and drilled on their roles and responsibilities in the event of a chlorine release. The WG has received numerous safety and loss prevention awards and is recognized within the wastewater treatment industry as a leader in safety and loss prevention on the national, regional and local levels. For e xample, in 1991 the WG received the Public Employer of Year Award from Oregon Occupational Safety and Health Administration (OSHA) and the American Society of Safety Engineers. The award recognized efforts to create a safe and healthy employment for Oregonians. The facility also received the National Safety Council Award, ranking 6th nationally in the Water Resource Division for occupational safety and health. The chlorine containment facility received two awards in 1992 from the Consulting Engineering Council of Oregon for Engineering Excellence. One was the Project of the Year and the other was the Grand Award. In 1997 the Pacific Northwest Water Pollution Control Association presented a Safety Award to the WG for leadership in occupational safety and health in the wastewater industry (the third award in six years). In 1998 Portland City Council recognized the WG Safety Committee for continued efforts in safety and loss prevention and exceeding regulatory requirements for saf ety committees, and the Safety Action Leadership Team for continued involvement and implementation of the "Challenge of Change" a Safety Perception Survey. Regulated substances Environmental Services Wastewater Group manages liquid chlorine at the Columbia Boulevard Wastewater Treatment Plant (CBWTP). The facility is located at 5001 North Columbia Boulevard, Portland, Oregon 97203. The liquid chlorine is stored in two 90-ton rail cars that are housed in a 50 by 70 foot chlorination facility that was constructed in 1992. The chlorine is used in the final stage of treating wastewater to ensure that the effluent is disinfected before discharge to the Columbia River. Worst-case release scenario and the alternative scenario The RMP program requirements include the development of a "worst case" and an "alternative scenario involving the accidental release of the regulated substance. These results do not predict the results of a release and actual concentrations of the chemical may be lower than predicted by the model. A brief description of each of the scenarios follows. Worst-case scenario For worst-case scenarios, under EPA guidelines, accidental releases are assumed to take place without consideration for physical cause or likelihood of occurrence. Only passive mitigation measures (e.g., dikes, buildings, and enclosures) can be considered, while active mitigation measures (scrubbers) can not be included. At the CBWTP, liquid chlorine is stored in two 90-ton rail cars. The cars are house in the chlorine facility built in 1992. For the worst-case scenario, a catastrophic rupture of a one 90-ton rail car was evaluated to determine the distance to a specific endpoint concentration for a worst-case release of chlorine. According to the rule, the toxic gas worst-case scenario must assume the release of the single largest vessel or container over a period of 10 minutes. However, because the rail cars are stored within a building, a passive mitigation factor may be applied. The chlorine in the railroad car tanks is stored under pressure so that the chlorine is in a liquid state. When the chlorine is suddenly released, the depressurization causes the releasing stream to cool to the chlorine boiling point. Therefore, a portion of the content flashes directly into vapor. The worst-case release rate is the entire rail car content released within 10 minutes. Since the cars are delivered to and kept in containment buildings, a building mitigation was included for this scenario. The Offsite Consequence Analysis guidance suggests a mitigation factor that reduces the release to 55 percent of the total amount that may be released in the scenario. However, the Risk Management Program Guidance for Wastewater Treatment Plants provides a more sophisticated method for estimating the building mitigation factor that takes into account the flashing characteristics of a gas under pressure. The release was modeled as a transient release because t he release time is less than the time it takes the cloud to reach the endpoint distance. The distance to the chlorine toxic endpoint (3 ppm) was determined to be 5.6 miles. The population within the circle is estimated to be 157,456 people. EPA requires that public and environmental receptors, as defined by the rule, be identified. Based on U.S. Geological Maps, Thomas registers, and other public media, the following public receptors were identified to be within the worst-case chlorine circle: residences, schools, hospitals (e.g. Kaiser Permanente Interstate Medical Offices, Emanuel Hospital, Good Samaritan Hospital), a prison (Columbia River Correctional Institution), parks, recreational areas (Columbia River), commercial areas, industrial areas, and office areas. The following environmental receptors were defined: Willamette Stone State Park, Fort Vancouver National Historical Site and the Sauvie Island Wildlife Area. Alternative scenario The alternative release scenario wa s defined as a release of chlorine from a 1/8 inch hole from the shearing of a pressure gauge on the liquid chlorine supply line during maintenance activity. The release was assumed to occur in the chlorinator room near the evaporators and that the doors to the chlorinator room were open-which compromises the containment features of the facility. This scenario was identified by the staff of CBWTP as a likely alternative release scenario for their facility. Because the travel time to the endpoint distance (approximately 2 minutes) was less than the time of release (3 to 10 minutes), the release was modeled as a continuous release. The distance to the chlorine toxic endpoint (3 ppm) was determined to be 0.3 miles The population within the circle is estimated to be 100 people. EPA requires that public and environmental receptors be identified. Based on U.S. Geological Maps, Thomas registers, and other public media, only a few residences and some businesses were found to be within t he alternative-case chlorine circle. No environmental receptors, as defined by the rule, were identified. Chemical Prevention Steps The WG has numerous written occupational safety and health programs. Programs specific to the chemical process are: process safety management (PSM), energy isolation, respiratory protection, emergency response, personal protective equipment and training/education. The treatment plant has the containment facility with scrubbers that will neutralize releases. The WG complies with the OSHA Process Safety Management rule. An independent contractor performed a Hazardous Operations (HAZOP) Study in April 1999 and a PSM audit in May of 1999 for chlorine. The Wastewater Group (WG) is actively taking the appropriate measures to implement the recommendations of both studies. Accident History There has been one accidental release of chlorine in the last 5 years where an employee was injured. The release was estimated at 5 pounds. It was contained and neutr alized in the containment building. There were no off site impacts. Emergency Response The WG staff will respond to unplanned events in a safe, prompt, and responsible manner. The staff recognizes that each set of conditions will be unique, and unpredictable. The goal of plant staff is to protect health and safety of the individual, coworkers and neighbors/community, plant equipment and continue to meet all discharge permit requirements. In order to minimize the amount of chlorine that is released, the plant staff will close the valve at the point of discharge at the tank car. The WG also has a comprehensive chlorine response plan that includes a partnership with Portland Fire Bureau and more specifically the Hazardous Materials Response Team. Public notification of an accidental release is in conjunction with the public safety entities in the area. Shelter in place, a response procedure requiring citizens to remain indoors with windows, doors and ventilation systems closed, i s considered the most appropriate community protection. The Wastewater Group will be actively discussing this program with the community. Planned Changes The WG just had a process safety management audit in May of 1999 and a hazard analysis was conducted in April 1999 by the engineering firm of CH2M Hill. A team of highly skilled employees familiar with the chemical process has been assembled to review the audit and analyze recommendations. The team will determine implementation strategies and assure that the recommendations are completed. For further information about the risk management plan and the wastewater treatment services provided by the City of Portland, please contact Tim Hall at 823-2410 |