South Regional Waste Water Treatment Facility - Executive Summary |
|
The South Regional Wastewater Treatment Plant is a coupled biofilter/activated sludge wastewater treatment plant with a nominal capacity of eighteen (18) million gallons per day. The plant uses chlorine as a disinfection agent and sulfur dioxide as a dechlorination agent prior to disharge of the final effluent to Days Creek. The facility's only activity is the primary and secondary treatment of municipal wastewater. Liquid chlorine and sulfur dioxide are the only two chemicals used in sufficient quantity at the facility to be regulated under the RMP program. Up to twenty (20) one ton cylinders of chlorine and twelve (12) one ton cylinders of sulfur dioxide are stored at the site. Up to four (4) cylinders of chlorine are used at any one time in the process and two (2) cylinders of sulfur dioxide. Texarkana Water Utilities is dedicated to the safe and proper handling of chemicals necessary for the production of drinking water and treatment of wastewater for its citizens. Utility manag ement has consistently budgeted and the elected bodies of the two Texarkana's have consistently approved funds to support personnel and citizen safety preventative maintenance training, chemical awareness and handling, emergency response and equipment related to chemicals used at the facility. The worst case scenario for chlorine considers the release of 2000 lbs of chlorine from a one ton cylinder in ten (10) minutes. The dispersion model ALOHA (Area Locations of Hazardous Atmospheres), which is recognized by EPA's RMP Offsite Consequence Analysis (OCA) Guidance, was used to determine the distance to the toxic endpoint for chlorine. Using digital census block files in conjunction with digital area maps, offsite impacts on population, public receptors and environmental receptors were analyzed. The estimated residential population within the distance to endpoint is 8,100 and at least one of each of the six major public receptors is found within the distance to endpoint. None of the lis ted environmental receptors are known to be found within the distance to endpoint. The worst case scenario for sulfur dioxide (anhydrous) considers a release of 2000 lbs of the chemical from a one ton cylinder in ten (10) minutes. Modeling and analysis tools for the sulfur dioxide release were the same as those for the chlorine release including the use of the ALOHA dispersion model. The estimated residential population within the distance to endpoint is 9,100. At least one of al the listed public receptors are found within the distance to endpoint except hospitals and there are no hospitals. None of the listed environmental receptors are within the distance to endpoint. Several training a procedural methods make a worst case release of either chlorine or sulfur dioxide unlikely. The site is staffed twenty-four (24) hous a day with periodic inspections of the chlorination facilities made on each of the three daily shifts. Highly trained personnel and an extensive preventative mainten ance program keep all chlorination equipment in like new condition. There are remote alarmed gas detectors for both chlorine and sulfur dioxide. Safety procedures, including those associated with chlorine and sulfur dioxide are standardized throuth Standard Operating Procedures (SOP's). Cylinder repair kits for both chemicals are kept at several locations in the system. The American Water Works Association publication Compliance Guidance and Model Risk Management Program for Water Treatment Plants, was used in the selection of an alternative release scenario for chlorine. Scenario I.D. CLA-3 was chosen, as most closely approximating a possible release at this facility. Site specific data was substituted in the ALOHA model and analyzed. The alternative release scenario considers the release of 317 lbs, over a sixty (60) minute period due to the failure of a transfer hose. The same methods were used in the analysis of the alternative scenario as were used for the worst case. The estimat ed residential population within the distance to endpoint is 692. There are residences and major commercial areas located within the distance to endpoint. None of the listed environmental receptors are located within the distance to endpoint. The alternative release scenario for sulfur dioxide considers the release of 317 lbs over a sixty (60) minute period due to the failure of a transfer hose. The same methods were used in the analysis of the alternative scenario as were used in the worst case analysis for chlorine and sulfur dioxide. The estimated population within the distance to endpoint is 692. There are no public or environmental receptors within the distance to endpoint. For the same reasons listed for the worst case scenario, even the alternative release of chlorine or sulfur dioxide is highly unlikely. The accidental release prevention program is predicated on well informed, well trained employees. The facility makes use of written, video and classroom training from the Te xas Natural Resource Conservation Commission, Arkansas Department of Health, Chlorine Institute, the American Water Works Association and the Water Environment Association. Facility management has developed written standard operational procedures for all chemical equipment and chemical handling. These SOP's set up and require extensive preventative maintenance programs that provide frequent checks and keep equipment in like new condition. Gas detection and alarm devices are used to provide early alert to any chlorine or sulfur dioxide releases. There have been no reportable chlorine or sulfur dioxide releases or accidents for a period exceeding five (5) years largely due to the previously described steps taken by Texarkana Wate Utilities management. The Utility is included in the written community emergency response plan and maintains a close working relationship with the local Emergency Management Office. The facility has its own written emergency response plan and participate in si te-specific, multi-agency response drills. Boots and Coots, a company which maintains a Hazardous Waste Operations and Emergency Response (HAZWOPER) team, is available to back up and respond to any chemical release. The Utility is currently considering the possibility of installation of a chlorine gas absorption unit to mitigate any release up to a one ton cylinder. The Utility has a geographic information system base map that is being developed to assist utility, fire, police and emergency management personnel in prevention and response planning for any chemical release. |