Metropolitan Sewerage District of Buncombe County - Executive Summary |
|
The Metropolitan Sewerage District of Buncombe County (MSD) operates a municipal wastewater treatment plant located at 225 Riverside Drive in Asheville, North Carolina. The plant provides domestic and industrial wastewater treatment for Asheville and surrounding communities. The plant capacity is 40 million gallons average per day flow. The plant utilizes rotating biological contactors (RBCs) for primary treatment and implements chlorination disinfection prior to discharge of treated wastewater. Chlorine used for the disinfection process is stored at the plant in 2000-pound canisters. Up to 12 canisters are stored at the site at one time. The quantity of chlorine stored on site exceeds the threshold quantity for both the OSHA standard 29 CFR 1910.119 (Process Safety Management) and EPA standard 40 CFR Part 68 Section 112(r)(7) (Risk Management Program). MSD's policies related to accidental release prevention and emergency response are detailed in the plant's existing Process Saf ety Management (PSM) plan. The PSM plan addresses the requirements of Subpart D-Program 3 Prevention Program and Subpart E-Emergency Response required by the EPA standard. MSD places a high priority on safety, particularly in association with chlorine use. The effectiveness of the existing program is reflected by the fact that there have been no serious incidents involving chlorine in the past five years at the plant. MSD conducted offsite consequence analyses for worst-case and alternative-case release scenarios as required in Subpart B. The worst-case scenario involved the rupture of one chlorine storage canister. The alternative-case scenario involved a chlorine release through a broken pipe inside the chlorine building. The worst-case toxic endpoint was 1.3 miles and encompassed an estimated population of 2900. The alternative-case toxic endpoint was 0.5 miles and encompassed an estimated population of 461. Emergency response in case of a chlorine release is coordinated wi th the Asheville fire department and includes procedures for informing the public and responding agencies. MSD currently plans to modify the disinfection system implemented at the plant. The modified approach will utilize hypochlorite (bleach solution) in place of chlorine. Hypochlorite is not a highly hazardous chemical. When this modification is complete, the facility will no longer be subject to the OSHA PSM or EPA RMP standards. The new disinfection system will pose a significantly lower threat to the community and the environment surrounding the plant. |