Harrisburg Advanced Wastewater Treatment Facility - Executive Summary |
|
The primary function of the Harrisburg Advanced Wastewater Treatment Facility (the "AWTF") is to provide wastewater treatment to the City of Harrisburg and six surrounding municipalities. Accordingly, the NAICS Code is 22132. The facility is located at 1662 South Cameron Street, Harrisburg, Pennsylvania and is owned by The Harrisburg Authority and operated by the City of Harrisburg. The AWTF is a stationary source with two processes assigned to Program Level 2. The regulated substances of the two processes include chlorine and methane. The chlorine disinfection process involves one building which includes a chlorine cylinder room which contains chlorine containers, chlorine scale and various safety equipment, and an adjacent room which houses two chlorinators with rotameters, water injectors and various safety equipment. The amount of chlorine handled is six one-ton cylinders. The methane process includes two primary anaerobic digesters, two secondary anaerobic digesters (one wi th a floating cover), one gas storage sphere, two compressors and various safety equipment. The maximum amount of methane stored on site is 10,450 pounds. The treatment facility is manned 24 hours per day seven day per week. The operators visit the chlorine and methane process at least twice per day and respond to trouble alarms which may occur. It is the policy of the AWTF to prevent accidental releases of substances that can cause serious harm to the public and the environment from short-term exposures and to mitigate the severity of releases that do occur. Management commitment to process safety is a critical element of the AWTF's Risk Management Program to ensure that program elements are integrated and implemented on an ongoing bases; and, all parties understand the lines of responsibility and communications. The offsite consequence analysis includes consideration for chlorine and methane release scenarios identified as worst case release and alternative scenario. Atmospher ic dispersion modeling was performed utilizing the RMP*Comp program. The worst case scenario for chlorine assumes that the entire quantity of the one-ton cylinder is completely released over a ten minute period. The toxic endpoint distance are calculated for releases that are assumed to take place outdoors. No passive mitigation systems are included in the assumptions. A toxic endpoint distance of 1.3 miles was obtained and an average residential population potentially affected was 12,631. The chlorine alternative release scenario is described as an event which is likely to occur. The AWTF scenario involves the breaking of the = - inch discharge line. The cylinder and line are located in an enclosed space with a temperature of 70 degrees F. The pressure within a full cylinder is 85 PSI. The response action to correct is to close the discharge valve on the cylinder, then replace the pipe. The time required to close the valve is ten minutes. A toxic endpoint distance of 0.1 mi les was obtained and an average residential population potentially affected was zero. The worst case scenario for methane assumes that the entire 7,375 pounds of gas contained in the sphere is completely released to the outdoors. No passive mitigation systems are included in the assumptions. A toxic endpoint distance of 0.2 miles was obtained and an average residential population potentially affected was zero. The methane alternative release scenario is described as an event which is likely to occur involves a one-inch release valve that stays open. The gas sphere is located outside with temperatures reaching 95 degrees F. The pressure with the sphere are 45 PSI. The response time to correct the stuck valve is approximately 30 minutes. No mitigation efforts are included in the scenario. A toxic endpoint distance of 0.1 miles was obtained and an average residential population potentially affected was zero. The purpose of the AWTF prevention program is to ensure that management staff and employees understand the safety related aspects of the equipment and processes, know what limits they place on operations, and adopt accepted standards and codes where they apply. Key elements to the program include: training, preventive maintenance, state-of-the-art process and safety equipment, operating procedures, hazard review, auditing, and inspection. The AWTF did not have any accidental release from regulated substances from a covered process nor any accidental release meeting specific criteria in the past five years. The AWTF is a non-responding facility, as such, the AWTF has coordinated efforts with local response agencies to ensure that they will be prepared to respond to an emergency and that the community has a strategy for responding to and mitigating the threat of a release of a regulated substance. |