Montoursville Regional Sewer System WWTP - Executive Summary |
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SECTION 1 EXECUTIVE SUMMARY A. The Montoursville Regional Sewer System (MRSS) Wastewater Treatment Plant (WWTP) owned and operated by the Lycoming County Water and Sewer Authority (LCWSA), was placed into operation to provide wastewater treatment services to the Borough of Montoursville and portions of Fairfield and Loyalsock Township in Lycoming County. The treatment plant is equipped with a chlorination facility to disinfect the effluent prior to discharge to the west branch of the Susquehanna River. The treatment plant is located at 216 Old Cement Road in Fairfield Township. The disinfection facilities include a chlorine cylinder room, which contains chlorine containers, chlorine scale, two (2) chlorinators with automatic switchover capabilities, and various safety equipment, and a chlorine room which houses a rotameter, plant water hydro-pneumatic tank, plant water strainer system and various safety equipment. The amount of chlorine handled is three (3) one (1)-ton containers. The treatment facility is manned during normal business hours including occasionally during the weekend period. Twenty-four (24) hour alarm notification from a chlorine monitor in the ton cylinder storage room is part of the system's automatic alarm process. The operators visit the disinfection facility on at least a daily basis and respond to any trouble alarms, which may occur. B. The offsite consequence analysis includes consideration of two (2) chlorine release scenarios, identified as "worst case release" and "alternative scenario". The first scenario is defined by the Environmental Protection Agency (EPA), which states that "the owner or operator shall assume that the ... maximum quantity in the largest vessel ... is released as a gas over ten (10) minutes," due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario". Atmospheric dispersion modeling was performed utilizing the RMP COMP program. This provi ded the distance traveled by the chlorine released before its concentration decreases to the "toxic endpoint". The residential population, determined through the use of LandView III, within a circle with a radius corresponding to the toxic endpoint distance has to be defined; "to estimate the population potentially affected". The worst-case release scenario at the MRSS facility involves a failure of one (1) of the two (2) ton-containers, which could be connected concurrently (a total of 2,000 pounds of chlorine). The offsite consequence analysis for this scenario was performed for two (2) sets of conditions. The first set followed conditions pre-defined by EPA, namely release of the entire amount as a gas in ten (10) minutes, use of the one (1)-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with a radius corresponding to the toxic endpoint distance. EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, air temperature (77x F) and average humidity were used for both sets. When atmospheric dispersion modeling for the worst case scenario was performed using the EPA assumptions, a distance to toxic endpoint of 3.5 miles and an estimate of residential population potentially affected of 6047 was obtained. The alternative release scenario involves the rupture of the flexible connections (pigtails) connected to two (2) ton-containers. The amount of chlorine released is 259 lb, at an average rate over ten (10) minutes (the duration of the release) of 25.9 lb/min. Toxic endpoint distances to ERPG-2 were obtained. The typical meteorological conditions used were Stability D, wind speed 3.0 m/s, average air temperature of 77x F. The estimated distances traveled to the toxic endpoint is 3,274 feet for the ERPG-2. Actuation of the chorine detector is an active mitigation measure that was considered. C. The LCWSA's accidental release prevention program is based on the following key elements: * Training of the operators. * Preventive maintenance program. * Use of state-of-the-art process and safety equipment. * Use of accurate and effective operating procedures, written with the participation of the operators. * Performance of a hazard review of equipment and procedures. * Implementation of an auditing and inspection program. * Local Agency Interaction: Montoursville Volunteer Fire Company. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), worn by the operators during connection/disconnection of chlorine supply, awareness of the hazardous and toxic properties of chlorine, and presence of chlorine detectors. D. No accidental releases of chlorine have occurred at this facility in the past five (5) years. E. The facility has an emergency response program developed through a Preparedness, Prevention and Contingency Plan, which has been coordinated (reviewed) by the Lycoming County Department of Public Safety. This program includes an emergency response decision tree and a notification plan. |