Pennridge Wastewater Treatment Authority WWTP - Executive Summary |
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BACKGROUND The Pennridge Wastewater Treatment Authority (PWTA) Wastewater Treatment Plant ( WWTP) is situated in the Borough of Sellersville which is located in Bucks County, Pennsylvania. The plant is owned and operated by the PWTA and treats sewage collected from the Boroughs of Sellersville, Perkasie, Telford and Silverdale as well as portions of Hilltown, East Rockhill and West Rockhill Townships. The WWTP is designed to treat average wastewater flows of up to 4.0 million gallons per day (mgd) and operates in accordance with the terms and conditions of its NPDES Permit No. PA 0020460. It is a small facility with only ten full time employees. The plant employs chemical and biological treatment processes to meet required effluent limitations defined in its NPDES permit. Wastewater treatment units and equipment include: mechanical screening, aerated grit removal, pumping, primary clarification with chemical addition, trickling filters, nitrification, activated sludge, final cl arification and disinfection. Effluent from the WWTP is discharged to the East Branch of the Perkiomen Creek. Sludge handling consists of gravity thickening, aerobic digestion and mechanical dewatering. Sludge from the WWTP is disposed of through land application or landfilling. Chlorine is utilized at the PWTA WWTP for two purposes. First, it is applied to the final clarifier effluent as it enters the chlorine contact tanks to provide disinfection. Chlorine is also added to the sludge thickening tank to reduce odors. The maximum amount of chlorine located at the site at any time is 12,000 pounds, stored in a pressurized liquid form in six separate 1-ton steel containers. All containers are maintained at the same central location, the plants chlorine storage and delivery area. The WWTPs existing chlorination equipment allows a maximum of two 1-ton containers to be interconnected at any time. PROGRAM SYNOPSIS EPA defines the equipment, storage vessels and activities that in volve a regulated substance and could lead to an accidental release as a process. The RMP Rule defines three different RMP levels for covered facilities based on a processes relative potential for public impacts, the level of effort needed to prevent accidents and coverage by other regulations. Based on EPA's criteria, the PWTA WWTP is subject to RMP Level Two requirements. As such, the required RMP must address the following items in accordance with the provisions of the RMP Rule: - Accident History - Offsite Consequence Evaluation - Management System - Level Two Prevention Program - Emergency Response Procedures - Plan Submittal - Summary of RMP ACCIDENT HISTORY During the five years prior to the preparation of this RMP, an accidental release of chlorine which is reportable under the terms of the RMP Rule has not occurred at the PWTA WWTP. OFFSITE CONSEQUENCE EVALUATION The RMP Rule requires that an offsite consequence evaluation be completed for all regulated toxic substances present above the threshold quantity. In the case of the PWTA WWTP, this evaluation was completed for chlorine and was required to include the following components: 1) A determination of the distance to the specific toxic endpoint of 0.0087 mg/l for chlorine using the worst case assumptions defined in '68.22 - 68.25 of the RMP Rule. 2) A determination of the distance to the specific toxic endpoint of 0.0087 mg/l using the alternative case assumptions defined in '68.28 of the RMP Rule. 3) An estimate of the residential population and types of public and environmental receptors within the circle of potential influence with its center at the point of release and a radius equal to the worst case distance to the toxic endpoint. 4) An estimate of the residential population and types of public and environmental receptors within the circle of potential influence with its center at the point of release and a radius equal to the alternative case distance to the toxic endpoint. For the official worst case release scenario, we assumed that an accident would occur during transfer of a single ton container from a supply truck to the PWTA WWTPs chlorine loading dock creating a catastrophic outdoor chlorine release at ground level. In accordance with the RMP Rule, all 2,000 pounds of chlorine would be released in 10 minutes. Default meteorological conditions, defined as atmospheric stability class F (stable atmosphere), wind speed of 3.4 miles per hour, 50 percent humidity and ambient air temperature of 77 degrees Fahrenheit were utilized. No passive mitigation measures were considered. The area in the vicinity of the PWTA WWTP contains a number of obstructions and therefore an urban topography condition was selected. Findings for the worst case analysis indicated that the distance to the toxic endpoint of 0.0087 mg/l for chlorine was 1.3 miles using EPAs RMP*Comp Version 1.06. The potentially affected circular area is 5.3 square miles which i ncludes an estimated residential population of 9,789 persons. The types of public receptors within this potentially affected area include (2) schools, residences, (1) hospital, recreation areas and commercial/industrial areas. It should be noted that one of the two schools and the hospital are considered at minimum risk from the effects of a chlorine release due prevailing wind patterns and their elevation relative to the PWTA WWTP. There are no environmental receptors, as defined by the RMP Rule, located within this potentially affected area. For the official alternative case release scenario, we presumed that an accident would occur in the PWTA WWTPs chlorine storage room during the changeover between full and empty ton containers causing chlorine to be released through a 3/4-inch outlet from a single ton container. Based upon an internal container pressure of 83 pounds per square inch and default meteorological conditions, defined as atmospheric stability class D, wind speed of 6.7 miles per hour, 50 percent humidity and ambient air temperature of 77 degrees Fahrenheit, all 2,000 pounds of chlorine would be released in approximately 32 minutes. Passive mitigation measures were accounted for following procedures listed in EPAs RMP Offsite Consequence Analysis Guidance. An urban topography condition was again selected. Results of the alternative case analysis indicated that the distance to the toxic endpoint of 0.0087 mg/l for chlorine was 0.6 miles following EPAs RMP Offsite Consequence Analysis Guidance. The potentially affected circular area is 1.1 square miles which includes an estimated residential population of 2,045 persons. The types of public receptors within this potentially affected area include (1) school, residences, recreation areas and commercial/industrial areas. There are no environmental receptors, as defined by the RMP Rule, located within this potentially affected area. MANAGEMENT SYSTEM Mr. Kevin L. Franks, the PWTA WWTP Manag er and the plants operator of record with the State of Pennsylvania, has been designated as the qualified individual responsible for implementing the entire RMP for the PWTA. In accordance with the EPAs RMP Guidance for WWTPs, since (1) the PWTA WWTP is a small facility with one regulated process (the chlorination facilities), (2) Mr. Franks directly oversees the employees operating and maintaining the chlorination facilities at the PWTA WWTP and (3) responsibility for executing specific elements of the RMP has not been assigned to different individuals, identifying Mr. Franks is the only action required to comply with the management system provision of the RMP Rule. LEVEL TWO PREVENTION PROGRAM The PWTA has a variety of existing protocols in place at the WWTP which are aimed at preventing any accidental releases of chlorine. Examples include an established health/safety training program, standard operating procedures (SOP) for chlorine handling, a preventative maintenance progra m, and use of specialized contractors for corrective maintenance. In addition, since the PWTA WWTP is a small facility, there are only six individuals who work in and around the chlorination system. According to EPAs RMP Rule, a Level Two Prevention Program must address seven elements for the covered process: safety information, hazard review, operating procedures, training, maintenance, compliance audits and incident investigation. A report which describes the PWTAs Level Two Prevention Program for its chlorination facilities is on file at the WWTP. This program was developed utilizing a combination of the existing practices, augmented with new procedures, to achieve compliance with the requirements of the RMP Rule. EMERGENCY RESPONSE PROCEDURES The PWTA WWTP (1) is considered a non-responding facility as defined by EPA, (2) is included in a community emergency response program prepared under the Federal Emergency Planning and Community Right-to-Know Act (EPCRA) and (3) has a ppropriate mechanisms in place to notify emergency responders. Based on these three facts, the PWTA WWTP meets the criteria defined in '68.90 of the RMP Rule, which exempts the owner or operator of a stationary source with a Program Level Two process from having to prepare and implement a new, separate emergency response program. The PWTA intends to continue to follow the County of Bucks - Emergency Management Agencys (Bucks County EMAs) Off-Site Emergency Response Plan for its WWTP prepared in accordance with EPCRA requirements. |