LBCJMA Wastewater Treatment Plant - Executive Summary |
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The Lower Bucks County Joint Municipal Authority (LBCJMA) owns, operates and maintains a Wastewater Treatment Plant (WWTP). The LBCJMA accidental release prevention policy involves a unified approach that integrates technologies, procedures and management practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to. The LBCJMA's emergency response policy plans are tailored to each facility and to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program requirements. The chlorination system has been installed at the LBCJMA WWTP to disinfect WWTP effluent prior to its discharge into the Delaware River, as per the LBCJMA National Pollution Discharge Elimination System (NPDES) permit. The LBCJMA Wastewater Treatment Plan serves Tullytown Borough and portions of Bristol Township, Middletown Township and Falls Township. The chlorination facility is located within the LBCJMA Wastewater Treatment Plant. The chlorination facility includes a chlorine cylinder weighing room, which contains liquid chlorine cylinders (four each one-ton cylinders), and a chlorine feeding room, which contains two chlorinators and electric panels. At any given time, two each one ton chlorine cylinders are turned on in the chlorine cylinder weighing room. The chlorine cylinders are connected to a manifold which transports chlorine to the chlorinators. Chlorine gas flows to the manifold is controlled by two valves: one at the each cylinder and one at the manifold. Generally, there are six (6) cylinders which are stored in a chlorine cylinder storage area. The chlorination facility is normally unmanned. The Wastewater Treatment Plant operators visit the facility daily and respon d to any trouble alarms which may occur. The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case release" and "Alternative scenario". The worst-case release scenario is defined by EPA, which states that "the owner or operator shall assume that the maximum quantity in the largest vessel is released as a gas over 10 minutes," due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario". Reference tables contained in RMP offsite consequence guidance were used to determine the distance traveled by the chlorine released before its concentration decreases to the "toxic endpoint" selected by EPA of 0.0087 mg/l or 3 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). This is defined by the American Industrial Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action." The residential population within a circle radius corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected". The worst-case release scenario at the LBCJMA WWTP Chlorination Facility involves a failure of the two each one ton-containers which could be connected concurrently (a total of 4,000 lb of chlorine). However, one ton cylinder is on at any given time of operation. The offsite consequence analysis for this scenario was performed for the set of conditions pre-defined by EPA, namely release of the entire amount of a gas in 10 minutes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circle with radius corresponding to the toxic endpoint distance. EPA set these condi tions to facilitate the performance of the offsite consequence analysis. EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, temperate of 25: (116:F), and humidity of 50% were used. When analysis of the worst case scenario was performed using the reference table and using the EPA assumptions and considering release of chlorine gas in enclosed space a distance to toxic endpoint of 4.3 miles and an estimate of residential population potentially affected of 132,576 was obtained. The alternative release scenario involves rupture of the flexible connections (pigtails) or pipe possibly due to corrosion. The amount of chlorine released is 4,000 lb, at an average rate over one hour (the duration of the release) of 67 lb/min. Toxic endpoint distance to ERPG-2 levels was obtained. The typical meteorological conditions used were Stability D, wind speed 3 m/s, average air temperature of 25:C, and 50% average humidity. The estimated distances traveled to the toxic endpoints are 1.2 miles for the ERPG-2 and an estimated residential population potentially affected of 11,167 was obtained. Since, chlorine cylinder weighing scale room and chlorine feeding system/chlorinators are located within the rooms enclosure is considered as a passive mitigation system. Actuation of the chorine detector is an active mitigation measure considered. An additional mitigation system, the Lower Bucks County Joint Municipal Authority is planning to convert the existing chlorinators to a vacuum type, with all pressurized chlorine gas piping replaced with vacuum piping. This will reduce significantly the amount of chlorine released in case of pigtail rupture/break or manifold pipe break. The general LBCJMA WWTP accidental release prevention program is based on the following key elements: 7 High level of training of the operators and mechanics 7 Preventive maintenance program 7 Use of state-of-the-art process and safety equipment 7 Use of accurate and eff ective operating procedures, written with the participation of the operators 7 Performance of a hazard review of equipment and procedures 7 Implementation of an auditing and inspection program Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), worn by the mechanics and operators during connection/disconnection of chlorine supply, awareness of the hazardous and toxic properties of chlorine, and presence of chlorine detectors. The facility has an emergency response program, which has been coordinated (reviewed) by the Bristol Township Fire Department and the Bucks County Emergency Planning Committee which is designated as the lead Local Emergency Response Planning Committee (LEPC). This program includes an emergency response decision tree and a notification plan. |