Northampton Borough Municipal Authority WTP - Executive Summary |
|
Executive Summary Executive Summary General The Northampton Borough Municipal Authority (NBMA) owns and operates a potable water treatment system and distribution system for the Borough of Northampton, Pennsylvania, and surrounding communities. The water treatment plant located at 5880 Roosevelt Street, Whitehall, PA, 18052 processes up to 6.0 million gallons per day of water drawn from the Lehigh River and Spring Mill Dam to yield potable water. Treatment processes include pretreatment, coagulation, flocculation, sedimentation, filtration and chlorine disinfection. This plan addresses chlorine used in the treatment process. The plant is operated 24 hours per day, all year. The water treatment plant includes a chlorine storage room, which contains up to four one-ton cylinders (8,000 pounds) of chlorine liquified under pressure, a hoist, scale(s), vacuum regulators and a gas detector/alarm unit. A chlorine feed room is located adjacent to this storage room and has a pre, post and spare chlorinator. The chlorination system uses remote-vacuum-actuated feed lines and has vacuum regulators attached directly to the chlorine container gas valves, mitigating against high-pressure gas releases through the chlorinator system. Water treatment operators regularly check the room and its equipment, inventorying the rate of chlorine use and adjusting the feed rate as necessary. Off-Site Consequence Analysis The off-site consequence analysis includes two chlorine release scenarios, one "worst-case" and one "alternative-case." The first scenario is defined by the regulations as the "maximum quantity in the largest vessel" being released "as a gas over ten minutes," due to an unspecified failure. The alternative-case scenario is defined as "more likely to occur than the worst-case scenario." Atmospheric dispersion modeling was performed using the RMP*Comp program distributed by the Chemical Emergency Preparedness and Prevention Office of the EPA. This model determ ined the distance traveled by the chlorine released until its concentration decreases to the"toxic endpoint" selected by EPA of 3 ppm, (0.0087 mg/L,) which is the Emergency Response Planning Guideline Level 2, defined by the American Industrial Hygiene Association 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 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 Northampton Borough Municipal Authority Treatment Plant involves a failure of one chlorine container, or a 2,000 pound release. The off-site consequence analysis was performed under the prescribed EPA conditions of all volume rel eased as gas within a ten minute period, to an ERPG-2 endpoint radius of 3.00 miles according to the RMP*Comp model. Within the 28.3 square-mile area bounded by this circle reside 28475 people who may potentially be affected by the release. The alternative-case scenario chosen involves a leak from a faulty gasket installation between the ton container and the vacuum regulator. The RMP*Comp model was run assuming a 10 minute duration release at 0.5 pounds per minute, which yielded a distance to endpoint of 0.1 miles and an impacted area of twenty acres surrounding the facility. The meteorological conditions used were taken from the Guidance to be stability class D and wind speed of 3.0 m/sec. Approximately 30 people would be affected by this release. Accidental Release Prevention The Northampton Borough Municipal Authority's water treatment plant accidental release prevention program is based upon the following elements: 1. High level of training for the operators. 2. Preventati ve maintenance program for equipment. 3. Use of state-of-the-art process and safety equipment. 4. Use of accurate and effective operating procedures, written with the participation of the operators. 5. Performance of a hazard review of the equipment and procedures. 6. Implementation of an auditing and inspection program. Chemical-specific prevention steps include availability of self-contained breathing apparatus (SCBA), personal protection equipment (PPE), awareness of the hazards and toxic properties of chlorine and the presence of a chlorine gas detector. Five Year Accident History No accidental release of chlorine has occurred at this facility in the past five years. Emergency Response Program The facility has an emergency response program which has been reviewed and coordinated by the Lehigh County Local Emergency Planning Committee (LEPC). This program includes an emergency response decision tree and a notification plan. Emergency response drills will be conducted with the fire companies, and the operation and response procedures will be reviewed and updated on a regular basis. Planned Facilities to Improve Safety Facilities to improve safety (recommended actions) were made following a May 5, 1999, inspection of the disinfection systems by the consulting engineer. These recommendations included additional signage, vent line modifications, high temperature alarm in storage room, egress provisions and ventilation modifications. To comply with local codes, it is also recommended to install a fire suppression system and chlorine scrubber system. |