The Section & Dutton Water System - Executive Summary |
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EXECUTIVE SUMMARY The Section/Dutton Water System Risk Management Plan (RMP) for Safe Chlorine Handling (Plan) integrates technologies, procedures, and management practices to monitor potential chlorine hazards and to minimize the risk of accidental chlorine releases. All applicable requirements of 40 Code of Federal Regulations (CFR) 68.170 are addressed in the Plan, including employee safety, public health, and response agency interaction. The Section/Dutton Water Treatment Plant (WTP) uses gaseous chlorine to disinfect raw water pumped from Gunthersville Lake (Tennessee River). The facility supplies water to residents in the towns of Section, Alabama; Dutton, Alabama; and outlying areas in Jackson County and Dekalb County, Alabama. The WTP chlorination process includes two 1-ton chlorine cylinders, chlorination equipment, an instrument room for process control, electrical equipment, and process-specific safety equipment. A Process Flow Diagram is located in Attachment 1. Raw water is pumped from Gunthersville Lake through three water intakes. The water is pumped to the plant through two 10-inch lines which combine into one 14-inch line prior to chlorination. Two 1-ton cylinders connected to a common header provide chlorination. The chlorinated water is flocculated, filtered, and eventually pumped to the distribution system. Only one cylinder delivers chlorine to the water at a time. When a cylinder is empty, manual valves are turned to switch cylinders. The empty cylinder is then replaced by a spare which is stored at the plant. Accidental release modeling was performed for the area surrounding the WTP to determine potential consequences associated with operating failures resulting in an accidental chlorine release. The "worst-case" scenario, as defined by the Environmental Protection Agency (EPA), states that "the owner or operator shall assume that the...maximum quantity in the largest vessel...is released as a gas over 10 minutes." The "alt ernative scenario" is defined as "more likely to occur than the worst-case release scenario." For both cases, atmospheric dispersion modeling was the basis for determining the distance traveled by the chlorine release before its concentration decreases to a theoretical toxic endpoint. The toxic endpoint is 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 life-threatening health effects." The residential population within a perimeter corresponding to the toxic endpoint distance was defined to estimate the population potentially affected. The worst-case release scenario for the Section/Dutton WTP involves a failure of two 1-ton cylinders, yielding a cumulative release of 4,000 pounds of chlorine. Atmospheric dispersion modeling for this unlikely scenario was performed using the EPA guidance document, Risk Managemen t Program Guidance for Wastewater Treatment Plants, producing a distance to toxic endpoint of 1.9 miles. The alternative release (more likely) scenario for the chlorination process involves the mechanical failure of one flexible manifold connection allowing the accidental release of one 1-ton cylinder of chlorine within the storage building. Alternate release modeling per EPA guidance predicts a more likely distance of a 0.2-mile distance to toxic endpoint under normal atmospheric conditions. Within these perimeters, the public and environmental receptors were identified. In support of the probability that a worst-case accidental release will not occur at the Section/Dutton WTP, a review of process history indicates that no reportable accidental releases (greater than 10 pounds) have occurred within the past five years at the facility. The Section/Dutton Water System Risk Management Program includes the following key elements to mitigate the effects or to eliminate the possibility of chlorine release hazards: ? Operator training ? Preventive maintenance program ? Process specific safety equipment ? Safe and effective standard operating procedures ? Hazard review of equipment and procedures ? Auditing and inspection programs The Section/Dutton Water System has a contingency plan which has been coordinated with the Jackson County Emergency Management Agency and the Scottsboro Fire Department. Emergency response drills, drill evaluations, and facility tours are conducted annually, at which time emergency operation and response procedures are also reviewed. The Section/Dutton Water System takes a proactive approach to risk management and emergency response. These preventive measures provide for effective procedures for the safe handling of and timely emergency response to potential chlorine release hazards. |