Hampton Wastewater Treatment Plant - Executive Summary |
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Executive Summary I. The Town of Hampton Department of Public Utilities owns and operates a Wastewater Treatment Plant on Saluda Street within the Town of Hampton limits. The facility is committed to providing Town employees a safe working environment. To ensure this standard, the Town has established safe working practices, standard operating procedures, and accident prevention programs. Management is dedicated to training employees on proper operating procedures, emergency response, and equipment use. To prevent accidental releases of chemicals, the Town follows all applicable sections of the United States Environmental Protection Agency (EPA) Prevention Program. The Town has enlisted the help of the Hampton Fire Department for emergency response to comply with the EPA Emergency Response Program requirements. II. The Town of Hampton Wastewater Treatment Plant treats domestic and industrial wastewater from the Town of Hampton and the Town of Varnville with a capacity of 2.0 m illion gallons per day. The plant consists of a mechanically cleaned bar screen, five aeration basins, filter beds, and a chlorine contact chamber and post aeration basin. The chlorination system, installed at the plant to disinfect the effluent flow before discharging the treated wastewater into Sanders Branch, is housed in stand alone buildings where the chlorinators, safety equipment and instrumentation are located. The chlorine containers are stored in one-ton cylinders liquefied under pressure outside the building under a separate cover. The maximum quantity of chlorine on site is contained in three cylinders totaling 6,000-pounds. III. For the Process Hazard Analysis, two release scenarios, a "worst-case release" and "alternate release scenario", were evaluated for impact on the plant and its surroundings. The worst-case release, as defined by EPA, is the "greater of the following: (1) For substances in a vessel, the greatest amount held in a single vessel, taking into accou nt administrative controls that limit the maximum quantity; or (2) For substances in pipes, the greatest amount in a pipe, taking into account administrative controls that limit the maximum quantity as a liquid under pressure, the owner or operator shall assume that the quantity in the vessel or pipe is released as a gas over 10 minutes." The alternative scenario is one "more likely to occur than the worst-case release scenario". The worst-case scenario for the Hampton Wastewater Treatment Plant evaluated the release of 2,000 pounds of chlorine as a gas within a ten-minute time span. The release was modeled using the EPA modeling tool, RMP*Comp to determine the distance to toxic endpoint. The distance to toxic endpoint is the distance the vapor cloud will travel before the maximum airborne concentration reaches a level that nearly all individuals can be exposed for up to one-hour without experiencing or developing irreversible or other serious health effects. For the chlorin e system at the wastewater treatment plant, the release of one ton-cylinder (2,000 pounds) would travel 2.2 miles before reaching its toxic endpoint. This distance accounts for the EPA-mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec, highest maximum daily temperature of 116:F and average humidity of 65%. This worst case release would affect approximately 4,000 people, a school, hospital, prison, and industrial/commercial areas as well as a river and creek for environmental receptors. The alternative release scenario involves a vapor release from a tubing failure, bad connection or valve failure resulting in the release of liquid through the 5/16-inch diameter valve body. The release was modeled using AWWA's "Compliance Guidance and Model Risk Management Program for Water Treatment Plants". The release accounted for a wind speeds of 3.0 m/sec, and Stability Class D in a rural environment. The release resulted in a distance to toxic endpoint of 0.5 6 miles. Approximately 2200 people and the environmental receptors above would be affected by this alternative release. No passive mitigation has been considered at the wastewater treatment plant. The installation of chlorine detectors and alarms in conjunction with a trained emergency response team has prepared the Town of Hampton for a chemical release. In the event of a release, employees are trained to assist the response team with area evacuations while the response team attempts to contain the situation. Emergency Repair Kits for the chlorine cylinders are on hand to control or stop a release. IV. The Department of Public Works follows the EPA guidelines for Risk Management and the guidelines established by OSHA for Process Safety Management. The two codes require the Town to evaluate the on and off site risks associated with a highly hazardous chemical and ensure that proper precautions and plans are implemented to minimize the impact of such release. The Town complet ed a Process Hazard Analysis to review the causes and effects of a chemical release. The Town of Hampton developed a preventative maintenance program to keep the chlorine equipment in optimum condition. Any equipment not in proper working order is immediately evaluated for repair or replacement. In addition to a preventative maintenance program, the Town has established standard operating procedures in conjunction with the Chlorine Institute and manufacturer's recommendations. Employees are required to follow the standard procedures at the plant, especially near a highly hazardous chemical area. All employees are trained prior to exposure to equipment and provided refresher training at least every three years. Chemical awareness is discussed both in training and during monthly safety meetings where employees can discuss any hazards or potential hazards of the chlorine system. Chemical specific prevention steps include the installation of the gas monitors and alarm system. Self -contained breathing apparatus, gloves, goggles and aprons are available for employees for protection against a chlorine leak. V. No accidental releases of chlorine have occurred at this facility within the last five years. VI. The Wastewater Treatment Plant is covered under the community emergency response program. The Fire Department, which is a member of the Local Emergency Planning Committee (LEPC), is qualified to handle a chlorine leak or spill at the wastewater treatment plant. Wastewater treatment plant employees are trained on proper emergency response during the employee training sessions. VII. During the Process Hazard Analysis, the Town of Hampton discussed the installation of secured entrances and exits to the wastewater treatment plant, the installation of pipe bollards around the chlorine cylinders, and the posting of "No Hot Work" signs around the chlorine area. The plant however is located in a rural area and the cylinders are located away from vehicular traffic, so these items were determined to be unnecessary at this time. The Town did decide to provide a system for permitting hot work at the wastewater treatment plant and update the Fire Department's Emergency Response Training for highly hazardous chemicals as a result of the PHA. These recommendations will be implemented to ensure a consistent safe record at the wastewater treatment plant. |