Reading Area Water Authority - Executive Summary |
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The Reading Area Water Authority's (RAWA) Off-Site Emergency Response Plan involves a unified approach that integrates technologies, procedures, and management practices. This plan details the emergency response policy and is tailored to the facility and emergency response services available in Berks County, Pennsylvania. This emergency response plan has been developed in accordance with the provisions of the Superfund Amendments and Reauthorization Act of 1968/Title III and the Local Emergency Planning Committee for the Emergency Planning District of Berks County. RAWA's Maidencreek Filtration Plant was constructed in 1934 as a municipal water purification plant for the City of Reading and surrounding communities. Raw water is conveyed from Lake Ontelaunee to the filtration plant via a 7 foot diameter concrete conduit. Once the raw water enters the head of the plant, it is put through various phases of treatment, including screening, coagulation, sedimentation, filtration, and di sinfection prior to being pumped into a distribution system. Chlorine and aqueous ammonia (24%), both EPA-regulated substances, are used in combination to form chloramines which are used to disinfect the finished/filtered water. Chlorine is stored on-site in amounts that exceed the regulatory threshold of 2,500 pounds. The maximum on-site inventory of aqueous ammonia is 13,020 pounds, which is belos the regulatory threshold of 20,000 pounds (based on weight of ammonia). However, the general duty clause (Clean Air Act 112(r)(1)) still requires facilities to design and maintain a safe plant, identify hazards and minimize the consequences of hazardous substance releases; therefore, aqueous ammonia has been included in the RMP. The filtration plant has a separate chlorination room that contains chlorine scales, chlorine feed lines, a chlorine evaporator and various safety equipment. The chlorine feeders are located in an adjacent isoloated room with access only from the outside. T he room is provided with positive floor level ventilation. Various monitoring instruments and a computer system are located in the main control building along with additional safety equipment. The amount of chlorine on-line at any given time is two one-ton cylinders. The facility operates 24 hours per day and is always manned by at least two licensed water treatment plant operators. The maximum amount of chlorine that can be stored onsite at any given time consists of twelve one-ton cylinders. This maximum event occurs typically after a delivery from the supplier. The cylinders are stored in an outdoor, three-walled, covered enclosure and are moved in to the chlorine room via an overhead trolley/hoist assembly as needed. In addition, twenty-five 150-lb cylinders are typically delivered to the facility for distribution to RAWA's four remote chlorine stations located in the distribution to RAWA's four remote chlorine stations located in the distribution system. Aqueous ammonia is stored in an outside 7,000 gallon aboveground storage tank (AST). The AST is protected by a dike (16' x 28' x 3') sized to fully contain the volume of the tank. The offsite consequence analysis includes consideration of two chlorine and aqueous ammonia release scenarios, identified as "worst-case release" and "alternative scenario". This worst-case scenario as defined by EPA, states that "the owner or operator shall analyze 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". Atmospheric dispersion modeling has to be performed to determine the distance traveled by the toxic gas and toxic liquid released before its concentration decreases to the "toxic endpoint". The endpoint concentration is defined by the EPA as a concentration that can result in significant public health impacts. The endpoints for toxi c chemicals, as defined in 40 CFR 68.22, are based on the ERPG-2 concentrations developed by the American Industrial Hygiene Association (AIHA). The ERPG-2 level of concern is defined as "the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptons that could impair an individual's ability to take protective action." The toxic endpoint selected by EPA is 3 parts per million (ppm) (0.0087 mg/l) for chlorine and 200 ppm (0.14 mg/l) for aqueous ammonia. EPA's RMPComp program was used to complete the consequence analyses required under the Risk Management Planning Rule. RMPComp was developed by the CAMEO Team at the Office of Response and Restoration, National Ocean Service, NOAA, and the Chemical Emergency Prevention and Preparedness Office of the EPA. This program uses fixed values for certain atmospheric parameters, and does not allow them to be set by the user. This is because the software is intended as a simplified mode, adhering to the EPA's Offsite Consequence Analysis Guidance, that is acceptable for compliance with the RMP Rule. WORST-CASE RELEASE SCENARIO As required by RMP regulations, the worst-case release scenarios for the two regulated substances involve the following; failure of a one-ton cylinder of chlorine over a ten minute period and the instantaneous release of aqueous ammonia (7,000 gallons) into the dike system. In using the RMPComp program for the worst-case scenario for chlorine, a distance to toxic endpoint was established at 1.3 miles (with urban surroundings). When the same modeling was performed for aqueous ammonia, a 10-minute average ERPG-2 yielded 11.9 ppm release rate to outside air. This in turn resulted in a distance to toxic endpoint of 0.1 miles when a quantitiy of 7,000 gallons was released at a liquid temperature of 68 degrees F. The mitigation measures included a diked area of 448 square feet and a dike height of 3 feet. The same conditions of Stability Class F existed. In using the toxic endpoint distance of 1.3 miles (the greater of the two worst-case scenarios), an estimate of a 2,660 residential population potentially was obtained. It must be noted, however, that realistically only the population within an elliptical plume extending downwind of the release point would potentially be affected. ALTERNATIVE RELEASE SCENARIO The rationale for selection of the alternative release scenarios used for both chlorine and aqueous ammonia were based on typical storage and use systems found at water treatment plants. These scenarios were developed by the American Water Works Association (AWWA). The alternative release scenario used for chlorine involves the rupture of the gas feed line connected to two, one-ton chlorine cylinders. The amount of chlorine released was calculated at 23.4 ppm with a duration of 27.1 minutes. Toxic endpoint distance s to ERPG-2 was obtained. Due to urban surroundings in the immediate area, the toxic endpoint was established at 0.1 miles. The following typical meteorological conditions were used: Stability Class D, wind speed 3.0 m/s, average air temperature of 77 degrees F and 63% average humidity. An aqueous ammonia alternative release scenario includes a leak from a line failure or a hole near the bottom of the tank. The amount of aqueous ammonia released over a 10-minute duration was 11,500 pounds. The release rate of the liquid at 68 degrees F was 1,145 lbs/min. The release rate to outside air is 15.1 ppm with an estimated distance to toxic endpoint to be less than 0.1 miles. The existing dike was used as the mitigation measure. The following typical meteorological conditions were used: Stability Class D, winds speed 3.0 m/s, average air temperature of 77 degrees F, and 63% average humidity. The general RAWA emergency response program is based on the following key elements: (1) Hig h level of training of the operators (2) Preventice maintenance program (3) Use of state-of-the-art process and safety equipment (4) Performance of a hazard review of equipment and procedures (5) Implementation of an auditing and inspection program. Chemical-specific prevention steps include the availability of self-contained breathing apparatus (SCBA), which are worn by the operators during connection/disconnection of chlorine supply and the availability of chlorine detectors. Two half face masks with ammonia canisters are also available to the operators whom are trained in the awareness of the hazardous and toxic properties of both chlorine and aqueous ammonia and the proper PPE to be used. Only one accidental release has occurred at this facility. A minor release of aqueous ammonia (approximately two gallons) occurred on June 15, 1994. This spill was immediately contained and did not involve any off-site impacts. From a review of existing records and plant data, it appear s that no accidental releases of chlorine have occurred at this facility in the past five years. The facility has an emergency response program, which has been coordinated and approved by the Berks County Emergency Management Agency, which is a member of the Local Emergency Response Planning Committee (LEPC) of Berks County. This program includes planning and prevention procedures, hazard analysis, internal response capabilities, resources, plan development, and maintenance activities and notification requirements. Recommended actions to improve safety were identified in the Hazard Review completed for the facility. These recommended actions are being evaluated and will be implemented as required. |