City of Elgin - Riverside facility - Executive Summary |
|
FACILITY BACKGROUND The City of Elgin Water Department stores chlorine and ammonia (both regulated toxic substances) in aboveground storage tanks (ASTs) at their Riverside facility. According to the RMP rule codified in 40 CFR 68 and clarifications to the rule published in the Federal Register, ammonia has a listed threshold concentrations (20% or greater) for applicability in the rule. If a facility stores this substance in solution and the concentration of the substance is less than the listed concentration, a facility does not need to complete an RMP submittal to cover this compounds. However, if a facility stores ammonia above its listed concentration, that facility must determine the weight of the substance in solution to determine whether the threshold quantity (TQ) is exceeded. It should be noted that only the quantity of the regulated substance present is considered and not the entire weight of the solution. If that quantity is greater than the threshold, the process is c overed. For example, aqueous ammonia is covered at concentrations above 20 percent, with a TQ of 20,000 pounds. If the solution is 29 percent ammonia, a facility would need 80,000 pounds of the solution to meet the TQ; if the solution is 44 percent ammonia, a facility would need 45,455 pounds to meet the TQ (quantity of mixture x percentage of regulated substance = quantity of regulated substance). This interpretation is marked in the Federal Register (Vol. 62, No. 164, page 45135 dated August 25, 1997). Currently, Elgin stores a maximum of 7,500 gallons of the ammonia solution that is 29 percent (29%) ammonia (2,175 gallons of ammonia contained in solution). In accordance with the interpretation of the rule, 20,000 pounds of ammonia would need to be stored to meet the TQ. 2,175 gallons of ammonia is equal to approximately 16,334 pounds of ammonia. Therefore, Elgin does not exceed the 20,000-pound threshold, and does not need to prepare an RMP submittal to cover ammonia. Elgin does, however, store chlorine at quantities greater than the adjusted threshold and is therefore, required to prepare an RMP for the Riverside facility. The Riverside facility does not qualify as a Program 3 facility, because its SIC code (5169 - SIC Designation) is not specified under 40 CFR 68.10(d)(1), and because Riverside's and chlorine storage is not subject to OSHA's PSM standard or located in close proximity (co-located) to other vessels containing another OSHA PSM-regulated substance. However, Riverside's worst-case accidental release endpoints do extend beyond the Riverside property, and would affect the surrounding public receptors, thereby resulting in Riverside being a Program 2 facility. As designated by the applicability requirements of 40 CFR 68.10, the Riverside facility in Elgin, Illinois is regulated under the Program 2 eligibility requirements of 40 CFR 68.12(c). Under these requirements, the following RMP summarizes the Program 2 management requirements for th e Riverside facility. It should be noted that, as required in 40 CFR 68.190(b), Elgin shall revise and update this RMP at least every five (5) years after its initial submission or most recent update, whichever is later. WORST-CASE RELEASE SCENARIO Chlorine The following is the worst-case release scenario analysis for chlorine at the Riverside facility in Elgin, Illinois. 7 The worst-case release scenario considers the potential failure of fourteen (14) 2,000 pound cylinders, resulting in a toxic chemical spill. A computer-based version (i.e., US EPA's RMP*Comp, version 1.06) of the methodology presented in US EPA's RMP Offsite Consequence Analysis Guidance (US EPA, May 24, 1996) was used to complete the worst-case release scenario modeling analysis. Utilizing RMP*Comp, the distance to the toxic endpoint was determined to be 3.8 miles. The affected public receptors under this worst-case release scenario include: private residences; major commercial, office, and industrial faci lities, schools, hospitals, nursing homes, and daycare centers. The affected environmental receptor under this worst-case release scenario is a forest preserve. The total residential population within this 3.8-mile radius is approximately 90,271, which was estimated based on data provided by the U.S. Census Bureau. ALTERNATIVE RELEASE SCENARIOS Chlorine The following alternative release scenarios were identified at the Riverside facility: 7 Process piping releases from failures at flanges, joints, welds, valves and valve seals, and drains or bleeds; 7 Process vessel or pump releases due to cracks, seal failure, drain bleed, or plug failure; 7 Vessel overfilling and spill, or overpressurization and venting through relief valves or rupture disks; and, 7 Shipping container mishandling and breakage or puncturing leading to a spill The following is the alternative release scenario analysis for chlorine stored at the Riverside facility in Elgin, Illinois. 7 Alternative release scena rio considers the potential release of chlorine contained in one-2,000 pound cylinder (due to a 0.05 square inch rupture of the cylinder), resulting in a toxic chemical spill. 7 This scenario assumes an initial release rate of 157 pounds per minute, that the release occurs over a 30-minute period, and a 99% efficient scrubber system capable of removing approximately 2,000 pounds of chlorine is in place, reducing the actual release rate to the atmosphere to 1.57 pounds per minute. 7 Therefore, this alternative release scenario modeled the release of a total of approximately 47 pounds of chlorine. Utilizing RMP*Comp, the distance to the toxic endpoint for this alternative release scenario was determined to be <0.1 miles. The affected public receptors under this alternative release scenario include: private residences and a school. The total residential population within this <0.1-mile radius is approximately 94, which was estimated based on data provided by the U.S. Census Bureau. This facility complies with all applicable state and local codes and regulations. The chlorine system is designed, installed, and maintained in accordance with all applicable industry standards and state laws. Based on facility records and interviews with Riverside personnel, no accidental releases of the covered chlorine storage processes has occurred at the Riverside facility in Elgin, Illinois over the past five (5) years. An accidental release from a covered process is one which results in deaths, injuries, or significant property damage on-site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage (40 CFR 68.42). Elgin has coordinated response actions with the local and fire department (City of Elgin Fire Department) in the event of a chlorine release. In the event of an accidental release, Elgin employees will respond to the emergency themselves in accordance with Elgin's written emergency response plan. If there is a minor leak that is easily controlled, Elgin's employees are instructed to repair the leak immediately and report the leak to their supervisor. If the leak is a major emergency, the person in charge will assign someone to contact the Elgin Fire Department and the supervisor if not on the scene. If chlorine is entering the building, a chlorine emergency will be announced over the intercom and an evacuation will take place. The City of Elgin Riverside Water Treatment Plant is equipped with a PurafilR emergency chlorine scrubber system, Model FOC1. This emergency gas scrubber is designed to meet or exceed the requirements of the 1997 Uniform Fire Code, Section 80. The scrubber is sized such that the total quantity of media is more than sufficient to remove the entire contents of one overfilled one-ton cylinder of chlorine. The emergency chlorine scrubber system is monitored by a computerized control system. A chlorine sensor is located within the chlorine storage and feed rooms. If the chlorine concentration inside the chlorine storage or feed rooms reaches 1 part per million (ppm) the system sounds an audible alarm and a yellow flashing light as well as notifies the control room via the computer system. Upon activation of the alarm, the system will start the scrubber fan to remove the air from the room through an exhaust air duct to the emergency scrubber. In addition, the power roof ventilators and the make-up air unit are shut down to seal the chlorine storage and feed rooms to contain the leak. Chlorine is removed from the exhaust air as it passes through the scrubber by chemical neutralization in the media beds where chemically impregnated media will absorb and react with chlorine from the air and produce a stable salt. The facility plans to continue the employee training program and update the Emergency Response Plan where appropriate and in accordance with applicable regulations. |