MSD- Coldwater Creek Wastewater Treatment Plant - Executive Summary |
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TABLE OF CONTENTS I. INTRODUCTION PAGE 1 1I. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES PAGE 1 III. PROCESS DESCRIPTION AND REGULATED SUBSTANCES PAGE 1 IV. WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS PAGE 2 IV.1 Worst-case Scenario page 2 IV.2 Alternative Release Scenario page 2 V. GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL-SPECIFIC PREVENTION STEPS PAGE 3 VI. FIVE-YEAR ACCIDENT HISTORY PAGE 3 VII. EMERGENCY RESPONSE PROGRAM PAGE 3 VIII. PLANNED CHANGES TO IMPROVE SAFETY PAGE 3 I. INTRODUCTION This document contains all the information that the MSD Coldwater Creek Treatment Plant (Coldwater) needs in order to meet the requirements of 40 CFR 68 "Risk Management Program" including the executive summary and registration data elements (68.155 through 68.185). II. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Coldwater plant generates methane (digester gas) from its wastewater treatment process. The Code of Federal Regulations (40 CFR 68 ), classifies methane as a flammable gas. The plant adheres to all applicable Federal, state, and local rules and regulations to ensure a safe environment within the plant as well as for the surrounding community. Access to the digester gas system is restricted to certified operators, authorized contractors, and the City of Black Jack fire department (the primary responder in the event of an accidental release). The Coldwater plant is a manned facility. In the event of an accidental release, the methane alarm will sound alerting personnel on site. The primary emergency responder is the Black Jack fire department. Procedures are in place for notification of the Black Jack fire department in the event of an accident. III. PROCESS DESCRIPTION AND REGULATED SUBSTANCES The Coldwater plant in Florissant, Missouri is a wastewater treatment plant. The plant has one regulated substance under 40 CFR 68: methane. Methane is a by-product of the treatment process and is used as a fuel for the plant's power generating system. The North American Industrial Classification System code (NAICS code) for the primary process at this facility is 22132. The process consists of four primary digesters and two secondary digesters and associated piping. Only the primary digesters can be used for digestion (and a small quantity of storage). The secondary digesters with floating covers are used for storage only as they have significant storage capacity. Under anaerobic conditions, the gas generated is called "digester gas" which contains approximately 65% methane and 35% carbon dioxide by volume. Methane (and digester gas) is classified as a flammable gas under 40 CFR 68. The threshold for triggering applicability of 40 CFR 68 is 10,000 pounds. The maximum quantity of digester gas that can be stored in all six digesters at any one time is approximately 15,900 pounds. Since this exceeds the threshold limit, the Coldwater plant is subject to 40 CFR 68 as a Program 2 facility. IV . WORST-CASE AND ALTERNATIVE RELEASE SCENARIOS The system has associated hazards that can potentially affect employees and the general public off-site if there is an accidental release from the system. Although the alternative release scenario is more probable, the US EPA requires that one worst-case and one alternative release scenario be reported for the regulated substance. Described below are the associated hazards and the worst-case and alternative release scenario for this substance. Methane/Digester Gas Methane is a colorless, flammable, non-toxic gas with a sweet, oil-type odor. Digester gas contains hydrogen sulfide and has a characteristic rotten egg odor. Either methane or digester gas can cause asphyxiation by displacing air. IV.1 Worst-case Scenario The worst-case release is defined as the release of the largest quantity of a regulated substance from a vessel or process line failure that results in the greatest distance to endpoint. The release quantity is defi ned as the greatest amount in a single vessel, taking into account administrative controls that limit the maximum quantity. Thus, for the Coldwater plant, the worst-case scenario is the loss of 6,210 pounds of digester gas in ten minutes from one of the two secondary digesters located outside of the administration building. Since the digester gas is 40.4% methane by weight at 100 0F, the quantity of methane released is 2,508 pounds. The methane worst case scenario does not impact any receptors. IV.2 Alternative Release Scenario The alternate release scenario examined involves the release of digester gas from the pressure relief valves on one of the secondary digesters. The digester gas will be released into the air at a rate of 21.4 pounds/minute of methane. The alternative release scenario distance to endpoint was obtained from Equation 6 from the Risk Management Program Guidance for Wastewater Treatment Plants. The distance to endpoint for the alternative scenario is 0.07 m iles. A release duration time of 30 minutes was used in calculating the distance to endpoint. The alternative release scenario goes off-site but does not affect any receptors. V. GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL-SPECIFIC PREVENTION STEPS This facility complies with EPA's Accidental Release Prevention Rule and with all Federal, state and local codes and regulations. The plant conducts frequent inspections to ensure the system is intact and operating correctly. These inspections ensure that the worst-case and alternative scenarios have a minimal chance of occurring. The plant has developed a prevention program for methane to meet the Program 2 requirements of the RMP rule. The prevention program was developed to comply with 40 CFR 68, to ensure the safety of the employees, and to ensure the safety of the surrounding community. The program covers a compilation of safety information, periodic conduct of hazard reviews, operating procedures, training, m aintenance, compliance auditing and incident investigation. VI. FIVE-YEAR ACCIDENT HISTORY The review of this facility's accident history includes the following range of dates: June 22, 1994 - June 21, 1999. There have been no releases at this facility as defined in 40 CFR Part 68.42(a). VII. EMERGENCY RESPONSE PROGRAM The Coldwater plant is not the primary emergency responder in the event of an accidental release but the plant will contact the Black Jack fire department, the primary responder. Procedures are in place for notification of the Black Jack fire department by dialing 911. VIII. PLANNED CHANGES TO IMPROVE SAFETY On April 15, 1999, a hazard review was performed for the digester gas system. The hazard review was conducted using of the "what-if/checklist" procedure. The result of the analysis was a recommendation that an audible high-pressure alarm be installed. No other recommendations were made. |