Maryville Water Treatment Plant - Executive Summary |
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Introduction The City of Maryville operates a 2.5-million gallon per day treatment, which will soon be expanded to 5.0-million gallons per day. This Risk Management Plan (RMP) covers the Section 112r regulated substances maintained at the existing Maryville Water Treatment Plant, which will be referred to herein as the Plant. This RMP will be updated when the expansion is brought on line. Plant Description The Plant maintains only one regulated substance on site: chlorine. The maximum chlorine storage is 10,000 pounds, which exceeds the RMP threshold quantity of 2,500 pounds. The storage and management of chlorine is addressed in this RMP. The Plant is located at 3613 E. 1st Street, Maryville, Missouri, which is in a rural area. The surrounding area is mostly open area. The Worst Case Release Scenario The worst case release scenario for chlorine was calculated as the release of a single one-ton cylinder in accordance with the definition provided in the Environmental Protec tion Agency guidance for RMP development. The Plant stores all chlorine cylinders outside, so no passive control systems can be considered for the worst-case release, such as the containment provided by a building. The conditions of the scenario, such as release time and weather status are those provided in the EPA Off-Site Consequence Analysis Guidance. The area of potential impact was determined using RMP*Comp, modeling software developed by the EPA. The results of the Off-Site Consequence Analysis indicated that the chlorine would travel approximately 3.0 miles under the specified weather conditions before dispersing in the atmosphere to a harmless concentration. Within that radius of the Plant, an estimated 6850 persons could potentially be affected. Maps of the area and a list of the types of receptors in the potential impact area are provided in the Off-Site Impact Analysis Section. The list of potential receptors includes: 7 5 schools 7 1 hospital 7 1 prison/correctional facility 7 8 major commercial, office or industrial areas 7 no environmental receptors This type of release would only occur if the valve was broken off the cylinder, or the cylinder was breached. The likelihood of such an incident occurring is minimal. Alternative Release Scenario The alternative release scenario is, by definition, a more likely release scenario than the worst case. The type of system failure selected for the alternative release was the loss of chlorine due to the rupture of both diaphragms in the vacuum regulator. The chlorine would leak from a =-inch opening. The leak would continue until the chlorine detection alarm sounded and the valve on the cylinder could be closed. The operator, or the Maryville Fire Service, would respond to the leak. The time for the response was estimated at 10 minutes. The operator or fire response personnel would enter the chlorine area in protective clothing and close the valve on the leaking cylinder. The results of the Of f-Site Consequence Analysis using RMP*Comp, indicated that the chlorine would travel approximately 1.2 miles under the specified weather conditions in order to disperse in the atmosphere to a harmless concentration. Within that radius of the Plant, an estimated 100 persons could potentially be affected. Maps of the area and a list of the types of receptors in the potential impact area are provided in the Off-Site Impact Analysis Section. Process Hazard Assessment A process hazard assessment was performed on the chlorine system beginning with cylinder unloading and ending with the chlorine in solution. A checklist and a modified "What if" analysis were used. General questions regarding the storage and use areas as well as protocols associated with the management of the chlorination system were answered. A copy of that checklist is included in this plan. Following the checklist, each valve, line, and piece of equipment in the system was assessed from the cylinder to point of chlor ine injection using a system flow diagram. The valves and other points in the system where chlorine could be released are numbered on the flow diagram. The assessment is formatted in accordance with those numbers. Compliance with code requirements, potential failures, maintenance and inspection concerns, and standard operating procedures were reviewed for each point in the system. Comments are summarized in the Process Hazard Assessment section. Prevention System The Plant has an operation, maintenance and inspection system designed to review each element of the chlorination system routinely. There are Operation and Maintenance manuals for each major piece of equipment, and personnel receive significant training before being allowed to work on the system. At the beginning and end of the daily operating period, and as each cylinder is changed, the valves and piping are tested for leaks. There are standard operating procedures (SOPs) for startup, shutdown, normal operation, and em ergency operation. The SOPs are written and posted in the chlorine process area. Personnel are trained routinely on safety concerns and general operation procedures as well as emergency procedures. All tanks are stored outside the building. They are shielded with a canopy to prevent over-heating. Emergency Response Plan The water plant operator is trained to use the chlorine "B" kit to make repairs in the event of a chlorine leak. Large leaks, however, will be managed by the Maryville Fire Department. The Plant has an agreement with the Fire Department, which is included in this plan. A complete copy of the Emergency Response Plan is also included. Accident History The Plant has had no chlorine releases in the past five years. |