JOHN W. PRAY WATER TREATMENT PLANT - Executive Summary |
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City of Fort Dodge Risk Management Program For Hazardous Chlorine Gas BACKGROUND INFORMATION: This plan has been developed to help the City of Fort Dodge comply with the United States Environmental Protection Agency's (EPA) Risk Management Program (RMP) regulations, and the Occupational Safety and Health Administration's (OSHA) Process Safety Management Standard. Both have regulations addressing chlorine gas in quantities greater than 1500 pounds. The City of Fort Dodge is an operator of a stationary source subject to the Risk Management Program Rule. For this reason, we are submitting this Risk Management Program to include all information required in 68.115 through 68.185 for all covered processes. As determined by 68.115, the presence of chlorine is above the threshold level for a regulated substance. EXECUTIVE SUMMARY The primary activity at the John W. Pray Water Treatment Plant is to treat and distribute drinking water to the residences and businesses in Fort Dodge, Iowa. To do that, it is imperative that a disinfection process be administered to maintain quality drinking water. This is accomplished through the use of chlorine gas. Source Identification: John W. Pray Water Treatment Plant 600 Phinney Park Drive Fort Dodge, Iowa 50501 Latitude: 42o 30' 29" Longitude: -94o 12' 13" Owner/Operator: City of Fort Dodge 819 1st Avenue South Fort Dodge, Iowa 50501 Name and Title of Person Responsible: John Horrell Water Plant Superintendent 515/576-6101 515/573-7353 24 hr. phone number Emergency Contact: Name: John Horrell Title: Water Plant Superintendent Phone: 515/573-7353 24 Hour Phone: 515/573-7353 Chemical Name: Hazardous Chemical: Chlorine CAS Number: 7782-50-5 Maximum inventory: 63,000 lb. NAICS Code: 22131 Program Level: 3 EPA Identifier: _______________ Number of Full-time employees: 7 Covered By: OSHA PSM ( X ) EPCRA Section 302 ( X ) Last Safety Inspection: __________________ 1.0 HAZARD ASSESSMENT 1.1 Worst-Case Release Scenario Analysis 1.1.1 Mandatory Input: The greatest amount of chlorine held in any one vessel is 2,000 pounds of liquid chlorine under pressure. Administrative controls that limit this amount from being released include manifolding of the cylinders and use of chlorinators that work on a vacuum system. Once the vacuum has been lost, the chlorine is not permitted to feed from the cylinder unless there is a leak on the cylinder itself from a cylinder rupture, from a melting fuse plug, or from a leaking valve. The worst case scenario is anticipated to occur from a release of a 1- ton chlorine cylinder. Chlorine is a gas at ambient temperature. It is handled as a liquid under its own pressure in the cylinder and as a gas in all other parts of the chlorinating system (from the cylinder to injection in the finished water). ALL DATA UTILIZED IN DET ERMINING WORST-CASE SCENARIO WAS OBTAINED UTILIZING THE EPA RISK MANAGEMENT PLAN OFFSITE CONSEQUENCE ANALYSIS GUIDANCE DOCUMENT. From information obtained from the Chlorine Institute and from review of past release scenarios from the EPA Guidance Document, a Mitigated Release of Gas formula was utilized. QR = (QS divided by 10) multiplied by 0.55 Where: QR = release rate (pounds per minute) QS = quantity released (pounds) Chlorine gas is handled inside of a storage room at the John W. Pray Water Treatment Plant, so a reduction in the release rate to the outside atmosphere was taken since the release is in an enclosure. For estimation purposes, it is anticipated a worst case scenario would be from shearing a tank valve. This would allow chlorine gas to release uncontrolled through the opening. In 10 minutes approximately 2,000 pounds of chlorine gas would be released or 200 pounds of chlorine gas per minute into the enclosure. Wind speed of 1.5 meters per seco nd and an F stability class are being utilized for determination of this worst case scenario. 1.1.2 Mass Released in the Worst-Case Release Scenario: The mass M (pounds) of chlorine is all of the contents of a one-ton cylinder and the attached piping. The John W. Pray Water Treatment Plant has a maximum of 4, 1-ton chlorine cylinders onsite at any one time. A limiting factor of administrative controls is included in the mass release calculations. Realistically, the tank valve of the other cylinder that is manifolded with the one in use is closed until the active tank has emptied its contents. Then a full tank replaces the empty one, is isolated by its tank valve, and the tank previously attached to the manifold is opened, tested and used. 1.1.3 Distance To Toxic Endpoint: The toxic end point of chlorine was determined by utilizing Appendix A Table of Toxic Endpoints for chlorine. This was listed as 0.0087 mg/L. Since chlorine is a gas at atmospheric temperature and will gener ate and accumulate as a dense cloud and is located in an urban topography--table #7 was selected to determine the evacuation distance. Release duration was chosen for 10 minutes. The Toxic End Point for chlorine gas is 4.3 miles according to Reference Table #7. The population area surrounding the Water Plant consists primarily of heavy residential to the north and west, and light industrial to the south. A unique factor in the determination of exposed population would be greatly controlled by the topography of the adjacent land. The water plant sits in a valley along the Des Moines River and is flanked by very high ridges that run parallel to the river from north to south. The east and west exposures form a very narrow band, minimizing much of the population of the City. A 1-mile radius would be classified as 90% residential. 1.1.4 Passive Mitigation: Credit is being taken for passive mitigation at the John W. Pray Water Treatment Plant since the chlorine cylinders are s tored in a separate room in the plant. During a chlorine release, it is anticipated the worst-case scenario would be a complete cylinder release into the room. The release would then be mitigated by the room it is stored in and the rest of the building. 1.2 Alternative Release Scenario: An alternative release scenario chosen for compliance with this RMP is TANK PIGTAIL LINE FAILURE. 1.2.1 Mandatory Inputs: Because cylinder changouts occur approximately every fourteen days, the potential for a chlorine release is most likely to occur during this process. Although the release rate is not likely to be sufficient to reach complete release of a 1-ton chlorine cylinder in 10 minutes, it has the greatest potential for chlorine release during normal operations at the water plant. It will likely not propagate offsite. An average wind speed of 3m/s and D stability class has been chosen for this alternative release scenario. 1.2.2 Choice of Alternative Scenario: Although there may be other choices for a potential alternative scenario for chlorine gas release, they will likely not be large enough to exceed the toxic end point offsite. Other alternative releases would be from: Leaking seals; leaking valves Delivery truck hoist failure and damage to the cylinder Process piping releases from failures at flanges, joints, welds, & valves. Process vessel releases due to cracks, seal failure, drain, or bleed failure. Failure of chlorine injector equipment. Release of chlorine through a melted fuse plug during a fire. As mentioned above, the alternative release scenario is anticipated to "most likely" occur from normal operational procedures when handling chlorine changeover. A release rate of less than 50 pounds per minute is anticipated for this type of release. The Toxic End Point for chlorine gas is 0.62 miles according to Reference Table #16 for an Alternative Release Scenario at the John W. Pray Water Treatment Plant, using Appendix D part 6 and enclosure mit igation factor . 1.3 Presentation of Results: See the attached maps for visual description of the affected areas for the WORST-CASE SCENARIO and the ALTERNATIVE RELEASE SCENARIO. It depicts the radius to which a vapor cloud might extend. As mentioned earlier, the affected area would be restricted by the topography of the land to a long narrow band either upriver or downstream. 1.4 Defining Offsite ImpactsPopulations: The population is estimated at 30,000 for the WORST-CASE SCENARIO. This includes: (X) schools (X) residences (X) hospitals; clinics (X) prisons (X) public recreation areas (X) commercial development areas (X) industrial development areas The population is estimated at 1,700 for the ALTERNATIVE RELEASE SCENARIO This includes: (X) residences (X) public recreation areas (X) industrial development areas 1.5 Defining Offsite ImpactsEnvironment: This includes: (X) parks 1.6 Documentation: See section 1.1 which identifies assumptions, parameters, and rationale used for determining WORST-CASE SCENARIOS and section 1.2 for the ALTERNATIVE SCENARIOS. 1.7 Review and Update: The offsite consequences for a chlorine release at the John W. Pray Water Treatment Plant must be reviewed and updated at least once by 2003. If changes occur in our processes, quantities stored or handled change significantly, or any other aspect of our chlorine equipment or processes change that increase or decrease the worst-case scenario toxic endpoint, a revised analysis must be done and included in this Risk Management Plan. 1.8 Five-Year Accident History: There have been no accidental releases of chlorine at the John W. Pray Water Treatment Plant that resulted in death, injuries, or property damage either on-site or off-site, nor any releases that required evacuation during the last 5 years (1993 1998). Should a release occur in the fu ture, the following information must be recorded in this plan: Date, time and approximate duration of release Chemical(s) released Estimated quantity released in pounds Type of release event and its source Weather conditions Onsite impacts Known offsite impacts Initiating event and contributing factors Whether offsite responders were notified Operational or process changes that resulted from investigation of the release 2.0 PREVENTION PROGRAM & EMERGENCY RESPONSE PLAN If the requirements of the OSHA regulation are met (PSM), the prevention provisions of this EPA Risk Management Plan will also be satisfied because EPA has prepared the RMP rules to avoid duplication of effort by owners and operators. However, the owner must be prepared to demonstrate a management system is in place to ensure continued fulfillment of prevention requirements. See the John W. Pray Water Treatment Plant PROCESS SAFETY MANAGEMENT PROGRAM for in-depth review of the items outlined below: 2.5.1 Maintenanc e 2.5.2 Process Safety Information 2.5.3 Process Hazard Analysis 2.5.4 Operating Procedures (SOP's) 2.5.5 Training 2.5.6 Management of Change 2.5.7 Pre-Startup Review 2.5.8 Compliance Audits 2.5.9 Accident Investigation 2.5.10 Employee Participation Plan 2.5.11 Hot Work Permits 2.5.12 Contractors 2.6 Emergency Response Program: For specific details on emergency response procedures, refer to the John W. Pray Water Treatment Plant Emergency Response Plan for chemical spills. Listed below are considerations for our written Emergency Response Plan. These are to be evaluated and updated on an annual basis to keep all emergency response activities current. Questions: Are details worked out with emergency responders through the local LEPC? Are there procedures for informing the public and local authorities? Are there procedures for protecting Water Plant employees and minimizing offsite consequences? Is there organization, assigned responsibilities, and training of responsi ble persons? Any internal alarms? Are there evacuation procedures, emergency response training and drills? Any emergency valve closures and equipment shutdown procedures? Any containment of releases? Any fixed fire protection equipment? Protective gear available; training in its use? Is there coordination of local emergency responders? Any provisions for communication? Any shelter in place and/or offsite evacuation? Any drills and critiques? Any spill cleanup; hazmat training? |