THOMAS MACKEY WATER TREATMENT PLANT - Executive Summary |
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EPA RISK MANAGEMENT PROGRAM EXECUTIVE SUMMARY The Thomas Mackey Water Treatment Plant produces drinking water for seven cities in Galveston County. The amount of chlorine used at the plant is above the 2000-lb. EPA threshold hazardous level. The owner and operator of the plant is Gulf Coast water Authority, a public water authority created by the State of Texas to provide water to municipalities, industry, and agriculture. Safety is a mission of all employees at GCWA; also, it is GCWA policy to adhere to all applicable safety Federal and state rules and regulations. For these two reasons GCWA has taken precautions to ensure the safe storage and handling of chlorine to minimize employees and the surrounding community to chlorine. CHLORINE: Quantities of chlorine gas above the 2000 lbs. EPA hazardous threshold level are kept at the plant at each of two chlorine processes: Post Filter Chlorination and Chlorine Dioxide Production 7 Post Filter Chlorination: Chlorine is feed t o the filter effluent to sterilize the purified water before sending it to storage. Chlorine feed at this process averages 550 lbs. per day. Two cylinders are kept on-line to provide the 550 lbs. per day, an additional two cylinders are kept as standby on the header to insure continuous sterilization, and 8 cylinders are kept outside the chemical feed building in storage. The total number of cylinders for this process is 12 cylinders (24,000 lbs.). 7 Chlorine Dioxide Production: Chlorine is feed to a chlorine dioxide generator to produce chlorine dioxide. The chlorine dioxide is fed after post chlorine feed to enhance sterilization. Chlorine feed to the chlorine dioxide generator averages 185 lbs./day. One cylinder is kept on line, an additional cylinder is kept hooked up as standby to switch over when the first empty, and a third cylinder is kept at the process for storage. The total number of cylinders on site for this process is three (6,000 lbs. chlorine). OFF SITE CONSEQ UENCES WORST CASE RELEASE SCENARIO The worst case release scenario is the release of the contents of a 2000 lbs. cylinder container over a 10 minute period (rate =200 lbs./min). The toxic end point distance of the release is 1.3 miles. This is the distance from the cylinders that the dissipated cloud must travel to drop to a concentration below a toxic level of 0.087 mg/liter (3 PPM) - a level that nearly all individuals can be exposed for up to one hour without experiencing or developing irreversible or serious health effects or symptoms which could impair an individual's ability to take protective action. The toxic end point distance is based on the EPA's RMP "Guidance for WasteWater Treatment Plants Reference Tables" that is found at http://www.epa.gov/swercepp/pubs/potw/pchap-04.pdf . ENDPOINT BASIS: The toxic end point dispersion distance is based on: 7 chlorine cylinders located at ground level in an urban environment with trees and buildings 7 1.5 meters pe r second wind speed and a F atmosphere stability class 7 25 C (77 f) ambient temperature and a 50% humidity level 7 chlorine gas density heavier than air 7 no building walls considered a release barrier (cylinder loading and storage is outdoors ) ESTIMATED OFFSITE RECEPTORS: The offsite receptors in a circular area with the center of the circle defined as the point of release and the radius is the distance to the endpoint. The types of receptors in the circle includes: 7 Residential population: 1,100 Residential (apartments dwellers and homes) 7 Other Public receptors : Major Commercial Sites 7 Environmental Receptors: No parks, monuments, wildlife sanctuaries ALTERNATIVE RELEASE SCENARIO The alternative case release scenario is a failure of the high pressure transfer header connection between two vessels and the release of chlorine as a result through a 5/16 inch opening at a rate of 240 LB/min , mitigated by building walls down to a rate of 130 lbs./min. The toxic en d point distance of the release is 0.2 miles. This is the distance from the cylinders to where the dissipated cloud concentration drops below the toxic level of 0.087 mg/liter (3 PPM) - a level that nearly all individuals can be exposed for up to one hour without experiencing or developing irreversible or serious health effects or symptoms which could impair an individual's ability to take protective action. The toxic end point distance is based on the EPA's RMP "Guidance for Waste Water Treatment Plants Reference Tables" that is found at http://www.epa.gov/swercepp/pubs/potw/pchap-04.pdf . ENDPOINT BASIS: The toxic end point dispersion distance is based on: 7 chlorine cylinders located at ground level in an urban environment with trees and buildings 7 1.5 meters per second wind speed and a F atmosphere stability class 7 25 C (77 f) ambient temperature and a 50% humidity level 7 chlorine gas density heavier than air 7 building walls provide a release rate barrier factor of 55% ESTIMATED OFFSITE RECEPTORS: The offsite receptors in a circular area with the center of the circle defined as the point of release and the radius is the distance to the endpoint. The types of receptors in the circle includes: 7 Residential population: 20 Residential (apartments dwellers and homes) 7 Other Pupil receptors : Commercial Sites 7 Environmental Receptors: No parks, monuments, wildlife sanctuaries FIVE YEAR ACCIDENT HISTORY There were no accidental chlorine releases the last five years. A blank copy of an incident release form and instructions for filling in the form are found in a file called Chlorine Incident Investigation. All completed Incident Investigation forms the last five years are found in the same file (Chlorine Incident Investigation.doc). ACCIDENT RELEASE PREVENTION PROGRAM PREVENTION PROGRAM DESCRIPTION The elements of the chlorine release prevention program described below applies to two chlorine processes: 1) Post Fil ter Chlorination to the treated water to disinfect the purified water leaving the filters and 2) 2) Chlorine Dioxide Production to enhance disinfect after post chlorinating except: 7 The Post Filter Chlorination Process utilizes two cylinders on-line together and the two cylinders are connected by a common high pressure header (used for the alternative case release scenario). Chlorine Dioxide Production Process utilizes only one cylinder (a high pressure header with another cylinders does not exist). Also the one cylinder is not in a building. 7 The Post filter Chlorination Process maximum inventory is 24,000 (12 one ton cylinders). The Chlorine Dioxide Production maximum inventory is 6,000 lbs. SAFETY INFORMATION The Thomas Mackey Water Treatment Plant was constructed in 1972; however, the Post Filter Chlorine Process facility was refurbished May 1,1999. The Chlorine Dioxide Production Chlorine Process was refurbished in 1991. Facilities and equipment were designed and c onstructed to comply with: Standards of National Electrical Manufacture Association, Recommendations of the Chlorine Institute, Joint Industrial Council, Instrument Society of America, Texas City Fire Codes, and Texas City Building Codes. Chlorine process Safety Information includes safety information on a) chlorine (MSDS) and b) chlorine process feed equipment (cylinders, headers, regulators, feeders,). The last reviews of the Process Safety Information along with recommendations and corrective action dates was conducted 3/31/99 and can be found with the process Safety Information. The next safety review must be within the next five year Risk Management Program Review / Submit. HAZARD REVIEW The major chlorine hazard is a toxic release. Preventive measures taken to mitigate a leak include: gas detection analyzers connected to an alarm system, automatic vacuum loss system shutoff, manual shut off valves, emergency air supply along with employee personnel protective equip ment to permit corrective actions, continuously operated chlorine room purge system, and annual operator & maintenance personnel training. Both the Post Chlorine and Chlorine Dioxide Generator Chlorine Process Hazard Reviews are updated each time the process is changed (revised operator procedures, new equipment,). The last Hazard Review for the Post Chlorine Process was 3/31/99. The last Hazard Review for the Chlorine Dioxide Generator Process was 3/31/99. OPERATING PROCEDURES AND TRAINING Operator Procedures were last reviewed and Operator training was completed 6/11/99. MAINTENANCE PROCEDURES AND TRAINING Maintenance Procedures were last reviewed and Maintenance Personnel Training was last completed 6/7/99. Manufacture recommended maintenance procedures are in a binder labeled "Chlorine Systems" found in the maintenance shop office. Maintenance PM procedures (see: Chlorine PM Checklists) are conduced every 6 months. PREVENTION PROGRAM COMPLIANCE AUDIT At least every three years, an audit of the prevention program is preformed for each covered process. The last two audits with findings are kept on file (below). An audit report (checklist is sufficient) is generated with audit finding / recommendations with responses to each finding / recommendation. At the bottom of the audit check lists, itemize all actions corrective actions recommended as a result of the audit were taken along with the date each action was completed. The last compliance audit occurred June 15,1999. The expected date of completing of all changes resulting from the compliance audit is June 15, 2000. EMMERGENCY RESPONSE PLAN The Thomas Mackey Water Treatment Plant is under the community emergency response plan managed by the Texas City Fire department at 409 643-5700. All accidental releases must be reported to the Texas City Fire Department. The Fire Dept will coordinate with the Local Emergency Planning Committee (LEPC). The emergency response plan was reviewed 5 -31-99. PLANNED CHANGES TO IMPROVE SAFETY Changes planned to be completed by 6/1/2000 to improve safety are: 7 Install Windsocks at both chlorine sites 7 Install a enclosed weather and rodent proof storage cabinet within 30 feet of the chlorine process areas for personal protective equipment, breathing air, leak detection equipment (ammonia and rags) and cylinder Kit B repair kit. 7 Purchase personnel protection equipment (gas tight suit with face shield, shoes and gloves) 7 Install cylinder scales 7 Install doors to enclose the chlorine room. 7 Discontinue parking plant vehicles with in 15 feet of stored cylinders. 7 Implement quarterly system maintenance PM schedule. 7 Review signage and correct as appropriate. 7 Wire Chlorine gas leek detector local alarm to plant computer in the control room and make the alarm a general plant broadcaster alarm. RMP SUBMIT & LETTER OF CERTIFICATION The first RMP program was submitted on a disc June 21, 1999 (postmarked date) along with a l etter of certification. Future submittals must occur: 7 no later than every five years on the anniversary date of the last program postmarked date 7 no later than the date a new regulated substance is present at the facility 7 within 6 months of a change that requires a revised PHA 7 within 6 months of a change that requires a new offsite consequences analyses. Future RMP program submittal postmark dates are: The RMP submit software, instructions on how to fill in the submit program can be acquired at http://www.epa.gov/swercepp/rmp-dev.html or by calling 1(800) 424-9346. http://www.epa.gov/swercepp/pubs/srmp/manual.pdf |