Robert A. Weese Water Filtration Plant - Executive Summary
1. RMP Executive Summary |
Chemicals are widely used in industry, in the home, in the environment. They are transported on roads, water, and railways. We at the Robert A. Weese Water Filtration Plant (Weese WFP) use chemicals, too. For example, we use chlorine and ammonia to disinfect our water supply to provide a safe drinking water to our customers. Storing large qualities of chlorine and ammonia can be a hazard. We take our safety obligations in storing and using these chemicals as seriously as we take providing the public safe disinfected water. The following document describes what could happen if there were to be an accident, the steps we take every day to ensure safety, and what to do in event of an emergency.
1.2 Accidental Release Prevention and Emergency Response Policies
The City of Oceanside and the Weese WFP accidental release prevention policy involves a unified approach that integrates proven technology, staff training on operation and mainte
nance practices, and tested management system practices. All applicable procedures of the State of California and U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures.
This document complies with the EPA Risk Management Program, under Section 112 (r) of the Clean Air Act (CAA) Amendments of 1990, 40 Code of Federal Regulations (CFR) Part 68 and the California Accidental Release Prevention (CalARP) Program under California Code of Regulations (CCF) Title 19, Division 2, Chapter 4.5. Weese WFP has two chlorination systems that use chlorine gas fed from liquid chlorine containers and an aqueous ammonia system that provides a small amount of ammonia in the water to limit the formation of possible harmful disinfection by-products. This document summarizes our existing health and safety programs, our internal response, procedures, and ongoing actions that are designed
to prevent or minimize impacts of accidental releases of chlorine or ammonia to the environment. Weese WFP has prepared an emergency action plan to handle any potential accidental releases. This plan will be reviewed by the San Diego County Hazardous Material Management Division (HMMD), which is a member of the Local Emergency Response Planning Committee (LEPC). To date, we have an excellent record in preventing accidents from occurring.
1.3 General Facility and Regulated Substances Information
Weese WFP is a water treatment plant located at 3885 Silverleaf Lane in Vista, California in rural San Diego County. Owned and operated by the City of Oceanside, consists of a 25-million-gallon-per-day (mgd) water filtration plant. The filtration plant finishes raw water that is supplied by either the Metropolitan Water District of Southern California or the State Project.
The processes at Weese WFP include:
7 Flash mixing
The facility currently stores chlorine and aqueous ammonia (24 percent), both regulated toxic substances under RMP and CalARP. Chlorine is used in two separate processes. The primary use of chlorine is chlorination of the plant effluent in the Chlorine Contact Tank. The plant also uses chlorine in 150-pound cylinders, located at the backwash sludge pump station, to inject chlorine into the backwash sludge basins. In both processes, gaseous chlorine is drawn from the storage vessel as a gas and injected. Prior to discharging the treated water into the distribution system, aqueous ammonia is injected into the chlorinated water to convert the residual chlorine to chloramines.
Chlorine is stored in 11 1-ton and three 150-pound cylindrical storage containers in the chlorine building, where the primary chlorine process is located. This chlorine storage exceeds the listed threshold quantities in the RMP and CalARP Rules. The 150-pound cylinder of chlorine located at the backwash slud
ge pump station, exceeds only the CalARP threshold of 100 pounds.
1.4 Offsite Consequence Analysis Results
The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case" and "alternative" release scenarios. The worst-case scenario requires that that a release of the entire contents of the single largest vessel or pipe be evaluated for offsite impacts from chlorine and ammonia. Only passive or administrative controls are allowed under the worst case scenario to reduce off-site impacts. The worst case scenario for Weese WFP is the rupture of a chlorine storage container with a maximum capacity of 1 ton, resulting in a release of 2,000 pounds of chlorine over a 10-minute duration. In practice this type of total release of a container would unlikely occur during the lifetime of the plant.
The released liquid is assumed to quickly volatilize and to disperse as a vapor cloud. The distance to the toxic endpoint was estimated using the Dense
Gas Air Dispersion (DEGADIS 3.0.3) model for chlorine. The toxic endpoint was conservatively set by EPA to ensure public notification and local emergency response planning takes into account the greatest possible impacted area surrounding the release point. The toxic endpoint selected by EPA and CalARP was 3 ppm for chlorine. In addition, all required EPA-model input parameters where included in completing this activity, including conservative meteorological conditions - a very stable atmosphere (F stability class), wind speed of 1.5 meters per second, highest daily maximum temperature (110 degrees F), and average humidity (51 percent). Results of the dispersion modeling analysis for this worst-case release scenario indicate that there will be an offsite impact.
The alternative release scenario is more likely to occur than the worst-case release scenario. Unlike the worst-case release scenario, active controls can be applied to minimize the leak or impacts. Active controls consi
st of mechanical, electrical, or human input. The alternative release scenario for chlorine consisted of a leaking gas chlorine valve or gasket. This scenario was selected because it was ranked with a likelihood of possibility in the process hazard analysis and because similar accidents have been reported to EPA (Risk Management Program for Wastewater Treatment Plants, EPA 550-B-98-010, October 27, 1998). Results of the chlorine alternative release scenario analysis indicated that there will be an offsite impact. The alternative release scenario for aqueous ammonia was a tank, site glass, valve, or PVC piping failure and a release to the containment area. It was assumed that the spill would be 100 gallons, which would cover the containment area to a depth of at least 1 centimeter. The distance to the toxic endpoint for the alternative ammonia release scenario is 134 feet.
1.5 Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps
WFP is in compliance with Federal and State Process Safety Management (PSM) requirements. Chemical-specific prevention steps include availability of self-contained escape breathing apparatus, worn by the operators during connection and disconnection of the chlorine and ammonia supplies; awareness of the hazardous and toxic properties of chlorine and ammonia; and the presence of chlorine detectors and alarms.
A chlorine leak detector monitors continuously for leaks in the chlorine storage room. The leak detectors are set to alarm at 0.5 ppm. At 0.5 ppm, an alarm is activated in the control room, and alarm and flashing lights are activated inside and outside the chlorination building. In addition to the audible and visual alarms to alert operators near the chlorine building, the central computer sends an alarm to all SCADA monitors.
All 1-ton chlorine containers are equipped with fusible metal type safety relief devices, called fusible plugs. Most 1-ton containers have six fusible p
lugs, three at each end, spaced 120 degrees apart. In the event of a fire or other high temperatures, the fusible plug is designed to melt between 150 degrees F and 165 degrees F to relieve pressure and prevent a catastrophic rupture of the container.
The chloramination process is a simple gravity system. Ammonia dosage is manually adjusted and fed by gravity into the plant effluent lines in a vault beneath the tank. The ammonia tank is surrounded by a concrete containment area designed to hold the entire contents of the ammonia tank.
The chlorine and ammonia processes are checked twice a day as part of the normal rounds at this facility. Emergency showers and eye wash stations are provided at the chlorine building and next to the ammonia tank. Three SCBA-type respiratory protection units are provided in the administration building, and one is located in the chemical building. The equipment provides a 30-minute air supply with back carrying harness and pressure gage. Fire extin
guishers are available at 13 sites.
Access to Weese WFP is controlled by a fence and gate, which is locked between the hours of 4 p.m. and 7 a.m. Visitors and contractors must be approved by Weese WFP staff prior to entry into the facility. The chemical building remains locked and only a limited number of Weese WFP staff have keys.
Weese WFP accidental release prevention program is based on the following key elements:
7 Detailed management system and clear levels of responsibilities and team member roles
7 Comprehensive process safety information that is readily available to staff, emergency responders, and contractors
7 Comprehensive preventive maintenance program
7 A process hazard analysis of equipment and procedures with operation and maintenance staff participation and review
7 Use of state-of-the-art process and safety equipment
7 Use of accurate and effective operating procedures, written with operations and maintenance staff participation
7 High level of training of operato
rs and maintenance staff
7 Implementation of an incident investigation, inspection, and auditing program using qualified staff
1.6 Five-Year Accident History Summary
No chlorine or ammonia releases that could have caused safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at Weese WFP during the last 5 years. Some minor, incidental releases may have occurred over this period, but they were quickly handled by staff, neutralized, or posed no safety or health hazards.
1.7 Planned Changes to Improve Safety
The safety of the chlorine and ammonia processes were reviewed in March 1999 in the process hazard analysis. Based on these reviews, additional changes were identified to improve the safety of the chlorination and chloramination systems. A leak containment system (scrubber), which will contain and neutralize any chlorine released in the chlorine building, is currently being designed. It is expected to be
installed by June 2001. It is expected that the remainder of the recommended actions will be evaluated and implemented by June 2001. The implementation of these recommendations will further improve the safety of the covered processes.