Royer Nesbit Treatment Plant - Executive Summary
Accidental Release Prevention and Emergency Response Policies |
Cucamonga County Water District (CCWD) has a well-established policy for the safe management of hazardous chemicals at the Royer Nesbit Treatment Plant. CCWD recognizes that the keys to chemical safety are safe system design, well-trained operations and supervisory staff, and tested emergency response procedures. The CCWD General Manager has oversight responsibility for development and implementation of District safety and emergency preparedness programs.
Facility and Regulated Substances
The Royer Nesbit Treatment Plant (RNTP) is a facility which treats raw water to produce drinking water for storage and distribution to a multicity service area. A critical element of the treatment process is the addition of chlorine for water purification and water quality improvement. Chlorine is stored at the facility as a pressurized gas in DOT-approved one-ton metal containers. This is the only EPA-RMP Regulated Substance used at the f
Worst-case Release Scenario
The RNTP chlorine operations configuration has two 1-ton containers individually connected to the chlorination control system. Regulators which maintain a vacuum in the gaseous chlorine process line are mounted on each 1-ton container. The worst-case scenario involves the shearing of a regulator from the mounting yoke on one of the containers, from either the impact of a replacement container slipping from the transfer hoist, or structural seismic failure. Although the chlorine storage room doors are normally closed (providing passive mitigation capability), the worst-case analysis assumes the room is open, allowing a direct release of 2000 lbs. of gaseous chlorine to the atmosphere over 10 minutes. Although the chlorine vapor scrubber would normally be enabled upon a release detection, the worst-case stipulations do not allow active mitigation to be considered.
A recognized computer air-dispersion model, ALOHA, was used to predict a radial impact
of 3.0 miles before the chlorine concentration would diminish to an EPA/RMP specified endpoint value of 3ppm.
Alternative Release Scenario
An alternative release scenario was selected for the RNTP facility, following a process hazard analysis, in which gaseous chlorine is released through a pressure relief valve as a result of a regulator failure. Since the relief line is presently vented outside the chlorine storage building, no active mitigation was considered. The average response time for operators to secure the leak, wearing protective equipment, was determined to be 20 minutes. The ALOHA model predicted that the release of 20 lbs. over 20 minutes would impact a radius of 0.18 miles to the 3 ppm endpoint.
Accidental Release Prevention Program
This facility complies with the OSHA PSM (Process Safety Management) Rule as it applies to chlorine storage and use. All operators and supervisors are trained in chlorine safety. All operators are state-certified water tre
atment plant operators according to their specific experience. Routine equipment and process status inspection and testing is conducted by operations staff, who also are trained to perform routine maintenance. Periodic preventive maintenance of critical systems is conducted by specialists in chlorine equipment and instrumentation. All CCWD treatment plants are monitored from a central computer control unit, which provides operations status and alarm displays, including process area chlorine detectors. The computer and instrumentation systems are backed up by battery-powered supply, and the overall plant electrical systems are backed up by emergency generators, allowing chlorine vapor scrubbers to operate in the event of line power failure.
Five-year Accident History
No CCWD treatment plants have had an accidental release of chlorine in their operating history, including the last five years.
Emergency Response Program
The facility Emergency Response Plan is submitted to the San Berna
rdino County Fire Dept. and coordinated with the Rancho Cucamonga Fire Dept. as a local emergency responder. All operators receive initial and annual refresher (HAZWOPER) training in emergency response, and are trained to respond to minor chlorine leaks if they should occur. The facility maintains an emergency response team and incident command structure, including in-plant alarms and public notification procedures.
Planned Changes to Improve Safety
The Process Hazard Analysis (PHA) conducted for this facility included recommendations to examine specific equipment and monitoring systems to determine if reconfiguration and seismic upgrades could improve the safety of the chlorine systems under unusual conditions (e.g., earthquakes, multiple component failures). Technical studies will be conducted in 1999 to follow up on these recommendations.