Conway Water Treatment Plant - Executive Summary
1. Corporate Prevention and Emergency Response Approach |
The Conway Water Treatment Plant (Conway WTP) is owned by the Orlando Utilities Commission (OUC). The facility has developed and maintains accident prevention programs and an emergency response plan to prevent and mitigate the effects of hazardous chemical releases. The OUC Corporate Environmental Department provides advice and funding on hazardous chemical emergency issues. The Emergency Response Plan for the water plant is coordinated through the Water Production Division Pershing Control Center, from which all OUC Water Plants are controlled and managed.
2. Description of Stationary Source
The Conway plant is located on at 2725 S. Conway Road, Orlando, Orange County, Florida. Conway adds chlorine through their chlorination process in order to disinfect the City's water supply.
Liquefied chlorine gas is stored in up to ten one-ton containers at the Chlorination process building. Ten one-ton containers are always connec
ted to the process. Five one-ton containers are on-line at all times feeding the system, with five containers on standby to draw from when the first five are exhausted. The total chlorine inventory in the process at any one time is 20,000 lbs. This is greater than the 2,500 lb. RMP threshold quantity for chlorine. This process is fully enclosed in a building.
The chlorine building at Conway is equipped with an automated chlorine scrubber system. The scrubber system is activated by two chlorine detectors which are located inside the building, one in the chlorine dock area and one in the chlorination room. If the chlorine detectors indicate that chlorine is present at a concentration above the preset level, the doors and louvers of the building will automatically close and the scrubber will start. The scrubber fan will pull the released chlorine gas through the scrubber, which chemically removes the chlorine from the air. The scrubber can handle a full one-ton container of chlo
rine before the scrubbing medium is exhausted. The chlorine detectors are also interlocked to an audible and visual alarm at the site and audible and visual alarms on the Operators control panel at the Pershing Control Center. The Control Panel will also indicate to the operator that the scrubber has started. When the Operator sees the chlorine alarm, he can dispatch OUC personnel and City or County emergency response personnel to the site immediately if necessary.
3. Description of the Worst Case and Alternative Release Scenarios
The Worst Case release scenario is the rupture of a one-ton container from the Chlorination process, releasing 2,000 lbs. of Chlorine gas over a ten minute period. Under worst case weather conditions, and taking into consideration the full enclosure, the chlorine gas could travel 0.8 miles before dispersing enough to no longer pose a hazard to the public or environment (reaching a concentration less than .0087 mg/L), using the WWTP Guidance lookup tabl
Several Alternative Case Release Scenarios were considered; however, no Alternative-Case Release Scenario resulted in an offsite consequence for the Conway plant. This is due to the active mitigation measures available, including both the 100 percent control efficiency of the chlorine scrubber and the ability to dispatch OUC and emergency response personnel to the site before the scrubber would be exhausted. However, to report an alternative-case scenario to EPA, a release was assumed to go beyond the ten minutes used in all the EPA Guidances. It was assumed that it would take OUC personnel 33.8 minutes to respond to the release and the scrubber would be exhausted after 23.8 minutes. This would result in an estimated mitigated release rate of 28.5 lb/min inside the building for ten minutes and an endpoint distance of 0.1 miles, after the scrubber was exhausted and personnel arrived, using the WWTP Guidance loolup tables.
4. Prevention Program
For the Chlorination process, t
his facility exceeds the chlorine threshold quantity of 1500 lbs. for the OSHA Process Safety Management (PSM) Standard, 1910.119; however, this is an unoccupied facility and is therefore not subject to the PSM requirements. For RMP compliance purposes, this places the Conway WTP Chlorination process in the Program 2 level. The Conway WTP facility will address all elements for the Prevention Program 2 as required by the RMP rule.
The Prevention Program 2 contains the following elements: a Process Hazard Review of the process, the collection and documentation of Process Safety Information, a Preventative Maintenance Program, written Operating Procedures, a Compliance Audits program, Safety Training for operations and maintenance personnel, and an Incident Investigation procedure. This Prevention Program will ensure continued safe operation and prompt correction of deficiencies. The Prevention Program receives full support of plant management and involvement of employees at all level
5. Accident History
The Conway facility has had no accidental releases of chlorine in the past five years.
6. Emergency Response Program
The Pershing Control Center has an Emergency Response Procedure in place. The Plant Operator at the Pershing Control Center has accident assessment capabilities and can respond immediately to all emergencies by dispatching appropriate personnel to the site. The OUC Water Production mechanics have been trained in chlorine safety and have a procedure for addressing small releases of chlorine. The current procedure has been coordinated with the Orlando Fire Department and Hazardous Materials Response Team, and the Regional Local Emergency Planning Committee. Notification is made locally by dialing 911, and by notifying Florida State Warning Point at (800) 320-0519.