Ft Myers Central Advanced Wastewater Treatment Fac - Executive Summary
It is the policy of the City of Fort Myers to operate safe wastewater treatment facilities, reducing to the greatest extent possible any hazards associated with our processes and reducing any subsequent risk to the surrounding community, employees and the environment. It is also our policy to work with the surrounding community and local emergency response agencies, and promote a spirit of cooperation and teamwork to provide an effective contingency plan in the unlikely event that a process incident occurs at one of our facilities. |
The primary activity at the Central Advanced Wastewater Treatment Facility (CAWWTF) is municipal wastewater treatment. Chlorine and sulfur dioxide are the only 40 CFR 68 regulated substances at the facility. Chlorine is used primarily as a disinfectant. Sulfur dioxide is used for dechlorination. The maximum amount of chlorine at the facility is 20 tons. The maximum amount of sulfur dioxide at the facility is 10 tons.
Release Scenario (WCS)
The Worst-Case release scenario according to EPA's Offsite Consequence Analysis Guidance document is "the greatest amount held in a single vessel." The worst-case scenario is the complete release of chlorine from a one-ton container.
The chlorine and sulfur dioxide toxic endpoints defined by 40 CFR Part 68 is 0.0087 mg/l which is equivalent to 3 parts per million by volume (ppm). According to the American Industrial Hygiene Association (AIHA) Emergency Response Planning Guideline (ERPG)-2, this toxic endpoint is specified as "the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action."
The SLAB computer model was used to simulate the worst-case scenario. The maximum distance to toxic endpoint is 2.93 miles for chlorine and 3.55 mile
s for sulfur dioxide.
A worst-case release is unlikely due to the materials of construction of the chlorine and sulfur dioxide containers. In addition, a comprehensive risk management program has been developed to prevent accidental releases.
Alternative Release Scenario
The alternative release scenario is most likely to occur than the worst-case scenario. For the CAWWTF, it is assumed that the pipe manifold connecting the two 1-ton chlorine or sulfur dioxide containers fails and the chemical is released for 2.5 hours. The maximum distance to the toxic endpoint for the alternative release scenario is 0.42 miles for chlorine and 0.39 miles for sulfur dioxide.
Accidental Release Prevention Program
The City of Fort Myers is in compliance with 40 CFR 68. The City has conducted a comprehensive review of the chlorine and sulfur dioxide systems as well as administrative, technical, operating and maintenance procedures, in addition to the other required program elements of the regulat
ions. The Risk Management Program addresses actions to minimize the likelihood of an accidental release and to minimize the impact if one occurs.
Five-Year Accident History
The CAWWTF has had one sulfur dioxide release which is documented in this form.
Emergency Response Program
This facility has an emergency response program that is coordinated with the Lee County Comprehensive Emergency Response Plan (ERP) that has been prepared in accordance with all local, state and federal regulations.
Planned Changes to Improve Safety
The hazard review resulted in the development of a list of improvements and an implementation schedule. This is included in the Risk Management Plan (RMP). Continued training and practices documented in the RMP will continue to improve safety at the facility. Some of the more significant improvements are listed below:
To Be Completed by August 1999
Include trunnion wheels in a regular maintenance program.
Due to the chemical nature of chlorine, any wor
k performed in the chlorine areas that involves heat or sparks should be closely monitored. Hot work permitting should be implemented.
Ammonia that has exceeded its shelf life is no longer effective in detecting leaks. Ammonia should be replaced every 60 days, with a date placed on the test bottle each time it is refilled.
Because the pigtail is the weakest point in the chlorine system, it is important to replace the pigtails at least once every six months.
Increase operator training in the use of escape units.
To Be Completed by November 1999
Chlorine containers must be rotated in the trunnions to properly align the valves prior to connection. Procurement of a specialized F-wrench for this use is recommended.
To Be Completed by January 2000
An annual preventive maintenance (PM) and replacement program for the chemical system should be prepared and implemented. The PM program should include the following equipment:
Metal manifold piping (replace every ten years)
VC system (replace every 5 years)
Injector check valves
Vent line from pressure relief valve
In case the vacuum regulator fails while it is open, a sensor with an alarm system should be installed on the vacuum release line.
The manifold pressure gauge should be moved to a better location. The valve should be tagged to identify its function and operating positions.
Replace air flow/indicator light that lets workers know that the ventilation system is working prior to entering the chlorinator room.
Institute quarterly tests of the sensors and detectors to verify their proper function.
For increased safety of operators during a container change out, add a face shield requirement to the hookup procedure. Replace the current rebreather oxygen mask with a non-rebreather mask.
Require all personnel to be certified in CPR and require SCBA training.
Restrictions are necessary regarding untrained personnel enterin
g the chemical storage area. Signage should be reviewed throughout the facility.
Verify that the severe weather plan includes provisions for securing bonnets on containers.
To Be Implemented by June 2000
Provide all operators with regular training regarding the proper use of the monorail mounted hoist system.
Reinforce hot work procedures as a part of operator training, as well as the importance of using new lead washers during each container change out.
Terminate unnecessary piping at the source to decrease in any leak opportunities. Specifically, terminate the influent injector gas piping at the source.
Alarm investigation procedures should be developed and implemented.
Develop a package to give to contractors outlining the specific hazards at the facility, as well as the policies to follow on site. Inform contractors that any of their subconsultants are required to follow the same policies.
Review labeling on piping and correct any deficiencies.
Install chemical release
sensor on pressure relief lines.
Provide operating status indicators for ventilation system in chemical buildings.
To Be Completed Prior To The Next Bid For A Chemical Supplier (By June 2000)
Procurement documents should specify that delivery truck drivers cannot off load without staff assistance from a trained operator, and should remind vendors that scheduling with the operator is a safety concern. Consider including contractor safety policies as required documents in procurement.
All containers should be marked in the upright position to maintain alignment during movement.
Require vendor to verify that containers meet all applicable codes and hydrostatic testing requirements.
Request vendor's Standard Operating Procedures and certification that chlorine and sulfur dioxide meet AWWA specifications.
To Be Completed by January 2001
Review alternative disinfection process regulatory, safety and costs considerations. Compare these processes to enclosing the chemical handling
areas and providing a emergency scrubber to provide additional protection for staff and public. Provide emergency chlorine scrubbers or replace chemical process that use chlorine and sulfur dioxide.
Because rolling chemical containers can cause a leak hazard, consider modifying the monorail mounted hoist to allow for off loading of containers without having a need to roll them. A bridge crane would accomplish this.
Containers could potentially be damaged by hitting a nearby wall during container movement. Consider installing an impact resistant stop.
Roller type trunnions make it easier to maneuver containers into proper alignment without rolling containers by hand. Consider changing the fixed cradles to a roller type trunnion.
Align containers during off loading from the delivery truck, rather than later.
The solenoid valve on the chlorinator discharge piping is not necessary for system operation. It should be removed.
To avoid low flow of injector water, consider providin
g a redundant water supply to the injectors.
For increased notification to operators of a potential chemical leak, provide redundant SO2 detectors at inside and outside locations.
Research methods for securing containers in the event of a flood, hurricane or severe storm event.