White Mills Treatment Plant - Executive Summary
EXECUTIVE SUMMARY |
White Mills Treatment plant is a water treatment facility that is owned and operated by Hardin County Water District No. 2. The treatment plant began operation as a new facility in October of 1990 and now provides drinking water to over 35,000 people in Hardin county. The facility has a capacity to produce 3.4 million gallons of water each day using coagulation, sedimentation, filtration, and disinfection. The disinfection process requires the use of chlorine gas, which is the process covered under this risk management program.
The chlorine is fed through two chlorinators from two -one ton chlorine cylinders at an average rate of 150 lbs. per day. Each chlorinator has the capacity to feed up to 2000 lbs. of chlorine per day. There are three chlorine cylinders maintained on site, each of which contains up to 2000 lbs. of chlorine. Two of the cylinders are continuously connected to a pair of vacuum regulators that control the flow of chlorine from the cylinders
to the chlorinators. The third cylinder is either an empty cylinder waiting to be picked up by the supplier or a full cylinder on stand by waiting to replace a cylinder in service that becomes empty.
As a user of chlorine, Hardin County Water District No. 2 understands the importance of safety when it comes to the use of such a dangerous product. Safety was a consideration when the plant was originally designed and when the equipment was selected and installed. The original equipment, which is still being used today, is still considered some of the best equipment in the industry. The same equipment is still being chosen for new processes and as replacement for old processes. The system is an all-vacuum operation, which reduces gas pressure from the cylinders to a vacuum. There is only a short section of tubing, which is less than two foot in length that contains gas under pressure from the cylinders. All lines and components carrying gas beyond that point are not under pressu
re. This means that if there is a loss of vacuum for any reason, the vacuum regulating valves will shut down the flow of chlorine. A sensitive spring-diaphragm device is designed to contain gas under pressure. The system also contains an additional spring-diaphragm check valve designed to confine the gas should the first valve stick due to dirt buildup on the seat.
Another safety consideration is the location of the process. The chlorine supply and equipment are maintained in a room, which is separate from the rest of the facility and always remains locked. Although the room is not airtight and would not prevent the release of gas into the atmosphere, it would considerably slow the escape of an accidental release of chlorine gas. The separate room also protects the process from fire and unnecessary traffic from employees and prevents access from unauthorized personnel. The room is equipped with a chlorine gas detector that provides a bright, red, flashing, light throughout the
plant in the event of a chlorine leak. The detector is very sensitive and able to detect very small amounts of chlorine gas, which would make operators aware of a leak at its earliest stage.
Other measures taken to assure the safety of this process are strict process operating procedures, an overall safety program, and preventative maintenance program. Each operator is required to know and follow the process operating procedures. Since a chlorine leak would most likely occur during chlorine deliveries or during the handling of chlorine cylinders, these procedures are required to be done only during the hours of 7:30 a.m. to 4:00 p.m. Monday through Friday. This would allow for quicker response from all agencies in the unlikely event of and accidental release. It would also allow for easier notification to public.
Along with the operating procedures, Hardin County Water District No. 2 also employs a company wide safety program. The safety program includes a safety committee,
made up of employees and management, that meets on a monthly basis. Safety training is also part of the program, which includes training topics such as chlorine safety, hazard communication, and respirator training. As part of the safety program, rewards are given to employees for maintaining good safety records, this gives employees an incentive to follow safety procedures.
Preventative maintenance is one of the most important parts of maintaining a process in a safe and efficient manor. White Mills Treatment Plant has a preventative maintenance program that includes the chlorine process. The maintenance program addresses regular inspection of all chlorine equipment, annual overhaul of chlorinators and vacuum regulators, regular replacement of critical components, and assurance of a clean supply of chlorine from the chlorine manufacturer. The annual overhauls and in depth inspection is performed by a chlorine equipment specialist that has many years of experience. Hardin County
Water District No. 2 employs an on site maintenance technician that has the experience to recognize potential problems with the chlorine process and make adjustments if necessary. All of the operators are also trained to perform regular inspections and follow all process procedures.
The worst case release scenario for this process is the release of the contents of one full cylinder of chlorine gas. The 2000 lb. release would be at the rate of 110 lbs./min over a 10 minute period as calculated by EPA's RMP*Comp program. Passive mitigation considered would be enclosure since the process is housed in an enclosed building, which would limit the release to the atmosphere to 1100 lbs. over the 10 minute period (as calculated by EPA's RMP*Comp). This release was based on an accidental impact to one of the valves on the cylinder while the cylinder was being moved off of the delivery truck. This would be highly unlikely since a protective cap is kept over the valves during transportation
and moving of the cylinders.
The off site impacts of such an incident would be the possible contamination of a 2.2 mile radius from the point of release. The 2.2-mile radius would include an estimated population of 2085 people. The area also includes several residences, one school, two "convenient" stores, a summer camp, and a small ballpark.
The alternate release scenario for this process is the release of 282 lbs. of chlorine gas. The 282 lb. release would be at the rate of 4.7 lbs./min over a 60 minute period as calculated by EPA's RMP*Comp program. Passive mitigation considered would be enclosure since the process is housed in an enclosed building, which would limit the release to the atmosphere to 155 lbs. over the 60 minute period (as calculated by EPA's RMP*Comp). This release was based on an operator failing to correctly connect a full chlorine cylinder to the system, allowing chlorine gas to escape from tubing with a 5/16" diameter. An estimated time of 60 minutes wa
s a conservative estimate of time that it would take for the closest response team to respond. Current written procedures and operator training would most likely prevent this incident from occurring.
The off site impacts of such an incident would be the possible contamination of a .1-mile radius from the point of release. The .1-mile radius would include four residences with a total estimated population of 12 people. No other public receptors besides the four residences are in the affected area.
The White Mills Treatment Plant is required to comply with the OSHA PSM rule as well as State and Local emergency response requirements. Our facility currently has a written emergency response plan, which is filed with the Local Emergency Planning Committee (LEPC) and State DES. The emergency plan is updated each year and re-submitted to the LEPC and State DES as required by State regulation. The plan is also exercised in house on an annual basis.
The emergency response plan is base
d on a release that would affect a 10-mile radius from the point of release, and therefore addresses a much greater risk potential. The plan also addresses protective actions such as evacuation of the affected area, evacuation of special facilities, evacuation routes, and medical attention. The plan also addresses spill containment, clean up, and disposal.
In the unlikely event of a chlorine release, the Elizabethtown fire department, which is hazmat trained, would be the initial responders. As a secondary measure, a Chlorep Response Team from Calvert City, KY would be available to respond.
In order to assist in the evacuation of affected areas and the containment of a release, White Mills Treatment Plant maintains certain equipment on site. A large siren is mounted on the roof of the facility to warn the local area in the event of a chlorine leak. The siren is tested each Wednesday at noon and can be heard for several miles. An on site weather center is available to determin
e wind speed and direction for more accurate estimating of the affected area. A repair kit for ton chlorine cylinders is maintained on site for the response team to repair damaged containers. And emergency escape packs are available for employees to safely evacuate the facility.
Since the White Mills Treatment Plant has been in operation (October 1990), there have been no accidental releases of chlorine. We feel this is in part due to the written operating procedures, employee training, and aggressive preventative maintenance program administered by Hardin County Water District No. 2. In our efforts to protect the public, the environment, and our employees, Hardin County Water District No. 2 will continue to review our operating procedures, continue to adequately train new employees, continue to require refresher training for all experienced employees, and continue with an aggressive preventative maintenance program.