CITY OF LORAIN, BLACK RIVER TREATMENT PLANT - Executive Summary |
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City of Lorain, Ohio, Black River Treatment Plant Risk Management Plan Executive Summary The Black River Sewage Treatment Plant is located on the east side of the mouth of the Black River. Lake Erie is immediately to the North. Sewage is recieved from the central west side, east and south sides of Lorain, as well as from Sheffield Lake to the East. The plant is manned by two operators 24 hours per day. Additionally a maintenance crew and administrative staff are on hand during normal workdays between 7:00 AM and 4:00 PM. Chlorine is the chosen method of disenfection at the plant, and is fed from ton cylinders located on two scales in the chlorine room. Each scale holds two 1-ton cylinders. This room is located just 80 feef beyond the main entrance. Extra full cylinders are stored outside to the North of this room. Up to four cylinders may be in use and feeding at one time, primarily during the summer months. At other times, no more than two cylinders are in use. Up to 6 additional full cylinders may be on hand outside the chlorine room. Gaseous chlorine is fed from the top valves of each pair of cylinders into a vacume chlorinator and injected into a PvC pipe waterstream, forming a strong hypochlorite soolution. It is this solution that is fed to other points in the plant as a disenfecctant. Since chlorine is pulled from the tanks under a vacume there is little risk of a raw chlorine leak beyond the tank valves. Accidental releases are limited by the vacuum chlorine system. Should a leak occor in the system between the tank and chlorinator, air would be drawn into the leak rather than chlorine leaking out, as the system is under vacume at this point. A large rupture here would cause the vacume operated valve on the tank to close immediately. Once a cylinder is in service, the main risk of any leakage is at the main valve and fittings connecting the feed system to the tanks. A chlorine leak sensor is mounted within several feet of the tanks,and produces a loud, shrill alarm should chlorine be detected. Should a leak occur, operators are trained in the use of the Scott Air Pack and B-kit for stopping leaks. If a chlorine leak is detected, both operators don the Air Paks. One operator enters the room to deal with the leak, while the other waits just outside and watches, assisting only if necessary. Should the leak be such that it cannot be readily stopped, the fire department is notified for assistance and evacuation as needed. Fire personnel are trained in the use of the B-Kit and have trained at this facility. The worst case senario would be a rupture to the cylinder tank itself, allowing the entire contents, 2000 lbs. to spill out in a matter of minutes. If this were to occur to a cylinder outside the chlorine room, the vulnerability is 1.3 miles, with a residential population of 15,000. Inside the chlorine room, the vulnerability is 0.9 miles. Since the plant is located on the edge of Lake Erie, the re are no residences to the west, northwest, north and northeast. During the summer, there is the possibility of a number of boaters in the circle of vulnerabily, particularly in the two nearby marinas. A U.S. Coast Guard station lies 100 yards to the south of the plant. In such a major event, evacuation of the plant and adjacent areas would be the top priority. The Fire Dept., Coast Guard and the Police Department would all be called to assist. A mitigating condition is that the plant is located at a somewhat lower elevation that the nearby residential areas and busnesses to the south. This could slow the spread of the gas up into these areas, as the heavy chlorine gas would tend to settle in the adjacent lower lake and river areas. No permanent damage would occur to the waterways or permanent structures, but hazard to health is very real, particularly in the nearby areas. This worst-case scenario is highly unlikely. No such event has ever occured. More likely is the alternate release scenerio. This could occur from an improperly connected fitting or a faulty main vavle. This kind of leak could be most often stopped by closing the main tank valve, correcting the source of the leak, then cautiously putting the tank back in service. If the vavle itself is faulty, equipment is readily available in the chlorine B-Kit to seal -off such a leak, afterwhich the chlorine supplier would be contacted to come and remove the problem cylinder. This scenerio is described as 200 lb. leaking over a 10 minute period. The vulnerability distance is 0.1 miles. Ther are no residences within this distance, other than up to a dozen persons at the Coast Guard station to the south. Plant personnel, boaters and fishermen in the immediate area would be the only ones affected. No leak of this size has ever occured, but it is a remote possibility. There have been no leaks of a measurable quantity at the Black River plant during the past five years. All oper ators are given training and drills in using the Scott Air-Pak SCBA, and Chlorine B-Kit. Chlorine supply is checked and adjusted several times each shift by operations personnel, insuring that a potential problem may be noticed long before it becomes an emergency. Chlorinators and ancillary equipment are overhauled and tested at least once a year; the chlorine detector is tested on a monthly basis. Our emergency contingency plan is reviewed annually each May prior to our summer effluent disinfection period. We have converted one of our two chlorinators to a simplier design. This newer system is smaller and less susceptable to problems that could occur. However in the last year have found, that on occasions with fluctuating water pressure, the older system does still have advantaages and therefore at this time choose to use both systems. |