Wilmette Water Plant - Executive Summary |
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Please refer to the attached file RMPWM_EX.txt for the Executive Summary Document Village of Wilmette Risk Management Plan Executive Summary - May 1999 Overview The Village of Wilmette owns and operates a 34-MGD water treatment facility, serving the needs of the 105,000 residents of Wilmette, Glenview and portions of Prospect Heights in Northeastern Illinois. Located at Lake & Michigan Avenues in Wilmette, the Wilmette Water Plant uses the unit processes of disinfection, coagulation, sedimentation and filtration to purify the water before distribution to its customers. Fifteen full time and two part-time employees staff the water plant. The Superintendent is responsible for overall supervision of the facility, assisted by the Chief Operator (operations group), Maintenance Supervisor (maintenance group) and the Meter Repair Technician II (meter group). Under the operations group there are six Operators and a Chemist; the Maintenance group includes a Mechanic, an Electrician, a Build ing Maintainer and an Instrument Maintainer. The meter group is staffed with a Meter Repair Technician I and a Meter Reader. The Village currently uses chlorine gas in the disinfection process. Water plant maintenance & operations employees accomplish handling and feeding of chlorine. Due to the size and complexity of Wilmette's chlorine feed system, the Village has prepared a Risk Management Plan (RMP) to reduce the risk of a chlorine leak and an Emergency Management Plan to mitigate a leak in the unlikely event that one occurs. The purpose of this document is to give an overview of the water plant and it's treatment processes and present an executive summary of the Village's Risk Management Plan. Village's Risk Management Plan In 1996, Congress passed the USEPA's Risk Management Plan (RMP) Rule, a regulation intended to prevent and minimize the impact of accidental releases of 77 listed hazardous substances. Under this rule, any facility with a hazardous chemical above a design ated threshold quantity and in proximity to the public is required to prepare an RMP. Chlorine is one of the listed chemicals, with a storage threshold of 2,500 lbs. The Village of Wilmette normally stores six one ton cylinders of chlorine (max capacity is 12,000 lbs.) in the chlorine cylinder room at the water plant. In 1998, the Village developed an RMP to minimize the risk of a chlorine leak to comply with the RMP Rule. The Village's plan includes a Hazard Assessment, a Prevention Program, an Emergency Response Program and an Executive Summary (this document). The Rule requires that the first RMP Plan be submitted to the USEPA by June 21, 1999. Water Plant Process Description Water enters the treatment process through two intake lines out in Lake Michigan. During the summertime, a small dose of chlorine is fed into the intake pipes to help control the growth of zebra mussels. After traveling under the lake bed to the roundhouse building pumping station, it is lifted about 15 fee t by low lift pumps and delivered to the rapid mix chamber inside the water plant. From the rapid mix, water flows by gravity through the rest of the treatment processes. At the rapid mix, the raw water receives chemical pretreatment. Chlorine (for disinfection), alum (for clarification), fluoride (for dental health) and activated carbon (for taste and odor control) are added to the raw water and thoroughly mixed. Only about one teaspoonful of chemicals are added for every 100 gallons of water treated. Following this, the "pretreated water" enters one of six slow mix basins where gentle mixing, or flocculation, enhances the formation of "floc" particles with the alum. These particles collide with and stick to suspended silt particles from the lake, causing them to settle out in the next treatment step -- sedimentation. Ninety percent of all solid material that enters the plant settles out in the four-hour trip through the settling basins. After sedimentation, the water enters one of the ten anthracite capped rapid sand filters for the final polishing step in the treatment process -- filtration. The filtered water receives an additional dose of chlorine to maintain a disinfectant "residual" in the water and ortho-polyphosphate to inhibit corrosion in the distribution system piping before entering the water plant's underground clearwell/reservoirs. The entire trip through the treatment processes takes about eight hours. From these storage tanks, the high lift pumps deliver water under pressure to the distribution system to fill the 4.0 million-gallon (MG) standpipe, 3.0-MG reservoir/pumping station and to supply the needs of the residents of Wilmette, Glenview and portions of Prospect Heights. The Wilmette Water Plant purifies and pumps 13 million gallons per day (MGD) on an average day. Under peak pumpage conditions during hot summer days the flow may exceed 30 MGD. The treated water that leaves the water plant meets and/or exceeds all State and Federal EPA reg ulations for chemicals, clarity and bacteria. Chlorine Feed Process Description Chlorine is used for the disinfection process at the water plant. Six one ton cylinders are stored in the chlorine cylinder room, located underground adjacent to Michigan Ave. at the Water Plant chemical unloading area. Chlorine cylinders are delivered by truck, four at a time, about once every six weeks and are lowered into the cylinder room using the chlorine elevator. Inside the cylinder room a two-ton hoist is used to move cylinders into position for hook-up. Water plant maintenance personnel accomplish the hook-up of chlorine cylinders. The hook-up process involves placing full cylinders on scales (for inventory control) and connecting them to a steel pipe manifold using chlorine "whip" connectors. Valves on the cylinder and on the manifold allow for isolation of each connected tank. The manifold is connected to two vacuum regulator w/check units connected in parallel. These units permit chlorine to flow from the cylinder room to the feed room when a vacuum is applied. Chlorine gas travels under vacuum through piping inside the water plant building to the chlorine feed room. In this room, chlorinators meter the gas flow and mix the gas with water to form a solution. (The vacuum is created when treated water is passed through the ejector.) This chlorine solution is piped to nine separate feed locations in the water plant as part of the disinfection process. The Operators control the rate of feed (or dose) of chlorine gas by adjusting the chlorinators. Under normal operations, the feed rate is set and controlled by the Water Plant Supervisory Control and Data Acquisition (SCADA) system located in the Water Plant control room. The chlorinators can also be adjusted manually in the feed room. Chlorine Leak Scenarios The Worst-Case leak scenario for the Village, as defined by the RMP Rule, would occur if a one ton cylinder of chlorine were to fail and empty all of it's contents wi thin 10 minutes at the chemical unloading area adjacent to Michigan Avenue. Using the ALOHA gas dispersion model developed by the National Safety Council, the "hazard zone" for the worst-case scenario would extend 2.6 miles from the water plant. The extent of the gas plume would depend upon the actual humidity, air temperature and wind direction and speed. The Worst-Case scenario is possible but highly unlikely due to the conservative construction of the chlorine cylinders themselves and the infrequent deliveries Wilmette receives. The Alternate-Case leak scenario for the Village would occur if a "whip" connection on a one ton cylinder of chlorine were to fail and leak 283 lbs. of chlorine into the cylinder storage room in one hour. Using the ALOHA gas dispersion model, the "hazard zone" for the Alternate-Case leak scenario would extend 0.29 mile from the water plant. The extent of the gas plume would depend upon the actual humidity, air temperature and wind direction and speed. If a leak were to develop, this is a likely scenario. Accidental Release Prevention Program The program for release prevention at the Wilmette Water Plant includes the following elements: RMP Management System -- Ensures that everyone who plays a part in the RMProgram understands their roles and responsibilities for all program elements. Employee Participation in RMP Plan -- Defines how employees will be involved in the development and implementation of an OSHA Process Safety Management and EPA Risk Management Program. Chlorine System Process Safety Information -- Ensures that current written process safety information is developed and maintained in a format that provides easy access by employees, Process Hazard Analysis teams and auditors. Chlorine System Process Hazard Analysis - Process Hazard Analysis (PHA) is a process used to identify, evaluate, and control the risk associated with process hazards or chlorine release scenarios at the water plant. PHAs are periodically conduct ed on the chlorine process to insure process changes will not compromise safety. Chlorine Operating Procedures - The Village of Wilmette maintains up-to-date, accurate, written operating and maintenance procedures for the chlorination processes. Chlorine Training - The Village provides training on operations and maintenance of water plant chlorination process. This training includes the inherent process hazards and appropriate response actions for accidental chlorine releases to all personnel working on the chlorination process at the water plant. Contractor Chlorine Safety -- Ensures that only contractors with good health and safety programs are selected to perform work on and around the chlorination process and that the contractors and the processes are properly prepared to safely complete the work. Pre-Startup Safety Review -- A Pre-Startup Safety Review is conducted to ensure that the Water Plant is ready to safely operate any new or modified chlorine feed process. Mechan ical Integrity of Chlorine Equipment -- Ensures the continued integrity of existing chlorination process equipment. Include documentation of all maintenance work on process equipment. Hot Work Permit -- Ensures that a hot work permit is issued for all hot work (any work that may generate a source of ignition) conducted on or near the chlorination processes. Management of Change -- Requires that system changes are properly reviewed against original system design specifications and can be accomplished safely, and that the systems are ready to operate safely in accordance with original system design intent following implementation of the change. Compliance Audits - Provides for periodic audits to evaluate the Wilmette Water Plant process safety and risk management program, and their implementation for compliance with the OSHA PSM and EPA RMP regulations. Incident Investigation - If a leak does occur, the incident investigation procedure identifies the underlying causes and recommends corrective actions to prevent a reoccurrence. Five Year Accident History Over the past five years, there were no measurable releases of chlorine above the 10-lb. threshold amount reportable to the USEPA. Village's Leak Control Measures Currently in Place In addition to the elements noted in the Prevention Program, the Village also has the following equipment, tools and procedures in place to minimize the impact of a chlorine leak: Chlorine Cylinder Room - The cylinder room is physically isolated from the public and the rest of the Water Plant buildings. A leak occurring in this room (e.g., the Alternate Scenario) would be contained, reducing the impact outside of the building. The ALOHA model Chlorine Leak Detector(s) - Located in the cylinder room and in the feed room, these detectors send an audible alarm to the Operator in the control room in the event of a leak. They can detect as little as 1 part per million (ppm) of chlorine gas. 24 Hour Staffing - There is an Operator a t the water plant 24 hrs per day, 7 days per week. Each Operator is trained on how to operate the chlorine equipment and what to do if a leak develops. Self-Contained Breathing Apparatus (SCBA) - SCBA equipment is available for Village employees trained on chlorine leak mitigation. Chlorine "B" Kits - The Village has two Chlorine Institute "B" Kits with tools and devices for controlling or stopping a leaking one ton chlorine cylinder. One is located at the water plant and one at Fire Station #1. Chlorine Leak Monitoring - The Village has licensed copies of ALOHA gas dispersion modeling software and laptop computers to run the model at the leak site. This, coupled with weather monitoring information, will permit the Fire Department to determine the extent of the chlorine leak "plume" so that affected residents & businesses can be notified. Village's Emergency Management Plan In the unlikely event that a leak does occur, Wilmette is well prepared to handle it. The water plant is st affed 24 hours per day. In the event of a leak in the cylinder room, a leak detector will sound an audible alarm and send an alarm to the Operator via the SCADA control system. The Operator will immediately call the Wilmette Fire/Police Departments for assistance. The Wilmette Fire Dept. has employees trained to mitigate emergency releases of toxic chemicals. They also have access to firefighters in neighboring communities through the Mutual Aid Box Alarm System (MABAS). The Fire Dept. will assess the extent of the leak, evacuate the area affected and isolate the leak using the Chlorine "B" Kit. Water plant staff will serve as a resource, providing facility specific technical information to the emergency responders. The Police Dept. will be responsible for activating the Village of Wilmette's Emergency Management Plan (EMP), if necessary. This plan assembles senior Village staff members at a remote site to assist in the emergency response. When the team is assembled, responsibility f or notification and public information will be allocated as outlined in the EMP. The Village's EMP complies with the USEPA's SARA Title III regulations and the Cook County Emergency Response Plan. The Fire Dept. incident vehicle carries a laptop computer with the ALOHA software loaded. Trained firefighters can plot the gas leak plume using ALOHA and determine the extent of the gas dispersion. A list of specific public facilities is maintained in the Police / Fire Dispatch Center and will be used to plan the evacuation of the leak area. Finally, the responding Wilmette Fire Dept. personnel will conduct first aid procedures for exposure to chlorine, subject to Wilmette Fire Department Standard Operating Guidelines and the local area hospital mass casualty disaster plan. Planned Safety Improvements To improve safety even further, the Village will be taking additional step in the coming months. These steps include: Chlorine Monitoring -- Add a second backup chlorine gas monitor to the cylinder room and connect it directly to the Fire Department alarm system to shorten response time. Modeling -- Add a weather monitoring station to the water plant site to provide site-specific weather information to the ALOHA modeling software. Alarm Improvements -- Expand the alarm and paging systems at the water plant to cover all process areas. Ventilation Improvements - Interlock the major ventilation systems in the water plant building with the chlorine gas monitor to help keep the gas contained in the cylinder room. It is hope that these planned improvements will make the chlorination process at the Wilmette Water Plant safer than it already is - both for the water plant employees and our neighbors. Ray S. Ames Jr., Water Plant Superintendent June 1, 1999 |