Thief River Falls Water Treatment Plant - Executive Summary |
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EXECUTIVE SUMMARY The Thief River Falls Water Treatment Plant Risk Management Plan was developed to protect both the residents of the community and Water Department personnel through policy and procedures governing the operation of the facility. This plan is a cooperative effort of plant staff, administration, and City Government. It is based on the requirements of OSHA Process Safety Management, USEPA Risk Management, and Minnesota's Workplace Accident and Incident Reduction (AWAIR) law requirement. The commitment of the City of Thief River Falls City Council is demonstrated by the Thief River Falls Employee Safety Committee. This is an independent committee reporting directly to the City Council. It includes supervisory, department head, union personal and two City Council members who take an active role in addressing safety issues and concerns for all City employees. RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES The Thief River Falls Water Treat ment Plant uses gaseous chlorine and anhydrous ammonia for disinfection of the drinking water supplied to the community. The anhydrous ammonia inventory is maintained below the minimum quantities as required by OSHA PSM and EPA RMP requirements. Maximum quantity is 560 pounds. The WTP Chlorine inventory control procedure calls for the chlorine inventory to be maintained between 500 and 3000 pounds, using cylinders of one ton capacity. When the on-line chlorine cylinder is reduced to approximately 1000 pounds, another cylinder is ordered. The replacement cylinder is delivered before the on-line cylinder reaches 500 pounds. This procedure limits the amount of chlorine on site to a maximum of one full cylinder and one partial cylinder. The purpose of this policy is to maintain an adequate inventory of chlorine for disinfection while limiting WTP operator and public exposure to a accidental chlorine release. RELEASE SCENARIOS Worst-case and alternative relea se scenarios have been determined after careful review of the regulation and consideration of the storage vessel configuration. No active mitigation measures or devices, such as scrubbers, could be considered for analysis of worst-case releases. For this worst-case scenario, the regulation specifies the release conditions and meteorological conditions at the time of the release. When these conditions were modeled, using the USEPA Off Site Consequence Analysis, the results were as follows: Worst-case release scenario: * Quantity released = 2000 pounds * Release duration = 10 minutes * Release rate = 200 pounds per minute * Distance to endpoint = 2.2 miles For the alternative release scenario, the following results were obtained: * Quantity release = 317 pounds * Release duration = 60 minutes * Release rate = 10.6 pounds per minute * Distance to end point = leaking gas contained in the sto rage room. No off site consequence. RELEASE PREVENTION PROGRAM FOR COVERED CHEMICALS: The Thief River Falls PSM/RMP and AWAIR prevention programs include the following sections: * Employee participation * Process safety information * Operating procedures * Personnel training * Contractor safety * Prestartup safety review * Preventative maintenance/mechanical integrity * Hot work permits * Management of change * Incident investigation * Compliance audits The first line of defense against an accidental chlorine release is the WTP Preventative Maintenance Program. This is a mechanical integrity program requiring annual inspection of all hazardous chemical equipment. Certain equipment components require monthly inspections. The schedule is based on and adjusted according to actual inspection and test results. Components such as gas pressure regulators, feeder master control units , and auto switch-over valves are tested and calibrated on a test bench that simulates the actual operation of the systems. New replacement components are tested in this manner before installation or placement in inventory. The spare parts inventory in maintained with all components necessary to repair any equipment failure. In addition, the chemical feed process equipment has redundancy to provide back-up equipment operation while problem equipment is in repair or inspection. ACCIDENT HISTORY There have been no reportable release incidents in the history of the Thief River Falls Water Treatment Plant. EMERGENCY RESPONSE Response to a leak is by plant personnel trained in mitigation of chlorine leaks, using self contained breathing apparatus, personal protection equipment, and a chlorine Emergency Kit "B" system. Evacuation of surrounding population, and back up safety personnel for the plant operators, is provided by the Thief River Falls Fire Depa rtment and local Law Enforcement Center officers. A leak in the chlorine system, as signaled by either of two chlorine detectors, triggers the start up of the chlorine scrubber system and triggers the WTP alarm system. This provides notification to the plant operator to implement the Water Treatment Plant Emergency Response Plan . The chlorine storage room is designed to contain a chlorine leak in the room while the scrubber neutralizes the gas or liquid release. The scrubber is designed to neutralize 2000 pounds of chlorine as either a liquid, gas, or both. PLANNED CHANGES TO IMPROVE SAFETY Employee input on improved safety and operations is encouraged and requested as a matter of City Policy. Training of WTP staff is conducted in-house, and at seminars and workshops sponsored by the Minnesota Section of the American Water Works Association, Minnesota Rural Water Association, and the Minnesota Department of Health. These seminars also provide a netwo rking vehicle for the sharing of information and innovations on the operations and safety procedures in the water works industry. Frequent training seminars are used as a tool to keep all safety issues on the minds of WTP staff. The full plan is available for review at the office of the Thief River Falls Water Superintendent. |