Darigold Rainier Plant - Executive Summary |
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SECTION 112(r) RISK MANAGEMENT PLAN DARIGOLD RAINIER AVENUE PLANT SEATTLE, WASHINGTON EXECUTIVE SUMMARY FACILITY DESCRIPTION Darigold Incorporateds Rainier Avenue Plant is located on Rainier Avenue South in Seattle, Washington (see Figure 1). The Seattle plant produces ice cream, milk, milk products, and juice for distribution throughout the Puget Sound region. Plant operations include bulk milk receiving and storage, milk processing, ice cream manufacture, packaging, warehousing, and shipping. The plant uses a mechanical ammonia refrigeration system to chill the product during processing and cool the cold storage warehouse that is used to store the product before shipment. The refrigeration system uses anhydrous ammonia at various locations throughout the plant. At any given time, 27,000 pounds of ammonia is typically stored and used at the facility. ACCIDENTAL RELEASES DURING PAST 5 YEARS During the past 5 years, Darigolds Rainier Avenue Plant has not expe rienced any ammonia releases that resulted in any injuries, offsite evacuations, or property damage. PROCESS SAFETY MANAGEMENT ACCIDENT PREVENTION PROGRAM Darigolds Rainier Avenue Plant is subject to OSHAs Process Safety Management (PSM) regulations for all equipment and operations associated with the ammonia refrigeration system. In response to safety reviews performed as part of EPAs ARPP, Darigolds safety management system is being upgraded to include the following PSM elements to minimize the potential for an accidental release: x Review of the design of all equipment and controls for the ammonia system to assess their proper design and installation. x Review of standard operating procedures for the ammonia system. All procedures must be reviewed and certified annually. x Regular inspection of all equipment, monitoring systems and controls for the ammonia system, with detailed documentation of all inspections. x Prompt corrective action for any non-conformin g items identified by the regular inspections. x Initial safety training and 3-year refresher training for all operators and maintenance staff working on the ammonia system. x Rigorous safety reviews prior to system startup, if any equipment or operations for the ammonia system are modified. x Stringent investigation of any incidents that had the potential to cause ammonia releases. x Periodic evaluation of the safety records of all outside contractors who work on the ammonia system. x Maintenance and training of staff in an effective emergency action plan. x Independent audits of the entire PSM program every 3 years. EMERGENCY RESPONSE PROCEDURES Darigold uses its corporate Safety Manual and the site-specific Emergency Action Plan as guidance for emergency response in the unlikely event of an accidental release. The key elements of the Emergency Action Plan are as follows: x All plant staff (including administrative and clerical staff) receives training i n the specific elements of the program. x Several supervisors and operators are trained, certified, and equipped for hazardous materials (HazMat) emergency operations to repair accidental releases in areas of high ammonia concentration. x Darigold is currently installing electronic ammonia gas detectors with audible alarms. The plant uses a combination of its 2-way radio system and its plant- wide loudspeaker system to alert staff of a potential accident and to conduct in-plant communications. x In the event of a large release, the facility would contact the Seattle Fire Department. Darigolds HazMat team and the Fire Department would jointly conduct emergency response actions and repair the ammonia leak. PLANT UPGRADES TO IMPROVE SAFETY As a result of the safety reviews conducted as part of the ARPP, Darigold is implementing the following upgrades to improve plant safety: x Install ammonia gas detectors at several processes inside the plant to improve emerge ncy response in the unlikely event of a large leak. x Install automatic emergency shutoffs in conjunction with ammonia gas detectors placed in process areas that could be subject to large accidental releases. For example, the plate freezer room that is the subject of the Alternate Release Scenario described below will be equipped with gas detectors and automatic emergency shutoffs. x Revise written operating and maintenance procedures to include all PSM- required information. HYPOTHETICAL ACCIDENTAL RELEASE SCENARIOS The Risk Management Plan must assess the downwind impacts of hypothetical accidental releases. EPA requires facilities to model the distance that a plume of released gas would travel before being dispersed to an ambient concentration equal to the Toxic Endpoint Concentration. The EPA-specified Toxic Endpoint Concentrations for various compounds are those concentrations that would cause no permanent harm but could interfere with peoples ability to leave the area. The Toxic Endpoint Concentration for ammonia is 200 parts per million (ppm). Darigold evaluated a wide range of hypothetical accidents that could result in releases of ammonia. In accordance with EPAs rule, two hypothetical accidental release scenarios were developed: Worst-Case Scenario In this scenario, the entire contents of the largest ammonia vessel (the 2,700-pound outdoor ammonia delivery tank) are accidentally released in a 10-minute period. EPA requires this extreme worst-case scenario to be evaluated for the Risk Management Plan, but Darigold knows of no event that could realistically cause such a large release. However, in accordance with this worst-case scenario, it is assumed that the release occurs during a period of exceptionally calm, stagnant conditions (1.5 meter/second wind speed and F stability) that would result in the highest downwind concentrations. Graphs from EPAs RMP Guidance for Ammonia Refrigeration indicate the gas cloud would travel 0.65 miles (3,400 feet) before being dispersed to the 200 ppm Toxic Endpoint Concentration. Figure 1 is a map that shows the circle defined by the 0.65-mile downwind distance. Alternate Release Scenario Darigold conducted a safety review to assess a range of accidents that could cause ammonia releases large enough to affect people beyond the facility boundary. The review team selected the following hypothetical accident as the Alternate Release Scenario. Note that this scenario incorporates the ammonia gas detectors and automatic shutoff systems described in the Plant Upgrades to Improve Safety section of this Executive Summary. A flexible hose on one of the 12 plates on the plate freezer suddenly breaks, causing all of the ammonia inside the plate to spill onto the floor of the freezer room. In reality, a worn hose would probably develop a slow pinhole leak that would be easily detected and repaired before the hose broke. However, to be conservative, it is assumed that the hose breaks instantaneously, before the electronic gas detector inside the freezer room can automatically shut off the system and alert the operators before the break occurs. Under this conservative scenario, 241 pounds of liquid ammonia spills onto the floor of the freezer room and begins to evaporate. The thermodynamic properties of ammonia dictate that 18 percent (i.e., 43 pounds) of the spilled liquid immediately flashes to vapor. The remainder of the spilled liquid immediately cools to ammonias boiling point temperature (-28 degrees F), forms a puddle of liquid ammonia, and slowly evaporates. The gas detector inside the freezer room automatically shuts off the freezer pumps and closes the rooms louvers to prevent the release from spreading to other parts of the building. The rooms ventilation fan then discharges the evaporating ammonia to the rooftop emergency vent. It is assumed that Darigolds HazMat team arrives at the scene 10 mi nutes after the break and cleans up the spilled liquid. EPAs RMP Guidance for Ammonia Refrigeration indicates that 40 percent of the puddled liquid ammonia would evaporate during this 10-minute period. A total of 122 pounds of ammonia (the sum of the initially flashed ammonia and the slowly evaporated ammonia) is released to the outside air during the 10-minute period. After the HazMat team neutralizes the spilled liquid, the emission rate from the emergency vent fan quickly decreases to zero. Graphs from EPAs RMP Guidance for Ammonia Refrigeration were used to model the downwind impacts. As shown on Figure 1, the Alternate Release Scenario plume was modeled to travel 0.04 miles (210 feet) before dispersing to a concentration of 200 ppm. 18 June 1999 |