Mennel Milling Company of Michigan - Executive Summary |
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EXECUTIVE SUMMARY The Mennel Milling Company of Michigan operates a large mill in Dowagiac, Michigan that processes wheat into many different grades of flour. Several of the grades involve a process in which chlorine is added to the milled flour to achieve a desired pH. In addition, a small amount of chlorine is added to the wheat prior to storage and milling to inhibit microbial growth. Chlorine is delivered to Mennel Milling Co. and used in one ton containers and 150-pound containers. The supplier delivers full chlorine containers to the site via truck. The containers are unloaded and stored in the indoor storage area by the use of an overhead crane rail hoist. Mennel Milling staff connects the ton containers and 150-pound cylinders to the feed system. The maximum number of ton containers is 6 (12,000 pounds) and 150-pound cylinders is 3 (450 pounds). Mennel Milling Co. uses vacuum feed systems that are inherently safe. These systems involve the use of air or water flowing through an eductor that creates a vacuum. This vacuum allows for the feed of chlorine from the containers into the piping system. If a chlorine line downstream of the vacuum regulator is broken or develops a leak, the vacuum is interrupted and the vacuum regulator automatically closes, preventing the discharge of chlorine gas. Mennel Milling Co. has contracted with Research Products Co. (REPCO) of Salina, Kansas to perform preventive and corrective maintenance on the chlorine feed systems. Mennel Milling Co. has developed a comprehensive, accidental release prevention program as part of the OSHA PSM program. The elements of this program include: 7 Process Safety Information 7 Process Hazard Analysis 7 Operating Procedures 7 Training 7 Management of Change 7 Pre-Startup Safety Review 7 Compliance Audits 7 Incident Investigation 7 Contractor Management 7 Hot Work Permits 7 Incident Investigation The worst-case release scenario has been defined by the USEPA. The worst-case release scenario involves the rupture and complete loss of chlorine from a full one-ton container outside the chlorine room at Mennel Milling. The distance to the specified endpoint (3-PPM chlorine in air) is estimated to be 1.3 miles. This distance was estimated using USEPA's tables provided in the guidance material. The worst-case release scenario does not take into account any administrative controls or passive mitigation measures. An alternative-case release scenario was also performed based on the experience of mill operators. The alternative scenario considers a leaking gasket at the connection between a one-ton chlorine container and the valve/piping system while the system is operating. It is assumed that the doors of the chlorine building are closed and the ventilation fan is running, exhausting fumes to the atmosphere. It is also assumed that the leak is detected and a response curtails the release in 10 minutes. The distance to the specified endpoint (3-PPM chlorine in air) i s estimated to be 0.1 miles. This distance was estimated using USEPA's tables provided in the guidance material. In the past five years, there have been no accidental releases of chlorine at Mennel Milling Co. that have resulted in deaths, injuries, or significant damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage. An Emergency Action Plan has been developed for the site. This plan contains measures that Mennel Milling Co. staff can take to alert employees to a release, how to distinguish between an incidental release and a significant release, and many other elements. Mennel Milling Co. staff will receive training to allow for defensive action in response to an on-site release. In the event of a chlorine release, Mennel Milling will contact the Dowagiac Fire Department for technical support. The fire department is trained and equipped to respond to chlorine incidents. The facility has coordinated its em ergency response activities with the City of Dowagiac Fire Department and the Cass County Local Emergency Planning Committee (LEPC). Mennel Milling Co. has performed hazard evaluations for the chlorination processes at the facility. As a result of this evaluation, several changes are planned to improve safety. These changes, to be implemented by June 1, 2000, include (but are not limited to): 7 Installation of chlorine gas detectors to sense a leak and to alert employees; 7 Establishment of a procedure to minimize the potential for accidents during unloading of full chlorine containers; 7 Installation of flow switches on the flour agitators to stop the flow of chlorine gas if the agitators become plugged; 7 Labeling of chlorine pipes; 7 Interlocking of agitator motors with the chlorine blower motor and/or the chlorine cabinet ball valve such that one or both shut off in the case of an agitator motor cut out. |