City of Dyersburg Water Plant - Executive Summary
1. The City of Dyersburg Water Plant's accidental release prevention policy includes maintaining chlorine |
detection alarm system and chlorination equipment by following manufacturers' maintenance recommendations. The DWP emergency response policy is carried out by the employees in conjunction with the Dyersburg Fire Department. Both policies are in compliance with EPA Emergency Response Program requirements.
2. The Dyersburg Water Plant serves the City of Dyersburg and Dyersburg's rural area. Chlorine is used at the plant to disinfect the drinking water. The chlorine building is located on the Water Plant Lot, south of the main plant and north of the Forked Deer River at 315 S. Main Ave. The chlorine building houses four one-ton containers of liquid chlorine, 2 chlorinators, chlorine detection alarm, heaters, ventilation fans, scales, and electrical panels. For safety precautions, the building is checked hourly by treamtent plant operators.
3. The offsite consequence analysi
s includes consideration of two chlorine release scenarios, identified as "worst case release" and "alternative scenario". The first scenario is defined by EPA, which states that "the owner or operator shall assume that the ... maximum quantity is the largest vessel .. is released as a gas over 10 minutes," due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case release scenario".
The Dyersburg Water Plant has only one container of chlorine on line at anytime; therefore, the worst case release scenario involves a failure of one container (2,000 lbs.). The worst case offsite consequency analysis was performed using the following information: quantity of toxic chlorine gas released - 2000 lbs.; release rate - 110 lbs/min; release duration - 10 minutes; wind speed 1.5 m/s; stability class F. A distance to toxic endpoint was 3.5 miles and the residential population potentially affected was 2,700.
The alternative releas
e scenario involves the rupture of a flexible connection or pipe leak. The alternative release analysis was performed using the following information: quantity of toxic chlorine gas released - 317 lbs; release rate - 10.5 lb/min; release duration - 60 minutes; wind speed 3.0 m/s; stability class D. A distance to toxic endpoint was 0.48 miles and the residential population potentially affected ws 51.
Passive mitigation considered for the worst case scenario was an enclosure. The tank was located inside the chlorine building. Active mitigation considered but not included for both scenarios is the activation of the chlorine alarm detector and an employee turning the valve off at the tank during his routine checks.
4. The general accidental release prevention program is based on the following key elements:
Preventive maintenance program
Operating procedures, written with the participation of the operators
Auditing and inspection programs
Chemcial-specific prevention steps include avaiability of self-contained breathing apparatus (SCBA), operator's awarness of the hazardous and toxic properties of chlorine, and the presence of chlorine alarm detectors.
5. No accidental releases of chlorine have ocurred at this facility in the past five years.
6. The Dyersburg Water Plant has an emergency response program which has been reviewed by the Dyersburg Fire Department. All plant employees are trained in emergency response and emergency response drills are conducted annually with the fire department.
7. At the present time there are no planned changes to improve safety.