Wenatchee Wastewater - Executive Summary

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A. Accidental Release Prevention and Emergency Response Policies 
 
The City of Wenatchee Wastewater treatment facility (hereafter referred to as Wenatchee wastewater) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices.  It is the policy of the City of Wenatchee to adhere to all applicable federal and state safety and environmental regulations. 
 
At Wenatchee wastewater chlorine is used on-site. Chlorine is considered hazardous by EPA and is listed on the Extremely Hazardous Substance (EHS) list.  Chemical properties of chlorine make it necessary to observe certain safety precautions in handling Chlorine in order to: 
7 Prevent unnecessary human exposure 
7 Reduce the threat to our personnel 
7 Reduce the threat to the community 
 
Wenatchee wastewater's emergency response policy involves the preparation of response plans and training of employees. Wenatchee wastewater has trained its personnel in the safe handlin 
g of chlorine.  Employees have been trained in the use of personal protective equipment and chlorine "patch" kits. 
 
B. Facility and Regulated Substance Handled 
 
Wenatchee wastewater is a wastewater treatment plant, located at 201 N. Worthen Wenatchee, Washington in Chelan County.  Wenatchee wastewater is located next to the Columbia River 
 
The regulated substance used at the treatment plant is chlorine (CAS# 7782-50-5). Chlorine is used for the sanitizing of wastewater, collected from the city of Wenatchee. 
 
Four thousand pounds (two 1-ton containers) is the maximum amount of chlorine in the process at any one time.  Chlorine is consumed in the water treatment process at the approximate rate of 119 pounds per day; therefore the actual amount of chlorine varies and could be less than 4,000 pounds. 
 
Wenatchee wastewater uses other hazardous substances on-site, however they do not meet or exceed the threshold limits established in 40 CFR 68.130.  However, the city of Wenatchee believes in 
the concept set forth in the "General Duty Clause" of the Clean Air Act.  To this effect, Wenatchee wastewater has established policies, procedures and training to reduce the risk of an accidental hazardous substance release for the safety of its employees and surrounding areas. 
 
C. Worst-Case and Alternative Scenarios 
 
The off-site consequence analysis considers two chlorine release scenarios identified as "worst case" and "alternative" scenarios.  The worst case scenario is defined by the Environmental Protection Agency (EPA), which states that "the owner or operator shall assume that the maximum quantity in the largest vessel is released ".  The alternative scenario is defined as "more likely to occur than the worst case scenario". 
 
Worst-Case Scenario - Failure of the largest vessel would release 2,000 pounds of chlorine.  The release would occur inside the chlorine room; its walls are in direct contact with the outside.  Although the release would occur inside of a building, enc 
losure mitigation, or any other type of mitigation, were used in the determination of the distance to the toxic end-point. 
 
The distance to the toxic end-point of 0.0087 mg/L (3 ppm) is 1.3 miles.  Distance was determined by use of RMP-COMP, base on the US EPA criteria for the "worst-case" scenario. 
 
The "risk radius" extends past the boundaries of the plant, into public receptor areas, especially recreation areas along the Columbia River. A worst-case release could have a major impact on the transient population using Riverfront Park and the Columbia River, depending on the time of year.  
 
Alternative Release Scenario -  The scenario chosen was a release from the "pigtail" of a full container.  The pigtail is the connector from the container to the process, which as a diameter of 0.5".  Although the pigtail connection is located just above the center of the container, it receives the chlorine from the vapor space, at the top of the container.  For this reason, the release modeled was  
based on a release from the top of the container.  For the purpose of this modeling no mitigation was used.  It was assumed that the release occurred from a "full" container, releasing directly into the atmosphere. 
 
The distance to the toxic end-point of 0.0087 mg/L (3 ppm) is 930 yards (0.52 mile). The alternative scenario was modeled, using ALOHA, version 5.2.1, and was modeled using a wind speed of 3 meters per second, stability class D, Temperature of 51o F, humidity of 25%, urban ground roughness, tank model and heavy gas modeling. 
 
The risk radius extends past the boundaries of the plant, into public receptor areas.  As stated in the worst-case scenario, the area of greatest concern is Riverfront Park and the Columbia River, which are in close proximity to the plant.  Riverfront Park is adjacent to the plant.  
 
Both scenarios are based on the 1-ton container being full when release.  The facility uses chlorine at a rate of approximately 119 pounds a day, therefore an actual rele 
ase may be less than a full container. 
                                                                                                                                                                             D. General Accidental Release Prevention Program 
 
Wenatchee wastewater's accidental release prevention program is based on the following key elements: 
7 Training of personnel 
7 Preventative maintenance program 
7 Use of safety equipment 
7 Use of accurate and effective written operating procedures 
 
Wenatchee Wastewater complies with: 
7 OSHA's and Washington State's process safety management 
7 Applicable Washington State's safety and environmental regulations 
7 The Chlorine Institute Manual for safe handling of chlorine 
7 The Uniform Fire Code. 
 
The chlorinating system was installed to standards and local codes at the time of installation.  Other safety systems Wenatchee wastewater utilizes include: 
7 Chlorine detection alarm that triggers an alarm and light indicator on the cont 
rol panel in the control room.  After hours this alarm triggers an auto-dialer which contacts the on-call operator. 
7 Appropriate overhead crane for handling the ton containers. 
7 Emergency exhaust fan and recirculating fan. 
7 Proper fitting and closing doors. 
 
Operating Procedures and checklists have been prepared by Wenatchee wastewater to be used by employees performing operational functions. Procedures are kept in the control room.  These procedures include:  
7 Pre-start up procedures 
7 Routine operations 
7 Maintenance 
7 Response to major and minor releases 
7 Emergency action plan 
 
E. Five-Year Accident History 
 
Wenatchee wastewater has not had any accidents involving chlorine in the last five years. 
 
F. Emergency Response Program 
 
In addition to the operating procedures, Wenatchee wastewater has established Emergency Response Guidelines for releases involving chlorine.  These procedures are part of the ongoing training of personnel and include: 
7 Response to chlorine releases. 
7  
Warning and notification to plant personnel, public safety responders, and the public. 
 
These procedures are coordinated with the Wenatchee Fire Department and the Chelan County LEPC and response actions have been discussed with Wenatchee Fire. 
 
G. Planned Changes to Improve Safety 
 
The only planned change to increase the safety of the system at Wenatchee wastewater is to separate the warning indicator for the detection alarm, in the control room. 
 
Wenatchee wastewater will continue to ensure ongoing training of personnel.
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