City of Tracy Wastewater Treatment Plant - Executive Summary
1. Accidental Release Prevention and Emergency Response Policies |
The City of Tracy Wastewater Treatment Plant (WWTP) handles chlorine, sulfur dioxide, and anhydrous ammonia, all of which are considered a hazardous material that is a regulated substance and is considered in the Risk Management Plan (RMP). The properties of these chemicals make it necessary to observe safety precautions in handling to prevent human exposure and to reduce the threat to the facility's workers and nearby members of the community.
It is the facility's policy to adhere to all applicable Federal and State of California rules and regulations. Safety depends upon the safe procedures used to handle chlorine, sulfur dioxide, and anhydrous ammonia; the safety devices and systems designed and constructed into the facility; and the training of the pertinent personnel.
2. Stationary Source and Regulated Substances Handled
Chlorine is used for odor control and plant effluent disinfecting. It is also used to st
abilize and disinfect wastewater sludge in the Purifax process (not currently used). Delivery of chlorine is made by the supplier from a bulk semi-trailer.
The chlorine is stored as a compressed liquefied gas in a supplier-owned bulk storage tank (10,000 gal fill capacity) located inside the Chlorine Storage Room of the Utility Building, which is a concrete block building. In the Chlorine Storage Room there are also two headers and an overhead bridge crane and trolley hoist used to stage chlorine ton containers for liquid and/or gas feed in the event the bulk tank is out of service for an extended period of time. Delivery of chlorine is made by supplier from a bulk load semi-trailer.
Sulfur dioxide gas is used for plant effluent dechlorination. It is stored outdoors as a compressed liquefied gas in a supplier-owned bulk storage tank (2,700 gal fill capacity). There is a header with provision for gas withdrawal from up to two one-ton containers, in the event that the bulk tank i
s out of service for an extended period of time. Delivery of sulfur dioxide is made by the supplier from a bulk load semi-trailer.
Anhydrous ammonia is used at the WWTP to condition plant effluent for better disinfection performance. Anhydrous ammonia is stored as a liquefied compressed gas in a bulk tank (1,000 gal fill capacity) located near the secondary clarifiers. Delivery of anhydrous ammonia is made by the supplier from a bulk load delivery vehicle.
The ammonia is fed as a gas through a rotometer at reduced pressure and absorbed directly into plant effluent. There is provision for withdrawal of liquid ammonia through an evaporator and ammoniators at the location of the 2,000 gallon anhydrous ammonia tank. This provision is not currently used.
The receipt, storage, and handling of the subject substances at the City of Tracy's Wastewater Treatment Plant is considered a single process.
3a. Worst Case Release Scenario
The 2,700 gallon (32,000 pound fill capacity) sul
fur dioxide container is the largest vessel in the sulfur dioxide system located at the Wastewater Treatment Facility. The Worst Case release scenario to be modeled for the 32,000 pound sulfur dioxide container assumes that the full container of sulfur dioxide is released over a ten-minute period resulting in a release rate of 3,200 pounds per minute. The distance to the endpoint of .0078 mg/l for the Worst Case scenario is 5.6 miles. This sulfur dioxide release will extend beyond the boundaries of the stationary source.
3b. Alternative Release Scenario
The Alternative Release scenario for chlorine, sulfur dioxide and anhydrous ammonia assumes a release from a valve packing, resulting in an estimated release of no more than 2 pounds per hour. The period of release is taken to be one hour in duration, resulting in a total release quantity of 2 pounds for each regulated substance.
The distance to the endpoint for each regulated substance for the Alternative Release scenario is l
ess than 0.1 mile, reported as 0.1 mile. The release of each regulated substance for the Alternative Release scenario will extend beyond the boundaries of the stationary source.
3c. Administrative Controls
Administrative controls to limit the distances for each reported scenario exists to restrict to a minimum the amount of regulated substances released, if a release were to occur, and preferably to prevent a release from occurring. These administrative controls are inherent in the operational procedures for each regulated substance's system and the training provided to the operators.
3d. Mitigation Measures
Mitigation measures to limit the distances for each reported scenario exists to restrict to a minimum the amount of regulated substances released, if a release were to occur, and preferably to prevent a release from occurring. The mitigation measures are based upon the design, inspection, testing, and maintenance of each regulated substance's system and its related equipme
nt and components.
4. General Accidental Release Prevention Program and Chemical Specific Prevention Steps
The facility complies with all applicable federal and state codes and regulations. There are safety meetings and safety training. The Process Safety Management (PSM) program implemented at the facility for each regulated substance 's system, and related activities and equipment, represents one of the facility's main active commitments to an accidental release prevention program.
5. Five-Year Accident History
There have been no incidents involving the release of any of the regulated substances handled at the Wastewater Treatment Plant within the past five years.
6. Emergency Response Program
The Emergency Response Program is based on alerting personnel at the facility of the need to evacuate the facility and await the arrival of responders from the City of Tracy Fire Department at the evacuation assembly location if a release occurs that causes the evacuation to be initiate
d. The San Joaquin County Office of Emergency Services incorporates this response into the County Area Plan for the Local Emergency Planning Commission.
7. Planned Changes to Improve Safety
There are commitments made under the Process Hazard Analysis element of the Process Safety Management (PSM) that are being implemented at this time for the next year. Current applicable codes and regulations are reviewed as part of the PSM to determine if other commitments need to be made to achieve increased operational safety for each regulated substance's system. These commitments include prevention and mitigation measures for accidental releases of the regulated substances.