Wastewater Treatment Plant - Executive Summary
FEDERALLY MANDATED RMP SUBMISSION |
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1. Accidental Release Prevention and Emergency Response Policies
This City of West Sacramento Wastewater Treatment Plant (WWTP), located at 1991 South River Road, West Sacramento, Ca., handles chlorine and sulfur dioxide, which are both considered a hazardous material that is a regulated substance and is considered in the Risk Management Plan (RMP). The properties of chlorine and sulfur dioxide 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 and sulfur dioxide; the safety devices and systems designed and constructed into the facility; and the training of the pertinent personnel.
2. Stationary Source and Regulated Subst
The City of West Sacramento's Wastewater Treatment Plant is designed to treat 7.5 million gallons per day (MGD) of wastewater from the residences and businesses of the City. The treatment process consists of bar screens, three primary clarifiers, an activated sludge aeration basin with an anoxic selector, two secondary clarifiers, a chlorine contact chamber, dechlorination and pH adjustment system, discharge pumps to treated wastewater to the Sacramento River, three anaerobic digesters, and two sludge dewatering belt presses.
Chlorine is used to disinfect the treated wastewater to prevent the spread of pathogenic organisms. Sulfur dioxide is used to neutralize the chlorine before it is discharged into the Sacramento River. Chlorine is toxic to the aquatic life-cycle.
Chlorine is delivered by a commercial chlorine supplier in one-ton containers for use at the WWTP. Off-loading of the one-ton containers from the commercial delivery vehicle is accomplished with a hoist.
All the one-ton containers are placed in the chlorine storage area. Four of the chlorine containers that are on-line are placed on the load-cell scale. Four other chlorine containers are placed on stand-by, and four more chlorine containers are in storage near-by. The WWTP has administrative procedures in place to limit the amount of chlorine at the facility to no more than 12 one-ton containers for a total of 24,000 pounds.
Sulfur dioxide is delivered by a commercial supplier in one-ton containers for use at the WWTP. Off-loading of the one-ton containers from the commercial delivery vehicle is accomplished with a hoist. All the one-ton containers are placed in the sulfur dioxide storage area. Five of the sulfur dioxide containers that are on-line are placed on the load- cell scale. Five of the sulfur dioxide containers are placed on stand-by, and five more sulfur dioxide containers are in storage near-by. The WWTP has administrative procedures in place to limit the amount of sul
fur dioxide system to no more than 15 one-ton containers for a total of 30,000 pounds.
Both the chlorine and sulfur dioxide one-ton containers are delivered during normal working hours. The driveway provides adequate room for the delivery and parking of the delivery vehicles during the off-loading of the full one-ton containers and loading of the empty one-ton containers. The buildings are not exposed to vehicular traffic. The building is locked after normal working hours. No unauthorized personnel are allowed entry into the building. The container storage and handling is conducted pursuant to Sections 2.6, 2.7, and 2.8 of the Chlorine Institute's Chlorine Manual for both chlorine and sulfur dioxide.
This treatment facility operates twenty-four hours per day, seven days per week. The chlorine and sulfur dioxide gas is withdrawn from the one-ton containers by vacuum. This vacuum opens the vacuum regulator diaphragm and withdraws the gas from the one-ton containers at a controlle
d feed rate set by the operators with the use of the rotometer at the chlorinator unit. The chlorine gas is injected into the feed water line, where it becomes a chlorine/ water solution and is feed where it is needed in the treatment process. The sulfur dioxide feed unit operates in similar fashion to the chlorine feed unit. The sulfur dioxide is feed after the chlorine contact chamber to de-chlorinate the wastewater effluent before it is discharged in to the Sacramento River.
The container storage building has inlet and outlet exhaust fans for fresh air entry, chlorine leak detectors, and alarm systems. The vacuum regulators are vented to the outside.
The receipt, storage, and handling of the subject substances are considered as part of one complete process.
3a. Worst Case Release Scenario
The one-ton (2,000 pounds) chlorine container is the largest vessel size (and only chlorine vessel size) in the chlorine system located at the WWTP. The Worst Case release scenario to be m
odeled for the one-ton chlorine container assumes that the full 2,000 pounds of chlorine is released over a ten minute period resulting in a release rate of 200 pounds per minute. The distance to the endpoint of 0.0087 mg/l (3 ppm) for the Worst Case scenario is 1.3 miles. This chlorine release will extend beyond the boundaries of the stationary source (the wastewater treatment facility).
3b. Alternative Release Scenario
The Alternative Release scenario for chlorine for the one-ton container located at the WWTP 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 of 0.0087 mg/l (3 ppm) for the Alternative Release scenario is 0.1 mile. This chlorine release will extend beyond the boundaries of the stationary source.
The Alternative Release scenario for sulfur
dioxide for the one-ton container located at the WWTP 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 of 0.0078 mg/l (3 ppm) for the Alternative Release scenario is 0.1 mile. This sulfur dioxide release 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 chlorine released, if a release were to occur, and preferably not to have a release occur. This administrative control is inherent in the operational procedures for the chlorine and sulfur dioxide systems 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 chlorine and sulfur dioxide released, if a release were to occur, and preferably to not have a release occur. The mitigation measures are based upon the design, inspection, testing, and maintenance of the chlorine and sulfur dioxide system and its related equipment 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 the chlorine and sulfur dioxide 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 chlorine or sulfur dioxide within the past five years at the facility.
6. Emergency Response Program
The Emergency Response Pro
gram 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 West Sacramento Fire Department at the evacuation assembly location if a release occurs that causes the evacuation to be initiated. The Yolo County Division of Environmental Health Services can incorporate 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 the regulated chlorine system. These commitments will be prevention and mitigation measures for accidental releases of the regulated substances.