Moss Landing Power Plant - Executive Summary

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In response to the requirements of the California Code of Regulations and Federal EPA, this California Accidental Release Prevention (EPA Risk Management) Program document (CalARP/RMP) has been developed for the Moss Landing Power Plant (MLPP) located in Moss Landing, California.  MLPP is owned by Duke Energy Moss Landing LLC and operated by DFD California Operations. 
Plant and Process Information 
MLPP has installed a new aqueous ammonia system as a component supporting selective catalytic reduction (SCR) of MLPP boiler emissions.  The ammonia vapor (in the presence of the SCR catalyst) reduces NOx compounds to elemental nitrogen and water to reduce the total NOx effluent emitted from the plant. 
The aqueous ammonia system is comprised of five storage tanks, each with a capacity of 30,000 gallons, along with feed and transfer pumps and vaporizing equipment.  The five tanks have an aggregate capacity of 150,000 gallons of 29.4% NH4OH solution containing approximately 328 
,104 pounds of NH3 as solute.  This quantity of ammonia exceeds the state and federal threshold quantities. 
Worst-Case Release Scenario 
MLPP has conducted an offsite consequence analysis as required by the regulations, including an extremely unlikely, worst-case release scenario (i.e., total release from the single largest container assuming worst case meteorological conditions).  Results of this worst-case event indicate that offsite receptors could be affected.  
A release represented by this worst-case scenario is extremely unlikely because of the design of system components and the prevention program in place at MLPP. 
EPA release reporting databases and industry experience suggest that the worst-case release scenario as defined in the RMP regulations is so unlikely that it should not be used as the basis for emergency planning.  A more reasonable potential release scenario for emergency planning is presented in "The alternative release scenario(s)" section below. 
Alternative Re 
lease Scenario 
A "credible" alternate release scenario was formulated in accordance with USEPA guidance. This scenario involves the postulate of a transfer hose failure during filling of the on-site tanks.  The resulting ammonia vapor that can volatize from the liquid spill is further mitigated by passive protective measures.  These measures include diking, drainage, and secondary containment which rapidly drain ammonia to a below grade vault.  This effectively reduces the surface area of any spills so that vapor emissions are also reduced.  Results of this credible alternative event indicate that offsite receptors could be affected.   
Accidental Release Prevention Steps 
MLPP is committed to public safety, personnel safety, continued reliable operation and regulatory compliance.  Based on this commitment, the Plant Manager has overall responsibility for the development and implementation of the Risk Management Program.  A management system has been developed with clearly defined acc 
ountability and responsibility for the RMP Program. 
To help ensure that a worst-case or alternative release scenario does not occur, MLPP maintains a release prevention program with the primary focus of protecting the public and plant employees from the hazards associated with an accident or release involving ammonia.  The multifaceted program includes the use of: 
Ammonia gas detectors and alarms to rapidly alert operators to any problems; 
Safety information to document the safe process design; 
Process hazards analyses to evaluate the chemical and process hazards; 
Operating procedures to ensure that the system is operated safely; 
Maintenance, inspection and testing to ensure that the system is properly maintained; 
Safe work practices to ensure that employees working on and around the processes are aware of the hazards, can perform their job duties safely and know the actions to be taken in an emergency; 
Incident Investigation procedure to investigate incidents and "near misses" 
to determine root causes and make needed safety improvements; and, 
Periodic Compliance Audits to ensure that our programs are working as they should. 
Five-Year Accident History 
There is no specific accident history for the aqueous ammonia system as this is a new installation. 
MLPP has previously and will continue to handle 28-30% by weight aqueous ammonia in small capacity systems (below EPA threshold) for pH treatment of boiler water.   The accident history for this existing use was reviewed for comparative purposes.  Within the past five years, MLPP has not had any accidental releases that resulted in injuries or property damage. The plant has maintained an excellent safety record throughout its operating history and has never had a major ammonia release that could have had adverse effects on the public.   
Emergency Response 
In the event that a ammonia release does occur, MLPP has an emergency response program that coordinates emergency response with the North County Fire Dis 
trict.  Additionally, the plant has emergency operations procedures in place detailing appropriate emergency actions to help mitigate the effects of any release.  
Maintaining A Safe Operation 
MLPP will continually work to safely manage the hazards of ammonia to protect the community we serve and the employees working for us. The Risk Management Program will be maintained to reduce the risk of accidental releases through training, procedures, equipment maintainenance, and safe work practices. Periodically, we will audit our program, review our Process Hazard Analysis, coordinate with the community emergency response organization, and will update our program as needed to assure safe and efficient control and management of the aqueous ammonia system.
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