Mandalay Generating Station - Executive Summary
1.0 EXECUTIVE SUMMARY |
The following provides a brief summary of the key components of the Risk Management Program for the aqueous ammonia storage and handling system at Mandalay Generating Station.
Pursuant to the requirements contained in Chapter 6.95, Article 2 of the California Health & Safety Code x 25531 through 25543.3, and the Clean Air Act 112r and Title 40 of the Code of Federal Regulations Part 68, this Risk Management Plan (RMP) is submitted on behalf of Mandalay Generating Station. This program is implemented in California as the California Accidental Release Prevention (CalARP) Program.
The scope of this RMP is based on discussions with the Administering Agency (AA), the city of Oxnard Fire Department, to ensure that all issues are resolved and to incorporate state requirements. With input from the AA, the ammonia storage and handling facility was identified as the only process that triggers the RMP/CalARP requirements. This process was determine
d to be covered by Program 2 requirements. The process hazard review technique was presented to and approved by the AA and the level of detail for this RMP submission agreed upon.
1.2 General Description of the Stationary Source and Regulated Substance
Mandalay Generating Station, located in Oxnard, California, is an electric generating station consisting of two units each rated at 215 MW, and a third peaking unit rated at 140 MW. Units 1 and 2, which are capable of combusting either fuel oil or natural gas, are equipped with Selective Catalytic Reduction Systems (SCR) units for the control of oxides of nitrogen (NOx) emissions. These SCRs employ ammonia injection technology which reduces NOx emissions by approximately 80%. Aqueous ammonia is classified as a toxic chemical subject to the requirements of the California Accidental Release Prevention (CalARP) Program. The aqueous ammonia used is a 30% solution of ammonia in water, ammonium hydroxide (CAS Number 7664-41-7).
monia storage and handling system at Mandalay Generating station is comprised of a single storage tank, pumps, and piping which terminate at the vaporizer where the aqueous ammonia is atomized to concentrations below 20%. The tank is 14650 gal in volume and is equipped with pressure relief valves, flame arrester, temperature, pressure, and level indicators. The piping consists of both 1 and 2 inch I.D. pipes.
Aqueous ammonia is also used in the station water treatment system for pH control, and in the demineralizer system where it is used for the regeneration of anion and cation exchange resins. These processes are separate from the main storage tank, however and the amounts are below thresholds.
All other regulated substances onsite are below applicable thresholds.
1.3 Offsite Consequence Analysis Results
The Offsite Consequence Analysis (OCA) prepared in support of this RMP utilized the methodologies recommended by EPA and employed the RMP*Comp, Version 1.06 modeling system
. The following release scenarios were hypothesized:
Release Scenario I - Worst-Case
The entire contents of the aqueous ammonia storage tank is released through a failed tank or pipe within the secondary containment dike large enough to contain the entire volume. Under worst-case meteorological conditions, 1.5 m/s wind speed and a stable (Pasquill F) atmospheric stability class, the ammonia cloud could travel 0.4 miles before dispersing sufficiently to no longer pose a health hazard to the public.
Release Scenario II - Alternative
The entire contents of the delivery truck's hose carrying aqueous ammonia between the shut-off valve on the truck and hook-up at the tank is released by a failed delivery hose outside of secondary containment. Active mitigation consists of the truck's operator closing the truck's shut-off valve and diluting the ammonia spill with water. Under average meteorological conditions, 3.0 m/s wind speed and a neutral (Pasquill D) atmospheric stability class
, the ammonia cloud could travel 0.1 miles before dispersing sufficiently to no longer pose a health hazard to the public.
Release Scenario III - Alternative
The entire contents of all piping carrying aqueous ammonia between the ammonia pump skid and the vaporizer is released through a failed pipe outside of secondary containment. Active mitigation includes manual or automatic shut down of the ammonia pumps by the plant operators. Under average meteorological conditions, the ammonia cloud could travel 0.1 miles before dispersing sufficiently to no longer pose a health hazard to the public.
Release Scenario IV - Alternative
A connector, flange, etc. fails resulting in the leak of approximately 50 gallons of aqueous ammonia outside of secondary containment. Active mitigation consists of automatic or manual shutoff of affected pump and its isolation pending repair and dilution of the spill with water. Under average meteorological conditions, the ammonia cloud could travel 0.1 mi
les before dispersing sufficiently to no longer pose a health hazard to the public.
Release Scenario V - Alternative
Aqueous ammonia is released though a corrosion caused hole = inch in diameter outside of the secondary containment between the secondary containment dike and the ammonia pump skid. Active mitigation consists of regular equipment inspection and maintenance program. Under average meteorological conditions, the ammonia cloud could travel 0.1 miles before dispersing sufficiently to no longer pose a health hazard to the public.
1.4 Summary of the Five-Year Accident History
There have been no accidental releases from the aqueous ammonia storage and handling system at Mandalay Generating Station in the past five years that have resulted in deaths, injuries, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage. (Statute: 40 CFR 68.42)
1.5 Summary of Prevention Program 2
Mandalay Generating Station is covered by an accidental release prevention program which includes the following:
7 Periodic hazard reviews and updates
7 Periodic audits of the system and its operation
7 Emergency Response Plan coordinated with local responding agencies
The aqueous ammonia storage and handling system prevention program includes the following components:
7 Comprehensive Station Order covering all components of the aqueous ammonia storage and handling system including,
7 Internal Compliance Audits
7 Incident Investigation
1.6 Summary of the Emergency Response Program
Mandalay Generating Station's emergency response plan has recently been updated to include the following core elements:
7 Specific actions to be taken in response to an accidental release of ammonia
7 Procedures to notify local and public agencies including the Oxnard Fire Department, the California Office of Emergency Services, and the National Res
ponse Center as necessary
7 Information regarding the training of employees
7 A list of other federal and state requirements to which the facility is subject
1.7 Planned Changes to Improve Safety
A hazard review of the aqueous ammonia storage and handling system at Mandalay Generating Station was conducted as part of this Risk Management Program. After thorough review, the existing system was found to be prudently designed, operated and maintained. Following are additional enhancements which will further ensure the safety of the aqueous ammonia storage and handling system:
7 Add flashing or rotating warning light in addition to existing audio alarm from ammonia gas detectors (April 30, 2000)
7 Install additional pipe supports per seismic assessment (April 30, 2000)