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HomeMy WebLinkAboutPA2022-063_Preliminary Site Consequence AnalysisCoyote Canyon Preliminary Site Consequence Assessment April 29, 2024 Note: This study has been preformed with the information available as of April 29, 2024 and is subject to change. Executive Summary •The purpose of this report is to outline the potential for flammable vapor clouds, jet fire, and toxic vapor clouds at Coyote Canyon and the possible effect they pose on the surrounding area, the Archaea control room, and the landfill county building. •Standard 3200 SCFM V1 Archaea design with 44.5 ppm H2S •Note that Santa Ana wind modelling showed minimal effect on jet fire scenarios and reduced the effect of vapor cloud formation. •This is divided into two parts: ground level occupied building, personnel and public receptor modelling and vegetation ignition modelling at 20 feet elevation. Study Contents: •Risk to Occupied Buildings, Personnel and Public Receptors (modelled at ground level) •Site Process Hazard Mapping (Summary of all potential hazards) – Slide 4 •Risk to Surrounding Public Receptors – Slide 5 •Occupied Building Recommendations – Slide 6 •Risk to Surrounding Vegetation (modelled at 20 feet elevation) •Jet Fire Radii Mapping– Slide 8 •Worst Case Jet Fire Case (XZ Plane) – Slide 9 •Consequence Prevention and Mitigations – Slide 10 •Conclusion – Slide 11 •Back Up Slides (Slides 12-21) 2 Clarification: The consequence radii are modelled as circles, representing the potential effect zone, should the wind be blowing in all directions at once. Should an event occur, the shape would realistically be conical depending on wind speed and direction. Risk to Occupied Buildings, Personnel and Public Receptors (Inside wall) 3 Site Process Hazard Mapping (Ground Level) 4 1.6 kW/ m2 Jet Fire Boundary 30 PPM H2S Boundary Lower Flammability Limit Boundary 0.4 PSIG Vapor Cloud Explosion Boundary 12 ft. Wall CR LF County Legend Risk to Surrounding Receptors Public receptors near by but not affected consequence radii: •Sage Hill Highschool •Newport Coast Drive •California State Route 73/ San Joaquin Hills Transportation Toll Road Private building affected by consequence radii: •Landfill county Building Occupied Building Mitigation Recommendations 6 Landfill County Building: Potential for 0.6 PSIG Worst case scenario is that windows facing process shatter from overpressure Suggested Mitigations: Archaea Control Room Building: Potential for 1 PSIG Suggested Mitigations: Risk to Surrounding Vegetation Wildfire Considerations & Mitigations 7 Jet Fire Radii (30 kW/m2, 50 kW/m2) 8 •A height of 20 feet is mapped on the XY plane because at 20 feet in the air, the jet fire thermal radiation reaches farthest. •Two Cases: •Prolonged Ignition Case o 30 kW/m2 o Ignites within 15-20 minutes of exposure o At 20 ft. elevation, reaches 10 ft. from wall •Instantaneous Ignition Case o 50 kW/m2 o Ignites with 0-2 minutes of exposure o At 20 ft. elevation, reached 7 ft. from wall •Mitigations preventing such events: •Fire and gas detection •Process control alarms •Process control shutdowns (Pressure safety high-highs, Pressure safety low-lows, composition analyzers) •Plant ESD System •Ignition Source Control, Hazardous Area Classification (Vapor cloud must find an ignition source to create jet fire depicted) Prolonged Ignition Case Instantaneous Ignition Case Worst Case Jet Fire (XZ plane) 9 •Under ideal conditions for vegetations ignition (moisture content, etc.), 50 kW/m2 can potentially instantaneously ignite vegetation in 0-2 minutes. •All other instantaneous ignition radii do not reach outside of the facility Consequence Prevention & Mitigations 10 Process Control Layer Process Control Layer Safety Layer Active Protection Layer Passive Protection Layer Emergency Response Layer Prevent Mitigate Process Alarm Trip Level Alarm, PSHH Basic Process Control System Operator Intervention Safety Instrumented System, ESD Relief Valve (PSV), fire and gas detection Dike (Wall), Occupied Building Placement Plant and Emergency Response, Evacuation Plan Jet Fire, Dispersion Cloud, Explosion Design (Equipment layout, Ignition Source Control, Hazardous Area Classification) Conclusion •With suggested occupied building enhancements, models generated indicate that personnel, occupied buildings and public receptors are inherently safe outside of the generated consequence contours. •Vegetation ignition is possible near the northeast portion of the wall within 10 feet. •Any potential consequence stated in this study is unlikely to occur given the following mitigations: •Fire and gas detection •Process control alarms •Process control shutdowns (Pressure safety high-highs, Pressure safety low-lows, composition analyzers) •Plant ESD System •Ignition Source Control, Hazardous Area Classification (Vapor cloud must find an ignition source to create jet fire depicted) •PSVs and other active protection devices 11 Back-up Slides Citations & Relevant Information 12 LFL (Lower Flammability Limit) Dispersion Cloud Radii Dispersion cloud scenario basis: Leak develops in process equipment AND process continues to operate (continuous leak at plant rate). Flammable vapor cloud accumulation with ignition can cause explosions and flash fires. All radii show the lower flammability limit (LFL) contours. The LFL is the lowest concentration of a gas in air capable of producing a flash fire in the presence of an ignition source. Inputs: •2” horizontal leak at 0 ft elevation •Plant normal operating conditions and flowrate •Process stream compositions Output: •Dispersion clouds are not large enough to migrate and gather outside of plant walls •The cloud would likely disperse before it is able to travel over the wall 13 CR LF County Jet Fire Radii (1.6 kW/m2) 14 Jet fire scenario basis: Leak develops in process equipment AND process continues to operate (continuous leak at plant rate). All radii are 1.6 kW/m2 radiant heat contours in accordance with API 521 Table 12. Inputs: •2” 45-degree leak at 3 ft elevation •Plant normal operating conditions and flowrate •Process stream compositions •Height of Interest is 0 ft. as the concern is occupied buildings and personnel CR LF County 12 ft. wall Jet Fire Radii 15 Jet fire scenario basis: Leak develops in process equipment AND process continues to operate (continuous leak at plant rate). Inputs: •2” 45-degree leak at 3 ft elevation •Plant normal operating conditions and flowrate •Process stream compositions 6.3 kW/m2 9.46 kW/m2 Vapor Cloud Explosion Radii 16 VCE scenario basis: Leak develops in process equipment AND process continues to operate (continuous leak at plant rate). The flammable mass grows and infiltrate areas of obstruction and confinement. If ignition occurs, these area(s) can generate explosive forces. Inputs: •2” horizontal leak at 0 ft elevation •Plant normal operating conditions and flowrates •Process stream compositions •Facility layout details (3D models, photos, drawings) to define obstructed regions Results: •Archaea Control room is reached by 1 PSIG contour (see slide 11 for mitigations) •Landfill building is reached by 0.6 PSIG contour (see slide 11 for mitigations •Wall is reached by ~1.2 psig and can absorb 2-3 psig. Pressure contours are not expected to reach outside of the facility due to the surrounding wall. 3 PSIG1 PSIG0.6 PSIG0.4 PSIG 5 PSIG CR LF County Toxic Cloud Radii (30 ppm radii) Toxic cloud scenario basis: Leak develops in process equipment AND process continues to operate (continuous leak at plant rate). All radii are 30 PPM H2S contours. Inputs: •2” horizontal leak at 0 ft elevation •Plant normal operating conditions •Process stream compositions •Process mass rate Output: •No significant toxic substance concerns 17 CR LF County Jet Fire Radiation Back-Up Info for Occupied Buildings and Personnel (API 521) 18 19 Site/ Wall Photos Vegetation Ignition 20 •https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004JE002279 Vegetation Ignition 21 •Drysdale Fire Dynamics Third Edition, 2011