Metropolitan Transit Authority - Fallbrook BOF - Executive Summary

| Accident History | Chemicals | Emergency Response | Registration | Source | Executive Summary |

Fallbrook Bus Operating Facility (FBBOF): 
    It is the Metropolitan Transit Authority's (METRO) policy to adhere to all applicable Federal and state rules and regulations.  METRO is committed to protect the health and safety of its employees and public.  In order to achieve this objective, METRO has allocated and invested considerable resources in implementing reasonable controls to prevent predictable releases of LNG by training its employees, by the safe design, installation, maintenance, and operation of this facility; also, by installing fire and leak detection and mitigation systems. 
    The FFBOF is owned and operated by METRO.  One of the primary purpose of this facility is to fuel the LNG bus fleet.  LNG is delivered by truck and stored in tw overticall cylindrical storage tanks.  Access to the site is restricted to authorized facility employees, management personnel, and contrac 
    The regulated substance handled at this fueling facility is LNG.  Methane, which is the major component of LNG, is considered hazardous by the USEPA.  LNG is a flammable liquified gas.  It is stored at -258.7 degrees Celsius.  It is a clean burning fuel.  The maximum intended inventory of LNG at this site is 57,000 gallons (202,000 lbs.). 
    The properties that make LNG a valuable fuel also necessitate the observance of certain precautions in handling LNG to prevent unnecessary human exposure, to reduce the threat to the health of METRO's personnel, and members of the nearby community. 
    As a Program 2 Process, a worst-case release scenario and alternative release scenarios will be assessed for the LNG facility. 
 ---  Worst Case Release Scenario:  The facility is required to complete a worst case release scenario.  Since LNG is classified as a flammable substance, the EPA requires the worst case release scenario to be a vapor clo 
ud explosion.  The worst case scenario is the rupture of one of the two LNG storage tanks, the complete vaporization of its content and the explosion of its vapor cloud.  The two tanks are physically isolated in separate dikes with a blast/fire wall between so that the failure on one tank will not lead to the failure of the other.  
    The two LNG tanks are of equal capacity.  Company policy limits the maximum filling capacity of this tank to 85%.  When filled to the greatest amount allowed, an accidental failure would release 100,919 lbs. (47,766 kg) of LNG.  The worst case assumes that the entire contents of one tank are released as a vapor.  The calculated distance to 1 psi over pressure results from this explosion is calculated by 914 feet (278.5 m). using the Multi-energy method.  Using 1990 census data, it is estimated that 1,100 people reside within the calculated hazard zone. 
 --- Alternative Release Scenario:  The facility is required to complete at lease one alternative re 
lease scenario.  The following release alternative release scenarios have been selected: 
1.  Flash fire due to the rupture of a 3-inch diameter and 20 feet long transfer hose in the unloading area.  The spill occurs in the unloading area and is not confined.  A 5 minute release is assumed.  There are at least two persons in the unloading area while LNG is being transferred.  The pump rate is 300 gal/min.  LNG vapor evaporating from the unconfined pool travels to the lower flammability limit (LFL) will cause a flash fire if ignited.  The distance to the endpoint (the LFL) for this alternative scenario was found to be 426.5 feet (130 m) using DEGADIS software.  The estimated number of people who may be affected by the flash fire is 246. 
2.  An unconfined pool fire due to a 1-inch pipe rupture in the bus fueling area.  The pipe is 48 feet long and the flow rate in the pipe is 30 gal/min.  A 10 minute release is assumed.  The bus fueling area has LNG detectors located near the floor and 
fire detectors located in the roof of the fueling bay.  These would automatically shut the pumps and close all valves, as soon as a leak or fire is detected.  METRO personnel estimate that this would occur within a couple of minutes.  However, a conservative value is chosen for time of release (10 minutes).  The spilled LNG forms a pool of 6 m radius and 1 cm thickness.  The calculated distance to the endpoint is 200 feet (61 m) using the LNGFIRE3 software.  It is estimated that 61 people may be affected by the thermal radiation from the pool fire. 
3.  A confined pool fire due to the rupture of the 28,500 gallon storage tank.  The concrete dike surrounding the storage tank limits the LNG pool from spreading.  The dike dimensions are 62.17 ft. x 24.25 ft. X 5 ft.  The LNG fire detectors located in the dike will activate the alarm.  The estimate distance to the endpoint is 207 feet (63 m) using LNGFIRE3 software.  It is estimated that 61 people may be affected by the thermal radiation  
from the pool fire. 
    METRO uses six layers of defense to protect the health and property of not only its own personnel but also members of the nearby community.   
1.  Design and construction of the facility and the buses.  Design safety reviews are conducted.  The safety devices inherent in the design of this facility, such as fail safe valves, automatic and manual shut down valves, use of secondary containment for storage tanks, pressure relief valves to prevent over pressurization, and alarm systems for critical control parameters, reduce the possibility of accidental releases. 
2.  Maintain equipment properly so as to avoid and prevent emergencies.  Entire facility is inspected and tested on a preventative maintenance schedule.  All equipment is inspected monthly. 
3.  Training of METRO's personnel:   METRO's personnel are trained in the safe operation of all equipment and systems, maintenace, inspection and testing of equipment and instru 
ments.  In addition, all of METRO's alternate fuel vehicle drivers have been thorougly trained. 
4.  Safe handling procedures:  written procedures for unloading LNG, and operating, maintaining, inspecting, and testing facilily equipment are used.  The guard ensures controlled entry into the facility at all hours.  Unloading of LNG is carried out only during the daytime. 
5.  Emergency plan for the facility:  leak and fire detection systems are installed which detect natural gas and LNG releases and fires.  A facility wide notification system is in place that alerts personnel about the LNG leaks and fires.  The emergency shutdown system and procedures ensure that the system is shut down, either automatically or manually, when a leak or fire is detected.  The emergency response plan also includes procedures for notification of the local fire authority. 
6.  Auditing of operations:  incident investigations and follow-up procedures are in place.  Operations are audited by internal teams and e 
xternal consultants. 
    There were no accidental releases of LNG to report at this site since its commission on January 19, 1997. 
    The FBBOF emergency response program is coordinated with the local Fire Department.  When an LNG leak or fire is observed, the facility personnel dial 911, and if necessary, activate the plant wide notification systems and evacuate the facility to meet at a predetermined location.  The local fire department responds to the incident and notifies the facility when it is safe for them to returm tot he facility premises.   
    A representative of the local fire department visited the facility on January 19, 1997, the day it was commissioned.  the facility is in compliance with NFPA-59A, Chapter 10 fire code relating to the storage and handling of LNG. 
    METRO is installing infra-red detectors at the FBBOF to improve safety at the faciliy.  Installation of dual-speed  
ventilation fans in the bus fueling buildings is underway.  The fans will automatically increase speed if methane is detected so that the building air may change once every minute.
Click to return to beginning