Today, we finish listing the landfill-related problems that County consultant SCS Engineers says aircraft can cause at Palomar. [SCS Engineers Report, 10/15/13, No. 01213281.00].
Next week: Has the County told the whole story?
Take-Off & Landing Scenarios & Safety Improvement
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SCS report pages 6-7 say that aircraft crashes into the landfill are more likely during landings than takeoffs, unless a mechanical problem forces an aborted takeoff.
SCS notes that one way to reduce possible crashes into the landfill is for the County to move the landing threshold (“that is, “displace the threshold”):
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During takeoff, aircraft would use the entire runway, while during landing aircraft would be required to extend their approach to touchdown at a location approximately 200 feet further east [west?] of the current touchdown location. In the event of failure to touchdown at the predetermined threshold and/or other mechanical issues that prevent a typical touchdown, there could be aircraft accidents with potential environmental impacts.
One test of the County’s good faith when preparing the 2015-2035 PMP and Palomar Runway Extension analysis and related CEQA EIRs will be whether the County considers displaced thresholds as a Palomar development option – as SCS recommends.
Vertical Impact Crash
SCS Engineers refers to a vertical crash into the landfill as the worst-case scenario. SCS describes an especially interesting problem related to the Palomar closed landfill methane gas collection system “blower/flare.”
The Palomar landfill produces methane gas that must be collected and eliminated. An intricate system of gas collection piping lies below the Palomar sandy area at the runway east end. These pipes collect the gas and funnel it to the “blower/flare” that burns off the gas. According to SCS, here is what could happen to the blower/flare if a plane crashed into the landfill area:
Based on the current location of the blower/flare facility (on the south side of Area 2), it is unlikely that it would be directly impacted or damaged as a result of an aircraft crash event. However, in the event that landfill cover soils are breached at the crash site and there is damage to the HDPE pipe network, air would be introduced into the collection system. With the GCCS [Gas Control Collection System] still being under vacuum, air drawn into the ruptured end of the piping would slowly move within the flare, to propagate back into the collection piping, depending on the composition of the residual gas mixture in the collection piping. It is difficult to predict the magnitude or duration of this scenario, however, there could be extensive damage to the flame arrestor at the flare, blowers, knockout pot and piping, unless the system shuts itself down due to a no-flame or low temperature alarm.
In short, a Palomar Airport crash of a large plane puts the entire gas control collection system at risk. No surprise. As noted two weeks ago, SCS also said that an underground landfill fire sparked by a plane crash could also destroy the GCCS and burn indefinitely.
Does the County authorization for SCS Engineers to prepare its report indicate at last a County desire to protect Palomar Airport users and to comply with the California Environmental Quality Act? Next week, we’ll see.
