Can we trust the traffic light system?
It seems as though the seismic traffic light system is open to rather more interpretation than one might have imagined from what is touted as being the pinnacle of our gold standard regulations for on-shore fracking.
Cuadrilla clearly seem to believe that if a seismic event occurs after injection has stopped then the traffic light system does not apply and they only need to take action if it is 0.5 ml or greater. If it occurs during injection then they conceded that the traffic light system would apply.
However there seems to be a contradiction, or at very least a loophole, in Cuadrilla’s Hydraulic Fracture Plan (HFP) because it clearly states that
This is relevant to last week’s 0.3 Ml event because the EA tell us that
So it appears that this event would have fallen within the 1 hour after pumping and should therefore have been detected as part of the real time monitoring process. Logic says it should therefore fall under the TLS regime and not be dismissed as irrelevant, and it seems reasonable to assume that the OGA signing off the HFP would have assumed this would be the case.
Why does this matter? Well if an event > 0 Ml within an hour of pumping triggers the TLS then certain steps have to be followed.
If on the other hand you ignore that hour you said you’d monitor for after pumping then you can dismiss the event as a “trailing event” and a trailing event has to be 0.5 magnitude to be followed up.
Now it is entirely possible that Cuadrilla have something “otherwise agreed in writing with the EA” which they haven’t shared with us, but if not then it might seem that they are being a bit over eager to dismiss Friday’s event, based on their own HFP.
It will be interesting to see how they deal with the 0.4ml quake that they would appear to have triggered at 14:45 today