Dear Sir, - There has been evidence for many years that oil and gas wells leak. Reports from Schlumberger, the Norwegian Safety Authority, the Queensland mines department, the US EPA have all confirmed that leaking wells are a fact of life in the oil and gas industry. The rate of leakage in new wells is 5%, by the time they are 15-20 years old 50% of wells leak. These figures are consistent whether they are on shore gas wells or multi billion off shore oil wells.

Those pushing for unconventional gas extraction to go ahead have denied this data implying that the wells were badly built in the first place and that it would never happen here under tight regulations.

One often quoted sentence from The House of Commons Select Committee on Energy and Climate Change report is: "There is no evidence that the hydraulic fracturing process poses any risk to underground water aquifers provided that the well-casing is intact before the process commences." The recent government report on the earthquakes in Blackpool provides evidence of that risk. It demonstrates clearly just one of the many mechanisms of well leakage.

It confirms: A, Earthquakes in Lancashire were induced by the hydraulic fracture treatments at Preese Hall.

B, Seismic activity induced by hydraulic fracturing caused deformation of 160 feet of the well bore.

The cement casing- the layer of cement providing the seal between the outside of the bore well and the formation is incredibly fragile- of the order of one inch thick. Yes, that is not a typo or a mistake, the cement casing is one inch thick. Yet that is what we are being told to rely on to prevent migration of toxic fluid from the formation up the outside of the bore past the aquifers.

At Preese Hall the well bore diameter was 5� inches. It was distorted by � inch over a total distance of 160 feet as a result of the seismic activity induced by hydraulic fracturing.

That means that for 160 feet that one inch of cement was not providing a seal between the well bore and the formation.

An earthquake does not have to be of an intensity to shake you out of bed to cause harm. It does not have to be at intensity to alarm someone on the surface. It just has to be intense enough to break the seal on the cement casing. Then the aquifers and everyone depending upon them are at risk.

Yours faithfully, Geralyn McCarron.