Holes in the well casing must be cut with a hole saw, not a torch.

The well casings that are meant to protect groundwater have occasionally failed.

The well casing is then scrubbed by use of brushes or other tools.

"But the real problem is the well casing and cement rather than fracking," he added.

Joints, cracks and connections in the well casing should be sealed.

However, bacterial contamination can also indicate a cracked well casing.

The base of the well was from then on bolted to the well casing.

The site includes concrete foundations, the capped well casing, and a sign.

The blaze started when workers began pumping heavy mud into a leaking well casing.

The capped well casing is the well's only remnant.

Faulty well casings have allowed natural gas to contaminate aquifers.

Generally, a slotted well casing is not recommended for use as a well screen.

She also has a scar on her forehead where her head rubbed against the well casing.

That's because of lousy construction quality: Bad well casings allow gas to leak into the aquifer.

Final approval for the well casing system has to given by the Health and Safety Executive.

The well casing should be watertight, properly capped, and extend a foot or more above ground.

Worst case: The increased pressure ruptures the weakened well casing, setting the recovery effort back to square one.

• entry through wells or around well casings.

These plastic well casings are not only cheaper but have a greater number of slots cut in them than steel easings.

The rest of the well casing will not experience any increase in pressure due to the sealing of the packer.

Materials should conform to recognised industry standards, including the cement slurry sealing well casings.

As for contamination problems, Meggs cited improper cementing of the well casings.

Subsurface damage, including collapsed or parted well casing, was observed only on 14 of 1,725 active wells.

Finer gravel may be used to fill the annular between the borehole and the well casing.

However, the well casing quickly failed, and the bore became jammed with debris and drilling tools.