Homeowners living just a mile away from shale gas or tight oil wells will likely have their drinking water contaminated by "stray gases."

That's the conclusion of a new U.S. study that looked at 141 drinking water wells in shale gas development area in northeastern Pennsylvania.

Shale gas drilling now provides about one half of U.S. natural gas production and the controversial industry is the subject of massive government subsidies in British Columbia.

Premier Christy Clark wants to kick start a liquefied natural gas export industry to Asia with low royalties, free water, government funded geoscience, and road and energy infrastructure paid for by taxpayers.

But hydraulic fracturing, a brute force technology that shatters rock with high-pressured water, sand and toxic chemicals to mine methane more than two kilometres underground, has raised serious environmental concerns.

The practice has caused water contamination, methane leakage, man-made earthquakes, fragmented landscapes, and depleted both surface and groundwater supplies throughout North America and B.C.'s Peace River region.

Using a cheap yet accurate tool that detects the fingerprint or isotopes of gases, the Duke University study found methane in 82 per cent of tested wells, with average concentrations six times higher for homes less than a kilometre away from shale gas wells.

Ethane and propane, tell-tale fingerprints of shale gas development, were also found in significant quantities.

The scientists gave two explanations for the higher dissolved gas concentrations that they found in homeowner's drinking water.

One was faulty or inadequate steel casings, which are designed to keep the gas and any water inside the well from leaking into the environment, and the other was "imperfections in the cement sealing of the annulus or gaps between casings and rock that keep fluids from moving up the outside of the well."

The scientists also suspect that horizontal drilling and hydraulic fracturing can connect to existing natural fractures in the rock.

Industry made fractures can also "stimulate fractures or mineralized veins, increasing secondary hydraulic connectivity. The upward transport of gases is theoretically possible, including pressure-driven flow through open, dry fractures and pressure-driven buoyancy of gas bubbles in aquifers and water-filled fractures."

The study concluded that more detailed case studies of water-quality measurements taken before, during, and after drilling and hydraulic fracturing are urgently needed to determine what is causing the contamination in different shale gas zones.

Fort Nelson First Nations want all long-term water licenses for shale gas fracking in the Horn Basin area to be suspended until the B.C. government has thoroughly consulted with First Nations and the public in the development of rigorous surface and groundwater management plans. More than 50,000 wells could be drilled in the region.

A new report for the Program On Water Studies at the University of Toronto Munk Centre recommends strict regulation of hydraulic fracturing to protect Canada's poorly mapped and monitored groundwater.

The report calls for baseline groundwater quality monitoring prior to drilling and that the provinces compel companies "to put up bonds that would cover the cost of cleanup if an accident or mistake results in groundwater contamination."

The provinces should also follow the lead of Denmark by imposing a temporary water tax on consumers and industry to pay for mapping of aquifers, it says.

In 2011, British Columbia's Auditor General reported the province's groundwater inventory and monitoring was insufficient to protect the resource.

Award-winning journalist Andrew Nikiforuk has written about the energy industry for two decades and is a contributing editor to The Tyee.