Marcellus gas drilling is major industrial activity that cannot be done without environmental impact, but its cumulative impact on water to date probably is less than the damage done by the single oil spill on the Kalamazoo river in Michigan.
There one spill of 834,000 gallons of oil 14 months ago has closed 35 miles of the river ever since the day of the spill. According to the September 10th New York Times, the oil spill will cost $500 million to clean up.
Oil is inherently orders of magnitude more damaging and threatening to water quality than gas. According to the NYT, each year 100 significant oil or hazardous liquids spills from just pipelines take place. Another major oil pipeline spill just this year fouled the Yellowstone River, a natural jewel.
Despite the significant leaks and spills from pipelines, pipelines are actually the safest, cleanest means of transporting oil. Therein lies a window to the full toll to water caused by oil releases.
To get the full impact of oil releases to the environment, one would need to add the enormous quantities spilled from ships, trucks, tanks, industrial processes, homes.
Few things would do more for water quality than using more gas to displace large quantities of oil. While that is true, it is not a reason for regulators of the gas industry and companies to become complacent about the impacts of gas production on water.
Recycling of driling wastewater, excellent practices to limit erosion and sediment impacts, reducing and containing spills at drilling sites, preventing gas migration are daily challenges requiring daily focus. The goal must be excellence every day in operations and regulation.