CHARLESTON, W.Va. -- "Flowback" is the liquid that returns to the surface when a shale well is fractured. Figures for the amount of water required to fracture a shale well usually range from 3 million gallons to 5 million. Likewise, figures for the amount returning to the surface vary, but 20 percent seems reasonable.
As a ballpark figure, let's say a typical Marcellus well requires 4 million gallons to fracture. That is a cube of water 81 feet per side, or 800 truckloads at 5,000 gallons each.
If the flowback is 20 percent, that's 800,000 gallons, a cube 47 feet per side, the volume of five very comfortable houses.
Disposal is a major problem, both physical and financial. The traditional way to handle disposal, dating back to pioneer days is to throw it in the creek. But that is bad for people downstream. It was cow manure, brush and sewage when population density was small, but we have largely ended the nasty habit of disposing of things that way today.
Flowback is far worse than what had to be disposed of in the past. It has the fracturing chemicals and a huge load of material dissolved while below. The temperature of the deep-down Marcellus Shale is a little below the boiling point of water at the surface, and the fracturing fluid is under great pressure. This makes it capable of dissolving a variety of compounds from the shale, including several uncommon in surface waters.
Sometimes it's referred to as "residual waste," more frequently "brine." Most people know brine as a table salt solution. The ocean is brine. However, most inorganic compounds that are soluble are salts. It is a mistake to think any naturally formed brine has only the properties of a sodium chloride solution. It may be far more corrosive, poisonous or concentrated.
Present in this Marcellus brine are barium and strontium, bromine, sometimes arsenic or manganese, along with the substances sent down by the driller. It is several times more concentrated than seawater.
So what to do with this brine is a major concern. The ingrained instinct is to dump it and forget it -- put it in a creek or anywhere out of sight. I have seen it sprayed on a dirt road in the summer for dust control. I noticed the spray did not stop when the truck got to hard road, though, but went on and on. Others have seen it used to melt ice on a road in winter. So where does the material go when it rains? In the creek.
In some times and places, a legal way to get rid of it was "land disposal." What happens to the vegetation? And where does it go when it rains?