The sun sets behind a drilling rig at a hydrofracking installation near Westhoff in DeWitt County. The shale oil boom is going strong south of San Antonio on a formation that stretches for about 300 miles across south Texas, one of the most prolific oil patches in the United States. Flaring of excess gas in drilling for oil is also a byproduct that's vented into the atmosphere releasing all sorts of volatile organic chemicals, causing air pollution and releasing climate changing methane gas.