electrocoagulation (EC) and forward osmosis (FO) is used for the treatment of produced water resulting in an energy effective removal in suspended solids and organic contaminants, resulting in a 21% increase in water reuse. Well blowouts and spills of fracturing fluids A well blowout in Clearfield County, Pennsylvania on June 3, 2010, sent more than 35,000 gallons of hydraulic fracturing fluids into the air and onto the surrounding landscape in a forested area. Campers were evacuated and the company EOG Resources and the well completion company C.C. Forbes were ordered to cease all operations in the state of Pennsylvania pending investigation. The Pennsylvania Department of Environmental Protection called it a "serious incident". Fluid injection and seismic events Injection of fluid into subsurface geological structures, such as faults and fractures, reduces the effective normal stress acting across these structures. If sufficient shear stress is present, the structure may slip in shear and generate seismic events over a range of magnitudes; natural gas drilling may have caused earthquakes in North Texas. Reports of minor tremors of no greater than 2.8 on the Richter scale were reported on June 2, 2009, in Cleburne, Texas, the first in the town's 140-year history. In July 2011, the Arkansas Oil and Gas Commission voted to shut down four produced water disposal wells, and to impose a permanent moratorium on Class II disposal wells in a faulted area of Faulkner, Van Buran, and Cleburne counties which has experienced numerous earthquakes. The U.S. Geological Survey is working on ways to avoid quakes from wastewater disposal wells. In 2014, Oklahoma had 585 earthquakes with a magnitude of 3.0 or greater. Between the years 1978 and 2008 the state averaged 1.6 quakes of these magnitudes a year. The quakes are very likely related to the deep injection of oil and gas wastewater, a significant portion of which comes from wells which have been hydraulically fractured. The fluid travels underground, often changing the pressure on fault lines. The Oklahoma Corporation Commission later put in place regulations of waste water injection to limit the induced earthquakes. Fluid withdrawal and land subsidence Subsidence (the sinking of land) may occur after considerable production of oil or ground water. Oil, and, less commonly, gas extraction, has caused land subsidence in a small percentage of fields. Significant subsidence has been observed only where the hydrocarbon reservoir is very thick, shallow, and composed of loose or weakly