The following is text from EPA Site.

"Water is an integral component of the hydraulic fracturing process. EPA Office of Water regulates waste disposal of flowback and sometimes the injection of fracturing fluids as authorized by the Safe Drinking Water Act and Clean Water Act.


Safe Drinking Water Act

Several statutes may be leveraged to protect water quality, but EPA’s central authority to protect drinking water is drawn from the Safe Drinking Water Act (SDWA). The protection of USDWs is focused in the Underground Injection Control (UIC) program, which regulates the subsurface emplacement of fluid. Congress provided for exclusions to UIC authority (SDWA § 1421(d)), however, with the most recent language added via the Energy Policy Act of 2005:

“The term ‘underground injection’ –
(A) means the subsurface emplacement of fluids by well injection; and
(B) excludes –
(i) the underground injection of natural gas for purposes of storage; and
(ii) the underground injection of fluids or propping agents (other than diesel fuels) pursuant to hydraulic fracturing operations related to oil, gas, or geothermal production activities.”

While the SDWA specifically excludes hydraulic fracturing from UIC regulation under SDWA § 1421 (d)(1), the use of diesel fuel during hydraulic fracturing is still regulated by the UIC program. Any service company that performs hydraulic fracturing using diesel fuel must receive prior authorization from the UIC program. Injection wells receiving diesel fuel as a hydraulic fracturing additive will be considered Class II wells by the UIC program. The UIC regulations can be found in Title 40 of the Code of Federal Regulations Parts 144-148. State oil and gas agencies may have additional regulations for hydraulic fracturing. In addition, states or EPA have authority under the Clean Water Act to regulate discharge of produced waters from hydraulic fracturing operations.

Clean Water Act

Disposal of flowback into surface waters of the United States is regulated by the National Pollutant Discharge Elimination System (NPDES) permit program. The Clean Water Act authorizes the NPDES program.
State regulations

In addition to federal authority to regulate the hydraulic fracturing process, states may have additional regulations on hydraulic fracturing and the production of fossil fuels."

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1. Good
2. They are regulated as Class 2 UIC Wells

What is a Class II well?

Class II wells inject fluids associated with oil and natural gas production. Most of the injected fluid is salt water (brine), which is brought to the surface in the process of producing (extracting) oil and gas. In addition, brine and other fluids are injected to enhance (improve) oil and gas production. The approximately 144,000 Class II wells in operation in the United States inject over 2 billion gallons of brine every day.

Sources
http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturin...
http://water.epa.gov/type/groundwater/uic/class2/index.cfm

Other Blog Posts

http://pennsylvania-solutions.blogspot.com/2011/01/hydraulic-fractu...