What environmental issues are associated with hydraulic fracturing?

U.S. Geological Survey Hydraulic Fracturing page:

"The actual practice of fracking is only a small part of the overall process of drilling, completing, and producing an oil and gas well. However, since fracking involves injecting a chemical solution into the ground to free up oil and gas resources, there are some potential environmental impacts related to this process. These include:

• spills of chemicals at the surface
• surface-water-quality degradation from waste fluid disposal
• groundwater quality contamination
• induced seismicity from the injection of waste fluids into deep disposal wells"

Learn More:

• Critical Issue: Hydraulic Fracturing (Webpage and Issue Brief), Geological Society of America
  This peer-reviewed report provides a thoroughly researched overview of hydraulic fracturing ("fracking"). Defines hydraulic fracturing, discusses its role in energy development, and addresses potential environmental issues associated with the use of the technology.

• Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources (Report), U.S. Environmental Protection Agency
  2015 report assessing the potential for hydraulic fracturing to affect drinking water resources.

• Unconventional Oil and Natural Gas Development (Webpage), U.S. Environmental Protection Agency
  Overview of hydraulic fracturing as a method of extracting oil and natural gas, including the regulatory framework surrounding hydraulic fracturing; wastewater treatment and disposal; and air quality impacts.