Check it out:
Not only could I see issues with bringing possibly radioactive water back to the surface, but here are some other issues they mention in the article:
Blowouts and Earthquakes
While a handful of small EGS plants are operating overseas, some have experienced setbacks ranging from blowouts to minor earthquakes caused by fracturing rocks deep underground. A project in Switzerland was shut down in 2006 after residents nearby started feeling tremors and voiced concerns that the installation may destabilize surrounding areas.
In September 2009, Seattle-based AltaRock Energy Inc. suspended a project at The Geysers due to drilling problems. Geodynamics Ltd. shut down a test in southern Australia after an uncontrolled leak in April of that year.