The document was developed to support the Ground Water Disinfection Rule (GWDR). The GWDR will establish treatment requirements for control of microbial contaminants in ground water not under the direct influence of surface water. The document identifies best technologies or generally available means for community or non-community ground water systems to inactivate microbial contaminants. Viruses are the most likely organisms to occur in ground waters and are the focus of the inactivation requirements. Non-treatment options are also discussed. Sections include one on currently available disinfection technologies and conditions under which application is appropriate, but it does not go into detail about operation and maintenance. Another presents criteria which would allow systems to avoid disinfection or provide lower levels. Others provide design assumptions used to develop cost estimates and cost estimates for each technology for various system size categories.