WGNHS hydrogeologists Ken Bradbury and Madeline Gotkowitz,
working with Dr.
Randy Hunt from the US Geological Survey and Dr. Mark Borchardt and
Susan Spencer at the Marshfield Clinic, have completed a one year
study of the occurrence of viruses in deep water-supply wells. Viruses
in these wells were unexpected because the wells draw water from
below a shale formation thought to provide protection from contamination. During
2007 and 2008 the investigators sampled six deep municipal wells
for viruses on a monthly basis. They also collected virus samples
from local lakes and from untreated sewage.
Viruses were detected at least twice in every one of the six wells,
but no well was virus-positive in every sampling round. Virus
results varied significantly with time, and there was apparent correlation
between virus levels in sewage, lakes, and groundwater. The most
likely source of the viruses in the wells is the leakage of untreated
sewage from the Madison sewer system. The investigators stress
that these viruses pose no threat to public health as long as the
water is disinfected, as it is in Madison.
The final report from this project is available as
WGNHS Open-File Report 2008-08 and can be downloaded here. This
study was also the focus of an article by Ron Seely in the Wisconsin
State Journal. [Used with permission of Ron Seely and the Wisconsin