Geophysical Well Logging Studies To Identify Saline Water Zones In The Cambrian-Ordovician Sandstone Aquiffer Of Southeasternwisconsin

The Cambrian-Ordovician sandstone aquifer is the major source of ground water<br>for municipal and industrial use in southeastern Wisconsin. Decades of pumping have<br>created a regional cone of depression centered in the western suburbs of Milwaukee.<br>Total dissolved solids (TDS) levels in several sandstone aquifer wells have more than<br>doubled over the last ten to fifteen years. A regional time-domain electromagnetic<br>induction (TEM) survey indicated that the saline water was migrating upward from<br>deeper portions of the aquifer. A well logging study was conducted on a municipal well<br>that had experienced a significant increase in TDS levels. The logging study indicated<br>that the lower 200 feet of the well was producing saline water. The lower portion of the<br>well was sealed and water quality improved significantly. Similar well rehabilitation<br>projects are planned for other wells in the same area.