By Jason Coleman, P.E.
General Manager
During the second portion of the Wolfforth test well project, a temporary production well was constructed in the Edwards-Trinity (High Plains) Aquifer (ETHP). 
The sediments in this aquifer that may yield significant quantities of water include limestone and sand.  Due to erosional processes, however, the existence and thickness of these units varies.
At this site, the geophysical log indicated the presence of limestone and sand in the 200-280 foot interval below land surface.  Where limestone rocks are fractured or contain significant void spaces, water is transmitted to a well bore in greater quantities than where the rocks are completely consolidated. 
Unfortunately, there is no certain way of predicting where these fractures and voids exist.  Hence, a drilling and test well project is currently the most reliable method of determining the nature of the limestone rocks. 
Also, quantifying the thickness and productivity of the sand units is quite difficult, since we have few records of wells in this area as a reference.
For the temporary ETHP well, the contractor used seven- inch diameter casing and screen.  The screened section of the well was 220-285 feet below land surface.  Using a tremie, the driller installed a bentonite plug in the annular borehole space from 170-210 feet below land surface.  This procedure isolated the overlying Ogallala sediments from the ETHP screened section.
When the temporary well was installed, the depth to water was 130.40 feet below land surface.  This water level is about 15 feet higher than the Ogallala water table, indicating a confined aquifer system at this location.
Results of the pump test and water quality test will be included in a future issue of the electronic newsletter.