Currently, the Flat Canyon Well is approximately 642 feet deep. It was drilled with a 14 ¾ – inch tricone bit with a rotary drill circulating bentonite mud in order to keep the hole open. Bedrock was encountered at approximately 625 feet deep, with sand and gravel above that.
Based on our seismic testing, we anticipated reaching 3 water-bearing zones at approximately 350 feet to 500 feet, 600 feet to 700 feet, and 950 feet to 1100 feet. For better or worse, the drilling did not play out the way that we anticipated. First, the alluvium was very unstable to drill through and was partially caving-in. Every time that the hole would cave-in, the drillers would have to pull out their drill rods and bits and re-start in the same hole, which happened twice. The sluffing or caving-in made it difficult for the drillers to remove their drilling tools from the hole, and to continue to drill. Ultimately, it was determined that full mud rotary would have to be used to drill the hole.
Drilling with the mud was very effective at keeping the hole open. However, it prevents water from entering the hole and masks the location of water producing zones. This makes it nearly impossible to know what kind of water the hole is producing until the mud is removed and the hole becomes stable by casing it. Because the entire hole is coated with drilling mud and the formation is unstable, there is no way of determining water quality and quantity sampling without casing the hole above the bedrock.
The well will be cased with 8-inch blank casing from just above surface elevation to 430 feet. Geophysical logging was completed on the hole once drilling concluded at 642 feet. This means that a probe was lowered down the hole which measured hole orientation, hole diameter, and some additional parameters such as estimates of water availability and location. Based on the interpretation of the geophysical logging, it was determined that most of the water likely to be found in this well would be located at below approximately 430 feet deep. Louvered casing (8-inch) will be installed from 430 feet to 610 feet deep, followed by another 20 feet of blank casing, which will be cemented in at the bottom. An appropriately sized gravel pack will fill the annular space between the hole walls and the casing, with the top 100 feet of the well grouted with neat cement.
Once the unstable portion of the well has been stabilized, testing for water quantity and quality will be conducted. At that point, we will know whether or not to drill deeper into the bedrock.