Ellingson-DTD installed eight single-ended (blind) coal ash dewatering wells within a closed and partially capped mixed ash basin. All eight wells were constructed utilizing the Knock Off (KO) well completion technology.
In this drilling/installation method, we used drillable casing to advance a pre-planned bore path to an underground termination point. Upon reaching the end of the bore, the crew pushed the well material down through the center of the casing. When the well material reached the end, it latched onto and pushed the sacrificial drill bit off the drill string. The drillable casing was then tripped out of the bore, leaving the well in place. This method allows us to install long single-ended wells in unconsolidated ash that may not allow an open-bore installation approach.
Two wells were navigated with a removable gyroscopic steering tool, and the other six wells utilized a walkover navigation method. The well screens are completed about 45’ below the entry point elevation and average roughly 845’ of screen per well. The total installed length of all eight wells is 8,593’ – making the average total well length 1,074’.
Biodegradable drilling fluid was used for drilling and well installation. Well development consisted of flushing and jetting with an enzyme breaker solution and overpumping with a submersible pump. Ellingson crews also installed permanent submersible pumping systems post-well development. During an eight-week operational period, flow rates from the wells range from 2 gpm to 30 gpm per well, with the total volume of water removed exceeding 9,800,000 gallons. Water levels in the basin dropped from 1.5 ft to 11.1 ft during the same time period.
Note from client in January 2025 – Pumped 21.4 million gallons. With pumps running, southern wells are showing only about 2 feet of head, with one being affected the most by stormwater, showing 7 feet of head. When pumps are off, only recharging to 10-12 ft of head. We started at 20-30 ft of head. So we are definitely dewatering. As of July 1, 2024: Northern perimeter piezometers are showing 3-5 feet of drawdown, while the southern ones are showing 10-12 feet of drawdown. Roughly 18’ of head reduction across the entire basin.
