What Drought? Deep Drilling For Groundwater Yields Rewards
By Dr. David E. Hansen, Ph.D., P.E.
The Utah Water District took a unique approach to discover new water for a rising population, with better-than-expected results.
Utah, like many arid western states, depends upon winter snow accumulations and surface water storage for much of its water supply. However, groundwater has also been a very significant portion of sustainable yields for many communities and suppliers.
To meet growing demands, the Central Utah Water Conservancy District (CUWCD) has taken a major progressive step forward to acquire and develop significant groundwater rights within Utah County. The process started in 2005 when CUWCD purchased and received state approval to utilize in excess of 42,000 acre-feet of groundwater rights historically associated with the former site of Geneva Steel Mill in Vineyard, UT, next to Utah Lake and 30 miles south of Salt Lake City. The existing water rights and wells (23 total on-site wells) had furnished water for the steel mill for more than 60 years.
Finding A Solution
Because existing industrial wells were failing, shallow, or not constructed to meet current drinking water standards, CUWCD developed and implemented an aggressive plan to plug all 23 existing wells and to drill 14 new deep, large-diameter wells to meet anticipated growth demands. In January 2011, CUWCD contracted with the engineering firm Hansen, Allen & Luce, Inc. (HAL), a Salt Lake City-based civil and water resource engineering firm, to assist them with the project. HAL’s contract included the groundwater evaluation, design and construction oversight of two deep triple-nested piezometer monitoring wells, five production wells and two well pump stations.
Each production well was anticipated by CUWCD and HAL to yield an approximate 3,500 gpm. Following the evaluation and design, a well drilling contract was entered into in September 2011 with Hydro Resources out of Fort Lupton, CO, to complete the wells. Hydro completed construction on the fifth well in October 2013. Widdison Turbine Service of Draper, UT, is completing well development under contract with Hydro using the dual-swab while pumping development technique.
To date, four of the five wells have been fully developed and tested (work on the remaining well is scheduled for completion in August 2014). The owner and engineer were both pleased to learn that the wells tested to date are capable of producing nearly double the original flow estimate.
“In all instances, the wells have exceeded our design estimate in terms of production,” said KC Shaw, the project manager with CUWCD. In fact, each well is good for about 6,000 gpm.
Bill Bigelow, HAL’s Senior Project Engineer for the project indicated that “although two of the wells are being equipped at a maximum flow of 6,000 gpm, it is believed that these wells could likely sustain even higher yields.”
Hydro’s drilling supervisor, Steve Bryan, was also thrilled with the drilling success. “There’s probably not many wells anywhere to compare to the amount of water these wells produce. Anybody would die, especially in the desert, for that kind of water.”
HAL is not aware of any other Utah project that matches this one in overall scope. This is believed to be the largest single groundwater development project of its type ever undertaken in the state.
Completing The Job
As required in the specification, Hydro used the flooded-reverse rotary drilling method using one of their Challenger 320 drilling rigs. This drilling method has been found locally to be preferred to maintain a stable bore-hole and reduce development time in the unconsolidated materials typical of the area, including interspersed clay, silt, sand, gravel, and large cobbles. Aquifers in the area that have historically been identified and developed include the Shallow Unconfined Aquifer (0 to 50 feet below ground surface [bgs]), the Shallow Confined Aquifer (100 to 200 feet bgs), the Intermediate Confined Aquifer (275 to 425 bgs)and the Deep Confined Aquifer (620 to 1,100 feet bgs) each separated by significant clay zones. The confined aquifers are most often developed for culinary water supplies due to their depth, production capacity, and protection against surface contamination. During exploration it was found that a significant, previously unexplored aquifer was found at depths exceeding 1,400 feet, separated from the Deep Confined Aquifer by 100 to 200 feet of clay. This lower aquifer was named the “Basement Aquifer” to distinguish it from those previously identified.
The three main aquifers encountered below 100 feet are in many instances under artesian pressure and created some drilling bit and mud challenges for the driller. However, Shaw said, “I think Hydro has just done a fantastic job in learning from that, and does a great job in managing their bit program and their mud program.”
Drilling of the first well by Hydro was a challenge where a great deal was learned about the mud program required, and the best drilling bit to use. A mill tooth bit designed for medium formations, clays, and gravel was initially used, but it was quickly learned that the coarse materials encountered were not uniform in nature, resulting in early failure of mill tooth bits. Each bit would last only 400 feet. It wasn’t until Hydro switched to long-toothed, carbide-tipped button bits that they found they could move through several thousand feet with a single bit. Even with the lessons learned, completion of the project was a challenge due to varying conditions at each well site.
Each well drilled by Hydro included a 54-inch bore-hole with a 48-inch surface casing set to a depth of about 80 feet and a 45-inch bore-hole with a 36-inch intermediate casing set to a depth of about 300 feet bgs. A 32-inch bore-hole was then drilled to the target depth wherein a 24-inch well screen and casing was set. The wells are separated by about 2,500 to 3,000 feet to minimize potential interference.
New Challenges
In spite of the efforts required to oversee and control the mud program, lost circulation was an issue that required careful attention. Drilling in flowing artesian conditions requires a proper weight of drilling mud. If it is not heavy enough, then pressures encountered within the formation overcomes the weight of the fluid, resulting in a flowing well with possible well collapse. If muds are too heavy then drilling the muds go out into the formation. To overcome these issues drillers often attempt to use lost circulation materials (LCMs), which are designed to plug the aquifer and prevent the dispersion of drilling fluids. Some drillers have historically used sawdust, hulls, or similar LCMs to stop the loss of muds into the formation. Utah regulations for well drillers specifically state that “Organic substances shall not be introduced into the well or borehole during drilling or construction.” The state does, however, allow the use of acid soluble calcium carbonate fiber LCMs that can be dissolved and removed from the well.
“We were reluctant to allow use of LCM in the drilling because our experience, and our consultant’s experience, has been that that’s a difficult thing to be able to get out,” Shaw said. “But the zones were so porous that it was very challenging to drill through those without the use of LCM.”
After losing a large amount of mud to a porous zone in one of the holes, Hydro, CUWCD, and HAL met to discuss the issue and worked together to develop a fluids program that allowed an acid soluble LCM to be used downhole. This program minimized its use by allowing it to be used only when porous zones were encountered that required stabilization. The acceptable use of these materials required the contractor to develop and implement a very controlled development method that would remove, with verification, the LCMs from the aquifers.
Million-Dollar Results
It is believed that the deepest of the wells, at just over 1,630 feet, set a new state record for the depth of a 24-inch culinary well. That well uses a Roscoe Moss louvered screen, which Hydro used on three of the five wells drilled. The other two wells used stainless steel wire-wrapped screens from Johnson Screens shown in the adjacent figure. The screens shown on the right and left are heavy duty screens developed for other projects. The screen shown in the middle is the screen developed specifically for CUWCD’s project.
In a discussion with Thom Hanna, a sales representative of Johnson Screens, special consideration was required to ensure adequate tensile and collapse strength for the anticipated installation depths. Hanna also indicated that square rods were used in lieu of the round rods typical of their design to gain strength, and that a new method of welding the vertical rods to the end fittings was developed for this project. When tested, this new method provided full tensile rod strength, a feat that had not previously been achieved. The tested tensile strength for the screen was more than 200,000 lbs, well over the calculated string weight of 164,100 lbs.
Tying It All Together
CUWCD’s new wells will supply water for the $325 million water development project that includes the use and blending of treated surface water, over 20 miles of large diameter (36” to 60”) pipeline with daily flow rates ranging from 21,050 to 56,700 gpm, a 40-million gallon water storage reservoir, water treatment plant upgrades, pump stations, and well houses. When completed, the project is expected to provide water to more than 225,000 people living in Utah and Salt Lake Counties.
The well project designed for CUWCD by HAL and completed by Hydro sits on the former site of the Geneva Steel Mill. The mill opened in the 1940s but closed permanently in 2002 following bankruptcy action. Groundwater rights equaling 43,400 acre-feet per year used for this project were purchased in 2005 from the company in liquidation for $88.5 million. Those rights, combined with previously purchased rights, formed the basis of this project. The Geneva water rights came with almost two dozen existing wells ranging from 160 to 1,300 feet. Those wells underwent geophysical analysis and video logging to investigate their condition.
“In the end, (we) determined that we couldn’t rehab them; we had to plug them all and then drill new wells,” Shaw said. “But it did provide us with a wealth of information about what to expect. We felt very confident in not only the water quality, but the water quantity and availability after doing all that work.”
HAL engineers attribute the success of the wells to a client that was willing to go the extra mile exploring previously untapped aquifer zones to depths exceeding 1,600 feet (400 to 500 feet deeper than other known large-diameter production wells in the state), to efficient on-site observation and coordination, to a well driller who paid attention to detail and worked to make things right, and to the well development contractor Widdison Turbine Service who efficiently developed each source.
The historic and unique project has been a major success. All involved — the owner, the engineer, the driller, and the consumer — have all come out winners.
Dr. David Hansen, a principal of Hansen, Allen & Luce, Inc., has more than 30 years’ experience in the management of water-related engineering studies and design projects. David has a B.S.C.E. degree from the University of Utah, and an M.S. degree in Civil and Environmental Engineering and a Ph.D. degree in Fluid Mechanics and Hydraulics from Utah State University.