Near Hutchinson, Kansas, about 500 to 750 feet below the earth’s surface, there lie a number of abandoned underground salt caverns, filled with brine water and capped with concrete. The caverns, initially created in the early to mid-1970s using the solution-mining process, were used to store liquid propane gas (LPG), which was then extracted for consumption. The cavern wells were used in this capacity until the early 1990s.
After that time, the caverns sat plugged, abandoned, and largely unnoticed until 2011, when three businessmen – Craig Pangburn, a licensed geologist; Kenneth Gates; and Kevin Gates – acquired the land and founded Underground Cavern Stabilization, LLC (UCS) as a commercial Class V emplacement facility to contain non-hazardous contaminated materials within the abandoned caverns. The company received its licenses and permits in 2012, and opened for business in 2013.
According to Steve Pangburn, UCS facility manager, the purpose behind the company’s process is two-fold. “We provide a method for backfilling, emplacing, and containing non-hazardous semi-solid or solid material into these plugged/abandoned underground salt caverns. At the same time, we are helping to stabilize the ground in this area,” he says.
Known as “beneficial reuse material,” the material matter accepted by UCS for containment includes such industrial material as drilling muds, cement slurry, and salt-saturated or high-chloride contaminated soils. “These are not hazardous materials, but they are considered contaminated, and we don’t want them getting into the environment and causing issues,” emphasizes Pangburn.
Process Within the Process
With only a narrow bore hole to access the brine-filled caverns, how does UCS remove the salt water in the caverns and replace it with the solid soils?
The caverns are filled one at a time. The company must first drill out the concrete seal left behind by the former owners on each individual plugged/abandoned cavern well. Then, using a patented, proprietary process, a slurry created by mixing salt water and the beneficial reuse material solids is emplaced down into the cavern via a 5-1/2-inch steel pipe, set within a larger 8-5/8-inch pipe in the bore hole. The 8-5/8-inch outer casing is cemented in the well from the surface to the bottom of the casing. The displaced brine water from the well is forced up the outer pipe and into above-ground containers, where it is reused to create more slurry or sold to customers who can use it – creating zero waste.
“Business has been good,” says Pangburn. “In fact it was so good that we were working hard to keep up with the material coming in.” He explains that the dry material brought to the UCS site is placed into a covered concrete slab with 6-foot walls, to contain it until it can be processed for the slurry. The dry material often is bulky, sticky, and clumped together, and he says the larger clumps would not pass through the hopper into the slurry.
“Over the years, we tried all kinds of ways to break down the dry material, including hitting it with the backside of a bucket and even using a grinding wheel, but nothing really worked,” he says. “Then one of our partners discovered ALLU’s material processing buckets online. We were steered toward Murphy Tractor, the local ALLU dealer, and Luke Fanshier from Murphy came out and had us try an ALLU bucket.”
According to Fanshier, “In January of this year, we took a wheel loader and an ALLU D-Series bucket out to the UCS site, and began using it to process and reduce their dry solids prior to their slurry pit. Immediately, it doubled their production. That’s when we started discussing how to fit the ALLU bucket to UCS’s John Deere 644 loader.”
The ALLU Transformer™ material processing bucket replaces a standard bucket on a wheel loader, excavator or other carrier machine. Turning drums in the bottom, outfitted with changeable blades and hammers, will crush, pulverize, separate and screen the dry material, allowing the sized dry material to pass through the bottom of the bucket.
“The ALLU unit has provided a huge advantage for us,” says Pangburn. “It quickly breaks apart and reduces the soils we receive, turning them into finer dry material that works better with our slurry. It’s been a huge time saver for us, and has helped us to increase our production by at least 100%.”
Material arriving at the UCS facility must be accompanied with documentation from the Kansas Department of Health and Environment (KDHE), verifying that it is non-hazardous. UCS also conducts testing on all incoming materials to check for pH levels, chlorides, conductivity, and temperature. The dry solid material deemed acceptable is unloaded onto the covered concrete slab where the ALLU Transformer™ DH 3-17 40 screener crusher bucket processes the solids. The reduced solids then are added into a hopper and fed into the emplacement slurry, which is introduced into the piping for emplacement.
The KDHE allows containment of the material within the caverns because they are located below the water table. The caverns were previously approved for use in storing LP gas because the salt formation is essentially impervious to liquid and gas, and it has a compressive strength comparable to concrete under the pressure of the overlying rock. In addition, the salt formation is somewhat self-healing because over time the formation creeps and re-seals any fractures or voids that may occur due to pressure. “The LP gas is gone. There’s no danger of catastrophic events with these caverns, as related to emplacement and backfilling of material,” notes Pangburn.
As part of its permit, UCS is required to test the longstring (interior pipe) and casing string (casing pipe) for mechanical integrity on each well as it is opened to ensure it has not been compromised. Opened and finished wells must also be retested regularly, with reports sent to the KDHE.
“This is an environmentally friendly process. We’re offering a different option to oil and gas operators instead of landfilling or landspreading (mixing additional solids into the material to render it inert), which is especially important in groundwater-sensitive areas,” Pangburn says. “We’re also creating beneficial reuse material out of discarded material, and putting it down into the caverns for better stabilization.”
The company’s containment site now encompasses 234 acres, with a total of 61 cavern wells available to fill – a number that is estimated to provide 180 years or more of stabilization activity.
ALLU Group Inc., 800/939-2558, www.alllu.net