The Uinta Basin in northeast Utah is known for its extensive in-place oil shale resource. Because this area produces crude with low containment levels, it contributes to the production of fuels that are compliant with the most rigorous environmental standards. When XCL Resources was tasked with building a produced process water pond for development and production of oil and gas in this region, a containment solution that fit within the company’s commitment to innovation and environmental stewardship was required.
Produced process water occurs during the extraction of oil and natural gas. It is generally brackish and may contain trace amounts of chemicals. The produced process water ponds are used for containment after a water treatment process. The Utah Department of Natural Resources (DNR) regulators stipulated that the 9-acre (3.6-h) pond must have zero leakage into the subgrade and provide a system to protect migratory birds from the process water. To achieve this stringent expectation, XCL chose to use the GSE Leak Location Suite by Solmax for the pond 11’s containment system to enhance electric leak location survey (ELLS) capabilities. ELLS is a field-proven technology and currently the only economically practiced method of locating leaks in installed geomembranes both before and after water or soil placement on the geomembrane. Various ELLS methods are available, but all operate on the principle that geomembranes are electrically isolative. Thus, when electricity is applied to the surface of the geomembrane and grounded to the layer beneath it, the path of electricity can be directly traced through any leaks present in the geomembrane. A challenge for these surveys is the conductivity of the material underneath the geomembrane, such as gravel, sand and drainage net as well as the air voids that can exist underneath wrinkles.
These limitations are what drove Solmax to develop the leak location conductive geomembrane. The use of this system began in the early 1990s with the introduction of the conductive geomembrane, which allowed the entire surface of the liner to be spark tested. This eliminated many of the challenges associated with traditional liners. However, during installation, electrical pathways could form during fusion welding of seams and negatively affect the ability to perform an ELLS. In response, Solmax designed the Leak Location Suite comprised of leak location conductive geomembrane, the S-100 Spark Tester and an installation technology utilizing a patented Iso-wedge tool. This allows testing to be performed on entire surface of the installed liner including the panel and underneath the exposed flap at the seam of the geomembrane. This is critical because under the exposed flap is a common location for holes to be found. Other conductive geomembrane systems are not as reliable because the conductivity will go through the seams and produce false positive readings, often leaving areas of untested geomembrane. The Iso-wedge allows for the proper preparation and testing of the geomembrane by isolating the upper seam flap and eliminating time-consuming false positives during the ELLS.
The design for the process pond containment system included a multilayered geosynthetic system with four separate barrier layers (Figure 1). The primary and secondary barrier systems are engineered with a co-extruded technology which allows for multiple layers to be extruded through the same die at one time. Utilizing this conservative approach was the best option to successfully meet the regulatory requirements for zero leakage. The primary barrier layer consisted of GSE HDPE 60 mil (1.5 mm) white single-sided textured, conductive geomembrane. This co-extruded geomembrane features an upper white, textured layer and bottom conductive layer that will allow for leak detection. This will accommodate both spark and dipole testing to be performed in the future. This material also eliminates the need to use soil and water to create a conductive layer underneath the geomembrane for testing. The textured layer provided a safety feature of slip resistance, and the white layer provided a higher quality installation due to less wrinkling and visual inspection.
Next a collection layer using FABRINET 200 mil (5.0 mm) geonet was installed to collect water from the primary barrier and pump it back into the pond. A composite barrier system composed of GSE HDPE 60 mil (1.5 mm) white smooth, conductive geomembrane and BENTOLINER BR, a geosynthetic clay liner (GCL) specifically designed for brine resistance created the third and fourth layers. Any liquid that passes this composite barrier system is considered leakage, which may lead to a needed repair. This is why the most advanced technology in ELLS was needed to detect any leaks before the pond was put into service. Lastly, GSE HDPE 40 mil (1.0 mm) black smooth geomembrane was the last barrier with the impoundment leak collection system above. This layer was installed to capture any leakage that may pass through the above composite barrier system. International Lining Technology, with Chuck Van Houten as the project manager, installed the geosynthetic layers and performed the bare electrical leak location survey. ACES Energy Solutions LLC was the general contractor with Shane Armendariz as the project manager.
Additionally, XCL Resources included a bird deterrent, considered the most recognized system above the impoundment, to protect migratory birds from produced process water. This system included steel cables that extend across the pond that are covered by a mesh top. The system chosen was by HRL Compliance Solutions Inc., with Justin Loy as the project manager.
Geomembranes are a critical component in the design of reliable containment solutions, providing an effective barrier system with very low permeability values. However, the integrity of these geomembrane systems can be compromised during installation of the geomembrane panels and during the service life of the containment system. ELLS are utilized in conjunction with other construction quality assurance (CQA ) methods to mitigate potential issues from construction and provide best practices for achieving zero leaks. These CQA practices mitigate potential leakage issues by finding them and allowing repair before the pond is put into service.
Traditionally, an ELLS includes running an electric current through two conductive layers that are separated by a nonconductive barrier, or liner. When the current encounters a breach in the liner, the current will flow through the breach to detect the leak. The two commonly used ELLS are the Spark Test method per ASTM D7240, which is used on exposed conductive geomembranes like ponds, reservoirs and impoundments, and the dipole test method per ASTM D7007, which is used on water and soil-covered geomembranes.
The S-100 Spark Tester performed an ELLS on both the primary GSE HD 60 mil (1.5 mm) white textured conductive and the secondary GSE HD 60 mil (1.5 mm) white smooth conductive to detect any leaks in the produced process water pond containment system. This test method uses a high-voltage, pulsed power supply to charge a capacitor, which is formed by connecting the nonconductive layer of geomembrane and its underlying conductive layer via the grounding pad. The geomembrane surface is swept with a test electrode to locate defects. The capacitor, which stores electrical energy in an electric field, will discharge current through any breach it encounters in the liner. This is picked up by the test electrode, triggering a visual and/or audible alarm.
International Lining performed the ELLS on both layers during construction, and it performed a second ELLS on the primary GSE HD 60 mil (1.5 mm) white textured conductive to ensure no damage occurred during installation of the bird deterrent system.
Once a liner is covered with water or soil, the dipole method is used for effective leak detection. One main reason for using the Leak Location Conductive System is that it is the only system with a conductive geomembrane that can utilize all the different ELLS.
This process pond was installed in spring/summer of 2022. More than a year later, it is performing as expected without any issues. The containment system was successful in keeping chemicals from leaching into the groundwater. The GSE Leak Location Suite will allow for future tests on the integrity of the liner system.
Jimmy Youngblood is the director of products and application development for the environmental infrastructure group at Solmax. He has been involved in the geosynthetics industry for 29 years with various responsibilities throughout the organization. He was the global geosynthetics manager for Solmax before switching to his current role to strategically position current products and innovate new products and services for Solmax on the environmental side.
All figures courtesy of Solmax.
Utah Process Pond Containment
Owner: XCL Resources
Location: Uinta Basin, Utah
Contractor: ACES Energy Solutions LLC
Construction company: International Lining Technology
GSE White HDPE 60 mil Geomembrane (conductive, textured)
FABRINET 200 mil geonet
GSE White HD 60 mil Geomembrane (conductive, smooth)
4BENTOLINER BR Geosynthetic Clay Liner (GCL)
GSE HDPE 40 mil black geomembrane (non-conductive, smooth)
Geo manufacturer: Solmax