Now it’s time to consider the final stages of frac pad liner installation, including securing the liner, sealing penetrations, and conducting a thorough inspection.
Anchor Trench Construction: Securing the Perimeter
Once the frac pad liner is in place, it must be secured along the entire perimeter to prevent slipping or shifting during operation. Anchor trenches are a simple yet effective technique. They require digging a trench around the frac pad’s edges and burying the liner’s edge within the trench.
Trench Excavation
Start by excavating a trench along the frac pad’s perimeter where the liner will be deployed, about 12 inches from the edge of the pad itself. While a trench that is 12 inches deep and 12 inches wide is often adequate, the dimensions will ultimately depend on factors such as the liner material, soil conditions, and anticipated stresses on the liner system. Always defer to the project specifications and the liner manufacturer’s recommendations for precise trench dimensions.
Liner Anchoring
Once the trench is excavated, the edge of the liner is placed into, across the bottom, and halfway up the opposite side of the trench and secured using one of several methods:
Backfilling with Compacted Soil
Traditionally, anchor trenches are backfilled with soil and then compacted in lifts to firmly embed the liner and prevent movement. When possible, use soil excavated to form the trench for backfill.
Mechanical Anchors
Alternatively, metal bars, plates, or other mechanical anchors may be driven into the ground or embedded in concrete for a secure attachment point. A combination of mechanical anchors and backfilling may be preferred for maximum stability in long-term installations.
Key Considerations
Trench Depth and Width
Verify engineering specifications and liner manufacturer’s recommendations during the securing process to ensure trench dimensions are appropriate for the liner material and site conditions.
Compaction
If soil is used for the backfill, follow best practices for compaction, such as lifts, to maintain anchor trench integrity.
Anchor Spacing
Mechanical anchors should be spaced appropriately to provide adequate support and prevent liner movement.
Drainage
Ensure the anchor trench design permits proper drainage to prevent water from accumulating, which can compromise anchoring.
Penetration Details: Maintaining Liner Integrity at Critical Points
Liner penetrations for essential infrastructure and operational needs are unavoidable for frac pads. When not adequately sealed, penetrations create potential leak points, so careful attention to sealing any penetration is essential for maintaining the effectiveness of the containment system.
Types of Penetrations
Pipe Penetrations
These are common for fluid transport lines, such as fracking fluids, flowback water, or produced water.
Conduit Penetrations
These are used for electrical cables or other utilities passing through the liner.
Sump Penetrations
Sumps are often installed to collect potential leaks or spills within the contained area. The liner must be completely sealed around the sump penetration to prevent leaks.
Drain Penetrations
Drains may be installed to remove accumulated rainwater or fluids from the contained area. Complete sealing around drain penetrations is crucial to prevent contamination.
Sealing Penetrations
Boots and Seals
Specialized boots or seals, typically made of flexible materials like rubber or EPDM, create a tight seal around pipes or conduits passing through the liner. These boots are usually secured to the liner using adhesives or welding techniques like extrusion welding for a reliably leak-proof connection.
Flanges
Metal or plastic flanges can create a seal around more significant penetrations or those requiring a more robust connection. The flange is typically attached using a gasket made of a compressible and chemically resistant material like rubber or PTFE (polytetrafluoroethylene). The gasket is placed between the flange and the liner so that when the flange is bolted down, the gasket compresses, creating a tight, leak-proof seal.
Sealants may also be used to improve the seal around the flange. Sealants are applied to the contact surfaces between the flange and the liner to fill any gaps or irregularities and create an additional barrier against leaks. Always verify that the sealant is compatible with the liner material and the contained fluids.
Welding
In some cases, the liner can be welded directly to the penetration for a permanent and impermeable seal. Direct welding is preferred for small penetrations or when the liner and penetration are made of compatible materials.
Key Considerations
Compatibility
Ensure the sealing materials are chemically compatible with the liner material and the contained fluids.
Durability
Choose durable sealing materials that can withstand the stresses and environmental conditions of the frac pad.
Installation
Following the manufacturer’s recommendations for installing boots, seals, or flanges will help create a secure and long-lasting seal.
Inspection
Since any penetration represents a potential failure point, they should be carefully inspected for signs of damage or leaks. Any questionable signs should be immediately addressed to maintain system integrity.
Final Inspection and Documentation: Ensuring a Fully Functional System
Once installation is complete, a thorough final inspection is conducted before the frac pad is approved for operation. State or corporate regulations may specify which qualified personnel can perform the inspections.
Visual Inspection
The final inspection begins with a comprehensive visual assessment of the liner system. The liner surface is surveyed for punctures, tears, wrinkles, creases, or other signs of damage. Close attention is paid to areas around seams, penetrations, and anchors. Seams are also examined for signs of separation, gaps, or inconsistencies.
The anchor trench is examined to ensure the liner is secured correctly and there are no signs of slipping, erosion, or settlement. The drainage system is checked to ensure it functions correctly and that water flows freely away from the frac pad.
Leak Testing
In addition to the visual inspection, leak testing may be performed using the techniques covered in Chapter 7.
Documentation
Thorough documentation of the final inspection is essential for quality control and traceability and to demonstrate the site is in compliance with regulations. The record should include:
- Inspection date and time
- The names and qualifications of individuals who conducted the inspection.
- A record of observations, defects, or areas of concern identified during the inspection.
- The results of any leak testing performed, including the method used and any leaks detected.
- Document any repairs or corrective actions taken to address any issues identified during the inspection.
- Photographs of the completed liner system, including close-ups of seams, penetrations, and areas of concern.
Detailed documentation provides a valuable record of the liner installation and its condition at completion. It provides evidence of compliance with project specifications and regulatory requirements. It can also be helpful for future maintenance, inspections, or audits.
