Installation Principles for Top Liner Performance
Following best practices for installation maximizes the performance and lifespan of a frac pad liner. This chapter provides a comprehensive guide to site preparation, covering critical elements for each stage of the process.
Site Preparation: Creating a Solid Base
Site Assessment
Before beginning construction on a frac pad site, assess the site’s characteristics, potential design challenges, and environmental considerations. This data guides the design and construction of both the frac pad and the liner system.
Topographic Survey
The first part of a detailed assessment is a topographic survey to map the site’s contours and identify characteristics like slopes, drainage patterns, and the precise location of existing structures or features. The topographic survey guides the frac pad layout to ensure proper drainage and minimize liner movement or erosion.
Geotechnical Investigation
A geotechnical investigation is conducted to evaluate the soil properties beneath the proposed frac pad. It analyzes characteristics such as soil type and classification, bearing capacity, compaction characteristics, settlement potential, and moisture content. Understanding the type of soil—whether it’s clay, sand, silt, or a combination—is necessary to determine its suitability as a foundation.
The soil’s bearing capacity indicates its ability to support the weight of the frac pad, equipment, and stored fluids without excessive settlement or deformation, which could exert undue stress on the liner.
The soil’s compaction characteristics determine how well it can be compacted during installation to create a stable and dense subgrade.
The soil’s settlement potential indicates the likelihood of the soil settling or subsiding over time. This movement could damage the liner or cause gaps and leaks.
Determining the soil’s moisture content helps evaluate its stability and potential for expansion or contraction, which, like bearing capacity, can reduce the liner’s performance and longevity.
Environmental Assessment
An environmental assessment identifies and evaluates environmentally sensitive areas on or near the proposed frac pad site. Designers refer to this mandatory assessment to minimize environmental impacts and ensure compliance with regulations.
One primary focus of the environmental assessment is identifying nearby surface water bodies such as rivers, streams, wetlands, and lakes. These water resources must be protected from contamination by fracking fluids, flowback water, and other potentially harmful substances. The assessment also includes locating groundwater resources, such as aquifers, to determine the necessary liner protection measures to prevent groundwater contamination.
An environmental assessment also identifies sensitive wildlife habitats that must be protected during construction and operation. These usually include habitats of endangered species, wetlands, or other ecologically significant areas. By identifying these sensitive areas early on, the frac pad can be designed and constructed to minimize habitat disturbance and protect biodiversity.
The environmental assessment also evaluates the potential for erosion and sedimentation to help engineers design appropriate erosion control measures and prevent sediment from reaching water bodies.
Hydrological Assessment
Hydrological assessments consider a site’s water balance and potential interactions between the fracking operation and surrounding water resources. It evaluates factors like precipitation patterns, groundwater flow, and surface water runoff.
Carefully mapped precipitation and surface runoff patterns are essential for effective water management on the frac pad. These analyses help engineers understand the amount and intensity of rainfall typical for the area and how water flows across the site during rainfall events.
This information is used to design appropriate drainage techniques for diverting runoff from the pad, preventing ponding, and minimizing erosion that could undermine the liner system. Effective runoff management also reduces the risk of contaminated runoff reaching nearby water bodies.
Clearing and Grubbing
The site must be cleared and prepared before any construction can begin on the frac pad. Preparation includes clearing and grubbing, which entails removing vegetation, debris, rocks, and other obstacles that could interfere with the construction process or damage the liner system.
Clearing typically involves removing trees, shrubs, and other vegetation from the site using mechanical equipment such as bulldozers, excavators, or chainsaws. The removed vegetation is then processed and disposed of properly, often through chipping, mulching, or off-site disposal according to local environmental regulations.
The stumps and root systems of trees and other vegetation are removed during grubbing to establish a stable and level subgrade for the liner system. Grubbing can be done manually or with specialized equipment, depending on the size and type of vegetation.
In addition to vegetation, any obstacles that could pose a risk to the liner system must be removed, including rocks, boulders, construction debris, or any sharp objects that could puncture or tear the liner. These materials are typically excavated and disposed of.
Subgrade Preparation
Once the frac pad site has been cleared and grubbed, the next crucial step is subgrade preparation, where a smooth, stable, and well-compacted foundation is created upon which the liner system will be placed. Proper subgrade preparation is essential for preventing liner damage, minimizing environmental risks, and ensuring a long functional lifespan.
Leveling and Compaction
The first step in subgrade preparation is establishing a level and uniform surface. This process begins by excavating high spots and filling in low spots to create a consistent grade across the entire frac pad area. Careful attention should be paid to achieving proper slopes for drainage so that water flows away from the pad and doesn’t pond on the liner.
Following clearing and leveling, the subgrade soil is compacted according to design parameters. Compaction increases the soil’s strength and stability and reduces the potential for settlement or deformation that could damage the liner. Standard compaction methods include rollers, vibratory plates, or tampers.
Geotextile Underlayment
In some cases, a layer of geotextile fabric may be placed between the subgrade and the liner. The geotextile layer protects the liner from punctures caused by sharp rocks or debris in the subgrade. It prevents the liner from becoming embedded in the subgrade soil, which can restrict movement and damage the liner.
