Ponds are a common construction type that serves everything from ecological needs to decorative functions. They are also used in processes such as water treatment, thermal storage, and farming. One of the most important considerations in designing a pond is ensuring containment by adding a pond liner. In this article, we will outline some guidelines for installing high-density polyethylene (HDPE) pond liner—a common pond liner material often chosen for its flexibility, strength, and resistance to corrosion.
HDPE pond liner preinstallation checklist
Because pond site conditions can vary significantly, site preparation is the first step that should be taken when installing pond liners. Site preparation includes ensuring, when possible, that the site does not experience flooding or high ground water pressure. The bottom of the pond should also be above the water table. Additionally, soil conditions should be inspected to anticipate gas buildup and whether a venting system should be installed.
Once the site is verified to be suitable for constructing a pond, the area should be cleared and leveled. An essential step is the removal of sharp rocks and other objects such as vegetation and stubble from the subgrade. The goal is to ensure intimate contact between the HDPE pond liner and the subgrade, which helps improve the long-term performance of the pond liner.
HDPE Pond liner material qualities
After the site has been chosen, inspected, and prepared, the next step is to begin selecting the right material for the pond liner. HDPE pond liners carry many benefits. They are both tough and flexible, while also demonstrating high resistance to chemicals and corrosion. Furthermore, HDPE liners are among the most durable and long-lasting polyethylene liners on the market.
Another benefit, which can streamline installation, is that HDPE liners can be fusion welded together. Being able to weld HDPE pond liners allows installers to form seals in the field, simplifying transportation logistics and overall installation complexity. To further reduce overhead, the pond liner can be fabricated into large sheets to reduce the number of field welds required. Another important consideration in regard to fusion welding is that additional equipment and experienced welders are required to ensure a quality installation.
Pond liner installation
The next step in the installation of HDPE pond liners is preparing anchor trenches and other site-specific structures like piping and drains. Once these structures are in place, installers can move onto liner placement. The HDPE pond liner should be unloaded and unrolled carefully to avoid damaging the liner. Often, sandbags are used to keep the panels in place during installation. Once the liner has been pulled across the site, welding preparations can begin.
After selecting a welding method, the properties of the chosen geomembrane such as its type (e.g., high-density polyethylene), melt index, and thickness should be considered. These properties will affect the weld settings. For example, a higher melt index allows the seaming process to take place at lower temperatures and at higher speeds. Prior to any welding, the specific seam area should be cleared from all soil particles and other foreign matter (1, 2). Finally, before creating production seams, trial seams should be conducted according to the construction quality assurance (CQA) plan (e.g., two trial seams a day, 3). For more information on field welding HDPE pond liners, see our 2020 refresher on field welding geomembranes.
The last step when installation HDPE pond liners is construction quality control. This step involves bringing in site test equipment, conducting non-destructive and destructive testing of the field seams, and inspections. Certain non-destructive tests, like spark testing, requires the use of a conductive geomembrane liner.
During the final inspection, the entire HDPE pond liner surface should be examined by the inspector to confirm that the liner does not have any defects, holes, blisters, or contamination. If necessary, the surface should be cleaned to facilitate the inspection process. Any areas that do not pass the inspector’s criteria will be marked for additional testing. If the pond liner passes the inspection process, then the installation is considered complete upon site cleanup and the submission of required certifications.
- 1. “Standard Specification: Seam Strength and Related Properties of Thermally Bonded Homogeneous Polyolefin Geomembranes/Barriers.” Geosynthetics Institute. (2017). Accessed online 30 November 2020 at https://geosynthetic-institute.org/grispecs/gm19a.pdf.
- 2. “How to Weld Geomembranes.” AGRU America. Accessed online 7 July 2020 at https://agruamerica.com/how-to-weld-geomembranes/.
- 3. “Standard Practice: Cold Weather Seaming of Geomembranes.” Geosynthetics Institute. (2013). Accessed online 7 July 2020 at https://geosynthetic-institute.org/grispecs/gm9.pdf.