Pond Liner Installation Guide

It's easy to assume that the excavation of a pond is the most challenging part of its construction. This assumption is usually wrong and a pond that is not properly lined will lose water and cost too much money to keep filled. 

It's therefore vital that any pond liner be properly installed, and it makes installing a pond liner a vital part of the construction process in order to conserve water and ensure constant water availability. 

This guide looks at how a HDPE freshwater pond liner should be installed properly.

The Benefits of Lining a Pond

When properly installed, HDPE pond liners provide the following benefits:

• Less water seepage. All ponds lose water through evaporation and seepage. However, unlined ponds may lose much more water compared to lined ponds. Seepage goes for further than losing water, though, and can also mean adding water to the pond. This is a concern in wastewater storage ponds where evaporation should take place.
• Mineral and chemical leaching. In wastewater storage ponds, seepage can lead to contamination of the surrounding ground water. Not only does this damage the environment, but can lead to expensive fines if the seepage of the wastewater and chemicals are not properly controlled.
• Evaporation speed. Ponds that are designed to promote water evaporation, like a wastewater pond, require a steady rate of water loss. Here, a black pond liner can heat up the water and encourage rapid evaporation. Likewise, for a freshwater storage pond, a lighter colored liner can be used that will slow the evaporation process.
• Maintenance costs. Both lined and unlined ponds require routine maintenance every year. However, properly lined ponds don't the need that much attention, which, in turn, reduces maintenance costs and the chance of leaks.
• Long-term stability. Because liners prevent seepage, they can prevent hollowed out areas under the soil which seepage causes over a period of time.
• Bank erosion. Because it protects against seepage and erosion on the surface of the pond, a liner keeps banks intact and without it, the soil is often lost before any vegetation can become established.

What Is HDPE?

High density polyethylene (HDPE) geomembrane liners are used in a variety of containment applications from water treatment to storage, and farming. They provide excellent durability and chemical resistance properties and are reliable in exposed applications where protection against ultraviolet rays and stresses from the weather is vital. 

Depending on the application, they’re available in smooth, textured, white, conductive, and high temperature variants. Here, a textured finish, for example, provides higher friction to prevent slippage and is useful when lining steep slopes. In contrast, smooth textured geomembranes are preferred for lining that require low permeability.

In simple terms, HDPE liners are among the most durable and long-lasting polyethylene liners on the market. 

Another benefit of HDPE liners are that they can be fusion welded together. This means that installers can form seals in the lining which, in turn, simplifies transportation because smaller pieces can be transported and then welded together on site at the time of installation. 

HDPE liners can also be fabricated into large sheets that makes for less welding if necessary. This brings down the costs and the requirement of experienced welders that need to be on-site to ensure a quality installation.

Pre-installation Checklist

For purposes of this guide, it's accepted that the location where the pond will be, has already been excavated, so it will focus on the installation of the liner.

Because pond site conditions vary substantially, site preparation is often the first crucial step necessary before installing the pond liners. Here, site preparation includes checking that the site does not experience flooding or high groundwater pressures from below, and that the bottom of the pond is above the water table.

Also, before installation, soil conditions should be inspected to ensure that there is no gas buildup and whether a venting system should be installed for this purpose.

Before construction, it's also vital that all sharp rocks and other objects that could cause damage to the liner be removed, and that the area where the liner will be installed, is cleared and leveled. Remember, the goal is to ensure that there is close contact between the HDPE pond liner and the ground below which helps to improve the long-term performance of the liner.

Pond Liner Installation

Once the site is prepared, the next step in the installation would be to prepare anchor trenches that will hold the liner in place at the edges, and also to prepare specific site structures like piping and drains if necessary. 

Once these structures are in place, installers can move to the next step, which is liner placement.

Here, it's vital to ensure that the liner is safely offloaded and unrolled in order to prevent any damage to the liner. Installers can then begin to pull the liner across the site and often, sandbags are used to keep the liner in place before it is welded.

After selecting the appropriate welding method, the welding properties of the HDPE should be considered because they will affect the weld settings.

Before welding begins, it's crucial to clear any of the seams from soil particles and other foreign matter so that they don't influence the quality of the welding and that the welds hold.

A useful tip is to start welding trial seams to ensure that the seams are properly welded. If they are, welding can then move on to the remainder of the pond liner.

Quality Control

The final step in the pond liner installation, is quality control. This involves bringing test equipment to the site and conducting nondestructive and destructive testing of the field seams. It also involves inspections to ensure that the liner is in good working order and has no defects or holes.

During a final inspection of the pond lining, the entire liner surface should be inspected by the inspector to make sure there aren't any holes, blisters, or contamination. In addition, the surface could be cleaned if necessary, to make the inspection process easier.

Based on the feedback of the inspector, certain areas may be marked for further inspection or testing or, if there are any defects, these areas will be marked for repair.

Once the inspection and any remedial work is complete, the site can be cleaned up and everything prepared for the required certifications.

The Bottom Line

Hopefully, this guide provided the necessary steps and guidance to install a HDPE freshwater pond liner. When properly installed it plays an important role in preserving water, while being cost effective and less prone to regular maintenance.