Where soil conditions are poor, quite often the only way to prevent leakage from a dam is with a dam liner. With the proper preparation it is possible to install a dam liners yourself. But there are some considerations:
- You must prepare the site, and there must be no water in it
- You will need a number of helpers, usually at least 1 person for every 8 m of dam liner that will have to be pulled. So if you are pulling an edge that is 40 m wide, we recommend at least 5 people help out.
- You will need to dig a suitable trench all the around to anchor the liner
- After installation you should cover or backfill liner to extend its life and protect the liner against UV degradation.
Prior to placing, unfolding and installing the dam or geomembrane liner, ensure that:
- all roots, stumps logs, boulders, rocks, outcrops are removed and replaced with approved fill.
- all vegetation, organic matter, loose clods, surface debris, mud, waterlogged ground and water is cleared.
- approved fill is used to replaced any removed matter with compaction by rolling or vibration to a finished grade.
- the surface is raked to a uniform texture to not exceed that of graded aggregate.
- all graded surfaces are sandblinded to a particle size not exceeding that of course sand, to a max of 3 mm.
- where needed, a geotextile protection underlay should be used. This will cushion and protect your dam liner or geomembrane from damage from sharp objects as well as elevating puncture, impact and abrasion resistance
- there is free drainage to all surfaces in contact with liner membrane.
- thedam liner is not installed in areas subject to flooding, tides, springs and thermal activity.
- no water accumulates in the excavated site. All water must be pumped out prior to installation.
- all rigid structures specified, including pipeworks, sumps etc. are to be completed before lining is installed.
Excavate a continuous perimeter trench on a stable berm surrounding the pond/dam site by means of trench digger or by means of an angled grader blade. The trench should be far enough from the edge of the berm to provide adequate anchorage. Allow for a minimum backfill of 500 mm over the buried liner.
Protrusions and Venting
Dam liner penetrations shall be subject to designed requirements for operational purposes. Approved foundations, pads and footings shall be provided to obtain a stable liner at penetrated positions. Sealing of protruded structural or servicing elements to the liner membrane shall be provided by an approved means that will avoid concentrated liner stress points and provide a permanently sealed point. Provision shall be made to allow the passage to the surface of all gasses and springs without damage to the liner.
One Piece Panel/Sheet Installation
- Place the unpacked liner at position on berm level ground and unroll to its full length at pond perimeter.
- Place the lower liner loose edge into the perimeter anchor trench allowing ample material to be secured to the full width and depth.
- Hold the dam liner edge down by means of temporary sand bags intermittently along trench at its anchor position.
- Subject to the stability of the berm, the material should be carried across the lining area by two separate installation crews each carrying half the total weight of the liner. Rapidly extend the liner from its concertina fold to the opposite perimeter trench while allowing ample liner to relax into its final position.
- Avoid pulling or tugging at the liner after it has settled on the pond/dam bed as friction against the ground of a large liner area can be difficult to overcome. Careful planning beforehand will make the avoidable.
- When the liner been loose laid with evenly distributed surface ripple, place all surplus liner material into the perimeter anchor trench, allowing ample liner on the pond/dam bed to avoid stretching from ground settlement after filling.
Multiple Piece Installation – On-site Welding
For very large liners, joining on site may be necessary. This is something that a professional must do as you risk leaks in the seams. A professional installation team from Fabric Solutions (or authorised installer), will be responsible for all on-site material welding. When directed by the professional installer, position the liners as explained above. Overlap panel edges approximately 200 mm.