Technical Challenge
Any time a synthetic geomembrane liner (e.g. HDPE, PVC, EPDM, etc.) is intentionally cut (e.g. to install piping for aeration, irrigation, or gas venting), a point of vulnerability is created that can lead to seepage immediately or at some point during the life of the liner. Boots and gaskets are often added to minimize the risk of water loss. But installation can be challenging, and even if properly fitted, movement and time can wear on these preferential pathways and eventually cause problems.
Additionally, incidental cuts or tears in synthetic liner materials are a fact of life. Whether it is a puncture from subsurface stone, damage from a rodent or reptile, deterioration from exposure to the sun’s ultraviolet light, or damage from ice, spot-repair is a reality of the long-term maintenance of any synthetic liner material. Tapes, welds, and adhesive patches are all options, but their usefulness is often complicated by standing water, dirt and debris, and uneven bonding surfaces.
AquaBlok® Solution
Because AquaBlok is derived from all earthen materials, it is physically and chemically compatible with all common geomembrane lining systems. The dry product’s physical weight also makes it self-compacting, making it functional and technically feasible even through a standing water column.
During construction/installation, AquaBlok can be placed beneath the synthetic liner material at seams and/or at any transition with related infrastructure. The clay-wrapped aggregate serves as inexpensive insurance as an underlayment around penetrations (e.g. methane vents) or beneath any region that is historically prone to damage or failure.
As an alternative to traditional repair options, dry product can either be mounded over a suspected tear prior to inundation, or the material can be dropped through the water directly over the problem area to create an earthen patch. Direct contact with the compromised liner material is recommended (i.e. cover soils should be removed prior to application). The adhesive properties of the bentonite will help to fortify a reliable seal, and intimate contact will help prevent water from migrating around, and ultimately under, the patch.
Equipment Needed
For small-scale spot treatments (i.e. less than 100 square feet), AquaBlok can either be hand shoveled (and raked, if working in the dry) or broadcast literally by hand. For applications over larger areas, loader buckets, long-stick excavators, and stone slingers provide the most uniform coverage with a modest labor investment.
Material Needed
Coverage area dictates material need. If a surface treatment of AquaBlok is the goal (e.g. as a veneer over the top of the synthetic liner material), then as little as 7-lbs of AquaBlok per square foot can typically suffice. This will provide a 1.5- to 2-inch hydrated layer.
If the area to be treated is highly irregular or is in relatively deep water (e.g. greater than 10 feet), an application rate of at least 10-lbs per square foot may be more appropriate, and if on a steep slope, some buttressing with gravel/stone rip-rap may be appropriate.
NOTE: 7-lbs of AquaBlok is needed per square foot for every inch of dry product thickness. Therefore, 2” thickness = 14-lbs/SF; 3” = 21-lbs/SF; 4” = 28-lbs/SF, etc. Thicker layers provide extra insurance.
Tips & Observations
Think of spot treatment over a liner like placing a band-aid – allow for enough AquaBlok so that the dimension of the blanket of product extends beyond the breach by at least one foot in all directions.
Direct contact with the compromised liner material is recommended (i.e. cover soils should be removed prior to application). Vacuuming or pressure washing are both effective methods provided they can be accomplished without further compromising the geomembrane.
More gentle slopes (e.g. 4:1 or less) are simpler to seal than steeper slopes (e.g. 3:1 or steeper). The texture of the geomembrane and the length of the slope will influence stability. Slope length and pitch will need to be addressed in final design. If you have questions relating to stability on slopes contact AquaBlok or talk to a distributor near you.
Cover media (e.g. sand, soil, stone) on the toe of the slope and atop the AquaBlok adds ballast and can contribute to overall stability. An armor layer can also provide erosion protection (from wind and ice) and provide site safety and visual appeal.