Technical Challenge
Many man-made waterways, independent of size and function, have been constructed in marginal soils that are not ideally suited to reliably hold water or when lined, liners have failed over time. When the native soil characteristics of a basin allow water outflow (e.g. seepage or leakage) to exceed water inflow consistently, low water levels result.
Even when basins are properly constructed from the onset in generally sound (e.g. clay-rich) substrates, a variety of environmental factors, such as repeated freeze/thaw cycles, prolonged desiccation (from drought), or underlying seams of sand or gravel that promote soil “piping,” can compromise an earthen liner. This causes increased water losses over time. Structural failures or construction oversights (e.g. a faulty control structure or a neglected, but hydrologically connected, agriculture tile) can also significantly increase the probability of leaks and excessive water loss.
In a basin that is currently partially full of water, conventional options to improve containment can be limited and expensive. Reinforcement using synthetic liner materials, traditional soil additives, or imported clay require that the basin be drained and more-or-less dry prior to repair or new liner installation to have any real chance of being effective. Beyond the substantial cost (in time and money) and significant aesthetic downside, this is often not a desirable option – particularly in more mature waterways, due to the tremendously disruptive impact such a disturbance has on the ecosystem and on the overall function of the basin. Additionally, proper soil preparation and compaction can be challenging or impossible under such site conditions.
AquaBlok® Solution
When contemplating a liner approach, AquaBlok offers two primary courses of remedial action for leaking ponds or other waterways:
Spot Treatment: Targeted reinforcement of isolated inconsistencies and points of vulnerability
Full-Basin Lining: General reinforcement and reduction of permeability over the majority of a waterway’s footprint
For spot treatment applications, the first task requires the identification of likely sources of accelerated seepage. Zones of inconsistency on the basin floor (e.g. sand, gravel, or stone seams amidst an otherwise clay bottom) and the deepest portions of the basin (where head pressures are the greatest) are common problem spots. Infrastructure adjacent to and/or penetrating through an earthen basin presents other preferential pathways that are common sources of water loss. Spot treatments to these isolated areas are far more cost-effective than full basin linings simply as a function of the reduction in size, scope, and volume of materials needed. Spot treatment, however, can only be effective if the source of the water loss can be pinpointed.
If seepage is suspected throughout a basin due to existing soil conditions and existing liner age, isolated treatments over a small percentage of the total surface area may do little to reduce water loss. In such cases, a more comprehensive approach may be deemed necessary. This approach may consist of treatment of the entire basin including side slopes or just the bottom footprint of the basin, (where head pressure is most acute). In either case, the goal is the same: to create a continuous blanket of AquaBlok along the entire substrate.
Specific suspect areas can be prioritized and the effects of partial sealing can often be obscured during the installation process, which can also be interrupted for extended periods of time without compromising the installed area to maintain progress.
Once one or more areas of concern are identified, the area(s) can be outlined in the field with floats and/or boundary markings on the shorelines. Aerial photography can be a valuable tool in this preparation for treatment. The resulting surface area can be calculated in square feet. Product quantities are then determined based on the square footage to be covered, existing substrate conditions, and the depth of the target water column in the area to be treated.
AquaBlok is surface applied such that it descends vertically through the water column. It is unique in that the dry material “sinks like a stone” – not surprising in that each particle actually contains an individual piece of limestone as its core. Again, the goal is to accumulate a thin, continuous layer or “blanket” of individual particles such that the clay surrounding each stone can hydrate, swell, and bond together to produce a flexible, durable, and extremely low-permeable earthen liner.
And unlike with conventional alternatives, AquaBlok (1) will not dust, drift or dissipate – providing accurate, targeted delivery; (2) does not require blending or any pretreatment – adding to the consistency of the finished liner; and (3) does not need to be physically compacted once it is placed – dramatically simplifying handling. The density of the stone coupled with the reliable swell of the high quality sodium bentonite coating essentially “self-compacts,” even when placed through a standing water column.
Equipment Needed
For very isolated treatment areas (e.g. over hundreds of square feet or less), AquaBlok can be applied literally by hand, pouring out of a stable boat or off a dock or pier. For intermediate-sized treatment areas (e.g. thousands of pounds of product) where muscling the material manually is not feasible or practical, applicators have used a broad range of equipment to uniformly disperse the composite particle. Examples include broadcast spreaders (like those designed to handle fertilizer or rock salt), water-driven trash-pumps, floating skiffs or mini-barges, and long-reach excavators. Material has even been applied pneumatically through a “bark blower,” a piece of equipment developed for the landscaping industry. When treating entire basin footprints or large surface areas over thousands of square feet, mobile conveyor systems like stone slingers or telebelts offer an ideal combination of consistency and efficiency.
Material Needed
Material quantities vary dramatically based on target coverage area and basin design. Fifty-pound bags of AquaBlok are typically only utilized for very isolated spot treatments or in situations where site access is extremely limited. Most blanket applications involve bulk material packaged in one cubic yard (2,400-lb) bulk bags. Five dry pounds per square foot is considered a light application rate. Conversely, 20-lbs/SF would be considered a heavy application rate. Most blanket applications fall in the range of 7- to 10-lbs/SF, particularly where water depths are designed to be 10-feet or less.
Tips & Observations
To achieve a 1-inch layer of dry AquaBlok (which will hydrate to ~2” when surface applied over standing water) apply right out of the packaging at 7-lbs/SF.
No blending with on-site soil or physical compaction of the product is needed (nor recommended) in this type of an application to create a reliable seal.
Think of spot treatment like placing a band-aid – allow for enough AquaBlok so that the dimension of the blanket of product extends well beyond the suspected area of concern (i.e. by at least three feet in all directions).
For the most uniform and consistent application, placement of dry AquaBlok is preferred (as opposed to attempting to apply hydrating or hydrated product).
Provided the equipment can access the site, a stone slinger is an extremely effective and cost-efficient tool for AquaBlok placement. They have a carrying capacity of 18-20 tons, are remote-operated, and can be run by a single person, can off-load in 15 minutes or less, and have a reach of 70 to 90-feet.
When spot-treating around points of vulnerability, like overflow/water control structures, pipes, etc., consider the possibility of limited (and careful) exploratory excavation to ensure stability beneath the area that will be supporting the AquaBlok.
Consider substrate conditions prior to the placement of AquaBlok. Extremely soft (e.g. organic) sediment and/or excessive rooted plant growth can make the placement of a uniform, thin lining of AquaBlok more challenging. Contact us to discuss steps that can be taken to address these challenges in the field.
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 earthen base and the length of the slope will influence stability. AquaBlok will typically adhere to a 3:1 slope, provided the length of slope is < 20-feet. If you have questions relating to stability on slopes contact AquaBlok or talk to a distributor near you.
Cover media (e.g. sand, soil, or stone) atop the AquaBlok adds ballast and can contribute to overall stability. An armor layer can also provide erosion protection (from wind and ice), help lock in moisture in areas prone to drawdown (due to evaporative loss), and provide site safety and visual appeal.
Photo documentation of the application, particularly when spot-treating an isolated area, can be very helpful. If a given treatment area is well identified, one can always come back and apply more product (over the same area or to expand the treatment area), should seepage rates slow but remain unacceptably high.
Sample calculations: If targeting 7-lbs/SF (~1” dry, ~2” hydrated product thickness), then each 2,400-lb bulk bag would cover ~342 SF (2,400/7); if targeting 10-lbs/SF (~1.5” dry, ~2.7” hydrated product thickness), then each 2,400-lb bulk bag would cover ~240 SF (2,400/10).
From the Field
Rarey Residential Pond Sealing (Findlay, OH)