Throughout history, permanent water flow control structures have been used to the benefit of humanity, starting with irrigation of early farms through canals formed by soil levees, to the concrete dams of New England which ran mills of all sorts, and generated some of the world’s first consumer electricity, to the reinforced, engineered mega-dams of the 1950s and ahead; these dams which smooth out storm-burst surges, which create reservoirs for gardens in the desert, which allow the generation of electrical power in amounts so great, the units are term “Megawatts”.
Despite the advances in this permanent water flow control technology, millions of people worldwide are still affected by the damaged caused by temporary flood waters. The changing climate, with the increased heat energy and concomitant moisture-carrying capacity, is forcing the flood plain maps to be redrawn, and redrawn again; the boundaries of these 100- and 500-year floods seem to expand by the decade. Neighborhoods all over the world are impacted by the floodwaters, and by what they carry. The cost to the community to recover from the damage caused by a flood event is tremendous.
Even in areas where flooding is not a concern, cofferdams are still required when constructing or repairing structures below water level. Bridge abutments, piers, sea walls, canals, intake structures; all must be constructed, inspected, repaired, and demolished over the course of their respective lifetimes. All such structures are typically partially or totally submerged. Some work cannot be done underwater. Some work can be done underwater, at great cost. Environmental concerns are greater on a submerged work site, due to the greater efficacy of water in spreading spilled contaminants, compared to the spread characteristics of a work area that’s been isolated behind a cofferdam, and dewatered. Working in the dry, behind a cofferdam, is much less expensive and much less hazardous, than working underwater.
What is the solution to these situations requiring temporary water control? Historically, people have used dirt or, more recently, bags of sand, to form temporary perimeter barriers around important structures. Most recently, plastic sheeting has been incorporated into these structures in an effort to mitigate the significant seepage flow and subsequent slumping that occurs once a dirt/sand structure has become saturated with water. Once the flood has gone, all the material used to form these temporary earth-fill barriers must be disposed of. The dirt/sand may be contaminated with sewage or hazardous chemicals. The sandbag material itself is lightweight, deteriorates quickly in the sun, and is typically not reusable. All must be disposed of at an appropriate waste facility, which will charge by the pound to accept this potentially hazardous waste.
Isolation of submerged infrastructure is accomplished by the installation of a cofferdam. Traditional cofferdams have used earth fill material of different types (soil, clay, gravel, stone), sometimes with plastic sheeting to improve the seal. This takes a long time, is subject to erosion and slumping, and leaves a big mess after removal. The impact to aquatic life from the resulting plumes of dirty water (turbidity) prompted, in part, the passage of the US Clean Water Act of 1972.
Isolating the work area by driving steel sheets into the ground with a crane- or excavator-mounted vibratory hammer is a more recently developed cofferdam method. This work requires sufficient vertical space, which may not be abundant at all job sites. The sound vibrations from the vibratory hammer used to drive the sheets travel long distances through the water, affecting aquatic life at the distance of miles, increasing the environmental impact of this method.
What about using water to control water? That was the premise behind the development of the revolutionary next step in temporary water flow control. Initially branded as a “Water Structure”, today’s “AquaDam” is a water-filled structure, with internal baffle, composed of dual watertight inner tubes constrained within a woven outer sleeve. The parallel inner tubes interact through a friction bond with the inside of the outer sleeve, and baffle, which makes the AquaDam structure capable of resisting lateral forces, allowing hydraulic isolation of the protected area from the greater body of water.
The AquaDam can tolerate a hydraulic differential across its width, up to a water depth of ~3/4 of the initial height of the AquaDam, with dry ground on the protected side. When an AquaDam is deployed around a protected area (flood control), or from high ground, through low ground, back to high ground (construction, flood control), isolation of the area behind the AquaDam will be achieved. This isolation will allow the submerged work area to be dewatered, or for floodwaters to be kept away from a home, business, or vital infrastructure such as roads, hospitals, power stations and water treatment plants.
The advantages of using water as a fill material, instead of dirt/sand, are multitudinous. Water is a liquid, which can be pumped long distances, is relatively dense compared to air (8.3lbs/gal), doesn’t contaminate the environment if spilled, and doesn’t require special disposal. Due to the liquid state of the AquaDams fill material (water), and the flexibility of the AquaDam material itself, a filled AquaDam will conform to uneven ground conditions, forming a good seal at the bottom, over most surfaces. The inner tubing of the AquaDam is potable-grade, so if you put clean water in, you get clean water out; this is very important after a flood, when the public water-treatment plant may be recovering from flood damage, unable to supply clean water for days or weeks.
When the AquaDam is no longer needed, it can be drained by siphon or pump, through a hose inserted through the fill-tube, into the main body of the inner tube of the AquaDam.
Once emptied to a practical degree, the AquaDam can be rolled up in place. For small dams, a 4”x4” wood beam is laid across the closed end of the AquaDam. Steel brackets fit over each end of the beam, and allow the attachment of a 3/4” drive ratchet. With a 4-5ft long cheater pipe slid over the handle of the ratchet, a person on each side of the beam will have enough strength and leverage to roll up the AquaDam into a roll, with the 4”x4” wood beam at the center of the roll.
For large dams, the same principle applies; a round log core beam is set at the closed end of the AquaDam. The closed end of the dam is tied off to the log. Ropes are wound around each end of the log and a piece of equipment on either side of the log lifts those ropes, moving forward to torque the log and roll up the AquaDam material.
As the AquaDam is rolled up, any remaining water within the dam will exit through the open fill-tubes at the start of the unit.
Once the AquaDam is completely rolled up, ropes are tied around the roll to prevent unplanned unrolling. Additionally, heavier ropes are tied around the roll, with lifting loops. These loops are used for handling. The brackets or ropes are removed from the ends of the beam, and the beam itself is trimmed with a chainsaw, if desired, to minimize storage volume requirements. Ideal storage for an AquaDam would be “Out of the Sun”, and “Away from Rodents”. Follow those rules and the AquaDam should have an indefinite lifespan in storage.
An AquaDam generally has a high potential for reuse. However, reuse of an AquaDam is not guaranteed. The AquaDam will not tolerate contact with chains, cables, or excavator buckets; metal beats plastic, every time. If an AquaDam is removed in a conscientious manner, it is likely to be reusable.
The AquaDam is truly the future of temporary water flow control structures, enabling the environmentally-conscious construction of new, and inspection/repair/removal of old, aquatic infrastructure. It is quick to deploy, quick to recover, high chance of reuse, minimal impact to the surrounding environment, uses on-site water as fill material, and conforms to uneven ground conditions. The AquaDam simply unrolls as it is filled with onsite water, which is then returned back to the environment when the job is complete. Water Controlling Water.
To learn more, please visit www.aquadam.net