AquaDams® are an effective method for providing a diversion or containment area, but before AquaDams® could be used, specific criteria required evaluation. Items considered were the water velocity, installation site conditions, climate/spring runoff, and water depth.
The area of the lake where remedial activities were planned consisted of a gentle grade sloping away from the shoreline. The normal water depth in the deepest areas where AquaDams® were to be placed were .91 meters (three feet) in depth, decreasing to .30 meters (one foot) and shallower approaching the shoreline area. Since the AquaDams® would be installed in a lake, currents were not a major concern. The lake bottom in the remediation area consisted of silt and sediment type materials which would provide an effective seal for the AquaDams®. Remediation activities were scheduled for late summer, therefore no site runoff into the area was expected with the possible exception being heavy rain. AquaDam® heights were selected based on normal expected water depths, including increased depths which could occur during normal rains. Based on these factors, 1.82 meter (6 foot) high AquaDams® were selected for the deeper areas of the containment area and .91 meter (3 foot) high AquaDams® for the shallower areas.
The sediment designated for removal extended out from the shore approximately 51.81 meters (170 feet) and covered an area 213.36 meters (700 feet) in width. Remedial activities for the area necessitated that the area be divided into smaller cells. Three zones were established, each perpendicular to the shore and approximately equal in size. Each zone covered a 51.81 meter (170 foot) by 71.62 meter (235 foot) area.
Once the AquaDams® were installed, dewatering of the cell commenced. Water was pumped from within the containment area ensuring that no impacted sediment was removed. Once the cell area was dry, impacted materials were removed for processing and disposal. The enclosed area was subdivided into smaller cells as required. At the completion of the remediation operations, the AquaDams® were removed and the site returned to its natural state.
During the excavation process, the local area experienced unusually heavy rains. There was a concern that water in the lake would rise to or above the height of the AquaDams® and lead to their eventual failure. Lake levels rose several feet during the rain storm with the lake elevation reaching a point nearly as high as the AquaDams®. Fortunately, the AquaDams® did not fail, and the integrity and isolation of the remediation area was maintained.
Remediation activities were conducted over a 120 day period. Over 2,000 cubic yards of material were removed for treatment and eventual disposal. 1,000,000 gallons of water were treated on-site and returned to the lake area. During this period of time, remedial activities continued without any disruptions due to problems with the AquaDams®.
AquaDams® proved to be an effective system for isolating a contaminated site for remediation. The AquaDams® were installed in a short period of time without significant modifications to the terrain ensuring minimal effect on the ecosystem. AquaDams® were also cost-effective when compared to other types of isolation type operations. With the quick installation and removal, on-site time was reduced. Additionally, no additional backfill had to be transported in or out of the area.