A 12' high x 120' long AquaDam was installed to keep this tidal canal dewatered while the California Department of Transportation (CalTrans) widened this new overpass to install new footings. The canal was approximately 90' wide.

Ecology blocks were used to back up the AquaDam and lend it extra support during high tide. Each ecology block was supposed to be wrapped in geotextile fabric to prevent damage to the AquaDam. This did not get accomplished on all of them. The far end of the AquaDam is left rolled up high on the bank.

This is tidal water in summer months, so storms were not a major consideration. However, super-high tides coinciding with full moons happened twice during the duration of the project. At this time, the AquaDam had to be strong enough to control these super-high tides, which were sometimes as much as 9' deep.

Most of the high tides (two per day) were only 6' deep next to the AquaDam. At low tide, there is only 12" of water next to the AquaDam. The white pipe going over the AquaDam is connected to a 2" electric pump to keep the work area dewatered.

It was not possible to put any more water into this AquaDam because it was not started higher up the bank. If it would have been started another 3' higher, another foot or two of height might have been possible. The concrete blocks are 5' high. Not starting the AquaDam high enough up the bank is a common mistake during installation.

Only this much footage at the other end of the AquaDam was left to spare (approximately 10'). The wooden core that the AquaDam came rolled up on has broken. These 6" white plastic discharge pipes going under the AquaDam are held in place by the water inside the AquaDam. They are pumping water from the upstream side of the work area to pass the stream flow.

Two tubes of inner plastic from a 1' high AquaDam are attached to the pipes and used to flume the water. The flume tubing has holes in the sides to dissipate the water over a wider area so that a scour hole will not develop.

A view of part of the newly-created highway bridge. Underneath the bridge the work area is being kept dewatered by an upstream 4' high AquaDam (not shown) and the downstream 12' high AquaDam.

The next year, the same AquaDam had to be reinstalled 300 feet downstream of the previous years' installation site. The added room was needed for construction of the I-880/Milpitas interchange ramp. The AquaDam has already started to fill and is completely across the canal. Notice the multiple pumps on the bank.

The AquaDam is still being inflated. The end is rolling up the bank. The sides of this AquaDam were folded in before it was rolled up. That is why the rolled-up segment is so narrow compared to the width of the AquaDam. Notice the white pipe with two smaller pipes inserted into the end of the AquaDam. Altogether, there are four 3" pumps and one 6" pump that is split, as shown above.

A backup 8' high unit was installed behind the larger AquaDam. The overall length of the backup unit is more than is needed, so it was pulled well up the bank. It's purpose was to provide support to the larger AquaDam during high tide.

The large AquaDam has completely covered the white discharge pipe running along the bank. These three pipes run from upstream to allow water flow to pass the work area. The black 8' high AquaDam is still being filled. It fits like a glove next to the larger unit. It was rolled the same way, so that the sides would fold out as it unrolled.

The 8' high AquaDam has still not unrolled completely. Putting down a geotextile mat allowed workers to walk on the mud without sinking up to their knees.

This is the end of the 8' backup AquaDam. The extra material on the end is a coupling collar, which will not be used and will remain rolled up. Ending the backup unit here, only 4' up the bank, allows all seepage water to flow around the end, rather than backing up between the two dams.

The two AquaDams are now completely full. The smaller unit is used to back up the larger unit. The channel will stay dewatered. The tidal flows will be on the far side of the white dam.

Normal high tide. The water depth is approximately 7'. This unit is good for 1.5' more water depth, which will occur at some point during the life of this project (probably during a full moon). This unit was installed on May 1st. It lasted for approximately 7 days before a tremendous storm washed it out.

Because of the washout, another AquaDam had to be installed a week later. Step 1 is to make sure that the end of the AquaDam is high enough up the bank so that it can inflate to 12' in height when completely full. The sides of the unit have been folded in prior to rolling it up on a beam. Three ropes are being used to restrain the unit from prematurely unrolling. Notice the water level upstream compared to the water level downstream.

Installation is being performed at low tide. Water is being pumped into the end of the AquaDam. The ropes are no longer necessary to hold the AquaDam back. Sufficient internal water pressure has been achieved to stabilize the unit, which will continue to unroll up the far bank. Three hoses are going in one side of the AquaDam, three more are going into the other side.

The AquaDam is still being installed. Notice the white pipe on the far side of the bank. Its elevation compared to the bottom of the canal is approximately 12'. These pipes are used to pump the flowing water around the work site. This is an open-ended AquaDam, however, no water comes out of the far end during installation. The remainder of the roll stays elevated and extends up the bank.

The upstream side of the work area, approximately 600' away from the AquaDam. A mud push-up dam has been built so that stream flow water can accumulate to be pumped around the work area. Pumping power consists of one 12" and two 8" discharge pumps. This is why the previous AquaDam washed out; the pumps could not keep up with a 1" rainfall.

Because of the washout, another AquaDam had to be installed a week later. Step 1 is to make sure that the end of the AquaDam is high enough up the bank so that it can inflate to 12' in height when completely full. The sides of the unit have been folded in prior to rolling it up on a beam. Three ropes are being used to restrain the unit from prematurely unrolling. Notice the water level upstream compared to the water level downstream.

An 8' high AquaDam has been installed on the upstream side of the 12' unit. This is the side that wasvdewatered to leave a dry work area. The 8' high unit does not go all the way up the bank so that trapped water may pass between the two units.

The two AquaDams fit next to each other like a glove. The smaller unit lends support to the bigger unit.

High tide is on the way in; the water is getting deeper and deeper.

This is the 12' high AquaDam that washed out during the rain storm. It was rerolled in the field using this piece of equipment.

While the other unit was filling, this one was rerolled and set back on the trailer. Once back in Carlotta, it was blown up for air and inspected for damage. Only minor damage to the first layer of the 4 ply outer tube occurred. The inside tubes had no holes. No repair was necessary and the unit was rerolled for later use. To install the other unit and reroll this one took less than 8 hours.