This retaining wall project for Main Event Entertainment’s new family entertainment center in the Kansas City, Missouri area is an instructive example of how a contractor and wall designer worked together to overcome unexpected site conditions during the installation of the segmental retaining wall to successfully build it to the engineering specifications.
The new center is nearly 50,000 sf and has a parking lot, which is the site of the two retaining walls. The smaller of the two was a fill wall needed to hold the dead load of the parking lot. Installation was very straightforward and accomplished without unexpected challenges.
Installing the second of the two walls was much more eventful. The issues that arose on-site revolved around a 20-inch water main line which was known to be there but had not been potholed yet. It serviced the entire west side of the city of Independence. Not only was there a risk of cutting off the water supply to half the population, there was eminent danger to everyone on the jobsite that the waterline could fail and flood the area as a result of the wall construction.
The approach that was decided on was to start construction at the low point and go away from the waterline to keep the soil in place for stabilization. When this was completed, the installer built the part of the wall going toward the line. As they neared it, the bank began to fail; they found they could only excavate 12 lineal feet at a time, just enough to put in the required geogrid, build the wall up and backfill to stabilize the bank and waterline.
Their method was working until at one point the bank collapsed and exposed 60 feet of the line. At this critical juncture, the installation team leader knew they had to leave in place what soils were left and move to the other end of the wall. They shot a laser on the last base course block that had been laid, made calculations, and began construction on the other end.
As the team worked toward the previous stopping point, they were paralleling the waterline and would frequently see sections of bank fail again and expose pipe. To add an additional measure of security against the waterline bursting, a 38,000-pound excavator was positioned to hold the back of its bucket as a brace against the waterline as digging continued. They also had a spotter watch the critical areas.
At last they reached the point where they had left off earlier. They were able to make a perfect match to that base course, then build up the middle, stabilizing the bank and the waterline. All involved were able to breathe an huge sigh of relief: no unwanted waterworks for this operation.
*At the time of the project contract, the wall product was known as Pavestone Anchor Diamond Pro Stonecut 3-piece.