Steve Goldberg 2017-05-12 12:44:19
Keeping Utah Moving After 22 months, 708,000 man-hours of work, nearly half a million tons of concrete, and $215 million, the massive Interstate 15 (I-15) reconstruction project in Utah has been completed. The Point project, as it was known, involved 7 miles of the most heavily traveled highway in the state. “Most of the population in Utah is centered around the I-15 corridor, so it’s the main route through a lot of the state’s cities,” explains Dan Tix, engineer and director of technical services for Keystone Retaining Wall Systems, the retaining wall engineering firm for the job. “The population has been growing. The expansion of the highway was necessary to accommodate the additional traffic going through the area. The expansion was particularly needed at this choke point.” The interstate was widened to six lanes in both directions, replacing the existing roadway with new 40-year concrete. According to the Utah Department of Transportation (UDOT), 160,000 vehicles travel through this section daily, with an increase to 220,000 vehicles daily expected within three years, leading to stop-and-go gridlock. A number of geogrid-reinforced retaining walls for roadway support were part of this major undertaking. An important requirement of UDOT, however, was that all of the existing freeway lanes were to be open and available during peak travel times every day, during the entire construction process. “We had to come up with solutions to help them maintain their lanes of traffic open during those peak hours,” says Tix. “There were specific work requirements so that we had to do x amount of work early in the day, but then had to stop for the morning commute. We could then work again from roughly 10 a.m. until 3 p.m., and so on. This schedule was determined and coordinated by the construction design-build team.” The retaining walls were all located at the outer perimeter of the interstate, supporting the highway, according to Tix. The Keystone Compac II/KeySystem II was selected for this project. “The expansion was pushed right out to the limit of the highway right-of-way line. They couldn’t go beyond that. For the retaining wall, they had construction easements to work from the frontage roads, but they had to confine all the work within the highway right of way. It was a matter of coordinating getting material in to the location, and how to place it in their work zone. “It was very tight. They shut down the highway to one lane when necessary—when they were bringing in backfill material, for example. Then at the end of the day, they had to reopen the highway.” James Grams, another project engineer with Keystone, worked on many of the engineering plans for this job. He explains that a number of Keystone walls were already in place from previous work on the interstate. “They had to maintain traffic,” he says, “so when they put in the new walls, they couldn’t undermine the existing walls. They couldn’t excavate below them. “The civil engineer, Wilson and Co., provided us with wall profiles they had planned that showed where they wanted a segment of block wall. We used their profiles to determine where the top and the bottom of the wall would be, and their plans also showed where the existing Keystone walls were. There were portions where the existing wall was within 5 or 6 feet of where the face of the new wall was going in. We had to determine where each of these locations were.” The new walls going in were mechanically stabilized earth (MSE) retaining walls with standard geogrid, but because, in many cases, the existing wall was quite close, there were instances in which the extent of the geogrid had to be shortened a bit. “We did have to shorten the geogrid in some sections, where it was close to the existing wall,” says Grams. “The standard AASHTO minimum for reinforcement length is 8 feet, but they have provisions within the code to be able to go down to 6 feet. So we had some latitude to go down to shorter geogrid lengths in those sections.” The original walls remained, but some slight modifications were required in certain places. “They had to remove part of the top of the old walls for their new roadway section, and we ended up extending our upper reinforcement layers over the existing walls,” explains Grams. “On one of the walls, for example, the wall was nine feet tall and the existing wall was five feet from the proposed wall face for a short distance. We made the lower geogrid layers five feet long. The top two feet of the existing wall was removed, and the upper geogrid layers extended five feet past the existing wall face. The reduced base width relied on the presence of the existing Keystone wall.” Tix notes that the existing retaining walls fit within the parameters of what the design-build team wanted, so Keystone came up with a plan in which the the new wall was built near the previous wall, then the highway expansion was constructed over the top of both walls, thereby supporting the new roadway. “It was a rather unique project, with the wall details we had to come up with,” he says. “And the construction staging with all the various contractors had to be carefully worked out. People had to coordinate well together. We couldn’t always get things done exactly when we wanted. “Design-build jobs here are often fast-track projects,” he adds. “Coordination, working together as a team, is a really big deal. Coordinating all the details, with staging, with all the various parties, is a big logistic effort.” As Tix describes, this teamwork is crucial to getting the job, as well as completing the job. “We are an approved block provider on the DOT product list. In addition, we have a relationship with the wall contractor, who has a relationship with the general contractor, as well as some of the other parties involved. So when they started working with the wall contractor, trying to come up with concepts, they brought us in to help them with ideas and design options. It started there, and once you become part of the team, you’re integrated. They usually try to pick a product to work with, or a team to work with, right away. “There might be three or four teams that bid on the job, and our team’s design-build plan was selected, so we started getting to work with them on providing the designs and began working on the little details.” As Grams notes, there were also a number of catch basins that had to be constructed. “The barrier was pretty close to the top of the wall. The catch basins normally line up on the barrier, where the barrier and the road meet. That put the edge of the catch basins about 2 feet from the face of the wall. “In that case, we used four-inch galvanized steel angles, and those are bolted to the back of the Keystone wall units, to withstand that load. We extend them three feet on either side of those catch basins. That’s how we handled those obstructions.” The UDOT tagline is “Keeping Utah Moving.” This I-15 project was a complex job requiring careful coordination among the many contractors involved, but they indeed were able to keep Utah motorists moving throughout the work, and now for many years to come as well. Waterfront Redevelopment A world-class trout stream runs through the community of Bellefonte, PA, but a quarter-mile stretch of the creek had fallen into a state of disrepair and was prone to flooding. “The city-run Bellefonte Redevelopment Authority had acquired a number of properties in this area over time,” explains Jeff Sturniolo, project manager with general contractor Glenn O. Hawbaker Inc. “They were basically abandoned. One was a burnt-out tavern, another was an abandoned industrial warehouse. So part of the project was demolishing those old abandoned structures. “We had to put in a stream diversion in for a quarter-mile and build a retaining wall. The purpose of the retaining wall was to give the public a river walk, and also to elevate the properties above the floodplain so it could be developed for commercial or industrial use.” Massive Redi-Rock gravity blocks in three different sizes were used to construct the retaining wall, which totaled approximately 17,000 square feet. Part of the wall is underwater, ranging from 4 to 7 feet deep, while the ground adjacent to the creek was raised between 4 and 6 feet. There were a number of unusual requirements for this project. One was that the city not only requested specific colors for the wall, but also asked that each stone in a block consist of a separate color. “They actually toured the factory,” says Sturniolo, “and worked with the block manufacturer to get the colors they wanted. It was a grey and a brown and a tan combination; they wanted it to look like the native limestone.” Sturniolo describes another requirement, to benefit the fish. “This was something the fish commission wanted us to do, where the wall is bumped out on the next course up to make a shelf for the fish to take refuge under. We also did a bunch of boulder placements out in the stream. While we were doing the work, we invited the fish commission onsite, and the fish commission biologist was there to be able to show us where he wanted the random boulders placed in the stream.” He notes that about 40 boulders were placed throughout the quarter-mile stretch of the creek on which the crews worked. Another necessity of the job was having lights inside a number of the blocks, to light up the walkway for pedestrians. “That was a phenomenal logistic nightmare,” says Sturniolo. “There were four-block sides, with each block repeated. There were 16 block faces, and the blocks were inverted, with an upside-down pair of faces. But there were only four of these that we could fit into the area. We had to get the electric, the chain, and the plastic housing into the block, and we had to run the electrical conduit behind the wall to attach to all those areas. So the electrician had to install the wiring behind the wall. It was really interesting. “One of the requirements was that we were not to shine any light directly onto the water, so we wouldn’t disturb the fish. That’s why we had to work out which course of blocks the light would be in, since the wall and the base changed elevation.” Another issue was the volume of water that had to be diverted during construction. “We erected a Portadam out into the stream for the whole length of the project to dewater where we had to work. We had two six-inch diesel pumps going, three four-inch 440-volt pumps going, and four three-inch 220-volt pumps going. There was a flood at one point, but we were able to withstand that. We were getting a lot of water migrating from all different directions, but after the flood we were able to seal everything off pretty well,” he says. “There were also some trout that got caught behind the dam, so we had to capture them and return them to the water.” Everyone seems pleased with how the project turned out—fishermen, kayakers, pedestrians strolling along the walkway, and probably the fish as well. Sturniolo shares a story that put a smile on his face: “One of my superintendents was there one time to witness an event where a guy was driving by and yelled out the window, ‘Really great-looking job!’ We get yelled at at work sometimes, but never like that! It was nice to see that the town really appreciated what we were doing.” Stunning in St. Louis A homeowner in a well-to-do neighborhood of suburban St. Louis, MO, was in the process of having a large room addition constructed at the back of his home. Rich Stephens, owner of Red Oak Landscaping, says that at the same time, his company was providing landscaping work on the property. “Eventually, we ended up ripping out all of the front and replaced it with retaining walls. There were no walls there at all in the beginning. We leveled off the yard and created several tiers to the retaining wall, none of them excessively high. The tallest wall was approximately 5 feet tall, but there were a lot of drainage issues related to this project. “We had to put many French drains in behind the retaining wall in order to handle the water. There was also a set of stairs involved—that was the most unique part about it. But there were multiple levels, stairs, and the French drains that we installed. We also installed cap lights on the wall, so there was lighting on all of the tiers.” Stephens used about 1,500 square feet of Belgard Anchor Diamond 9D blocks for the retaining walls. “The customer liked the look and the color. There was good color variation in the stone, and it was a multi-piece stone, so there was more than one size. It created a more broken-up look, as opposed to the same standard block throughout the entire wall.” The stairs that Stephens installed were an added touch to the project. “It wasn’t a big set of stairs,” he says, “but we needed a way to transition on the side of the house from one of the levels that he had us create. So we had to build a set of stairs, and we used the same Belgard product and cap to create the stairs.” He notes, “The drainage was the biggest concern that we had on this project. He has a large creek that comes through the yard, and we really had to manage water flow through the project. We put in a perforated flexible drain pipe that had a sock around it. This pipe will usually exit at the lowest point, or every 50 feet, if it’s a longer wall, as it was in this case.” In addition, Stephens used 1-inch clean rock as backfill for the walls. “We do that on almost all of our retaining walls,” he notes. The back retaining walls had geogrid reinforcement, but the walls at the front did not. “They were only about two feet tall. The walls with the tiers had tiers far enough apart that they did not require geogrid.” There was also substantial revegetation to accomplish. “In the front, it was all landscaped with plants and mulch,” says Stephens. “In the back, we created a swale to control water. We used an erosion mat and seed.” He says that not all of the new vegetation was native plants. “There are varieties that customers demand. These plants can grow well in this environment, but they’re not necessarily native to this area. There are lots of species of plants that would never be here if it wasn’t for the commercial landscape industry.” On many similar projects, getting heavy equipment and materials to where they need to be can be problematic, but Stephens was pleased that this was not an issue on this job. “Access was good because the customer was doing a large renovation in the back. We were allowed to stage materials anywhere we needed. The yard was going to be restored with new irrigation and sod at the end, and we didn’t have to worry about damaging the grass, so the access situation was to our benefit.” Weather issues, however, did slow down progress on the project. “The project was extended for a period of time because there were weeks that we weren’t there at all,” says Stephens. “Then there were also changes that the customer requested. The job took about three months, and about 700 man-hours for the whole project; from retaining walls, to landscaping, to drainage issues, to sod.” Reclaiming Eroded Golf Course Grounds The Lake Arlington Golf Course in Arlington, TX, was beginning to experience some major problems. “The creek running through the golf course is called Village Creek, and it had had a couple of pressure points where it was starting to erode,” explains Jody DuBois, president of Stone Strong of Texas. “It was extending into the greens and the fairway. There was one particular area where it was approaching the green, and they were going to shut the green down as a safety precaution. “We came in and did an erosion control project and put up a Stone Strong wall. This was about 23 feet tall in some places, and we were able to regain the land that was lost to erosion, as much as 25 feet. “These were gravity retaining walls, but we also used geogrid with this application because it was a fill wall. We were able to bring fill dirt in and lay down the geogrid as we went.” DuBois explains that although it is not common to combine geogrid with gravity walls, geogrid reinforcement may be necessary with taller applications or if bad soils are involved. There were several issues that DuBois and his crew had to contend with. “In one area we had limits on how much excavation we could do because it was under a golf cart bridge. For that, we had to go to a true gravity wall to make it work. That was a pretty tight spot.” In addition, one of the requirements of the project was to keep the entire golf course open and available. “With the limited excavation, we were able to arrange the installation as we went along, under the bridge or around the bridge. We were able to put a wall in quickly enough so that it didn’t have an impact on having to shut down the golf course.” Yet another obstacle was the weather. But DuBois indicated that he was able to work around it. “We had heavy spring rains, in abnormal amounts. There were some 10-year rains and even a 100-year rain. Once any section of the wall was put up, whatever section it was, was good. It was a gravity wall, and once you go six feet up, the nature of the installation and the strength of the system allowed them to put in the wall through the rain, thanks to the stability of the wall itself. “The floodwaters and the groundwater that would come up were a bit of an issue, but we were able to control that with the type of basin and type of system we had. We were still able to install the wall in a few places, even where it was a bit under water.” Finding backfill, however, was not a problem. “We were able to use what native dirt was there with our system. We did bring in some select backfill as well. But mainly we used what was available onsite—the material from the excavation—for the backfill, and then we incorporated the select backfill to top it off.” From Temporary to Permanent In Portland, OR, a plot of land was cleared for the construction of a four-story apartment building, with retail or mixed-use space on the ground floor and an underground parking garage. Dan Redmond, owner of Redmond Geotechnical Services, explains a major issue that had to be addressed. “Because we went 10 feet or so into the ground to build the parking garage, and we were bordered on all four sides by either a public right of way or an existing commercial building, we had to provide some type of shoring to keep the public rights of way from coming in on them or having the adjoining buildings’ foundations compromised.” To accomplish this, Redmond used 328 standard Ultrablock concrete blocks to build a gravity wall, but with a twist. “We used this Ultrablock product basically as temporary shoring walls rather than conventional shoring systems. Then, once we were done with those temporary shoring walls, those blocks were taken down and moved to another project, where they became a permanent retaining wall for another job. “In this case, it worked because it was an Ultrablock product, and the client on this job had another job where they needed a permanent retaining wall, and they had opted to use Ultrablock for that retaining wall as well. So this saved them a little money in the long run, since they had the blocks on this job as a temporary shoring wall. “The timing worked out well, and the cost savings was beneficial, so the two projects tied together perfectly.” An important consideration was the protection of an existing building adjacent to the work site. “The commercial building had a below-grade wall, because our property and the adjoining property sloped downward to the south. The old building didn’t have all of its design records available, the plans and specifications, so we had to make some assumptions in a way to protect that building and from having any negative impact when we excavated and removed material that was helping confine and control that building’s below-grade wall. We basically replaced the dirt with the Ultrablock gravity wall system.” The Ultrablock product wasn’t the only option considered, but it appeared to best meet the needs of the project, according to Redmond. “Some of the things that resulted in us deciding to go in this direction, with the Ultrablock, were that a conventional cantilevered soldier pile wall wouldn’t be as cost effective using tiebacks. Existing utilities in the public right-of-way corridor prevented us from using the tiebacks to provide a more stable conventional shoring wall. “By the time we eliminated all of these problems, we came back to a gravity wall, and we had enough room on the site to construct it, and to incline it with the proper batter that gave it enough resisting moment to support the cuts. “The Ultrablock is a large, heavy concrete block. In order to make a gravity wall work most efficiently, the larger the mass you’re working with, the better the resisting moments are. There are smaller blocks available, but they don’t do as good a job as these large blocks do. That was the primary reason they were selected, because they are the heaviest material available.” The blocks fit together similarly to a Lego building set. “They have a four-star pattern on the top of the block,” explains Redmond, “that interlocks them with the recessed four-star pattern under the adjoining upper block, so they self-align. You stack them and then you overlap them with the block on top to the two sides of the blocks below, and that gives you some structural integrity as you set them.” To help the area drain, Redmond used between 6 and 12 inches of granular material as backfill. After about 8 months in place, the temporary shoring wall was removed, having accomplished the task for which it was designed. Those blocks have now found a permanent home in the next project down the street. EC Steve Goldberg writes on issues related to erosion control and the environment.
Published by Forester Media. View All Articles.
This page can be found at http://digital.erosioncontrol.com/article/The+Right+Wall+for+the+Site+Gravity+walls+and+geogrid-reinforced+walls+each+have+a+place+%E2%80%94sometimes+on+the+same+project./2787859/408278/article.html.