Midway Middle School
Roane County Schools Gets New, Long-Lasting Retaining Wall
Dealing with a failed wall that was creating a safety hazard and keeping a critical transportation route closed, Midway Middle School used a big engineered retaining wall block from C.R. Barger & Sons, Inc., to create a strong, sturdy precast wall that’s designed to withstand the test of time and elements.
When the existing, 8-year-old retaining wall located behind Midway Middle School started crumbling and spilling out onto the adjacent roadway last year, Roane County Schools’ administrators knew that they had to act fast in shoring up the failing structure. After reviewing its options, the Roane County, Tenn., school district decided that a new precast concrete structure made from Stone Strong Systems’ blocks and components would be a perfect fit for the project - engineered, strong and reliable.
Unlike a traditional poured-in-place concrete wall, Stone Strong’s precast retaining wall system eliminates the need for long forming and curing times before backfilling. A quicker method that doesn’t require leaving open excavations for extended periods of time, the system allows contractors to install more than 700 square feet of new retaining wall daily – a critical advantage for a project that had to be completed within a compressed timeframe.
“We had less than 30 days to install the structure, which needed to be in place and functioning before the new 2014-15 school year started,” says Kevin Alley, operations manager for contracting firm Charles Blalock & Sons, Inc., of Sevierville, Tenn. “That timeline gave us no room for error or inclement weather conditions; we had to get it done quickly.
As the licensed Stone Strong manufacturer for the state of Tennessee, C.R. Barger & Sons, Inc., of Lenoir City, was enlisted to build approximately 170 precast blocks that would cover a total area of 2,140 square feet. “Our block was specified on the job, so the engineering firm designed a wall that incorporated Stone Strong retaining wall block,” says Kelly Barger, C.R. Barger’s sales and customer development manager.
For the project, the precast concrete manufacturer built a variety of Stone Strong retaining wall blocks in a chiseled granite pattern – 24-square-foot mass extenders and standard block plus a number of 6-square-foot and 3-square-foot pieces for the wall’s top and ends. Barger says the tight project timeline was the only challenge that the precaster faced on this particular job. “It was pretty much business as usual for us, save for the very tight deadline,” says Barger, “and the fact that the wall had to be built and the adjacent road usable in time for school.”
The latter requirement was particularly important, says Robert Jones, the district’s maintenance director, because the road – used daily by school buses – had been closed for nearly a year due to the failure of the existing retaining wall. “When we had to close that road down, it created some real issues for our transportation system,” says Jones. “Once we selected the new precast wall for its durability and the fact that it was made by a local provider, we needed to move quickly to get the project completed in time for school.”
Designed to Withstand
Designed by Josh Cole of S&ME, an engineering and design firm in Knoxville, TN, the new wall is made from extremely heavy, engineered block. The 24-square-foot pieces, for example, weigh roughly 6,000 pounds (10,000 lbs. for the mass extenders) and the 6-square-foot pieces weigh 1,600 pounds. “Using the right leveling pad and backfill,” says Barger, “the large blocks are guaranteed to be successful and not to fail like the previous structure did.” Stone Strong provides technical documents, design details, and a detailed design spreadsheet for engineers and designers to use as tools to complete the design of a Stone Strong retaining wall. Cole said, “In particular, the [Stone Strong design] spreadsheet is pretty powerful. It performs numerous calculations in a fairly compact format.”
Brad Salsbury, vice president at civil engineering firm Cannon & Cannon, Inc., in Knoxville, says his firm got involved with the retaining wall project when Roane County Schools’ contacted the company about providing a design for a replacement structure. “The district wanted to remove the existing wall and then slope the new structure back as far as it possibly could,” says Salsbury. “Due to property constraints, we wound up having to rebuild one section of the existing wall.”
When initially contacted by the school district, Salsbury says he learned that the administrators were specifically interested in using Stone Strong precast retaining wall blocks due to its aesthetics. “They really like the look and finish of the Stone Strong product,” says Salsbury.
From the engineering perspective, he says the project was pretty straightforward: create a new structure that wouldn’t fail before its useful life ran out. “The goal was to come up with a solution that would accommodate the wall size and make up for an elevation difference.” says Salsbury.
Fast Delivery and Installation
The fact that all planning, preparation, manufacturing, and construction had to be completed between May and August of 2014 also impacted the Roane County Schools project, according to Salsbury. That svelte 90-day timeframe had to be accommodated in order to meet the district’s planned road opening schedule. “The entire project was finished within 90 days – from start to finish,” says Salsbury, whose company didn’t receive the official contract award until early-June. “At that point, we were down to about six weeks to have the entire thing ready by the first day of school.”
Because C. R. Barger manufactured the precast Stone Strong blocks at its own plant just a few miles from the middle school, Charles Blalock & Sons was able to pick up the ball and run with it – installing up to 750 square feet of wall daily. “The actual construction of the wall took under one week to complete,” says Salsbury. “That was very fast for a project of this size and scope.”
Alley, concurs, and says the contractor learned of the project via an advertised, public bid put out by Roane County Schools and Cannon & Cannon. The existing, failed structure was likely a “case of the wrong application and improper installation,” says Alley, whose firm was contracted to remove that structure, grade the slope, and then install the new retaining wall. Before the previous wall was removed, Blalock & Sons cleared and graded the site behind it and then “cut as much of the new slope as possible,” says Alley.
“That way, we were able to pull the existing wall back into the slope, load it into trucks, and haul it to a designated waste area,” remarks Alley, “as opposed to pulling the debris out onto the school’s access road – a process that could have resulted in an unbalancing of the asphalt.”
When excavating the foundations, Alley says the contractor found a few areas where the soils were soft and/or unstable. “We removed those areas and replaced them with fresh stone, and then we starting installing the retaining wall blocks,” says Alley, “which were built according to plans, specifications, and the manufacturer’s recommendations.” Once the new wall was in place, Blalock & Sons backfilled the wall with fresh stone and then re-graded, seeded, and matted the slope.
Positive Feedback and Results
With school back in session and its buses able to navigate the once-closed road, Roane County Schools no longer has to worry about the retaining wall that it watched slowly crumble over the last few years. Barger says the district has given Barger & Sons positive feedback on the project. “They love the look of the wall and the work that was done out there,” states Barger. “The installer was also very happy with the quality of the precast block and how everything came together on the project.”
Perhaps most importantly, says Salsbury, is the fact that the middle school came away with a quality, reliable wall that will hold up over time – unlike it’s previous structure. “The school was dealing with a real safety issue, what with numerous school buses traveling back and forth daily on the adjacent road,” says Salsbury. “The wall was literally falling out into the street.”
Salsbury gives credit to C.R. Barger for its quick, quality-controlled Stone Strong manufacturing process and to Charles Blalock and Sons for meeting the district’s extremely tight deadline. “They did a phenomenal job of getting in and out of there quickly,” says Salsbury, “and completing what turned out to be a really good project.”
Jones says the district is “thoroughly impressed” with the new wall and pleased with the materials, processes, and providers selected on this project. “We now have a much better looking wall that was not only done before our targeted schedule,” says Jones, “but that also isn’t going to fail.”