Meritex Lenexa Executive Park – Surface Buildings 1-2, 9800 and 9850 Britton Street, Lenexa, KS 66219
Customized Solution Launches Construction of Key Surface Buildings
AOG has been involved for decades in the ongoing development of industrial space west of I-435 between Renner Boulevard and Ridgeview Road in Lenexa. Our geotech expertise jump-started the underground business park in the 1990s. Then in 2017, we returned in full force for the complicated challenge of establishing new buildings directly above it.
Assessing the Challenge Beneath Buildings 1 and 2
Both of the completed Class A industrial buildings at the center of the Meritex Lenexa Executive Park are long and massive. Building 1 and Building 2 each stretch over 120,000 square feet with 28 feet of clearance, drive-in doors, dock doors, high-efficiency lighting, insulation, climate control — the works. Perfect for storage, distribution, and light manufacturing.
At first glance, the untrained eye might assume the site is stereotypical Kansas farmland with predictable subgrade conditions. But that’s not the case at all. “It’s really complicated and tough to get your head around to come up with effective geotech solutions,” says AOG President Allan Bush. “There are non-uniform conditions and lots of unknowns. Very little consistency.”
The site used to be limestone mines, abandoned long ago until developers saw an opportunity for transformation. The underground business park came together first, and now development is progressing across the surface, separated by roughly 80 to 100 feet of mainly hard limestone and shale.
Previous investigations confirmed the subgrade above the underground business park is strong enough to handle the load of industrial structures. What wasn’t clear was how exactly to go about getting the Buildings 1 and 2 ‘out of the ground.’ That’s where AOG’s work began in 2017. After a decade of planning and discussions, we dug in to analyze all the existing data, gather more of our own, and do additional boring work to zero in on the right solution.
“We immediately found a lot of terrain elevation change from areas of shallow limestone near the surface, down to deep, unknown fill material,” explains Garic Abendroth, AOG’s Director of Engineering and the project’s lead geotechnical engineer.
“The site was easily 20 feet low on the south end, and at that level, there was a large amount of buried mine spoils with no documentation about its strength or stability. A big challenge.”
Steep elevation plus buried mine spoils, a gnarly combination of mainly shale, limestone, and clay all dumped with no engineering control and no intent to build on it. AOG huddled with the project owner and structural engineers to help finalize general building design parameters. Then, we brought three geotechnical engineering options to the table for meeting the challenge of establishing and evening-out essential subgrade support.
Weighing Geotech Options
The first option was the most conservative, calling for the total removal of the mine spoil undocumented fill and then carefully engineering the process of putting it back. The benefit would be shedding light on the quality of the material but the cost in time and money would likely soar. “We didn’t gravitate to that option because we were confident we could work with project leaders to come up with something smarter and more efficient,” recalls Bush.
The second option was a deep foundation that would likely involve drilled piers reaching all the way down to the rock ledge right above the underground business park. It would come with the risk of getting very expensive quickly and would be inherently tricky. “You’re drilling deep and not sure what you’ll run into,” says Abendroth.
“You could hit truck-size limestone boulders and then you’ve got problems.” There were other drawbacks too. “I just didn’t prefer the idea of point loads transferring weight directly to the roof of the subsurface business park,” says Bush. “I thought we could avoid that altogether if we put our heads together.”
Option three-hinged on advanced geotech expertise and steady project team collaboration and seemed to be the right fit. AOG proposed removing only portions of the undocumented fill material, putting it back, and then adding a surcharge load of fill material on top to mimic the weight of the planned buildings. A surveyor would monitor the site until the fill fully settled, then the surcharge would be removed, leaving behind a compacted subgrade ready for foundations.
“This approach would allow the load to dissipate through the soil in the subgrade,” explains Bush, ”And without directly connecting to the rock ceiling of the business park below.”
But option three depended on two major conditions: the availability of a large amount of surcharge fill material and months of waiting for it all to settle. Fortunately, the Meritex development is an unusually long-term endeavor.
Most commercial projects are tied to rigid, unforgiving timelines, but this one was different. The owner understood the complexity of the real estate and was more interested in taking a little extra time to do things right than trying to do them fast. The availability of surcharge fill material was also unlike most commercial projects. Years of ongoing development around abandoned limestone mines in the immediate area had resulted in a plentiful supply of fill material.
“The costs in time and fill material were acceptable to the owner,” says Bush. “And no piers or point loads meant lower construction risks. It was a custom approach that was a good idea for this particular project.”
Engineering the subgrade’s direct connection to foundations called for further customization. Abendroth worked closely with the project owner, the general contractor, and structural engineers to lay out a plan for matching foundation designs to multiple zones right beneath them.
“Most projects have a single zone, so this was unusual. There were three zones arranged differently beneath each of the two buildings, and foundation designs needed slight adjustments to fit each zone. One zone was shallow limestone where several feet would be jackhammered out. Another zone was the engineered fill where the surcharge material had been placed and removed. And the third zone was sort of a transition between the other two, with a thin layer of native clay over the limestone.”
Special Inspections Get It Exactly Right
AOG was hired to develop both the geotechnical solution and perform the special inspections that would go along with getting Buildings 1 and 2 out of the ground. Sometimes project owners split up geotech work and special inspections among different firms, but Bush says this project is an example of why that’s not a good idea.
“Honestly, this project couldn’t have been done the way we did it with a second firm involved. Our inspections were critical to our geotech solution. They were really dependent on each other. It was truly the Alpha through the Omega. It was seamless.”
“Both were equally important,” adds Abendroth, nodding his head in agreement. “You needed the geotechnical engineering for an understanding of what you’re up against, to give designers the confidence to put the right plans together. And then the special inspections made sure what actually happened matched the plans and informed constant adjustments along the way. Two parts making the whole. You can’t separate them. Otherwise, the strategy gets too complicated and difficult to still be viable.”
Just imagine the earth moving effort across so much land. And it wasn’t simply a matter of pushing soil around to shape the grade. Abendroth says an AOG technician with advanced expertise had to visually evaluate every truckload of fill material dumped at the site to ensure it was handled and positioned properly.
“This was truckload after truckload of rocky mine spoils in various conditions. Some of it wet, some of it dry, etc. You have to see every load and understand the different soil types involved and how they’re going to fit into what you’re trying to do. You can’t just put any technician out there to observe. You have to have a skilled veteran who understands the mechanical placement of what amounts to engineered fill material at that point.”
Painstaking earth movement was just the beginning of special inspections. Multiple AOG technicians were frequently on the scene watching concrete pours while others monitored construction as scores of precast walls were hoisted into place on a tight schedule that included precisely timed placement of supporting steel, the floor, and the roof. Bush says the synchronization of AOG engineers and technicians kept the overall project moving in a way that mattered.
“We understand how our role impacts the timing and we really don’t want to hold anyone up. We make a priority of minimizing wait time. A project like this requires more commitment than one technician running around trying to do everything. We put the right people with the right skills in place to keep our services as close to real-time as possible. We were there when we were needed to prevent delays at every step.”
AOG’s focus on collaboration and sticking with a project for the long haul always leads to good things as well as quick, valuable solutions in a pinch. Meritex was no different. When builders hit a snag with hoisting precast walls, they knew Abendroth was just a phone call away.
“Those walls are massive and you’ve got to set anchoring in the ground to lift them up. The team ran into a problem with finding good spots to anchor so I hurried back out there to figure out a solution to keep the installation of the wall going without missing a beat.”
AOG’s success at the Meritex Lenexa Executive Park speaks to many of our strengths, all of them centered on our experience and savvy in giving each project exactly what it needs from planning through construction. Intelligent use of existing materials is a hallmark of our work and fielding uncertain conditions fill us with excitement, not fear. We’ve become specialists in situations where other geotech firms are shaky; abandoned mines, industrial brownfields, and other subgrades full of history and mystery.
We’re always more interested in smart, creative solutions than overly conservative approaches that squeeze budgets and waste valuable time. But, as Abendroth emphasizes, very little of our success is possible without partners ready to collaborate for the very best work.
“I don’t have all the answers. I have some of the answers and the general contractor has some of the answers. The owner has expectations and a budget. No one person or firm can bring everything to the table. You have to collaborate to really make the most of your expertise and your experience, and deliver in the best way possible.”
“The people we work with are so important,” adds Bush.
“Collaboration is critical and when you’re pooling ideas and strategies with partners like Merit General Contractors and BSE Structural Engineers, smarter, better ways of doing things result. We always strive to work closely within our own team to operate ‘as one,’ and when that spirit extends to the larger project team, a higher level of performance becomes possible for all of us.”
As development west of I-435 expands, builders will find unique subgrade challenges at each project site. Anything from shallow rock to mine spoils is possible, including unusual combinations. We look forward to helping our partners navigate each challenge to turn a fast-growing area of Greater Kansas City into a thriving addition to the metropolitan community.
“The ground out there is hilly, shaped by man-made history, and predictably unpredictable,” says Bush. “Solid, level ground is something you have to create and it’s especially important for commercial structures. That’s where AOG will really leave its mark.”