DPA getting off on right footing
Posted: Friday, November 14, 2008 9:18 pm
By GLENDA H. CAUDLE
Special Features Editor
“Robust” is the word Matt Caskey uses to describe the “foundation” work at Discovery Park of America.
Caskey is the Geopier designer of record and Geopier Foundation Co. Inc. is the Mooresville, N.C.-based company drilling 600-plus 30-inch diameter holes in the earth to a depth of 15-25 feet at the DPA site on Everett Boulevard in Union City, just south of Goodyear Tire & Rubber Co. and west of Union City Second Baptist Church.
DPA, the multi-million dollar educational complex that will beckon the curious, the fun-loving and the serious student from the surrounding area and from across the nation and beyond as I-65 is built and opened linking Canada and Mexico, has been “pier”less to this point. But this week, that all began to change and now the proposed complex can simply claim to be “without peer,” thanks to the boundless dreams and unparalleled generosity of the Robert E. and Jenny D. Kirkland Foundation, which is underwriting most of the start-up cost of the project.
The Discovery Park of America announcement was made Oct. 10, 2007, in The Messenger. Throughout the months following that exciting news, renowned Canadian architect Douglas Cardinal and his team met with groups of 200-plus local volunteers to plan the complex. July 1, 2008, marked an exciting groundbreaking on the 50-acre construction site, which included property that was in the homestead of Union City’s founder, Gen. George Gibbs, more than a century and a half ago.
Since that time, local citizens and curious travelers on the bypass that will form the eastern boundary of the DPA complex have watched eagerly for more signs of progress.
Earth-moving equipment leveled some areas and scooped out drainage ponds in others and then began creating an earthwork ramp rising toward the west and seeming to point to the proposed path of I-69, which will border the property on that side. Sod was laid and then the area rested in the sun during the long, hot, dry days of summer and into fall.
Behind the scenes, in the minds of engineers and architects, the work went on, however.
Now, with colder weather and wetter days moving in, another phase is obviously under way. While much of the activity is hidden from view because of the height of the newly-constructed traffic ramp that will one day funnel visitors to the entrance to the Discovery Park of America museum and Grand Hall convention center, something vital is taking place.
On Tuesday, a trio of machines belonging to subcontractor Peterson Contractors Inc. Iowa began executing a carefully choreographed dance in the center of the plot where the unique DPA museum building, with its majestic soaring “fin,” will soon take shape.
This is their routine: One drill-monster bites far down into the “mushy” soil that characterizes West Tennessee and brings up packed slabs of dirt on its spiraling blade, time after time. As it spins around to dump this load for the last time, having reached the appropriate depth, a second machine — this one outfitted with a sizable bucket — scoops up a load of “clean rock,” moves it quickly to the newly-dug and seemingly bottomless black pit and pours it in like a playful giant-child intent on filling in a backyard mystery hole. The third partner then “tamps” the load down, down, down — good and tight.
The dance’s first movement is over when the 2- to 3-inch pieces of limestone fill the hole to a depth of approximately two feet.
Now the “driller” must wait patiently while the “scooper” and the “tamper” finish off the geopier with load after load of dumped and tamped finely crushed limestone from another waiting pile. This second rock-fill is smaller than the first loads — from 2-inch diameter size down to sand-sized particles. After each foot-worth of the smaller limestone is dropped, it is firmly packed, too, until the geopier rises to within 12 inches or so of the surface, in most of the holes. Concrete footings will top off these holes later to create a level landscape, and then concrete flooring will be added over the entire area as a solid base for the multi-story structure Cardinal has designed.
The geopier-supported footings will literally carry the weight of the building. They are positioned in clusters, as needed, according to how much of the load they must sustain. The groupings are designed so the holes are as close as four to six feet “on center,” meaning from the center of one hole to the center of its neighbor.
“The heaviest structural portions of the building will have the largest number of piers beneath them,” says Caskey, who created the drawings (after consultation with the project’s design team) that show the monsters’ masters where to concentrate their efforts. “It’s all based on the weight of the building.”
Caskey completed his drawings in a Geopier office in Arlington, where the company’s design work is done, but he could not begin his efforts until a scale model of the museum and Grand Hall had been built and shipped to a lab in Canada where wind tunnel testing was carried out. The building presents a unique challenge because it must not only be able to withstand tornadoes, but also earthquakes. And it must sink its feet in soil that does not comprehend the meaning of the term “compact.”
Once Caskey received the testing results, he had to factor that into his plans for the foundation.
“Any time you are working in northwest Tennessee, the soil conditions are very poor. It’s soft and wet, so for a building of this size and importance, something very ‘robust’ has to be done. The New Madrid Seismic Zone location was a key design factor,” says the engineer, who has also worked on the new ethanol plant in Obion and the Redbirds’ stadium and Baptist Memorial Hospital in Memphis. Each of those jobs was challenging, he says, but for different reasons than the DPA project.
Caskey says the Geopier concept has advantages over traditional foundation construction techniques, which led to its use on this project.
“In the Geopier process, you don’t have to use the more expensive concrete and steel for foundation support for a very heavy structure. Instead, you can use the less expensive crushed limestone for the same level of building performance and this, of course, interested the designer and the constructor. The geopiers have to perform with the exact same seismic resistance as traditional concrete and steel foundations. They have to provide exactly the same load-carrying ability, settlement control and seismic protection as a normal deep foundation would,” Caskey explains.
By noon Thursday — even with a day off because of rainy weather Wednesday — the Geopier crew had completed close to 50 holes.
The prospect of hitting water with the drill is the least appealing scenario, according to Jason Woods, who was on site Thursday as a quality control representative. If that happens, the team must sink a steel “sleeve” into the hole before they can fill in with limestone, but so far there have been no such problems.
In other news …
As work progresses at the building site, Cardinal and his team of engineers are gearing up to return to Union City Monday and work with the volunteer committees on final design plans through Wednesday. Also on hand will be representatives of Gresham Smith and Partners from Nashville, who provide “design services for the built environment,” and who will be reviewing their own drawings for areas outside the museum, proper, with members of the Pioneer Village and botanical gardens committees.
Cardinal, who was specially selected for the project, has been invited to be the featured speaker at Thursday night’s annual banquet of the Obion County Joint Economic Development Council, Obion County Chamber of Commerce and Obion County Industrial Development Corp. at the Hampton Centré in Union City.
And beginning the morning of Nov. 21, Larry Snider, the project’s new director of marketing and communications, and members of his marketing committee will be guiding chairmen of the various DPA volunteer teams through a “brand workshop” that will help determine the “personality” of DPA. The group will be putting themselves in the shoes of potential visitors and trying to anticipate their functional and emotional expectations from a visit to the complex. The emotional reactions of those important guests will provide a priceless source of communications and connections, Snider says.
General contractor Allen Searcy Builder Contractor Inc. of Union City says bids for the concrete foundation work are being let currently and, locally, Revell Construction Co., has been awarded the contract for water and sewer installation, coming under Everett Boulevard.
Mrs. Caudle may be contacted at email@example.com
Peterson Contractors Inc. quality control employee Jason Woods watches heavy equipment dig and fill limestone-packed geopiers at the Discovery Park of America site Thursday.