Challenging Site Work In Canton

By Steve Hudson | September 28, 2010

Site work, including some major cut-and-fill excavation as well as extensive utility construction, has been in the spotlight recently in Canton, Ga., at Canton Marketplace, a large retail development being constructed near I-575 for the Sembler Company.

Ellis Astin Grading Co., based in Villa Rica, Ga., has the contract for the earthwork, storm drain, sewer and water, fine grading, and paving and curbing on the 100-acre project site.

Although all of the project elements are impressive, the most dramatic is certainly the earthwork. The totals are impressive — about 2.7 million yards of dirt to move, including about 750,000 yards of rock that had to be drilled and shot. Additionally, because of the extremely hilly nature of the site, numerous large cuts have been required. In some areas of the site, cuts of up to 65 feet were called for; other areas have required fills approaching 70 feet in depth. By any measure, it is most definitely a rugged site.

Among the Ellis Astin personnel involved in the project are Eli McManus, project manager/estimator; and Shawn Midkiff, Mark West, and Jason Cody, superintendents.

Clearing And Site Work

Work began last fall when subcontractor Roger West Clearing moved onto the site to begin clearing. Crews began work on the eastern portion of the project, then moved to the western portion. Overall, the entire clearing operation was completed in just 30 days.

As soon as the eastern portion was cleared, Ellis Astin's crews went to work on the first earthwork. Ellis Astin's grading crews have used a fleet of 15 Cat 621 scrapers, push-loaded by dozers, to handle most of the mass excavation.

The loaded scrapers have transported the material to areas where fill was needed. Once placed at the fill areas, material was compacted as required by Cat 815 sheepsfoot rollers.

Dealing With Rock

A major site work complication was the matter of dealing with three-quarters of a million yards of rock. Some of that rock could be ripped and excavated without blasting, but in some areas — for example, on the eastern side of the project in the 5-acre area where 55- to 60-foot-deep cuts were required for construction of the site's major detention pond — blasting was required. Advanced Explosives out of Douglasville, Ga., handled the drilling and shooting.

Because of the nature of the material and the shot patterns used, the resulting shot rock was generally of a size that was suitable for use as fill. The material was loaded into trucks for transport to other areas of the site.

Occasionally, a large boulder — too large to handle as it stood — would result from the blasting. When that happened, hydraulic breakers mounted on excavators were used to reduce the boulder to pieces of manageable size.

Infrastructure Construction

In addition to the earthwork, Ellis Astin's contract included installation of infrastructure including storm drain, sanitary sewer and water lines.

Two of Ellis Astin's utility crews have stayed busy on the site installing the storm drain, which utilizes reinforced concrete pipe up to 72 inches in diameter as well as corrugated metal pipe up to 84 inches in diameter. Numerous excavators have stayed busy on the pipe placement operation, with other machines such as a variety of compactors coming into play once the pipe was in the ground and backfilling began.

Other elements of infrastructure construction include sanitary sewer and water lines, which are being installed by subcontractor Duncan Pipeline, based in Dawsonville, Ga.

As the project has moved ahead, subcontractor Extruded Curb has begun placing concrete curbing for the access roads and parking areas, and Northwest Georgia Paving is working on the asphalt parking lot and roadway paving.

Fast-Track Building Pads

As fill was used in areas where buildings will be located, particular attention was given to fast-tracking the fill and compaction operations. The reason? Plans called for the use of settlement plates to monitor the fills in those building areas, with specified settlement periods ranging from 45 days to 120 days, and getting those fills in place early in the operation was critical to the overall progress of the project.

Overall, some 13 different settlement plates were installed and monitored during this phase of the work.

"We knew we had to get those fills in place quickly," notes superintendent Midkiff, "so that the settlement periods wouldn't slow the overall project." To that end, he adds, Ellis Astin brought in an unusually large fleet of earthmoving equipment to complete the pads as quickly as possible.

Retaining Walls

The Canton Marketplace project also includes construction of a number of retaining walls.

The walls, which range in height up to 40 feet and include complicated two-tiered wall construction in some areas, have been constructed by subcontractor Contour, Inc., of Douglasville, Ga. Most of the walls have been constructed using modular concrete block, some with total lengths of close to 1,000 feet. The project also includes construction of a small number of poured-in-place walls.

Construction of some of these walls is on the project's critical path. This has called for additional attention to scheduling the related earthwork, adding another element to an already complex project. In some cases, crews even worked at night under lights to meet the wall construction schedules.

Focus On Equipment

Because of the tight schedule and numerous site work challenges, Ellis Astin has been utilizing a large fleet of equipment to tackle the enormous amount of dirt work.

In addition to the scrapers and compactors noted earlier, numerous other machines have been busy on the project. These include a fleet of Cat, Deere and Volvo articulated trucks; Cat, Deere, Hitachi, and Komatsu excavators; and many other machines including compactors, graders, dozers, and loaders.

Other machines have also been used to handle more specialized assignments during various parts of the site work operation. For example, a Deere 270C LC long-stick excavator has been used not only to dress long, steep slopes but also to clean out the settlement ponds on the site.

To further enhance production rates, Ellis Astin engineer/surveyor John Sorrell has been utilizing a GPS-based surveying system during staking operations.

Focusing On Productivity

Throughout this project, one of Ellis Astin's goals has been to maximize productivity. From bringing in large fleets of equipment, to careful sequencing of various project elements, to working after regular hours when such work was required, the project has been managed to make the most out of every construction day.

Clearly, the focus on productivity has paid off. In fact, Ellis Astin has been able to move an average of about 40,000 yards of material per day — enough to put this ambitious project well on its way toward an on-time completion.