Colorado-based contractor meets critical grade slope without stringlines and bolsters leading safety program by keeping surveyors out of harm’s way

Overview

Customer Profile  

Headquartered in southwest Colorado, Crossfire is a premier oil and gas field services company that works on projects across the Western United States. Crossfire specializes in pipeline construction and hauling services, well servicing, hydro excavation and utility construction work.

Business Challenge 

In 2013, Crossfire was hired to excavate and prepare for building the foundation for a 120,000 square foot (11,148 square meter) Walmart in Pagosa Springs, Colorado. Looking for precise grade accuracy and to improve efficiencies across this project and others, Crossfire adopted Trimble 3D modeling and data management tools as well as the Cat grade control system.

Solution

The team adopted Trimble® Business Center - HCE, Trimble GCS900 Grade Control System and the Cat® AccuGrade™ system.

Benefits:

• Completed civil and utility work for a 120,000 square foot (11,148 square meter) Walmart; excavated 70,000 yards (1,890,000 cubic feet) for the foundation and placed utility lines in less than six months
• Met sub grade preparation for building footers and parking within +/- 0.1 foot (30 millimeter) tolerance with zero rework
• Successfully graded drainage lines to a 2% critical grade slope without rework
• With a stakeless environment and grade control, productivity improved at least 25% and survey costs were cut by 90%
• Increased grading production for Fort Lewis College build by 300% and met OSHA requirements excavating near 20 feet (6 meter) deep vertical wall, keeping grade checkers and machines out of harm’s way

Crossfire is a premier oil and gas field services company that offers a breadth of experience and excels in oil and gas construction, oil and gas maintenance and civil and commercial construction. The company has 1,400 employees and projects underway in 15 states. Crossfire also has an excellent safety program and is well known for its environmentally conscious practice.

In 2013, Crossfire was hired to excavate and prepare for civil and utility work on a new 120,000 square foot (11,148 square meter) Walmart in Pagosa Springs, Colorado. Sub grade preparation for the building footers and parking lot had to be within +/- 0.1 foot (30 millimeter) tolerance. The project required excavating and laying 70,000 cubic yards (1,890,000 cubic feet) of material for the foundation as well as trenching all utility lines — including the storm sewer — at a critical grade slope. The project also included placing concrete pipes ranging from eight to 24 inches in diameter (20 to 60 centimeters) and creating approximately 35 manholes.

Faced with these parameters, Crossfire adopted Trimble 3D modeling and data management tools as well as Trimble and Cat machine control systems. Matt Mathers, engineer and quality control administrator at Crossfire, explains that he used Trimble Business Center - HCE to create a workable model for the project. He loaded AutoCad files and survey points into Business-Center and then used the software’s 3D visualization capabilities to generate multiple surface views, plans, corridors, textures and images to work from. From here, he prepped the data and created 3D surface models for construction. Business Center-HCE is integrated with Trimble Connected Community, which facilitates file sharing and data visualization capabilities. Three-dimensional models could then be shared through Connected Community and read by the on-machine grade control system.

For the Walmart project, Crossfire relied on an excavator and motor grader equipped with 3D grade control. The team used the excavator and machine control to move 70,000 cubic yards (1,890,000 cubic feet) of dirt for the foundation. Mathers set up two GNSS receivers and solid state angle sensors to measure the precise 3D position of the bucket and blade. The surface models were accessed inside the cab on the control box, and then the models guided the operator to the correct grade by displaying real-time horizontal and vertical cut or fill values. 

Mathers explains that Business Center-HCE was useful in designing a working model for the project as well as verifying material quantities and exposing minor discrepancies in the project design. He also used it to create cut/fill maps for crews, report elevation verifications for accuracies of finished grades and to create as built information of installed structures such as piping and utility work.

“For the invert elevations I took all of the CAD line work and elevated it to 3D based on the engineer's design,” said Mathers. “Our utility lines had to come into 35 manholes and all of the paving in the parking lots was tied into the surface at the top of those manholes, so it was critical that our excavation and grade were on target.”

With GPS, Crossfire was able to grade to the specified tolerances on the first pass. During site preparation for the building footers and parking lot, grade had to be within +/- 0.1 foot (30 millimeter) tolerance. Using grade control, Crossfire stayed within the tolerance needed without any additional rework.

The system also eliminated time-consuming repeated instrument setups. Unlike traditional grading with survey and stringlines, operators achieved grade without waiting on surveyors or the need to add additional material. Design changes and adjustments to ramps and slopes were also shared quickly using Trimble’s Business Center - HCE and Connected Community. In less than six months the team moved 70,000 cubic yards (1,890,000 cubic feet) of dirt and placed all utility lines. With a stakeless environment, Mathers said productivity improved at least 25% and survey costs were cut by 90%. 

“The technology gave us the advantage of not having the additional grade checkers setting up and running lasers,” said Mathers. “On top of that, the operator didn't need any kind of staking, so they knew what they were digging and what grade to hit, all while sitting inside of the cab, so there was zero wasted time. We had to stay within plus or minus one inch (2.5 centimeters) tolerance and our grade had to be certified, and we achieved this accuracy with ease. We also didn't have people down in the ditch, which was a huge safety factor.” Following the Walmart project, Crossfire used the grade control equipment for a build project on the campus of Fort Lewis College in Durango, Colorado. That project involved constructing a 16,000 square foot (1,486 square meter) multiple level building. With 25 people on the jobsite, Crossfire was responsible for all civil work on the project, including backfill, parking lots and foundation work. Crossfire again used Business Center - HCE to create a 3D surface model that was read by the machine control system. Mathers believes that without machine control, his team wouldn’t have been able to hit tolerance targets in the allotted time; in part because the design of the basement required adding stabilization in order to meet requirements set by the Occupational Safety and Health Administration (OSHA). Engineers proposed a steep slope in which workers could work nearby without a risk of potential cave in. The design involved excavating a near vertical wall nearly 20 feet (6 meters) deep. From here, they laid a wire netting attaching it with soil nails approximately 9 feet (2.7 meters) long. Mathers explains grade control from Trimble was essential for this step because machine operators could see precisely where to cut and fill from inside the cab and grade checkers were not placed in harm’s way near the un-stabilized bank. The operator was also able to keep the excavator far enough away from the earth wall. He estimates that Trimble construction technology on this project increased productivity by about 300%. “We definitely see that leveraging Trimble construction technology is the way to stay competitive in bidding and completing projects; now even a lot of transportation agencies are requiring it,” said Mathers. “Plus, safety is everything. We place a lot of value on being able to keep our people safe, which means keeping them off of the ground and away from equipment that's working. There is major intrinsic value in using Trimble technology and we certainly know that equipment brings efficiency to the operation that we can pass on to our clients.”