By Patrick Royce, Senior Project Manager, Ahtna Design-Build, Inc.
Ahtna Design-Build, Inc. (ADB), in a joint venture with CDM Smith known as Ahtna-CDM Smith JV (the JV), was awarded a contract under its AFCEC Regional Engineering & Construction (RE&C) contract to repair aircraft Parking Ramp 400, Phases 2 and 3, along with the repair of the adjacent Taxiway November at Travis Air Force Base (AFB). The initial contract was awarded in April 2020 for $22,417,927, and since that time the JV has been awarded three additional contract modifications bringing the contract total to $23,256,935. As the prime contractor on this project, the JV self-performed 20 percent of the contract value while the balance of the work was performed by Southwest Concrete Paving as the JV’s subcontractor.
Travis AFB, located in California near Sacramento, is home to the Air Force, Army, and Navy air units and is known for handling more cargo and passenger traffic than any other military air terminal in the United States. For this reason, the base is in a constant state of infrastructure maintenance and repair. One repair project is at Parking Ramp 400, where the Air Force parks its fleet of C-17 cargo planes while on standby waiting for their next training flight or military mission in the U.S. and abroad. After decades of usage under the weight of these massive workhorses and the exposure to the weather extremes under the northern California sun, Parking Ramp 400 was slated for removal and replacement to bring this area up to current standards and to reduce the potential for dangerous foreign object debris (FOD) from impacting these vital planes. An engineering review was performed on the parking ramp and determined that replacement was necessary, requiring a 12-phase project to allow incremental replacement while maintaining airfield operations.
This project entailed the demolition of 500,000 square feet of the existing concrete at Ramp 400, along with a portion of the adjacent Taxiway November. The concrete was removed and transported to a laydown area on base for crushing to be reused as aggregate in the making of concrete for the replacement taxiways. The JV then excavated approximately 30,000 cubic yards (CY) of existing subgrade materials beneath the removed concrete to achieve the desired subgrade elevation prior to placing new concrete. Soil analytical testing revealed that 24,000 CY of this material was determined to be contaminated non-hazardous material that required specialized transportation and disposal to meet the contractual terms of this project. The JV then introduced a mixture of 4% hydrated lime to lower the moisture level of the in-situ subgrade soils prior to placing cement to add strength to the existing soils and achieve the contractually required 200 pounds per square inch (psi) strength test. These steps were performed to meet the specifications for the subgrade and to prolong the life of the new concrete surface. The JV then added a new underdrain system to control any water that migrates into the new subgrade, from above surface (rain) or below surface (rising groundwater). The JV then added a new 8-inch aggregate separation layer and topped with a new 6-inch cement drainage layer. This will be the foundation beneath the new 17.5-inch and 22.5-inch Portland Cement Concrete Pavement (PCCP) surface, the final step to these improvements. The JV completed all subgrade improvements by the end of May 2021 and started placement of the new PCCP, which is expected to be complete by the middle of July 2021.
Following placement of the new PCCP, we will install expansion joints into the concrete and grounding points for the C-17 planes while parked on the taxiway. Approximately 2,000 tons of hot-mix asphalt paving will be placed along the edges of the new taxiways, followed by new pavement markings applied in accordance with stringent airfield standards. Following removal of all construction materials and equipment, the work areas will be cleaned up in preparation for release of these taxiways back to the Air Force and the crews at Travis AFB.
During the execution of the contract, the Ahtna team met or exceeded the expectations of the government. Our latest contract modification (003) was for a Period of Performance acceleration to complete ahead of schedule and increase our daily work week from 40 to 50 hours. This acceleration and the quality work performed in the field will allow this project to be completed 4-5 months before the contractual end date of February 7, 2022.
Southwest Concrete Paving Company (SWCP) has proven to be a very experienced, high-quality airfield concrete paving company, which specializes in military airfield concrete paving projects. The respect was mutual — SWCP stated to our project management team that they had not previously worked with a prime contractor who is so well suited for this type of work, understands the scope, and can effectively interact with the client. This working relationship has developed into the Ahtna-SWCP JV under recent mentor protégé program certification through the Small Business Administration (SBA). The Ahtna-SWCP JV is now actively pursuing additional small business and 8(a) set-aside airfield paving opportunities and other projects that can benefit from our combined experience, specialized equipment, and professional staff.