ANDERSEN AIR FORCE BASE, Guam -- In August of 2023, the 513th Expeditionary RED HORSE Squadron was activated by Pacific Air Forces at Andersen Air Force Base, Guam, to advance theater posture and enable resilient basing in the Indo-Pacific region by setting infrastructure to facilitate Agile Combat Employment operations.
Eight months later, Montana-based Airmen from the 819th RED HORSE Squadron, Malmstrom Air Force Base, became the second rotation to deploy as the 513 ERHS and assume responsibility for the ongoing projects in support of PACAF Strategy 2030: Evolving Airpower.
Shortly after arriving on station the 513 ERHS Horizontal Construction Team and their engineering assistant counterparts began excavating materials for a ramp project at Northwest Field, Andersen AFB, to test a new design technique that became an industry first for Air Force civil engineers: using a milling machine equipped with a three-dimensional Trimble grade control system in place of an excavator, dozer or grader to develop a multi-leveled base course profile.
Of the unique challenges presented by the Northern Mariana Islands’ tropical biome, the team faced hard-packed soil made mostly of coral and limestone—two materials that make excavating with typical construction methods nearly impossible. Rather than crumble into re-compactible soil as usual, the material would break apart into large pieces up to six feet wide, requiring additional labor and materials to properly backfill the giant pits created. These challenges threatened to hinder progress not only at Northwest Field, but for projects at spoke locations such as Tinian Island.
To combat this issue, the team developed an innovative plan to use the pavement milling machine equipped with a Trimble three-dimensional grade control system to remove the material to a specific desired depth as it was ground into smaller usable pieces. This solution not only proved efficient for breaking down the hard soil, but for creating drainage slopes and various cut depths during the process.
The team implemented their plan by performing initial Dynamic Cone Penetrometer tests on the compacted soil to determine its strength. Next, they simulated Tinian runway construction by using their milling machine equipped with the Trimble GCS to grind a test area down to 12 inches. Finally, three methods for replacing the soil were tried and evaluated with a secondary DCP test:
- Replacing the area using only the milled material, compacting into four-inch layers.
- Replacing the area using the milled material and 10% of reclaimed asphalt pavement, compacting into four-inch layers.
- Replacing the area using the milled material, 10% of RAP and 4% Portland cement, compacting into four-inch layers.
By conducting these tests, the team determined soil strength increased 5%, 10% and 15% respectively between the first and third method. Based on this outcome, all three third methods provided improved strength and prevented the need to purchase and transport as much base course material as would be required for a full depth repair.
Investing in this pivotal research allowed the team to develop a realistic design for the Tinian runway that negated major time and resource constrictions due to geographic seclusion. Their work significantly reduced the need to transport material and personnel on and/or off the island, allowing for the long-term reallocation of such assets to airfield revitalization.
In total, the team’s innovative approach to runway construction will save 162,000 tons of material, $7.4 million, and nearly 5,000 hours of labor!