PICP Lift Peterson Air Force Base in Colorado
Permeable Interlocking and Permeable Interlocking Concrete Pavements Lift Peterson Air Force Base in Colorado
Arriving at the base operations building at Peterson Air Force Base in Colorado, civil engineer Fred Brooks, P.E., LEED AP, is still struck by the beauty of an intricate compass design (Figure 1). It’s created with multi-colored concrete pavers, arranged in a huge circle. But he’s equally thrilled by the pavers in the parking lot. “Everyone loves these pavers,” says Mr. Brooks, U.S. Air Force Environmental Element Chief, 21st Civil Engineering Squadron. “We may have started these projects on this base as a way to handle stormwater, but they’ve done much more than that. They’ve shown how attractive and welcoming a base can look.”
Peterson AFB first started considering pavers to help meet the stormwater runoff requirements established in the 2007 Energy Independence and Security Act. Section 438 mandates all federal facilities manage runoff from 95 percent of all storms. Meeting this requirement often requires permeable pavements. In Colorado, storms can come up suddenly with short-term deluges, causing flooding. Mr. Brooks says airfields quickly became submerged and buildings flood as well. Even without Section 438’s mandate, Mr. Brooks knew something had to change. After attending a seminar in Spokane, WA, and hearing about permeable pavers, he experienced a light-bulb moment. “This was the answer we needed,” he says. “I just had to get everyone else to see the light, too.”
Mr. Brooks began by dividing the base into drainage catchments, focusing on the most problematic sections first. For example, one particular street with a catchment area of 35 acres included several older buildings that drained into the street. Flooding was a frequent concern, but a detention pond was deemed unfeasible and a complete sewer replacement would have been costly. Mr. Brooks knew getting buy-in from others on base was crucial for such a significant project. Thus, he had the road to McDonald’s replaced with pavers. “Almost everyone on our base uses that road,” he says with a laugh. “I’m not sure if that’s good or not, but it’s the way it is. By paving that road first, I was able to expose people to the value of pavers, aesthetically and functionally.”
He also addressed costs by calling a special meeting and composing a presentation about short-term versus long-term costs to assure base decision-makers that pavers were worth the investment. For instance, he noted that maintenance crews repainted road stripes nearly every year. By utilizing pavers as the striping instead, repainting costs would be eliminated (Figure 3). Vehicle load concerns were addressed for the permeable pavement by using 3 1/8 inch (80 mm) thick pavers, 2 inch (50 mm) bedding of No. 8 stone, 4 inches (100 mm) of No. 57 stone and 11 inches (275 mm) of No. 2 stone for the reservoir. In his presentation, Mr. Brooks emphasized how easily utilities could be accessed, as well as the advantages of more efficient road repair. He also discussed the aesthetic appeal of pavers. “Ultimately, we want people who are working here to be happy, and everyone feels better when they’re at a place that looks nice,” says Mr. Brooks.
After managing and shaping perceptions about cost and vehicle loads, Mr. Brooks embarked on a multi-stage project that involved several roads and parking lots, as well as a compass design for the entrance to the base operations building. The pavers feature a minimal chamfer and smooth surface. While meeting ADA requirements, these features made them more suitable for pedestrian areas and comfortable for wheelchair users.
Mr. Brooks designed two separate permeable pavement sections based on flow and infiltration conditions. The first included a perforated underdrain at the subgrade level below the open-graded aggregate reservoir layer. During periods of heavy runoff from storms producing flash flooding, the aggregate reservoir layer buffered the discharge rate from the drainage pipe.
The other section which didn’t require an underdrain allows Mr. Brooks to assess the system’s ability to handle direct infiltration into the sandy subgrade. The first installation involved more than 18,000 sf (1,670 m2) of pavers in a herringbone pattern, followed by another installation of the same area. In the second project, a roadway section of the street had a low point that often flooded after storms. Although extension of storm sewer lines would have resolved flooding, that was deemed too expensive. PICP eliminated the need for storm sewers and the pavement was projected to outlast asphalt by a considerable amount of time.
The next phase for the base operations building included 20,000 sf (1,860 m2) of permeable pavers for the parking bays and for the compass design. The effort was so notable that the contractor, ICPI member Rocky Mountain Hardscapes, won a Hardscape North America Award in 2011 for installing the project. From there, two more parking lots were placed in 2012 and 2013 with more than 56,000 sf (5,200 m2) of pavers (Figure 4). The permeable pavements dramatically reduced, and in many cases eliminated, the need for detention ponds for managing stormwater and snowmelt. In fact, when Mr. Brooks provides tours of the facility, he often dumps a bottle of water on the pavers to demonstrate their infiltration efficiency.
Since achieving LEED credits is also important for U.S. Air Force bases, the designers were able to qualify for stormwater credits by demonstrating reduced peak flows, erosion mitigation, and increased on-site infiltration. “It’s human nature to resist change, and to look at the cheapest option,” says Mr. Brooks. “But what these projects have shown is that you can implement change in a way that’s cost-effective and appealing on a number of levels.”
Following Peterson’s Lead
Peterson Air Force Base’s use of concrete pavers serves as an example to other military bases and federal facilities, especially in meeting the requirements of the Energy Independence and Security Act. Like Peterson AFB, many will be searching for ways to handle runoff while implementing long-term solutions that are durable, cost-effective, and sustainable. This appears to be happening. Mr. Brooks notes that since Peterson AFB installed the permeable pavement, the Air Force Academy installed pavers for a 58,000 sf (5,400 m2) parking lot attached to its medical clinic, and Fort Carson utilized pavers for a test pad for tanks.
Looking to the future, it’s likely that paver projects will continue at Peterson AFB, since Mr. Brooks has mandated it. He revised the base’s “facilities of excellence” plan that outlines requirements to contractors so that permeable pavers must be used on any parking lots and low volume roads in the future. “I wanted to make sure that these efforts wouldn’t be lost when I move on,” he says. “The pavers have made such a difference on this base, and I want that to continue.”
Figure 1 caption
Peterson AFB visitors are greeted by a large compass made with interlocking concrete pavers.
Figure 2 caption
Thule Street, the first paver roadway installed on the base, leads to McDonalds making it the most heavily trafficked.
Figure 3 caption
By using pavers to delineate parking stalls, the annual maintenance cost of repainting lines is eliminated.
Figure 4 caption
Mechanical installation expedited the 30,000 sf (2,787 m2) phase two expansion of a parking lot for the Rapid Attack Identification Detection Reporting System.