The finished bridge over Deer Creek meets AASHTO/LRFD standards, as well as the aesthetic desires of Chatfield State Park. The sunset-orange columns and collar complement the Ledgestone textured Redi-Rock blocks.
Project Engineer, GROUND Engineering
“Readi-Rock has an advantage in many applications. The bridge was behind schedule…and they were able to catch up because of how fast the walls went in I like to use Redi-Rock whenever it’s feasible.”
In 1965, a massive flood surged through Denver, Colorado, wiping out homes, roads, and a major center of industry. To prevent such disaster from striking again, the Army Corps of Engineers constructed the Chatfield Dam Reservoir near the foot of the Front Range. Its primary purpose was flood control, but its secondary purpose as a water supply reservoir would become increasingly vital.
As the region’s water demands have ballooned with the growth of Metro Denver and surrounding farms, the Army Corps looked once again to the Chatfield Reservoir. They determined it could handle additional 20,600 acre feet (2.5 million cubic meters) of water-storage capacity without compromising its flood control, but that solution brought its own challenges. Accommodating space for the additional water would require relocating and/or modifying several facilities, recreation areas, and roads and bridges in Chatfield State Park, one of the busiest parks in the state.
A critical part of the project was rerouting and elevating the heavily trafficked Perimeter Road, including the bridge over Deer Creek. The new bridge demands were exacting:
When the project came across the desk of HDR Inc.’s Rob Thompson, P.E., the specifying engineer for the project, he clearly recognized that the park wanted the bridge to be economical, but it also would be highly visible. Its aesthetic appeal was as vital to park officials as its AASHTO and LRFD compliance would be to the Colorado Department of Transportation (CDOT).
“The bulk of what you would see would be the walls, of course — the headwall and the wingwalls. I’d used a Redi-Rock retaining wall up along I-70 in Vail, and I thought it looked nice,” he said. “Vail and CDOT seemed to be happy with it up there, and I thought, ‘Well, that would look good here,’ which is what the park was after.”
“The bottom line is, it’s relatively easy to build once they cast that collar on there. Redi-Rock comes in, and they just stack the shorter 9-inch and standard 18-inch-tall blocks up there in a step pattern to align with the curve of the culvert.”
Redi-Rock’s dual-faced freestanding blocks seamlessly integrated on top of the bridge’s walls, forming stunning capped parapets. Clark and Thompson chose to go with Redi-Rock’s Ledgestone texture for the project because of its natural stone look. Signature Stone stained the blocks a mix of light tans to complement the slate gray of the culvert, the sunset-orange of the columns, and the park’s landscape overall.
GROUND Engineering’s Sean Chiang, Ph.D., P.E., a geotechnical and wall design engineer, also worked on the Deer Creek bridge design and finished the shop drawings. Chiang, who has been designing retaining walls for more than 25 years and working with Redi-Rock for more than 10 years, is an avid fan of the product.
“It has an advantage in many applications,” he said, noting its exceptional freeze-thaw durability; its variety of heights, depths, and even knob size (which make it easy for designers and installers to work within most any slope and create various batter); and the ability to seamlessly marry gravity and MSE wall systems on the same project. All those factors were essential to this project.
“I like to use Redi-Rock whenever it’s feasible,” he said.
Thompson’s decision to use Redi-Rock blocks in the design offered the benefit of an easy, speedy installation — something that became crucial when the bridgework got waylaid due to some issues from another supplier. When the time came to begin building the bridge’s walls, said Clark, Redi-Rock made it possible to get back on track.
“The bridge was behind schedule…and they were able to catch up because of how fast the walls went in,” he said.
Although Thompson couldn’t have foreseen the problem he’d ultimately solve because he’d specified Redi-Rock in his design, he wasn’t particularly surprised either.
“I chose it because it looks great, and it’s easy to build with,” he said.
With the Deer Creek bridge in place, the additional phases of the Chatfield Reservoir Reallocation Project can continue, ensuring access to water along the Front Range for generations to come.