By Tyler M. Stalker
SACRAMENTO, Calif. – In the film “Honey, I Shrunk the Kids,” a scientist creates a machine that shrinks large items down to very small sizes. But something goes wrong when he mistakenly shrinks four kids to the size of ants, providing them with a very different view of their world, and some wild adventures as they try to get back to reality - and their normal size.
The U.S. Army Corps of Engineers Sacramento District uses a similar machine to design its most complicated projects - minus the hi-jinks.
For the past four years, the Sacramento District has used a 3-D printer to build scale models of two of its largest construction projects, the Folsom Dam auxiliary spillway and upgrades to Isabella Lake Dam.
Based on computer-aided design, the 3-D printer allows full-scale project components to be shrunk into a handheld model that team members can use to better visualize and conceptualize their work like never before.
“While this printer is becoming common throughout the industry, the only way we would’ve been able to get models like this before would’ve been to hand-craft it,” said building information modeling manager Kevin Russ, who transforms a computer drawing into the final model.
Now, thanks to precision accuracy and durable parts, the scaled models are not only proving to be invaluable to project staff, but also superior showpieces to help explain complicated Corps construction projects.
The printer uses strands of ABS plastic, material typically used for household drainage pipes, less than a tenth-of-an-inch thick to create perfectly-scaled 3-D models in a matter of hours.
About 25 miles northeast of downtown Sacramento, construction crews are working to complete one of the Corps’ biggest projects—a new spillway at Folsom Dam, designed to help reduce the risk of flooding throughout the Sacramento region.
The centerpiece of the project is a 367-foot-wide by 146-foot-high control structure, essentially a second dam. With an estimated project cost of more than $750 million, it’s important to be able to show and describe how the project will work to government leaders, the public and project staff.
“When compared to a 2-D drawing or rendering that only shows the outer surface of the project, a 3-D model provides a much better way to help explain what the project is and how all of its pieces will function to a non-technical audience,” said Dave Neff, technical lead for the auxiliary spillway project.
While many models can be printed in three or four hours, a 1/240-scale model of Folsom Dam’s new dam took more than three days to complete. It’s built in sections that come apart like building blocks, revealing the interior workings of the structure.
“Having the various components allows you to peel back and see how it all fits together and how the pieces interact on the inside,” Neff said. “The shafts, stairways and even the equipment room are all there for you to see.”
Seeing it all together instead of on separate pages of plans helps the project staff better understand how maintenance or other facility needs can be met, Neff said.
The models have helped on other major projects, as well.
Isabella Lake Dam, located 40 miles northeast of Bakersfield, is nearly 60 years old and among the Corps’ most at-risk dams. In 2006, the Sacramento District began studying how it could best modernize the dam and reduce the likelihood of dam failure, which would inundate most of Bakersfield and imperil most of its 350,000 residents.
The Isabella Dam Safety Modification Project was approved by Corps headquarters in December 2012. But to get there, project staff considered a wide array of solutions including some uncommon design proposals. 3-D models helped them evaluate the options.
“It’s said a picture is worth a thousand words, well a 3-D model is worth 10 times that,” said Nathan Cox, lead hydraulic engineer for the Isabella Dam project.
Moving forward, the team plans to continue taking advantage of the 3-D printer as the project shifts from study to design.
“It has been extremely helpful to have the technology in-house,” Cox said. “As we move into the preconstruction engineering and design phase, we plan on creating a model of the Borel Tunnel to better see its unique, non-conventional design.”
While all four kids in the movie return to their normal size, only a few Corps 3-D models eventually become life-size. But even the ones that don’t make the cut help designers conceptualize the final project.
“It really is just an invaluable tool,” Neff said.