Contractor: RMC Consultants
Techno Metal Post Engineer Involved: JAC Engineering, LLC
Location: Belmar Park, Lakewood, CO
Project Goals and Challenges: Installing helical piles/piers over wet/saturated soil for a new public boardwalk. The new boardwalk would be over water/wetland areas and have an observation deck for the public to enjoy. The old deck structure was small and did not allow many people to be on the observation area at one time. The new design incorporated helical piles/piers for the foundation and provided a long-term solution for freezing and thawing around the structural support elements of the boardwalk.
Type of Soil: Expensive Soils/Clay with high water table
Advantages using TMP: The area of the restored boardwalk was under water when we first visited the site. The Parks Dept. was able to drain the water down so the soil was simply soft mud to slightly frozen mud. The big advantage of using helical piles/piers were the fast and easy installation of a deep pile/pier system and no digging or concrete, while leaving a minimal footprint in this natural environment.
Materials used: (37) P3, 10” helix, 10’-6” long, galvanized; (37) custom caps; P3 galvanized extensions.
Equipment Used: EM1
Bearing capacity: Minimum of 3 Kips per the Engineered design but we ended up at 12-15 Kips geotechnical capacity. One unique thing about this job is that it had expansive clay soil that we wanted to get past. We were confident that once we went past this expansive layer, the structure would be stable. So, we exceeded the design bearing capacity which is often the case when you have to install piles/piers through clay soils to obtain a minimum depth specification. This is, however, a great advantage over using concrete caissons which are more susceptible to expansive soil and freeze thaw due to their larger diameters and increased friction to surrounding soils.
Depth: 8’ minimum but we ended up 12’-6” deep on average to get through some expansive clay that was shown in some old soils testing documents.
Structure Details: Wood framed substructure with composite decking all supported by TMP helical piles/piers.
Testimonials: The Contractor was super impressed how quickly we completed the pile/pier installation. He said, “I didn’t think those would go so fast!” and “now I’d better get my act together and get this thing built!”