California-based developers Baldwin & Sons began the design and development of a housing complex on 99 acres of land in the city of Lake Forest, at the base of the Santa Ana Mountains, in 2014. About two-thirds complete, the 931-unit development, The Oaks at Portola Hills, is comprised of seven neighborhoods of both single-family and multi-family residences. It boasts many amenities, including a location in one of the fastest-growing yet safest cities in the state, with nearby restaurants and shops and easy access to interstates. It also sits at the edge of the Limestone Whiting Ranch Wilderness Park, one of Orange County’s largest wilderness preserves. However, developing Portola Hills required converting the site from its natural state of valleys and steep hillsides into acres of construction- ready flat pads. A variety of Belgard Diamond Pro blocks engineered by Anchor Wall Systems as well as Belgard’s Vertica Virtual Joint (VJ) and Planter blocks were chosen to make up the expansive segmental retaining wall system that created the buildable space. To design and build the retaining wall, Baldwin & Sons chose to work with Geogrid Retaining Wall Systems, Inc., the largest segmental re - taining wall installer in Southern California. Geogrid’s owner, Mike Stevenson, has more than 28 years’ experience, including pioneering some retaining wall technologies. “Geogrid checked all the boxes in terms of the competency of their people, value-engineering and the products they were going to use. Their previous projects and references also gave us a high comfort lev- el,” said Jose Capati, vice president of land development for Baldwin & Sons. “They were very proactive and responsive from design stage to construction and we are happy with the result of the collaboration.” “There’s not much flat land left in Southern California, and there is a shortage of homes in Orange County, so installation of a retaining wall system is an investment in creating more property square footage to build homes on,” explained Stevenson. The project was broken into three phases: Portola Northwest, Portola Northeast and Portola South. While the first two feature single family homes, the last phase saw construction of 313 single-family, 256 multi-family and 58 affordable housing/mixed use dwellings. Portola North West and Portola South are completed. Phase 1 of Portola North East is substantially complet - Belgard® Diamond Pro Segmental Wall Systems Address Geological, Aesthetic Concerns in Creating Nearly 100 Buildable Acres for Prime Housing in California
ed and Phase 2 is currently being worked on as well, with completion scheduled for December, 2023. Geogrid has an in-house design engineer, Matthew Merritt, P.E., of Red One Engineering, who exclusively designs the segmental retain - ing walls for their clients. For Portola Hills, the company designed and built walls comprising the entire perimeter of the project to develop “super pads,” acres of flat land for Baldwin to build on. Many of these walls reached up to 49 feet tall and 1,000 feet long. “We were involved with each phase of the project early in the design process and that allowed us to collaborate with the owner, civil engi- neer and geotechnical engineer on incorporating the various Belgard wall products into the project,” said Merritt. Weekly project meetings with the project management and engineering team also helped avoid issues during construction. Among the main concerns for the project initially, according to Capati, were the poor soil quality of the site and the weather. Early in the project, they started to experience landslides because
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csengineermag.com
july 2021
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