The project was completed by the Bend Park and Recreation District (BPRD). The total project cost was estimated at about $7.3 to $8.3 million, which was funded primarily from property tax allocation and grant funding. Geotechnical services for the project were solicited by BPRD in August 2018. CGT was awarded the project in September of 2018.
This project included bank, trail, and park improvements along the south end of Mirror Pond and the Deschutes River within Drake Park in downtown Bend, Oregon. As part of this project, the proposed construction included an approximately ¼-mile, elevated boardwalk which was to be installed along the south bank of Mirror Pond from approximately Drake Park to the Newport Bridge. Other proposed improvements included a new boat launch, new pedestrian pathways, and new ADA-accessible ramps along an approximately ¾-mile section of the pond.
To assist in the design and construction of the new park improvements, CGT completed a geotechnical investigation at the site consisting of six drilled borings and five hand auger explorations. The results of the investigation indicated the presence of soft riverbed silts in the vicinity of the elevated boardwalk, and the presence of bedrock at variable depths throughout the project site. Our analysis indicated that the soft riverbed silts were too soft to be economically supported on shallow, spread foundations. Accordingly, CGT recommended that the elevated boardwalk be supported on micro-piles embedded within the bedrock layer that was underlying the soft riverbed silts. Given Mirror Pond’s association with historic logging activities in Bend, the presence of undocumented, often organic-laden fill materials within new park improvement areas was a key consideration identified at the site. Based on the results of our analysis, to support new park features, plans were drawn up to include the installation of approximately 400 micro-piles along the south bank of Mirror Pond.
In our role as geotechnical engineer-of-record and project special inspector, CGT observed the installation of nearly 400 micro-piles along the south bank of Mirror Pond. These micro-piles were installed to support timber decking which supported the new, approximately ¼-mile suspended boardwalk. Recognizing the sensitive of the riparian area in which the piles were installed and severe access limitations, the piles had to be installed using small, track-mounted drilling equipment with materials often needed to be barged in as installation of the piles progressed down the riverbank.
The significant presence of undocumented fill encountered throughout the site also posed challenges to the completion of the project. Several existing bridge foundations and high concentrations of buried organics were encountered within beneath significant site features which were difficult to remediate due to the presence of shallow groundwater from the adjacent Mirror Pond. CGT worked in close collaboration with BPRD to remediate these issues as they came up, and helped the project reach a successful completion in the summer of 2022.