HWA provided geotechnical engineering design support for the replacement of parallel bridges. HWA's work determined that reductions in seismic waves associated with soft lake sediments were large enough that utilizing site-specific seismic parameters negated the need for implementing slope stabilization methods. This saved the City 18M in construction costs and this project was the winner of the 2022 APWA National Gold Award.

The Post Alley Bridge exceeded its design life, and Seattle replaced it with an at-grade soil-supported roadway. This added load on loose fill soils risked settlement and damaging down drag on adjacent foundations. HWA analyzed alternatives and recommended lightweight fill to offset dead and live loads. After evaluating configurations, HWA advised using lightweight cellular concrete for the roadway section to mitigate settlement and protect nearby structures.

HWA served as geotechnical engineering for the replacement of the twin parallel bridges crossing the Sammamish River, evaluations were broken into several phases including a scour repair evaluation, bridge rehabilitation evaluation, and final design of a new bridge structure if rehabilitation was not feasible. HWA developed a solution to reduce load increments due to grade changes by recommending over excavation and replacement with Geofoam to offset the anticipated load increments.