HWA provided geotechnical engineering services for the replacement of the box culvert below a busy City arterial with a fish friendly 4-sided box culvert. HWA provided recommendations for design and construction of the culvert and the associated wing walls. HWA also provided recommendations to provide protection against erosion for rehabilitation of stream both upstream and downstream of the new culvert and provided materials testing and special inspection during construction.

HWA provided geotechnical engineer for design of a bridge to replace an existing culvert for WSDOT on SR 305. Investigation consisted of drilling borings to assess the subsurface conditions. Liquefaction induced instability was a critical design element and it was determined that jet grouting would be used to stabilize the soils. HWA worked with the design team and WSDOT geotechnical engineers to provide specifications for the jet grouting work and construction inspection during install.

The Cochran Springs Creek formerly flowed through two pipes at its crossing under Lake Washington Boulevard, HWA performed a geotechnical investigation for design of the replacement of these two pipes with a box culvert opening up this fish bearing stream. HWA explored and evaluated subsurface conditions and provided foundation recommendations for a culvert-type that would allow construction without having to mitigate for the liquefiable materials or impact the existing sanitary sewer.