Lower Coal Creek Culvert Replacements and Flood Hazards Reduction

The Problem

Bellevue’s Newport Shores neighborhood lies on a low floodplain of Coal Creek near Lake Washington. Increased development in the area created more frequent and severe flooding of the neighborhood, due partly to five undersized culverts beneath the major roads. Replacing each culvert with a bridge will improve stormwater drainage and flow to Lake Washington and restore the creek habitat for endangered fisheries.

Photo Credit: City of Bellevue

How We Helped

Aspect is providing the geotechnical engineering and construction observation expertise to design and construct the five bridges along with two new stormwater outfalls. Design innovations to evaluate the deep and seismically sensitive soils include state-of-the-art methods developed by the University of Washington to evaluate large-scale lateral spreading acting on bridge foundations and options for reducing lateral loading using new-to-the-region grouted helical piles. Our team worked with the City of Bellevue to select a deep drilled-shaft foundation system and coordinated closely with the City and the other consultants to keep neighborhood residents informed of our work and progress.

Aspect also worked with the City to evaluate risks and cost-effectiveness of options for mitigation for settlement of bridge approaches using articulated approach slabs, lightweight fills, and maintenance pavement.

Milestones for the City

Work is progressing, with three of the bridges already constructed and design work on the last two underway. As proof of the project’s effectiveness, salmon returned to Coal Creek this winter, and are now spawning upstream of the recently completed bridges.

Photo Credit: City of Bellevue

Pier 62/63 Reconstruction

The Problem

Pier 62 has always been vital part of the Seattle waterfront. It brings the city and visitors on to Elliott Bay and to the doorstep of the Olympic Mountains beyond. Throughout the 1990 and early 2000s, it was also home to popular events such as the Summer Nights at the Pier concert series. But over time, Pier 62 started to show its age. The wood foundations--affected by tidal influences, waves, and marine foes like gribbles taking millions of tiny bites out of the wood--deteriorated to a point where the pier could no longer support the weight of a large crowd, or even heavy equipment. The City’s plan to bring the public back to Pier 62 starts with new foundations.

Time-lapse video to see the first part of the process to rebuild Pier 62.

Due to schedule constraints in this busy urban waterfront – home to daily influx from tourists, international cruise lines, and ongoing Seattle ferry terminal and viaduct construction -- work needed to be completed on an accelerated timeline with significate coordination between City staff, neighborhood stakeholders, and the structural engineering team.

How We Helped

Aspect provided geotechnical services as part of the City’s team to design these foundations and ultimately replace the pier. We completed a geotechnical engineering study to create geotechnical design criteria and parameters for pile foundations as well as modeling to forecast seismic events. Over the course of 5 months, Aspect staff were onsite and monitoring the installation of 175 steel pipe piles.

A unique feature of this project was the length the project team went to take care of Elliot Bay’s marine life, during pipe foundation installation, through the use of bubble curtains. Bubble curtains are created through a set of aerated rings, like big hula hoops, that have compressed air pumped through them to create a watery ‘curtain’ of air/bubbles to dampen the sound/vibration blasting outward from the loud underwater ringing made by pile driving, thereby protecting marine habitat.

Pier 62 Drilling with Bubble Screen

Milestones for the City

The City met its accelerated timeline to finish the geotechnical design and pile installation. Through the bubble curtain approach, the health of marine life near the pier was carefully considered. Now that the foundations of the project have been completed, construction can continue on schedule. With the Pier being rebuilt, the recent SR-99 tunnel opening, and the ongoing viaduct removal, Seattle residents will soon once again be celebrating summer and music on a revitalized Seattle waterfront in the near future.

Green River - Lower Russell Road Levee Setback Project

To meet current engineering standards and improve riparian and aquatic habitat, Aspect is providing geotechnical services for the replacement of a levee and river revetment for a 1.4 mile length of the Lower Russell Road flood protection system along the east bank of the Green River in the City of Kent. The project will improve flood protection for the residents and businesses of Kent, Tukwila, Renton and the Green River valley.  Aspect Consulting is the lead geotechnical engineer for the project. They completed field investigations to characterize the subsurface conditions in support of the design and construction of the new levees and ecosystem restoration features. Aspect is completing seepage and slope stability analyses for levee design, and providing geotechnical recommendations for levee embankment material, roads, utilities, and habitat features. The project objectives include designing a system that minimizes long-term maintenance needs and associated costs, and balancing policy directives regarding flood protection (e.g. scour protection, stability and vegetation maintenance), habitat restoration, and recreational use.

Port Angeles Landfill Accelerated Geotechnical Investigation and Design

Quick action was required to prevent an imminent release of refuse to the marine environment from a landfill perched atop a rapidly eroding high coastal bluff above the Straits of Juan de Fuca. We met the challenges posed by the site’s complex geometry with design elements including: aggressively steep cut and fill slopes (2.5H:1V) in refuse and a 110-foot-high mechanically reinforced earth buttress to stabilize the seismically unstable slope, a new cover system with a bentonite-amended low-permeability soil layer below a synthetic turf cap, and shoreline stabilization seawalls and revetments. Successfully accelerated, the project was completed in about half the time typical of similar projects.

University Link Light Rail Tunnel Geologic and Hydrogeologic Analyses

Crossing below the Montlake Cut waterway and connecting the University District and Capitol Hill with downtown Seattle, the University Link extension is anticipated to add 71,000 riders to Sound Transit’s light rail system by 2030. Reducing design uncertainty and construction risks, Aspect’s geologic and hydrogeologic analyses for the 3.15-mile twin-rail tunnel and two deep underground stations contributed to the overall success of the tunnel boring project, which came in $100M under budget and 6 months ahead of schedule. Our dewatering analysis and construction oversight further helped the project sustain progress on schedule-critical construction elements.

Madison Valley Stormwater Project

Shaped by a glacier and eroded by floods, Madison Valley has steep hillsides and a history of stormwater flooding and sewer backups in the neighborhood. We helped address the perpetual urban flooding problem, contributing geotechnical and environmental recommendations in the design and construction of a 1.3M-gallon, underground stormwater storage tank. Our input to the alternatives analysis resulted in a tunneled alignment with several jacking/receiving shafts. Working with soft landfill soils and resolving historical contamination, we designed excavation, shoring, and deep foundations for tank support. As a result of our subsurface studies, change orders were minimized providing a degree of surety in cost and schedule. Our attention during construction further helped keep the project moving forward and on schedule while minimizing impacts to the community.

Old Highway 97 Road Repair

Aspect provided geologic and geotechnical engineering support for road repairs and subgrade improvements on 1.5-miles of Old Highway 97 near Brewster. We completed subsurface explorations, geotechnical engineering analyses, and pavement design alternatives including multiple subgrade improvement strategies. We provided cost-effective repairs tailored to individual problem areas while meeting WSDOT standards and local agency guidelines to fulfill funding requirements. We prepared a full geotechnical report along with design-level plans, specifications, and cost estimates for the proposed improvements.

Fragaria Road Stabilization

The only road in, Fragaria Road was in danger of collapsing and thereby isolating a Kitsap County waterfront community. Responding quickly with geotechnical design to help stabilize the failing roadway, we expedited the project through repair options analysis and design; and into construction planning, bidding, contracting, and oversight. Combining soldier pile wall and driven soil nails, our design solution both met County design standards cost effectively, and was appropriately scaled to the community’s road use.

Washington Harbor Utility Bridge and Estuary Restoration

Aspect provided geotechnical design for a pile system for a new utility bridge to help restore hydraulic continuity and the marine estuary. Key project challenges included pile design within the site's soft marine sediments and re-routing utilities beneath the estuary using directional drilling technology. The project involved collaboration with several stakeholders including the Jamestown S’Klallam Tribe, project engineer, contractor, and private land owner. Aspect also provided written specifications for the foundation components of the project and construction support.

Bucklin Hill Bridge Replacement

Aspect is providing geotechnical and environmental services for estuary rehabilitation and traffic congestion relief where existing twin 72-inch culverts will be replaced by a new bridge. The project includes rehabilitating the Clear Creek estuary and widening the existing two-lane road. The culverts will be replaced by a four-lane bridge along NW Bucklin Hill Road at the Clear Creek crossing to relieve traffic congestion and restore pre-existing estuary conditions. Aspect is providing design recommendations in accordance with WSDOT Local Agency Guidelines and LRFD methodology.

Rockaway Beach Road Stabilization

For more than a decade, Aspect has provided ongoing geotechnical engineering and construction services for the landslide-damaged Rockaway Beach Road site.  Aspect’s local knowledge of the geology and on-going erosion processes provided the basis for the development of the roadway repair. The repair included a shoreline revetment wall, mechanically reinforced earth slope, and re-built roadway shoulder. Aspect provided expedited support and recommendations for design changes that occurred late in the project and responsive field support during construction.  

Washington Boulevard Landslide Monitoring, Kitsap County, WA

Washington Boulevard, located along a steep coastal bluff, has exhibited landslide movement several times in the past decade. Aspect performed multi-phase geologic and geotechnical assessments of earth movement with focused deep-subsurface explorations. Results of the exploration and slope-stability analysis were verified with slope inclinometers and groundwater level monitoring. Based on our targeted remediation concepts and cost estimates, Kitsap County decided to add drainage improvements to enhance stormwater handling. In addition, Kitsap County implemented a groundwater and landslide monitoring program, which Aspect is effecting.


Construction Damage Support, Private Residence, Seattle, WA

Owners of a high-end custom residence on a steep slope overlooking Lake Washington hired Aspect to provide geologic/geotechnical expertise to evaluate potential construction impacts from an adjacent property, which would have deep cuts and excavations into a slope with a landslide history. Prior to construction, Aspect reviewed geotechnical documents and helped design a slope movement and foundation settlement monitoring program. During the adjacent work, the client’s foundations were damaged because of poor construction practices and lapses in engineering oversight. A settlement awarded our client all damages and expenses.

Curley Creek Restoration and Bridge Replacement

This project incorporated the restoration of the mouth of Curley Creek along with replacement of the existing bridge. Aspect conducted geotechnical explorations, completed bridge foundation design including drilled shaft recommendations, developed liquefaction mitigation alternatives, and reviewed off-site groundwater and soil contamination concerns. We also assisted in writing project specifications and provided field observation during construction. This was the first bridge in Kitsap County to use drilled shaft foundations.