Bow Lake Recycling and Transfer Station, Master Plan Update and Implementation

Tukwila, Washington

HWA is providing geotechnical engineering and geo-environmental services as part of the design team for reconstruction of the Bow Lake Recycling and Transfer Station.

Bow Lake Transfer Station, Tukwila, WashingtonA new transfer building will be built on an adjacent property, and the existing transfer station site will be redeveloped with support facilities, roads, and trailer parking after the new transfer building is completed. The existing transfer station was built at the top of a steep slope over a landfill that operated between the 1940s and 1960s, and the new facility will be constructed on an adjacent area comprised of contaminated fill soils stockpiled during the initial I-5 construction. Site development offers challenging geotechnical issues, including the presence of landfill waste, burn fill, earthen fill, steep slopes, and extensive planned grading (cut and fill).

HWA conducted an extensive exploration program including geologic reconnaissance of steep slopes; drilling 47 borings using four different drilling technologies due to varying access and terrain conditions; installing standpipe piezometers in several of the borings; and excavating 18 large scale test pits. HWA collected samples from the explorations for geotechnical laboratory testing, and for chemical laboratory analysis for use in the Phase II Environmental studies.

Bow Lake Transfer Station, Tukwila, WashingtonHWA prepared detailed geotechnical reports that evaluated site conditions and provided final design recommendations for earthwork, pre-loading over refuse, dewatering, slope stability, building foundations, retaining walls, pavement design, and methods for dealing with refuse and contaminated soils. In addition, HWA performed a Phase I Environmental Site Assessment on the portion of the project undergoing property transfer and Phase II Environmental Site Assessments on both the King County property and adjacent transferred property. HWA provided recommendations for soil and water handling, reuse, and disposal during construction.