Fieldwork at Port of Tacoma
On Aug. 31, we started fieldwork at the Port of Tacoma to determine if it might be a possible location for building some of the pontoons and anchors we need for a new SR 520 floating bridge.
We need 77 total pontoons of various sizes for the new six-lane floating bridge. Crews are scheduled to begin construction on the first 33 pontoons at a casting basin in Grays Harbor in spring 2011.
This fieldwork will help to determine if the Port of Tacoma site could be used to build some of the remaining 44 pontoons. The Concrete Technology Corporation site in Tacoma and the Grays Harbor site could also be used to build these remaining 44 pontoons.
Fieldwork at the Port of Tacoma is planned Monday through Friday for up to 20 working days. Crews will drill four borings measuring up to 150 feet deep, including two groundwater observation wells, and conduct other soil tests.
Cultural resources study on Foster Island
WSDOT is conducting a cultural resources study on Foster Island as part of the I-5 to Medina: Bridge Replacement and HOV Project. This important safety and mobility project will build a safer floating bridge and give new options to people crossing Lake Washington.
Vicinity map of cultural resources study. |
WSDOT is conducting this study in order to confirm that no significant archaeological resources are near the proposed locations of permanent and temporary support structures for the planned SR 520 bridge.
This study will be completed on Foster Island to the north and south of SR 520. WSDOT archeologists will limit disturbances on the island while completing this study.
What work is involved in the cultural resources study? WSDOT archeologists will excavate several areas on Foster Island. The WSDOT field team will use a variety of hand tools to complete this study, including shovels, trowels, and hand augers.
No mechanical, power or forced-pressure tools will be used. All excavated areas will be backfilled and returned to their pre-investigation appearance to the greatest extent possible.
What is the timeline for this study? The proposed work will be conducted over approximately 75 consecutive days, including weekends, and is expected to be complete by mid-October. Work will occur for approximately 10 hours per day during daylight hours only.
What is the cultural significance of Foster Island? The historic record shows that the areas on and around Lake Washington were used by several regional tribes. In coordination with tribes, WSDOT is working to minimize the future construction disturbance on Foster Island.
How will WSDOT coordinate with other local agencies on this study?
WSDOT will coordinate with the
University of Washington Botanical Gardens and Seattle Parks and Recreation to replace surface vegetation according to the wishes of groundskeepers and established policies of the Washington Park Arboretum.
Geotechnical drilling on Lake Washington
We are conducting geotechnical drilling from barges on Lake Washington from July through September 2010. We are conducting this work to study the lakebed where support columns and anchors will be placed for a new SR 520 bridge.
What the work look like?
Crews plan to use barge-mounted drill rigs alongside the floating bridge between Medina and the west end of the floating bridge. They will drill approximately 40 borings, with depths of 60 feet to more than 100 feet into the lakebed.
How will this work be used in designing the new SR 520 floating bridge?
Learning the strength and composition of the underwater soils is a key step to properly designing the columns and anchors for the new bridge. We will share the results of the fieldwork with potential design-build teams as the SR 520 program moves closer to construction.
While we have previously conducted smaller efforts for the preliminary anchor design, this more robust work allows WSDOT to advance the design of the anchors prior to issuing contract documents for the floating bridge.
Will the work affect traffic?
Daytime traffic slowdowns are possible on the floating bridge if distracted drivers watch the work. The work is scheduled 7 a.m. to 7 p.m. in 10-day shifts, with four days off in between shifts. Nearby residents may see and hear the daytime work. Crews plan to complete this phase of work by the end of September, and then will move to other sites within the corridor.
Photos of previous fieldwork
Nov. 17, 2008 - Land drilling on the Eastside
Oct. 29, 2008 - The smaller barge operating in the Montlake cut area.
Oct. 15, 2008 - The Seahorse barge in Lake Washington photographed from an SR 520 bridge camera
Oct. 7, 2008 - The Seahorse barge used for drilling in Lake Washington. Its dimensions are 40 feet wide by 110 feet long.
