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Duwamish Services is a specialty marine and industrial construction contractor located on the Duwamish waterway in Seattle's industrial district. Our team has the experience and knowledge to support your project.

Quillayute Sea Dike

Location: La Push, Washington
Customer: US Army Corps of Engineers, Seattle
Completion Date: October 2023
Description: This project was to restore a relic dike structure to an elevation of 8' above MLLW. The structure consisted of 6-9 ton armor stones mined in western Washington. Armor and Base rock was placed by barge utilizing a 150 ton material handler during high tides and then keyed in by a land based excavator during low tides. The project helps protect the La Push community within the Quileute Tribes reservation land on the Olympic Peninsula's northwest coast, a region exposed to severe winter storms and ocean swells.  


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Neah Bay Federal Channel Construction

Location: Neah Bay, Washington
Customer: US Army Corps of Engineers, Seattle
Completion Date: February 2024
Description: Hydraulic dredging to construct a new channel to a depth of 22 feet below MMLW. Approximately 10,000 cubic yards of material was dredged and placed on a nearby shoreline for beneficial re-use. Material dredged was consolidated sand and cobbles up to 12". 


Elfin Cove Outer and Inner Channel Dredging

Location: Elfin Cove, Alaska
Customer: US Army Corps of Engineers, Alaska District
Completion Date: April 2023
Description: Mechanical dredging of two channels within Elfin Cove Alaska. Disposal was by bottom dumping scow at a Government open ocean disposal site. Dredging was mostly new work including some hard rock which was removed with a hydraulic breaker.


Howard Prairie Resort Marina Phase II

Location: Howard Prairie Reservoir, Ashland Oregon
Customer: Jackson County, OR
Completion Date: June 2023
Description: New work marina with steel floats including two floating breakwaters and aluminum gangways. The marina is designed for a 28 foot water level differential. It includes a sewer pump out and fueling dock.


Midway Atoll Seawall Materials Transport

Location: Midway Atoll
Customer: US Fish & Wildlife
Completion Date: June 2023
Description: Duwamish Services was contracted to deliver 3,000 tons of armor rock to Midway national monument and wildlife refuge, approximately 1,300 miles NW of Honolulu. The rock was mined from the Skaglund quarry near Darington, WA and trucked to the Duwamish River dock before being loaded and transported to Midway. To mitigate invasive species being brought to the monument, every rock was pressure washed and inspected by an independent biologist in Seattle before being loaded. Additional freight was also transported and unloaded on Midway.


Cooper River Outfall

Location: Charleston, South Carolina
Customer: Global Diving & Salvage 
Completion Date: February 2023
Description: Duwamish Services was contracted to support dredging a sheet pile cofferdam for the installation of a sewer outfall. Dredging was performed using Duwamish Services' hydraulic dredge pumping equipment. The dredged material was hard clay and removed by high pressure water jetting and slurry pumping. All the material was pumped into geobags.


Port of Anchorage South Floating Dock

Location: Seattle WA & Anchorage AK
Customer: Port of Alaska
Completion Date: December 2021
Description: Duwamish Services was contracted to custom fabricate a modular dock system which could be assembled and disassembled each season by port staff. The dock sections were constructed from new Flexi-Floats and customization of bull rails, ladders, cleats, handrails and fenders were added. The marine coatings were provided by Duwamish Services under a separate contract. Duwamish Services packaged and transported the sections and appurtenances to site in Anchorage Alaska for installation by another contractor.


FY 21 Snohomish River Maintenance Dredging

Location: Everett Washington
Customer: US Army Corps of Engineers, Seattle District
Completion Date: February 2022
Description: Hydraulic dredging approximately 110,000 cubic yards of the upper navigation channel with placement on Jetty Island for beach nourishment and an upriver settling basin with upland placement at a Port of Everett sand resale lot.


Wells Dam Debris Boom Repair

Location: Columbia River, Near Chelan Washington

Customer: Douglas County Public Utility

Completion Date: March 2021

Description: Miscellaneous repairs to the precast floating debris boom upriver of the Wells Hydroelectric Project. Repairs included: cable hardware replacement, timber skirt repairs, thru-rod replacement and realignment of system. Additionally, Duwamish Services was tasked with performing an overall underwater inspection and assessment report for the customer. 


Mouth of the Columbia Sand Island Test Pile Project

Location: Mouth of the Columbia River
Customer: US Army Corps of Engineers, Portland District
Completion Date: October 2020
Description: The Sand Island Test Piles project consists of 29 pile tests in 13 locations along the alignment of pile dike 4.01 and 6.37 in the proximity of the West and East Sand Island near the mouth of the Columbia River. Due to the uncertainty surrounding drivability through the existing enrockment, the test program was established utilizing several levels of installation effort that can be used to inform the final design. Drivability using impact and vibratory hammers with several shoe variations were used to complete the test. Four variations were required in the testing outline; no shoe, open-end cutting (ring) shoe, conical (cone) shoe, and rock-breaking shoe. Dynamic pile testing was required on all piles driven with an impact hammer to estimate integrity of the piles, hammer performance, pile stresses, and soil dynamic characteristics. The project also required turbidity monitoring, acoustic monitoring, marine mammal monitoring, and seabird monitoring during pile driving operations.


Lower Monumental Dam Fish Ladder Diffuser Grating Replacement

Location: Lower Snake River, Near Kahlotus Washington 
Customer: US Army Corps of Engineers, Walla Walla District
Completion Date: January 2020
Description: Remove and replace aluminum grating in the LOMO fish ladder diffuser sections. The project required significant water management, pumping and diversion to accomplish the work. Environmental demands required the work be completed on an accelerated timeline with a hard and fast completion date.


Friday Harbor Floating Breakwater Minor Repairs

Location: Friday Harbor, Washington
Customer: US Army Corps of Engineers, Seattle District
Completion Date: November 2019
Description: Miscellaneous small concrete and steel repairs. Concrete repair included pressure injection of repair epoxy and surface chipping and patching. Additional small repairs to steel handrails and coatings.


Lower Monumental Dam Navigation Locks Upstream Guidewall Key Replacement

Location: Lower Snake River, Near Kahlotus Washington 

Customer: US Army Corps of Engineers, Walla Walla District

Completion Date: March 2019

Description: The purpose of this project was to replace an aging 1980's era steel key. The key functions as the sole structural connection for
a 500' long concrete pontoon to the dam monolith. The guidewall needed to be temporarily restrained using heavy lugs and
cross wires which were engineered by Duwamish Services. The guidewall needed to be hydraulically jacked away from the dam
monolith and blocked to allow space for divers to work in between the guidewall and the dam. The old key was removed and
the new key installed. The key required the installation of 10ea 4' long 2" diameter bolts through the floating guidewall using
holes which were 2 ‐1/32" in diameter to prevent water intrusion. This was a challenging project in a remote area during the


Bonneville Dam Washington Shore Fish Ladder Lamprey Passage

Location: Columbia River, Near Cascade Locks Washington

Customer: US Army Corps of Engineers, Portland District

Completion Date: January 2019

Description: The purpose of this project was to install orifices in the fish ladder baffle walls for Lamprey passage. Scope of work was to cut
holes in the weir walls, install and then pressure grout in fabricated steel orifices. This work was done during a fish window
closure and was time sensitive. The work required installation of cofferdams and continuous dewatering maintenance using
several pumps to keep access to the work zone and prevent contamination of water with slurry dust.


Stoddard Pack Bridge Demolition & Debris Removal

Location: Salmon River, Near Shoup Idaho

Customer: USDA Forest Service, Salmon Idaho District

Completion Date: May 2018

Description: Duwamish Services was hired to remove a partially damaged cable suspension bridge over the Salmon River. One tower had
been struck by a boulder and had collapsed, the other tower was in tact and the suspension cables were spanned over the
river. No road access was available on the river bank with damaged tower so a white water jet boat was utalized to remove
the timber debris from the area. Aproximately 25,000 pounds of timber was loaded into a jet boat, transported down river to
a boat ramp, unloaded then trucked to a landfill. The suspension cables were cut and pulled accross the river with heavy
equipmnet then removed from site. The intact tower was demolished and the debris trucked to a landfill. This project was in a
very remote location with no cellular service where workers stayed in a camp.


Old Town Docks Seasonal Removal/Replacement

Location: Tacoma Washington
Customer: Metro Parks Tacoma
Completion Date: Multiyear 2017-2019
Description: Duwamish Services was contracted to remove seasonal floating docks at the Old Town Dock. Floats were removed in the fall, towed to a Duwamish Services furnished moorage location, and then reinstalled in the spring.


Barge Unloading & Debris Disposal

Location: Duwamish River, Seattle Washington
Customer: Turnagain Marine Contractors
Completion Date: Multi Year 2017-2021
Description: This was Duwamish Services first contract and where we got our name. We were hired by Turnagain Marine Contractors to provide multiple tasks related to barge loading and unloading on the Duwamish Waterway in Seattle. We were primarily tasked with unloading barges full of demolition debris which came from Western Alaska. Duwamish Services separated all the different materials which included steel, creosote timbers, clean timbers, contaminated soils, and other contaminated and or hazardous materials. All materials were properly disposed and or recycled in Washington. Duwamish Services completed many other support tasks for Turnagain including loading and lashing new materials for transport to Alaska.

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