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Geotechnical Projects

Sound Transit Northgate Link and Lynwood Extension Projects
Client: JCM Northlink, LLC
Location: North Seattle

Holocene is providing geotechnical drilling services on both the Sound Transit Northgate and Lynnwood Link Extension projects. Drilling methods on these ongoing, long term projects include a combination of track mounted mud rotary and sonic drilling. Sites are located in difficult, urban settings and have been drilled in both day and night shifts. Holes have been precleared for utilities using Holocene’s vacuum hole clearing trucks. Significant on-site coordination is required to manage traffic control and work hour restrictions. Project also includes well rehabilitation, decontamination, low overhead and angle drilling techniques. Holes are completed between 40 and 140’ in depth.

Emergency Response – Sonic Drilling and Void Grouting

Client: Confidential
Location: Seattle Waterfront Bluff

Due to a water main failure, Holocene Drilling was contracted to drill 14 soil borings in an upscale urban area along a washed out, subsurface water main alignment. Hole depths ranged from 130 up to 180’ below grade. Grouting volumes ranged from 2 cubic yards up to 198 cubic yards depending on the void size for a total of nearly 600 cubic yards. Exceptional care was taken working around multi-million dollar homes and vehicles.

Washington State Department of Transportation I-405/SR167 Direct Connector Project

Client: WSDOT
Location: Federal Way

Holocene drilled this congested roadway intersection site using both truck and track mounted auger and mud rotary up to 250’ in depth as well as confirmation NQ coring. Site is on a high-profile freeway intersection with traffic control, work hour restrictions, night work and extensive coordination with many other construction companies. Holes were precleared for utilities using Holocene’s vacuum hole clearing trucks.

Swinomish Tribe deep mud rotary

Client: HWA
Location: Anacortes, WA

This challenging project included mud rotary drilling to nearly 500’ with SPT samples from 300’ to total depth with a 2” well installation. Drilling was completed using a truck mounted mud rotary rig in 9 days.

New SR 520 Floating Bridge

Client: WSDOT
Location: Bellevue/Seattle

Overwater barge auger drilling

This marine access project included the use of a barge platform north of the existing 520 floating bridge on the Pier 1 footprint to obtain overwater geotechnical samples. The project included the use of a truck-mounted drill and crew to complete the overwater sampling approximately 40’-50’ below the waterline and advance the geotechnical borings and take SPT samples. The information was used in the design of the Pier 1 cofferdam structure and piling placements.

East Approach – Pier 2 Dewatering Wells and Vibrating Wire Piezometers

This difficult access project included the use of a CME 850 track-mounted drill to access the beach embankment and Pier 2 cofferdam. Drilling and installation included placing 4” dewatering wells and submersible pumps as well as the installation of 2” monitoring wells within the Pier 2 footprint and cofferdam. This dewatering system was used during the construction of Pier 2 and included operation and maintenance for the duration of the project.

East Approach – Pier 2 & 3 Groundwater Study & Monitoring Wells

The scope of this project included the use of a CME 850 Track-mounted drill to support the groundwater study associated with the dewatering requirements of the cofferdam structures. This included drilling and installation of 2” dewatering observation wells near the Pier 2 & 3 footprint and adjacent retaining walls. Work included observation well construction as well as development of the wells and 24 hour step pump testing at several observation locations.

U-220 TBM Project – Vertical Inclinometers and Extensometers

Client: Sound Transit
Location: Seattle, WA

Holocene performed geotechnical instrumentation installation of inclinometers and extensometers in conjunction with tunnel boring machine advancement and subsurface surveying and monitoring along the tunnel alignment at the U of W Station, Seattle, WA. This work included difficult access borings located near sensitive environmental habitats accessed by barge along the Montlake Cut of the Lake Washington Ship Canal under the direction of the Army Corps of Engineers. Holocene fabricated custom flush-mount monuments to house data acquisition system instrumentation

Former Shipyard Superfund Site

Client: Tetra Tech, Bothell, WA
Location: Seattle, WA

Holocene Drilling provided upland and offshore barge drilling using sonic drilling technologies. The project was conducted along a Puget Sound waterway and provided geotechnical and environmental sampling plus cone penetrometer testing (CPT) data. All was in support of remediation activities on this high-profile superfund site. Upland drilling consisted of over 20 borings up to of 100. Overwater barge drilling was nearly 40 borings some as deep as 70’ below the mudline. This project required the use of standard auger, mud rotary, sonic techniques and sampling as well as CPT sampling. All Holocene Drilling crews were required to be HAZWOPER certified to perform this work.

NQ Rock Coring, Chelan County PUD No. 1, 230 kV Line Relocation

Client: Chelan County PUD No. 1
Location: Rocky Reach Dam, Chelan, WA

Scope of work included difficult access drilling along rock formations above Rocky Reach Dam on the Columbia River. NQ rock coring was employed using a low clearance/limited access track mounted Diedrich D-50 rig for drilling under Power Lines. Sampling included rock core samples for foundation design analysis for a 230 kV Transmission Line Relocation project above the Dam. In addition to difficulty associated with access to the drilling locations, water also had to be trucked into the site twice daily by 4 wheel drive to support rock coring operations.

Port of Seattle T-117 Uplands Project- Offshore and Onshore (CPT) Support

Client: Port of Seattle Duwamish Waterway, Seattle, WA
Location: Seattle, WA

Offshore drilling from a barge along the Duwamish waterway provided geotechnical sampling and cone penetrometer testing (CPT) support during overwater geotechnical explorations. Additional drilling and sampling was performed at near shore intertidal zones and on land at the Port’s Terminal 117. This project required mud rotary techniques and sampling as well as CPT sampling. All crews were required to be HAZWOPER certified to perform this work.

Sound Transit U-220 TBM Project – Jet Block Grout Coring

Client: Sound Transit
Location: U of W, Seattle, WA

This project included a rock coring investigation of jet block grout wall to prove the depth and extent of grout penetration and to provide quality control sampling of jet block grout materials used in construction. Jet grouting was performed along the tunnel boring machine alignment in advance of the tunneling boring operations. The contractor required an in-situ sampling investigation to determine the subsurface jet block horizon interface. This drilling project was completed using open-hole mud rotary drilling methods in the overburden and then switching to NQ rock coring to sample the jet block wall in place.

Swamp Buggy Drilling over Regulated Waterway

Client: GeoEngineers, Seattle Area
Location: Lynnwood, WA Park & Ride Facility

Holocene Drilling worked with GeoEngineers to drill and install multiple piezometers, monitoring wells and instrumentation wells up to 150’ in depth in a regulated, urban wetland as part of the Sound Transit light rail Lynnwood Link Extension at the Scriber Creek wetland. A motorized, track mounted pontoon swamp buggy was the best option to transit both deep and shallow water environments without damaging the root systems of sensitive wetland. The swamp buggy, measured 20 feet wide and 35 feet long has a ground loading of only 2 pounds/square inch. All rig re-fueling, supplies and crew were transported from the staging area to the swamp buggy via a flat-bottomed boat.