Deep Rock Tunnel Connect

Case study narrative

Project narrative

Current 7NT personnel have been involved on the Deep Rock Tunnel Connect project since 2007. 7NT drill crews, engineers, and laboratory personnel have been responsible for performing the geotechnical subsurface investigation and laboratory services, including soil and rock, for the Design Phase of this project. 7NT construction inspectors have continued to provide inspection services into the construction phase.

7NT inspectors currently supplement the construction inspection team for the project. Full time roles on the site for the four- to five-year duration of the project include tunnel inspectors who work shifts in the 250 to 285-foot deep tunnel documenting all activities of the Tunnel Boring Machine (TBM), including mining, re-gripping, probe hole drilling, pre-excavation grouting, installing rock supports, maintenance, and other activities.

Additional roles include the surficial inspection of the drilled launch, access/utility, and retrieval shafts of the levee extension and spoil hauling. 7NT personnel also supplement the construction inspection team with a full time administrative role maintaining document control of the project record through Contract Manager software for schedule, progress, and reporting.

7NT is responsible for all construction material testing on the project. This included in-depth testing of the levee extension for all material used to verify conformance with project specifications for type and compaction to aid in certification of the levee prior to mobilization of the TBM down the launch shaft.

This task was crucial early in the project because the quantity of usable on-site material was much less than originally expected. The project faced significant issues in terms of delay and cost increase. 7NT helped determine suitable usage for on-site material in different components of the levee through a rigorous testing schedule. This allowed more permeable material to be used as fill in the central part of the levee while more appropriate and impermeable material sufficiently capped the levee system.

The team also includes a Quality Assurance (QA) Manager responsible for overseeing all aspects of QA for the project, especially conformance of construction materials to project specifications. Additional QA services include submittal and RFI review/commenting and scoping development of inspection and materials testing related activities.

7NT maintains a rigorous cost control system for this project. With a firm budget established, cost control is crucial to overall success. 7NT maintains a monthly log of all project allocated costs and projects them against the project budget forecast.

On a multi-year project, budget overages can accumulate to large sums over time. 7NT regularly works with the Client and Owner to adjust the level of service to meet both project needs and requirements, and to address project-related issues as they arise.

As part of the increased levee testing program, 7NT staff found other areas to reduce the level of service and save cost in order to create a net-zero impact to the project budget while maintaining the highest level of service for the project.

Being an integral part of such a large project for five to ten years speaks to the level of quality that 7NT staff members are known to regularly deliver on projects.

Scope of work

Technical scope