Knik Arm Tunnel Feasibility Study (Anchorage, Alaska)
Emprise Geotechnical Team Supports Tunnel Alternatives Assessment Beneath Knik Arm
The Knik Arm Tunnel Feasibility Study evaluated tunnel alternatives beneath Knik Arm to improve long-term connectivity between Anchorage and Port MacKenzie. The study integrated alignment design, geotechnical data, geological assessment, and current tunneling technology to identify technically and economically viable crossing options and narrow the field to preferred alternative alignments. Subsurface conditions along the candidate alignments were documented almost entirely by historic investigations, recorded in separate campaigns and held in non-digital form. Emprise Concepts consolidated over 100 historic borings into a unified geotechnical database and performed geostatistical and subsurface modeling to deliver an updated geologic interpretation for the alternatives evaluation.
Project Information
Project Scope:
Feasibility evaluation of tunnel alternatives for the Knik Arm crossing, integrating alignment design, geotechnical data, geological assessment, and current tunneling technology to identify preferred alternative alignments.
Unique Features:
Maximum Reuse of Historic Subsurface Data
Review and Digitization of Legacy Boring Records
Geostatistical Quantification of Subsurface Uncertainty
Single Consolidated Database for Future Design Phases
Our Services:
Geotechnical and Geological Analysis
Historic Data Review and Digitization
Geotechnical Database Development
Geostatistical Analysis
Subsurface Modeling
Site Investigation Recommendations
Emprise Personnel:
Project Manager: Jacob Grasmick
Project Engineer: Noah Kimmes
Project Engineer: Veronica Rodriguez Chavarria
Impacts & Benefits
Consolidated Subsurface Database: Over 100 historic borings were reviewed, digitized, and combined into a single geotechnical database available to subsequent design phases.
Quantified Ground Uncertainty: Geostatistical analysis reduced uncertainty in the subsurface interpretation along the candidate alignments and expressed the remaining uncertainty in explicit terms.
Updated Geologic Interpretation: Subsurface modeling produced a revised interpretation of conditions beneath Knik Arm for direct use in the alternatives evaluation.
Targeted Investigation Planning: Data gaps controlling further assessment of the tunneling alternative were identified and carried into recommendations for future site investigations.
Project Gallery
Project Summary
The Knik Arm Tunnel Feasibility Study evaluated tunnel alternatives beneath Knik Arm to improve long-term connectivity between Anchorage and Port MacKenzie. AKDOT&PF commissioned the study, with Stantec as prime consultant and Mott MacDonald and Emprise Concepts supporting the geotechnical and tunneling assessment. The work combined alignment design, geotechnical data, geological assessment, and current tunneling technology to determine which crossing options were technically and economically viable. Emprise performed the geotechnical and geological analyses supporting that determination between March and December 2025, working from historic subsurface data rather than a new investigation program. The result was an updated geologic interpretation of the crossing, a consolidated database, and a defined path for future site investigation.
Project Writeup
Stantec engaged Emprise Concepts to conduct the geotechnical and geological analyses used to evaluate tunnel alternatives beneath Knik Arm. Emprise located and reviewed over 100 historic borings, digitized the records, and consolidated them into a single geotechnical database structured for reuse in later design phases. Geostatistical analysis was applied to the consolidated dataset to reduce uncertainty in ground conditions along the candidate alignments and to quantify the uncertainty that remained. Subsurface modeling built on that analysis produced an updated geologic interpretation of the crossing, replacing interpretations drawn from the historic investigations individually. Emprise then identified the data gaps that constrained further assessment of the tunneling alternative and issued recommendations for future site investigations, giving AKDOT&PF a defined framework for advancing the alternatives and scoping the next phase of investigation.
