- Geotechnical Engineering for Pipeline Expansions
- Subsurface Exploration Program
- Construction of Crossings
- HDD and Cut-and-Cover Crossings
- Geotechnical Evaluations of Valve Stations
- Work in Close Proximity to Gas Pipelines
- Extensive Health and Safety Measures
Challenge
GZA was asked to provide extensive geotechnical engineering services, in challenging settings, for two major natural gas pipeline expansions.
Solution
Complex subsurface exploration programs conducted from the water and on land, matting, and a temporary bridge were completed to assist in the design and construction of 13 horizontal directional drilling (HDD) and cut-and-cover crossings over an aqueduct and beneath rivers, major highways, local roads, railroads, and sensitive communities. GZA oversaw the work of a drilling contractor that completed more than 60 test borings for these projects over an approximately 18-month period. Test borings extended as deep as 200 feet below ground surface, including up to 180 feet of bedrock coring where HDD crossings are planned. GZA conducted extensive soil index testing and bedrock strength and hardness testing.
A site-specific health and safety plan that met Spectra’s requirements was developed for each project, as well as a work plan for drilling, logistics, environmental controls, and managing subcontractors. Several GZA field engineers obtained Operator Qualified (OQ) status, as required by Spectra to oversee work in close proximity to gas pipelines. GZA field engineers and the project manager worked closely with a Spectra field liaison and safety and coordination managers to maintain environmental protection, minimal impact to stakeholders, and safe work conditions.
Benefit
GZA’s extensive experience with the geotechnical engineering, project management and health and safety requirements for pipeline projects contributed to the safe and successful completion of the subsurface explorations required for this pipeline expansion.