Project Description:
The Massachusetts Bay Transportation Authority (MBTA) will open a transit corridor less than 10 ft. below the 100-year old Russia Building in downtown Boston. The corridor will pass beneath the Russia Wharf complex and Fort Point Channel on its way to South Boston and will be designated as the Silver Line section of MBTA’s subway system. To minimize damage to the buildings, the MBTA selected the New Austrian Tunneling Method (NATM); selective underpinning; and ground freezing to temporarily support building loads and prevent groundwater infiltration.

Coler & Colantonio, inc. was contracted by Modern Continental/Beton-und Monierbau, A Joint Venture to design and establish a geodetic control network to support surveying and deformation monitoring activities associated with the construction of the NATM tunnel segment of the project. A survey control network was established using the Global Position System (GPS), which was used to determine the geodetic positions of several new control points within the project area. A unique wall mounted surface control network was then established around the vicinity and at the access shaft to the tunnel to facilitate the transfer of survey control for underground excavation and deformation monitoring.

Special Considerations:
• Busy urban environment experiencing significant construction activity.
• Restricted and limited survey control and site access.
• Conventional ground monuments would be subject to construction damage and localized ground or structural movements.

Detailed List of Services:
• Site reconnaissance and preparation of a proposal for the design, execution, and analysis of a geodetic network to support the excavation and deformation monitoring activities associated with the NATM tunnel.
• Performed a pre-analysis of the surface control network using rigorous least squares analysis techniques that would meet the project specifications for survey control to support excavation of the tunnel, in this case Second Order, Class I standards for horizontal and vertical control.
• Performed a pre-analysis of the surface control network using rigorous least squares analysis techniques that would meet the project specifications for survey control to support deformation monitoring activities, in this case ± 5mm or better for horizontal control and ± 2 mm / km for vertical accuracy, both at the 95% confidence level..
• Assisted Modern Continental with a GPS control survey to tie site control points into existing Central Artery/Tunnel geodetic control to Second Order Class I horizontal accuracy standards.
• Provided Modern Continental with guidance on survey target/reflector selection and placement. Designed a surface control network based on a wall mounted survey control points located on substantial buildings located around the project site.
• Designed a survey methodology based on the proposed network configuration and prepared field procedures for Modern Continental surveying personnel outlining types of observations, methods of observation, and data quality control parameters required during the field data acquisition.
• Performed all surface control network data reduction and processing tasks, least squares adjustments and statistical analyses of the data, and preparation of a control survey report