Understanding geological history when selecting trenchless installation methods: Part two

On many large, engineered trenchless installations, it is imperative for the engineer to understand the geological history of the subsurface and determine the possible consequences and controlling effects the geology has on the proposed crossing. Deciphering the underlying geologic history (and its local anomalies) drives selection of the most appropriate trenchless method.

Part two of this three-part series looks closely at the complications associated with an HDD crossing in an over-deepened, coastal New England pre-glacial bedrock valley. The article will also look at how it was affected by glacial advance and catastrophic meltwater releases from an upstream glacial lake that filled the valley with large cobbles and boulders, at thicknesses approaching 100 feet. This paper will review the regional bedrock and local glacial geology, and its effect on the engineering complications encountered during HDD drilling and pipe installation.

Click here to read part two of this series in the Northeast Journal of Trenchless Technology Practices.