Client: Berlin Water Works, City of Berlin Location: Berlin, New Hampshire

Improving Municipal Drinking Water Supply Delivery As part of a significant initiative to improve municipal drinking water supply delivery to the residents of Berlin, New Hampshire, the Berlin Water Works retained GeoInsight, Inc. (GeoInsight) to evaluate subsurface conditions at locations where new high pressure HDPE water line pipe would be installed via pipe jacking below existing live railroad lines operated by the St. Lawrence and Atlantic Railroad (SL&ARR). The new pipes were 12-inch inside diameter and were tied into the existing distribution system at strategic locations to improve pressure and allow better and more redundant flow control in the event of a break or line replacement in older sections of the lines.

Construction Agreement The work required developing a detailed Construction Agreement as an investigation plan for SL&ARR based upon their internal specifications for Construction of Pipelines on Railroad Land and a subsequent special insurance binder, Access Agreement, and Health and Safety Plan to address the activities to be performed on their property. Proposed profiles of the crossings were developed in conjunction with the City of Berlin’s hydraulic engineering consultant, then revised, based upon the findings of field measurements and the geotechnical investigation. Geotechnical Reporting: Overcoming Construction Site Challenges Because shallow refusals were encountered at two of the crossings and access at each site was difficult, GeoInsight provided assistance with the design location and depth of the alignments, and prepared correspondence and design information for review by SL&ARR to obtain approval for pipe jacking and final alignment configurations that varied slightly from the default design requirements provided in their default specifications. Our geotechnical report identified considerations for the crossings, including shoring and excavation safety for the launching and receiving pits with regard to the live rail lines and their associated loads. We also consulted during construction to assess actual setback distances and related changes to design and specification criteria regarding slopes and elevations, and conducted an analysis to determine acceptable alternate pipe cover thicknesses and pipe installation methods.

GEOTECHNICAL INVESTIGATION FOR PIPE JACKING OPERATION St. Lawrence and Atlantic Railroad

Case History No. 70