Leveraging Collaborative Delivery and Innovation for Record-Breaking HDD, Saving $10M

The Boat Harbor Treatment Plant Conversion projects are a part of Hampton Roads Sanitation District's ongoing Sustainable Water Initiative for Tomorrow (SWIFT) program. The Section 1 subaqueous force main project, which is also known as the James River Crossing, is being executed using a fixed price design-build delivery. The project includes installing a wastewater force main across the James River. The total crossing is over 4 mi, comprising HDPE pipe ranging in size from 42″ to 54″ diameter. The project includes installing the new force main under the Newport News Shipping Channel and through a heavily used marine terminal. The basis for the RFP was to perform a water-to-water drill of approximately 3,200 LF using HDPE pipe across the channel. During procurement, the D/B team analyzed the feasibility of extending the HDD to the shoreline, adding over 2,400 LF of length to a new total length of over 5,600 LF, resulting in a savings of nearly $10M. The installation is the longest single HDD installation of large diameter HDPE pipe. The HDD crossed nearly 100 ft below the channel, at Elevation—160 ft. The deep HDD geometry was necessitated by regional geology, with very soft clays overlying older loose-to-medium dense silty sands and fine sands. Advancing the HDD through these materials required careful steering and mud control. The purpose of the presentation will be to present the process for planning, designing, and constructing this record-breaking HDD. The presentation will discuss how early collaboration supported the execution of such an installation. It will include risk mitigation features, such as the use of a $1M pipe pusher, geologic and geotechnical challenges during the design and construction of the installation, pipeline stresses associated with the HDD installation, HDD intersect method drilling, and cost savings.