Portwalk Place

Location: Portsmouth, NH

Client: Pro Con, Inc.

Scope of Work

  • Install approximately 1,110 linear feet of steel sheet piles to serve as an excavation support system with excavation depths up to 18 feet.
  • Installation of approximately 170 helical soil anchors, rock pins, raking braces, and external framework to support the sheet pile wall.

The Portwalk Place project presented several challenges, including varying soil conditions, exposed ledge within the excavation limits, and several existing utilities. In order to maximize the building footprint, the foundation and basement walls were placed directly against the sheet piles. This concept required extremely tight tolerances during sheet pile installation.

The varying soil and rock conditions on site coupled with an extensive array of existing utilities added difficulty to this project. The anchors that were installed to support the sheet piles had to be located so as not to conflict with any of the existing utilities but also be able to terminate in soils that were capable of providing sufficient anchorage capacity. Due to the localized presence of ledge within the excavation, drilled in place pins were needed to supplement some of the anchors.

H.B. Fleming overcame the many challenges presented by this project. All of the sheet piles were installed within the required tolerances. Anchors were successfully installed around the many obstacles present. Our ability to provide in-house engineering services when unanticipated conditions arose allowed us to quickly react and allowed our field staff to execute the changes without disrupting the flow of work on site.

Sheet pile wall with two levels of helical soil anchors.

Sheet pile wall with two levels of helical soil anchors installed.

Formwork is being placed directly against the sheet pile wall in preparation for concrete.

Formwork is being placed directly against the sheet pile wall in preparation for concrete.

Raking braces were used in an isolated area of the wall where installation of anchors simply was not possible because of the existing utility array. In this photo, the building footing has been placed and the wall reinforcement is being installed.

Raking braces were used in an isolated area of the wall where installation of anchors simply was not possible because of the existing utility array. In this photo, the building footing has been placed and the wall reinforcement is being installed.