Earth Support Corp
Completed· October 2026

Earth Support · Cambridge

Soldier Pile & Lagging Wall, 33 Thingvalla Ave

A new four-story building on a tight Cambridge lot needed its excavation held back along the west property line, with the neighbor's fence and yard right at the edge of the cut.

An excavation in front of a timber-lagged soldier pile wall, with the neighbor's chain-link fence and house directly behind it.

The problem

A new four-story building on a tight Cambridge lot needed its excavation held back along the west property line, with the neighbor's fence and yard right at the edge of the cut.

The engineered approach

Six HP12x53 steel soldier piles, each 22.5 ft long, were set in drilled holes lined with temporary steel casing, backfilled with excavatable flowable fill, and the casing pulled. With no tiebacks or bracing the wall works as a cantilever, and timber lagging went in between the flanges as the cut was taken down.

Outcomes for the GC

  • Drilled, set and lagged in a single mobilization
  • Cantilevered: nothing anchored under the neighbor's lot
  • Dig Safe ticket and a site safety plan in place before drilling

From the site

6 photos from this job. Select one to see it full size.

An excavation in front of a timber-lagged soldier pile wall, with the neighbor's chain-link fence and house directly behind it.(opens the full-size photo)
The finished wall: soldier piles and timber lagging on the west property line.
A timber-lagged soldier pile wall along a chain-link fence, with two workers in hard hats and vests at the top, one in the cut, and an excavator digging at the right, with houses behind.(opens the full-size photo)
Lagging going in as the excavator takes the cut down, 21 October.
A drill rig lifting a steel H-pile upright on a residential lot while a worker in a hard hat and safety vest looks on.(opens the full-size photo)
Picking a 22.5 ft HP12x53 soldier pile with the rig.
The drill rig lowering a steel H-pile toward a drilled hole as a crew member guides it.(opens the full-size photo)
Lowering a pile into its cased hole.
Looking down into a round drilled hole lined with temporary steel casing, beside the property-line fence.(opens the full-size photo)
A drilled hole in its temporary steel casing, ready for a pile.
Two steel H-piles standing in backfilled holes next to a chain-link fence, with cut sections of steel casing at their base.(opens the full-size photo)
Piles set along the fence line, with the temporary casing coming back out.

How we built it

A schematic section of the earth support system for this Cambridge job. Scroll to build it in construction order, or select a callout to read the detail.

Schematic cross-section of the cantilever soldier pile and timber lagging wall on the west property line at 33 Thingvalla Ave, Cambridge: a 22.5 ft HP12x53 pile set in a cased drilled hole, backfilled with flowable fill, and lagged between its flanges as the cut was taken down, with the neighbor's fence right behind it.An illustrative section, looking south, through the soldier pile and lagging wall Earth Support built on the west property line at 33 Thingvalla Avenue in Cambridge, completed in October 2026. On the right, right behind the wall, are the neighbor's chain-link fence, yard and house. On the left is the excavation for a new four-story building. In construction order: a hole is drilled at the wall line with temporary steel casing holding it open; a steel HP12x53 H-pile, 22.5 feet long, is set in the cased hole; the hole is backfilled with excavatable flowable fill and the casing is pulled back out; then the general contractor excavates in lifts while Earth Support places timber lagging boards between the pile flanges as the cut goes down. There are no tiebacks, no bracing and no wales: each pile works as a cantilever, held by the length embedded below the bottom of the cut. An inset at top left shows the wall in elevation from the excavation: six piles along about 40 linear feet, with lagging boards spanning between them from grade down to the cut, and the embedded lengths of the piles dashed below it. The cut is dimensioned as up to 10 feet, which was the basis of Earth Support's quote and within the cantilever range the geotechnical summary gave (8 to 10 feet); it is not an as-built measurement. The ground, from the project geotechnical summary with borings to 22 feet, is 2 to 4 feet of fill over compact glacial outwash sand and gravel, with no rock within 22 feet. Groundwater is 10 to 12 feet below grade, shown with a water-table mark at about the bottom of the cut. A dashed line marks where the borings ended at 22 feet with no rock, and the band below it is labeled not explored. Drawn ghosted and dashed, because they are by others, are the excavation and the new four-story building, whose footing, foundation wall and slabs sit in the cut on the left. Schematic only: apart from the pile length, the pile count and wall length, and the cut basis, sizes are not to scale; pending professional-engineer review.Surface soils / fillGlacial outwash / sandNot explored
Schematic — illustrative, not for construction; pending PE review.

Callouts

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