Earth Support Corp
Completed· September 2026

Drilled Shafts · Northborough, MA

Drilled Piers for a Solar Carport, Northborough

Fourteen 36 in drilled concrete piers for a solar carport over a parking lot being rebuilt, through dense glacial till with groundwater as high as 4 ft below grade, timed to the lot's paving.

A round concrete pier standing out of the ground with four threaded anchor rods capped in blue, on a graded site with more piers in a row behind and a wooded hillside beyond.

The problem

Fourteen 36 in drilled concrete piers for a solar carport over a parking lot being rebuilt, through dense glacial till with groundwater as high as 4 ft below grade, timed to the lot's paving.

The engineered approach

The piers were drilled 10 ft into dense till from the paving base course, with temporary steel casing holding the wet holes open. A reinforcing cage and anchor-rod template went into each hole, and each pier was poured with a formed stick-up above grade, ready for the canopy steel.

Outcomes for the GC

  • 14 piers drilled and poured in September 2026
  • Wet holes held open with temporary steel casing
  • Prevailing-wage job, with certified payroll filed every week

From the site

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

A round concrete pier standing out of the ground with four threaded anchor rods capped in blue, on a graded site with more piers in a row behind and a wooded hillside beyond.(opens the full-size photo)
A finished pier with its anchor-rod group, and the rest of the row behind it.
An orange drill rig with its kelly bar raised over a hole on a gravel lot, with crew in safety vests and a survey instrument on a tripod in the foreground.(opens the full-size photo)
Drilling a 36 in pier while the survey crew checks layout.
A round steel form over a drilled hole, held by a frame on adjustable stands between two concrete blocks, with a worker beside it and the drill rig on the next hole behind.(opens the full-size photo)
Stick-up form and anchor-rod template held level on adjustable stands, with the rig on the next hole.
A freshly poured round concrete pier with a steel anchor-rod template still bolted on top, beside a parking lot full of vehicles.(opens the full-size photo)
The template stays on a fresh pier, holding the rods in place until the concrete sets.
A graded construction site with several finished concrete piers, the drill rig, a compact loader, and conduit pipe beside a trench, with an apartment building on the hill behind.(opens the full-size photo)
Finished piers across the lot as conduit trenching starts around them.

How we built it

A schematic section of the drilled shafts system for this Northborough, MA job. Scroll to build it in construction order, or select a callout to read the detail.

Schematic cross-section of one of the fourteen 36 inch drilled piers for a solar carport in Northborough, Massachusetts, drilled 10 feet from the paving base course into dense glacial till with groundwater at about 4.2 to 6 feet, held open by temporary steel casing, and shown during the pour with its stick-up form and anchor-rod template on four screw-jack stands.An illustrative section through one of the fourteen 36 inch drilled, cast-in-place concrete piers Earth Support built for a solar carport over a parking lot being rebuilt in Northborough, Massachusetts, completed in September 2026. The piers were drilled from the gravel paving base course, with the final paving placed after them. Below the base course is dense glacial till, with SPT N values of about 44 to 97 in the project geotechnical report and auger refusal at about 14 to 16 feet in places. Groundwater stood about 4.2 to 6 feet below grade, so most of each 10 foot hole was below the water table. There is no rock socket: the geotechnical report shows no bedrock above 32 feet, with rock mapped 32 to 66 feet down, below the bottom of this figure. In construction order: temporary steel casing is set and the hole is drilled 10 feet through the base course and the wet till, with the casing holding it open; a reinforcing cage is set; a round steel stick-up form is set over the hole, held level by a frame on four adjustable screw-jack stands, two of which show in this section, with timber across the top of the form carrying the anchor-rod template and the anchor-rod group hanging from it into the hole; the pier is poured up into the form, and the casing is pulled as the concrete goes in. Drawn dashed and ghosted, because it is by others rather than Earth Support, is the final paving placed on the base course afterwards; the canopy steel that later lands on the anchor rods is also by others. The base course thickness, the refusal surface, the stick-up height and the form and stand hardware are schematic, not to scale beyond the dimensioned figures, and not for construction, pending professional-engineer review.Base courseDense tillTill below water
Schematic — illustrative, not for construction; pending PE review.

Callouts

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