A tracked excavator carefully peels back the top layers of a construction site in Manchester, New Hampshire, revealing what lies beneath the surface. Exploratory test pits give us that direct, visual access to the subsurface that no drilling method can match. You see the actual soil profile, the changes in color, the cobbles mixed into the glacial till, and the groundwater seepage—all in real time. For projects near the Merrimack River or in the dense till deposits common across Hillsborough County, this method cuts through uncertainty. It is a practical, fast way to collect bulk samples and map stratigraphy before committing to a foundation design. Our team uses these pits to verify conditions where SPT drilling data needs ground-truthing or where access for a drill rig is tight.
In Manchester's glacial terrain, a single exploratory pit can reveal more about bearing capacity than a dozen lab tests on disturbed samples.
Frequently asked questions
How deep can you dig an exploratory test pit in Manchester, NH?
With a standard mid-size excavator, we typically reach 12 to 14 feet in the dense glacial till common around Manchester. Depth is limited by the machine's reach and the stability of the sidewalls. In loose sandy zones near the river, we may stop shallower for safety unless shoring is installed. For deeper investigations, we recommend supplementing with SPT drilling.
What permits are required for a test pit on commercial property in Hillsborough County?
Manchester city regulations generally require a street opening or excavation permit if the pit is within the public right-of-way. On private commercial lots, permits are usually tied to the overall building permit application. We coordinate with the city's Public Works Department and always call DigSafe (811) at least 72 hours in advance to locate underground utilities.
Do you backfill the test pit after the inspection?
Yes, same-day backfilling is standard. We place the excavated material back in lifts and compact it with the excavator bucket or a plate compactor. If the pit will be under a future foundation, we can use controlled structural fill and perform density testing on the backfill to ensure it meets project specifications.
What is the typical cost for an exploratory test pit in the Manchester area?
For a standard exploratory pit up to 10 feet deep, the cost typically ranges from US$480 to US$880 per pit. The price varies based on depth, access constraints, the need for shoring in unstable ground, and the number of samples collected. Mobilization fees for the excavator and operator are usually included in this range for a single-day program.
Can you take soil samples from the pit walls for laboratory testing?
Absolutely. We collect disturbed bulk samples for classification tests like grain size and Atterberg limits. More importantly, we can carve undisturbed block samples from the pit face. These preserve the natural soil fabric for advanced testing such as triaxial shear or one-dimensional consolidation, giving you design parameters that remolded samples simply cannot provide.
