Foundations on Fill (Analysis) in Gatineau

A recent project on Boulevard de la Gappe needed a three-story commercial slab on an old sand and gravel fill. The fill ran about four meters deep with scattered debris from past grading. We ran test pits and compaction control to map the layering. Before pouring any footings, we combined the fill analysis with a plate load test to confirm the modulus of subgrade reaction. That data gave the structural team a reliable settlement estimate. The whole process took less than two weeks.

A four-meter fill with scattered debris required test pits, plate load testing, and MASW surveys to confirm bearing capacity.

Scope of work in Gatineau

Gatineau's freeze-thaw cycles put extra stress on fills. Water from spring thaw can soften poorly compacted layers. We check moisture content and density at multiple depths. The analysis follows NBCC 2020 settlement criteria and CSA A23.3 for foundation design. For fills with organic pockets or random boulders, we also run MASW surveys to detect stiffness anomalies between test pits. Our lab holds ISO 17025 accreditation for compaction and grain-size tests. Sampling includes undisturbed tube samples for consolidation testing when the fill is cohesive.

Foundations on Fill (Analysis) in Gatineau

Parameter	Typical value
Fill thickness range	1.5 m - 6.0 m
Typical SPT N-value (granular fill)	8 - 25 blows/300mm
Allowable bearing pressure (compacted fill)	80 kPa - 200 kPa
Maximum differential settlement target	25 mm over 10 m span
Compaction control standard	ASTM D698 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) / D1557

Typical technical challenges in Gatineau

We often see old fills in the Hull sector that were dumped without compaction. A site on Rue Montcalm had a five-meter fill from the 1960s with loose zones and buried stumps. Without proper foundation on fill analysis, that slab would have settled unevenly within two winters. The risk is hidden voids or soft lenses that only show up after freeze-thaw cycles. We always recommend a phased investigation: test pits first, then deeper borings if the fill is thick.

Need a geotechnical assessment?

Reply within 24h.

Email: contact@geotechnical-engineering.org

Applicable standards: NBCC 2020 (Section 4.2 – Foundations), CSA A23.3-19 (Concrete design for foundations), CFEM (soil description for fills), CSA + CSA + CSA + CSA + ASTM D422 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) / D6913 (grain-size analysis)

Our services

Our team provides three core services for foundation on fill analysis in Gatineau:

Field Test Pits & Sampling

Backhoe excavation to full fill depth. Logging soil types, debris, and compaction. Taking bulk and undisturbed samples for lab testing.

Compaction & Settlement Lab

Proctor tests, density checks, and one-dimensional consolidation on cohesive fills. Results feed directly into settlement calculations.

Bearing Capacity Report

Combining field and lab data to produce allowable bearing pressures per NBCC. Includes settlement estimates and recommendations for over-excavation if needed.

Frequently asked questions

How deep do test pits need to go for fill analysis in Gatineau?

We go at least one meter below the planned foundation depth or until we hit natural ground. For fills deeper than four meters, we often supplement with borings.

What is the typical cost range for a foundation on fill analysis?

For a standard residential or small commercial site in Gatineau, the cost ranges between CA$1,300 and CA$3,260 depending on fill depth and number of test pits.

Can you test fill that contains demolition debris?

Yes. We log and photograph the debris, take representative samples where possible, and adjust the compaction target based on the material's actual gradation.