(And How to Avoid Them)

Top 5 Mistakes in Winter Geotechnical Investigations (And How to Avoid Them)

Winter site investigations are tricky. Frozen ground, equipment failures, and misleading data create a minefield of potential errors that can cost millions when spring arrives.

After 30+ years of winter geotechnical work across the northern United States, we’ve seen every mistake possible—and cleaned up after many of them. Here are the five most costly errors teams make when investigating sites in cold weather, and more importantly, how to avoid them.

Mistake #5: Trusting Winter SPT Values Without Adjustment

The Problem

Standard Penetration Test results from frozen soil look impressive. N-values of 40, 50, even 60+ are common in frozen clay that would show N-values of 8-12 when thawed. Design foundations based on those frozen values, and you’re building on quicksand come spring.

Real Consequences

A retail development in Minneapolis used January SPT data without seasonal adjustment. The geotechnical report showed “excellent” bearing capacity. By April, the foundation was settling differentially. Repair costs: $1.2 million. Construction delay: four months.

How to Avoid It

• Never use frozen SPT values directly for bearing capacity calculations
• Document frost depth at every boring location during winter investigations
• Apply engineering judgment based on soil type and expected thaw behavior
• Recommend spring verification testing when winter data seems unusually favorable
• Use conservative design approaches that account for worst-case seasonal conditions

Pro Tip: Clay and silt show the most dramatic strength changes between frozen and thawed states. Sandy soils are less affected but still require adjustment.

Mistake #4: Scheduling Investigations Without Weather Contingency

The Problem

“We need borings completed in two weeks.” Sure—if equipment doesn’t freeze, ground isn’t rock-hard, and your crew doesn’t spend three hours each morning thawing equipment.

Winter drilling takes 2-3 times longer than summer work. Equipment breaks down more frequently. Weather delays are inevitable. Yet schedules rarely account for these realities.

Real Consequences

A hospital expansion in Wisconsin scheduled a 10-day geotechnical investigation in January. Actual completion: 28 days. The delay cascaded through design and permitting, pushing construction start past the optimal spring window. Total project delay: 6 months.

How to Avoid It

• Triple your timeline estimate from summer conditions
• Build in weather delay contingency of 30-40% for winter scheduling
• Plan for equipment failures and have backup resources identified
• Consider phased investigations with critical areas drilled first
• Maintain flexible scheduling to take advantage of brief warm periods

Cost Reality Check:

• Summer drilling: $200-300 per linear foot
• Winter drilling: $350-500 per linear foot (or more in extreme cold)
• But premium costs are minor compared to schedule delay impacts

Mistake #3: Ignoring Seasonal Groundwater Variations

The Problem

That dry boring in February? It might be 10 feet underwater in April.

Winter investigations often miss seasonal high groundwater tables because water is frozen or hasn’t yet risen from spring snowmelt. Foundations designed based on winter observations can experience unexpected buoyancy, bearing capacity loss, and settlement when water tables rise.

Real Consequences

An industrial building in Michigan showed no groundwater during December borings. Foundation design assumed dry conditions. Spring revealed water within 3 feet of grade. Emergency dewatering system: $450,000. Delayed occupancy: 8 weeks.

How to Avoid It

• Never assume winter water levels represent annual highs
• Research historical water table data from local agencies and adjacent sites
• Interview local contractors about seasonal water table behavior
• Install monitoring wells for long-term observation when feasible
• Design for conservative water table assumptions based on topography and soil types
• Return for spring verification on critical projects

Hidden Risk: Perched water tables from snowmelt can create temporary high water conditions that exceed even historical seasonal highs. Clay layers can trap this water, creating unexpected foundation challenges.

Warning Signs You Might Miss Spring Water Issues:

• Low-lying topography relative to surroundings
• Heavy clay soils that impede drainage
• Proximity to water bodies or wetlands
• Historical aerial photos showing seasonal ponding
• Basement flooding in adjacent buildings

Mistake #2: Using Standard Equipment and Expecting Standard Results

The Problem

Your regular drilling rig isn’t designed for 10°F temperatures and frozen ground. Hydraulic systems fail. Augers break. Batteries die. Crews freeze.

Winter drilling requires specialized equipment, not just your summer fleet with block heaters added.

Real Consequences

A developer brought their standard drill rig to a North Dakota site in January. Three days, multiple breakdowns, and $40,000 in emergency repairs later, they still had zero usable borings. They called us. We mobilized cold-weather equipment and completed the investigation in four days.

Equipment That Actually Works in Winter:

Drilling Systems:

• Cold-weather hydraulic fluid rated to -40°F
• Insulated hydraulic lines and pump housings
• Oversized heating systems for operator cabs
• Backup power systems for critical components

Sampling Equipment:

• Modified SPT hammers that function in extreme cold
• Heated sample storage for transport
• Cold-resistant sample tubes and caps
• Battery warming systems

Support Equipment:

• Heated work shelters for sampling operations
• Generator backups for heating systems
• Emergency repair kits specific to cold failures
• Communication systems (cell phones die in extreme cold)

How to Avoid It:

• Hire firms with proven winter experience and specialized equipment
• Verify equipment capabilities before mobilizing to site
• Expect premium costs for proper winter equipment
• Don’t cut corners trying to use standard equipment in extreme conditions

Cost Comparison:

• Attempting winter work with summer equipment: High failure rate, expensive delays
• Proper winter equipment: Higher daily costs, but actually gets the job done

Mistake #1: Conducting Winter Investigations Without Understanding Thaw Implications

The Problem

This is the big one. The mistake that costs millions.

Frozen ground provides temporary strength that disappears during thaw. Soil that seems stable and strong in winter can become soft, compressible, and potentially unstable in spring. Foundation designs must account for thawed conditions, not frozen observations.

The Catastrophic Example

A warehouse development in Minnesota conducted winter borings showing excellent soil conditions. The geotechnical engineer—with limited cold-climate experience—designed foundations based on winter observations. The building was framed by April when soil thaw revealed actual conditions: soft clay with high compressibility.

The result:

• Complete foundation redesign required
• Emergency underpinning operations
• 6-month construction delay
• $3.2 million in additional costs
• Litigation that lasted three years

Why This Happens:

Frozen Soil Deception: Frozen soil exhibits 10-50 times the strength of thawed soil. Clay that’s rock-hard in January becomes soft and plastic in April. This isn’t a minor adjustment—it’s a fundamental behavior change.

Inadequate Experience: Engineers without cold-climate experience often don’t understand the magnitude of seasonal strength variations. They see good numbers in winter and design accordingly.

Schedule Pressure: Pressure to complete designs and start construction leads to accepting winter data without proper seasonal adjustments or spring verification.

How to Avoid It:

1. Work with Local Experience

• Hire geotechnical firms with proven cold-climate expertise
• Verify engineers understand seasonal soil behavior in your region
• Check references for similar winter investigation projects

2. Implement Conservative Design Approaches

• Design for thawed soil conditions, not frozen observations
• Apply appropriate safety factors for seasonal uncertainty
• Consider worst-case spring thaw scenarios

3. Plan Verification Testing

• Schedule spring borings to verify winter observations on critical projects
• Install instrumentation to monitor actual seasonal performance
• Build verification costs into project budgets

4. Communicate Limitations Clearly

• Ensure all project stakeholders understand winter data limitations
• Document seasonal conditions in all reports
• Provide explicit warnings about design limitations from winter data

5. Consider Timing Alternatives

• Evaluate whether spring/summer investigations might be more cost-effective
• If winter work is necessary, plan for spring verification
• Build adequate contingency into schedules and budgets

The Bottom Line: Winter geotechnical data can support foundation design, but only when properly interpreted by engineers who understand seasonal soil behavior. The cheapest investigation is worthless if the foundation fails when the ground thaws.

Bonus Mistake: Cutting Corners on Winter Investigation Costs

We’ve saved this for last because it underlies many of the mistakes above.

The False Economy

Winter geotechnical investigations cost 50-100% more than summer work. That’s reality. Specialized equipment, slower progress, and experienced personnel command premium prices.

Some developers try to minimize costs by:

• Using firms without winter experience
• Reducing boring quantities
• Skipping laboratory testing
• Eliminating spring verification testing
• Accepting inadequate data rather than paying for proper investigations

The Real Cost:

Every dollar “saved” on winter investigations can cost $100 in construction problems. Foundation failures. Schedule delays. Emergency repairs. Litigation.

Smart Investment Strategy:

• Budget realistically for winter investigation costs
• Work with experienced firms who understand cold-weather challenges
• Plan for spring verification on critical projects
• Accept that proper winter geotechnical work costs more—and delivers value through avoided problems