Subgrade, Proof-Rolling & Compaction: A GC & EC Guide to Preventing Settlement Under ADA Routes and Site Concrete in Middle Tennessee

If you’ve nailed ADA layout, coordinated bollards/light poles, and built a clean joint plan, there’s still one issue that can wreck closeout months later:

Settlement.

Sidewalk panels drop. Handholes sink. Curb ramps develop lips. And suddenly you’ve got trip hazards, ponding, cracked panels, and warranty calls.

Why Settlement Is the Real Enemy of “Finished” Site Concrete

Concrete doesn’t usually “sink” on its own. It settles because the material underneath it changes:

• Loose fill consolidates under traffic

• Trench backfill wasn’t compacted in lifts

• Subgrade was too wet (pumping) or too dry (won’t knit)

• Frozen material thaws and leaves voids

• Soft spots were covered instead of corrected

The frustrating part: you can pass inspection and still fail later.

GC takeaway: If you want ADA routes and exterior flatwork to stay compliant, treat subgrade and compaction like finish work.

The Most Common Settlement Hotspots on Commercial Jobs

If you only focus on a few areas, make it these:

• Utility trench crossings under sidewalks

• Around pull boxes/handholes/valve boxes

• At curb returns and curb ramps

• At transitions from cut to fill

• Near building entries where foot traffic concentrates

• Around light pole bases and sign bases

These are the zones where the subgrade is disturbed, patched, or built up—exactly where settlement likes to show up.

Subgrade 101 (Practical, Not Academic)

Subgrade success comes down to three things:

1. Correct material (or corrected material)

2. Correct moisture (workable, not pumping)

3. Correct compaction effort (in lifts, with the right equipment)

If any one of those is off, you can get a slab that looks great on day one and fails later.

Proof-Rolling: The Fastest Way to Find Problems Before Concrete

Proof-rolling is a simple concept: apply a consistent load and watch how the subgrade behaves.

What you’re looking for

• Pumping (water/soil moving under load)

• Rutting or deflection

• Soft pockets that “give” compared to surrounding areas

Why it matters for ADA routes

ADA flatwork is thin compared to structural slabs. It doesn’t tolerate subgrade movement well. A small soft spot can become a panel lip or a crack that turns into a trip hazard.

Common proof-roll mistakes

• Proof-rolling too early (before grading is final)

• Proof-rolling only “open areas” and skipping trench crossings

• Ignoring minor pumping because “it’ll dry out”

GC takeaway: Proof-roll results should trigger action—undercut, stabilize, rework—before forms go in.

Moisture Conditioning: The Thing Crews Skip Under Schedule Pressure

Compaction isn’t just “run the plate compactor.” Soil needs the right moisture to compact properly.

Too wet

• Pumps under equipment

• Won’t densify

• Creates future consolidation

Too dry

• Won’t knit together

• Compacts “on top” but stays loose below

Field reality in Middle Tennessee

We see quick swings—rain events, clayey soils, freeze/thaw in winter—so moisture conditioning is often the difference between a stable sidewalk and a settlement callback.

Trench Backfill: Where Settlement Is Born

If your project includes site lighting, power, communications, or utilities, you have trenches. And trenches are the #1 settlement driver.

The classic failure pattern

1. Trench is dug

2. Conduit is installed

3. Trench is backfilled quickly with spoils

4. Compaction is inconsistent (or skipped)

5. Sidewalk/paving goes over it

6. Months later: settlement and cracking

Best practices that prevent it

• Backfill in lifts (not one big dump)

• Use appropriate material (not frozen, not oversized, not saturated)

• Compact with equipment that matches trench width

• Pay special attention at:

  • Trench crossings under sidewalks

  • Around handholes/pull boxes

  • At curb lines and ramps

EC takeaway: If your scope includes trenching, your closeout success depends on backfill discipline as much as conduit installation.

Handholes and Pull Boxes: “Flush Today” Isn’t Good Enough

Handholes/pull boxes can create ADA issues in two ways:

• Lid is proud or frame is mis-set (immediate trip hazard)

• Box settles later (delayed trip hazard)

What helps

• Set elevations using the same benchmark as flatwork

• Compact around the box in lifts

• Protect the frame during concrete placement so it doesn’t shift

• Avoid placing boxes in the accessible route when possible (coordinate early)

Cut/Fill Transitions: The Hidden Crack Line

Where cut meets fill, the subgrade behaves differently. If you don’t manage it, you’ll often see cracking right along that transition.

Practical prevention

• Over-excavate and rework the transition zone

• Proof-roll specifically at transitions

• Don’t “feather” fill without compaction control

Winter Compaction: Frozen Material Is a Time Bomb

What goes wrong in winter

• Backfill includes frozen clods

• Material looks compacted but thaws later

• Voids form → settlement

Field rule

Never backfill with frozen material in areas that will support sidewalks, ramps, paving, or pads.

If you’re forced to work through winter conditions, plan for:

• Material management (keep stockpiles workable)

• Protection of open trenches

• Rework of any questionable areas before concrete

Inspection and Documentation: How to Avoid “He Said / She Said” Later

Settlement disputes often turn into finger-pointing because no one documented the subgrade condition.

What to document (simple but effective)

• Photos of trench crossings before concrete

• Proof-roll notes (where soft spots were corrected)

• Backfill/compaction approach around boxes

• Any undercut/stabilization performed

GC takeaway: A few photos and notes can save thousands in disputes.

One-Page Field Checklist

• Identify settlement hotspots (trenches, boxes, ramps, curb returns)

• Proof-roll subgrade and trench crossings before forming

• Correct soft spots (don’t cover and hope)

• Moisture-condition material before compaction

• Backfill trenches in lifts; compact with appropriate equipment

• Set handholes/pull boxes to benchmark elevation; compact around frames

• Avoid frozen material in backfill (winter)

• Document corrections and pre-pour conditions (photos + notes)

How Halemeyer Group Helps Prevent Settlement-Driven Rework

We support GCs and ECs by:

• Executing site work and excavation with a quality-first mindset

• Coordinating trenching and backfill so it supports long-term performance

• Building site concrete with awareness of ADA route risk

• Communicating early when soils, moisture, or sequencing will create settlement issues

If you’re building in Lebanon, TN or across Middle Tennessee and want a partner who treats subgrade and compaction like a critical scope—not an afterthought—we’re ready to help.

Conclusion: The Best Sidewalk Is the One That Looks the Same in 12 Months

ADA routes and exterior flatwork don’t fail because the broom finish wasn’t perfect. They fail because the ground underneath wasn’t stable.

If you proof-roll, manage moisture, compact in lifts, and treat trench crossings like high-risk zones, you can prevent most settlement callbacks and protect your closeout.

Need help with site work, trenching, light pole bases, or site concrete in Middle Tennessee? Reach out to Halemeyer Group and we’ll align on a field plan that keeps your flatwork stable and your schedule intact.

Halemeyer Group LLC is a commercial concrete and construction specialist serving Middle Tennessee. We partner with general contractors and electrical contractors on foundations, slabs, site work, light pole bases, and trenching—delivering safety-first practices, innovative techniques, and unwavering quality.