Excavate and Prepare a Hardscape Subgrade

A. Finished Project Specification

Deliverable: one excavated and compacted subgrade for the project area established in Chapter 3, at the design depth and slope stated on the approved plan, with unsuitable soil removed and corrected, overexcavated areas refilled in compacted lifts, finished elevation verified on a grid relative to the fixed reference, slope and drainage direction verified, and the excavation documented and accepted before Chapter 5 aggregate-base work begins.

B. Excavation and Compaction Record Schedule

Record	Required Content	Source
Plan verification	Approved layout, design depth, utility markings, spoil location, equipment limits	Chapter 3 layout and approved plan
Vegetation and organic strip	Sod, topsoil, roots, and organic material removed to full excavation limits	Field observation
Excavation passes	Depth and location of each controlled pass, foundation and utility separation maintained	Field record
Soil inspection	Soft spots, pumping soil, organic material, debris, uncontrolled fill, or contamination identified and located	Field inspection and probing
Unsuitable material removal	Extent and depth of removed material, replacement material used	Field record
Subgrade shaping	Slope achieved across the project area, drainage direction confirmed	Line level or laser level readings
Compaction record	Equipment used, lift thickness, moisture condition, pass count and pattern	Field record
Elevation grid	Elevation at every grid point relative to the fixed reference	Line level or laser level readings
Proof-roll or density test	Method used, locations tested, results, corrections made	Field test where specified
Acceptance decision	Approved, corrected-and-reinspected, or referred, with reasoning	Full record review

C. Governing Document Checklist

• Chapter 3 layout: confirms excavation limits, reference lines, and finished elevations.
• Approved plan design depth and slope: confirms the exact subgrade elevation and drainage direction required.
• Utility-locate confirmation: confirms utility positions and validity period before excavation begins.
• Geotechnical information, where supplied: confirms soil type, compaction equipment, and lift-thickness requirements.
• Chapter 1 readiness plan: confirms soil, drainage, and access findings affecting the excavation.

D. Acceptance Standards

Check	Standard
Design depth	Finished subgrade elevation matches the design depth stated on the approved plan, measured relative to the fixed reference, within the tolerance the plan states
Unsuitable material	No organic material, roots, debris, uncontrolled fill, soft spot, or contamination remains within the excavation limits
Overexcavation refill	Every overexcavated area is refilled only with approved material, placed and compacted in lifts no thicker than the plan specifies
Subgrade slope	Slope across the project area matches the approved plan's stated slope and drainage direction at every grid point
Compaction	Compaction equipment, lift thickness, moisture condition, and pass count match the approved plan or geotechnical information for the soil type present
Elevation grid	Every grid-point elevation, including corners, edges, and drain locations, is recorded and matches the design depth within tolerance
Proof-roll or density test	Where specified, the test is performed, results recorded, and any failed location corrected and retested
Documentation	Excavation depth, soil conditions, corrections, and final acceptance are recorded and signed before aggregate-base work begins

E. Preparation — Verify Plan and Set Up the Work Area

1. Verify layout, excavation depth, utility markings, spoil location, and equipment limits. Compare the Chapter 3 layout and approved plan against current utility markings and confirm they remain valid before excavation begins.
2. Barricade the area and establish machine and hand-excavation zones. Mark the boundary between areas approved for machine excavation and areas requiring hand excavation near utilities, foundations, or other sensitive features.
3. Strip vegetation, sod, topsoil, roots, and organic material. Remove all organic material across the full excavation footprint and place it in the approved spoil location, separate from reusable subgrade or base material.

F. Excavation — Controlled Passes and Utility Protection

1. Excavate in controlled passes. Remove soil in limited-depth cuts, observing continuously for utilities, soil change, and proximity to foundations or other structures.
2. Maintain separation from foundations, utilities, trees, irrigation, and property lines. Do not excavate closer than the approved plan's stated clearance to any of these features.
3. Hand expose utilities where required. Use hand tools only within the clearance zone around any marked utility, and confirm exact utility position and depth before continuing machine excavation nearby.
4. Do not undermine foundations, footings, slabs, walls, fences, posts, or adjacent paving. Stop excavation at the approved limit next to any of these features and refer the condition if the design requires closer work.
5. Stockpile or remove spoil without blocking drainage. Place spoil only in the approved location, clear of existing swales, catch basins, and discharge paths.

G. Soil Inspection and Correction

1. Inspect exposed soil for soft spots, pumping, organic material, debris, uncontrolled fill, or contamination. Probe at a regular interval across the excavated area and record every location where a deficiency is found.
2. Remove unsuitable material to approved limits. Excavate deficient soil to the depth and extent required to reach stable, suitable material, as confirmed by inspection or probing.
3. Stop work when conditions differ materially from the plan. Halt excavation in the affected area and refer the condition to the required qualified professional before continuing.

H. Shaping and Compaction

1. Shape subgrade to the required slope. Grade the exposed subgrade to the slope and drainage direction stated on the approved plan.
2. Moisture-condition soil only as specified. Add or dry soil only to the moisture condition stated by the approved plan or geotechnical information, and do not compact soil outside that stated range.
3. Compact with equipment appropriate to soil type and area. Select compactor type and lift thickness matching the soil type and area size specified.
4. Overlap compactor passes. Maintain the overlap pattern specified by the approved plan or, absent a stated pattern, an overlap sufficient to compact the full area with no untreated strip.
5. Compact corners and confined areas using suitable equipment. Use hand-operated compaction equipment sized for corners, edges, and areas a plate compactor cannot reach.
6. Refill overexcavated areas only with approved material in compacted lifts. Place refill material in lifts no thicker than specified and compact each lift before placing the next.

I. Verification and Acceptance

1. Check elevation on a grid. Measure subgrade elevation at every grid point, corner, edge, and drain location relative to the fixed reference, and record each reading.
2. Verify slope and drainage direction. Confirm the recorded grid elevations produce the slope and drainage direction stated on the approved plan.
3. Perform proof-rolling, probing, or density testing where specified. Conduct the test method stated by the approved plan or geotechnical information and record the results.
4. Correct soft, loose, high, low, or unstable areas. Rework any area that fails the elevation, slope, compaction, or test check, then repeat the affected verification step.
5. Document excavation depth, soil conditions, corrections, and acceptance. Complete the excavation record with final elevations, soil conditions found and corrected, test results, and a signed acceptance before Chapter 5 begins.