SynC™

SynC · Editorial revision

Earthwork

Revision7
EditedOct 2, 2026
StatusCurrent
Contents

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Current revision. This is editorial revision 7, the current text of this standard. Read it on the standard's page.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Remade for neutrality: every choice explained, project facts as parameters, scope boundaries linked both ways

1 Scope

NOTE This standard governs the excavation, fill, backfill, compaction, and subgrade acceptance that shape the site and prepare it to carry foundations, slabs, pavements, utilities, and landscape. (1.1)
NOTE The work begins at the cleared, grubbed, and demolished condition delivered by the clearing and demolition scopes and ends at an accepted subgrade or bearing surface on which the following trade builds. (1.2)
NOTE Earthwork is the one scope every later scope inherits, and its defects surface as someone else's problem: a footing settles because the fill beneath it was placed in lifts the roller could not reach, a pavement dishes along a utility trench because the upper backfill was never tested, and a slab cracks because the subgrade was proof-rolled on a dry day and placed on a wet one. (1.3)
NOTE The geotechnical investigation report is the primary governing document for the soil-specific values in this standard: fill suitability, compaction targets, lift thickness, moisture windows, over-excavation and replacement rules, and allowable bearing. Where this standard carries a value in a datasheet field that defers to the geotechnical report, the report's value governs and the fallback stated here applies only where the report is silent. (1.4)
NOTE This standard ends at the completion of mass earthwork; Site Rough GradingSite Grading and Subgrade PreparationResolves to the current adopted revision.sync/site-rough-grading takes over from that point through delivery of an accepted subgrade and fine-graded surface, and it applies the proof-rolling procedure and acceptance criteria stated in this standard rather than restating them. (1.5)
NOTE Proof rolling and subgrade acceptance beneath foundations, slabs, pavements, and structural fill are stated once, in this standard, because the standards for those surfaces cite them here. (1.6)
NOTE The pipe zone of a utility trench, from the trench bottom through the bedding, haunch, and initial backfill to 12 in. above the pipe crown, belongs to the standard for the utility installed: Site UtilitiesSite UtilitiesResolves to the current adopted revision.sync/site-utilities, Storm DrainageStorm DrainageResolves to the current adopted revision.sync/storm-drainage, Sanitary Sewer SystemsSanitary Sewer Systems (Site)Resolves to the current adopted revision.sync/sanitary-sewer-systems, Water Distribution PipingSite Water Distribution PipingResolves to the current adopted revision.sync/water-distribution-piping, Underground Fire Service MainsUnderground Fire Service MainsResolves to the current adopted revision.sync/underground-fire-service-mains, Foundation DrainageFoundation DrainageResolves to the current adopted revision.sync/foundation-drainage, SubdrainageSubdrainageResolves to the current adopted revision.sync/subdrainage, Landscape IrrigationLandscape IrrigationResolves to the current adopted revision.sync/landscape-irrigation, and Packaged Pump StationsPackaged Pump and Lift StationsResolves to the current adopted revision.sync/packaged-pump-stations. This standard resumes above the pipe zone, and it supplies a default pipe-zone material only where the utility standard states none. (1.7)
NOTE Worker protection in ordinary excavations and trenches, by sloping, benching, trench shields, and tabulated shoring, is within this standard. An excavation that needs an engineered support system, underpinning of an adjacent foundation, or a designed dewatering system is the work of Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering, and this standard states where that threshold is crossed. (1.8)
NOTE The following are outside this standard: (1.9)
  • Clearing, grubbing, topsoil stripping, and tree protection, which precede this work under Site ClearingSite ClearingResolves to the current adopted revision.sync/site-clearing
  • Demolition of structures and their foundations under Building DemolitionStructure DemolitionResolves to the current adopted revision.sync/building-demolition, and selective removal within a retained structure under Selective DemolitionSelective DemolitionResolves to the current adopted revision.sync/selective-demolition
  • Finish grading of site surfaces to trade tolerances under Site Rough GradingSite Grading and Subgrade PreparationResolves to the current adopted revision.sync/site-rough-grading
  • Erosion prevention, sediment control, and the SWPPP under Erosion And Sediment ControlErosion and Sediment ControlResolves to the current adopted revision.sync/erosion-and-sediment-control
  • Aggregate base course under Aggregate Base CourseAggregate Base CourseResolves to the current adopted revision.sync/aggregate-base-course, and the granular subbase and vapor retarder directly beneath a building slab under Slab On GradeSlab-on-GradeResolves to the current adopted revision.sync/slab-on-grade and Vapor Barriers Under SlabUnder-Slab Vapor BarriersResolves to the current adopted revision.sync/vapor-barriers-under-slab
  • Chemical treatment of subgrade under Soil StabilizationSoil Stabilization and ModificationResolves to the current adopted revision.sync/soil-stabilization, geotextiles and geogrids under GeosyntheticsGeosynthetics and GeotextilesResolves to the current adopted revision.sync/geosynthetics, and aggregate piers, deep mixing, and jet grouting under Ground ImprovementGround Improvement (Aggregate Piers and Soil Mixing)Resolves to the current adopted revision.sync/ground-improvement
  • Deep foundations under Deep FoundationsDeep Foundations (Piles and Drilled Piers)Resolves to the current adopted revision.sync/deep-foundations, footings under Shallow FoundationsShallow Foundations (Spread and Strip Footings)Resolves to the current adopted revision.sync/shallow-foundations, waterproofing under Below Grade WaterproofingBelow-Grade WaterproofingResolves to the current adopted revision.sync/below-grade-waterproofing, and permanent site retaining walls under Retaining WallsSite Retaining WallsResolves to the current adopted revision.sync/retaining-walls
1.10 All earthwork shall conform to the recommendations of the geotechnical investigation report prepared for the project.
1.11 Where this standard and the geotechnical report conflict, the geotechnical report shall govern for soil-specific criteria and this standard shall govern for procedure, testing, and submittal requirements, unless the Engineer of Record directs otherwise in writing.
1.12 The Contractor shall perform excavation and fill to the lines, grades, and limits shown on the grading plan and sections.
1.13 The Contractor shall coordinate work under this standard with Erosion And Sediment ControlErosion and Sediment ControlResolves to the current adopted revision.sync/erosion-and-sediment-control for the grading sequence, stockpile protection, and sediment control on dewatering discharge; with Site ClearingSite ClearingResolves to the current adopted revision.sync/site-clearing and Building DemolitionStructure DemolitionResolves to the current adopted revision.sync/building-demolition for the condition of the site at handover; with Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering for every excavation that needs an engineered system; with the utility standards for the pipe zone of each trench; and with Aggregate Base CourseAggregate Base CourseResolves to the current adopted revision.sync/aggregate-base-course, Slab On GradeSlab-on-GradeResolves to the current adopted revision.sync/slab-on-grade, Shallow FoundationsShallow Foundations (Spread and Strip Footings)Resolves to the current adopted revision.sync/shallow-foundations, and Retaining WallsSite Retaining WallsResolves to the current adopted revision.sync/retaining-walls for the surfaces this standard delivers to them.

2 Referenced Standards

2.1 Materials, testing, and execution shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ASTM D698 Laboratory Compaction Characteristics of Soil Using Standard Effort
ASTM D1557 Laboratory Compaction Characteristics of Soil Using Modified Effort
ASTM D1140 Determining the Amount of Material Finer than 75-µm (No. 200) Sieve in Soils by Washing
ASTM D1556/D1556M Density and Unit Weight of Soil in Place by Sand-Cone Method
ASTM D2167 Density and Unit Weight of Soil in Place by the Rubber Balloon Method
ASTM D2216 Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
ASTM D2321 Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity-Flow Applications
ASTM D2487 Classification of Soils for Engineering Purposes (Unified Soil Classification System)
ASTM D2488 Description and Identification of Soils (Visual-Manual Procedures)
ASTM D2937 Density of Soil in Place by the Drive-Cylinder Method
ASTM D2974 Determining the Water (Moisture) Content, Ash Content, and Organic Material of Peat and Other Organic Soils
ASTM D4253 Maximum Index Density and Unit Weight of Soils Using a Vibratory Table
ASTM D4254 Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density
ASTM D4318 Liquid Limit, Plastic Limit, and Plasticity Index of Soils
ASTM D4832 Preparation and Testing of Controlled Low Strength Material (CLSM) Test Cylinders
ASTM D6103 Flow Consistency of Controlled Low Strength Material (CLSM)
ASTM D6938 In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
ASTM D7928 Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
ASTM C136/C136M Sieve Analysis of Fine and Coarse Aggregates
AASHTO T 99 Moisture-Density Relations of Soils Using a 2.5-kg Rammer and a 305-mm Drop
AASHTO T 180 Moisture-Density Relations of Soils Using a 4.54-kg Rammer and a 457-mm Drop
ACI 229R Report on Controlled Low-Strength Materials
IBC Chapter 17 Special Inspections and Tests (International Building Code)
IBC Chapter 18 Soils and Foundations (International Building Code)
29 CFR 1926 Subpart P Excavations (OSHA Safety and Health Regulations for Construction)

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review by the Engineer of Record before the earthwork they describe begins:
  • Fill source report for each on-site stockpile and each import source proposed as fill: USCS classification per ASTM D2487, gradation per ASTM C136/C136M and ASTM D7928, Atterberg limits per ASTM D4318, organic content per ASTM D2974 where the material is suspected of containing organics, and the laboratory compaction curve by the reference method selected in the datasheet
  • Environmental source documentation for imported fill, where the datasheet requires it
  • Recycled concrete aggregate source report, where the datasheet permits its use as fill
  • Controlled low-strength material mix design with flow per ASTM D6103 and strength per ASTM D4832, where the datasheet permits its use
  • Excavation safety plan prepared or reviewed by the competent person, describing the soil classification method, the protective systems to be used for each excavation 5 ft or deeper, and the means of access and egress
  • Groundwater control plan where sump pumping is anticipated, describing sump locations, pump capacity, the discharge route, and the sediment control it discharges through
  • Earthwork sequence showing the order of mass cut and fill, stockpile locations, and haul routes, coordinated with the sequence in the SWPPP
Action Submittals Requiredcheckbox
☑ Fill source report for each on-site and imported source
☐ Environmental source documentation for imported fill
☐ Recycled concrete aggregate source report
☐ CLSM mix design
☑ Excavation safety plan
☐ Groundwater control plan for sump pumping
☑ Earthwork sequence and stockpile plan
3.1.2 Fill shall not be placed from any source until the fill source report for that source has been reviewed and the source accepted by the geotechnical engineer of record.
3.1.3 Review of a submittal does not relieve the Contractor of responsibility for compliance with the Contract Documents.

3.2 Closeout Submittals

3.2.1 The Contractor shall deliver the following before the subgrade or bearing surface is turned over to the following trade, and shall deliver the compiled set before substantial completion:
  • Field density test reports for every test taken, passing and failing, with the location, lift, material, reference curve, dry density, moisture content, percent compaction, and disposition of each
  • Proof-rolling records for each area proof-rolled, with the date, the vehicle and its loaded weight, the areas that failed, and the stabilization applied
  • Geotechnical engineer of record's written observation report for each foundation bearing surface
  • As-built grading survey showing the finished earthwork surface against the design grades
  • Record of each differing site condition encountered, the direction received, and the work performed under it
  • Record of each over-excavation and replacement, with its location, depth, and replacement material
Closeout Submittals Requiredcheckbox
☑ Field density test reports, passing and failing
☑ Proof-rolling records
☑ Foundation bearing surface observation reports
☑ As-built grading survey
☑ Differing site condition record
☑ Over-excavation and replacement record

4 Quality Assurance

4.1 Geotechnical Engineer of Record

4.1.1 The Owner shall retain a licensed geotechnical engineer of record to observe earthwork and to interpret the geotechnical report in light of the conditions actually encountered.
4.1.2 The geotechnical engineer of record shall observe every foundation bearing surface before concrete, lean concrete, or fill is placed on it.
4.1.3 The geotechnical engineer of record shall observe every proof-rolling operation.
4.1.4 The geotechnical engineer of record shall accept or reject each proposed fill source on the basis of the fill source report and the requirements of this standard.
4.1.5 The geotechnical engineer of record shall evaluate each differing site condition reported by the Contractor and shall direct the response in writing.
4.1.6 The geotechnical engineer of record may stop earthwork that does not conform to the geotechnical report or to this standard, and the Contractor shall comply with that direction.
4.1.7 The Contractor shall give the geotechnical engineer of record not less than 24 hours notice before each bearing surface, proof-rolling operation, or fill lift is ready for observation.
NOTE The geotechnical engineer's observation is a hold point rather than a courtesy: the bearing stratum identified in the report from a handful of borings is confirmed or contradicted at every footing, and the only person positioned to make that call is the one who wrote the report. (4.1.8)

4.2 Testing Agency and Special Inspection

4.2.1 Field density testing and fill material testing shall be performed by the testing agency retained as indicated in the datasheet.
Earthwork Testing Agency Retained Byradio
● Owner
○ Contractor, with results reported directly to the Owner
NOTE Owner retention keeps the testing agency independent of the party whose work it accepts, which is the arrangement IBC Chapter 17 requires where special inspection applies; Contractor retention with direct reporting to the Owner is used on projects below the special inspection threshold and on design-build work where the Owner has no separate testing contract, and it depends on the reporting path being enforced. (4.2.2)
4.2.3 Where the statement of special inspections on the structural drawings requires special inspection of fill placement under Adopted Building CodeAdopted Building CodeParameterEach project supplies its own value.adopted-building-code Chapter 17, the special inspector shall perform the periodic or continuous inspection that statement requires and shall report each nonconformance to the Owner and the Engineer of Record.
Special Inspection of Fill Placementradio
○ Required
○ Not required
Derived — the statement of special inspections on the structural drawings under Adopted Building CodeAdopted Building CodeParameterEach project supplies its own value.adopted-building-code Chapter 17 (by default)
4.2.4 Special inspection does not relieve the geotechnical engineer of record of the separate observation obligations stated in this standard.
4.2.5 The testing agency shall standardize each nuclear gauge at the start and end of every testing day in accordance with ASTM D6938 and shall record the standard counts.
4.2.6 The testing agency shall verify nuclear gauge results against the sand-cone method of ASTM D1556/D1556M at a frequency of not less than one verification test per 20 nuclear tests on each material.

4.3 Excavation Competent Person

4.3.1 The Contractor shall designate a competent person, as defined in 29 CFR 1926 Subpart P, for every excavation 5 ft or deeper and for every excavation in which a cave-in hazard exists regardless of depth.
4.3.2 The competent person shall classify the soil of each excavation by the visual and manual tests of 29 CFR 1926 Subpart P Appendix A, shall select or confirm the protective system, and shall inspect the excavation daily before work begins and after every rain, thaw, vibration event, or change in loading.
4.3.3 The Contractor shall remove workers from any excavation the competent person finds unsafe until the hazard is corrected.
4.3.4 The Contractor shall not replace the designated competent person with a person who does not meet the same qualification.

4.4 Pre-Earthwork Conference

4.4.1 Before mass excavation or fill placement begins, the Contractor shall convene a conference attended by the Contractor's earthwork superintendent, the competent person, the geotechnical engineer of record, the testing agency, the special inspector where one is required, and the Engineer of Record.
4.4.2 The conference shall review the geotechnical report recommendations, the accepted fill sources, the compaction targets and reference method, the testing frequency and reporting path, the excavation safety plan, the groundwater control plan, the earthwork sequence, and the procedure for reporting differing site conditions.

4.5 Differing Site Conditions

NOTE The geotechnical report characterizes the subsurface from a limited number of borings and test pits, and the conditions encountered between them differ from the report on most sites in some respect; the procedure below exists so the difference is recorded and resolved rather than argued about after the fill is in place. (4.5.1)
4.5.2 The Contractor shall notify the Engineer of Record and the geotechnical engineer of record in writing within one working day of encountering groundwater, rock, soft or organic soil, buried structures or utilities, or suspected contamination that the geotechnical report and the Contract Documents do not identify at that location.
4.5.3 The Contractor shall suspend work in the affected area, except work required for immediate safety, until the geotechnical engineer of record directs the response in writing.
4.5.4 The Contractor shall not remove, cover, or backfill over a differing condition before the geotechnical engineer of record has observed it, except where immediate safety requires it.
4.5.5 Where the parties disagree whether a condition differs materially from the geotechnical report, the Engineer of Record shall make the initial determination.

5 Site and Weather Conditions

5.1 Groundwater Basis

5.1.1 The groundwater condition for earthwork planning shall be Seasonal High Groundwater ElevationSeasonal High Groundwater ElevationParameterEach project supplies its own value.seasonal-high-groundwater-elevation as established by the geotechnical report, and not the water level observed in the borings on the day they were drilled.
5.1.2 Excavations whose bottom lies below Seasonal High Groundwater ElevationSeasonal High Groundwater ElevationParameterEach project supplies its own value.seasonal-high-groundwater-elevation shall be planned for groundwater control before excavation begins, as indicated in the datasheet.
Groundwater Control Anticipatedradio
○ Not anticipated
○ Sump pumping within the excavation
○ Engineered dewatering system
Derived — Seasonal High Groundwater ElevationSeasonal High Groundwater ElevationParameterEach project supplies its own value.seasonal-high-groundwater-elevation and the lowest excavation elevation shown on the grading and foundation drawings (by default)
NOTE Sump pumping handles seepage that enters an excavation through its walls and bottom and can be collected at a low point; it is adequate where the excavation bottom is not far below the water table and the soil is not so fine that pumping draws the bottom up with the water. An engineered system, under Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering, lowers the water table before the excavation reaches it and is the answer where the bottom lies well below the water table, where the soil is a silt or fine sand that will boil or pipe, or where the drawdown reaches adjacent structures. (5.1.3)

5.2 Frost and Freezing Weather

5.2.1 Fill shall not be placed on a frozen surface.
5.2.2 Fill placed during freezing weather shall be compacted and tested before it freezes, and a lift that freezes before it is tested shall be removed or thawed, moisture-conditioned, and recompacted before the next lift is placed.
5.2.3 Foundation bearing surfaces exposed during freezing weather shall be protected from frost by insulation, heated enclosure, or a covering of loose fill, and the geotechnical engineer of record shall confirm the bearing surface unfrozen before concrete is placed.
5.2.4 Frost-susceptible soil shall not be placed as fill within Frost DepthFrost DepthParameterEach project supplies its own value.frost-depth of the finished surface beneath pavements, exterior slabs, and footings, unless the geotechnical report permits it for that location.
NOTE A frozen lift looks compacted and tests dense, and then thaws into the loose material it always was; the settlement arrives in the spring, beneath whatever was built on it over the winter. (5.2.5)

5.3 Wet Weather

5.3.1 The Contractor shall grade every exposed subgrade and fill surface to drain, and shall seal the surface with a smooth-drum roller before leaving it at the end of each working day and ahead of forecast rain.
5.3.2 Fill operations shall stop when rain raises the moisture content of the fill or the receiving surface above the upper limit of the moisture window in the datasheet.
5.3.3 After rain, the Contractor shall remove or dry back the wetted material to within the moisture window before placing the next lift, and shall not blend wet material into a thicker lift to average the moisture.
5.3.4 Fill shall not be placed on a surface with standing water, mud, or a pumping condition, and the surface shall be restored and re-accepted before placement resumes.

6 Fill Materials

6.1 Fill Classes and Sources

NOTE This standard uses five fill classes, each defined by the properties the use demands rather than by where the material came from: structural fill beneath foundations, slabs, and pavements; free-draining granular fill where water must pass or capillary rise must be stopped; general site fill in landscape and other areas where some long-term settlement is tolerable; recycled concrete aggregate as a processed substitute for either of the first two where the datasheet permits it; and controlled low-strength material where a flowable, self-compacting fill replaces compaction. (6.1.1)
6.1.2 Every fill material, whether excavated on the site or imported, shall be classified per ASTM D2487 and described per ASTM D2488, and shall be identified in the fill source report by its USCS group symbol.
6.1.3 Every fill material shall be free of organic matter, frozen lumps, ice, snow, debris, and other deleterious material.
6.1.4 The Contractor shall not change a fill source, and shall not blend sources, without submitting a fill source report for the new or blended material and receiving the geotechnical engineer's acceptance of it.
6.1.5 The Contractor shall stockpile fill of different classes separately and shall protect each stockpile from contamination, saturation, and drying beyond the moisture window.
6.1.6 The limits of structural fill beneath the building and beneath pavements shall be as shown on the building pad and pavement limits on the grading plan.

6.2 Structural Fill

6.2.1 Structural fill shall be placed beneath footings, slabs on grade, grade beams, pavements, equipment pads, and site concrete structures, and wherever the drawings call for engineered or compacted fill.
6.2.2 The USCS groups permitted as structural fill shall be as indicated in the datasheet.
Structural Fill Permitted USCS Groupscheckbox
☐ GW
☐ GP
☐ GM
☐ GC
☐ SW
☐ SP
☐ SM
☐ SC
☐ CL
☐ ML
Per drawings — the geotechnical report fill recommendations (deferred by default)
6.2.3 Where the geotechnical report does not state which groups are permitted, structural fill shall be a GW, GP, GM, GC, SW, SP, SM, or SC material.
NOTE The clean gravels and sands (GW, GP, SW, SP) compact readily over a wide moisture range and are the least sensitive to weather, at the cost of import price where the site has none; the silty and clayey sands and gravels (GM, GC, SM, SC) are what most sites yield and compact well inside a narrower moisture window; a low-plasticity clay or silt (CL, ML) can serve as structural fill where the geotechnical engineer has evaluated it for the loads involved, and it is admitted where the alternative is importing everything beneath a large pad, at the cost of a moisture window a wet week can close. (6.2.4)
6.2.5 The maximum particle size in structural fill shall be as indicated in the datasheet.
Structural Fill Maximum Particle Sizerange
in
11.52346
6.2.6 No particle in any fill lift shall exceed two-thirds of the compacted thickness of that lift.
6.2.7 The maximum liquid limit of structural fill shall be as indicated in the datasheet.
Structural Fill Maximum Liquid Limitrange
2050
Default: 40
6.2.8 The maximum plasticity index of structural fill shall be as indicated in the datasheet.
Structural Fill Maximum Plasticity Indexrange
025
Default: 15
6.2.9 Where the geotechnical report sets a liquid limit, plasticity index, or particle size limit for structural fill, the report's limit shall govern over the datasheet value.
6.2.10 Structural fill shall contain not more than 3 percent organic material by mass when tested per ASTM D2974.

6.3 Free-Draining Granular Fill

6.3.1 Free-draining granular fill shall be a GW, GP, SW, or SP material, or a clean crushed stone, wherever the drawings call for drainage fill, free-draining backfill, or a capillary break outside the building slab.
6.3.2 The maximum fines content of free-draining granular fill, as the percentage passing the No. 200 sieve when tested per ASTM D1140, shall be as indicated in the datasheet.
Free-Draining Granular Fill Maximum Fines Contentrange
% passing No. 200
015
Default: 5 % passing No. 200
NOTE A fines content at or below 5 percent keeps the material permeable and non-frost-susceptible after it has been handled and compacted; a limit of 8 to 12 percent admits a wider range of pit-run sources at the cost of permeability that drops sharply as the fines fill the voids, and it suits locations where the material is a working platform first and a drain second. (6.3.3)
6.3.4 Free-draining granular fill shall be non-plastic.
6.3.5 The maximum particle size of free-draining granular fill shall not exceed the structural fill maximum particle size in the datasheet, and shall not exceed 2 in. within 24 in. of a waterproofed or dampproofed surface.

6.4 General Site Fill

6.4.1 General site fill shall be placed in landscape areas, berms, and other areas that carry no foundation, slab, pavement, or utility, and shall not be placed within 10 ft of a building foundation, beneath any pavement, or in any utility trench unless the geotechnical engineer of record accepts it for that location in writing.
6.4.2 General site fill shall be a GW, GP, GM, GC, SW, SP, SM, SC, ML, CL, or CL-ML material.
6.4.3 The maximum plasticity index of general site fill shall be as indicated in the datasheet.
General Site Fill Maximum Plasticity Indexrange
040
Per drawings — the geotechnical report fill recommendations (deferred by default)
6.4.4 Where the geotechnical report does not state a plasticity limit for general site fill, the maximum plasticity index shall be 30.
NOTE A higher plasticity limit lets the site's own clay be used as landscape fill instead of being hauled off, at the cost of shrink-swell movement in the finished surface and a moisture window that is slow to recover after rain; a lower limit costs import or disposal and buys a surface that stays where it was graded. (6.4.5)

6.5 Recycled Concrete Aggregate

6.5.1 Recycled concrete aggregate from demolition on the site or from an off-site processor shall be used as fill only as permitted in the datasheet.
Recycled Concrete Aggregate as Fillradio
○ Not permitted
○ Permitted as general site fill
○ Permitted as structural fill and as general site fill
NOTE Crushed concrete from the demolition scopes is a sound, well-graded, free-draining fill when it is processed to a gradation and freed of reinforcing steel, wood, and soil, and using it on the site avoids both a disposal haul and an import haul; it carries a high pH leachate that can harm vegetation and corrode aluminum and galvanized steel in contact with it, it can contain gypsum or other contaminants from the structure it came from, and as structural fill it depends on a processor who can hold a gradation. Prohibiting it is the position where the source cannot be verified; permitting it as general site fill keeps it away from foundations and buried metal; permitting it as structural fill is the position where the source is a controlled processor with gradation and contaminant data. (6.5.2)
6.5.3 Where permitted, recycled concrete aggregate shall be crushed and screened to a maximum particle size not exceeding the structural fill maximum particle size in the datasheet, shall be free of reinforcing steel, wood, gypsum, asphalt, and soil, and shall be reported in the fill source report with gradation per ASTM C136/C136M and a description of the source structure.
6.5.4 Recycled concrete aggregate shall not be placed within 24 in. of aluminum, galvanized steel, or copper that remains in service, and shall not be placed as general site fill within the root zone of planting shown on the landscape drawings.
6.5.5 Compaction of recycled concrete aggregate shall be accepted by the method stated in this standard for crushed stone where the material has no usable laboratory compaction curve.

6.6 Controlled Low-Strength Material

6.6.1 Controlled low-strength material, a flowable mixture of cement, fly ash or other fine aggregate, water, and admixtures that consolidates without compaction, shall be used as fill or backfill only as permitted in the datasheet.
Controlled Low-Strength Material as Backfillradio
○ Not permitted
● Permitted at designated locations
○ Permitted at the Contractor's option in confined locations
NOTE CLSM fills a space no compactor can reach, under a pipe haunch, around a tank, in a narrow trench against a wall, and it does so without the lift-by-lift testing that compacted fill requires; it costs several times the price of compacted fill by volume, it floats an empty pipe or tank it is placed around, and once it has hardened it is excavated with a breaker rather than a shovel. Restricting it to designated locations keeps the choice with the designer; permitting it at the Contractor's option in confined locations lets the field substitute it wherever compaction cannot be achieved or tested, at the Contractor's cost. (6.6.2)
6.6.3 Where CLSM is used, it shall be proportioned per ACI 229R, shall have a flow of 8 in. or greater per ASTM D6103 at placement, and shall be tested for strength per ASTM D4832.
6.6.4 The excavatability of CLSM shall be as indicated in the datasheet.
CLSM Excavatabilityradio
● Excavatable
○ Non-excavatable
6.6.5 Excavatable CLSM shall have a 28-day compressive strength of 50 to 150 psi and a long-term strength not exceeding 300 psi.
6.6.6 Non-excavatable CLSM shall have a 28-day compressive strength of 300 to 1,200 psi.
6.6.7 CLSM placed around a pipe, tank, or vault shall be placed in lifts whose height does not float or displace the element, and the element shall be ballasted or restrained during placement.

6.7 Unsuitable Material

6.7.1 The following shall not be used as fill in any class: topsoil, peat, muck, and other soil with more than 3 percent organic material by mass per ASTM D2974; frozen material; soil with a liquid limit above 50 or a plasticity index above 25, unless the geotechnical engineer of record accepts it in writing for a stated location; construction debris, trash, wood, and combustible material; and contaminated material.
6.7.2 Unsuitable material encountered within the limits of a footing, slab, pavement, or structural fill zone shall be removed to the depth directed by the geotechnical engineer of record and replaced with structural fill or as directed under the over-excavation provisions of this standard.
6.7.3 Unsuitable material shall be disposed of as indicated in the datasheet.
Unsuitable Material Dispositionradio
● Removed from the site and legally disposed
○ Placed in a designated on-site disposal area
NOTE Removal is the certain disposition; an on-site disposal area, used where the site has a landscape berm or a non-structural area that can absorb organic or high-plasticity spoil, saves the haul at the cost of a location that can never carry a structure and has to be recorded as such. (6.7.4)

6.8 Imported Fill Certification

6.8.1 Imported fill shall be certified by a fill source report, tested on a sample representative of the material to be delivered, before the first load is accepted on the site.
6.8.2 Environmental documentation for imported fill shall be as indicated in the datasheet.
Imported Fill Environmental Documentationradio
○ Not required
○ Source documentation of origin as clean fill
○ Source documentation and laboratory analysis for contaminants
NOTE Fill that arrives from an unknown excavation can carry petroleum, metals, or asbestos from the site it left, and the party that accepts it owns the problem thereafter; source documentation names the site and use the material came from, which is enough where the origin is a known construction excavation, while laboratory analysis is the position on a site with a sensitive use, a regulatory clean-fill program, or an import source that is a soil broker rather than a known excavation. (6.8.3)
6.8.4 The testing agency shall sample each import source at the frequency the geotechnical engineer of record directs, and not less than once per 2,000 cubic yards delivered, and shall report any change in classification, gradation, or plasticity from the fill source report.

7 Excavation

7.1 Lines, Grades, and Classification

7.1.1 Excavation shall be performed to the lines, grades, and dimensions shown on the drawings, with unformed excavation finished within ±0.1 ft of the design elevation.
7.1.2 Excavated material that meets a fill class in this standard shall be stockpiled for reuse in that class, and material that meets no fill class shall be handled as unsuitable material or as surplus.
7.1.3 Excavation shall be classified for measurement and payment as indicated in the datasheet.
Excavation Classification Basisradio
● Unclassified
○ Classified, with rock excavation measured separately
NOTE Unclassified excavation puts the whole subsurface at the Contractor's risk and price, which is the usual position on a building site with a geotechnical report and no rock in the borings; classified excavation pays rock separately at a unit price, which moves that risk to the Owner and is the position where the borings show rock within the excavation depth and the quantity cannot be estimated closely enough to price. (7.1.4)
7.1.5 Where excavation is classified, rock shall be defined as material that cannot be excavated with a hydraulic excavator of the class the Contractor has on the site, and the geotechnical engineer of record shall confirm the classification of each occurrence before it is measured.

7.2 Rock Excavation

7.2.1 Rock encountered within the excavation shall be removed by a method permitted in the datasheet.
Rock Removal Methods Permittedcheckbox
☑ Mechanical ripping
☑ Hydraulic breaker
☐ Drilling and blasting
☐ Expansive chemical agents
NOTE Ripping and hydraulic breaking remove weathered, fractured, and soft rock with the equipment already on the site and are limited by the hardness and continuity of the rock; blasting removes sound rock at a fraction of the cost per cubic yard but needs a licensed blaster, a permit, a vibration and air-blast monitoring program, and distance from structures the jurisdiction and the neighbors will tolerate; expansive chemical agents break rock without vibration or flyrock, at a slow rate and a high cost per cubic yard, and are the method next to a structure that blasting could not be brought near. (7.2.2)
7.2.3 Where blasting is permitted, the Contractor shall obtain the permits the jurisdiction requires, shall conduct a pre-blast condition survey of every structure within the distance the permit or the Engineer of Record specifies, and shall monitor ground vibration and air overpressure at the nearest structure for every blast.
7.2.4 Rock excavated beneath a footing or slab shall be removed to the elevation directed by the geotechnical engineer of record, and the void shall be filled with lean concrete or compacted crushed stone to the design bearing elevation.
7.2.5 Rock excavated in a trench shall be removed to not less than 6 in. below the pipe invert, and the trench bottom shall be brought back to grade with the bedding material the utility standard requires.
NOTE A pipe laid on a rock trench bottom bears on a point that never moves while the soil on either side of it settles, and the pipe shears at that point; the bedding course over rock exists to spread that reaction. (7.2.6)

7.3 Unsuitable Material Removal

7.3.1 Where soft, organic, loose, or otherwise unsuitable material is encountered at the design excavation bottom beneath a footing, slab, or structural fill zone, the Contractor shall notify the geotechnical engineer of record and shall over-excavate to the depth and lateral extent the geotechnical engineer directs.
7.3.2 The over-excavation beneath a footing shall extend laterally beyond each footing edge a distance not less than the depth of over-excavation, unless the geotechnical engineer of record directs otherwise.
7.3.3 Over-excavation beneath a footing or slab shall be replaced with the material indicated in the datasheet.
Over-Excavation Replacement Beneath Footings and Slabsselect
Lean concrete
Compacted structural fill
Compacted crushed stone
Controlled low-strength material
NOTE Lean concrete restores the bearing elevation in one pour with no compaction testing and no dependence on the weather, at a material cost that governs where the over-excavation is deep or wide; compacted structural fill is the economical replacement for a large area where the replacement can be placed in lifts and tested; compacted crushed stone is the replacement where the bottom is wet, because it can be placed and worked into a soft bottom without a moisture window; CLSM behaves like lean concrete in a narrow or irregular hole where a concrete truck chute cannot reach the bottom. (7.3.4)
7.3.5 Over-excavation and replacement directed by the geotechnical engineer of record for a condition the geotechnical report did not identify shall be paid as a change; over-excavation to correct the Contractor's own over-digging or disturbance shall be at the Contractor's expense.
7.3.6 The Contractor shall record the location, depth, lateral extent, and replacement material of each over-excavation and shall include the record in the closeout submittals.

7.4 Foundation Excavation

7.4.1 Foundation excavation shall be performed to the neat lines and bearing elevations shown on the foundation plan and footing schedule, plus the working space required for forming, waterproofing, and drainage.
7.4.2 The final 6 in. of excavation to a bearing surface shall be removed by a smooth-edged bucket or by hand immediately before the geotechnical engineer's observation, so the bearing surface is undisturbed and has not been exposed to drying or wetting.
7.4.3 A bearing surface exposed for more than two hours before concrete placement, or exposed to rain, shall be trimmed to fresh material before concrete is placed.
7.4.4 The bearing surface shall be level, free of loose material and standing water, and at the elevation shown, and the geotechnical engineer of record shall confirm in writing that the material exposed is the bearing stratum on which the design bearing pressure is based.
7.4.5 Where the material exposed is not the bearing stratum identified in the geotechnical report, the geotechnical engineer of record shall direct over-excavation and replacement under this standard, or shall direct a change to the foundation under the Engineer of Record's authority.
NOTE A footing excavation that is dug too deep is not fixed by throwing the spoil back in: the loosened material beneath the footing compresses under the first load it sees, and the footing follows it down. (7.4.6)

7.5 Trench Excavation

7.5.1 Trenches for utilities shall be excavated to the alignment, depth, and grade shown on the utility plan and profiles.
7.5.2 Trench width at the pipe springline shall be as required by the standard for the utility installed, and where that standard states none, not less than the pipe outside diameter plus 16 in. and not less than the width needed to place and compact the embedment on each side of the pipe.
7.5.3 The trench bottom shall be excavated to undisturbed material at the grade required by the utility standard, and shall not be brought back to grade with loose spoil where it is over-excavated.
7.5.4 Where the trench bottom is soft, pumping, or otherwise unable to support the pipe and its embedment, the trench bottom shall be stabilized by over-excavation and replacement with compacted crushed stone, with a separation geotextile under GeosyntheticsGeosynthetics and GeotextilesResolves to the current adopted revision.sync/geosynthetics where the stone is placed against fine-grained soil, to the depth the geotechnical engineer of record directs at each occurrence.
7.5.5 The pipe zone of each trench shall be constructed under the standard for the utility installed, and where that standard states no pipe-zone material, the pipe-zone material shall be as indicated in the datasheet.
Default Pipe-Zone Material Where the Utility Standard States Noneselect
ASTM D2321 Class I crushed stone
ASTM D2321 Class II clean sand and gravel
Native soil free of stones larger than 1 in.
Controlled low-strength material
NOTE Crushed stone gives a flexible pipe its haunch support on placement, with no compaction effort in the one place a compactor cannot reach, and is the material where the trench is wet; clean sand is the material for small-diameter irrigation and conduit where stone would abrade the pipe and a shovel-placed sand envelope is all the support the pipe needs; screened native soil is the least-cost envelope for a rigid pipe or a conduit in a dry trench in sandy soil, and it is the material a wet or clayey trench cannot use; CLSM encases the pipe without compaction where the trench is too narrow to work in, at the cost of floating the pipe unless it is restrained. (7.5.6)
7.5.7 Where the utility standard and this standard both state a pipe-zone requirement, the more stringent shall govern.
7.5.8 Excavated material shall not be stockpiled within 2 ft of the edge of a trench, and the setback shall increase to the height of the stockpile where the stockpile is more than 2 ft high.
7.5.9 Trenches shall not be left open overnight within 50 ft of an occupied building or a public way without barricades and lighting, and no trench shall be left open longer than the time needed to install, test, and backfill the utility in it.

7.6 Excavation Adjacent to Existing Structures

7.6.1 Before excavating within a horizontal distance from an existing foundation, pavement, or utility equal to the depth of the excavation below it, the Contractor shall survey and document the condition of that structure and shall deliver the survey to the Owner and the Engineer of Record.
7.6.2 Excavation shall not remove lateral or vertical support from an existing foundation, as required by IBC Chapter 18, by excavating below a plane rising at 1H:1V from the bottom edge of that foundation, unless the foundation is first underpinned or supported by an engineered system designed and installed under Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering.
7.6.3 The Contractor shall monitor each existing structure within the surveyed distance for movement or distress for the duration of the excavation adjacent to it, and shall report any change from the condition survey to the Engineer of Record within one working day.
7.6.4 Existing structures and utilities adjacent to the excavation shall be as shown on the existing conditions and demolition plans, and the Contractor shall locate every underground utility in the area of work by the one-call service and by hand digging within the tolerance zone the utility owner specifies before excavating with equipment.
NOTE A footing undermined by an adjacent excavation does not fail during the excavation; it fails later, after the backfill has been placed and nobody is watching, because the soil beneath its edge moved toward the open face and the footing rotated to follow it. (7.6.5)

7.7 Worker Protection in Excavations

7.7.1 Every excavation 5 ft or deeper, and every shallower excavation in which the competent person finds a cave-in hazard, shall be protected by sloping, benching, a trench shield, or a shoring system that conforms to 29 CFR 1926 Subpart P.
7.7.2 Sloping and benching shall conform to the maximum allowable slopes of 29 CFR 1926 Subpart P Appendix B for the soil type the competent person has classified, and timber and aluminum hydraulic shoring shall conform to the tabulated data of Appendices C and D.
7.7.3 An excavation deeper than 20 ft, an excavation whose protective system cannot be selected from the tabulated appendices, and an excavation whose support restrains movement of an adjacent structure shall be protected by a system designed under Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering.
7.7.4 Selection of the protective system is the Contractor's responsibility, and the Engineer of Record's review of the excavation safety plan does not approve or warrant the protective system.
7.7.5 The Contractor shall provide a ladder, ramp, or other means of egress within 25 ft of lateral travel of every worker in an excavation 4 ft or deeper.
7.7.6 No worker shall enter an unprotected excavation 5 ft or deeper for any purpose, including hand trimming, pipe laying, grade checking, or inspection.
7.7.7 A worker shall not work beneath a load suspended over an excavation, beneath the raised bucket of an excavator, or on the downhill side of a stockpile that can slide into the excavation.
7.7.8 Permanent cut slopes shall be finished to the slopes shown on the grading drawings and shall not be steeper than the maximum the geotechnical report permits for the soil at that location.

7.8 Stockpiles, Surplus, and Borrow

7.8.1 Stockpiles shall be located as shown on the staging and stockpile areas on the site plan, outside the limits of structural fill, foundations, and pavements, and outside the drip line of trees to remain.
7.8.2 Each stockpile shall be surrounded by the sediment controls required by Erosion And Sediment ControlErosion and Sediment ControlResolves to the current adopted revision.sync/erosion-and-sediment-control and shall be shaped to shed water.
7.8.3 The surcharge of a stockpile shall not be placed within a horizontal distance of any excavation, retaining wall, or buried structure equal to the height of the stockpile.
7.8.4 Excavated material in excess of the fill needed on the site shall be disposed of as indicated in the datasheet.
Surplus Excavated Material Dispositionradio
● Removed from the site and legally disposed
○ Placed as general site fill in designated areas
○ Stockpiled on the site for the Owner's use
NOTE Removal is the clean closeout and the position on a tight site; placing surplus as general site fill in a berm or a landscape area avoids the haul where the grading plan has room for it and the material meets the general site fill class; stockpiling for the Owner suits a campus or industrial site that will use the material on later work, at the cost of a stockpile the Owner then owns and has to protect. (7.8.5)
7.8.6 Where the fill needed on the site exceeds the suitable material excavated, the Contractor shall furnish borrow from an off-site source that has been accepted on a fill source report, or from an on-site borrow area where one is designated on the grading drawings.
7.8.7 An on-site borrow area shall be excavated to the limits and finished slopes the grading drawings show for it and shall be left draining, and material shall not be borrowed from any area that will carry a foundation, slab, or pavement.
7.8.8 Cut and fill quantities are the Contractor's to estimate from the grading drawings and the geotechnical report, and the Contractor shall not claim a change for a shortfall or surplus of on-site material unless it results from a differing site condition recorded under this standard.

8 Groundwater Control

NOTE Routine groundwater control within this standard is the collection and removal of seepage by sumps and pumps inside the excavation; the design and operation of wellpoint, deep well, eductor, and cutoff systems are the work of Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering, and this standard requires that work wherever sump pumping cannot hold the condition stated below. (8.1)
8.2 The Contractor shall keep every excavation free of standing water from the time it is opened until the fill, concrete, or utility in it has been placed to the height stated below.
8.3 The groundwater level within an excavation shall be held below the working surface by not less than the drawdown indicated in the datasheet throughout excavation, bearing surface preparation, fill placement, and compaction.
Minimum Drawdown Below the Working Surfacerange
ft
12345
8.4 Sumps shall be located outside the footprint of any footing and outside the pipe zone of any trench, and a sump excavated below the bearing elevation shall be backfilled with compacted crushed stone or lean concrete when it is abandoned.
8.5 Where sump pumping draws fines out of the excavation bottom or walls, causes the bottom to heave or boil, or cannot hold the groundwater at the required drawdown, the Contractor shall stop excavation, notify the geotechnical engineer of record, and provide an engineered dewatering system under Excavation Support And DewateringExcavation Support and DewateringResolves to the current adopted revision.sync/excavation-support-and-dewatering before resuming.
8.6 Groundwater control shall continue without interruption until the structure or fill in the excavation has reached a height at which the groundwater no longer affects its bearing, compaction, or stability, and shall not be discontinued abruptly where the geotechnical engineer of record has identified adjacent soils subject to consolidation on recharge.
8.7 A pipe, tank, vault, or basin placed in a trench or pit below the groundwater level shall be backfilled to a cover sufficient to resist flotation, or ballasted as its manufacturer requires, before groundwater control is discontinued.
8.8 Dewatering discharge shall pass through the sediment controls required by Erosion And Sediment ControlErosion and Sediment ControlResolves to the current adopted revision.sync/erosion-and-sediment-control and shall be routed to the destination indicated in the datasheet.
Dewatering Discharge Destinationselect
Storm drainage system through a sediment control device
Sanitary sewer with the utility owner's written approval
Vegetated area or infiltration basin on the site
Surface water under a discharge permit
Per drawings — the SWPPP (deferred by default)
NOTE Discharge to the storm system is the usual route and depends on the sediment control being sized for the pump rate rather than for runoff; discharge to the sanitary sewer is available only where the utility owner agrees and charges for it, and is the route where the groundwater is contaminated; land application on the site is the route where the site has room and the soil can take the flow; a surface-water discharge needs its own permit and its own monitoring and is the route where no other is available. (8.9)
8.10 Dewatering discharge shall not be routed into a storm or sanitary line that has not yet been tested and accepted, and shall not cause erosion, flooding, or sediment deposition on adjacent property.
8.11 Where groundwater control causes settlement of adjacent ground or structures, the Contractor shall stop pumping, notify the Owner and the Engineer of Record, and resume only under a revised plan the geotechnical engineer of record has accepted.

9 Fill and Backfill Placement

9.1 Preparation of the Surface to Receive Fill

9.1.1 Before fill is placed on any surface, that surface shall be stripped of topsoil, vegetation, and unsuitable material, and shall be proof-rolled and accepted under this standard where it will carry structural fill.
9.1.2 Where fill is placed on a slope steeper than 5H:1V, the slope shall be benched into firm material in steps not less than 2 ft high and wide enough for the compaction equipment, so each lift of fill is keyed into the slope.
9.1.3 Where the surface to receive fill is scarified, moisture-conditioned, and recompacted, the top 8 in. of that surface shall be compacted to the target for the fill above it before the first lift is placed.
NOTE Fill placed on an unbenched slope is a lift sitting on a ramp, and it moves down the ramp as a unit the first time the slope is saturated. (9.1.4)

9.2 Lift Placement

9.2.1 Fill shall be placed in horizontal lifts of uniform thickness across the full width of the fill area, and each lift shall be compacted and accepted before the next lift is placed.
9.2.2 The maximum loose lift thickness for fill compacted by rollers shall be as indicated in the datasheet.
Maximum Loose Lift Thickness, Roller-Compacted Fillrange
in
4681012
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.2.3 Where the geotechnical report does not state a lift thickness, the maximum loose lift thickness for roller-compacted fill shall be 8 in.
9.2.4 The maximum loose lift thickness for fill compacted by hand-operated plate compactors or rammers, in trenches above the pipe zone, against structures, and wherever rollers cannot operate, shall be as indicated in the datasheet.
Maximum Loose Lift Thickness, Hand-Compacted Fillrange
in
3468
NOTE A thick lift compacts at the top and stays loose at the bottom, and a density test taken in the top 6 in. passes it; the lift limit is set by the depth the compactor actually densifies, which is why the hand-compactor limit is lower than the roller limit and why a heavier roller can earn a thicker lift from the geotechnical engineer and a lighter one cannot. (9.2.5)
9.2.6 The Contractor shall select compaction equipment suited to the material: vibratory smooth-drum rollers for granular fill, padfoot or sheepsfoot rollers for cohesive fill, and plate compactors or rammers in confined zones.
9.2.7 Where the Contractor proposes a lift thickness greater than the datasheet value for a specific roller, the Contractor shall demonstrate it on a test strip of not less than 100 ft by 20 ft, with density tests at the top, middle, and bottom of the lift, and the geotechnical engineer of record shall accept or reject the thicker lift in writing for that roller and that material.

9.3 Moisture Conditioning

9.3.1 Fill shall be compacted at a moisture content within the window below and above the optimum moisture content of the reference compaction curve, as indicated in the datasheet.
Moisture Window Below Optimumrange
percentage points
05
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.3.2 The upper limit of the moisture window above optimum shall be as indicated in the datasheet.
Moisture Window Above Optimumrange
percentage points
05
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.3.3 Where the geotechnical report does not state a moisture window, fill shall be compacted at a moisture content within 2 percentage points below and 2 percentage points above optimum.
NOTE A window set dry of optimum, such as 3 below to 1 above, suits a clean granular fill that collapses on wetting if it is compacted dry and loose; a window set wet of optimum, such as 0 below to 4 above, suits an expansive clay that swells less when it is compacted wet and close to its final moisture; a symmetrical window is the general-purpose setting for the silty and clayey sands that make up most structural fill. The geotechnical report sets the window for the site's soil, and the fallback here is the symmetrical one. (9.3.4)
9.3.5 The Contractor shall measure the moisture content of each lift before compaction, by nuclear gauge per ASTM D6938 or by oven drying per ASTM D2216, and shall add water by distributor truck and mix it through the lift, or shall dry the lift by discing and aeration, until the moisture content is within the window.
NOTE Water sprayed on the surface of a lift and not mixed through it does not condition the lift, and a lift that is wet on top and dry below will not reach density at any number of passes. (9.3.6)
9.3.7 The Contractor shall not attempt to compact material outside the moisture window on the expectation that the density test will pass.

9.4 Compaction Targets by Use

NOTE Compaction targets in this standard are expressed as a percentage of the maximum dry density from the reference compaction curve selected under the field density testing provisions, and each target is tied to the surface the fill supports rather than to the material placed. (9.4.1)
9.4.2 Structural fill beneath footings, grade beams, slabs on grade, and equipment pads, and the upper 12 in. of native subgrade beneath them, shall be compacted to not less than the percentage of maximum dry density indicated in the datasheet.
Compaction Target, Fill Beneath Foundations and Slabsrange
% of maximum dry density
90929598100
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.4.3 Where the geotechnical report does not state a target for fill beneath foundations and slabs, the target shall be 95 percent of maximum dry density.
9.4.4 Fill beneath pavements and the upper 12 in. of native subgrade beneath them shall be compacted to not less than the percentage of maximum dry density indicated in the datasheet.
Compaction Target, Fill Beneath Pavementsrange
% of maximum dry density
90929598100
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.4.5 Where the geotechnical report does not state a target for fill beneath pavements, the target shall be 95 percent of maximum dry density.
9.4.6 General site fill in landscape areas, berms, and other areas that carry no structure, pavement, or utility shall be compacted to not less than the percentage of maximum dry density indicated in the datasheet.
Compaction Target, General Site Fillrange
% of maximum dry density
8588909295
Per drawings — the geotechnical report compaction recommendations (deferred by default)
9.4.7 Where the geotechnical report does not state a target for general site fill, the target shall be 90 percent of maximum dry density.
NOTE A higher target buys less settlement and a stiffer subgrade at the cost of more passes, a narrower moisture window, and more failed tests on a wet day; the 95 percent fallback is the figure beneath which footings and slabs are designed on most sites, a 98 or 100 percent target is set where the geotechnical report has a settlement-sensitive structure or a heavily loaded floor, and the general site fill target is set lower so landscape areas are not compacted to a density roots cannot penetrate. (9.4.8)
9.4.9 Where the geotechnical report states a compaction target for a use not listed above, that target shall govern for that use.
9.4.10 Where the fill is a clean crushed stone or a recycled concrete aggregate with no usable laboratory compaction curve, the geotechnical engineer of record shall accept compaction by relative density per ASTM D4253 and ASTM D4254 at not less than 70 percent, or by a method specification of lift thickness and roller passes demonstrated on a test strip, and the datasheet target shall not be applied to that material.

9.5 Backfill Adjacent to Structures and Walls

9.5.1 Backfill against foundation walls, retaining walls, and buried structures shall not be placed until the structure has reached the strength its standard requires for backfilling, until waterproofing and drainage against it have been installed and accepted, and until the wall is braced or its supporting floor is in place where the wall design depends on that support.
9.5.2 Backfill material against below-grade walls, beyond the drainage envelope required by Foundation DrainageFoundation DrainageResolves to the current adopted revision.sync/foundation-drainage, shall be as indicated in the datasheet.
Backfill Material Against Below-Grade Wallsselect
Free-draining granular fill
Structural fill
General site fill
Controlled low-strength material
NOTE Free-draining fill behind a wall keeps hydrostatic pressure off the wall and the waterproofing and is the material where no drainage composite is installed on the wall face; structural fill is the material where the backfill also carries a slab, pavement, or footing above it; general site fill is the economical backfill where a drainage composite handles the water and the surface above is landscape, at the cost of a clay that swells against the wall if the window is not held; CLSM backfills a narrow space between a wall and a shored excavation face where nothing else can be compacted, and loads the wall as a fluid while it sets. (9.5.3)
9.5.4 Backfill against a structure shall be placed in lifts on both sides of the structure at the same time, with the difference in fill height across a wall not exceeding 2 ft unless the wall is designed for the unbalanced load.
9.5.5 The maximum particle size in backfill within 24 in. of a structure, a waterproofed or dampproofed surface, or a drainage composite shall be as indicated in the datasheet.
Maximum Particle Size in Backfill Adjacent to Structuresrange
in
0.7511.5234
9.5.6 Heavy compaction equipment shall not operate within the setback from a wall, buried structure, or waterproofed surface indicated in the datasheet, and backfill within that setback shall be compacted with hand-operated plate compactors or rammers in lifts not exceeding the hand-compacted lift thickness in the datasheet.
Heavy Equipment Setback From Walls and Buried Structuresrange
ft
23456810
NOTE A roller against a wall delivers a lateral load the wall was not designed for and a vibration that cracks the waterproofing and dislodges the drainage composite, while hand equipment in thin lifts reaches the same density without either; the setback is set wider where the wall is tall, cantilevered, or carries a brittle coating, and narrower where it is a short wall with a membrane that tolerates it, and the particle size limit keeps the stone that would puncture a membrane out of the zone where it would be pressed against one. (9.5.7)
9.5.8 Backfill against a structure shall be compacted to the target for the surface it supports, and not less than the general site fill target.
9.5.9 Backfill against waterproofed surfaces shall also conform to the lift and equipment limits of Below Grade WaterproofingBelow-Grade WaterproofingResolves to the current adopted revision.sync/below-grade-waterproofing, and the more stringent limit shall govern.

9.6 Trench Backfill Above the Pipe Zone

9.6.1 Trench backfill above the pipe zone shall be placed in lifts not exceeding the hand-compacted lift thickness in the datasheet until 24 in. of compacted cover is in place over the pipe crown, and in roller-compacted lifts thereafter.
9.6.2 Trench backfill above the pipe zone shall be compacted to the target in this standard for the area in which the trench falls: the foundation and slab target within the building footprint and within 5 ft of any footing, the pavement target beneath pavements and within 5 ft of the pavement edge, and the general site fill target elsewhere.
9.6.3 Trench backfill above the pipe zone shall be structural fill wherever the trench falls within the building footprint, beneath a pavement, or within 5 ft of a footing or pavement edge, and shall be general site fill or structural fill elsewhere.
9.6.4 Compaction equipment shall not be operated over a pipe until the cover the utility standard requires for construction loading is in place.
9.6.5 Water jetting and flooding shall not be used to consolidate trench backfill.
NOTE Jetting consolidates a clean sand and does nothing to anything else, and the trench it is used in is rarely clean sand all the way up; the pavement over a jetted trench settles into the voids the water left behind. (9.6.6)
9.6.7 Where a trench crosses a pavement or a slab that is already in place, the Contractor shall saw-cut the edges, shall backfill the trench with structural fill or CLSM to the subgrade, and shall restore the aggregate base and the surface under the standards for those materials.

9.7 Backfill of Cavities and Voids

9.7.1 Cavities left by grubbing, by removal of foundations, basements, tanks, utilities, and other buried structures, and by extraction of sheet piles, soldier piles, and wellpoints, shall be backfilled under this standard after the removal has been verified by the party responsible for it.
9.7.2 A cavity within the building footprint, beneath a pavement, or within the structural fill zone shall be backfilled with structural fill compacted to the target for the surface above it, after the sides of the cavity have been benched or the loose material removed so the fill keys into firm ground.
9.7.3 A cavity below the groundwater level, a cavity too narrow to compact in, and a cavity beneath a structure that cannot be undermined shall be backfilled with CLSM or compacted crushed stone placed through the water or into the void, as the geotechnical engineer of record directs.
9.7.4 Where a basement or foundation wall is left in place below grade under the demolition scope, the Contractor shall breach the floor and walls at the intervals the demolition standard requires before backfilling, so the backfilled cavity drains.
NOTE An intact basement slab left under a new building is a bathtub, and the fill placed in it stays saturated and soft no matter how it was compacted. (9.7.5)

10 Subgrade Acceptance and Proof Rolling

10.1 Proof Rolling Procedure

10.1.1 Every subgrade that will carry structural fill, a slab, a pavement, or an aggregate base course, and every structural fill surface on which a slab, pavement, or base course will be placed, shall be proof-rolled in the presence of the geotechnical engineer of record and accepted in writing before the next material is placed on it.
10.1.2 Proof rolling shall be performed with a loaded rubber-tired vehicle, a tandem-axle or tri-axle dump truck or a pneumatic-tired roller, with a gross loaded weight not less than that indicated in the datasheet.
Proof-Rolling Vehicle Minimum Gross Weightrange
tons
101520253040
10.1.3 Proof rolling shall cover the entire area in overlapping passes in two perpendicular directions, at a speed not exceeding 3 mph, and the geotechnical engineer of record shall mark every area that ruts, pumps, deflects, or rebounds.
10.1.4 An area that deflects or ruts more than the limit indicated in the datasheet under the proof-rolling vehicle, or that pumps or rebounds visibly, shall be rejected and stabilized under this standard before it is re-proof-rolled.
Proof-Rolling Deflection Limitrange
in
0.511.52
NOTE A heavier vehicle and a tighter deflection limit find the soft spots that a slab or a pavement would find later, at the cost of rejecting a subgrade that a lighter check would have passed and of a rejected area the Contractor has to stabilize; the 20-ton tandem and a 1 in. limit are the usual pairing beneath pavements and building pads, a 25 to 30 ton tri-axle and a 0.5 in. limit are set where the pavement carries heavy truck traffic or the floor carries racking, and a lighter vehicle and a looser limit are set over a utility corridor where a heavy truck would damage the pipes beneath. (10.1.5)
10.1.6 Proof rolling shall not be performed on a subgrade that is frozen, that has standing water on it, or that was wetted by rain within the previous 24 hours unless the geotechnical engineer of record directs that it proceed.
10.1.7 A subgrade accepted by proof rolling shall be re-proof-rolled if it is exposed to rain, freezing, or construction traffic after acceptance and before the next material is placed, and the Contractor shall protect an accepted subgrade from each of these.
NOTE Proof rolling is the test the density test cannot replace: a density test proves the top 6 in. of one spot, while a loaded truck proves the whole area to the depth its load reaches, and it is the soft lens 18 in. down beneath a passing density test that a proof roll finds. (10.1.8)

10.2 Subgrade Stabilization Where Proof Rolling Fails

10.2.1 An area rejected by proof rolling shall be stabilized by the method indicated in the datasheet, to the depth and extent the geotechnical engineer of record directs at each occurrence, and shall be re-proof-rolled and accepted before the next material is placed.
Subgrade Stabilization Method Where Proof Rolling Failsselect
Scarify, moisture-condition, and recompact
Undercut and replace with structural fill
Undercut and replace with crushed stone
Undercut, separation geotextile, and crushed stone
Geogrid-reinforced crushed stone platform
Chemical treatment
NOTE Scarifying and recompacting corrects a surface that is wet or loose but sound below, and does nothing for a soft stratum beneath it; undercutting and replacing with structural fill corrects a shallow soft zone where the replacement can be compacted in lifts and tested; crushed stone replaces fill where the undercut bottom is wet and nothing with a Proctor curve could be compacted on it; a separation geotextile beneath the stone, under GeosyntheticsGeosynthetics and GeotextilesResolves to the current adopted revision.sync/geosynthetics, keeps the stone from being pushed into a fine-grained bottom and lets a thinner stone layer do the work; a geogrid platform bridges a deep soft zone with the least stone where undercutting to firm material is not practical; chemical treatment under Soil StabilizationSoil Stabilization and ModificationResolves to the current adopted revision.sync/soil-stabilization dries and strengthens a wet clay in place over a large area where undercutting would move too much material. (10.2.2)
10.2.3 Where the rejected area results from a soft or wet condition the geotechnical report identified at that location, or from the Contractor's own traffic, exposure, or failure to protect an accepted subgrade, stabilization shall be at the Contractor's expense; where it results from a condition the geotechnical report did not identify, stabilization shall be paid as a change.
10.2.4 The Contractor shall record each stabilized area, its extent and depth, and the method used, and shall include the record in the proof-rolling records.

11 Field Density Testing and Acceptance

11.1 Compaction Reference and Test Methods

11.1.1 The laboratory compaction curve against which field density is compared shall be developed for each fill material by the reference method indicated in the datasheet, which shall be the method on which the geotechnical report's compaction recommendations are based.
Laboratory Compaction Reference Methodradio
○ ASTM D698 standard effort
○ ASTM D1557 modified effort
Derived — the compaction test method on which the geotechnical report states its compaction recommendations (by default)
NOTE Modified effort produces a maximum dry density several pounds per cubic foot higher and an optimum moisture several points lower than standard effort on the same soil, so 95 percent of one is not 95 percent of the other, and a target stated against the wrong curve is either unachievable or meaningless; the method follows the geotechnical report because the report's bearing and settlement analysis assumed one of them, and the field cannot choose the other. (11.1.2)
11.1.3 A new laboratory compaction curve shall be developed whenever the fill material changes in classification, gradation, or plasticity from the material on which the current curve was run, and the geotechnical engineer of record shall direct a one-point check per ASTM D698 or ASTM D1557 whenever field results suggest the curve no longer represents the material.
11.1.4 Field density and moisture shall be measured by the method indicated in the datasheet.
Field Density Test Methodselect
Nuclear gauge, ASTM D6938
Sand cone, ASTM D1556/D1556M
Rubber balloon, ASTM D2167
Drive cylinder, ASTM D2937
NOTE The nuclear gauge tests a spot in a few minutes without disturbing it, which lets the same spot be retested after more passes and lets a technician keep pace with the fill; the sand cone is the reference method that the gauge is checked against and the method where a gauge cannot be licensed or carried; the rubber balloon serves the same role in a fine-grained soil where the sand cone's hole will not hold; the drive cylinder tests a cohesive soil where a sample can be taken intact, and cannot test gravel or stone. (11.1.5)
11.1.6 Field density tests shall be taken in the full depth of the lift being tested, with the gauge probe set to the depth of the lift, and not in the surface crust.

11.2 Testing Frequency

11.2.1 Field density tests on fill and backfill beneath foundations, slabs, pavements, and within the structural fill zone shall be taken at not less than one test per lift for each area of fill surface indicated in the datasheet, and not less than one test per lift in any such area.
Fill Area Per Density Test, Structural Fill Zonesrange
sq ft per test per lift
500100015002000250030005000
11.2.2 Field density tests on general site fill shall be taken at not less than one test per lift for each area of fill surface indicated in the datasheet, and not less than one test per lift in any such area.
Fill Area Per Density Test, General Site Fillrange
sq ft per test per lift
100025005000750010000
11.2.3 Field density tests on trench backfill above the pipe zone shall be taken at not less than one test per lift for each length of trench indicated in the datasheet, and not less than one test per lift in any trench.
Trench Length Per Density Testrange
linear ft per test per lift
50100150200300
NOTE A denser testing grid catches a thin lift or a dry zone before the next lift buries it, at the cost of a technician who cannot keep pace with a large fill; the 2,500 sq ft grid beneath structures and the 100 ft trench interval are the usual settings, a 500 to 1,000 sq ft grid is set beneath a mat foundation or a heavily loaded floor, and the general site fill grid is opened up because the consequence of a soft spot in a lawn is a depression rather than a crack. (11.2.4)
11.2.5 Where the geotechnical report states a testing frequency, the report's frequency shall govern, and the geotechnical engineer of record may increase the frequency in any area that shows variable material, variable moisture, or failing tests.
11.2.6 The testing agency shall take not less than one field density test on each day on which fill is placed, in each distinct fill area, regardless of the area placed.

11.3 Failing Tests and Retesting

11.3.1 Where a field density test fails the target, the Contractor shall scarify the lift, adjust its moisture to within the window, recompact it, and request a retest at the same location before placing the next lift.
11.3.2 Where the retest also fails, the Contractor shall remove the lift to the previously accepted surface, or shall rework the lift with the material, moisture, equipment, or lift thickness changed as the geotechnical engineer of record directs, and shall retest.
11.3.3 The cost of retesting after a failed test, and of the rework, shall be borne by the Contractor.
11.3.4 Where tests in an area fail repeatedly, the geotechnical engineer of record shall determine whether the material, the moisture, the equipment, or the lift thickness is the cause and shall direct the change in writing.
NOTE A failed test reported after the next lift is placed cannot be retested at the same location, and the lift above it has to come off to reach it; the reporting requirement below exists so the failure is known before that happens. (11.3.5)
11.3.6 Fill placed over a failed lift before the retest has passed shall be removed at the Contractor's expense.

11.4 Test Records

11.4.1 Each field density test shall be recorded with the project, date, test number, location by coordinates or by station and offset, lift number and elevation, material and its reference curve, wet density, moisture content, dry density, percent of maximum dry density, the target, and the pass or fail result.
11.4.2 The testing agency shall report each failing test to the Contractor's superintendent and to the geotechnical engineer of record on the day the test is taken, before the next lift is placed over it.
11.4.3 The testing agency shall deliver the written report of each day's tests to the Owner, the Engineer of Record, the geotechnical engineer of record, and the Contractor within 24 hours of the tests.
11.4.4 Failing tests shall appear in the written reports with their retests, and a report that omits a failing test shall be corrected and reissued.

12 Warranty

12.1 The Contractor shall warrant the earthwork against settlement, heave, and loss of grade attributable to nonconforming fill material, placement, moisture, or compaction for the period indicated in the datasheet, beginning at substantial completion.
Earthwork Warranty Periodrange
years
1235
NOTE A one-year correction period matches the general warranty of most construction contracts and catches the settlement that appears through the first wet season and the first freeze; a longer period is set where the fill is deep, where the structure above it is settlement-sensitive, or where the Owner has had fill settle on earlier work and wants the exposure to last past the second winter. (12.2)
12.3 Warranty correction shall include removal and replacement of the nonconforming fill, restoration of the surface and of the structure, pavement, utility, or landscape above it, and the repair of damage to adjacent work caused by the settlement or by the correction, at the Contractor's expense.
12.4 Where the parties disagree whether settlement is attributable to nonconforming earthwork or to a cause outside the Contractor's control, the geotechnical engineer of record shall make the initial determination.
12.5 The warranty does not limit the Owner's remedies for a latent defect in fill or compaction discovered after the warranty period.