315000 - Excavation Backfill and Compaction.pdf

WCU Project No. WC2608 SWOPE Stormwater Basin Retrofit Project

October 8, 2026

EXCAVATION, BACKFILL, AND COMPACTION 315000-1

RETTEW Project No.: 0272903615

DIVISION 31 - EARTHWORK

SECTION 315000 - EXCAVATION, BACKFILL AND COMPACTION

PART 1 - GENERAL

1.1 SECTION INCLUDES

A. Excavation, backfill and compaction requirements for buildings and other site structures.

B. Excavation, backfill and compaction requirements for general site.

C. Site grading.

1.2 DEFINITIONS

A. Excavation: Removal of all materials of any kind or nature encountered in completion of the Work, including rock, to the elevations required and subsequent disposal of materials removed.

B. Subgrade: Areas upon which the planned bottoms of foundations, footers, slabs, paving base courses, sidewalks or additional materials including topsoil shall rest; or if foundation fill or subbase is to be utilized beneath a structure, the surface upon which the foundation fill or subbase shall rest.

C. Fill: Material required to bring the proposed finished grades above the existing grades.

D. Random Backfill: Non-select material required to replace material excavated for the purpose of constructing site structures.

E. Structure Backfill: Select open-graded, free-draining material for use in backfilling against structure walls.

F. Foundation Fill: Structure fill material to be utilized beneath structure foundations, where required to replace unsuitable soil or rock encountered.

G. Subbase: Compacted aggregate material utilized under sidewalks, slabs-on-grade, and paving sections.

1.3 REFERENCES

A. ASTM D698-00a Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort.

B. ANSI/ASTM D1556- Test methods for density of soil in place by the sand-cone method.

C. ASTM D2922- Test methods for density of soil and soil-aggregate in place by nuclear methods (Shallow Depth).

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D. ASTM D3017-01 Standard Test Method for Water Content of Soil and Rock in Place by Nuclear Methods (Shallow Depth).

E. Pennsylvania Department of Transportation (PennDOT) Specifications Publication 408, as amended.

1.4 SUBMITTALS

A. Material Test Reports: From a qualified testing agency indicating and interpreting test results for compliance of the following with requirements indicated:

1. Classification according to ASTM D 2487 of each on-site or borrow soil material proposed for fill and backfill.

2. Laboratory compaction curve according to ASTM D 1557 for each on-site or borrow soil material proposed for fill and backfill.

3. Laboratory compaction curve according to ASTM D 1557 for each aggregate material proposed for fill and backfill.

4. Density test reports for subgrades, fills and backfills.

B. Comply with applicable requirements of NFPA 495, "Explosive Materials Code."

C. Seismic Survey Agency: An independent testing agency, acceptable to authorities having jurisdiction, experience in seismic surveys and blasting procedures to perform the following services:

1. Report types of explosive and sizes of charge to be used in each area of rock removal, types of blasting mats, sequence of blasting operations, and procedures that will prevent damage to site improvements and structures on Project site and adjacent properties.

2. Seismographic monitoring services during blasting operations.

D. Geotechnical Testing Agency Qualifications: An independent testing agency qualified according to ASTM E 329 to conduct soil materials and rock-definition testing, as documented according to ASTM D 3740 and ASTM E 548.

1.5 QUALITY ASSURANCE

A. Source Quality Control

1. Independent Laboratory Tests: Furnish Engineer two copies of test result reports.

B. Aggregate Material Test

1. Conduct aggregate quality tests in accordance with requirements of appropriate

Referenced Standard for such material.

2. All aggregate material must be certified from supplier that the aggregate originates from a source approved by PennDOT and that the aggregate complies with specified PennDOT requirements.

C. Field Quality Control

1. All field quality control testing must be supervised by a Professional Engineer.

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1.6 JOB CONDITIONS

A. Unclassified Excavation: No consideration will be given to the nature of materials encountered in excavating operations for structures. Therefore, as unclassified excavation, no additional payment will be made for difficulties occurring in excavating and handling of materials.

B. Borrow Excavation: If the required quantity of backfill exceeds the quantity of suitable material excavated within the limits of the project site and rights-of-way, obtain sufficient material to complete the backfill at no additional cost to OWNER. If borrow excavation is needed, notify ENGINEER sufficiently in advance of borrow excavation requirements to permit ENGINEER to verify the need for such borrow excavation and to view the proposed borrow pit and determine the suitability of the material to be provided. Use of borrow excavation from offsite must be approved by ENGINEER. Any tests required by ENGINEER to assist in determining suitability of the borrow materials shall be responsibility of CONTRACTOR and completed at no increase in Contract Price.

PART 2 - PRODUCTS

2.1 MATERIALS

A. Subbase Material: Coarse aggregate consisting of naturally or artificially graded mixture of natural or crushed gravel, crushed stone, or crushed slag meeting the requirements of PennDOT Publication 408 for No. 2A material or No. OGS material, Type C or better.

B. Foundation Fill: Evenly graded mixture of crushed stone or crushed or uncrushed gravel meeting the requirements of PennDOT Publication 408, Section 703.3 for Select Granular Material.

C. Random Backfill and Fill Materials: Suitable material conforming to the requirements of PennDOT Publication 408, Section 206.2(a), reasonably free of organic matter such as leaves, grass, roots, sod, sewage, coal or coal blossom, or other unsuitable material. Frozen material shall not be utilized.

D. Structure Backfill: Open-graded coarse aggregate meeting the requirements of PennDOT Publication 408 for AASHTO No. 57.

PART 3 - EXECUTION

3.1 REQUIREMENTS AND RESTRICTIONS

A. Keep excavations free from water.

1. If required, lower water table below excavation bottom by deep wells, well points and pumping. Initiate dewatering activities sufficiently in advance of excavating to stabilize groundwater table in area of excavation below excavation bottom, prior to starting any excavating. Provide and operate pumps of sufficient capacity for dewatering the excavations. Dispose of water removed from excavations in a manner that will not cause injury to the public health, to public or private property, to the work of other contractors, to any portion of the Work completed or in progress, or to produce impediment to the use

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RETTEW Project No.: 0272903615 of highways, roads, lanes, and streets by the public. No additional payment will be made for pumping or other difficulties encountered due to water.

B. Maintain sewers, drains and ditches free of debris to convey surface drainage. No damming or ponding of water in gutters or other waterways will be permitted. Do not direct flow of water across pavements except through approved pipes or properly constructed troughs. Provide pipes or troughs of such sizes and lengths as may be required. Control grading in the vicinity of excavations so the ground surface is properly pitched to prevent water from running into excavated areas.

C. Control groundwater and surface water during construction in order to maintain soil stability.

Maintain the water table elevation sufficiently below the levels of excavations that slopes will remain stable and bottoms of excavations will not become loosened by flow of water. If the foundation material loses its strength due to improper dewatering techniques, over-excavate the material and replace it with Foundation Fill at no additional cost to OWNER.

D. Do not perform excavating, backfilling, or compacting when weather conditions or the condition of materials are such, that in the opinion of ENGINEER, the Work cannot be completed in accordance with the Specifications.

E. Do not use as backfill or fill, frozen materials or wet materials containing moisture in excess of the amount necessary for satisfactory compaction.

F. Prior to use, moisten dry backfill material not having sufficient moisture to obtain satisfactory placement or compaction.

G. Prevent spread of dust during performance of work by thoroughly moistening excavation areas by sprinkling or other methods approved by ENGINEER.

H. No right of ownership of excavated materials is granted to CONTRACTOR prior to backfilling.

This provision does not relieve CONTRACTOR of his responsibility to remove and dispose of surplus excavated material. Excess excavated material that cannot be used at the site shall be removed and disposed of in a legal manner at no additional expense to OWNER.

I. Assume sole responsibility for the condition and results of excavations. Slides and cave-ins shall be removed without additional compensation at whatever time and under whatever circumstances they may occur.

J. Protect all pipes, conduits, walls, buildings and other structures or property whether above or below ground, or that may appear in the excavation. Maintain sufficient quantity of material and equipment on the site and for use as necessary for sheeting, sustaining, and supporting any pipes, conduits, walls, building, structure or property.

3.2 EXPLOSIVES

A. The use of explosives shall be prohibited.

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3.3 EXCAVATION

A. General Procedures:

1. Perform excavation using machinery, except where hand excavation may be required to protect existing structures, process piping, plant conduits, utilities or private or public properties. No additional compensation will be paid for hand excavation instead of machine excavation as may be necessary from any cause whatever.

2. Perform excavation of every description and of whatever substances encountered to the elevations indicated by the Drawings and as specified herein.

3. Where work space is limited, remove excavated material from the limited area and replace the material after the work has been completed. No additional compensation will be made for such removal and replacement of the excavated material.

4. Extend excavation a sufficient distance from footings and foundations to permit placing and removal of concrete formwork, installation of services, other construction and for inspection.

B. Remove rock that has been shattered due to rock removal operations and in the opinion of ENGINEER is unfit for foundations to an elevation below subgrade. Fill to subgrade with Foundation Fill those areas where shattered rock has been removed. Perform such backfilling to the satisfaction of ENGINEER. No separate or additional payment will be made for such removal and backfill.

C. Excavation Below Planned Subgrade:

1. Do not excavate below depths indicated on the Drawings or such depths as required for the proper installation of the Work, unless otherwise directed by ENGINEER.

2. Excavation below depths indicated on the Drawings or as required for the proper installation of the Work through the fault of the CONTRACTOR, shall be restored to the indicated or required depths with Foundation Fill at the expense of CONTRACTOR.

3. If the foundation for any structure is required by ENGINEER to be carried lower than the planned subgrade elevation, the over-excavation shall be backfilled up to planned subgrade elevation with Foundation Fill. Payment for this additional work will be made in accordance with the applicable General Provisions.

D. Storage of Approved Materials:

1. Store on site all unused approved materials.

2. Do not mix unused approved materials of differing types.

3. Do not mix unused approved materials with unapproved materials.

3.4 SUBGRADE PREPARATION

A. General Procedures:

1. Where subgrade consists of an excavated soil surface, thoroughly machine-tamp the existing material. Compact the exposed soils until no movement is observed or as directed by the ENGINEER. Remove and replace soft, loose, and disturbed zones disclosed by the tamping. Over-excavate to the depth directed by ENGINEER and replace with Foundation Fill; compact as indicated in these specifications.

2. Where subgrade consists of an elevated fill surface, compact the fill as indicated elsewhere in these specifications. Shape the surface to the required lines and grades.

3. Where subgrade consists of an excavated rock surface, thoroughly inspect the bedrock bearing surfaces, and clean any exposed soil-filled seams with water jets or compressed

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4. If Foundation Fill is indicated on the Drawings or required by these specifications, or if required to replace unsuitable material as directed in the field by the ENGINEER, place the material uniformly and without segregation of coarse and fine material. Place the material in maximum 12-inch lifts and compact with vibratory equipment. Satisfactory compaction will be based on non-movement of the material.

B. Approval of Subgrade

1. Notify Geotechnical Engineer when excavations have reached required subgrade.

2. If Geotechnical Engineer determines that unsatisfactory soil is present, continue excavation and replace with compacted backfill or fill material as directed.

3. Proof roll subgrade with heavy pneumatic-tired equipment to identify soft pockets and areas of excess yielding. Do not proof roll wet or saturated subgrades.

4. Reconstruct subgrades damaged by freezing temperatures, frost, rain, accumulated water, or construction activities, as directed by Geotechnical Engineer.

3.5 BACKFILLING

A. General Procedures:

1. Perform backfilling using machinery, except where hand backfilling is required to prevent damage to walls, foundations, utilities, plant conduits or process piping. No additional compensation will be paid where backfilling by hand is required.

2. Remove any trash and debris from excavation prior to backfilling.

3. Do not place backfill material prior to seven days after completion of structure walls, and then only if the concrete or mortar has achieved 80 percent of the specified 28-day compressive strength.

4. Do not place backfill material on wet or frozen areas.

5. Do not operate heavy equipment closer to walls than a distance equal to the height of backfill material above the top of the structure footing.

6. Do not place backfill material against exterior walls until supporting floors, other reinforcing or supporting members, or slabs at top of walls are in place.

7. Do not place backfill material against water containing concrete structures or manholes until water testing has been satisfactorily completed.

8. Perform compaction using power driven tampers or compactors suitable for material being placed.

B. Random Backfill:

1. Use random backfill where structure backfill is not required or specified. Use of structure backfill in lieu of random backfill is allowed.

2. Place random backfill in loose, uniform horizontal layers not exceeding eight inches in depth.

3. Maintain moisture content of random backfill at compaction within two percent of optimum moisture as determined by ASTM D 698.

4. Compact random backfill to at least 95 percent of the maximum dry-weight density based on ASTM D 698.

C. Structure Backfill:

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1. Place structure backfill behind all structure walls if indicated on the drawings. Place structure backfill in 8-inch lifts and thoroughly compact each lift with a vibratory compactor to the satisfaction of ENGINEER.

3.6 EMBANKMENTS AND FILLS

A. Where fill is required to raise the subgrade to the elevations indicated on the Drawings, such fills shall be made with suitable materials, equipment, and workmanship, and under control and supervision of an approved testing laboratory. Where such fills exceed 8 inches in depth, the fill shall be constructed before proceeding with work on the subgrade.

B. Testing: Include in Bid Price costs for performing all laboratory and field compaction tests necessary to insure an adequate fill of uniform quality. Prior to commencing fill work, laboratory tests shall be performed based on ASTM D1557 on the material to be used to establish the compacted dry weight at optimum moisture. Results shall be submitted to ENGINEER for approval. Field tests of moisture content prior to compaction and dry weight after compaction shall be made and submitted to ENGINEER for approval; one set of these tests shall be made for each 100 square yards of each layer; additional tests shall be made if soil or moisture conditions change; results of tests shall be submitted to ENGINEER.

C. Construction

1. Area to be filled shall be cleared of all loose material and inspected and approved by

ENGINEER. The surface shall then be loosened to a depth of at least 4 inches and satisfactorily compacted. Fill material shall be free from frost and shall not be placed on frozen ground. It shall be deposited in layers of such thickness as required by the nature of the soil or as directed, but the uncompacted thickness of each layer shall not exceed 8 inches. Each layer shall be separately compacted to a uniform solid mass by machine rolling or other approved means. Fill shall be placed in horizontal layers, beginning with the lowest areas and building up until the entire areas to be filled is at a uniform elevation.

CONTRACTOR shall control the moisture content of the fill material, to insure maximum density by either the addition of water, or by harrowing and working the soil prior to compacting. Each layer shall be free of ruts and shall meet compaction requirements before a succeeding layer is placed. Compaction of each layer shall continue until no weaving or creeping takes place.

2. Field tests of moisture content prior to compaction and density after compaction shall be made to insure thorough and uniform compaction. One set of the latter tests shall be made for each 200 square yards of each layer. Additional tests shall be made if soil or moisture conditions change.

D. Required Compaction Results

1. All fills under concrete floor slabs or areas for vehicular traffic shall be compacted to not less than 100 percent of the maximum dry-weight density at optimum moisture as specified above.

2. All other fills or embankments shall be compacted to not less than 95 percent of the maximum dry-weight density at optimum moisture as specified above.

3. Whenever in-place density, according to the tests noted above, is found to be below acceptable limits, additional compaction will be required to produce the specified density, as shown by additional tests.

E. Required Grading Tolerances

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1. Foundations: ±0.02 feet of indicated grade

2. Vehicular Traffic Areas: ±0.10 feet of indicated grade

3. Topsoiled Areas: ±0.15 feet of indicated grade

4. Swales or Stormwater Management Areas: ±0.10 feet of indicated grade

3.7 SUBBASE

A. General:

1. Do not place subbase material on soft, muddy, or frozen subgrades. Satisfactorily correct irregularities or soft zones in the prepared area.

B. Placement and Compaction:

1. Place subbase material in maximum 8" lifts. When using PennDOT No. 2A material, compact to 100 percent of the maximum dry-weight density. When using PennDOT No.

OGS material, satisfactory compaction will be based on non-movement of the material.

3.8 FIELD QUALITY CONTROL

A. Testing

1. ENGINEER shall inspect and approve subgrades and fill layers before further construction work is performed. CONTRACTOR shall have field density tests performed in accordance with ASTM D 1556, ASTM D 2167 or ASTM D 2922. If methods of ASTM D 2922 are used for density testing, moisture content must be determined by ASTM D 3017.

2. All testing to be completed by independent testing agency.

3. Soil Subgrades for Structure Foundations: For each strata of soil on which footing or foundation will be placed, conduct at least one test to verify required design bearing capacities. Subsequent verification and approval of each footing or foundation subgrade may be based on a visual comparison of each subgrade with related tested strata, when acceptable to ENGINEER.

4. Subgrades and Subbase for Floor Slabs on Grade and Areas for Vehicular Traffic: Make at least one field density test of subgrade and subbase for every 200 sq. ft. of paved area or floor slab, but in no case less than 3 tests. In each compacted fill layer, make one field density test for every 200 sq. ft. of overlaying building slab, but in no case less than 3 tests.

5. Subgrades and subbase for Other Areas: Make at least one field density test of subgrade and subbase for every 500 ft. of embankment for each 1.5 feet elevation lift, but in no case less than 3 tests. In each compacted fill layer, make one field density test for every 500 sq.

ft. of overlaying building slab, but in no case less than 3 tests.

6. Random Backfill: Take at least 2 field density tests per lift, when applicable, at locations and elevations as directed.

B. Corrective Measures:

1. Whenever tests indicate that the field moisture or density does not meet specified requirements, take corrective action as approved by ENGINEER.

2. Corrective measures may include loosening the soil and wetting or drying it prior to recompaction, additional compaction, or removing and replacing the material.

3. Retest material that did not meet the moisture and density requirements after corrective measures have been performed.

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C. Retesting: ENGINEER may at any time require retesting of any material, whether in stockpiles or being placed, if it appears that the material differs from that which has previously been approved for use.

D. Surface Tolerance:

1. Check finished subgrade for smoothness and elevation in accordance with the following:

a. Use approved template conforming the required design requirement indicated on the Drawings for checking crown, contour and sideslopes.

b. Use approved 10-foot straight edge to check longitudinal irregularities in the subgrade.

c. Use string lines for controlling the finished elevation.

2. Corrective Measures:

a. Whenever tests indicate the surface tolerances does not meet the requirements, take corrective action as approved by ENGINEER.

b. Corrective measures may include scarifying soil or aggregate, removing excess material, filling low spots, reshaping and compacting to the required surface.

c. Retest material (including moisture and compaction) that did not meet the surface tolerance after corrective measures have been performed.

3.9 DISPOSAL OF SURPLUS AND WASTE MATERIALS

A. Disposal: Transport surplus satisfactory soil to designated storage areas on Owner's property.

Stockpile or spread soil as directed by Engineer.

B. Remove waste material, including unsatisfactory soil, trash, and debris, and legally dispose of it off Owner's property.

END OF SECTION 315000

D. Geotechnical Testing Agency Qualifications: An independent testing agency qualified according to ASTM E 329 to conduct soil materials and rock-definition testing, as documented according to ASTM D 3740 and ASTM E 548.