64-Sec 31 23 33 Excavation Backfill and Compaction.pdf

EXCAVATION, BACKFILL AND COMPACTION

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SECTION 31 23 33

PART 1 - GENERAL

1.01 SECTION DESCRIPTION

A. The Work of this Section Includes:

1. Excavation, backfill and compaction associated with utility construction, including such related features as protection of adjacent utilities and structures, maintenance and protection of traffic, cutting paved surfaces, support of excavation, control of excavated materials, dewatering, pipe bedding, disposal of excavated materials, rough grading and restoration.

2. Excavation, backfill and compaction associated with construction or installation of structures including such related features as protection of adjacent utilities and structures, support of excavation, control of excavated materials, dewatering, structure bedding, disposal of excavated materials, rough grading and restoration.

1.02 RELATED SECTIONS

A. Related Work Specified Elsewhere:

1. Section 01 56 39: Landscape Protection.

2. Section 01 57 13: Soil Erosion and Sediment Control.

3. Section 31 11 00: Clearing and Grubbing.

4. Section 32 92 00: Finish Grading, Seeding and Sodding.

1.03 QUALITY ASSURANCE

A. Testing Agent:

1. Any required compaction testing for this Work shall be performed by a soils testing agent engaged and paid for by Contractor and approved by Engineer.

B. Reference Standards:

1. Pennsylvania Department of Transportation:

Regulations Governing Occupancy of Highways by Utilities (67 PA Code, Chapter 459) Publication 408 Specifications Pennsylvania Test Method, PTM 106 Pennsylvania Test Method, PTM 402 Publication 203, Work Zone Traffic Control

2. American Society for Testing and Materials (ASTM):

ASTM D1557 Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft.- lbf/ft3)

ASTM D2922 Standard Test Method for Density of Soil and Soil - Aggregate in

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Place by Nuclear Methods (Shallow Depth)

C. Compaction Testing:

1. Conduct compaction tests at locations during backfilling operations as required by the

Resident Project Representative.

1.04 SUBMITTALS

A. Certificates:

1. Submit certification attesting that the composition analysis of pipe embedment and select material stone backfill materials meet specification requirements in accordance with Section 01 33 00.

2. Submit certified compaction testing results from the soils testing agency for any required compaction testing in accordance with Section 01 33 00.

1.05 JOB CONDITIONS

A. Classification of Excavation:

1. All excavation work performed under this contract is UNCLASSIFIED.

B. Rock Removal:

1. There is no anticipated rock removal from this site.

C. Compaction of Backfill:

1. Excavations shall be backfilled in lifts not exceeding compacted thicknesses noted in

Paragraph 3.11.C. Each lift shall be individually compacted.

2. The following percentages of maximum dry density shall be achieved:

Modified Effort

ASTM D1557

• Backfill under Pavement 93% (not including base course materials)

• Backfill in Unpaved Areas 90%

• Detention Basin Berms 95%

3. Contractor shall maintain moisture content of backfill materials at or near the optimum moisture content to attain the required compaction density.

D. Control of Traffic:

1. Employ traffic control measures in accordance with Pennsylvania Department of

Transportation Publication 203, "Work Zone Traffic Control" and as shown on Drawings.

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2. See Section 01 55 26 - Traffic Regulation.

E. Protection of Existing Utilities and Structures:

1. Take all precautions and utilize all facilities required to protect existing utilities and structures. In compliance with Pennsylvania Act 287 (1974) as last amended by Pennsylvania Act 121 (2008), advise each Utility at least three (3) working days in advance of intent to excavate, do demolition work or use explosives and give the location of the job site. Request cooperative steps of the Utility and suggestions for procedures to avoid damage to its lines.

2. Advise each person in physical control of powered equipment or explosives used in excavation or demolition work of the type and location of utility lines at the job site, the Utility assistance to expect, and procedures to follow to prevent damage.

3. Immediately report to the Utility and the Resident Project Representative any break, leak or other damage to the lines or protective coatings made or discovered during the work and immediately alert the occupants of premises of any emergency created or discovered.

4. Allow free access to Utility personnel at all times for purposes of maintenance, repair and inspection.

F. Protection of Trees and Shrubs

1. See Section 01 56 39.

2. Any trees and/or shrubs to be protected which are damaged or destroyed during construction shall be replaced in kind as required by Owner.

PART 2 - PRODUCTS

2.01 PIPE BEDDING OR EMBEDMENT MATERIAL

A. PVC Pipe or PE Pipe:

1. Bedding to Springline of Pipe: AASHTO No. 8 (former PennDOT No. 1B) coarse aggregate or AASHTO No. 57 (former PennDOT No. 2B) coarse aggregate if trench water present, Table C, Section 703.2, Publication 408 Specifications. Do not use slag or cinders.

2. Springline of Pipe to 12" over Pipe: PennDOT Select Granular Material (2RC), Section

703.3, Publication 408 Specifications (required for State Highways); PennDOT No. 2A coarse aggregate (required for Township Roads); AASHTO No. 8 (former PennDOT 1B) coarse aggregate or AASHTO #57 (former PennDOT 2B) coarse aggregate if trench water present (for easements), Table C, Section 703.2, Publication 408 Specifications.

Do not use slag or cinders.

B. Concrete Pipe (Reinforced or Non-Reinforced):

1. Bedding to Springline of Pipe: AASHTO No. 57 (former PennDOT 2B), Table C, Section

703.2, Publication 408 Specifications. Do not use slag or cinders.

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2. Springline of Pipe to 12" over Pipe: PennDOT Select Granular Material (2RC), Section

703.3, Publication 408 Specifications (required for State Highways); PennDOT No. 2A coarse aggregate (required for Township Roads), Table C, Section 703.2, Publication 408 Specifications; excavated material, if free of stone larger than 2" and free of wet, frozen or organic material (for easements). Do not use slag or cinders.

C. Corrugated Galvanized Steel Pipe:

1. Bedding to Springline of Pipe: AASHTO No. 57 (former PennDOT 2B), Table C, Section

703.2, Publication 408 Specifications. Do not use slag or cinders.

2. Springline of Pipe to 12" over Pipe: PennDOT Select Granular Material (2RC), Section

703.3, Publication 408 Specifications (required for State Highways); PennDOT No. 2A coarse aggregate (required for Township Roads), Table C, Section 703.2, Publication 408 Specifications; excavated material, if free of stone larger than 2" and free of wet, frozen or organic material (for easements). Do not use slag or cinders.

2.02 SLAB OR BASE MATERIAL

A. Concrete Slab or Precast Base:

1. AASHTO No. 8 (former PennDOT No. 1B) coarse aggregate or AASHTO No. 57

(former PennDOT No. 2B) coarse aggregate if trench water present, Table C, Section 703.2, Publication 408 Specifications. Do not use slag or cinders.

2.03 BACKFILL MATERIAL

A. State Highways and Shoulders:

1. From top of pipe bedding or embedment material to subgrade elevation: PennDOT

Select Granular Material (2RC), Section 703.3, Publication 408 Specifications.

B. Existing Municipal Streets, Parking Areas and Driveways (All Paved Surfaces):

1. From top of pipe bedding or embedment material to subgrade elevation: Same as for

State Highways and Shoulders or PennDOT No. 2A coarse aggregate, Table C, Section 703.2, Publication 408 Specifications.

C. New Municipal Streets, Parking Areas and Driveways (All Paved Surfaces):

1. From top of pipe bedding or embedment material to 12" over top of pipe: Excavated material if free of stones larger than 2" in size and free of wet, frozen, or organic materials.

2. From top of pipe embedment or 12" over top of pipe to subgrade elevation: Excavated material if free of stones larger than 8" in size and free of wet, frozen, or organic

D. Unimproved Areas (All Non-Paved Surfaces):

1. From top of pipe bedding or embedment material to 12" over top of pipe: Excavated material if free of stones larger than 2" in size and free of wet, frozen, or organic

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2. From top of pipe embedment or 12" over top of pipe to subgrade elevation: Excavated material if free of stones larger than 8" in size and free of wet, frozen, or organic

PART 3 - EXECUTION

3.01 EXAMINATION & PREPARATION

A. Identify required lines, levels, contours and datum.

B. Notify Engineer of unexpected subsurface conditions and discontinue work in area until notified to resume work.

C. Maintain and protect existing utilities identified by utility users within the Work area (see paragraph 1.05E).

D. Verify that structure walls are braced to support surcharge forces imposed by backfilling operations.

3.02 PROTECTION OF ADJACENT WORK

A. Underpin adjacent structures which may be damaged by excavation work, including utilities and pipe chases.

B. Grade excavation top perimeter to prevent surface water runoff into excavation or to adjacent properties.

3.03 MAINTENANCE AND PROTECTION OF TRAFFIC

A. Coordinate the work to insure the least inconvenience to traffic and maintain traffic in one or more unobstructed lanes unless closing the roadway is authorized.

B. Maintain access to all streets and private drives.

C. Provide and maintain signs, flashing warning lights, barricades, markers, and other protective devices as required to conform with construction operations and to keep traffic flowing with minimum restrictions.

D. Comply with State and local Municipal codes, permits and regulations.

E. See Section 01 55 26 - Traffic Regulation.

3.04 CUTTING PAVED SURFACES

A. Where installation of pipelines, structures, and appurtenances necessitate breaking a paved surface, make cuts in a neat uniform fashion forming straight lines parallel with the edge of the excavation. Cut offsets at right angles to the edge of the excavation.

B. Protect edges of cut pavement during excavation to prevent raveling or breaking; square edges prior to pavement replacement.

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C. The requirement for neat line cuts, in other than state highways, may be waived if the final paving restoration indicates overlay beyond the width of the excavation.

3.05 EXCAVATION

A. Depth of Excavation:

1. Gravity Pipelines:

a. Excavate trenches to the depth and grade shown on the Drawings for the invert of the pipe plus that excavation necessary for placement of pipe bedding material.

2. Structures:

a. Excavate to the minimum depth necessary to install or remove footings, concrete slab or precast base plus that excavation necessary to place the required base material as shown on the Drawings.

3. Where unsuitable bearing material including shattered rock due to drilling or blasting operations is encountered in the bottom of the excavation, continue excavation until the unsuitable material is removed, solid bearing is obtained or can be established, or concrete/concrete cradle can be placed. If no concrete/concrete cradle is to be installed, refill the excavation to required grade with pipe bedding/embedment or slab/base material as appropriate.

4. Where Contractor, by error or intent, excavates beyond the minimum required depth, backfill the excavation to the required depth with pipe bedding/embedment or slab/base material as appropriate.

B. Width of Excavation:

1. Gravity and Pressure Pipelines:

a. Excavate trenches, including laterals, to a width necessary for placement and jointing of the pipe, and for placing and compacting pipe embedment under, around and over the pipe, but not less than 6" or more than 12" on each side of the pipe.

b. Shape trench walls completely vertical from trench bottom to at least two (2) feet above the top of the pipe.

c. For pressure pipeline fittings, excavate trenches to a width that will permit placement of concrete thrust blocks. Provide earth surfaces for thrust blocks that are perpendicular to the direction of thrust and are free of loose or soft material.

2. Structures:

a. Excavate to the minimum distance necessary for placement/installation/removal of the footings, concrete slab, walls or prefabricated structures and to permit proper backfill procedures to be performed.

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C. Length of Open Trench:

1. Do not advance trenching operations more than 200' ahead of completed pipeline provided the PennDOT Highway Occupancy Permit and/or local Municipal Road Opening Permit does not impose a more restrictive requirement.

2. Backfill completed construction and any open trench in advance of construction at the end of each working day except for a limited area (no greater than 10 LF) at the end of pipe construction which may remain open but shall be protected by fencing or other secure means acceptable to Owner.

3.06 SUPPORT OF EXCAVATION

A. Support excavations with sheeting, shoring, and bracing or in the case of pipeline construction, a

"trench box" as required to comply with Federal and State laws and codes.

B. Install adequate excavation supports to prevent ground movement or settlement to adjacent structures, pipelines or utilities. Damage due to settlement because of failure to provide support or through negligence or fault of Contractor in any other manner, shall be repaired at Contractor's expense.

C. Withdraw shoring, bracing, and sheeting as backfilling proceeds unless otherwise directed by the

Resident Project Representative.

D. The neglect, failure or refusal of the Resident Project Representative to order the use of bracing or sheeting, or a better quality, grade, or section, or larger sizes of steel or timber, or to order sheeting, bracing, struts, or shoring to be left in place, or the giving or failure to give orders or directions as to the manner or methods of placing or driving sheetings, bracing, jacks, wales, stringers, etc., shall not in any way or to any extent relieve Contractor of any responsibility concerning the condition of excavation or of any of his obligations under the Contract, nor shall any delay, whether caused by any action or want of action on the part of Contractor, or by any act of Owner and Engineer or their agents, or employees, resulting in the keeping of an excavation open longer than would otherwise have been necessary, relieve Contractor from the necessity of properly and adequately protecting the excavation from caving or slipping, nor from any of their obligations under the Contract relating to injury of persons or property, nor entitle them to any claim for extra compensation.

3.07 CONTROL OF EXCAVATED MATERIAL

A. Keep the ground surface, within a minimum of 2' of the sides of the excavation, free of excavated material.

B. Provide temporary barricades to prevent excavated material from encroaching on private property, walks, gutters, and storm drains.

C. Maintain accessibility to all fire hydrants, valve pit covers, valve boxes, curb boxes, fire and police call boxes, and other utility controls at all times. Keep gutters clear or provide other satisfactory facilities for street drainage. Do not obstruct natural water courses. Where necessary, provide temporary channels to allow the flow of water either along or across the site of the work.

D. In areas where excavations parallel or cross streams, ensure that no material slides, is washed, or dumped into the stream course. Remove diversion structures and/or cofferdams immediately

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3.08 DEWATERING

A. Keep excavations dry and free of water. Dispose of precipitation and subsurface water clear of the work.

B. Maintain pipe trenches dry until pipe has been jointed, inspected, and backfilled, and concrete work has been completed. Prevent trench water from entering pipelines under construction.

C. Intercept and divert surface drainage away from excavations. Design surface drainage systems so that they do not cause erosion on or off the site, or cause unwanted flow of water.

D. Comply with Federal and State requirements for dewatering to any watercourse, prevention of stream degradation, and erosion and sediment control.

3.09 PIPE LAYING

A. Provide required pipe bedding placed in accordance with the Drawings and Specifications

(Paragraph 2.01). A minimum bedding depth of 6" shall be provided when bedding is required.

B. Shape recesses for the joints or bell of the pipe by hand. Assure that the pipe is supported on the lower quadrant for the entire length of the barrel.

C. Lay pipe as specified in the appropriate Section of these Specifications for pipeline construction.

3.10 STRUCTURE PLACEMENT/INSTALLATION

A. Provide required base material in accordance with the Drawings and Specifications (Paragraph

2.02).

3.11 BACKFILLING EXCAVATIONS

A. Pipeline Trench:

1. After pipe installation and inspection, provide material to complete the pipe embedment in accordance with the Drawings and Specifications.

2. Unless otherwise shown on the Drawings, the bedding or embedment requirements using the material noted in Paragraph 2.01 shall apply.

3. The material shall be hand-placed and carefully compacted with hand-operated mechanical tampers in layers of suitable thickness to provide specified compaction around and under the haunches of the pipe. Backfill and compact the remainder of the trench with specified backfill material in accordance with the Drawings and any relevant permit conditions. Employ a placement method so not to disturb or damage the utility line in the trench. Use of a Hydra-hammer or jumping-jack type compaction device is not permitted within two (2) feet of the utility line. A vibratory plate type compaction device and/or trench roller is acceptable. Vibratory compaction equipment or trench rollers shall be used for the lifts of coarse aggregate backfill within existing streets and paved areas. Any settlement which occurs because of consolidation of the backfill during the construction period or during the required maintenance period shall be corrected by Contractor.

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B. Structure Excavation:

1. After structure installation/demolition and inspection, backfill the excavation with specified backfill material in accordance with the Drawings and Section 2.03 of this specification. Employ a placement method so not to disturb or damage foundation perimeter drainage, foundation damp proofing or water proofing and protective cover or utility lines. Backfill against supported foundation walls; backfill simultaneously on each side of unsupported foundation walls. Pipelines entering the structure must be provided with the specified bedding material hand placed and carefully compacted with hand-operated mechanical tampers in layers of suitable thickness to provide specified compaction around and under the haunches of the pipe. Use of a Hydra-hammer or jumping-jack type compaction device is not permitted within two (2) feet of a pipeline. A vibratory plate type compaction device and/or trench roller is acceptable and shall be used for the lifts of coarse aggregate backfill within existing paved areas. Any settlement which occurs because of consolidation of the backfill during the construction period or during the required maintenance period shall be corrected by Contractor.

C. Lift Thickness Limitations:

1. Lift thicknesses shall be limited to six (6) inches for pipe embedment, eight (8) inches maximum for pipeline trenches within paved areas and twelve (12) inches maximum for pipeline trenches in non-paved areas and for structure excavations. Lift thicknesses shall also comply with requirements imposed by any State Highway Occupancy Permit.

In no case shall maximum lift thickness placed exceed the maximum limits specified by the manufacturer's recommendations for the compaction equipment to be utilized.

Compaction equipment shall not be used over the pipe until sufficient backfill has been placed to ensure that such equipment will not damage or disturb the pipe.

2. Lift thickness limitations specified for State highways, shoulders, or embankments govern over the compaction equipment manufacturer's recommendations.

D. Unsuitable Backfill Material and/or Compaction:

1. Where the Resident Project Representative deems backfill material to be unsuitable and rejects all or part thereof due to conditions prevailing at the time of construction, remove the unsuitable material and replace with suitable backfill material.

2. If, during progress of the Work, tests indicate that compacted materials do not meet specified requirements, remove defective material, replace and retest at no cost to Owner, as directed by the Resident Project Representative.

3.12 DISPOSAL OF EXCAVATED MATERIAL

A. Excavated material remaining after completion of backfilling shall remain the property of

Contractor, removed from the construction area, and disposed of legally. Contractor shall either allow saturated soils to sufficiently dry prior to any hauling off-site or else use a sealed, watertight truck.

3.13 ROUGH AND FINE GRADING

A. Grade areas disturbed by construction to a uniform finish. Form the bases for terraces, banks, lawns and paved areas.

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B. Grade areas to be paved to depths required for placing subbase and paving materials. Top surface of exposed subgrade to be plus or minus one inch.

C. Grade areas to be topsoiled and seeded to 6" below indicated finish contours.

D. Slope grade away from structures at a minimum 2 inches in 10 feet unless otherwise noted on

Drawings.

3.14 RESTORATION OF UNPAVED SURFACES

A. Restore unpaved surfaces disturbed by construction equal to the surface condition prior to construction.

B. Restore grassed areas in accordance with Section 32 92 00, Finish Grading, Seeding and

Sodding.

3.15 RESTORATION OF PAVED SURFACES

A. Restore paved surfaces disturbed by construction equal to the surface condition prior to construction.

END OF SECTION