50-Sec 31 23 33 - Excavation, Backfill and Compaction.pdf

EXCAVATION, BACKFILL AND COMPACTION

31 23 33-1

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 material, 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 03 30 00: Concrete Work for Structures

4. Section 03 30 53: Concrete Work for Utilities

5. Section 22 11 34: Water Service Facility

6. Section 31 11 00: Clearing and Grubbing

7. Section 31 23 16.26: Rock Removal

8. Section 32 12 23: Restoration of Paved Surfaces

9. Section 32 93 00: Landscaping

10. Section 33 05 23.16: Boring or Jacking Operations

11. Section 33 05 29: Stream Crossing

12. Section 33 11 00: Water Mains

13. Section 33 12 13: Water Service Connections

14. Section 33 31 13: Gravity Sanitary Sewer Pipe

15. Section 33 32 18: Sewage Pumping Station

16. Section 33 34 00: Sanitary Force Main and Appurtenances

17. Section 33 39 13: Sanitary Manholes

1.03 QUALITY ASSURANCE

A. Testing Agent:

1. Compaction testing for this Work shall be performed by Contractor at the discretion of the Resident Project Representative except if required by the PennDOT Highway

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Occupancy Permit or Township Road Opening Permit. Where compaction testing is required by permit, such compaction testing shall be performed by an independent soils testing agent engaged and paid for by Contractor and approved by Engineer.

2. Contractor shall pay the cost of one series of tests on the area being evaluated.

Contractor shall also pay the cost for additional testing as required in the event of improper performance of the Work.

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 nPlace by Nuclear Methods (Shallow Depth)

C. Compaction Testing: (N/A)

1.04 SUBMITTALS

A. None

1.05 JOB CONDITIONS

A. Classification of Excavation:

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

DEFAULT CHOICE

D. Control of Traffic: (N/A)

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

31 23 33-3 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: (N/A)

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. N/A

2.02 SLAB OR BASE MATERIAL

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

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3.04 CUTTING PAVED SURFACES

3.05 EXCAVATION

A. Depth of Excavation:

1. Gravity Pipelines:

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

b. Excavation for laterals to shallow sewers shall provide a straight uniform grade from the main pipeline to the required elevation at the right-of-way line, plus that excavation necessary for placement of pipe bedding material.

c. Excavation for laterals to deep sewers shall provide a straight grade at 45o from horizontal from the main pipeline to the required elevation, then continuing at a straight uniform grade to the required elevation at the right-of-way line, plus the excavation necessary for placement of pipe bedding material.

2. Pressure Pipelines:

a. Excavate trenches to the minimum depth necessary to place required pipe bedding material and to provide four (4) feet from the top of the pipe to the finished ground elevation, except where specific depths are otherwise shown on the Drawings.

3. Structures:

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

4. 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.

5. 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:

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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

2. Structures:

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

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

31 23 33-6 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

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 upon completion of construction within the stream (See Section 33 05 29).

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. (See Section 01 57 13).

3.09 PIPE LAYING

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

(Paragraph 2.0l). 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.

31 23 33-7

3.10 STRUCTURE PLACEMENT/INSTALLATION

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 following bedding or embedment requirements using the material noted in Paragraph 2.01 shall apply:

a. Water Mains, Sanitary Sewers, Laterals, Sewage Force Mains and Air Mains

(DIP): pipe bedding to [invert] [springline] of pipe [where trench bottom is unsuitable for direct placement (i.e., rock, poor bearing material).]

**OR**

a. Water Mains, Sanitary Sewers, Laterals and Sewage Force Mains (DIP): pipe bedding to 12” above the crown of pipe (State highway or local municipal road);

pipe bedding to springline of pipe (easement or grassed area).

b. Sanitary Sewers, Laterals, Force Mains and Water Lines (PVC or PE): pipe embedment to 12" above the crown of pipe.

c. Air Mains (Steel or DIP): pipe bedding to springline of pipe.

d. Copper Service Lines: pipe embedment to 6" above crown of pipe.

e. Storm Sewer (Concrete): pipe bedding to [invert] [springline] of pipe [where trench bottom is unsuitable for direct placement (i.e. rock, poor bearing material).]

f. Storm Sewers (Corrugated Metal Pipe): pipe bedding to springline of pipe.

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.

B. Structure Excavation:

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1. After structure installation and inspection, backfill the excavation with specified backfill material in accordance with the Drawings. 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, 31 23 33-9 lawns and paved areas.

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 4" 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 to equal the surface condition prior to construction.

B. Restore grassed areas in accordance with Section 32 93 00, Landscaping.

3.15 RESTORATION OF PAVED SURFACES

A. See Section 32 12 23.

END OF SECTION