54-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 demolition and construction or installation of concrete curbs and curb ramps including such related features as protection of adjacent utilities and structures, support of excavation, control of excavated materials, dewatering, structure bedding, tree removal and stump grinding, disposal of excavated material, rough grading and restoration.

1.02 RELATED SECTIONS

A. Related Work Specified Elsewhere:

1. Section 02 41 16: Demolition

1.03 QUALITY ASSURANCE

A. Testing Agent:

1. Compaction testing for this Work shall be performed by Contractor.

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

Place by Nuclear Methods (Shallow Depth)

1.04 JOB CONDITIONS

A. Classification of Excavation:

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

B. Compaction of Backfill:

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

Paragraph 3.11C. Each lift shall be individually compacted.

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

Modified

Effort

ASTM D1557

• Building Foundation and 95%

Structural Slab-on-Grade

• Exterior Side of Structure Walls 95% to point 5' from building wall, then 90%

• Trench Backfill under Pavement 95%

(not including base course materials)

• Trench Backfill within Unpaved Areas 90%

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

C. 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.

D. 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

31 23 33-3 discovered.

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

E. Protection of Trees and Shrubs

1. 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 CONCRETE

A. Concrete curb and curb ramps:

1. PennDOT No. 2A coarse aggregate; 4” compacted thickness.

2.02 BACKFILL MATERIAL

A. Paved Areas:

1. In accordance with Section 32 12 23 Restoration of Paved Surfaces.

B. Unimproved Areas:

1. Excavated material if free of stones larger than 2" in size and free of wet, frozen, or organic materials.

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.

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

31 23 33-4 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.

3.04 EXCAVATION

A. Depth of Excavation:

1. Concrete:

a. Excavate to the minimum depth necessary to install concrete plus that excavation necessary to place the required base material as shown on the

Drawings.

2. 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.

3. 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. Concrete:

a. Excavate to the minimum distance necessary for placement/installation of the concrete curbs and curb ramps and to permit proper backfill procedures to be performed.

3.05 SUPPORT OF EXCAVATION

A. 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

31 23 33-5

Contractor's expense.

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

Resident Project Representative.

C. 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 sheeting’s, 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.

3.06 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.

3.07 DEWATERING

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

B. 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).

3.08 CONCRETE PLACEMENT/INSTALLATION

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

2.02).

3.09 BACKFILLING EXCAVATIONS

A. Unsuitable Backfill Material and/or Compaction:

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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.

3.10 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.

3.11 ROUGH AND FINE GRADING

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

3.12 RESTORATION OF UNPAVED SURFACES

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

B. Restore grassed areas.

3.13 RESTORATION OF PAVED SURFACES

A. See Section 32 12 23.

END OF SECTION