31 23 33 Trenching and Backfilling for Utilities.pdf

SECTION 31 23 33 – TRENCHING AND BACKFILLING FOR UTILITIES

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PART 1 - GENERAL

1.01 SECTION INCLUDES

A. Excavating trenches for utilities.

B. Backfilling and compaction of utility trenches.

1.02 REFERENCES

A. American Association of State Highway and Transportation Officials:

1. AASHTO T 99, Moisture-Density Relations of Soils, Using a 5.5-lb. Rammer and a

12-inch Drop.

B. American Society for Testing and Materials:

1. ASTM D6938 – Standard Test Method for In-Place Density and Water Content of

Soil and Soil-Aggregate by Nuclear Methods.

C. Pennsylvania Department of Transportation:

1. PennDOT Publication 408, Latest edition.

a. PennDOT Section 220, Flowable Backfill.

b. PennDOT Section 601, Pipe Culverts.

c. PennDOT Section 703.2, Coarse Aggregate.

d. PennDOT Section 703.3, Select Granular Material.

2. PennDOT Chapter 459, Occupancy of Highways by Utilities, latest edition.

3. PennDOT Chapter 213, Temporary Control Guidelines, latest edition.

4. PennDOT Publication 72 – Standards for Roadway Construction (RC’s), latest edition, as referenced throughout these Specifications.

D. Department of Environmental Protection, Bureau of Waste Management, “Clean Fill” Policy (Effective August 7, 2010)

1.03 DEFINITIONS

A. Clean Fill: Uncontaminated, non-water-soluble, non-decomposable inert solid material.

The term includes soil, rock, stone, dredged material, used asphalt, and brick, block or concrete from construction and demolition activities that is separate from other waste and recognizable as such.

B. Clean Organic Backfill: On site excavated material free of vegetation, lumber, metal and refuse, and free of rocks or similar hard objects larger than one inch in greatest dimension. Rock to soil ratio shall not exceed one part rock to three parts soil.

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C. Regulated Fill: Soil, rock, stone, dredged material, used asphalt, historic fill, and brick, block or concrete from construction and demolition activities that is separate from other waste and recognizable as such that has been affected by a spill or release of a regulated substance.

D. Historic Fill: Material used to bring an area to grade prior to 1988 that is a conglomeration of soil and residuals, such as ashes from the residential burning of wood and coal, incinerator ash, coal ash, slag, dredged material and construction and demolition waste.

E. Unclassified Excavation: Removal of materials of any kind in the excavation, including rock excavation.

F. Miscellaneous Unclassified Excavation: Unclassified excavation required by the Engineer and not included in other items for payment.

G. Miscellaneous Aggregate Backfill: Aggregate backfill required by the Engineer and not included in other items of payment.

H. Miscellaneous Earth Backfill: Earth backfill required by the Engineer and not included in other items of payment.

I. Subgrade: Trench bottom prepared as specified to receive first class bedding, concrete cradle or concrete encasement or the bottom of excavations prepared to receive pipeline structures.

J. Suitable Trench Backfill: On site excavated soil or soil-rock mixed materials free of topsoil, vegetation, lumber, metal and refuse; and free of rock or similar hard objects larger than six inches in greatest dimension. Rock to soil ratio shall not exceed one part rock to three parts soil.

K. Utility: Any buried pipe, duct, conduit or cable as defined by Pennsylvania Underground

Utility Line Protection Law – PA Act 287 of 1974, as amended.

L. Final Surfacing Elevation: Elevation of bottom of final surfacing operation such as bottom of topsoil depth or paving subgrade.

1.04 SUBMITTALS

A. Submit under provisions of Section 01 33 00 – Submittal Procedures.

B. Samples: Submit aggregate samples and other required submissions when requested by Engineer.

C. Test Reports:

1. Submit testing laboratory aggregate test reports based on requirements stated in

Source Quality Control.

2. Compaction density test reports based on method of density determination as specified in Reference Standards and the method as approved by the Engineer.

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D. Certificates: Submit certificate from aggregate supplier based on requirements stated in

Source Quality Control, when requested by Engineer.

1.05 QUALITY ASSURANCE

A. Source Quality Control:

1. Laboratory Tests: In accordance with Section 01 40 00 – Quality Requirements, aggregate and other backfill materials specified herein under Products require advance examination or testing according to methods referenced, or as required by the Engineer.

a. Testing laboratory shall furnish both Engineer and Contractor two copies of test result reports. Same reports will be considered as sufficient evidence of acceptance or rejection of materials represented.

b. Conduct aggregate quality tests in accordance with requirements of appropriate Referenced Standard for such materials.

c. The Engineer reserves the right to accept aggregate materials based on certification from supplier that the aggregate originates from a source approved by PennDOT and that the aggregate complies with specified PennDOT requirements.

d. The Contractor is responsible for the cost of all testing required by this section.

1.06 PROJECT CONDITIONS

A. Classification of Excavated Materials: Unclassified excavation as defined herein. No consideration will be given to the nature of the materials encountered in trenching operations or for difficulties encountered during excavating or handling of materials.

B. Obstructions:

1. Where utilities require adjustment or relocation to construct the Work, and those utilities are shown on the Contract Drawings, relocation or adjustment is a part of the Work and shall be completed at no additional expense to the Owner.

2. Where utilities require adjustment or relocation to construct the Work, and those utilities are not shown on the Contract Drawings, notify the Engineer before proceeding. Relocate or adjust utility as directed. The Contractor is required to submit any claims for damage or extra compensation due to the presence of such obstruction or delay in the removal or rearrangement of same in accordance with the General Conditions of the Contract.

3. Do not interfere with persons, firms, corporations or utilities employing protective measures, removing, changing or replacing their property or structures, but allow said persons, firms, corporations or utilities to take such measures as they may consider necessary or advisable under the circumstances;

which shall not relieve the responsibilities of the Contractor.

C. Environmental Requirements:

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1. Do not perform trenching, backfilling or compacting when weather conditions or the condition of materials are such, in the opinion of the Engineer, that work cannot be performed satisfactorily.

2. Do not use frozen materials as backfill nor wet materials containing moisture in excess of the amount necessary for satisfactory compaction.

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

4. Plan work so as to provide adequate protection during storms with provisions available for preventing flood damage. Protect installed piping and other work against damage from uplift due to high ground water levels.

5. Accommodation of Drainage: Keep gutters, sewers, drains and ditches open for surface drainage. No damming or ponding of water in gutters or other waterways will be permitted. Do not direct water flows across or over pavements except through approved pipes or properly constructed troughs. When so required, provide pipes or troughs of such sizes and lengths as required, and place the same as required at no expense to the Owner. Perform grading in the vicinity of trenches so that the ground surface is properly pitched to prevent water running into the trenches.

6. Pumping: Keep excavations free from water during the performance of the work under this Contract at no expense to the Owner. Build dams and other devices necessary for this purpose, and provide and operate pumps of sufficient capacity for dewatering the excavations. Provide for the disposal of the water removed from excavations in such manner as not to cause injury to the public health, to public or private property, to the work of others, to the portion of the work completed or in progress or produce an impediment to the use of streets, roads and highways. Refer to Section 31 23 19 – Dewatering.

7. When it is necessary to haul soft or wet soil material over roadways, use suitably tight vehicles to prevent spillage. Clear away spillage of materials caused by hauling on roadways.

8. Provide effective dust and mud control.

D. Protection: Assume the risks attending and presence or proximity of overhead or underground public utility and private lines, pipes, conduits and support work for same, existing structures and property of whatever nature. Damages and expenses for direct or indirect injury to such structures or to any person or property by reason of them or by reason of injury to them; whether such structures are or are not shown on the Contract Drawings, by work of this Contract, rests solely with the Contractor.

1. Outside Rights-of-Way: Take necessary precautions to protect trees, shrubs, lawns and such other landscaping from damage. Complete restitution work for damages at no additional cost to Owner.

2. Pipe Supports: Adequately support underground pipes or conduits exposed as a result of excavations. Provide adequate support along their entire exposed length. Install such supports in such manner that backfilling may be performed without dislodging such pipes or conduits. Place and carefully compact Aggregate Backfill around the supports and leave such supports in place as a guard against breakage due to backfill settlement. No additional payment will be due the Contractor for support material left in place or for the labor of installing and maintaining supports.

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3. Temporary Protective Construction:

a. Temporary Fence Barricade: Erect and maintain substantial temporary fences surrounding excavation to prevent unauthorized persons from entering such areas.

b. Barricades: Furnish and erect substantial barricades at crossings of trenches, or along trenches, to protect the traveling public.

c. Excavation Covers: Cover open excavation when work therein is suspended or left unattended, including the end of a workday. For such covers, use materials of sufficient strength and weight to prevent their removal by unauthorized persons, and support required traffic where required.

d. Remove temporary protective construction at the completion of work on the Project.

e. Comply with Elizabethtown Area Water Authority requirements.

E. Structure Supports: It is the Contractor’s sole responsibility to determine if the support of buildings or structures may be impacted due to trenching. It is the Contractor’s sole responsibility to determine that such buildings or structures be underpinned; or supported and protected; or special sheeting be driven; or that short lengths of trench be opened at one time. Failure of Engineer to recommend said protection shall not relieve Contractor of his responsibility to protect structures near the construction.

F. Accommodation of Traffic: (Comply with the requirements of Section 01 50 00 –

Temporary Facilities and Controls and the Contract Drawings.) Do Not Obstruct Fire Hydrants. Employ traffic control measures in accordance with PennDOT, Title 67, Chapter 213 and the City of Harrisburg requirements.

G. Explosives and Blasting: Blasting will not be permitted.

H. Removal of Rock by Means Other Than Blasting: Where removal of rock by means other than blasting is required, in accordance with the requirements of State and local laws, rules and regulations, and utility owner requirements, remove by the use of mechanical surface impact equipment, or by drilling and hydraulic rock splitting equipment, or by other methods.

I. Responsibility for Condition of Excavation: Condition and results of excavation are solely the responsibility of the Contractor.

J. Excess Materials: No right of property in materials is granted to the Contractor of excavated materials prior to backfilling. This provision does not relieve the Contractor of his responsibility to remove and dispose of surplus excavated materials.

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K. Borrow Material: When the required quantity of backfill material exceeds the quantity of suitable on site material, provide borrow material. If borrow material is needed, notify the Engineer sufficiently in advance to permit the Engineer to verify such need and to view the proposed borrow pit to determine the material suitability. Borrow excavation will be subject to the Engineer's approval whose written consent shall be obtained prior to its use. Contractor shall be responsible for all sampling and testing required by Engineer to determine suitability.

L. Change of Trench Location or Depth:

1. Should the Engineer require a change in location of a trench from that indicated on the Contract Drawings due to the presence of an obstruction, or from other cause and such change is made before the excavation is begun, the Contractor shall not be entitled to extra compensation or to a claim for damages. Work will be paid per the unit prices established in the Contract.

2. If a change in trench location made at the request of the Engineer involves the abandonment of excavation already made, such abandoned excavation, together with the necessary backfill will be classified as Additional Unclassified Excavation and Additional Aggregate Backfill.

3. The Contractor shall have no claim for additional compensation as a result of changes in trench depths other than the unit price bid for trenches of the revised depth. However, if the change results in abandonment of excavation already made, such abandoned excavation together with the necessary backfill will be classified as Additional Unclassified Excavation and Additional Aggregate Backfill.

4. If a changed location of a trench is authorized by the Engineer upon the Contractor's request, the Contractor shall not be entitled to extra compensation or to a claim. If such change of trench location involves the abandonment of excavation already made, the abandoned excavation and backfill shall be at the Contractor's expense.

M. Advance Trenching: Where existing Utilities or other suspected underground obstructions as indicated on the Contract Drawings are within close proximity of proposed pipelines, uncover and verify the exact location of Utilities and other underground obstructions far enough in advance of pipe laying to allow any changes in pipe alignment or grade required to bypass the obstructions to avoid removing sections of pipe already installed. If any sections of installed pipe must be removed and reinstalled as a result of not verifying Utilities or other underground obstructions far enough in advance, the Contractor shall remove and reinstall the pipe at no additional cost to Owner.

1.07 COORDINATION

A. Coordinate work under provisions of Section 01 10 00 – Project Summary.

B. Verify work associated with lower elevation Utilities is complete before placing higher elevation Utilities.

PART 2 - PRODUCTS

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2.01 FILL MATERIAL

A. Backfill:

1. Aggregate Backfill: PennDOT 2A Coarse Aggregate conforming to PennDOT

Publication 408, Section 703.

2. Clean Fill Material: The evaluation of fill materials shall be in accordance with

DEP’s “Clean Fill” regulations and procedures for determining whether material is clean or regulated.

3. Suitable Trench Backfill Material: On site excavated soil or soil-rock mixed materials free of topsoil, vegetation, lumber, metal and refuse; and free of rock or similar hard objects larger than six inches in greatest dimension. Rock to soil ratio shall not exceed one part rock to three parts soil.

4. Clean Organic Material Backfill: On site excavated material free of vegetation, lumber, metal and refuse, and free of rocks or similar hard objects larger than one inch in greatest dimension. Rock to soil ratio shall not exceed one part rock to three parts soil.

5. Flowable Backfill: Type B: In accordance with PennDOT Publication 408, Section 220.

B. Pipe Bedding:

1. First Class Bedding: Coarse Aggregate conforming to PennDOT Publication 408, Section 703.2.

a. For piping having a diameter of 24 inches and less, use AASHTO No. 8

Coarse Aggregate.

b. For pipes having a diameter greater than 24-inches, use AASHTO No. 57

Coarse Aggregate.

2. Initial Backfill: Coarse Aggregate conforming to PennDOT Publication 408, Section

703.2.

a. For piping having a diameter of 24 inches and less, use AASHTO No. 8

Coarse Aggregate.

b. For pipes having a diameter greater than 24-inches, use AASHTO No. 57

Coarse Aggregate.

C. Suitable Bearing Material: AASHTO No. 3 Coarse Aggregate to within six (6) inches of subgrade followed by No. 57 Coarse Aggregate to subgrade conforming to PennDOT Publication 408, Section 703.2.

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PART 3 - EXECUTION

3.01 PREPARATION

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

B. Protect plant life, lawns, rock outcropping and other features remaining as a portion of final landscaping.

C. Protect benchmarks, existing structures, fences, sidewalks, paving, and curbs from excavating equipment and vehicular traffic.

D. Maintain and protect above and below-grade utilities which are to remain.

3.02 EXCAVATING

A. Notify PA One Call System in accordance with Act 287, as amended.

B. Perform soil erosion and sedimentation control work in accordance with Section 31 25 00

– Erosion and Sedimentation Controls.

C. General:

1. Excavation shall be performed to the lines and grades indicated on the Contract

Drawings or as directed by the Engineer.

2. Perform excavation and backfilling using machinery except where hand excavation and backfilling is required or is necessary to protect existing structures, utilities, or other private or public properties.

4. Remove pavement according to requirements of Section 32 12 16 – Asphalt Paving.

5. Do not interfere with 45 degree bearing splay of structure foundations.

D. Subgrade Preparation:

1. Do not excavate below depths indicated or specified except where unsuitable material is encountered at subgrade.

2. Remove unsuitable material found below subgrade to a depth determined by

Engineer and backfill with Suitable Bearing Material or as directed by Engineer to required Subgrade.

3. Remove rocks or other hard matter protruding through trench bottom at Subgrade which could damage pipe or impede consistent backfilling or compaction. Backfill with first class bedding to required Subgrade. Compact in four (4) inch lifts.

4. Remove rock below subgrade if shattered due to excessive drilling impact or splitting operations and in the opinion of the Engineer it is unfit for sub-grade.

Backfill to Subgrade with concrete or other material acceptable to the Engineer.

No separate or additional payment will be made for such removal and backfill.

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E. Excavated Material Storage:

1. Separate Suitable Trench Backfill Material excavated and stockpile in designated area. Excess materials not suitable for backfill shall be removed from site.

2. In no case shall excavated materials be stockpiled outside of the construction easements or the permanent right-of-way if construction easements are not in place.

F. Trench Width:

1. From subgrade elevation to an elevation at least twelve (12) inches above the top of the outside barrel of the pipe, excavate trench banks to vertical lines and not less than the minimum or more than the maximum widths specified in Table A.

TABLE A

Diameter of Pipe Minimum Trench Width Maximum Trench Width

1½ through 24 inches OD + 12 inches OD + 16 inches

2. Top of trench shall not exceed limits of right-of-way or construction easements if such is in place.

3. Maintain trenches such that there is no conflict with State or OSHA regulations.

4. The Contractor is solely responsible for the means and methods of the trench excavation and width required to ensure safety of its employees and proper installation of the Work.

G. Length of Open Trench:

1. Complete trench excavation at least twenty-five (25) feet but not more than one hundred (100) feet in advance of pipe laying, Contractor shall request approval from Engineer for trench excavations in excess of more than one (100) feet in advance of pipe laying, and keep trenches free from obstructions, except that at the end of a work day or at the discontinuance of work, the pipe laying may be completed to within five (5) feet of the end of the open trench.

2. The Contractor shall limit all trench openings to a distance commensurate with all rules of safety.

3. If the work is stopped either totally or partially, the Contractor shall refill the trench and temporarily repave over the same at his expense. The trench shall not be opened until he is ready to proceed with the construction of the pipeline.

4. Engineer reserves the right to request trench refilling over completed pipe if, in his judgment, such action is necessary. No claim for extra compensation will be allowed for such refilling even though work may be stopped elsewhere as a result.

3.03 PIPE BEDDING

A. Place Pipe Bedding and Initial Backfill as specified herein unless indicated otherwise on Contract Drawings. Place material in trench for full width. Place on each side of pipe and fittings simultaneously.

B. First Class Bedding: Carefully place on undisturbed subgrade or compacted subgrade as approved by the Engineer, pipe bedding material from six (6) inches below outside of pipe barrel to pipe springline. Work pipe bedding material by hand under pipe haunching to provide adequate side support. Place in three (3) inch layers.

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C. Initial Backfill: From pipe springline to twelve (12) inches above outside of pipe barrel, carefully place initial backfill in four (4) inch layers. Place carefully so as not to disturb pipe.

3.04 BACKFILL

A. Backfill trenches to contours and elevations indicated on Contract Drawings.

B. Maintain optimum moisture content of fill materials to attain required compaction density.

C. Do not use frozen backfill materials or place backfill on frozen subgrades or trench subgrades.

D. Perform backfilling by methods which will result in thorough compaction of backfill material.

E. Backfill to Final Restoration Elevation: Backfill from one (1) foot above the top of pipe to

Final Restoration Elevation using backfill materials specified in Schedule at end of this Section. Consolidate backfill materials evenly from center to side of trench to prevent arching.

F. If there is a deficiency of Suitable Trench Backfill Material, provide borrow material as required at no additional cost to Owner.

G. The maximum backfill layer thickness shall be eight (8) inches in accordance with PennDOT Publication 408, Section 601.

3.05 COMPACTION

A. Solidly tamp each layer of bedding around the pipeline and above pipeline using proper tamping tools made especially for this purpose. Compact each layer to the densities specified in the Schedule contained at the end of this Section using Standard Proctor Test Methods determined at maximum density at optimum moisture content as determined by AASHTO T-99.

B. Do not use rolling equipment or heavy tampers to consolidate backfill until at least two

(2) feet of backfill is placed over the top of the pipe.

C. The use of HYDRA-HAMMER for compacting backfill in trenches is prohibited.

D. The use of puddling or jetting for compacting backfill in trenches is prohibited.

E. Compaction Tests: During the course of backfilling and compacting, the Owner or

Engineer reserves the right to require the Contractor shall make field tests to verify that specified compactions are being achieved at no additional cost to the Owner. Perform field density tests according to AASHTO T-310 or AASHTO T-191.

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F. If compaction tests indicate that Work does not meet specified requirements, remove

Work, replace, compact and retest at no additional cost to the Owner.

3.06 CLEAN-UP AND MAINTENANCE

A. General: During construction, the surfaces of all areas including, but not limited to, roads, streets, and driveways shall be maintained on a daily basis to produce a safe, desirable, and convenient condition. Streets shall be swept and flushed after backfilling, and re-cleaned as dust, mud, stones and debris caused by the work, or related to the work again accumulates.

B. Remove surplus excavated materials, rubbish and other construction debris from the site after backfilling is completed.

C. Construction site shall be left clean at end of each working day to satisfaction of Engineer.

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3.07 RESTORATION SCHEDULE

END OF SECTION 31 23 33

SURFACING PER SECTION 32 12 16 and 32 13 13

Backfill and Compaction per Section 31 23 33

Temporary Permanent

Surfacing ID. No.

Description Type Compaction % (Note 1)

Base Surface Base Binder Surface

1.00 Vegetation

S-1.01

Vegetative Area (> 3 FT from edge of shoulder)

Suitable 90 PennDOT Formula E (Note 5) PennDOT Formula B (Note 5)

Vegetative Area (<= 3 FT from edge of shoulder) Aggregate 100 PennDOT Formula E (Note 5) PennDOT Formula B (Note 5)

2.00 Private

S-2.01 Private Bituminous

Pavement Restoration Aggregate 100 Note 4

S-2.02 Concrete Pavement

Restoration, Driveway Aggregate 100 Note 4

3.00 Municipal

S-3.01 Municipal Bituminous Pavement Restoration

Aggregate 100 Note 4

4.00 PennDOT

S-4.01 PennDOT Pavement Restoration

Aggregate 100 Note 4

Note 1 Percent (minimum) of maximum dry density as determined by Standard Proctor Test.

Note 2 Comply with requirements of Erosion & Sedimentation Section.

Note 3 Comply with requirements of Final Grading and Seeding Section.

Note 4 Refer to Contract Drawings for Pavement Restoration Requirements.

Note 5 Seeding shall be in accordance with PennDOT Publication 408, Section 804.