B09_-_SolicitationAmendment4_Atch_6_31200_Trenching_0004.pdf

140P6221Q0011 Attachment 6 Amendment 4

EARTH MOVING - TRENCHING 312000 - 1

SECTION 312000 - EARTH MOVING – TRENCHING FOR UTILITIES

PART 1 - GENERAL

1.1 SUMMARY

A. Section Includes:

1. Excavating and backfilling trenches for utilities and pits for buried utility structures.

1.2 DEFINITIONS

A. Backfill: Soil material used to fill an excavation.

1. Initial Backfill: Backfill placed beside and over pipe in a trench, including haunches to support sides of pipe.

2. Final Backfill: Backfill placed over initial backfill to fill a trench.

B. Borrow Soil: Satisfactory soil imported from off-site for use as fill or backfill.

C. Drainage Course: Aggregate layer supporting the slab-on-grade that also minimizes upward capillary flow of pore water.

D. Excavation: Removal of material encountered above subgrade elevations and to lines and dimensions indicated.

1. Authorized Additional Excavation: Excavation below subgrade elevations or beyond indicated lines and dimensions as directed by CO. Authorized additional excavation and replacement material will be paid for according to Contract provisions for changes in the Work.

2. Unauthorized Excavation: Excavation below subgrade elevations or beyond indicated lines and dimensions without direction by CO. Unauthorized excavation, as well as remedial work directed by Architect, shall be without additional compensation.

E. Fill: Soil materials used to raise existing grades.

F. Structures: Buildings, footings, foundations, retaining walls, slabs, tanks, curbs, mechanical and electrical appurtenances, or other man-made stationary features constructed above or below the ground surface.

G. Subgrade: Uppermost surface of an excavation or the top surface of a fill or backfill immediately below subbase, drainage fill, drainage course, or topsoil materials.

H. Utilities: On-site underground pipes, conduits, ducts, and cables as well as underground services within buildings.

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1.3 FIELD CONDITIONS

A. Utility Locator Service: Notify utility locator service for area where Project is located before beginning earth-moving trenching operations.

PART 2 - PRODUCTS

2.1 SOIL MATERIALS

A. General: Provide borrow soil materials when sufficient satisfactory soil materials are not available from excavations.

2.2 ACCESSORIES

A. Detectable Warning Tape: Acid- and alkali-resistant, polyethylene film warning tape manufactured for marking and identifying underground utilities, a minimum of 6 inches wide and 4 mils thick, continuously inscribed with a description of the utility, with metallic core encased in a protective jacket for corrosion protection, detectable by metal detector when tape is buried up to 30 inches deep; colored to comply with local practice or requirements of authorities having jurisdiction.

PART 3 - EXECUTION

3.1 PREPARATION

A. Protect structures, utilities, sidewalks, pavements, and other facilities from damage caused by settlement, lateral movement, undermining, washout, and other hazards created by trenching operations.

3.2 EXCAVATION FOR UTILITY TRENCHES

A. Excavate trenches:

Gas line trenches: excavate to a depth of 36” and a width of 18” to accommodate CenterPoint Entergy supplied gas line. Coordinate with COR two business prior to any excavating.

Electrical Conduit trenches: excavate to a depth of 24” and a width to accommodate new electrical service conduits or minimum of 12 “.

B. Excavate trenches to uniform widths to provide the following clearance on each side of pipe or conduit. Excavate trench walls vertically from trench bottom to 12 inches higher than top of pipe or conduit unless otherwise indicated.

C. Trench Bottoms: Excavate and shape trench bottoms to provide uniform bearing and support of pipes and conduit. Shape subgrade to provide continuous support for bells, joints, and barrels of

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pipes and for joints, fittings, and bodies of conduits. Remove projecting stones and sharp objects along trench subgrade.

D. Trench excavating required method:

1. All natural gas line trenching shall be conducted by manual/hand-excavation methods.

2. All trenching operations shall be done after notification 2 business days to the COR prior to commencing. Trenching shall be allowed to be observed by Park resources staff for archeological or other purposes.

3. Hand-excavate to indicated lines, cross sections, elevations, and subgrades.

4. Remove top turfgrass strippings and remove from site. Lawfully dispose of off of Park property.

5. Excavate and stockpile top 4-inch topsoil layer separate from general soils for replacement as topsoil over trench once backfilled.

3.3 STORAGE OF SOIL MATERIALS

A. Stockpile soil materials and excavated satisfactory soil materials or windrow along alignment of trench in direct proximity to work to keep limits of disturbance to the site minimized. Use filter fabric or other means to prevent stockpiled soil material from contaminating existing turf/grass.

Cover to prevent windblown dust or water to keep soil material moist and not subject to wind erosion.

1. Stockpile soil materials away from edge of excavations. Do not store within drip line of remaining trees.

3.4 UTILITY TRENCH BACKFILL

A. Place backfill on subgrades free of mud, frost, snow, or ice.

B. Place and compact bedding course on trench bottoms and where indicated. Shape bedding course to provide continuous support for bells, joints, and barrels of pipes and for joints, fittings, and bodies of conduits.

C. Initial Backfill: Place sand 8 inches around CenterPoint Energy supplied gas line. Use select backfill material for electrical trenches

1. Carefully compact initial backfill under pipe haunches and compact evenly up on both sides and along the full length of piping or conduit to avoid damage or displacement of piping or conduit. Coordinate backfilling with utilities testing.

D. Final Backfill: Place and compact final backfill of satisfactory soil (to final subgrade elevation.

Utilize the existing topsoil material separately stockpiled as final 4-inch lift of soil fill.

E. Warning Tape: Install warning tape directly above utilities, 12 inches below finished grade, except 6 inches below subgrade under pavements and slabs.

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3.5 COMPACTION OF SOIL BACKFILLS AND FILLS

1. For utility trenches, compact each layer of initial and final backfill soil material with mechanical tamping equipment as necessary to a compaction that prevents settling of the trench and can support germination of turf restoration within the topsoil layer.

3.6 PROTECTION

A. Protecting Graded Areas: Protect newly graded areas from traffic, freezing, and erosion. Keep free of trash and debris.

B. Repair and reestablish grades to specified tolerances where completed or partially completed surfaces become eroded, rutted, settled, or where they lose compaction due to subsequent construction operations or weather conditions.

C. Where settling occurs before Project correction period elapses, remove finished surfacing, backfill with additional soil material, compact, and reconstruct surfacing.

1. Restore appearance, quality, and condition of finished surfacing to match adjacent work, and eliminate evidence of restoration to greatest extent possible.

3.7 DISPOSAL OF SURPLUS AND WASTE MATERIALS

A. Remove surplus satisfactory soil and waste materials, including unsatisfactory soil, trash, and debris, and legally dispose of them off Park property.

END OF SECTION 312000