§ 11.2. Excavation, trenching and backfilling.

This section covers the excavation, trenching, and backfilling for all reuse water mains.

11.2.1 Density tests.

1)

All trenches 12 inches or wider, as measured at the top, that are within roadways, or roadway rights-of-way, parking areas, and areas to be paved shall be tested for conformance to specified compaction requirements:

(a)

These trenches shall be backfilled and compacted to their full depth.

(b)

Tests shall be made within each 400 square feet of trench areas for each one foot of lift above top of conduit. Tests taken in one foot lifts shall be staggered.

(c)

Compaction shall not be less than that of the surrounding areas or 95 percent of the maximum dry density as determined by the standard proctor test. The top 12 inches shall be compacted to a minimum of 98 percent of the maximum dry density.

(d)

Backfill within the Georgia Department of Transportation right-of-way shall meet all requirements as stipulated in the "Utility Accommodation Policy and Standards", as published by the Georgia Department of Transportation.

(e)

All trenches 12 inches or wider, as measured at the top, that are not within roadways, or other areas to be paved shall be compacted to not less than that of surrounding areas or 90 percent of the maximum dry density.

11.2.2 Sheeting and shoring materials.

1)

Construction wood sheeting may be new or used lumber of a species or grade suitable for the proposed use.

2)

If steel sheet piling is used, it shall conform to ASTM A328 and consist of rolled sections of the continuous interlocking type. Minimum thickness of the web and flange metal shall be 3/8 -inch, unless otherwise approved or specified. Rivet steel and structural material as fabricated connections and accessories shall conform to requirements of ASTM A502 and ASTM A36. All steel sheet piles shall be furnished with standard pulling holes located approximately four inches below the top of the pile.

3)

The contractor shall retain full responsibility for the structural integrity and adequacy of the sheeting.

11.2.3 Sheeting and shoring activities.

1)

All excavations shall be properly shored, sheeted and braced or cut back at the proper slope to furnish safe working conditions; to prevent shifting of material; to prevent damage to structures or other work; and to avoid delay to the work. Work shall be performed in all compliance with the most recent U.S. Department of Labor Occupational Safety and Health Administration 29CFR part 1926 Occupational Safety and Health Standards-Excavations, Final Rule. Bracing shall be so arranged as not to place any strain on portions of completed work until the general construction has proceeded far enough to provide ample strength.

2)

Timber sheet piles shall be sharpened in a manner which will assist in holding them in true alignment during driving and the tops shall be protected with caps or other means to prevent damage by the driving equipment. Any pieces damaged or split below the point of cutoff shall be removed and replaced with undamaged pieces.

3)

Sheet piles shall be carefully located and driven straight and true to the desired elevation with secure interlocking for the entire length. Damaged piling or one with faulty alignment shall be withdrawn and new piling driven properly in its place. Jetting will not be permitted. Excavation shall not be carried in advance of the sheet piling.

4)

Sheeting and bracing shall be removed as the excavation is refilled in such a manner as to avoid caving in of areas or structures. Voids left by withdrawal of the sheeting shall be carefully filled by ramming.

11.2.4 Excavation.

1)

The contractor shall perform all excavation in accordance with the most recent OSHA standards and to the depths required or as shown on standard details. During excavation, materials suitable for backfilling shall be piled a minimum distance of two feet from the banks of the excavation to avoid overloading and to prevent slides and cave-ins.

2)

Excavated materials not required for fill or back-fill shall be removed from the site. Unless otherwise indicated or specified, all excavation shall be made by open cut. No tunneling shall be done.

3)

Excavation shall not be carried below the designated level except where special bedding required due to unforeseen conditions, or is specified or shown on the standard details. Excess excavation below the designated level shall be backfilled with crushed stone and tamped.

4)

Excess excavation for manholes and other structures shall be filled with crushed stone or concrete to the required elevation.

5)

Trenches shall be only of sufficient width to provide a free working space on each side of the pipe. To prevent excess pressure on the pipe, the maximum width of pipe trench at the top of the pipe shall not be greater than two feet more than the pipe diameter. If this maximum width is exceeded for water or sewer pipelines, the contractor shall provide Class A bedding as presented in article 7 of these regulations. The top portion of the trench above four feet shall be excavated with sloping sides in accordance with OSHA standards to any width which will not damage adjoining structures, roadways, pavements, utilities or private property. If it is deemed necessary to excavate trench with vertical sides, then OSHA approved shoring and sheeting methods shall be used.

6)

All reuse water mains shall have a minimum of 48 inches of cover above the top of the pipe or 48 inches below edge of pavement, whichever is greater. All reuse water mains 12 inches and larger shall have a minimum of 60 inches of cover above the top of pipe or 60 inches below edge of pavement, whichever is greater unless otherwise indicated by the department.

7)

The trench bottom shall be made to conform as near as possible to the shape of the lower third of the pipe. Excavation shall be made for joints of all pipes, and shall be of sufficient depth to permit access to the joint for construction and inspection. In no case shall the joints be used to support the body of the pipe. Bell holes shall be excavated in the trenches so as to relieve pipe bells of all load, but small enough to insure that support is provided throughout the length of the pipe barrel.

8)

Unstable soil or soil unable to achieve 95 percent compaction as per Standard Proctor shall be removed and replaced with crushed stone, which shall be tamped.

9)

Ground adjacent to all excavations shall be graded to prevent inflow of water.

10)

The excavation of the trench shall not advance more than 100 feet ahead of the completed pipe work.

11)

The contractor shall remove any water accumulated during excavation, whether from ground or surface sources.

12)

The inspector shall be notified immediately upon encountering site conditions at variance to those indicated and any active or inactive utility encountered not indicated on the standard details.

13)

No work shall be done to correct or incorporate unforeseen conditions until written instructions are issued.

14)

No trenches will be permitted to be left open overnight, on weekends, or on holidays.

11.2.5 Rock excavation.

1)

All rock encountered shall be removed six inches below the bottom grade of the trench where pipe is being laid, and the trench built back to the correct grade with suitable select material thoroughly tamped into place, unless the contractor is specifically directed to place stabilization material.

2)

Blasting permits for each development shall be required. Blasting shall be done with the precautions specified by the state fire marshal and the Paulding County Fire Chief.

3)

The contractor shall notify county fire departments prior to blasting operations.

4)

All blasting operations and all handling, storage and use of blasting materials shall be in strict accordance with federal, state and local ordinances and regulations and shall be approved by the state fire marshal. Blasts shall be restricted to the extent that no appreciable shock will be transmitted to existing structures, pipelines, sewers, cables or other public or private facilities. The contractor shall be wholly responsible for any and all personal injury or property damage resulting from blasting.

11.2.6 Backfilling.

1)

No backfilling shall be done over pipelines until all pipes have been inspected and approval received from the inspector, unless otherwise directed by the department.

2)

Trenches shall be backfilled with earth backfill materials according to Water, Reuse Water and Sewer Pipe Bedding Details shown on Dwg. No. W&S-01. Bedding for Ductile Iron Pipe shall be minimum Class D. Bedding for all other pipe shall be minimum Class B. Backfill or bedding material shall be placed evenly around and on both sides of the pipe in six-inches maximum layers, and tamped until pipe has cover of not less than 18 inches above top of pipe or top of granular bedding material. The remaining backfill shall be placed evenly in 12-inch layers compacting each layer thoroughly to the specified compaction. Water settling shall not be permitted. Any trenches where settlement occurs shall be reopened, refilled and compacted, with the surface restored to the specified grade and compaction, and leveled for grassing.

3)

Prior to backfilling at manholes, structures, and other accessories, all forms, trash and debris shall be removed. Backfill material shall be symmetrical on all sides in eight-inch maximum layers. Each layer shall be moistened and compacted with tamps.

4)

Where pipes are in a fill section or are projecting into fill sections, ductile iron pipe shall be installed. Where material beneath the pipe is determined by the department to be unstable, then concrete foundation supports at each joint shall be provided and joints will be restrained. Where pipe is not structurally supported, unstable material shall be removed and trench stabilization provided. A pipe bed shall be constructed of No. 57 crushed stone and be compacted to at least 90 percent of the maximum dry density, unless otherwise specified.

5)

The material shall be placed evenly in six-inch maximum layers to the proper sub-grade unless otherwise directed by the department. After the trench has been stabilized, normal backfill and compaction operations shall resume as specified herein.

6)

Prior to final acceptance of the pipeline installations, the contractor shall refill all sunken trenches and excavations to final grade.

7)

Earth backfill shall be free of stone and boulders. Acceptable backfill material may be from excavation or borrow areas.

8)

No rock will be allowed in the backfill within a distance of 12 inches from the pipe or the ground surface, and rock larger than six inches in the greatest dimension will not be permitted in any part of the trench.

11.2.7 Subsurface obstructions.

1)

The standard details indicate underground utilities or obstructions that are known to exist according to the best information available to the department. The contractor, as required by Georgia law, shall call the utilities protection center (UPC) and those utilities, agencies or departments that own and/or operate utilities in the vicinity of the construction work site to verify the location of, and possible interference with, the existing utilities, arrange for necessary suspension of service and make arrangements to locate and avoid interference with said utilities. Where these or unforeseen underground utilities are encountered, the location and alignment of the new facilities may be changed to avoid interference, upon written approval from the department.

2)

The contractor shall furnish and have available at all times an electronic pipe detector, in good working order, to locate existing pipelines or other obstructions.

3)

While excavating, backfilling and laying pipe, care must be taken not to remove, disturb, or injure any existing water, sewer, reuse water, gas pipes, or other conduits or structures. If necessary, the contractor, shall sling, shore up and maintain such structures in operation, and within a reasonable time shall repair any damage done to them. Before final acceptance of the work, he shall return all such structures to original condition.

4)

The contractor shall give sufficient notice to the interested utility of his intention of removing or disturbing any pipes, conduits, etc., and shall abide by their regulations governing such work. In the event that any subsurface structure becomes broken or damaged in the course of the work, the contractor shall immediately notify the proper authorities, and shall be responsible for all damage to persons or property caused by such damage.

5)

When pipes or conduits providing services to adjoining buildings are broken during the progress of the work, the contractor shall repair them at once, or if repaired by the utility involved, shall pay the utility any charges for having such repairs made by the utility.

6)

The department will not be liable for any claim made by the contractor based on underground obstructions being different to that indicated in these regulations or on the plans.