Town of Groton, MA Article IV Trenching

§ 407-20 Applicability.

The following work shall be included:

A. Excavating trenches for water mains and appurtenances.

B. Furnishing, placing and compacting bedding under and backfill over water mains and appurtenances.

§ 407-21 Tests.

Tests and analysis of fill materials will be performed in accordance with ASTM D1557 and with Section 01410.

§ 407-22 Reference standards.

The following reference standards shall apply:

A. ASTM D1556, Density of Soil in Place by Sand Cone Method.

B. ASTM D2167, Density of Soil in Place by Rubber Balloon Method.

C. ASTM D698, Moisture-Density Relations of Soils and Soil-Aggregate Mixtures, Using 5.5 lb Rammer and 12 inch Drop: Standard Proctor.

D. ASTM D2922, Density of Soil and Soil-Aggregate in Place by Nuclear Methods (Shallow Depth).

§ 407-23 Samples.

A ten-pound sample of each type of fill in airtight containers shall be submitted to the engineer to be tested by others. Retests of materials not meeting specifications shall be paid for by the contractor. The contractor shall pay for additional tests required when the same material is obtained from more than one source.

§ 407-24 Bedding and fill materials.

A. Structural fill. Structural fill shall be well-graded, sandy gravel having the following gradation:

	United States Sieve Size	Percent Passing by Weight
	6-inch	100
	No. 4	40 to 95
	No. 40	15 to 60
	No. 100	0 to 18
	No. 200	0 to 8

B. Screened or crushed gravel. Screened or crushed gravel shall consist of clean mineral aggregate with particle size limits as follows:

	United States Sieve Size	Percent Passing by Weight
	3/4-inch	100
	1/2-inch	90 to 100
	3/8-inch	40 to 70
	No. 4	0 to 15

C. Sand. Sand shall consist of clean mineral aggregate with particle size limits as follows:

	United States Sieve Size	Percent Passing by Weight
	No. 4	100
	No. 100	0 to 30
	No. 200	0 to 12

D. Processed gravel for subbase.

(1) Processed gravel for subbase shall consist of clean mineral aggregate with particle size limits as follows:

	United States Sieve Size	Percent Passing by Weight
	3-inch	100
	1 1/2-inch	95 to 100
	3/4-inch	50 to 85
	No. 4	30 to 60
	No. 200	0 to 12
	(Based on fraction passing the No. 4 sieve)

(2) At least 50% by weight of the materials retained in the one-inch sieve shall have a fractured face.

E. Gravel for subbase. Gravel fill for subbase shall be well-graded, sandy gravel having the following gradation:

	United States Sieve Size	Percent Passing by Weight
	1/2-inch	50 to 85
	No. 4	40 to 75
	No. 50	8 to 28
	No. 200	0 to 8
	(Based on fraction passing the No. 4 sieve)

F. Suitable material from subsoil. In roads, road shoulders, walkways and traveled ways, suitable material for trench backfill shall be the natural material excavated during the course of construction but shall exclude debris, pieces of pavement, organic matter, top soil, all wet or soft muck, peat or clay, all excavated ledge material and all rocks over six inches in largest dimension or any material which, as determined by Water Superintendent and/or his representative, will not provide sufficient support or maintain the completed construction in a stable condition.

G. Common fill material. Common fill material for trench backfill shall exclude debris, concrete or other rubble, organic matter, topsoil, all wet or soft muck, peat or clay and all rocks over six inches in largest dimension or any material which, as determined by the Water Superintendent and/or his representative, will not provide sufficient support or maintain the completed construction in a stable condition.

§ 407-25 Inspection.

The inspection shall:

A. Verify that stockpiled fill to be reused is approved.

B. Verify that areas to be backfilled are free of debris, snow, ice or water and surfaces are not frozen.

§ 407-26 Preparation.

Preparation shall include:

A. Identification of required lines, levels, contours and datum.

B. Coordination with Section 01050.

§ 407-27 Protection of existing structures.

A. All existing pipes, poles, wires, fences, curbings, property line markers and other structures, which the Water Superintendent and/or his representative decides must be preserved in place without being temporarily or permanently relocated, shall be carefully supported and protected from injury by the contractor. Should such items be injured, they shall be restored by the contractor, without compensation therefor, to at least as good condition as that in which they were found immediately before the work was begun.

B. When fences interfere with the contractor's operations, he shall remove and (unless otherwise specified) later restore them to their original condition.

C. The contractor shall enclose the trunks of trees adjacent to his work and not to be cut with substantial wooden boxes of such height as may be necessary to protect them from injury from piled material, from equipment, from his operations or otherwise due to his work. Excavating machinery shall be handled with care to prevent injury to trees not to be cut and particularly to overhanging branches and limbs.

D. Branches, limbs and roots shall not be cut except by permission of the engineer. All cutting shall be smoothly and neatly done without splitting or crushing. In case of cutting or unavoidable injury to branches, limbs and trunks of trees, the cut or injured portions shall be neatly trimmed and covered with an application of grafting wax or tree healing paint as directed.

E. Cultivated hedges, shrubs and plants which might be injured by the contractor's operations shall be protected by suitable means or shall be dug up, balled and temporarily replanted and maintained. After the construction operations have been substantially complete, they shall be replanted in their original positions and cared for until growth is reestablished. If cultivated hedges, shrubs and plants are injured to such a degree as to affect their growth or diminish their beauty or usefulness, they shall be replaced by items of kind and quality at least equal to the kind of quality existing at the start of the work.

F. On paved surfaces, the contractor shall not use or operate tractors, bulldozers or other power-operated equipment the treads or wheels or which are so shaped as to cut or otherwise injure such surfaces.

G. All surfaces which have been injured by the contractor's operations shall be restored to a condition at least equal to that in which they were found immediately before work was begun. Suitable materials and methods shall be used for such restoration. The restoration of existing property or structures shall be done as promptly as practicable and shall not be left until the end of the construction period.

§ 407-28 Excavation.

A. Pipe trenches shall be made as narrow as practicable and shall not be widened by scraping or loosening materials from the sides. Every effort shall be made to keep the sides of the trenches firm and undisturbed until backfilling has been completed and consolidated.

B. Pavements shall be cut sufficiently wide and removed to enable installation of pipe and allow inspection. Pavement cutting shall be done by saw cut pavement breaker or wheel cutter of sufficient size to properly penetrate the total thickness of the pavement. Cutting shall be made in a neat, true, straight line established by chalk line or painting of existing pavement. All cutting methods will be approved by the Water Superintendent and/or his representative before any pavement cutting begins. Proper disposal of excavated pavement and/or soils is the responsibility of the contractor.

C. Muck, peat or other unsuitable material below grade which, in the opinion of the engineer, is incapable of supporting the pipe shall be removed from within trench limits. The trench shall then be backfilled with an approved backfill material placed in six-inch layers. Each lift shall be thoroughly compacted.

D. Unauthorized excavation shall be corrected at no cost to the owner. Backfill with material shall be approved by the Water Superintendent and/or his representative.

E. Excavated material shall be stockpiled in the area designated on site, and unsuitable subsoil or excess subsoil not being reused from site shall be removed.

F. Excavation shall be hand trimmed and left free of loose matter.

§ 407-29 Backfilling.

A. When necessary, subgrade surfaces shall be compacted to 95% of maximum density.

B. Areas beneath pipe from which unsuitable bearing material has been removed shall be backfilled with bedding material.

C. Pipe and conduit shall be supported as specified by the pipe manufacturer during placement and compaction of bedding fill.

D. Bed for polyvinyl chloride and ductile iron pipe shall be as shown on the drawings and as shown herein.[1]

[1] Editor's Note: The drawings are located at the end of this chapter.

E. Ductile iron pipe shall be covered to six over crown with common fill in six-inch layers properly tamped by hand using standard tamping bars.

F. Machine backfill to within 12 inches of trench resurfacing in eighteen-inch minimum lifts compacting to 95% maximum density using mechanical compaction methods. Water jetting and/or puddling will not be allowed. Backfill material shall contain no stones larger than six inches in diameter.

G. Frozen material shall not be placed in the backfill nor shall backfill be placed on frozen material. Previously frozen material shall be removed or otherwise treated before new backfill is placed.

H. Where the trench occurs adjacent to paved streets in shoulders or sidewalks, the contractor shall compact as specified elsewhere in these specifications the backfill and shall maintain the surface as the work progresses. If settlement takes place, he shall immediately deposit additional fill to restore the level of the ground.

I. Adjacent to streets and highways, the top twelve-inch layer of trench backfill shall consist of compacted gravel base course as specified under Section 02575 or 02578, Paving, as applicable. If, in the opinion of the engineer, the existing top twelve-inch layer is unsuitable for use as subgrade or shoulder material, he may order the contractor to remove this layer and to backfill with gravel borrow compacted to at least 95% of maximum dry density as determined by ASTM D1557, Method C.

J. All common and backfill materials are to be compacted to 95% of maximum density as computed using ASTM D1557.

§ 407-30 Surplus excavated materials.

A. No excavated material shall be removed from the site of the work or disposed of by the contractor except as directed or approved by the Water Superintendent and/or his representative.

B. Surplus excavated materials shall, with the approval of the Water Superintendent and/or his representative, be used to backfill normal excavations in rock or to replace other materials unacceptable for use as backfill; shall be neatly deposited and graded so as to make or widen fills, flatten side slopes or fill depressions; or shall be neatly deposited for other purposes indicated by the owner, within its jurisdiction limits, all as directed or approved and without additional compensation.

C. Surplus excavated material, other than those suitable for backfill, shall be neatly deposited for other purposes as indicated by the owner, within its jurisdictional limits, as directed or approved and without additional compensation.

D. Surplus excavated material not needed as specified above shall be hauled away and dumped by the contractor at his expense, at appropriate locations and in accordance with arrangements made by him.

§ 407-31 Tolerances.

Top surface of backfilling shall be plus or minus one inch.

§ 407-32 Compaction testing.

Compaction testing will be performed in accordance with ASTM D1556, D2167 or D2922 and the general conditions.