06_02294 Minor Earth Dams and Pits MVO 8.26.20.doc

SECTION 02294

MINOR EARTH DAMS AND PITS

PART 1: GENERAL

1.01 WORK INCLUDED:

A. Description: Clearing, grubbing, embankment development, and core trenching for the repair of two dams as shown on the drawings and in the Work Data Sheets.

1.02 RELATED WORK:

A. Specification Sections:

General Information and Requirements

Section 01009

Mobilization

Section 01505

Riprap and Rock Lining

Section 02378

1.03 REFERENCES:

A. American Association of State Highway and Transportation Officials

AASHTO T 99-81

The Moisture-Density Relations of Soils Using a 5.5 lb (2.5 kg) Rammer and a 12-inch (305 mm) Drop

AASHTO T 239-76

Moisture Content of Soil and Soil-Aggregate in Place by Nuclear Methods (Shallow Depth)

1.04 PROJECT CONDITIONS:

A. Work Limits: Work limits will be staked, and control points established by the Government. Contractor shall not borrow outside staked areas (usually located below reservoir high water lines) without permission from the Contracting Officer.

B. Climatic Conditions: No work required under this section will be allowed when materials are frozen or excessively wet.

PART 2: PRODUCTS

2.01

MATERIALS:

A. Waste Material: Waste material is brush, trees, stumps, frozen lumps, non-plastic silts, and oversized rocks. Oversized rocks are rocks of such size and shape that will interfere with the uniform placement of earthfill materials in layers of specified thickness.

B. Topsoil: Topsoil material is material which will sustain plant growth and includes sod, roots, and other small vegetative matter which can be uniformly placed to a thickness of 6 inches without protruding from the finished grade.

C. Permeable Material: Permeable material is sand, gravel, and rock.

D. Common Excavation: Materials to be removed from excavation, except igneous, metamorphic and sedimentary rock which cannot be excavated without blasting, will be considered common excavation. When ripping is required, the material will also be considered common excavation. Ripping equipment shall be a rear‑mounted, heavy duty, single‑tooth, ripping attachment mounted on a crawler tractor having a power rating of at least 195 net horsepower.

E. Common Embankment: Embankment materials shall be free of topsoil and waste material. Excavation required for embankment shall be subject to the same material requirements as common excavation. Excavated materials shall be placed in the embankment. Pervious materials, such as sand and gravel, shall be placed above the high-water level.

PART 3: EXECUTION.

3.01 PREPARATION:

A. Clearing and Grubbing: The surface area to be covered by embankments, surface of borrow areas and cut spillways shall be thoroughly cleared and stripped of vegetative matter, brush, trees, stumps, roots, loose rocks, and other objectionable materials, including sand, gravel, silt, and debris in channels within the foundation areas.

B. Conservation of Topsoil: Suitable material removed in conjunction with clearing, grubbing, bank sloping, and borrow area preparation shall be conserved in neat stockpiles at locations in the vicinity of the project site.

C. Depth of Stripping: Normal stripping depth is not expected to exceed 6 inches, although variations may be encountered. The Contractor is to conserve available topsoil.

3.02 INSTALLATION:

A. Placement of Topsoil: After construction of the embankment and excavation areas is completed, the stockpiled topsoil shall be uniformly placed over cut and fill areas above high water line including the top and upstream slopes of reservoirs, spillways, borrow pits, and downstream slope below high water line to form a seeded for planting. Spreading of topsoil shall not be done when the ground or topsoil is frozen, or excessively wet. Topsoil shall be spread to depths as shown on the plans or as designated by the Contracting Officer.

B. Bank Sloping: Slopes within the foundation area, including channel banks, shall be trimmed to a slope not steeper than 1:1. Suitable material resulting from the bank‑trimming operations shall be removed and deposited in the embankment, or stockpiled for use in the embankment.

C. Foundation: After required clearing, stripping, bank sloping, and excavation have been completed, the foundation for embankment shall be prepared by scarifying. Scarifying shall consist of ripping to a depth of not less than 6 inches. Scarified furrows shall be a maximum of 3 feet apart and parallel to the axis of the embankment.

D. Excavation: Additional excavation for the convenience of the Contractor, or due to careless operations, including the cost of backfilling, shall be at the expense of the Contractor. Contractor shall use care not to disturb sod or vegetation in natural spillways or sodded watercourse areas below excavated spillways.

E. Principle spillway pipe installation: The principle spillway pipes shall be installed according to the drawings. Under and around the pipe shall be thoroughly tamped and compacted. The pipe shall be government –furnished. Install concrete thrust blocks along the pipe to prevent pipe movement and separation. One thrust block at each end and two on either side of an elbow are required. Concrete shall be 4000 psi 6 sack with fiber. Use number 4 rebar to reinforce each thrust block.

Further requirements are:

1.

End and side slopes of the borrow excavation shall be as shown on the Work Data Sheet. The dimensions of excavation shall be as shown on the drawings and the Work Data Sheet.

2.

Suitable materials from excavations for specified permanent construction shall be used in the embankment and shall either be placed in the embankment directly from excavation or shall be placed in temporary stockpiles and later placed in the embankment.

3.

Excavated materials which are unsuitable for, or are in excess of the requirements, for the embankment or other earthwork, shall be deposited as waste. The material shall be placed immediately below the downstream toe of embankment in a manner that will not leave windrows. Compaction of such waste materials will not be required. Costs of placing material in temporary stockpiles shall be included in the unit price for common excavation.

4.

Core trenches, where required, shall be excavated and suitable materials shall be placed in the embankment. Material determined not suitable shall be wasted at the downstream toe of the embankment in a manner that will not leave windrows.

F. Core Trenches: Core trenches shall be backfilled with the best clay-bearing material available and compacted in accordance with the requirements for embankment compaction. The core trench shall be dug 4ft. below the lowest point of the cut to be backfilled.

H. Embankment: The embankment rehabilitation construction work shall be constructed downstream from the borrow excavation, as shown on the drawings. Embankment materials shall be free of sod, roots, brush, snow, other waste matter and rocks of a shape or size that will interfere with uniform placement of materials in layers of specified thickness. Fill materials shall not be placed when either materials, or surface on which they will be placed, are frozen or too wet for satisfactory compaction. The scarified surface shall be compacted with the first layer of earthfill. Further requirements are:

1.

Materials shall be placed parallel to the axis of the embankment in even, continuous, horizontal layers not more than 8 inches in thickness. The full cross section of the fill shall be maintained as each successive layer is placed.

2.

Successive loads of material shall be dumped on earthfill so as to produce the best practical distribution of material. Distribution and gradation of materials throughout earthfill shall be free from lenses, pockets, streaks, or layers of material differing substantially in texture or gradation from surrounding material. Combined excavation and placement operations shall be such that materials, when compacted in the embankment, shall be blended sufficiently to secure the best practicable degree of compaction and stability.

3.

Slopes of embankments shall be finished to conform to lines and grades shown on the Work Data Sheet. The top of the embankment shall be constructed level.

4.

Core trenches, where required, shall be backfilled with material excavated from the pit borrow area.

I. Compaction: The contractor shall route hauling equipment over the layers of embankment material already in place and shall distribute travel evenly over the entire width of the embankment to obtain maximum compaction while placing material. Sheep’s foot rollers, jumping jacks, hand tamping are also acceptable compaction methods. Acceptable compaction will be determined by the COR. Over compaction shall be avoided along hauling route.

PART 4: MEASUREMENT AND PAYMENT

4.01 METHOD OF MEASUREMENT:

A. General: Excavated materials actually placed and accepted will be paid for as common embankment. Materials from required excavation which cannot be used for embankment construction will be paid for as common excavation. Stripping, stockpiling and placement of topsoil will not be measured for payment.

B. Units:

1. Common Embankment: Measurement for payment of compacted embankment will be based on the number of cubic yards of common earthfill, placed in embankments and core trenches, as determined by the average end-area method. Measurement of common earthfill will also include space occupied by the outlet structure and outlet structure backfill.

2. Common Excavation: Excavation not used in the embankment will be measured and paid for by cubic yards in the space excavated by the average end area method.

4.02 BASIS OF PAYMENT:

A. Payment: Prices and payment will be full compensation for the work described in this section. Payment will be made under:

Pay Item

Pay Unit 02294(1) Common Embankment

Cubic Yard

02294(2) Common Excavation

Cubic Yard

END OF SECTION 02294

Measel Spring and Leo Reservoir Repair

MINOR EARTH DAMS AND PITS

02294-2