Section 5 9. Excavation:



9. Excavation:

Regular Excavation:

A. Regular Excavation shall include roadway excavation and borrow excavation, as defined for each.

1. Roadway Excavation: Roadway Excavation shall consist of the excavation and the utilization or satisfactory disposal, of all materials necessary for the construction of the roadway, side ditches, etc., within the limits of the roadway right of way as show in the plans.

2. Borrow Excavation shall consist of the excavation and satisfactory utilization of material from authorized borrow pits.  It shall include only material that is suitable for the construction of roadway embankments or of other work of constructing embankment covered by the contract and unsuitable material in borrow areas furnished by the Department, which must be excavated as determined by the Engineer, in order to obtain the suitable material.

3. Lateral Ditch Excavation:  Lateral ditches shall include inlet and outlet ditches to structures and roadway, changes in channels of streams, and ditches parallel to the roadway right of way, as shown in the plans.  Unless otherwise shown in the plans all excavation in that portion of lateral ditches beyond the limits of the roadway right of way, including the sections where dressing is required as provided in 120-11.1, shall be classified as Lateral Ditch Excavation.

4. Subsoil Excavation:  Where muck, rock, clay or other material within the limits of the roadway is unsuitable in its original position, the Contractor shall excavate such material to the cross sections shown in the plans or indicated by the Engineer, and shall backfill with suitable material, which shall be shaped to conform to the required cross sections.  Where the removal of plastic soils below the finished earthwork grade is required, a construction tolerance from the lines shown in the plans as the removal limits, of plus or minus 0.2 foot in depth and plus or minus six inches (each side) in width will be allowed.

5. Trench Excavation:

5.1 General

A.  Design, Provide, and maintain shoring, sheeting and bracing as necessary to support the side of excavations and to prevent detrimental settlement and lateral movement of existing facilities, adjacent property, and completed Work.

5.2 Trench Excavation Plan

A. Prepare Trench Excavation Plan Addressing Following Topics:

1. Details or shoring, sloping, or other provisions for worker protection from hazards of caving ground.

2. Design assumptions and calculations.

3. Methods and sequencing of installing excavation support.

4. Proposed locations of stockpiled excavated material.

5. Minimum lateral distance from the crest of slopes for vehicles and stockpiled excavated materials.

6. Anticipated difficulties and proposed resolutions.

B. Excavation Support and Protection:

Provide excavation support as necessary to support sides of excavations and prevent detrimental settlement and lateral movement of existing facilities, adjacent property, and completed work.

5.3 Removal of Excavation Support

A. Remove excavation support in a manner that will maintain support as excavation is backfilled or leave voids of backfill.

B. Do not begin to remove excavation support until support can be removed without damage to existing facilities, completed work, or adjacent property.

5.4 Trenches

A. For trench exceeding 5 feet in depth, provide adequate safety system meeting requirements of applicable state and local construction safety order, and federal requirements.

6.0 Dewatering Systems

A. Provide, operate, and maintain dewatering system of sufficient size and capacity to permit excavation and subsequent construction in dry and to lower and maintain groundwater level a minimum of 5 feet below the lowest point of excavation.  Continuously maintain excavation free of water regardless of source, and until backfilled to final grade.

B. Design and Operate Dewatering Systems:

1. To prevent loss of grounds as water is removed.

2. To avoid inducing settlement or damage to existing facilities completed work, or adjacent property.

3. To relieve artesian pressure and resultant uplift of excavation bottom.

C. Provide supplemental ditches and sump only as necessary to collect water from local seeps.  Do not use ditches and stumps as primary means of dewatering.

6.1 Settlement

A. Monitoring Dewatering – Induced Settlement:  Established monuments for monitoring settlement at locations selected by ENGINEER.  Monitor vertical movement of each settlement monument, relative to remote benchmark selected by the ENGINEER, at frequency CONTRACTOR’s Dewatering Plan.

6.2 Disposal of Water

A. Obtain discharge permit for water disposal from authorities having jurisdiction.

B. Treat water collected by dewatering operations, as required by regulatory agencies, prior to discharge.

C. Discharge water as required by discharge permit and in manner that will not cause erosion or flooding, or otherwise damage existing facilities, completed work, or adjacent property.

D. Remove solid from treatment facilities and perform other maintenance of treatment facilities as necessary to maintain their efficiency.

6.3 Protection of Property

A. Make assessment of potential for dewatering induced settlement.  Provide and operate devices or systems, including but not limited to re-injection wells, infiltration trenches and cutoff walls, necessary to prevent damage to existing facilities, completed work, and adjacent property.

B. Securely support existing facilities, completed work, and adjacent property vulnerable to settlement due to dewatering operations.  Support shall include, but not be limited to, bracing, underpinning, or compacting grouting.

7.0 Stockpiling Excavated Material

A. Stockpile excavated material that is suitable for use as fill or backfill until material is needed.

B. Post signs indicating proposed use of material stockpiled.  Post signs that are readable from all directions of approach to each stockpile.  Signs should be clearly worded and readable by equipment operators from their normal seated position.

C. Confine stockpiles to within easements, right-of-way, and approved work areas.  Do not obstruct road or streets.

D. Do not stockpile excavated material adjacent to trenches and other excavations unless excavation side-slopes and excavation support systems are designed, constructed, and maintained for stockpile loads.

E. Do not stockpile excavated materials near or over existing facilities, adjacent property, or completed work, if weight of stockpiled material could induce excessive settlement.

7.1 Disposal of Spoil