Amendment 0004 - Section 31 23 16 (28 June 21).pdf

SECTION 31 23 16

EXCAVATION

PART 1 GENERAL

1.1 REFERENCES

The publications listed below form a part of this Section to the extent referenced. The publications are referred to within the text by the basic designation only.

U.S. ARMY CORPS OF ENGINEERS (USACE)

EM 1110-1-2908 (1994) Rock Foundations

EM 385-1-1 (2014) Safety and Health Requirements Manual

Aviation Policy Letter 19-08 (Rev

2020_oct_01 or newest revision)

AVN USACE Approved SUAS Systems Appendix A

& B

1.2 SCOPE

This Section covers requirements for excavation of the walls, OGEE weir apron and cut slopes.

Refer to Section 31 00 00 EARTHWORK for requirements related to excavations for general site work, building construction, and road realignments.

1.3 EXCAVATED MATERIALS CLASSIFICATION

Excavation will not be classified by material for measurement and payment purposes

1.4 DRILLING AND BLASTING

Drilling and blasting will be required and permitted as specified in

Section 31 23 16.27 CONTROLLED BLASTING except at the locations listed in paragraph LOCATIONS BLASTING PROHIBITED. Refer to the Geotechnical Data

Report and the Logs of Exploration for description of subsurface conditions.

1.5 DEFINITIONS

1.5.1 Soil / Earth

As described on the Logs of Exploration and in the Geotechnical Data Report. Includes all types of man-made fill materials and naturally deposited soil, alluvium, colluvium, other sediments, and residual soil.

The alluvium and colluvium may be partially cemented.

1.5.2 Rock

The bedrock types occurring in the region are gray quartz-mica schist;

light gray quartzite; dark gray slate; gray to black meta-basalt, amphibolite, and related types; brown ultra-basic rock; dark gray gabbro;

dark gray to gray diorite; and gray to light gray granite. The bedrock term are further defined in the Geotechnical Data Report (GDR).

1.5.3 Rock Weathering

The degree of weathering of rock and rock masses used in this specification is classified as unweathered, slightly weathered, moderately weathered, highly weathered, and decomposed. Determination of the degree of weathering must follow the degree of weathering descriptors found in

Chapter 4 of USACE EM 1110-1-2908.

1.5.4 Rock Hardness

The degree of rock hardness used in this specification is classified as very soft, soft, moderately hard, hard, and very hard. Determination of rock hardness must follow the hardness descriptors found in Chapter 4 of

USACE EM 1110-1-2908.

1.6 SUBMITTALS

Government approval is required for submittals with a "G" designation.

Submittals not having a "G" designation are for information only. A designation following the "G" designation identifies the Government office that will review the submittal. Office symbols are as follows:

EDG: Engineering Division, Geotechnical Branch

Submit the following in accordance with Section 01 33 00 SUBMITTAL

PROCEDURES:

SD-01 Preconstruction Submittals

Drainage and Dewatering Work Plan; G

Excavation Work Plan; G, EDG

Master Drilling and Blasting Work Plan; G, EDG Stockpiling Work Plan; G

Temporary Shoring and Sheeting Design and Installation Plan; G, EDG

Professional Geotechnical Engineer; G, EDG

Certified Engineering Geologist; G, EDG

SD-06 Test Reports

Monthly Excavation Status Report; G, EDG

1.7 QUALITY CONTROL

Quality control must be in accordance with 01 45 00 QUALITY CONTROL.

1.8 GEOTECHNICAL ENGINEER OR ENGINEERING GEOLOGIST

Hire a Professional Geotechnical Engineer or Certified Engineering Geologist to provide inspection of excavations and soil, rock and groundwater conditions during construction. The Geotechnical Engineer or Engineering

Geologist must perform pre-construction and periodic site visits throughout construction to assess site conditions. The Geotechnical Engineer or

Engineering Geologist must update the excavation, sheeting and dewatering plans as construction progresses to reflect changing conditions and must submit updated plans. The Geotechnical Engineer or Engineering Geologist must submit a written Monthly Excavation Status Report at least monthly that informs the Contractor and Contracting Officer of the status of the plan and provide an accounting of the Contractor's adherence to the plans and addresses any present or potential problems. The Geotechnical Engineer or Engineering Geologist must be available to meet with the Contracting

Officer and Government representatives at any time throughout the Contract duration.

The Geotechnical Engineer must be a licensed Geotechnical Engineer in the

State of California with a minimum of 10 years experience designing excavations and constructing excavations, installing slope stabilization support, designing and installing gabion structures, and evaluating soil, rock, and groundwater conditions for spillways or flood control projects.

The Engineering Geologist must be a Certified Engineering Geologist in the

State of California with a minimum of 10 years experience designing and constructing excavations, installing slope stabilization support, designing and installing gabion structures, and evaluating soil, rock, and groundwater conditions for spillways or flood control projects.

1.9 SITE CHARACTERIZATION, SUBSURFACE DATA AND GROUNDWATER CONDITIONS

Refer to the Geotechnical Data Report for information about the subsurface conditions at the project.

1.10 DRAINAGE AND DEWATERING WORK PLAN

At least 60 days prior to starting work, submit a drainage and dewatering work plan describing the methods and procedures for accomplishing drainage and dewatering work as required in paragraph DEWATERING PLANS of Section

01 57 30 DEWATERING, DIVERSION AND CONTROL OF WATER.

1.11 EXCAVATION WORK PLAN

At least 60 days prior to starting work, submit a detailed excavation work plan describing the proposed methods, access and sequencing of the excavations. After acceptance of the work plan, changes must not be made to the work plan without the prior written acceptance of the Contracting

Officer. Include in the work plan a list of equipment proposed for use in all operations during excavation.

1.12 MASTER DRILLING AND BLASTING WORK PLAN

At least 60 days prior to starting drilling and blasting operations, submit a Master Drilling and Blasting Work Plan (also referred to as the General

Blast Plan) for drilling and blasting as required in Section 31 23 16.27

CONTROLLED BLASTING.

1.13 STOCKPILING WORK PLAN

At least 60 days prior to starting work, submit a detailed stockpiling work plan describing the proposed methods, access to, and design of the stockpiles for the soil and rock materials; proposed stockpile locations;

proposed locations of haul roads; proposed methods of protecting (dust control, contaminations, etc.) of stockpiles. After acceptance of the work plan, changes must not be made to the work plan without the prior written acceptance of the Contracting Officer.

1.14 TEMPORARY SHORING AND SHEETING DESIGN AND INSTALLATION PLAN

At least 60 days prior to beginning excavation, submit a Temporary Shoring and Sheeting Design and Installation Plan that provides details of the design and installation of temporary shoring, sheeting, sheet pile, and bracing designs. Include details of the anchorages, bracing, removal sequence. The submittal must also include allowable deflection and a defection monitoring plan. Submit drawings and calculations, certified by a registered Professional Engineer (Structural or Geotechnical) describing the means and methods for temporary shoring and sheeting of excavations.

Drawings must include sizes and types of materials, arrangement of members, panels and reinforcing, and the sequencing and method of installation and removal. Include references used for the calculations.

In addition to the requirements in Sections 25 A and B of EM 385-1-1, include provisions in the Plan to accomplish the following:

a. Prevent undermining of slopes, pavements, foundations and slabs; and

b. Prevent slippage or movement in banks or slopes adjacent to the excavation.

PART 2 PRODUCTS

Not Used

PART 3 EXECUTION

3.1 DRAINAGE AND DEWATERING

Provide for the collection and disposal of surface and subsurface water encountered during construction. Assess the foundation and groundwater conditions, topography, and historical rainfall and lake levels presented by the plans and specifications, Section 01 57 30 DEWATERING, DIVERSION, AND CONTROL OF WATERS, and the Geotechnical Data Report.

3.1.1 Drainage

Accomplish site drainage in accordance with Sections 01 57 23 TEMPORARY STORM WATER POLLUTION CONTROL and 01 57 19 ENVIRONMENTAL PROTECTION.

Establish and construct drainage features (ponds, basins, ditches, and pipes) prior to earth moving activities that would cause runoff to pond on the site or to flow off from the site. Maintain the drainage features throughout construction, to provide positive surface water runoff away from the construction activity. Provide temporary ditches, dikes, swales, and other drainage features and equipment as required to control and direct storm and subsurface seepage flows away from excavations.

Employ measures necessary to permit construction to proceed without damaging the foundation or destabilize the working sub-grade surface.

Protect excavated slopes and backfill surfaces to prevent erosion and sloughing. Excavation must be performed so that the site, the area immediately surrounding the site, and the area affecting operations at the site must be continually and effectively drained, do not experience heaving or uplift conditions, sloughs, slumps, or otherwise become unstable or impassible to construction equipment.

3.1.2 Dewatering

Control groundwater flowing toward or into excavations to prevent interference with the orderly progress of construction, maintain stable working sub-grades, and prevent bottom heave and sloughing of cut slopes.

Initiate control measures well in advance of excavation and no later than by the time the lowest point in the excavation reaches the local groundwater elevation or reservoir pool elevation at that time, whichever is higher. While the excavation is open, the water level within the limits of the excavation must be maintained continuously, at least one foot (1 foot) below the working level in moderately hard to very hard rock and four feet (4 feet) below the working level in soil and decomposed rock. French drains, sumps, ditches or trenches will not be permitted within three feet

(3 feet) of the foundation of any structure or embankment without the specific written approval of the Contracting Officer and unless Contractual provisions for restoration of the foundation area have been made.

Dispose of water in such a manner as to cause no injury or nuisance to public or private property, or be a danger to public health. Dispose of the water in accordance with applicable regulatory agency requirements.

Prevent disposal of sediments from the soils to adjacent lands or waterways by employing necessary methods, including settling basins. Do not allow water containing mud, silt or other pollutants from construction activities to enter a watercourse, the reservoir area, the lake, or be placed in locations that could be subjected to high storm flows or high lake levels.

Operate dewatering systems continuously until construction work in the vicinity is complete. Submit surveillance and monitoring and performance records daily. Measure and record performance of dewatering system at the same time each day using measurements of water levels in the sumps and observation wells or piezometers installed in conjunction with the dewatering system.

3.2 EXCAVATION

Excavate soil and rock to elevations and dimensions indicated or as directed in a manner that will leave foundation material in an unshattered, undisturbed, and solid condition and soil foundations and excavation lines stable. Submit a Temporary Shoring and Sheeting Design and Installation

Plan for approval prior to start of work. Excavate in the dry in accordance with the requirements in Section 01 57 30 DEWATERING, DIVERSION AND CONTROL OF WATER. Determine the means and methods to excavate the materials. Blasting is required and permitted as specified in Section

31 23 16.27 CONTROLLED BLASTING.

Reuse excavated materials that meet the specified requirements for the material type required at the intended location. If final foundation materials are disturbed or damaged by construction activity or inadequate dewatering or drainage, the disturbed or weakened materials must be excavated and replaced as directed at no additional cost to the

Government. Excavations below specified depths will not be permitted except to remove unsatisfactory material. Satisfactory materials removed below the depths indicated, without specific direction, must be replaced with properly compacted satisfactory materials or leveling concrete, as directed, to the indicated excavation grade.

The Contractor is responsible for constructing and removing temporary access ramps into the excavation. These ramps must not cross the final excavated slopes that have slope support and/or drainage installed. The temporary access ramps must comply with EM 385-1-1. Haul routes and ramps across the filter and drain materials must be minimized. Where a haul road crosses filter and drain materials, the filter and drain materials must be protected with bridging, extra material placed and removed, separation fabric, etc. as approved. The overall slope inclinations for the excavation slopes must not be steeper than that indicated, and in all cases must conform to EM 385-1-1 and OSHA requirements. All fill materials forming the temporary access ramps must be removed at completion of the project.

Tolerances for all soil excavations are zero to minus 0.2 feet vertical and plus/minus 0.2 feet horizontal. Tolerances for rock excavation for foundation and slope subgrades are zero to minus 0.5 feet perpendicular to any such surface to the lines and grades shown on the Contract Drawings.

Note these tolerances are at the final excavation profile after cleanup.

Excavation at the invert, and side slopes must follow the lines and grades shown. The tolerances will be determined by projecting a line paralleling the lines and grades shown on the project drawings (e.g., design neatlines) at the foundation invert, vertical cuts and side slopes. Any excavation beyond the lines shown on the drawings must be backfilled or replaced with concrete at no cost to the Government.

The spillway invert excavation, 200 feet downstream of the concrete ogee weir apron has a tolerance of minus 12 inches from the design excavation line.

Unsatisfactory materials encountered below the grades shown that is determined to be detrimental to the stability and safety of the slopes or the project must be removed as directed.

Place satisfactory excavated material required for fill or backfill in the proper section of the permanent work required or separately stockpile fill, weathered rock, and unweathered rock if it cannot be readily placed.

Dispose of satisfactory material in excess of that required for the permanent work in the onsite disposal areas as specified in Paragraph

"DISPOSITION OF SURPLUS MATERIALS."

Prepare foundation subgrades for fill or concrete in accordance with

31 60 00 FOUNDATION PREPARATION.

3.3 DISPOSITION OF EXCAVATED MATERIALS

Excavated materials may be used to produce the soil and rock materials required for this project. These materials as produced must meet project requirements and be submitted for approval. Design the excavation sequence and methods to efficiently produce materials for construction.

3.4 DISPOSITION OF SURPLUS MATERIALS

Hard to very hard, slightly weathered to unweathered rock must not be wasted or disposed of without approval from the Contracting Office.

Dispose of excess satisfactory soil and rock materials in the designated

Government disposal area as indicated for future phase of the project.

Dispose of excess soil and rock materials in the designated Government disposal areas as indicated on the Plans.

3.5 SUPPORT OF EXCAVATION

3.5.1 Excavation in Rock

Take necessary measures to protect excavations and adjacent improvements from raveling, caving, rock falls, sliding, or other instability problems associated with the materials excavated. The locations and extent of slope support and drainage for final slopes will be as indicated or as directed by the Contracting Officer based on the actual conditions encountered during the excavation. For each lift, scale the final excavation surfaces of all loose, hanging or unstable rock fragments during or upon completion of the excavation. Each lift is limited to 10 feet in height and excavation of the next lift will not be allowed until the Contracting

Officer has approved the completed scaling and the geologist mapping has been performed. After scaling of the final excavation surfaces has been performed and the geologist mapping has been completed, then the slope support and drainage can be installed prior to the excavation progressing downward. Rock slope support and drainage must be constructed in accordance with Section 31 33 15, ROCK REINFORCEMENT, Section 03 37 13 SHOTCRETE and EM 385-1-1.

3.5.2 Excavation in Soil

Provide shoring bracing, cribbing, trench boxes, underpinning, and sheeting where indicated. In addition to Section 25 A and B of EM 385-1-1 and other requirements set forth in this Contract, include provisions in the shoring and sheeting plan that will accomplish the following:

a. Prevent undermining of slopes, pavements, foundations and slabs.

b. Prevent slippage or movement in banks or slopes adjacent to the excavation.

c. Allow for the abandonment of shoring and sheeting materials in place in critical areas as the work is completed. In these areas, backfill the excavation to the elevation indicated and remove the remaining exposed portion of the shoring before completing the backfill.

3.6 INSPECTION AND GEOLOGIC MAPPING OF EXCAVATED SURFACES

3.6.1 Rock Surfaces

The Government will inspect and a geologist will map the rock surfaces to obtain a geologic record of the excavated surfaces and to aid in identifying possible unstable rock blocks and provide guidance concerning mitigating potential safety hazards. The Government will inspect and a geologist will map all final rock faces, walls and slopes, all rock surfaces where shotcrete, gabions, riprap, concrete, embankment or other final features are placed. Inspection and geologic mapping will not be performed until: (1) the final excavation surfaces are scaled in accordance with Section 31 23 16.27 CONTROLLED BLASTING and prepared in accordance with Section 31 60 00 FOUNDATION PREPARATION; (2) the Contractor provides for the safety of the excavation and all personnel entering the excavation. If the Government geologist and/or representative determines at any time that additional excavation and/or scaling is required to stabilize the foundation or slope, the Contracting Officer will direct the additional excavation and scaling. The decision to remove or anchor a rock block may be made by the Contracting Officer at any time during the mapping and evaluation of the final excavated surface, (3) the Government geologist and/or representative will install survey targets and (4) Contractor will supply surveyors to support the mapping by Government geologist. This consists of surveying the target coordinates and providing locational data to the Government geologists, all data will include but not limited to station, offset, and elevation and will be provided in the field; 5)Upon completion of scaling and cleanup, and prior to rock reinforcement, and dental or leveling concrete of each segment of excavated rock face and area of invert,(2) conduct digital photogrammetry which includes verifying the photogramerty processes, and 6) a geologist will map all final excavated rock slope faces and areas of the invert. Rock slope support and drainage must be constructed in accordance with Section 31 33 15, ROCK

REINFORCEMENT, Section 03 37 13 SHOTCRETE and EM 385-1-1.

Photogrammetry and mapping activities will occur during daylight hours

Monday through Friday and must be performed prior to anchor, drainage, slope reinforcement or mesh installation, drilling, shotcrete application or dental concrete, leveling concrete, dental mortar, and structural concrete or other placement. The Contractor must notify the Contracting Officer and the Government Project Geologist at least two (2) working day in advance of a slope and/or foundation surface ready and available for inspection and/or mapping, if the slope and/or foundations are not ready by the notified time and date, the government will reschedule the mapping base on field geologist availability. The dimensions of an excavated rock face, which will be inspected and mapped by the Government geologists at any given time, is a segment not to exceed 100 feet in length and 10 feet in height. The maximum area of excavated invert surface which will be inspected and mapped by the Government geologists at any given time is an area not to exceed 50 feet by 50 feet. Final excavated faces and invert surfaces must be unobstructed and survey targets remain undisturbed during photogrammetry. Provide access (ladders, cherry pickers, man-lifts, etc.)

for Government workers to any final excavated face for the purpose of geologic mapping, photogrammetry, inspection for safety issues, locating spot anchors, and placement of survey targets, etc. The Contractor must provide a stabilized camera platform to provide access at a minimum elevation of 60 feet directly above all invert surfaces to allow the

Government geologists to take photogrammetry photos for all inverts for the purpose of geologic mapping. The camera platform can be substituted by a drone that complies with USACE Aviation Policy Letter 19-08 guidance and has a gimbal with at least 2 axes of movement and a camera with a minimum image sensor size of width: 6.2-mm and height: 4.6-mm. Mapping and photogrammetry activities for a final slope measuring 100 feet in length by

10 feet in height may be expected to take approximately 12 hours. Mapping and photogrammetry activities for a final invert surface whose area measures 50 feet by 50 feet may be expected to take approximately 18 hours. Inspection and geologic mapping may be performed in conjunction with other Contractor activities as directed in Section 31 60 00 FOUNDATION

PREPARATION. Provide sufficient opportunity for inspection, geologic mapping and photogrammetry. The Government mapping will be performed periodically throughout the construction operations. The Government will interrupt Contract work in the area, if necessary, to complete these activities, and these interruptions must not be a basis for a claim or time extension.

3.6.2 Soil and Embankment Fill

The Government will inspect and geologically map surfaces of excavated soil and embankment fill materials to obtain a geologic record of the excavated surfaces and to aid in identifying possible unstable subgrades and provide guidance concerning mitigating potential safety hazards. Inspection and geologic mapping will not be performed until: (1) the final excavation surfaces are prepared in accordance with Section 31 60 00 FOUNDATION

PREPARATION and (2) the Contractor provides for the safety of the excavation and all personnel entering the excavation. If the Government geologist and/or representative determines during inspection that additional excavation, shoring, or slope stabilization is required to improve foundation or slope conditions, additional excavation and support will be directed by the Contracting Officer. Upon completion of preliminary and final excavation or cleanup, the Government geologist and/or representative will (1) install survey targets, (2) conduct digital photogrammetry and (3) a geologist will map all final excavated foundation surfaces, slopes, and areas of invert.

Steps:

1) Area must be at preliminary clean up level.

2) install survey targets

3) All targets surveyed and Station, Offset, and Elevation of the targets designated by the USACE Geologist or their representative will be provided in the field

4) conduct digital photogrammetry 5)The USACE geologists will verify digital photogrammetry processes

6) The USACE geologist or their representative will map all final excavated foundation surfaces, slopes, and areas of the invert. Slope support must comply with EM 385-1-1

Photogrammetry and mapping activities will occur during daylight hours

Monday through Friday. The Contractor must notify the Contracting Officer and the Government Project Geologist at least one (1) working day in advance of a slope and/or foundation surface ready and available for inspection and/or mapping. The maximum excavated slope and/or foundation surface which will be inspected and mapped by the Government geologists at any given time is an area not to exceed 100 feet by 100 feet. Final excavated slopes and foundation surfaces must be unobstructed and survey targets remain undisturbed during photogrammetry. Provide access (ladders, cherry pickers, man-lifts, etc.) for Government workers to any final excavated face which is in excess of 10 feet in height for the purpose of geologic mapping, photogrammetry, inspection for safety issues and placement of survey targets, etc. The Contractor must provide a stabilized camera platform to provide access at a minimum elevation of 60 feet directly above all invert surfaces to allow the Government geologists to take photogrammetry photos for all inverts for the purpose of geologic mapping. The camera platform can be substituted by a drone that complies with USACE Aviation Policy Letter 19-08 guidance and has a gimbal with at least 2 axes of movement and a camera with a minimum image sensor size of width: 6.2-mm and height: 4.6-mm.. Mapping and photogrammetry activities for a final slope and/or foundation surface whose area measures 100 feet by

100 feet may be expected to take approximately 18 hours. Inspection and geologic mapping may be performed in conjunction with other Contractor activities as directed in Section 31 60 00 FOUNDATION PREPARATION. Provide sufficient opportunity for inspection, geologic mapping and photogrammetry. The Government will interrupt Contract work in the area, if necessary, to complete these activities, and these interruptions must not be a basis for a claim or time extension.

3.6.3 Monthly Excavation Status Report

Submit a monthly Excavation Status Report written by a registered

Professional Geotechnical Engineer or Certified Engineering Geologist describing the status of the excavation, sheeting and dewatering plans, the

Contractor's adherence to the plans, a resolution of present or potential excavation work and dewatering problems. Submit the Report no later than two (2) weeks after the end of the month.

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