Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10)

Shafts 6-19

During drilling or excavation of the shaft, the Contractor shall make frequent checks on
the plumbness, alignment, and dimensions of the shaft. Any deviation exceeding the
allowable tolerances shall be corrected with a procedure approved by the Engineer.

Shaft steel reinforcing bar placement tolerances shall conform to

Section 6-02.3(24)C

The elevation of the top of the reinforcing cage for drilled shafts shall be within +6 inches
and -3 inches from the elevation shown in the Plans.

6-19.3(1)B

Nondestructive Testing of Shafts

6-19.3(1)B1

Nondestructive Quality Assurance (QA) Testing of Shafts

Unless otherwise specified in the Special Provisions, the Contractor shall perform
nondestructive QA testing of shafts, except for those constructed completely in the dry.
Either crosshole sonic log (CSL) testing in accordance with ASTM D 6760 or thermal
integrity profiling (TIP) testing in accordance with ASTM D 7949 shall be used.

6-19.3(1)B2

Nondestructive Quality Verification (QV) Testing of Shafts

The Contracting Agency may perform QV nondestructive testing of shafts that have
been QA tested by the Contractor. The Contracting Agency may test up to ten percent
of the shafts. The Engineer will identify the shafts selected for QV testing and the testing
method the Contracting Agency will use.

The Contractor shall accommodate the Contracting Agency’s nondestructive testing.

6-19.3(1)C

Shaft Preconstruction Conference

A shaft preconstruction conference shall be held at least 5 working days prior to the
Contractor beginning any shaft construction work at the site to discuss construction
procedures, personnel, and equipment to be used, and other elements of the approved
shaft installation narrative as specified in

Section 6-19.3(2)B

. Those attending shall

include:
1. (Representing the Contractor) – The superintendent, on site supervisors, and all

foremen in charge of excavating the shaft, placing the casing and slurry as applicable,
placing the steel reinforcing bars, and placing the concrete. If synthetic slurry is
used to construct the shafts, the slurry manufacturer’s representative or approved
Contractor’s employees trained in the use of the synthetic slurry shall also attend.

2. (Representing the Contracting Agency) – The Engineer, key inspection personnel,

and representatives from the WSDOT Construction Office and Materials Laboratory,
Geotechnical Division.

If the Contractor proposes a significant revision of the approved shaft installation
narrative, as determined by the Engineer, an additional conference shall be held before
any additional shaft construction operations are performed.

Page 6-336

6-19.3(2) Shaft Construction Submittal

The shaft construction submittal shall be comprised of the following four components:
construction experience; shaft installation narrative; shaft slurry technical assistance; and
nondestructive QA testing personnel. The submittals shall be Type 2 Working Drawings,
except the shaft slurry technical assistance and nondestructive QA testing personnel
submittals shall be Type 1.

6-19.3(2)A

Construction Experience

The Contractor shall submit a project reference list to the Engineer for approval verifying
the successful completion by the Contractor of at least three separate foundation projects
with shafts of diameters and depths similar to or larger than those shown in the Plans,
and ground conditions similar to those identified in the Contract. A brief description of
each listed project shall be provided along with the name and current phone number of
the project owner or the owner’s Contractor.

The Contractor shall submit a list identifying the on-site supervisors and drill rig
operators potentially assigned to the project to the Engineer. The list shall contain a brief
description of each individual’s experience in shaft excavation operations and placement
of assembled steel reinforcing bar cages and concrete in shafts. The individual experience
lists shall be limited to a single page for each supervisor or operator.
1. On-site supervisors shall have a minimum 2 years experience in supervising

construction of shaft foundations of similar size (diameter and depth) and scope to
those shown in the Plans, and similar geotechnical conditions to those described
in the boring logs and summary of geotechnical conditions. Work experience shall
be direct supervisory responsibility for the on-site shaft construction operations.
Project management level positions indirectly supervising on-site shaft construction
operations is not acceptable for this experience requirement.

2. Drill rig operators shall have a minimum of 1 year experience in construction of shaft

foundations.

The Engineer may suspend the shaft construction if the Contractor substitutes
unapproved personnel. The Contractor shall be fully liable for the additional costs
resulting from the suspension of work, and no adjustments in contract time resulting from
the suspension of work will be allowed.

6-19.3(2)B

Shaft Installation Narrative

The Contractor shall submit a shaft installation narrative to the Engineer. In preparing
the narrative, the Contractor shall reference the available subsurface data provided in
the contract test hole boring logs, the Summary of Geotechnical Conditions provided in
the Appendix to the Special Provisions, and the geotechnical report(s) prepared for this
project. This narrative shall provide at least the following information:
1. Proposed overall construction operation sequence.
2. Description, size, and capacities of proposed equipment, including but not limited to,

cranes, drills, auger, bailing buckets, final cleaning equipment, and drilling unit. The

Shafts 6-19

narrative shall describe why the equipment was selected, and describe equipment
suitability to the anticipated site conditions and work methods. The narrative shall
include a project history of the drilling equipment demonstrating the successful use
of the equipment on shafts of equal or greater size in similar soil/rock conditions.
The narrative shall also include details of shaft excavation and cleanout methods.

3. Details of the method(s) to be used to ensure shaft stability (i.e., prevention of

caving, bottom heave, using temporary casing, slurry, or other means) during
excavation (including pauses and stoppages during excavation) and concrete
placement. If permanent casings are required, casing dimensions and detailed
procedures for installation shall be provided.

4. A slurry mix design, including all additives and their specific purpose in the slurry

mix, with a discussion of its suitability to the anticipated subsurface conditions, shall
be submitted and include the procedures for mixing, using, and maintaining the
slurry.

A detailed plan for quality control of the selected slurry, including tests to be
performed, test methods to be used, and minimum and/or maximum property
requirements which must be met to ensure the slurry functions as intended,
considering the anticipated subsurface conditions and shaft construction methods,
in accordance with the slurry manufacturer’s recommendations and these Special
Provisions shall be included. As a minimum, the slurry quality control plan shall
include the following tests:

Property

Test Method

Density

Mud Weight (Density), API 13B-1, Section 1

Viscosity

Marsh Funnel and Cup, API 13B-1, Section 2.2

Glass Electrode, pH Meter, or pH Paper

Sand Content Sand, API 13B-1, Section 5

5. Description of the method used to fill or eliminate all voids below the top of shaft

between the plan shaft diameter and excavated shaft diameter, when permanent
casing is specified.

6. Details of concrete placement, including proposed operational procedures for

pumping methods, and a sample uniform yield form to be used by the Contractor for
plotting the approximate volume of concrete placed versus the depth of shaft for all
shaft concrete placement (except concrete placement in the dry).

7. When shafts are constructed in water, the submittal shall include seal thickness

calculations, seal placement procedure, and descriptions of provisions for casing
shoring dewatering and flooding.

8. Description and details of the storage and disposal plan for excavated material and

drilling slurry (if applicable).

Page 6-338

9. Reinforcing steel shop drawings with details of reinforcement placement, including

bracing, centering, and lifting methods, and the method to ensure the reinforcing
cage position is maintained during construction, including use of bar boots and/or
rebar cage base plates, and including placement of rock backfill below the bottom of
shaft elevation, provided the conditions of

Section 6-19.3(5)D

are satisfied.

The reinforcing steel shop drawings and shaft installation narrative shall include, at a
minimum:
a. Procedure and sequence of steel reinforcing bar cage assembly.
b. The tie pattern, tie types, and tie wire gages for all ties on permanent

reinforcing and temporary bracing.

c. Number and location of primary handling steel reinforcing bars used during

lifting operations.

d. Type and location of all steel reinforcing bar splices.
e. Details and orientation of all internal cross-bracing, including a description of

connections to the steel reinforcing bar cage.

Description of how temporary bracing is to be removed.

g. Location of support points during transportation.
h. Cage weight and location of the center of gravity.
i.

Number and location of pick points used for lifting for installation and for
transport (if assembled off-site).

Crane charts and a description and/or catalog cuts for all spreaders, blocks,
sheaves, and chockers used to equalize or control lifting loads.

k. The sequence and minimum inclination angle at which intermediate belly

rigging lines (if used) are released.

Pick point loads at 0, 45, 60, and 90 degrees and at all intermediate stages of
inclination where rigging lines are engaged or slackened.

m. Methods and temporary supports required for cage splicing.
n. For picks involving multiple cranes, the relative locations of the boom tips at

various stages of lifting, along with corresponding net horizontal forces imposed
on each crane.

The Engineer will evaluate the shaft installation narrative for conformance with the
Plans, Specifications, and Special Provisions, within the review time specified. If deemed
necessary by the Engineer, a Shaft Installation Narrative Submittal Teleconference
Meeting will be scheduled by the Contracting Agency following review of the Contractor’s
initial submittal of the narrative and prior to Contracting Agency’s formal response to the
initial submittal. Teleconference participants shall include the following:

Shafts 6-19

1. (Representing the Contractor) – The superintendent, on-site supervisors, and other

Contractor personnel involved in the preparation of the shaft installation narrative.

2. (Representing the Contracting Agency) – The Engineer, key inspection personnel,

and representatives from the Materials Laboratory, Geotechnical Division, and the
WSDOT Construction Office.

6-19.3(2)C

Shaft Slurry Technical Assistance

If slurry other than water slurry is used to construct the shafts, the Contractor shall
provide or arrange for technical assistance in the use of the slurry as specified in

Section

6-19.3(4)A

. The Contractor shall submit the following to the Engineer:

1. The name and current phone number of the slurry manufacturer’s technical

representative assigned to the project, and the frequency of scheduled visits to the
project site by the synthetic slurry manufacturer’s representative.

2. The name(s) of the Contractor’s personnel assigned to the project and trained by

the slurry manufacturer in the proper use of the slurry. The submittal shall include
a signed training certification letter from the slurry manufacturer for each trained
Contractor’s employee listed, including the date of the training.

6-19.3(2)D

Nondestructive QA Testing Organization and Personnel

The Contractor shall submit the names of the testing organizations, and the names of
the personnel who will conduct nondestructive QA testing of shafts. The submittal shall
include documentation that the qualifications specified below are satisfied. For TIP
testing, the testing organization is the group that performs the data analysis and produces
the final report. The testing organizations and the testing personnel shall meet the
following minimum qualifications:
1. The testing organization shall have performed nondestructive tests on a minimum of

three deep foundation projects in the last two years.

2. Personnel conducting the tests for the testing organization shall have a minimum of

one year experience in nondestructive testing and interpretation.

3. The experience requirements for the organization and personnel shall be consistent

with the testing methods the Contractor has selected for nondestructive testing of
shafts.

4. Personnel preparing test reports shall be a Professional Engineer, licensed under

Title 18 RCW, State of Washington, and shall seal the report in accordance with

WAC 196-23-020

Page 6-340

6-19.3(3) Shaft Excavation

Shafts shall be excavated to the required depth as shown in the Plans. Shaft excavation
operations shall conform to this section and the shaft installation narrative.

Shaft excavation shall not be started until the Contractor has received the Engineer’s
acceptance for the reinforcing steel centralizers required when the casing is to be pulled
during concrete placement.

Except as otherwise noted, the Contractor shall not commence subsequent shaft
excavations until receiving the Engineer’s acceptance of the first shaft, based on the
results and analysis of the nondestructive testing for the first shaft. The Contractor may
commence subsequent shaft excavations prior to receiving the Engineer’s acceptance of
the first shaft, provided the following condition is satisfied:

The Engineer permits continuing with shaft construction based on the Engineer’s
observations of the construction of the first shaft, including, but not limited
to, conformance to the shaft installation narrative in accordance with

Section

6-19.3(2)B

, and the Engineer’s review of Contractor’s daily reports and Inspector’s

daily logs concerning excavation, steel reinforcing bar placement, and concrete
placement.

6-19.3(3)A

Conduct of Shaft Excavation Operations

Once the excavation operation has been started, the excavation shall be conducted in a
continuous operation until the excavation of the shaft is completed, except for pauses
and stops as noted, using approved equipment capable of excavating through the type
of material expected. Pauses during this excavation operation, except for casing splicing,
tooling changes, slurry maintenance, and removal of obstructions, are not allowed.

Pauses, defined as momentary interruptions of the excavation operation, will be allowed
only for casing splicing, tooling changes, slurry maintenance, and removal of obstructions.
Shaft excavation operation interruptions not conforming to this definition shall be
considered stops. Stops for uncased excavations (including partially cased excavations)
shall not exceed 16 hours duration. Stops for fully cased excavations, excavations in rock,
and excavations with casing seated into rock, shall not exceed 65 hours duration.

For stops exceeding the time durations specified above, the Contractor shall stabilize the
excavation using one or both of the following methods:
1. For an uncased excavation, before the end of the work day, install casing in the

hole to the depth of the excavation. The outside diameter of the casing shall not be
smaller than 6 inches less than either the plan diameter of the shaft or the actual
excavated diameter of the hole, whichever is greater. Prior to removing the casing
and resumption of shaft excavation, the annular space between the casing and the
excavation shall be sounded. If the sounding operation indicates that caving has
occurred, the casing shall not be removed and shaft excavation shall not resume until
the Contractor has stabilized the excavation in accordance with the shaft installation
narrative conforming to

Section 6-19.3(2)B

, item 3.

Shafts 6-19

2. For both a cased and uncased excavation, backfill the hole with either CDF or

granular material. The Contractor shall backfill the hole to the ground surface, if
the excavation is not cased, or to a minimum of 5 feet above the bottom of casing
(temporary or permanent), if the excavation is cased. Backfilling of shafts with casing
fully seated into rock, as determined by the Engineer, will not be required.

During stops, the Contractor shall stabilize the shaft excavation to prevent bottom heave,
caving, head loss, and loss of ground. The Contractor bears full responsibility for selection
and execution of the method(s) of stabilizing and maintaining the shaft excavation, in
accordance with

Section 1-07.13

. Shaft stabilization shall conform to the shaft installation

narrative in accordance with

Section 6-19.3(2)B

, item 3.

If slurry is present in the shaft excavation, the Contractor shall conform to the
requirements of

Section 6-19.3(4)B

of this Special Provision regarding the maintenance

of the slurry and the minimum level of drilling slurry throughout the stoppage of the shaft
excavation operation, and shall recondition the slurry to the required slurry properties in
accordance with

Section 9-36.2

prior to recommencing shaft excavation operations.

6-19.3(3)B

Temporary and Permanent Shaft Casing

The Contractor shall furnish and install required temporary and permanent shaft casings
as shown in the Plans and as specified in the Special Provisions.

6-19.3(3)B1

General Shaft Casing Requirements

Shaft casing shall be watertight and clean prior to placement in the excavation.

The outside diameter of the casing shall not be less than the specified diameter of the
shaft. The inside diameter of the casing shall not be greater than the specified diameter
of the shaft plus 6 inches, except as otherwise noted for shafts 5 feet or less in diameter,
and as otherwise noted in

Section 6-19.3(3)B4

for temporary telescoping casing. The

inside diameter of casings for shafts 5 feet or less in diameter shall not be greater than the
specified diameter of the shaft plus 1 foot.

6-19.3(3)B2

Permanent Shaft Casing

Permanent casing is defined as casing designed as part of the shaft structure and installed
to remain in place after construction is complete. All permanent casing shall be of ample
strength to resist damage and deformation from transportation and handling, installation
stresses, and all pressures and forces acting on the casing. Where the minimum thickness
of permanent casing is specified in the Plans, it is specified to satisfy structural design
requirements only. The Contractor shall increase the casing thickness as necessary to
satisfy the requirements of this section.

Page 6-342

6-19.3(3)B3

Temporary Shaft Casing

Temporary casing is defined as casing installed to facilitate shaft construction only, which
is not designed as part of the shaft structure, and which shall be completely removed
after shaft construction is complete unless otherwise shown in the Plans. All temporary
casing shall be of ample strength to resist damage and deformation from transportation
and handling, installation and extraction stresses, and all pressures and forces acting on
the casing. The casing shall be capable of being removed without deforming and causing
damage to the completed shaft and without disturbing the surrounding soil.

To maintain stable excavations and to facilitate construction, the Contractor may furnish
and install temporary casing in addition to the required casing specified in the Special
Provisions. The Contractor shall provide temporary casing at the site in sufficient
quantities to meet the needs of the anticipated construction method.

6-19.3(3)B4

Temporary Telescoping Shaft Casing

Where the acceleration coefficient used for seismic design of the structure, as specified in
the General Notes of the Structure Plans, is less than or equal to 0.16, the Contractor may
use temporary telescoping casing for the shafts at any bridge intermediate or interior pier,
subject to the following conditions:
1. The Contractor shall submit the request to use temporary telescoping casing as a

Type 2 Working Drawing. The request shall specify the diameters of the temporary
telescoping casing, and shall specify the shafts where use is requested. The
Contractor shall not proceed with the use of temporary telescoping casing until
receiving the Engineer’s approval.

2. The minimum diameter of the shaft shall be as shown in the Plans.
3. The temporary telescoping casing shall conform to Sections

The Contractor may use temporary telescoping casing for the shafts of any bridge end
pier, regardless of the acceleration coefficient used for the seismic design of the structure,
subject to conditions 2 and 3 specified above and the following two additional conditions:
4. A maximum of two telescoping casing diameter changes will be allowed.
5. The maximum diameter change at each casing diameter transition shall be 12 inches.

6-19.3(3)B5

Permanent Slip Casing

Permanent slip casing is defined as casing installed vertically inside the temporary casing
within the limits of the column-shaft splice zone, and wet-set into the shaft concrete no
more than 3 feet below the column-shaft construction joint, allowing subsequent removal
of the temporary casing. The casing diameter requirements of

Section 6-19.3(3)B1

do not

apply to permanent slip casing, but the inside diameter of the permanent slip casing shall
provide the steel reinforcing bar clearance specified in

Section 6-19.3(5)C

Shafts 6-19

6-19.3(3)C

Conduct of Shaft Casing Installation and Removal and Shaft

Excavation Operations

The Contractor shall conduct casing installation and removal operations and shaft
excavation operations such that the adjacent soil outside the casing and shaft excavation
for the full height of the shaft is not disturbed. Disturbed soil is defined as soil whose
geotechnical properties have been changed from those of the original in situ soil, and
whose altered condition adversely affects the structural integrity of the shaft foundation.
In no case shall shaft excavation and casing placement extend below the bottom of shaft
excavation as shown in the Plans.

6-19.3(3)D

Bottom of Shaft Excavation

The Contractor shall use appropriate means such as a cleanout bucket or air lift to clean
the bottom of the excavation of all shafts. No more than 2 inches of loose or disturbed
material shall be present at the bottom of the shaft just prior to placing concrete.

The excavated shaft shall be inspected and accepted by the Engineer prior to proceeding
with construction. The bottom of the excavated shaft shall be sounded with an airlift pipe,
a tape with a heavy weight attached to the end of the tape, or other means acceptable to
the Engineer to determine that the shaft bottom meets the requirements in the Contract.

6-19.3(3)E

Shaft Obstructions

When obstructions are encountered, the Contractor shall notify the Engineer promptly.
An obstruction is defined as a specific object (including, but not limited to, boulders,
logs, and man made objects) encountered during the shaft excavation operation which
prevents or hinders the advance of the shaft excavation. When efforts to advance past
the obstruction to the design shaft tip elevation result in the rate of advance of the shaft
drilling equipment being significantly reduced relative to the rate of advance for the
portion of the shaft excavation in the geological unit that contains the obstruction, then
the Contractor shall remove, break up, or push aside the obstruction under the provisions
of

Section 6-19.5

. The method of dealing with such obstructions, and the continuation of

excavation shall be as proposed by the Contractor and accepted by the Engineer.

6-19.3(3)F

Voids Between Permanent Casing and Shaft Excavation

When permanent casing is specified, excavation shall conform to the specified outside
diameter of the shaft. After the casing has been filled with concrete, all void space
occurring between the casing and shaft excavation shall be filled with a material which
approximates the geotechnical properties of the in situ soils, in accordance with the shaft
installation narrative specified in

Section 6-19.3(2)B

, item 5.

6-19.3(3)G

Operating Shaft Excavation Equipment From an Existing Bridge

Drilling equipment shall not be operated from an existing bridge, except as otherwise
noted. If necessary and safe to do so, and if the Contractor submits a Type 2 Working
Drawing consisting of a written request in accordance with

Section 6-01.6

, the Engineer

may permit operation of drilling equipment on a bridge.

Page 6-344

6-19.3(3)H

Seals for Shaft Excavation in Water

When shafts are constructed in water and the Plans show a seal between the casing
shoring and the upper portion of the permanent casing of the shaft, the Contractor shall
construct a seal in accordance with the shaft installation narrative specified in

Section

6-19.3(2)B

, item 7.

Concrete for the casing shoring seal shall be Class 4000W conforming to

Section 6-02

The seal thickness shown in the Plans is designed to resist the hydrostatic uplift force
with the corresponding seal weight and adhesion of the seal to the permanent casing
and the casing shoring of 20 psi, based on the casing shoring dimension and the seal vent
water surface elevation specified in the Plans. If the Contractor uses a casing shoring
diameter other than that specified in the Plans, the Contractor shall submit a revised seal
design in accordance with

Section 6-19.3(2)B

, item 7.

6-19.3(3)I

Required Use of Slurry in Shaft Excavation

The Contractor shall use slurry, in accordance with

Section 6-19.3(4)

, to maintain a stable

excavation during excavation and concrete placement operations once water begins to
enter the shaft excavation at an infiltration rate of 12 inches of depth or more in 1 hour. If
concrete is to be placed in the dry, the Contractor shall pump all accumulated water in the
shaft excavation down to a 3-inch maximum depth prior to beginning concrete placement
operations.

6-19.3(4) Slurry Installation Requirements

6-19.3(4)A

Slurry Technical Assistance

If slurry other than water slurry is used, the manufacturer’s representative, as identified to
the Engineer in accordance with

Section 6-19.3(2)C

, shall:

1. Provide technical assistance for the use of the slurry,
2. Be at the site prior to introduction of the slurry into the first drilled hole requiring

slurry, and

3. Remain at the site during the construction of at least the first shaft excavated to

adjust the slurry mix to the specific site conditions.

After the manufacturer’s representative is no longer present at the site, the Contractor’s
employee trained in the use of the slurry, as identified to the Engineer in accordance with

Section 6-19.3(2)C

, shall be present at the site throughout the remainder of shaft slurry

operations for this project to perform the duties specified in items 1 through 3 above.

Shafts 6-19

6-19.3(4)B

Minimum Level of Slurry in the Excavation

When slurry is used in a shaft excavation the following is required:
1. The height of the slurry shall be as required to provide and maintain a stable hole to

prevent bottom heave, caving, or sloughing of all unstable zones.

2. The Contractor shall provide casing, or other means, as necessary to meet these

requirements.

3. The slurry level in the shaft while excavating shall be maintained above the

groundwater level the greater of the following dimensions:
a.  Not less than 5 feet for mineral slurries.
b.  Not less than 10 feet for water slurries.
c.  Not less than 10 feet for synthetic slurries.

4. The slurry level in the shaft throughout all stops as specified in

Section

6-19.3(3)A

and during concrete placement as specified in

Section 6-19.3(7)

shall be no lower than the water level elevation outside the shaft.

6-19.3(4)C

Slurry Sampling and Testing

Mineral slurry and synthetic slurry shall be mixed and thoroughly hydrated in slurry
tanks, ponds, or storage areas. The Contractor shall draw sample sets from the slurry
storage facility and test the samples for conformance with the specified viscosity and
pH properties before beginning slurry placement in the drilled hole. Mineral slurry shall
conform to the material specifications in

Section 9-36.2(1)

. Synthetic slurry shall conform

Section 9-36.2(2)

, the quality control plan included in the shaft installation narrative in

accordance with

Section 6-19.3(2)B

, item 4. A sample set shall be composed of samples

taken at mid-height and within 2 feet of the bottom of the storage area.

When synthetic slurry is used, the Contractor shall keep a written record of all
additives and concentrations of the additives in the synthetic slurry. These records
shall be submitted as a Type 1 Working Drawing once the slurry system has been
established in the first drilled shaft on the project. The Contractor shall provide revised
data to the Engineer if changes are made to the type or concentration of additives
during construction.

The Contractor shall sample and test all slurry in the presence of the Engineer, unless
otherwise directed. The date, time, names of the persons sampling and testing the
slurry, and the results of the tests shall be recorded. A copy of the recorded slurry test
results shall be submitted to the Engineer at the completion of each shaft, and during
construction of each shaft when requested by the Engineer.

Sample sets of all slurry, composed of samples taken at mid-height and within 2 feet
of the bottom of the shaft and the storage area, shall be taken and tested once every
4 hours minimum at the beginning and during drilling shifts and prior to cleaning the
bottom of the hole to verify the control of the viscosity and pH properties of the slurry.
Sample sets of all slurry shall be taken and tested at least once every 2 hours if the
previous sample set did not have consistent viscosity and pH properties. All slurry shall be

Page 6-346

recirculated, or agitated with the drilling equipment, when tests show that the sample sets
do not have consistent viscosity and pH properties. Cleaning of the bottom of the hole
shall not begin until tests show that the samples taken at mid-height and within 2 feet of
the bottom of the hole have consistent viscosity and pH properties.

Sample sets of all slurry, as specified, shall be taken and tested to verify control of the
viscosity, pH, density, and sand content properties after final cleaning of the bottom of
the hole just prior to placing concrete. Placement of the concrete shall not start until tests
show that the samples taken at mid-height and within 2 feet of the bottom of the hole
have consistent specified properties.

6-19.3(4)D

Maintenance of Required Slurry Properties

The Contractor shall clean, recirculate, de-sand, or replace the slurry to maintain the
required slurry properties.

6-19.3(4)E

Maintenance of a Stable Shaft Excavation

The Contractor shall demonstrate to the satisfaction of the Engineer that stable
conditions are being maintained. If the Engineer determines that stable conditions are
not being maintained, the Contractor shall immediately take action to stabilize the shaft.
The Contractor shall submit a revised shaft installation narrative that addresses the
problem and prevents future instability. The Contractor shall not continue with shaft
construction until the damage that has already occurred is repaired in accordance with the
specifications, and until receiving the Engineer’s review of the revised shaft installation
narrative.

When mineral slurry conforming to

Section 9-36.2(1)

is used to stabilize the unfilled

portion of the shaft, the Contractor shall remove the excess slurry buildup inside of the
shaft diameter prior to continuing with concrete placement. The Contractor shall use the
same methods of shaft excavation and the same diameter of drill tools to remove the
excess slurry buildup as was used to excavate the shaft to its current depth.

6-19.3(4)F

Disposal of Slurry and Slurry Contacted Spoils

The Contractor shall manage and dispose of the slurry wastewater in accordance with

Section 8-01.3(1)C

. Slurry-contacted spoils shall be disposed of as specified in the shaft

installation narrative in accordance with

Section 6-19.3(2)B

, item 8, and in accordance

with the following requirements:
1. Uncontaminated spoils in contact with water-only slurry may be disposed of as

clean fill.

2. Uncontaminated spoils in contact with water slurry mixed with flocculants approved

Section 8-01.3(1)C3

may be disposed of as clean fill away from areas that drain to

surface waters of the state.

3. Spoils in contact with synthetic slurry or water slurry with polymer-based additives

or flocculants not approved in

Section 8-01.3(1)C3

shall be disposed of in

accordance with

Section 2-03.3(7)C

. With permission of the Engineer, the Contractor

may re-use these spoils on-site.

Shafts 6-19

4. Spoils in contact with mineral slurry shall be disposed of in accordance with

Section 2-03.3(7)C

. With permission of the Engineer, the Contractor may re-use

these spoils on-site.

6-19.3(5) Assembly and Placement of Reinforcing Steel

6-19.3(5)A

Steel Reinforcing Bar Cage Assembly

The reinforcing cage shall be rigidly braced to retain its configuration during handling
and construction. Individual or loose bars will not be permitted. The Contractor shall
show bracing and any extra reinforcing steel required for fabrication of the cage on the
shop drawings. Shaft reinforcing bar cages shall be supported on a continuous surface
to the extent possible. All rigging connections shall be located at primary handling bars,
as identified in the reinforcing steel assembly and installation plan. Internal bracing is
required at each support and lift point.

The reinforcement shall be carefully positioned and securely fastened to provide the
minimum clearances listed below, and to ensure no displacement of the reinforcing steel
bars occurs during placement of the concrete. The steel reinforcing bars shall be securely
held in position throughout the concrete placement operation.

6-19.3(5)B

Steel Reinforcing Bar Cage Centralizers

The Contractor shall submit details of the proposed reinforcing cage centralizers along
with the shop drawings. The reinforcing steel centralizers at each longitudinal space
plane shall be placed at least at the quarter points around the circumference of the steel
reinforcing bar cage, and at a maximum longitudinal spacing of either 2.5 times the shaft
diameter or 20 feet, whichever is less. The Contractor shall furnish and install additional
centralizers as required to maintain the specified concrete cover throughout the length of
the shaft.

6-19.3(5)C

Concrete Cover Over Steel Reinforcing Bars

Steel reinforcing bars shall be placed as shown in the Plans with minimum concrete cover
as shown below:

Shaft Diameter (feet)

Minimum Concrete Cover, and

Concrete Cover Tolerance, Except

at Permanent Slip Casing (inches)

Minimum Concrete Cover

at Permanent Slip Casing

(inches)

Less than or equal to 3

3, -1½

1½

Greater than 3 and less than 4

4, -2

1½

Greater than or equal to 4 and

less than 5

4, -2

5 or larger

6, -3

The concrete cover tolerances specified above apply to the concrete cover specified in
the Plans, even if it exceeds the minimum concrete cover.

Page 6-348

6-19.3(5)D

Steel Reinforcing Bar Cage Support at Base of Shaft Excavation

For shafts with temporary casing within 15 feet of the bottom of shaft elevation as
specified in the Plans, the Contractor may place quarry spalls or other rock backfill
acceptable to the Engineer into the shaft below the specified bottom of shaft elevation as
a means to support the steel reinforcing bar cage, provided that the materials and means
to accomplish this have been addressed by the shaft installation narrative, as specified in

Section 6-19.3(2)B

, item 9. The use of bar boots and/or rebar cage base plates is required

when quarry spalls or other rock backfill is placed at the base of the shaft excavation.

6-19.3(6) Contractor Furnished Accessories for Nondestructive QA Testing

6-19.3(6)A

Shafts Requiring Access Tubes

The Contractor shall furnish and install access tubes in all shafts receiving CSL
testing or the thermal probe method of TIP testing, except as otherwise noted in

Section 6-19.3(1)B1

6-19.3(6)B

Orientation and Assembly of the Access Tubes

The Contractor shall securely attach the access tubes to the interior of the reinforcement
cage of the shaft. One access tube shall be furnished and installed for each foot of shaft
diameter, rounded to the nearest whole number, as shown in the Plans. The number of
access tubes for shaft diameters specified as “X feet 6 inches” shall be rounded up to
the next higher whole number. The access tubes shall be placed around the shaft, inside
the spiral or hoop reinforcement, and bundled with the vertical reinforcement. Where
circumferential components of the rebar cage bracing system prevent bundling the access
tubes directly to the vertical reinforcement, the access tubes shall be placed inside the
circumferential components of the rebar cage bracing system as close as possible to the
nearest vertical steel reinforcement bar.

The access tubes shall be installed in straight alignment and as near to parallel to the
vertical axis of the reinforcement cage as possible. The access tubes shall extend from
the bottom of the reinforcement cage to at least 2 feet above the top of the shaft.
Splice joints in the access tubes, if required to achieve full length access tubes, shall
be watertight. The Contractor shall clear the access tubes of all debris and extraneous
materials before installing the access tubes. The tops of access tubes shall be deburred.
Care shall be taken to prevent damaging the access tubes during reinforcement cage
installation and concrete placement operations in the shaft excavation.

6-19.3(6)C

Care for Access Tubes From Erection Through Nondestructive

QA Testing

The access tubes shall be filled with potable water before concrete placement, and the
top watertight PVC caps shall be reinstalled and secured in accordance with

Section

9-36.4

. The Contractor shall keep all of a shaft’s access tubes full of water through

the completion of nondestructive QA testing of that shaft. When temperatures below
freezing are possible, the Contractor shall protect the access tubes against freezing by

Shafts 6-19

wrapping the exposed tubes with insulating material, adding antifreeze to the water in the
tubes, or other methods acceptable to the Engineer.

6-19.3(6)D

Shafts Requiring Thermal Wire

The Contractor shall furnish and install thermal wire in all shafts receiving the thermal
wire method of TIP testing, except as otherwise noted in

Section 6-19.3(1)B1

6-19.3(6)E

Thermal Wire and Thermal Access Points (TAPs)

The thermal wire and associated couplers shall be obtained from the source specified in
the Special Provisions.

The Contractor shall securely attach the thermal wire to the interior of the reinforcement
cage of the shaft in conformance with the supplier’s instructions. At a minimum, one
thermal wire shall be furnished and installed for each foot of shaft diameter, rounded to
the nearest whole number, as shown in the Plans. The number of thermal wires for shaft
diameters specified as “X feet 6 inches” shall be rounded up to the next higher whole
number. The thermal wires shall be placed around the shaft, inside the spiral or hoop
reinforcement, and tied to the vertical reinforcement with plastic “zip” ties at a maximum
spacing of 2-feet. Steel tie wire shall not be used.

The thermal wire shall be installed in straight alignment and taut, but with enough slack
to not be damaged during reinforcing cage lofting. The wires shall be as near to parallel to
the vertical axis of the reinforcement cage as possible. The thermal wire shall extend from
the bottom of the reinforcement cage to the top of the shaft, with a minimum of 5-feet
of slack wire provided above the top of shaft. All thermal wires in a shaft shall be equal
lengths. Care shall be taken to prevent damaging the thermal wires during reinforcement
cage installation and concrete placement operations in the shaft excavation.

After completing shaft reinforcement cage fabrication at the site and prior to installation
of the cage into the shaft excavation, the Contractor shall install and connect thermal
access points (TAPs) to the thermal wires. The TAPs shall record data for at least one hour
after the cage is placed in the excavation to measure the slurry temperature and enable
the steel and slurry temperatures to equilibrate prior to placing concrete in the shaft. The
TAPs shall record and store data every 15 minutes. The TAPs shall remain active for a
minimum of 36 hours.

Prior to beginning concrete placement the TAPs shall be checked to ensure they are
recording data and that the wires have not been damaged. If a TAP unit is not functioning
due to a damaged wire, the Contractor shall repair or replace the wire. If a TAP unit fails
or a wire breaks after concrete placement has started, the Contractor shall not stop the
concrete placement operation to repair the wire.

Page 6-350

6-19.3(6)F

Use of Access Tubes for TIP Testing Under the Thermal Probe

Method

The Contractor may use access tubes for TIP testing under the thermal probe method.
Access tubes shall be cared for in accordance with

Section 6-19.3(6)C

. Prior to TIP testing

under the thermal probe method, the water in each tube shall be removed, collected,
and stored in an insulated container. The access tube shall be blown dry and swabbed
to remove residual water. After TIP testing, the collected and stored tube water shall
be introduced back into the access tube. New potable water may be used, provided the
water temperature is not more than 10°F cooler than the average concrete temperature
measured by the probe.

6-19.3(7) Placing Concrete

6-19.3(7)A

Concrete Class for Shaft Concrete

Shaft concrete shall be Class 5000P conforming to

Section 6-02

6-19.3(7)B

Concrete Placement Requirements

Concrete placement shall commence immediately after completion of excavation by the
Contractor and inspection by the Engineer. Immediately prior to commencing concrete
placement, the shaft excavation and the properties of the slurry (if used) shall conform
to Sections

6-19.3(3)D

and

6-19.3(4)

, respectively. Concrete placement shall continue in

one operation to the top of the shaft, or as shown in the Plans. The Contractor shall place
concrete between the upper construction joint of the shaft and the top of the shaft in
the dry.

During concrete placement, the Contractor shall monitor, and minimize, the difference in
the level of concrete inside and outside of the steel reinforcing bar cage. The Contractor
shall conduct concrete placement operations to maintain the differential concrete head as
1-foot maximum.

If water is not present, the concrete shall be deposited through the center of the
reinforcement cage by a method that prevents segregation of aggregates and splashing
of concrete on the reinforcement cage. The concrete shall be placed such that the free-
fall is vertical down the center of the shaft without hitting the sides, the steel reinforcing
bars, or the steel reinforcing bar cage bracing. The

Section 6-02.3(6)

restriction for 5 feet

maximum free fall shall not apply to placement of concrete into a shaft.

6-19.3(7)C

Concrete Vibration Requirements

When placing concrete in the dry, only the top 5 feet of concrete shall be vibrated, in
accordance with

Section 6-02.3(9)

, except that the entire depth of concrete placed in the

shaft-column steel reinforcing bar splice zone shall be vibrated. If a temporary casing is
used, it shall be removed before vibration. This requirement may be waived if a temporary
casing is used and removed with a vibratory hammer during the concrete placement
operation. Vibration of concrete does not affect the maximum slump allowed for the
concrete class specified.

Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10) - page 72