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

The structural earth wall manufacturer shall provide a qualified and experienced
representative to resolve wall construction problems. The structural earth wall
manufacturer’s representative shall be present at the beginning of wall construction
activities, and at other times as needed throughout construction. Recommendations
made by the structural earth wall manufacturer’s representative shall be followed by
the Contractor.

The completed wall shall meet the following tolerances:
1. Deviation from the design batter and horizontal alignment, when measured along a

10-foot straightedge, shall not exceed the following:
a. Welded wire faced structural earth wall: 2 inches
b. Precast concrete panel and concrete block faced structural earth wall: ¾ inch

2. Deviation from the overall design batter of the wall shall not exceed the following

per 10 feet of wall height:
a. Welded wire faced structural earth wall: 1½ inches
b. Precast concrete panel and concrete block faced structural earth wall: ½ inch

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Structural Earth Walls

3. The maximum outward bulge of the face between welded wire faced structural earth

wall reinforcement layers shall not exceed 2 inches. The maximum allowable offset
in any precast concrete facing panel joint shall be ¾ inch. The maximum allowable
offset in any concrete block joint shall be ¾ inch.

4. The base of the structural earth wall excavation shall be within 3 inches of the staked

elevations, unless otherwise accepted or specified by the Engineer.

5. The external structural earth wall dimensions shall be placed within 2 inches of that

staked on the ground.

6. The backfill reinforcement layers shall be located horizontally and vertically within

1 inch of the locations shown in the structural earth wall Working Drawings.

At least 5 working days prior to the Contractor beginning any structural earth wall Work
at the site, a structural earth wall preconstruction conference shall be held to discuss
construction procedures, personnel, and equipment to be used, and other elements of
structural earth wall construction. Those attending shall include:
1. (representing the Contractor) The superintendent, on site supervisors, and all

foremen in charge of excavation, leveling pad placement, concrete block and
soil reinforcement placement, and structural earth wall backfill placement and
compaction.

2. (representing the Structural Earth Wall Manufacturer) The qualified and experienced

representative of the structural earth wall manufacturer as specified at the beginning
of this section.

3. (representing the Contracting Agency) The Engineer, key inspection personnel, and

representatives from the WSDOT Construction Office and Materials Laboratory
Geotechnical Services Branch.

6-13.3(2) Submittals

The Contractor, or the supplier as the Contractor’s agent, shall furnish a Manufacturer’s
Certificate of Compliance certifying that the structural earth wall materials conform to the
specified material requirements. This includes providing a Manufacturer’s Certificate of
Compliance for all concrete admixtures, cement, fly ash, steel reinforcing bars, reinforcing
strips, reinforcing mesh, tie strips, fasteners, welded wire mats, backing mats, construction
geotextile for wall facing, drainage geosynthetic fabric, block connectors, and joint
materials. The Manufacturer’s Certificate of Compliance for geogrid reinforcement shall
include the information specified in

Section 9-33.4(4)

for each geogrid roll, and shall

specify the geogrid polymer types for each geogrid roll.

A Type 1 Working Drawing of all test results performed by the Contractor or the
Contractor’s supplier, which are necessary to ensure compliance with the specifications,
shall be submitted along with each Manufacturer’s Certificate of Compliance.

Before fabrication, the Contractor shall submit a Type 1 Working Drawing consisting
of the field construction manual for the structural earth walls, prepared by the wall
manufacturer. This manual shall provide step-by-step directions for construction of the
wall system.

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The Contractor, through the license/patent holder for the structural earth wall system,
shall submit Type 2E Working Drawings consisting of detailed design calculations and
details. If not prepared by the license/patent holder for the structural earth system, the
design calculation and working drawing submittal shall include documentation that the
design calculation and working drawing submittal has been reviewed by, and received the
concurrence of, the headquarters organization of the structural earth wall manufacturer
as identified in the Special Provisions. Review and concurrence by a sales representative
office is not acceptable.

6-13.3(2)A

Design Calculation Content Requirements

The design calculation submittal shall include detailed design calculations based on the
wall geometry and design parameters specified in the Plans and Special Provisions. The
calculations shall include detailed explanations of any symbols, design input, materials
property values, and computer programs used in the design of the walls. All computer
output submitted shall be accompanied by supporting hand calculations detailing the
calculation process. If MSEW 3.0, or a later version, is used for the wall design, hand
calculations supporting MSEW are not required.

The design calculations shall be based on the current AASHTO LRFD Bridge Design
Specifications, including current interims, the current WSDOT

Bridge Design Manual

LRFD (BDM), and the WSDOT

Geotechnical Design Manual

(GDM), and also based

on the following:
1. The wall design calculations shall address all aspects of wall internal stability for the

service, strength, and extreme event limit states.

2. The wall surcharge conditions (backfill slope) shown in the Plans.
3. If a highway is adjacent to and on top of the wall, a 2-foot surcharge shall be used in

the design.

4. If the Plans detail an SEW traffic barrier or SEW pedestrian barrier on top of the

wall, the barrier shall be designed for a minimum TL-4 impact load, unless otherwise
specified in the Plans or Special Provisions.

5. If the Plans detail an SEW traffic barrier or SEW pedestrian barrier on top of the wall,

the wall shall be designed for the impact load transferred from the barrier to the wall.

6. The geotechnical design parameters for the wall shall be as specified in the Special

Provisions.

7. The soil reinforcement length shall be as shown in the Plans. If the Plans do not

show a length, the length shall be either 6 feet or 0.7 times the wall design height H,
whichever is greater.

If there are differences in design requirements between the AASHTO LRFD Bridge Design
Specifications and the BDM or GDM, the BDM and GDM requirements shall govern.

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6-13.3(2)B

Working Drawing Content Requirements

All design details shown in the working drawings shall be selected from the design
details and products specified for the specific structural earth wall manufacturer in the
Preapproved Wall Appendix in the current WSDOT

Geotechnical Design Manual

(GDM).

Geosynthetic reinforcement shown in the working drawings shall be selected from
the products listed in the current WSDOT Qualified Products List (QPL). Substitution
of design details and products not listed in the current WSDOT GDM or QPL will not
be allowed.

The working drawing submittal shall include all details, dimensions, quantities, and
cross sections necessary to construct the wall based on the wall geometry and design
parameters specified in the Plans and Special Provisions, and shall include, but not be
limited to, the following items:
1. A plan and elevation sheet or sheets for each wall, containing the following:

a. An elevation view of the wall that includes the following:

i. The elevation at the top of the wall, at all horizontal and vertical break

points, and at least every 50 feet along the wall;

ii. Elevations at the base of welded wire mats or the top of leveling pads and

foundations, and the distance along the face of the wall to all steps in the
welded wire mats, foundations, and leveling pads;

iii. The designation as to the type of panel, block, or module;
iv. The length, size, and number of geogrids or mesh or strips, and the distance

along the face of the wall to where changes in length of the geogrids or
mesh or strips occur; or

v. The length, size, and wire sizes and spacing of the welded wire mats and

backing mats, and the distance along the face of the wall to where changes
in length, size, and wire sizes and spacing of the welded wire mats and
backing mats occur; and

vi. The location of the original and final ground line.

b. A plan view of the wall that indicates the offset from the construction

centerline to the face of the wall at all changes in horizontal alignment; the
limit of the widest module, geogrid, mesh, strip, or welded wire mat, and the
centerline of any drainage structure or drainage pipe that is behind or passes
under or through the wall.

c.  General notes, if any, required for design and construction of the wall.
d.  All horizontal and vertical curve data affecting wall construction.
e.  A listing of the summary of quantities provided on the elevation sheet of each

wall for all items, including incidental items.

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A cross section showing limits of construction. In fill sections, the cross section
shall show the limits and extent of select granular backfill material placed above
original ground.

g. Limits and extent of reinforced soil volume.

2. All details, including steel reinforcing bar bending details. Bar bending details shall be

in accordance with

Section 9-07.1

3. All details for foundations and leveling pads, including details for steps in the

foundations or leveling pads.

4. All modules and facing elements shall be detailed. The details shall show all

dimensions necessary to construct the element, all steel reinforcing bars in the
element, and the location of reinforcement element attachment devices embedded
in the precast concrete facing panel or concrete block.

5. All details for construction of the wall around drainage facilities, sign, signal,

luminaire, and noise barrier wall foundations, and structural abutment and
foundation elements shall be clearly shown.

6. All details for connections to SEW traffic or pedestrian barriers, coping, parapets,

noise barrier walls, and attached lighting shall be shown.

7. All details for the SEW traffic or pedestrian barrier attached to the top of the wall

(if shown in the Plans), including interaction with bridge approach slabs.

6-13.3(3) Excavation and Foundation Preparation

Excavation shall conform to

Section 2-09.3(3)

. Foundation soils found to be unsuitable

shall be removed and replaced in accordance with

Section 2-09.3(1)C.

The foundation

for the Structure shall be graded level for a width equal to or exceeding the length of
reinforcing as shown in the structural earth wall Working Drawings and, for walls with
geogrid reinforcing, in accordance with

Section 2-12.3

. Prior to wall construction, the

foundation, if not in rock, shall be compacted as accepted by the Engineer.

At the foundation level of the bottom course of precast concrete facing panels and
concrete blocks, an unreinforced concrete leveling pad shall be provided as shown in
the Plans. The leveling pad shall be cured a minimum of 12 hours and have a minimum
compressive strength of 1,500 psi before placement of the precast concrete facing panels
or concrete blocks.

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6-13.3(4) Precast Concrete Facing Panel and Concrete Block Fabrication

Concrete for precast concrete facing panels shall meet the following requirements:
1. Have a minimum 28-day compressive strength of 4,000 pounds per square inch,

unless otherwise specified in the Special Provisions for specific proprietary wall
systems. If Self-Consolidating Concrete is used, the concrete shall conform to
Sections

6-02.3(27)B

and

6-02.3(27)C

2. Contain a water-reducing admixture meeting AASHTO M194 Type A, D, F, or G.
3. Be air-entrained, 6 percent

1½ percent.

4. Have a maximum slump of 4 inches, or 6 inches if a Type F or G water reducer

is used.

Concrete for dry cast concrete blocks shall meet the following requirements:
1.  Have a minimum 28-day compressive strength of 4,000 psi.
2.  Conform to ASTM C1372, except as otherwise specified.
3.  The lot of blocks produced for use in this project shall conform to the following

freeze-thaw test requirements when tested in accordance with ASTM C1262.
Minimum acceptable performance shall be defined as weight loss at the conclusion
of 150 freeze-thaw cycles not exceeding 1 percent of the block’s initial weight for a
minimum of four of the five block specimens tested.

4. The concrete blocks shall have a maximum water absorption of 1 percent above the

water absorption content of the lot of blocks produced and successfully tested for
the freeze-thaw test specified in item 3 above.

Precast concrete facing panels and concrete blocks will be accepted based on successful
compressive strength tests, WSDOT “Approved for Shipment” stamp or tag, and visual
inspection at the jobsite. The precast concrete facing panels and concrete blocks shall be
considered acceptable regardless of curing age when compressive test results indicate
that the compressive strength conforms to the 28-day requirements and when the visual
inspection is satisfactorily completed. Fabrication of precast concrete facing panels and
blocks shall conform to

Section 6-02.3(28)

. Testing of dry cast concrete blocks shall

conform to ASTM C140.

All precast concrete facing panels shall be 5 feet square, except:
1. for partial panels at the top, bottom, and ends of the wall; and
2. as otherwise shown in the Plans.

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All precast concrete facing panels shall be manufactured within the following tolerances:

1. All dimensions ± 3/16 inch.

2. Squareness, as determined by the difference between the two diagonals, shall not

exceed ½ inch.

3. Surface defects on smooth formed surfaces measured on a length of 5 feet shall not

exceed ⅛ inch. Surface defects on textured-finished surfaces measured on a length
of 5 feet shall not exceed 5/16 inch.

All concrete blocks shall be manufactured within the following tolerances:
1. Vertical dimensions shall be ±

1/16

inch of the Plan dimension, and the rear height

shall not exceed the front height.

2. The dimensions of the grooves in the top and bottom faces of the concrete blocks

shall be formed within the tolerances specified by the proprietary wall manufacturer,
for the fit required for the block connectors.

3. All other dimensions shall be ± ¼ inch of the Plan dimension.

Tie attachment devices, except for geosynthetic reinforcement, shall be set in place to the
dimensions and tolerances shown in the Plans prior to casting.

The forms forming precast concrete facing panels, including the forms for loop pockets
and access pockets, and the forms forming the concrete blocks, shall be removed in
accordance with the recommendations of the wall manufacturer, without damaging the
concrete.

The concrete surface for the precast concrete facing panel shall have the finish shown
in the Plans for the front face and an unformed finish for the rear face. The rear face of
the precast concrete facing panel shall be roughly screeded to eliminate open pockets of
aggregate and surface distortions in excess of ¼ inch.

The concrete surface for the front face of the concrete block shall be flat, and shall be a
conventional “split face” finish in accordance with the wall manufacturer’s Specifications.The
concrete surface of all other faces shall be Class 2 in accordance with

Section 6-02.3(14)B

The finish and appearance of the concrete blocks shall also conform to ASTM C1372. The
color of the concrete block shall be concrete gray, unless otherwise shown in the Plans.

The date of manufacture, production lot number, and the piece-mark, shall be clearly
marked on the rear face of each precast concrete facing panel, and marked or tagged on
each pallet of concrete blocks.

All precast concrete facing panels and concrete blocks shall be handled, stored, and
shipped in accordance with Sections

6-02.3(28)G

and

6-02.3(28)H

to prevent chipping,

cracks, fractures, and excessive bending stresses.

Precast concrete facing panels in storage shall be supported on firm blocking located
immediately adjacent to tie strips to avoid bending the tie strips.

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6-13.3(5) Precast Concrete Facing Panel and Concrete Block Erection

The precast concrete facing panels shall be placed vertically. During erection, precast
concrete facing panels shall be handled by means of a lifting device set into the upper
edge of the panels.

Concrete blocks shall be erected in a running bond fashion in accordance with the wall
manufacturer’s field construction manual, and may be placed by hand. The top surface
of each course of concrete blocks, including all pockets and recesses, shall be cleaned
of backfill and all extraneous materials prior to connecting the reinforcing strips or
geosynthetic reinforcing, and placing the next course of concrete blocks. Concrete blocks
receiving geosynthetic reinforcement shall be connected as specified in the Special
Provisions. Cap block top courses shall be bonded to the lower course of concrete blocks
as specified below. All other concrete blocks shall be connected with block connectors or
pins placed into the connector slots.

Precast concrete facing panels and concrete blocks shall be placed in successive
horizontal lifts as backfill placement proceeds in the sequence shown in the structural
earth wall Working Drawings as approved by the Engineer.

External bracing is required for the initial lift for precast concrete facing panels.

As backfill material is placed behind the precast concrete facing panels, the panels shall
be maintained in vertical position by means of temporary wooden wedges placed in the
joint at the junction of the two adjacent panels on the external side of the wall.

Reinforcing shall be placed normal to the face of the wall, unless otherwise shown in the
Plans or directed by the Engineer. Prior to placement of the reinforcing, backfill shall be
compacted.

Geosynthetic reinforcing shall be placed in accordance with

Section 2-12.3

and as follows:

1. The Contractor shall stretch out the geosynthetic in the direction perpendicular

to the wall face to remove all slack and wrinkles, and shall hold the geosynthetic
in place with soil piles or other methods as recommended by the geosynthetic
manufacturer, before placing backfill material over the geosynthetic to the specified
cover.

2. The geosynthetic reinforcement shall be continuous in the direction perpendicular to

the wall face from the back face of the concrete panel to the end of the geosynthetic
or to the last geogrid node at the end of the specified reinforcement length.
Geosynthetic splices parallel to the wall face will not be allowed.

At the completion of each course of concrete blocks and prior to installing any block
connectors or geosynthetic reinforcement at this level, the Contractor shall check the
blocks for level placement in all directions, and shall adjust the blocks by grinding or
rear face shimming, or other method as recommended by the structural earth wall
manufacturer’s representative and as approved by the Engineer, to bring the blocks into a
level plane.

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6-13

For concrete block wall systems receiving a cap block top course, the cap blocks shall be
bonded to the lower course either with mortar conforming to

Section 9-20.4(3)

, or with

an adhesive capable of bonding the concrete block courses together.

6-13.3(6) Welded Wire Faced Structural Earth Wall Erection

The Contractor shall erect the welded wire wall reinforcement in accordance with the wall
manufacturer’s field construction manual. Construction geotextile for wall facing shall be
placed between the backfill material within the reinforced zone and the coarse granular
material immediately behind the welded wire wall facing, as shown in the Plans and the
structural earth wall Working Drawings. Geosynthetic reinforcing, when used, shall be
placed in accordance with Sections

2-12.3

and

6-13.3(5)

6-13.3(7) Backfill

Backfill placement shall closely follow erection of each course of welded wire mats
and backing mats, precast concrete facing panels, or concrete blocks. Backfill shall be
placed in such a manner as to avoid any damage or disturbance to the wall materials or
misalignment of the welded wire mats and backing mats, precast concrete facing panels,
or concrete blocks. Backfill shall be placed in a manner that segregation does not occur.
Construction equipment shall not operate directly on the wall reinforcement. A minimum
backfill thickness of 6 inches over the reinforcement shall be required prior to operation
of vehicles or equipment.

The Contractor shall place wall backfill over geosynthetic reinforcement, or construction
geotextile for wall facing, in accordance with

Section 2-12.3

Misalignment or distortion of the precast concrete facing panels or concrete blocks due to
placement of backfill outside the limits of this Specification shall be corrected in a manner
acceptable to the Engineer.

The moisture content of the backfill material prior to and during compaction shall be
uniformly distributed throughout each layer of material. The moisture content of all
backfill material shall conform to Sections

2-03.3(14)C

and

2-03.3(14)D

Backfill shall be compacted in accordance with Method C of

Section 2-03.3(14)C

, except

as follows:
1. The maximum lift thickness after compaction shall not exceed 10 inches.
2. The Contractor shall decrease this lift thickness, if necessary, to obtain the specified

density.

3. The Contractor shall not use sheepsfoot rollers or rollers with protrusions for

compacting backfill reinforced with geosynthetic layers, or for compacting the first
lift of backfill above the construction geosynthetic for wall facing for each layer
of welded wire mats. Rollers shall have sufficient capacity to achieve compaction
without causing distortion to the face of the wall in accordance with the tolerances
specified in

Section 6-13.3(1)

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4. The Contractor shall compact the zone within 3 feet of the back of the wall facing

panels without causing damage to or distortion of the wall facing elements (welded
wire mats, backing mats, construction geotextile for wall facing, precast concrete
facing panels, and concrete blocks) by using a plate compactor. No soil density tests
will be taken within this area.

5. For wall systems with geosynthetic reinforcement, the minimum compacted backfill

lift thickness of the first lift above each geosynthetic reinforcement layer shall be
6 inches.

At the end of each day’s operation, the Contractor shall shape the last level of backfill to
permit runoff of rainwater away from the wall face. In addition, the Contractor shall not
allow surface runoff from adjacent areas to enter the wall construction site.

6-13.3(8) Guardrail Placement

Where guardrail posts are required, the Contractor shall not begin installing guardrail
posts until completing the structural earth wall to the top of wall elevation shown in the
Plans. The Contractor shall install the posts in a manner that prevents movement of the
precast concrete facing panels or concrete blocks, and prevents ripping, tearing, or pulling
of the wall reinforcement.

The Contractor may cut welded wire reinforcement of welded wire faced structural
earth walls to facilitate placing the guardrail posts, but only in the top two welded wire
reinforcement layers and only with the permission of the Engineer in a manner that
prevents bulging of the wall face and prevents ripping or pulling of the welded wire
reinforcement. Holes through the welded wire reinforcement shall be the minimum
size necessary for the post. The Contractor shall demonstrate to the Engineer prior to
beginning guardrail post installation that the installation method will not rip, tear, or pull
the wall reinforcement.

The Contractor shall place guardrail posts between the reinforcing strips, reinforcing
mesh, and tie strips of the non-geosynthetic reinforced precast concrete panel or
concrete block faced structural earth walls. Holes through the reinforcement of
geosynthetic reinforced walls, if necessary, shall be the minimum size necessary for the
guardrail post.

6-13.3(9) SEW Traffic Barrier and SEW Pedestrian Barrier

The Contractor, in conjunction with the structural earth wall manufacturer, shall design
and detail the SEW traffic barrier and SEW pedestrian barrier in accordance with

Section

6-13.3(2)

and the above ground geometry details shown in the Plans. The barrier Working

Drawings and supporting calculations shall be Type 2E and shall include, at a minimum,
the following:
1. Complete details of barrier cross section geometry, including the portion below

ground, and accommodations necessary for bridge approach slabs, PCCP, drainage
facilities, underground utilities, and sign support, luminaire pole, traffic signal
standard, and other barrier attachments.

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2. Details of the steel reinforcement of the barrier, including a bar list and bending

diagram in accordance with

Section 6-02.3(24)

, and including additional

reinforcement required at sign support, luminaire pole, traffic signal standard, and
other barrier attachment locations.

3. Details of the interface of, and the interaction between, the barrier and the top

layers of structural earth wall reinforcement and facing.

4. When the Plans specify placement of conduit pipes through the barrier, details of

conduit pipe and junction box placement.

SEW traffic barrier and SEW pedestrian barrier shall be constructed in accordance with
Sections

6-02.3(11)A

and

6-10.3(2)

, and the details in the Plans and in the structural earth

wall Working Drawings as approved by the Engineer. The moment slab supporting the
SEW traffic or pedestrian barrier shall be continuously wet cured for 3 days in accordance
with

Section 6-02.3(11)

6-13.4 Measurement

Structural earth wall will be measured by the square foot of completed wall in place. The
bottom limits for vertical measurement will be the bottom of the bottom mat, for welded
wire faced structural earth walls, or the top of the leveling pad (or bottom of wall if no
leveling pad is present) for precast concrete panel or concrete block faced structural earth
walls. The top limit for vertical measurement will be the top of wall as shown in the Plans.
The horizontal limits for measurement are from the end of the wall to the end of the wall.

Gravel borrow for structural earth wall including haul will be measured by the cubic yard
in place determined by the limits shown in the Plans.

SEW traffic barrier, and SEW pedestrian barrier will be measured as specified in

Section 6-10.4

for cast-in-place concrete barrier.

6-13.5 Payment

Payment will be made for each of the following Bid items when they are included in the
Proposal:

“Structural Earth Wall”, per square foot.
The unit Contract price per square foot for “Structural Earth Wall” shall be full
payment for all costs to perform the Work in connection with constructing structural
earth walls, including leveling pads and copings when specified.
“Gravel Borrow for Structural Earth Wall incl. Haul”, per cubic yard.
The unit Contract price per cubic yard for “Gravel Borrow for Structural Earth Wall
incl. Haul” shall be full payment for all costs to perform the Work in connection
with furnishing and placing backfill for structural earth wall, including hauling and
compacting the backfill, and furnishing and placing the wall-facing backfill for welded
wire-faced structural earth walls.
“SEW Traffic Barrier”, per linear foot.

Geosynthetic Retaining Walls

6-14

Geosynthetic Retaining Walls

6-14.1 Description

This Work consists of constructing geosynthetic retaining walls, including those shown in
the

Standard Plans

6-14.2 Materials

Materials shall meet the requirements of the following sections:
Cement

9-01

Aggregates for Concrete

9-03.1

Sand

9-03.13(1)

Gravel Borrow for Structural Earth Wall

9-03.14(4)

Polyurethane Sealant

9-04.2(3)

Closed Cell Foam Backer Rod

9-04.2(3)A

Anchor Rods and Associated Nuts, Washers, and Couplers

9-06.5(4)

Reinforcing Steel

9-07

Welded Wire Reinforcement

9-07.7

Grout

9-20.3(4)

Construction Geosynthetic

9-33

Anchor plate shall conform to ASTM A36, ASTM A572 Grade 50, or ASTM A588.

The requirements specified in

Section 2-12.2

for geotextile shall also apply to

geosynthetic and geogrid materials used for permanent and temporary geosynthetic
retaining walls.

Other materials required shall be as specified in the Special Provisions.

6-14.3

Construction Requirements

Temporary geosynthetic retaining walls are defined as those walls and wall components
constructed and removed or abandoned before the Physical Completion Date of the
project or as shown in the Plans. All other geosynthetic retaining walls shall be considered
as permanent.

6-14.3(1) Quality Assurance

The Contractor shall complete the base of the retaining wall excavation to within plus or
minus 3 inches of the staked elevations unless otherwise directed by the Engineer. The
Contractor shall place the external wall dimensions to within plus or minus 2 inches of
that staked on the ground. The Contractor shall space the reinforcement layers vertically
and place the overlaps to within plus or minus 1 inch of that shown in the Plans.

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The completed wall(s) shall meet the following tolerances:

Permanent

Wall

Temporary

Wall

Deviation from the design batter and horizontal alignment for the

face when measured along a 10-foot straightedge at the midpoint of

each wall layer shall not exceed:

3 inches

5 inches

Deviation from the overall design batter per 10 feet of wall height

shall not exceed:

2 inches

3 inches

Maximum outward bulge of the face between backfill reinforcement

layers shall not exceed:

4 inches

6 inches

6-14.3(2) Submittals

The Contractor shall submit Type 2E Working Drawings consisting of detailed plans
for each wall. The Working Drawing submittal shall include all details, dimensions, and
cross sections necessary to construct the wall based on the wall geometry and design
parameters specified in the Plans, including at a minimum, the following:
1. Detailed wall plans, with plan and elevation views for each wall, showing the actual

lengths proposed for the geosynthetic reinforcing layers and the locations of each
geosynthetic product proposed for use in each of the geosynthetic reinforcing layers.

2. Detailed cross sections showing the geosynthetic reinforcing layers, fascia

connection dowels or anchor rods, and fascia formwork connection or support
details located within or adjacent to the wall backfill.

3. The Contractor’s proposed wall construction method, including proposed forming

systems, types of equipment to be used, proposed erection sequence and details of
how the backfill will be retained during each stage of construction.

4. Manufacturer’s Certificate of Compliance, samples of the retaining wall geosynthetic

and sewn seams for the purpose of acceptance as specified.

5. Details of geosynthetic retaining wall corner construction, including details of the

positive connection between the wall sections on both sides of the corner.

6. Details of terminating a top layer of retaining wall geosynthetic and backfill due

to a changing retaining wall profile.

Acceptance of the Contractor’s proposed wall construction details and methods shall not
relieve the Contractor of their responsibility to construct the walls in accordance with the
requirements of these Specifications.

6-14.3(3) Excavation and Foundation Preparation

Excavation shall conform to

Section 2-09.3(3)

. Foundations soils found to be unsuitable

shall be removed and replaced in accordance with

Section 2-09.3(1)C.

The Contractor shall direct all surface runoff from adjacent areas away from the retaining
wall construction site.

Geosynthetic Retaining Walls

6-14

6-14.3(4) Erection and Backfill

The Contractor shall begin wall construction at the lowest portion of the excavation and
shall place each layer horizontally as shown in the Plans. The Contractor shall complete
each layer entirely before beginning the next layer.

Geotextile splices shall consist of a sewn seam or a minimum 1-foot overlap. Geogrid
splices shall consist of adjacent geogrid strips butted together and fastened using hog
rings, or other methods acceptable to the Engineer, in such a manner to prevent the
splices from separating during geogrid installation and backfilling. Splices exposed at the
wall face shall prevent loss of backfill material through the face. The splicing material
exposed at the wall face shall be as durable and strong as the material to which the
splices are tied. The Contractor shall offset geosynthetic splices in one layer from those in
the other layers such that the splices shall not line up vertically. Splices parallel to the wall
face will not be allowed, as shown in the Plans.

The Contractor shall stretch out the geosynthetic in the direction perpendicular to the
wall face to ensure that no slack or wrinkles exist in the geosynthetic prior to backfilling.

For geogrids, the length of the reinforcement required as shown in the Plans shall be
defined as the distance between the geosynthetic wrapped face and the last geogrid
node at the end of the reinforcement in the wall backfill.

The Contractor shall place fill material on the geosynthetic in lifts such that 6 inches
minimum of fill material is between the vehicle or equipment tires or tracks and the
geosynthetic at all times. The Contractor shall remove all particles within the backfill
material greater than 3 inches in size. Turning of vehicles on the first lift above the
geosynthetic will not be permitted. The Contractor shall not end dump fill material
directly on the geosynthetic without the prior permission of the Engineer.

The Contractor shall use a temporary form system to prevent sagging of the geosynthetic
facing elements during construction. A typical example of a temporary form system and
sequence of wall construction required when using this form are detailed in the Plans. Soil
piles or the geosynthetic manufacturer’s recommended method, in combination with the
forming system shall be used to hold the geosynthetic in place until the specified cover
material is placed.

The Contractor shall place and compact the wall backfill in accordance with the wall
construction sequence detailed in the Plans and Method C of

Section 2-03.3(14)C

except as follows:
1. The maximum lift thickness after compaction shall not exceed 10 inches
2. The Contractor shall decrease this lift thickness, if necessary, to obtain the specified

density.

3. Rollers shall have sufficient capacity to achieve compaction without causing

distortion to the face of the wall in accordance with

Section 6-14.3(1)

4. The Contractor shall not use sheepsfoot rollers or rollers with protrusions.

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Geosynthetic Retaining Walls

5. The Contractor shall compact the zone within 3 feet of the back of the wall facing

6. For wall systems with geosynthetic reinforcement, the minimum compacted backfill

lift thickness of the first lift above each geosynthetic reinforcement layer shall be
6 inches.

The Contractor shall construct wall corners at the locations shown in the Plans, and
in accordance with the wall corner construction sequence and method in the Working
Drawing submittal. Wall angle points with an interior angle of less than 150 degrees shall
be considered to be a wall corner. The wall corner shall provide a positive connection
between the sections of the wall on each side of the corner such that the wall backfill
material cannot spill out through the corner at any time during the design life of the wall.
The Contractor shall construct the wall corner such that the wall sections on both sides of
the corner attain the full geosynthetic layer embedment lengths shown in the Plans.

Where required by retaining wall profile grade, the Contractor shall terminate top layers
of retaining wall geosynthetic and backfill in accordance with the method in the Working
Drawing submittal. The end of each layer at the top of the wall shall be constructed
in a manner that prevents wall backfill material from spilling out the face of the wall
throughout the life of the wall. If the profile of the top of the wall changes at a rate of
1:1 or steeper, this change in top of wall profile shall be considered to be a corner.

6-14.3(5) Guardrail Placement

The Contractor shall install guardrail posts as shown in the Plans after completing the
wall, but before the permanent facing is installed. The Contractor shall install the posts in
a manner that prevents bulging of the wall face and prevents ripping, tearing, or pulling
of the geosynthetic reinforcement. Holes through the geosynthetic reinforcement shall
be the minimum size necessary for the post. The Contractor shall demonstrate to the
Engineer prior to beginning guardrail post installation that the installation method will not
rip, tear, or pull the geosynthetic reinforcement.

6-14.3(6) Permanent Facing

The Contractor shall apply a permanent facing to the surface of all permanent
geosynthetic retaining walls as shown in the Plans. Shotcrete facing, if shown in the Plans,
shall conform to

Section 6-18

. Concrete fascia panel, if shown in the Plans, shall conform

Section 6-15.3(9)

, if cast-in-place, and shall conform to

Section 6-02.3(28)

, if precast.

Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10) - page 39