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

Structure Excavation

2-09

Controlled Density Fill (CDF) or Controlled Low-Strength Material (CLSM) – CDF is a
self compacting, cementitious, flowable material requiring no subsequent vibration or
tamping to achieve consolidation. The Contractor shall provide a mix design in writing
to the Engineer on WSDOT

Form 350-040

and utilize ACI 229 as a guide to develop the

CDF mix design. No CDF shall be placed until the Engineer has reviewed the mix design.
CDF shall be designed to have a minimum 28-day strength of 50 psi and a maximum 28-
day strength not to exceed 300 psi. The CDF consistency shall be flowable (approximate
slump 3 to 10 inches).

The following testing methods shall be used by the Contractor to develop the CDF
mix design:

28-day compressive strength – ASTM D4832;

Unit weight, yield, and air content – ASTM D6023;

Slump – FOP for AASHTO T 119.

The water/cement ratio shall be calculated on the total weight of cementitious material.
Cementitious materials are those listed in

Section 5-05.2

Admixtures used in CDF shall meet the requirements of

Section 9-23.6

, Admixtures

for Concrete, and foaming agents, if used, shall meet the requirements of ASTM C869.
Admixtures shall be used in accordance with the manufacturer’s recommendations and
non-chloride accelerating admixtures may be used to accelerate the hardening of CDF.

CDF shall meet the requirement of

Section 6-02.3(5)C

and shall be accepted based on a

Certificate of Compliance. The producer shall provide a Certificate of Compliance for each
truckload of CDF in accordance with

Section 6-02.3(5)B

Stockpiling – The Engineer may require the Contractor to selectively remove and
stockpile any usable material excavated for a Structure. If this material meets the
requirements for gravel backfill for walls it may replace gravel as wall or abutment backfill.

If the Contractor stockpiles excavated material for use as backfill, it shall be protected
with plastic sheeting or by some other method from contamination and weather damage.
If the material becomes too wet or contaminated in the stockpile, the Contractor shall
dispose of and replace it with an equal amount of suitable material, all at no expense
to the Contracting Agency. All costs for storing, protecting, rehandling, and placing
stockpiled material shall be included in the unit Contract price for Structure excavation,
Class A or B.

Compaction – Backfill from Structure excavation shall be placed and compacted in
keeping with the following requirements:
1. Backfill supporting Roadbed, Roadway embankments, or Structures, including backfill

providing lateral support for noise barrier wall foundations, luminaire poles, traffic
signal standards, and roadside and overhead sign Structure foundations shall be
placed in horizontal layers no more than 6 inches thick with each layer compacted
to 95 percent of the maximum density determined by the Compaction Control Test
according to

Section 2-03.3(14)D

Page 2-40

Structure Excavation

2. Gravel backfill for drains shall be placed in horizontal layers no more than 12 inches

thick, with each layer compacted by at least three passes of a vibratory compactor
approved by the Engineer.

3. All other structure excavation backfill shall be placed in layers no more than 2 feet

thick (loose), with each layer tamped and graded so that final settling will leave the
backfill flush with surrounding ground.

4. Compaction of controlled density fill will not be required.

Timing – Backfill shall not be placed against any concrete Structure until the concrete
has attained 90 percent of its design strength and a minimum age of 14 days, except that
reinforced concrete retaining walls 15 feet in height or less may be backfilled after the
wall has attained 90 percent of its design compressive strength and curing requirements
of

Section 6-02.3(11)

are met. Footings and columns may be backfilled as soon as forms

have been removed, so long as the backfill is brought up evenly on all sides.

The Engineer may order the Contractor to use lean concrete in backfilling around piers
and in front of abutments and walls. The Contracting Agency will pay for such backfilling
as provided in

Section 1-04.4

If water prevents the Contractor from properly placing and compacting backfill, it shall be
removed by pumping or other means.

All costs not defined in this section that relate to providing, placing, and compacting
backfill shall be at the Contractor’s expense.

2-09.3(1)F

Items to Remain

If the Contractor damages or removes pavement or anything else meant to remain outside
the excavation area, it shall be repaired or replaced at no expense to the Contracting
Agency.

2-09.3(2) Classification of Structure Excavation

1. Class A – Structure excavation required for bridge and retaining wall footings,

precast reinforced concrete three sided structure footings, geosynthetic retaining
walls, structural earth walls, sign structure footings, pile or drilled shaft caps, seals,
wingwall footings, precast reinforced concrete box culverts, precast reinforced
concrete split box culverts, detention vaults, and noise barrier wall footings shall be
classified as Structure excavation Class A. If the excavation requires a cofferdam,
structural shoring, or extra excavation, the work outside the neat lines of the
Structure excavation Class A shall be classified as shoring or extra excavation
Class A.

2. Class B – All other Structure excavation shall be Class B. If this excavation requires

cofferdams, shoring, or extra excavation, the work outside the neat lines of the
Structure excavation Class B shall be classified as shoring or extra excavation
Class B.

Structure Excavation

2-09

2-09.3(3) Construction Requirements, Structure Excavation, Class A

2-09.3(3)A

Preservation of Channel

When foundations or Substructures are to be built in or next to running streams, the
Contractor shall:
1. Excavate inside cofferdams, caissons, or sheet piling unless dredging or open pit

excavation is permitted.

2. Backfill foundations placed inside cofferdams and behind sheet piling prior to

removing cofferdams or sheet piling. This backfill shall be level with the original
streambed and shall prevent scouring.

3. Remove any excavation material that may have been deposited in or near the stream

so that the watercourse is free from obstruction.

4. Maintain water depth and horizontal clearances required for traffic to pass

on navigable streams, furnishing any channel signals or lights required during
construction.

5. Place riprap around the outside of cofferdams, as specified, to repair local scour.

2-09.3(3)B

Excavation Using Open Pits – Extra Excavation

The Contractor may dig open pits or perform extra excavation without shoring or
cofferdams, if:
1.  Footings can be placed in dry material away from running water.
2.  The integrity of the completed Structure and its surroundings is not reduced.
3.  Worker safety is ensured as required by law.
4.  The excavation does not disturb the existing pavement or any other adjacent

structural elements.

If a slide occurs in an open pit, the Contractor shall remove the slide material. If the
slide disturbs an area over which a Highway will be built, the Contractor shall backfill
and compact the site to the original ground line as approved by the Engineer. If the slide
damages an existing facility such as a Roadway or Structure, the Contractor shall repair
the damage caused by the slide. The Contractor shall pay all costs related to removing
slide material and restoring the slide area, including the repair of any pavement or
structural elements damaged by the slide.

The Contractor shall drain or pump any water from the pit, taking care not to stir up
or soften the bottom. If equipment in the pit or inadequate water removal makes the
foundation material unstable, the Contractor shall, at no expense to the Contracting
Agency, remove and replace it with material acceptable to the Engineer.

When the Engineer believes ground water flow may impair a concrete footing, the
Contractor shall place under it a layer of gravel at least 6 inches thick. Before placing
the gravel, the Contractor shall excavate to whatever grade the Engineer requires. This
provision shall not apply to the building of concrete seals.

Page 2-42

Structure Excavation

The Contractor may omit forms when the earthen sides of a footing excavation will stand
vertically. In this case, the Contractor may excavate to the neat line dimensions of the
footing and pour concrete against the undisturbed earth. If the hole is larger than neat
line dimensions, the Contractor shall bear the cost of the extra concrete.

For open temporary cuts, the following requirements shall be met:
1. No vehicular or construction traffic, or construction surcharge loads will be allowed

within a distance of 5 feet from the top of the cut.

2. Exposed soil along the slope shall be protected from surface erosion.
3. Construction activities shall be scheduled so that the length of time the temporary

cut is left open is reduced to the extent practical.

4. Surface water shall be diverted away from the excavation.

The excavation height (Ht) shall be calculated within a vertical plane as the difference
between the lowest elevation in the excavation and the highest elevation of the
ground surface immediately adjacent to the excavation. Pavement thickness and
other surface treatments existing at the time of the excavation shall be included in the
height calculation.

Submittals and Design Requirements

Excavations 4-feet and less in height do not require design and submittals. The Contractor
shall provide a safe work environment and shall execute the work in a manner that does
not damage adjacent pavements, utilities, or structures. If the Engineer determines
the Contractor’s work may potentially affect adjacent traffic, pavements, utilities, or
structures, the Engineer may request a Type 1 Working Drawing from the Contractor. The
Contractor shall explain in the Type 1 Working Drawing how the Engineer’s concerns will
be addressed, why infrastructure will not be damaged by the work, and how worker safety
will be preserved.

For excavations that have soil types and slope geometries defined in WAC 296-155
part N and are between 4-feet and 20-feet in height, the Contractor shall submit Type 2
Working Drawings. Required submittal elements include, at a minimum, the following:
1. A plan view showing the limits of the excavation and its relationship to traffic,

structures, utilities and other pertinent project elements. If the stability of the
excavation requires no-load zones or equipment setback distances, those shall be
shown on the plan view.

2. A typical or controlling cross section showing the proposed excavation, original

ground line, and locations of traffic, existing structures, utilities, site constraints,
surcharge loads, or other conditions that could affect the stability of the slope. If the
stability of the excavation requires no-load zones or equipment setback distances,
those shall be shown in cross section.

3. A summary clearly describing subsurface conditions, soil type for WAC 296-155

part N, and groundwater conditions, sequencing considerations, and governing
assumptions.

Structure Excavation

2-09

Where WAC 296-155 part N requires an engineer’s design, the Contractor shall submit
Type 2E Working Drawings. Required submittal elements include, at a minimum, the three
items above and the following additional items:
4. Supporting calculations for the design of the excavation, the soil and material

properties selected for design, and the justification for the selection for those
properties, in accordance with the WSDOT Geotechnical Design Manual M 46-03.

5. Safety factors, or load and resistance factors used, and justification for their

selection, in accordance with the WSDOT Geotechnical Design Manual M 46-03,
and referenced AASHTO design manuals.

6. A monitoring plan to evaluate the excavation performance throughout its design life
7. Any supplemental subsurface explorations made by the Contractor to meet the

requirements for geotechnical design of excavation slopes, in accordance with the
WSDOT Geotechnical Design Manual M 46-03.

2-09.3(3)C

Preparation for Placing Foundations

When a foundation will rest on rock, excavation shall penetrate it at least 1 foot, or more
if the Plans require, to form a key for the footing. The Contractor shall cut the bottom of
the excavation to a firm surface, level, stepped, or serrated as the Engineer directs, and
remove all loose material.

For an arch abutment, the back face shall be trimmed to true lines so that concrete can be
poured against undisturbed material.

If concrete will rest on any excavated surface other than solid rock, the Contractor shall
not disturb the bottom of the excavation. The Contractor shall also remove all loose or
soft material just before pouring the concrete.

Upon completing any foundation excavation, the Contractor shall notify the Engineer. No
concrete or other permanent part of the Structure may be placed until the Engineer has
given permission to proceed.

2-09.3(3)D

Shoring and Cofferdams

Definitions – Structural shoring is defined as a shoring system that is installed prior
to excavation. Structural shoring shall provide lateral support of soils and limit lateral
movement of soils supporting Structures, Roadways, utilities, railroads, etc., such that
these items are not damaged as a result of the lateral movement of the supporting soils.

Structural shoring systems includes driven cantilever sheet piles, sheet piles with
tiebacks, sheet pile cofferdams with wale rings or struts, prestressed spud piles, cantilever
soldier piles with lagging, soldier piles with lagging and tiebacks, and multiple tier
tieback systems.

Trench boxes, sliding trench shields, jacked shores, shoring systems that are installed
after excavation, and soldier pile, sheet pile, or similar shoring walls installed in front
of a pre-excavated slope, are not allowed as structural shoring.

Page 2-44

Structure Excavation

A cofferdam is any watertight enclosure, sealed at the bottom and designed for the
dewatering operation, that surrounds the excavated area of a Structure. The Contractor
shall use steel sheet pile or interlocking steel pile cofferdams in all excavation that is
under water or affected by ground water.

Submittals and Design Requirements – The Contractor shall submit Type 2E
Working Drawings with supporting calculations showing the proposed methods and
construction details of structural shoring or cofferdams in accordance with Sections

1-05.3

and

6-02.3(16)

Structural shoring and cofferdams shall be designed in accordance with the WSDOT
Geotechnical Design Manual M 46-03. Allowable stresses for materials shall not exceed
stresses and conditions allowed by

Section 6-02.3(17)B

For open temporary cuts associated with a shoring system, the requirements for open
temporary cuts specified in

Section 2-09.3(3)B

shall be met.

The structural shoring system shall be designed for site specific conditions which
shall be shown and described in the Working Drawings. The structural shoring system
design shall include the design of the slopes for stability above and below the shoring
system. Except as otherwise noted, the design height of all structural shoring in design
calculations and Working Drawings shall be for the depth of excavation as required by
the Plans, plus an additional 2 feet to account for the possibility of overexcavation. If the
Contractor provides written documentation to the satisfaction of the Engineer that the
soil conditions at the site are not likely to require overexcavation, the Engineer may waive
the requirement for 2 feet of overexcavation design height.

Examples of such items that shall be shown on the structural shoring submittal and
supported by calculations include, but are not limited to, the following:
1. Heights; soil slopes; soil benches; and controlling cross sections showing adjacent

existing foundations, utilities, site constraints, and any surcharge loading conditions
that could affect the stability of the shoring system, including any slopes above or
below the shoring.

2. A summary clearly describing performance objectives, subsurface soil and

groundwater conditions, sequencing considerations, and governing assumptions.

3. Any supplemental subsurface explorations made to meet the requirements for

geotechnical design of excavation slopes, shoring walls, and other means of ground
support, in accordance with the WSDOT

Geotechnical Design Manual

M 46-03.

4. Supporting geotechnical calculations used to design the shoring system, including

the stability evaluation of the shoring system in its completed form as well as
intermediate shoring system construction stages, the soil and material properties
selected for design, and the justification for the selection for those properties, in
accordance with the WSDOT

Geotechnical Design Manual

M 46-03.

Structure Excavation

2-09

5. Safety factors, or load and resistance factors used, and justification for their

selection.

6. Location and weight of construction equipment adjacent to the excavation; location

of adjacent traffic; and structural shoring system material properties, spacing, size,
connection details, weld sizes, and embedment depths.

7. Structural shoring installation and construction sequence, procedure, length of

time for procedure and time between operations; proof load testing procedure if
any; deadman anchor design and geometry; no load zones; grouting material and
strengths; and a list of all assumptions.

8. Methods and materials to be used to fill voids behind lagging, when soldier piles with

lagging are used as structural shoring.

9. A monitoring/testing plan to evaluate the performance of the excavation/shoring

system throughout its design life, and

10. An estimate of expected displacements or vibrations, threshold limits that would

trigger remedial actions, and a list of potential remedial actions should thresholds be
exceeded. Thresholds shall be established to prevent damage to adjacent facilities, as
well as degradation of the soil properties due to deformation.

Construction Requirements – Structural shoring or cofferdams shall be provided for all
excavations near completed Structures (foundations of bridges, walls, or buildings), near
utilities, and near railroads.

All other excavations 4 feet or more in depth shall either be shored with structural shoring
or cofferdams, or shall meet the open-pit requirements of

Section 2-09.3(3)B

Existing foundations shall be supported with structural shoring if the excavation is within
the limits defined by a plane which extends out from the nearest edge of the existing
footing a level distance of ½ the width of the existing footing and then down a slope
of 1.5:1.

When structural shoring or cofferdams are utilized, all excavation and structural shoring
shall be constructed in accordance with the processed structural shoring submittal,
including any required construction sequence noted in the Working Drawings. The
Contractor shall remain responsible for satisfactory results.

If soldier piles are placed in drilled holes, and lagging is installed concurrently with the
excavation, all backfill above the bottom of the lagging shall consist of controlled-density
fill or lean concrete. Backfill below the bottom of the lagging may consist of pea gravel.
If full-height steel sheet lagging is installed prior to excavation, soldier pile holes may be
backfilled with pea gravel.

Page 2-46

Structure Excavation

If lagging is used, void space behind the lagging shall be minimized. If the Engineer
determines that the voids present could result in damage or serviceability problems for
the structural shoring system or any Structures or facilities adjacent to the structural
shoring system, the Contractor shall cease excavation and lagging installation, and shall
fill the voids specified by the Engineer in accordance with the approved structural shoring
submittal. Further excavation and lagging placement shall not continue until the specified
voids are filled to the satisfaction of the Engineer.

Excavation shall not proceed ahead of lagging installation by more than 4 feet or by the
height that the soil will safely stand, whichever is least. For tieback shoring systems,
excavation shall not proceed ahead by more than 4 feet of the tie installation and
proof testing.

In using cofferdams or structural shoring, the Contractor shall:
1. Extend cofferdams well below the bottom of the excavation, and embed structural

shoring as shown in the structural shoring submittal as approved by the Engineer.

2. Provide enough clearance for constructing forms, inspecting concrete exteriors, and

pumping water that collects outside the forms. If cofferdams tilt or move laterally
during placement, the Contractor, at no expense to the Contracting Agency, shall
straighten or enlarge them to provide the required clearance.

3. Secure the cofferdam in place to prevent tipping or movement.
4. Place structural shoring or cofferdams so that they will not interfere with any pile

driving required.

5. Not place any shoring, braces, or kickers inside the cofferdams and structural shoring

that will induce stress, shock, or vibration to the permanent Structure.

6. Vent cofferdams at the elevation commensurate with seal weight design, or as

shown in the Plans.

7. Remove all bracing extending into the concrete being placed.

When the Work is completed, the Contractor shall:
1. Remove all structural shoring to at least 2 feet below the finished ground line.
2. Remove all cofferdams to the natural bed of the waterway.

2-09.3(3)E

Bearing Tests

The Engineer may stop the excavation to make bearing tests at any time. The Contractor
shall assist with these tests in any way the Engineer requires.

During any test period, the Contractor shall, at no expense to the Contracting Agency,
maintain ordinary working conditions at the bottom of the hole. The Contracting Agency
will pay force account for all labor and materials the Contractor supplies for such tests.
A single test shall not exceed 72 hours.

Structure Excavation

2-09

2-09.3(4) Construction Requirements, Structure Excavation, Class B

The above requirements for Structure excavation Class A, shall apply also to Structure
excavation Class B, except as revised below. In addition, the Contractor shall follow
Division 7 of these Specifications as it applies to the specific kinds of Work.

The hole for any catch basin or manhole shall provide at least 1 foot of clearance between
outside structural surfaces and the undisturbed earth bank.

If workers enter any trench or other excavation 4 feet or more in depth that does
not meet the open pit requirements of

Section 2-09.3(3)B

, it shall be shored or other

safety method constructed in conformance with WISHA requirements. The Contractor
alone shall be responsible for worker safety and the Contracting Agency assumes no
responsibility.

The Contractor shall submit Type 2E Working Drawings in accordance with

Section 2-09.3(3)D

Trench boxes may be used for Structure excavation, Class B. Acceptance of trench boxes
as a shoring method for Class B Structure excavation can be done by the Engineer
provided it is not used to support adjacent traffic, existing footings, or other Structures.
The Working Drawing submittal shall include the manufacturer’s certified trench box
plans with depth restrictions, and the serial number for field verification of the trench box.

Upon completing the Work, the Contractor shall remove all shoring unless the Plans or
the Engineer direct otherwise.

2-09.4 Measurement

Excavated materials will be measured in their original position by the cubic yard. The
Contracting Agency will measure and pay for only the material excavated from inside the
limits this section defines. If the Contractor excavates outside these limits or performs
extra excavation as described in

Section 2-09.3(3)B

, it shall be considered for the

Contractor’s benefit and shall be included in the cost of other Bid items.

Horizontal Limits – The Contracting Agency will use the sides of the trench or pit as
horizontal limits in measuring excavation. No payment for Structure excavation will be
made for material removed (1) more than 1 foot outside the perimeter of any pile cap,
footing, or seal; (2) more than 3 feet beyond the Roadway side of a wing wall; (3) more
than 1 foot beyond the other sides and end of a wing wall; (4) more than 1 foot outside
the perimeter of the soil reinforcement area for geosynthetic and structural earth walls;
and (5) more than 4-feet beyond the inside opening of precast reinforced concrete
box culverts and precast reinforced concrete split box culverts. For precast reinforced
concrete three sided structures, no payment for Structure excavation will be made for
material removed more than 1 foot outside the perimeter of the footing or more than 4
feet beyond the inside opening, whichever is greater.

Page 2-48

Structure Excavation

For all pipes, pipe arches, structural plate pipes, and underpasses, the Structure
excavation quantity will be calculated based on the following trench widths:

For drain and underdrain pipes, trench width = I.D. + 12 inches.

For pipes 15 inches and under, trench width = I.D. + 30 inches.

For pipes 18 inches and over, trench width = (1.5 × I.D.) + 18 inches.

For a manhole, catch basin, grate inlet, or drop inlet, the limits will be 1 foot outside the
perimeter of the Structure.

For drywells, the limits shall be in accordance with the

Standard Plans

Lower Limits – For a pile cap, footing, or seal, the bottom elevation shown in the Plans, or
set by the Engineer, will serve as the lower limit in measuring Structure excavation. For a
wing wall, the lower limit will follow a line parallel to the bottom and 1 foot below it. Any
swell from pile driving will be excluded from excavation quantities.

For pipelines the lower limit in measuring structure excavation will be the foundation level
as shown in the Plans or as directed by the Engineer.

Upper Limits – The top surface of the ground or streambed as the Work begins will be
the upper limit for measuring excavation. If the Contract, or a separate contract, includes
a pay item for grading to remove materials, the upper limit will be the neat lines of the
grading section shown in the Plans.

The Engineer may order the Contractor to partially build the embankment before
placing pipe. In this case, the upper limit for measurement will be not more than 4 feet
above the invert of the pipe. For a structural plate pipe, pipe arch, or underpass, the
upper limit will be the top of the embankment at the time of installation as specified in

Section 7-03.3(1)A

Gravel Backfill – Gravel backfill, except when used as bedding for culvert, storm sewer,
sanitary sewer, manholes, and catch basins, will be measured by the cubic yard in place
determined by the neat lines required by the Plans.

Shoring or Extra Excavation – No specific unit of measurement shall apply to the lump
sum item of shoring or extra excavation Class A. Shoring or extra excavation Class B will
be measured by the square foot as follows:

The area for payment will be one vertical plane measured along the centerline of the
trench, including Structures. Measurement will be made from the existing ground line
to the bottom of the excavation and for the length of the Work actually performed. If
the Contract includes a pay item for grading to remove materials, the upper limit for
measurement will be the neat lines of the grading section shown in the Plans. The bottom
elevation for measurement will be the bottom of the excavation as shown in the Plans or
as otherwise established by the Engineer.

Controlled density fill will be measured by the cubic yard for the quantity of material
placed in accordance with the producer’s invoice.

Structure Excavation

2-09

2-09.5 Payment

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

“Structure Excavation Class A”, per cubic yard.
“Structure Excavation Class B”, per cubic yard.
“Structure Excavation Class A Incl. Haul”, per cubic yard.
“Structure Excavation Class B Incl. Haul”, per cubic yard.
Payment for reconstruction of surfacing and paving within the limits of Structure
excavation will be at the applicable unit prices for the items involved.
If the Engineer orders the Contractor to excavate below the elevations shown in
the Plans, the unit Contract price per cubic yard for “Structure Excavation Class
A or B” will apply. But if the Contractor excavates deeper than the Plans or the
Engineer requires, the Contracting Agency will not pay for material removed from
below the required elevations. In this case, the Contractor, at no expense to the
Contracting Agency, shall replace such material with concrete or other material the
Engineer approves.
“Shoring or Extra Excavation Cl. A _____”, lump sum.
When extra excavation is used in lieu of constructing the shoring, cofferdam or
caisson, the lump sum Contract price shall be full pay for all excavation, backfill,
compaction, and other Work required. If select backfill material is required for
backfilling within the limits of Structure excavation, it shall also be required as
backfill material for the extra excavation at the Contractor’s expense.
If it is necessary to place riprap outside of cofferdams to repair local scour, it shall be
paid by agreed price or force account.
If the Engineer requires shoring, cofferdams, or caissons when the Contract
provides no Bid item for such Work, the Contracting Agency will pay as provided in

Section 1-04.4

If the Engineer requires the Contractor to build shoring or extra excavation Class
A that extends below the elevation shown in the Plans, the Contracting Agency
shall pay the lump sum price and no more when the extra depth does not exceed 3
feet. For depths greater than 3 feet below the elevations shown, payment will be as
provided in

Section 1-04.4

“Shoring or Extra Excavation Class B”, per square foot.
The unit Contract price per square foot shall be full pay for all excavation, backfill,
compaction, and other Work required when extra excavation is used in lieu of
constructing shoring. If select backfill material is required for backfilling within the
limits of the Structure excavation, it shall also be required as backfill material for the
extra excavation at the Contractor’s expense.

Page 2-52

Trimming and Cleanup

2-11

Trimming and Cleanup

2-11.1 Description

This Work consists of dressing and trimming the entire Roadway(s) improved under the
Contract, including Frontage Roads, connecting ramps, Auxiliary Lanes, and approach
roads. This Work extends to Roadbeds, Shoulders, and ditches.

2-11.2 Vacant
2-11.3

Construction Requirements

The Contractor shall:
1. Trim Shoulders and ditches to produce smooth surfaces and uniform cross-sections

that conform to the grades set by the Engineer.

2. Open and clean all channels, ditches, and gutters to ensure proper drainage.
3. Dress the back slope of any ditch or borrow pit that will remain adjacent to the

Roadway. Round off the top of the back slope and distribute the material evenly
along its base.

4. Remove and dispose of all weeds, brush, refuse, and debris that lie on the Roadbed,

Shoulders, ditches, and slopes.

5. Remove from paved Shoulders all loose rocks and gravel.
6. Distribute evenly along the embankment any material not needed to bring the

Shoulders to the required cross-section.

The Contractor shall not:
1. Use heavy equipment (tractors, graders, etc.) to trim the Shoulders of an existing

or new bituminous surface.

2. Drag, push, or scrape Shoulder material across completed surfacing or pavement.

When the Contract requires the Contractor to rebuild part of a Roadway only the rebuilt
areas shall be trimmed and cleaned up. If the Contractor’s Work obstructs ditches or side
roads, they shall be cleared and the debris disposed of as the Engineer directs.

2-11.4 Vacant
2-11.5 Payment

Payment shall be made for the following Bid item when it is included in the Proposal:

“Trimming and Cleanup”, lump sum.

Construction Geosynthetic

2-12

Construction Geosynthetic

2-12.1 Description

The Contractor shall furnish and place construction geosynthetic in accordance with the
details shown in the Plans.

2-12.2 Materials

Materials shall meet the requirements of the following section:

Construction Geosynthetic

9-33

Geosynthetic roll identification, storage, and handling shall be in conformance to ASTM
D4873. During periods of shipment and storage, the geosynthetic shall be stored off the
ground. The geosynthetic shall be covered at all times during shipment and storage such
that it is fully protected from ultraviolet radiation including sunlight, site construction
damage, precipitation, chemicals that are strong acids or strong bases, flames including
welding sparks, temperatures in excess of 160ºF, and any other environmental condition
that may damage the physical property values of the geosynthetic.

Unless specified otherwise in the Plans, the geotextile required for underground drainage
shall be “Moderate Survivability” and “Drainage Class C” and permanent erosion control
applications shall be “High Survivability” and “Drainage Class C”.

2-12.3

Construction Requirements

The area to be covered by the geosynthetic shall be graded to a smooth, uniform
condition free from ruts, potholes, and protruding objects such as rocks or sticks.
The geosynthetic shall be spread immediately ahead of the covering operation. The
geosynthetic shall not be left exposed to sunlight during installation for a total of more
than 14 calendar days. The geosynthetic shall be laid smooth without excessive wrinkles.
Under no circumstances shall the geosynthetic be dragged through mud or over sharp
objects which could damage the geosynthetic. The cover material shall be placed on the
geosynthetic such that the minimum initial lift thickness required will be between the
equipment tires or tracks and the geosynthetic at all times. Construction vehicles shall
be limited in size and weight, to reduce rutting in the initial lift above the geosynthetic,
to not greater than 3 inches deep to prevent overstressing the geosynthetic. Turning of
vehicles on the first lift above the geosynthetic will not be permitted.

Soil piles or the manufacturer’s recommended method, shall be used as needed to hold
the geosynthetic in place until the specified cover material is placed.

Should the geosynthetic be torn, punctured, or the overlaps or sewn joints disturbed,
as evidenced by visible geosynthetic damage, Subgrade pumping, intrusion, or Roadbed
distortion, the backfill around the damaged or displaced area shall be removed and the
damaged area repaired or replaced by the Contractor at no expense to the Contracting
Agency. The repair shall consist of a patch of the same type of geosynthetic placed over
the damaged area. The patch shall overlap the existing geosynthetic from the edge of any
part of the damaged area by the minimum required overlap for the application.

Page 2-54

Construction Geosynthetic

If geotextile seams are to be sewn in the field or at the factory, the seams shall consist of
one row of stitching unless the geotextile where the seam is to be sewn does not have a
selvage edge. If a selvage edge is not present, the seams shall consist of two parallel rows
of stitching, or shall consist of a J-seam, Type SSn-1, using a single row of stitching. The
two rows of stitching shall be 1.0 inch apart with a tolerance of plus or minus 0.5 inch
and shall not cross except for restitching. The stitching shall be a lock-type stitch. The
minimum seam allowance, i.e., the minimum distance from the geotextile edge to the
stitch line nearest to that edge, shall be 1½ inches if a flat or prayer seam, Type SSa-2,
is used. The minimum seam allowance for all other seam types shall be 1.0 inch. The seam,
stitch type, and the equipment used to perform the stitching shall be as recommended
by the manufacturer of the geotextile and as approved by the Engineer.

The seams shall be sewn in such a manner that the seam can be inspected readily
by the Engineer or a representative. The seam strength will be tested and shall meet
the requirements stated herein.

2-12.3(1) Underground Drainage

Trench walls shall be smooth and stable. The geotextile shall be placed in a manner which
will ensure intimate contact between the soil and the geotextile (i.e., no voids, folds,
or wrinkles).

The geotextile shall either be overlapped a minimum of 12 inches at all longitudinal and
transverse joints, or the geotextile joints shall be sewn for medium survivability drainage
applications. In those cases where the trench width is less than 12 inches, the minimum
overlap shall be the trench width.

In moderate survivability geotextile underdrain applications, the minimum overlap shall
be 12 inches, or the geotextile joints shall be sewn, except where the geotextile is used in
area drains. An area drain is defined as a geotextile layer placed over or under a horizontal
to moderately sloping layer of drainage aggregate. For area drains, the geotextile shall be
overlapped a minimum of 2 feet at all longitudinal and transverse joints, or the geotextile
joints shall be sewn together. The minimum initial lift thickness over the geotextile in the
area drain shall be 12 inches.

In all cases, the upstream geotextile sheet shall overlap the next downstream sheet.

2-12.3(2) Separation

The geotextile shall either be overlapped a minimum of 2 feet at all longitudinal and
transverse joints, or the geotextile joints shall be sewn together. The initial lift thickness
shall be 6 inches or more.

Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10) - page 27