227MECHANICALLY STABILIZED EARTH RETAINING WALL

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2-124SECTION 227 – MECHANICALLY STABILIZED EARTH RETAINING WALL

227.01DESCRIPTION . This work shall consist of designing, detailing, fabricating, furnishing, and

erecting mechanically stabilized earth (MSE) retaining walls constructed in accordance with these specifications and in conformance with the lines, grades, d etails, and dimensions shown on the Plans or as directed by the Engineer. Construction of the MSE retaining wall system shall consist of placement and compaction of select granular backfill, a non -structural leveling pad, precast concrete face panels, an d membrane and soil reinforcement elements mechanically connected to each facing panel.

227.02MATERIALS . Materials shall meet the requirements of the following subsections:

Drainage Aggregate ................................ ................................ ................................ ...704.16 Select Backfill for MSE Structures ................................ ................................ ............ 704.18 Polyvinyl Ch loride (PVC) Plastic Pipe ................................ ................................ ......710.0 5 Bar Reinforcement ................................ ................................ ................................ .....713.01 Mechanical Splices for Bar Reinforcement ................................ ............................... 713.02 Geotextile for Roadbed Separator ................................ ................................ .............. 720.02 Mechanically Stabilized Earth (MSE) Wall Systems ................................ ................ 760.0 6 Geomembrane Liner ................................ ................................ ................................ ..760.07 Precast concrete shall meet t he requirements of Section 540 . Reinforcing steel shall meet the requirements for Level II corrosion resistance unless otherwise specified in the Plans.

227.03DESIGN REQUIREMENTS . The MSE retaining wall system shall be designed and constructed

in accordance with the AASHTO LRFD Bridge Design Specifications, the Plans, the design criteria, and the geotechnical information specified in the Contract. The system shall be designed for a design life of 100 years, and any wall reinforcing located above the geomembrane shall have a design li fe of 125 years, both using the corrosion rates given in the AASHTO LRFD Bridge Design Specifications for non -aggressive soil.

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2-125All appurtenances behind, in front of, under, mounted upon, or passing through the wall such as drainage

structures, utilities, or other appurtenances shown on the Plans shall be accounted for in the stability design of the wall. MSE wall panels shall have a minimum structural thickness of 5 inches and a minimum cover for steel reinforcement of 1 -1/2 inches. The design shall follow the dimensions of the wall envelope and minimum embedment shown on the Plans. Where a wall coping is utilized, the wall face panel shall extend up into the coping the minimum distance specified on the Plans. The top of the face panels may be level or sloped to meet the top of the wall. Cast -in-place concrete will not be an acceptable replacement for panel areas, except for minor grouting of pipe penetrations and leveling required for coping. Where walls or wall sections intersect with an angle of 130° or less, a special vertical corner element panel shall cover the joint of the panels that abut the corner and allow for independent movement along the abutting panels. The face panels shall be designed to accommodate diffe rential settlement of 12 inches in 100 feet between the substructure and wall system. The design of the wall system shall include a provision to accommodate settlement of this magnitude. The spacing between adjacent panels shall be designed to be 0.75 inches. Where shown on the Plans, slip joints to accommodate excessive differential settlement shall be included.

227.04SUBMITTALS . As soon as practical after award of the Contract, the following information shall

be prepared and submitted:

approval in accordance with Subsection 105.06 and shall include the following:

satisfies the design parameters specified in the Contract. Wall design drawings and calculations shall be signed and sealed by a professional engineer employed by the wall system supplier.

accommodate the wall system.

227 2-126 (3) An elevation view of the wall, which shall include the elevations at the top of the wall, at all horizontal and vertical break points and at least every 50 feet along the face of the wall, and at all steps in the leveling pads, the designation as to the type of panel, the length of soil reinforcing elements. The elevation view shall also include the distance along the face of the wall to where changes in length of the soil reinforcing elements occur, and an indication of the final ground line.

grades, including existing ground elevations that have been verified by the Contractor for each location involving construction w holly or partially in original ground.

and other utilities.

reinforcing steel in the element, the location of soil reinforci ng connection devices embedded in the panels, and an indication of the architectural treatment.

227.05MSE WALL PANEL FABRICATION REQUIREMENTS

of the MSE wall panels. The panel shall be available for review a minimum of 5 working days prior to the start of production. The approved test panel shall be used as a benchmark for the correct color and form liner finish.

227 2-127 (b) Concrete Finish . No surface voids or bug holes greater than 5/8 inch in diameter and more than 1/4 inch deep will be allowed in the finished exposed surface. Surface voids or bug holes that are smaller than the size describe d shall not exceed 1% of the finished exposed surface with no 6 inch by 6 inch area containing more than 3 surface voids or bug holes. The concrete surface for the front face shall meet requirements as noted on the Plans. Any repairs to the front face shall match the color and finish of the surface and be approved by the Engineer. The concrete surface for the front face shall have a form liner finish as required on the approved fabrication drawings. The concrete surface on the rear face shall be an unf ormed flat finish. The concrete panels shall be constructed using colored concrete as specified in the Plans.

respect to the dimensions shown on the approved fabrication drawings:

attachment devices shall be within 1 inch. The embedment measured from the back face of the panel shall be 4 inches (+ 1/4 inch, - 1/2 inch) .

in the panel except for attachment devices shall be within ± 1/4 inch.

two diagonals, shall not exceed 1/2 inch.

5 feet, shall not exceed 1/4 inch. Surface defects on textured -finished surfaces, measured on a length of 5 feet, shall n ot exceed 5/16 inch.

panel immediately following finishing.

down. Firm blocking of sufficient thickness to prevent the reinforcement attachments from contacting the adjacent panels shall be used. Lifting inserts shall be installed on the top edge of the MSE wall panels to permit lifting at the pr oject site. Reinforcement connection inserts (tie strips) shall not be used for lifting or handling the panel at the project site.

227 2-128 (f) Panel Acceptance Criteria . MSE wall panels will be accepted for use in wall construction provided the concrete streng th meets or exceeds the design compressive strength, the soil reinforcement connection devices and the panel dimensions are within tolerances, and any chipping, cracks, honeycombing, or other defects are repaired to the satisfaction of the Structural Concr ete Engineer using methods submitted and approved as specified in Subsection 540.07(g) . The MSE wall panels will be subject to inspection by the Engineer at the time of unloading and once placed in their final position. MSE wall panels that do not meet th e requirements of this subsection may be subject to rejection.

227.06CONSTRUCTION REQUIREMENTS

wall supplier to have a technical representative on the proje ct to supervise the first level of panel placement of the mechanically stabilized earth retaining wall system. The technical representative shall also be required to be on -site or available for consultation any time during wall installation as requested by the Engineer.

as applicable and shall conform with the limits shown on the Plans.

or exceeding the length of the soil reinforcements, or as shown on the Plans. The Contractor shall proof roll the foundation using a minimum 5 -ton, self -propelled vibratory roller to compact soils disturbed by excavation. Areas exhibiting excess weaving or soft, unsuitable soils sh all be excavated and replaced with compacted granular fill. Wet foundation soils sh all be proof rolled without vibration. Any foundation soils found to be unsuitable shall be removed and replaced as directed by the Engineer. At each panel foundation level, an unreinforced concrete leveling pad shall be provided as shown on the Plans. Allowable elevation tolerances are +0.01 feet and -0.02 feet from the design elevation. Prior to placement of the levelin g pad, the Agency’s Geotechnical Engineer or designated representative shall inspect the foundation soils to evaluate the suitability of the bearing soils. Leveling pads shall be required to cure a minimum of 24 hours before wall panels are erected on them.

227 2-129 (d) Wall Erection . Precast concrete panels shall be placed vertically with the aid of a crane or other construction equipment capable of handling the anticipated loads. For erection, panels shall be handled by means of lifting devices set into the up per edge of the panels. Panels shall be placed in

successive horizontal lifts in the sequence shown on the working drawings as select granular

backfill placement proceeds.

The maximum allowable offset in any panel joint shall be 0.75 inches. The overall vertical

tolerance of the wall (plumbness from top to bottom) shall not exceed 0.50 inches per 10 feet of

wall height.

shall be placed and compacted in accordance with Subsection 227.06(f).

Soil reinforcements shall be placed normal to the face of the wall, unless otherwise shown on the

working drawings or directed by the Engineer.

If skewing of the soil reinforcements is required due to obstructions in the reinforced fill, or in

other cases justified by calculation, the maximum skew angle shall not exceed 15 degrees from the

normal position, except in case of acute corners where redundant reinforcements are used, or in

other cases justified by calculation.

Backfill shall be placed in such a manner as to avoid any damage or disturbance to the wall

materials or misalignment of the facing panels. Any wall materials which become damaged or

disturbed during backfill placement shall be corrected or removed and replaced at the Contractor’s

expense, as directed by the Engineer.

Backfill shall be compacted to 95% of the maximum density as determined in accordance with

AASHTO T 99, Method C or AASHTO T 99, Method D (with oversize correction). The optimum

moisture content shall be determined in accordance with AASHTO T 99, Method C or AASHTO T

99, Method D (with oversize correction). The moisture content of the select backfill material prior

to and during compaction shall be uniform throughout each layer. Backfill material shall have a

placement moisture content less than or equal to the optimum moisture content. Backfill material

with a placement moisture content in excess of the optimum moisture content shall be removed

and reworked until the moisture content is uniform and acceptable throughout the entire lift. Field

density and moisture content quality control shall be conducted by the Contractor in accordance

with AASHTO T 310 at a frequency of no less than once per 500 cubic yards.

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The maximum lift thickness after compaction shall not exceed 10 inches, regardless of the vertical

spacing between the reinforced soil layers. The Contractor shall decrease this lift thickness, if

necessary, to obtain the specified density. Prior to placement of the soil reinforcement elements,

the backfill elevation, after compaction, shall be equal to or up to 2 inches above the attachment

device elevation from a point approximately 12 inches behind the back face of the panels to the

free end of the soil reinforcements, unless otherwise shown on the Plans.

Compaction within 3 feet of the back face of the panels shall be achieved by a minimum of three

passes of a lightweight mechanical tamper, roller, or vibratory system. The specified lift thickness

shall be adjusted as warranted by the type of compaction equipment actually used, but no soil

density tests need be taken within this area. Care shall be exercised in the compaction process to

avoid misalignment of the panels or damage to the attachment devices. Heavy compaction

equipment shall not be used to compact backfill within 3 feet of the wall face.

At the end of each day’s operation, the Contractor shall slope the last level of backfill away from

the wall facing to direct 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.

in the field. Seams shall be formed by lapping the edges of panels a minimum of 6 inches. The

contact surfaces of the panels shall be wiped clean to remove all dirt, dust, or other substance. A

vinyl-to-vinyl solvent shall be applied to the contact surface in the seam area as recommended by

the manufacturer, and the two surfaces pressed together immediately. Any wrinkles shall be

smoothed out. Field seams shall have a strength of at least 85% of the specified sheet strength.

All curing compounds and coatings shall be completely removed from the joint area. Joining of

the PVC to the back of panel shall be done with an adhesive. Unless otherwise shown on the Plans,

the minimum width of concrete to PVC joint shall be 6 inches. In addition, mechanical attachments

may be necessary.

Any necessary repairs to the PVC shall be made with the lining material itself and cold applied

vinyl to vinyl splicing adhesives. Patches shall be cut so as to cover the area to be repaired by a

minimum of 4 inches in all directions. Patches shall be cut with rounded corners. The splicing

adhesive shall be applied to the contact surface between the patch and the lining, and the two

surfaces pressed together immediately.

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earth retaining wall system, the Contractor shall establish horizontal and vertical survey points at

a minimum of three locations across the top and at mid-elevation on the wall with an additional

set of points for each 100 feet of wall required to monitor future movements. These points shall be

tied into a minimum of two control markers that are sufficiently removed from the wall so as not

to be influenced by wall movement. The control shall be located to allow the Agency to gather

additional measurements to be made after all construction is complete. A plan with the northings

and eastings of all survey points and ties, along with distances and elevations recorded to the

nearest 0.001 feet, shall be provided to the Engineer within 48 hours of the completion of the

mechanically stabilized earth retaining wall system.

227.07METHOD OF MEASUREMENT. The quantity of Retaining Wall, Mechanically Stabilized

Earth to be measured for payment will be on a lump sum basis in the complete and accepted work.

227.08BASIS OF PAYMENT. The accepted quantity of Retaining Wall, Mechanically Stabilized Earth

will be paid for at the Contract lump sum price. Payment shall include full compensation for designing,

detailing, fabricating, furnishing, transporting, erecting, and baseline monitoring the mechanically

stabilized earth retaining wall system; for preparing all required submittals; for supervision by the

manufacturer’s representative; for materials required, including but not limited to, select granular backfill,

PVC pipe, drainage aggregate, filter fabric, adhesive, underdrain pipe, concrete facing panels, reinforcing

steel, concrete coping, soil reinforcements, attachment devices, fasteners, bearing blocks, shims, joint

materials, geomembrane, and geotextiles; for preparing the wall foundation, proof rolling foundation soils,

and constructing the concrete leveling pad; all required excavation; and for furnishing all labor, tools,

equipment, and incidentals necessary to complete the work.

Payment will be made under:

Pay Item Pay Unit

00 Retaining Wall, Mechanically Stabilized Earth ........................................Lump Sum

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2-132SECTION 230 – CONTAMINATED MATERIALS

230.01DESCRIPTION . This work shall consist of the management and disposal of contaminated soil

and groundwater encountered during construction in accordance with these specifications.

230.02GENERAL REQUIREMENTS . The Contractor shall follow the soil management plans (SMP ),

corrective action plans (CAP), and other supporting documentation incorporated by reference as part of the Contract. The work shall include identification, handling, sampling, testing, classification, segregation, temporary stockpiling, loading, transpo rtation, disposal, treatment, and final placement of the contaminated materials in accordance with any such referenced plan. The work will also include management, treatment, and disposal when contaminated groundwater is encountered. Initial excavation of the contaminated material shall be performed in accordance with the appropriate excavation item included in the Contract. The Contractor shall engage the services of an environmental professional (EP), as defined in ASTM E1527 , to prepare and submit a project operations plan (POP) to the Agency, provide environmental oversight, identify and classify contaminated soils, coordinate with and submit relevant documents to regulatory agencies, obtain any required regulatory permits, including, but not limited to National Pollutant Discharge Elimination System discharge permits or other deviations to the approved SMP or CAP. The EP shall also prepare and submit a project operations completion report (POCR).

230.03SUBMITTALS . Prior t o the commencement of construction, the Contractor’s EP shall prepare

and submit to the Agency a site -specific POP in accordance with the referenced plans and all other relevant specifications in the Contract. The POP shall include the name and qualifications of the EP, discuss applicable authorizations, and propose and detail means and methods for meeting applicable regulatory requirements, including the following:

contaminated soi ls and waste materials.