6-20Buried Structures

6-20 Buried Structures6-20 Buried Structures

6-20.1 Description

This Work consists of designing and constructing Buried Structures of the various types including associated approach slabs, footings, headwalls, wingwalls, Class 4000D concrete topping slab, connected barriers, rails, and fall protection in accordance with the Contract documents.

6-20.1(1) Definitions

Buried Structure: A Structure consisting of one of the types defined below: Concrete Three Sided Structure: A precast or cast-in-place reinforced concrete structure with vertical walls and an integral top slab placed on reinforced concrete foundations. It may be arched or corded and may contain chamfers or fillets. Concrete Box: A precast or cast-in-place reinforced concrete structure with vertical walls, an integral top slab and an integral bottom slab. The top and bottom slabs are usually flat and at 90-degrees to the walls forming a rectangular structure. The corners may contain chamfers or fillets. Concrete Split Box: A concrete box culvert split into upper and lower units by horizontal joints in the vertical walls. The upper unit may be prestressed. Structural Plate Pipe: A steel or aluminum structural plate around the entire circumference of a pipe shape. Structural plate pipes may contain external reinforcing members and multiple radiuses and plate thicknesses. Structural plate pipe shapes include but are not limited to round, ellipse, underpass, pipe-arch and pear. Structural Plate Arch: A steel or aluminum structural plate arch shape placed on reinforced concrete foundations. Structural plate arches may contain external reinforcing members and multiple radiuses and plate thicknesses. Structural Plate Box: A steel or aluminum structural plate box shape that meets the requirements of the AASHTO LRFD Bridge Design Specifications Section 12.9 (or Section 12.8.9 for deep corrugated structural plate structures with ratio of crown radius to haunch radius > 5). Headwall: Structure elements employed as end treatments connected to or constructed on top of Buried Structures, including, at a minimum, parapets, slope collars, and cutoff walls. Wingwall: A retaining wall structure element adjacent to or above a Buried Structure end or headwall. Class 4000D Concrete Topping Slab: A 5.0-inch minimum thickness composite cast-in- place system with at least one mat of epoxy coated reinforcement. Structure Free Zone (SFZ): An imaginary prism defined in the Contract documents which represents the minimum boundary within which no part of the buried structure including foundations, headwalls and wingwalls shall be allowed. For a Contracting Agency Supplied Design the SFZ shall be defined by the interior horizontal and vertical dimensions and the length of the structure shown in the Contract documents, unless noted otherwise. Hydraulic Design Flood Elevation: 100-year or the 2080 projected 100-year flood elevation. Zone of Influence: A prism defined in the Contract documents representing the boundary within which the Structure derives support from the surrounding granular backfill or native soil through soil-structure interaction. M 41-10 Page 6-299 Buried Structures 6-206-20.2 Materials Materials shall meet the requirements of the following sections: Controlled Density Fill (CDF) 2-09.3(1)E Lean Concrete 6-02.3(2)D Cement 9-01 Aggregates for Concrete 9-03.1 AASHTO Grading No. 57 9-03.1(4)C Aggregates for Ballast and Crushed Surfacing 9-03.9 Streambed Aggregates 9-03.11 Gravel Backfill 9-03.12 Borrow 9-03.14 Joint Sealing Materials 9-04 Structural Plate Pipes, Arches and Boxes 9-05.6 Deformed Steel Bars 9-07.2 Epoxy-Coated Steel Reinforcing Bars 9-07.3 Galvanizing Repair Paint, High Zinc Dust Content 9-08.1(2)B Primer, Zinc-Rich, Single-Component, Moisture-Cured Polyurethane 9-08.1(2)F NEPCOAT Qualified Business Products List B Primer 9-08.1(2)N Grout Type 2 for Nonshrink Applications 9-20.3(2) Mortar 9-20.4 Concrete Curing Materials and Admixtures Water 9-25 Concrete class shall be as specified but in no case shall be less than Class 4000. Materials for Class 4000D concrete topping slab shall meet all the requirements of Class 4000D concrete as specified in Section 6-02.2.

6-20.3 Construction Requirements

6-20.3(1) Design

6-20.3(1)A Design Delivery Method

Buried Structures shall be considered a Contractor Supplied Design when the Contract documents do not include a complete set of design details for a Structure (consisting of, at a minimum, defining material requirements, shapes, dimensions, reinforcing details, joint and connection details, etc.). Buried Structures shall be considered a Contracting Agency Supplied Design when the Contract documents include a complete set of Structural Engineer stamped design details for a Structure, which may include Standard Plans.

6-20.3(1)A1 Contractor Supplied Design

The Contractor shall prepare the design in accordance with Sections 6-20.3(1)C through

6-20.3(1)I All submittal requirements of Section 6-20.3(2) shall apply.

The Buried Structure, headwalls and wingwalls shall be located as specified in the Contract documents, including but not limited to the alignment, length, profile, and elevation. The Buried Structure shall accommodate the geometry required in the Contract documents. No part of the Buried Structure, including but not limited to foundations, headwalls and wingwalls, shall be allowed within the Structure Free Zone. The Buried Structure and wall types shall be as specified in the Contract documents. Page 6-300 M 41-10

6-20 Buried Structures6-20.3(1)A2 Contracting Agency Supplied Design

The Buried Structure design shall be as presented in the Contract documents, which may include Standard Plans. The requirements of Sections 6-20.3(1)C through 6-20.3(1) I, 6-20.3(2)A and 6-20.3(2)B shall not apply for the Structure. All other submittal requirements of Section 6-20.3(2) shall apply. When allowed by the Engineer, the Contractor may propose an alternate Structure to replace a Contracting Agency Supplied Design. No part of the alternate structure, including but not limited to foundations, headwalls and wingwalls, shall be allowed within the Structure Free Zone. When the alternate structure is located as specified in the Contract documents, is of the same type as specified in the Contract documents, is the same length as specified in the Contract documents and does not affect other portions of the design except adjustments to interface location with headwalls and wingwalls, it is not required to follow the requirements of Section 1-04.4(2) . Otherwise, the alternate structure proposal shall meet the requirements of Section 1-04.4(2) . The Contractor shall prepare the alternate structure design in accordance with Section

6-20.3(1)A1 The Contractor shall be responsible for the entire design of an alternate

structure and associated structure elements including, at a minimum, approach slabs, headwalls, wingwalls and connected barriers, rails and fall protection. The Contractor may substitute welded wire reinforcement (WWR) conforming to Section

9-07.7 for plain deformed bar. The WWR shall provide an equivalent bar area, equal

or reduced bar spacing , and shall satisfy crack control and minimum reinforcement requirements of the AASHTO LRFD Bridge Design Specifications. The WWR shall be deformed, and the specified minimum yield strength shall be limited to a maximum of 75 ksi. The proposed WWR substitution, with supporting calculations, shall be submitted to the Engineer as a Type 2E Working Drawing.

6-20.3(1)B Buried Structure Class

The Structural Clear Span of a Buried Structure shall be used to determine the Buried Structure class. When supporting a Roadway, the Structural Clear Span shall be the widest horizontal opening from interior face to interior face of the end walls measured parallel to the Roadway centerline. When not supporting a Roadway, the Structural Clear Span shall be the widest horizontal opening from interior face to interior face of the end walls measured perpendicular to the Buried Structure centerline. Structure Class Structural Clear Span Class 1 Less than 20.0 feet Class 2 20.0 feet and greater

6-20.3(1)C General Design Criteria

Buried Structures and associated headwalls, wingwalls and connected barriers, rails and fall protection shall be designed in accordance with the WSDOT Geotechnical Design Manual M 46-03, WSDOT Hydraulics Manual M 23-03, WSDOT Bridge Design Manual LRFD M 23-50, AASHTO LRFD Bridge Design Specifications, AASHTO LRFD Road Tunnel Design and Construction Guide Specifications, Sections 10.8, AASTHO Technical Manual for Design and Construction of Road Tunnels – Civil Elements, Section 13, and the AASHTO LRFD Bridge Construction Specifications. The AASHTO operational classification load modifier for the buried structure shall be that for typical bridges unless noted otherwise. Buried Structures shall be designed for a minimum Service Life of 75-years. Corrosion and abrasion shall be considered as specified in the WSDOT Bridge Design Manual LRFD M 23-50. M 41-10 Page 6-301 Buried Structures 6-20Class 2 Buried Structures and associated headwalls and wingwalls, as defined in Section

6-20.1(1) , shall include seismic design and mitigation of seismic geological hazards

in accordance with the WSDOT Bridge Design Manual LRFD M 23-50 and WSDOT Geotechnical Design Manual M 46-03. This includes, at a minimum, design for seismic effects in accordance with the AASHTO LRFD Road Tunnel Design and Construction Guide Specifications, Section 10.8, and the AASHTO Technical Manual for Design and Construction of Road Tunnels – Civil Elements, Chapter 13. The AASHTO LRFD Bridge Design Specifications exemption from seismic loading shall not apply.

6-20.3(1)D Geotechnical Considerations

The Contractor shall use the Geotechnical Report prepared for the Buried Structure and available through the source(s) specified in the Special Provisions under Section 1-02.4(2) . The Contractor shall complete all additional geotechnical investigations and designs necessary for this Work as required by the WSDOT Geotechnical Design Manual . This includes but is not limited to performing additional permitting, surveying, field investigation, subsurface borings, analysis and modeling. The type, compacted density, and strength properties of the fill adjacent to the Buried Structure shall be established.

6-20.3(1)E Hydraulic Considerations

The Contractor shall complete all additional hydraulic investigation and design necessary for this Work as required by the WSDOT Hydraulics Manual . This includes but is not limited to performing additional permitting, surveying, field investigation, subsurface borings, analysis and modeling. All Buried Structures and associated headwalls and wingwalls shall be designed for scour from the design flood (100 year flood event) and the check flood (500 year flood event) in accordance with the WSDOT Bridge Design Manual LRFD and the AASHTO LRFD Bridge Design Specifications unless additional design criteria is documented in the Final Hydraulic Design report. Channel lateral migration shall be considered. Buried Structures and associated headwalls and wingwalls shall include the effects of scour in accordance with the WSDOT Bridge Design Manual LRFD. Alternative methods of protection against scour may be used with the concurrence of the Engineer.

6-20.3(1)F Worker, Pedestrian, and Bicycle Fall Protection

For Buried Structures and associated headwalls and wingwalls, worker, pedestrian and bicycle fall protection shall be provided in accordance with the WSDOT Design Manual, and shall be designed in accordance with the WSDOT Bridge Design Manual LRFD.

6-20.3(1)G Traffic Barrier and Guardrail

Traffic barrier shall be designed for a minimum Test Level Four (TL-4) impact load, unless otherwise specified. When traffic barrier or guardrail is connected to the Buried Structure, the supporting Structure shall be designed for the loads transferred from the barrier or guardrail to the Structure.

6-20.3(1)H Concrete Structures

When the Buried Structure is located in a marine or non-marine corrosive environment as defined in the WSDOT Bridge Design Manual LRFD , corrosion-resistant reinforcement defined in the WSDOT Bridge Design Manual LRFD shall be used. The minimum cover requirements for direct exposure to salt water and coastal situations of the AASHTO LRFD Bridge Design Specifications shall apply. When the fill depth is less than 2.0 feet at any point above the Buried Structure and is supporting a Roadway, it shall be considered directly exposed to vehicular traffic in accordance with the WSDOT Bridge Design Manual LRFD. Page 6-302 M 41-10

6-20 Buried StructuresAll Work for constructing Class 4000D concrete topping slab shall meet the requirements

specified in Section 6-02.3. Bridge approach slabs shall be required for Buried Structures as specified in the WSDOT Bridge Design Manual LRFD.

6-20.3(1)I Structural Plate Structures

Steel structural plate shall not be used in locations conforming to marine or non-marine: corrosive environments as defined in Chapter 6 of the WSDOT Bridge Design Manual LRFD . When using galvanized or zinc coated metal structural plate Structures below the Hydraulic Design Flood Elevation, a reinforced concrete splash wall is required. See the WSDOT Bridge Design Manual LRFD for additional details and requirements. Minimum backfill cover over the top of the Structure and the minimum backfill width on each side of the Structure shall be in accordance with the AASHTO LRFD Bridge Design Specifications.

6-20.3(2) Submittals

6-20.3(2)A Plans, Specifications and Calculations

For a Contractor Supplied Design the Contractor shall submit Type 2E Working Drawings, with a 30-day review period, consisting of site specific plans, specifications, supporting calculations and fabrication shop drawings. All components of the Buried Structure system including but not limited to, the Structure, associated headwalls, wingwalls and other components shall be submitted simultaneously as a comprehensive submittal. The Contractor shall be responsible for carrying out a thorough check of the Plans and calculations in accordance with WSDOT Bridge Design Manual LRFD. The recommendations and requirements contained in the Geotechnical Report and Final Hydraulic Design report for the Structure shall be met. At a minimum, the site-specific plans and specifications shall include:

6-20.3(2)B Load Rating Report

For a Contractor Supplied Design, for a Class 2 Buried Structure, the Contractor shall submit a Load Rating Report except when the effects of live load may be neglected in accordance with the WSDOT Bridge Design Manual LRFD. The Load Rating Report shall be submitted as a Type 2E Working Drawing prepared in accordance with the AASHTO Manual for Bridge Evaluation and the WSDOT Bridge Design Manual LRFD , Chapter 13. Soil parameters shall be in accordance with the design requirements, the WSDOT Geotechnical Design Manual and the Geotechnical Report prepared for the project. If the Contractor elects to use Buried Structure Standard Plans, a Load Rating Report is not required to be submitted.

6-20.3(2)C Dewatering System

If water is expected to be present in the excavation, or is found to be present once excavation begins, the Contractor shall submit a Type 2 Working Drawing consisting of a dewatering plan.

6-20.3(2)D Manufacturer’s Installation Instructions

For Class 1 structural plate Structures and other Class 1 proprietary Buried Structure systems, the Contractor shall submit a Type 1 Working Drawing consisting of the manufacturer’s installation instructions for the Structure prior to the preconstruction conference and construction. The manufacturer's instructions shall provide step-by-step directions for construction of the Structure.

6-20.3(2)E Installation Plan

For Class 2 Buried Structures, prior to the preconstruction conference, the Contractor shall submit a Type 2E Working Drawing consisting of an installation plan, including the manufacturer’s installation instructions, Working Drawings and substantiating calculations. The installation plan shall cover all aspects of installation, including but not limited to native subgrade preparation, bedding, leveling, and foundation construction, unit identifier and placement location, assembly, how alignment of the units will be maintained and how adjustments to alignment will be accomplished, how units will be pulled together to attain the proper joint gap, bolting requirements, backfilling requirements and shape control during backfilling. The installation plan shall address all bracing requirements and how the Structure is monitored during and after construction and backfilling to ensure the finished product meets all design and construction requirements and all geometric tolerances. Minimum backfill cover over the structure to support construction equipment loadings shall be specified. Page 6-304 M 41-10

6-20 Buried Structures6-20.3(3) Tolerances

Tolerances for cast-in-place concrete components of Buried Structures shall be in accordance with Section 6-02.3(7). Reinforcement placement shall meet the tolerances specified in Section 6-02.3(24)C. For the Buried Structure location:

6-20.3(3)A Concrete Structures

Precast concrete Buried Structures shall conform to the fabrication tolerances of Section 6-02.3(9)F. Fabrication tolerances for precast concrete three-sided Structures shall be as follows:

6-20.3(4) Preconstruction Conference

Preconstruction conferences are required for all Buried Structures. Class 1 Buried Structures conferences may be omitted when approved by the Engineer. All submittals required in Section 6-20.3(2) , except for the Section 6-20.3(2)B Load Rating Report, shall be accepted and/or approved at least 5 working days before holding the preconstruction conference. The preconstruction conference shall be held at least 5 working days prior to the Contractor beginning Buried Structure construction at the site to discuss safety, maintenance of traffic, environmental compliance, construction procedures, critical functions during backfilling, quality control steps to control loads, shape and movement, personnel, equipment to be used, and other elements of construction. Those attending shall include: Representing the Contractor: The superintendent, on site supervisors, and all forepersons in charge of safety, traffic, environmental, excavation, structure construction, and backfilling. Representing the Manufacturer: For Class 2 Buried Structures, a qualified and experienced manufacturer’s representative conforming to Section 6-20.3(4)A .

6-20.3(4)A Manufacturer’s Representative

A manufacturer’s representative shall be provided for Class 2 Buried Structures. The manufacturer’s representative shall be a qualified and experienced representative able to resolve construction problems. The manufacturer’s representative shall be present at the preconstruction conference, on site during initial installation and available at other times as needed throughout construction. Recommendations made by the manufacturer’s representative shall be followed by the Contractor unless the recommendations deviate from the Contract requirements. In the instance where a recommendation deviates from the Contract, the Contractor shall request acceptance from the Engineer for the Change.

6-20.3(5) Excavation

Excavation shall conform to Section 2-09.3(3) . The Contractor shall excavate to the lines and grades identified in the Plans and Working Drawings. The excavation limits shall be increased to account for the placement of Buried Structure bedding and leveling materials and structural backfill. Material at the bottom of the excavation that is unstable or unsuitable shall be removed in accordance with Section 2-09.3(1)C . If the excavation is dry enough that replacement material can be compacted without causing pumping or further degradation of the material exposed in the bottom of the excavation (after unstable removal), the unstable material shall be replaced in accordance with Section 2-09.3(1)C . Quarry spalls may be used in the overexcavation area if needed but shall be capped with a minimum of 6 inches of Crushed Surfacing Base Course (CSBC). If the bottom of the excavation is too wet for compaction to occur, the Contractor shall place Construction Geosynthetic for Soil Stabilization - Woven, conforming to Section

9-33 2(1), on the exposed bottom of the excavation. Geosynthetic shall be overlapped as

required by the manufacturer, but not less than 1.0 foot at seams. The Contractor shall Page 6-306 M 41-10

6-20 Buried Structuresstretch out the Geosynthetic to ensure that no slack or wrinkles exist in the geosynthetic

prior to backfilling. Backfill consisting of CSBC or AASHTO Grading No. 57 shall be placed on top of the Geosynthetic to reestablish lines and grade. Compaction of the CSBC or AASHTO Grading No. 57 shall be by static methods or by track walking and shall impart only enough energy to seat the granular materials together and provide a stable, non- shifting, working surface. Controlled Density Fill (CDF) or lean concrete may be used with no geosynthetic and no compaction. Upon completing the excavation, the Contractor shall notify the Engineer. No other permanent part of the Buried Structure or associated headwalls or wingwalls shall be placed until the Engineer has given permission to proceed. If water is present within the excavation, the Contractor shall dewater the excavated area in accordance with the Section 6-20.3(2) C Working Drawing submittal before placing the bedding material. Existing structures and obstructions shall be removed in accordance with Section 2-02.3.

6-20.3(5)A Construction Dewatering

The Contractor shall design, install, operate, maintain, and remove a construction dewatering system. The construction dewatering system shall be used to remove precipitation from the work area, surface water that enters the work area, and seepage when excavations extend below groundwater. The system shall be capable of handling surface water, precipitation, and groundwater flow associated with seasonal groundwater variations and storm events. The system shall provide for a reasonably dry excavation free of standing water that impedes construction or degrades the working surface of the excavation. Discharge from the dewatering system shall be handled in accordance with Section 8-01.3(1)C1 .

6-20.3(6) Bedding and Foundations

6-20.3(6)A Bedding and Leveling

Buried Structure bedding material shall be placed in accordance with the Contract documents and the submittals of Sections 6-20.3(2)A , 6-20.3(2)D , and 6-20.3(2)E . Cast-in-place and precast reinforced concrete foundation elements require a 6.0-inch minimum thickness layer of Buried Structure bedding material, defined as either CSBC or AASHTO Grading No. 57. In addition to the bedding material, precast reinforced split box Structures require a 2-inch maximum leveling course on top of the bedding. The leveling course shall meet the requirements of Section 9-03.1(2)B for Grading Class 1 or Class 2 sand. Alternative leveling material may be submitted for acceptance by the Engineer, but in no cases shall the particle size be greater than ⅜-inch. The plan limits of the Buried Structure bedding and leveling material, when applicable, shall extend 1.0 foot beyond the plan limits of the foundation or the Structure as applicable. The Buried Structure bedding and leveling material shall be compacted in accordance with the Section 2-09.3(1)E requirements for backfill supporting Structures. If the bedding material has voids after compaction, then a Filter Fabric, conforming to Section 9-08.6, shall be placed over the bedding to separate the leveling course from the bedding material. Leveling material shall not be placed under precast reinforced concrete retaining walls. All Buried Structure bedding material adjacent to structural plate structures shall meet the material requirements for backfill material in Section 6-20.3(9) . Structures with a curved, nonplanar bottom, such as structural plate pipes, require Buried Structure bedding material with a minimum thickness of twice the corrugation depth, but not less than 6.0 inches. The Buried Structure bedding material shall be shaped to conform to the bottom of the structure and shall provide a uniform bearing throughout the Buried Structure length. The Buried Structure bedding material shall be centered beneath the Structure and shall have a minimum width of one-third the Structural Clear M 41-10 Page 6-307 Buried Structures 6-20Span for horizontal elliptic shapes and one-half the Structural Clear Span otherwise. Bedding material shall be compacted in accordance with Section 2-09.3(1)E except that the top layer of bedding (thickness of outside diameter of the pipe minus the inside diameter of the pipe) shall be loosely placed (not compacted), to cushion the invert and allow corrugations to nest or seat into it. Rock, in either ledge or boulder formation, hard pan, or cemented gravel occurring in the base material shall be excavated to below the Buried Structure bedding material.

6-20.3(6)B Foundations

Cast-in-place concrete foundations and components of foundations shall be constructed in accordance with Section 6-02. Precast concrete foundations shall be constructed in accordance with Section 6-02.3(9) .

6-20.3(7) Fabrication

Welding of steel shall be in accordance with Section 6-03.3(25) . Welding of steel structural plate Structures shall comply with the AWS D1.1/D1.1M Structural Welding Code. Welding of aluminum shall conform to the ANSI/AWS D1.2/D1.2M Structural Welding Code – Aluminum.

6-20.3(7)A Precast Concrete Structures

Except as otherwise noted by these specifications, precast concrete buried structures shall conform to all requirements of Section 6-02.3(9). Precast prestressed units shall be fabricated and transported in accordance with Section 6-02.3(25). For Class 1 and Class 2 precast concrete, three-sided and split box Structures, unless otherwise shown in the Plans, the Contractor shall, at a minimum for each set of forms used, progressively shop assemble the top and bottom units of the first three adjacent segments for inspection of fit up. The installing Contractor shall observe the shop fit up. The date and time of the shop fit up shall be scheduled during normal business hours and communicated to both the installing Contractor and the Engineer. As an alternative to physically being present to observe the fit-up, the Contractor and the Engineer may agree to observe the fit-up via video conference. Units shall not be disassembled prior to receiving the Engineer’s acceptance. If the Engineer accepts the initial assembly then no additional shop assembly will be required unless the Contractor changes forms, the forms show signs of damage, or there is a geometric change to the forms. If issues are found during the progressive shop assembly, the Contractor shall make corrections and continue the progressive shop assembly until three, consecutive segments have been successfully shop assembled. The shop assembly shall be done on a flat level surface at the fabrication plant. Bunking or shimming shall not be allowed during the shop assembly. The following information shall be legibly and permanently marked on one inside face of each precast unit by indentation, waterproof paint or other means acceptable to the Engineer:

6-20 Buried Structures6-20.3(7)B Structural Plate Structures

The following information shall be legibly and permanently marked on the inside face of each structural plate by waterproof paint or other means acceptable to the Engineer:

6-20.3(8) Placement and Assembly

Buried Structures shall be placed and assembled in accordance with the Contract documents and the submittals of Sections 6-20.3(2)A , 6-20.3(2)D , and 6-20.3(2)E . Components with identified pick points or lifting locations shall be handled using those locations. Component pieces shall be set into their final position in a manner that preserves the lines and grade established for the structure. Base units, precast foundation units, and bearing surfaces may be slid on grade to adjust their position, but if sliding results in grade changes, misalignment, or native subgrade, bedding, or leveling material infiltration within the annular joint space (inhibiting jointing between components), the component shall be removed, the grade adjusted, and foreign material(s) cleared. Grade shall be adjusted such that components can be assembled in accordance with the required tolerances. Shims used by the Contractor to position components for assembly shall be removed unless the shims are specified as permanent in the Plans or Working Drawings. Components that are not self-supporting shall be braced or supported by the Contractor during assembly. Construction of cast-in-place concrete components shall be in accordance with Section 6-02 .

6-20.3(8)A Precast Concrete Structures

For Structures that are expected to support traffic within 7 days after the placement of prefabricated segments is complete, the Contractor shall designate an individual to verify and record conformance to the erection tolerances for each segment as it is placed. Components with weld-ties shall be connected by welding the weld-tie anchors in accordance with Section 6-03.3(25). The welding ground shall be attached directly to the plates being welded. After connecting the weld-tie anchors, the Contractor shall paint the exposed metal surfaces with one coat of zinc-rich primer conforming to Section

9-08.1(2)F or Section 9-08.1(2)N. Keyways shall be filled with Grout Type 2 for Nonshrink

Applications, unless specified otherwise. The Contractor shall install a continuous strip of Butyl Rubber Sealant within all tongue and groove (ship lap) and butt joints prior to connecting the precast elements together. The Butyl Rubber Sealant shall be sized in accordance with the manufacturer’s recommendations but shall not have a cross section smaller than ½-inch by 1½-inch. The Contractor shall wrap all exterior joints along the top and sides of precast concrete structures (except top surfaces that will have a waterproof membrane with an HMA overlay, a concrete overlay or a concrete topping slab) with a 12.0-inch wide strip of External Sealing Band centered about the joint and adhesively bonded to the concrete surface. M 41-10 Page 6-309 Buried Structures 6-206-20.3(8)B Structural Plate Structures Construction of structural plate pipes, arches and boxes shall conform to the AASHTO LRFD Bridge Construction Specifications, Section 26. Plates at longitudinal and circumferential seams shall be configured with the seams staggered so that not more than three-barrel plates come together at any one point. When required, temporary bracing shall be installed and shall remain in place as long as necessary to protect workers and to maintain structure shape during placement and assembly. Bolts and bolted connections shall conform to the requirements of AASHTO M 167 for steel and AASHTO M 219 for aluminum. Bolts shall be sufficiently torqued to avoid backing out while compacting backfill. Where aluminum will contact concrete or grout, two coats of paint shall be applied to the aluminum at the contact surface in accordance with Section 7-08.3(2)D . Where the galvanized coating on structural plate has been damaged in handling or installing, such damaged areas shall be thoroughly painted with galvanizing repair paint, high zinc dust content.

6-20.3(9) Backfilling

The backfill outside of Buried Structures shall be granular material meeting the requirements in the Working Drawings, meeting the Buried Structure manufacturer’s requirements and conforming to the requirements of AASHTO M 145 A-1 or A-3. Granular material shall consist of a crushed rock and/or processed angular material. On site granular soils may be considered for backfill around the Structure if the material meets the requirements in this specification. The following backfill materials generally meet the AASHTO M 145 A-1 or A-3 requirements. Additional gradation requirements by the Structure manufacturer may apply.

6-20 Buried StructuresWhen specified in the Contract documents or Working Drawings, the Contractor

shall place and compact materials within the Buried Structure. The Contractor may place and compact materials prior to finishing assembly provided the placement and compaction does not damage or distort the Structure or hinder the achievement of the specified tolerances.

6-20.3(9)A Backfilling of Structural Plate Structures

The Zone of Influence shall include the structural backfill outside of the Buried Structure within the following limits:

6-20.3(3) For Class 2 Buried Structures, a manufacturer’s representative shall assist as

described in Section 6-20.3(4)A . Installation deflection inspections by direct measurement shall be performed by the Contractor immediately after construction and 30 days or more after construction. Inspection results shall be reported to the Contracting Agency within 2 working days of performing the inspection. Installation deflections shall meet the requirements of

6-20.3(10) Wingwalls and Headwalls

The Contractor shall construct wingwalls and headwalls associated with Buried Structures in conformance with the Contract documents and Working Drawing submittals. For Buried Structures crossing water, portions of headwalls and wingwalls below the water surface of the Hydraulic Design Flood Elevation shall be reinforced concrete or have a reinforced concrete fascia. M 41-10 Page 6-311 Buried Structures 6-20Structural Earth Wall wingwalls shall not use metallic ground reinforcement below the water surface of the Hydraulic Design Flood Elevation unless the pH, in accordance with WSDOT T 417, of the water in front of the wall and of the groundwater are within the range of 5.0 and 10.0. Cast-in-place concrete components of headwalls and wingwalls shall be constructed in accordance with Section 6-02. Precast concrete construction shall conform to Sections 6-02.3(9) and 6-11.3(3). Bedding material shall be furnished, placed, and compacted in accordance with

6-20.4 Vacant

6-20.5 Payment

Payment will be made for each of the following Bid items that are included in the Proposal: “Agency Designed Buried Structure No. _____”, lump sum. The lump sum Contract price for “Agency Designed Buried Structure No. _____” shall be full payment to perform the Work as specified in Section 6-20.3 . The approximate quantities of materials and work for the lump sum item “Agency Designed Buried Structure No. _____” may be provided in the Contract documents. If so, the quantities listed are only for the convenience of the Contractor in determining the volume of work involved and are not guaranteed to be accurate. Quantities may vary depending on the Contractor’s Work methods, order of work, suitability of excavated materials, and structure dimensions. The prospective bidders shall verify these quantities before submitting a bid. No adjustments other than for accepted changes will be made in the lump sum Contract price for “Agency Designed Buried Structure No. _____” even though the actual quantities required may deviate from those listed. “Contractor Designed Buried Structure No. _____”, lump sum. The lump sum Contract price for “Contractor Designed Buried Structure No. _____” shall be full payment to perform the Work as specified in Section 6-20.3 . The approximate quantities of materials and work for the lump sum item “Contractor Designed Buried Structure No. _____” may be provided in the Contract documents. If so, the quantities listed are only for the convenience of the Contractor in determining the volume of work involved and are not guaranteed to be accurate. Quantities may vary depending on the Contractor’s Work methods, order of work, suitability of excavated materials, and structure dimensions. The prospective bidders shall verify these quantities before submitting a bid. No adjustments other than for accepted changes will be made in the lump sum Contract price for “Contractor Designed Buried Structure No. _____” even though the actual quantities required may deviate from those listed. Payment for Class 4000D concrete topping slab shall be included in the lump sum item, “Contractor Designed Buried Structure No. ____”. “Shoring or Extra Excavation Cl. A _____”, lump sum.