SECTION 210: EXCAVATION AND BACKFILL FOR MAJOR STRUCTURES
210.1 Description
This Work consists of excavati ng, disposing of Material, suppl ying and placing backfill Material related to the construc tion of Bridges, cast-in-place retaining walls, and CBC’s 20 feet or greater measured along the centerline of the Roadway. Excav ation and backfill for Major Structures includes dewatering, temporary shoring and bracing a nd other Incidentals required for proper execution of the Work.
210.2 Materials
210.2.1 Select Backfill
The Contractor shall use Base Course per Section 303 “Base Cou rse”, A-1 or A-2-4 Material as determined by AASHTO M145 composed of stone, crushe d stone, crushed or screened gravel, caliche, sand, or a combination thereof, unles s otherwise specified in the Contract. The Contractor shall use Material that is free of De leterious Materials, peat, gypsum, shale or other Materials that may degrade with time or are contaminated. Material shall not contain lumps or stones with an average dimension gre ater than two (2) inches. The Contractor shall not use Recycled Asphalt Pavement (RAP) a s select backfill Materials. The Contractor shall not use Base Course containing RAP for use as select backfill Materials.
210.2.2 Approach Slab
The Contractor shall use AASHTO Soil Classifications A-1-a Mat erial with a maximum coarse fraction size of 1.5 inches or Base Course per Section 3 03, “Base Course” under the approach slab. The Contractor shall extend the Material to a m inimum of ten (10) feet beyond the end of the approach, unless otherwise specified in the Cont ract, for the full width of the abutment and to the depth indicated in the Contract. Recycled Asphalt Material (RAP) shall not be used within this prism.
210.2.3 Unsuitable Material
Unsuitable Material includes or ganic Materials, frozen lumps, i ce, and soil/rock such as peat, shale, gypsum or other Materials that may degrade with ti me, or are contaminated. Suitable Material that is unstable may be reworked to create a stable platform as directed by the Project Manager. Material identified by the Project Manager and determined to b e unsuitable shall be excavated and disposed of in accordance with Section 107, “Lega l Relations, Environmental Requirements, and Responsibility to the Public” unless otherwis e specified in the Contract. When unsuitable Material is remo ved and disposed of, the resul ting void shall be filled with Material suitable for its planned use as directed by the P roject Manager. Such suitable Material shall be placed and com pacted in accordance with Secti on 210.3.2, “Compaction.”
210.3 Construction Requirements
210.3.1 General
The Contractor shall excavate Material to the elevations estab lished in the Contract. The Contractor shall not remove Material, except unsuitable Materia l, below the final grade, if Section 210: Excavation and Backfill for Major Structures Page 123 placing footings on excavated surfaces other than rock. The Co ntractor shall remove rock and other unyielding foundation Material a maximum of 12 inches bel ow the bottom of the Structure. The Contractor shall clean rock seams and cavities, and fill with concrete or grout. This additional concrete or grout is Extra Work. The Contracto r shall notify the Project Manager after each footing excavation. The Contractor shall no t place footings until the Project Manager approves the excavation depth and the foundatio n Material. The Contractor shall dewater wet pits for inspection and for c onstruction of footings. When necessary, the Contractor shall install well-braced coffer dams, built as watertight as practical. The Contractor shall not use timber or bracing insi de cofferdams that cannot be removed without damage to the concrete. The Contractor shall m ake temporary Structures large enough to provide ample room for pile driving, drilled sh aft construction, form construction, inspection, and sump pumps. The Contractor shall straighten or move cofferdams that threaten to damage the Structure. The Contract or shall submit to the Project Manager Working Drawings showing proposed methods of constructi ng cofferdams, cribs, shoring, or similar temporary Structures sealed by a New Mexico licensed Engineer. The submittal of Working Drawings does not relieve the Contractor o f any responsibility. The Contractor shall backfill excavated areas not occupied by piles, shafts, abutments, or other permanent Structures to the adjoining finished surface el evation. The Contractor shall not use rock in backfill that is within two (2) ft of the Struc ture. The Contractor shall place backfill Material in approximatel y level layers for the length and width of the backfilled area. When necessary to prevent wedge action, the Contractor shall be nch the slopes bounding the area being backfilled in accordance with Section 203.3.5.1, “Ro adbed Embankments.” The Contractor shall dispose of unsuitable excavated Material outsi de of the Roadway Prism as directed by the Project Manager. Before placing backfill Mater ial against new masonry or concrete Structures, the Contractor shall wait until the concre te has developed its specified design strength as determined in Section 510.3.5.1, “Concrete S trength” or until the concrete reaches 80% of the specified compressive strength but no less t han 2,500 psi, as determined by the Maturity Method, in accordance with Section 510.3.5.2, “ In-place Concrete Strength Measurements.” The Contractor shall prevent unbalanced loading while placing and compacting backfill Material.
210.3.2 Compaction
The Contractor shall place layers of uncompacted backfill no m ore than eight (8) inches thick. Before placing the next layer, the Contractor shall com pact the Material to 95% of the maximum density near optimum moisture content as determined by AASHTO T 180 (Modified Proctor), Method A or D (TTCP M odified). Test for field densit y and moisture content using nuclear methods in accordance with AASHTO T 310 and Section 906 , “Minimum Testing Requirements.” Prior to concrete placement the foundation soils shall be comp acted to at least 95% of maximum density as determined by AASHTO T 180 (Modified Proctor ), Method A or D (TTCP Modified).
210.4 Method of Measurement
210.4.1 Major Structure Excavation
For each phase of the Project, identified in the Contract or a pproved by the Department, the Contractor shall measure the original ground surface of any areas that are designated as Structure Excavation. Prior to any Work continuing in complete d excavation areas, the Section 210: Excavation and Backfill for Major Structures Page 124 Contractor shall measure the newly excavated ground surface “fi nal surface.” Major Structure excavation quantities shall be measured and calculated as the n eat volume below the original ground surface between the limits shown in the Contract, and/or approved changes by the Project Manager, and the final e xcavated ground surface. For the measurements described above, the Contractor shall sur vey and submit the original ground surface and fi nal excavated ground surface data at completion of each phase of construction or completed Majo r Structure using an electroni c XML- compatible format approved by the Project Manager with a volume summary report su mmarizing the basis for the final volumes. If no cross section intervals are shown in the Plans, the Contractor shall propose cross-section intervals, to the Project Manager, that a dequately quantify the volumes. The approved intervals shall be used for the entire Project unl ess otherwise specified in the Contract and/or approved by the Project Manager prior to commen cement of earthwork operations. The Contractor shall use a New Mexico licensed Eng ineer or New Mexico licensed surveyor to stamp and certify the surveyed cross-secti ons and the volume summary report. The Contractor shall not include the following volumes in stru cture excavation: 1. Material excavated outside vertical planes located 18 inches outside and parallel to the limits of the footings or foundations; 2. Excavation required because of slides, cave-ins, silting or filling due to lack of support of sides, the action of the elements or carelessness of the Contractor; 3. Any Material included within the staked limits of the surfac ing and unclassified excavation for which measuremen t is covered under other section s; 4. Water or other liquid Material; 5. Material excavated before measurements of the original groun d or embankment placement; 6. Material rehandled, except when the contract specifically re quires excavation after Embankment placement; and 7. Rock encountered during structural excavation will be paid p er Section 203.4.1, “Rock Excavation.”
210.4.2 Major Structure Backfill
For each phase of the Project, identified in the Contract or a pproved by the Department, the Contractor shall measure major structure backfill by the cu bic yard compacted in place in accordance with the limits shown in the Contract. The Contract or shall calculate major Structure backfill as the neat volume above the existing or exc avated ground su rface between the limits shown on the Plans, and/or authorized changes by the Project Manager, and the final compacted ground surface. The Department will not apply any shrinkage or swell factors due to payment being made on the final cross sectioned volume. For the measurements described above the Contractor shall surv ey and submit the existing or excavated ground su rface and final compacted ground surface data at completion of each phase of construction or completed major Structure usin g an electronic XML- compatible format approved by the Project Manager with a volume summary report summarizing the basis for the final volumes. If no cross secti on intervals are shown in the Plans, the Contractor shall propose cross-section intervals, to the Project Manager, that adequately quantify the volumes. The approved intervals shall be used for the entire Project unless otherwise specified in the Contract and/or approved by t he Project Manager prior to commencement of earthwork operations. The Contractor shall use a New Mexico licensed Section 210: Excavation and Backfill for Major Structures Page 125 Engineer or New Mexico licensed surveyor to stamp and certify t he surveyed cross-sections and the volume summary report. No measurement for payment will be made of backfill required b ecause of slides, cave- ins, silting or filling due to lack of support of sides, over e xcavation or any other action of the elements or carelessness of the Contractor.
210.5 Basis of Payment
Pay Item Pay Unit Major Structure Excavation Cubic Yard Major Structure Backfill Cubic Yard Unsuitable Material Excavation Cubic Yard
210.5.1 Work Included in Payment
Payment will be full compensation for the Work and Materials p rescribed in this Section. Excavation and Backfill for Majo r Structures includes the foll owing: 1. Material compaction to 95% of maximum density as determined by AASHTO T 180 (Modified Proctor), Method A or D (TTCP Modified); 2. All temporary shoring and bracing; 3. Dewatering; 4. Suitable backfill Material for Unsuitable Material Excavatio n; 5. Hauling and disposal of Materi al related to Structure Excava tion and Unsuitable Material Excavation; and 6. Survey, calculations, and engineering. The Contractor shall dispose of Material in accordance with Se ction 107, “Legal Relations, Environmental Requirements, and Responsibility to th e Public” unless otherwise specified in the Contract. The Contractor shall not dispose of Material within the Project limits without written approval from the Project Manager. Section 213: Obliterating Old Road Page 126