206Structural Excavation

206.01 Description This work shall consist of excavating, rem oving, hauling

backfilling and compacting or disposing, as required, of all material encountered for the installation and construction of Drainage and Minor Structures and for Major Structures in accordance with these specifications and in reasonably close conformity with the lines, grades and typical cross sections shown in the Contract Documents or established by the Department. Excavating for structures below designated excavation limits a s specified or shown in the Contract Documents will be included under this section. Material which is required to be excavated or paid for under a nother section shall not be included under this section.. Ditches at inlets and outlets of culverts, special ditches and outlet ditches, all as indicated in the Contract Documents, shall be constructed and paid for under Section 203 - Excavation and Embankment. The following definitions shall apply to this section: Drainage and Minor Structures shall include pipe culverts, pipe arches, underdrains, catch basins, manholes, structural plate units, box culverts, culvert end walls, concrete steps and other minor structures. Major Structures shall include abutments and piers for bridges, rigid frame structures, and masonry retaining walls. Special Backfill shall consist of obtaining, hauling, and placing selected material suitable for the location where it is to be used. Special Backfill as a Contract item will be called for in the Contract Documents. Structural Earth Excavation shall consist of excavation and removal of all material encountered, except for Structural Rock Excavation. Structural Earth Excavation shall also include the removal of: All boulders, solid mortared stone masonry and concrete masonry when each is less than 2 cubic yards in volume; and all soft and disintegrated rock which can be removed with ordinary excavating machinery. Structural Rock Excavation shall consist of removing: Hard igneous, metamorphic and sedimentary bedrock which cannot be excavated with ordinary excavating machinery and cannot be excavated without employing means such as, but not limited to, drilling and blasting, drilling and splitting, or hoe-ramming; and all boulders, solid mortared stone masonry; and concrete masonry each having a volume of 2 cubic yards or more. 2-35 Structural Earth Excavation, Below Grade shall consist of removal of excavation required below a plane parallel with, and 12 inches below, the bottom of Drainage and Minor Structures, as shown in the Contract Documents.

206.02 Construction Methods The Contractor shall notify the R esident a sufficient

length of time in advance of the beginning of Structural Excavation so that necessary elevations and measurements may be taken of the undisturbed ground. When solid bedrock is encountered which is to be removed, the Contractor shall uncover the rock and provide ample opportunity for the Resident to take the necessary survey measurements of the undisturbed rock. When the foundation material is soft or otherwise unsatisfacto ry and must be removed below the elevation shown in the Contract Documents, the excavation shall be carried to a depth designated by the Resident and the material shall be removed and replaced with approved granular material and thoroughly compacted; alternately, a lower elevation for the bottom of the structure may be established by, and at the discretion of, the Department. Suitable material removed from the excavation area, including that material removed from beyond the specified excavation pay limits, shall be used for backfilling or for the formation of embankments and no additional payment will be made. Unsuitable or surplus material shall be disposed of accordingly. When the structure is to be placed on solid bedrock, the rock shall be excavated to a firm surface, either level, stepped or serrated. When solid or disintegrated rock or boulders are encountered, the rock shall be excavated to a designated depth below the bottom of the proposed structures, as shown in the Contract Documents or as directed by the Resident. Except for installations of underdrain, the material so removed shall be replaced with selected fine compressible material such as sand and uniformly compacted and shaped in accordance with Section 603.04 - Bedding. When the structure is to rest on an excavated surface other th an bedrock, particular care shall be taken not to disturb the bottom of the excavation. If the surface upon which the structure is to rest is disturbed, it shall be regraded and recompacted as directed by the Resident and no additional payment shall be made. After each excavation is completed, the Contractor shall notif y the Resident and no culverts or masonry shall be placed, foundation piles driven or other installations made, until the depth of the excavation and the character of the foundation material has been approved. Before drainage or underdrain pipe is installed in cut areas w here common excavation, unclassified excavation or muck excavation is removed below the subgrade elevation shown on the plans, the undercut roadbed shall be filled with approved granular material to a depth sufficient to support construction equipment. All fill material shall be compacted as required. 2-36

206.03 Backfilling Backfilling shall consist of placing suita ble material in all spaces

excavated and not occupied by Drainage and Minor Structures, Major Structures and other permanent structures up to the elevation of the existing ground or other elevations shown in the Contract Documents. Except for underdrain backfill and for structural plate pipe units, backfill material for Drainage and Minor Structures shall be fine readily compressible soil or granular material, at, or near, optimum moisture content, and shall not contain stones larger than 3 inches, frozen lumps, chunks of clay, mineral matter or any other objectionable material. Backfill material for Major Structures shall be Granular Borrow or other material indicated in the Contract Documents and shall be at, or near, optimum moisture content and shall not contain stones larger than 3 inches, frozen lumps, chunks of clay, mineral matter or any other objectionable matter. Backfill shall not be placed against gravity sections of any s tructure, including those comprised of masonry and/or concrete, until the structure has been in place for at least 7 days or until mortar and/or concrete cubes/cylinders cured with the structure establish that design strength has been reached. For structures other than gravity structures that require reinforcing designed to resist applied dead and live loads, backfill shall not be placed against the structure until the concrete has been in place for at least 14 days or until concrete cylinders cured with the structure establish that the design strength has been reached. Backfilling around pipes, catch basins and manholes that include joints with cement-based mortar shall not commence until the mortar has been in place at least 12 hours unless methods approved by the Resident are used to protect the mortar from being disturbed. Except for structural plate units, backfill material shall be uniformly distributed in layers of not more than 8 inches in depth, loose measure, and each layer thoroughly compacted by use of approved compactors before successive layers are placed. When backfill is being placed around a pipe or structure, operations shall be conducted so that the fill is always at approximately the same elevation on both sides. Water shall be added when necessary to increase the moisture content of the backfill material to obtain compaction. Puddling or jetting of backfill will not be allowed unless specified in the Contract Documents. Structural plate units shall be backfilled in accordance with Section 509 - Structural Plate Pipes, Pipe Arches, Arches, and Metal Box Culverts. Unless otherwise indicated in the Contract Documents or direct ed, all sheeting and bracing used during Structural Excavation shall be removed by the Contractor following the completion of the work, and all voids resulting from use of the sheeting and bracing backfilled where necessary, at no additional cost to the Department.

206.04 Method of Measurement Structural Excavation will be me asured by the

number of cubic yards of material removed, measured in its original position, and acceptably excavated in conformity with the Contract Documents or as directed. When structures are to be installed where roadway excavation i s to be removed, only the excavation beyond and below the roadway excavation limits will be classified as Structural Excavation. 2-37 Drainage and Minor Structures For these structures there will be no measurement for Structural Earth Excavation, except for Structural Earth Excavation, Below Grade. When measured for payment, the quantity of Structural Earth Excavation, Below Grade, will be the amount actually excavated, provided the maximum allowable horizontal dimensions do not exceed those bounded by vertical surfaces 18 inches outside the base or extreme limits of the structure and to the vertical neat lines of underdrain trenches, as shown in the Contract Documents. When bedrock is required to be excavated for installation of these structures, the depth for measurement will be the actual depth required in accordance with the Contract Documents or as otherwise designated, except: For culvert pipe and underdrain, the depth for measurement will be a maximum of 1 foot below the bottom of the invert; and for catch basins and manholes, the depth of measurement will be a maximum of 1 foot below the bottom of the base. Any removal of solid rock for leveling, stepping or serrating, as shown in the Contract Documents, or as determined, shall be measured within the aforementioned limits. The quantity of rock will be the number of cubic yards actually removed provided the maximum allowable horizontal dimensions do not exceed those bounded by vertical surfaces specified in the preceding paragraph. Major Structures For Major Structures, the quantity measured for payment will be the number of cubic yards shown on the Schedule of Items in the Contract Documents. This quantity is considered final and no adjustments will be made, except under the following conditions: When the structure is founded on bedrock, the quantity measured will be what is actually excavated to the top of the bedrock and to maximum allowable horizontal dimensions bounded by vertical surfaces 18 inches outside the neat lines of the base as indicated in the Contract Documents. When changes to the Contract Documents are made by the Resident. When the outermost limit of French drains exceeds the vertical planes stated above, the limit to be measured for payment will be extended upward from the bottom of the French drain on a vertical plane bounded by the outermost limit of the French drains. When bedrock is required to be excavated for the construction of Major Structures to definite elevations as indicated in the Contract Documents, or elevations designated by the Resident after the rock has been exposed, the maximum depth of measurement for payment will be to a horizontal plane or planes located 12 inches below the elevation shown or designated. Removal of solid bedrock, for leveling, stepping or serrating, as indicated in the Contract Documents or determined, shall be measured within the aforementioned limits and 2-38 paid for as Structural Rock Excavation. When earth is required to be removed to uncover existing rock, it will mean to excavate to undisturbed solid bedrock and will be so measured for payment. Special Backfill The quantity measured for payment will be the number of cubic yards of material acceptably placed and measured in place.

206.05 Basis of Payment The accepted quantities of Structural Excavation, when

specified to be paid for separately, will be paid for at the Contract unit price per cubic yard. The work, whether paid for separately or incidental to the structure, shall include the placing and compacting of backfill, the formation of any embankments made with material from Structural Excavation and the disposal of all surplus or unsuitable material, unless otherwise specified. Earth excavation for installation of Drainage and Minor Struct ures, except that which is defined as "Below Grade", will not be paid for and all costs for such excavation and disposal of materials will be considered incidental to the Contract unit price per item for the structure being installed or constructed. Rock excavation for the installation of these structures will be paid for at the Contract unit price for Pay Item 206.07 - Structural Rock Excavation - Drainage and Minor Structures. The accepted quantity of Structural Earth Excavation - Drainag e and Minor Structures, Below Grade and of Structural Rock Excavation - Drainage and Minor Structures, will be paid for at the Contract unit price per cubic yard. When bedrock is encountered and no Structural Rock Excavation - Drainage and Minor Structures item is included in the Contract, the excavation of the rock will be paid for at 16 times the Contract unit price per cubic yard for Common Excavation. When bedrock is encountered and no Structural Rock Excavation - Major Structures is included in the Contract Documents, the excavation of the rock will be paid for at 6 times the Contract unit price for Structural Earth Excavation. When it is necessary to excavate below the elevation indicated in the Contact Documents for Major Structures, payment for such excavation will be made at 1½ times the Contract unit price for the item classification applying where the extra depth is required. Protective systems and/or additional excavation for backslopin g required for Structural Excavation will not be measured for payment, but will be considered incidental to related Contract item(s). When no bid item appears in the Contract for work such as, but not limited to, clearing drainage ways, maintenance of traffic, special detours or cofferdams, payment for such work shall not be made directly, but will be considered incidental to related Contract pay items. Unless otherwise specified, payment for all pumping, bailing, drainage, 2-39 sheeting, bracing and incidentals required for proper execution of the work shall be considered incidental to related Contract pay items. Backfill or bedding materials, except for material used to bac kfill underdrain, whose source is other than Structural Excavation, will be paid for under the class of material used. Material used to backfill underdrain will not be paid for but shall be considered incidental to the cost of the underdrain. Special Backfill will be paid for at the Contract unit price per cubic yard, in place and accepted, but will not include replacement of material excavated beyond the specified pay limits for Structural Excavation. Payment will be made under: P a y I t e m P a y U n i t 206.061 Structural Earth Excavation - Drainage & Cubic Yard M i n o r S t r u c t u r e s B e l o w G r a d e

206.07 Structural Rock Excavation - Drainage & C u b i c Y a r d

M i n o r S t r u c t u r e s 206.082 Structural Earth Excavation - Major Structures, C ubic Yard P l a n Q u a n tity 206.092 Structural Rock Excavation - Major Structures Cu bic Yard

206.14 Special Backfill C u b i c Y a r d