801Excavation and Fill

801.01 Description. Foundation excavation shall include the removal of all material, of

whatever nature, necessary for the construction of foundations and substructures of structures in accordance with the plans or as directed by the Engineer. When shown as a pay item, it shall include the furnishing of all necessary equipment and the construction of all cribs, cofferdams, dewatering, etc. necessary for execution of the work. It shall also include the subsequent removal of cofferdams and cribs and the placement of all necessary backfill as hereinafter specified. It shall also include the disposal of excavated material that is not required for backfill or other specified usage, in a manner and in locations that will not affect the carrying capacity of the channel or other drainage or be unsightly. Unless a greater area is necessary for construction, the bridge site shall be the area defined in Subsection 101.02. Clearing and grubbing shall be in accordance with the provisions of Subsection 201.04. All substructures, where practicable, shall be constructed in open excavation, and where necessary, the excavation shall be shored, braced, or protected by cofferdams in accordance with approved methods. When footings can be placed in the dry without the use of cribs or cofferdams, backforms may be omitted with the approval of the Engineer and the entire excavation filled with concrete to the top of the footing. The additional concrete required shall be placed at the expense of the Contractor.

801.02 Materials. Unless designated otherwise, all material used for backfill shall meet

the requirements of Subsection 203.03.8.6.

801.03 Construction Requirements.

801.03.1 Preservation of Channel. Unless otherwise specified, no excavation shall be

made outside of cribs, cofferdams, or sheet piling, and the natural stream bed adjacent to the structure shall not be disturbed without permission of the Engineer. If any excavation or dredging is made at the site of the structure before cribs or cofferdams are in place, the Contractor shall, without extra compensation and after the foundation base is in place, backfill all such excavation to the original ground surface or river bed with material satisfactory to the Engineer. Material deposited within the stream area from foundation or other excavation or from the filling of cofferdams shall be removed and the stream area freed from obstruction thereby.

801.03.2 Depth of Footings. The elevations shown on the plans for bottoms of footings

shall be considered as approximate, and the Engineer may order in writing changes in dimensions or elevations necessary for a satisfactory foundation.

801.03.3 Preparation of Foundations for Footings. All rock or other hard foundation

material shall be cut to a firm surface, either level, stepped, or roughened as may be directed by the Engineer, and then cleaned of all loose material. All seams shall be cleaned out and filled with concrete, mortar, or grout. When masonry is to rest on an excavated surface other than rock, special care shall be taken not to disturb the bottom of the excavation, and the final removal of the foundation material to grade shall not be made until just before the masonry is to be placed. Excavation and preparation of foundations for footings for box bridges shall be in accordance with the provisions of Section 206.

801.03.4 Cofferdams and Cribs.

801.03.4 1--General. Cofferdams and cribs shall be safely designed and constructed to

adequate depths and heights, and be made as water-tight as is necessary for the proper performance of the work to be done inside them. In general, the interior dimensions of cofferdams and cribs shall be sufficient to permit construction of forms and the inspection of their exteriors and to permit pumping outside of the forms. Cofferdams or cribs which tilt or move laterally during the process of sinking shall be righted, reset, or enlarged so as to provide the necessary clearance. All corrective work shall be at the expense of the Contractor. When conditions are encountered that, in the opinion of the Engineer, make it impracticable to dewater the foundation, the Engineer may require the construction of a concrete seal of the dimensions necessary. The foundation shall then be pumped out and the balance of the masonry placed in the dry. When weighted cribs are employed, and the weight is utilized to partially overcome the hydrostatic pressure acting against the bottom of the foundation seal, special anchorage such as dowels or ke ys shall be provided to transfer the entire weight of the crib into the foundation seal. During the placing of a foundation seal, the water elevation inside the cofferdam shall be controlled to prevent any flow through the seal, and if the cofferdam is to remain in pl ace, it shall be vented or ported at low water level.

801.03.4 2--Protection of Concrete . Cofferdams or cribs shall be constructed so as to

protect green concrete against damage from a sudden rising of the stream and to prevent damage to the foundation by erosion. Timber or bracing that will extend into the substructure masonry shall not be left in cofferdams without written permission from the Engineer.

801.03.4 3--Drawings Required. The Contractor shall submit to the Engineer four copies

of structural design analysis and detail drawings that show the proposed method of constructing the cofferdam. These drawings shall include the types and sizes of sheeting, wales, bracing, and struts, the connections therefore, and the proposed method of installing, sealing, dewatering, cut-off and/or removal. The cofferdam analysis and details shall be prepared by and bear the seal of a Regist ered Professional Engineer experienced in cofferdam design. The Registered Professional Engineer shall certify that the actual material and material fabrication used for cofferdam construction are capable of supporting the loads. When submitting drawings and design analysis, the Contractor shall list the bent numbers on which the construction of cofferdams is proposed.

801.03.4 4--Removal. Unless otherwise provided, cofferdams or cribs with all sheeting

and bracing shall be removed after the completion of the substructure. Care shall be taken not to disturb or otherwise injure the finished masonry.

801.03.5 Pumping. Pumping from the interior of a foundation enclosure shall be done so

as to preclude the possibility of movement of water through fresh concrete. There shall be no pumping during the placing of concrete or for a period of at least 24 hours thereafter, unless it can be done from a suitable sump separated from the concrete work by a water- tight wall or other effective means. Pumping to dewater a sealed cofferdam shall not commence until the seal has set sufficiently to withstand the hydrostatic pressure.

801.03.6 Inspection. After each excavation is completed, the Contractor shall notify the

Engineer, and no masonry shall be placed until the Engineer has approved the depth of the excavation and the character of the foundation material.

801.03.7 Backfill. Backfill of solid structures may commence upon removal of forms.

Backfill of wall structures shall be in accordance with Subsection 601.03.6.3. Adequate provision shall be made for thorough drainage of all backfilling. French drains shall be placed at weep holes as specified. All excavated space not occupied by the perm anent structure shall be backfilled to the surface of the surrounding ground or to the typical secti on indicated on the plans. All backfill shall be thoroughly compacted and sufficient allowance shall be made for settlement. Where it provides drainage, bearing strength, or lateral support to the permanent construction, all backfilling shall be performed in accordance with the provisions of Subsection 203.03.8.6. In general, the top surface of backfilled area shall be neatly graded to the section indicated on the plans or established.

801.03.8 Approach Embankment . When approach embankments are required, they

shall be constructed and will be paid for in accordance with Section 203.

801.04 Method of Measurement. Foundation excavation, satisfactorily performed, will

be measured by the cubic yard in the original position with dimensions determined as follows:

801.03.4 3.

801.05 Basis of Payment . Foundation excavation, measured to the elevation of the

bottom of the footing or seal as shown on the plans, will be paid for at the contract unit price per cubic yard. Extra depth excavation, required below the foo ting or seal elevation shown on the plans, will be paid for per cubic yard in accordance with the following schedule: Established Elevation of the Footing Payment Below the Elevation Shown on the Plans Percent of Contract Price 0.00 to 1.99 feet 100% 2.00 to 3.99 feet 120% 4.00 to 5.99 feet 150% 6.00 to 7.99 feet 165% 8.00 to 9.99 feet 195%

10.00 feet or more 230%

Selected backfill material, shown on the plans or ordered by the Engineer, to be obtained from sources other than from foundation excavation will be paid for at the contract unit price for the material specified and used. All necessary cofferdams or cribs will be paid for at the contract lump sum price. The prices thus paid shall be full compensation for completing the work. All work required under this section for which no pay items are included in the proposal will not be measured for separate payment. Compensation for this work shall be considered as included in the prices and payment for bid items.