SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL — STRUCTURE EXCAVATION AND BACKFILL
203.01 Description.
This work includes the removal and disposal of all material necessary for the construction of all structures and incidental foundations not included elsewhere in the Specifications . The work includes preserving channels, shoring and bracing, constructing cofferdams, sealing foundations, dewatering, excavating, preparing foundations, backfilling, and subsequent removal of safety features and cofferdams. This work also includes all necessary on-site or borrow backfill. The material to be excavated is material not otherwise classified in either SECTION 202 or SECTION 205. Structure Excavation and Backfill is subdivided into the following six classifications. Structure Excavation – Earth. Structure Excavation – Earth includes all excavation not classified as rock, rock -mechanical, masonry, or unclassified excavation. Structure Excavation – Rock. Structure Excavation – Rock includes the removal of bedrock or boulders and detached bedrock fragments over 1 cu yd in volume when encountered within the limits of Structure Excavation. Boulder and rock fragments less than 1 cu yd volume are considered Structure Excavation – Earth. Structure Excavation – Rock-Mechanical. Structure Excavation – Rock-Mechanical is used where blasting is prohibited. Structure Excavation – Masonry. Structure Excavation – Masonry includes the removal of all concrete or stone masonry built either with or without mortar (includes incidental structures in excess of 1 cu yd) where encountered within the limits of Structure Excavation, if the masonry has not been included under SECTION 201. Unclassified Structure Excavation. Unclassified Structure Excavation includes the removal and disposal of the composite mixture of various types of materials that the Engineer determines is impractical to classify into separate classifications for payment.
Part 200 — Earthwork and Erosion Control August 2025
SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL 200-39 C rushed Stone Fill Under Structures . This work includes providing one or more courses of crushed stone fill and filter fabric under structure footings on prepared subgrade surfaces in reasonably close conformity with the required lines, grades, thicknesses, and typical cross sections.
203.02 Materials.
Provide backfill materials that conform to SECTION M01. Use a crushed stone that conforms to the gradation requirements of Subsection M01.09, Table I, Column II. Filter fabric is included on the Department’s Approved Materials List.
203.03 Construction Methods.
E xcavation.
a.Notification. Notify the Engineer sufficiently in advance of the beginning of excavation, and immediately if there may be a change in classification of structure excavation, so that cross-sectional elevations and measurements can be taken of the undisturbed ground.
b.Dimensions of Excavation. Ensure that t he excavation for footings has sufficient size to accommodate both the placement of the structure and the placement and compaction of backfill. Extend the excavation at least 2 ft horizontally beyond the vertical face of footings and a minimum of 12 in. below the base of footings.
c.Change in Elevation or Dimension of Excavation. The E ngineer may direct the Contractor to make necessary changes in the elevation or dimensions of the excavation to secure a satisfactory foundation.
d.Approval of Foundation. D o not initiate formwork or permanent work until the Engineer has approved the depth and dimensions of the excavation, the character of the material , and the condition of the foundation. Drive s ounding rods at the points and depths as directed by the Engineer. Provide as sistance to the Engineer as necessary to conduct an adequate inspection of the foundation material. E nsure that all unsheathed excavation has sufficient side slopes to prevent earth from encroaching onto the work.
e.U tilization of Excavated Materials . Use suitable excavated material as backfill or in embankments. Dispose of surplus excavation or unsuitable materials in non-critical areas within the Project limits.
f.Blasting. Complete all blasting associated with rock excavation before placing any structure concrete.
g.Alternatives & Unsatisfactory Bearing Surfaces . If the natural foundation material is inadequate to safely support the structure, proceed with alternative methods as directed by the Engineer.
Part 200 — Earthwork and Erosion Control August 2025
200-40 SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL
h.Water. When water is encountered, make provisions for draining or dewatering within the excavation. Ensure that the dewatering work prevent s disturbing the bottoms of excavations or adjacent structures. When foundation material is relatively impermeable and water accumulations soften the cementing material or puddle the surface, make provisions to drain the excavation by suitable channels outside of and slightly below the footing level. Ensure that t hese channels convey the water to outfalls or sump pumps . Remove foundation material unduly disturbed or softened by the use of equipment or by inadequate handling of water, and replace with satisfactory material at no additional cost to the Department.
i.P reparation of Bearing Surface . Extract all rock or other hard foundation material from all loose material, cleaned and cut to a firm surface, either level, stepped, or serrated. Clean out all seams and fill with concrete mortar or grout . S hape all ledge rock to avoid any unnecessary excavation of sound rock. Cofferdams. Use cofferdams when the bottoms of excavation are below the prevailing water surface. Cofferdams include timber, steel sheet piling, cylindrical metal shells, or other structural components. Earthen embankments and dikes are not classified as cofferdams.
a.Shop Drawings. For substructure work, submit Shop Drawings showing the proposed method of cofferdam construction and other discretionary details not fully shown on the Plans. The Engineer will approve the Drawings in writing before construction begins. The approval does not relieve the Contractor of the responsibility to secure a safe and satisfactory cofferdam. Prepare the Shop Drawings according to Subsection 105.02.
b.C onstruction. Brace c offerdams for foundation construction to be as watertight as practical. Ensure that t he interior dimensions of cofferdams provide sufficient clearance for the construction of forms and the inspection of their exteriors and permit dewatering outside of the forms. Where piles are required, ensure that the cofferdam is of sufficient size to permit the driving of the piles in the exact positions shown on the Plans without interference from the wales or bracing or requiring excessive rebr acing. Ensure that cofferdams that are tilted or moved laterally during the process of installation are righted, reset, or enlarged to provide the necessary clearance. Perform these corrective measures at no additional cost to the Department. Construct and dewater cofferdams to protect green concrete against damage from water and to prevent damage to the foundation by erosion. Do not leave any construction materials in cofferdams that extend into the substructure masonry.
c.Tremie Seal. Dewater cofferdams and place the foundations in the dry. The Engineer will approve the well point systems and methods at suitable locations, if required. However, where conditions are anticipated that would render it impractical to dewater the cofferdam before placing masonry, use a tremie seal according to Subsection 808.03.5(f).
Part 200 — Earthwork and Erosion Control August 2025
SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL 200-41 During the placing of a tremie seal and until the seal has set, control the elevation of the water inside the cofferdam to prevent any flow through the seal. Do not initiate pumping to dewater a sealed cofferdam of the gravity type until the concrete seal has been in place for at least three days for spread footing foundations and at least seven days for pile-supported foundations. After dewatering, place the balance of the foundations in the dry, with the necessary modifications for structural purposes.
d.Removal of Cofferdams . Remove cofferdams including all sheeting and bracing as directed by the Engineer. During the removal operation, avoid disturbing or otherwise damaging the work. If the cofferdam will remain in place, ensure that the cofferdam is vented or ported below low water level when dewatering is no longer necessary. Dewatering. Dewater the interior of all foundation enclosures to preclude the possibility of movement of water through any fresh concrete. Do not pump during the placement of concrete or for a period of at least 24 hours thereafter, unless a suitable sump is used separated from the concrete work by a mortar-tight form, bulkhead, or other effective means. Adhere to the requirements of SECTION 208. Embankments Under Structure Foundations. Construct embankments under stub abutments, walls, culverts, footings, and other foundations where stability requirements are essential with gravel borrow conforming to Subsection M01.09, Table I , Column I . Ensure that the material does not contain particles greater than a 6 -in. maximum dimension. Construct embankments such that side slopes are sufficiently stable and such that the widths of embankments extend horizontally 2 ft beyond the vertical faces of footings. Place the gravel borrow in layers not exceeding 12 in. in depth before compaction, and compact to 95 percent of maximum density as determined by AASHTO T180. Compact embankments under pile supported foundations to 90 percent of maximum density as determined by AASHTO T180. Backfilling.
a.Protection of Structures During Backfilling. Do not place fill material against any structure until permission to place fill has been granted by the Engineer and not until the masonry has obtained the 28-day compressive strength. Exercise proper precautions to ensure that the method of backfilling does not cause movement of or undue strain on any part of the structure. Deposit and compact fill material behind abutments, walls , and miscellaneous structures as specified . W hen placing fill
Part 200 — Earthwork and Erosion Control August 2025
200-42 SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL around slender foundations, rigid frame legs, piers , or over and around arches and box culverts, deposit the material on both sides of the structures to approximately the same elevation at the same time. Place backfill materials to avoid damage to masonry and waterproofing treatments . If backfilling or other operations damage masonry or waterproofing, remove the backfill and replace or repair the damaged work or waterproofing. Perform all repairs, replacement of materials, and labor at no additional cost to the Department.
b.Pervious Fill Adjacent to Structures. Use pervious fill for the material placed adjacent to, or in contact with, arches, culverts, retaining walls, wingwalls, secondary structures, and other areas. Place pervious fill in layers not over 12 in. in depth before compaction. Compact to 95 percent of maximum density as determined by AASHTO T180. Where not accessible for normal placing and rolling and for minor operations, place pervious fill in lifts not to exceed 8 in., and compact by means of mechanical tampers or suitable vibratory equipment. For minor operations, hand tamping with heavy iron tampers may be used.
c.Common Backfill. Backfill a ll spaces excavated and not occupied by permanent works, pervious fill, or gravel borrow with suitable material . Compact the material in 1-ft lifts up to the surface of the surrounding ground. Ensure that the material is free of vegetative matter and organic or compressible soils and that it meets the requirements for Common Borrow, except that the material can not contain particles larger than 6 in. The Engineer may approve excavated soil for re-use as suitable material. Smoothly grade the surface. Compact backfill to 95 percent of maximum density as determined by AASHTO T180. No separate payment will be made for this work. Crushed Stone Fill Under Structures. Place the crushed stone and compact on a prepared surface to the required thickness. Place a filter fabric, that conforms to Subsection M20.01, between the crushed stone and surrounding soils. Ensure that the surface of the crushed stone is placed so that a reasonably uniform texture is provided. The surface will have a tolerance of ±½ in. to the required grade.
203.04 Method of Measurement.
Structure Excavation.
a.General. Structure excavation will be measured by the cubic yards of material removed. The volume will be computed by taking the difference in elevation between the existing ground surface or the bottom of roadway excavation or channel excavation, whichever is lower, and the surface of the completed structure excavation at plan grade or approved revised plan grade, all between the designated horizontal pay lines described below. Structure excavation in roadway cuts, or embankment areas where the removal of muck is indicated, will include only that portion below the bottom of the muck.
Part 200 — Earthwork and Erosion Control August 2025
SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL 200-43 Structure excavation in roadway cuts will include only that portion below the subgrade, shoulder foundations, and cut slope lines. When bedrock, boulders, or masonry are encountered, notify the Engineer and expose the items so that the necessary measurements can be taken for structure excavation. If this notice is not provided or if any material is removed before measure ments are taken, the Engineer will presume that measurements taken when the Engineer first observes the material in question will provide the true quantity of excavation.
b.Pay Lines . Horizontal payment limits will be measured between plumb lines and 2 ft outside of the neat lines of the original foundations only as shown on the Plans. However, should the size of the footing be increased by more than 2 ft in any direction, the area of the footing that extends beyond the original payment lines will be used for determining the additional amount of excavation. No allowance for rock overbreak will be made beyond the above limits or more than 6 in. below the bottom of footing. Pervious Fill, Gravel Borrow, and Common Borrow. Pervious Fill, Gravel Borrow, and Common Borrow will be measured by the cubic yards placed. Crushed Stone Fill Under Structures. Crushed stone fill under structures will be measured by the cubic yards placed. Cofferdams. Cofferdams do not require a measurement for payment. Tremie Seals. When underwater concrete is specified, the horizontal and vertical pay limits will be those specified for the tremie seal. When underwater concrete is not specified but is required, the horizontal pay limits will be extended to the actual inside face of the cofferdam, and the vertical pay limits will be established by the Engineer.
203.05 Basis of Payment.
The Department will pay for the completed and accepted quantities at the Contract unit prices as follows.
Part 200 — Earthwork and Erosion Control August 2025
200-44 SECTION 203 — STRUCTURE EXCAVATION AND BACKFILL Pay Item Pay Unit Structure Excavation – Earth CY Structure Excavation – Rock CY Structure Excavation – Rock-Mechanical CY Structure Excavation – Masonry CY Unclassified Structure Excavation CY Pervious Fill CY Gravel Borrow CY Common Borrow CY Crushed Stone Fill Under Structures CY Cofferdams LS Tremie Seals CY The prices constitute full compensation for all labor, materials, and equipment, including dewatering, removal within the prescribed limits, backfilling and disposal of surplus material, stockpiling, hauling, placing, compaction, preparation of the subgrade, filter fabric , and all incidentals required to finish the work, complete and accepted.
Referenced in this section
Structure Excavation and Backfill in other states
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Source: Standard Specifications for Road and Bridge Construction (Blue Book), 2022 (Aug 2025 compilation) Edition. Pages 164–170 of 951. View official source ↗