for Highway Construction Page 164 of 71 5 SECTION 210 – STRUCTURE EXCAVATION AND COMPACTING BACKFILL
210.01 Description.
Excavate and dispose of materials required for the construction of structures , unless otherwise specified as structural excavation. Include necessary drainage, pumping, bailing, sheeting, shoring, and the construction and removal of cribs and cofferdams. Remove old structures or parts as required. Place and compact backf ill material as compacting backfill. Include sloping and cleaning up the sites.
210.02 Materials.
Provide materials as specified in: Granular Borrow ...................................................................................................................... 205.02 Controlled Density Fill .............................................................................................................. 522.02 Aggregate for Untreated Base ................................................................................................. 703.04 Aggregate for Granular Subbase ............................................................................................. 703.11
210.03 Construction Requirements.
A.Gene ral. Remove and dispose of unsuitable foundation material below the designed elevation as directed. Use suitable surplus excavated material in the construction of embankments. Replace material removed below the designed elevation with approved material. Sheet and brace trenches if necessary. Do not remove sheeting or bracing until backfill has progressed enough to prevent damage to pipelines or structures . Remove sheeting and bracing used in supporting structure excavation. Where rock, hardpan, or other unyielding material is encountered and a yielding material is required, remove the unyielding material below the grade specified and backfill as directed. Do not begin structure construction or backfill placement until the foundation has been approved. Do not use frozen material as backfill, and do not place backfill on snow -covered or frozen surfaces. Place backfill consisting of suitable material in 8- inch maximum, uncompacted layers and compact to Class A compaction as specified in 205.03.G. For backfill material placed within 3 feet of a concrete structure or retaining wal l, uniformly distribute the backfill material in layers of no more than 8 inches and compact with lightweight compacting equipment having an impact force of 1,000 to 3,000 pounds. Compact the backfill to the density r equirements for Class A compaction as specified in 205.03.G, before successive layers are placed. For backfill material determined by the Engineer as too granular to test, apply at least 5 overlapping compacting equipment passes per 8-inch lift or less. Compact backfill in areas not within a roadway prism, or special backfill around pipe underdrains not requiring a higher degree of compaction for some other purpose, to approximately the same density as the adjacent undisturbed soil or gravel. Perform compaction by any effective means. for Highway Construction Page 165 of 715 B. Structures . For structures or retaining walls founded on rock, excavate rock to the elevation shown. Remove any weathered, highly broken rock at the excavation bottom. Level excavated rock surfaces to the plan elevation with Class 15 or higher class concrete before constructing the structure or wall foundations. Use appropriate equipment and take precautions to ensur e that structure and retaining wall foundation soils are not disturbed during excavation that may affect their bearing capacity. Remove disturbed, soft, or unsuitable materials from the excavation and backfill with granular borrow or other approved material to the plan elevation. Replace material disturbed by the Contractor’s operations at no addit ional cost to the Department. Compact the bottom of soil excavations with at least 5 overlapping passes with an approved compactor. Take precaution when pumping water from foundation enclosure interiors to prevent the possibility of conc rete materials being carried away. Do not pump during the placing of concrete or for at least 24 hours after, unless it is done from a suitable sump or well point separated from the concrete work. When placing b ackfill material under water, place backfill in layers not thicker than 2 feet. Compaction is not required for this placement type. Do not place backfill against newly constructed masonry or concrete structures before meeting the requirements in Table 502.03- 5.
210.04 Method of Measurement.
The Engineer will measure acceptably completed work by the cubic yard based on planned quantity .
1.Structure Excava tion: The Engineer will measure structure excavation as the volume of material within prism -limiting planes as follows:
a.The bottom of the foundation.
b.The vertical planes 2 feet outside of and parallel to the outside lines of the structure, in the case of bents with individual column footings, the entire bent are considered as 1 structure.
c.With upper limits as follows:
1.In embankment sections, the existing ground surface as cross -sectioned.
2.In roadway cut sections or channel changes, the planes of the roadway cut or channel change as excavated.
2.Compacting Backfill . The E ngineer will me asure compacting backfill by the cubic yard of backfill material placed and as follows:
a.Below the original ground surface. A volume equal to the volume of structure excavation less the volume of the permanent structure, including the opening, contained within the limits of measurement for structure excavation. for Highway Construction Page 166 of 71 5 b. Above the original ground surface. The volume contained between the outside walls of the structur e and vertical planes 4 feet outside the original ground surface or the horizontal plane 1 foot above the top of the structure or of the subgrade, whichever is less.
c.Volumes of backfill placed through water around abutments , wing walls, and piers will not be included in the measurement of quantities for compacting backfill .
210.05 Basis of Payment .
The Department will pay for acceptable quantiti es at the contract unit prices as follows: Pay Item Pay Unit Structure Excavation Schedule No. 1 ..................................................... CY Structure Excavation Schedule No. 2 ..................................................... CY Compacting Backfill ................................................................................ CY The contract pay item Structure Excavation Schedule No. 1 includes excavation for bridges, boxes, and stiffleg culverts. The contract pay item Structure Excavation Schedule No. 2 includes excavation for other structures . When the contract does not include a contract pay item for structure excavation or compacting backfill , this work is incidental and included in other contract pay items . The Department will pay for required structure backfill or bedding material whose source is other than structure excavation at the contract unit price for the material being used or as extra work (104.02) if no unit price was established. If the Contractor is directed to remove material below the elevation specified, the Department will pay for the excavation work at the contract unit price or as extra work (104.02) . The Department will pay for Class 15 concrete used to backfill rock excavati on below the bottom of the design footing grade based on the actual quantity used, but not to exceed a prism 1 foot outside the footing neat lines with an average depth of 1 foot below the bottom of footing. Payment will not be made by the Department to excavate, backfill, and compact material removed for safety purposes or foundation soils that become disturbed due to the Contractor’s operations. The Department will pay using plan quantities as specified in 109.01. Procedures to do the work including drainage, pumping, bailing, sheeting, shoring, cribs, and cofferdams are incidental unless separate items are included in the contract . for Highway Construction Page 167 of 715 SECTION 211 – SOURCE RECLAMATION
211.01 Description.
Reclaim land used for borrowing material or mining for aggregates in Department -controlled sources .
211.02 Materials.
Provide materials as specified in: Topsoil ..................................................................................................................................... 213.02 Seed ........................................................................................................................................ 711.05 Fertilizer ................................................................................................................................... 711.07 Mulch ....................................................................................................................................... 711.10
211.03 Construction Requireme nts.
Do the following where usable material has been removed from the source:
1.Salvage and replace the top 1 foot of topsoil .
2.Grade and contour the slopes and floor to a pleasing, natural appearance.
3.Replace topsoil , seed , fertilize, and mulch .
4.Perform ot her work required by the reclamation plan and contract .
5.Seed the area as specified in 621.03 and 711.05.
211.04 Method of Measurement.
The Engineer will measure acceptably completed work by the lump sum for each source inv olved.
211.05 Basis of Payment .
The Department will pay for acceptable quantities as follows: Pay Item Pay Unit Source Reclamation ............................................................................... Lump Sum When the contract does not include an item for source reclamation, the Department will consider the work incidental and the cost included in ot her contract pay items . If the Contractor receives approval to use an alternate source of material, the Department will not pay for source reclamation. The Department will provide seed to the Contractor at no cost for designated sources only.
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 200–202 of 768.