101 ALASKA 2020 SECTION 204
204-1.01 DESCRIPTION . Excavate and backfill for pipe culverts, storm drains, manholes, inlets
and other minor structures. Perform all pumping, bailing, draining, sheeting, bracing, and incidentals required for proper execution of the work.
204-2.01 MATERIALS . Use selected material, Type A (Subsection 703- 2.07) passing the 3- inch
sieve for bedding material, and for backfill material to 12 inches above the pipe. Use excavated native material for the remainder of the backfill if i t meets the requirements of Selected Material, Type C. Use bedding material, and backfill material within the pavement structure, meeting the requirements for the applicable lift of material. Use all suitable material from structure excavation for beddin g and backfill prior to using material from another source.
204-3.01 CONSTRUCTIO N REQUIREMENTS. Remove and dispose of unsuitable foundation
material below the designed elevation as directed. Replace with approved material. Remove rock or other unyielding material, when encountered, to the depth shown on the Plans or as directed and replace with approved material. Place bedding and backfill in uniform layers not more than 6 inches deep and compact to meet Subsection 203- 3.04. Ponding or jetting is not perm itted. Native material may be utilized for electrical conduit backfill outside the pavement structure if it meets the minimum requirements of Selected Material, Type C, as specified in Subsection 703- 2.07. Compaction may be as approved by the Engineer. Place backfill as uniformly as possible on all sides of structural units. Avoid unbalanced loading of backfill which could damage the structure. When placed against concrete, place backfill according to the requirements of Section 550. Support and protect exi sting conduits or utilities, which are not scheduled for removal or abandonment, when encountered in the excavation. Remove all sheeting and bracing used in structure excavation upon completion of the work.
204-4.01 METHOD OF M EASUREMENT. See Section 109 using neat line method as follows:
Structure excavation for:
1.Masonry culverts, headwalls, and drainage structures other than conduit . Between vertical planes 18 inches outside the base of the masonry sections shown on the Plans for the depth required.
2.Cond uit, including culverts, storm drains, underdrains, structural plate pipe and pipe arches . Between parallel vertical planes located 18 inches outside the horizontal projection of the outside diameter of the pipe and to the depth shown on the Plans. Structu re excavation will only be measured below the limits of other classes of excavation. When structures are to be placed in embankment sections, the natural ground line as cross -sectioned will be the uppermost level of computation. 102 ALASKA 2020 204-5.01 BASIS OF PA YMENT. The contract price includes the placing and compacting of all backfill and bedding when the materials used are obtained from excavation, any clearing and grubbing required and not paid for under some other item, formation of any embankments made with surpl us material from structure excavation and disposal of all surplus or unsuitable excavation. Additional excavation to provide for shoring, sheet piles, excavation shields or flattening the excavation slopes, is subsidiary. When items 204.0001.____ through 204.0003. ____, Structure Excavation, do not appear in the bid schedule, structure excavation required to complete other items of work is subsidiary except that excavation and disposal of unsuitable material required from below a plane 12 inches below the invert elevation of conduits and 12 inches below the bottom of structures will be paid for as extra work. Any backfill or bedding material required whose source is other than project excavation will be paid for at the contract unit price for the material being used, or as extra work if no unit price has been established. Payment will be made under: PAY ITEM Item Number Item Description Unit 204.0001.____ Structure Excavation CY 204.0002.____ Structure Excavation TON 204.0003.____ Structure Excavation LS 103 ALASKA 2020 SECTION 205 EXCAVATION AND FILL FOR MAJOR STRUCTURES
205-1.01 DESCRIPTION . Excavate and backfill for bridges, retaining walls, concrete box culverts,
and other major structures. Furnish all resources to place and remove cribbing. Perform all required sheeting, bracing, bailing, pumping, draining, and grouting. Replace unsuitable material encountered below the elevation of the bottom of footings.
205-2.01 MATERIALS. Use materials that conform to the following:
Selected Material, Type C Subsection 703- 2.07 Porous Backfill Material Subsection 703- 2.10 Structural Fill Subsection 703- 2.13 Controlled Low -Strength Material Subsection 712- 2.22 CONSTRUCTION REQUIREMENTS
205-3.01 Excavation.
1.General . Clear and grub prior to starting excavation according to t he requirements of Section 201. Cut all rock or other hard foundation material to a firm surface, either level, stepped, or serrated, as directed, and remove all loose material. Within areas that will be filled, bench excavated slopes not made of rock or other hard foundation material. Excavate to the bottom of spread footings and approach slabs or to the depth shown on the plans, whichever is lower. Do not disturb material below the bottom of spread footings or approach slabs, unless otherwise noted in th e Contract. Excavate to the bottom of footing prior to driving piles. Do not excavate below the footing elevation unless otherwise noted in the Contract. When swell results from driving piles, excavate the footing area, to the elevation of the bottom of t he footing, as shown on the Plans. When subsidence results from driving piles, backfill with structural fill material, to the elevation of the bottom of the footing, as shown on the Plans. Dispose of all necessary excavated material as provided in Subsect ion 203- 3.01. Do not alter streambed channel and do not place excavated materials in natural stream channels, unless shown on the Plans or approved in writing. Give the Engineer in writing no less than 15 days advance notice prior to beginning excavation f or spread footings to allow for inspection of the excavated surface. With this notification, identify the location and specify a time period of no less than two days for the Department to inspect the excavated surface. Dewater and remove all debris from the surface prior to the Department's inspection. Obtain the Engineer’s approval of the excavated surface prior to the placement of any formwork or foundation materials. Account for the time required by the Department to perform the inspection in the progres s schedule submitted under Subsection 108- 1.03. Pausing work to allow for inspection is not a suspension of work per Subsection 108- 1.06 and additional contract time will not be allowed.
2.Foundations on Bedrock . Excavate for footings founded on bedrock, to the neat lines of the footings. Fill overbreak areas outside the neat lines of footings, with Class A concrete, at no additional cost to the Department.
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 129–130 of 584.