103 ALASKA 2020 SECTION 205
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. SECTION 2 05 104 ALASKA 2020 205-3.02 STRUCTURAL FILL. Remove material that is unsuitable for supporting foundations, from the bottom of the footing to the depth as shown on the Plans. Remove material that is unsuitable for approach slabs shown on the Plans. Place structural fill in 6- inch layers, compacted to meet Subsection 205- 3.05. Place structural fill as uniformly as possible on all sides of structural units as shown on the Plans. Avoid unbalanced loading of structural fill material which could damage the structure. When placed against concrete, place structural fill in accordance with Section 501. Controlled low -strength mater ial may be used as an alternative source for structural fill if approved by the Engineer.
205-3.03 BACKFILL. Unless otherwise noted, reuse excavated material for backfill where shown
on the Plans. If additional backfill is required, use material meeting Selected Material, Type C, or as approved by the Engineer. Place backfill material in layers and compact to meet Subsection
205-3 05.
Place underwater backfill in natural stream channels without compaction or layer requirements. Place backfill as unifor mly 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 501. No ponding or jetting of backfill is allow ed.
205-3.04 POROUS BACK FILL MATERIAL. Place porous backfill material continuously within a
vertical plane 1 foot behind retaining walls and abutments, unless otherwise shown on the Plans. Compact to the satisfaction of the Engineer. Where weep holes are shown on the Plans or required by the Specifications, place not less than 1 cubic foot of porous backfill material in the fill at each hole, securely tied in a burlap bag, or wrapped with an acceptable geotextile fabric. Extend the wrapped porous backfill material at least 6 inches above the hole.
205-3.05 COMPACTION. Compact material in conformance with the following, using moisture
and density control unless the Engineer determines that such controls are not feasible.
1.Compaction With Moisture and Densi ty Control . The maximum density will be determined by ATM 207 or ATM 212. Water or aerate as necessary to provide the approximate optimum moisture content for compaction. Compact each layer to not less than 98 percent of the maximum density. Acceptance de nsities will be determined by ATM 213 and ATM 214.
2.Compaction Without Moisture and Density Control . Compact by routing construction equipment and/or rollers uniformly over the entire surface of each layer before the next layer is placed. Compact to the satisfaction of the Engineer. Keep dumping and rolling areas separate. Do not cover any lift by another until the Engineer has determined the required compaction is obtained.
205-3.06 CONTROLLED LOW -STRENGTH MATERIA L. Acceptance will be based on a
certificat e of compliance. Provide a certificate of compliance for each batch of controlled low - strength material (CLSM) in accordance with Subsection 106- 1.05. Do not place CLSM on frozen ground, in standing water, or during wet weather conditions. Do not place CL SM if ambient air temperature is expected to be less than 40 °F within 48 hours. Ensure the material temperature is at least 50 °F while being placed. 105 ALASKA 2020 Do not apply loads to the CLSM until the compressive strength reaches 50 psi.
205-4.01 METHOD OF M EASUREME NT. See Section 109 and the following:
1.Excavation. By the actual volume of material removed, excluding the following:
a.Material removed prior to measurement of the original ground surface.
b.Material outside of the vertical planes 18 inches outside of and parallel to the neat lines of the footings, except that the limit will be vertical planes coinciding with the neat lines of the seals when seals are shown on the Plans.
c.Material outside of vertical planes coinciding with the neat lines of footings excavated in solid rock.
d.Embankment material placed above the elevation of the bottom of footings.
e.Material within the staked limits of other types of excavation for which payment is otherwise provided.
2.Structural Fill . By the actual volume of material accepted in f inal position.
3.Porous Backfill Material . By the actual volume of material accepted in final position.
4.Controlled Low -Strength Material . By the actual volume of material accepted in final position.
205-5.01 BASIS OF PA YMENT. Backfill material, obtained f rom within the limits of structure
excavation, is subsidiary to item 205.0001.____. Any backfill material from sources other than excavation for structures 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. Porous backfill material includes all materials and construction operations for making weep holes. When Items205.0004.____, 205.0007.___, and 205.0008.____, Porous Backfill Material, do not appear in the bid schedule, porous backfill material is subsidiary. Excavation for Structures includes removal, and disposal of unsuitable material. Excavation for footings ordered by the Engineer, at a depth greater than 3 feet below the bottom of such footings shown on the Plans will be pai d for as extra work. When controlled low -strength material is used as an alternative to structural fill, controlled low - strength material is paid for at the Contract price for structural fill. Payment will be made under: PAY ITEM Item Number Item Descri ption Unit 205.0001.____ Excavation for Structures CY 205.0004.____ Porous Backfill Material CY 205.0005.____ Controlled Low -Strength Material CY 205.0006.____ Structural Fill CY 205.0007.____ Porous Backfill Material TON 205.0008.____ Porous Backfil l Material LS 205.0009.____ Structural Fill TON 205.0010.____ Structural Fill LS 106 ALASKA 2020 SECTION 206 FILTER BLANKET
206-1.01 DESCRIPTION. Construct a layer of specified material in conformance to the plan
dimensions and elevations.
206-2.01 MATERIALS. Use materials that conform to the following:
Filter Blanket Subsection 703- 2.08
206-3.01 CONSTRUCTIO N REQUIREMENTS. Construct Filter Blanket in an even,
homogeneous layer, avoiding contamination by the underlying material. Place the layer to full thickness in on e application or end- dump and spread by tracked equipment.
206-4.01 METHOD OF MEASUREMENT. See Section 109, by volume in final position or by
weight.
206-5.01 BASIS OF PA YMENT. The contract price includes excavating, processing, hauling,
spreading and lev eling of the filter blanket layer. Payment will be made under: PAY ITEM Item Number Item Description Unit 206.0001.____ Filter Blanket CY 206.0002.____ Filter Blanket TON
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 131–133 of 584.