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Section C-5
Bidding on Unclassified Excavation

The Joint Committee recommends that Contract Documents allow Contractors the means to be fairly compensated for Work, and to that end, favors classifying types of excavation.

COMMENTARY: The Joint Committee believes that the purpose of the bidding process is to provide a means by which the Owner can obtain comparative pricing of like products. In the ideal world, the process produces a win-win relationship between the Owner and Contractor.

Excavation work has been specified as either classified or unclassified. Unclassified excavation makes no distinction between the requirements to remove loose fill at one extreme to rock at the other extreme. The Bidder, by accepting the conditions of unclassified excavation, assumes the risk for whatever appears. Because it is impossible, even with an investigation of the subsurface conditions, to know with absolute certainty what will be encountered during excavation, it is highly likely that someone loses.

Excavation should be classified with a description of material and a definition of the effort required for removal. It is recommended that specific language be incorporated into the specifications to quantify the anticipated type of excavation to be included in the base bid and clearly define rock excavation. An example of such language is:

  1. Work, in general, consists of, but is not necessarily limited to:
    a. Bulk excavation for building pad and foundations, parking lots, access roads, sidewalks and other structures and site improvements as indicated on the Drawings.
    b. Trench excavation, backfilling, compaction, thrust blocks, and related items to complete installation of sanitary and storm sewers, natural gas piping, underground electrical service, water service, and other site utilities as indicated on the Drawings.
    i. All excavation shall be assumed to be earth (non-rock).
    ii. Bidder shall provide a unit price for rock excavation as an extra to the Contract.
    iii. Bidder shall provide a unit price for off-site disposal of unsuitable material and replacement with suitable backfill material compacted in place as an extra to the Contract.
  2. Earth excavation includes excavation of pavements and other obstructions visible on surface; underground structures, utilities, and other items indicated to be demolished and removed; together with earth and other materials encountered that are not classified as rock or unauthorized excavation.
  3. Rock Excavation:
    a. When rock is encountered within the limits of the excavation, immediately notify the Owner and Architect and do not proceed further until instructions are received and measurements made for the purpose of establishing the and volume of rock excavation.
    b. Volume of rock excavation shall be determined by the location of the "pay lines." Pay lines shall be determined with the Owner and Architect prior to commencement of rock excavation and shall be the basis for payment. Pay lines shall be defined as:
    i. The elevation of the bottom of the foundation of the structure or the designated over-excavation below pipes, conduits, floor slabs, foundations, site amenities, etc.
    ii. The vertical side planes which will afford an adequate and safe working area between the structure wall and face of the cut.
    c. Rock excavation consists of the removal of hard igneous, metamorphic, and/or sedimentary rock which cannot be excavated without blasting or by means of a track mounted power excavator, equivalent to Caterpillar Model No. 215C LC, and rated at not less than 115 HP flywheel power and 32,000 pound drawbar pull and equipped with a short stick and a 42 inch wide, short tip radius rock bucket rated at 0.81 cubic yard (heaped) capacity, and all boulders or other detached stones each having a volume of ½ cubic yard or more. Trenches in excess of 10 feet in width and pits in excess of 30 feet in either length or width are classified as open excavation.
    d. Unit Prices, measured in place, shall be provided for:
    i. Mass cut, spoiled - over 7'-0" wide, fractured by blasting or machine, loaded, removed, and disposed of on-site.
    ii. Mass cut, hauled - over 7'-0" wide, fractured by blasting or machine, loaded, removed, and disposed of off-site.
    iii. Trench cut, spoiled - under 7'-0" wide, fractured by blasting or machine, loaded, removed, and disposed of on-site.
    iv. Trench cut, hauled - under 7'-0" wide, fractured by blasting or machine, loaded, removed, and disposed of off-site.
    v. Hand removal, spoiled - rock fractured by hand tools (i.e. pneumatic) loaded, removed, and disposed of on-site.
    vi. Hand removal, hauled - rock fractured by hand tools (i.e. pneumatic) loaded, removed, and disposed of off-site.
    e. Unit prices shall be used to calculate the net change to the contract amount by means of multiplying the volume of rock excavation determined under Section 2.b by the Unit Price determined under Section 2.g less the value of earth excavation for this volume already included in the contract.
  4. Unsuitable Material:
    a. Materials unsuitable to be used for fill include:
    i. Unsatisfactory Soils: ASTM D 2487 soil classification groups GC, SC, ML, MH, CL, CH, OL, OH, and PT, or a combination of these group symbols.
    ii. Expansive clay or carbonaceous soils.
    iii. Materials such as coal ash, wood chips, stumps, branches, boughs, or construction and demolition debris.
    iv. Satisfactory soils not maintained within 2 percent of optimum moisture content at time of compaction.

It is recommendation of this Committee that all project budgets have a contingency included in anticipation of excavation of unsuitable material.

Users are directed to AIA/MBA Joint Committee Best Practices Guide C-7: "Investigation of Soil and Sub-Surface Conditions" for related information regarding excavation and D-6: "Unit Prices" for related information regarding cost control of excavation.

To post a comment on this recommendation click here.

TAGS: Sections C-7 and D-6.

Glossary Terms for the Best Practices Guide

History of Recommendation:
Revised October, 2008
Revised May, 1996
Revised April, 1987
Reviewed February, 1986
Revised February, 1976
Revised November, 1971
Reviewed January, 1967

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