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Section C-7
Investigation of Soil and Sub-Surface Conditions

The Joint Committee recommends that, prior to bidding, Owners obtain the services of a geotechnical engineer to investigate subsurface conditions. The extent of the investigation should assure that the geo-technical data and bearing capacity tests necessary to make foundation recommendations are secured for the building site. The geotechnical report should also address areas of major excavation and grading required to support site utilities and significant site amenities. Areas of excavation which will be unsuitable for reuse as fill, areas of rock excavation, and anticipated groundwater levels should be delineated in the report.

The full geo-technical report including data pertinent to the sub-surface conditions and foundation design recommendations should be made available to Bidders. It is recommended that the geo-technical report, including design recommendations of the geotechnical engineer, be included as part of the Contract Documents, not simply attached 'For Information Only'. The design professional should follow the recommendations of the geotechnical engineer in execution of the Contract Documents or provide alternative design criteria used instead as an amendment to the geotechnical report. Further, we recommend that the contract documents require monitoring and testing by a geotechnical engineer during construction to confirm suitable bearing conditions and compliance with the recommendations. And, in addition, if the recommendations of the geotechnical engineer requires the evaluation of qualitative rather than quantitative performance criteria to determine compliance, we recommend that the construction monitoring and testing services be contracted directly with the owner.

COMMENT: It is possible for a project to be completed without conducting a subsurface investigation. It is however, considered good and prudent practice to review subsurface conditions to insure that proper bearing capacity can be developed to carry the anticipated loads of the structure, as well as the suitability of the material upon which the structure will bear. Neither the Architect nor the Contractor has the expertise to evaluate subsurface conditions and, therefore, they rely on the recommendations of the geo-technical engineer. A contract with the Owner establishes an independent, non-conflicting evaluation of the sufficiency and quality of the work completed by the Contractor

By making the geo-technical report available to the Contractor during bidding, the Contractor can develop reliable costs based upon conditions that will be encountered during construction. If such information is not available, the Contractor may qualify or adjust their bid to reflect the added risk associated with respect to the unknown sub-surface conditions. Consideration needs to be given to a time extension of the excavation schedule, and overall construction schedule, if rock or unsuitable subsurface soils not identified before the award of Contract are encountered during the course of the work.

Users are directed to AIA-MBA Joint Committee Best Practices Guide Section C-5: "Bidding on Unclassified Excavation" for related information regarding excavation.

Users are directed to AIA-MBA Joint Committee Best Practices Guide Section D-6: "Unit Prices" for related information regarding cost control of excavation.

TAGS: Sections C-5 and D-6.

Glossary Terms for the Best Practices Guide

History of Recommendation:
Revised October, 2008
Revised January, 1996
Revised April, 1987
Reviewed September, 1981
Revised February, 1976
Revised November, 1971
Approved May 4, 1970

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