Guidelines for Managing Geotechnical Risks in Design–Build Projects (2018)

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A-1 A.1 Geotechnical Terms The definitions for the primary geotechnical reports that will be referenced in the synthesis are drawn from the FHWA Technical Manual for Design and Construction of Road Tunnels—Civil Elements (Hung et al. 2009). (See also Essex 2007.) • Geotechnical Design Memoranda (GDM): “interpretive reports are used to evaluate design alter- natives, assess the impact of construction on adjacent structures and facilities, focus on individual elements of the project, and discuss construction issues . . . the GDM may be prepared at different stages of a project, and therefore may not accurately reflect the final design or final contract docu- ments. Since GDMs are used internally within the design team and with the owner as part of the project development effort, it is not appropriate to include GDMs as part of the contract documents” (Hung et al. 2009). Also termed geotechnical interpretive report. • Geotechnical Data Report (GDR): “a document that presents the factual subsurface data for the project without including an interpretation of these data. The purpose of the GDR is to compile all factual geological, geotechnical, groundwater, and other data obtained from the geotechnical investigations for use by the various participants in the project, including the owner, designers, contractors and third parties that may be impacted by the project. It serves as a single and comprehensive source of geotechnical information obtained for the project.” The GDR should contain the following information: – “Descriptions of the geologic setting; – Descriptions of the site exploration program(s); – Logs of all borings, trenches, and other site investigations; – Descriptions/discussions of all field and laboratory test programs; and – Results of all field and laboratory testing” (Hung et al. 2009). • Geotechnical Baseline Report (GBR): a document developed “to define the baseline conditions on which contractors will base their bids and select their means, methods and equipment, and that will be used as a basis for determining the merits of contractor claims of differing site conditions during construction” (Hung et al. 2009). The GBR should contain the following information: – “The amounts and distribution of different materials along the selected alignment; – Description, strength, compressibility, grain size, and permeability of the existing materials; – Description, strength and permeability of the ground mass as a whole; – Groundwater levels and expected groundwater conditions, including baseline estimates of inflows and pumping rates; – Anticipated ground behavior, and the influence of groundwater, with regard to methods of excavation and installation of ground support; – Construction impacts on adjacent facilities; and A P P E N D I X A Glossary of Geotechnical and Risk Terms

A-2 Guidelines for Managing Geotechnical Risks in Design–Build Projects – Potential geotechnical and man-made sources of potential difficulty or hazard that could impact construction, including the presence of faults, gas, boulders, solution cavities, existing foundation piles, and the like” (Hung et al. 2009). In addition to the above terms, there are several other terms used to describe commonly practiced methods for conveying geotechnical information in DB RFPs. They are as follows: • Reconnaissance Report. A document that contains the results of a review of records and observations from the project site. • Geotechnical Summary Report. A document that contains the results of a review of records and geotechnical investigation of critical areas. • Preliminary Geotechnical Data Report. A document that contains the results of a partial geotechnical investigation that will eventually be included in a final GDR. A.2 Project Delivery Terms Since the application of geotechnical information in the context of a DB contract is the sub- ject of this report, it is also important to have standard terms that relate to DB project delivery. Those terms follow. • Design-Bid-Build (DBB). The “traditional” project delivery approach where the owner com- missions a designer to prepare drawings and specifications under a design services contract, and separately contracts for construction, by engaging a contractor through competitive bidding or negotiation. • Design-Build (DB). The system of contracting under which one entity performs both architecture/engineering and construction under a single contract with the owner. • Progressive Design-Build (PDB). PDB’s attraction in the geotechnical risk management realm is the ability to negotiate the geotechnical risk after award and after the geotechnical investiga- tion has been completed rather than depending on the DSC clause to allocate the subsurface risk. With PDB, the first design and construction package released for construction could commence the subsurface investigation and conduct selected excavation on the project site to identify where the geotechnical issues will be encountered and their magnitude. Thus, a fair and equitable amount for the realized subsurface risk can be established. This eliminates the need for adding unnecessary contingencies in the price, as the uncertainty of the subsurface conditions is eliminated early in the project. • Alternative Technical Concepts (ATC). An ATC is a specific modification of the baseline scope of work and its attendant contract requirements in a manner that is equal to or better than the baseline scope of work articulated in the projects solicitation. • Differing Site Conditions (DSC) Clause. A contract clause designed to give a contractor cost and time relief for (1) subsurface or latent physical conditions encountered at the site dif- fering materially from those indicated in the contract; or (2) unknown physical conditions at the site of an unusual nature, differing materially from those ordinarily encountered and generally recognized as inherent in the work provided for in the contract [U.S. Code, Differing Site Conditions, Title 23 CFR 635.109 (2013)]. There are two types: Type 1 and Type 2. The definitions are in Chapter 2. References Essex, R. J. (2007). Geotechnical Baseline Reports for Construction. American Society for Civil Engineers, Reston, Va. Hung, C. J., J. Monsees, N. Munfah, and J. Wisniewski. (2009). Technical Manual for Design and Construction of Road Tunnels—Civil Elements. Technical Report FHWA-NHI-10-034. U.S. Department of Transportation, FHWA, National Highway Institute, Washington, D.C.