Manual on Subsurface Investigations (2019)

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238 C H A P T E R 1 1 Compiling, Reporting, and Presenting Geotechnical Information Introduction This chapter presents guidelines regarding compiling, reporting, and presenting factual and interpretive geotechnical information for geotechnical data and baseline reports and discusses the contractual implications of geotechnical reports for alternative project delivery methods. Uses of Geotechnical Information Geotechnical information is used to develop and define the ground model for an area or site of interest. The ground model is defined as the geotechnical and geological model used for engineering evaluation. The ground model comprises the spatial distribution of subsurface materials and the engineering properties of these materials. Geotechnical engineers use the information in the ground model for many tasks during the planning, design, construction, and long-term maintenance of transportation facilities: • Engineering analyses • Developing design recommendations • Suggesting a construction technology (for design-bid-build projects) • Estimating material quantities and costs • Controlling construction quality • Supporting the bidding process • Evaluating soil-structure or geotechnical performance Geotechnical information is also used to avoid or mitigate geohazards (e.g., reroute a road to avoid an active landslide) and identify geotechnical construction issues, and is frequently referenced during the design and construction process and during potential claims or operation issues related to subsurface conditions. Factual Information Factual information is typically obtained by subsurface investigation and characterization methods; it is information that has not been modified or interpreted. It represents the actual geotechnical, geological, hydrogeological, and geophysical conditions that exist at a specific location and time. The factual information should be properly mapped and plotted on plans, profiles, or cross sections in reference to specific features of a project. The current technologies for data integration and management, such as GIS, are becoming common tools for engineers to present the factual and interpretive information. Sources of factual information are described in the following subsections.

239 11.3.1 Preexisting Data Resources As discussed in Chapter 3, preexisting information should be compiled and evaluated prior to developing a project-specific subsurface exploration program. A qualified engineer should decide whether the preexisting information is applicable to a project. In making this decision, the engineer should identify the source of any information and its limitations. For example, the preexisting soil boring logs near a project site can be considered factual data, but the site condition (e.g., high water table) and the technique used at the time of data collection (e.g., poorly controlled SPTs) might not be applicable for design. Sources for preexisting information can include the following publicly available materials: • USGS quadrangle topographic maps • USGS geologic maps of surficial geology • USDA soil survey maps and reports, including descriptions and properties of surficial soils • USGS hydrologic and groundwater reports and maps • Historical climate information from NOAA or other local weather stations • Historical and current aerial and satellite imagery available from local, state, or federal agencies, or private companies • Light detection and ranging (LiDAR) information and digital elevation models from the state or federal agencies • Geological, hydrological, and geotechnical engineering reports from nearby sites that include information such as groundwater condition, subsurface conditions, boring logs, and drilled well logs, available from local government agencies (city, county, state, or federal) • Published geotechnical databases and public records of problematic geotechnical conditions available from a State DOT. Preexisting information also might be related to the existing final construction records for previous construction activity at the site, including as-built bridge or other structure layouts, existing subsurface exploration logs, geologic maps, and previous or current geologic reconnaissance results (New York State DOT 2013). Along with preexisting factual data, the project team may need to collect project-specific factual data by a variety of means, as described in the following sections. 11.3.2 Remote Sensing Data There are a variety of remote sensing techniques, including satellite, aerial or land-based digital photography, video imagery, satellite sensing (e.g., interferometric synthetic aperture radar [InSAR]), digital scanning (e.g., LiDAR) of the earth surface and features. Publicly available remote sensing data from airborne or satellite-borne sensors are typically obtained from federal agencies (e.g., USDA, National Aeronautics and Space Administration [NASA], USGS, NOAA) or appropriate state agencies. 11.3.3 Geophysical Information Geophysical data may be acquired and interpreted to identify and characterize contrasts between different geological materials or subsurface features such as voids. Geophysical data are typically integrated with subsurface geotechnical exploration data (e.g., that obtained from boring logs) to develop the ground model. Experienced and qualified personnel should select the most appropriate techniques for the project. While geophysical data are typically processed and preliminarily interpreted by a qualified geophysicist, the reporting of these data is considered factual information. If the geophysical data is interpreted to provide geological context or input in the ground model, the data is considered interpretive information. Chapter 4 of this manual provides details regarding different surface and borehole geophysical methods and their applications.

240 11.3.4 In Situ Testing In situ testing of soil or rock can provide representative geotechnical information. In situ testing methods and details of these tests are provided in Chapter 5 of this manual. Specialized geotechnical field test reports, such as PMT or CPT, may include an interpretation of the test results rather than just factual test data. These specialized test interpretations are relatively standardized and, despite the interpretation, are commonly considered factual data in geotechnical practice. 11.3.5 Hydrogeologic Information Hydrogeologic information pertains to groundwater levels, pressures, and rate of groundwater flow through subsurface materials. While some of this information is factual, some aspects may be interpreted based on groundwater models developed for the site. Methods used to acquire hydrogeological information are described in Chapter 7. 11.3.6 Laboratory Testing Laboratory testing on disturbed and undisturbed soil samples and rock samples provides factual geotechnical information. Nevertheless, this information will require interpretation by qualified personnel before being useful for design. Methods for drilling and sampling, and geotechnical laboratory tests commonly used for transportation projects are described in Chapters 6 and 8, respectively. 11.3.7 Construction-Phase Testing and Monitoring Results Although geotechnical exploration is usually conducted during the design phase of a project, additional geotechnical exploration may be conducted during the construction phase depending on the project complexity and performance requirements. For example, rock structure mapping and visual logging of the soil strata exposed during construction while excavating or conducting other earthwork can provide additional geotechnical information that may be used to modify the design or the construction means and methods. Geotechnical data can also be obtained from load tests (e.g., pile load tests) and instrumentation (e.g., observation wells, piezometers, inclinometers, settlement measuring devices, extensometers, strain gauges, load cells, vibration monitoring devices). Interpretive Information Interpretive geotechnical information is the modified or interpreted geological, hydrogeological, geophysical, and geotechnical data as presented in geotechnical reports. This information has been modified or interpreted by geoprofessionals. The interpretation of factual data helps to develop (i) the ground model, which includes subsurface stratigraphy and soil and rock design parameters; (ii) performance expectations or serviceability; and (iii) preliminary and final design and construction recommendations. The interpretive information represents the opinion of geoprofessionals for planning and constructing a specific project: the interpretive information prepared for one project is not applicable to another project. Geotechnical interpretive reports (geotechnical reports for design-bid-built and geotechnical data memoranda [GDM] or GBR for design-build contracts) document the interpretive information, including geotechnical analysis and design for transportation-related structures. Components of geotechnical interpretive reports are described below.

241 11.4.1 Performance Criteria Performance criteria are the tolerable limits for a structure used to develop the basis of design. Geotechnical performance criteria typically include tolerable displacements (e.g., settlement, differential settlement, heave, lateral movement, tilt), tolerable vibration levels, and other local damage and deterioration that can affect the serviceability of the structure. Interpretive geotechnical reports should include estimates of performance for various project-specific conditions for comparison with tolerable limits. 11.4.2 Ground Model The ground model is the basis of geotechnical interpretive reports. All available geological, hydrogeological, geophysical, and geotechnical data is integrated into a model that describes the subsurface conditions (i.e., stratigraphy, material properties) and their variability. The ground model is depicted through soil and rock maps, soil and rock profiles or cross sections, and maps of potential geohazards. Knowledge uncertainty in developing the ground model can be conveyed while presenting the model by providing likely ranges for material properties and parameters as well as likely ranges of contacts between subsurface materials. 11.4.3 Design Recommendations Design recommendations address the design and construction considerations that should be implemented to ensure that the project meets the design criteria. Necessary interpretive information for different considerations of the design recommendations are presented below, and more details are presented in FHWA (2003) and New York State DOT (2013). • Interpretive information that should be presented for the general project requirement: – Environmental axial and lateral loading on the foundation, including static, dynamic, and seismic loads – Limits of excavation and dewatering – Scour depth • Interpretive information that should be presented for the foundations: – Foundation type and reason for selection (e.g., drilled piers [shaft], driven piles, caisson, shallow spread footings, mat foundations, or slab on grade) – Bearing capacity, side resistance, subgrade modulus, and estimated settlement for shallow foundations – Frost depth – Embedment depths for shallow foundations – Side resistance and tip resistance for deep foundations; lateral resistance of vertical and battered piles; p-y, t-z, and q-z curves; settlement potential as a function of project-specific load combinations; suitable pile type; pile tip elevation; group effects; drag load; provisions for scour and corrosion, among others. • Interpretive information that should be presented for embankments and approach fills: – Estimated settlement, unsuitable soils that should be removed, ground improvement or stabilization requirements, seepage and groundwater issues, pile-supported embankments on soft ground, drag load on pile, among others. – Construction sequences (i.e., staged construction and limitations) – Slope stability • Interpretive information that should be presented for excavations: – Rock profile and rippability, boulder contents, shrinkage and swell during excavation, and development of grading, bulking, or earthwork factor – Groundwater seepage, dewatering, and underdrain requirements

242 – Slope stability for permanent or temporary slopes with static or dynamic loads • Interpretive information that should be presented for retaining-walls: – Selected wall type (e.g., soil-nail walls, mechanically stabilized walls, secant walls, soldier piles and lagging, anchored or braced, cantilever walls) and the reason for selection – Lateral earth pressure for braced and cantilever walls, hydrostatic load, surcharge load, and dynamic loads – Global stability and the lateral and vertical extent of the earth-retaining structures – Backfill materials and drainage requirements • Interpretive information that should be presented for the pavement and roadway: – Unsuitable materials, frost susceptibility, expansive soils, corrosion of subgrade soils, and potential excavation and replacement – Resilient modulus of subgrade soils – Support capacity (e.g. truck loads, traffic intensity, dynamic conditions) – Pavement design, thickness, and maintenance • Interpretive information that should be presented for groundwater and surface water management: – Groundwater and seepage control requirements (e.g., dewatering systems for excavations) – Erosion protection and filter materials and fabrics • Interpretive information that should be presented for the tunnel or underground structures: – Design considerations, shape, lining, groundwater conditions, constructability, temporary support, access, materials, groundwater control, and blasting limitations in rocks 11.4.4 Construction Considerations Geotechnical considerations related to construction should be provided in geotechnical interpretive reports. The following are some of the construction recommendations and considerations that should be included: • Uncertainty in subsurface conditions, quantity estimates, adverse weather, and contractor performance • Environmental concerns (e.g., noise, vibration, runoff, erosion, dust) • Unsuitable materials, stabilization, excavation, dewatering, and use of structural fill • Pile installation requirements, construction issues, and pile load testing • Excavation support (e.g., shoring, sheeting, bracing) • Protection of adjacent structures due to excavation, pile or shoring driving, settlement, and drainage • Quality control roles and responsibilities and testing requirements 11.4.5 Geotechnical Instrumentation and Monitoring If required, a geotechnical monitoring plan should be provided with the geotechnical interpretive reports to acquire pertinent geotechnical information to validate the design and check the specified performance criteria. The geotechnical instrumentation plan during design or construction phase may contain the following: • Settlement monitoring devices • Slope stability monitoring devices (e.g., inclinometers, surface displacement markers) • Groundwater level monitoring devices (e.g., observation wells, piezometers) • Bearing pressure and strain monitoring for anchors, soil nails, or pile testing • Vibration monitoring using seismographs • Load testing, crosshole logging, pile driving monitoring, among others

243 11.4.6 Geotechnical Information for LRFD The state agency’s geoprofessional preparing an interpretive report must provide the following information to the structural design team for LRFD. Required information may change from one state to the other. Additional information can be found in New York State DOT (2013). 11.4.6.1 Footings For footings with various depths, the nominal bearing resistance for strength and extreme event limit states with associated resistance factors should be provided. The settlement-limited nominal bearing resistance for the service limit state (typically 1 in. [2 cm]) with associated resistance factors should also be provided. For sliding and eccentricity calculations, the resistance factors for strength and extreme event limit states should be provided to calculate the shear and passive resistance and active forces. To evaluate the soil-structure response and develop forces in foundations during seismic events (i.e., extreme event limit state), the shear modulus and Poisson’s ratio of the soil and rock should be provided. 11.4.6.2 Drilled Shafts and Piles To calculate the bearing resistance for strength and extreme event limit states, the nominal (ultimate) end bearing, tip resistance, and side resistance as a function of depth, and shaft diameters should be provided. For the service limit state, the nominal bearing resistance at a specified settlement (e.g., 0.5 to 1.0 in. [1 to 2 cm]) should be provided. Resistance factors for bearing resistance for the various limit states should be included in the interpretive report. Similar information should be provided to calculate the lateral resistance for service, strength, and extreme event limit states. Group effects on the end and lateral resistance should also be evaluated. For calculating downdrag, the calculation of the neutral axis, the nominal drag load as a function of shaft diameter, drag load factor, and cause of downdrag should be provided. If drag load is caused by soil liquefaction, the instructions by FHWA (2010) should be followed. For the cases where lateral loads are imposed by soil, the nominal lateral load and the load factors should be provided. For the cases with uplift forces, the nominal uplift load and the load factors should be provided. For evaluation of the effect of scour, the magnitude and depth of the skin friction loss due to scour should be provided. 11.4.6.3 Earth-Retaining Structures For gravity walls, bearing capacity, sliding resistance, and eccentricity calculations should follow the requirements described for footings. The geotechnical report should provide active and passive earth pressure calculations for strength and extreme limit states. For nongravity walls, nominal bearing resistance of walls with depth, lateral active and passive earth pressure distribution, the minimum embedment depth required for overall stability, the no-load-zone dimensions, ultimate anchor resistance for anchored walls, and the associated resistance factors should be provided. Geotechnical Reports Geotechnical information is compiled, reported, and presented in geotechnical reports. The type of report(s) required for a project can vary depending on how the project will be contracted: as a design-bid- build or a design-build. Geotechnical reports for design-bid-build projects are conventionally prepared as preliminary and final geotechnical reports. For design-build projects there are three main categories of reports: geotechnical data report (GDR), GBR, and GDM (New York State DOT 2013).

244 11.5.1 Uncertainty of Geotechnical Information The uncertainty in geotechnical information is related to the unknown subsurface conditions (variation in the depth and lateral extent of subsurface materials and the properties of the materials), geotechnical performance, and interpretive and predictive models for engineering analysis. To develop geotechnical reports, the design team must evaluate the uncertainty in the geotechnical factual and interpretive information and how it will be addressed throughout the design. The uncertainties in geotechnical information can be managed by engaging qualified and experienced personnel for the following tasks: • Acquire and interpret the geotechnical information • Quantify uncertainty associated with geotechnical data • Prepare the geotechnical reports • Select load and resistance factors (LRFD), or factors of safety (ASD) • Provide the proper design solutions • Identify the quality management roles and responsibilities 11.5.2 Geotechnical Reports for Conventional Project Delivery Method For the conventional project delivery method (i.e., design-bid-build), the geotechnical information is typically presented as a single geotechnical report or combination of geotechnical reports and memoranda. These geotechnical reports are used by the state agency’s design team to present the analysis, design recommendations, and construction considerations for footings, drilled shafts, piles, earth-retaining structures, and other project components. The geotechnical reports are commonly produced in two stages of design: preliminary and final (New York State DOT 2013). 11.5.2.1 Preliminary Geotechnical Reports Preliminary geotechnical reports provide preliminary geotechnical input for developing the project scope, engineering analyses (e.g., temporary earth-retaining structures for structure replacements, preliminary grading analyses, preliminary foundation analysis), bridge layouts, preliminary route selection and geohazard evaluation (e.g., landslides, rockfall, structure foundation scour), and environmental permitting. Preliminary geotechnical reports can be used to address some elements of design and will be incorporated in the final report. Per New York State DOT (2013), the preliminary geotechnical report should contain the following elements: • General project description • Project constraints, including environmental and permitting requirements • Summary of regional and site geology • Summary of available data, field exploration, and laboratory testing • Description of the project soil and rock conditions • Summary of geological hazards at the site (e.g., landslides, rockfall, debris flows, liquefaction, soft ground or otherwise unstable soils, seismic hazards) • Limitations of factual data and additional data collection requirements • Preliminary geotechnical recommendations (e.g., how the subsurface conditions can potentially affect alternative approaches for design and construction) • Feasibility of proposed alignments with consideration to feasible slopes or need for walls and the potential effect of the fill or cut slopes and walls on adjacent facilities • Structure foundation feasibility (including any associated constructability issues that could contribute to risk and potential impacts to adjacent facilities) • Feasibility of ground improvement and dewatering, if needed • Impacts of construction on adjacent structures

245 • Appendices with geophysical test reports, boring logs and laboratory test data, preliminary site-specific seismic response analysis, liquefaction analysis, and geoenvironmental analysis, as applicable. 11.5.2.2 Final Geotechnical Report The final geotechnical report is used to provide final geotechnical interpretive information, analysis, and design for the various elements of the project. The level of detail and information for each report element varies with the size and complexity of the project. The final geotechnical report should contain the following elements. More details can be found in New York State DOT (2013): • General project description • Surface conditions and current use • Regional and site geology, including surficial geology and bedrock, site stress history, and deposition and erosion history • Regional and site seismicity • Available preexisting data, summary of the field exploration, and summary of laboratory testing • Subsurface conditions, including soils and rocks, structural geology, groundwater condition with identification of any confined aquifers, artesian pressures, perched water tables, potential seasonal variations, and gradient of groundwater • Subsurface profile or cross section to illustrate the spatial variation of soil and rock units • Geological hazards (e.g., landslides, subsidence, scour, liquefaction, soft ground or otherwise unstable soils, seismic hazards) • Analysis of unstable slopes, cuts, and fills • Geotechnical recommendations for earthwork cut and fill, rock slopes and rock excavation, stabilization of unstable slopes, bridges, tunnels, hydraulic structures, and other structures such as earth-retaining structures, reinforced slopes, and infiltration and detention facilities • Long-term performance or construction monitoring • Construction considerations Appendices to the final report typically include design charts, subsurface profiles, geophysical test reports, boring logs, laboratory test results, and instrumentation data. If applicable, other geotechnical memoranda such as site-specific seismic response analysis, liquefaction analysis, and geoenvironmental reports can be presented as appendices to the final geotechnical report. 11.5.3 Geotechnical Reports for Alternative Project Delivery Method Geotechnical reports for design-build contracts include GDR, GBR, and GDM. However, as discussed later in this section, these reports can be applied to other project delivery methods such as design-bid-build. 11.5.4 Geotechnical Data Reports The primary objective of the GDR is to document the factual geotechnical information for the project. The GDR does not include the interpretive information, and it is usually included in the request for proposal for the design-build bidding process. The GDR contains factual information (described in Section 11.3) and should include the following (Essex 2007): • A description of the geologic and seismic setting • A description of the site exploration program • The logs of borings, test pits, trenches, and other site investigations • The measurement results of field tests and geotechnical field instrumentation • A description of field and laboratory test programs • The results of all field and laboratory testing

246 11.5.5 Geotechnical Baseline Report In projects with significant earthwork and subsurface excavation, there are many risks that the owner and contractor should recognize. The main risk is related to the subsurface materials and their behavior. The GBR defines and allocates these risks between the owner and contractor by establishing geotechnical baselines. 11.5.5.1 GBR Purpose The GBR is an interpretive geotechnical report that establishes a common understanding between the contractor and the state agencies regarding design and construction issues related to subsurface conditions. The financial risk associated with conditions consistent with or less adverse than the baseline conditions is allocated to the contractor, while the financial risk associated with conditions more adverse than the baseline are accepted by the owner (Essex 2007). The GBR establishes baselines regarding geotechnical subsurface conditions present within the project and related to the design and construction. These baselines provide the contractors the basis for developing their bid price, quantities, and schedule, and allocate risk between the contractor and state agencies. The baseline statements in the GBR are a contractual commitment by the state agencies that those baseline conditions will be applied in the administration of the DSC clause. Therefore, state agencies should contribute to how the GBR is presented and understand the consequences of the information provided in the GBR. State agencies may allocate some risks and associated costs for potential DSCs to the contractor by using more adverse baselines. Alternatively, state agencies may share the risks and costs by using less adverse baselines (New York State DOT 2013, Essex 2007). The baselines in the GBR can consist of physical and behavioral baselines. The physical baselines are mainly related to the physical properties of the soil and rock (e.g., type of soil, presence of cobbles, boulders, obstructions, groundwater table, contamination, and rock type, strength, minerology, hydraulic conductivity). The behavioral baselines are mainly related to how the ground responds to certain construction equipment, means, methods, and technology. 11.5.5.2 GBR Organization GBR should be a concise document that can be read and understood in a short time period. Essex (2007) suggests a limit of 5 to 10 pages for a deep foundation or pipeline project, up to 30 pages for straightforward tunneling projects, and up to 50 pages for more complicated projects. The content of the GBR should follow the general recommendations by Essex (2007) and provide the information summarized below: • Project introduction, including project name, design team, purpose of the report, etc. • Project description, including project location, type, key features, and references to drawings or specifications • Source of geotechnical and geological information, including reference to GDR • Project geologic setting, including brief description of geologic and hydrogeologic conditions • Previous construction experience, including nearby projects and their subsurface conditions and relevance to this project, as well as a summary of problems during construction and how they were overcome • Ground characterization, including physical and mechanical properties of subsurface layers, groundwater conditions, contaminations, and ranges of values for baseline purposes • Design considerations, including methods and criteria used for the design; environmental performance criteria such as settlement and lateral movement; and rationale for geotechnical instrumentation • Construction considerations, including anticipated ground behavior, construction sequences, anticipated construction difficulties, rationale for requirements set in the construction specifications, and potential source of delay

247 The GBR should be prepared by the design team so that the GBR document is consistent with the developing design, drawings, specifications, and payment items. 11.5.5.3 GBR for Design-Bid-Build Contracts For design-bid-build contracts, the GBR is typically prepared at 50 to 60 percent completion level (Essex 2007). It is necessary to distinguish between interpretations addressed by the design team during the design process and interpretations that relate specifically to the design and construction methods addressed in the contract documents. In design-bid-build contracts, GBR is used for the following: • Technical construction specifications • Construction cost estimate for the state agency’s budgeting purposes • Anticipated subsurface conditions for the bidders and allocation of geotechnical risks • Contractual baselines for identifying DSC and resolution of disputes 11.5.5.4 GBR for Design-Build Contracts For design-build contracts, Essex (2007) proposes a three-step process for GBR preparation. In the first step, the owner’s design team prepares a common basis for bidders. In the second step, the GBR report is furnished to each design-build team. Each design-build team supplements the GBR with their design-based information and, if necessary, requests a supplemental subsurface exploration by the bidders to minimize contingency costs and manage risk. In the third step, the final GBR is developed jointly by the owner and the preferred design-build team. More details are presented in Essex (2007) and New York State DOT (2013). 11.5.6 Geotechnical Design Memoranda After completing the site exploration program and preparing a draft GDR, the design team may prepare GDM to document interpretive information for evaluating the feasibility of the design approaches, alternative final design concepts, and geotechnical risks for the project. The GDM is commonly used for the project team's internal consideration. The GDM can be disclosed to the bidders as available information but cannot be part of the contract documents. The GDM should include an introductory statement that the document is preliminary and not for construction purposes and will be superseded by final GBR. The GDM may be used for the following (Essex 2007, New York State DOT 2013): • To discuss factual data and additional data collection requirements • To present initial interpretations of the factual data • To present how the subsurface conditions can potentially affect the alternative approaches for the design and construction • To evaluate project risks for alternative construction approaches • To assess impacts of construction on adjacent structures and facilities • To present the feasibility of proposed alignments and consideration for slopes or walls • To discuss foundation feasibility and constructability issues • To evaluate seismic hazards, including site-specific ground motion studies and liquefaction analysis • To assess the potential geologic hazards and the mitigation strategies • To assess the need for ground improvement to stabilize unstable ground conditions (e.g., soft ground with excessive settlement) • To assess the feasibility of site conditions to infiltrate runoff water • To present the need for dewatering and its potential impact to adjacent structures • To present preliminary geotechnical design needed to assess risks and set up the baselines for the GBR

248 Contractual Implications of Geotechnical Reports Factual and interpretive reports should be made available to bidders so their bid price and schedule reflect a reasonable understanding of subsurface conditions. This is of particular importance for alternative project delivery methods. 11.6.1 Alternative Delivery Methods The contracting methods used by state agencies are (i) design-bid-build, (ii) construction manager at risk (CMAR), (iii) design-build, and (iv) negotiated general contractor. Regardless of the type of project delivery, geotechnical information is presented in the geotechnical reports that should become part of the contract documents and should provide a clear basis for development of project cost and schedule. 11.6.1.1 Design-Bid-Build The conventional design-bid-build delivery method includes engaging the design team to provide all contracting documents prior to construction bid. The geotechnical information for design-bid-build delivery methods is typically presented in the final geotechnical reports that are described in this chapter. This type of project delivery is more appropriate if uncertainty in geotechnical site conditions is relatively high and insufficient subsurface information exists to pursue a design-build contract. 11.6.1.2 CMAR CMAR is a method for delivering the project within a guaranteed maximum price. The CMAR typically fills the role of the owner with the owner’s best interest in mind. The CMAR manages and controls the construction costs to not exceed the guaranteed maximum price. Therefore, any cost exceedances that are not the result of changes in contract conditions are the financial liability of the CMAR. The guaranteed maximum price is based on the contract documents at the time of the guaranteed maximum price with reasonable assumptions and contingency. Any changes in the contract conditions may trigger a change order. This project delivery method is based on the construction documents and specifications; geotechnical reports are part of contract documents. The geotechnical information for this project delivery method is collected during the preliminary and final design (similar to conventional design- bid-build projects). 11.6.1.3 Design-Build Most state agencies are moving toward the design-build method of delivery. The design-build is a contract with one responsible party (i.e., design-build contractor). This type of contract reduces the project schedule by combining the design and construction phases and optimizes the financial risks to the project owner by sharing the risks among the owner and the design-build contractor. The state agencies’ design- build procurement process requires that the bidder commit to a firm fixed price before the design is complete. For this type of contract, the geotechnical information can be presented in definition phase, preliminary design phase, and final design phase. Ideally, the bidders require sufficient subsurface information to produce conceptual designs for the foundation, embankment, and other features of work that are dependent on the geotechnical conditions (Gransberg and Loulakis 2012). Insufficient information would result in either higher initial bid or too much risk for the contractor to bid on the project, which negatively affects the contracting process. As described earlier, the geotechnical information for design- build delivery methods is presented typically in GDR, GBR, and GDM.

249 11.6.1.4 Negotiated General Contractor For negotiated general contractor delivery method, the owner selects the most qualified contractor. The final construction cost will be provided as either cost plus a markup or guaranteed maximum price. The project cost for these delivery methods is also developed based on the contract document and geotechnical reports. 11.6.2 Contractor Briefings Pertinent geotechnical information and the risks allocated to the contractors are typically set and described in the geotechnical reports such as GBR or final geotechnical reports. This information is part of the contract documents or becomes available to the contractors. Also, informational meetings for potential contractor’s teams are commonly held to disseminate more information about the project and the procurement process. These meetings provide opportunities for questions and discussions that will strengthen the partnership and communication between the state agencies, design teams, and contractors and will help the contractors develop a realistic understanding of the subsurface conditions during the bid process. 11.6.3 Legal Implications Because the geotechnical reports are being included as part of the contract or presented to the contractors for information, it is recommended that a contract clause be included to state the limitations and applicability of the presented geotechnical information. Despite including disclaimers and exculpatory clauses in the contracts for use of boring logs and information obtained during the design, the court system believes that contractors can rely on the geotechnical information available to bidders (Essex 2007). Due to frequent litigation and escalating construction costs, owners and the construction industry were motivated to adopt approaches for dispute resolution and use of the DSC clause, which is detailed below. Therefore, there has been a greater need for clear contract stipulations regarding the purpose of the information and the obligation of the contractor to draw his own conclusions. Developing the GBR, as described by Essex (2007), was an important step to balancing the risk allocated to state agencies and contractors. 11.6.4 Differing Site Conditions Clause The DSC clause was originally developed to remove some of the risk associated with subsurface conditions from the bidding process and, thereby, reduce bid prices. Without the DSC clause, the owner would allocate all the risk to the contractor, which results in higher contractor contingency costs for adverse conditions, whether the adverse conditions were actually encountered or not. Use of DSC clauses in federally funded construction contracting is encouraged. A DSC clause is a contract clause designed to give a contractor cost and time relief for (i) subsurface or other physical conditions encountered at the site that differ from those indicated in the contract or (ii) unknown physical conditions of an unusual nature that differ from those commonly encountered. The DSC clause is a standard clause in a contract that involves subsurface construction. Under 23 Code of Federal Regulations (CFR) 635.109 Standardized Changed Condition Clause by the 1987 Surface Transportation and Uniform Relocation Assistance Act, the FHWA mandates the use of a DSC clause on federal-aid highway projects. The FHWA does not mandate the DSC clause for design-build projects (Gransberg and Loulakis 2012). Instead, it encourages state agencies to use the clause when appropriate for the risk and responsibilities that are shared with the design-builder. More information about the DSC is presented in Essex (2007).

250 Chapter 11 References Essex, R.J. 2007. Geotechnical Baseline Reports for Construction, Suggested Guidelines. The Technical Committee on Geotechnical Reports of the Underground Technology Research Council. ASCE, Reston, Virginia. FHWA 2003. Checklist and Guidelines for Review of Geotechnical Reports and Preliminary Plans and Specifications. FHWA ED-88-053, Federal Highway Administration, Washington, DC. FHWA. 2010. Drilled Shafts: Construction Procedures and LRFD Design Methods. NIH Course No. 132014 U.S. Department of Transportation Federal Highway Administration. May. Gransberg D.D. and M.C. Loulakis. 2012. Geotechnical Information Practices in Design-Build Projects, a Synthesis of Highway Practice. NCHRP Synthetics 429. Transportation Research Board, Washington, DC. New York State DOT. 2013. Geotechnical Design Manual. New York State Department of Transportation.