clemente 2015 geo characterization - bechtel

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Geo-Characterization of Brownfield Site for Modernization of a Large Industrial Facility

About Bechtel Bechtel is among the most respected engineering, project management, and construction companies in the world. We stand apart for our ability to get the job done right—no matter how big, how complex, or how remote. Bechtel operates through four global business units that specialize in infrastructure; mining and metals; nuclear, security and environmental; and oil, gas, and chemicals. Since its founding in 1898, Bechtel has worked on more than 25,000 projects in 160 countries on all seven continents. Today, our 58,000 colleagues team with customers, partners, and suppliers on diverse projects in nearly 40 countries.

Refer to http://ascelibrary.org/doi/abs/10.1061/9780784479087.059 for published paper

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Geo-Characterization of Brownfield Site for Modernization of a Large Industrial Facility

José LM Clemente1, Ph.D., F.ASCE, D.GE, P.E; Dena G Morgan2, P.E.;

and Michael R. Lewis3, F.ASCE, P.E.

1Chief Engineer, Geotechnical & Hydraulic Engineering Services (G&HES), Bechtel Power Corporation, 5275 Westview Drive, Frederick, MD 21703; [email protected] 2Sr. Engineer, G&HES, Bechtel Power Corporation, 5275 Westview Drive, Frederick, MD 21703; [email protected] 3Corporate Geotechnical Engineering Lead and Geotechnical Engineering Manager, G&HES, Bechtel Corporation, 5275 Westview Drive, Frederick, MD 21703; [email protected]

ABSTRACT: A multi-phase subsurface investigation (SI) program was performed to provide geo-characterization of a brownfield site for the modernization of a large industrial facility. During the planning and implementation of the sitewide SI, the following factors were considered: (1) facility/structure loading, geometry, and function; (2) site subsurface conditions disclosed by multiple previous SI programs; (3) field testing methodology, (4) new and revised geohazard evaluation criteria; and (5) funding and schedule constraints. The adopted SI program planning and implementation approach/philosophy is described, and the work carried out for one specific structure is used for illustration. The benefits of the SI approach in mitigating subsurface risk in a cost effective manner is demonstrated. Lessons learned that could be useful to practitioners confronted with site geo-characterization for large-scale projects are discussed. The focus of this manuscript is on the geotechnical aspects of the site; environmental considerations are not addressed. INTRODUCTION The benefits of adequate geo-characterization in the successful completion of projects in various industries have been discussed in literature, e.g., Lewis et al. (2009), Temple and Stukhart (1985), and Whyte (1995). Similarly, there are published accounts of the negative effects of inadequate subsurface investigations on project cost and schedules (Goldsworthy et al. 2004, ICE 1991). Goldsworthy (2006) presents a probabilistic study of the relative benefits of undertaking subsurface investigations with increasing and differing scopes. There are currently numerous documents that describe SI items and establish minimum guidelines for SI programs. Some of these documents have wide application, e.g., ASCE (1976), USACE (2001), and some are geared toward specific industry segments such as (1) dams and hydroelectric projects (FERC 1991, USBOR


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2004), (2) power plants and other nuclear facilities (IAEA 2004, NRC 2003), and (3) transportation projects (FHWA 1997 and 2002, NYDOT 2013). The multi-phase SI program for geo-characterization of a brownfield site is used to illustrate the attributes of a good site geo-characterization program for a mega-project ($2 billion plus project cost). Brownfield is used here to designate a previously developed site with existing facilities, as opposed to an undeveloped (greenfield) site. While environmental issues were present, they did not affect the part of the site (Structure A site) that is described in this paper. A summary of the desired attributes of a good site geo-characterization program (Lewis et al. 2009) is presented, followed by a description of one structure (Structure A) that is used for illustration. A brief description of the sitewide conditions for the mega-project, and more specifically for Structure A, is presented. The geo-characterization of the Structure A site is then described within the context of the desired attributes of a good site geo-characterization program, taking into account historical site subsurface data, foundation performance requirements, current day investigation tools and procedures, and state-of-the-practice methods of subsurface data interpretation. Challenges arising from schedule and budget constraints and foundation design changes, based on limited subsurface data, are discussed and were used to develop lessons learned. Despite these challenges, design and construction of Structure A was successfully completed, and a settlement monitoring program was implemented to track the performance of the foundations. The multi-phase geo-characterization program for Structure A, which generally mimicked the sitewide geo-characterization, resulted in substantial foundation savings to the project. ATTRIBUTES OF A GOOD GEO-CHARACTERIZATION PROGRAM For a geo-characterization program to be as successful as possible, it must be tailored to the specific project under consideration and must be sufficiently flexible to adapt to changing conditions as they are encountered. A general approach consists of phasing the investigation and employing the observational method principles described by Peck (1969).

A successful geo-characterization program for a greenfield site is generally done in five phases (Lewis et al. 2009): (1) reconnaissance, (2) proposal or preliminary design, (3) detailed design, (4) construction, and (5) post-construction monitoring. Each phase has a specific purpose and can vary considerably, given the specific project conditions. The reconnaissance phase (Phase 1) is generally done for planning purposes and feasibility studies. The effort generally entails researching the site and surrounding area by reviewing historical reports, topographic maps, geologic maps, soil surveys, aerial photographs, field visits, and performance surveys of existing structures. The proposal or preliminary design phase (Phase 2) may include only the reconnaissance phase, but it could also include a limited field exploration with widely spaced boreholes, cone penetration testing (CPT) soundings, and geophysical tests. It can include some limited laboratory testing and simplified analyses for conceptual design and/or cost estimating purposes. It is the authors’ opinion that seismicpiezocone soundings should be performed whenever cone soundings are specified. The cost/benefit ratio is so high that it is uneconomical not to do so.


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The detailed design phase (Phase 3) is where the bulk of the characterization program is performed. It includes detailed field exploration, such as sample boreholes (standard penetration test [SPT] and intact samples); CPT, dilatometer, and pressuremeter soundings; field vane shear testing; geophysics; and laboratory testing. Depending on the size of the project and the complexity of the subsurface, this phase may be subdivided into additional phases, such as in the case used for illustration here. Phases 1, 2, and 3 should be carried out on every project. The inclusion of Phase 4 (construction phase) and Phase 5 (post-construction monitoring phase) depends on the success of the initial program and on any scope changes or unknown subsurface conditions encountered during construction. For the case that will be used for illustration here, no Phase 4 investigation was required. However, a settlement monitoring program was established during construction and continued through post-construction (Phase 5). Results of settlement monitoring will be summarized and discussed. A critical part of this and any investigation program is continuous data evaluation and communication with the decision makers who manage the effort. It cannot be emphasized enough that a good exploration program requires changes to adapt to the conditions that are encountered in real time. It is therefore imperative that the geotechnical engineer and/or geologist managing the program stay in constant contact with the project manager. In other words, expect the unexpected, and ensure the program has provisions for managing risk. This is where the overall project manager must understand the fundamentals of the program and have the ability to communicate in an effective way to the ultimate decision makers and/or client. STRUCTURE A Structure A consists of a new building with a footprint measuring about 40 x 240 m. The length of the building (240 m) is oriented north-south, and the building is located near the northwest corner of the site. Minor demolition of existing structures had to be performed prior to construction of Structure A. Figure 1 shows the outline of Structure A in its initial (dashed lines) and final, as-built configuration (solid lines). Figure 1 includes other information that will be discussed later in this paper. Structure A is about 30 m high with no basement. A gantry crane operates along most of the length of the building, and the crane rails are located about 12 m above the floor level. The crane rails end about 20 m to the north of the southern end of the building. Also, most of the floor loads are located to the north of this 20 m zone. Strict settlement criteria had to be followed during foundation design for Structure A to ensure proper operation of the gantry crane and other equipment. Even though Structure A is very large, there were four other structures built on-site with a footprint measurement of about 25 x 600 m each. Significant demolition of existing structures built from the 1950s onward had to be performed prior to construction of these four structures. Structure A (and associated equipment) was built at a cost estimated to be more than $100 million, and it is one of many new structures built at the site. The overall project cost is estimated to be over $2 billion.


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SITE CONDITIONS Site Description The industrial facility is located in a valley at a site measuring about 600 (east-west) x 1,100 m (north-south). Creeks running west to east serve as the northern and southern site boundaries. A third, smaller creek is located on the west side of the site, runs north to south for about 900 m, and discharges into the creek that serves as the southern site boundary. Roads aligned in a north-south direction serve as the western and eastern site boundaries. A river located farther east discharges into a fjord-like feature. The site is located about 100 km away from the ocean. The site is mostly flat with generally small grade differences (on the order of a few meters) along its northern end. The side slopes of the valley rise sharply on the west side of the site, and shallow rock is often exposed on these slopes. Historical pre-construction site grades from the 1950s in the area of Structure A ranged from about El. 18.0 m in the southeast to about El. 21.0 m in the northwest. Existing site grades immediately before construction of Structure A (final location shown in Figure 1) ranged from approximately El. 15.3 m in the south to 22.3 m in the north. These values suggested previous cuts at the final location of Structure A. Site grading for construction of new Structure A required cuts and fills to create a flat platform at El. 18.0 m. Cuts ranged from 0.0 m at the cut-fill line to about 4.3 m at the northern end of the platform. Fill ranged from 0.0 m at the cut-fill line to about 2.7 m at the southern end of the platform. Figure 2 shows a subsurface profile through the length of Structure A (final location shown in Figure 1) and also illustrates the site grading requirements for construction of this structure. Figure 2 also includes additional information that will be discussed later in this paper. Most of the existing facilities built from the 1950s onward were located about 250 to 300 m south of the northern site boundary. Subsurface and Groundwater Conditions The shallow rock surface exposed on the slopes at the western side of the site dips sharply toward the east beneath the site. The depth to the top of bedrock reaches as much as 110 m below existing grade. Some glacial till, but predominantly alluvial Holocene soils, are encountered above the bedrock. The alluvial Holocene soils generally consist of two primary layers comprising granular materials (Layer I) and fine-grained materials (Layer II). The granular materials consist of sand and gravel and overlie the fine-grained layer. Layer I is thicker near the creeks at the south and north ends of the site, measuring more than 50 m. Elsewhere, it is thinner, measuring only up to 7 m thick. The fine-grained materials consisting of silt and clay layers are present beneath Layer I. There are occasional instances where zones of predominantly silty material are sandwiched within Layer I at a relatively shallow depth. Layer II extends to glacial till (implied where rock was not cored) or bedrock.


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A west-east subsurface profile is shown in Figure 3. This profile extends for a great distance from the eastern edge of Structure A (final location shown in Figure 1) and illustrates the general subsurface conditions throughout the site, including Structure A. Note that not all boreholes used in Figure 3 are shown in Figure 1. Groundwater levels are generally flat throughout most of the site and are located within a few meters of the ground surface. Groundwater contours tend to reflect the site topography and rise along the slopes on the western side of the site. Groundwater levels at the Structure A area range from El. 9.5 m (south) to 16.5 m (north), i.e., about 6 m below existing grade. GEO-CHARACTERIZATION PROGRAM FOR STRUCTURE A Several of the five phases of a good geo-characterization program were implemented for the site, particularly Structure A. Structure A was selected for illustration because geo-characterization for this building site also included useful lessons learned. The reconnaissance phase (Phase 1) consisted primarily of reviewing historical geotechnical reports and topographic maps to understand previous site grading operations. Historical settlement monitoring results dating back to the 1950s were also available. Most of this effort was performed by a geotechnical consultant working for the owner, and some information was gathered directly from the owner. A major effort was conducted in summer/fall 2007 to select the location of Structure A. It was known from historical subsurface data, settlement monitoring data, and foundation performance requirements that special care was required in the selection of a site location and foundation system for Structure A. Based on historical subsurface data, the location near the northwestern corner of the site was selected. This location is shown as initial location in Figure 1. A Phase 2 SI was then implemented in fall 2007 to obtain additional data to supplement the available historical data in the initial location of Structure A shown in Figure 1. The 2007 SI consisted of a limited number of Becker hammer boreholes. Becker hammer boreholes were selected by the consultant because of the presence of gravel in Layer I that tended to affect SPT hammer blow counts. The Becker hammer boreholes drilled in 2007 in the vicinity of Structure A are designated by BK07 in Figure 1. Only the Becker hammer boreholes drilled in 2007, plus the Becker hammer borehole BOC/BPT98-02 drilled in 1998, contained detailed subsurface information, including hammer blow counts and descriptions of subsurface materials. Historical boreholes usually provided limited stratigraphic information only. The stratigraphy above the bedrock indicated the presence of silt/clay pockets within the sand/gravel layer in two of the Becker hammer boreholes drilled in 2007, similar to what is shown for SPT borehole B10-01 in Figure 2. Considering the dimensions of the footprint of Structure A, it was apparent that an additional SI would be required for detailed design (Phase 3).


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Based on the available information, it was decided that Structure A would be supported on piles consisting of thick-walled, open-ended pipes driven to rock and complemented by a rock socket. The cost of these piles was estimated to be about $12 million. This pile system was selected to resist static and operational loads as well as loads arising from possible liquefaction of the Layer I granular materials. Installation risks associated with this foundation system were mostly related to length of piles (depth to bedrock) and constructability issues related to driving pipes through potential cobbles/boulders to the sloping bedrock surface. The silt/clay pockets were of no significance for pile design. The installation risks were deemed acceptable, pile bids were invited, a piling contractor was selected, and pipes were ordered in spring 2008. A draft geotechnical data report for the SI performed in 2007 was issued by the consultant in January 2008, and a draft interpretive geotechnical report was issued in June 2008. Bechtel reviewed and offered comments on both reports before they were finalized. These events eliminated the need for a Phase 3 (detailed design) SI until the owner decided to have a third-party review of the interpretive geotechnical report. The third-party reviewer suggested that the soils beneath the proposed footprint of Structure A could be improved (densified) using vibro-replacement (stone columns) at a fraction of the cost of piling. As a result, the piling contract was cancelled, and the stone column option was pursued under a very tight schedule. Because the presence of silt/clay pockets could be significant for a foundation system supported by stone column–improved ground, a detailed SI was recommended. This Phase 3 investigation was performed at the end of summer 2008 and included probe borings (no sampling) to determine the depth to bedrock, additional Becker hammer boreholes, and CPT soundings. The 2008 Becker hammer boreholes are designated by BK08 in Figure 1, and the CPTs are designated by CPT08. The locations of probe borings are shown in Figure 1, but the probe borings are not labeled. The 2008 SI results indicated that the silt/clay pockets detected in two of the 2007 Becker hammer boreholes are actually widespread. The southern half of the footprint of Structure A (initial location in Figure 1) is underlain mostly by thick deposits of loose silts and soft clays, which rendered unfeasible the use of stone columns alone. An alternative preloading scheme was recommended by the geotechnical consultant that would be less expensive than piles. However, the consultant could not conclusively state the foundation system built on the preloaded soils would meet the performance requirements. Also, preloading (with wick drains) would result in at least a 6 month construction delay to allow consolidation to occur. Owner-funding constraints (not specifically related to this program) forced construction to be halted near the end of 2008. This provided additional time to revisit the foundation approach for Structure A. Historical subsurface data suggested that conditions farther north of the initial location of Structure A, closer to the northern site boundary creek, consisted essentially of Layer I granular materials and minimal to no Layer II silts/clays. It was proposed to move the building farther north so that the entire footprint of Structure A would be supported essentially by Layer I granular materials. Before any such decision could be made, another Phase 3 SI was performed at the final location of Structure A shown in Figure 1, and the necessary foundation analyses were carried out to justify the change.


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A Phase 3 (detailed design) SI was conducted in 2010 at the final location of Structure A shown in Figure 1. The 2010 SI employed state-of-the-practice investigation tools and consisted of SPT boreholes, designated by B10 in Figure 1, and laboratory testing. Two spectral analysis of surface wave (SASW-10 and SASW-12) tests and one downhole geophysical test (at B10-04) were performed within the footprint of Structure A to provide profiles of shear wave velocity for SHAKE (Schnabel et al. 1972) analysis for liquefaction assessment. SPT hammer blows were measured for every 25 mm of penetration to allow for N-value adjustments in case large gravel pieces affected the results. The SPT hammer efficiency was also measured to allow adjustment of N values for hammer efficiency. Accurate N-value measurements were needed to predict liquefaction-induced settlements (Ishihara and Yoshimine 1992). The 2010 investigation disclosed mostly granular soils throughout the footprint of Structure A (final location shown in Figure 1), except for SPT boreholes B10-01 and B10-48, which showed zones of loose sand and silts. The loose zone in B10-01 can be seen in the subsurface profile shown in Figure 3. Static settlement calculations indicated that the foundations for the structure and floor slabs could be built directly on the existing soils at the final location shown in Figure 1, with some soil remediation being recommended near the south end of Structure A. The recommended remediation consisted of removing the top 3 m of existing soils within a 60 x 60 m square at the south end and extending 10 m outside the building footprint. The removed soils were to be replaced by compacted structural fill. Deeper excavation and removal of existing soils was not attempted because of groundwater conditions, and static settlement calculations indicated that deeper excavations would not be needed to meet foundation performance requirements. A state-of-the-practice liquefaction assessment was conducted that included post-liquefaction settlement calculations. Details of this assessment are not presented here, but calculated maximum post-liquefaction settlements ignoring depth factor were estimated to be about 25 mm throughout most of the footprint of Structure A, except for a small zone near the southwest corner of the building. Based on these results, it was decided that no ground densification would be performed for Structure A. Even though no construction (Phase 4) SI was required, removal of the existing soils and replacement with compacted structural fill was observed full time by a resident geotechnical engineer. A resident geotechnical engineer also witnessed all field investigation phases. A settlement monitoring program was established during construction and continued through post-construction (Phase 5). Settlement monitoring points were installed at selected building columns along the eastern and western sides of the building. Figure 4 shows settlement monitoring results in April 2014, several months after completion of Structure A. Figure 5 presents settlement vs. log time for several points near and at the south end of the Structure A where settlements are the highest due to the underlying softer soils left in place. Settlement marker #1 is located at the southwestern corner of the building, and markers #2 and #3 are located north of marker #1 along the western wall of the building. Settlement marker #24 is located at the southeastern corner of the building, and markers #23 and #22 are located north of marker #24 along the eastern wall of the building.


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FIG. 4. Settlement profiles along the eastern and western sides of Structure A. Structure A is complete and full structural loads have been applied. The settlement monitoring results to date indicate the following: • Settlements are less than 10 mm for about 200 m, and then they become

increasingly larger toward the south end of the building (Figure 4). • The two settlement profiles shown in Figure 4 are very similar and indicate

negligible differential settlement in east-west direction, i.e., between the eastern and western sides of the building, except at the south end of the building where the differential settlement (east-west) is about 16 mm over 40 m (1/2,500).

• Settlements increased suddenly between June and October 2013 (300 days<t<600 days), as shown by the data in Figure 5. The sudden increase is more pronounced on the western side of the building. It is noted that these movements were also observed on the crane rail inside the building, thus ruling out possible survey errors. The exact cause of this sudden increase could not be determined, but the authors believe that temporary loads, e.g., stockpiling of material/equipment being used during construction were applied at this end of the building.

• The settlement of marker #24 (56 mm) shown in Figures 4 and 5 exceed the prescribed limit of 50 mm. Also, the settlement trend in Figure 5 suggests that additional settlements should be expected at the south end of the building. This required adjusting the crane rails to accommodate the measured settlement.

• Monitoring is expected to continue throughout construction, and the information will be used to make any additional adjustments to Structure A.

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Despite some of the difficulties experienced throughout the planning, design and construction phases of Structure A, the effort and expense put into implementing an adequate SI resulted in substantial savings.

FIG. 5. Settlement vs. time plots for selected settlement markers (Structure A).

LESSONS LEARNED A few lessons learned related to the geo-characterization program for Structure A (and the overall site as well) are described in the next bullets. • Design Changes: On many projects, but mega projects in particular, design change

is inevitable. On many large and complex projects the site layout is not frozen in the early stages. Thus, change throughout the exploration phase is somewhat routine. The program must have contingency (budget and schedule) built in to handle these inevitable changes.

• Adequate Data: If changes do occur, they require adequate subsurface data and supporting analysis to validate the decision. In other words, a change should never be made based on limited subsurface data that leave unanswered questions about the feasibility of the proposed change. This is particularly true when the decision is made under schedule pressure.

• Unanticipated conditions: No site is uniform enough that surprises don’t occur. Thus, the program needs to be flexible enough, including adequate budget and schedule float, to handle these inevitabilities. This also includes potential changes in exploration and testing methods. Unanticipated conditions also develop during

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construction. In the case of Structure A, a sudden increase in settlement was observed that required adjustment of the crane rails inside the building.

• Communication flow: Establish the communication flow prior to implementing the program in the field. All parties need to understand the project structure and the decision-making process before the work begins. Typically, pre-job briefs/meetings help solve these issues. However there can’t be too much communication.

• Scope freeze: At some point the overall scope must be frozen in order to complete the work. There always may need to be a scope change later or even during the original program, but from a contract perspective there needs to be finality such that final data is the outcome.

• Seismic piezocone soundings: Over the years we have come to utilize the piezocone penetrometer (CPTu) with more and more regularity. However, it’s only in the last 15 years or so when it has become routine to include the seismic piezocone (SCPTu). Our experience suggests that use of the SCPTu should be the standard on every project, large or small. The difference in cost is outweighed by the usefulness of the acquired data. SCPTu was not used at the Structure A location because of difficulties penetrating through the sand/gravel profile, but it was widely used at other parts of the site where the sand/gravel layer was underlain by the silt/clay layer.

CONCLUSIONS The attributes of a good site geo-characterization program are described, and implementation of such a program for a mega-project is discussed, using one structure for illustration purposes. A multi-phase SI program was implemented that incorporated existing/historical information from previous investigations as well as state-of-the-practice tools and procedures. Difficulties associated with changes of foundation system are discussed and lessons learned are highlighted. Results of these investigations along with state-of-the-practice analyses of static and post-liquefaction settlements yielded a cost-effective foundation system for the structure. A construction and post-construction settlement monitoring program provided data to allow for adjustments to be made to crane rails inside Structure A. Overall the multi-phase SI program provided data for layout and foundation optimization that resulted in substantial savings to the project. REFERENCES ASCE (American Society of Civil Engineers) (1976). “Subsurface investigation for

design and construction of foundations of buildings.” Manuals and Reports on Engineering Practice No. 56, New York, NY, 61 pp.

FERC (Federal Energy Regulatory Commission) (1991). “Geotechnical investigations and studies.” Ch. 5 in Engineering Guidelines for the Evaluation of Hydropower Projects, Washington, DC, http://www.ferc.gov/ industries/hydropower/safety/guidelines/eng-guide/ chap5.PDF.


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FHWA (Federal Highway Administration) (1997). “Subsurface investigation.” Participant’s Manual for NHI Course No. 13231-Module 1 (FHWA HI-97-021), McLean, VA, 314 pp., http://isddc.dot.gov/OLPFiles/FHWA/007919.pdf.

FHWA (Federal Highway Administration) (2002). “Subsurface investigation – geotechnical site characterization.” Reference Manual for NHI Course No. 132031 (FHWA NHI-01-031), McLean, VA, 332 pp., http://isddc.dot.gov/ OLPFiles/FHWA/012546.pdf.

Goldsworthy, J.S. (2006). “Quantifying the risk of onsite investigations.” Ph.D. Thesis, University of Adelaide, Australia, 536 pp.

Goldsworthy, J.S., Fenton, G.A., Griffiths, D.V., Jaksa, M.B., Poulos, H.G., and Kaggwa, W.S. (2004). “Cost of foundation failures due to limited site investigations.” Proc. Int. Conf. Structural and Foundation Failures, Singapore: 398-409.

IAEA (International Atomic Energy Agency) (2004). “Geotechnical aspects of site evaluation and foundations for nuclear power plants.” Safety Guide No. NS-G-3.6, Vienna, Austria, 67 pp.

ICE (Institution of Civil Engineers) (1991). Inadequate Site Investigation, prepared by the Ground Board, Thomas Telford, London, England, 32 pp.

Ishihara, K., and Yoshimine, M. (1992). “Evaluation of settlements in sand deposits following liquefaction during earthquakes.” Soils and Foundations, 32 (1): 173-188.

Lewis, M.R., Arango, I., and McHood, M.D. (2009). “Site characterization philosophy and liquefaction evaluation of aged sands.” Bechtel Technology Journal, San Francisco, CA, 2 (1): 183-197.

NRC (U.S. Nuclear Regulatory Commission) (2003). “Site investigation for foundations of nuclear power plants.” Regulatory Guide 1.132, Rockville, MD, 21 pp., http://pbadupws.nrc.gov/docs/ML0327/ML032790474.pdf.

NYDOT (New York State Department of Transportation) (2013). Geotechnical Design Manual, Albany, NY, https://www.dot.ny.gov/divisions/engineering/ technical-services/geotechnical-engineering-bureau/gdm.

Peck, R.B. (1969). “Advantages and limitations of the observational method in applied soil mechanics.” Géotechnique, 19 (2): 171-187.

Schnabel, P.B., Lismer, J., and Seed, H.B. (1972). “SHAKE: A computer program for earthquake response analysis of horizontally layered sites.” Report No. UCB/ EERC72-12, University of California, Berkeley, CA, 102 pp.

Temple, M.W.B., and Stukhart, G. (1985). “Cost effectiveness of subsurface investigations.” J Management in Engineering, ASCE, New York, NY, 3 (1): 8-19.

USACE (U.S. Army Corps of Engineers) (2001). “Geotechnical investigations.” EM 1110-1-1804, Washington, DC., http://www.usace.army.mil/inet/usace-docs/.

USBOR (U.S. Bureau of Reclamation) (2004). Guidelines for Performing Foundation Investigations for Miscellaneous Structures, Denver, CO., http://www.usbr.gov/pmts/ client_service/recent/reportfoundation.pdf.

Whyte, I.L. (1995). “The financial benefit from site investigation strategy.” Ground Engineering, 10: 33-36.

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