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Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
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Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
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Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
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Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
×
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Page 32
Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
×
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Suggested Citation:"Chapter Four - Case Examples ." National Academies of Sciences, Engineering, and Medicine. 2016. Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns. Washington, DC: The National Academies Press. doi: 10.17226/21926.
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29 chapter four CASE EXAMPLES The survey results presented in chapter three were used to select five agencies for further examination. The agencies were primarily identified based on responses that indicated agency success in reducing claims, change orders, and overruns result­ ing from subsurface conditions. The agencies selected were Indiana, Florida, Minnesota, Washington State, and South Carolina DOTs. For each agency, the geotechnical engineer survey contact was interviewed and agency documentation was reviewed to identify how agency practice has reduced claims, change orders, and claims due to subsurface conditions. FLORIDA DEPARTMENT OF TRANSPORTATION In the survey, Florida DOT (FDOT) indicated that recent changes to site characterization practices had led to a notice­ able decrease in the occurrence of claims, change orders, and overruns. The changes in site characterization practices noted in the survey included increasing boring frequency for highly variable sites, performing borings at locations of every non­ redundant drilled shaft, and requiring more accurate surveying for boring locations. Based on information from the agency interview, each revision has been successful in reducing a particularly problematic type of claim that the DOT had pre­ viously been experiencing. Drilled Shafts in Extremely Variable Geology During construction of an elevated portion of the Lee Roy Selmon Crosstown Expressway in Tampa in 2004, one of the bridge piers suddenly sank more than 10 ft (Graham et al. 2013). The karstic limestone geology in central Florida is noto­ riously variable, with depths to competent rock varying signifi­ cantly. Based on a boring that was approximately 8 ft from the failed shaft location, the shaft would have been socketed 2 ft into hard material with standard penetration test (SPT) blow counts of 50 blows for less than 2 in.; however, coring through the shaft after failure indicated more than 10 ft of soft material below the shaft (L. Jones, Florida Department of Transpor­ tation, Tallahassee, personal communication, May 2015). Similar, but far less extreme, problems were encountered for other piers on the project, which were eventually retrofitted with micropiles and “sister” drilled shafts as documented by Graham et al. (2013). In response to the Lee Roy Selmon project and other proj­ ects with contractor claims of differing conditions for drilled shafts, FDOT implemented stricter requirements for founda­ tion subsurface investigation (FDOT 2015): • Bridge boring locations must be surveyed. • One boring is required at the location of every non­ redundant drilled shaft. • At variable sites or sites in karstic areas, two borings are required for each nonredundant shaft larger than 8 ft in diameter. These areas include “known variable geo­ logic areas and those determined to be (difficult to pre­ dict based on other borings) variable during the subsoil exploration program.” • Also at variable sites, all shafts (including redundant shafts) must be within 20 ft of a boring location. FDOT indicated in the agency interview that the revi­ sions have led to considerably fewer claims for drilled shaft excavations, although detailed quantitative information is unavailable. Earthwork FDOT has historically encountered frequent claims from con­ tractors having to excavate more unsuitable material (e.g., highly plastic clays, and organic material) than indicated by contract borings. The unexpected unsuitable material problem was frequently encountered for retention pond projects; often when problems were encountered, grout mounds indicating the actual boring location would be observed far from the intended boring location and outside the limits of the pond excavation. When a retention pond excavation was begun, the improperly located borings frequently resulted in surprises. The extent of the issue was significant, requiring additional excavation on the order of acre­ft. To resolve this, FDOT began requiring pond borings to be located by handheld Global Positioning System survey with an accuracy of ±10 ft and increased the boring fre­ quency to 1 per 40,000 ft2 of pond surface area. The changes have resulted in significantly fewer earthwork claims, although detailed quantitative information is unavailable. The agency has made other similar adjustments to its Soils and Foundations Handbook (FDOT 2015) to reduce earth­ work claims. For example, the manual requires retention pond plan sheets to show shallow hard materials with rock patterning to indicate materials that cannot be excavated with a typical backhoe. In addition, the manual requires materials

30 encountered in pond borings to be assigned different strati­ graphic units from materials encountered in roadway bor­ ings to prevent claims associated with a contractor assuming pond material could be used as embankment fill or pavement subgrade. The pond material is typically too soft for such applications, even when the pond material classification is the same as material encountered in the roadway borings. Florida DOT: Lessons Learned The reduction in claims experienced by FDOT provides two valuable lessons. First, boring information is only as good as its location information, especially at sites where spatial variabil­ ity is significant. Having accurate boring location information was helpful in reducing claims associated with foundations as well as earthwork. Second, targeted subsurface investiga­ tion practices such as increasing boring location accuracy and increasing boring frequency for specific problematic design elements can effectively address specific subsurface claim, change order, or cost overrun issues. Focused efforts such as those implemented by FDOT are likely easier and less costly to implement than across­the­board measures. SOUTH CAROLINA DEPARTMENT OF TRANSPORTATION Based on responses to Part Two of the survey, subsurface con­ ditions claims, change orders, and cost overruns are a recog­ nized problem and priority concern for South Carolina DOT (SCDOT). In the agency interview, SCDOT indicated that it addressed concerns regarding subsurface claims, change orders, and cost overruns by implementing a new Geotechni- cal Design Manual (2010), which has resulted in a general decrease. The manual and its effect on claims, change orders, and cost overruns is detailed in the following sections. Geotechnical Design Manual SCDOT first published its Geotechnical Design Manual in 2008 (SCDOT 2010). Prior to its publication, the agency had rule of thumb guidelines for subsurface investigation; however, the guidelines were not enforceable and subsurface investigation decisions were left to the engineer of record on a project­by­project basis. Chapter four of the manual, “Subsurface Investigation Guidelines,” outlines requirements for two phases of investi­ gation, preliminary and final. The preliminary investigation includes collection of shear wave velocity data for use with the agency’s guidelines for seismic design as well as labo­ ratory testing associated with earthwork design (Standard Proctor tests and consolidated­undrained triaxial tests with pore pressure measurements on compacted specimens). The final investigation requirements vary with project type, as do the minimum testing requirements. For example, non­ redundant drilled shafts require one boring per shaft, two borings per bent multiple­shaft bents, and one boring per bent for driven pile bents. CPT and dilatometer tests (DMT) can be substituted for borings for up to half of the required locations. In the agency interview, SCDOT indicated that its projects frequently include multiple CPT soundings as supplemental information rather than for substitution. In the state’s Lowcountry Region and some additional counties the agency requires rotary wash boring methods. Other chapters of the manual also affect SCDOT site char­ acterization practices. In Chapter 7, “GeoMechanics,” the manual defines site variability levels based on the coefficient of variation of shear strength samples. The site variability level is considered when selecting geotechnical resistance factors, as outlined in Chapter 9. Effect on Claims, Change Orders, and Cost Overruns During the agency interview, SCDOT discussed the effect of its manual on claims, change orders, and cost overruns. In general, the manual has improved agency practice by providing stan­ dard minimum guidelines for subsurface investigation as well as technical background information to justify the subsurface investigation requirements. Specifically, the manual’s require­ ments have helped reduce several persistent types of claims, change orders, and cost overruns. One of the most significant decreases was for rock excavation for drilled shaft construc­ tion. The manual guidelines have resulted in better character­ ization of the strength and hardness of material to be excavated, which makes it easier for the contractor to select proper tool­ ing. The benefits have also carried over into embankment construction on soft soils. Because preliminary investigation requirements include characterization of subsurface materi­ als for earthwork designs, contractors have a better sense of whether soil close to the proposed embankment can be used for embankment construction or if a long­distance haul will be required to transport more appropriate borrow material further from the proposed embankment. The borrow material infor­ mation is also available earlier in the project cycle because of the preliminary investigation requirements. Finally, SCDOT noted that the manual has reduced instances of value engineer­ ing. Prior to the manual’s publication, contractors would fre­ quently do their own subsurface investigation and propose a value engineered design, especially for large projects. South Carolina DOT: Lessons Learned The experience of SCDOT illustrates the benefits of estab­ lishing standard minimum subsurface investigation and site characterization guidelines. The requirements result in con­ tractors being more prepared for the subsurface materials they will encounter at the project site, which has reduced incidents related to drilled shaft excavation and improved the accuracy of earthwork quantities for SCDOT. Publication of

31 standard practices for subsurface investigation and geotech­ nical design, including resistance factors that consider site variability, also produced design efficiencies, as evidenced by the reduction in value engineered projects. WASHINGTON STATE DEPARTMENT OF TRANSPORTATION Claims, change orders, and cost overruns attributed to sub­ surface conditions are not currently considered a significant problem for Washington State DOT (WSDOT), as noted in the agency’s survey response. However, the agency experi­ enced several projects with large geotechnical claims in the 1960s and 70s, prompting it to centralize major geotechnical work in the 1980s (Badger and Ybarra 2015). Further cen­ tralization occurred throughout the 1980s and 1990s, primar­ ily motivated by efficiency. Based on an interview with the agency, the resulting program has been effective at managing claims, change orders, and cost overruns attributed to sub­ surface conditions through a strategy that seeks to “minimize risk and balance cost as much as possible.” Agency Geotechnical Practice In addition to centralizing geotechnical operations in the 1980s, the agency modernized its drilling equipment to include, for example, rotary wash boring equipment and wireline casing advancers. The agency also uses track drills, skid drills, and barges to perform subsurface investigation in areas with lim­ ited access, which are frequently encountered in the state. The agency performs most of its own subsurface investigations, except when access is extremely difficult (e.g., a helicopter is required) or when specialized equipment such as a percussive hammer or rotary vibratory drill is necessary. Other than those exceptions, the agency’s subsurface investigation is internal, even when geotechnical design is external, which is the case for approximately one­quarter of all projects. WSDOT’s drill crews do not typically include a geologist or an engineer; instead, crew training is emphasized, and engineers and geol­ ogists examine all samples with borehole logging personnel (crew inspectors), resulting in a relatively active editing pro­ cess for boring logs. The benefits of in­house and centralized subsurface inves­ tigation were outlined by Badger and Ybarra in a presentation at TRB’s 94th annual meeting in January 2015. The presenters noted that subsurface investigation costs typically account for 50% to 80% of the total cost of geotechnical work. Keeping those expenses in house allows the agency to “closely moni­ tor costs and production,” and centralization of the work has benefitted the agency’s training efforts for drilling personnel. Agency subsurface investigation requirements are pre­ sented in the Geotechnical Design Manual (WSDOT 2014). The manual and the subsurface investigation requirements it includes are primarily organized by feature (e.g., Chapter 8 “Foundations,” Chapter 9 “Embankments,” etc.). The sub­ surface investigation requirements reference AASHTO’s LRFD Bridge Design Specifications (2014); however, the agency has supplemental requirements. For example, the manual notes one boring per drilled shaft may be necessary at sites with large boulders, karst, or mine voids. The man­ ual also requires establishing a well­defined groundwater regime with piezometer data for each drilled shaft founda­ tion location. Occasional Claims Although WSDOT’s site characterization practices have suc­ cessfully reduced claims, the agency still occasionally encoun­ ters differing site condition claims, because the amount of drilling that would be required to prevent all claims would be cost­prohibitive. Some of the occasional subsurface claims encountered by WSDOT included: • One of the more frequent issues encountered by the agency occurs when construction encounters soils that are more fine­grained than anticipated requiring, for example, more overexcavation for a retaining wall or shallow foundation. • Foundation and retaining wall construction is also asso­ ciated with claims, change orders, and cost overruns attributed to groundwater location. Overexcavation, a working platform, or pumping can be required when the construction groundwater location is different from that indicated by the subsurface investigation. The agency also indicated in the interview that dewatering claims are among the most costly of the subsurface condition claims encountered by WSDOT. • The most recent subsurface change order encountered by WSDOT involved a soil nail wall for which the contractor had to abandon shotcrete and move to verti­ cal elements because sand at the site was cleaner than anticipated. The project geology involves a braided stream channel; laboratory analysis of boring samples indicted 10% to 15% fines; however, field conditions are closer to 7%. Washington State DOT: Lessons Learned WSDOT’s reported success in limiting claims, change orders, and cost overruns attributed to subsurface conditions is evi­ dence of the importance of agency exploration and design guidelines, as well as the potential value of in­house, cen­ tralized drilling operations, including equipment capable of accessing all relevant investigation locations. The agency credits its drilling program, training of borehole logging per­ sonnel, and lab testing program for limiting claims, change orders, and cost overruns. The agency’s lab efforts for material characterization are especially significant in a state where fines contents frequently fall between 35% and 65%. Success aside, the occasional claims encountered by the agency are a

32 reminder that some claims, change orders, and cost overruns attributed to subsurface conditions are inevitable and that a target of zero claims is impractical. INDIANA DEPARTMENT OF TRANSPORTATION Indiana DOT (INDOT) was selected as a case example for several reasons. First, the agency has expressed interest in the synthesis topic as demonstrated by the research of Prezzi et al. (2011) and the presentation by Khan (2014), both described in chapter two. Second, INDOT’s survey response noted that changes in site characterization practice including implemen­ tation of LFRD, decreasing boring spacing, implementing new laboratory and field tests, increasing use of CPT, and introduction of several better technologies for compaction and ground improvement had led to a noticeable decrease in claims, change orders, and cost overruns. The agency interview identi­ fied how each of these practice changes had affected claims, change orders, and cost overruns. Based on the interview, the most significant changes and their effects are described in the following sections. Pavement Subgrade Change orders associated with subgrade preparation are one of the most significant sources of claims, change orders, and cost overruns attributed to subsurface conditions encountered by INDOT. The agency has addressed the problem through a series of specification and subsurface investigation revisions. One of the first specification revisions was to provide a formal definition for “unsuitable” material that might be encountered by a contractor during excavation of subgrade. Previously, the specifications included no definition of the term and con­ tractors would successfully file change orders as a result of this ambiguity. These change orders have been reduced since current specifications that provide moisture content­dry den­ sity criteria to define unsuitable have been adopted (INDOT 2014, 2016). More recent efforts to reduce change orders attributed to pavement subgrade include implementation of tighter speci­ fication language. Recent specification revisions have also been paired with the improvements to subsurface investiga­ tion practice summarized earlier, and the combined effect has been to reduce the number of change orders. INDOT’s subgrade specification previously allowed the contractor sig­ nificant flexibility in choosing subgrade options, which could include various forms of chemical modification, removal and replacement with aggregate, geogrid with aggregate, or conventional compaction techniques to achieve density and moisture requirements. Change orders frequently occurred when the option selected by the contractor did not stabilize the subgrade; for example, lime kiln dust would not stabi­ lize the soils encountered; therefore, the contractor would file a change order for the cost of substituting cement for kiln dust. To prevent this, INDOT has started collecting more sub surface information and has limited contractor subgrade options in the standard specifications (INDOT 2014, 2016). Based on available subsurface information for a given proj­ ect, some options that had been allowed for all projects are now only allowed by special provision (e.g., stabilization by lime and fly ash). In the agency interview, INDOT also emphasized the importance of internal agency communication and training associated with these revisions. Previously, engi­ neers developing roadway and paving plans were frequently unaware of what geotechnical information was available for a project. INDOT reported that as a result of training the same engineers now request a geotech report immediately upon starting any new roadway or paving project. Driven Piling Specification Revisions Although not directly related to subsurface investigation, one of the practice updates used by INDOT that was most effec­ tive in reducing claims was implementation of revised driven pile specifications. The pile driving specification changes predate the Prezzi report and the ten­year time period cov­ ered with the survey described in chapter three. In the late 1990s, the agency updated its driven pile specification to require pile driving analysis for most projects and Gates Formula for some smaller projects. Previously, the agency had used the Engineering News (ENR) pile driving formula and experienced significant costs associated with pile over­ runs and underruns. Since implementing the specification revisions, INDOT has experienced very few change orders related to pile overruns. Indiana DOT: Lessons Learned Perhaps the most important lesson provided by INDOT is that effective subsurface investigation practice is only success­ ful when it is coupled with effective specification language. Prescriptive specifications can find success when sufficient subsurface information is collected; alternatively, without sufficient subsurface information, project specifications may result in change orders when they include; for example, sub­ grade options that are incompatible with potential site soils. For INDOT, effective subsurface investigation practice requires including sufficient intra­agency training and com­ munication so that all designers know how to use geotechni­ cal information. MINNESOTA DEPARTMENT OF TRANSPORTATION Subsurface conditions claims, change orders, and cost overruns have decreased significantly for Minnesota DOT (MnDOT) according to results from Part Two of the survey.

33 Agency Practice MnDOT attempts to perform all subsurface investigations in­house, but uses subcontracts to complete approximately 20% of the work in order to accommodate agency workload limitations. MnDOT’s subsurface investigation guidelines are published in the agency’s 2013 Geotechnical Engineer- ing Manual (2013). The minimum exploration requirements (number and depth) for all applications (foundations, slopes, walls, etc.) are largely consistent with AASHTO’s LRFD Bridge Design Specifications (2014). However, the mini­ mum requirements largely focus on SPT borings, and the agency regularly supplements the SPT borings with a sig­ nificant number of CPT soundings for all applications. The agency has three CPT rigs, which are the most frequently used pieces of equipment in its subsurface investigation fleet. When MnDOT first began using CPT around 2001, CPT soundings and SPT borings were frequently performed side by side. Since that time, the agency has become suffi­ ciently familiar with CPT “signatures” to recognize material types, which allows the agency to exclusively use CPT for some small earthwork projects; for bridge projects, CPT soundings are primarily supplemental. CPT use increases the density of subsurface investigation locations, although there are no specific data to support such a reduction in claims, change orders, and cost overruns as a result of increased CPT use. MnDOT has also increased use of the design­build delivery mechanism, which now accounts for 10% to 20% of total agency construction. Claims In the agency interview, MnDOT provided information about the most frequently encountered subsurface conditions claims, change orders, and cost overruns. A common cause for subsurface conditions claims occurs during construction of sound barrier walls when predrill holes for foundations encounter unanticipated cobbles. Pile overruns, which occur when pile foundations are driven deeper than anticipated, are also common. The agency also mentioned higher than anticipated groundwater as a frequent claim for installation of storm sewers and utilities or any other construction requir­ ing trenching. The survey response indicated that claims, change orders, and cost overruns are less common on design­build projects than on design­bid­build projects. It was also noted that con­ tractors conduct themselves differently on design­build proj­ ects with respect to mitigating delays. Minnesota DOT: Lessons Learned Since its introduction in 2001, MnDOT has significantly increased the use of CPT. CPT is now frequently used to supplement SPT borings, resulting in greater density of sub­ surface investigation locations. MnDOT has also increased the use of the design­build delivery method, which the agency noted is associated with fewer claims, change orders, and cost overruns than design­bid­build projects. SUMMARY OF COMMON CAUSES OF SUBSURFACE CONDITIONS CLAIMS, CHANGE ORDERS, AND COST OVERRUNS AND LESSONS LEARNED FROM ALL CASE EXAMPLES Common Causes of Subsurface Conditions Claims, Change Orders, and Cost Overruns The agency interviews focused primarily on methods of reduc­ ing claims, change orders, and cost overruns attributed to sub­ surface conditions; however, the conversations also revealed common causes. The following list summarizes some of the most frequent situations and applications associated with sub­ surface conditions claims, change orders, and cost overruns. • Pile overruns and underruns. • Higher than expected groundwater for – Retaining walls, – Earthworks, – Utility and sewer work, and – Drilled shaft installation. • Misclassified or mischaracterized subgrade for – Pavements, – Embankments, and – Retention ponds. • Unanticipated rock during foundation construction; such claims are especially frequent for sound barrier walls and other secondary structures with relatively small loads, relatively large numbers of foundations, and relatively sparse borings compared with more significant structures. • Mischaracterized rock for drilled shaft construction, lead­ ing to improper equipment selection and construction delays. The cost of claims, change orders, and cost overruns asso­ ciated with the situations listed previously varies depend­ ing on the scope of the project and the degree of difference between anticipated and encountered conditions. Claims, change orders, and cost overruns associated with installation of dewatering systems were noted as being particularly costly. Summary of Lessons Learned Experiences of the five agencies described in this chapter vary substantially; however, each provides valuable lessons regarding methods for reducing claims, change orders, and cost overruns attributed to subsurface conditions. • Modest changes to subsurface investigation practices can produce significant reductions, particularly when

34 the changes are tailored to a specific, recurring claim, change order, or cost overrun. • Development of minimum standards for subsurface investigation and site characterization can result in more accurate plan quantities and better prepared contractors. • In­house, centralized drilling and laboratory services provide a consistent standard of care, potentially associ­ ated with reduced claims, change orders, and cost over­ runs, especially when accompanied by robust training of agency personnel. • Intra­agency training and communication to improve the implementation of subsurface information can be effec­ tive in reducing claims, change orders, and cost overruns attributed to subsurface conditions. • The accuracy of boring locations can effectively reduce the occurrence of claims, change orders, and cost over­ runs, especially in locations with significant spatial variability. • Implementation of minimum standards for subsurface investigation and site characterization can also produce design efficiencies. • Drilling equipment capable of accessing difficult­to­ reach locations is valuable, particularly for states with considerable areas of difficult terrain. • Specification language that is incompatible with sub­ surface investigation and site characterization results or the lack thereof can result in claims, change orders, and cost overruns.

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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 484: Influence of Geotechnical Investigation and Subsurface Conditions on Claims, Change Orders, and Overruns documents the extent and type of claims, change orders, and cost overruns from subsurface conditions for state departments of transportation (DOTs). The report also identifies practices used by agencies to reduce such claims, change orders, and cost overruns.

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