Managing Geotechnical Risks in Design–Build Projects (2018) / Chapter Skim
Currently Skimming:
Pages 49-116
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 49... ...
49 Chapter 3: Findings and Applications 3.1 Introduction The completed research developed a number of findings as a result of the research instruments listed in Chapter 2. These will be presented in this chapter by research instrument.
|
From page 50... ...
50 "The cost of subsurface condition change orders approaches 1% of the agencies' total budgets for new construction" (Boeckmann and Loehr 2016)
|
From page 51... ...
51 Figure 3.1 Differing Site Conditions Risk Liability Flow Chart (Hanna et al.
|
From page 52... ...
52 Figure 3.2 Color Coding for a Section of the Borinquen Dam 1E Foundation Geological Profile (Tapia et al.
|
From page 53... ...
53 geotechnical risk is to start the subsurface work (in this case the grout curtain) as soon as practical.
|
From page 54... ...
54 the DSC delay. The analyst can compare the pre-DSC production rate with the planned production rates in the approved baseline schedule and quickly determine whether the contractor was achieving its as-bid production and whether it was behind schedule at the time the DSC was discovered (McLain et al.
|
From page 55... ...
55 risk can be established. On the owner's side, PDB provides a means to avoid paying for unrealized contingencies in the design-builder's lump sum price.
|
From page 56... ...
56 site. Given that, the question is no longer whether DB is an appropriate procurement method, but rather how to mitigate the risks posed by geotechnical uncertainty at the time of DB contract award.
|
From page 57... ...
57 Table 3.1 List of Projects in Content Analysis State Agency Project Value of project (thousands $) Type document Publish Year AK ADOT&PF 7 Mile ADA Accessibility 1,000 RFP 2011 AK Alaska RR Corporation Northern Rail Extension 100,000 RFP 2010 CA Riverside County State Route 91 Corridor Projects 1,700,000 RFP 2012 CA California High Speed Rail Authority California High Speed Train Project 1,800,000 RFP 2012 CA Caltrans Fresno 180 55,000 RFP 2011 CA Caltrans Los Angeles I-10/605 Interchange 61,800 RFP 2011 CA Caltrans Cajon Pass 115,000 RFP 2013 DE DelDOT Indian River Inlet Bridge 150,000 RFP 2008 DE DelDOT Dover Transit Center 5,000 RFP 2009 FL Florida DOT Central Florida Commuter Rail Transit 158,000 RFP 2008 FL Hillsborough County Tampa Airport 925 RFQ 2009 FL FlaDOT Hathaway Bridge 86,000 RFP 2000 FL FlaDOT Southbound I-95 Weigh Station 15,500 RFP 2008 FL FlaDOT I-75 Freeway Management System 7,000 RFP 2008 FL FlaDOT Central Florida Commuter Rail Transit 158,000 RFP 2008 GA GaDOT P.I.
|
From page 58... ...
58 State Agency Project Value of project (thousands $) Type document Publish Year MO MoDOT "The New I-64" 535,000 RFP 2005 MT MDT US-2 Rockfall Mitigation 3,000 RFQ 2011 NV City of Reno ReTrac Reno Railway 157,000 RFP 2001 NV Nevada DOT Project NEON DB 550,000 RFP 2015 NM NMDOT I-40/Coors interchange 92,000 RFP 2006 NC NCDOT C2011288 Mecklenburg County - RFP - NC NCDOT Rec.
|
From page 59... ...
59 were identified by the research team and their frequency of occurrence in the analyzed documents is shown in Table 3.2. It was found that 24 out of 53 occurrences were at the level of geotechnical data report.
|
From page 60... ...
60 Another aspect analyzed was whether or not owners explicitly describe a project as one with significant geotechnical-related issues. By doing so, the owner might be able to obtain insight from the proposers as to identify ways to mitigate the risk, or avoid having proposers that did not consider a potential problem in their proposals.
|
From page 61... ...
61 Since the owner allocates design responsibilities to the contractor in DB delivery, contracts often include qualification requirements as a way to ensure the design is performed up to certain standards. The research team identified 11 different geotechnical-related aspects that owners can include in the evaluation as part of the contractor selection process.
|
From page 62... ...
62 A way in which owners seek to obtain information regarding the assumptions and interpretations that the contractor has made in order to submit a proposal is to require specific geotechnical-related supporting documents. The research team identified five different types of supporting information that are required by some owners in the requests for proposal, Table 3.8 shows the frequency in which these requirements were found in the 59 projects that conform the content analysis; 34 projects did not include any explicit requirement and varying instances of required design and performance criteria were found in 47 projects.
|
From page 63... ...
63 from those expected. There are many different wordings for this DSC clause in construction contracts.
|
From page 64... ...
64 submit alternative solutions to potential problems before the contract is awarded. As shown in Table 3.12, the content analysis found that the majority of the projects (32)
|
From page 65... ...
65 3.3 Summary and Analysis Surveys This section discusses the findings of the two surveys conducted as part of this project. The complete questionnaires are attached in Appendix C
|
From page 66... ...
66 The survey was initially issued to the members of the AASHTO Subcommittees on Construction and Design in each of the 50 DOTs. The subcommittee members were asked to then forward the survey to the person best qualified to respond on an overall department basis.
|
From page 67... ...
67 3.3.1.2 General Information and DOT Alternative Contracting Methods Use and Experience Figure 3.5 shows the contracting methods that the responding 38 states are allowed to use. As seen, all state DOTs are allowed to use DBB.
|
From page 68... ...
68 Of the 27 DOTs remaining that use at least a form of DB project delivery, 18 reported delivering more than 10 DB projects, 4 had 6-10 projects, 1 DOT had 3-5 projects, 3 DOTs had 12 projects, and one failed to report this data (Figure 3.6)
|
From page 69... ...
69 Figure 3.7 How long has your agency been using DB projects delivery? 3.3.1.3 Geotechnical Risk Management Information This section presents how agencies manage the geotechnical risk in their DB projects.
|
From page 70... ...
70 Figure 3.8 How much preliminary geotechnical investigation is completed before making the decision to use DB project delivery for a given project? Of the DOTs that responded that they use DB project delivery on projects where the geotechnical risks are considered to be significant, almost 80% affirmed they used DB and only five DOTs did not.
|
From page 71... ...
71 Minnesota, and Ohio DOTs reported managing these geotechnical issues not only by GBR or by DSC clause, but also by mandatory design. Figure 3.9 Steps Taken to Address Geotechnical Issues in the DB RFQ/RFP Where the Geotechnical Risks Are Considered Significant DOTs who do not use DB project delivery where the geotechnical risk is significant reported reasons such as liability consideration, political issues preventing its use.
|
From page 72... ...
72 geotechnical risk analysis pointed out that risk analysis is only carried out for major projects or those who have a high cost, and that geotechnical aspects are considered within the overall project risk analysis. Figure 3.10 Is a formal geotechnical risk analysis conducted on a typical DB project in any of the following areas?
|
From page 73... ...
73 Figure 3.11 Within the geotechnical risk management process that is conducted by the agency or required of the design-builder? Regarding risk register content, 8 DOTs reported using both a risk register containing geotechnical risks with probabilistic estimate of cost and schedule impact of risk, and that the risk register developed by the agency determines the risk management mitigation strategies applicable to the geotechnical risks identified (such as share, transfer, and avoid)
|
From page 74... ...
74 Figure 3.12 Which of the following best describes the content of the risk register of geotechnical issues? Figure 3.13 illustrates geotechnical risks encountered during the process and how such risk is allocated.
|
From page 75... ...
75 Figure 3.13 What types of geotechnical risks do you typically encounter on DB projects and how are they allocated? Respondents were asked whether their project cost estimates included a quantitative analysis of geotechnical uncertainty.
|
From page 76... ...
76 Geotechnical Aspects of DB Procurement Process This section of the report presents the results on how DOTs perceive geotechnical factors in DB projects, and details the amount of geotechnical information provided by DOTs. Figure 3.14 shows that 10 DOTs reported assigning a weight to geotechnical factors with regard to all other evaluated factors.
|
From page 77... ...
77 level of investigation. Other DOTs indicated that all subsurface uncertainties should be addressed in the pre-award phase because after the contract is awarded, the design-builder is responsible to develop geotechnical solutions.
|
From page 78... ...
78 Figure 3.16 RFP Additional Geotechnical Information by Design-Builders. DOTs were asked about what they allow and/or give during the bidding stage for DB projects with significant geotechnical issues.
|
From page 79... ...
79 Figure 3.18, details the results of the survey with regard to the impact on project success of various aspects that are part of the procurement process. One and see that ‘sufficient geotechnical information to allow the competitors to price the project without excessive contingencies' was rated the highest with an average of 2.84, followed by ‘highly qualified geotechnical design engineers' with an average of 2.52.
|
From page 80... ...
80 Figure 3.18 Average Scores of Importance of Geotechnical Aspects During the Procurement Process to the Overall Success of the Project 3.3.1.4 Geotechnical Aspects of DB Contracts This section reports the results of the last section of the survey that addresses the geotechnical aspects of DB contracts. Respondents were asked to select what type of payment provisions are contained in both typical DB projects and those with significant geotechnical issues.
|
From page 81... ...
81 Figure 3.19 Type of Payments in a DB Project DOTs were asked a question on how the contract document is set up to address various geotechnical aspects (with ‘yes', ‘no', and ‘don't know' response options)
|
From page 82... ...
82 to use a DB project and also provides a GBR study in the RFP in a project with significant geotechnical issue. On the other hand, Michigan, Missouri, and Washington DOTs, for example, are agencies that not only use GBR as a contract document, but also include the GBR in their RFP for a DB project with a significant geotechnical issue.
|
From page 83... ...
83 change order. Of that group, the Connecticut DOT is the only agency that does not use DB delivery when the geotechnical risks are considered to be significant.
|
From page 84... ...
84 the evaluation plan, nor completes a formal geotechnical risk analysis. On the other hand, Connecticut, Louisiana, Maine, Maryland, New York, and Utah marked none as a percent of its projects.
|
From page 85... ...
85 during mini-pile installation, karst terrain, landslide during construction, and tunnel launch pit dewatering. In order to compare DB and DBB projects, agencies were asked to rate the final quality of geotechnical work on DB projects compared to DBB projects.
|
From page 86... ...
86 It should be noted that South Carolina DOT formally assesses design-builder's performance and uses that for the future DB selection. SCDOT was the only agency that selected better on comparing the final quality of geotechnical work on DB projects with DBB projects.
|
From page 87... ...
87 Figure 3.23 Please rate the following geotechnical factors for their impact on the final quality/performance of the DB project. Finally, the questionnaire asked DOTs that work with DB project delivery method if there is something that they would like to share regarding geotechnical aspects on their DB projects.
|
From page 88... ...
88 geotechnical risks on their DB projects. Experienced agencies are defined as those having completed more than 10 DB projects.
|
From page 89... ...
89 Figure 3.24 Geotechnical Evaluation Criteria Weighting As for the three geotechnical factors, shown in Figure 3.25, in terms of their impact on the final quality/performance of the DB project, a consistent difference is observed in the higher consideration of experienced DOTs when compared with the non-experienced DOTs. For instance, 100% of experienced DOTs not only agree in rating the qualification of the design-builder's geotechnical staff as a very/high impact, but also agree in rating the design-builder's past project experience with geotechnical issues as very/high impact.
|
From page 90... ...
90 Figure 3.25 Impact of Geotechnical Risk Factors Further statistical analysis was conducted using the Pearson Chi-Square Test to see if there is a statistical significant difference in the perception of DB's geotechnical aspects between the two groups. Table 3.15 shows the different aspects tested.
|
From page 91... ...
91 DOTs are more willing to share the geotechnical risk uncertainty rather than bear it, more than 50% of non-experienced DOTs are willing to bear the geotechnical risk rather than share it, and only 14% of these DOTs allocate it to the owner. This could be attributed to the better understanding of the DB project delivery method as compared to the traditional methods in terms of risk allocation.
|
From page 92... ...
92 Figure 3.27 Formal Geotechnical Risk Analysis 3.3.1.5 Consolidated DOT Survey Findings Based on the survey findings and the comparison between experienced and non-experienced DOTs, the following conclusions are drawn: Before Making a Decision to Use DB Project Delivery 1. Geotechnical factors, as well as geotechnical information available before making the decision to use DB delivery, not only are independent of the use of DB delivery in agencies, but also do not preclude a given project from using a DB contract.
|
From page 93... ...
93 3. A formal geotechnical risk analysis affords the DOT project staff the ability to identify, quantify and mitigate the geotechnical risk before the procurement process starts and thus adds value to the DB project delivery process.
|
From page 94... ...
94 9. One major concern that was repeatedly reported by DOTs related to the success of the project is to have sufficient geotechnical information during the procurement phase to allow competitors to price the project without excessive contingencies.
|
From page 95... ...
95 15. Based on the results, it seems that DOTs, in general, do not conduct a formal geotechnical risk analysis in the preparation of the project scope, schedule, and costs.
|
From page 96... ...
96 design engineers are important to the success of the project. Also that the qualifications of the design-builder's geotechnical staff and its past project experience with geotechnical issues have a high impact on the final quality/ performance of the DB project.
|
From page 97... ...
97 frequency assessment and to provide the necessary data to develop an objective ranking of those factors based on importance index theory (Assaf and Al Hejji 2006)
|
From page 98... ...
98 underground construction activities risks are broadly recognized as being one of the major areas of risk exposure in DB contracts to all parties (Dwyre 2012)
|
From page 99... ...
99 the project. These factors, in order, are contaminated material, slope instability, landslides, settlement of adjacent structure, and highly compressive soils.
|
From page 100... ...
100 The results are consistent with the findings of NCHRP Synthesis 429 (Gransberg and Loulakis 2012) , affirming that geotechnical conditions not only have an enormous impact on DB projects, but also directly affect project cost and schedule.
|
From page 101... ...
101 Table 3.18 Importance Index of Geotechnical Factor Risk in DB Projects FACTOR/RISK Importance Index [%] Rank Groundwater/ Water table 42.64 1 Settlement in general 37.69 2 Contaminated material 37.22 3 Soft compressible soil 36.04 4 Scour of bridge piers 35.37 5 Slope instability 34.87 6 Settlement of bridge approaches 34.87 7 Highly compressive soils 33.77 8 Presence of rock/boulders 32.65 9 Seismic risk 32.42 10 Soft clays, organic silts, or peat 32.10 11 Settlement of adjacent structure 31.82 12 Existing structures likely to be impacted by the work (other than utilities)
|
From page 102... ...
102 trend towards high impact, while DOTs' view the majority of these factors to have low impact. Only "replace in situ material with borrowed material" and "unsuitable material" are common factors belonging to the low impact zone, while "contaminated material" and "landslides" are the highest impact from only DB industry's perspective.
|
From page 103... ...
103 Table 3.19 List of Geotechnical Risk Factors Factor/Risk Number Factor/Risk Number Caverns/voids 1 Subsidence (subsurface voids) 15 Chemically reactive ground 2 Existing structures likely to be impacted by the work (other than utilities)
|
From page 104... ...
104 Figure 3.29 Importance Index of Geotechnical Risk Factors Similarly, "eroding/mobile ground condition" and "chemically reactive ground" are factors that have the lowest importance for both groups. The DOTs and industry only rated "replace in IMPORTANCE INDEX [%]
|
From page 105... ...
105 situ material with borrowed material" at the same level of importance. On the other hand, Figure 3.29 shows that "seismic risk" had the highest difference of perceived risk.
|
From page 106... ...
106 regardless of the level of geotechnical risk. However, the importance index analysis results lead to recommending that the prioritized list of geotechnical risk factors can be used to guide the preliminary investigations for inclusion in the DB RFP.
|
From page 107... ...
107 shown in Table 3.21. The ten factors were then plotted against the differences in the importance index of the two groups found in Figure 3.30, which illustrates the percentage of risk allocation versus the difference in importance index for the ten factors.
|
From page 108... ...
108 are shared in some manner, the DOT could potentially benefit from reduced price contingencies, mitigating the risk of not awarding in timely manner because all proposals are over budget or the engineer's estimate. 3.3.2.8 Geotechnical Risk Expert Survey Findings Based on the survey findings and the comparison between the perceptions of DOTs and industry professional ranking of DB geotechnical risks, the following conclusions are drawn: 1.
|
From page 109... ...
109 c. Contaminated material d.
|
From page 110... ...
110 Carolina, Texas and Utah. All of these case studies are projects that involved significant geotechnical risks and several differences and similarities were found in the way the DOTs managed them, which provided valuable insight towards identifying different strategies, tools and methods that are currently being used to handle the geotechnical risk.
|
From page 111... ...
111 Table 3.23 Summary of Case Studies–Geotechnical Risk Mitigation Actions Case No. State Case Study Mitigation Action 1 Missouri I-64 Daniel Boone Provide as much information as possible to proposers, accepting requests for additional investigation.
|
From page 112... ...
112 The courts generally hold the owner in a DB project liable for differing site conditions regardless of the presence of exculpatory language that attempts to shift the differing site conditions risk to the design-builder. In those cases where the owner prevailed, it was generally due to a technicality such as untimely notification rather than contract risk shedding verbiage.
|
From page 113... ...
113 section will synthesize the effective practices (tools) identified in the research within the context of available strategies and methods for managing geotechnical risk for DB projects.
|
From page 114... ...
114 Promote an atmosphere of life cycle-based design and construction decision-making with respect to geotechnical risk on DB projects. The tools identified in the research can be implemented using the specific methods for the purpose of executing the five risk mitigation strategies, as presented in this section.
|
From page 115... ...
115 Table 3.25 Involve Third Party Stakeholders as Early as Practical Method Tool Source Pre-advertising Flexible footprint for NEPA clearance Site conditions history from property owners during ROW acquisition MO Literature Procurement Request of utility-related ATCs GA Preconstruction Assign design-builder responsibility for utility coordination Multiple NTPs with one designated for geotechnical investigation, design, and a second specifically to commence excavations, utility work, etc. TX+ Literature Construction Multiple NTPs with one designated for geotechnical investigation, design, and a second specifically to commence excavations, utility work, etc.
|
From page 116... ...
116 Table 3.27 Enhanced DB Geotechnical Contract Mechanisms Method Tool Source Pre-advertising Geotechnical conditions database Furnish GBR Include GBR-C provision Prescriptive geotechnical design Performance specifications for post-construction performance (subsidence, etc.) VA WA+ OH OR DE+ Procurement Request of geotechnical ATCs Define no-go zones for geotechnical ATCs Competitor designated boring locations Competitors permitted to conduct supplementary borings at own expense Unit prices for contaminated material, over-excavation, etc.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.