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Risk-Based Construction Inspection: A Guide (2023)

Chapter: Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods

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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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Suggested Citation:"Chapter 3 - Risk Assessment to Determine Priority of Inspections and Acceptance Methods." National Research Council. 2023. Risk-Based Construction Inspection: A Guide. Washington, DC: The National Academies Press. doi: 10.17226/27099.
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16 This guide presents a three-stage analytical framework to help DOTs implement RBI. The framework may be applied to either a program or a project. The selection of which stage(s) to use will depend in part on the application (e.g., programmatic or project-level assessment), the quality of input data, and the desired level of analytical rigor. 3.1 Overview of Risk-Based Construction Inspection Framework A risk-based framework consisting of three stages has been developed for risk-based con- struction inspection. Stage 1 focuses on developing a core list of construction inspection activi- ties or items. The goal of Stage 2 is to conduct a risk assessment of these core inspection activities. Stage 3 develops a prioritized list of risk-based inspection strategies (See Figure 3.1). This chap- ter will focus on Stages 1 and 2. Chapter 4 will focus on Stage 3, particularly on the optimization of project-level inspection resources. 3.2 Identification of Baseline Listing of Construction Inspection Activities Stage 1 is a programmatic (top-down) identification of key construction items or activities requiring inspections. This is derived from the common listing of construction inspection and testing activities. First, a DOT should identify the standard inspection program and acceptance protocols for materials and workmanship (i.e., including standard rigor and minimum fre- quency) for salient work items and operations, based on information obtained from inspection manuals, inspection checklists, or a schedule providing standard methods and frequencies of inspection and testing referred to as an Inspection and Testing Plan (ITP) that can be adapted to each project. A DOT may also maintain its own inspection list. Some DOTs (e.g., Ohio DOT), have applied RBI to their entire catalog of items to prioritize inspection activities. This approach is useful for prioritizing inspections for developing pro- grammatic inspection checklists or a risk-based construction inspection manual. However, experience has shown that many related items with similar risk levels can be grouped together. Also, within highway construction projects, certain types of inspection and testing activities have more influence on the quality of the end product than others. These activities may relate to the cost or criticality of the materials or work products, or the number or types of inspections needed to assure the quality of a specific construction operation. To develop a core list of items, a DOT should screen and filter the comprehensive list of inspection and testing activities identified in the first step, by seeking the insight of subject C H A P T E R 3 Risk Assessment to Determine Priority of Inspections and Acceptance Methods

Risk Assessment to Determine Priority of Inspections and Acceptance Methods 17   Core List of Inspection Activities Stage 1: Development of a Core List of Inspection Activities Predefined List of Construction Inspections(*) Start Yes Project fil s Required s ti il l s ti s Construction Manuals, Standard Specifications, Others l s ti l l ti li s ti s ti ti ` Stage 2: Risk Assessment Does an agency have a specific list of inspection activities? M ML L L H Consequence Pr ob ab ilit y M HH ifi s ti s ti s i ls is ss ss Core Construction Inspection Activities - Earthwork - Base course - Pavement (PCCP, HMA) - Structural Concrete - Others (**) A process of optimizing the risk-based materials QA can be found in the NCHRP Research Report 838. Stage 3: Risk-Based Inspection Strategies Prioritized Construction Inspections Guidance & Risk Mitigation Strategies Ins. Strategies No. Construction Operation Inspection Activity Tier Risk Impact Inspection Frequency Inspector Experience Inspection Doc. e-inspection Availability 1 Earthwork Provided Provided Provided Provided l l 2 … … … … … … … * … … … … … … … … No (*) DOTs can use a core list developed in this study as a reference. Ins. Exp. Ins. Doc. Ins. Freq. Figure 3.1. Risk-based inspection framework.

18 Risk-Based Construction Inspection: A Guide matter experts within the DOT who would identify and verify a shortlist or core list of inspec- tions for materials and construction for a representative range of project types. The approach to shortlisting can be accomplished using an aggregation of individual responses to achieve a consensus on a core list of inspections for different project scenarios. A DOT’s time or resource constraints will dictate the approach used. An example list of core inspection activities for typi- cal work types derived from standard AASHTO specifications and other mature DOTs on RBI- based inspection is presented in Table 3.1. A list of key inspection activities for typical work types can be found in Appendix A.1: Risk Input/Assessment Forms. DOTs can use the sample core list provided in Appendix A as a “checklist” to develop their own core inspection activities. 3.3 Risk Assessment of Core Inspection Activities and Construction Materials 3.3.1 Overview of the Risk Assessment Process The primary goal of Stage 2 is to conduct a risk assessment of core inspection activities and construction materials. Qualitative risk management principles can be used to evaluate the work 1 Lift Thickness: Verify material placement within specified lift thickness. 2 Embankment Stability: Ensure stability of embankment and slope against sliding by providing suitable materials, construction, foundation and a suitable bond. 3 Embankment Fine Grade Line: Ensure embankment to be constructed according to plan limits, and finished to specified line and grade. ….... Erosion Control: Verify installation and maintenance of temporary erosion control devices and compliance with permits and Contract requirements. … Others:_______________________________ 1 Compaction Control: Verify moisture content, watering operations, and compaction. 2 Placement Inspection: Inspect placement of base course material and review checklist including required construction operations and tests. ….... Surface Smoothness/Tolerance: Inspect and document finished grade for smoothness and line and grade, and determine if all loose and segregated areas are repaired. … Others:_______________________________ 1 Expansion Joint Inspection: Verify construction of expansion joints according to plans and specifications. 3 Assembly, Erection, and Testing of Steel Girder Elements: Verify assembly, erection, and testing of steel girder elements according to contract plans and specifications. 4 Precast Concrete Deck and Girders Placement: Inspect placement of precast concrete deck panels and girders; check for any damage or cracks. ….... Monitoring Concrete Placement Duration: Verify concrete placement within specified duration to avoid hardening. … Others:_______________________________ Earthwork and Embankment (including structural backfills) Subbase/Base Course Bridge Deck and Girder TYPICAL WORK TYPES CORE INSPECTION ACTIVITY Table 3.1. Example list of core inspection activities for typical work types (based on AASHTO specifications and other mature DOTs on risk-based inspections).

Risk Assessment to Determine Priority of Inspections and Acceptance Methods 19   items and materials of interest based on their relative risk of failure (or nonconformance) and to prioritize inspection and testing eorts. Once activities and materials have been prioritized in this manner, resources can be allocated accordingly (i.e., the higher the risk of failure for a given activity or material, the greater the number of resources that should be dedicated to inspection and testing). Figure 3.2 shows the key steps in the risk assessment process conducted in Stage 2. For the material QA risk assessment, DOTs can refer to NCHRP Research Report 838: Guidelines for Optimizing the Risk and Cost of Materials QA Programs (Hill International, Inc. et al., 2017) for a full understanding of the process to optimize the risk and cost of materials QA. While this guide includes the material risk assessment, it focuses primarily on eld construction inspection activities. To evaluate the risks related to eld inspection in highway construction projects, the rst step is to identify the uncertainties related to constructed work. en these sources of uncertainty are transformed into measurable risks. To prioritize inspections based on risk, a DOT needs to assess risks for the core list of items or end products and materials that require inspection and testing. e risk-based inspection assessment includes two main components: • e probability (or likelihood) of work failing to meet specications (e.g., excessive material variability, noncompliant or defective work), and • e impact (or consequence) of failing to meet specications (e.g., replacement or rework, increased maintenance or decreased service life, and safety issues). For example, possible impacts could range from low (e.g., acceptance at reduced pay or increased maintenance) to high (e.g., early failure of a safety-critical material or product). e Expected Value (EV) or aggregate risk impact can be determined by using Equation 3.1 ( ) = ×EV Risk Impact Probability of Occurrence Risk Impact (3.1) Typically, a group of subject matter experts (SMEs) and interested stakeholders will system- atically arrive at a collective assessment in a workshop setting. Individuals may hold diering attitudes and tolerance levels about risk initially. Eventually, all participants will need to share a common understanding of the probability of occurrence (e.g., “high” probability should mean the same thing to all participants) for such a process to be eective. Because this process may be prone to cognitive bias, a Delphi process is used to overcome such biases. e Delphi method is a systematic and interactive research technique used to obtain the judg- ment of a panel of independent experts on a specic topic. e experts are selected according to a set of predened guidelines and asked to participate in two or more rounds of structured Stage 2: Risk Assessment M ML L L H Consequence Pr ob ab ili ty M HH ifi s ti s ti s i ls is ss ss Core Construction Inspection Activities - Earthwork - Base course - Pavement (PCCP, HMA) - Structural Concrete - Others (*) A process of optimizing the risk-based materials QA can be found in the NCHRP Research Report 838 Ins. Exp. Ins. Doc. Ins. Freq. Ins. Strategies Figure 3.2. Risk assessment process (Note: PCCP = Portland cement concrete pavement, HMA = hot mix asphalt).

20 Risk-Based Construction Inspection: A Guide surveys. After each round, the research team provides an anonymous summary of the experts’ input from the previous survey as a part of the subsequent survey. In each subsequent round, participants are encouraged to review the anonymous opinion of the other panelists and con- sider revising their previous responses. The goal during this process is to decrease the variability of the responses and achieve group consensus about the correct value. The process is concluded after a predefined criterion (e.g., the number of rounds or the achievement of consensus) is met, and statistical aggregation of the responses in the final round determines the results. The Delphi method helps to preserve the heterogeneity of the participants and to assure the validity of the results. It can help the group achieve consensus and avoid being dominated by the strength of individual personalities (“bandwagon effect”). 3.3.2 Risk Assessment Process for Core Construction Inspection Activities The risk assessment process of core construction inspection activities can be conducted using the following four steps. • Step 1: Assess the probability of failure or nonconformance. A key initial task is to define the probability scales that will be used to assess risk. Establishing this range upfront lends structure to the analysis exercise and ensures that all participants are viewing probability in a consistent manner. Table 3.2 provides an example of possible risk probability definitions. Either numerical (1, 2, 3, and 4) or adjectival (rare, low, moderate, and high) rating scales may be used. • Step 2: Assess the impact of failure or nonconformance. For each work item or activity, the project team must determine the potential impact associated with failure or nonconformance. The assessment could range from no impact on performance or safety to a potentially cata- strophic impact requiring complete removal and replacement of a safety-critical item. Similar to estimating probabilities, all participants must share a common understanding of what “impact” means for the process to be effective. Possible perspectives from which to consider impacts include safety, difficulty to repair or replace, maintenance costs, and cost of rework. Before conducting the assessment, the evaluators should reach an agreement on the impact definitions that will be used. Table 3.3 provides an example of the definition of consequence for nonconformance, focusing on performance issues. • Step 3: Determine the risk score. Once probability and impact ratings are determined, a risk score using a probability-impact (PI) index can be determined. This score reflects the com- bined effect of an inspected item’s probability of failure or nonconformance, and the estimated severity of any unmitigated consequences associated with that failure or non conformance. The Rating Occurrence Level Description 1 Rare Remote likelihood of failure/ nonconformance 2 Low Low likelihood of failure/ nonconformance 3 Moderate Moderate likelihood of failure/ nonconformance 4 High High likelihood of failure/ nonconformance Table 3.2. Example of probability definitions.

Risk Assessment to Determine Priority of Inspections and Acceptance Methods 21   PI matrix will assist with generating prioritized inspection protocols where each color indicates a priority level for inspection (i.e., tier). The vertical axis represents the likelihood, and the horizontal axis represents the consequence of the item’s failure or not meeting specification requirements. Figure 3.3 indicates that the composite index (CI) value ranges from “1” to “16.” There are three color-coded risk zones or tiers—high, moderate, and low—depending on the range of the CI values. • Step 4: Assign construction inspection levels based on risk score. The risk scores established in the Step 3 assessment are used to assign different levels of inspection using a scale similar to that shown in Table 3.4. The risk score (PI rating) is translated to different levels of inspec- tion (continual, intermittent, and end product) based on the item/activity risks of failure or nonconformance. The highest inspection priorities may require continual inspection during the entire operation, while activities with the lowest risk scores may require random or end- product inspection after the construction item is complete. Note that the risk scores included in Table 3.4, along with the other risk-related definitions and criteria included in this framework, are intended to be illustrative. Users can tailor these rating scales based on their own agency’s overall tolerance or appetite for risk. An example of risk-based determination of inspection frequencies is shown in Table 3.5. Inspection frequency, particularly “intermittent,” may take different forms depending on the type and criticality of the work. Intermittent could mean inspection based on quantity thresh- olds, specific hold points, or other scheduled intervals. Appendix A.2 includes an example input form for inspection frequencies derived from risk scores for core inspection activities. Rating Consequence Level Description 1 Contractual Minimal consequence/the requirement is established only to provide uniform standards for bidding 2 Minor Materially affects performance/highway service interruption 3 Major Substantial economic loss/uselessness of the highway system or component 4 Critical Results in life loss/severe injury/critical safety issues Table 3.3. Example of consequence definitions. Consequence 1 2 3 4 Contractual Minor Major Critical Pr ob ab ili ty 4 High 4 8 12 16 3 Moderate 3 6 9 12 2 Low 2 4 6 8 1 Rare 1 2 3 4 Figure 3.3. Example of risk score matrix for construction inspection risk assessment.

22 Risk-Based Construction Inspection: A Guide Risk Score Risk Tier Inspection Frequency Description 8 < Risk Score < 16 High Continual Required inspection during the entire operation (full-time inspection) 3 < Risk Score < 8 Moderate Intermittent Required inspection at critical times in the operation Risk Score < 3 Low Random/End-Product Random inspection or required end- product inspection after completion of operation or project Table 3.4. Example of construction inspection level based on risk score. TYPICAL WORK TYPES Inspection Frequency 1 Lift Thickness: Verify material placement within specified lift thickness. 2 Embankment Stability: Ensure stability of embankment and slope against sliding by providing suitable materials, construction, foundation and a suitable bond. 3 Embankment Fine Grade Line: Ensure embankment to be constructed according to plan limits, and finished to specified line and grade. ….... Erosion Control: Verify installation and maintenance of temporary erosion control devices and compliance with permits and Contract requirements. … Others:_______________________________ 1 Compaction Control: Verify moisture content, watering operations, and compaction. 2 Placement Inspection: Inspect placement of base course material and review checklist including required construction operations and tests. ….... Surface Smoothness/Tolerance: Inspect and document finished grade for smoothness and line and grade, and determine if all loose and segregated areas are repaired. … Others:_______________________________ 1 Expansion Joint Inspection: Verify construction of expansion joints according to plans and specifications. 3 Assembly, Erection, and Testing of Steel Girder Elements: Verify assembly, erection, and testing of steel girder elements according to contract plans and specifications. 4 Precast Concrete Deck and Girders Placement: Inspect placement of precast concrete deck panels and girders; check for any damage or cracks. ….... Monitoring Concrete Placement Duration: Verify concrete placement within specified duration to avoid hardening. … Others:_______________________________ Earthwork and Embankment (including structural backfills) Subbase/Base Course Bridge Deck and Girder CORE INSPECTION ACTIVITY 1. Continual 2. Intermittent 3. End Product 1. Continual 2. Intermittent 1. Continual 3. End Product 1. Continual 1. Continual 2. Intermittent 3. End Product Table 3.5. Sample of risk-based determination of inspection frequencies.

Risk Assessment to Determine Priority of Inspections and Acceptance Methods 23   3.3.3 Risk Assessment Process for Construction Materials Field inspection also encompasses material inspection, testing, and acceptance as part of qual- ity assurance programs among DOTs. As shown in Figure 3.4, quality-related inspections focus on both material and construction quality. Materials inspection is oen managed through the DOT materials division and conducted by qualied materials testing technicians and inspec- tors. Construction inspection, conducted by construction eld inspectors, focuses on assuring that eld construction and assembly processes are performed according to the project plans and specications. However, the two types of inspections might be performed by the same inspec- tors, complement each other, and contribute to the nal product. A risk-based materials ranking is similar to the procedure discussed in Section 3.3.2, by rating material types rather than construction activities. Material types include project-produced, fab- ricated materials, and standard manufactured materials considering the acceptance method. Acceptance methods can range from sampling and testing to materials certication to visual inspection or a combination of these methods. e material inspection typically includes three acceptance methods from the most to least rigorous. e most rigorous method is where the material is accepted based on sampling testing; the second includes the manufacturer’s certica- tion of compliance with a quality system plan; and the third includes visual inspection. Table 3.6 exhibits examples of acceptance methods. Based on material risk ratings, material tiers can then be aligned to the frequency of testing and acceptance methods. A risk-based construction inspection methodology can include similar steps for optimizing material QA inspection protocols for materials included in their Standard Specications. If such a programmatic exercise is not practical, smaller subsets of materials could be explored on a project basis (e.g., safety-critical materials, fabricated items, project- or eld-produced materials). If operating on a project level rather than a programmatic basis, a decision to optimize the QA processes for all construction pay items or for only a few select or high-priority items would have to be made. A similar series of steps can be utilized to optimize material inspection and testing based on material risks as follows: • Step 1. Identify materials of interest. Identify a core list of key material items requiring inspection and testing. Risk-based protocols for material testing and acceptance are mature and have been more widely implemented as part of materials management. Inspection Types Material Inspection Construction Inspection Typically Managed by Construction Division Typically Managed by Material Division Material Types Project produced Fabricated materials Standard manufacturedAcceptance Methods Acceptance Methods Visual inspection Certificate Sampling and testing Comply with project specifications and plans Figure 3.4. Inspection and acceptance types (adapted from Hill International, Inc. et al., 2017).

24 Risk-Based Construction Inspection: A Guide • Step 2. Assess the risk of nonconformance for each material of interest. To determine a given material’s risk of failure requires assessing both the probability (or likelihood) of receiv- ing non-conforming material and the impact (or consequence) of the material failing to meet specifications. – Assessing the probability of nonconformance. For each material of interest, determine the likelihood or probability of that material failing to meet specifications. The likelihood of nonconformance will be driven in part by the material’s inherent variability. Standard manufactured items produced under highly controlled conditions would be expected to have more stable properties (and thus be more likely to conform to specifications) than project-produced materials that are subject to subsequent mixing, compacting, finish- ing, curing, or other operations at the jobsite that could substantively impact quality and material variability. A scale similar to the one shown in Table 3.2 with numerical (1, 2, 3, and 4) or adjectival (remote, low, medium, and high) may be used to assess the probability of nonconformance. – Assessing the impact of nonconformance. For each material of interest, the project team must also determine the potential impact associated with the nonconformance. The assess- ment could range from minimal impact on performance or safety to a potentially cata- strophic impact requiring complete removal and replacement of a safety-critical item. Like estimating probabilities, all participants must share a common understanding of what “impact” means for the process to be effective. Possible perspectives from which to consider impacts include safety, difficulty to repair or replace, maintenance costs, reduced life-cycle performance (e.g., using performance-related specification predictive modeling), and cost of work. Before conducting the assessment, evaluators need to reach an agreement on the impact definitions that will be used. A scale like the one shown in Table 3.3 may be used to assess the consequence of nonconformance. – Determining the risk score. Once probability and impact ratings are determined, they can then be combined (by multiplying the probability and impact ratings, or by using a PI matrix similar to that shown in Figure 3.3) to arrive at a “score” for each material of inter- est. This score reflects the combined effect of a material’s probability of nonconformance, and the estimated severity of any unmitigated consequences associated with that noncon- formance. This score will then be used in the following steps to prioritize materials for the purpose of efficiently allocating QA resources based on material criticality. Acceptance Method Examples Sampling and Testing Field–statistical such as percent within limits (PWL) or use of contractor QC in acceptance, Field–non-statistical, Central lab verification, Source of supply, Small quantities, High volume (Reduced frequency), and others Materials Certification Manufactured products from certified suppliers, Certified sources of supply, Qualified/Certified products by The National Transportation Product Evaluation Program (NTPEP), Qualified/Certified products by materials on a qualified products list (QPL), Preapproved materials by DOT, Tiered certification (criticality of products), Statements of compliance, and others Visual Inspection Shop or source inspection, Desktop, Diary documentation, Visual field inspection, and others Table 3.6. Materials acceptance methods (adapted from Hill International, Inc. et al., 2017).

Risk Assessment to Determine Priority of Inspections and Acceptance Methods 25   • Step 3. Assign material risk tiers based on risk scores for each material of interest. The risk scores established in Step 2 can be used to assign materials to different tiers of criticality using a scale like that shown in Table 3.7, which translates the risk score (probability x impact) to different material criticality (low-, moderate-, and high-risk) based on the risk of material nonconformance. Note that the risk scores included in Table 3.7 along with the other risk- related definitions and criteria included throughout this report are intended to be illustrative only. Users should tailor these rating scales based on their own agency’s overall tolerance or appetite for risk. The risk tolerance (as reflected in the probability and impact definitions, PI matrix, and risk scoring cutoffs) may change over time. Changing circumstances (e.g., heightened public, political, or regulatory scrutiny) may trigger a reevaluation of what constitutes an acceptable level of risk for the agency. • Step 4. Align material criticality to the frequency of testing and acceptance methods for materials of interest. The material criticality established in Step 3 can be used to determine the type and level of QA acceptance needed for a particular item; the higher the risk (likeli- hood and impact) of failure for a given material, the greater the level of resources that should be allocated to QA acceptance. For example, certification and intermittent inspection may be sufficient for low-risk Tier 3 materials, whereas more frequent inspection and sampling and testing may be necessary for more risk-critical materials. Focusing first just on an owner’s materials acceptance practices, this risk-based philosophy of QA resource allocation can be used to align the material criticality established in Step 3 to acceptance methods that would provide an appropriate degree of confidence in the quality of the material provided. Table 3.8 provides an example of how acceptance methods could vary based on material tiers. In addition to material criticality, it is important to recognize (as reflected in Table 3.8) that the mode of material production (i.e., project-produced, fabricated, and standard man- ufactured item) will also influence the selection of an appropriate materials acceptance strat- egy. Materials produced in a similar manner will generally exhibit similar characteristics regarding variability and stability of properties and will likely require comparable levels and types of QA to assure product acceptability. Materials acceptance levels may also be adjusted depending on project size and the criticality of work type (structural vs. nonstruc- tural applications). In summary, for the material QA risk assessment, DOTs can follow the four steps discussed in this section in tandem with the procedure for optimizing risk-based materials presented in NCHRP Research Report 838: Guidelines for Optimizing the Risk and Cost of Materials QA Pro- grams (Hill International, Inc. et al., 2017). Appendix B includes additional information regard- ing the application of materials RBI using a property-based optimization of materials accepted by sampling and testing. It includes an example for DOT-performed acceptance testing and an example where contractor QC test results are used in the acceptance decision. Risk Score Material Risk Tiers Description 8 < Risk Score < 16 High Materials having the greatest risk of failure 3 < Risk Score < 8 Moderate Moderate-risk materials Risk Score < 3 Low Low-risk materials Table 3.7. Example of material QA risk tiers.

26 Risk-Based Construction Inspection: A Guide Material Tier QA Strategy Primary Acceptance Methods Project-Produced Fabricated Manufactured 1 QA methods designed to provide maximum confidence in the quality of the materials provided DOT Acceptance Sampling and Testing, or DOT Verification Sampling and Testing (if using contractor QC data) Continuous DOT fabrication inspection combined with a requirement for a Fabricator Quality Management System Plan Certificates of Compliance backed by periodic sampling and testing by the manufacturer and random DOT verification testing 2 QA methods designed to provide a high level of confidence in the quality of the materials provided Same as above Intermittent DOT inspection combined with certificates of compliance Certificates of Compliance backed by random or programmatic sampling and testing by the manufacturer 3 QA methods designed to ensure that the specified material has been supplied Random or programmatic sampling and testing Random or programmatic assessment of fabricator combined with certificates of compliance Certificates of Compliance or Catalog Cuts Table 3.8. Example of alignment of primary acceptance methods to material criticality.

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Due to budget cuts and reduced experience levels of inspectors and engineers, state departments of transportation (DOTs) have implemented risk-based strategies to achieve greater efficiency in construction inspection. These strategies include prioritizing inspection based on inherent risks related to construction operations, using emerging technology applications to save time, and accepting certification and contractors' test results to offset shortages of experienced inspection resources.

NCHRP Research Report 1039: Risk-Based Construction Inspection: A Guide, from TRB's National Cooperative Highway Research Program, discusses the importance of construction inspection and aims to assist state DOTs and the U.S. Federal Highway Administration in meeting quality standards.

Supplemental to the report are NCHRP Web-Only Document 344: Risk-Based Construction Inspection: Conduct of Research Report and an Inspection Risk Assessment Questionnaire.

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