Guide for Conducting Forensic Investigations of Highway Pavements (2013)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1 1.1 Background The concept of pavement forensic investigations has been around for a long time. Hundreds of such investi- gations have been performed in the United States in past decades, mostly to investigate the underlying causes of pre- mature pavement failures. Other reasons for conducting forensic investigations include one or a combination of the following: • Determining reasons for poor pavement performance/ premature failures, • Understanding exceptional pavement performance and/ or longevity, • Validating pavement performance prediction (actual ver- sus predicted), • Closing-out/conducting final investigations of experimen- tal test sections, • Collecting project specific data for: – Rehabilitation design, – Litigation purposes (e.g., settling disputes or defending/ supporting claims and lawsuits), • Collecting general data to: – Support development and/or calibration of pavement performance prediction models, – Understand/quantify long-term effects of traffic and environment on material properties, – Evaluate specific design and/or construction practices, • Certifying pavement-related warranties, and • Evaluating new pavement-related products or techniques. C h a p t e r 1 Introduction The word forensic comes from the Latin adjec- tive forensis, meaning “of or before the forum.” In Roman times, a criminal charge meant pre- A forensic investigation may be conducted to achieve one or more of these objectives. This guide addresses the planning and conduct of investigations for any of these applications. senting the case before a group of public indi- viduals in the forum. Both the person accused of the crime and the accuser would give speeches based on their side of the story. The individual with the best argument and delivery would determine the outcome of the case. In modern use, the term “forensics” in place of “forensic science” can be considered incor- rect, as the term “forensic” is effectively a syn- onym for legal or related to courts. However, the term is now so closely associated with the scientific field that many dictionaries include the meaning that equates the word “foren- sics” with “forensic science.” Within that con- text, the term forensics now encompasses the accepted scientific methodology and norms under which the facts regarding an event, or an artifact, or some other physical item are ascertained as being the case. In that regard the concept is related to the notion of authen- tication, whereby an interest outside of a legal form exists in determining whether an object is what it purports to be, or is alleged as being. A literature review and survey questionnaire responses from state highway agencies identi- fied poor performance or pavement failures as a primary reason for conducting a forensic investigation.

1.2 Objectives The objective of this guide is to provide a systematic pro- cess for conducting forensic investigations of highway pave- ments. It includes guidance on organization and planning of the investigation, sampling and testing requirements, inter- pretation of results, and decision-making processes. Several case studies are presented to illustrate each of these activities. An important element in a forensic investigation is achiev- ing a balance between requirements, priorities, and available resources. Implementation of the guide will help focus the investigation on the factors relevant to the issues being raised and lead to benefits, such as: • Enhanced utilization of the collected information, • More cost-effective investigations, • Improved understanding of pavement behavior/ performance and insight into extending pavement life and eliminating premature failures, and • Improved collection of data to support development of models for pavement evaluation and design. A standard format is suggested for reporting and storing the findings from these investigations to facilitate future use and reference. 1.3 Scope There are many reasons for performing forensic investiga- tions. Certain key elements must be addressed for each rea- son to ensure a successful outcome of the investigation. It is important to understand the reasons why the investigation is needed, and how the results from the investigation will be used. However, it is also necessary to adopt an agency-wide protocol or standard for forensic investigations that addresses generic agency and project specific issues. The generic agency issues relate to the establishment of the agency’s forensic investigation protocol and should be in place prior to initiating an investigation. These issues only need to be addressed once, with periodic monitoring and revision to ensure they are still appropriate. While not part of the investi- gation, these issues are vital to the success of an agency’s foren- sic investigation program. Generic agency issues are discussed in Appendix A. Project specific issues, on the other hand, focus on the procedures necessary for carrying out a forensic inves- tigation, from planning of the investigation to the close-out activities. These issues are discussed in Chapters 3 through 9 and illustrated through case studies in Appendix B. Although pavement forensic investigations are con- ducted for different purposes, they all seek an understand- ing of pavement performance. Accordingly, the success of a forensic investigation can be measured by its contribution to the understanding of the performance of the investi- gated pavement. Four sets of factors, separately or in combination, influ- ence the performance of pavements: (1) pavement structure (including pavement type, pavement layers, and construc- tion); (2) subgrade soil; (3) traffic; and (4) drainage and environmental conditions. For example, good pavement per- formance or premature pavement failures are typically the result of a combination of these factors and the investigation must ensure that all relevant factors have been adequately and properly considered and addressed. Gathering information on every possible pavement per- formance measure and every factor potentially affecting pavement performance is unnecessary and often beyond the available resources of most agencies. Forensic investiga- tions will contain common elements (e.g., environment), but specific investigation elements will ultimately depend on the issues being investigated and the associated relevant pavement factors. Falling Weight Deflectometer (FWD) testing, distress surveys, Ground Penetrating Radar (GPR) surveys, and cor- ing, for example, may be common to many investigations of poor pavement performance or premature pavement failures, but are not required for investigating pavement friction and/or noise-related issues. Therefore, achieving an appropriate bal- ance between requirements, priorities, and available resources is a requisite for each investigation. Clearly establishing and understanding the investigation objectives and using them as the basis for collecting and analyzing the appropriate data will help eliminate the collection of unnecessary data and ensure a successful outcome. Ideally, a series of flowcharts or a decision support system that guides the forensic investigator to the most likely reason for the observed pavement performance would be developed. However, because pavement performance is dependent on many factors and their interactions, both poor and excep- tional performance is usually attributed to a combination of factors, and often to some unique and/or unexpected factors. Attempting to cover all of these factors in a single flow chart or decision support system is impractical and would often lead to misleading or incorrect conclusions, which could have serious implications. A phased approach that encourages the investigator to consider a range of factors is therefore fol- lowed in this guide. The reasons for adopting this approach are discussed in Chapter 2. 1.4 Investigation Approach A phased approach, starting with a formal request for a forensic investigation and ending with a formal investigation close-out, is necessary to ensure that the appropriate combi- nations of contributing factors are investigated and that no unnecessary work, especially destructive testing, is under- 2

3 Chapter 2 summarizes the philosophy behind forensic inves- tigations and the approach followed in this guide. Chapter 3 addresses requests for and initiation of a forensic investigation, including conduct of a preliminary investigation or background study. Chapter 4 covers the planning of the investigation, including selection of the investigation team, pre-investigation site visit, and non-destructive testing requirements. Chapter 5 discusses non-destructive testing, analysis of the data collected, the preparation of an interim report, and making a decision on the adequacy of the collected information to address the issues being investigated. Chapter 6 covers updating the taken. This approach, which is used in this guide, encourages the use of formalized (but quick and easy to complete) docu- mentation procedures at all stages to record the investiga- tion. A flowchart summarizing this approach (with relevant section numbers in this guide) is shown in Figure 1.1. 1.5 Organization of the Guide This guide is organized into nine chapters. This intro- ductory chapter provides background information and the objectives, scope, approach, and organization of the guide. Evaluate investigation request Complete preliminary investigation and report Close out project Request supported? Detailed Investigation justified? Undertake forensic investigation in phases Prepare investigation plan Investigation plan approved? Request for investigation submitted to team leader Record of decision Record of decision Record of decision Record of decision Yes Yes Yes No No No Analyze data and write investigation report Record of decision Section 3.1 Section 3.3 Section 3.2 Sections 3.5 – 3.6 Chapters 5 – 8 Section 4.5 Sections 4.1 – 4.4 Section 3.6 Sections 8.1 – 8.3 Sections 9.1 – 9.3 Figure 1.1. Recommended general approach to forensic investigations.

4establishment of an agency’s forensic investigation proto- col; these issues are not part of the investigation, but are critical to the success of an agency’s forensic investigation program. Appendix B includes a series of case studies that illustrate the use of the process described in this guide. Appendix C and Appendix D include example forms and checklists, respectively, for use during the conduct of the investigation. These forms can be modified to suit the par- ticular requirements and procedures for the agency. The example forms are provided on a CD-ROM (CRP-CD-135), attached to the guide in a format that permits entering data and thus facilitates use of the guide. investigation plan based on the non-destructive testing analy- sis. Chapter 7 discusses destructive field testing and laboratory testing of samples and specimens removed from the pave- ment. Data analysis and hypothesis testing and preparation of the final report are covered in Chapter 8. Chapter 9 includes review of the investigation, actions resulting from the investi- gation, and close-out of the investigation. Chapters 3 through 9 offer a suggested approach and are written in a procedural style to improve readability. This approach can be modified to suit agency procedures and expertise. References cited in the guide are listed after Chapter 9. Appendix A addresses generic issues associated with the