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CHAPTER 2. LITERATURE REVIEWINTRODUCTIONThis chapter summarizes the results of the literature review the research team completed inpreparation for conducting the practitioner survey. It covers the following topics: • UR impacts on project delivery. • Use of utility impact assessment tools during project delivery. • Construction and utility inspection practices.UTILITY-RELATED IMPACTS ON PROJECT DELIVERYImpacts on Project DelaysIn 1999, the United States General Accounting Office (GAO) published a report on the impactsof utility relocations on highway projects (1). GAO conducted a national survey of state DOTsand conducted interviews with officials at FHWA, both at headquarters and field offices,selected DOTs, and construction contractors. GAO also interviewed utility owners in nine states.The survey included a list of reasons for delays on highway and bridge projects. Table 1 showsthe results of feedback from DOTs. The top three reasons mentioned were utility owners lackingresources to conduct relocations, insufficient time at the DOT for planning and design, and utilityowners’ not assigning enough priority to utility relocations. Table 1. DOT Reasons for Delays in Utility Relocations. Number of Reason for Project Delays DOTs Utility owner lacked resources 34 Short timeframe for state to plan and design project 33 Utility owners gave low priority to relocations 28 Increased workload on utility relocation crews because highway/bridge construction had 28 increased Delays in starting utility relocation work: Some utility owners would not start until construction 28 contract was advertised or let Phasing of construction and utility relocation work out of sequence 26 Inaccurate locating and marking of existing utility facilities 23 Delays in obtaining right-of-way for utility relocations 23 Shortages of labor and equipment for utility contractor 19 Project design changes required changes to utility relocation designs 19 Utility owners were slow in responding to contractor’ requests to locate and mark underground 16 utility facilities Inadequate coordination or sequencing among utility owners using common poles or ducts 13Ten DOTs responded that utility relocation delays had a “great” or “very great” impact onconstruction schedules and/or costs of highway and bridge projects. A total of 30 DOTs 12

indicated they incurred additional costs due to claims resulting from utility relocation delays.Interestingly, contractors indicated that cost increases due to utility relocation delays were eithernot covered entirely by DOTs, or the time required to prepare the paperwork for reimbursem*ntwas not worth their time and effort. However, the GAO report also noted that DOTs werefrequently not aware of the magnitude of the impacts of utility relocation delays on constructionschedules or costs because contractors shifted work crews and equipment to other segments ofthe project or to a different project altogether as a strategy to deal with utility relocation delays(rather than submitting schedule extension requests or change orders).DOTs highlighted strategies to make utility coordination more effective. A total of 41 stateDOTs used early planning and coordination, and 33 states used special contracting methods toalleviate the impacts of utility relocation delays during construction. The TxDOT highlighted aUtility Cooperative Management process to incorporate utility facilities into all project deliveryprocess phases. Only seven DOTs indicated they conducted utility investigations usingsubsurface utility engineering (SUE) procedures on more than half of their projects. However,with the information that was available at the time, the GAO report highlighted that it wasunclear whether the use of SUE practices contributed to a reduction in utility relocations anddelays. A total of 44 state DOTs allowed contractors to extend project deadlines.In 2001, NCHRP completed a survey of DOT officials, design consultants, and highwaycontractors to establish causes of project delays during the construction phase (2). Theresearchers prepared a list of 20 potential causes of project delays (Table 2) and asked surveyparticipants to rank those causes by order of frequency. As Table 3 shows, all three groupsranked utility relocation delays as the top cause of project delays. DOTs and design consultantsidentified DSCs—utility conflicts as the second most frequent reason for delays. In contrast,contractors identified errors in plans and specifications as the second most frequent cause ofproject delay.Interestingly, groups responded differently with respect to what they considered less frequentcauses of project delays. For example, owner-requested changes were No. 11 for DOTs and No.10 for consultants, but contractors indicated this cause was No. 5. Errors in design andspecifications were No. 13 for design consultants but were No. 3 for DOTs and No. 2 forcontractors. Insufficient work by contractor was No. 18 for contractors but was No. 8 for DOTsand No. 5 for design consultants.The researchers analyzed a database of contract supplemental agreements they received from theFlorida Department of Transportation (FDOT). The database included 2,616 contract changes.The researchers grouped these records by contract change reason code and concluded that a littleover 5 percent were related to utility conflicts. The researchers also analyzed 150 FDOT projectsof varied sizes and types (3). These projects involved 27 different construction contractors, ofwhich 9 (or 33 percent) accounted for 80 percent of total time delays. 13

Table 2. Potential Causes of Project Delays Included in the 2002 Survey (2). Potential Causes of Project Delays Conflict with other construction projects Delays in environmental planning Delays in receiving materials Delays in right-of-way acquisition Delays in design Differing site conditions—utility conflicts Differing site conditions—other causes Equipment shortages Errors in plans or specifications Funding issues Insufficient work effort by contractor Labor shortages Late start on work by contractor Owner-requested changes Pay items do not match scope of work Permitting issues Poor coordination of work by contractor Utility relocations delayed Weather Other Table 3. Ranking of Top Ten Causes of Project Delays Based on Survey Results (2). Cause of Delay DOTs Designers Contractors Delays in utility relocations 1 1 1 Differing site conditions—utility conflicts 2 2 3 Errors in plans and specifications 3 13 2 Weather 4 6 4 Permitting issues 5 4 7 Delays in right-of-way acquisition 6 9 11 Delays in environmental process 7 3 8 Insufficient work effort by contractor 8 5 18 Owner-requested changes 11 10 5 Differing site conditions—other causes 9 7 6In 2003, FDOT analyzed causes of UR delays during the construction phase (4). The analysisincluded a review of cut damage reports and supplemental agreements in District 2 betweenJanuary 2000 and June 2002. A cut damage report is generated after a utility facility is damagedduring construction. The study concluded that utility facilities were damaged 77 percent of thetime because of contractor actions, 15 percent of the time because of inaccurate plans, and 8 14

percent of the time because of utility owner actions. The study also noted that utility facilitydamages caused contractor delays in 30 percent of their projects. One of the reasons for URdelays mentioned in the report was inaccurate or inexistent location data about utility facilities.The FDOT study also noted UR delays in cases where a utility owner did not allocate resourcesto conduct a relocation but instead used those resources to respond to customer demands,maintenance needs, or service upgrades. Other UR delays were caused by utility coordinators notbeing aware of changes the contractor made to the construction schedule, which resulted inconflicts between highway construction activities and utility relocation activities.In 2006, the South Carolina Department of Transportation (SCDOT) completed a study listingfactors that delay construction projects (5). The research included a survey of SCDOTconstruction engineers and an aggregated analysis of contract extension data. The reportidentified six main reasons for delays in construction projects, including utility delays(21 percent of contract extensions), extra work (17 percent), administrative delays (15 percent),design changes (12 percent), weather delays (10 percent), quantity adjustments (10 percent), andunknown (17 percent). The study also noted that SCDOT was beginning to use SUE more oftento help with an earlier identification of utility conflicts.In 2011, the FHWA Office of Inspector General (OIG) completed an audit of highway projectsadministered by local public agencies (LPAs) (6). The audit noted that state DOTs wereresponsible for providing oversight of billions of dollars in federal-aid program funds given toLPAs for highway infrastructure projects. The 2009 American Recovery and Reinvestment Actalso invested billions of dollars in LPA-led infrastructure projects. The audit reviewed 59federal-aid projects in four states. For the 59 LPA-led projects, OIG conducted compliancereviews in 12 key activities, ranging from change orders and claims to project bidding, projectreporting and tracking, and construction close-outs. Of the 42 projects reviewed under thecategory of change orders and claims, 33 projects had errors (although the analysis did notdisaggregate these data). Of the three projects reviewed under the category of utility agreementsand reimbursem*nts, two projects had errors.In 2018, FHWA completed a national review to assess whether utility coordination practicesposed a risk to the federal-aid highway program (7). The review included two phases. DuringPhase 1, FHWA reviewed utility coordination practices in all 50 states, the District of Columbia,and Puerto Rico, with a focus on utility agreements; utility relocation plans, schedules, and costestimates; information in contract bid documents; and impacts during construction, such as timedelays and cost increases. During Phase 2, FHWA conducted site visits at five state DOTsrepresenting different geographic regions and federal-aid program sizes. The site visits includeda more in-depth review of available information and discussions with state DOT officials,construction contractors, and utility owners.Issues found during the national review included the following: • Lack of accurate utility location information on plans. • Incomplete utility relocation plans. • Lack of justification for utility relocation estimates. • Lack of utility relocation schedules. 15

• Lack of utility information in bid packages. • Inability to quantify utility cost-and-time increases on highway construction projects. • Lack of utility relocation oversight and inspection as well as source documents to support utility payments (utility final vouchers).The FHWA report highlighted that lack of adequate data about existing utility facilities causedutility conflicts to be misidentified or not identified at all prior to construction, resulting, in turn,in contractors finding utility facilities during construction unexpectedly and causing projectdelays or cost increases.The FHWA report also documented successful practices with examples on how to address theissues listed above. Worth noting were practices related to the preparation of utility relocationplans, utility relocation schedules, and cost estimates. FHWA outlined a series of high-levelrecommendations for FWHA division offices to discuss with state DOTs. Theserecommendations provided the basis for the National Highway Institute’s web-based course“Preparing and Communicating Effective Utility Relocation Requirements” (8).Impacts on Project CostsThe technical literature is scant on the impact of UR issues on project costs. In 1984, NCHRPcompleted a synthesis project that examined UR delays and costs on highway projects (9). Thesynthesis summarized information received from several states, including California, Florida,Illinois, New Jersey, and New York. In California, the California Department of Transportation(Caltrans) noted that the state compensates the contractor if the contractor is delayed becausehigh-risk utility facilities are not shown on the plans or because utility relocations are notcompleted within the specified period of time. In New York, the dollar amount of claimsrepresented nearly one percent of the value of the construction contracts awarded. However, theaverage settlement of UR claims was on the order of 10 percent of the amount filed.The synthesis highlighted that UR claims were typically the result of delays caused by unknownutility facilities, utility facilities that were not located properly, and untimely relocations. It alsohighlighted that the stated reason associated with a claim frequently masked the actual reasonsbecause it was common to group several items in the same claim but label the entire claim usingone of the items.In 2004, the Indiana Department of Transportation (INDOT) completed a research project thatexamined cost overruns and time delays in INDOT projects (10). The research included a surveyof DOTs on the causes of cost overruns and time delays, an analysis of cost overrun dataprovided by other DOTs, and a detailed analysis of change order data that INDOT provided. Thestudy concluded that INDOT was average in terms of cost overrun rates compared to other states.The overall rate for cost overrun amounts at INDOT between 1996 and 2001 was 4.5 percent.Some 55 percent of all INDOT contracts experienced cost overruns. In addition, 12 percent of allINDOT contracts experienced time delays, and the average delay per contract was 115 days.Factors that influenced cost overruns, time delays, and change orders included contract bidamount, difference between the winning bid and the second bid, difference between the winningbid and the engineer’s estimate, and project type and location. 16

From a review of 18,000 change order records between 1996 and 2001, the study found mostchange orders were under the categories of errors and omissions in PS&E followed byconstructability and changed field conditions. The review found 123 UR change orders,including 13 change orders under errors and omissions in PS&E, 74 change orders underconstructability, and 36 change orders under changed field conditions.The research also highlighted that different DOTs organize and group change orders differently.The level of disaggregation in change order classifications varies widely. How DOTs account forUR change orders also varies widely, ranging from not having a separate category for URreasons to disaggregated categories such as not relocating on time or unknown utility facilitiesaffecting the project. As an illustration, Table 4 lists codes or groupings for UR change ordersmentioned in the INDOT research report. Table 4. Codes or Groupings of Change Orders (10). State Code/Grouping Description Florida 1 Utility delays Minnesota UD Utility delay New Jersey H Change to address a utility issue Ohio 14 Utility relocation delay Ohio 15 Improperly located utility Ohio 16 Unknown utility South Dakota 14 Utility agreements Texas 6 Untimely right-of-way/utilitiesIn 2009, TxDOT completed a research project that examined opportunities for integration ofutility and environmental activities in the project delivery process (11). The research included ananalysis of 30,043 change order records from July 1999 to February 2007 and 17 UR claimrecords from June 1996 to October 2007. Table 5 lists the categories and reason codes used forchange orders at TxDOT. Table 5. Change Order Categories and Reason Codes at TxDOT (12). Category Code Change Order Reason Incorrect PS&E (TxDOT design): TxDOT prepared the PS&E and an error and/or omission is1. Design Error or 1A discovered, but there is no additional cost to the project, nor any contractor delay, rework orOmission inefficiencies. Incorrect PS&E (consultant design): A consultant prepared the PS&E and an error and/or 1B omission is discovered, but there is no additional cost to TxDOT, nor any contractor delay, rework or inefficiencies to the project. Design error or omission (other): There is an error and/or omission, (TxDOT or consultant) but 1C the cause (all or partial) cannot be assigned to TxDOT or the consultant and other codes in this category are not appropriate. Design error or omission that resulted in delay, rework, or inefficiencies (TxDOT design): 1D TxDOT prepared the PS&E and an error and/or omission is discovered and additional cost, contactor delay, rework or inefficiencies occur on the project. Design error or omission that resulted in delay, rework, or inefficiencies (consultant design): A 1E consultant prepared the PS&E and an error and/or omission is discovered and additional cost to TxDOT or contractor delay, rework or inefficiencies occur on the project. 17

Category Code Change Order Reason2. DSCs DSCs (unforeseeable): Actual site conditions are found to be different than depicted in the plans, 2A(Unforeseeable) soil borings or other project information. 2F Site conditions altered by Act of God: The project is impacted by Acts of God. Unadjusted utility (unforeseeable): Unknown utilities impact the project. [Note: This reason code 2G is no longer active.]3. TxDOT 3A Dispute resolution.Convenience 3B Public request after letting: A change is made, or work is added to accommodate a public request. Reduction of future maintenance: A change is made with the intent of minimizing the need for 3E future maintenance. Coordination should be untaken to determine FHWA participation. 3F Additional work desired by TxDOT: TxDOT adds needed work. 3H Cost savings opportunity: The project cost and/or project duration are reduced. Implementation of improved technology or better process: Improved technologies or better 3I processes are utilized in the project. Addition of stock account or material supplied by TxDOT provision: This code should be used to 3K buy material purchased by the contractor and not incorporated into the project. It should also be used when TxDOT supplies material to the contractor that is incorporated in the project. Revising safety measures: Safety measures on the project are revised. The safety enhancement 3L may be suggested either by TxDOT or the contractor. 3M Other. [Note: This reason code is no longer active.] Upgrade to current standards: Necessary changes are introduced to upgrade to current design 3N standards where standards have changed subsequent to PS&E preparation. 3O Time extension: Time to the contract is added. No other work is included in the change order. 3P Repair due to third party damage. A third party causes damage to TxDOT property. Emergency declaration. An Act of God happens, such as earthquake, tornado, hurricane or other 3Q cataclysmic phenomena of nature. 3S Maintenance contract extension. A special provision to Item 4 is activated. 3T Activation corrections. Corrections are needed to entries made or omitted in error at activation.4. Third Party Failure of a third party to meet commitment: A third party to the contract fails to fulfill any part of 4AAccommodation their commitment. Third party request for additional work: Additional work is requested by a third party. Generally, 4B this will require a modification to the advance funding agreement. 4D Third party accommodation: Other codes in this category are not appropriate.5. Contractor Contractor requested change in traffic control plan or sequence of work: The contractor requested 5AConvenience change to the traffic control plan or sequence of work and must be acceptable to TxDOT. Contractor requested change in materials and/or method of work: The contractor changed 5B materials and/or method of work. The change must be acceptable to TxDOT. Payment for partnering workshop. The contractor is reimbursed for TxDOT’s agreed share of 5C partnering expenses in accordance with Special Provision 000-002. 5E Contractor convenience: Other codes in this category are not appropriate. Price reduction: Contract items have deficiencies and TxDOT is willing to accept work at a 5F reduced price. Right-of-way not clear (third party responsible): The contractor is impacted because right-of-way6. Right-of-Way 6A was not cleared on the date(s) specified in the plans where a third party is responsible for theand Utilities right-of-way acquisition. Right-of-way not clear (TxDOT responsible): The contractor is impacted because right-of-way 6B was not cleared on the date(s) specified in the plans where TxDOT is responsible for the right-of- way acquisition. 18

Category Code Change Order Reason Utilities not clear: The contractor is impacted by known utilities not being adjusted or relocated on 6C the date(s) specified in the plans. [Note: This reason code is no longer active.] Other: Other codes in this category are not appropriate. [Note: This reason code is no longer 6D active.] 6E Untimely right-of-way: Other codes in this category are not applicable. 6F Joint-bid utilities: This code should be used for all joint-bid project change orders. Known unadjusted utilities: Utilities are known to be in the vicinity and are potentially in conflict, 6G but the utility was not properly marked or a utility did not finish the utility adjustment as scheduled. 6H Unknown unadjusted utilities: Utilities are not known to be in the vicinity and are in conflict. Contract terminated–design error TxDOT: A project is terminated or a significant portion of a7. Termination 7A project is eliminated due to a major design error and/or omission where TxDOT prepared the PS&E. Contract terminated–design error consultant: A project is terminated or a significant portion of a 7B project is eliminated due to a major design error and/or omission where a consultant prepared the PS&E. Contract terminated–utilities: A project is terminated or a significant portion of a project is 7C eliminated due to a major utility delay or impact. The utility impact could be the result of either a known or an unknown utility. Contract terminated–right-of-way: A project is terminated or a significant portion of a project is 7D eliminated due to a significant right-of-way acquisition delay. Contract terminated–third party: A project is terminated or a significant portion of a project is 7E eliminated when it becomes known or evident that a third party will not be able or is unwilling to fulfill its obligation under an advance funding agreement. Contract terminated–Acts of God: A project is terminated or a significant portion of a project is 7F eliminated due to an Act of God. Contract terminated–other: A project is terminated or a significant portion of a project is 7G eliminated due to reasons where other codes in this category are not appropriate.The first database query involved using UR change order reason codes. However, for somerecords, the description turned out to be unrelated to a utility issue. Separate queries using thedescription explanation columns produced records that were UR, even though the correspondingreason code was not one of the UR codes in Table 5. After adding a list of 25 UR keywords tothe query of the description and explanation fields, the result was a dataset of 1,144 change orderrecords. On average, using the UR codes accounted for only 53 percent of the total number ofrecords retrieved. A total of 139 change orders were associated with change orders that includedterms such as “delay” or “add days” in the description and explanation fields. Of these records,only 72 change orders included a description sufficiently reliable to estimate the total time delay.An additional 41 records were for no-cost extensions.Table 6 shows the list of contractor claim categories at TxDOT. From June 1996 to October2007, there were 17 contractor claim records for which the category was unknown utilityinterference (UU claim code) or known utility interference (UK claim code). At the time of theanalysis, 13 claims had been settled or closed. The time to settle UR contractor claims rangedfrom 210–848 days, for an overall average of 492 days (or about 1 year and 4 months). 19

Table 6. Contractor Claim Categories at TxDOT. Category Description CA Contract administration CA-Insp Contract administration – Inspection CA-Qty Contract Administration – Quantities CA-TA Contract Administration – Time CA-Test Contract Administration – Testing CIS Change in scope DSC Differing site conditions EW Extra work O Other PSE PS&E R Late right-of-way acquisition RW Rework UK Known utility interference UU Unknown utility interferenceCost overruns on infrastructure projects are frequently the reason DOTs get negative reports inthe media. A sample of situations where the media has reported on UR costs affectinginfrastructure projects follows: • In 2015, newspapers in Texas reported that TxDOT had listed $25 million in additional payments to contractors because of issues with communication lines over a three-year period (13, 14). Project delays of several months were also noted. In one case, issues with existing communication lines accounted for a one-year delay in starting the highway construction. • In 2013, the California High-Speed Rail Authority awarded its first contract for the construction of the high-speed train route in Fresno and Madera counties. At that point, the estimated cost to relocate utility facilities was $25 million. In 2018, the press reported that change orders, penalties for delays in acquiring right-of-way, and increases in utility relocation costs had resulted in a project cost estimate increase from $1.2 billion initially to nearly $1.5 billion (15). • In 2019, a trade magazine article drew attention to highway construction projects in South Carolina, North Carolina, Montana, and other states, regarding utility relocation delays and the impact these delays have on the overall construction schedules (16). The article discussed situations where utility owners did not relocate their facilities on time, affecting highway construction activities. It also mentioned issues with late design changes, and projects going to letting without having all utility facilities relocated. • In 2021, a television channel in Indiana reported on the impact of utility relocation delays on the progress of a highway construction project (17). Local officials indicated that the delays were causing higher costs on taxpayers, as well as generating an inconvenience to drivers. A communication line had to be relocated by April 2021, but by September the relocation had not yet taken place. 20

Impacts to ContractorsAs in the case of impacts on project costs, the technical literature is scant on the impact of URissues to contractors. The previous sections already included references to the 1999 GAO reportand the 2001 NCHRP report, which included survey and interview responses from contractors(1, 2).In 2003, a highway contractor in Indiana compiled a list of UR effects on construction projectsand the process they follow to systematically understand the level of risk and how to manage itduring the bidding stage, the pre-construction stage, and the construction stage (18). Thecontractor noted the following unknown impacts and costs related to utility conflicts duringconstruction: • Lower production rates than planned (i.e., higher unit costs) for installing underground appurtenances that were in conflict with existing or unknow utility facilities. • Increased costs because of the need to work around existing utility facilities that had not been relocated. • Crew delays while waiting on decisions regarding unknown utility facilities. • Having to schedule work during more expensive seasons (e.g., late fall or winter), or push the overall construction schedule into the next construction season.UR items they consider prior to deciding whether to bid include the following: • How much is known about utility issues from the bidding documentation: o UR information in notes or special provisions. o Whether SUE was used. o Level of detail about utility facilities on plans to determine existing conditions. o Utility contact information in special provisions. • Right-of-way status in relation to utility relocations: o Potential conflicts between right-of-way staking and clearing, utility relocation schedules, and highway construction schedule. o Particularly in urban areas, space availability for utility relocations. • During or after a site visit: o Utility facility markings. o Confirmation of existing utility conflicts. o Status of all utility relocations. o Confirmation of utility owner’s point of contact.UR items they consider after deciding to bid on the project include the following: • Determine how to build the project, including utility relocation schedules. • Identify productivity costs associated with existing utility facilities. • Identify productivity costs associated with utility relocation disruptions. • Assess UR risks and attempt to quantify costs to include in bid costs. • Estimate overhead recovery costs and supervisory costs to include in bid costs.UR items they consider during pre-construction include the following: 21

• Finalize project construction schedule. • Establish the project workflow to minimize disruptions and maximize time efficiency. • Schedule crew, equipment, material, and subcontractor resources. • Conduct pre-construction meeting, including participation of project owner, contractor, subcontractors, utility owners, local agencies, and other stakeholders.UR items they consider during construction include the following: • Monitor the work schedule. • Assess time and cost impacts resulting from utility conflicts and delays, as well as identify resolution strategies.In 2004, a task force led by INDOT and that included representatives of highway contractors(including the contractor mentioned previously), utility owners, and consultants identified keyissues related to utilities and strategies to address those issues (19). Construction phaserecommendations for INDOT included strategies to improve the coordination process, preparingthe right-of-way to expedite utility relocation work, and strategies to develop a policy andspecifications for dealing with unexpected utility facilities that are discovered duringconstruction.USE OF UTILITY IMPACT ASSESSMENT TOOLS DURING PROJECT DELIVERYAssessment and Management of Utility RisksThe technical literature is abundant on the topic of risk and risk management. However, it isscant on the topic of UR risks and management of these risks. The International Organization forStandardization (ISO) 31000 standard defines risk as the “effect of uncertainty on objectives”and risk management as “coordinated activities to direct and control an organization with regardto risk” (20). In the context of infrastructure projects, the 2010 NCHRP Report 658 defined riskmanagement as the “sequence of analysis and management activities focused on creating aproject-specific response to the inherent risks of developing a new capital facility” (21). The2012 international scan report on transportation risk management practices defined risk as“anything that could be an obstacle to achieving goals and objectives” (22). The report definedrisk management as a “process of analytical and management activities that focus on identifyingand responding to the inherent uncertainties of managing a complex organization and its assets.”Risk is related to uncertainty but is different from uncertainty. Uncertainty is a state of limitedknowledge, which is quite difficult or impossible to measure. Risk is an outcome of uncertaintyand normally has a negative connotation. Opportunity is also an outcome of uncertainty but has apositive meaning. Opportunities are sometimes called positive risks.The risk management process includes five iterative steps (Figure 1) (21): • Risk identification involves determining and documenting risks. • Risk assessment or analysis involves conducting a quantitative or qualitative analysis to assess the probability and impact of a risk. 22

• Risk mitigation and planning involves evaluating risk response options and preparing a risk management plan. • Risk allocation involves assigning risk responsibilities to stakeholders. • Risk monitoring and control involves gathering performance data and comparing against the risk management plan. Figure 1. Risk Management Process Steps.Risk registers are commonly used to manage risk. A key component of a risk register is a matrixthat combines the effect of probability of events and impact if the event happens. Matrix cells arenormally color coded to visualize risk level (e.g., green for low risk, yellow for moderate risk,and red for high risk).FHWA developed a risk register spreadsheet tool that includes a spreadsheet to document thefive risk management steps (23). The spreadsheet tool includes a risk register matrix (Figure 2)and examples to help users conceptualize and classify risk probability levels (Table 7) andimpact levels (Table 8). Notice that the impact level examples include suggested approaches forcost, time, scope, and quality. 23

VHProbability H HR M MR L LR VL VL L M H VH ImpactVL = Very Low L = Low M = Medium H = High VH = Very High LR Low Risk (green) MR Moderate Risk (yellow) HR High Risk (red) Figure 2. Risk Register Matrix (Adapted from [23]). Table 7. Example Approaches for Probability Levels (23). Example Level Probability Very Low Remote (10%) Low Unlikely (30%) Example 1 Medium Likely (50%) High Highly likely (70%) Very High Near certainty (90%) Very Low 1–9% Low 10–19% Example 2 Medium 20–39% High 40–59% Very High 60–99% 24

Table 8. Example Approaches for Impact Levels (23). Primary Objective Level Cost Time Scope Quality Example 1 No significant cost Minimal schedule Quality degradation Very Low Minimal scope change increase impact barely noticeable Changes in project limits Low <5% cost increase <3-month delay or features with <5% No deficiencies apparent cost increase Changes in project limits Minimal deficiencies in Medium 5–7% cost increase 3–6-month delay or features with 5–10% constructability, cost increase operability, and safety Major changes in project Major deficiencies in the High 7–10% cost increase 6–9-month delay limits and features with technical adequacy of >10% cost increase the final product Scope does not meet Final product notVery High >10% cost increase >9-month delay original purpose and acceptable due to need deficiencies Example 2 Insignificant cost Insignificant time Scope decrease barely Quality degradation Very Low increase increase noticeable barely noticeable Minor areas of scope Only very demanding Low <10% cost increase <5% time increase affected applications are affected Major area of scope Quality reduction Medium 10–20% cost increase 5–10% time increase affected requires owner approval Scope reduction Quality reduction High 20–40% cost increase 10–20% time increase unacceptable to owner unacceptable to owner Project end item is Project end item isVery High >40% cost increase >20% time increase effectively useless effectively uselessRisk assessments can be completed at various levels (e.g., agency or enterprise, program, andproject). In 2016, NCHRP completed a research project that examined the use of risk registerspreadsheet tools at the enterprise and program levels (24). The research included a survey ofstate DOTs, international transportation agencies, and non-transportation organizations. Of the27 state DOTs that responded to the survey, 19 DOTs indicated they had active enterprise-and/or program-level risk management programs.The risk register spreadsheet tool developed by FHWA includes a suggested list of risks for riskmanagement purposes (Table 9). The list includes only one UR risk: Unidentified utility impacts(under the construction functional area). 25

Table 9. Suggested Risks in FHWA’s Risk Register Management Tool (23). Functional Area Design or Construction Risk Construction Unidentified utility impacts Unexpected archeological findings Changes during construction not covered by the contract Unidentified hazardous waste Site is unsafe for workers Delays due to traffic management and lane closures Design Incomplete quantity estimates Insufficient design analysis Complex hydraulic features Surveys incomplete Inaccurate assumptions during the planning phase Environmental Unanticipated noise impacts Unforeseen Section 4(f) resources affected Environmental clearance for borrow site required Unanticipated barriers to wildlife Unforeseen air quality issues External Project not fully funded Politically driven accelerated schedule Permit agency actions cause unexpected delays Public objections Inflation and other market forces Organizational Resource conflicts with other projects Inexperienced staff assigned to project Lack of specialized staff Approval and decision processes cause delays Priorities change on existing programs Project Management Inadequate project scoping and scope creep Consultant and contractor delays Estimating and/or scheduling errors Lack of coordination and communication Unforeseen agreements required Right-of-Way Unanticipated escalation in right-of-way values Additional right-of-way may be needed Acquisition of right-of-way may take longer than anticipated Discovery of hazardous waste during the right-of-way phase Unforeseen railroad involvementEvery DOT manages UR risks during project delivery. However, based on a review of DOTpolicy documents and manuals, it is unclear to what degree DOTs use the risk management stepsdescribed above to manage utility risks systematically. The following sections illustrate 26

examples of techniques some DOTs use. In addition, the national survey summarized in Chapter3 sheds light on what kind of UR risk factors DOTs use.Utility Investigations and Impact AnalysisIt is widely known that existing utility data are frequently unreliable. Typically, agencies sendproject files to utility owners, either in portable document format (PDF) or computer-aideddesign (CAD) format, with a request to mark up those files with relevant utility information. Inmany cases, the marked-up files only show approximate utility facility locations. Sometimes,utility owners submit a copy of as-built files they already had, but these files are rarely scaled orgeoreferenced and follow a variety of formats, making it necessary to convert the files to ausable format and adjust their scale and alignment to match the project files. In any case, it isunclear how reliable the existing utility data are.An NCHRP synthesis completed in 2023, which focused on the collection, management, and useof utility as-built data, confirmed these observations (25). DOTs also reported not having survey-grade accuracy or mapping-grade accuracy requirements for the submission of utility as-builts.DOTs typically receive information such as owner’s name and contact information along withdata such as location, size, and material type. However, more detailed data are normally missing,such as number of lines and horizontal accuracy, contributing to poor quality and lack ofcompleteness in the utility as-built information provided.Questions about the completeness and quality of existing underground utility as-built datainformation and the potential liability of using this information by project designers promptedthe emergence of national standards. In 2022, the Utility Engineering and SurveyingInstitute (UESI) and the Construction Institute (CI) at the American Society of CivilEngineers (ASCE) published an updated version of the 2002 consensus standard for utilityinvestigations (labeled ASCE/UESI/CI 38-22 or ASCE 38 for short) (26). The ASCE 38 standardguideline outlines typical activities for conducting utility investigations and describes fourquality level attributes for individual utility features: quality level D (QLD), quality level C(QLC), quality level B (QLB), and quality level A (QLA). ASCE 38 includes examples showingutility facilities and their quality levels on utility investigation deliverables. However, it is worthnoting that ASCE 38 is not a standard guideline for utility data attribution or feature symbology.In 2022, ASCE published a new consensus standard (ASCE/UESI/CI 75-22 or ASCE 75 forshort) (27). The ASCE 75 standard guideline describes essential elements for recording andexchanging data about the location and other attributes of underground and aboveground utilityinfrastructure. The guideline focuses on newly installed, repaired, or otherwise exposed oraccessible utility infrastructure. The guideline establishes minimum, optional, and conditionalelements of spatial and non-spatial attribute data associated with utility infrastructure. Thestandard guideline also provides recommendations for effective practices to facilitate dataexchange among project stakeholders. Typical situations for application of the standard guidelinein the context of construction and utility inspections include the following: • New construction or repair of existing utility infrastructure. • Adjustment or relocation of existing utility infrastructure. • Any construction activity that exposes utility infrastructure. 27

• Trenchless utility installation or rehabilitation of existing utility infrastructure.The guideline specifies that the horizontal and vertical accuracies of all utility infrastructureobservation points should be reported at the 95 percent confidence level in accordance withFGDC-STD-007.4-2002 (28). The guideline further specifies that all positions should conform toan established datum referenced to the National Spatial Reference System and avoid relativespatial positioning. The guideline did not specify a specific horizontal or vertical accuracy,leaving it to be specified by agreement between the parties. Another critical part is the definitionof a framework for utility data exchange, which includes feature types, geometry types, andfeature attributes. Importantly, the list of feature types includes minimum, optional, andconditional data requirements. Examples of minimum data requirements include owner, utilitytype, feature type, operational status, horizontal spatial reference and positional accuracy, andvertical spatial reference and positional accuracy.The technical literature is abundant on the techniques and methods to conduct utilityinvestigations. Most of the available literature focuses on underground facilities. For example, in2009, a Second Strategic Highway Research Program (SHRP2) research report documentedunderground utility location techniques that were available at the time (29). The reporthighlighted the capabilities of the techniques as well as their limitations. It also highlighted thatmost geophysical methods require professional interpretation. In 2017, a research project in TheNetherlands completed an assessment of detection technologies for underground features (30).The research compares electromagnetic, magnetic, ground penetrating radar (GPR), and acoustictechnologies (Table 10). Table 10. Comparison of Underground Detection Technologies (Adapted from [30]). Electromagnetic Magnetic GPR Acoustic Characteristic Inductive Passive Cables X X X Detectable Metal X X X X X material Non-metal X X Functional at excavation speed Yes Yes Yes Yes No 0.1 m (0.3 0.1–0.2 m Accuracy 5% of depth 5–10% depth ft) (0.3–0.6 ft) 3–6 m Depth range <2 m (7 ft) <2 m (7 ft) <4 m (13 ft) <3 m (10 ft) (10–20 ft) Frequency 50–480 Hz 50–60 Hz 50 Hz–4 GHz 132–210 Hz Impact of soil Wet soil High High Low High High condition on Salty soil High High High High Low functionality Clay soil Low Low Low Low Low Sensitivity to terrain conditions Low Low Low High Low Swinging Swinging Swinging along along along Scanning pattern estimated estimated estimated In grid n/a pipeline pipeline pipeline location location location Real time X X X Data processing Post processing X X Estimated maturity level (scale 1–10) 7 7 6 8 4 28

Utility investigations based on the ASCE 38 standard (particularly QLB and QLA investigations)are almost always conducted during the design phase. Increasingly, DOTs are beginning toconduct utility investigations earlier (i.e., during preliminary design). It is rare to use SUE duringconstruction. Test pits are common during construction, primarily as a tool to confirm thelocation of underground features (Figure 3). Often, contractors begin digging test pits but end updigging slit trenches, particularly in situations where they cannot find underground featuresbased on the information available to them on project plans. In complex urban environments, it isalso common to complete “mass excavations” to expose underground utility installations over awide area (Figure 4).Courtesy of the Texas A&M Transportation Institute Figure 3. Test Pit to Expose Underground Utility Facilities.According to a survey conducted in 2002, 22 state DOTs used SUE on highway projects, but itwas not clear how systematically or to what degree (31). From the survey responses, most DOTsthat used SUE left it to discretion of the project manager or district utility coordinators to decidewhether to use SUE. 29

Courtesy of the Texas A&M Transportation Institute Figure 4. Mass Excavation to Expose Underground Utility Facilities During Construction.As part of Phase 1 of the national utility review mentioned previously, FHWA asked state DOTsto explain the process to document existing utility facilities and whether they used utility ownerinput, as-built plans, or SUE for this purpose (7). A total of 27 DOTs (53 percent) indicated thattheir primary utility investigation method was as-built plans and the One-Call process.Contractors, utility owners, and DOT staff indicated as-built location data were unreliable and, atbest, provided a general indication of X–Y utility location data.As part of the literature review, the research team gathered DOT manuals (typically utility ordesign manual) from the agencies’ websites. The review revealed that 38 DOTs mention ordescribe procedures or requirements for utility investigations in their policy documents.Some DOTs have developed tools to determine when to use SUE. The Pennsylvania Departmentof Transportation (PennDOT) developed a spreadsheet tool called utility impact analysis (UIA)to choose the appropriate utility investigation quality level for a project, more specificallywhether QLB or QLB and QLA would be necessary (32, 33). In general, UIA assumes thatpreliminary utility data are available prior to starting the analysis.UIA uses a two-step process. Step 1 is usually at the project level. Step 2 normally applies at theproject segment or location levels because projects are not completely hom*ogeneous regardingfactors such as density or age of utility facilities.As part of Step 1, the user answers four questions related to whether there is evidence ofunderground utility facilities; whether any excavation of more than 2 feet is necessary, includingexcavation on temporary construction easem*nts or other easem*nts; likelihood the project will 30

impact subsurface utility facilities; and lack of accurate utility facility data. A yes answer to anythese questions (which is a common scenario), could indicate that a QLB or QLA investigation isnecessary, and the user proceeds with Step 2.As part of Step 2, the user evaluates the potential impact associated with the following 13complexity factors: • Density (i.e., number) of utility facilities. • Type of utility facilities. • Pattern of utility facilities. • Material of utility facilities. • Access to utility facilities. • Age of utility facilities. • Project area description. • Type of project. • Quality of utility record. • Estimated business impact. • Estimated environmental impact. • Estimated safety impact. • Other impact.For example, for density of utility facilities, the user selects one of the following options: Low (ifone pipeline is crossing the road), Medium (if two-three pipelines are crossing the road), or High(more than three pipelines are crossing the road, or if there are unknown pipelines). Likewise, fortype of utility facilities, the user selects one of the following options: Less-Critical (in the case ofwater, forced sewer main, or stormwater), Sub-Critical (in the case of telephone, electric, cabletelevision, or gravity sewer), or Critical (in the case of fiber optic cable, oil or gas pipelines,high-voltage electric lines, or unknown facilities). Each impact level has a numerical value: 1 forLow, 2 for Medium, and 3 for High.After adding the numerical values for the complexity factors used and dividing by the number ofcomplexity factors used, the average impact score is compared against a reference table todetermine the quality level required (Table 11). Table 11. PennDOT’s Utility Impact Scores (33). Utility Impact Score Descriptor 1.01–1.67 1.68–2.33 2.34–3.00 Recommended minimum SUE quality level QLB QLB or QLA QLA Relative cost factor 16.67 33.33 66.67The Georgia Department of Transportation (GDOT) developed a utility impact rating form todetermine the quality level needed (34, 35). The form used 10 factors, where the impact level foreach factor could be low, medium, or high. Combining the impact levels for the 10 factorsproduced an overall utility impact score, which could be low (minimum project impact), medium(moderate project impact), or high (high project impact). GDOT recommended gathering QLD 31

data during the project concept development, QLC if the utility impact rating was low, and QLBif the utility impact rating was medium or high. These recommendations were at the projectlevel.More recently, GDOT modified the process to determine quality levels (36). Currently, GDOTrecommends conducting utility investigations as follows: • QLD: This level of information is typically recommended during the project concept development. • QLC: This level of information is typically used on rural projects and is recommended when preliminary design begins, and project mapping and survey control have been established. • QLB: This level of information is used to make preliminary decisions about storm drainage systems, footings, and foundations with a focus on avoiding existing utility facilities. QLB is typically used on urban projects and is recommended when preliminary design begins, and project mapping and survey control have been established. • QLA: This level of information is needed at specific locations for final design and utility placement decisions where the potential for cost savings is significant. It is recommended after the preliminary field plan review, preferably after completing a UIA.GDOT’s UIA methodology is different from what PennDOT uses. GDOT’s UIA methodologyrelies on a utility conflict list to determine to what extent the project affects existing utilityfacilities (37). The analysis is typically recommended after gathering QLB data and is used todetermine where QLA test holes are necessary (around 30 percent design). GDOT recommendsconducting a second UIA after the second submission of project files to utility owners to resolveany new or remaining utility conflicts (around 70–90 percent design if applicable). GDOT alsohas checklists for SUE deliverables. The checklists vary depending on the SUE quality level thatGDOT requested (37).The Washington State Department of Transportation (WSDOT) determines the type of utilityinvestigation needed depending on the type of project activity (38). Table 12 shows theminimum quality levels that are normally required for each type of project activity, along withrecommended quality levels depending on the information that is found during the analysis.WSDOT highlights that project teams should identify and apply appropriate techniques based onbudgets and expectations. In particular, project teams should evaluate the costs of a higherquality level versus the potential costs associated with the risk of accepting a lower quality level.Until recently, Caltrans did not use geophysical techniques for utility investigations. At Caltrans,a positive verification of utility locations (using test holes) is necessary if the utility facility isconsidered a high priority (39). High-priority utilities are: • Natural gas pipelines larger than 15 cm (6 inches) in diameter or with an operating pressure greater than 60 psi. • Petroleum pipelines. • Pressurized sanitary sewer pipelines. • High-voltage electric supply lines, conductors, or cables of at least 60 kV. • Pipelines transporting hazardous materials. 32

The project engineer can also order a test hole if a utility facility is within 3 m (10 ft) of aproposed excavation area. Table 12. WSDOT’s SUE Quality Level Requirements (38). Quality Level Required Type of Work QLD QLC QLB QLA Curbing ● Concrete barrier ● Striping ● Hot mix asphalt (HMA) overlay only ● ○ HMA or Portland cement concrete pavement ● ○ Clearing and grubbing operations ● ○ Removal of structures and obstructions ● ○ Surfacing ● ○ Sidewalks ● ○ Guideposts ● ○ Monuments ● ○ Pit site production ● ○ Signing ● Mailboxes ● Guardrail installation ● ○ Roadside planting ● ○ Fencing ● ○ Irrigation systems ● ○ Temporary erosion control ● ○ Pipe/drainage structures ● ○ Ditch/pond excavation ● ○ Roadway excavation/widening ● ○ Advanced geotechnical work ● ○ Bridge structures ● ○ Retaining walls ● ○ Piling ● ○ Signal systems ● ○ Illumination systems ● ○ Intelligent transportation systems ● ○ Railroad crossings ● ○ Sanitary sewers ● ○ Water mains ● ○ ● – Minimum level required ○ – Optional, depending on what is foundIn 2018, the Colorado legislature passed a law that mandated the use of utility investigations inaccordance with ASCE 38 (more specifically QLB and/or QLA) on any project that meets thefollowing requirements (40): 33

• The project has a construction contract with a public entity. • The project involves primarily horizontal construction. • The project involves utility boring or has an anticipated excavation of more than 60 cm (2 ft) in depth and covers at least 93 m2 (1,000 ft2).If the project meets these requirements, it then requires the services of a licensed professionalengineer.Utility Conflict ManagementUCM is a comprehensive multi-stage process that involves the systematic identification andresolution of utility conflicts. A term sometimes used in the United States instead of conflict isinterference. Abroad, the term interference is more common. In 2012, SHRP2 completed projectSHRP2 R15B, which involved the development of a systematic UCM framework to identify andresolve utility conflicts (41). The research produced three implementable products: A standalonetemplate for utility conflict lists, a utility conflict data model and database, and a one-daytraining course.As part of the SHRP2 Implementation Assistance Program, 18 state DOTs received grants fromFHWA to conduct pilot implementations (Table 13) (42). Members of the research teamconducted the research and provided technical support for the implementations. The goals andscope of the implementations varied depending on the needs of the individual DOTs, but, ingeneral, they ranged from implementation of the standalone utility conflict list at a sample ofpilot projects to the development and implementation of enterprise system modules to automatespecific UCM features.The results of the FHWA pilot implementations were positive, including tangible economic andproject delivery savings. For example, TxDOT identified almost $10 million in monetary savingsand 38 months in project delivery time savings after implementing the UCM approach at fivepilot projects. The savings were primarily the result of identifying changes in project design thatavoided utility relocations. TxDOT also identified additional benefits totaling $13 million fromprojects elsewhere in the state that started using the UCM approach. 34

Table 13. Agencies that Received Funds to Implement the R01A, R01B, and R15B Products. Round 3 Round 5 Round 6 Round 7 R15B: R01A: R01B: R01A: Iowa California Arkansas Indiana Kentucky DC California Michigan Michigan Kentucky Ohio Montana New Hampshire Texas Oregon Oregon Oklahoma Utah Pennsylvania South Dakota R15B: Washington Texas California Delaware R01B: Indiana California Maryland Indiana Oregon Montana Utah R15B: Montana Pennsylvania South Carolina Utah Vermont Washington R01A focused on database implementations of utility inventories. R01B focused on advanced geophysical techniques to conduct utility investigations. R15B focused on the implementation of UCM techniques.UCM stages can vary depending on project characteristics. As a reference, Figure 5 shows ageneric depiction of the project delivery process assuming a design-bid-build project deliverymethod. Members of the research team have conducted hundreds of UCM training sessions sincethe initial SHRP2 R15B research was completed. Through interactions with practitioners all overthe country, the research team has developed a generic, reference sequence of UCM activitiesthroughout project delivery. Figure 5 shows six concurrence points that correspond to importantUCM stages, along with a summary of UCM activities by stage.In practice, the number and placement of the UCM activities could vary from project to project.However, the stage structure and UCM activities described above provides a framework forimplementation.Members of the research team have been involved in the TxDOT UCM program since itsinception by providing technical support and training to all 25 TxDOT districts. As part of thisprogram, TxDOT selected 25 pilot projects that were in the preliminary stages of project delivery(typically no more than 30 percent design). The pilot projects range from small two-lane ruralprojects to multi-lane urban freeway projects. As of this writing, half of the pilot projects hadfinalized design and moved to construction. This wide range of pilot projects has given theresearch team a unique opportunity to see first-hand a multiplicity of practices for managingutility conflicts. The research team has also documented lessons learned and providedrecommendations to TxDOT officials (district and division level) and consultants to improveUCM practices. 35

Stage UCM Activities Utility field investigations are not conducted at this stage. Identify major UR issues that might affect the project route, scope, 1 Prepare realistic project scope (fiscally constrained). or schedule. Meet with utility owners about planned project. Send notifications of the highway project to utility owners. Focus on major physical constraints associated with utility Conduct preliminary utility investigation based on existing records facilities. 2 (QLD). Determine where additional utility investigation is needed. Identify utility conflicts and conduct initial assessment using a utility layout and a preliminary utility conflict list. Survey aboveground utility facilities (QLC). Request utility owners to confirm conflict locations, assess Conduct utility investigation using geophysical techniques (QLB). constructability challenges, and discuss potential resolution 3 Identify or update utility conflicts using utility layout and strategies. preliminary utility conflict list. Determine where more detailed investigations are needed. Develop preliminary critical path schedule for utility relocations. Conduct geophysical investigation (QLB) as soon as possible if not Design and coordinate utility relocation and protect-in-place done before. measures. Conduct utility test holes at specific locations (QLA). Prepare utility relocation plans and schedules for inclusion in utility 4 Identify or update utility conflicts. agreements. Analyze and review resolution strategies. Prepare or revise critical path schedule for utility relocations. Notify utility owners of required relocation or adjustment. Monitor and inspect utility relocations. Prepare utility as-built plans. Need for a utility investigation at this point should be minimal. Prepare UCP. Finalize design of utility relocation and protect-in-place measures. Include utility plans and utility relocation schedules in PS&E Finalize utility agreements. package. 5 Refine utility relocation schedules. Prepare utility statement to include in the construction bid Monitor and inspect utility relocations and prepare utility as-built package. plans. Need for a utility investigation at this point should be minimal. Assess and resolve new utility conflicts and corresponding impacts Conduct pre-construction utility coordination meeting. that are uncovered during construction. 6 Conduct construction utility coordination meetings. Update utility relocation schedules. Monitor and inspect utility relocations and prepare as-built plans.Courtesy of the Texas A&M Transportation Institute. Figure 5. UCM Stages and Activities (Assuming a Design-Bid-Build Project Delivery Method). 36

Involvement of the research team during the construction phase has included participation inutility coordination meetings and documenting lessons learned that could be applied for futureprojects during the design phase. For example: • A lesson learned from a utility coordinator involved in construction management indicated that focusing on flexibility and anticipating activities by the highway contractor instead of waiting for requests for information (RFIs) makes utility relocations during construction more expedited. Developing a working relationship with utility contractors is as important as developing a working relationship with highway contractors. • For one of the projects, the design team designed the project in three dimensions (3D) including utilities, but the bid package was prepared in two dimensions (2D). The contractor only received 2D plan sheets. The construction utility coordinator and the construction management team commented that if they had received the 3D design files, it would have helped them to manage utility situations during construction more effectively. • For another project, a proposed storm sewer inlet was designed a few feet away from an existing water line end cap. The location of the inlet was based on QLB data, which showed the location of the end cap. During construction, the contractor found a sizable thrust block providing critical structural support for the end cap, but the plans did not show the thrust block. None of the stakeholders during the design phase (SUE provider, project manager, designer, utility coordinator, or utility owner) thought a waterline end cap would need a thrust block for structural integrity. This conflict caused a delay during construction while a redesign of the stormwater was completed. This case highlights the need to strengthen SUE investigation requirements to make sure the deliverables depict all critical structural elements (such as thrust blocks, as shown in Figure 6), whether detected or suspected. • For another project, some utility owners did not receive information about existing wetlands, which was critical considering the time required to obtain United States Army Corps of Engineers permits. In addition, for the relocation of a communication line, the plans the utility owner received showed stormwater information, but not an existing sanitary sewer. With this information, the utility owner conducted the design and proceeded with the relocation in the field. After finding the sanitary sewer, the utility owner had to redesign and relocate their line again.Chapter 4 includes a more detailed description of the case study on United States (US) 281 inSan Antonio, Texas, which is part of the TxDOT UCM implementation. 37

Courtesy of the Texas A&M Transportation Institute. Figure 6. Sample Thrust Block Providing Structural Support to Pressure Pipelines.Decision Support SystemsA decision support system (DSS) is a system that facilitates the decision-making process insituations where the data needed to address a problem are unstructured (i.e., without a structure)or semi-structured. One of the applications of DSSs is risk management. DSSs could be fullycomputerized or manual.The literature is scant on the application of DSSs to address utility risks during project delivery.Based on the definition above, the PennDOT UIA tool described previously could be considereda DSS because it relies on a combination of unstructured and semi-structured data to determinewhether QLB or QLA may be recommended for a project.In 2006, TxDOT completed a research project to analyze the effectiveness of including utilityrelocations in the highway contract (43). The research included the development of a prototypeCombined Transportation and Utility Construction (CTUC) decision support tool. The tool,which was developed using Visual Basic for Applications in an Excel spreadsheet framework,was not implemented.For proposed utility relocations, the decision support tool isolated significant issues anddisplayed feedback from project owners and utility owners in favor or against including utilityrelocations in the highway contract. The feedback was based on a list of 53 factors calleddecision drivers that described unique circ*mstances that called for including (or not) a utilityrelocation in a highway contract. Each decision driver had an impact level that ranged from 4(No Impact) to 1 (High). The decision support tool also had a list of 17 questions that providedcontext to the decision drivers considered in the analysis. 38

The impact level associated with each decision driver was the result of feedback provided byTxDOT and utility owner stakeholders. As an illustration, Table 14 lists the top five pro-CTUCdecision drivers and the corresponding impact levels as well as the top five anti-CTUC decisiondrivers and the corresponding impact levels. Table 14. Top Five Decision Drivers (43). Impact Impact Rank TxDOT Decision Driver Utility Owner Decision Driver Level Level Pro-CTUC Decision Drivers 1 Severe schedule pressures 2.81 Reduced delay costs due to CTUC 2.61 Relocation can only happen during Relocation can only happen during 2 2.73 2.56 construction construction 3 Reduced delay costs due to CTUC 2.62 Substantial clearing and grubbing 2.47 4 Reduced delay costs due to CTUC 2.44 Reduced delay costs due to CTUC 2.45 5 Shared underground facility (all CTUC) 2.37 Severe schedule pressures 2.44 Anti-CTUC Decision Drivers Front-end loading: Increased costs with 1 Only utility crew can do –3.75 –3.5 CTUC Change order: Increased costs with 2 Utility cannot pay in advance –3.38 –3.47 CTUC 3 Utility work beyond right-of-way –3.29 Utility cannot pay in advance –3.44 Added contract tier: Increased costs 4 Utility plans are unacceptable –3.00 –3.37 with CTUC Utility owner does not qualify for State 5 –3.00 Only utility crew can do –3.33 Infrastructure Bank financial assistanceIn 2011, the SHRP2 research mentioned previously also produced a reference database of utilitylocating and characterization methods, which led to the development of a prototype decisionsupport tool called Selection Assistant for Utility Locating Technologies (SAULT) (29, 44). Theresearchers examined several design approaches for developing SAULT, including deterministic,fuzzy logic, case-based selection, choices and preferences, and artificial neuralnetworks (ANNs). The researchers noted that a robust database of real-world examples was notavailable and settled for a system that would provide strategies based on a range of conditionsbut would not be a substitute for first-hand experience with specific equipment under specificsite conditions. SAULT was written in Jess, which is a rule engine for the Java platform. Thesystem was based on a series of flowcharts describing site conditions and locating technologyoptions.CONSTRUCTION AND UTILITY INSPECTION REQUIREMENTSThe research team reviewed available information about construction and utility inspectionrequirements from all 50 states. The research team found 29 DOT websites that had specificrequirements for construction or utility inspections. This review reflects standard requirementsthat apply to a wide range of highway construction projects, utility relocations, and new utility 39

installations within the right-of-way (typically via permit). It does not reflect specificrequirements at the district or project level, which may be shared directly with stakeholders viaspecial provisions in utility agreements and permits. DOTs do not normally publish these specialprovisions on their websites. Readers should also be aware that the review reflects inspectionrequirements that are available in regulations and manuals but does not capture the degree towhich actual inspections conform to those requirements. Subsequent sections documentinspection practices and the collection of utility as-built data after utility relocations of newutility installations.AlabamaThe Alabama Department of Transportation (ALDOT) requires as-builts depicting the locationof existing and relocated utility facilities within the right-of-way. As-built files may be necessaryfrom a 3D field survey tied to project control points or GNSS coordinates, including elevationsof underground utility facilities (45). ALDOT does not require utility owners to submit as-builtfiles if there is not a significant deviation from plans, specifications, locations, and conditionscovered by the original approved permit or agreement. However, the utility owner must submit aletter to the region engineer stating that there is not a significant deviation and that original planscan be stamped “as-built.” If the deviation from the original plans is substantial, the utility ownermust submit as-built files showing actual horizontal (and vertical if necessary) locations, types,sizes, and other descriptive data.Sections 640–649 of the ALDOT standard construction specifications include utility constructionrequirements for minor utility adjustments, water lines, sanitary sewers, natural gas lines, andencasem*nt pipes, which can be used as inspection criteria for utility inspections (46). Forexample, construction requirements for water lines are as follows: • Excavate a drainage pit of 0.6×0.6×0.6 m (2×2×2 ft) below each hydrant. • Include 0.9 m (3 ft) of pipe to connect fire hydrants to the water line. • Excavate at least 0.45 cm (18 inches) plus the outside diameter of the water line. • Ensure a minimum depth of cover of 1.2 m (4 ft) under pavement and 0.9 m (3 ft) under ditches. • Install thrust blocks or other approved restraints on all water lines that are least 10 cm (4 inches) in diameter, at all wyes, tees, plugs, caps, and at bends with a deflection angle of at least 22.5 degrees.AlaskaAt the Alaska Department of Transportation and Public Facilities (DOT&PF), regional utilityengineers decide actual inspection levels for utility relocations (47). General guidelines todetermine the frequency and level of inspection include the complexity of the utility relocation;cost of the relocation; location of work and impact to the traveling public, businesses, andresidences; duration of the relocation; and sensitivity of location in terms of environmental,historical, and potentially contaminated areas.Table 15 shows survey accuracy requirements and Table 16 shows survey spacing requirementsas a function of curve radius (R) at DOT&PF (48). 40

Table 15. Survey Accuracy Requirements (48). Distance to Centerline Grade Highway Facility (cm [ft]) (cm [ft]) Bridges 0.6 (0.02) Clearing and grubbing 10 (0.3) Culverts 1 (0.03) Curb and gutter 1 (0.03) 0.6 (0.02) Guardrail 10 (0.3) Manholes, catch basins, and inlets 1 (0.03) 0.6 (0.02) Riprap 10 (0.3) 5 (0.2) Signs 10 (0.3) Underdrains and sewers 1 (0.03) 0.6 (0.02) Table 16. Survey Spacing Requirements as a Function of Curve Radius (48). R>250 m (820 ft) 125<R≤250 m (410<R≤820 ft) R≤125m (410 ft) Highway Facility (m [ft]) (m [ft]) (m [ft]) Centerline 25 (82) 12.5 (41) 10 (33) Clearing 25 (82) 12.5 (41) 10 (33) Curb and gutter 10 (33) 10 (33) 10 (33) Guardrail 10 (33) 10 (33) 10 (33) Riprap 20 (66) 20 (66) 20 (66) Slope stake/cross sections 25 (82) 12.5 (41) 10 (33) Under drains and sewers 10 (33) 10 (33)ArizonaThe Arizona Department of Transportation (ADOT) has a list of inspection activities forhighway construction projects (Table 17) (49). This list includes inspection activity descriptionsand frequency (or spacing) for individual construction work items.ADOT requires the collection of as-built data to document the final installation of contract biditems, such as pavement, signs, light poles, manholes, valves, storm drains, catch basins, curband gutter, and utility facilities (49). ADOT requires as-built files to be compatible with ADOT’sCAD and geographic information system (GIS) software. ADOT provides GIS file formats andfeature codes to assist with digital as-built file submissions.ADOT requires as-built data to include line and point features and sufficient photo links toensure the GNSS data properly describe the feature being captured (49). For example, for a signstructure that shows up as a point feature on the as-built plans, the construction manual requires aphoto showing the actual sign placard on the structure. ADOT requires all as-built data(including elevations) to link to the project datum. ADOT also requires location precisions to bethe same as the precision used to stake the project item. 41

Table 17. Construction Survey Task List (49).Specification Specification Survey Activity Description Inspector Frequency/Spacing Section Work Item Crew Clearing and Check staking limits with right-angle prism and 100-ft 201 X Beginning of job Grubbing chain Remove Structures 202 Measurements and records X Prior to removals and Obstructions Review plans; check contractor’s survey staking: Check catch points X 152 m (500 ft) maximum Check 90-degree angles X 152 m (500 ft) maximum203 and 204 Earthwork Check slope stakes X 152 m (500 ft) maximum Check alignment X 152 m (500 ft) maximum Spot check slopes with hand level X 152 m (500 ft) maximum Check each progressive lift depth X 152 m (500 ft) maximum Grading Roadway Check contractor bluetop survey staking X 61 m (200 ft) average 205 for Pavement Stringline all bluetops X All Subgrades, Subgrade only: Check contractor survey control bluetops X 61 m (200 ft) average 301 to 304 Subbases, and Subbases and bases: Check bluetops X By request only Bases Stringline each lift of subgrades, subbases, and bases X All Lean Concrete Check horizontal and vertical alignment of wire staking X 61 m (200 ft) maximum 305 Base Check hub and tack control with plumbline and stringline X 30 m (100 ft) intervals Portland Cement Check horizontal and vertical alignment of wire staking X 61 m (200 ft) maximum 401 Concrete Pavement (PCCP) Check hub and tack control with plumbline and stringline X 30 m (100 ft) intervals 402 PCCP repairs Measure, locate, record work X As required Asphaltic concrete 406 to 408 Check depths and offsets, stationing, and straight edging X 30 m (100 ft) intervals classes 42

Specification Specification Survey Activity Description Inspector Frequency/Spacing Section Work Item Crew Check Contractor's survey cut stakes: vertical and X Short runs - both ends horizontal control Pipes, culverts, and All large sizes, long runs;501 and 502 Use appropriate survey instruments X Drains others by request only Check pipe excavation and backfill using hand level, watch X Check each advance grade checker Catch Basins, Check position: Alignment and elevations X Check only upon request 503 to 505 Standpipes, Manholes Verify conformance with design X Field verify each location Forms/soffit/falsework: Verify edge of deck horizontal and Check every structure. Check X X vertical control. Check offsets, grades, screeds from control all items Abutments and piers: Check location and elevation of X Check every structure foundations prior to major pours Verify layout at beginning of Bearing pads: Check initial placement and control points, X job only, and by request prepare as-builts Concrete thereafter 601 Structures: Bridges Check bearing pads prior to concreting X Subsequent construction Check approach and anchor slabs X By request only Verify layout at beginning of Bid-Well: Provide fill marks for inspector to check bid-well X job only, and by request initial setup thereafter Continue progress checks: Depths, joint locations, etc. X Subsequent construction Verify layout at beginning of Check contractor’s initial staking, check footings placement Concrete X job only, and by request and elevations, etc. 601 Structures: Walls thereafter and Miscellaneous Check locations and grades; check all wall forms and Check all items miscellaneous structures for plumbness and alignment Check contractor’s survey control hubs, check elevations Pilings and Drilled X Initially all, then random603 and 609 and horizontal placement Shaft Foundations Check lines and grades X Check all structures 43

Specification Specification Survey Activity Description Inspector Frequency/Spacing Section Work Item Crew Forms/soffit/falsework: verify edge of deck horizontal and X Check every structure vertical control Check offsets, grades, screeds from control X Check all items Abutments: initial location and elevation X Check every structure Verify layout at beginning of Bearing pads: check initial placement and control points, X job only, and by request 604 Steel Structures prepare as-builts thereafter Check bearing pads prior to concreting X Subsequent construction Verify layout at beginning of Bid-Well: provide fill marks for inspector to check Bid- X job only, and by request Well initial setup thereafter Continue progress checks: depths, joint locations, etc. X Subsequent construction Verify layout at beginning of Check installation layouts, foundation elevations, and Sign Structures and X job only, and by request 606 to 608 slopes Support thereafter Check lines and grades X All major units Landscape Check contractor survey control bluetops X By request only 801 to 804 Earthwork Inspect final grading and depth of soil X All Check contractor’s survey cut stakes: Vertical and X Short runs–both ends horizontal control Water Distribution All large sizes, long runs; 808 / 809 Use appropriate survey instruments X and Sewer System others by request only Check pipe excavation and backfill using hand level, watch X Check each advance grade checker902 and 903 Fences Check layout work and measure for payment X Prior to and when complete Check contractor’s layouts X By request only 905 Guardrail Check layout and placement X Subsequent construction Only if curb and gutter is placed prior to paving; 908 Curb and Gutter Check alignment and grade control points X otherwise checked by inspectors Check contractor’s survey on permanent section corner 909 Survey Monuments X Verify all key monuments replacements and similar 44

Specification Specification Survey Activity Description Inspector Frequency/Spacing Section Work Item Crew 910 Concrete Barriers Check placement and dimensions X All critical points Right-of-way 911 Check placement X Verify all markers Markers Verify layout at beginning of Sound Barrier Check contractor’s initial staking, check footings placement 914 X job only, and by request Walls and elevations, etc. thereafter Construction Check locations, grades, and plumbness Check all structures 925 Surveying and Inspections and random checks as detailed above per Layout X As directed instructions of the engineer (per the specification) 45

ArkansasThe Arkansas Department of Transportation (ARDOT) has requirements for locating andsurveying existing utility facilities within the survey limits (50). The requirements, which are fordesign surveys, also include attributes for underground and overhead utility facilities. ARDOTrequires measuring the lowest point of the catenary of overhead transmission lines, but not of thecatenary of overhead service lines. ARDOT also requires recording utility pole locations with theprism placed on the roadside of the utility pole. For storm and sanitary sewer systems, ARDOTrequires collecting manhole rim elevations, manhole invert elevations, pipe sizes, pipe types, andpipe flowline elevations. For underground utility facilities such as water, gas, electric, andcommunication lines, locations based on 811 paint markings are acceptable, unless a SUEinvestigation is necessary. ARDOT requires boxes, meters, valves, and other appurtenances to bemeasured and recorded.CaliforniaAt the California Department of Transportation (Caltrans), the utility coordinator is responsiblefor ensuring that inspections are conducted for utility relocations and for locations where apositive location (i.e., requiring a test hole) is necessary (51). The utility coordinator must notifydistrict construction of any planned relocation and positive location work requiring inspection. Adistrict resident engineer is responsible for conducting the inspection and maintaining diaries todocument the work. Without an assigned engineer to inspect the work, a utility relocation shouldnot proceed (52). Inspection objectives include the following: • Ensure the utility owner’s work complies with relevant design, construction, and traffic requirements. • Ensure utility facilities are cleared per the notice to owner, the encroachment permit, and the utility agreement. • Observe and record labor, equipment, and materials used to accomplish the work and materials removed for salvage when the utility relocation is completed at state expense.ColoradoAt the CDOT, utility owners must submit as-constructed (as-built) plans within 45 days ofcompleting a utility facility relocation, showing actual final aboveground and underground utilityfacilities, including location, alignment, profile, and depth (53). Utility owners must submit as-constructed plans in a 300-dpi, PDF file. In addition, utility owners must provide the depth andelevation of each structure, as specified in the special provisions of each permit (53). CDOT’sSUE scope of work requires the collection of X-Y-Z coordinates for all newly installed orrelocated utility facilities (54). Table 18 shows minimum horizontal and vertical tolerances forselected highway features that can be used as guidance while preparing the as-constructed plans(55). 47

Table 18. Minimum Horizontal and Vertical Tolerances for Highway Features (55). Accuracy Tolerance in cm (ft) Facility Horizontal Vertical Culverts and sewers 0.9 (0.03) 0.6 (0.02) Manholes, inlets, and meter vaults 0.6 (0.02) 0.3 (0.01) Drainage pipe 0.9 (0.03) 0.6 (0.02) Water line 0.9 (0.03) 0.6 (0.02) Subsurface drains 0.9 (0.03) 0.6 (0.02) Major structures 0.3 (0.01) 0.3 (0.01) Steel Structures 0.3 (0.01) 0.3 (0.01) Traffic control devices 2 (0.07) 0.6 (0.02) Riprap 30 (1) 3 (0.10)In 2019, CDOT started a program to collect location and attribute data about utility facilitiesusing a web-based platform that includes three components: a data collection platform, dataintegration tools, and a web-based dashboard application (56). The data collection platform is aGNSS-based mobile software application that enables users to capture asset location andattribute data in the field, as well as upload the data to an online geospatial database in real time.Users can also georeference photos, prepare electronic forms, mark up design files, take fieldnotes, and create sketches. The data collection platform is 2D-based, but users can capture depthdata using an attribute.The web-based dashboard application enables users to visualize and analyze utility and pipelinefacilities based on information received from data collection devices via a real-time interface,such as aboveground or underground facilities, as-built information, photos, and documents. Thedashboard application enables users to mark up and edit map and tabular data and serve thatinformation to field users via the cloud.ConnecticutThe Connecticut Department of Transportation (CTDOT) utility accommodation manual listshorizontal and vertical clearances for various utility facilities. It is not clear whether CTDOTalso uses these requirements as guidance for utility relocation inspections. Examples of clearancerequirements include (57): • Utility poles: Minimum setback of 3 m (10 ft) measured from the edge of pavement or face of curb, when feasible and sufficient right-of-way exists. If a 3 m (10 ft) offset is not feasible, the pole may be positioned as close to the right-of-way line as possible. Utility poles man not be located less than 45 cm (18 inches) from the edge of pavement or face of curb. • Overhead distribution lines: Minimum vertical clearance of 4.7 m (15.5 ft) measured from the road surface at maximum sag condition of the line. For communication lines, the minimum vertical clearance can be reduced to 4.1 m (13.5 ft) at locations where the line does not cross a street or driveway. 48

• Underground lines: Minimum depth of cover of 0.9 m (3 ft) from the top of the structure to the pavement or ground surface. • Casing extension: At least 0.9 m (3 ft) beyond the slope or ditch and 5 m (15 ft) outside the edge of pavement.The construction manual requires the use of station IDs for documenting utility relocations (58).For overhead utility facilities, a pole number is required.GeorgiaGDOT’s standard specifications include requirements for as-built information about utilityfacilities that are included in the highway contract (59). For example, for fiber optic lines, as-built documentation should include final splicing and fiber allocation details for every splicelocation. GDOT requires as-built files to include red markups on the original plans and a separatespreadsheet with GNSS coordinates for each item. For intelligent transportation system (ITS)components, GDOT requires a separate spreadsheet with the GNSS coordinates of eachcomponent, with a submeter or better positional accuracy.IdahoThe Idaho Transportation Department (ITD) has a requirement for utility as-built plans to“accurately reflect” completed work including approved changes to original plans (60). Thisrequirement applies to both utility permits and utility agreements. Upon completion of the work,the utility owner submits as-built plans to the district maintenance section. After verifying theinformation is correct, the maintenance section forwards the utility as-built plans to the district’sutility permit official. ITD allows utility owners to use the approved utility plans of the utilitypermit or agreement as as-built utility plans if the actual location of the utility facility did notdeviate from what was approved. Otherwise, the utility owner must provide as-built utility plansshowing the actual locations.For highway construction, ITD’s standard construction specifications require as-built files tomeet construction tolerances (61). For areas with specified tolerance values (as specified in thecontract), the contractor must meet the tolerances shown in Table 19. For areas without specifiedtolerance values in the contract (e.g., ditches and side slopes), what values to use is at thediscretion of the construction engineer.ITD has a requirement for the collection of confidence point data to verify the accuracy of thenatural ground digital terrain model (DTM). The confidence points must be evenly distributedover the entire DTM area. The number and density of confidence points depends on the area(e.g., at least 10 points every 457 m [1,500 ft]). Vertical tolerance values depend on the type ofsurface: 3 cm (0.1 ft) for paved or concrete surfaces, 9 cm (0.3 ft) for machine graded orcompacted surfaces, 18 cm (0.6 ft) for irregular natural ground, and 45 cm (1.5 ft) for extremelyrugged and rock surfaces. ITD also has a requirement for the collection of grade verificationpoint data: one point for every 46 m2 (500 ft2) of grade (for grades within the subgrade area) andone point for every 93 m2 (1,000 ft2) of roadbed side and ditches (for grades outside the subgradearea). The district then uses the verification point data to evaluate the grade using any industry- 49

standard technique or method before the end of the first full business day following receipt of thegrade verification point data. Table 19. Control and Survey Tolerances (61). Tolerance in cm (feet) Description Horizontal Vertical Control (absolute position, independent of provided control) 0.9 (0.03) 0.9 (0.03) Control (relative to nearest provided control) 0.3 (0.01) 0.3 (0.01) Centerline points, including offsets 1.5 (0.05) Cross sections, slope stakes, and references 9 (0.3) 1.5 (0.05) Walks and bike paths 0.9 (0.03) 0.6 (0.02) Curb and gutter 0.6 (0.02) 0.3 (0.01) Culverts, ditches, and minor drainage structures 3 (0.1) 0.9 (0.03) Walls (e.g., retaining, mechanized stabilized earth [MSE], sound) 3 (0.1) 1.5 (0.05) Bridge substructure 0.6 (0.02) 0.6 (0.02) Bridge superstructure components 0.6 (0.02) 0.6 (0.02) Clearing and grubbing limits 30 (1) Right-of-way limits 3 (0.1) Roadway subgrade finish stakes 6 (0.2) 1.5 (0.05) Roadway finish grade stakes 3 (0.1) 0.6 (0.02) Paving reference line 1.2 (0.04) 0.6 (0.02)For highway construction, ITD has the following requirements for as-built files (61): • Use the ASB abbreviation (i.e., as-built) to denote actual horizontal, vertical, dimension, or quantity measured by the survey or otherwise representing as-constructed conditions. • Use the F.C. abbreviation (i.e., field change) for revisions or changes from the original design made in the field. In addition, mark as-constructed work in red ink or red pencil to identify the changes to the original design. • Use the DELETED label for not constructed elements.ITD requires the contractor to consolidate markings for all revisions and modifications on aclean, complete set of ITD-published plans.IllinoisThe Illinois Department of Transportation (IDOT) has the following requirements with respect toitems that must be checked, corrected, and added to the original plan sheets (62): • Horizontal and vertical control. • Horizontal alignment (including curve changes and control point ties), profile grade, and changes in typical sections. • Location, dimensions, and elevations of drainage structures. • Underground structures such as cable, conduits, and pipes. 50

IDOT also requires that original details should not be removed from the plan sheets.Sections 560–565 of the IDOT standard construction specifications include utility constructionrequirements for cast iron soil pipes, water lines, sanitary sewers, and hydrants, which can beused to facilitate utility inspections (63).IowaThe Iowa Department of Transportation (IOWADOT) requires utility owners to submit, within90 days after completion of construction, as-built files or a letter certifying the actual location ofthe utility facility was the same as described in the original plan (64). If the utility owner fails tomeet this requirement, IOWADOT has the option to hire an independent contractor to locate theutility facility and prepare an as-built file at the expense of the utility owner.The Iowa Statewide Urban Design and Specifications (SUDAS) Program is a non-profitorganization that receives funding from metropolitan planning organizations, regional planningauthorities, and local and state transportation agencies. SUDAS developed and maintainsstatewide urban design standards and construction specifications (65, 66). Several divisions andsections in these documents cover items such as water lines, sanitary and storm sewers. Althoughthey do not include specific inspection requirements, some of the provisions and visual aids canbe used to facilitate utility inspections.KansasThe Kansas Department of Transportation (KDOT) requires the inspection of all relocated utilityfacilities to ensure the locations are located as shown on the approved plans. The inspectionprocedure varies depending on what stakeholder is responsible for the utility relocation: utilityowner, KDOT’s contractor, or local public agency (67).For highway construction, KDOT requires the contractor to visually inspect right-of-way surveymonuments, establish or re-establish the project centerline and plan benchmarks, and perform allconstruction layout and reference staking necessary for proper control and completion of allstructures. KDOT also requires the contractor’s surveyor to undertake training on the use of thecontractor’s GNSS equipment. Table 20 shows relevant construction tolerances that KDOTuses (68). The specifications also include requirements for the site calibration of GNSSequipment and total stations. For bridges, KDOT has a list of critical bridge elements for whichsurveys must be within the tolerances established in contract documents (Table 21) (69). Table 20. Construction Survey Tolerances (68). Tolerance in cm (feet) Description Horizontal Vertical Slope staking 3 (0.1) 3 (0.1) Finish staking 1.5 (0.05) 0.3 (0.01) Critical bridge member staking 0.6 (0.02) 0.3 (0.01) Right-of-way survey monuments: Use Kansas Minimum Standards for Boundary Surveys Project control points 1.5 (0.05) 1.5 (0.05) 51

Table 21. Critical Elements Bridge Elements (69). Critical Element Critical Component Spread footing Location and elevation of centerline Pile cap footing Location and elevation of centerline Drilled shaft Location and elevation of center Drilled shaft cap Location and elevation of centerline Column Location and elevation of center Pile bent with web wall Location and elevation of centerline Abutment beam/bearing seat Location and elevation of centerline Pier beam/bearing seat Location and elevation of centerline Bearing devices Location and elevation of centerline, temperature offset Bearing stiffener Location and elevation of centerline, temperature offset Girder/beam Location of centerline Anchor bolts/preformed holes Location of centerline Expansion device Gap (corrected for temperature) and alignment Fillets (tenth point) Elevation Surface of forms (slab bridge tenth points) Elevation Post-tensioning duct Location and elevation Bolted field splice ElevationMassachusettsThe Massachusetts Department of Transportation (MassDOT) has standard specifications forstormwater facilities and traffic control devices (including conduit, manholes, handholes, andpull boxes) (70). MassDOT requires the contractor to submit five complete copies of as-built orcorrected copies of the contract plans, including locations and depths. For utility permits,MassDOT requires utility owners to submit as-built plans (in paper, AutoCAD, or PDF) showingthe horizontal alignment and grade elevations of all utility facilities, referenced to the roadwayalignment or state station numbers (71).MichiganThe Michigan Department of Transportation (MDOT) has a standard specification for watermains, which includes the pipe and related facilities such as valves, valve boxes, curb boxes,hydrants, and service connections (from the distribution main to the right-of-way line or asapproved by the engineer) (72). MDOT requires the contractor to submit two sets of as-builtplans within 30 days after completion of the work. The as-built plans must include pipe locationsand sizes, fittings, valve locations, hydrant locations, and service tap locations. The plans mustalso show the location of underground obstructions that required the relocation of the watermain. MDOT also has a standard specification for sanitary sewer systems, including pipes,manholes, cleanouts, and service leads. MDOT requires the contractor to submit as-built plans,including pipe and manhole locations (station and offsets), pipe size and slope, manhole size,invert elevations, tees, tie-ins, and individual service connections. 52

For highway construction, MDOT has construction survey tolerances, as shown in Table 22. Table 22. Construction Survey Tolerances (72). Tolerance in cm (feet) Description Horizontal Vertical Right-of-way 1.2 (0.04) Clearing 3 (0.1) Slope, subgrade, utility tunnel, and miscellaneous 3 (0.1) 0.9 (0.03) Pavement and drainage 1.2 (0.04) 0.3 (0.01) Bridges 0.3 (0.01) 0.3 (0.01) Cross sections 3 (0.1)For utility permitting, MDOT implemented a program called Geospatial Utility InfrastructureData Exchange (GUIDE) to facilitate the collection of X-Y-Z utility data at the time ofinstallation and organization of the data in a spatial database (73). Data collection requirementsinclude a positional accuracy of 5 cm (0.16 ft) horizontally and vertically and attribute data suchas utility type, installation method, feature type, traceability method, and material. Observationrequirements are as follows: • Start and end points. • At least every 30 m (100 ft) with the following additional points: o Deviations in installation alignment, including, but not limited to, intentional changes in geometry (e.g., to avoid obstacles) and fittings such as elbows. o Changes in facility characteristics (e.g., change in size, material, or encasem*nt size). o Start and end points for vaults. • Appurtenances installed concurrently with new main installations (e.g., service leads or stubs). • New appurtenances from existing mains. • Transverse utility crossings installed via trenchless methods.GUIDE also includes data collection requirements for a variety of trenchless installation methodsituations.MinnesotaThe Minnesota Department of Transportation (MnDOT) requires utility owners to submit apermit certificate of completion form along with as-built plans (74). The as-built plans mustinclude the location and elevation of newly installed or relocated utility facilities, referenced tohighway stations or the state grid system. MnDOT inspectors are responsible for: • Noting the depth of trenches and the type of required and installed materials. • Reviewing the method to backfill trenches and performing tests (or observing tests the utility owner conducts). 53

• Checking the depth of excavation for and placement of manholes to make sure there is not a conflict with other utility systems. • Looking for any bad soil conditions. • Making sure the utility owner covers out-of-service underground facilities or removes them from the right-of-way. • Checking the location of facilities and their proximity to structures such as planned fences, signposts, light standards, drain structures, storm sewers, bridge structures, approaches, and pier footings.New JerseyThe New Jersey Department of Transportation (NJDOT) has standard construction specificationsfor water mains, sanitary sewers, and gas lines (75). The specifications for water mains includepipes, service connections, hydrants, valves, valve boxes, and thrust blocks. The specificationsfor sanitary sewers include pipes, service connections, and manholes. The specifications for gaslines include pipes, service connections, and valve boxes.NJDOT requires the contractor to submit as-built plans in a format acceptable to the utilityowner. For water utility facilities, the as-built plans must include the location of all constructionitems (except reset fire hydrant and reset water valve box) and depth of the water pipe andservice connections at least every 30 m (100 ft). The as-built plans must also include stationing,distances referenced to the curb line, and three ties for each valve box, curb box, and hydrantwithin 15 m (50 ft) of aboveground physical features. The standard specifications are similar forsanitary sewer and gas utilities. As-built plans for gravity sewer mains must include rim, invertelevations, and pipe slopes.New MexicoThe New Mexico Department of Transportation (NMDOT) requires utility owners to submit as-built plans within 30 days after completion of the work (76). The as-built plans must be inAutoCAD .dwg or Microstation .dgn 3D file format. All utility location data must be tied to thedepartment’s monuments and use the North American Datum of 1983 (NAD83), the NorthAmerican Vertical Datum of 1988 (NAVD 88), and the New Mexico State Plane CoordinateSystem of 1983 (NMSPCS83). A New Mexico registered land surveyor must certify the utilitylocation data. In addition, NMDOT requires a metadata text file along with the as-built plans,including the district utility permit number; name, address, and phone number of the responsibleland surveyor; date of completion of the survey; equipment used to conduct the survey;horizontal and vertical control marks used to tie the survey to the NMSPCS83 and NAVD 88;ground-to-grid combined scale factor used; and elevation data at every 153 m (500 ft) and allsurvey break points.North CarolinaThe North Carolina Department of Transportation (NCDOT) has the authority to charge utilityowners for the cost to conduct inspections that, in the view of the division engineer, arenecessary to ensure the installation is completed according to what was permitted (77). The levelof inspection can vary from spot-checking overhead installations to continuous and close 54

observation of the installation and backfilling of underground facilities. Charging utility ownersfor inspection costs does not usually apply to highway construction projects.For horizontal drilling installations, NCDOT requires utility owners to submit as-built planswithin 30 days after completing the work. The as-built plans must be in GIS format (eitherEsri™ shapefile or geodatabase format or Google Earth™ .kmz format) and a PDF filecontaining the following data: Actual path alignment, depth of cover for the casing, actuallength, product diameter, casing diameter, and final elevations.North DakotaThe North Dakota Department of Transportation (NDDOT) has a construction records manualand companion checklists that provide detailed guidance on what inspection activities shouldfocus on and what information to collect during the construction phase (78, 79, 80, 81, 82). Forwater mains, sanitary sewers, and storm sewers, the inspection checklists cover preconstruction,construction, and post-construction phases.NDDOT requires contractors to submit a set of as-built plans. The plans can be hand drawn andscanned to PDF or prepared electronically, in which case they should follow NDDOT CADstandards. As-built plans should document changes to the following information (78): • Beginning and ending project stations. • Horizontal and vertical alignments. • Typical sections, including, but not limited to base or surfacing thickness, width of lanes and shoulders, and super elevation. • Features such as pavement tapers and transitions, driveway locations and sizes, sidewalk width and location, curb size and location, fencing, striping and pavement markings, location of safety appurtenances and shoulder rumble strips, and location of signal and lighting elements. • Location, elevation, or size of pipes and drainage structures. • Right-of-way and borrow easem*nts. • Location, elevations, dimensions, and other characteristics of box culverts and bridges. • Permanent benchmarks. • Removal items. • Placement of trees, shrubs, planters, and retaining walls.OregonThe Oregon Department of Transportation (OrDOT) requires contractors to submit as-built plansdocumenting changes to the contract plans during construction (83). As-built plans include thefollowing information: • Nonstandard or changed superelevation details. • Corrected typical sections, base, and surfacing details. • Changes in vertical and horizontal alignment. • Established or re-established right-of-way markers, monuments, and benchmarks. • Areas where subgrade or slope stabilization occurred. 55

• Changes to pipes and other drainage details. • New, replaced, removed, or abandoned utility facilities. • Road approaches and access locations.PennsylvaniaPennDOT has a section in its design manual, which provides instructions for conducting utilityrelocation inspections (33). The assigned inspector is responsible for maintaining an accuraterecord of the relocation work in the Utility Section of the Project Site Activity (PSA) Report oron the Utility Inspection Report Form D-4298. Inspection information includes locationreferences where the work took place and a confirmation that construction was in accordancewith the approved locations. The inspection report also documents items such as majorinstallation items (e.g., poles, length of pipe, and length of cable), equipment used, and numberof workers. The frequency of inspection should be determined by the type of utility facilityinvolved, the magnitude and location of the utility relocation work, and the quality of previouswork and billing accuracy of the specific utility involved.After completing the relocation work, utility owners must submit a certification of completion,certifying that all work has been accomplished in accordance with the plans, permits, estimates,materials, and other applicable data approved by PennDOT. Both the utility owner andPennDOT sign the certification of completion.South CarolinaSCDOT requires utility owners to submit as-built plans within 60 days after completing thepermitted work (84). As-built plans for directional drilling installations must include thefollowing information: • Actual path alignment. • Utility facility geometry. • Latitude and longitude data as well as elevations at each end. • Rate of grade. • Carrier pipe diameter. • Casing pipe diameter. • Depth of cover for the casing/carrier pipe • Bore hole diameter. • Actual viscosity, density, and composition of the drilling fluid. • Actual fluid pumping capacity. • Pressure and flow rates. • Carrier pipe field pressure test results.TexasTxDOT now has a rule that requires utility owners to submit as-built plans or certified as-installed construction plans after completing the relocation of a utility facility or the installationof a new utility facility within the right-of-way (85). As-built plans or certified as-installedconstruction plans must include the horizontal alignment and vertical elevations of the utility 56

facility using TxDOT’s horizontal and vertical datums, the relationship to existing highwayfacilities and the right-of-way line, and access procedures for maintenance of the utility facility.TxDOT requires as-built plans to comply with ASCE guidelines and standards.TxDOT requires as-installed construction plans certified by a utility owner or its representativefor each relocation or new installation within the right-of-way. TxDOT can also require a utilityowner to submit as-installed construction plans that are certified by an independent party or finalas-built plans that are signed and sealed by an engineer or registered professional land surveyor.Factors that influence this decision include: • Amount of available right-of-way or the proposed utility facility’s proximity to TxDOT facilities and other utility facilities. • Type of utility facility. • Complexity of required traffic control plans. • Need for a storm water pollution prevention plan. • Past performance of the utility owner providing accurate location data and conformance with its construction plans.For design surveys, TxDOT has the accuracy error allowances shown in Table 23 (86): Table 23. Accuracy Error Allowances for Design Surveys (86). Tolerance in cm (ft) Description Horizontal Vertical Bridges and other roadway structures 3 (0.1) 6 (0.02) Utility facilities and improvements 6 (0.2) 3 (0.1) Cross sections and profiles 30 (1) 6 (0.2) Bore holes 90 (3) 15 (0.5)The TxDOT Survey Manual does not include requirements for construction surveys. However,older versions of the manual did. For example, the 2011 version included a reference to theTexas Society of Professional Surveyors (TSPS) Manual of Practice for Land Surveying in theState of Texas (87, 88). The TSPS manual provides a uniform standard for professionalsurveying services in Texas. The standard defines the following categories of surveying services: • Category 1A—Land title surveys. • Category 1B—Standard land surveys. • Category 2—Route surveys. • Category 5—Construction surveys. • Category 6—Topographic surveys. • Category 7—Horizontal control surveys. • Category 8—Vertical control surveys. • Category 9—Investigative surveys. • Category 10—GIS products. • Category 11—3D control surveys. 57

The manual of practice includes survey tolerances for categories 1A, 1B, 2, 6, 7, 8, 9, 10, and 11.For Category 5—Construction surveys, the manual indicates that staked locations should be asaccurate as practicable and necessary. The manual recognizes that accuracy depends on manyproject-specific factors that require professional judgment.The North Central Council of Governments (NCTCOG) publishes and maintains public worksconstruction standards for use by cities, counties, and special districts in North Texas (89).Several divisions and items cover construction or rehabilitation of underground facilities, mainlywater lines, sanitary sewers, and storm sewers.UtahThe Utah Department of Transportation (UDOT) has a requirement for utility owners to submitutility facility data based on survey-grade accuracy. Another requirement is to submit as-builtrecords for each permit or relocation activity (90). UDOT keeps as-built survey data aboutcertain utility facilities and makes it available to highway contractors upon request (91).VermontThe Vermont Agency of Transportation (VTrans) can require utility owners to submit as-builtplans (92). Proposed plans must include the following information: • Offset from the right-of-way line, edge of the traveled way, or both. If the offset is not uniform, the plans must show all the locations and distance changes. • Depth at various locations (or, alternatively, show depths using typical sections). • Depths and locations of other adjacent utility facilities. • Location of directional bores, plowing, or trenching operations. • Treatment of roadside vegetation, especially if the vegetation is for aesthetics or snow control. • Replacement vegetation to replace items that were damaged or removed during utility installation. • Location of sensitive environmental areas, such as wetlands, hazardous material sites, historical sites, or endangered species habitats. • Type and location of erosion control measures. • Access points to utility facility. • Locations of permanent locked gates. • Special provisions by other regulatory agencies. • Traffic control plan.VirginiaThe VDOT has an inspection manual that provides guidance for inspections at pre-determinedstages of completion of a highway construction project (93). The inspection manual definesinspection levels, inspection objectives, and inspector activities. Inspection levels refer toinspection frequency (continuous, intermittent, or end product). Inspection objectives refer to theexpected outcome of a construction activity. Inspector activities refer to specific tasks aninspector must complete to achieve one or more inspection objectives. 58

The inspection manual includes inspection objectives and inspector activities for water andsanitary sewer lines, manholes, junction boxes, and ITS components. For example, inspectionobjectives for water and sanitary sewer lines are as follows: • Ensure uniform foundation and proper line and grade. • Verify pipe layout and placement of pipe bedding material and pipe. • Ensure uniform foundation and proper line and grade. • Ensure placement and depth of bedding material as outlined in the specification. • Ensure the pipe is of the correct type and size. • Ensure pipe joints are installed according to the contract. • Ensure pipe joints and fittings are sealed to the degree needed for the type and purpose of the pipe. • Ensure that quality water is provided to the public. • Ensure proper compacted cover has been achieved. • Verify backfill operations, suitability of materials, depth of layers, density, and moisture.Inspector activities needed to meet these objectives are as follows: • Before the contractor begins excavation: o Verify pipe layout. o Verify the contractor has contacted Virginia 811. • Before placement of bedding material: o Sketch and compute minor structure excavations, probe foundation, check line, grade, termini, and verify source of pipe bedding. • Before installing the pipe: o Verify the type, size, and evidence of inspection. • Before beginning the backfill operation: o Inspect installed pipe including line and grade, termini, length, and joint treatment. o Check for pipe damage during placement. • Before tie-in into the existing system: o Verify that contractor has disinfected the water mains. o Review the contractor report of satisfactory test results. • Before accepting pipe: o Check for correct joining and sealing of pipe. o Document testing for pipe leakage. • Before allowing construction traffic over the pipe: o Verify proper cover over the pipe.For design-build projects, VDOT requires the contractor to prepare as-built plans. The utilityfacilities depicted on the plans must be color coded according to the Underground UtilityDamage Prevention Act (94). The plans must show horizontal alignments and depths of therelocated underground utility facilities. 59

WashingtonWSDOT requires utility owners to submit as-built plans within 90 days after completing theutility facility installation (95). This requirement applies if there was an approved field change tothe accommodation document. Utility owners do not have to submit as-built plans if a WSDOTinspector document the changes. WSDOT notes these changes in the original accommodationdocument and in the utility franchise and permit database.West VirginiaThe West Virginia Department of Transportation (WVDOT) uses several forms to track theprogress of high construction projects (96). In addition to daily inspection reports and surveyfield books, the WVDOT construction manual includes a provision to use FHWA constructioninspection reports (96, 97). The FHWA inspection forms cover a wide range of construction-related items and include a reference to whether delays are attributed to utilities and right-of-way. These forms do not address location tolerances or errors.The daily reports enable inspectors to verify that the location, measurement, quantity, quality,and progress of work meet contract requirements. Relevant accuracy levels are as follows: • Right-of-way and temporary fence: 3 cm (0.1 ft) • Waterline pipe or casing: 3 cm (0.1 ft) • Sanitary sewer pipe or casing: 3 cm (0.1 ft)WVDOT requires contractors to submit as-built plans that include plan views, profile sheets, andcross sections. WVDOT recommends considering the following major items for preparing as-built plans: • Horizontal and vertical alignment: o Show changes in the alignment by recording the revised control points (i.e., points of intersection, points of curvature, and points of tangency). o Show the revised grade, right-of-way, and/or controlled access lines. o Collect sufficient data to re-establish the centerline, right-of-way line, and grade line at any location. o Show equations in stationing due to line revisions. • Excavation: o Show revised original cross sections, revised grades, and slopes with pay lines. • Drainage structures: o Show any change in location, length, flow line, type, or size. • Bases and pavement: o Show any changes in type or dimensions, with typical cross sections showing the area affected. • Bridges: o Show any change to bridge elements. 60

WisconsinThe Wisconsin Department of Transportation (WisDOT) require utility owners to submit X-Y-Zas-built coordinate data for all open cut or trenched utility work, as well as other situations inwhich a utility facility is exposed to facilitate a survey (98). Specific data collection requirementsinclude the following: • Collect data every 50 feet and all angle points or direction changes along the utility facility centerline. • Survey the top-center of each utility facility. • For multiple facilities (e.g., duct banks), measure the total outside-to-outside width. Facility depths may be determined using permit information.WisDOT recommends using RTK surveys. In areas with urban canyons or heavily wooded areas,WisDOT recommends using longer observation times, surveying more data points along a line,performing multiple or redundant measurements and averaging the results, or using establishedbenchmarks that have published X-Y-Z data.WisDOT requires using boring logs if they can be used to produce X-Y-Z data.WisDOT requires utility owners to submit as-built plans using the Wisconsin CoordinateReference System (WISCRS). In WISCRS, grid and ground coordinates are the same value,making it unnecessary to convert from grid to ground values using a combination factor. (Note:Combination factors were needed when WisDOT mapped projects using state plane coordinates).CONSTRUCTION AND UTILITY INSPECTION PRACTICESHistorically, conducting complete, accurate, and reliable construction and utility inspections atDOTs has been challenging. Inspectors usually have a heavy workload that, in practice, makes itextremely difficult for them to be at all the job sites where inspections need to take place. Insituations that involve excavation (e.g., for the installation of an underground facility such as apipeline and subsequent backfill), a common occurrence is for contractors to finish thebackfilling operation, but by the time the inspector shows up, the only way to verify theunderground installation would be to re-excavate and remove the backfill to expose the facilitythat needs to be inspected. In practice, asking the contractor to do this rarely happens.Furthermore, it is unusual for inspectors to have access or training to use surveying equipment toverify locations in the field.What follows is a summary of technologies and procedures that have been documented in theliterature, which have been used or have potential to make the utility inspection work moreeffective.Markers and Radio Frequency IdentificationFor decades, a widespread practice has been to use markers of various types to facilitate theidentification and location of underground utility facilities. Table 24 shows a summary ofcommonly used markers (29). 61

Table 24. Commonly Used Utility Facility Markers (29). Marker Type Description A marker (usually a 5-cm [2-inch] polyvinyl chloride [PVC] pipe) isSurface-to-structure marker embedded in the soil from the ground surface down to the utility facility. An aboveground sign or maker is placed near a utility facility (e.g., aUtility sign or pipeline marker high-pressure gas line, major water pipeline, or fiber optic line). Tracer tapes and wires are placed in the backfill, typically above newlyContinuous buried marker constructed nonmetallic water and gas lines. PK nails, surveying hubs, and surveying lathes are placed directly overParker-Kalon (PK) nail or survey marker a utility facility after excavating a test hole. Small magnets are placed in the roadway material directly over aSingle point buried marker utility facility after it was exposed.In 2015, FHWA completed a research project that documented the feasibility of managing utilityfacilities within the highway right-of-way in a 3D environment (99). One of the tasks included areview of the use of radio frequency identification (RFID) technology to mark and manageunderground utility installations.RFID systems can be passive or active. RFID tags in passive systems do not have an internalpower supply and store tiny amounts of data (typically tag ID and limited, pre-recorded attributedata). Range is limited. RFID tags in active systems have their own internal power source, whichextends the range considerably. Active tags can store more information than passive tags buttend to be bigger and more expensive.VDOT uses RFIDs to reduce the level of uncertainty with respect to newly installed utilityfacilities and, more specifically, as a damage prevention strategy. VDOT’s policy is to installRFID markers at the following locations: • Every 8 m (25 ft) along straight utility facility alignments. • At (significant) horizontal and vertical changes in direction. • At critical utility crossings, tees, and service connections. • On specific facilities that are important to the utility owner. • On out-of-service facilities when they are encountered or uncovered in the field.VDOT officials read the coordinates of each tag using a GNSS receiver as the tags are deployedin the field. VDOT also generates as-built polylines showing utility alignments and preparesclickable PDF files that users can query. VDOT makes these files available to utility ownersthroughout the construction phase so that they can update their records accordingly. Benefits ofthe RFID implementation at VDOT include the following: • Availability of georeferenced utility segment information that enables the establishment of protection zones to avoid utility damages. Another benefit is the availability of as-built information that highway contractors can use for test hole or test pit planning purposes. VDOT has also been able to catalog many cases of mismarks between One-Call locates and RFID marker-derived locations. 62

• Improvement in the horizontal and vertical accuracy of utility facility information. • Linkages between attribute data associated with each RFID marker with georeferenced coordinates for mapping and locating purposes. • Production and conveyance of reliable, as-built utility information to utility owners, locators, excavators, and design engineers. • Improved effectiveness of utility inspections by helping inspectors to verify that actual utility locations on the ground are consistent with design documentation. • Improved coordination with other VDOT officials, including construction inspectors, for any UR issues that might arise during construction. • No conflict with One-Call laws or regulations. • Installation of RFID markers in proximity to existing gas markers without interference. • Reduction in the risk of confusion between active line and out-of-service lines.Utility Data Available During ConstructionThe current practice for designing projects involves the use of CAD software that relies primarilyon vector graphics (which use primitives such as points, lines, and curves, as well as shapes orpolygons) as opposed to raster images (i.e., based on pixels). Most highway projects are designedusing 2D representations of the project by using plan views, cross sections, and profiles.Increasingly, DOTs are using 3D modeling techniques to visualize, design, and constructprojects (99). BIM has emerged as an evolution of 3D modeling, where facility components aremodeled as individual objects that have geometry, attributes, and relationships. BIM is nowstandard for vertical construction applications. In recent years, interest has increased in the use ofBIM for horizontal construction projects (100).Ideally, utility facility data should be depicted and used the same way as other data layers inhighway design files. In practice, utility facility data vary in source, detail, accuracy, andcollection timeframe, making it difficult to depict the data correctly and reliably. Typicalexamples that reflect current practices include the following: • Utility facility symbology (including, but not limited to, line weights, colors, symbols, legends, and notes) differs widely from project to project and even within the same project. • Utility lines and features are shown on utility maps right after collecting the data but are not necessarily shown or referenced on all relevant project design files. It is common to lose quality levels and/or notes as the layers showing utility facility data progress through the design phase. At some point, all that remains is a set of lines but without any context to help designers and contractors understand the significance and reliability of the linework. • Utility lines and features are frequently not included in PS&E files or bid packages, even if utility statements or certifications in these assemblies list utility relocations that are still pending. • Design plans, PS&E packages, or bid packages do not consistently show utility conflict data. Utility conflict locations are also not consistently shown on documents that are exchanged with various stakeholders during utility coordination. Utility installations that are relocated before or during the construction phase (and associated attribute data) do 63

not appear on construction plans, or changes to the operational status of previously documented existing installations are not updated.Unmanned Aircraft SystemsExamples of UAS applications that have been mentioned recently include (101): • Structures: Bridge inspections, high mast lighting inspections, retaining wall inspections, and tunnel inspections. • Operations and safety: Site monitoring, emergency response and incident management including crash reconstructions, search and rescue, route management, mud slide assessments, and snow avalanche management. • Construction: Estimates and bidding, topographic surveys and elevations, construction monitoring, inspections and quality control, land surveying, break-line surveys, quantities, surface validations, work zone traffic monitoring, and as-builts. • Maintenance: Roadside condition assessment, pavement inspections, vegetation management, overhead sign inspections, rockfall hazard mapping, and slope failures. • Planning and design: Vehicle counting, traffic volumes, site analysis, land surveys, geotechnical investigations, and environmental assessments. • Utilities: Utility investigations, utility design verifications, utility relocation monitoring, utility inspections, and utility as-builts.UASs equipped with miniaturized cameras enable the collection of high resolution, 3Dgeospatial data at lower costs than traditional techniques. New technologies also make it possibleto gather pictures and video using smartphones, which can be fed to structure-from-motion (SfM)/multi-view stereo (MVS) (or SfM for short) photogrammetry software to develophighly accurate 3D products. Operating UASs requires trained pilots and observers, butsmartphones do not. Anyone with a smartphone and the correct app would be able to capturedata in the field, which could be used to support the inspection process.A variety of flight designs may be possible depending on the purpose and size of the UAS datacollection activity. A flight design includes the trajectory the UAS will follow, endlap andsidelap requirements, and whether the operation of the aircraft will be autonomous ormanual (101).According to 14 Code of Federal Regulations (CFR) 107, a small unmanned aircraft is anunmanned aircraft that weighs less than 25 kg (55 lb) on takeoff, inclusive of everything that isonboard or attached to the aircraft (102). Most UASs that are used for highway applications aresmall UASs that weigh substantially less than 25 kg (55 lb), including payload.The Federal Aviation Administration (FAA) requires pilots to register UASs. FAA also issues acertificate of registration that must be carried with the UAS whenever the UAS is being used.Under 14 CFR 107 rules, the UAS pilot, or remote pilot in command, must obtain a remote pilotcertificate from FAA. The certificate is valid for 2 years and must be available during all UASoperations. Part 107 imposes several additional limitations on UAS operations (102). 64

Structure-from-Motion PhotogrammetrySeveral commercial and open-source SfM software suites are available for processing UASimagery to derive mapping products. The typical SfM image processing workflow is asfollows (101): • Stage 1 (Keypoint Extraction and Matching)—Image sequences are input into the software and a keypoint detection algorithm is used to automatically extract features and find keypoint correspondences between overlapping images using a keypoint descriptor. • Stage 2 (Bundle Adjustment and Sparse Point Cloud Creation)—A least squares iterative bundle adjustment is performed to minimize the errors in the keypoint correspondences. The matching points are verified, and their 3D coordinates simultaneously calculated to generate a sparse point cloud. To further constrain the problem and develop a georectified point cloud, camera geolocations from an onboard GNSS receiver and GCPs (if available) are introduced to constrain the solution. • Stage 3 (3D Point Cloud Densification)—Finally, parameters for each image are used as input into an MVS algorithm to densify the point cloud by projecting every pixel at the full image scale or projecting pixels at a reduced image scale.The basic output of the UAS-SfM image processing workflow is a densified set of X-Y-Zcoordinates of the imaged scene. This set, called a point cloud, is typically colorized by the red,green, and blue (RGB) pixel values of the digital camera. UAS-SfM point clouds can have highpoint density (easily exceeding 1,000 points/m2) due to the high camera resolutions and typicallow altitudes at which data are collected. The 3D point cloud can then be used to generate adigital surface model (DSM) of the terrain, which can then be used to orthorectify the imagesand produce an orthom*osaic image or a 3D textured mesh. Output for these derivative mappingproducts is commonly performed by commercial SfM software.As an illustration, Figure 7 shows a sample image of a 3D textured mesh resulting from adensified 3D point cloud. The 3D textured mesh is a surface composed by triangles (i.e., atriangulated irregular network), whose vertices are defined so as to minimize the distancebetween points of the 3D point cloud and the surface. It is worth noting that the image shown inFigure 7 is not a picture taken by the UAS. The 3D textured mesh is a true 3D model that enablesthe user to complete tasks such as reading X-Y-Z coordinates of any point, measuring 3Ddistances between any two points, and calculating volumes. For example, it would be possible toread the bottom and top X-Y-Z coordinates of the traffic sign; measure the width, length, andheight of the vehicle; and calculate the approximate volume of the 3D surface that represents thevehicle with respect to the pavement. 65

Courtesy of the Texas A&M Transportation Institute. Figure 7. Image of 3D Textured Mesh Resulting from Densified 3D Point Cloud (101).Smartphones and SfM ProcessingRecent advances in SfM photogrammetry software now make it possible to feed pictures andvideo gathered using smartphones to SfM software to develop highly accurate 3D products. Thebasic process involves walking along or around the area of interest, taking pictures and/or videowith the smartphone, running these files through a software component to generate pictures withpositional and orientation data, and then running these pictures through the SfM software. Theresult is a 3D model that is ready for measurement and inspection. As an illustration, Figure 8shows the 3D model of a hydrant and other adjacent utility facilities. Once the 3D model isproduced, it is possible to conduct measurements, including the extraction of X-Y-Z coordinatesassociated with features of interest.Courtesy of the Texas A&M Transportation Institute. Figure 8. 3D Model Resulting from Using a Smartphone and SfM Photogrammetry Software. 66

Light Detection and Ranging (LiDAR)LiDAR is widely used at DOTs, primarily for surveying applications, but not for construction orutility inspections. However, proliferation of small LiDAR sensors in recent years has openedthe door for a wide range of uses. Small LiDAR sensors are now mounted on small UASs andare also included as a feature in some smartphones and tablets.Compared with traditional airborne LiDAR mapping, UAS platforms offer more flexibility interms of flight design and data collection, higher scan density due to lower flight altitudes, rapidresponse capabilities, and reduced costs at localized geographic scales.Raw LiDAR data consist of a 3D point cloud of the ground and land cover with intensityinformation typically provided. LiDAR intensity is a measure of the return signal strength of thelaser pulse energy for each point that can also be used for object detection. A UAS-LiDAR pointcloud, relative to a UAS-SfM point cloud generated from the camera detector array, is irregularlydistributed (with varying levels of point density) due to the scan pattern, flight pattern, and swathoverlap. UAS-LiDAR point densities can exceed several hundreds of points per square meter,i.e., much denser than traditional airborne LiDAR (103).New Relevant Research ProjectsSeveral initiatives are starting at the federal and state levels, which are relevant to this research.For example, NCHRP recently started NCHRP 15-81, Guideline for Depicting Existing andProposed Utility Facilities in Design Plans (104). The main objective of the research is todevelop approaches to depict existing, proposed, and relocated utility facilities; prioritize thedepiction of data from multiple sources; reconcile inconsistent utility facility data from varioussources; and determine reliability of depicted data for design standards.Recently, NCHRP also started NCHRP 10-112, Guidelines for Digital Technologies and Systemsfor Remote Construction Inspection for Highway Infrastructure Projects (105). The rationale forthe research is that using mobile devices and modern surveying equipment for constructioninspection has been beneficial, and that remote virtual inspection (RVI) offers numerous benefitsthat support onsite construction inspection activities and enable the collection of digital data forseveral applications such as estimation of quantities, verification and acceptance, payment, anddevelopment of as-built records. The research will cover aspects of highway construction thatcan benefit from the use of RVI and will identify relevant technologies and systems (e.g., AI,LiDAR, UASs, augmented reality, and virtual reality). 67

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