CHAPTER 3
Utility Data for Depiction

3.1 Overview

Various data sources are available for identifying the presence, location, and attributes of existing utility facilities. Oftentimes, these data sources provide unique insight into the characteristics of an existing utility facility and can be complementary. When the data are collectively reviewed, properly evaluated, and thoroughly synthesized, the accuracy and completeness of the resulting utility base map are significantly enhanced. Integrating these various utility data sources into a utility base map yields one that is not only accurate and comprehensive but also provides a solid basis for optimal decision-making throughout the design phase. This approach enables all potential data discrepancies and gaps to be addressed and established as a best practice, leading to better planning, design development, and project management. However, a significant inconsistency within the engineering industry is the lack of standardized utility depiction, symbology, and various attributes. These depiction variabilities lead to scenarios in which data from various sources present incomplete or contradictory information, raising concerns about reliability.

The integration of data from these various sources was the prime motivation for the ASCE to create ASCE 38, with its emphasis being on using utility quality levels to communicate uncertainty in location data. Although suggestions about the potential look of the utility data visualizations were included, they were not prescriptive because CAD and other depiction software were not standardized at the time, and because of the nascent state of attempting to avoid project conflicts with utilities. Entropy over time has exacerbated this depiction variability.

3.2 Data Sources

Utility data vary in source, detail, accuracy, and collection time frame, making it difficult to integrate them into a cohesive depicted utility base map. Data sources used to identify and document existing utilities include the following:

• Utility owner records
• DOT/agency records – permits or project as-builts
• Utility staff historical knowledge/verbal accounts
• One Call markings
• Field survey/field edits
• Utility field investigations – visual indications in the field that can be observed and transferred to a set of plans
• Geophysics (e.g., ground-penetrating radar [GPR], electromagnetic locators)
• Satellite imagery
• AI-assembled mapping

• Exposure of underground utilities and gathering of specific point information, including location, type, size, condition, material, and other characteristics of underground features
• Utility subject-matter expertise – completion of the existing utility system from the evaluation of the data obtained from various data collection sources

Each of these data sources contributes to a specific achieved utility quality level result from a SUE utility investigation. ASCE/UESI/CI 38-22 describes SUE as a branch of engineering practice that involves managing utility risks throughout the project delivery process. The data sources previously identified are predominately associated with SUE activities, which are utilized in the development of the projectʼs utility base map. The data gathered from these sources vary in presentation, are typically depicted per the owner of record or the agency project sponsorʼs requirements, and are frequently limited in important utility attributes.

Note: While the following data sources are described according to the ASCE/UESI/CI 38-22 SUE quality levels, they only achieve these quality levels when judged to be so within a sealed SUE investigation. The sources are also still very useful in non-SUE investigations. These data sources are further defined as follows:

Data Source – Quality Level D: [Utility owner records; DOT/agency records – as-builts; utility staff historical knowledge/verbal accounts; One Call mark-outs]

These data sources are the most basic level of available information for determining the existence and location of existing utilities. The data are obtained from unreliable sources, such as existing utility owner records, indeterminate geophysics, verbal recollections, DOT/agency records/as-builts, and historical knowledge of anyone expressing familiarity with the existing facilities based on the presence of persons expressing knowledge of the utilities during the installation of the utilities and/or maintenance involvement. Of note, newer forms of data exist that may be considered as Quality Level D. Satellite imagery and AI-assembled sources of information should be considered at this quality level because they are external, third-party sources of information, and a utility investigation professional should judge the accuracy of the information.

Data Source – Quality Level C: [Field survey/field edits; utility field investigations – visual indications of actual utility structures in the field that can be measured and accurately transferred to a set of plans]

These surveyed utility features are typically the most frequently gathered information from surveyors, which indicate where manholes, utility vaults, junction and/or pull-boxes, water and gas valve boxes, air vents, sanitary cleanouts, pipeline and/or conduit system markers, open-cut trench repairs, utility riser poles, utility mark-outs, and so forth are likely to connect to hidden underground utilities. These surveyed data are used to correlate a known fixed point to better interpret and place record data between or proximate to the surveyed structure. These underground record data then become a utility segment that a SUE professional judges to have a certain quality level. Because of at least some surveyed visible structures, Quality Level C data become slightly more certain than Quality Level D data, which have no reliable fixed points.

Note: The most appropriate time to assign Quality Level C or D is after the SUE consultant has attempted to achieve Quality Level B but has failed. Consequently, the SUE professional of record assigns a Quality Level of C or D. While attempts to achieve Quality Level C or D without attempting to achieve Quality Level B have occurred, these attempts are rare and should only be made when the project owner and SUE professional of record understand and are willing to risk unnecessary project delays and budgets.

Data Source – Quality Level B: (Geophysics [GPR, electromagnetic locators])

These data sources obtain utility data through designating—the application of appropriate surface geophysical methods to determine the existence and horizontal position of subsurface utilities

within the study limits. The data obtained in this manner, if deemed reliable, are surveyed to the project control point. The findings further refine the accuracy and completeness of the utility base map and address unknowns and/or problems caused by inaccurate utility records, abandoned or unrecorded facilities, and lost references. Because of the intricate nature of interpreting tool readings and determining the appropriate tool for specific utilities, depths, and soil types, it is imperative that experienced technicians operate these tools under the direction of the SUE professional of record.

Data Source – Quality Level A: [Nondestructive exposure]

These data sources obtain utility data through locating—the exposure of underground utilities, including location, type, size, condition, material, and other characteristics of underground facilities. The result is the precise horizontal and vertical locations of utilities and other reliable observable or measurable data obtained through the exposure of subsurface utilities.

Table 1 summarizes attempted or achieved utility data sources and the corresponding potential quality level they are used to attain.

Note: Quality Levels A and B, by definition, report and depict information based on a nondestructive exposure (Quality Level A) or geophysics (Quality Level B).

However, achieving these quality levels will be contingent upon many or all of the other data sources. For instance, geophysics is commonly performed to properly identify underground utility locations to perform the nondestructive exposures efficiently and effectively. Additionally, Quality Level A exposures may anchor a Quality Level C segment.

However, data can only be assigned a quality level by a SUE professional of record. If these same data sources are captured outside of a SUE investigation, they do not carry a quality level association. While they may still have a similar one or add the same value to the project when collected outside of a SUE investigation, they cannot be assigned a quality level. Therefore, these data, collected outside of a SUE investigation, must be more carefully described according to the identifying source information described previously. Namely, if the data are collected outside of a SUE investigation, they must be described as such and with details to inform the user regarding their reliability and potential accuracy in comments, metadata, or notes.

Long Description.

The table is titled Utility Investigation Data Source Representative Quality Level. It contains nine rows and five columns. The headings of this table row-wise are Data Source; Quality Level D; Quality Level C; Quality Level B; and Quality Level A. The data provided row-wise are as follows (an X denotes that a particular quality level is used to attain the corresponding data source, and a blank cell denotes that particular quality level is not used to attain the corresponding data source):

Row 1: Utility Owner Records; X; X; X; X.

Row 2: DOT or Agency Records; X; X; X; X.

Row 3: Historical or Verbal Recollection; X; X; X; X.

Row 4: One Call; X; X; X; X.

Row 5: Field Survey; blank; X; X; X.

Row 6: Field Investigations; blank; X; X; X.

Row 7: Geophysics; blank; X; X; X.

Row 8: Non-destructive Exposure; blank; X; blank; X.

3.3 Factors Affecting the Accuracy of Collected Data/Information

The accuracy and completeness of utility data can be influenced by various factors, each of which, individually or in combination, can adversely affect the development of a comprehensive utility base map that accurately depicts all existing utilities. The reliability of the data sources used to collect utility information is paramount. Inaccurate or outdated records can lead to significant discrepancies in the utility base map. Factors affecting the accuracy and completeness of utility data include the following:

• No available utility records and/or as-builts
• Incomplete and/or inaccurate utility records and maps
• Withheld or limited distribution of utility records due to a prohibition on sharing sensitive critical infrastructure data (e.g., gas)
• Inaccurate or incomplete field One Call mark-outs
• Reconfigured roadway, resulting in physical field reference points being eliminated or referenced incorrectly
• Missing or inaccurate utility identification, such as type, size, material, condition, depth
• Existing utility attributes, including type, material (e.g., metallic/non-metallic), density, configuration, condition, encasements, abandonments
• Affected geophysics due to subsurface conditions (e.g., soil type, water table, proximity of several utilities, rebar, excessive depth, road salt run-off)
• Restricted and/or constrained access points to existing utilities
• Work performed without statutory direction from a SUE professional of record
• Inexperienced utility coordinator and/or engineer
• Inconsistencies in depicting existing utility data and attributes on utility base maps
• Ineffective coordination of information about multiple utilities existing in a closely proximate location
• Failure of utility representatives to respond timely to utility record requests, causing projects to move forward without that particular utility data (causing high risk for all parties involved)

Note: Accommodating utilities that are unwilling or unable to share records or information should be done so with caution. Where possible, sharing records and location information should be a permit requirement.

The previously identified factors that affect the accuracy of collected utility data are described in greater detail here.

Utility Records – Factors Affecting Accuracy and Completeness: [No available utility records; distribution of utility records is prohibited because of the sensitivity of records for critical infrastructure (e.g., gas); incorrect maps and incomplete records]

Lack of existing utility records means that a utility company does not have accurate or complete information about the location and details of their own underground utility structures, potentially leading to issues such as damage during construction, which is frequently a result of inadequate recordkeeping practices or changes in infrastructure over time. Utility records are often plagued by issues such as inaccuracy, incompleteness, unavailability, and past construction projects lacking detailed as-built plans. Additionally, they can be challenging to interpret and are frequently not referenced to a recoverable datum. Abandoned or no-longer-in-service utility structures can be a particularly pervasive problem. DOTs can consider updating utility-permitting systems to supplement utility records with well-documented placement of any facility in its ROW so that this infrastructure can be known and addressed appropriately within projects.

Field Reconnaissance and Survey – Factors Affecting Accuracy and Completeness: [Inaccurate field One Call mark-outs; inaccurate utility identification and attributes; restricted

and/or constrained access to an existing utility; field survey and/or investigations performed by inexperienced utility staff]

Inaccurate field mark-outs and incorrect utility identification, including details such as type, configuration, aerial cable and/or wire types, inaccurate mark-outs, misidentification of utility vault type, and so forth, can lead to significant challenges in utility management. Restricted or constrained access points to existing utilities further complicate the situation. In addition, when field surveys or investigations are conducted by inexperienced utility staff and oversight from experienced utility coordinators or engineers is lacking, the risk of errors and uncertainties increases.

Utility Designating – Factors Affecting Accuracy and Completeness: [Reconfigured roadway; inaccurate utility identification; subsurface conditions adversely affecting Quality Level B results: Restricted and/or constrained access point to existing utility; work performed by inexperienced/unqualified utility designator]

Over time, the reconfiguration of roadways and surrounding areas has often resulted in the elimination of physical field reference points. Additionally, challenges related to inaccurate utility identification exist, including details such as type, size, material, condition, and depth. Subsurface conditions affecting the Quality Level B results include soil type, water table levels, and the proximity of multiple utilities. Existing utility attributes, such as type, material (i.e., metallic or non-metallic), density, configuration, condition, encasements, and abandonments, further complicate the matter. Moreover, work performed by inexperienced or unqualified SUE-designating equipment operators, coupled with the involvement of inexperienced utility coordinators or engineers, exacerbates the risk of errors. In addition, the technical limitations of the equipment and software used for data collection and analysis can also affect accuracy. Two highly important factors are traffic control and roadway access safety. Geophysics is performed in traffic, and some methods require intense concentration to evaluate real-time data. Without adequate traffic control, geophysical data can be highly suspect.

Utility Locating – Factors Affecting Accuracy and Completeness: [Nondestructive exposure]

Subsurface conditions that may prohibit the accurate identification of utility type, size, material, and configurations are typically a result of the type of soil restricting full utility access, a high-water table, the proximity of several utility crossings, and so forth. Additionally, when work occurs on highways and freeways, the ability to conduct locating may be affected by traffic levels, signal distortion, and so forth.

Note: Utility locating and depiction performed by public and private locators, who work without the accountability of a professional license applied to the deliverable, often increase data confusion, reduce reliability, and ultimately produce inaccurate depictions of the data.

3.4 Impacts of Data Uncertainty

Clear and consistent utility depiction requires an understanding and communication of data certainty. Failing to communicate a level of certainty about the data, or representing uncertain data as though they are certain, can have significant impacts. The implications of not clearly depicting existing utility uncertainties are as follows:

• Safety hazards—Incorrect information about utility locations can lead to accidental damage during excavation, posing risks to workers and the public. Moreover, misidentified or inaccurately marked utilities can result in accidental damage during excavation or construction activities, posing significant safety risks to workers and the public.
• Project delays—Incomplete utility depiction contributes to uncertainty about the location, attributes, and condition of the utilities, which can cause delays in construction projects.

Additional time and resources may be required to locate and verify utilities, leading to extended project timelines and potential cost overruns, especially in cases of an unexpected major relocation.

• Increased costs—Inaccurate and incomplete utility depictions can lead to unexpected expenses. These expenses may include costs for emergency repairs, additional surveys, modifications to project plans, changes in maintenance of traffic, and changes in construction phasing. The financial impact can be substantial, especially for large-scale infrastructure projects.
• Service interruptions—Utility damage can result in service outages, affecting businesses and residents. These interruptions can have wide-ranging economic and social impacts and potential legal liabilities for the construction entity. They are especially vexing for local business owners.
• Environmental impact—If hazardous materials are not accurately documented, damage to certain utilities may result in leaks or releases that pose environmental risks and cause harm to the surrounding ecosystem. When proposed utility relocations are not depicted clearly and reviewed appropriately, the installation of that utility can significantly affect environmental and cultural resources.
• Unforeseen ROW or environmental mitigation—A last-minute relocation may create the need for additional easement or ROW negotiations or environmental-permitting considerations.

To mitigate these risks due to data uncertainty, it is essential to improve best practices for data collection and depiction, regularly update utility base maps, and ensure that experienced professionals are involved in utility management and oversight. Placing a single entity or professional in charge of creating, updating, and maintaining a utility base map throughout project development has proven to be a good solution. Effective mitigation strategies and stakeholder collaboration can help minimize these risks and improve project success. By comprehensively addressing these factors and striving for consistency in utility data depiction, the engineering industry can significantly enhance the accuracy, reliability, and use of project utility base maps for design and construction. This improvement supports the successful planning and execution of construction projects, ultimately resulting in safer, more efficient, and more cost-effective outcomes.

The complete, accurate, and sufficient depiction of existing and proposed utilities is the responsibility of the engineer of record. The design, utility coordinator, and SUE team play significant roles in that depiction.

3.5 Data Ownership, Storage, and Management

Effective utility coordination and data depiction require clear policies and practices regarding the ownership, storage, and management of utility data. These policies and practices must include considerations for state DOTs to ensure data integrity, accessibility, and legal compliance throughout the projectʼs life cycle.

Ownership of the utility data used in highway projects may be navigated through the use of data-sharing agreements or memoranda of understanding to define rights and responsibilities related to data use, updates, and redistribution. These rights and responsibilities must be considered between utility owners and the state DOT because they set the stage for storage.

Various approaches could be used for storage, such as centralized, secure data repositories (e.g., GIS-based systems or cloud platforms) to store utility data. Ensuring that these systems support version control and audit trails is important. The data should be stored in standardized, interoperable formats (e.g., GIS shapefiles, GML, IFC, or LandXML) to facilitate integration with design and construction needs. Regular backup protocols and redundant storage solutions should also be in place to prevent data loss.

Privacy and security should be considered in managing utility data to ensure compliance with applicable data privacy laws and cybersecurity standards, particularly when handling sensitive infrastructure data. Protection from responses to Freedom of Information Act requests or other public records inquiries will be necessary when balancing transparency with security and proprietary concerns. The management of utility data also necessitates considerations of access control; data quality maintenance throughout projects and over time; metadata needs, such as collection and update dates; established data-sharing protocols; and mechanisms for feedback loops with utility owners to update and verify accuracy.

ASCE 38 (related to standardized utility investigations) and ASCE 75 (related to the collection and exchange of utility data based on their installations) offer DOTs a thorough standard for utility investigation and as-built data. DOTs can require all utilities to be installed to pre-approved geospatial positions. For example, utility permits could require utility companies to collect and share geospatially referenced as-builts, which could be stored in a statewide data system. These utility data are extremely helpful to the DOT in managing the ROW, planning new projects, and performing maintenance responsibilities.