Utility-Locating Technology Development Using Multisensor Platforms (2014)

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

1The purpose of SHRP 2 R01B research is to bring together and develop creditable nondestructive geophysical techniques for use on a land-based towed platform capable of detecting and locating underground utilities under all geologic conditions. Varying geologic conditions inhibit the effec- tiveness of geophysical detection techniques in different ways; therefore, a need exists for a multi- sensor approach that will offer subsurface utility engineers and geophysical service providers the best chance to completely and accurately detect, locate, and characterize subsurface utilities at any location across the United States and the world. The strategy for developing this multisensor platform technology centered on existing systems of Underground Imaging Technologies, LLC (UIT). UIT’s systems consist of a towed geophysical sensor array, capable of digital data acquisition of both detection sensor data and high-precision location data. The research described here builds on several features of UIT’s current system. One aspect is the refinement of TerraVision II, a multichannel ground-penetrating radar (GPR) system. Another aspect is the development of a new multisensor advanced time-domain electro- magnetic induction (TDEMI) system. Other aspects involve development of and enhancements to software used for the gathering, processing, visualization, fusion, and interpretation of mul- tiple geophysical data sets. The R01B project also researched an innovative seismic detection technology at an early proof-of-concept level. The proposed seismic application called for a shear wave seismic imaging system with an intended detection capability similar to GPR but for use in soils that are not compatible with GPR. As part of the seismic research, the project team con- ducted a series of seismic soil properties tests at various locations in the United States, and also studied and developed modeling capabilities useful in helping to predict and understand the high-resolution seismic measurements. A practical prototype incorporating the seismic technol- ogy was not fully developed under the R01B project; however, a simplified seismic prototype is planned for development as a follow-on to these preliminary research findings. The R01B project resulted in the development of two functional prototypes: a multichannel GPR system and a new advanced multisensor TDEMI system. The TerraVision II, UIT’s multi- channel GPR system, was thoroughly tested with refinements applied to the associated software. Based on an array system previously designed collaboratively with SAIC and the U.S. Naval Research Laboratory (NRL), the TDEMI system was developed with the aim of improving our ability to locate and characterize metallic utility targets. Enhancements to Semiautomated Pro- cess and Detect (SPADE), UIT’s proprietary data analysis software, were also a major focus of the research effort to improve 3-D data visualization and efficiency of data analysis procedures. Several software additions and improvements were developed for incorporation into the geo- physical systems. These advancements were designed to assist the software user at all stages of the utility investigation workflow, including geophysical data acquisition, data processing, data analysis, and data interpretation. Executive Summary

2To evaluate and validate the hardware and software components of the research prototypes, the project team tested the platform(s) on appropriate live projects with an established Subsurface Utility Engineering (SUE) firm (not associated with UIT or the research) acting as independent evaluators of results. The live-project SUE evaluation was based on comparisons between records and project data gathered using conventional SUE methods versus data collected and analyzed by the project research team using the R01B prototypes. During this in-service testing at project loca- tions in Virginia and Georgia, the project team demonstrated all features of work necessary to execute a subsurface utility investigation, including digital geophysical mapping, field and office quality control procedures, methods for data transfer, initial data processing, advanced data analy- sis and interpretation, the data fusion process, and the construction of geo-referenced mapping deliverables. Field testing results of the R01B prototypes were reviewed within the context of the Sub- surface Utility Engineering Guidelines ASCE 38-02 Standard, where it is anticipated that these tools will partly contribute to the creation of Quality Level B (QL-B) data. The review process included observing the ease of operations of the new tools, the field data collection activities, and the computer-aided design and drafting (CADD) processing of collected data. Additionally, test holes were selected at one of the testing sites to investigate differences between the UIT and the SUE firm utility plots and to compare depths. Test holes were also selected to investigate potential nonutility anomalies found by the new tools. Ultimately, it was determined that these advanced geophysical tools offer their greatest value if they are used as an enhancement, not a replacement, to traditional utility mapping methods. On certain projects the cost–benefits of using these advanced tools can be significant if used early enough within construction phases. Further test- ing and verification measures are required to more completely assess these systems’ capabilities in providing reliable utility depth estimates; to resolve unknown, small, and deep utility targets; and to accurately identify the cost–benefits directly associated with their use.