Trenchless technology applications are in extensive use in India, serviced by one of the largest equipment fleet in the region. Till recently, one issue dogging the industry, however, has been the application of technology with very limited subsurface information, both of manmade structures as well as natural soil strata. This information is an essential part of any trenchless project. In the absence of credible subsurface information, operators are often forced to use guesstimates in project execution. Such assumptions and guesses, at times, lead to inaccurate or faulty installations, and damage the existing subsurface structures. Installation accuracy and damage prevention could be achieved by adequate and credible subsurface information. In addition, another essential part of this information generation process is the properly trained professionals capable of recording, assimilating and reporting credible and actionable subsurface information. Till recently, Indian trenchless industry did not have such processes and professionals and the problem was aggravating with each new set of trenchless equipment. Indian trenchless industry assisted by international counterparts have now evolved trenchless code of practices that helps in charting the proper course of action and a new cadre of professionals titled SUE Engineer has been created. These developments have taken place within the last year and now the industry is moving towards a robust project execution system assisted by these SUE Engineers. This article discusses such developments to report the progress and sensitise the readers so that they could consider replicating these in their subsurface construction projects.

Geophysical information
Various latest technologies including trenchless technology are being used for creating and maintaining subsurface infrastructure in India at an increasing rate. The successful use of these technologies, and benefits in terms of speed and least inconvenience to people, are well known. The subsurface infrastructure being developed through these applications share a few characteristics like them being remotely controlled, or them using minimum trenches in project. These characteristics, however, enhance the importance of geophysical information. Data on soil profile, rock, local heterogeneities and subsurface conditions are critical for safe and successful execution.

For example, in horizontal directional drilling (HDD) process, one of the most commonly used trenchless technique, the hardness and abrasivity of the strata decides how long the drill head will last, the drilling production rates and thrust requirements. Harder and abrasive strata would require a higher strength HDD equipment set-up and one need to have adequate and actionable information to make an optimum equipment and methodology.

Subsurface utility information
In addition, having accurate knowledge of subsurface, underground and buried utilities (pipes, cables, drains etc) is critical for any infrastructure project as well. The successful detection and mapping of buried utilities involves the combination of several techniques, the results of which are synthesised down to a single interpreted plot. The techniques and methodologies used will primarily depend upon the required outcome for the survey, the site conditions and the type of pipes or cables being targeted. The real difficulties of trenchless technology sector start here. Till recently, the industry has been using different geophysical investigation methods in isolation. The most common being Ground Penetration Radar (GPR) surveying where the surveyor deploys a GPR tool to find buried objects through reflection and refraction of RF waves. Each survey report was being prepared with several disclaimers leaving much for the decision of the project execution team. Such decisions, in turn lead to deployment of guesstimates by the project team and any failure in the guesswork leads to damage of existing utilities.

Solutions for geophysical information and subsurface utility information challenges For trenchless applications, soil strata survey plays a vital role and since the project work locations are inaccessible for direct surveying, geophysical techniques are deployed for getting the desired information.

Various geophysical techniques are available which are capable of providing the subsurface data in quick, totally non-destructive and economical manner. These advanced technologies can effectively be used to handle the present-day complex problems related to optimum utilisation of available resources and infrastructure.

Engineering geophysics is an efficient means of subsurface investigation. The merit of application of this low-cost aid lies in its ease of deployment and rapidity in providing a reliable knowledge of the underground over a large area, substantiating the requisite geotechnical evaluation studies thereby. Technological advancements and development of portable digital data acquisition instrument systems have increased the versatility in evaluating underground conditions and site characterisation.

Geophysical tools such as
GPR, seismic refraction, seismic reflection, electrical imaging etc, can be used for the accurate mapping of the underground infrastructure facilities (electrical and telecommunication cables, pipelines etc), soil-rock interface, geological identification of soil, water table mapping, dimension of a sub stratum, elastic properties of the medium, geometry of various layers and other subsurface features.

Similarly, for subsurface utility information, Subsurface Utility Engineering (SUE) is an upcoming field dealing with procedure and standards for detection, mapping and designating underground utilities. Under this technology segment, buried utilities are surveyed, mapped, and recorded, and the information quality is designated. The subsurface utility maps thus created, provide actionable information to project execution team. This information is better than the previous subsurface survey information and is expected to help in mitigating risks in a better way.

To provide comprehensive and actionable information, specifically trained professionals specialising in SUE are the next important part of this process.

SUE Engineer - A profession in demand
INDSTT: 401-2018- Code of Practice for Subsurface Utility Engineering Suiting Indian Conditions -Guidelines and Specifications for Detection, Verification and Depiction of Existing Subsurface Utility Data, was released in December 2018 and is likely to be adopted by a large number of organisations in the coming years. The code stipulates that "The drawings prepared using the process of subsurface utility engineering should finally be stamped and signed by a certified Subsurface Utility Engineer".

Presently, there are almost 63 SUE engineers available in the country, and the demand is likely to be in thousands shortly. Title of SUE Engineer is granted upon acquiring the necessary professional skills in Subsurface Utility Engineering field through SUE Engineer training program. The program comprises three levels of training and respective level end tests conducted by IndSTT followed by the certification and grant of SUE Engineer Seal with distinct serial number for each qualified and certified SUE Engineer. SUE Engineer is functioning in any of the following five different roles:

• Project owner's engineer or advisor
• Service provider's engineer or advisor
• Right of way owner's engineer or advisor
• Third-party consultant
• Expert witness

SUE Engineer: skills required
SUE Engineer can help in reducing risks and costs involved while meeting an existing utility unexpectedly during construction. This professional is expected to help the organisation's plan towards creating database of existing utilities in their area (refineries, plants, urban and public areas, and factories) for future reference, expansion plans and repair and rehabilitation. Smart utility maps are prerequisite for smart cities, making this profession very important for smart city planners.

• Basic understanding of Subsurface Utility Engineering (SUE)
• Knowledge about Utility Quality Level Attributes - Quality Level D, C, B, A
• Understanding about steps and procedures for various quality level data collection
• Survey procedures for collecting QL-C data (including use of total station, DGPS etc) Field procedure and approaches for GPR surveys
• Data processing of GPR data
• Data interpretation of GPR data
• Field procedure and approaches for EPL surveys
• Capabilities of SUE map preparation, including plan, L-section etc
• Understanding about various trenchless techniques

Indian trenchless scenario
Though there are several soil investigation methods available in India, common approach in India for trenchless projects have been generally to deploy ground penetration radar for detecting anomalies in ground and plotting them on maps. These maps subsequently are provided to drilling or tunnelling machine operators who would read those maps and chart their course of action and the alignments. The shortcomings therein are the absence of real-time information on the complete 3D coordinates of the various buried utilities and unverified vertical locations. Both these lead to non-actionable inputs for project works and the operators are often forced to apply guesstimate in charting the installation locations. Such subjectivities often lead to faulty installations.

Another major issue facing the trenchless industry is the failure of "As-Built-Drawing' stipulation of contracts. As per the standard contract clauses the trenchless contractor is required to submit the As-Built-Drawings of the installed pipeline. Failure in adhering to the as-built condition can lead to reduced or truncated payments for works. When the project is designed, generally the site subsurface investigations are not completed and the designer, on the basis of the above ground features, assumes a theoretical installation location. This becomes the benchmark for the contract payments, unless a real-time subsurface investigation proves those assumptions incorrect. As this investigation is never done, the contractors are forced to submit the "As-Designed-Drawings" as the "As-Built" to secure their payments. This leads to erroneous reporting in case the installation location got altered due to geological challenges or utility presence. The long-term loss is that no real-time information is available for the new utility even! Through the changes, these anomalies are now being addressed.

Need for standards
In order to remove uncertainties, any engineering activity requires standards in place. For trenchless works, the IndSTT has published several codes of practice suiting Indian conditions. Such codes are in use for quite some time. With increasing service provider and equipment population, instances of failures due to erroneous geophysical or SUE interpretation had been increasing. To contain such issues, in 2018 the industry decided to include stipulations of geophysical investigations in the current codes and promulgate a new code titled Subsurface Utility Engineering Code of Practice. This code provides a system for preparing Subsurface Utility Maps (SUM) and prescribes the competencies of SUE Engineer.

Creation of professionals
Systems promulgated require SUE engineers and during the intervening period, more than 100 individuals were trained in the field of SUE. Till the date of reporting, 63 SUE engineers have been trained, tested, and certified. Details of such SUE engineers could be seen on http://www.indstt.com/SUE_Seal.html. The remaining individuals have to complete Level 3 to receive the SUE Engineer's authority and distinguishing seal. These professionals are rendering service to the trenchless industry. The industry size, however, is substantially large, and the numbers of professionals trained are quite small. The industry therefore requires more professionals in this sector to induce safer working practices.

Looking forward
Trenchless technology provides an efficient method to create, maintain, and manage subsurface utility networks by drilling, tunnelling, or lining the existing ones remotely. Most of the actions are undertaken through the use of smart equipment and materials. The humans operating those, therefore, need to be smarter for a successful project. Quality of subsurface information is the vital input for such smart decisions as it greatly influences the project outputs. Limitation in quality control of this input, however, gets generated due to trenchless nature. As most of the strata remains out of sight, it fails to come to the mind of operators. Through geophysical investigations and deployment of SUE engineers, this limitation can be removed. The Indian trenchless industry, through its recent actions have promulgated the codes for various techniques and defined the skill set of SUE engineers. Interested trenchless operators are invited to join this movement by implementing the stipulations on their projects.