SIM Explained



According to the Common Ground Alliance (CGA), over the last 20 years, improperly located or unlocated subsurface utilities have caused $1.7 billion in damages and resulted in thousands of injuries and hundreds of fatalities.

The CGA represents a body of industry stakeholders that advocate for the 811/One Call utility-funded public property locating service. Part of this advocacy is publishing the DIRT Report, an awareness document of the previous year’s utility strikes nationwide. Their efforts to mandate the use of the 811/One Call system have resulted in legislation across the US that requires calling the service before excavation.

Most –if not all –of these losses could have been avoided through a detailed site investigation using multiple technologies and highly trained personnel.

Why is a standard necessary for subsurface investigations?

“Call Before You Dig” services are a key place to start when performing subsurface investigations, but they do not cover private utilities. There is currently no industry-wide standard used in private utility locating and concrete scanning. The purpose of SIM is to establish an industry standard to act as a guide when performing such subsurface investigations. The use of SIM is expected to ensure site safety, limit damage to subsurface and structural elements, and increase contractor accountability.


Specifications are essential. They can provide a client with a certain quality of work by following a set of rules, guidelines, and procedures. They can also serve as a guide to workers that help keep them safer while on the job. Previously, there have been no widely adopted standards or specifications for utility locating or concrete imaging. With no widespread adopted specification, the safety of workers and quality of work can vary significantly from service provider to service provider.

Currently, these industries, at a minimum, utilize a “Call Before You Dig” service contracted by local utilities to use as-built drawings and standard pipe location equipment to mark out known underground utilities. This is a free service with limitations in technology and private property access. The service has successfully raised awareness and greatly enhanced site safety but is not a complete solution.

SIM represents the first comprehensive specification for private subsurface locating professionals. This specification also provides standards and codes for subsurface locating technologies combined with proven field methods to produce the best non-destructive results.

Subsurface Investigation Methodology


SIM or Subsurface Investigation Methodology aims to raise the quality of private subsurface investigation results by creating industry specifications. These specifications combine the requirements of experienced-based training, tested technologies, and proven application methods—the combination results in an industry standard for non-destructive investigation of underground utilities and scanning concrete. SIM as a standard will ensure safety, limit damage to underground and structural assets, and increase location contractor accountability on site. SIM focuses on three primary aspects of subsurface methodology: training, equipment expertise, and best methodology practices.


SIM requires multiple technologies to be used in an investigation. This multiple technology strategy provides redundancy in findings, thus increasing the precision of the investigation. The most influential technologies in the industry are the traditional pipe locator/electromagnetic receiver and ground penetrating radar (GPR).

Occupational Safety and Health Administration (OSHA), American Society for Nondestructive Testing (ASNT),American Society for Testing and Materials (ASTM), The Federal Communications Commission (FCC), Common Ground Alliance (CGA),

SIM not only creates its codes and standards but also requires compliance to a variety of other related construction industry standards as well. SIM requires compliance with Occupational Safety and Health Administration (OSHA), American Society for Nondestructive Testing (ASNT),American Society for Testing and Materials (ASTM), The Federal Communications Commission (FCC), Common Ground Alliance (CGA), and more to maintain a safe and high standard of utility locating.

Regarding utility locating and concrete imaging, accuracy and precision are at the core of SIM. More data points will bear out the best results as with any investigation. Results that are as close as possible to accurate and precise will yield the best outcome.

utility locating and concrete imaging

In addition to GPR being used to image steel reinforcement in the slab, SIM also calls for a passive sweep of the pipe locator/EM receiver to confirm the area has no energized conduits. GPR can image a plastic pipe in concrete but cannot determine if the conduit is energized.

The need for SIM is to provide clients with the ability to hold location contractors accountable to the three metrics of required experience-based training, multiple location technologies, and applied methods to enhance results and overcome weaknesses in the equipment.


SIM emphasizes training, equipment expertise, and understanding the best methodologies. While these three elements are essential, they create something more significant than the sum of their parts.

While SIM is technically an industry specification, it also serves as a guide to work culture. To ensure safety, thoroughness and efficiency must be balanced. Being too thorough can end up wasting a client's time and money,and being too brief can lead to safety risks. We understand that safety is of the utmost importance, and we know that clients won't hire SIM-certified technicians if the specification takes too long to apply.

The use of SIM on the job site is a guide to critical thinking that gives technicians the confidence to work cost-effectively while following a repeatable, accurate methodology.

For example, SIM-certified technicians could use GPS equipment to mark locations with millimeter accuracy, they know how to synthesize their training and the methodologies to produce the best, most accurate, and applicable job quality. Marking and notating with millimeter accuracy would be exponentially more expensive and unnecessary on most projects. SIM-certified technicians are trained to take all aspects of a project into account to produce the safest, most accurate, and most effective results.

Every situation is different, which is why SIM has flexibility within a repeatable methodology that can help a Project Manager think specifically about the project's needs.

The SIM specification teaches Project Managers to be efficient and thorough at the same time.Instead of making over-generalized rules that add time to each scanning or locating project, SIM emphasizes using methodologies that make sense for each situation.


SIM is dedicated to providing the subsurface damage prevention industry with high-quality standards and specifications. Through these specifications, we can make the industry safer and more productive. While creating these specifications is difficult and promoting adoption can be challenging, we’re confident that SIM will significantly aid the industry over time.

In the future, we can expect to see more specifications for other subsurface damage prevention industries such as CCTV Video Pipe Inspection and possibly even mapping and modeling services.

GPRS specializes in ground penetrating radar, video pipe inspection, and mapping and modeling services. Our Project Managers have the equipment and expertise to handle all subsurface challenges presented. GPRS does this by utilizing various equipment paired with their industry-leading SIM process. So don't wait. Schedule a project with GPRS and allow our highly trained Project Managers to keep your projects on time, on budget, and safe.