Subsurface Utility Investigation

Utilizing Electromagnetic Induction and Ground Penetrating Radar (GPR), GdB incorporates this service into our suite of Land Surveying and Geospatial options, providing cost and time savings to our valued clients.

GdB provides Subsurface Utility Investigation according to ASCE/CI 38-02, Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. This standard was developed and published in 2002 by the American Society of Civil Engineers (ASCE). Commonly referred to as “ASCE 38”, this standard is defined by four “Quality Levels” which allow the Subsurface Utility Locator to work with design and construction professionals to gather the necessary data for their projects. These standards are defined as follows:

Quality Level D – Second Hand Information

Quality Level D (QLD) is the most simple depiction of utility information. GdB researchers utilize existing records from service providers and municipalities to depict what is expected underground without any field investigation. This quality level is assigned when records or One-Call marks are the only available data and is the least certain depiction of existing conditions.

Quality Level C – Surface-Visible Survey

The most common level of quality, Quality Level C (QLC) has GdB field crews use high-accuracy survey techniques to locate existing surface utility hardware (Manholes, Valve Boxes, etc.). The measured field data is then used to confirm utility data found and drafted through record research with service providers and municipalities.

Quality Level B – Derived through Geophysics

Quality Level B (QLB) utilizes technology such as GPR and Electromagnetic Induction to determine the horizontal position of all underground utilities in the examined area. This data is tied into Survey Control for the project, creating the most accurate depiction of existing underground utilities without excavation.

Quality Level A – Derived through Excavation

The most accurate method of Subsurface Utility Investigation, Quality Level A (QLA) builds on QLB by confirming the existence, horizontal and vertical location and direction of subsurface utility assets, typically through excavation. Data collected through these methods allow the accurate plan and profile mapping of subsurface utilities to be described.

Projects

SUNY Stony Brook Underground Utility Replacement

Article VII Survey – PSEG LI

Subsurface Utility Investigation Project
Valley Stream to East Garden City, NY

To begin the survey of the lengthy 7.5 mile long corridor, GdB employed the use of a local Aerial Photogrammetrist to procure a new flight and photogrammetric mapping. Supported by high accuracy ground control, the photogrammetry provided high resolution digital Orthophotos and Topographic mapping with 1’ contours for the entire length of the project. Once the mapping was processed and completed, GdB used traditional ground survey to verify the data gathered by the aerial mapping and locate any and all missing features in the field.

GdB requested record plans from any and all utility providers in the area of the project using the 811 service. All surface utility hardware was located as well as any other utility evidence seen in the field. Utility Markout was performed using electromagnetic induction equipment. Any sewer and drainage features were opened and investigated, measuring pipe size, inverts, connectivity and structure shape/size. GdB developed and uses custom software and equipment to measure underground structures which do not require field personnel to be put in unsafe situations. Markout, field data and utility record plans were all reconciled together and compiled into a comprehensive base map.

SUNY Stony Brook Underground Utility Replacement

Subsurface Utility Investigation Project
Stony Brook, NY

GdB performed a survey of underground utilities at the State University of New York at Stony Brook. GdB was the sub-consultant to Schuyler (an O’Brien & Gere Company).

The project involved the replacement of existing direct-buried high temperature hot-water (HTHW) piping with a new system. A majority of the new system was not installed in the same physical location as the existing system. Therefore, surveying the proposed HTHW piping route was required to identify all potential interferences with existing buried utilities. The new HTHW system will run adjacent to a number of utilities which include city water, high-voltage electric, low-voltage electric, telephone, fiber optic lines, sanitary, & storm. The buried utilities consist of steel pipe, concrete electrical duct banks, conduit, direct-buried cables, ductile-iron pipe, plastic pipe, concrete pipe, clay pipe, fiber optic cable, and any other materials of construction commonly used in underground services.