Subsurface Utility Mapping (SUM)
Subsurface Utility Mapping (SUM) is the collection and depiction of utility data for reference use in the design of various infrastructure projects. The use of SUM allows for better design considerations regarding the impact to existing utilities and the proposed project. When SUM data is provided early in design, the project design team can adjust structures and improvements to avoid existing utilities, thus reducing delays associated with utility relocations, project design changes and the discovery of unknown utilities. The reliability of utility data depicted is based on the quality level of the data shown and is intended for mapping design use only. For a better understanding of the quality levels and how to determine what quality level is needed, refer to ASCE Standard Guideline for The Collection and Depiction of Existing Subsurface Utility Data, CI/ASCE 38-02.
QUALITY LEVEL-D UTILITY RECORDS RESEARCH: Information derived from existing utility records
or oral recollection.
Depiction of information from utility records research is to be considered approximate and unreliable for design or construction. No verification of the existence of or the horizontal and vertical location of the underground utility has been obtained. Survey of 811 One Call markings is to be considered Quality Level-D data.
QUALITY LEVEL-C SURFACE EVIDENT UTILITY FEATURE SURVEY: Information obtained by surveying and plotting visible above-ground utility features and using professional judgement in correlating this information to Quality Level-D data.
Depiction of information from the correlation of Quality Level-D utility records research and Quality Level-C surface evident utility feature survey is to be considered approximate and unreliable for design or construction. No verification of the existence of the horizontal and vertical location of the underground utility has been performed.
QUALITY LEVEL-B UTILITY DESIGNATION: Information is obtained through the application of appropriate
surface geophysical methods to determine the existence and approximate horizontal position of
subsurface utilities. Quality Level-B data should be reproduceable by surface geophysics at any point of
their depiction. This information is surveyed to applicable tolerances defined by the project, compared
to the Quality Level-D & C data and reduced onto plan documents.
Utility data gathered in the Quality Level-B investigation is appropriate for design of projects allowing
the design engineer to adjust and avoid utility conflicts within the design. Although the horizontal
location of the underground utility has been identified, areas where direct conflict between the utility
and design are determined, further data will be required to determine the vertical location of the
underground utility and eliminate potential conflicts.
QUALITY LEVEL A – UTILITY TEST HOLE: Precise horizontal and vertical location of utilities by the actual
exposure (or verification of previously exposed and surveyed utilities) and subsequent measurement of
subsurface utilities, usually at a specific point. Minimally intrusive excavation equipment is typically used
to minimize the potential for utility damage.
A precise horizontal and vertical location, as well as other utility attributes are recorded and provided to the design engineer. Accuracy is typically set to vertical and horizontal survey & mapping accuracy as defined or expected by project owner. Precise utility horizontal and vertical location of a utility is determined at the location of potential conflict with the design where identified. Design engineer, using available utility data, can then decide if adjustments to the design or utility relocations can eliminate the utility conflict.
Private Utility Locating (PUL)
Over 30 billion dollars from close to 500k utility damages in the United Sates, according to the Common Ground Alliance Damage Information Reporting Tool (DIRT). These are the ones that have been reported, private utilities account thousands more with an unknown cost. Why? Private utilities are not required to be part of the 811 / One-Call system.
Not all utilities are created equal…811 is for utilities that are required by law to participate, Public Utilities, like your local cable television, electric, telephone and water & sewer providers. Private utilities are not part of the 811 system and not marked when public utilities are. Who owns that line from the meter to the building? The property owner, not the utility company. Chilled water, private communication lines, access control cables and more can be privately owned costing thousands to be repaired and even more in down time when damaged.
A privately owned fiber optic can cost thousands of dollars when damaged. The lost revenue the fiber optic owner may experience during an outage, the contractor is liable for the damaged and revenue lost. On a project at a company’s call center private campus, a fiber optic line was damaged, and the call center was shut down. The estimated cost for the repair was relatively low, the lost revenue for the call center was not, estimated to be in the high six figures.
Did you know that airports, hospitals, shopping centers, universities and most large business campuses have utilities that are privately owned? Who is responsible for ensuring these are not damaged during construction? The excavation contractor is responsible and tasked with having them located, but how? Private utility locating companies like CS4 Services with over 30 years’ experience in the utility locating industry.
Ground Penetrating Radar (GPR)
Ground Penetrating Radar (GPR) is used to detect the presence of near surface buried facilities, structures, and other objects beneath the ground’s surface, i.e., the “target”. From buried utilities, unmarked graves to underground storage tanks (UST), GPR may be the answer to finding what cannot be seen.
With 2D and 3D GPR technology, GPR can identify and map the underground infrastructure to complete the picture that standard electromagnetic utility location may not detect. Non-conductive utilities can be found and mapped eliminating an “unknown” utility being missed that could greatly impact the project.
GPR is not the “Silver Bullet” that will save the day, but another tool in CS4’s toolbox to assist our clients in identifying and understanding what is buried on their project. GPR is dependent on numerous factors, target’s material composition, depth, and size as well most importantly soil composition in the area to be investigated. The United States Department of Agriculture’s Natural Resources Conservation Service has developed a database of state maps to better understand the probable penetration depth and suitability of soils to determine if the use of GPR in areas would achieve acceptable results.
These maps are available at:
Test Holes, Potholing & Daylighting – no matter what you call it, it’s where the utility IS. Minimally
intrusive use of Vacuum Excavation allows CS4 to provide precise horizontal and vertical location of
utilities that have direct impact on the design and construction of a project. Air/Hydro excavation has
proven to be the safest and quickest method to expose and determine the exact location of a utility.
CS4 has the expertise and equipment available to perform these services for our clients.
Through a narrow excavation on the surface, air or hydro excavation methods can safely dig down to
expose the utility, allowing CS4’s technicians to measure the depth and dimensions of a utility. These
excavations provide exact utility location data and assist in determining the best course of action to
resolve a utility conflict. The location of the excavation can be surveyed providing the client precise
location of the utility to be incorporated in the design documents allowing both utility owner and
design engineer to collaborate in the resolution process.