GPRS (Ground Penetrating Radar Systems, Inc.) performed scanning for underground utilities at an Army Reserve Base. The purpose of the scanning was to clear a path for trenching so that conduit could be laid in and routed into a building. There were numerous utilities densely packed into a road easement. The contractor performing the work needed approximate depth information to effectively trench.
The scan area featured a water pump house, fire hydrant, 25,000 gallon propane tank, and numerous manholes and catch basins.
Known utilities were located with the EM cable and pipe locator first. This step included signal conduction, induction, and the use of a duct rodder to place a conductive linear element inside of non-conductive pipes and conduit. Using this method, fire water, domestic water, and propane lines were located. Once all the known utilities had been located, the next step was passive EM scanning.
Passive scanning is used secondarily once all known utilities have been located in order to narrow down unknown signal reception and speed up utility identification efforts.
After identifying all known and unknown metallic utilities, GPR scans were conducted to identify any remaining unknown, non-conductive utilities. Typically, in this phase, inaccessible plastic utilities such as sanitary sewer, storm sewer, and plastic gas and water lines can be detected. Known utility locations are also double checked for accuracy. GPR was effective at confirming storm and sanitary lines at this site.
To provide the most accurate and useful information to the contractor pipe inverts were taken with a tape measure at manholes and catch basins. These approximate depths were communicated verbally and with paint on the ground.
Even for a seemingly simple excavation where a small trench over a short run were planned, utility locating prevented potentially thousands of dollars of damage and possibly even injury or death.
It is important to call GPRS and have each area being excavated scanned with GPR prior to any work being done. Contact Sean Murphy (412) 732-4940, Sean.Murphy@gprsinc.com for any of your concrete or utility scanning needs.
GPRS does not provide geophysical, geological, land surveying or engineering services. If you need such services, please contact an appropriate professional.