Mapping water table with GPR

G eology & Geophysics Mapping Water Table Depth Project Description The purpose of the investigation was to map the depth and extent of a perched water table and to delineate the extent of an intermittent aquiclude clay layer known to exist at depth, as well as identify any other sedimentary features which could act as subsurface controls on groundwater recharge and groundwater flow. The ultimate goal of the survey was to establish that the subsurface structure and hydrology were capable of sustaining significant exploitable groundwater reserves beneath the property prior to purchase of the site. The survey was carried out with a GSSI SIR-2000 and a 40 MHz MLF antenna mounted on a non-metallic cart. The antenna cart was towed with an ATV equipped with a survey wheel. The profiles were collected with a scan pacing of four scans per foot. Distance markers were placed on the records at 100 foot intervals. A total of fifteen survey profiles were collected at the site, totaling five miles of continuous GPR data. The Project A local New Hampshire Geosciences consulting firm was contracted to perform a hydrogeologic investigation as part of a site evaluation for Poland Springs, Inc., a well-known bottled water company based in Maine. The survey was conducted in and around an active potato farm in central Maine. Outcome The GPR survey accurately established that the water table depth and continuity throughout the survey area made it satisfactory for the water company’s purchase. The GPR data was also useful in detecting and delineating the extent of the aquiclude clay layer as well as other subsurface sedimentary features, which served as structural controls on groundwater flow and local groundwater recharge capacity. 12 Industrial Way • Salem, NH 03079-4843 USA 603.893.1109 • [email protected] Copyright © 2006 Geophysical Survey Systems, Inc. www.geophysical.com GSSI Case Study

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Transcript of Mapping water table with GPR

Geology & GeophysicsMapping Water Table Depth

Project Description

The purpose of the investigation was to map the depth and extent of a perched water table and to delineate the extent of an intermittent aquiclude clay layer known to exist at depth, as well as identify any other sedimentary features which could act as subsurface controls on groundwater recharge and groundwater flow. The ultimate goal of the survey was to establish that the subsurface structure and hydrology were capable of sustaining significant exploitable groundwater reserves beneath the property prior to purchase of the site.

The survey was carried out with a GSSI SIR-2000 and a 40 MHz MLF antenna mounted on a non-metallic cart. The antenna cart was towed with an ATV equipped with a survey wheel. The profiles were collected with a scan pacing of four scans per foot. Distance markers were placed on the records at 100 foot intervals. A total of fifteen survey profiles were collected at the site, totaling five miles of continuous GPR data.

The Project

A local New Hampshire Geosciences consulting firm was contracted to perform a hydrogeologic investigation as part of a site evaluation for Poland Springs, Inc., a well-known bottled water company based in Maine. The survey was conducted in and around an active potato farm in central Maine.

Outcome

The GPR survey accurately established that the water table depth and continuity throughout the survey area made it satisfactory for the water company’s purchase. The GPR data was also useful in detecting and delineating the extent of the aquiclude clay layer as well as other subsurface sedimentary features, which served as structural controls on groundwater flow and local groundwater recharge capacity.

12 Industrial Way • Salem, NH 03079-4843 USA603.893.1109 • [email protected]

GSSI Case Study