GSI Mid-Atlantic, Inc. recently completed monitoring well installation on two DNREC sites using the Geoprobe 4.5″ dual tube system (DT45).

The first site was a former waste site along the Delaware Bay. The scope of work consisted of installing 6 shallow piezometers, 3 along each side of a remediation trench, and 2 deeper (20′) monitoring wells. All wells were specified to be 1.5″ diameter conventional PVC monitoring wells. The challenges of the site included extremely shallow water table (2 to 3′ BGS) and several feet of large gravel in some areas. GSI determined that the DT45 system would provide enough annular space with the 1.5″ casing to install the sand pack and bentonite seal through the annular space inside the DT45 casing. This would ensure a good sand pack and well seal despite the challenges of the shallow water and collapsing gravel. All 6 piezometers and the 2 monitoring wells were installed in 2 days.

The second site, also a former waste site, was follow-up to a previous Geoprobe investigation. The scope of work called for installation of five 2-inch diameter standard monitoring wells. GSI again utilized the Geoprobe DT45 system. Use of an oversize cutting shoe created a nominal 6″ diameter bore-hole, which provides the 2″ annular space required for a standard built 2″ diameter monitoring well. Using the DT45 system allowed the wells to be installed using direct-push, rather than conventional hollow-stem auger. This created a significant savings on time and generation of investigation derived waste. All five wells were installed and developed in 2 days.

September found GSI Mid-Atlantic, Inc. completing work on two different landfill sites in Maryland.

On the first site, GSI was contracted to complete continuous soil borings at an inactive landfill site in Anne Arundel County.  Using the Geoprobe dual tube 22 system and one of our Geoprobe 7822 machines, GSI successfully completed 13 soil borings ranging in depths from 55’ below ground surface to 75’ below ground surface.  The purpose of the borings were for logging and identifying specific zones and geologic layers in the subsurface.  During boring advancement, GSI successfully collected groundwater samples from multiple water bearing zones as identified by the on-site geologist.  Below is a photo of soil cores from a 75’ boring.  All borings were pressure grouted upon completion.

GSI was also contracted to install landfill gas monitoring wells along the perimeter of 2 landfills in Howard County.  In a single day, GSI installed 3 landfill gas monitoring wells ranging from 20 to 35 feet below ground surface.  Wells were installed using the Geoprobe dual-tube 32 system.  This system creates a 3.5” borehole while continuously sampling the soil.  Half-inch PVC well-screen and riser were installed though the casing.  As seen below, the gravel pack was placed through the casing as the casing was removed.  Each landfill gas monitoring well was completed with steel stick-up protection.