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.