The Issue
The New Jersey Department of Environmental Protection (NJDEP) mandated groundwater and soil sampling under an active pharmaceutical company manufacturing building in order to address vapor intrusion inside the building. Installation of vertical borings and vertical wells through the building slab was not practicable without profound disruption of manufacturing activities inside the building.  Soil conditions under the large building slab were unknown, presenting potential problems for either vertical or horizontal drilling. Groundwater sampling below building slabs is frequently required in order to assess groundwater remediation requirements for protecting indoor air quality. Subslab soil sampling and soil vapor extraction may likewise be required to manage vapor intrusion into a building.

The Solution
During the high profile project in New Jersey, Directional Technologies Inc. completed multiple 2-inch PVC monitoring wells at a location 120 feet inside of the building wall and at target depth of 20 feet below the building slab. The horizontal wells continue to serve as a compliance monitoring well for groundwater contaminants. The same directional drilling technology can be used to install horizontal soil vapor extraction (SVE) wells either in native vadose zone soils or in subslab backfill material as part of a vapor intrusion management program. Completed in vadose zone soils under a building, horizontal SVE wells can remove the vadose zone source of vapor intrusion. Completed in backfill material immediately below the building slab, such wells may supplement or replace a traditional subslab mitigation system.

The Technology
Directional Technologies placed their drilling rigs outside of the building and drilled continuous wellbores, first through the 6-inch concrete footer and then through rock beneath the building slab, which the site owners believed to have been underlain by fill material. The directional drilling crews successfully steered through rock fragments to the target point, successfully executing the soil sampling before completing the monitoring well. The horizontal wells were drilled blind, with no exit hole, thereby maintaining sufficient similarity with standard vertical monitoring wells to facilitate approval of the wells by the regulatory agency for compliance monitoring. Directional Technologies’ experience installing long blind horizontal wells makes subslab SVE wells possible at manufacturing facilities or in residential areas with limited access around the buildings for drilling activities. If subslab horizontal SVE wells are used to address vapor intrusion, Directional Technologies designs the screens to accommodate low vacuum requirements typical of vapor intrusion systems.