Subsurface remediation in a big city setting is complicated. Limited work space, heavy traffic, noise restrictions, and a dense network of utilities are just some of the factors that conspire to make the installation of any in situ plume control or plume reduction system a seemingly unsolvable logistical puzzle. Horizontal wells placed directly beneath a building can provide protection from soil and groundwater sources of vapor intrusion, and are more effective for plume remediation than wells that are placed down-gradient or up-gradient of the plume just to avoid having to drill wells inside the building.
Directional Technologies, Inc. has mastered this puzzle over many years’ experience working in big cities in the northeast and throughout the USA. An example of this is in New York City, near the boundary between Yonkers and the Bronx, where a former paint plant leaked mineral spirits into soil beneath a building that is currently used by ExtraSpace for public storage. Besides being under a large portion of the building, the groundwater plume extended outside, under a railroad track, and entered a nearby stream.
A combined SVE and groundwater extraction system was installed using three horizontal wells: one SVE well and one groundwater extraction well under the building, and one groundwater extraction well outside the building, along the railroad track. Directional Technologies, Inc. completed all three wells with four-inch stainless steel wire-wrapped
screen. The wells under the building have 50-foot long screens, and the well along the railroad track has a 100-foot long screen. All three are “blind” wells, with riser extending from only one end of the screen section, while the other end of the screen terminates under ground.
Directional Technologies, Inc., is an industry leader in the installation of blind wells. The soil vapor and groundwater extraction wells under the building are 5 and 22 feet deep, respectively. The wells have 50-foot long risers, demonstrating Directional Technology, Inc.’s expertise in minimizing riser length, which was crucial at this site because the wellheads needed to be inside the building. The outside well has a 170-foot long riser in order to accommodate both screen placement and wellhead location requirements.
The wells have performed to the satisfaction of the site owner and New York State Department of Environmental Conservation. The SVE well developed a symmetrical zone of influence extending at least 50 feet away from the well. The groundwater extraction well under the building depressed the water table beneath the building, creating a trough of depression that increased the distance between the water table and the building slab. The well outside the building provides hydraulic control, preventing impact to the nearby stream.
Directional Technologies, Inc.