Horizontal Soil Vapor Extraction Wells – Directional Technologies

Horizontal Soil Vapor Extraction Wells
Upgrade Vapor Mitigation System
at NY State Superfund Site
by Seth Croy

After declaring bankruptcy in the late 80’s, a printing company in New York disposed of its chemicals over the years, including tetrachloroethylene (PCE) and trichloroethylene (TCE). By dumping materials into an on-site leaching pool located behind the main building, a common practice for many years, concentration levels were elevated resulting in total Volatile Organic Compounds (VOCs) exceeding 1,000 ppb in many areas, with a maximum VOC in excess of 12,000 ppb.

The New York State Department of Environmental Conservation (NYSDEC) determined the location to be a Class 2 Hazardous Waste Site due to the significant threat to the public health, and an environmental action was required. In 2012, on-site and off-site in-well air stripping and soil vapor extraction (SVE) systems were installed. In 2016, it was discovered that the on-site SVE system did not sufficiently address the chlorinated VOC impacts below the building.

As part of the Corrective Action Plan (CAP) submitted to NYSDEC, the consultant selected Horizontal Soil Vapor Extraction Wells (HSVE) to expand the on-site vapor extraction system. Directional Technologies worked with the consultant on the horizontal well screen design and well layout of three (3) HSVE wells, spaced 50-feet apart, and constructed with 4-inch Schedule 80 PVC materials. Due to site constraints, the HSVE wells were installed utilizing “blind” installation methods, meaning that no exit was required on the other end of the building.

After mobilization and upon set-up, it was discovered that the foundation wall was deeper than the plans had specified. With this new information, the Directional Technologies’ team quickly collaborated with the consultant for a new design and solution which kept the project moving forward. The horizontal wells were shifted from the north side of the building to the west side, with new bore angles required to avoid the foundation walls. Also, the treatment area was expanded which required the addition of two horizontal wells. The HSVE screens ranged from 120 feet to 220 feet in length with each placed at a depth of four to five feet below the slab to avoid utilities and to stay above the groundwater table.

Aerial view of the site with Horizontal Soil Vapor Extraction Wells

Why Horizontal Remediation Wells?

• Reduced installation costs by removing the need for internal extraction points, floor trenching for well hook-up, and restoration.
• Current business operations were not disrupted since remedial construction performed on the exterior of the building.
• Long, continuous horizontal well screen sections expand extraction area and volume from a single well point.
• Provide sound and proven technology for mitigation system upgrades at sites where other alternatives are unfeasible.