Horizontal Remediation Wells
Applications
History of HDD
HDD was developed by the oil industry in the 1930s and adapted for utility installation in the 1970s. Its application for installing horizontal remediation wells (HRWs) grew in the late 1980s with demonstration projects sponsored by the Department of Energy
.
Horizontal directional drilling (HDD) has been used to install wells for the extraction of oil and natural gas since the 1930s. HDD was used subsequently for underground utilities, and then in the late 1980s, the technology was repurposed for environmental remediation applications. These are some of the remediation technologies that can be implemented with HDD. (For specific site examples, visit the Site Application Examples.)
- Groundwater pump and treat, extraction of free-phase product, and dual-phase extraction.
- Groundwater recirculation.
- Air sparging and soil vapor extraction.
- Nutrient injection for bioremediation.
- Chemical injection (including in situ chemical oxidation or reduction).
- In situ thermal treatment (e.g., hot air and steam injection, and electrical resistance heating).
- Permeable reactive barriers and biobarriers.
- Reactive wells: Similar to a permeable reactive barrier, but placed within the groundwater plume, in a parallel direction. It creates a preferential flow pathway through which groundwater is treated by reactive media.
- Vapor intrusion mitigation.
Schematic of an SVE/Air Sparging System that
Incorporates Horizontal Wells. (EPA, 2017)
In addition to remediation, horizontal wells are used for:
- Injecting treated water back into the subsurface to reduce the potential for groundwater mounding and other adverse gradient changes associated with vertical injection wells.
- Controlling the migration of groundwater plumes and capturing leachate from landfills for treatment.
- Sampling groundwater.
Sampling from horizontal borings and wells has an advantage over vertical wells when determining if contamination is present beneath or is migrating from surface or subsurface obstructions. For example, samples can be collected below landfills without puncturing liners. Custom soil and groundwater sampling equipment have been developed for use with HDD equipment. Downhole geotechnical equipment such as logging tools, resistivity probes, and miniature cone penetrometers are also available for use in horizontal wells.
