Free product recovery can often be accomplished in areas affected by floating product by using horizontal wells to draw down the water table and extract free product.
Actual design of a recovery system will depend on site-specific circumstances, but all of the general advantages of horizontal wells can be applied to free product recovery. In some cases a dual-phase extraction system can be installed to remove both free product and soil vapor.
Horizontal wells may be an excellent choice for the recovery of Dense, Non-Aqueous Phase Liquids (DNAPLs) that have ponded on aquitards in a geohydrologic system. The precision with which horizontal wells may be installed enables the designer to place extraction wells at specified elevations and locations to intercept migrating DNAPLs, while greatly reducing the danger of punching through the aquitard and permitting cross-contamination of aquifers.
At sites where there is considerable fluctuation of the water table, either seasonally or due to other influences, horizontal wells may not be the best choice. Generally the zone of floating product is not more than a couple of feet thick and water table fluctuations that exceed this may lift the product above the well or drop it out of range.
If you have questions about a free product recovery scenario or the advantages of applying horizontal wells to your extraction system, please contact our environmental remediation experts.