Subsurface Technologies, Inc. offers a broad range of well rehabilitation and development techniques to the water supply and environmental remediation markets. STI features Aqua Freed^®, the patented, environmentally sound and highly effective well rehabilitation/development technique for many well rehabilitation projects.  Tailored chemical treatments and mechanical development methods are also available.

It is common for wells to experience lost capacity and a variety of water quality problems as they age. Most of the problems occur in wells as a result of material becoming deposited on the surfaces (rock surfaces, gravel pack, well screen) in water environments. Once this material becomes extensive then wells and aquifers can experience lost capacity and also a variety of water quality changes from discoloration, taste and odor problems and "unsafe" (Total Coliform Positive) bacterial problems. It is very common for a well to have years of operation prior to experiencing loss of capacity. When a well gets older it is common for wells to experience lost capacity problems more frequently. The increased frequency of lost capacity and the need for rehabilitation treatments is due to the incomplete removal of plugging deposits and not maintaining the original pore volume of the gravel pack, well screen, or fractures of a rock well.

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Effective well rehabilitation requires the removal of all deposited material thereby allowing the specific capacity to be restored. There are many different strategies and methods used in water well rehabilitation, some successful, others less successful.  The success in using many of the physical and chemical methods is dependant on the user being able to fully identify the plugging material, or combination of plugging material and design a specific treatment to remove the plugging.  This becomes a daunting task due to the variability of the complex geochemical and microbiological underground environment and the reliance of the user to design a specific chemical combination required to fully remove the plugging, while not effecting well construction.

Aqua Freed^® is relatively broad range in its ability to effectively disrupt and remove a wide variety of plugging deposits, in a wide variety of well construction types and materials.

Before Aqua Freed® treatment	After Aqua Freed® treatment

The Aqua Freed^® process uses gaseous and liquid carbon dioxide to rehabilitate water wells. The Aqua Freed^® process has been used on many thousands of wells to-date. The Aqua Freed^Í process has been used on a wide variety of wells including vertical wells, horizontal wells, extraction wells, from shallow to very deep wells, from small diameter to large diameter, screened and open hole. Many of the wells treated have been rock open-hole wells that do not have a well screen but are completed in fractured formations of limestone, dolomite, granite and sandstone.

The Aqua Freed^® process is more effective at removing deposits from both inside the well screen and the formation surrounding the well. One of the active components from the injected gas is carbonic acid, a mild acid, which under atmospheric conditions produces a pH of +/-6.0.  However, there is pressure in an aquifer or a sealed well, allowing the pH values to become reduced to as low as 5.0., still relatively mild.   When the pressure is released the pH will return above pH 6 and therefore does not become a neutralization or disposal concern. There is also the effect of localized freezing and agitation as the liquid carbon dioxide is injected at approximately 0ÿF. That is the normal temperature for injection based upon the pressure. The Aqua Freed^® process is not an overly aggressive process, yet is capable of delivering the necessary energy required to be effective in wells constructed using PVC or HDPE wells, without problems.

The success is not achieved through the freezing but rather because of a combination of carbonic acid, agitation, and freezing resulting in disruption of material! Where the agitation and combined action occurs, it is good at slime dispersion, good at agitation, and also good at breaking up mineral scale. The bulk of the activity is due to phase changes. The expansion rate from a liquid to a gaseous state of the carbon dioxide is 570 times in volume. The agitation achieved with liquid carbon dioxide is the same action as when dry ice is placed in water. There is agitation as the carbon dioxide changes, in this case, from a solid to a gaseous state. The Aqua Freed® process is the controlled injection of carbon dioxide, as injection pressure and down-hole pressure are monitored to regulate the feed rate the well will comfortably accept. The rate and volume of carbon dioxide injected is regulated to assure that the pressures (and energy) going down the well can dissipate into the surrounding formations. Gaseous and liquid carbon dioxide contain a lot of energy that can be described as energy of dissolution, energy of detachment and energy of agitation. This energy results in the detachment, dissolution and removal of sediments and encrustation from the surfaces within the well screen and the surrounding aquifer.

Mechanical Rehabilitation

Mechanical Well Rehabilitation the STI offers include:
Wire Brushing
Swabbing
Simultaneous airlift swabbing

Chemical Rehabilitation

STI can offer chemical rehabilitation with a variety of chemicals commonly used in Well Rehabilitation. Chemical treatments are more limited than Aqua Freed^® in getting removal of deposited plugging material and therefore only partial removal of deposits is often achieved.
The chemicals that are commonly used include:
Acids: Hydrochloric, Sulfamic, Hydroxyacetic, Citric, Phosphoric.
Disinfectants: Sodium Hypochlorite, Calcium Hypochlorite.

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