ANS operates as a hybrid remediation consultant and contractor. We typically work alongside a site owner's environmental consultant to develop site-wide remedial strategies, rather than acting as a standalone installer. We also often partner with local consultants and contractors, which gives a project team direct familiarity with local permitting requirements and, frequently, existing relationships with regulators in that jurisdiction.

ANS is typically contracted by a site owner or, more often, a site owner's environmental consultant. Depending on the size and complexity of the site, the time from first contact to field implementation can range from months to years.

ANS stays involved through the full project lifecycle:

• Early feasibility conversations and site planning

• Pre-design investigation (PDI) and TreeWell system design

• Installation

• Ongoing maintenance and long-term performance monitoring

This continuity — from initial feasibility through years of post-installation monitoring — distinguishes ANS's engagement model from a single-phase installation contractor.

A TreeWell System is installed by excavating a large-diameter borehole, placing a Root_Sleeve™ liner to a depth targeting the contaminated groundwater zone, and backfilling with soil amended with organic matter. This amended soil column and its native bacterial populations reduce phytotoxic effects on the tree and allow precise targeting of specific water-bearing strata.

Once established, the tree and its root-zone microbial community work together to treat the site:

• The tree acts as a natural pump, drawing groundwater upward through the amended soil column (hydraulic uptake)

• Tree root exudates — sugars and organic compounds released into the soil — stimulate and sustain the native microbial community, encouraging the biodegradation of contaminants in the root zone

• This soil column functions as a bioreactor, where the resulting microbial activity degrades contaminants before they reach the tree's roots

• Any residual contaminants are degraded within the plant, sequestered in plant tissue, or transpired into the atmosphere

• Because the tree continuously draws groundwater, it can also alter local flow direction — helping control or redirect a migrating contaminant plume

TreeWell systems can access deep groundwater and bedrock aquifers, with depth capability depending on system design:

• Standard TreeWell units generally reach groundwater up to 20 ft bgs without irrigation

• With strategic temporary supplemental irrigation, standard units can access groundwater to 35-40 ft bgs

• A Straw TreeWell System — a closed-bottom variant of the standard unit — can address contaminated groundwater exceeding 100 ft bgs, when head pressure in the target stratum is sufficient to move groundwater up to the unit's upper screen

This depth range is achieved through soil texture engineered for sufficient capillary rise, allowing selected fast-growing tree species to reach the targeted groundwater zone within a single growing season.

Most commonly, willows and poplars — including hybrid poplar cultivars and Salix (willow) varieties selected for phytoremediation — are planted in TreeWell units. These species are favored for their fast growth rate, aggressive rooting, high water consumption, and an established base of phytoremediation research supporting their use.

Species diversity can help manage site-specific unknowns — various stressors that can affect tree health — so we also draw from a broader list of high-biomass, high-water-consumption tree species (such as cottonwoods) selected and tailored to each site's specific conditions.

The TreeWell soil column is engineered specifically to protect the tree from phytotoxic effects. The column is backfilled with organic-matter-amended sandy loam soil, which supports a dense native microbial community — one that's further stimulated by the tree's own root exudates. Many of the contaminants targeted by TreeWell systems are metabolized by these soil microbes before ever reaching the tree's roots, significantly reducing the concentration and toxicity the tree is actually exposed to.

This soil-microbial buffering is effective even in conditions generally considered too phytotoxic for direct planting. ANS has successfully planted trees in DNAPL-impacted areas with concentrations greater than 65 ppm — a level well beyond what unprotected root systems could typically tolerate.

TreeWell systems have successfully treated a wide range of contaminants, including:

• Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), including 1,4-dioxane

• Pesticides and petroleum hydrocarbons

• Agricultural inorganics, including nitrates, ammonium, and phosphorous

• Tritium

• Solubilized metals, including lead, arsenic, zinc, boron, and cadmium — commonly encountered at sites such as those impacted by coal combustion residuals (CCRs)

ANS is also currently running pilot-scale studies evaluating the fate, transport, and remediation potential of TreeWell systems for PFAS compounds.

Most targeted organic contaminants are degraded in situ by the microbial community within the TreeWell soil column — the same microbial activity sustained by the tree's root exudates. Because this degradation happens in the soil before contaminants reach the tree in significant concentrations, the tree itself does not accumulate hazardous levels of contaminants and will not need to be disposed of as hazardous waste in the future.

Less commonly, some contaminants are taken up into the tree, where they are degraded or metabolized within plant tissue, sequestered in tissue, or transpired into the atmosphere.

Not every site is a good candidate for a TreeWell System, and ANS conducts a thorough feasibility assessment before committing to a project rather than a "buyer beware" approach common elsewhere in the remediation industry.

The assessment starts with a site's broader goals — contaminant mass reduction, hydraulic control, or another objective — along with any regulatory drivers and other stakeholders involved. ANS then reviews the site conceptual model, including operational history, contamination sources and transport mechanisms, and available planting area.

From there, ANS evaluates site-specific hydrogeology, including:

• Whether the aquifer is confined or unconfined

• Whether there are single or multiple water-bearing units

• The position of clean water-bearing units relative to impacted ones

• Whether contaminated water is present in unconsolidated material, bedrock, or both

• Whether data show vertical variability in contaminant concentration

Preliminary hydraulic calculations — particularly estimated groundwater lateral flow velocity combined with groundwater volume — are often the deciding factor: if groundwater flow is too rapid or the impacted water-bearing unit is too thick, a TreeWell-based solution may not be feasible.

While complete site data isn't required to start a conversation, feasibility assessments are refined by information such as: aquifer confinement (confined vs. unconfined), the number and depth of water-bearing units, whether contamination is present in unconsolidated material or bedrock, and vertical contaminant concentration data. Preliminary hydraulic calculations — particularly groundwater lateral flow velocity and volume — are typically the final determining factor in feasibility and rough project scope.

Safety is a top priority given the inherent risks of heavy equipment operation and ground crew work, including the specific risks posed by large-diameter (42-60") boreholes as deep as 30 feet.

ANS has developed and continually refines a patented TreeWell Safety Platform, which is placed over an open borehole immediately after drilling to prevent accidental falls during backfilling. Combined with decades-long working relationships with preferred drillers and construction crews, this approach has allowed ANS to install over 3,500 TreeWell units over 30 years with zero worker injuries.