The Geo-Cleanse® Process utilizes patented and
specialized injector points on all of our sites.
The injector design is site-specific and based on
where the contamination is present in the subsurface
and the geology of the area. Typical injectors are
comprised of either CPVC or stainless piping.
For each treatment program, GCI develops an injector
layout, which is made up of a grid of equally spaced
injectors. The spacing of the injectors depends on
the geology in the impacted area of the site. Injector
spacing usually ranges from 15 feet to 25 feet in source
area applications. The spacing is tighter for tight
soils (clays) and larger for looser soils (sands).
Accurate spacing is essential in establishing an effective
radius of influence (ROI) of injected materials.
Once the injector spacing is defined, GCI
must establish the vertical extent of the contamination at
the site based on information from our clients. This determines
the number of injector layers required for the treatment
program. The injectors typically have 5-foot screened intervals
for maximum reagent distribution. Therefore, several layers
of injectors with discreet screened intervals may be used
at a site to remediate the impacted soil column. GCI incorporates
the installation of permanent injection wells for treatment
programs using Fenton’s reagent. Permanent injectors can
be utilized as long-term monitoring points and also allow
for additional treatment, if necessary. For permanganate
injections, temporary injection wells (using direct push
technology (DPT)) are usually installed. Both temporary and
permanent injection wells are generally installed using DPT.
Vent Well Construction
In addition to injectors, GCI sometimes
incorporates vent wells into the injector installation design
at some sites. Vent wells are usually installed at sites
that are inside or near a building or in close proximity
to other structures. Vent wells are used to direct the flow
of offgas by-products from the oxidation process. During
injection, offgasses (carbon dioxide and oxygen) are often
generated due to the breakdown of organic contaminants in
the subsurface that occurs during an ISCO treatment program
using Fenton’s reagent. The vent wells provide a pathway that offgasses do not build up underneath concrete
or surficial structures on-site. Vent wells allow GCI to
monitor the effects of the injection in the vadose zone.
Vent wells are also used for monitoring mounding groundwater
in areas where the water table is shallow. During the injection
if groundwater enters any of the vent well locations, GCI
can adjust the injection system accordingly, depressurizing
the vadose zone and minimizing any surficial expressions.
During the injector installation, GCI
requests that our clients obtain baseline analytical soil
and groundwater samples from 20% or more of the injectors
installed. The analytical results should be provided to GCI
prior to the beginning of injection activities. The data
from the lab analysis coupled with other baseline data will help GCI confirm the contaminant
mass present at the site and will serve as the basis for reagent proportioning.
In addition to the samples obtained for laboratory analysis, soil and groundwater
samples will be collected during the injector installation and sent to GCI’s laboratory
for pre-injection testing. Tests are performed to determine the buffering capacity
of the soil and to observe the reactivity of the soil and groundwater to hydrogen
peroxide. Overall, the laboratory testing serves as a basis to develop the site-specific
catalyst for use during the ISCO treatment program.