resulted in an almost complete dechlorination of PCE. Nevertheless, data exhibited
high TCE concentrations in the groundwater—in the range from 1500 to
4500 μg L
À1 , and up to 9000 μg L
À1
—demonstrating the significance of the
contamination and the low degradation rates.
Because the principal witness of COCs impact is piezometer F5, located downstream from the Western zone of the old quarry, the pilot was implemented in a
convenient location, in the direction of the water flow, in parallel with the F5
piezometer, in a topographically accessible place to the installing and handling the
work apparatuses. Before any implementation of the network, geological and
hydrogeological investigations allowed dimensioning the pilot area, namely the
small area.
6.5.2.3 The Small Area
The small area was implemented is a 50 m  50 m zone (2500 m², Fig. 6.13). A
review of topographic maps indicates that the site slopes gently northward with high
bedrock ridges to the East. The ridge trends in the North-South direction. The
average ground surface elevation at the site is 45 m above sea level. Locally, the
site is underlain by very fine sand, between 10 and 15 m deep, silt, gravel, clays
(Cuisian sands), natural organic matter, and other organic compounds, e.g., BTEX,
methanol, and ethanol. Coring showed a roof of the Sparnacian clays in the range
from 22.60 m to 23.10 m. Groundwater pumping tests in wells were measured to
characterize the groundwater flow. Results of these measurements indicated that
groundwater flows to the North-East, and the horizontal flow velocities were estimated to be higher than 40 cm d
À1 .
A network of 12 piezometers (PZs) of an average depth of 22–23 m was installed
in order to define the initial conditions and later to perform and monitor the chemical
treatment. They were disposed along a transect intercepting perpendicularly to the
polluted groundwater flow. Three of them, schemed in red in Fig. 6.13, were
designed as injection wells (I1, I2, and I3 in Figs. 6.14 and 6.15) and were equipped
for simultaneous injection over four different levels, from 0 to À25 m. The other
nine PZs—respectively distanced at 5, 10, and 25 m from the injection wells—were
designed as monitoring wells (control piezometers, or cPZs) and fully equipped with
probes (C11, C12, C13; C21, C22, C23; and C31, C32, C33 in Figs. 6.14 and 6.15).
The groundwater quality was carried out in depth between August 18 and August
21, 2014. Series of in situ measurements and sampling were achieved in each PZ, at a
high point (H) at À10 m depth and at a low point (B) at À20 m depth. The sampling
was carried out by the use of inflatable packers in order to isolate a zone when the
sampling is operated in the other point. This initial pollution state of the pilot zone
was carried out in order to be used as reference before any injection of reductant, for
the comparison of the total COCs content, as well as the nature, abundance, and
relative distribution of COCs within the pilot area.
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R. Rodrigues et al.
high TCE concentrations in the groundwater—in the range from 1500 to
4500 μg L
À1 , and up to 9000 μg L
À1
—demonstrating the significance of the
contamination and the low degradation rates.
Because the principal witness of COCs impact is piezometer F5, located downstream from the Western zone of the old quarry, the pilot was implemented in a
convenient location, in the direction of the water flow, in parallel with the F5
piezometer, in a topographically accessible place to the installing and handling the
work apparatuses. Before any implementation of the network, geological and
hydrogeological investigations allowed dimensioning the pilot area, namely the
small area.
6.5.2.3 The Small Area
The small area was implemented is a 50 m  50 m zone (2500 m², Fig. 6.13). A
review of topographic maps indicates that the site slopes gently northward with high
bedrock ridges to the East. The ridge trends in the North-South direction. The
average ground surface elevation at the site is 45 m above sea level. Locally, the
site is underlain by very fine sand, between 10 and 15 m deep, silt, gravel, clays
(Cuisian sands), natural organic matter, and other organic compounds, e.g., BTEX,
methanol, and ethanol. Coring showed a roof of the Sparnacian clays in the range
from 22.60 m to 23.10 m. Groundwater pumping tests in wells were measured to
characterize the groundwater flow. Results of these measurements indicated that
groundwater flows to the North-East, and the horizontal flow velocities were estimated to be higher than 40 cm d
À1 .
A network of 12 piezometers (PZs) of an average depth of 22–23 m was installed
in order to define the initial conditions and later to perform and monitor the chemical
treatment. They were disposed along a transect intercepting perpendicularly to the
polluted groundwater flow. Three of them, schemed in red in Fig. 6.13, were
designed as injection wells (I1, I2, and I3 in Figs. 6.14 and 6.15) and were equipped
for simultaneous injection over four different levels, from 0 to À25 m. The other
nine PZs—respectively distanced at 5, 10, and 25 m from the injection wells—were
designed as monitoring wells (control piezometers, or cPZs) and fully equipped with
probes (C11, C12, C13; C21, C22, C23; and C31, C32, C33 in Figs. 6.14 and 6.15).
The groundwater quality was carried out in depth between August 18 and August
21, 2014. Series of in situ measurements and sampling were achieved in each PZ, at a
high point (H) at À10 m depth and at a low point (B) at À20 m depth. The sampling
was carried out by the use of inflatable packers in order to isolate a zone when the
sampling is operated in the other point. This initial pollution state of the pilot zone
was carried out in order to be used as reference before any injection of reductant, for
the comparison of the total COCs content, as well as the nature, abundance, and
relative distribution of COCs within the pilot area.
348
R. Rodrigues et al.