Permeable Reactive Barriers in Europe - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 291

performance has reached a relatively stable level, varying between 70% and
90%. Remediation efficacy is lower than expected from the known material
properties and column experiments conducted prior to the setup of the pilot-
scale PRB. The possible reasons include a flow bypass, fast passivation, or
construction problems, namely layers of gravel with only small amounts of
iron filling.
13.3 PRB Sites in Austria and Switzerland
13.3.1 Brunn am Gebirge
Set up in 1999, type: EC-PRB (“AR&B”-system, “Adsorptive Reactor and
Barrier,” full-scale, four ISVs in accessible shafts), loaded with GAC; con-
taminants and cleanup performance: PAHs, BTEX, cVOCs, benzene, con-
centrations of all contaminants below the detection limit, and remediation
goals achieved since 1999 (Birke et al., 2004; Niederbacher and Nahold, 2005;
PEREBAR, 2014).
A full-scale PRB system was installed at an abandoned site of a former tar
and linoleum production and processing plant in Brunn am Gebirge (nearby
Vienna), Austria in 1999 (Figures 13.6 and 13.7). The system consists of four
adsorptive reactors packed with GAC and a hydraulic barrier (“Adsorptive
reactor and barrier”). PAHs, phenols, BTEX, cVOCs (mainly TCE and cis-
DCE), and HCs are the contaminants of concern. Extensive investigations
of the site showed contamination both of the vadose and the saturated zone
with concentrations up to 8.6 mg/L for PAH, 0.34 mg/L for phenols, 29 μg/L
for benzene, 50 μg/L for toluene, 6.6 mg/L for HC, 0.8 μg/L for TCE, and
27 μg/L for cis-DCE. The total area involved covers more than 376,600 ft 2 .
The geological profile is characterized by 0-7 ft of anthropogenic deposits
and alluvial sediments (sandy silty gravel) that are 10-20 ft thick below the
ground surface. These sediments are underlain by shales of the mid-Panno-
nian age. There are intercalations of coarser layers, in which artesic water can
be encountered. The groundwater table is 7-13 ft below ground surface (bgs).
The base of the aquifer is 10-20 ft bgs. Tests indicated permeabilities rang-
ing from 9.8 × 10 −3 to 3.3 × 10 −5 ft/s. The natural groundwater flow is west
to east with a bend to the southeast, following an erosional depression. A
migration of the plume toward the property's boundary has been verified. A
site-adapted solution was developed including accommodating a pond fed
with clean groundwater (at 5 ft below the actual groundwater level) so that
it cannot be polluted. Four adsorptive reactors packed with 23 tons of GAC
in total were combined with a 2-5-ft-thick hydraulic barrier. This west-to-
east-directed, 720-ft-long barrier, made by jet grouting, cuts into the shoulder
of tertiary shales at its Eastern edge. An L-shaped barrier was constructed,
which efficiently keeps contaminated groundwater apart from the artificial