Journal of Water Resource and Protection, 2013, 5, 699-708 Published Online July 2013 (
Numerical Simulation for Remediation Planning for
1,4-Dioxane-Contaminated Groundwater at Kuwana
Illegal Dumping Site in Japan Based on the
Concept of Verified Follow Up
Ramrav Hem, Toru Furuichi, Kazuei Ishii, Yu-Chi Weng
Laboratory of Sound Material-Cycle Systems Planning, Graduate School of Engineering,
Hokkaido University, Sapporo, Japan
Received April 29, 2013; revised May 30, 2013; accepted June 20, 2013
Copyright © 2013 Ramrav Hem et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
At Kuwana illegal dumping site in Japan, where hazardous waste was illegally dumped, groundwater was severely con-
taminated by Volatile Organic Compounds (VOCs). Groundwater was already remedied by conducting Pump-and-Treat
(P&T) after containment of all the waste by vertical slurry walls from 2002 to 2007. However, 1,4-dioxane was de-
tected in both waste and groundwater outside of slurry walls after it was newly added into Japan environmental stan-
dards in late 2009, which suggested that the walls did not contain 1,4-dioxane completely. Our previous study devel-
oped a model to predict the 1,4-dioxane distribution in groundwater after the previous remediation at the site. In this
study, numerical simulation was applied for remediation planning at the site based on the concept of Verified Follow
Up (VF-UP) that had been proposed as a new approach to complete remediation effectively with consideration of future
risks. The amount of waste to be removed and pumping plans were discussed by numerical simulation to achieve the
remedial objective in which 1,4-dioxane in groundwater outside of walls is remedied within 10 years and 1,4-dioxane
spreading throughout the walls is prevented in the case where a portion of waste is remained. Firstly, the amount of
waste to be removed considering pumping plans for P&T was determined by scenario analysis. As a result, at least
two-third of waste should be removed by combining with P&T. However, if the waste is remained, future risks of
1,4-dioxane spreading through the slurry walls may occur. Our simulation suggested that groundwater within the re-
maining waste must be pumped up at least 20 m3/d for containment of 1,4-dioxane within the remaining waste. In con-
clusion, our numerical simulation determined the amount of waste to be removed and the pumping plans for P&T to
achieve the remedial objective effectively considering future risks based on the concept of VF-UP.
Keywords: Remediation Planning; Numerical Simulation; Verified Follow Up; Pump-and-Treat;
1,4-Dioxane-Contaminated Groundwater; Illegal Dumping Site
1. Introduction
In Japan, after the rapid economic growth in mid-20th
century, environmental pollution has become a serious
issue caused by industrial activities [1]. The problem of
illegal dumping of industrial waste has been prolonged
through decades because of, e.g., lack of landfills, high
cost for waste management, and many mountainous areas
where illegal dumping can be easily carried out [2,3].
The number of illegal dumping increased over 1000 cases
from 1998 to 2001 [4]. Recently, the solution of illegal
dumping has become a major importance, since illegal
dumping threatens the society’s safety and security [5-8].
The restoration and recovery of illegal dumping sites to
meet the conditions regulated by law or environmental
standards poses a variety of problems including not only
the impacts on the surrounding environments but also
major economic losses because it requires sophisticated
technologies and long remediation period [4,5,8].
Kuwana illegal dumping site is one of those cases
where the contaminated waste was illegally dumped be-
tween 1995 and 1996. Since then, groundwater had been
contaminated by Volatile Organic Compounds (VOCs).
From 2002 to 2007, remedial measures, e.g., containment
all the waste by constructing vertical slurry walls and
opyright © 2013 SciRes. JWARP
treatment by conducting Pump-and-Treat (P&T) were
carried out to treat VOCs completely. Groundwater qual-
ity has been monitored after completion of VOCs reme-
diation for future risks. In late 2009, after 1,4-dioxane
was added into Japan environmental standards with the
limit concentration of 0.05 mg/L, 1,4-dioxane with high
concentration was detected in groundwater at Kuwana
site inside and outside of the walls [9]. Similarly, studies
had reported that leachate at several landfill sites in Japan
contains significant levels of 1,4-dioxane [10-12]. The
US EPA and International Agency for Research on Can-
cer classified 1,4-dioxane as Group 2B (possibly carcino-
genic to human being) [13]. Therefore, remediation plan
should be developed and implemented immediately to
treat 1,4-dioxane in groundwater at the site and to pre-
vent 1,4-dioxane from spreading into the surrounding
Although previous measures have been applied for
VOCs remediation at Kuwana site, they could not be ef-
fective to complete 1,4-dioxane remediation because 1,4-
dioxane is expected to migrate in groundwater without
biodegradation and adsorption to soil according to its
unique properties [14-18]. Consequently, 1,4-dioxane
might be more difficult to be contained by groundwater
level control without waste removal. Regarding this pro-
blem, this study focused on developing remediation plan
by using numerical simulation based on the concept of
Verified Follow Up (VF-UP). VF-UP is a new approach
developed by [19] for remedial planning for groundwa-
ter-contaminated sites, considering future expected and/
or unexpected uncertain events to complete remediation
effectively. Several studies have been conducted by ap-
plying the numerical simulation for groundwater con-
taminated site remediation focusing on mostly the par-
ticular elemental technique e.g., optimization of pumping
rates, pumping locations, remediation time and costs
[14,20-26]. However, our study focused on the applica-
tion of numerical simulation for the whole remediation
plan considering the element techniques. The element
techniques can be flexible to be changed based on the
actual conditions of remediation at the site. Moreover,
since VF-UP was newly developed, there is no study that
proves its application to the real contaminated site, espe-
cially in remediation planning using numerical simula-
Our previous study [27] developed a model to predict
the 1,4-dioxane distribution in groundwater to represent
the groundwater flow and 1,4-dioxane distribution condi-
tions after the previous remediation at the site. The de-
veloped model will be modified regarding the condition
in remediation planning considering the same parameters
and setting. The remedial objective in this study is to
treat 1,4-dioxane in groundwater outside of slurry walls
within 10 years which is limited to national subsidy and
to prevent 1,4-dioxane from spreading throughout the
walls to the surrounding environment. In this study, nu-
merical simulation was applied to analyze the amount of
waste to be removed and the pumping plans for treating
1,4-dioxane-contaminated groundwater at Kuwana illegal
dumping site based on the concept of VF-UP.
2. Site Description and Previous Study
Kuwana illegal dumping site is located in Kuwana city,
Mie Prefecture, Japan (see Figures 1(a) and (b)). This
site was originally designed and operated as an inert-type
landfill. Due to the poor control, hazardous wastes, e.g.,
ash, sludge, and waste oil including hazardous materials
Figure 1. Location map (a), base map (b), and simplified south-north section (c) of study area. Source: (a) Map’s link: (Retrieved 2013), (b) Report of Mie Prefecture, 2011.
Copyright © 2013 SciRes. JWARP
R. HEM ET AL. 701
were illegally dumped into this site between 1995 and
1996. The dumped waste has approximately the area of
2800 m2 and the volume of about 30,000 to 40,000 m3
with the maximum depth of 14.7 m [28]. Groundwater
around the site had been contaminated by the hazardous
chemicals including chlorinated organic compounds and
aromatics [28]. From 2002 to 2007, the countermeasures
for treating the contaminated groundwater had been ap-
plied, construction of vertical slurry walls around dum-
ped waste, soil capping, P&T, and circulated water flash-
ing on waste layers. As a result, the contaminated ground-
water was treated to a great extent. Yet, 1,4-dioxane was
detected in groundwater with high concentration after it
was added into standards in late 2009.
The alternating sand and clay layers occur above the
bedrock. The aquifer bed presents about 22 m below the
ground surface. Based on the hydrogeological data, the
aquifer beneath this illegal dumping site is separated into
three aquifers by confining clay layers. The aquifer name
was denoted from the top to the bottom as the first, sec-
ond, and third aquifer respectively. The three aquifers
have interaction in which groundwater flow directions of
first and second aquifer mainly toward the north while
that of third aquifer are in reverse direction. However,
groundwater of the second and third aquifers were con-
taminated by 1,4-dioxane. Figure 1(b) shows contami-
nated area with concentration higher than standards which
were obtained from the observed data in February, 2011.
Numerical simulation of groundwater at Kuwana ille-
gal dumping site during condition without pumping was
developed in a previous study by [27]. The geological
model was developed using 14 geological cross-sections
(see Figure 1(b)) provided by Mie Prefecture. Vertical
slurry walls and underground tank were also considered.
With model domain of 30,000 m2, the finite element
mesh of 6 m and vertical division of 55 layers were con-
sidered. Figure 2 shows the results of geological model
with vertical exaggeration of 1.5 (see Figure 1(b) for
locations of the viewing sections). Moreover, the previ-
ous model was calibrated so that hydraulic conductivity
of each aquifer material, retardation factor, dispersion
coefficients, boundary conditions, and other setting were
3. Roles of Numerical Simulation in
Remediation Planning Based on VF-UP
3.1. What Is VF-UP
VF-UP is a new approach developed by [19] for remedial
planning for groundwater-contaminated sites, consider-
ing expected and/or unexpected uncertain events in the
future to complete remediation effectively (see Figure 3).
The expected uncertain events should be considered as
much as possible during the remediation planning. On
the other hand, unexpected uncertain events, VF-UP pro-
vides intermediate review processes during remediation
and post review processes after completion of remedia-
tion. During the intermediate review, the remediation
plans are flexible for adaption of any improvements if the
remediation does not progress or not be completed as
planned. In this case, remediation objectives and plans
might be changed, e.g., additional or new remedial tech-
nologies will be applied after intermediate review proc-
ess. Once the remediation is completed, and the site will
be monitored to ensure whether the site is completely
remedied. In the meant time, post review involved with
local residents needs to be conducted for risk commuta-
tion. Actually, risk communication with residents is nec-
essary from the early phase of revelation of the site, how-
ever it is very important to conduct risk communication
after completion of remediation to restore the confidence
of the residents and get their acceptance of remediation
Aquifer type
Aquifer materialBackfilled soilClaySand Clay WasteSand ClaySand GravelClay (base)WallTank
Hydraulic Conductivity, cm/s1.0×10
Second aquiferFirst aquiferThird aquiferUnderground structure
(a) (b)
Figure 2. South-north (a) and w e st-east (b) geological cross-section.
Copyright © 2013 SciRes. JWARP
3.2. Uncertain Factors in Remediation Planning
The expected and unexpected events caused by many
factors categorized as technical and social uncertain fac-
tors. Remediation planning based on VF-UP requires
planners to consider expected uncertain events as much
as possible. Once the uncertain events occur in the future,
during remediation or after completion of remediation,
they may exert a significant influence on the progress of
the remediation. In Table 1, the first column shows the
process of remedial planning from site discovering to the
completion of remediation and followed by the technical
and social uncertain factors [19].
The uncertain events may happen due to technical un-
certain factors that might happen at each phase from the
site investigation to the completion of remediation. Once
the contaminated site is discovered, field investigation is
carried out for data collection for analysis. Generally, the
number of data is limited and discrete over space and
time, therefore, the analysis of hydrogeological condition,
waste distribution, and contaminant distribution contains
much uncertainty. Next, remedial alternatives and plans
were decided and implemented uncertainly. The selected
technologies might not be good enough for specific site
condition and contaminants to be treated. Moreover, de-
sign and implementation of technologies might not be
proper because the predicted hydrogeological condition,
waste and contaminant distribution also contain uncer-
tainty. In addition, operation and maintenance might not
be well progress as planned because uncertain events
may occur. Lastly, the completion of remediation might
be judged in different ways from person to person which
required the adequate knowledge and experiences. Be-
sides, enough information must be required to be prop-
erly judged the completion of remediation.
For the uncertain events caused by the social uncertain
factors, may occur at any time of the whole processes for
remediation planning. There is no good communication
in society structure and not enough disclosure for resi-
dents about the site information. The registration or law
could be revised any time in which a new compound
might be added into environmental standards. Likewise,
the remediation could be terminated due to the cuts in
national subsidy. Furthermore, the new residents would
complaint or protest against the contaminated site. Last
but not least, sometimes the remediation is slower than
available period of fund so that the remediation might be
left incomplete.
3.3. Objective of Numerical Simulation for
Remediation Planning Based on VF-UP
Considering the above technical uncertain factors, there
might be many uncertain events will occur at Kuwana
illegal dumping site during the remediation and after
completion of remediation because the site has complex
hydrogeological features. There are three aquifers with
interaction and groundwater flows in different directions.
Moreover, the site has a steep slope so that groundwater
control for 1,4-dioxane containment is difficult. Since the
Figure 3. Remediation planning based on the conc e pt of VF -UP.
Table 1. Uncertain factors considered in remediation planning based on VF-UP.
Remediation planning phase Technical uncertain factors Social uncertain factors
Investigation and analysis after site discovering
Hydrogeological condition
Waste distribution
Contaminant distribution
Remedial alternatives, remedial plans and implementation
Selected technologies
Design and implementation
Operation and maintenance
Completion of remediation How is “completion” judged?
Society structure
Not enough disclosure
Registration or law
new standard
subsidy cut
New residents
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R. HEM ET AL. 703
number of data is limited and discrete over space and
time, prediction of groundwater flow and 1,4-dioxane
distribution might involve much uncertainty which exert
the remediation to progress slowly or remediation could
not be completed within time as planned. Due to the
above conditions, the uncertain events might occur dur-
ing remediation and after completion of remediation.
Therefore, in this study, two uncertain events were con-
sidered for remediation planning for Kuwana site:
1) Decreasing of remediation efficiency in P&T for
1,4-dioxane-contaminated groundwater out of the verti-
cal wall.
2) Emitting of 1,4-dioxane through the vertical walls
because the remaining waste might contain 1,4-dioxane
with high concentration.
Waste removal and P&T were considered as remedial
methods for 1,4-dioxane-contaminated groundwater at
Kuwana illegal dumping site. The objective of numerical
simulation for remediation planning based on the concept
of VF-UP is to treat 1,4-dioxoane outside of the walls
within 10 years and to prevent the spreading of 1,4-diox-
ane within the walls in case where a part of waste is re-
mained. Numerical simulation will play an important role
for estimating the effectiveness of waste removal and P
& T plans by considering the above mentioned expected
uncertain events. During remediation, the performance of
remediation was reviewed if any additional measures are
needed for improving the effectiveness of remediation.
However, if a portion of waste is remained, future risks
of 1,4-dioxane spreading through the walls into the sur-
rounding environment might occur. The future risks
might occur after completion of remediation. For that
reason, numerical simulation can be used to predict the
possible occurrence of future risks so that the measures
against future risks can be considered beforehand.
4. Model Development for Remediation
4.1. Governing Equations
Basically, the development of any deterministic model
for the groundwater flow and contaminant transport in
groundwater flow system is a set of representative partial
differential equations [29]. Equation (1) represents the
net inflow into the volume that must be equal to the rate
at which water is accumulating within the investigated
volume [30],
where are principal coordinate directions;
is the hydraulic conductivity (m/s); h is the hydrau-
lic head (m);
is the specific storage of porous me-
dium (1/m); is the local sources and sinks per unit-
volume (1/s);
is the space coordinate (m); denotes
time (s).
The transport model can be represented by the follow-
ing advection-dispersion equation [30]:
ii j
cc c
 
where 1
 is retardation factor of sol-
ute (dimensionless),
is density of dry matrix mate-
rial (kg/m3), is total porosity (dimensionless),
is distribution coefficient (m3/kg) ; c is the concentration
(mg/L); is the Darcy velocity (m/s); D is the disper- v
sion coefficient (m2/s);
Q is the concentration of solute
of water that added from sources or sinks (mg/L·s).
4.2. Solving Method and Used Software
The application of finite element method to groundwater
problem simulation was recently developed comparing to
the finite difference method. For the finite difference
model, the heads throughout the domain are defined only
at the nodal points themselves while the finite element
model permits the application of variational or weighted
residual principles. Finite element method is flexible for
irregular boundaries of problem and, moreover, in solv-
ing coupled problems, e.g., contaminant transport, or in
solving moving boundary problems, such as moving wa-
ter table [31].
For this model, numerical finite element methods ba-
sed on the mixed Eulerian-Lagrangian approaches were
used to solve the advection-dispersion equations. The La-
grangian methods are particularly suitable for solving ad-
vection term, while the Eulerian methods are more effec-
tive in dealing with dispersion term [32]. In this paper, a
three-dimensional numerical model was developed by
using GeoModeler software for simulating the ground-
water flow and 1,4-dioxane transport. GeoModeler is a
numerical finite element-based software for modeling
subsurface flow, solute transport, and heat transport pro-
cesses which was recently developed by a Japanese com-
pany, GMLabo Inc (
4.3. New Model Development for P&T
4.3.1. Grou ndwater Data fo r Pumpi ng Conditi on
Based on the data given by Mie Prefecture, groundwater
had been normally pumped from the first and second
aquifers for VOCs treatment. However, during two peri-
ods, groundwater from the third aquifer also pumped,
from November, 2007 to March, 2008 and from Decem-
ber, 2009 to March, 2010. During these two periods, the
Copyright © 2013 SciRes. JWARP
maximum pumped water was found in February, 2010.
The average pumping rate was about 52 m3/d, in which
36 m3/d from the inside the walls (21 pumping wells) and
16 m3/d from the outside of the walls (six pumping
wells), and much water was pumped from the second and
third aquifers. Therefore, the groundwater data in Febru-
ary, 2010 will be used for the model calibration for pum-
ping condition.
4.3.2. Model Calibr ation
It is never possible that one model can correspond to all
the conditions on groundwater behavior [33]. For the
case of Kuwana site, since the model domain is narrow,
the pumping activities might influence the model bound-
ary, e.g., the boundary might be lower than the condition
without pumping. Therefore, the model calibrated using
the data during the absence of pumping cannot be used to
represent the groundwater behavior during pumping. For
that reason, the existing model developed by [27] re-
quires to be calibrated for pumping condition. The avail-
able measured groundwater head data in the first, second,
and third aquifers were obtained from 12, 12, and 14
monitoring wells respectively. These data were used for
comparing within the model result from each calibration.
An error index, root mean square error (RMSE) calcu-
lated by comparing the calculated and observed heads
was used to compare the goodness-of-fit of each calibra-
tion result. Firstly, the existing model was run for the
pumping condition by inputting all the above pumping
data, case 0. As a result, the mean error of each aquifer
ranged from 0.5 to +0.5 m so that the decreasing bound-
ary will be done for calibration limited to 0.5 m. Nor-
mally, the boundary at the upstream (UB) is much influ-
enced than that in the downstream (DB) of aquifer,
therefore, the decreasing upstream boundary was priori-
tized for the calibration.
Table 2 shows that case 3 gave the better minimum
RMSE value. In this case, only the upstream boundary of
the third aquifer was decreased by 0.5 m while that of the
first and second aquifers were kept the same as their
original levels. The boundary of the third aquifer was
influenced by the pumping because there was not enough
water supplied from the boundary due to the low hydrau-
lic conductivity and the aquifer thickness is relatively
thin comparing the other two aquifers. For the first and
second aquifers, plenty of water was supplied from the
boundary, especially from the upstream boundary. Fig-
ure 4 shows the comparison between the calculated and
observed head at monitoring wells in each aquifer. Addi-
tionally, groundwater flow directions in each aquifer
from case 3 were found to be consistent with those ob-
tained from the measured groundwater head data during
pumping. And, if there is no such calibration, groundwa-
ter flow direction of the third aquifer would be in rever-
sion directions with those from measured data during
5. Remediation Planning Based on VF-UP
5.1. Estimation of Removed Waste and Pumping
Rates for Remediation Plan
The required time for contaminated groundwater reme-
Figure 4. Comparison of calculated and observed ground-
water head.
Table 2. Scenarios for model calibration and RMSE results.
Case 0 Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
Calibration Case
First aquifer × × × × × × ×
× ×
Second aquifer × × × × × × ×
× ×
Third aquifer × × × × × × × × × ×
RMSE 0.624 0.668 0.608 0.558 0.666 0.620 0.798
× Groundwater head boundary was not changed.
Groundwater head boundary was decreased 0.5 m from the original level.
Copyright © 2013 SciRes. JWARP
R. HEM ET AL. 705
diation will depend on several factors, which vary from
site to site, e.g., it may take longer for the site where the
contaminant source has not been completely removed
[34]. Since the national subsidy is limited for Kuwana
illegal dumping site, complete removal of waste from the
site is impossible. This study has supposed four cases of
waste removal with the same depth of about 15 m from
ground surface, (a) no removal of waste, (b) one-third of
waste is removed, (c) two-third of waste is removed, and
(d) all of waste is removed. Based on the waste distribu-
tion and current 1,4-dioxane concentration distribution,
the zone of waste to be removed is considered to start
from eastern part of walls. For plan (c) and (d), extra wall
which has similar property with the vertical slurry walls
was added for the calculation (see Figure 1(b)). In order
to determine pumping well locations and rates, plan (c) is
considered because it is the most considerable case based
on the waste distribution and 1,4-dioxane concentration
distribution. In case where a portion of waste is remained,
the remaining waste is considered as the continuous
source of 1,4-dioxane with relative concentration of 1
unit. The 1,4-dioxane concentration distribution calcu-
lated in the previous model was used as initial condition,
however, 1,4-dioxane within the removed waste was ex-
cluded in calculation.
According to 1,4-dioxane distribution in the previous
study [27], locations of four pumping wells outside and
two wells inside of walls were considered for plan (b).
The wells inside of walls were used to pump groundwa-
ter from all aquifers, while the two wells outside the
walls for only groundwater from the second and third
aquifers. 1,4-Dioxane transport with 14 pumping plans
were analyzed (see Table 3). The total pumping rates
from each combination were limited by the capacity of
treatment facilities of 60 m3/d. As a result, the last pump-
ing plan (P14) gives minimum average concentration
outside of walls in each aquifer. Reviewing all the result
from the 14 pumping plans, remediation is more effective
when pumping rates of wells within waste layers in-
creased, however, at least 10 m3/d of water should be
pumped to treat 1,4-dioxane outside of the walls.
From this result, 50 m3/d is needed for pumping
groundwater from the remaining waste for 1,4-dioxane
containment and 10 m3/d is needed for pumping ground-
water from outside of walls for 1,4-dioxane remediation.
The estimated pumping plan was used then to calculate
the effectiveness of remediation of other plans. Since the
spatial distribution of waste is large, six and four pump-
ing wells are required for plan (a) and (b) respectively.
For plan (d), even all waste was removed, the remaining
pumping capacity should focused on the treatment of
1,4-dioxane in groundwater of the third aquifer. There-
fore, six pumping wells installed in only third aquifer.
The average concentration observed at 19, 29 and 30
monitoring wells outside of the walls of the first, second,
and third aquifer respectively is used to evaluate the ef-
fectiveness of each plan. Corresponding to the each pum-
ping plan, the results of remaining average concentration
measured from those observation wells are shown in
Figure 5. Groundwater outside of walls can be com-
pletely treated to lower than standard limit only by plan
(d). For plan (a) and (b), there is no further ways to im-
prove the efficiency of remediation because the 1,4-diox-
ane remained high in all aquifers. In contrast, in plan (c),
groundwater of the first and second aquifers was com-
pletely treated, but the third aquifer is still contaminated.
In addition, since the waste remained only in the first
aquifer, the third aquifer will be easily remedied. For that
reason, remediation in plan (c) suggested to review pum-
ping plans if there is uncertain event that may exert the
significant influence on remediation efficiency. During
the review of pumping plans, two wells outside the wall
found to be no longer effective and they were relocated
into the zones where concentration was slowly decreased
during remediation. Moreover, only groundwater from
the third aquifer should be pumped. In addition, a new
Table 3. Scenarios of pumping plans and average 1,4-dioxane concentration result from wells outside of walls.
Scenario of pumping plans P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13P14
Inside of walls 15 20 30 40 50
South of walls 5 10 15 20 5 10 15 20 5 10 15 5 10 5
North of walls 5 10 15 20 5 10 15 20 5 10 15 5 10 5
Pumping rate
Total 25 35 45 55 30 40 50 60 40 50 60 50 60 60
First aquifer 0.0370.036 0.034 0.0330.0350.0320.0310.0300.0310.030 0.029 0.029 0.0290.029
Second aquifer 0.0480.044 0.043 0.0410.0450.0410.0400.0380.0400.038 0.038 0.038 0.0370.036
Third aquifer 0.1220.112 0.105 0.0980.1130.0990.0930.0870.0850.080 0.073 0.073 0.0690.066
outside of
All aquifers 0.0690.064 0.061 0.0570.0640.0580.0550.0520.0520.049 0.047 0.047 0.0450.044
Copyright © 2013 SciRes. JWARP
Figure 5. Average concentration of 1,4-dioxane in 10 years
after remediati o n started.
well is required to the zone of removed waste because
the concentration was remaining high.
After the plan (c) was completely revised, simulation
was rerun for another 10 years using the 5th year concen-
tration of its result as initial concentration. As a result,
Figure 6 shows that 1,4-dioxane concentration especially
in the third aquifer was decreased drastically from the
first year and gradually decreased to lower than standard
limit in four to five years after the review of plan (c) (see
Figure 6). Thus, in remediation planning, revised plan (c)
and plan (d) could be proposed. However, if revised plan
(c) is selected for the site, when P&T will be shut down
in future, risks of 1,4-dioxane spreading out of the walls
might occur. Therefore, further study for future risks
management should be conducted.
5.2. Estimation of Pumping Rate for Future
Risks Management after Completion of
In order to predict the future risks that may occur after
completion of remediation, we assumed that the remain-
ing waste contains high 1,4-dioxane concentration. In
this case, the whole remaining waste was assumed to
contain 1,4-dioxane with relative concentration of 1 unit
release constantly over calculation period for 15 years.
As a result, if there is no pumping, 1,4-dioxane could
spread out of the walls into the surrounding environment.
For that reason, P&T is required. Using two pumping
wells as similar as in plan (c), in which groundwater was
pumped from the waste layer of all aquifers with pump-
ing rates varied from 0 to 60 m3/d in order to observe the
trench of decreasing rate of concentration until the mini-
mum spreading concentration is achieved.
To observe the spreading concentration, eight and nine
observation points were placed from the south and north
walls respectively until the model boundary. 1,4-dioxane
spreading was simulated for 15 years with pumping. As a
result, the average concentration of 1,4-dioxane from 17
observation points were plotted corresponding to the
each pumping rate in Figure 7. In case of pumping rate
reached 20 m3/d the average spreading concentration was
minimized. Therefore, the required pumping rate for hy-
draulic containment to prevent future spreading of 1,4-
dioxane into surrounding environment was determined as
20 m3/d.
6. Conclusions
With regardless of national subsidy, the removal of all
Figure 6. Decreasing average concentration in plan (c) from 1 day to 15 years.
Copyright © 2013 SciRes. JWARP
R. HEM ET AL. 707
Figure 7. Average concentration of 1,4-dioxane outside of
walls in 15 years simulation for each pumping rate.
the waste can be considered so that 1,4-dioxane-contami-
nated groundwater inside and outside of the walls at
Kuwana site could be completely treated by P&T within
10 years. However, since the national subsidy is limited,
our study proposed a proper remediation plan to com-
plete the remediation of 1,4-dioxane at Kuwana site in
which at least two-third of waste should be removed and
P&T should be carried out simultaneously. For P&T plan,
two pumping wells are needed for pumping groundwater
from the remaining waste with the total capacity of 50
m3/d. Concurrently, for remediation of 1,4-dioxane out-
side of walls, four pumping wells were required with the
total capacity of 10 m3/d. However, to improve the effec-
tiveness of remediation for the completion of remediation
within 10 years, regarding the concept of VF-UP, pump-
ing plan was changed at 5 years after remediation started.
Furthermore, the future risks of spreading of 1,4-dioxane
from the remaining waste throughout the walls into the
surrounding environment was predicted by our numerical
simulation by assuming that the remaining may contain
1,4-dioxane with high concentration. Therefore, the study
suggested that groundwater within remaining waste must
be pumped up at least 20 m3/d to keep containment of
1,4-dioxane within the remaining waste.
In conclusion, our numerical simulation was success-
fully applied to estimate the amount of waste to be re-
moved and a proper pumping plan to achieve the objec-
tive of remediation planning for the real illegal dumping
site based on the concept of VF-UP.
7. Acknowledgements
The authors sincerely thank Mie Prefecture for providing
all the valuable data and documents for supporting this
research. The authors also appreciate the financial sup-
ports for this research provided by Japan International
Cooperation Agency (JICA) through its ASEAN Univer-
sity Network/Southeast Asia Engineering Education De-
velopment Network (AUN/SEED-Net) project.
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