K. Polanska, M. Sc. Eng., T. Sukowski, Dr Sc. Eng. J. Sawicki, Asst

Bulletin of the Maritime Institute
Gdansk, 1993, 20, 2
K. Polanska, M. Sc. Eng., T. Sukowski, Dr Sc. Eng.
Department of Environment Protection
The Maritime Ins titute in Gdansk
J. Sawicki, Asst. Prof. Dr hab. Eng.
Technical University of Gdansk
HYDROGEOLOGICAL METHOD OF GROUND
WATER PROTECTION
Abstract
A special hydrogeological method of groundw'ater protection
is presented. It has an application in the case of local pollution
caused b.Y industrial w'aste storage yards, especially in the
case of vertical gradient of pollution concentration. The method
· vertical, gravitational drainage barrier - each time should be
based
on
carefully
recognized
hydrodynamical
and
h .vdrochemical conditions of groundwater. The paper describes
two barriers installed up to now.
INTRODUCTION
Two types of sources of ground water pollution are usually described:
regional caused by agricultural activity, and local caused by industrial
wastes storage yards. Below local type of the source of ground water
pollution is described.
K. Polanska, T. Sukowski, J. Sawicki
54
On fig. 1 typical example of the type is presented.
crec
~ ~.
-
. in i ti~l . ·.
. water table
0
&"" .- ;;;:.. .- - .- '--.:.
-~:-/]a_'"~·~ ·. ~·
y.- · , ·
-:-_
migration
of
1
-
po ~ lutonts
Figure 1. Industrial factory's influence on ground water
Eluted from srored industrial wastes chemical compounds moved
by infiltration of rain water caused pollution of ground water. Besides
of pollution , changes of ground water regime occur such like arising
of ground water level, and swampy surface around the storage yard.
Elution and washout of wastes is always long-term process so the
danger to ground water pollution is serious.
METHOD OF PREVENTION
Two groups of method of prevention of ground water pollution
could be distinguished, geotechnical and hydrogeological. Both could
be used together or separately.
The essence of the geotechnical methods
IS
based on isolation of
ENVIRONMENT PROTECTION
55
wastes, and waste polluted water from ground on which storage yard
is located. Different of protective screens are used, plastic film on the
bottom of the yard [fig.2a] or sheet pile wall, separating in vertical,
storage yard and ground, down to impermeable strata [fig.2b ]. Isolated
area should have been drained by system of dewatering to remove
surplus of water or waste water.
insu l a hng
storage
toil
draining
yard
/well
sheet
pilling
_LC:,LJic::.:::::..:::=-:=-:=-=.111.~>....:.29_~.
. ;J
-----
ermeob~ e ld_ye r" ~•
• • •• • • • •
•
••
·.
IT/
.
~ '
I
' •
TTITT/ TT! .r(f tTl!
1 mpermeoble
, •
laye r
Figure 2. Examples of geotechnical methods
Geotechnical methods have some disadvantages, they a re very expensive, often ineffective [problems connected with tightness] , influence on geotechnical parameters of waste [stability of slopes of waste
saturated with water]. Geotechnical method not always could be used
e.g. installing plastic film in old existing storages, or sheet pile walls
when impermeable strata lies on big deep.
Hydrogeological method are: open ditches, drainage systems, dewatering wells. They are used to keep polluted water as close as possible
to waste storage yard, preventing from outside migration and removing water to treatment installation .
K. Polanska, T. Sukowski, J. Sawicki
56
Ditches and shallow drainage systems have some limitation in using,
because of collecting mainly rain water, usually less polluted as deeper
ground water. Meanwhile in ecological point of view, infiltration of
rain water washes polluted ground, which is the positive process, so as
to protect environment, deeper more polluted ground water collecting is
needed. Therefore wells are more effective than shallow, drainage
system. But using wells it has to be taken in consideration that important
intluence on wells effectiveness has got relation between parameters
of well Q
=
f(s), and characteristic of pomp and pipes Q
=
f(H),
where:
Q- yield of water,
s - depression,
H - effective head.
Because of hydrogeological conditions changes, e.g. rainfall, changes
of exploitation parameters occur, which could have negative intluence on
results of system work. It should be emphasised that the main condition for proper functioning of hydrogeological system of water protection is stability of ground water level.
Below, solution is presented which takes advantage of positive characters of wells and in the same time secures stability of water level.
HYDROGEOLOGICAL BARRIER
Mentioned above solution consists of needed quantity of wells located perpendicularly to ground water flow direction. Depend on waste
storage terrain situation, barrier would be located as one line of wells
[fig. 3a] or even all around the storage yard [fig. 3b ].
ENVIRONMENT PROTECTION
1
57
outflow -
( P)
~._~~~-=~~~
of
drain
water
(c
l
·
storage -----yard
direchon
of
_./'---
catchwater
linear
barrier
ot draining wells
circular
barrier
Figure 3 Schemes of barrier locations
wcter well ·
s t a rage
yard
water
table
caused by
the storage
yard
water
in.it i a l /- .
water
table
final
water
ta ble
we ll
mmrniTTm rn mmmn-
Figure 4 Cross-section of barrier
--
K. Polanska, T. Sukowski, J. Sawicki
58
Each wells is drilled in the same way as the hydrogeological well for
water supply is drilled, but water outflow is trough circural orifice cut
in filter pipe on the level on which needed water level is designed. To
the orifice collector is attached connected with main outflow pipe,
located parallel to the line of wells [fig. 4).
Diameter and decline of collector and main pipe is designed with
using classical hydraulic methods, so as to be sure, that gravitational
water flow is achieved. Collected water is removed to reservoir of
pumping station from where could be send to next step of treatment.
The solution secures to keep very steady ground water level. Even
much bigger flow could be carry away, because the collector and main
pipes could temporarily work as a pressure pipes.
Parameters of barrier exploitation should be designed very carefully, because when barrier is done, it works by itself, and correction of
work parameters is difficult to perform. Especially ground water level,
quantity and spacing, localisation of wells, predicted yield should be
designed exactly. As it shown by hitherto existing barriers, there is no
need in solving equation of three dimensional filtration of ground
water.
Satisfactory results could be achieved using numerical solution of
Boussinesq equation [method of finite element).
aH
a
aH
Sat= ax [Kxx (H-z) ax]
where:
+
a
iJy [Ksutyy (H-z)
H -water potential,
S- effective porosity,
K- coordinates of transmissivity tensor.
uH
ayl + W(x,y,t)
(I)
ENVIRONMENT PROTECTION
59
Velocity field , according to Darcy Law is described by relation:
U=-[K] VH
(2)
Important to get good final solution is exact reproducing of area
geometry and parameters, and precise determination of boundary
conditions. In our calculations we used boundary condition as follows:
-
boundary condition such like lakes, river:
H
= f(x,y)
(3)
- . open boundary:
(4)
Working conditions of barriers should be established to gain as big
as possible polluted water flow from direction of waste storage yard,
and as small as possible less polluted water flow from outside area,
and keep ground water level on level which it was before waste storage
yard was erected.
Reasonable is to solve dispersion equation, which allow to prognoses
migration of polluted ground water before and after barrier is applied:
(5)
where:
C
- concentration of pollution
Dx, Dy - coefficients of dispersion
60
K. Polanska , T. Sukowski , J. Sawicki
EXAMPLES OF APPLICATIONS
c
~N·
2
3 km
@)
piezorre\er
7.91
lr:,9 . 6 l
-
------~
N
l
Figure 5. Location of working barriers
Up to now two barriers were installed:
Janikowo Soda Factory [fig.5a]- barrier consist of25 wells. Exploitation started in 1990. Result of water level, and chloride concentration decrease is shown on fig. 6.
Inowrodaw Chemical Factory [fig. 5b]- barrier consist of 10 wells.
Exploitation began in November 1992. So it is to ea rly to discuss
the results.
Designing works of next barriers are in progress .
ENVIRONMENT PROTECTION
I JANlKOWO
--41
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Hltl
' '.,., ....
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\
C N~u lt)
-::
"'
\
64
~
•
\
\
u
<=Q)
~
<11
~
.E
I
I
Q)
0
T
II\\'
\
Q_U"l
X -
~
,
-
I
E=<l..i
·:v ~
Vl
a_
.:?. E
~
Vl
r s l~:
60
0
\
\
81
!
1Piezometer291 I
)\
64
82
61
~
•
r
I I \I
)~;A
55
50
45
\ I\
..,
0
"' .D
Figure 6. Effects of barriers work in Janikowo
LITERATURE
Burzynski K. and Sadurski A. 1990: the Ground Water Exchange Rate of The
Southern Baltic Coastal Lowlands. Journal of Hydrology. Vol. 119. pp.
293-306.
Fundamentals of Transport Phenomena in Porous Media. Development in Soil
Science 2. IAHR, Elsevier Publication Company. Amsterdam - London -New York. 1972.