Civil Engineering Reference
In-Depth Information
2.
Flow of contaminated water with constant flow rate
Q
c
(m
3
/day) with
corresponding percolation rate
w
c
= Q
c
/F
, where
F
(m
2
) is the recharge surface
area. In the case of
w
c
≤ k
, where
k
(m/day) is the hydraulic conductivity of the
unsaturated zone, the percolation time is determined by the formula
mn
wk
(1.3)
t
=
w
2
3
c
For
w
c
>
k
(a temporary layer of contaminated water is formed on the sur-
face), the time
t
w
is determined by the formula
m
t
w
=
.
(1.4)
(
)
(
)
1
−
nk
n
2
2
1
−
nk
n
qk
n
+
+
2
4
2
In a heterogeneous stratified unsaturated zone, the equivalent hydraulic
conductivity of the averaged section can be determined by the formula
m
mk mk mk
k
=
,
(1.5)
e
/
/
/
+
+
+
11 22
i
i
where
m
1
,
m
2
, …,
m
i
and
k
1
,
k
2
,…,
k
i
are the thicknesses and hydraulic conduc-
tivities, respectively, of the layers.
The groundwater protectability index
ε
for the
upper
(
unconfined
)
groundwater
is assessed using Goldberg's qualitative groundwater protectability assessment by
an integer sum of two scores: (1) for the depth to groundwater table,
H
, and (2) for
the low-permeable layers in the unsaturated zone (if present). The first one takes
values 1-5 for corresponding intervals of groundwater table depth, as determined
in Table 1.1.
If low-permeable deposits (
k
≤ 0.1) are present in the unsaturated zone then the
second (additional) score is determined by the total thickness
m
0
and hydraulic
conductivity
k
as given in Table 1.2 for different lithology groups. The resulting
groundwater protectability index
ε
is assessed by finding the sum of the scores
(Tables 1.1 and 1.2) ranging from 1 to 30; according to this range, Goldberg deter-
mined six groundwater protectability categories:
Category I:
ε
≤ 5
Category II: 5
< ε
≤ 10
Category III: 10
< ε
≤ 15
Category IV: 15
< ε
≤ 20
Category V: 20
< ε
≤ 25
Category VI:
ε
> 25
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