TM 5-815-5/AFM 88-5, Chap 6/NAVFAC P-418
tering systems have been completely installed and ini-
ined at the New Orleans District Office or at the office
tially tested. When, and if, the first full-scale pumping
_ _ _ _ _ . The Government guar-
of
test conducted on the dewatering system shows the
antees the accuracy of the basic river stage and pump-
system adequate to lower and maintain the hydrostat-
ing test data as obtained for the particular wells in-
ic water level in the deep underlying foundation 3 to 5
stalled at the locations tested; however, as the logs of
feet below the water level in the excavation as it is un-
borings indicate, the characteristics of the subsurface
watered, the Contracting Officer will advise in writing
soils at the site vary considerably, and therefore the
that the Contractor may proceed with unwatering the
Contractor should not assume that the data obtained
excavation. The water level in the Phase I excavation
from the pumping tests made at the locations specified
shall be lowered at a rate not to exceed 1 foot per day
are representative of all conditions that exist at the
or slower if there is any sign of raveling or instability
site. Therefore, it shall be the responsibility of the
of the excavated slopes.
Contractor to make his or her own evaluation of the re-
(9) Surface water control. The Contractor shall in-
lation of the pumping test data to subsurface condi-
stall, operate, and maintain dikes, ditches, sumps,
tions at other locations at the site.
pumps, and discharge piping for controlling surface
(c) The subsurface soils at the site consist of a
water so as to prevent flooding of the work area for
top stratum of clays, silts, and fine sands, with widely
driving the test and foundation piles for the dam.
varying degrees of arrangement and stratification,
(10) Available soil and pumping test data.
with a depth of about 80 to 120 feet. A stratum of
(a) Some of the soil test data obtained by the
rather pervious sand underlies the entire site with a
Government are shown on the boring logs. Additional
thickness of approximately 220 feet. The top of this
logs of borings made for the project are plotted in _ _
deep thick sand stratum varies from about elevation
-------------------
- 20.0 to - 70.0 feet. Logs of three borings (M-1, M-2,
- - - - - - - - - - - - - dated
and M-3) made 500 feet deep indicate that this sand
. The above report and additional labora-
stratum is underlain by a clay stratum about 120 feet
tory data and samples of soils from the borings shown
thick at a depth of about 290 to 380 feet. This clay
on the plans are available in the _ _ _ _ _ _ _ _
stratum may or may not be continuous. It is underlain
_ _ office of _ _ _ _ _ _ _ _ .
by more sand to a depth of about 400 feet.
(d) The Red River flows along and around a por-
(b) Pumping tests have been performed on three
tion of the site for the excavation, the deeper parts of
wells installed at the site. One of these test wells (Well
the river in the vicinity of the excavation range from
A) was installed with 190 feet of l6-inch nominal di-
approximately elevation 10.0 to -20.0 feet. To what
ameter well screen that more or less fully penetrated
extent the channel of the river provides an open source
the deep sand aquifer beneath the excavation site; two
of seepage into the underlying deep sand formation is
of the test wells (Wells B and C) were installed to a
not known; the logs of a few borings made in the bed
depth of approximately 80 feet for the purpose of test-
and along the bank of the river are shown in the pre-
ing the upper top strata of silty sands and sandy silts.
viously referenced report by
. It will be
The locations of the test wells and some of the piez-
the responsibility of the Contractor to make his or her
ometers installed in connection with making the
own evaluation of the effect of the Red River on dewa-
pumping tests are shown on the drawings. The eleva-
tering and control of seepage into the excavation, not
tion of the well screens for the test wells and piezome-
otherwise covered by these specifications.
ters and logs of borings made along the piezometer
lines radiating out from the test wells were plotted. A
taken from Test Wells A, B, and C on 28 April 1978
hydrograph of the Red River and Piezometers PA9 and
gave the following results:
PA9A installed 2970 and 3970 feet from Test Well A,
Well A
observed during the test on Well A, are shown on a
drawing of these specifications. Plots were made of
137-ft
260-ft
depth
Well B
Well C
depth
Total
drawdown observed while pumping Test Well A, cor-
6.8
7.0
rected for an estimated (natural) change in the ground-
7.0
6.9
pH
115
60
110
30
Chloride (Cl)
water table during these tests as a result of a rise on
52
62
37
34
Suspended Solids (ppm)
the Red River. Results of the pumping tests made on
7
Volatile Solids (ppm)
5
8
5.5
Test Wells B and C were also plotted. No correction
1620
Total Solids (ppm)
520
762
977
was made for any natural change in the groundwater
Total Dissolved Solids
table during the pumping test on Wells B and C inas-
468
728
915
1583
(ppm)
Total Volatile Solids
much as there was very little change in the river stage
50
65
88
227
(ppm)
during the pumping test on these wells. A report on
7
9
539
202
Sulfate (ppm)
the pumping test made at the site by
390
694
1066
423
and design of the dewatering systems may be exam-
Magnesium
26
94
28
54
G-11
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