DWR_3391241

• Document Date: 3/1/1983
• Document Type - Dam Safety: Report
• Division: 3
• Dam ID: 200224
• Subject: HOMESTAKE TAILING POND, LOWER DAM - ENGINEER'S REPORT, STABILITY EVALUATION
• DWR Send/Recipient: DSB
• Outside Send/Recipient: DAPPOLONIA CONSULTING ENGINEERS, INC.

I
2-5
2.2 ADDITIONAL D'APPOLONIA INVESTIGATION AND OBSERVATIONS
The experimental grouting program beneath the dam conducted in July and
August of 1982 provided information useful to the stability evaluation,
During the grouting program, water losses during drilling and high grout
takes were observed within the dam core. To evalute the significance of
these conditions, 17 piezometers were installed in the dam in December
of 1982. Soil samples and observations were made during the drilling of
the holes for the piezometers. The piezometers were also designed to
act as long term monitoring systems.
1 2.2.1 Grouting Program Observations
including (a) evaluation of
the ability of grouting
to reduce seepage
and (b) collection of additional
data to define the
conditions within
initially presented
and beneath the embankment.
The data collected and
observations made
been revised based
added to the knowledge needed
to assess the dam and are
discussed below.
During the grouting program, water losses during drilling and high grout
takes were observed within the dam core. To evalute the significance of
these conditions, 17 piezometers were installed in the dam in December
of 1982. Soil samples and observations were made during the drilling of
the holes for the piezometers. The piezometers were also designed to
act as long term monitoring systems.
1 2.2.1 Grouting Program Observations
prior to grouting. Grout takes were recorded in each hole. Soil
samples were taken where possible in the borings.
General Subsurface Conditions
Figure 3 shows the foundation conditions beneath the dam as developed
from new and existing data. The foundation generally consists of a
three layer system as follows:
o ' aAlluvial=soils''9from.4 to 36; feet thick consisting
of silty to clayey sands and clean sands and
gravels.
J
0
The grouting program
consisted of
nine borings, 4G-1 through G-9, shown
in plan in Figure 1
and in Section A -A' in Figure 3. Section A -A' was
initially presented
in a previous
report (D'Appolonia, 1981b) and has
been revised based
on additional
information obtained from the grout
borings. The grout
borings were
drilled with water and packer tested
prior to grouting. Grout takes were recorded in each hole. Soil
samples were taken where possible in the borings.
General Subsurface Conditions
Figure 3 shows the foundation conditions beneath the dam as developed
from new and existing data. The foundation generally consists of a
three layer system as follows:
o ' aAlluvial=soils''9from.4 to 36; feet thick consisting
of silty to clayey sands and clean sands and
gravels.
J
0