CONSTRUCTION
OBSERVATION REPORT
STEGNER FARMS PIT
SLURRY WALL
Prepared for:
HALL-IRWIN CONSTRUCTION
3026 4th Avenue
Greeley, Colorado 80631
Prepared by:
ROCKY MOUNTAIN CONSULTANTS, INC.
Premiere Building
825 Delaware Avenue, Suite 500
Longmont, Colorado 80501
RMC Job No. 19-0636.059.00
August, 2000
TABLE OF CONTENTS
Page
INTRODUCTION .............................................................................................................................. 1
PROJECT DESCRIPTION................................................................................................................ 1
CONSTRUCTION SUMMARY.......................................................................................................... 2
QUALITY ASSURANCE TESTING................................................................................................... 3
DISCUSSION .................................................................................................................................. 4
General ................................................................................................................................. 4
Desanding Operation ............................................................................................................ 4
Sloughing of Overburden Soils ............................................................................................. 5
Slurry Wall Test Holes........................................................................................................... 6
CONCLUSIONS AND RECOMMENDATIONS................................................................................. 6
List of Tables
Table 1
Materials Quality Control Program, Soil/Bentonite, Slurry Trench Cut-Off
Wall
Table 2
Table 3
Table 4
Stegner Farms Pit Slurry Wall Test Summary
Stegner Farms Pit Slurry Wall Areas of Concern
Stegner Farms Pit Slurry Wall Results of Slurry Wall As-Built Geotechnical
Investigation
List of Figures
Figure 1
Figure 2
Figure 3A
Figure 3B
Figure 4
Slurry Wall Vicinity Map
As-Built Slurry Wall Test Hole Locations
Slurry Wall Summary Logs
Slurry Wall Summary Logs
Slurry Wall Photos
List of Appendices
Appendix A
Appendix B
Appendix C
Appendix D
Daily Construction Logs
Sand Content and Filtrate Analysis
S-B Backfill Gradation
Trench Depth Worksheets
C:\WINNT\Profiles\Colby\Desktop\Construction.rpt.doc
INTRODUCTION
This report summarizes construction observation results for the on-site and laboratory quality
assurance testing conducted during the construction of the Stegner Farms Pit slurry wall.
Information contained within this report was collected as part of the construction related
engineering services that were provided by Rocky Mountain Consultants, Inc. (RMC) throughout
the slurry wall construction. The slurry wall was constructed by Hall-Irwin Construction under a
contract with Camas Colorado Inc. Camas Colorado Inc. is preparing to mine gravel aggregate at
the site. Upon completion of the mining operations, control of the site will return to the current
property owners, John Stegner and Gary Stegner.
Construction began on the slurry wall lining project at the Stegner Farms Pit in early April 2000.
The construction consisted of lining a proposed gravel pit with approximately 7,500 feet of soilbentonite slurry wall. The goal of the slurry wall liner is to minimize hydraulic interaction between
the proposed gravel pit and the surrounding alluvium. The reduction in hydraulic interaction will aid
mining efficiency in two ways: 1) by reducing dewatering requirements during mining operations,
and 2) by reducing drawdown effects on neighboring wells. Upon completion of the mining
activities, the final goal of the slurry wall construction is to provide a low permeability liner for a
below grade water storage reservoir.
The slurry wall was constructed using a design/build approach. The scope of RMC’s work during
construction included on-site quality control and observation of the slurry wall construction. The
scope of our work did not include groundwater monitoring or future reservoir design. Hall-Irwin
Construction supplied labor, equipment, and materials to construct the slurry wall.
PROJECT DESCRIPTION
The site is located east of LaPorte, Colorado and is bounded by County Road 54G (old U.S.
Highway 287) along the north side, Taft Hill Road along the east, and Brookhill Road along the
west. The southern boundary of the project site is parallel to and approximately one-quarter mile
south of County Road 54G. The site is more particularly described as being located in Section 33,
Township 8 North, Range 69 West of the 6th Principal Meridian, Larimer County, Colorado, as
shown on Figure 1.
Prior to slurry wall construction activities, the site was agricultural land. The Taylor and Gill Ditch
runs parallel to and just south of the southern site boundary. The Cache La Poudre River is
located approximately one-half mile south of the project site. The ground surface across the site
falls from an elevation of approximately 5045 feet in the northwest corner to approximately 5030
feet in the southwest corner. The slope of the ground from northwest to southeast is a somewhat
consistent 0.5 percent across the site.
The project area is located approximately one mile east of the eastern flank of the Rocky Mountain
Front Range. Regional geologic mapping of the area (Colton, 1978) indicates the near surface
bedrock at the site is the lower shale member of the Pierre Shale Formation. Regionally, the lower
1
shale member is described as being comprised of dark olive-gray bentonitic shale. Bedrock at the
site is overlain by alluvium regionally mapped as the Post-Piney Creek Alluvium.
The site is in an alluvial plain setting. Both the ground surface and bedrock surface slope gently to
the southeast in the general direction of flow of the Cache La Poudre River. Geotechnical test
holes were drilled along the proposed slurry wall alignment prior to construction. Observed drill
cuttings, soil types and depth to bedrock measurements were used as reference during
construction. Test hole locations and summary logs are presented on Figures 2 and 3. Depth to
bedrock and total trench depths observed during construction are illustrated on the as-built
construction drawing (Plate 1).
The natural site stratigraphy generally consists of three main units: 1) near surface sandy, silty
clay; 2) sand, gravel and cobble alluvial deposits; and 3) claystone and shale bedrock. Depth to
bedrock is variable at this site. Bedrock depths ranged from 13 to 22 feet with most of the
variations encountered along the north and south sides of the project. Along the east and west
sides of the project, bedrock depth was less variable ranging from 15 to 17 feet.
The slurry wall as-built dimensions are as follows: an average total width of two feet, total trench
depth from 16 to 27 feet with an average value of approximately 19.6 feet, overall slurry wall length
of 7,387 feet, and overall trench curtain area of approximately 145,000 square feet. The total area
surrounded by the slurry wall is approximately 62.3 acres.
CONSTRUCTION SUMMARY
The typical slurry wall construction crew consisted of four to five men managed by one
superintendent who oversaw and coordinated construction activities. Motor equipment used
included a trackhoe excavator, Kamatsu PC400, which excavated the trench through a bentonite
slurry; a smaller trackhoe that provided initial soil-bentonite backfill mixing and constructed the
slurry mixing pond; one Caterpillar dozer that provided final soil-bentonite backfill mixing, trench
backfilling, and slurry mixing pond construction; and a stand-alone pneumatic trailer for on-site
storage of bulk bentonite. A slurry pump/desanding unit was at the site to clean the trench bottom
and reduce sands suspended in the slurry.
Prior to construction of the slurry wall, berms were constructed along the inside of the slurry wall
alignment. These backfill berms consisted of overburden soils from on-site, as well as dry
bentonite delivered from offsite. The dry bentonite was added at a rate of approximately 120
pounds per linear foot, or approximately 1.5 percent of the dry weight of the backfill soils.
One slurry mixing/holding pond was constructed along the slurry wall alignment. A reservoir of
slurry was produced by combining and mixing bulk bentonite powder with local groundwater using
a conical static mixer. Once in the pond, the slurry was continuously circulated until thoroughly
hydrated. The finished slurry product was pumped through four-inch high density polyethylene
piping to the open trench section under construction. Pond recirculation and slurry delivery was
accomplished using an eight-inch pump.
2
The soil-bentonite (S-B) backfill was composed of four components: 1) soil excavated from the
trench, 2) high clay content soil material borrowed on-site, 3) slurry removed from the trench
heading during excavation, and 4) dry bentonite applied at an approximate rate of 1.5 percent of
the dry weight of the backfill soils.
QUALITY ASSURANCE TESTING
Resident engineering services were provided by RMC during the slurry wall construction. These
services included extensive on-site construction observation, sampling, field testing of various
slurry trench parameters, and the assimilation of as-built information. A daily log of construction
progress was kept (Appendix A).
A material quality control program was followed throughout the slurry wall construction. Test types,
frequency, and specified values are summarized on Table 1. In order to provide the quickest
possible testing result turn-around time, a testing laboratory was set up on-site. Testing equipment
included a mud balance, Marsh funnel, portable electric bench oven, electronic scale, portable
sieve shaker, various sieves, wet washing apparatus, ambient temperature filter press, pH meter,
sand content kit, and slump cone apparatus. General field results, listed by station/location, are
presented on Table 2. Specific test results are shown in Appendices B and C.
A rapid turn-around time of the test results allowed for near real time adjustments to the various
slurry trench parameters throughout the project. Testing conformed with industry standards,
including the American Petroleum Institute - Specifications 13A, the American Petroleum Institute
Recommended Practice - Specifications 13-B-2, and ASTM C-143. Slurry viscosity, as measured
using a Marsh funnel apparatus, and unit weight values, as measured using a mud balance, were
maintained within the acceptable range (V 40 seconds-Marsh, S.G. = 1.03 gm/cc to 1.40
gm/cc). In a few instances the viscosity dropped below the 40 seconds-Marsh due to an excess of
water in the slurry mix. These cases of low viscosity occurred at either the mixing pond or the
discharge hose. The viscosities were corrected at these locations so that the slurry viscosity in the
trench was maintained above the minimum acceptable levels.
Filter cake formation of the slurry and filtrate loss were analyzed using an ambient temperature
filter press assembly. Filter cake thickness and filtrate loss was generally within the acceptable
range. The texture of the cake formation ranged from slightly sandy to very sandy. In a few
instances the filtrate loss increased above the acceptable range (30 cc in 30 minutes@100 psi)
due to a high sand content (20+ percent). This situation was corrected by replacing the high sand
content slurry in the trench with fresh slurry from the slurry pond as quickly as possible. A sand
content kit was used to measure the percent sand by volume suspended in the slurry. Sand
content was found to range from six to greater than 20 percent.
Slump cone, gradation, and moisture content test results on the S-B backfill material were used to
control the backfill material properties. Test results in each of these areas were consistently within
the acceptable range. In a few instances the slump test results fell outside the acceptable range of
3
two to six inches which resulted in construction directives which specified corrective actions that
were carried out immediately. Corrective actions included addition/reduction of slurry added to
backfill material and adjustments to the mixing operations.
Visual inspection of excavated soils and bedrock were extensively conducted during trenching to
detect when adequate bedrock was encountered. As the trenching progressed, the depth of the
trench was periodically checked to determine if the bedrock key was maintained and not filling with
sediment or other material (Appendix D). At the start-up of slurry wall construction, sedimentation
of the trench bottom was observed beyond what was expected. To accommodate the excess
sedimentation, the bedrock key was extended a minimum of four feet into bedrock instead of the
three-feet specified in the design. Once desanding equipment was delivered to the site and
desanding/trench cleaning operations commenced, the minimum bedrock key requirements
reverted back to the three-foot minimum as specified in the design. The desanding equipment was
then used to clean sediments from the trench slurry and trench bottom to maintain an effective
three-foot bedrock key.
Comparison of quality control requirements to the field testing and observations indicate that the
project requirements were adequately met. Adjustments were made when required as indicated by
test results and visual observations.
DISCUSSION
General
Slurry wall construction began in early April 2000 and was completed in late June 2000.
Construction was delayed temporarily on occasion due to mechanical breakdowns and poor
weather.
When necessary, field adjustments were made to the slurry wall alignment. The slurry wall
alignment in the southeast corner of the property was rounded to avoid driving heavy equipment
over the existing 42-inch City of Greeley water transmission line which parallels the south side of
the project area. Other corners were rounded to allow room for the desanding equipment and to
avoid property fencing. A portion of the alignment along the north-central area of the project was
offset by approximately five feet to the south to avoid damaging existing trees and to allow room for
the desanding equipment. The slurry wall as-built alignment is shown on Plate 1.
Desanding Operation
Slurry wall construction began at Station 0+00 without the use of a desander. Trench depth
measurements indicated that sand was settling out of the slurry and depositing on the bottom of
the trench. A recommendation was made that desanding equipment be mobilized to the site. To
allow work to proceed prior to mobilization of desanding equipment to the site, the trench was
extended a minimum of four feet into bedrock, rather than the three feet specified in the design,
allowing for approximately one foot of sedimentation and three feet of slurry wall bedrock key. In
4
addition, attempts were made to clean the bedrock key prior to beginning additional trenching each
day. The excavator would track over the extent of open trench completed the prior day and scrape
the bottom to remove any sediment which had accumulated. This trench cleaning was performed
each day until trench side wall sloughing problems (discussed below) widened the trench at the
surface to the extent that the track excavator could no longer track back over the open trench. Use
of the excavator to clean sediment from the trench was no longer possible beyond Station 17+40
due to sloughing problems.
Desanding equipment was mobilized to the construction site on May 3, 2000. The initial desanding
equipment consisted of a submersible pump, tank reservoir, and screened shaker mounted to a
reinforced steel sled with a diesel generator towed behind. This equipment was mobilized for use
due to concerns regarding the settlement of sands from the slurry to the bottom of the trench. The
equipment used was specifically manufactured for use in cleaning sand from the trench bottom and
reducing the volume of sand suspended in the slurry.
Due to malfunctions with the electrical system and the submersible pump, regular operation of the
desander did not begin until May 17th near Station 27+00. During the initial operation of the
desander, the submersible pump could not be lowered to the bottom of the trench without
overloading the electrical components. As a result, sand was removed only from suspension
within the trench slurry. Table 3 outlines areas where we suspect a significant amount of sediment
has settled into the bedrock key as indicated by measuring trench depths with a weighted line
marked at one-foot intervals.
On May 26th, the initial desanding equipment was removed from the site and replaced with a
smaller desanding unit which was easier to maneuver along the side of the slurry wall trench. The
replacement desanding equipment was in operation on May 30th, the next working day. The
replacement equipment consisted of similar, but smaller components, mounted on a smaller
reinforced steel sled.
On May 31st, the submersible pump impeller was replaced with a smaller impeller which allowed
the pump to be lowered to the bottom of the trench without overloading the electrical components.
From Station 42+25 to the end of the project at Station 75+03, the desanding equipment was felt to
be effective in reducing the deposition of sand in the trench bottom.
Sloughing of Overburden Soils
In a few areas of the slurry wall alignment, sloughing of the overburden soils caused the surface of
the trench to widen from approximately two feet to as much as ten feet in some areas (Figure 4).
The overburden soils in some areas of the project thinned to approximately one to two feet thick.
In addition, slopes of 0.5 to 1.0 percent in some areas of the site resulted in slurry levels along
portions of the open trench periodically falling to as much as two to three feet below the ground
surface. The combination of thin overburden and low slurry levels contributed to sidewall instability
resulting in the observed sloughing.
5
In general, when the sloughing occurred at the point of trenching, the trenching hoe operator was
able to clean out the overburden soil as it sloughed into the trench. Attempts were also made to
keep the sides of the trench sloped so that overburden soil would not fall into the trench after
completion of each trenching set. In a few areas, the overburden soil sloughed into the trench after
trenching had been completed in the area and the trackhoe could no longer reach the sloughed
material. Table 3 outlines areas where sloughing was observed in areas where the soil could no
longer be cleaned from the trench. The presence of the sloughed material was confirmed by
checking trench depths using a weighted line marked at one-foot intervals.
Slurry Wall Test Holes
Five test holes were drilled through the backfilled trench to investigate the as-built condition of the
slurry wall with regard to the presence of sloughed overburden soils and sediment that may have
settled into the bedrock key. Table 4 outlines the results of the investigation.
TH-17 at Station 25+75 encountered approximately four feet of wet, clayey sands and gravels
below the S-B backfill, but no material which resembled overburden soils. TH-18 at Station 40+50
encountered four feet of overburden soils, but was not extended deep enough to evaluate the total
thickness of overburden soils which had sloughed into the trench. TH-19 at Station 40+75
confirmed that the overburden soils which had sloughed into the trench in this area extend below
the top of bedrock a distance of approximately one foot and are underlain by approximately two
feet of sediment.
TH-15 and TH-16 each encountered a minimal amount of sloughed soils and sediment and also
encountered bedrock above the depth to which the trench was completed. This may be attributed
to the possibility of the test hole being located at the edge of the slurry wall instead of at the center.
Gradation tests were performed on samples collected from test holes TH-15, TH-17, TH-18, and
TH-19 to determine the percent of fines (materials passing the #200 sieve) content by weight. The
sloughed overburden materials collected from TH-17, TH-18, and TH-19 contained fines materials
ranging from 42 to 67 percent by weight. The sediments collected from TH-15 and TH-19
contained 27 and 25 percent fines materials by weight, respectively.
The design parameters for the S-B backfill require a fines content of 25 to 40 percent. The results
of the gradation testing indicate that the fines content of the sloughed overburden and sediments
which have filled the bedrock key meet the minimum fines content requirements for the S-B backfill
material. Based on these test results, RMC has recommended that no remedial actions take place
at this time to remove the sloughed overburden and sediments from the areas investigated.
CONCLUSION AND RECOMMENDATIONS
In general, construction of the Stegner Farms Pit slurry wall was performed in conformance with
the specified quality control standards. Corrective field actions were quickly implemented when
necessary due to visual observations or results of quality control testing. When sand content and
filtrate test results did not meet the specifications, fresh slurry was introduced into the trench.
6
When results of slump testing for the S-B backfill did not meet specifications, corrective actions
included addition/reduction of slurry added to backfill material and adjustments to the mixing
operations.
As a final quality control measure, periodic inspections during mining are recommended to check
for localized seep zones. Table 3 outlines areas along the slurry wall where either sloughing or
excessive sedimentation are suspected to have occurred based on visual observations, trench
depth measurements, and/or the results of the drilling investigation. The potential for seepage
through the slurry wall in these areas may be greater than the areas of the wall which did not
experience sloughing and where desanding operations were effective. If seepage is observed as
mining progresses, remedial activities may need to be implemented such as the construction of a
low permeability embankment slope liner.
7
TABLE 1
Materials Quality Control Program
Soil/Bentonite
Slurry Trench Cut-Off Wall
SUBJECT
Material
STANDARD
MINIMUM FREQUENCY
SPECIFIED VALUES
Water
----
-pH
-Total Hardness
Per water source or as
changes occur
As required to properly
hydrate bentonite with
approved additives
Additives
----
Manufacturers certificate of
compliance with stated
characteristics
One time
As approved by Engineer
Bentonite
API Std 13A
Manufacturers certificate of
compliance
One time
Premium grade sodium
cation montomorillonite
Selected soils obtained from a
borrow area approved by the
Engineer
Per borrow source or as
changes occur
-65 to 100% passing 3/8"
-40 to 85% passing #20
-25 to 40% passing #200
Roll to 1/8" thread
Backfill Soils
Prepared for
Placement into the
trench
----
API Std 13B
-Unit Weight
-Viscosity
-Filtrate Loss
1 set per shift or per batch
(pond)
-pH
Slurry
Backfill Mix
TYPE OF TEST
Unit weight ≥1.03 gm/cc
V ≥ 40 sec-March @ 68°
Loss ≤ 30 cc in 30 min.
@ 100 psi
pH ≥ 8
In Trench
API Std 13B 1
-Unit Weight
-Sand Content
1 set per shift at point of
trenching
-Unit weight = 1.03 - 1.40
gm/cc
-Sand content = 20% by
volume
At Trench
ASTM C 143
-Slump
-Gradation
1 set per 100 cu/yds.
1 set per 300 cu/yds.
-Slump 2 to 6 inches
-65 to 100% passing 3/8"
sieve
-40 to 85% passing #20
sieve
-25 to 40% passing #200
sieve
Table 2
Stegner Farms Pit Slurry Wall
Test Summary
Slurry Mixture
Test Location
(sta.)
Water Pond
Slurry Pond
Slurry Pond
1+00
Slurry Pond
1+75
Slurry Pond
2+75
3+00
Slurry Pond
Slurry Pond
3+80
5+25
Slurry Pipe
7+00
Slurry Pipe
7+70
Slurry Pipe
8+45
Slurry Pipe
9+10
Slurry Pipe
10+25
Slurry Pipe
Date
4/10
4/12
4/12
4/12
4/13
4/13
4/24
4/24
4/24
4/24
4/25
4/25
4/26
4/28
4/28
4/29
4/29
4/29
4/29
5/1
5/1
5/1
5/1
5/2
Marsh
Funnel
Viscosity
(sec)
Unit Weight Filtrate Loss
(gm/cc)
(ml)
35
44
1.12
1.07
54
1.09
30
1.05
32
29
Soil-Bentonite Backfill Mix
Sand
Content
(vol %)
22.8
Cake
Thickness
(in)
0.0625
8.25
27.6
11
0.125
27.0
10
0.125
23.6
22.8
7
7
0.125
0.125
28.6
6
0.1875
1.06
1.03
39
44
1.19
1.06
36
1.06
26.6
10
0.1875
27.6
12
0.1875
36
36
37
30.2
40
44
35
1.07
1.15
pH
7.10
11
Test
Location
(sta.)
Date
0+00
0+50
1+50
1+50
4/25
4/25
4/26
4/26
0.50
5.50
7.50
5.50
2+75
3+50
4+00
4+00
4+25
5+00
6+00
6+50
7+50
4/27
4/27
4/29
4/29
4/29
5/1
5/1
5/1
5/2
5.25
5.25
7.50
5.00
4.00
5.00
6.00
4.00
5.00
8+50
5/2
9+20
10+00
10+60
5/2
5/3
5/3
Slump
(in)
3/8"
(%)
#20
(%)
#200
(%)
Moisture
Content (%)
98
80
85
66
49
34
26
20
93
77
48
28
85
95
69
78
42
48
27
29
96
80
50
26
3.50
94
82
55
26
4.00
6.00
3.75
97
72
42
28
0.125
Signature of Technician
Page 1 of 5
Table 2
Stegner Farms Pit Slurry Wall
Test Summary
Slurry Mixture
Test Location
(sta.)
11+05
11+75
Slurry Pond
Slurry Pipe
Slurry Pond
13+50
Slurry Pipe
16+45
Slurry Pipe
17+50
Slurry Pipe
Slurry Pond
19+80
Slurry Pond
21+50
Slurry Pond
23+00
Slurry Pond
24+00
Slurry Pond
Slurry Pond
25+80
Slurry Pipe
28+50
Date
5/2
5/2
5/3
5/3
5/3
5/3
5/3
5/5
5/5
5/5
5/6
5/9
5/9
5/10
5/10
5/11
5/11
5/12
5/12
5/13
5/13
5/13
5/15
5/18
Marsh
Funnel
Viscosity
(sec)
39
45
44
52
45
47
49
Sand
Content
(vol %)
Cake
Thickness
(in)
20
0.1875
30.8
16
0.1875
18.8
10
0.125
18.4
16
0.125
20.2
18
0.125
Unit Weight Filtrate Loss
(gm/cc)
(ml)
1.17
37.6
1.06
1.07
43
1.07
1.19
1.07
1.17
1.06
1.07
1.26
1.06
96
1.08
34
1.03
1.23
37
48
Soil-Bentonite Backfill Mix
17.4
34
41
53
43
1.06
1.39
1.07
1.26
27.2
0.125
14
0.125
20+
22.6
20
0.125
pH
Test
Location
(sta.)
11+00
11+50
Date
5/3
5/4
Slump
(in)
5.50
6.25
3/8"
(%)
#20
(%)
#200
(%)
Moisture
Content (%)
93
81
48
27
14+00
15+50
16+00
17+00
17+50
18+00
18+50
20+00
21+00
21+50
5/5
5/9
5/9
5/9
5/10
5/10
5/10
5/12
5/13
5/13
3.50
3.00
2.50
4.00
5.50
5.00
5.00
5.00
6.50
4.50
76
84
64
69
38
42
22
24
97
79
50
27
91
89
86
94
68
73
70
75
41
45
40
40
26
26
24
23
23+00
23+50
24+00
24+75
25+50
26+00
26+75
27+50
5/15
5/15
5/15
5/18
5/19
5/19
5/19
5/20
2.50
3.00
3.50
5.00
5.00
4.00
6.00
5.50
94
75
40
23
76
57
27
26
87
72
37
27
Signature of Technician
Page 2 of 5
Table 2
Stegner Farms Pit Slurry Wall
Test Summary
Slurry Mixture
Test Location
(sta.)
Slurry Pond
31+40
33+90
Slurry Pond
Desander
36+00
Slurry Pond
Slurry Pond
Date
5/19
Marsh
Funnel
Viscosity
(sec)
46
5/19
5/22
5/23
5/23
5/23
5/24
5/25
41+30
Slurry Pond
Slurry Pond
42+50
5/30
5/31
5/31
5/31
45+00
Slurry Pond
6/1
6/2
47+45
6/3
Unit Weight Filtrate Loss
(gm/cc)
(ml)
1.06
1.35
51
50
41
48
41
42
44
Soil-Bentonite Backfill Mix
1.36
1.05
1.35
1.39
29.0
Sand
Content
(vol %)
20+
Cake
Thickness
(in)
0.1875
39.8
20+
0.1875
30.5
29.1
20
20+
0.125
0.1875
1.05
1.34
1.06
33.1
1.24
25.8
1.34
1.06
1.24
20
15
0.125
0.125
20
21.9
13
0.125
pH
Test
Location
(sta.)
28+00
29+00
29+50
30+50
31+50
32+50
33+75
34+50
35+50
36+50
37+00
37+50
38+00
38+50
39+50
40+00
41+00
42+50
43+50
44+50
45+00
45+50
46+00
46+50
Date
5/20
5/22
5/22
5/22
5/23
5/23
5/24
5/24
5/25
5/26
5/26
5/30
5/30
5/30
5/31
5/31
6/1
6/1
6/2
6/3
6/3
6/5
6/5
6/5
Slump
(in)
5.50
6.00
4.50
4.50
5.00
4.50
3.50
4.00
4.50
6.00
5.50
5.50
5.00
5.00
4.50
5.00
5.50
5.50
5.00
5.00
4.00
5.50
5.00
5.00
3/8"
(%)
92
#20
(%)
76
#200
(%)
39
Moisture
Content (%)
27
91
74
38
25
80
62
39
21
81
63
29
21
81
85
61
69
29
35
21
25
89
69
38
25
90
79
49
26
97
77
83
62
55
38
27
24
89
67
41
25
94
82
51
25
Signature of Technician
Page 3 of 5
Table 2
Stegner Farms Pit Slurry Wall
Test Summary
Slurry Mixture
Test Location
(sta.)
Slurry Pond
Date
6/6
49+50
Slurry Pond
6/6
6/7
51+00
Slurry Pond
6/7
6/8
53+00
6/8
56+00
Slurry Pond
Slurry Pond
Slurry Pond
58+00
Slurry Pond
60+50
6/9
6/9
6/9
6/10
6/10
6/12
6/12
63+00
6/13
Slurry Pond
6/14
Marsh
Funnel
Viscosity
(sec)
38
Soil-Bentonite Backfill Mix
Unit Weight Filtrate Loss
(gm/cc)
(ml)
1.05
Sand
Content
(vol %)
Cake
Thickness
(in)
11
47
1.02
12
44
1.22
1.06
1.19
7
38
45
40
44
1.24
1.06
1.06
1.26
1.08
1.26
47
1.06
9
19.4
11
0.125
14.0
7
0.1875
13
pH
Test
Location
(sta.)
47+50
48+00
49+00
50+00
50+50
51+00
52+00
52+50
54+00
54+50
55+00
56+00
57+00
57+50
58+00
59+00
59+50
60+25
61+50
62+00
62+50
63+00
63+50
64+00
Date
6/7
6/7
6/7
6/8
6/8
6/9
6/9
6/9
6/10
6/10
6/10
6/12
6/13
6/13
6/13
6/13
6/13
6/14
6/15
6/15
6/16
6/16
6/16
6/16
Slump
(in)
2.50
7.00
6.00
4.00
2.00
3.00
5.00
5.00
3.50
4.50
5.00
4.50
4.00
4.50
6.00
3.00
6.00
1.00
4.50
4.50
6.50
3.50
5.50
3.50
3/8"
(%)
93
#20
(%)
75
#200
(%)
47
Moisture
Content (%)
28
92
71
41
26
77
60
32
20
86
69
37
24
93
76
43
23
93
97
75
83
38
39
25
29
93
74
41
27
96
90
78
76
42
43
28
26
28
92
75
38
25
Signature of Technician
Page 4 of 5
Table 2
Stegner Farms Pit Slurry Wall
Test Summary
Slurry Mixture
Marsh
Funnel
Viscosity
(sec)
Soil-Bentonite Backfill Mix
Test Location
(sta.)
6470
Slurry Pond
Slurry Pond
6660
Date
6/14
6/15
6/16
6/16
Slurry Pond
6885
6/19
6/19
46
Slurry Pond
6/20
43
1.05
7210
Slurry Pond
6/21
6/21
19.7
43
1.31
1.05
7470
6/22
1.35
23.1
62
44
Unit Weight Filtrate Loss
(gm/cc)
(ml)
20.8
1.06
1.06
1.23
15.6
1.06
1.32
20.8
Sand
Content
(vol %)
20
11
20
18
20+
Cake
Thickness
(in)
0.125
0.125
0.125
0.125
0.1875
pH
Test
Location
(sta.)
6500
6575
6650
6700
6800
6875
6950
7050
7100
7150
7200
7300
7400
7450
Date
6/19
6/19
6/19
6/19
6/20
6/21
6/21
6/22
6/22
6/22
6/22
6/22
6/23
6/23
Slump
(in)
5.50
6.50
5.50
5.00
6.00
5.50
4.50
4.50
3.50
3.00
3.50
4.50
5.50
5.00
3/8"
(%)
87
#20
(%)
71
#200
(%)
35
Moisture
Content (%)
24
76
60
33
24
90
73
41
28
86
70
37
25
92
81
38
24
90
71
34
24
Signature of Technician
Page 5 of 5
Table 3
Stegner Farms Pit Slurry Wall
Areas of Concern
Station
5+75 to 6+50
6+90 to 7+10
17+00 to 18+50
Reason for Concern
Other Notes
Visually observed localized sloughing of overburden soils; approximately 3 to 4.5 feet of
material in 5-foot key based on use of weighted measuring line; material is likely a combination Good results from filter press test on slurry from this area of
of sediment overlain by the sloughed soils; could not return to area
trenching. Sand content 10 percent.
Good results from filter press test on slurry from this area of
Bedrock key full or nearly full of sediment based on depth measurements.
trenching. Sand content 10 percent.
Sediment approximately 2 to 3 feet deep in 4-foot key based on depth measurements; could
Good results from filter press test on slurry from this area of
not return to area with track hoe to clean out bedrock key.
trenching. Sand content 10 percent.
Visually observed localized sloughing of overburden soils; bedrock key full of material based
on depth measurements; material is likely a combination of sediment overlain by sloughed
Poor results from filter press test on slurry from this area of
soils; could not return to area with track hoe to clean out bedrock key
trenching. Sand content 20+ percent.
24+00 to 26+00
28+50 to 30+00; 32+00
to 33+00; 34+75 to
35+25; 35+75 to 36+25; Bedrock key full or nearly full of sediment based on depth measurements; could not return to
36+75 to 37+75
area with track hoe to clean out bedrock key.
40+25 to 41+00
Sloughing of overburden soils suspected based on visual appearance of trench banks upon
returning from weekend; 2 to 8 feet of material in 3-foot bedrock key based on depth
measurements; presence of sediment and sloughed overburden soils confirmed by te
63+75 to 64+25
Bedrock key full or nearly full of sediment based on depth measurements.
Poor results from filter press test on slurry from this area of
trenching. Sand content 20+ percent. Desander in operation
but pump could not be lowered to bottom of trench.
Poor results from filter press test on slurry from this area of
trenching. Sand content 20 percent. Desander in operation
but pump could not be lowered to bottom of trench.
Good results from filter press test on slurry from this area of
trenching. Sand content 13 to 20 percent. Desander in
operation with pump being set at bottom of trench.
Table 4
Stegner Farms Pit Slurry Wall
Results of Slurry Wall As-Built Geotechnical Investigation
As-Trenched
As-Built Investigation
Top of
Sand
(ft)
Bedrock
Encountered
(ft)
Sampled
Interval
(ft)
Dry Weight
Passing
#200
(%)
18.5
18.0
19.6
17 - 19
27
16.5 / 21.0
NE
17.0
17.3
-----
-----
2575
16.5 / 20.5
NE
16.0
20.0
18 - 20
42
TH-18
4050
15.0 / 18.0
10.0
NE
NE
12 - 14
67
TH-19
4075
15.0 / 18.0
13.0
17.0
19.0
15 - 17
17 - 19
50
25
Test Hole
ID
Top of Bedrock
Top of
/ Total Depth Sloughed Soils
(ft/ft)
(ft)
Station
TH-15
710
19.0 / 23.0
TH-16
905
TH-17
R:\0636_059\CoverSheet.dwg, 11/13/2008 1:31:26 PM
R:\0636_059\PlanView.dwg, 11/13/2008 1:44:48 PM
R:\0636_059\Testholes.dwg, 11/13/2008 11:43:14 AM
R:\0636_059\Testholes.dwg, 11/13/2008 11:45:28 AM
R:\0636_059\Photos Figure.dwg, 11/13/2008 12:03:30 PM
APPENDIX A
DAILY CONSTRUCTION LOGS
Stegner Farms Pit
Slurry Wall
Daily Construction Logs-4/10/00 to 5/6/00
4/10/00 and 4/11/00
- Site preparation was started on approximately April 4. Platform preparation has begun with backfill
berms being placed on the inside of the slurry wall with bentonite
_ A soils testing lab has been set up on site for quality control of construction materials.
_ A plastic lined slurry pond was built near Station 20+00 for the purpose of mixing trench slurry.
_ Construction equipment arrived at varying times after April 4.
_ A water pond was dug next to the slurry pond to enable the use of groundwater for mixing of
trench slurry. The pH of the water source was 7.10 on the first day of production.
_ Construction of a pair of backfill berms on the inside of the slurry wall has begun and will be
ongoing during the first few days of construction. Bentonite is being mixed into the berm closest
to the slurry wall for inclusion in the backfill mix.
4/12/00
- First day of digging trench. Trenched 0+00 to 1+25.
_ Bedrock encountered at 16.5 to 17.0 feet. Initial bedrock key is 3 feet. Bedrock is layered and
somewhat crumbly with water apparent in the layering. May need to dig deeper to find more
competent bedrock.
_ Dug water pond bigger to keep from running out before each slurry bentonite truck is offloaded.
4/13/00
- Trenched 1+25 to 2+00.
_ Some sediment in bedrock key from 0+00 to 1+25. Delayed to discuss depth of bedrock key to
look for better bedrock and to accommodate sediment while maintaining 3-foot key. We will try to
get a 4- to 5-foot key into bedrock.
4/14/00
- Cleaned out 0+00 to 0+25 and recovered mainly sand from the bottom of the trench.
_ Shutdown until all parties can agree on a depth of key based on bedrock conditions as well as a
solution for sediment build-up in the trench.
4/19/00
- RMC, Hall-Irwin, and Camas have agreed to get a desander for the site to removed sediment buildup in the trench. Until the desander is operational, the length of trench dug each day will be
cleaned again the following morning to remove sediment. Until the desander is operation, the
bedrock key will extend a minimum of four feet into bedrock. Once the desander is operational,
the bedrock key will extend a minimum of three feet into bedrock.
4/24/00
- Work resumed with bedrock key a minimum of four feet.
_ Trenched 2+00 to 3+15.
_ Trench slurry is a thin at 32 seconds through the Marsh funnel. Hall-Irwin crew having troubles
with some of the equipment at the bentonite mixing pond.
_ 0+00 to 2+00 should be re-keyed as the wall is completed to remove sediment from key.
F:\0636_059\CONSTRUCTION\CONSTRUCTION LOG 4-10 TO 5-6.DOC
4/25/00
- Trenched 3+15 to 4+55 with 4-foot key.
_ Trench slurry still thin. Mixing hopper is not working right. Bentonite and water are not mixing
properly out of the hopper. It needs to have some veins welded to the inside of the discharge pipe
to create turbulence in the mixture.
_ Backfilled 0+00 to 1+25. First couple of batches were too dry but have improved significantly.
4/26/00
- Trenched 4+55 to 5+25.
_ Backfilled 1+25 to 2+50
_ Cleaned trench back to 3+50 (approximate location of toe of slope for backfill)
_ No bentonite slurry added to trench today.
4/27/00
- Still having trouble at bentonite mixing pond. Hall-Irwin now has a trailer on site to hold the
bentonite powder until mixing it so that delivery trucks don’t have to stay at site while backfill
mixes straight from their trucks. The trailer is not working right and slurry is thin again.
_ Trenched 5+25 to 5+50
_ Backfilled 2+50 to 3+50
4/28/00
- Trenched 5+50 to 7+00
_ Backfilled 3+50 to 3+70
_ Slurry going into trench has improved to 44 seconds through the Marsh funnel.
4/29/00
- Trenched 7+00 to 8+95
_ Backfilled 3+70 to 4+75
_ Possible leaky area in wall between 5+50 and 6+50, particularly near 5+90 to 6+00. Banks of
trench have sloughed off and there is no way for the excavating hoe to get back to the area now
that we have turned the corner and are heading west.
5/1/00
- Trenched 8+95 to 10+95
_ Backfilled 4+75 to 7+00
_ The corner (approximately 6+90 to 7+10) appears to have a significant amount of sediment and
material in the key. It tagged at 19 feet and bedrock tagged at approximately 19 feet. Spoke with
Hall-Irwin about cleaning it out but due to the configuration of the corner (the backhoe would
need to sit to the side of the trench to clean it) we would cause more problems if we tried to clean
it.
5/2/00
- Trenched 10+95 to 12+85
_ Backfilled 7+00 to 9+50
_ Cleaned trench 9+15 to 10+95
_ Slurry still mixing thin.
5/3/00
F:\0636_059\CONSTRUCTION\CONSTRUCTION LOG 4-10 TO 5-6.DOC
_
_
_
_
_
Trenched 12+85 to 15+10
Backfilled 9+50 to 11+30
Cleaned trench 11+00 to 12+85
Bentonite slurry has improved significantly to 45 seconds through Marsh funnel.
Desander is almost ready for operation and has been placed next to trench at 14+80.
Possible leaky area at 12+50 to 12+75. This is the area of the trench that we cleaned to in the
morning. Sloughing of the trench walls at 12+95 has prevented us from getting back to the area to
clean it again.
5/4/00
- Trenched 15+10 to 16+35
_ Backfilled 11+30 to 13+50
_ Desander operated for approximately three hours before the submersible pump burned up.
_ Down for approximately four hours to repair mixing backhoe.
5/5/00
- Trenched 16+35 to 17+60
_ Backfilled 13+50 to 14+75
_ Cleaned trench 15+75 to 16+35
_ Mixing backhoe and dozer broke down after lunch. Backhoe has a broken hydraulic hose. Dozer
has a bad hydraulic pump.
5/6/00
- Mixing backhoe and dozer still down.
_ Could not clean trench to sloughing of walls at 17+70
_ Trenched 17+60 to 18+25
_ No backfilling
Conclusions:
The first two weeks of production have gone somewhat slowly due to equipment problems.
The bedrock has been consistently around 17 feet deep and locally up to 19 feet deep. The
bedrock generally consists of a one-foot weathered orange-brown claystone zone that is
slightly moist. Below the weathered zone, the claystone becomes shaley with layering more
apparent at increasing depths. The initial layering is disorganized and slightly moist. The
layering in the deeper bedrock becomes thicker and slightly moist to wet between layers.
The bedrock also becomes harder with the thicker layering. Below the weathered zone the
bedrock becomes gray with occasional orange-brown areas. The backfill has been generally
within the specifications on all tests beyond Station 0+50. The fines content (-200 material
by weight) has been in the 45 to 50 percent range which is slightly higher than called for in
the specifications but should not pose a problem as long as the backfill mixture remains
workable. The desanding operations are expected to resume on Wednesday, May 10.
F:\0636_059\CONSTRUCTION\CONSTRUCTION LOG 4-10 TO 5-6.DOC
Stegner Farms Pit
Slurry Wall
Daily Construction Logs-5/8/00 to 5/20/00
5/8/00
- Trenched 18+25 to 19+40.
_ Backfilled 14+75 to 15+25.
5/9/00
- Trenched 19+40 to 20+40.
_ Backfilled 15+25 to 17+25.
_ Could not clean trenching from previous day due to sloughing of overburden along trench sides.
_ Potential problem area from 17+50 to 18+50 where bedrock key was tagged at less than 3 feet.
_ Desander not running yet.
5/10/00
- Trenched 20+40 to 22+20.
_ Backfilled 17+25 to 19+30.
- Could not clean trenching from previous day due to sloughing of overburden along trench sides.
- Potential problem areas at 19+75 and 20+50 where bedrock key was tagged at less than 3 feet.
_ Desander not running yet.
5/11/00
- Trenched 22+20 to 23+30.
_ No backfilling.
- Could not clean trenching from previous day due to sloughing of overburden along trench sides.
- Potential problem areas at 20+50, 21+00, 21+25 and 21+75 where bedrock key was tagged at less
than 3 feet.
_ Desander not running yet.
5/12/00
- Trenched 23+30 to 24+25.
_ Backfilled 19+30 to 20+50.
- Could not clean trenching from previous day due to sloughing of overburden along trench sides.
- Desander not running yet.
5/13/00
- Trenched 24+25 to 26+30.
_ Backfilled 20+50 to 22+75.
- Could not clean trenching from previous day due to sloughing of overburden along trench sides.
- Sloughing continues to worsen due to thinning overburden. Trying to control it by removing areas
of cracking before finishing each set. Some sloughing has occurred after completion of sets in
areas that can no longer be reached by the backhoe.
5/15/00
- Trenched 26+30 to 27+50.
_ Backfilled 22+75 to 24+45.
- Could not clean trenching from previous day due to sloughing of overburden along trench sides.
_ Extensive sloughing during trenching has resulted in trench widths of 7 to 10 feet at surface. This
makes it very difficult to accurately check trench depths.
- Potential problem areas from 24+00 to 26+00 where bedrock key was tagged at less than 3 feet.
5/16/00
- No work completed due to equipment problems.
5/17/00
- Trenched 27+50 to 27+70
_ No backfilling
_ Work day shortened by equipment problems and heavy rains.
5/18/00
- Trenched 27+70 to 30+00.
_ Backfilled 24+45 to 25+40.
- Desander in operation.
5/19/00
- Trenched 30+00 to 31+70.
_ Backfilled 25+40 to 26+75.
- Sloughing continues during trenching but we have been able to significantly reduce the occurrence
of sloughing after each trenching set is completed. Width of trench still makes it difficult to
accurately check trench depths.
_ Potential problem areas from 28+50 to 30+00 where bedrock key was tagged at less than 3 feet.
_ Desander in operation.
5/20/00
- Trenched 31+70 to 33+00.
_ Backfilled 26+75 to 28+75.
- Potential problem area from 32+50 to 32+60 where sloughing occurred beyond the reach of the
trenching backhoe.
_ Desander in operation.
Conclusions:
Construction progress has improved. However, due to thinning of the overburden along the south
side of the project, the overburden has been sloughing during and after completion of trenching in
some areas. We are trying to control the amount of sloughing material that falls into the trench by
removing any unstable areas of overburden before the completion of each trenching set. Several
areas of the bedrock key along the south side have tagged at less than 3 feet. This may be due to
sediment accumulation or sloughing of overburden. It may also be due to the difficulty in accurately
checking the trench depth due to the increase in width of the trench at the surface due to the
sloughing. Desanding operations began on May 18 and have continued.
Stegner Farms Pit
Slurry Wall
Daily Construction Logs-5/22/00 to 6/3/00
5/22/00
- Trenched 33+00 to 34+95.
_ Backfilled 28+75 to 31+40.
_ Sloughing of overburden has improved significantly.
_ Slurry sand content very high. Need to get fresh slurry introduced into trench.
_ Desander in operation but pump cannot be lowered to bottom of trench with overloading.
_ Potential problem area from 32+00 to 33+00 where bedrock key was tagged at less than 3 feet.
5/23/00
- Trenched 34+95 to 37+05.
_ Backfilled 31+40 to 33+60.
_ Slurry sand content remains high (20+%).
- Desander in operation but pump cannot be lowered to bottom of trench with overloading.
- Potential problem areas at 35+00 and 36+00 where bedrock key was tagged at less than 3 feet.
5/24/00
- Trenched 37+05 to 38+60.
_ Backfilled 33+60 to 35+20.
_ Desander in operation but pump cannot be lowered to bottom of trench with overloading.
_ Potential problem area from 36+00 to 37+50 where bedrock key was tagged at less than 3 feet.
5/25/00
- Trenched 38+60 to 39+81.
_ Backfilled 35+20 to 36+25.
_ Trying to improve sand content in slurry by removing high sand-content slurry at point of trenching and at
backfill while pumping fresh slurry into trench near desander.
_ Desander in operation but pump cannot be lowered to bottom of trench with overloading.
_ Potential problem area from 37+50 to 38+50 where bedrock key was tagged at less than 3 feet.
5/26/00
- Trenched 39+81 to 41+25.
_ Backfilled 36+25 to 37+00.
_ Potential problem area from 39+00 to 40+50 where bedrock key was tagged at less than 3 feet.
_ Replacement desander arrived on-site. Old desander pulled away from trench at 8:40am. New desander
not set up yet.
5/30/00
- Trenched 41+25 to 42+15.
_
_
_
_
Backfilled 37+00 to 39+00.
Replacement desander began operation at 1:40pm.
Localized minor sloughing of overburden evident throughout open trench.
Potential problem area from 40+25 to 41+00 where significant sloughing occurred and trench tagged very
shallow.
531/00
- Trenched 42+15 to 43+40.
_ Backfilled 39+00 to 40+50.
_ A new impeller has been put on the desander pump. It is now being set at the bottom of the trench key.
_ Slurry sand content has improved (15%).
6/1/00
- Trenched 43+40 to 45+39.
_ Backfilled 40+50 to 42+70.
_ Desander in operation with pump set at bottom of trench key.
6/2/00
- Trenched 45+39 to 46+45.
_ Backfilled 42+70 to 43+50.
6/3/00
- Trenched 46+45 to 47+67.
_ Backfilled 43+50 to 45+00.
Conclusions:
Sloughing has improved with one problem area between 40+25 and 41+00. Several areas of the bedrock key
along the west side have tagged at less than 3 feet. This may be due to sediment accumulation or sloughing of
overburden. A new desander was put into operation on 5/30/00. The desander pump was retrofitted with a
smaller impeller on 5/31/00 which allows the pump to now be set at the bottom of the trench key.
Stegner Farms Pit
Slurry Wall
Daily Construction Logs-6/5/00 to 6/23/00
6/5/00
-
Trenched 47+67 to 48+72.
-
Backfilled 45+00 to 46+70.
-
Minor sloughing of overburden visible near backfill. Should not impact bedrock key.
6/6/00
- Trenched 48+72 to 50+12.
- Backfilled 46+70 to 46+90.
- No areas of overburden sloughing visible.
6/7/00
- Trenched 50+12 to 51+50.
- Backfilled 46+90 to 49+50.
- No areas of overburden sloughing visible. Minimal amounts of material have settled into
bedrock key.
6/8/00
- Trenched 51+50 to 53+60.
- Backfilled 49+50 to 50+50.
- Three to six inches of material settled into bedrock key.
6/9/00
- Trenched 53+60 to 56+10.
- Backfilled 50+50 to 54+00.
- No areas of overburden sloughing visible. Minimal amounts of material have settled into
bedrock key.
6/10/00
- Trenched 56+10 to 58+20.
- Backfilled 54+00 to 55+50.
- No areas of overburden sloughing visible. Minimal amounts of material have settled into
bedrock key.
6/12/00
- Trenched 58+20 to 61+15.
- Backfilled 55+50 to 56+50.
- No areas of overburden sloughing visible from weekend.
6/13/00
- Trenched 61+15 to 63+57.
- Backfilled 56+50 to 59+50.
6/14/00
- Trenched 63+57 to 65+18.
- Backfilled 59+50 to 61+00.
- No areas of overburden sloughing visible.
6/15/00
- Trenched 65+18 to 66+00.
- Backfilled 61+00 to 62+25.
- No areas of overburden sloughing visible. Six to 12 inches of material has collected in bedrock
key. Station 64+00 tagged as if bedrock key was full of sediment.
6/16/00
- Trenched 66+00 to 67+60.
- Backfilled 62+25 to 64+50.
6/17/00
- No work completed due to heavy rain.
6/19/00
- Trenched 67+60 to 69+60.
- Backfilled 64+50 to 67+20.
6/20/00
- Trenched 69+60 to 71+25.
- Backfilled 67+20 to 68+40.
- Drilled five test holes in completed slurry wall to evaluate condition of bedrock key.
- Sloughing has begun again but crew has been able to keep sides sloped so that material does not
fall into trench after completion of trenching sets.
6/21/00
- Trenched 71+25 to 73+25.
- Backfilled 68+40 to 71+10.
- Sloughing continues at point of trenching but no areas of sloughing are visible after completing
and leaving each set.
- Zero to 12 inches of material has collected in the bedrock key.
6/22/00
- Trenched 73+25 to 75+03 (also 0+00).
- Backfilled 71+10 to 73+50.
- Sloughing continues at point of trenching but no areas of sloughing are visible after completing
and leaving each set.
6/23/00
- Re-trenched 0+00 to 1+20.
- Backfilled 73+50 to 75+03 (also 0+00) to 1+20.
- Slurry wall has been completed. Crew will begin site cleanup on June 26.
Conclusions:
The desander was fully operational throughout this period. Sloughing began again near 70+00 but
crew was able to remove loose material during each trenching set so that material did not fall into
bedrock key after completion of each set. Trench depths indicated that approximately six to twelve
inches of sediment was collecting along the bedrock key with localized areas of deeper sediment.
Locally, the bedrock was too hard for the key to be extended a full three feet into bedrock. In these
areas, the minimum key was two feet into bedrock. The slurry wall construction was complete on
June 23 after re-trenching and backfilling the 0+00 to 1+20 interval.
APPENDIX B
SAND CONTENT AND FILTRATE ANALYSIS
STEGNER FARMS PIT SLURRY WALL
SAND CONTENT AND FILTRATE ANALYSIS
SAMPLE I.D.
Slurry Pond
100
175
275
300
380
700
770
910
4/12
4/12
4/13
4/24
4/24
4/25
4/28
4/29
5/1
TEST
PRESSURE
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
1175
5/2
100 psi
240
310
37.6
0.1875
1350
5/3
100 psi
301
331
30.8
0.1875
1750
5/5
100 psi
355
425
18.8
0.125
1980
2150
2300
2400
5/9
5/10
5/11
5/12
100 psi
100 psi
100 psi
100 psi
202
249
312
146
232
319
342
216
0.125
0.125
0.125
0.125
2580
5/13
100 psi
239
259
18.4
20.2
17.4
27.2
28.8 / 20 min ; filter press
leaking CO2
2850
3140
3390
34+00
(Desander)
3600
4130
4250
4500
4745
4950
5100
5300
5600
5800
6050
6300
DATE
TIME
API - 30 MIN.
FILTER CAKE
START
END
FILTRATE LOSS (ML)
THICKNESS (IN)
1253
318
331
1106
246
1237
257
126
153
103
328
341
1136
316
107
327
156
223
7.6 / 10 min
9.2 / 10 min
9.0 / 10 min
23.6
22.8
28.6
26.6
27.6
30.2
0.0625
0.125
0.125
0.125
0.125
0.1875
0.1875
0.1875
0.125
100 psi
100 psi
100 psi
1238
1207
206
108
1237
236
22.6
29.0
39.8
0.125
0.1875
0.1875
5/23
5/23
5/30
100 psi
100 psi
100 psi
1046
916
132
1116
946
202
30.5
29.1
33.1
0.125
0.1875
0.125
6/3
6/6
6/7
6/8
6/9
6/10
6/12
6/13
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
100 psi
152
1142
725
204
1235
145
250
130
125
227
222
25.8
0.125
More troubles with filter press leaking CO2
755
234
1240
----200
253
235
21.9
20.0; Valve leaked CO2
Valve leaked CO2
Valve leaked CO2
Valve leaked CO2
19.4
14.0
Valve leaked CO2
Slightly Sandy
Moderately
Sandy
Moderately
Sandy
Moderately
Sandy
Moderately
Sandy
Very Sandy
Very Sandy
Very Sandy
% BY VOLUME
11
10
7
7
6
10
12
11
20
16
10
16
18
14
20+
5/18
5/19
5/22
5/31
6/1
SAND CONTENT
COMMENT
0.125
0.1875
0.125
0.1875
6470
6/14
100 psi
727
757
20.8
0.125
6660
6/16
100 psi
838
908
15.6
0.125
6885
6/19
100 psi
226
256
20.8
0.125
7210
6/21
100 psi
119
149
19.7
0.125
7470
6/22
100 psi
854
924
23.1
0.1875
Moderately
Sandy
Very Sandy
Very Sandy
Moderately
Sandy
Very Sandy
Moderately
Sandy; Good
Cohesive Cake
Slightly Sandy;
Good Cohesive
Cake
Cohesive Cake
Slightly Sandy
Moderately
Sandy; Good
Cohesive Cake
Moderately
Sandy; Good
Cohesive Cake
Moderately
Sandy; Good
Cohesive Cake
Moderately
Sandy; Good
Cohesive Cake
Slightly Sandy;
Good Cohesive
Cake
20
20+
20+
20
20+
20
15
20
13
11
12
7
9
11
7
13
20
11
20
18
20+
APPENDIX C
S-B BACKFILL GRADATION
STEGNER FARMS PIT SLURRY WALL
S-B BACKFILL GRADATION
SAMPLE I.D.
0
50
400
500
600
750
850
1000
1150
1400
1550
1700
1850
2000
2150
2300
2475
2675
2800
2950
3150
3375
3550
3650
3800
3950
4100
4250
4450
4600
4750
4900
5050
5200
5400
5500
5610
5800
5950
6025
6150
6300
6500
6650
6800
6950
7100
7300
DATE
TARE
WEIGHT
SAMPLE WEIGHT
(-TARE)
DRY WEIGHT
(-TARE)
MOISTURE
CONTENT
4/25
4/25
4/29
5/1
5/1
5/2
5/2
5/3
5/4
5/5
5/9
5/9
5/10
5/12
5/13
5/15
5/18
5/19
5/20
5/22
5/23
5/24
5/25
5/26
5/30
5/31
6/1
6/1
6/3
6/5
6/7
6/7
6/8
6/9
6/10
6/10
6/12
6/13
6/13
6/14
6/15
6/16
6/19
1/0
6/20
6/21
6/22
6/22
(gm)
250
245
320
320
335
315
315
335
330
315
320
335
335
335
335
320
335
335
315
315
335
335
335
320
315
325
335
335
335
320
335
335
335
335
15
335
340
325
315
330
325
335
335
320
315
335
325
335
(gm)
1015
1000
690
1030
1060
1230
1350
1285
1355
1120
1375
1265
1585
1450
1370
1245
1445
1275
1650
1345
1420
1555
1640
1415
1385
1465
1630
1520
1625
1440
1365
1365
1325
1200
1230
1350
1420
1310
1460
1725
1350
1820
1740
1985
1640
1765
1130
1595
(gm)
750
800
500
750
755
905
1000
920
990
870
1045
925
1170
1075
1035
955
1070
935
1210
1010
1120
1235
1290
1065
1035
1080
1190
1150
1220
1080
980
1015
1065
915
940
1010
1005
955
1050
1270
975
1365
1315
1515
1185
1330
855
1220
(%)
26.1
20.0
27.5
27.2
28.8
26.4
25.9
28.4
26.9
22.3
24.0
26.9
26.2
25.9
24.5
23.3
26.0
26.7
26.7
24.9
21.1
20.6
21.3
24.7
25.3
26.3
27.0
24.3
24.9
25.0
28.2
25.6
19.6
23.8
23.6
25.2
29.2
27.1
28.1
26.4
27.8
25.0
24.4
23.7
27.7
24.6
24.3
23.5
DRY WEIGHT PASSING
3/8'
#20
(%)
98
80
93
85
95
96
94
97
93
76
84
97
91
89
86
94
76
87
92
91
80
81
81
85
89
90
97
77
89
94
93
92
77
86
93
93
97
93
96
90
93
92
87
76
90
86
92
90
(%)
85
66
77
69
78
80
82
72
81
64
69
79
68
73
70
75
57
72
76
74
62
63
61
69
69
79
83
62
67
82
75
71
60
69
76
75
83
74
78
76
77
75
71
60
73
70
81
71
#200
(%)
49
34
48
42
48
50
55
42
48
38
42
50
41
45
40
40
27
37
39
38
29
29
29
35
38
49
55
38
41
51
47
41
32
37
43
38
39
41
42
43
42
38
35
33
41
37
38
34
APPENDIX D
TRENCH DEPTH WORKSHEETS
Stegner Farms Pit Slurry Wall
Trench Depth Worksheet
(Work Completed May 8 through May 20, 2000)
Station
15+50
16+00
16+50
17+00
17+50
Depth to
Bedrock
17.0
18.0
18.0
19.0
17.0
Depth of
Trench
21.0
22.5
22.5
23.0
21.0
Depth Tagged Between Trenching and Backfill
8-May
9-May
10-May
11-May
12-May
18+00
17.0
21.0
19.0
18+50
18.0
22.5
20.5
19+00
18.0
22.5
22.5
19+50
19.0
23.0
18.0
7.0
20+00
17.0
21.0
20.0
19.0
20+50
16.0
20.0
18.5
18.0
21+00
16.0
20.0
19.5
18.0
21+50
17.0
21.0
20.0
22+00
16.5
20.5
20.0
22+50
16.5
20.5
20.5
23+00
18.5
22.5
7.5
23+50
22.0
25.0
16.5
24+00
17.0
21.0
24+50
19.0
23.0
22.0
17.0
25+00
16.0
20.0
19.0
16.0
25+50
19.0
23.0
12.0
26+00
16.5
20.5
12.5
26+50
18.0
22.0
27+00
18.5
22.5
27+50
21.0
24.0
11.0
28+00
19.0
22.0
18.5
28+50
17.0
20.0
16.0
29+00
17.0
20.0
16.5
29+50
16.5
19.5
17.0
30+00
16.0
19.0
17.0
30+50
16.0
19.0
19.0
31+00
17.0
20.0
31+50
15.5
18.5
32+00
18.5
21.5
32+50
15.0
18.0
13-May
15-May
16-May
17-May
18-May
19-May
BTS
13.5
19.0
BTS
BTS
16.5
BTS = Backfilled To Surface
Note: Due to the increasing width of trench at the ground surface (see Daily Construction Logs), trench depths checked on 5/15 and 5/19 may not be representative
of actual trench depths. Can not reach out to centerline of trench so tag line may be getting caught along edge of trench.
BTS
20-May
Stegner Farms Pit Slurry Wall
Trench Depth Worksheet
(Work Completed May 22 through June 3, 2000)
Station
29+50
30+00
30+50
31+00
31+50
Depth to
Bedrock
16.5
16.0
16.0
17.0
15.5
Depth of
Trench
19.5
19.0
19.0
20.0
18.5
Depth Tagged Between Trenching and Backfill
22-May
23-May
24-May
25-May
26-May
32+00
18.5
21.5
15.0
32+50
15.0
18.0
14.0
33+00
15.5
18.5
15.0
33+50
16.0
19.0
34+00
16.5
19.5
15.5
34+50
17.0
20.0
18.0
35+00
16.0
19.0
15.0
35+50
16.0
19.0
18.5
36+00
15.0
18.0
16.0
36+50
15.0
18.0
16.5
37+00
15.0
18.0
15.0
15.0
37+50
15.0
18.0
17.0
16.0
38+00
16.0
19.0
18.0
13.0
38+50
15.0
18.0
17.0
16.5
39+00
15.0
18.0
16.0
7.5
39+50
16.0
19.0
17.5
13.0
40+00
15.0
18.0
17.0
16.5
40+50
15.0
18.0
16.5
10.0
41+00
15.0
18.0
16.0
41+50
16.0
19.0
19.0
42+00
17.0
20.0
42+50
16.0
19.0
43+00
15.0
18.0
30-May
31-May
1-Jun
2-Jun
3-Jun
BTS
11.0
16.0
16.0
BTS
BTS
BTS
16.5
12.5
BTS
BTS
BTS
43+50
15.0
18.0
11.0
44+00
15.0
18.0
16.0
44+50
16.0
19.0
16.0
45+00
14.0
18.0
14.0
BTS
45+50
15.0
18.0
15.0
46+00
15.5
18.5
17.5
46+50
14.0
17.0
BTS = Backfilled To Surface
Stegner Farms Pit Slurry Wall
Trench Depth Worksheet
(Work Completed June 5 through June 14, 2000)
Station
45+00
45+50
46+00
46+50
4700
Depth to
Bedrock
14.0
15.0
15.5
14.0
14.5
Depth of
Trench
18.0
18.0
18.5
17.0
17.5
4750
19.0
21.0
4800
17.5
20.0
4850
16.0
19.0
4900
16.0
19.0
4950
15.0
18.0
5000
17.0
20.0
5050
15.0
18.0
5100
15.0
18.0
5150
15.0
18.0
5200
14.0
17.0
5250
13.0
16.0
5300
13.5
17.0
5350
15.0
18.0
5400
15.0
18.0
5450
15.0
18.0
5500
17.0
20.0
5550
15.0
18.0
5600
15.0
18.0
5650
15.0
18.0
5700
14.0
17.0
5750
17.0
20.0
5800
16.0
19.0
5850
16.0
19.0
5900
16.0
19.0
5950
16.0
19.0
6000
15.0
19.0
6050
17.0
20.0
6100
18.0
21.0
6150
16.0
19.0
6200
16.0
19.0
BTS = Backfilled To Surface
Depth Tagged Between Trenching and Backfill
5-Jun
6-Jun
7-Jun
8-Jun
9-Jun
BTS
13.5
16.5
16.5
20.0
10-Jun
12-Jun
13-Jun
14-Jun
Stegner Farms Pit Slurry Wall
Trench Depth Worksheet
(Work Completed June 15 through June 23, 2000)
Station
6100
6150
6200
6250
6300
Depth to
Bedrock
18.0
16.0
16.0
17.0
16.0
Depth of
Trench
21.0
19.0
19.0
20.0
19.0
6350
15.0
18.0
18.0
6400
17.0
20.0
17.0
6450
16.0
19.0
18.0
6500
21.0
23.0
6550
17.0
20.0
6600
16.0
19.0
6650
15.0
18.0
6700
14.0
17.5
6750
15.0
17.5
6800
14.0
17.0
6850
14.0
17.0
6900
14.0
17.0
6950
14.0
17.0
7000
14.0
17.0
7050
14.0
17.0
15.0
7100
14.0
17.0
17.0
7150
16.0
19.0
7200
14.5
17.5
7250
13.0
16.0
7300
13.0
16.0
7350
15.0
18.0
7400
14.0
17.0
7450
14.0
17.0
7500
15.0
18.0
BTS = Backfilled To Surface
Depth Tagged Between Trenching and Backfill
15-Jun
16-Jun
17-Jun
19-Jun
20-Jun
BTS
21-Jun
10.0
17.5
17.5
BTS
22-Jun
23-Jun