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APPENDIX D AE Slope Stability Study
AndersonEngineeringInc.com 2045 W. Woodland, Springfield, Missouri 65807 • Phone: 417.866.2741 • E‐mail: info@andersonengineeringinc.com
September 20, 2018 City Utilities of Springfield (CU) Attn: Mr. Ted Salveter, Mr. Mark Haden P.O. Box 551 Springfield, MO 65801
Re: Assignment #7 ‐ Slope Stability Study, Utility Waste Landfill James River Power Station (JRPS), Permit # 0707705 S. Kissick Ave, Springfield, Missouri
Anderson Engineering Project #18SP40030 Gentlemen, Attached is the report for this project. Should you have any questions regarding the report, please give me or John Snider a call. Thank you for the opportunity to be of service. Sincerely, ANDERSON ENGINEERING, INC. by
____________________________ John T. Snider, P.E. VP/Principal Geotechnical Engineer Enclosures Ted.Salveter@cityutilities.net Mark.Haden@cityutilities.net jsnider@andersonengineeringinc.com cwhite@andersonengineeringinc.com bkeith@andersonengineeringinc.com
GEOTECHNICAL INVESTIGATION REPORT Assignment #7 ‐ Slope Stability Study, Utility Waste Landfill
James River Power Station (JRPS), Permit # 0707705 S. Kissick Ave, Springfield, Missouri
September 20, 2018
PREPARED BY: ANDERSON ENGINEERING, INC.
2045 WEST WOODLAND SPRINGFIELD, MISOURI 65807
417‐866‐2741
811 EAST THIRD STREET JOPLIN, MISSOURI 64801
417‐782‐7399
Anderson Engineering WO #18SP40030
______________________________ ______________________________ John T. Snider, P.E. Cody R. White, P.E. VP/Principal Geotechnical Engineer Construction Testing Manager
9/20/2018
TABLE OF CONTENTS INTRODUCTION‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐1
TECHNICAL APPROACH‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐1
WORK PERFORMED‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐2
ON‐SITE BORINGS‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐2 LABORATORY TESTING‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐3
GEOLOGY OF THE SITE‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐4
GENERAL SITE CONDITIONS‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐4
ASH FILL AND PERIMETER SUBGRADE CHARACTERISTICS ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐6
GROUNDWATER CONDITIONS ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐8
SLOPE STABILITY ANALYSES ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐8
ADDITIONAL ENGINEERING ANALYSES ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐11
CONCLUSIONS AND RECOMMENDATIONS ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐12
LIMITATIONS‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐14
APPENDIX I‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ SITE LOCATION
SURVEY CROSS SECTIONS BORING LOCATION SKETCH
APPENDIX II‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ BORING LOG LEGEND UNIFIED SOIL CLASSIFICATION SYSTEM BORING LOGS
APPENDIX III‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ IMPORTANT INFORMATION CONCERNING YOUR GEOTECHNICAL ENGINEERING REPORT
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 1
INTRODUCTION:
This report presents the results of a geotechnical investigation of the existing utility waste landfill (UWL)
at the James River Power Station (JRPS) in Springfield, Missouri. The investigation consists of slope
stability studies for the UWL at JRPS. Currently the Southern and Southeastern ends of the landfill have
slopes that are steeper than 3 H to 1 V at the lower part of the slope; and 3 H to 1 V or flatter at the
upper part of the slope. The investigation also included slope stability analyses of the complete buildout
of the UWL to the final permitted contours allowed under Permit Number 707705 issued by the Solid
Waste Management Program of the Missouri Department of Natural Resources (MDNR). A current
topographic map of the UWL is included as Appendix I.
The investigation was performed for City of Utilities of Springfield, Missouri under our Geotechnical
Consultant Services Contract dated November 16, 2016 (City Utilities Contract #2708). This portion of
the contract is Assignment #7 – Proposed Slope Stability Study, Utility Waste Landfill, James River Power
Station. This investigation addresses MDNR’s concern with the stability of the existing slopes at the
south and southeastern end of the UWL, and complete buildout of the landfill.
TECHNICAL APPROACH:
The following general approach was used to investigate and assess the stability of the UWL.
Review past geotechnical work performed at the ash landfill (geotechnical investigations,
laboratory testing, surveying)
Investigate the geology of the site
Investigate the ash wastes, and soil and groundwater conditions at the site (through visual field
reconnaissance, geotechnical borings with sampling of in‐place ash wastes and soil, and test
pits)
Perform laboratory testing of sampled ash wastes and soil for slope stability purposes
Review ash waste landfill literature (to compare against lab and field results obtained)
Survey the current surface conditions for critical slope locations
Develop an ash waste, soil, rock and groundwater profile
Perform deep seated slope stability analyses using PCSTABL‐based iterative software
Perform shallow slope cover slope stability analysis for shallow sliding failure
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
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Make conclusions regarding slope stability and additional engineering analyses.
WORK PERFORMED:
ON‐SITE BORINGS: We performed drilling and sampling of a total of eight (8) borings on the site. We
surveyed the boring locations and used existing survey data and engineering drawings to complete the
stability analysis.
Four (4) borings in the ash landfill were drilled and sampled to a depth approximately 5 feet above the
landfill synthetic and/or clay liner – which was generally approximately 40 to 45 feet depth at locations
selected.
See Appendix I for attached Boring location sketch for boring locations. Also attached in Appendix I is
Survey showing current elevations and surface. Drawings for typical cross section through the original
landfill with a clay liner is also included; the 2nd cross section is a typical through the newer landfill with a
synthetic liner.
Four (4) borings were drilled just outside of the existing landfill until rock was encountered. The borings
were then advanced a few feet into rock to verify its competency. We also performed a visual
reconnaissance of the landfill surface conditions for slope stability performance.
All of the borings were staked by our surveyors. The Missouri State Plane Coordinates and the ground
surface at the original boring location are shown below. The odd numbered borings correspond to
borings drilled within the landfill.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 3
BORING ELEVATION STATE PLANE COORDINATES
NORTHING EASTING
B‐1 1177.2 462443.9 1416123.4
B‐2 1124.6 462093.4 1416144.6
B‐3 1177.9 462622.0 1416256.6
B‐4 1125.7 462372.2 1416434.4
B‐5 1167.3 464084.6 1416564.5
B‐6 1126.8 463356.0 1416887.2
B‐7 1178.9 463109.5 1416263.3
B‐8 1146.0 464003.1 1416417.1
Representative samples were taken of the landfill fly ash and bottom ash, and soil encountered in the
borings. Testing of the ash and soil samples included the following:
Grain Size Distribution
Water Content
Shear Strength
Unconfined Compressive Strength
Triaxial Compressive Strength
Atterberg Limits
Unit Weight
Boreholes were drilled using a CME 75 rig outfitted with six‐inch hollow‐stem continuous flight augers.
Drilling and sampling were conducted on July 18, 19, and 21, 2018.
Boring logs, showing descriptions of the ash and soil encountered as well as results of standard
penetration tests, penetrometer readings and moisture content, are presented in Appendix II.
The primary sample type used in this investigation was the split spoon sample which was obtained while
performing the standard penetration test. This test, described in ASTM D1586, consists of driving a two‐
inch diameter split spoon sampler using a weight of 140 pounds with a free fall of 30 inches. The
number of blows to drive the sampler each of three successive 6 inch increments of depth in advance of
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 4
drilling was recorded and is presented on the boring logs. The sum of the last two blow counts is
normally taken as the penetration value expressed in blows per foot. These samples are used for strata
identification, natural moisture content, Atterberg limit values, and an occasional unconfined
compressive strength value.
All auger cuttings and ash samples were visually examined, and logged by the drilling crew chief. Our
Project Engineer was also present at selected boring locations to make assessments of samples taken
and modify the field sampling and testing program to better characterize conditions encountered.
Observations were also made for the presence of groundwater and cave‐in of the bore holes. The bore
holes were backfilled with cuttings and bentonite chips upon completion of drilling and water level
determinations.
LABORATORY TESTING: All samples were transported to Anderson Engineering's materials
laboratory for further evaluation and testing. Our Project Engineer reviewed field results and observed
laboratory samples to select samples for testing and determine which tests would be performed.
Laboratory testing of the fly ash, bottom ash, and soil samples followed general ASTM methods and the
Project Engineer’s guidelines. Some laboratory test results on ash samples recovered from the borings
are recorded on the Boring Logs contained in Appendix II, while the remaining laboratory results are
included in Appendix III.
The final logs, shown in Appendix II, represent our interpretation of the field logs based on the
additional information obtained from the laboratory testing program.
GEOLOGY OF THE SITE:
The site is mapped by MDNR as Mk, Mississippian Kinderhookian series. This formation is
consists of primarily limestone and siltstone, with minor constituents of shale and sandstone.
GENERAL SITE CONDITIONS:
An inspection of the landfill surface for indications of slope instability was performed by the
Project Engineer. Checks were made for: tension cracks, fissures, slumping, toe cracks, active seepage,
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 5
excessive settlements, and other signs of instability. No significant signs of instability were observed.
The sloped portions of the landfill were observed for erosion rills, and no significant evidence of slope
erosion was observed. The landfill was generally tall grass and vegetation covered. The vegetative cover
was generally moderately to well established.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 6
ASH FILL AND PERIMETER SUBGRADE CHARACTERISTICS:
The subsurface conditions encountered at the boring locations are shown on the boring logs. The
findings of the site are discussed below. In general, what we observed in the ash landfill agreed well
with information we obtained from past landfill investigations (Slope Stability Analysis with Additional
Engineering Analysis for John Twitty Energy Center (JTEC) Ash Landfill, AE Work Order 70045‐11, report
dated December 9, 2011).
Generally the waste ash encountered in the borings appeared to be Type C and Type F fly ash and
bottom ash mixed as a composite blend. However, it also appeared that some of the layers had greater
concentrations of fly ash in the samples, as evident by higher blow counts or N values, and higher
unconfined compressive strengths from pocket penetrometer test results. There were layers of more
predominantly bottom ash mixtures from the ash ponds. The samples obtained were generally
cemented and had unconfined compressive strengths generally well in excess of 1,000 psf. The relative
density of these fills based on N‐values or blow counts were generally “loose” to “medium dense”.
What became apparent from the drilling and sampling of the fill was that the fly ash and bottom ash
were in layers and not always well blended. This was also found in 2011 JTEC report referenced above.
Also our laboratory testing of these materials confirmed that they exhibit significant cohesion and
friction. See attached boring logs, Appendix II, for greater details of materials encountered. However,
due to the variability of the ash encountered in the borings, conservative values of friction were
assigned and no cohesion was used for slope stability analyses.
Perimeter Subgrade Conditions
Four borings, B‐2, B‐4, B‐6, and B‐8, were performed at the toe around the perimeter of the landfill. The
purpose of these borings was to characterize the soil and rock at the toe of the slope and underlying the
landfill for slope stability purposes. In general the subsoils consist of stiff, lean to fat clays, with varying
amounts of chert. Depth to bedrock varied between 8 and 20 feet. The rock encountered was a
moderately hard limestone.
A conservative approach based on lab testing, known correlations, and experience in the area was used
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 7
to develop the cohesion and nominal friction values used for this residual soil and rock layer.
Laboratory Testing
A multitude of laboratory tests were performed. See attached laboratory summary sheet and individual
lab sheets for details, Appendix III. Some of those test results are also on the attached boring logs,
Appendix II. In general, the laboratory tests provided the following Unified Soil Classification System
(USCS) classifications.
Landfill Clayey Cap Material
Type: USCS Classification: Comments:
Landfill Clayey Cap Fill Material Lean Clay (CL) Grass and vegetation covered
brown to reddish brown lean clay
with chert gravel
Ash Waste Landfill
Waste: USCS Classification: Comments:
Type F fly ash, bottom ash,
and/or Type C fly ash
Non‐plastic silt (ML), Non‐plastic
sandy silt (ML), to silty sand (SM)
Medium gray to dark gray, to
black
Residual Clayey Soil
Type: USCS Classification: Comments:
Upper soil Lean clay (CL) Reddish brown
Lower soil Fat clay (CH) Dark reddish brown
Rock
Type: Hardness: Comments:
Limestone Moderately hard Light gray
A few of these layers were classified using the visual‐manual method (ASTM D2488) in the laboratory to
augment other laboratory tests.
This study’s laboratory results compare well with published literature of fly ash and bottom ash
geotechnical properties. The strength properties of fly ash and bottom ash compare well with results
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 8
expected of natural silty sand (SM) to sand silt (ML). The main geotechnical difference is the lighter
weight for the coal waste materials compared to natural silica based soils.
GROUNDWATER CONDITIONS:
Saturated and or very moist water conditions were generally encountered in near the bottom 5
feet of the 3 of 4 landfill borings (Borings B1, B3, and B5, but not B7). As such we modeled slope
stability with a groundwater surface near this depth.
Groundwater was not encountered in any of the perimeter borings around the ash landfill from
this investigation. However, based on the above and experience in the area, we conservatively assumed
that groundwater was at a depth of 5 feet above the top of rock.
We reviewed groundwater data provided by City Utilities that was taken on or about 3/5/2018.
The water level depths were generally a few feet below our assumption. This should then make our
modeled water level a conservative elevation for slope stability purposes.
Groundwater can be encountered at any depths in these residual soils and in the limestone
during wet weather conditions and often at the soil/limestone interface. Groundwater conditions also
vary with rainfall and weather conditions.
The above is a generalized description of the conditions encountered in the borings and
observations around the site. For more specific information, the reader should refer to the boring logs
and attachments included with the final report.
SLOPE STABILITY ANALSYES:
Introduction
PC STABL, a slope stability program, was used to perform slope stability analyses of the present and
anticipated future landfill conditions. PC STABL is a two‐dimensional slope stability software that
computes the minimum critical factors of safety between soil layer interfaces. This model uses the
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 9
method of vertical slices to analyze slopes and calculate factors of safety based on limiting equilibrium.
PC STABL allows the user to employ a variety of trial failure surface methods to determine slope stability
including: the Bishop Method (applicable to circular shaped failure surfaces), the Janbu method
(applicable to failure surfaces of general shape), and the Spencer method (applicable to any type of
surface).
PC STABL can account for heterogeneous soil systems, anisotropic soil strength properties, excess pore
water pressure due to shear, static ground water and surface water, pseudo‐static earthquake loading,
surcharge boundary, loading, and tieback loading.
PC STABL features unique random techniques and iterative methods to calculate hundreds of slope
stability calculations for each software‐run. The generation of multiple potential failure surfaces
provides for the subsequent determination of the more critical slope stability surfaces and their
corresponding factors of safety. This allows for multiple runs to be performed. For example, changes
can be made to the location of failure, changes in loading, and changes in soil properties.
Modeling
For slope stability purposes, the different fill types, soil, and rock layers were modeled with following
properties.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 10
Soil Number Materials Wet unit
weight, pcf
Saturated Unit
Weight, pcf
Friction,
degrees
Cohesion, psf
1 Clayey landfill cap 120 125 0 350
2 Waste Coal Ash 105 107 29 0
3 Residual Clayey Soil 105 110 22 350
4 Limestone 140 145 35 10,000
The existing soil and rock underlying the ash landfill was modeled as natural subgrade as sampled on the
perimeter of the landfill.
Slope Stability Results
We performed multiple runs, with varying parameters to determine the critical factors of safety for the
various slope conditions desired. The following summarize those runs and provide the critical factor of
safety. In general, a factor of safety between 1.3 and 1.5 for static slope stability analyses is desired.
For this project, we understand the MDNR is requires an overall slope stability of 1.5 or greater. Based
on conservative values used for friction of ash fill materials these factors of safety are expected to be
greater. For greater details, see attached slope stability results in Appendices VI and VI‐a.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 11
Section Scenario Critical Factor of
Safety
Comments
A‐A’ 1. Existing slope, SE portion of existing
landfill, water surface added, no cohesion
in ash
1.7 Deep critical failure near
the toe
B‐B’ 2. Existing slope, SE portion of existing
landfill, water surface added, no cohesion
in ash
1.7 Deep critical failure
through the toe
B‐B’ 3. With future build‐out 1.6 Deep critical failure from
upper mid‐slope through
the toe
C‐C’ 4. Proposed slope, future build‐out,
tallest slope height planned, water
surface added, no cohesion in ash
1.6 Deep critical failure
through the toe
ADDITIONAL ENGINEERING ANALYSES
Shallow Surface Sliding Slope Stability Analysis
A shallow surface sliding slope stability analysis was performed for the landfill cover material. The
analysis we performed followed the Army Technical Manual (TM 5‐818‐1) and Air Force Technical
Manual (AFM 88‐3, Chap. 7) for infinite slopes. This approach considers slopes with a relatively thin layer
of soil overlying a different soil group. The critical failure mechanism is sliding along a plane parallel to
the slope, near the interface between two soil groups. We used this procedure to analyze the relatively
thin clayey landfill cap material over the ash waste portion of the landfill. When using this approach it is
important to realize that surface soils can lose strength when subjected to shrink‐swell cycles and
freeze‐thaw cycles. These cycles create planes of weaknesses that can result in a decrease of shear
strength and ultimately shallow sliding slope failures. The impact of vegetative cover on soil strength
was also considered in this methodology. Roots of vegetation contribute to the increase in soil shear
strength, specifically the cohesion component. Considering mechanisms associated with both loss of
shear strength and increase in shear strength, we analyzed the cap material for shallow sliding failures.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 12
Using the laboratory strength test data obtained from the borings and adjusting for
environmental effects and effect of vegetative cover, the analysis resulted in a satisfactory factor of
safety meeting 1.5. With that said, you should continue to establish vegetative cover, and routinely
observe the slopes for possibly signs of instability.
Section Scenario Critical Factor
of Safety
Comments
A‐A’ 1. 2.0 Thin layer of soil overlying other soil on a slope
steeper than existing condition, shallow sliding
failure, groundwater emerging from slope.
B‐B’ 2. ‐‐‐ Existing slope is more flat than A‐A’, so not critical
C‐C’ 3. ‐‐‐ Existing slope is more flat than A‐A’, so not critical
CONCLUSIONS AND RECOMMENDATIONS:
The following conclusions and recommendations are based on the project as previously
described. It is assumed that the conditions observed in our field work, laboratory testing performed,
and the information received about past and future operations will be as we have described previously.
It is also assumed that the conditions observed in the borings and test pits are representative of the
subsurface conditions throughout the landfill.
Slope Stability
1. The study has shown that the current or existing slopes for the critical portions of the JRPS ash
landfill meet and exceed generally accepted standards for slope stability (factor of safety of 1.3 to 1.5).
2. The study has shown that the proposed or future slopes for the future build‐out plans to
increase the height of the ash landfill meet and exceed generally accepted standards for slope stability
(factor of safety of 1.3 to 1.5).
3. Overall the current or existing slopes for the landfill are quite stable due to moderate levels of
friction and cementation of the waste ash and good final cover over the closed portion of the landfill.
4. We recommend that for future landfill maintenance operations:
That you continue to develop, establish, and maintain the existing vegetation cover.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 13
Continually and routinely observe the slope for signs of slope distress such as tension
cracking, bulging, and/or seepage.
Removal and dewatering of any water within the ash landfill will further increase the
total factor of safety.
Geotechnical Investigation – City Utilities of Springfield (CU) ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station, Springfield, MO September, 2018
p. 14
LIMITATIONS:
This report has been prepared for the exclusive use of our client for specific application to the
project discussed in accordance with generally accepted soils engineering practice common to the local
area. No other warranty, express or implied, is made.
The analyses and recommendations contained in this report are preliminary and are based on the data
obtained from the referenced subsurface explorations. The borings indicate subsurface conditions only
at the specific locations and time, and only to the depths penetrated. They do not necessarily reflect
strata variations that may exist between such locations. The validity of the recommendations is based
in part on assumptions about the stratigraphy made by the geotechnical engineer.
The scope of our services does not include any environmental assessment or investigation for the
presence or absence of hazardous or toxic materials in the ash, soil, groundwater or surface water
within or beyond the site studied. Any statements in this report regarding odors, staining of soils, or
other unusual conditions observed are strictly for the information of our client.
Anderson Engineering, Inc., is not responsible for any claims, damages, or liability associated with
interpretation of subsurface data or reuse of the subsurface data or engineering analyses without the
express written authorization of Anderson Engineering, Inc.
APPENDIX I
SITE LOCATION SKETCH
SURVEY CROSS SECTIONS
SOIL BORING LOCATIONS
SITE LOCATION SKETCH – Geotechnical Investigation – City Utilities of Springfield (CU) 18SP40030 EXP – Assignment #7 ‐ Slope Stability Study – Utility Waste Landfill – James River Power Station August 17, 2018
NOT TO SCALE – FOR ILLUSTRATIVE USE ONLY NORTH IS TO TOP OF PAGE
NE 1/4 OF THE SE 1/4 OFNORTHWEST CORNER OF THE SECTION 30, T-28-N, R-21-W
EXISTING ASH LANDFILL
SURVEY DESCRIPTION
EAST QUARTER CORNER OFSECTION 30, T-28-N, R-21-W
SECTION 30, T-28-N, R-21-WNE 1/4 OF THE NE 1/4 OFNORTHWEST CORNER OF THE
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APPENDIX II
LOG LEGEND UNIFIED SOIL CLASSIFICATION SYSTEM
BORING LOGS LABORATORY TEST RESULTS
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@A
@A
@A
@A
@A
@A
@A
@A
MW-SA-1
PZ-SA-U-1
MW-SA-4
PZ-SA-U-5
MW-SA-5
PZ-SA-U-4
MW-2
PZ-SA-U-3
PZ-SA-U-2
Site Diagram
City Utilities of Springfield - James River Power StationGreene County, Missouri
Figure 2
µ500 0 500
FeetLegend@A Monitoring Wells
Site Boundary
Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attacheddocument. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master fileis stored by GeoEngineers, Inc. and will serve as the official record of this communication.
Projection: NAD 1983 UTM Zone 15N
W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\SiteDiagram_JRPS.mxd Date Exported: 09/14/17 by emayle
Data Source:
9/14/2018 Anderson Engineering Inc Mail - FW: JRPS UWL Potentiometric Data
https://mail.google.com/mail/u/0?ik=0574d9f30f&view=pt&search=all&permthid=thread-f%3A1611605288274933137&simpl=msg-f%3A161160528827… 1/2
John Snider <jsnider@andersonengineeringinc.com>
FW: JRPS UWL Potentiometric Data 2 messages
Ted Salveter <Ted.Salveter@cityutilities.net> Fri, Sep 14, 2018 at 12:36 PMTo: John Snider <jsnider@andersonengineeringinc.com>
John,
Here are well water levels for your review.
Ted C. Salveter, P.E. Manager-Environmental Compliance Office: 417.831.8848
From: Justin W. Brown <jbrown@geoengineers.com> Sent: Friday, September 14, 2018 12:27 PM To: Ted Salveter <Ted.Salveter@cityutilities.net> Subject: RE: JRPS UWL Potentiometric Data
Let me know if this will work for you.
Table 1
Summary of Groundwater Monitoring Well Measurements
City Utilities of Springfield - James River Power Station
Greene County, Missouri
Piezometer Number MW-2 MW-SA-1 MW-SA-4 MW-SA-5 PZ-SA-U-1 PZ-SA-U-2 PZ-SA-U-4 PZ-SA-U-5
Top of Casing Elevation 1,127.76 1,142.24 1,128.45 1,123.66 1,132.86 1,140.87 1,121.76 1,126.80
Measurement Date Piezometric Elevations
03/05/18 1,114.48 1,124.17 1,118.74 1,117.51 1119.24 1119.29 1116.45 1118.08
From: Ted Salveter <Ted.Salveter@cityutilities.net> Sent: Friday, September 14, 2018 11:51 AM To: Justin W. Brown <jbrown@geoengineers.com> Subject: FW: JRPS UWL Potentiometric Data
9/14/2018 Anderson Engineering Inc Mail - FW: JRPS UWL Potentiometric Data
https://mail.google.com/mail/u/0?ik=0574d9f30f&view=pt&search=all&permthid=thread-f%3A1611605288274933137&simpl=msg-f%3A161160528827… 2/2
Hey Justin,
Just checking on those water level readings.
Thanks.
Ted C. Salveter, P.E. Manager-Environmental Compliance Office: 417.831.8848
PO Box 551 | Springfield, MO 65801-0551 cityutilities.net
John Snider <jsnider@andersonengineeringinc.com> Fri, Sep 14, 2018 at 12:53 PMTo: Ted Salveter <Ted.Salveter@cityutilities.net>
Thanks Ted[Quoted text hidden]
APPENDIX III SLOPE STABILITY GRAPHIC RESULTS SLOPE STABILITY CROSS SECTIONS
SLOPE STABILITY INPUT, OUTPUT FILES SHALLOW SLOPE STABILITY ANALYSIS RESULTS
TRIAXIAL COMPRESSION TEST RESULTS
APPENDIX IV IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL
ENGINEERING REPORT
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