HomeMy WebLinkAboutChefornak Wind Energy Geotechnical Data Review & Wind Turbine Feasibility Report - Jun 2014 - REF Grant 7040056
Chefornak Wind Turbine Feasibility
Golder Associates Inc.
2121 Abbott Road, Suite 100
Anchorage, AK 99507 USA
Tel: (907) 344-6001 Fax: (907) 344-6011 www.golder.com
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June 5, 2014 14-01361
Mr. Patrick Boonstra
Intelligent Energy Systems LLC
110 W. 15th Ave #B
Anchorage, AK 99501
RE: GEOTECHNICAL DATA REVIEW, WIND TURBINE FEASIBILITY, CHEFORNAK, AK
Dear Mr. Boonstra:
Golder Associates Inc. (Golder) is pleased to present the results of our geotechnical data review for the
feasibility study of proposed wind turbine generation planned for Chefornak, Alaska. This phase of the
project is supported by th Renewable Energy Fund Grant Program.
1.0 INTRODUCTION
We understand that up to five wind turbine generators (WTGs) are currently planned in the village of
Chefornak (see Figure 1). The WTG sites are planned to extend beyond the eastern end of the
community, and may require a new access road that roughly parallels the river. The preliminary planned
locations are shown in Figure 2, based on a site map provided by you, dated September 23, 2013. We
understand that various turbine models are being considered, including Windmatic, Northwind 100 (kW),
or other units. The turbines will likely be supported by steel mono-pole towers, but could also include
multi-leg steel lattice structures. The foundation systems supporting the towers are expected to be
groups of steel piles that will most likely require passive subgrade cooling, rock anchors, and/or helices.
Our scope of work for this initial phase included reviewing the following: existing geotechnical data near
the proposed sites; aerial photography; and geologic maps; to develop preliminary conclusions regarding
expected soil, bedrock and permafrost conditions at the proposed wind turbine sites. Data review
-house subsurface data and our general experience in Chefornak. Readily available
third party geotechnical/geological data or data provided by permission from client projects in the area
was also incorporated. No field work by Golder was authorized under this scope of work. Based on the
findings of the data review, preliminary conceptual-level foundation options are presented in Section 6.0
of this letter report. Results of this initial effort will be used by you to refine the subsequent project phase
scope, schedule and costs, including tower erection and power grid tie-in. Our services have been
conducted in general accordance with our proposal to you dated February 27, 2014.
2.0 GEOLOGY AND CLIMATE
Chefornak is located on the south bank of the Kinia River at its junction with the Keguk River in the
Yukon-Kuskokwim Delta. The community of Chefornak is located 98 air miles southwest of Bethel and
490 air miles southwest of Anchorage. Tern Mountain, a volcanic feature, lies 5.5 miles to the south, as
shown on Figure 1, and volcanic flows extend from the mountain to the community. This area has been
developed as a material source for the recent airstrip completion. Large boulders of vesicular basalt are
located along the edge of the flow, and are visible on aerial imagery. The volcanic flow is overlain by fine-
grained organic silt and inorganic silt, which can have plastic consistency. The U.S. Geologic Survey
(USGS, 1957) has mapped the soils in the area as undifferentiated surface deposits consisting of marine,
river and deltaic sediments. Areas not submerged by ponds or lakes are blanketed with peat and organic
silt.
Patrick Boonstra June 5, 2014
Intelligent Energy Systems 2 14-01361
Chefornak Wind Turbine Feasibility
Chefornak has a marine climate. According to the Community Database, precipitation averages 22
inches with 43 inches of snowfall annually (DCCED, 2014). Summer temperatures range from 41 to 57
degrees Fahrenheit (oF), and winter temperatures range from 6 to 24
oF (DCCED, 2014). The community
of Chefornak is in a zone of warm, discontinuous to sporadic permafrost (Jorgenson, et al, 2008, Ferrians,
1965). Vegetation consists mainly of undulating tundra and muskeg. The undulating tundra terrain is
considered to be a result of thermal degradation of ice-rich permafrost.
Based on a review of climate data for the Chefornak area, historic average air temperatures have been
increasing and are predicted to continue increasing over the design life of the structures. The average air
temperature in Chefornak is predicted to transition from below freezing to above freezing during the
design life of the structure. We believe that the increase in air temperature, among other factors such as
ground disturbance, may increase the ground temperature under the structures.
3.0 SITE CONDITIONS
The proposed project area is located east of the community of Chefornak, roughly parallel to the current
river bank. The planned WTG sites extend about 600 to 1,800 feet east of the currently developed
community, and are approximately 200 to 500 feet offset from the river bank. Ground surface elevations
range from about 75 to 82 feet, based on interpolation of the Community Map of Chefornak (DCCED,
2004). The sites are in an area of undulating tundra, and many tundra lakes are present nearby. The
area s high water table, including water that may be perched on permafrost, is exhibited with pervasively
wet terrain (City of Chefornak, 2014).
4.0 EXISTING GEOTECHNICAL INFORMATION
Our in-house files contain many projects within the Chefornak area; however most of those were located
to the east of the project area in the main portion of the village. The available data sources most relevant
to the project area are summarized below. The locations of each site are shown in Figure 1. Select
pages from these past reports are included in Appendices A thru C, and approximate locations of historic
explorations are shown on
Water Wells, 1994 Public Health Service (PHS) drilled a series of water wells on the
eastern edge of the community, along the south bank of the Kiniak River. The wells
encountered surficial silt and organic material overlying a layer of basalt rock.
Discontinuous permafrost was found in the area. See Appendix A for select water well
logs. Well logs were obtained from Alaska Department of Natural Resources WELTS.
Water and Sewer Projects, 1997/1998 In 1997, a reconnaissance trip included
advancing two test pits and active layer probes at the proposed water treatment plant and
water tank site and along the boardwalk. A total of 5 borings (B-3 thru B-7) were
completed in 1998 within the project area. The surficial organic mat, 1.5 to 3 feet in
thickness was underlain by gray, icy silt over black, plastic organic silt. The black, plastic
organic silt was noted to exhibit thixotropic behavior. Boring B-5, located in a slough,
encountered bedrock at a depth of 13.5 feet. Four of the five borings were fully frozen to
the depths explored, while Boring B-5 was unfrozen below 4 feet. The two hand dug test
pits (CHEF-1 and CHEF-2) encountered frozen ground at 2.5 feet, while probes of the
lower lying surrounding area encountered no resistance to 5 feet, the depth of the probe.
See Appendix B for reference.
UUI Communication Tower, Geotechnical Investigations and Construction Related
Services, 2005/2006 Three boreholes were advanced, one at the initial tower location
and two at an alternate site to the southeast of the initial site for United Utilities, Inc.
(UUI). Subsurface conditions encountered at each are discussed below. Golder also
provided geotechnical services foundation, and our
experience from that is expressed below. See Appendix C for reference.
Exploration for Initial UUI Tower Site: At the initial tower site , an
approximate 3-foot organic mat was underlain by 3 feet of organic silt, 11.2 feet of
Patrick Boonstra June 5, 2014
Intelligent Energy Systems 3 14-01361
Chefornak Wind Turbine Feasibility
dark gray to black, wet to saturated (unfrozen) and moderately plastic, volcanic ash,
and 0.6 feet of dark gray, vesicular basalt at 17.2 foot depth. Seasonal frost was
present to depths of 3.5 to 4 feet, but sediments were unfrozen below that depth.
Groundwater intrusion into the borehole was noted near the ash / basalt contact.
Continued infilling of groundwater caused sloughing of the borehole. Another boring
was attempted nearby, but was terminated at 10 feet below grade reportedly due to
excessive sloughing, which is inferred to be a result of unfrozen soils with excess
water.
Exploration for Alternate UUI Tower Site: The two boreholes completed at the
alternate site encountered an approximate 3-foot thick frozen organic mat that grades
to dark gray organic silt, underlain by 4 feet of unfrozen, damp to moist, black to dark
gray silt, 5 feet of frozen dark gray silt with ice crystals, and below 13 foot depth there
was 18 to 22 feet of dark gray icy silt, with ice lenses. No bedrock or basalt was
encountered within the depths of exploration (30 to 34 feet) in these two test holes.
The alternate site explored was in an area slightly elevated by 3 to 4 feet above
nearby grades. These areas of slightly higher elevation tend to be wind swept of
snow accumulation in the winter, and therefore, the ground experiences
significantly more freezing compared to lower areas where snow may
accumulate.
Subsurface Conditions Encountered During Construction of UUI Tower: The UUI
tower is a 105 foot tall, three-legged free-standing lattice tower structure that is
supported by 30-inch diameter steel piles at each leg. The pipe piles are integrated
with rock anchors for axial tension support and thermo-syphon probes for maintaining
frozen soils to provide lateral support. Discussion of key points during construction
follows.
The pile foundations were installed down to bedrock by pre-drilling with an
oversized auger, placing the pipe pile in the hole, and slurry backfilling along the
exterior annulus. Groundwater was encountered while drilling, causing sloughing
of the hole, and in some cases required temporary casing for borehole
stabilization. After seating on rock, insides of the piles were cleaned of soil, rock
fragments, and drill cuttings. A grout plug was placed inside the piles near the
bedrock interface as an attempted measure to seal out groundwater.
Two grouted rock anchors, per each leg foundation, were advanced below the
piles about 30 feet into basalt bedrock for uplift resistance. Despite the attempts
to control groundwater intrusion within the overburden, groundwater was also
prevalent permeating through the bedrock while drilling and grouting of the rock
anchors. Groundwater may have been hydraulically connected to the nearby
river. The permeability of the rock not only caused groundwater intrusion into the
anchor drillholes, it also resulted in highly-excessive losses of grout into the rock
formation during pumping. Bedrock was near or below freezing temperature; and
therefore, Fondu grout, formulated for cold-temperature curing, was used for the
anchors, and at times, was mixed with sand.
Passive cooling was integrated into the foundation by installing independent
thermo-syphon probes at each leg. The intent was to maintain frozen
overburden soils along the piles for providing lateral soil resistance on the tower.
CVRF Fisheries Support Facility, Geotechnical Services, 2005 A site
reconnaissance was completed at two proposed sites including shallow, hand dug test
pits, and active layer probes. The organic mat was underlain by gray silt to 3.5 feet. No
frozen ground was encountered in the test pit or in any of the 10 probe locations.
Other geotechnical data from elsewhere in the community was reviewed, as follows. Select data is
included in Appendices D and E.
Patrick Boonstra June 5, 2014
Intelligent Energy Systems 4 14-01361
Chefornak Wind Turbine Feasibility
Chefornak K-12 School Addition and Fuel Storage, 2009 & 2011 (see Appendix D)
Chefornak Secondary School (Original), R&M Consultants, 1979 (see Appendix D)
Chefornak Wastewater Lagoon Siting, 2011 (see Appendix E)
Chefornak Power Plant, 2003
Village Store Foundation Rehabilitation, 1995
Thaw Probes for Subdivision, 1999
5.0 CONCLUSIONS OF ANTICIPATED SUBSURFACE CONDITIONS
Based on our previous experience in Chefornak, subsurface and permafrost conditions are expected to
be complex and highly variable, particularly related to degrading thermal conditions, discontinuous basalt
flows, and the influence of adjacent water bodies on groundwater and permafrost conditions. Therefore,
a geotechnical drilling program will be necessary to further define site-specific subsurface soil, rock and
thermal condition in order to develop foundation recommendations.
In general, an organic mat (consisting of tundra vegetation and peat grading to organic silt) is anticipated
to be underlain by variable thickness of silt and organic silt. Volcanic ash, vesicular basalt or scoria
boulders, and gravel and cobble sized rock fragments may also be encountered at variable depths
intermixed within the silt. Discontinuous volcanic flow, consisting of vesicular basalt, has been
encountered below the silt at variable depths, and is commonly found below 20 to 35 feet depths below
the ground surface, with a range of about 15 to 55 feet depths. Considering the discontinuous and erratic
nature of volcanic flow, the bedrock surface could be highly variable across a site, or could be non-
existent within the expected depth of the foundations, or could be relatively thin in extent. The thickness
of the basalt is typically about 30 feet, but had been reported as thin as 5 feet. Basalt boulders, both as
independent fragments and layered, have been located closer to ground surface in certain areas in and
around the community, and these have potential to impact foundation installations.
Thermal conditions are expected to range from fully frozen, ice-rich soils to fully thawed below the active
layer. Moisture content ranges from moist to over-saturated, and soils may be plastic. Degrading
permafrost is present in the community, particularly near surface water bodies, in disturbed tundra or filled
areas, in lower-lying areas, and under snow drifts. Important to note is that there is a correlation between
local variations in terrain elevations and condition / existence of permafrost. That is, slightly elevated
areas (by 3 to 4 feet) tend to be wind-swept in the winter, which conveys significantly more freezing
temperature into the ground, and thus permafrost is better preserved. Conversely, lower-lying areas
receive drifting snow which insulates the ground, and are wetter in the summer, which can attract more
solar absorption and transfer convective heat, and therefore, permafrost is more or fully degraded here.
In thawed conditions (below the active layer), flow and seepage of groundwater is common, particularly
close to the river, and should be expected and planned for during construction. In past investigations,
groundwater has been encountered within the following zones: 1) within the thawed sediments, 2) near
the contact between sediments and basalt, 3) perched on top of permafrost, and 4) permeating through
the basalt bedrock.
6.0 CONCEPTUAL FOUNDATION OPTIONS AND CONSIDERATIONS
The exact size, type, location, and number of wind turbines, and associated supporting towers, have yet
to be refined in this phase of the project. However, at this time we understand Northwind 100 WTGs are
preferred. Therefore, no foundation configuration or loads are known at this time. Wind turbine / tower
structures experience significant lateral loading from wind pressure that is transferred as overturning
moment and lateral force at the base of the towers. It is this overturning moment, resulting from design-
level wind gusts, often with tower ice condition, that is most often the controlling loading scenario.
Overturning moment at the base of the tower will be resisted by coupled tension (uplift) and compression
forces on the supporting set of piles, and piles will also have to resist the lateral shear forces. Dynamic
loading from the structures, including vibration and resonance frequencies, may also be a structural
Patrick Boonstra June 5, 2014
Intelligent Energy Systems 5 14-01361
Chefornak Wind Turbine Feasibility
foundation design consideration. Long-term condition of permafrost should also be accounted for in the
design of the substructure.
Based on this presumptive understanding of subsurface conditions, the most appropriate foundation
option for supporting the wind towers are groups of steel pipe piles. Various types of suitable piles are
presented here, including associated methods of installation.
Pile foundations should be installed down to, and seated firmly on, bedrock. That is, if bedrock is found to
be present within a reasonable depth, estimated within 50 to 60 feet of the ground surface, at the tower
sites. Subsurface conditions that are revealed during investigation will determine whether driven piles or
drilled-and-slurry piles are the most suitable installation method. In this scenario, grouted rock anchors
would need to be installed inside the pile interior into competent bedrock in order to develop sufficient
uplift resistance. Special consideration will need to be given when designing the rock anchors to account
for: the variable and finite thickness of basalt bedrock, the potential for fragmented rock condition or
boulders, and permeability of the rock. Prior to installing anchors, the inside annulus of the piles should
be thoroughly cleaned of soil and rock fragments to the bedrock seating surface.
If bedrock is non-existent at the sites, or is deeper than stated, large diameter helical piles, and helical
thermo-piles would need to be considered as foundation options, and as a means to provide uplift
resistance.
As an example, many wind projects in Western Alaskan villages (particularly those served by Alaska
Village Electrical Cooperative - AVEC), where conditions are similar, the typical installation consists of
steel mono-pole towers bolted onto structural pile caps that are supported slightly above grade by six or
more steel pipe piles. For structural pile caps at these sites, reinforced concrete, both pre-cast and cast-
in-place, and pre-fabricated structural steel frames have been used. Pile caps have often been
hexagonal in shape. This foundation option may be suitable at this site depending on subsurface soil and
thermal states.
As with each of these pile options, we recommend integrating passive cooling into the foundation system.
Preserving soils in a frozen state will provide lateral soil resistance and stiffness to the foundations, and
will increase uplift resistance where rock anchors are not placed. Thermo-syphons, fabricated by Arctic
Foundations, Inc. of Anchorage, Alaska, can be installed as either independent thermo-probes adjacent to
each of the piles, or as pressurized helical thermo-piles. Thermo-piles should also be fabricated to
accommodate future conversion to mechanical refrigeration, to account for possible future climate change
impacts. Placing thermo-probes inside the standard steel piles may also be an option, but is not preferred
over installation within independent drillholes.
The fill pad placed at the tower sites should be insulated with at least 4 inches of extruded polystyrene
insulation. The required thickness of insulation is to be determined during detailed design. Insulation
should extend at least 8 feet beyond the foundation footprint. Disturbance of the tundra surface should be
minimized.
A few obstacles have been experienced from past foundation installations in Chefornak that should be
taken into consideration when planning this project. Firstly, cobbles and boulders, of volcanic rock origin,
are known to be present randomly throughout the village and as distinct boulder layers, and can have the
potential to impede foundation installation and drilling. Secondly, permafrost is degrading, making the
thermal regime complex and variable. Even with mostly frozen conditions, thawed zones contained within
are possible. Thawed soils, either in zones noted or in the active layer, will collapse and slough within
borings during construction and will need to be stabilized. Lastly, groundwater, which is present both
within overburden and bedrock, presents challenges to foundation construction and needs to be
addressed during design.
Once more detailed selection of wind turbine type, tower, and exact location(s) are known, it is
recommended that additional site-specific geotechnical subsurface investigation and detailed foundation
Chefornak Wind Turbine Feasibility
REFERENCES
Alaska Department of Natural Resources, Well Log Tracking System (WELTS), available on-line at
dnr.alaska.gov/mlw/welts/
American Society of Civil Engineers (ASCE), 2001, Design and Construction of Frost-Protected Shallow
Foundations, SEI/ASCE 32-01.
City of Chefornak, Hazard Mitigation Planning Team, Feb 2014, City of Chefornak, Draft Hazard
Mitigation Plan, prepared under grant from FEMA, U.S. Department of Homeland Security, and State
of Alaska.
Department of Commerce, Community, and Economic Development (DCCED). Community Database
Online, accessed 04/2014 (http://commerce.alaska.gov/cra/DCRAExternal). State of Alaska, Division
of Community and Regional Affairs.
Department of Commerce, Community and Economic Development (DCCED), Community Map,
Chefornak, prepared by Coastal Villages Fund Inc. in cooperation with the State of Alaska
Department of Commerce, Community and Economic Development, ANTHC, City of Chefornak,
USDA, ADOT&PF, and IAID. Photography dated 2004-09-16.
Ferrians, O.J., Jr., 1965, Permafrost Map of Alaska: U.S. Geological Survey Miscellaneous Geological
Investigations Map I-445, Scale 1:2,500,000.
Jorgenson, et al, 2008, Institute of Northern Engineering, University of Alaska Fairbanks, Permafrost and
Ground Ice Map of Alaska
USGS, Coonrad, W.L., 1957, Geologic Reconnaissance in the Yukon-Kuskokwim Delta Region, Alaska.
FIGURES
CONSULTANT
DESIGN
PREPARED
REVIEW
APPROVED
YYYY-MM-DD TITLE
PROJECT No. Rev.
PROJECTCLIENT
1401361.100
CONTROL FIGURE
A
2014-05-28
DBC
TFR
RAM 1
CHEFORNAK WIND TURBINE FEASIBILITY
INTELLIGENT ENGINEERING SERVICES
110 W. 15TH AVE. #B
ANCHORAGE, AK 99501
PROJECT VICINITY MAP
2
MILES
10
SCALESCALE
REFERENCE
BASE MAP TAKEN FROM USGS DRG, DATED 1996 DELIVERED IN GEO-PDF FORMAT
KEY MAP
PROJECT
AREA
PROJECT
LOCATION
IF THIS MEASUREMENT DOES NOT MATCH WHAT IS SHOWN, THE SHEET SIZE HAS BEEN MODIFIED FROM: ANSI BPath: \\anchorage\Public\Geomatics\IES\Chefornak\99_PROJECTS\1401361 IES Chefornak Wind Turbines AK\100_Engineering\02_Production\DWG\ | File Name: 1401361_100_001.dwg0 1 in
APPENDIX A
Water Well Logs and Cross Section from:
Alaska DNR
WELL LOG TRACKING SYSTEM (WELTS)
And
Duane Miller & Associates
FOUNDATION CONSULTATION
COMMUNICATION TOWER
CHEFORNAK, ALASKA
Dated August 2005
APPENDIX B
Pages from:
Duane Miller & Associates
GEOTECHNICAL INVESTIGATION
WATER AND SEWER PROJECTS
CHEFORNAK, ALASKA
Dated May 1998
APPENDIX C
Pages from:
Duane Miller & Associates
FOUNDATION CONSULTATION
COMMUNICATION TOWER
CHEFORNAK, ALASKA
Dated August 2005
And
Duane Miller & Associates
CHEFORNAK ALTERNATE TOWER SITE MEMORANDUM
Dated March 2006
APPENDIX D
Pages from:
Duane Miller & Associates
GEOTECHNICAL REPORT, CHEFORNAK K-12 SCHOOL ADDITION
AND FUEL STORAGE
CHEFORNAK, ALASKA
Dated February 2009
And
R&M Consultants
Soil and Foundation Investigation
For Original Secondary School
Dated 1979
Note: Picture provided by Aero-Metric dated 10/2/2004.
Duane Miller Associates LLC
Job No.:
Date:
4102.013
February 2008
Chefornak K-12 School Addition
Chefornak, Alaska
VICINITY MAP
1KINIA RIVERPlate
Existing School Facility
Existing Village
Fuel Storage
Area
0 300
Approximate Scale In FeetN
B-01
B-02
B-03
B-04
T-4
T-3
T-1
T-2
2008 DMA Boring
Existing Pile Location
Temperature Pipe at Pile
2008 DMA Temp ProbeN
I-13
H-11
I-8
G-5
G-8 D-7
C-9
C-10
D-12
PlateDuane Miller Associates LLC
Job No.:
Date:
4102.013
February 2008
Chefornak K-12 School Addition
Chefornak, Alaska
SITE LOCATION MAP
2.1
0 90
Approximate Scale In Feet
Note: Picture provided by Aero-Metric dated 10/2/2004.
Plate2.2Chefornak K-12 School AdditionChefornak, AlaskaFUEL STORAGE SITE BORING LOCATIONB-052008 DMA BoringN01020Scale in feet1” = 20, approximatelyApproximate final locationtwo each 20,000-gallon, double walledabove grade pile supported fuel tankslocation and orientation of tanks to be determinedOriginal proposed locationSingle-walled, 40,000-gallonat-grade fuel tank
PlateDuane Miller Associates LLC
Moisture Content % ( ),
PL & LL ( ),Salinity ( )
and Sampling Blows/ft ( ) Other
0 20 40 60 >80 P200 Tests Sampler Type Sampling Interval GraphicLogFrozenSamplesDescriptionBlow Counts Job No.:
Date:
DUANE MILLER ASSOCIATES LLC
Project:
DMA Job No.:
Logged By:
Log of HOLE:
Date Drilled:
Contractor.:
Equipment:
GPS Coord.:
4102.013
Chefornak K-12 School Addition July 17, 2008
Salzbrun Drilling &Services, Inc.
SSD2, 4''OD/SF Auger
N60°9'27.75'' W164°16'58.75'' (NAD-83)
-Elevation:
4102.013
J. Kenzie
February 2009
Chefornak K-12 School Addition
Chefornak, Alaska
LOG OF TEST BORING B-01
B-01
3
0
5
10
15
20
25
30
35
40
ORGANIC MAT (Pt) Brown, saturated, fibrous
organic material
SILT (ML) (Vx+Vs) Gray, 10-40% white visible ice as
crystals and striations
ICE (ICE) White, massive ice inferred by drilling
action
SILT (ML) (Vx+Vs) Gray, 10% white visible ice as
crystals and striations
Test boring completed at 29.5 feet on 7/17/2008
Installed 1-inch closed-end PVC to 29.5 feet
PlateDuane Miller Associates LLC
Moisture Content % ( ),
PL & LL ( ),Salinity ( )
and Sampling Blows/ft ( ) Other
0 20 40 60 >80 P200 Tests Sampler Type Sampling Interval GraphicLogFrozenSamplesDescriptionBlow Counts Job No.:
Date:
DUANE MILLER ASSOCIATES LLC
Project:
DMA Job No.:
Logged By:
Log of HOLE:
Date Drilled:
Contractor.:
Equipment:
GPS Coord.:
4102.013
Chefornak K-12 School Addition July 18, 2008
Salzbrun Drilling &Services, Inc.
SSD2, 4''OD/SF Auger
N60°9'26.54'' W164°16'54.26'' (NAD-83)
-Elevation:
4102.013
J. Kenzie
February 2009
Chefornak K-12 School Addition
Chefornak, Alaska
LOG OF TEST BORING B-02
B-02
4
0
5
10
15
20
25
30
35
40
ORGANIC MAT (Pt) Grass roots, saturated
ORGANIC SILT (OH) (Vx+Vs) Dark brown, moist in
unfrozen areas, with 15-25% fine-grained sand
and fibrous organic material, 30-40% visible ice
as crystals and striations
SILT (ML) (Nbn) Gray
(Vx) gray to brown, 5% visible ice as crystals and
< 5% fibrous organic material from 14 to 18 feet
Test boring completed due to refusal on rock at
23.5 feet on 7/18/2008
Installed 1-inch closed-end PVC to 23.5 feet
PlateDuane Miller Associates LLC
Moisture Content % ( ),
PL & LL ( ),Salinity ( )
and Sampling Blows/ft ( ) Other
0 20 40 60 >80 P200 Tests Sampler Type Sampling Interval GraphicLogFrozenSamplesDescriptionBlow Counts Job No.:
Date:
DUANE MILLER ASSOCIATES LLC
Project:
DMA Job No.:
Logged By:
Log of HOLE:
Date Drilled:
Contractor.:
Equipment:
GPS Coord.:
4102.013
Chefornak K-12 School Addition July 18, 2008
Salzbrun Drilling &Services, Inc.
SSD2, 4''OD/SF Auger
N60°9'25.64'' W164°16'55.49'' (NAD-83)
-Elevation:
4102.013
J. Kenzie
February 2008
Chefornak K-12 School Addition
Chefornak, Alaska
LOG OF TEST BORING B-03
B-03
5
0
5
10
15
20
25
30
35
40
ORGANIC MAT (Pt) Brown, saturated, fibrous
organic material
SILT (ML) (Vx+Vs) Brown to gray, with 5-10%
fine-grained sand and 5-35% visible ice as
white crystals and striations
gray below 9 feet
cobble encountered at 27 feet able to drill past
Test boring completed at 30.5 feet on 7/18/2008
Installed 1-inch closed-end PVC to 30.5 feet
PlateDuane Miller Associates LLC
Moisture Content % ( ),
PL & LL ( ),Salinity ( )
and Sampling Blows/ft ( ) Other
0 20 40 60 >80 P200 Tests Sampler Type Sampling Interval GraphicLogFrozenSamplesDescriptionBlow Counts Job No.:
Date:
DUANE MILLER ASSOCIATES LLC
Project:
DMA Job No.:
Logged By:
Log of HOLE:
Date Drilled:
Contractor.:
Equipment:
GPS Coord.:
4102.013
Chefornak K-12 School Addition July 19, 2008
Salzbrun Drilling &Services, Inc.
SSD2, 4''OD/SF Auger
N60°9'27.57'' W164°16'53.24'' (NAD-83)
-Elevation:
4102.013
J. Kenzie
February 2009
Chefornak K-12 School Addition
Chefornak, Alaska
LOG OF TEST BORING B-04
B-04
6
0
5
10
15
20
25
30
35
40
ORGANIC MAT (Pt) Brown, saturated, fibrous
organic material
SILT (ML) Gray to brown, moist, with 5-15%
fine-grained sand and < 5% fibrous organic
material
SILT (ML) (Vx+Vs) Gray to brown, with 5-15%
fine-grained sand and 5-35% visble ice as white
crystals and striations
gray below 19 feet
dark gray below 28.5 feet
Test boring completed at 29.6 feet on 7/19/2008
Installed 1-inch closed-end PVC to 29.6 feet
PlateDuane Miller Associates LLC
Moisture Content % ( ),
PL & LL ( ),Salinity ( )
and Sampling Blows/ft ( ) Other
0 20 40 60 >80 P200 Tests Sampler Type Sampling Interval GraphicLogFrozenSamplesDescriptionBlow Counts Job No.:
Date:
DUANE MILLER ASSOCIATES LLC
Project:
DMA Job No.:
Logged By:
Log of HOLE:
Date Drilled:
Contractor.:
Equipment:
GPS Coord.:
4102.013
Chefornak K-12 School Addition July 19, 2008
Salzbrun Drilling &Services, Inc.
SSD2, 4''OD/SF Auger
N60°9'37.12'' W164°17'14.10'' (NAD-83)
-Elevation:
4102.013
J. Kenzie
February 2009
Chefornak K-12 School Addition
Chefornak, Alaska
LOG OF TEST BORING B-05
B-05
7
0
5
10
15
20
25
30
35
40
ORGANIC MAT (Pt) Brown, saturated, fibrous
organic material
SILT (ML) Dark gray, saturated, with < 5% fibrous
organic material to 9 feet and 20-25%
fine-grained sand
cobble encountered at 23 feet able to drill past
Test boring completed at 29 feet on 7/19/2008
Installed 1-inch closed-end PVC to 29 feet
Well graded gravels,
sandy gravel
Poorly graded
gravels, sandy gravel
Silty gravels, silt sand
gravel mixtures
Poorly graded
sands, gravelly sand
Silty sand, silt gravel
sand mixtures
Clayey gravels, clay
sand gravel mixtures
Inorganic silt and very
fine sand, rock flour
Clayey sand, clay
gravel sand mixtures
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
Pt
Inorganic clay, gravelly and
sandy clay, silty clay
Organic silts and clay of
low plasticity
Inorganic silt
Inorganic clay, fat clay
Organic silt and clay of
high plasticity
Peat and other highly
organic soil
MAJOR DIVISIONS SYMBOL TYPICAL NAMES
Clean gravels with
little or no fines
Gravels with more
than 12% fines
Sands with more
than 12% fines
Clean sands
with little or no
fines
GRAVELS
More than half of the
coarse fraction is
larger than #4 sieve
size, > 4.75 mm.
SANDS
More than half of the
coarse fraction is
smaller than #4 sieve
size, < 4.75 mm.
HIGHLY ORGANIC SOILS
SILTS and CLAYS
Liquid limit less
than 50
Liquid limit greater
than 50
UNIFIED SOIL CLASSIFICATION SYSTEM
20
40
0
0 50
Plasticity Chart
Liquid Limit
CL
CH
MH
ML
GROUP ICE VISIBILITY DESCRIPTION SYMBOL
Nf
Nbn
Nbe
Vx
Vc
Vr
Vs
ICE + soil type
ICE
Nb
Poorly bonded or friable
No excess ice
Excess microscopic ice
Individual ice crystals or inclusions
Ice coatings on particles
Random or irregularly oriented ice
Stratified or distinctly oriented ice
Ice with soil inclusions
Ice without soil inclusions
N
V
ICE
Segregated ice not
visible by eye
Segregated ice is
visible by eye and
is one inch or less
in thickness
Ice greater than one
inch in thickness
Well bonded
ICE CLASSIFICATION SYSTEM
gravelly sand
Well graded sand,
KEY TO TEST
DATA
PP = Pocket Penetrometer
Dd = Dry Density (pcf )
LL = Liquid Limit
PL = Plastic Limit
PI = Plastic Index
NP = non Plastic
SpG = Specific Gravity
SA = Sieve Analysis
MA = Sieve and Hydrometer Analysis
OLI = Organic Loss
RD = Relative Density
D1557
TS = Thaw Consolidation
Con = Consolidation
TXUU = Unconsolidated
Undrained Triaxial
TXCU = Consolidated
Undrained Triaxial
TXCD = Consolidated
Drained Triaxial
KEY TO
SAMPLE TYPE
Gr = Grab sample
Ab = Auger bulk
Ag = Auger grab
Ac = Air chip
Sh = 2.5" ID split
w/ 340 lb.manual hammer
Sh* = 2.5" ID split barrel
lb.manual hammerSha= 2.5" ID split barrel
lb.automatic hammer
Tw = Shelby tube
Ss = 1.4" ID split barrel
lb.manual hammer
Cc = 1.625" continuous core barrel
Strength Data
XXX (YYY), where:
XXX = (1 -3 )/2
YYY = 3COARSE GRAINED SOILS 50% or more larger than #200 sieve, 0.075 mm FINE GRAINED SOILS > 50% finer than #200 sieve Plasticity Index Vu Uniformly distributed ice
TV = Torvane
barrel
w/ 140
w/ 340
S2a = 2.0" ID split barrel
lb.automatic hammerw/ 140
w/ 140
Ssa = 1.4" ID split barrel
lb.w/ 140 automatic hammer
(Standard Penetration Test Method)
S2*= 2.0" ID split barrel
lb.manual hammerw/ 140
PlateDuane Miller Associates LLC
Job No.:
Date:
4102.013
February2008
Chefornak K-12 School Addition
Chefornak, Alaska
SOIL & ICE CLASSIFICATION KEY
8
PlateDuane Miller Associates LLC
Job No.:
Date:
4102.013
February 2008
Chefornak K-12 School Addition
Chefornak, Alaska
SUMMARY OF SAMPLES
9
Test
Hole
Sample
Depth
Soil
Type
(USCS)
Thermal
State
Sampler
Type
Sampling
Blows/ ft
Moisture
Content
Organic
Loss Salinity
Gravel
%
Sand
%
Passing
#200
Other
Tests
B-01 3.0 ft.ML Frozen Ss 47 40.0%0 ppt
B-01 8.0 ft.ML Frozen Ss 60 56.3%0 ppt PI
B-01 14.0 ft.ML Frozen Ss 67 98.4%15.7%0 ppt OLI
B-01 18.5 ft.ML Frozen Ss 69 48.9%1 ppt
B-01 23.5 ft.ML Frozen Ss 76 49.8%1 ppt
B-01 28.0 ft.ML Frozen Ss 79 50.9%3 ppt
B-02 4.0 ft.OH
Marginally
Frozen Ss 10 78.8%0 ppt 0%20%80.0%PI
B-02 9.0 ft.ML Frozen Ss 70 29.9%0 ppt
B-02 14.0 ft.ML Frozen Ss 60 52.6%0 ppt
B-02 19.0 ft.ML Frozen Ss 88 26.7%0 ppt
B-03 4.0 ft.ML
Marginally
Frozen Ss 15 86.4%0 ppt
B-03 9.0 ft.ML Frozen Ss 37 41.5%0 ppt
B-03 14.0 ft.ML Frozen Ss 73 34.7%0 ppt
B-03 19.0 ft.ML Frozen Ss 89 29.5%0 ppt 0%6%94.0%
B-03 24.0 ft.ML Frozen Ss 48 34.7%2 ppt PI
B-03 29.0 ft.ML Frozen Ss 49 56.0%3 ppt
B-04 4.0 ft.ML Unfrozen Ss 14 27.2%0 ppt
B-04 9.0 ft.ML Frozen Ss 35 72.8%0 ppt
B-04 14.0 ft.ML Frozen Ss 41 65.6%0 ppt 0%11%89.4%
B-04 19.0 ft.ML Frozen Ss 47 27.9%0 ppt
B-04 24.0 ft.ML Frozen Ss 57 43.2%3 ppt
B-04 28.5 ft.ML Frozen Ss 204 42.8%3 ppt 0%6%94.4%PI
B-05 3.0 ft.ML Unfrozen Ag 57.8%7.3%2 ppt OLI
B-05 8.0 ft.ML Frozen Ag 60.9%3 ppt 0%25%75.2%PI
B-05 13.0 ft. ML Frozen Ag 66.2% 4 ppt
Duane Miller & Associates
Job No.: 4095.102
Date: April 2003
Arctic & Geotechnical Engineering PlateSITE MAP
Power Plant
Chefornak, Alaska 1
0 200 400 600
APPENDIX E
Pages from:
Golder Associates
GEOTECHNICAL SERVICES FOR
WASTEWATER LAGOON SITING,
CHEFORNAK, ALASKA
Dated July 2011
J:\2011 jobs\113-95619 ce2 chefornak lagoon\CAD\VICINITY MAP.dwg | 7/19/2011 4:47 PM | AGarrigus | Anchorage, AKSCALE0FEET4004001---- ----APG 7/19/11BBS 7/19/11RAM 7/19/110 ----FIG.113-95619VICINITY MAP.dwgCE2 / CHEFORNAK / AKSITE MAPCHEFORNAK LAGOONCHEFORNAK, AKCHECKREVIEWDESIGNCADDSCALEFILE No.PROJECT No.TITLEAS SHOWNREV.1. ORIGINAL BASEMAP PREPARED BY CE2ENGINEERS, INC. AND MODIFIED BY GOLDERASSOCIATES.REFERENCEPROJECTLOCATION
DESCRIPTIVE TERMINOLOGY FOR
PERCENTAGES (ASTM D 2488-00)
CU 6 AND 1 CC 3
CU < 6 AND/OR 1 > CC > 3
CLEAN SANDS
<5% FINES
SANDS AND FINES
>12% FINES
SANDS
HIGHLY ORGANIC SOILS
SILTS AND CLAYS
LIQUID LIMIT <50
SILTS AND CLAYS
LIQUID LIMIT 50
50% OF COARSE
FRACTION PASSES
ON NO 4. SIEVE
If soil contains 15% gravel, add"with gravel"VERY LOOSE
LOOSE
COMPACT
DENSE
VERY DENSE
VERY SOFT
SOFT
FIRM
STIFF
VERY STIFF
HARD
CONSISTENCY
0 - 2
2 - 4
4 - 8
8 - 15
15 - 30
OVER 30
0 - 0.25
0.25 - 0.50
0.50 - 1.0
1.0 - 2.0
2.0 - 4.0
OVER 4.0
RELATIVE DENSITY
0 - 4
4 - 10
10 - 30
30 - 50
OVER 50
COHESIONLESS SOILS (a)COHESIVE SOILS(b)
RELATIVE DENSITY / CONSISTENCY ESTIMATE
USING STANDARD PENETRATION TEST (SPT) VALUES
D 30( )
2
PRIMARILY ORGANIC MATTER, DARK IN COLOR, AND ORGANIC ODOR
SOIL GROUP NAMES & LEGEND
>50% OF COARSE
FRACTION RETAINED
ON NO 4. SIEVE
DPLASTICITY INDEX (PI)Figure
2SOIL CLASSIFICATION / LEGEND
LIBRARY-ANC(6-29-11).GLB [ANC_SOIL_LEGEND] 6/30/11Gravels or sands with 5% to 12% fines require dual symbols (GW-GM, GW-GC, GP-GM, GP-GC, SW-SM, SW-SC, SP-SM, SP-SC)
and add "with clay" or "with silt" to group name. If fines classify as CL-ML for GM or SM, use dual symbol GC-GM or SC-SM.
Optional Abbeviations: Lower case "s" after USCS group symbol
denotes either "sandy" or "with sand" and
"g" denotes either "gravelly" or "with gravel"
N1 (BLOWS/
FOOT)(c)N1 (BLOWS/
FOOT)(c)
UNCONFINED
COMPRESSIVE
STRENGTH (TSF)(d)
10D =
LL (oven dried)
LL (not dried)
ORGANIC CLAY OR SILT
(OH, OL) if:
(4 PI 7)
x
60
DC
60
PEATCOARSE-GRAINED SOILS>50% RETAINED ONNO. 200 SIEVEGRAVELS CLEAN GRAVELS
<5% FINES
GRAVELS WITH
FINES
>12% FINES
0
10
20
30
40
50
60
7
CC
10D=U
GW
GP
GM
GC
SW
SP
SM
SC
CL
ML
OL
CH
MH
OH
TRACE
FEW
LITTLE
SOME
MOSTLY
DESCRIPTIVE
TERMS
RANGE OF
PROPORTION
0 - 5%
5 - 10%
10 - 25%
30 - 45%
50 - 100%
LABORATORY TEST ABBREVIATIONS
C
TW
MS
GP
RC
AG
Core (Rock)
Thin Wall (Shelby Tube)
Modified Shelby
Geoprobe
Air Rotary Cuttings
Auger Cuttings
SS
SSO
HD
BD
CA
GS
SAMPLER ABBREVIATIONS
CRITERIA FOR DESCRIBING
MOISTURE CONDITION (ASTM D 2488-00)
SIZE RANGE
ABOVE 12 IN.
3 IN. TO 12 IN.
3 IN. TO NO. 4 (4.76 mm)
3 IN. TO 3/4 IN.
3/4 IN. TO NO. 4 (4.76 mm)
NO. 4 (4.76 mm) TO NO. 200 (0.074 mm)
NO. 4 (4.76 mm) TO NO. 10 (2.0 mm)
NO. 10 (2.0 mm) TO NO. 40 (0.42 mm)
NO. 40 (0.42 mm) TO NO. 200 (0.074 mm)
SMALLER THAN NO. 200 (0.074 mm)
0.074 mm TO 0.005 mm
LESS THAN 0.005 mm
SPT Sampler (2 in. OD, 140 lb hammer)
Oversize Split Spoon (2.5 in. OD, 140 lb typ.)
Heavy Duty Split Spoon (3 in. OD, 300/340 lb typ.)
Bulk Drive (4 in. OD, 300/340 lb hammer typ.)
Continous Core (Soil in Hollow-Stem Auger)
Grab Sample from Surface / Testpit
BOULDERS
COBBLES
GRAVEL
COARSE GRAVEL
FINE GRAVEL
SAND
COARSE SAND
MEDIUM SAND
FINE SAND
SILT AND CLAY
SILT
CLAY
COMPONENT DEFINITIONS BY GRADATION
COMPONENT
ABSENCE OF MOISTURE, DUSTY, DRY TO THE TOUCH
DAMP BUT NO VISIBLE WATER
VISIBLE FREE WATER, USUALLY SOIL IS BELOW
WATER TABLE
DRY
MOIST
WET
WELL-GRADED GRAVEL
POORLY GRADED GRAVEL
SILTY GRAVEL
CLAYEY GRAVEL
WELL-GRADED SAND
POORLY GRADED SAND
SILTY SAND
CLAYEY SAND
LEAN CLAY
SILT
ORGANIC CLAY OR SILT
FAT CLAY
ELASTIC SILT
ORGANIC CLAY OR SILT
4
MATERIAL
TYPES
FINE-GRAINED SOILS>50% PASSESNO. 200 SIEVELIQUID LIMIT (LL)
0 10 20 30 40 50 60 70 80 90 100
FINES CLASSIFY AS ML OR CL
FINES CLASSIFY AS CL OR CH
(PI > 7)
FINES CLASSIFY AS ML OR MH
FINES CLASSIFY AS CL OR CH
PT
GROUP
SYMBOL
If soil contains 15% sand, add"with sand"If soil contains coarse-grained soil from15% to 29%, add "with sand" or "withgravel" for whichever type is prominent,or for 30%, add "sandy" or "gravelly"PLASTICITY CHARTUNIFIED SOIL CLASSIFICATION (ASTM D 2487-00)
(a) Soils consisting of gravel, sand, and silt, either separately or in combination possessing no characteristics of
plasticity, and exhibiting drained behavior.
(b) Soils possessing the characteristics of plasticity, and exhibiting undrained behavior.
(c) Refer to ASTM D 1586-99 for a definition of N. Values shown are based on N values corrected for
overburden pressure (N1). N values may be affected by a number of factors including material size, depth,
drilling method, and borehole disturbance. N values are only an approximate guide for frozen soil or
cohesive soil.
(d) Undrained shear strength, su= 1/2 unconfined compression strength, Uc. Note that Torvane measures suand Pocket Penetrometer measures Uc
< 0.75
CRITERIA FOR ASSIGNING SOIL GROUP NAMES
AND GROUP SYMBOLS USING LABORATORY TESTS
(PI < 4)
Con
Comp
Dd
K
MA
NP
OLI
Consolidation
Proctor Compaction (D698/D1557)
Dry Density
Thermal Conductivity
Sieve and Hydrometer Analysis
Non-plastic
Organic Loss
Percent Fines (Silt & Clay)
Soil pH
Photoionization Detector
Modified Proctor
Pocket Penetrometer
Point Load
Sieve Analysis
P200
pH
PID
PM
PP
PTLD
SA
Specific Gravity
Thaw Consolidation/Strain
Torvane
Unconfined Compression
Liquid Limit (LL)
Plastic Limit (PL)
Soil Resistivity
SpG
TC
TV
TX
WC
WP(atorabove"A "line)ML
CL
MH
CH
CU 4 AND 1 CC 3
CU < 4 AND/OR 1 > CC > 3
CL-ML (LL < 50)(LL 50)"A "LIN E
(below "A "line)
Excess
ice
Well
bonded
Individual ice crystals
or inclusions
FROZEN SOIL CLASSIFICATION / LEGEND
LIBRARY-ANC(6-29-11).GLB [ANC_ICE_LEGEND] 6/30/11No ice-bonded soil observed
Poorly bonded or friable
Well bonded
ICE BONDING SYMBOLS
Figure
3
3. MODIFY SOIL
DESCRIPTION BY
DESCRIPTION OF
SUBSTANTIAL
ICE STRATA
2. MODIFY SOIL
DESCRIPTION BY
DESCRIPTION OF
FROZEN SOIL
1. DESCRIBE SOIL
INDEPENDENT
OF FROZEN STATE
DEFINITIONS
DESIGNATION
Nf
Nbn
Nbe
Vx
Vc
Vr
Vs
Vu
ICE+soil type
ICE
SUBGROUP
DESIGNATION
N
V
ICE
FROZEN SOIL CLASSIFICATION (ASTM D 4083-89)
TYPICAL USCS SOIL CLASSGENERAL SOIL TYPE
% FINER
THAN 0.02
mm BY
WEIGHT
(a) Gravels
Crushed stone
Crushed rock
(b) Sands
GW, GP
SW, SP
(a) Gravels
Crushed stone
Crushed rock
(b) Sands
GW, GP
SW, SP
PFS(4)
[MOA NFS]
S1
[MOA F1]Gravelly soils GW, GP GW-GM, GP-GM,
GW-GC, GP-GC
[MOA F2]
S2
[MOA F2]Sandy soils SW, SP SW-SM, SP-SM,
SW-SC, SP-SC
Gravelly soils GM, GC, GM-GC, GW-GM,
GP-GM, GW-GC, GP-GC
GW, GP GW-GM, GP-GM,
GW-GC, GP-GC(a) Gravelly soils
(b) Sands
FROST
GROUP(2)
1.5 to 3
3 to 10
3 to 6
3 to 6
6 to 10
10 to 20
6 to 15
F1
[MOA F1]
SM, SW-SM, SP-SM, SC,
SW-SC, SP-SC, SM-SC
(a) Gravelly soils
(b) Sands, except very fine silty sands
(c) Clays, PI>12
GM, GC, GM-GC
SM, SC, SM-SC
CL, CH
(a) Silts
(b) Very fine silty sands
(c) Clays, PI<12
ML, MH, ML-CL
SM, SC, SM-SC
CL, ML-CL
FROST DESIGN SOIL CLASSIFICATION (1)
--
Over 15
--
(d) Varved clays or other fine-
grained banded sediments --CL or CH layered with ML, MH,
ML-CL, SM, SC, or SM-SC
DESCRIPTION
MAJOR GROUP
Segregated
ice not
visible by eye
Segregated
ice visible by
eye (ice less
than 25 mm
thick)
F3
[MOA F3]
F4
[MOA F4]
Over 20
Over 15
--
Ice greater
than 25 mm
thick
DESCRIPTION
Poorly bonded
of friable
Ice without
soil inclusions
Ice with soil
inclusions
Uniformly
distributed ice
Stratified or distincltly
oriented ice formations
Random or irregularly
oriented ice formations
Ice coatings
on particles
CLASSIFY SOIL BY THE UNIFIED SOIL CLASSIFICATION SYSTEM
No excess
ice
Candled Ice is ice which has rotted or
otherwise formed into long columnar
crystals, very loosely bonded together.
Clear Ice is transparent and contains
only a moderate number of air bubbles.
Cloudy Ice is translucent, but essentially
sound and non-pervious
Friable denotes a condition in which
material is easily broken up under light to
moderate pressure.
Granular Ice is composed of coarse,
more or less equidimensional, ice
crystals weakly bonded together.
Ice Coatings on particles are discernible
layers of ice found on or below the larger
soil particles in a frozen soil mass. They
are sometimes associated with hoarfrost
crystals, which have grown into voids
produced by the freezing action.
Ice Crystal is a very small individual ice
particle visible in the face of a soil mass.
Crystals may be present alone or in a
combination with other ice formations.
Ice Lenses are lenticular ice formations
in soil occurring essentially parallel to
each other, generally normal to the
direction of heat loss and commonly in
repeated layers.
Ice Segregation is the growth of ice as
distinct lenses, layers, veins and masses
in soils, commonly but not always
oriented normal to direction of heat loss.
Massive Ice is a large mass of ice,
typically nearly pure and relatively
homogeneous.
Poorly-bonded signifies that the soil
particles are weakly held together by the
ice and that the frozen soil consequently
has poor resistance to chipping or
breaking.
Porous Ice contains numerous voids,
usually interconnected and usually
resulting from melting at air bubbles or
along crystal interfaces from presence of
salt or other materials in the water, or
from the freezing of saturated snow.
Though porous, the mass retains its
structural unity.
Thaw-Stable frozen soils do not, on
thawing, show loss of strength below
normal, long-time thawed values nor
produce detrimental settlement.
Thaw-Unstable frozen soils show on
thawing, significant loss of strength below
normal, long-time thawed values and/or
significant settlement, as a direct result of
the melting of the excess ice in the soil.
Well-Bonded signifies that the soil
particles are strongly held together by the
ice and that the frozen soil possesses
relatively high resistance to chipping or
breaking.
NFS(3)
[MOA NFS]
F2
[MOA F2]
(1) From U.S. Army Corps of Engineers (USACE), EM 1110-3-138, "Pavement Criteria for Seasonal Frost Conditions," April 1984
(2) USACE frost groups directly correspond to frost groups listed in Municipality of Anchorage (MOA) design criteria manual (DCM),
2007; except as noted.
(3) Non-frost susceptible
(4) Possibly frost susceptible, requires lab test for void ratio to determine frost design soil classification. Gravel with void ratio > 0.25
would be NFS; Gravel with void ratio < 0.25 would be S1; Sands with void ratio > 0.30 would be NFS; Sands with void ratio < 0.30
would be S2 or F2
0 to 1.5
0 to 3