HomeMy WebLinkAboutConstruction Specification Geo-Tech Report 2002-11-12
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GEOTECHNICAL INVESTIGATION
prepared for
FRONTIER lAND COMPANY, llC
for the
MOUNTAINGATE SUBDIVISION - PHASES 1 AND 2
SPRINGFIELD, OREGON
IEXPIRES: 12/310 T
November 12, 2002
Prepared by:
II SalRE ASSOCIATES INC. !
5160 SW Beals Avenue . Corvallis, OR 97333 . Tel: 541.753.5344 . Fax: 541.753.5347
.. SOlRE ASSOCIATEf'NC.
_II Geotechnical Engineering Solutions
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Soire Associates Inc.
5160 SW aeals Avenue
Corvallis, Oregon 97333
TEL 541.753.5344
FAX 541.753.5347
Norman McDougal
Frontier Land Company, LLC
PO Sox 518
Creswell, Oregon 97426
November 12, 2002
Re: Geotechnicallnvestigation
Mountain Gate Subdivision - Phases 1 and 2
Springfield, Oregon
Proiect 201.037
Dear Mr. McDougal:
As requested, Soire Associates Inc. has completed a geotechnical investigation for the
proposed Mountain Gate Subdivision project in Springfield; Oregon. This report provides a
description of our work, a discussion of site conditions, and recommendations for site
preparation, earthwork, area-wide drainage, and general home site development.
In general, our multiple investigations of the site (Phases 1 and 2) suggest complicated
.subsurface conditions are present within the development area. We have determined the site
should be suitable to support the planned development provided some special site preparations
. are included. Specifically, we have recommended the installation of horizontal trench drains
and placed restrictions of cutting and filling to mitigate potentially unstable terrain and expansive
soil conditions at the site. Individual lot development and home construction may require site-
specific work following mass grading, depending on individual building plans. Our broad-based
knowledge of the site indicates subsequent phases of development should be less restrictive.
We have reviewed a variety of documents prepared by the City of Springfield for conditional
approval of the project the including staff reports, hearing summaries, and other fact-finding
statements regarding the tentative plan application. We find our work is consistent with various
drainage and grading requirements required by the City to minimize instabilities at the site.
It has been a pleasure assisting you with this phase of the project. Please contact us at your
convenience with any questions.
Sincerely,
Soire Associates Inc.
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GEOTECHNICAL INVESTIGATION. MOUNTAIN GATE SUBDIVISION
TABLE OF CONTENTS
1.0 PROJECT INFORMATION ...,..,..........,..................,..........:........,....,.........,......................."..................1
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2.0 PREVIOUS' WORK".........:"..........................,.....,.......:....."..,,,,...........,..........""....."...:.....:....:..........., 1
3,0 OUR INVLOVEMENT "....................,,,,...........,..,,,,,..,,..,;.....................,.........................,......."..............2
4.0 SITE TOPOGRAPHY AND VEGETATION"..,........"..""...........,..,............................:..:.............".".....2
5.0 SUBSU RF ACE CONDITIONS ..,..,..............,...."....",...........,..,..,.."........................,..........."..............,,2
5.1 Genera I ........... ~...............,..........................................................................................................,....... 2
5.2 Soil Conditions..................................................................................................................... ..............3
5.2.1 Upper Areas .......................................................................... ........,............................. 3
5.2.2 Northern Entrance Area .............................................................................................. 4
5.3 Bedrock (Geology Review) .............................................................................................".................4
5.4 Groundwater........................................................................................................................ ..............5
5.5 Springs...,..............:..:.................................................................................................... .....................5
6.0 CONCLUSIONS AND RECOMMENDATIONS ..............................,...................,,,.........................,....,5
6.1 Genera I ........................................................................................................................:.......... ...........5
6.2 Subsurface Drainage (Horizontal Trench Drain Installation).............................................................6
6.3 Earthwork Recommendations (General Grading) .............................................................................7
6.3.1 Stripping .., ..,...................... ................................................. ...............:......................... 7
6.3.2 Temporary Cuts.........................................................................................................., 7
6.3.3 Permanent Cuts - Most Areas .................................................................................... 8
6.3.4 Permanent (Open) Cuts - Excepted Area................................................................... 8
6.3.5 Fills and Embankments (General)............................................................................... 8
6.3.6 Rock Removal..................................................".........,...............................................9
6.3.7 Wet Weather Construction ..................."...................,.,...",.........................................9
6.4 Roadway Development... .... ............................ ....... ........ ..........................,...... ................ ................1 0
6.4.1 General .... ................................................................................................................. 10
6.4.2 Drainage.................................................................................................................... 10
6.4.3 Embankment FiII- Special Condition..................................................................".... 10
6.4.4 Pavement Design ...................................................................................................... 11
6.5 Home Site Development..........................................................................:.......................................12
6.5.1 Phase I .................................................,....... ..........................................".,..........,.." 12
6.5.2 Phase 2 ..................................,.."..............................................................................14
6.6 Retaining Structures........................................................................................................................ 14
6.7 Util ities............................................................................................................................. ................. 14
6.7.1 Excavations ...................,............................................ ............................................... 14
6.7.2 Flow in trench backfill................................................................................................14
6.7.3 Waterline Extension .................... ............. ................................................................. 15
6.8 Erosion Control ................................................................................................................................15
8.0 SPECIFICATIONS .................,................................................."..."....................................................15
8.1 Material Definitions ..........................................................................................................................15
8.2 Placement and Compaction SpecifiCation (Subgrade, Fill, etc.)' ......................................................16
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9.0 LIMITATIONS AND USE OF THIS REPORT ......................................................;..............................16
Appendices A (Figures), B (Test pit logs), and C (Laboratory testing)
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1,0 PROJECT IN,FORMATlON
The proposed project consists of a new subdivision' located west of South 67'h'Street, south' of
Main Street, and east of South 581h Street. Legally; the subject property is described as Tax
Lots 303 (Map 18-02-03); 1100, 1101, 1102 (Map 17-02-34, 34); and 602 (Map 17-02-34, 43).
In its entirety, the project area includes approximately 330 acres. The completed development
would incorporate about 240 acres (800 units) for single and multi-family housing.
Housing developments would generally be located around the main peak that is characteristic of
the site and referred to herein in as "Potato Hill." The flat area comprising the north section of
the site (off Main Street) would be used as the primary siie access and to accommodate onsite
storm water detention/retention systems. The existing rock quarry at the southwest might be
reopened or abandoned and reclaimed for other uses. Remaining areas, which generally
comprise the steepest terrain within the central afld western portions of the site (i.e., the peak of
the hill), would consist of a park. Any wetlands would be mitigated on site or protected.
The first and second phases of the development (referred to herein as "Phase 1" and "Phase 2")
would be located on the generally north-facing slope of the property. Details provided to us
suggest Phases 1 and 2 would incorporate about 18 acres (42 lots) and 10 acres (29 lots),
respectively. Our investigations, conclusions, and recommendations provided herein relate.
primarily to the proposed Phase 1 and 2 developments. However, a broad-level examination of
the total property was also completed in order to describe general conditions within the entire
site area.
2.0 PREVIOUS WORK
Planning work on the project has been ongoing for the past 8 to 9 years, and since 1993 a
substantial amount of information has been developed for the site. With regard to soil-related
studies, we cite two reports ("Geotechnical Evaluations") prepared by Douglas A. Williamson,
RPG, CEG in 1993 and 1995, which were conducted to establish the overall geology and
related engineering-geology for the site. The engineering-geology reports provide a basic
description of the development area, including the overall topography and broad-based soil/rock
conditions that are present in the region. With regard to future development, the engineering-
geology reports ultimately state, "...there is no evidence of significant past slope movement."
In addition to the Williamson reports, we were provided with a report titled "Hillside Pavement
Distress Study" prepared by Dames & Moore in September 1994. That report discusses various
instabilities within two hillside developments in south Springfield area. This work is relevant to
the current project as one study area examined ("Study Area 1") included a portion of the
Mountain Gate site. The Dames & Report has also been referenced by the City of Springfield
on numerous occasions to establish basic design requirements and limitations for hillside
development. As practical, we have attempted to incorporate the City requirements into our
recommendations.
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3.0 OUR INVLOVEMENT
Boire Associates Inc. became involved with the' project in early August 2001- to provide
geotechnical engineering support services resulting .from early construction disturbances that
occurred on the property. At that time, our work was based on exposed soil are,as only and did
not involve any formal subsurface explorations at the site. Recently, our work scope was
expanded to include exploratory test pits and related testing in order to develop specific soil-
related design recommendations for the proposed Phase 1 and' 2 developments. As
appropriate, we have included discussions of the entire property to illustrate
similarities/differences for the general region.
4,0 SITE TOPOGRAPHY AND VEGETATION
In its entirety, the subject property is generally associated with a raised terrain feature known as
Potato Hill, which extends from a base elevation of about 510 ft to an elevation of almost 1200
ft. As shown on Figure 1, the topography within the property is extremely variable, ranging from
relatively flat grades at the far north to steeper slopes in excess of 65% at the higher elevations.
Intermediate slopes are present at the south and between the west ridge and main peak. Most
of the site is forested with a variety of conifer trees and deciduous hardwood species. The site
also contains brushy areas of undergrowth and grass-covered lands typical of open meadows.
In certain locations within the Phase 1 and 2 development areas, a notable feature that is
readily identifiable from the surface is the presence of many bowed, curved and/or leaning
trees. Similar features were noted on the east-facing slope of west saddle (outside the Phase I
or Phase 2 developments). Such characteristics often indicate soil instabilities are present,
although we did not observe any obvious scarps, tension cracks, sag ponds, hummocky terrain,
or other features within development areas that might suggest definable areas of soil movement
are present. Some indications of bowl-shaped slumps were noted within the upper portions of
the Phase 1 and 2 areas, but these features are not well defined. A more in depth discussion
relating to slope stability is provided below.
To date, we have not observed any indications of flow slides, or other rapid mass movements
that would involve a particular high risk with regard to development or life-safety, However, the
potential for flow slides should be examined as development proceeds along the east side of
Potato Hill where grades are generally steeper (beyond Phases 1 and 2).
5.0 SUBSURFACE CONDITIONS
5.1 General
A total of three visits were made to the site on February 18, 21, and March 28, 2002 to explore
conditions at the site and excavate a total of 39 exploratory test pits. Laboratory testing was
conducted on select samples to support this work and provide quantitative data regarding the
engineering characteristics of the soil: Detailed descriptions regarding the fieldwork and testing
procedures are attached. !
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5.2 Soil Conditions
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A broad-based exploration of the subsurface conditions within the project site was completed to
determine the general characteristics of the area. This section of the report details our findings.
We have primarily concentrated our discussion of site conditions to the Phase 1 ~nd 2 areas.
5.2.1 Upper Areas
Most areas of the site, including Phases 1 and 2, typically contain a random mixture of soil and
rock conditions at various depths. In general, subsurface conditions consist of a thin mantle
(about 2 ft) of low plasticity silt (ML) followed by a thicker layer of high plasticity, clayey silt (MH).
In some cases, especially within the main drainage area of Phase I, we encountered a 1 to 2 ft
thick seam of high plasticity clay soil immediately below the topsoil layer.
The most prev~lent soil type within the development is high plasticity, clayey silt. This material
is typically yellow-brown to rust-brown in color, moist, and has a fractured or blocky and
weathered appearance. The shallowest soil appears to represent colluvium that was likely
deposited from erosion and raveling (weathering) upslope. As profile depths increase, the high'
plasticity silt typically grades to a residual soil that has a relic structure, as if weathered in place
from the underlying rock. In some cases, the silt contains a substantial amount of sand,
pebbles, and gravel material.
Laboratory strength testing of undisturbed samples of the colluvial or weathered-in-place silt
could not be completed due to the presence of coarse-grained sand, pebbles, gravel, and
various other rock fragments. However, we did conduct several classification tests such as
Atterberg Limits (PI's) and water contents (WC's) to establish the overall engineering
characteristics of the various soil types at the site. The test results are summarized on
Figure C-1.
The testing indicates the high plasticity silt has high to very high plastic and liquid limits. This
suggests an "elastic" material that is relatively sensitive to disturbance. Changes in moisture
content are likely to have significant impact on the strength and compressibility properties. High
water contents also suggest the presence of tuff within the soirmatrix, which confirms the soil is
highly variable and originates from sedimentary and volcanic formations. Shear strength tests
conducted in the field indicates the soil exhibits relatively low residual shear strengths with a
relatively high shrink/swell potential.
Using existing slope angles, water levels, and other site factors, we used the field conditions to
back-calculate an angle of effective shearing resistance for the soil. Based on our testing and
analyses, we estimate the high plasticity silt is characterized by <p'-values ranging from 8' to
16'. These values are relatively low, but not atypical for MH soil types that exhibit low residual
shear strengths. A more detailed discussion of the soil strength conditions is included in
subsequent sections of this report.
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Our experience with this soil type as an "engineered material" indicates fair workability. Manual
remolding of the soil should produce a'stable and competent engineered fill, if compacted at the
proper water content and density. Specifically, we recommend compacting the soil near the
optimum moisture content with a kneading type of effort. The goal is to create a dispersed or
striated soil structure that has a higher density and increased strength. Such materials are less
susceptible to disturbance, shearing, and shrink/swell. We expect the engineering properties of
the remolded soil to be significantly better than native material due to the improved (dispersed)
soil structure that could be obtained.
5.2.2 Northern Entrance Area
Conditions within the flat part of the site to the north (i.e., the main entrance off Main Street) are
substantially different than discussed above. However. the subsurface conditions are much
more typical of those that would normally be encountered in the general Springfield area. That
is, we found this portion of the site typically contains about 5 to 6 ft of silt and clay soil over
shallow gravel.
Development plans provided to us indicate this portion of the site would contain the main
access road. The remainder of the areas would be dedicated to wetlands and/or construction of
storm water collection systems (i.e., storage ponds).
5.3 Bedrock (Geoloov Review)
Shallow bedrock was encountered over most of the site at depths often less than 10ft. In some
cases, the rock is as shallow as 1 to 3 ft and is very hard (i.e., that is practical refusal was
encountered with the hoe). In other cases, the rock is weathered such that excavations were
possible.
A main exception to the presence of shallow rock can be found within the general drainage
basins (i.e., broad, swallow swales) that comprise the central portions of the Phase 1 and
Phase 2 development areas. In these areas, the upper mantle of soil is at least 16 ft thick and
rock was generally not encountered within reach of the excavation equipment. However, based
on the interpolated subsurface geometry generated from the other test pits (see Figures A-2 and
A-3), we estimate the rock is probably not deeper than 20 ft in the worse case.
We reviewed geology studies previously completed for the site and find the rock. types
encountered follow the geologic descriptions relatively well. That is, the predominant rock
consists of weathered, sandy siltstone with varying degrees of hardness. Previous geologic
reports also described an underlying volcanic series (basalt), which we believe was
encountered at many locations. Where encountered, volcanic materials are extremely hard.
For reference, the rock type is similar in appearance and quality to. the material exposed in the
road cut at the north end of the site and in the quarry at the southwest. The published geology
suggests the basalt rock represents a'n intrusive igneous ridge.
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5.4 Groundwater
Subsurface seepage was encountered in several of the exploratory test pits. With regard to the
Phase 1 and 2 development areas, the most significant points of subsurface water were found
within two general drainages that are relatively poorly defined. Seepage was most prevalent in
the Phase 1 drainage basin, where shallow/rapid infiltration occurred in several'of the test pits.
Where subsurface water was extensive, we noted the soil above the rock to be saturated and
very sensitive to disturbance. In some cases, caving of the test pit sidewalls occurred.
Subsurface seepage within the general drainage area of Phase 2, where encountered, tends to
be perched on the surface of the underlying rock layer. We did not typically find elevated water
conditions within the soil column; however, we did observe water levels rise within the test pits
after penetrating the phreatic surface. This suggests the water is confined under a piezometric
(pressure) head,
5.5 Sorinas
We noted discrete springs at random locations on the property within the Phase 1 and Phase 2
development areas. The most significant area of surface springs is located on the slight ridge
that generally represents the future alignment of Mountain Gate Drive. Test pit TP-24 was dug
in a suspected spring area where water was emanating from the ground surface. We found the
water to be perched on a layer of shallow and hard, impenetrable rock.
Based on the topography and subsurface conditions encountered, it appears these "springs"
originate from runoff upslope that has infiltrated the ground and perched on layers of less
pervious soil. The presence of this water should not preclude development in our opinion, but
does suggest the need for additional site drainage as part of development.
6.0 CONCLUSIONS AND RECOMMENDATIONS
6.1 General
We have concluded site conditions are relatively complex due to a variety of colluvial and
residual soils present, which have weathered from rock types of differing origins. Most
significantly, the prevalent soil type in the development areas consists of high plasticity silt,
which has relatively high natural water contents, liquid limits, and maintains a blocky
appearance with water contained within soil fractures. We typically observed the high plasticity
silt maintains a relic rock structure and/or a "jumbled" appearance. This could relate solely from
the mode of deposition, previous weathering, or from past shearing and/or shrink-swell.
In many test pits, we encountered lenses of discoloration and/or disturbance that could suggest
previous soil shear has occurred. We attempted to relate possible subsurface shearing planes
to indications of ground surface movement, but could not make any direct correlations. That is,
aside from leaning and bowed trees, we did not find any observable tension cracks, sag ponds,
or discrete areas of hummocky terrain that might suggest definable areas ,of mass movements
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are present. We did note the general. drainage areas within the Phase 1 and Phase 2 contain
bowl-shaped formations onthe upper portions; however, no traditional slumps, grobins, or block
failures' were observed. Our surface reconnaissance' included stereoscopic examinations of
aerial photographs to identify possible areas of large-scale mass movement.
Based on the terrain and subsurface conditions encountered, we believe the greatest potential
for slope instability. within the Phase 1 and 2 development areas results from continued soil
creep. If present, this relatively slow advancement of soil down slope is likely being driven by
poor drainage, sensitive soil conditions, and an underlying sloping rock surface.
We developed several cross-sections for the slope (see Figures A-2 and A-3) to depict the
average subsurface conditions apparent with the main development areas. As shown, when the
section is drawn to scale it becomes apparent the slopes are relatively flat and the profile
contains an ur.1derlying rock surface that approximately parallels the ground surface. Within the
main drainages, water is typically present at the surface of the rock or slightly higher. Based on
the conditions shown, it is unlikely deep rotational instabilities 'are adversely affecting the site.
We modeled the stability of the ground conditions depicted on Figures A-2 and A-3 using an
infinite-type slope method, and the soil parameters and effective stress conditions established
for the site. Our general approach involved establishing a baseline by assuming soil creep is
occurring (or has occurred) such that slopes are presently slightly unstable with a safety factor
of 0.95 to 1.0. That is, the safety factor (or factor of safety) is defined as the ratio of the forces
resisting soil movement to those forces driving soil movement. A safety factor less than 1.0
indicates some amount of instability is present, while a safety factor greater than 1.0 implies a
more stable condition has been achieved.
Soil strength parameters were assigned based on the soil classification tests and the back-
calculation procedures described. We made subsequent changes to the slope model to
evaluate how the installation of drainage could improve sliding resistances and overall slope
stability. Specifically, we assumed horizontal drainage would be installed such that the average
water level at the soil-rock interface (i.e., the assumed slip plane) would be reduced by 4 ft
(about 250 psf). Our analysis indicates this simple drainage would increase the factor of safety
against sliding to about 1.25 (a stability increase of about 30%).
6.2 Subsurface Drainaae (Horizontal Trench Drain Installation'.
With regard to the Phase 1 and Phase 2 developments, we have determined drainage is critical
to maintaining, and improving slope stability in both areas. This conclusion is consistent with
previous studies conducted by other consultants and other requirements implemented by the
City. Specifically, we recommend installing a series of horizontal trench-drains that extend
upslope in order to provide relief for confined subsurface runoff. Our investigation and
subsequent analyses indicate the most critical areas requiring drainage are the generalized
draws or central portions of the two development areas. "
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The intent of the drainage is to prevent excess water and pore-water pressures from developing
within the soil column and/or at the contact between the soil and rock. Figure A-4 shows the
recommended trench locations, select depths, and a typical section. These trenches would be
a permanent installation and not necessarily serviceable. We have established their locations in
utility easements and other future development areas to minimize tree removal and required
ground disturbances. We also attempted to avoid trenching parallel to slope contours, which
could introduce other instability issues. The recommended locations have been incorporated
into the civil plans.
The depths of the horizontal trench-drains may vary depending on the actual subsurface
conditions encountered. In general, we recommend all trenches extend to the surface of the
rock to penetrate.any water that is perched or confined at the soil-rock interface. Trenches for
the draiQs should be excavated in a clean manner and lined with a Drainage Geotextile if
sloughing 'or r<lveling becomes problematic. A Drain Pipe (graded to transmit water down slope)
should be set in ihe bottom of the trench and the remaining volume backfilled with Drain Rock to
within 3 or 4 ft of the ground surface. The upper portion of the trenches in pavement areas
should consist of Fine Granu/ar Fill. Other areas may contain topsoil, as needed for
landscaping. A typical detail is shown in Figure A-4.
We assume the horizontal trench-drains would daylight at the approximate locations shown on
Figure A-4. Specific details are shown on the civil plans. We recommend an extra (solid) pipe
be run in all of the trenches to provide a disposal option for discharging future drainage from
other structures such as retaining walls, roofs, and/or or foundations. If used, we recommend
extra pipes be identified with riser stub-outs, or green tracer wires. We encourage installing the
horizontal trench drains before any other site improvements are made.
6.3 Earthwork Recommendations (General Gradina\
6.3.1 Stripping
Generally, it should be expected that at least 12 inches of stripping would be required in most
development areas to remove the organic topsoil. This depth could increase within the main
drainage areas to as much as 24 inches where thicker deposits of organic materials and/or high
plasticity clay might be present. Stripping and/or over-excavation depths might be less where
shallow rock is present.
6.3.2 Temporary Cuts
Temporary cuts should only be made to accommodate future retaining structures. Any
excavations that are required should be made during the dry season and not left exposed for
longer than one month. We should be contacted in the event temporary cuts exceed 6 ft to
verify the adequacy of our recommendations.
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6.3.3 Permanent Cut~ - Most Areas
Preliminary grading plans provided to us indicate a permanent cuts would be 'required at the
northern portion of a private loop road and at the sQuthwest corner of Forest Loop. At these
locations cut on the order of 6 ft are expected in order to establish an adequate vertical
alignment for the road. Even though the cuts are relatively minor, we do not recommend
allowing any permanent unsupported slopes within the main portions of the Phase 1 or 2
development areas. to avoid creating a loss of soil support. Therefore, retaining structures
would be needed - see Section 6.6. Rock exposures may be an exception.
6.3.4 Permanent (Open) Cuts - Excepted Area
An exception to the requirement for retaining structures involves the rock cut exposed along the
entrance section of Mountain Gate Drive, which proceeds up the north slope (see Figure A-3).
In this case, open cuts would be a'lIowed. In fact, where hard rock is exposed, relatively steep
slope angles of 1 (horizontal) to 6 (vertical) are recommended to control erosion and rockfall.
Provisions to mitigate any subsurface water that might be encountered, and/or protect cuts from
erosion after exposure would have to be developed during construction. Note however, rock is
not present near the bottom of the entrance road.
6.3.5 Fills and Embankments (General)
The City has expressed concerns regarding fill placement and embankment construction over
soils with a Plasticity Index (PI) greater than 30. In this regard, we tested a total of six soil
samples obtained from the site at various locations and depths. Three of these samples
showed PI's greater than 30; however two of the samples (S-3-1 and S-30-3) were only slightly
over the established limit. Sample S-12-1 had a PI of 61, which is significantly greater than 30.
With regard to placement of fill on top of plastic soils, we are not especially concerned with
shrink or swell of underlying materials, as the fill would provide additional cover and
confinement. A greater concern is identifying shallow areas of potentially expansive soil that
might affect building foundations.
We have examined most of the "typical" soils at the site and have determined the organic topsoil
and underlying plastic clay soil (where present) are not well suited for use as fill, or to support
new fills. Our examination of the high plasticity silts typically found below the upper soil mantle
indicates this material is not ideal for the support of new fills, or for reuse as structural fill.
However, we believe the silt could be made adequate if processed in the manner prescribed
herein. Other rock materials from the site would likely create good-quality fills.
As for fill support, our analyses indicate limited filling (i.e., less than 6 ft) should have negligible
impact on overall stability of existing slopes, if areas are prepared properly prior to fill
placement. In fact, some fill areas could actually show an increase in overall stability, if normal
(resisting) forces increase at a greater rate than the opposing driving forces. This is due to the
fact both ground surface and underlying rock layers generally slope at relatiyely shallow angles.
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The following re,commendations have been developed as a broad-based set of guidelines to aid
in general fill construction: Construction of the filled embankment fill for the main entrance road
is a special case.
1. Do not build any fills in excess of 6 ft without specific approval from us. All fill areas
should be clearly identified on the grading plans for review. Waste materials from
excavations should only be disposed of in approved areas designated in the field. This
includes temporary and permanent materials.
2. Assume the upper topsoil and any underlying plastic clays would not be adequate to
support new fills. These materials should be stripped from all fill areas and are not
suitable for reuse as fill.
3. After stripping, create flat benches that are at least 4 ft wide to accept new fill. Each
benched surface should be thoroughly aerated, moistened, and compacted to a
minimum depth of 12 inches and to at least 95% relative compaction (ASTM D1557).
4. Assume the high plasticity silt, weathered rock, and rock materials would be acceptable
for reuse as general fill for minor grading within the Phase 1 and 2 development areas.
If used, this material should be compacted to 95% relative compaction according to
ASTM D1557. All soil should be compacted within :t2% of the optimum water content
using a sheepsfoot or padfootlype of roller.
5. Placed the remolded silt no steeper than 2 (horizontal) to 1 (vertical).
6. Contact us prior to building structures on any fill.
7. Refer to Section 6.4 for the larger embankment fill that will be required for the main
Mountain Gate entrance road.
6.3.6 Rock Remova/
We encountered "hard rock" at several locations within the Phase 1 and 2 development areas,
as well as at various other locations at the site. Contractors should expect utility excavations
could be difficult in some areas. We recommend referring to the test pit logs for actual depths
of rock and comments regarding excavation difficulty at the exploratory locations. In general,
we attempted to account for the presence of hard rock when specifying the depths and locations
of the horizontal trench drains. Trench drain depths may be adjusted in the field to
accommodate varying and/or unanticipated rock elevations.
6.3.7 Wet Weather Construction
During wet weather, we expect the mostly fine-grained native soils and the sloping topography
(which promotes runoff toward the site), could contribute to wet and sensitive site conditions.
Grading of native soils would be difficult and Subgrade compaction would likely not be possible.
As a result, stripping and/or over-excavation depths are likely to increase to remove wet and
soft materials that cannot be ae'rated and re-compacted. Therefore, for imass grading, road
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No.vember 12, 2002
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construction, and utility installafion during .wet weather construction is discouraged. Actual
home construction ~ould likely occur during wet weather, depending on the a.bility house
contractors to prepared specific lots and foundation area's.
6.4 Roadwav Develooment
6.4.1 General
With regard to general Subgrade preparation, and placement and compaction of the aggregate
base, we recommend the work be completed in accordance with the specifications provided
below. Coarse Granular Fill is preferred where bulk aggregate fills are needed.
6.4.2 Drainage
We have reviewed several documents that specify trench-drains be used in cut areas (on the
uphill side of (oads) to intercept subsurface water that could contribute to premature failures
within pavement areas. However, we have already recommended fairly extensive drainage and
many cut slopes would be retained with rock-fill buttresses that are also drained. In addition, we
understand individual residences would be required to tight-line roof, foundation, and yard
drainage directly to the storm drains. Therefore, uphill roadside drains do not appear needed in
cut areas. In the event such drainage is still required, we recommend their use be directed to
specific areas of concentrated runoff, rather than applying the drainage on a regional basis.
This recommendation is consistent with the Dames & Moore report.
We also caution that continual trenching parallel to slope contours has the potential of creating
artificial tension cracks, which could affect existing slope stability. As a result, we would
suggest limiting the installation of noncontiguous pavement trench-drains to specific areas
where springs are likely to occur. If possible, we would also recommend allowing the developer
to combine pavement trench-drains with other utilities to minimize subsurface disturbances.
~.4.3 Embankment Fill - Special Condition
Grading plans provided to us indicate a significant embankment fill 'would be required at the
northern end of the development to establish the entrance portion of Mountain Gate Drive,
which extends up the slope. Explorations in this area encountered a variety of materials ranging
from plastic silt to hard rock. The lower grades at the base of the slope contain softer silts and
clays underlain gravel at about 9 ft. A significant amount of subsurface water is presentin the
area.
Our greatest concern with regard to embankment construction is not stability of the actual fill,
but rather adequacy of support at the base. Specifically, weak/compressible soils, inadequate
ground surface preparation, and improper filling techniques could create problems with regard
to fill settlement and/or bearing capacity. To mitigate any such concerns, we recommend the
following for embankment construction:
Mountain Gate Subdivision
Geotechnical Investigation
10
Project 201.037
November 12. 2002
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1. Clear the area that will suppo(t the future embankment of any vegetation and debris. .
This includes existing fill that has been deposited on the slope. Dispose of all stripped
materials away from the construction area. Any materials that qualify' as .Coarse
Granular Fill (see Section 8.1) should be stockpiled for potential reuse.
2. Construct a minimum of three intermediate benches or terraces on the slope to receive
new fill. The benches/terraces may be located as is convenient, but should have a
minimum width of 4 ft. Bench widths may be adjusted where hard rock is exposed. The
main goal is to create a roughened surface to promote positive contact between the
existing slope and any new fill.
3. Over-excavate the base of the slope as necessary to remove any thicker organic
materials. It should be assumed that excavations below 2 ft could encounter
groundwater. Consequently, contractors should 'expect initial preparations might involve
stabilization of native soils that are wet and soft.
4. Do not compact the native soil. Place an initial lift of about 18 inches of Drain Rock to
create a stable working surface and seat this material using 4 to 6 passes of a D-4 or
other tracked equipment of a similar mass.
5. Construct the remaining embankment using Buttress Fill. Mixed combinations of
Buttress Fill, Coarse Granular Fill, and Drain Rock may also be used. All materials
should be placed and compacted (or seated) as recommended.
6. Assume the new rock-filled embankment could be constructed at a slope of 1.5
(horizontal) to 1 (vertical). Erosion protection is not required for the final surface.
7. Delay paving for at least two weeks following embankment construction to allow any
settlement to occur. Elevation hubs can be used to monitor settlement of the fill if
needed.
6.4.4 Pavement Design
We understand the City of Springfield specifies a standard pavement section of 4 inches of
asphalt over 12 inches of aggregate base, which was used by the civil engineer to design road
surfaces. Based on our investigation of the site, we did not encounter any particularly unusual
or atypical conditions for the area that would warrant special considerations. Therefore, the
standard pavement section should be adequate. However, it is extremely difficult to verify the
adequacy of this pavement section since native soil/rock conditions vary extensively; the
Subgrade will consist of new cuts and/or fills in some areas; build-out will occur incrementally;
and traffic volumes are not known (specifically trucks and construction vehicles). Our best
recommendation is that our guidelines for "Roadway Development" be followed accurately. A
reduction in the pavement section might be warranted in certain areas if hard rock is exposed at
the Subgrade level.
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Geotechnical Investigation
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Project 201.031'
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6.5 Home Site Develooment
The proposed lot locations, as provided to us, are sl:lOwn on Figure A-1. However, actual
"building envelopes" were not known. We expect actual home site locations would be
dependent on final street grades, as well as the actual structure selection (i.e., size, type,
configuration, etc.). Due to the variety of soil conditions encountered, foundation design
between lots could vary. We expect foundation construction on many lots to be relatively
straightforward, as shallow rock is exposed. On other lots, site-specific geotechnical work may
be required to identify and mitigate potentially soft, unstable, and/or expansive soil conditions.
Our primary concern is that homebuilders adhere to the recommendations provided herein
regarding cuts, fills and drainage. In that regard, we understand covenants and restrictions
have been developed to control building. Specific considerations should be placed to ensure
uncontrolled grading does not adversely impact specific lots, neighboring properties,. or the site
in general. Future builders should be aware foundations and slabs might require site-specific
designs. With regard to foundation conditions within the Phase 1 and 2 development areas, we
have summarized the foundation conditions that are most likely to be present in the various lot
areas. These comments have been incorporated into the "Hillside Grading Report" to depict
general allowable building envelopes. Note however, geotechnical conditions could vary greatly
and should be verified during construction.
6.5.1 Phase I
. Lots 1,through 3 - We expect foundation excavations on these lots to encounter high
plasticity soil. Suspicious topography (i.e., an indication of unstable terrain) is present
between Lots 2 and 3, which also extends north through the middle of Lot 1.
Development should be restricted to the northern one-third of Lot 1 (below the base of
the slope), and within the southern half of Lots 2 and 3. Some over-excavation and
replacement might be required to mitigate potentially unstable soils. Lot 1 shows
evidence of soil with slick-en-sides at the south, which might indicate soil creep and/or
shrink-swell. Within the northern portion of Lot 1 (at the base of the slope), we found
deposits of organic silt above the gravel layer that could be compressible. Site-specific
geotechnical work would be required prior to house construction.
. Lots 4 through 6 - We expect buildings on these lots would encounter high plasticity silt
followed by relatively shallow (hard) rock. Development would likely be most practical at
the southern limits of the lots. Conventional foundations are anticipated.
. Lots 7 through 10 - We expect building excavations on these lots would encounter high
plasticity silt followed by relatively hard rock at medium depths. Development should be
limited to the south half of the lots, as conditions could become unstable near the
northern ends. Some over-excavation and replacement might be required to mitigate
potentially unstable soils. We recommend avoiding earthwork within the northern one-
third of Lot 9.
;
,
Mountain Gate Subdivision
Geotechnical Investigation
12
Project 201.037
November 12. 2002
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. Lots 11, through 17 - We expect excavations on these lots would encounter high
plasticity silt followed by relatively shallow, hard rock at medium depths, ~evelopmen't
should be limited to the southeastern one:half of the lots, as conditions could become
unstable to the northwest (i.e. farther down slope where the upper soil mantle is thicker).
Some over-excavation and replacement might be required to mitigate potentially
unstable soils. However, foundations should be relatively conventional.
. Lots 18 through 20 - We expect excavations on these lots would encounter high
plasticity silt followed by highly weathered rock. "Hard rock" is not expected.
Foundation systems should be conventional, but may require limited over-excavation
and replacement to extend below unstable terrain.
. Lots 21 through 27 - Foundation conditions could vary extensively. Development at the
west could encounter rock at shallow depths; however, deeper soil deposits might also
be pre:;ent. Conditions could deteriorate to the east where organic materials, high
plasticity clay, expansive silt, and high ground water conditions were found.
Development on these lots should require site-specific' evaluation to properly identify and
mitigate potentially sensitive foundation conditions.
. Lots 28 and 29 - Foundation conditions could vary extensively. Development at the
north might encounter high plasticity soils followed by hard rock or weathered rock at
shallow depths. Foundation conditions will likely become more complicated to the south
where deeper deposits of organic material, high plasticity clay, expansive silt, and/or
unstable soils could be present. Site-specific evaluation might be needed.
. Lots 32 and 33 - Foundation conditions are not well defined but would likely encounter
high plasticity soil followed by weathered rock. Building sites would have to be
evaluated on a case-by-case basis. We expect some amount over-excavation and
replacement may be necessary to mitigate unstable terrain near the surface. Special
building systems might also be necessary such as rigid mats and/or deep foundations.
. Lots 30, 31, and 34 through 39 - Foundation conditions could vary extensively. Special
foundations might be necessary' to mitigate unstable terrain. The worst areas appear to
include Lots 30, and 34 through 39. In these areas, soft soils or other unsuitable
foundation conditions might be present. Buildings on these lots would require site-
specific evaluation.
. Lots 40 through 42 - Foundation conditions are not well defined, but would. likely
encounter high plasticity soils followed by weathered rock. Building sites would have to
be evaluated on a case-by-case basis. We expect some amount over-excavation and
replacement may be necessary to mitigate unstable terrain near the surface.
Development would likely be most practical near the southern one-half of the lots where
the terrain is less steep. Special foundations could be necessary if local slope
instabilities are found. Buildings on these lots would require site-specific evaluation.
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Mountain Gate Subdivision
Geotechnical Investigation
13
Project 201.037
No'vember 12, 2002
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6.5.2 Phase 2
. Lots 43 through 46 - We expect building excavations on these lots '!o encounter a
thin mantle of soil followed by relatively. shallow (hard) rock. Conventional (i.e.,
normal) foundations should be adequate under most circumstances: Development
should be limited to the southern two-thirds of the lots where shallow rock was found.
A large-scale instability might be present immediately north of the lots (off the
property). Construction near this area should be avoided.
. Lots 47 through 60, 63 through 65, 70, and 71 - We expect buildings on these lots
would encounter high plasticity silt followed by highly weathered rock. "Hard rock" is
not expected. Foundation systems might have to be made rigid, or extend
sufficiently deep to bypass potentially unstable soil. Buildings on these lots would
require site-specific evaluation.
. Lots 61, 62 and 66 through 69 - We expect buildings on these lots would encounter
high plasticity silt. Weathered rock and/or hard rock are not expected. Foundation
systems might have to be made rigid, or extend sufficiently deep to bypass
potentially unstable soil. Site-specific evaluation is recommended.
6.6 Retainina Structures
As previously discussed, we recommend all cuts be properly retained. Throughout the course
of the project, we have discussed various options for cut retention including concrete retaining
walls, rockeries, and the use of rock-fill buttresses. Ultimately, the design team elected to
retain/stabilize new cuts using rock-fill buttresses (or in-lays) because these structures can be
modified after installation to allow greater flexibility in establishing private driveways. The rock-
fill would also be naturally drained and could better accommodate limited slope creep. Specific
details are shown in the construction plans.
6.7 Utilities
6.7.1 Excavations
Conditions encountered in trench excavations for utilities are likely to vary extensively within the
development areas. That is, excavations in some case could encounter hard rock, while other
locations might expose weak or unstable soils with shallow subsurface infiltration. In general,
contractors should be prepared to accommodate a variety of subsurface conditions. All
excavations should be made/shored in accordance with OSHA guidelines.
6.7.2 F/ow in trench backfil/
The City has raised concerns with regard to subsurface flow in trench backfill for utilities
extending down slopes. Specifically, the concern is that flow and seepage pressures could
develop in the zone between the pipe and surrounding backfill. Extensive flow and pressure
could create piping and possibly blowout of the trench backfill at down slope locations if
significant water pressures develop. /
Mountain Gate Subdivision
Geotechnical Investigation
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Projec1201.037
November 12. 2002
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There are many acceptable ways to mitigate water flow in backfill. In this case, we believe the
most economical approach would likely be to include a Drain Pipe in each utility trench (near thEi
utility line) that is surrounded by about 24 inches of Drain Rock and separated from the
remaining backfill with a Drainage GeotextJ/e. The Drain Pipe should be designed to
accumulate, carry, and discharge water to an appropriate disposal system. Other options might
include cut-off dams or other trench barriers.
6.7.3 Waterline Extension
Part of the utility improvements will include a waterline extension along Park Drive to tap an
existing source currently stubbed at the end of South 671h Street. We suggest minimum
requirements made herein for all utilities apply to permanent and temporary sections of that line
extension as well.' Other details are discussed in the "Hillside Grading Report."
6.8 Erosion Control
We have not included any recommendations regarding erosion control as a significant amount
of details have already been developed for this subject. Based on our most current knowledge
of existing materials at the site, we have concluded the soils most susceptible to erosion are
located within the upper 1 to 3 ft of the soil profile. However, we expect overall transport rates
and sediment outfall distances to be relatively limited. The erosion potential of deeper soil and
rock layers is expected to be relatively low. Past erosion control measures have been very
effective. The erosion control specialist is specifically responsible for these considerations.
8.0 SPECIFICATIONS
8.1 Material Definitions
The following are general descriptions and definitions for materials that have been used within
this report. Unless otherwise specified, all materials should conform to Oregon Department of
Transportation (ODOT) specifications for gradation and quality.
. Fine Granular Fill should consist of 1 Yo to '!I.-inch minus, well-graded, clean, hard, angular,
crushed rock with less than 5% material passing the No. 200 sieve.
. Coarse Granular Fill should consist of 6 to 3-inch minus, well-graded, clean, hard, angular
crushed rock with less than 5% material passing the No. 200 sieve. Material generated from
the onsite pit may be adequate if it is properly graded.
. Drain Rock should consist of 2 to 3-inch, open-graded, clean, hard, free-draining, angular
quarry rock. Material generated onsite pit would be adequate if it is open-graded and clean.
. Buttress Fill should consist of 2 to 8-inch, clean, hard, angular, quarry rock. We expect
material generated from the on site pit would be adequate.
. Native Structural Fill refers to on-site soil/rock that is approved by us for reuse in building
and pavement areas. Strippings, organic topsoil, and plastic clays above a depth of about 2
to 3 ft would not be considered appropriate native materials acceptable tor reuse.
Mountain Gate Subdivision
Geotechnical Investigation
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Projec1201.037
November 12, 2002
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. Subgrade refers to the native' grade after stripping (compacted) that would receive fill.
. Drainage Geotextile refers to a non-woven Amoco 4.545 fabric. An alternate' geotextile type
may be substituted if deemed comparable and approved by us.
. Drain Pipe refers to a 6-inch diameter perforated or slotted pipe that has a rigid section and
is of a sufficient thickness to resist crushing.
.8.2 Placement and Comoaction Soecification lSuborade. Fill. etc.)
The following recommendations are provided as general specification for earthwork.
. Strip/remove all organic topsoil in development areas as described in Section 3.2.1.
. Compact all Subgrade prior to placing new site fill, slabs, or pavements. The Subgrade
should be compacted to 95% relative compaction according to ASTM D698. Subgrade
compactiol] will likely not be possible when soil moisture contents exceed optimum levels.
In this case, some over-excavation and replacement may be necessary. Hard rock, if
exposed at the Subgrade level, need not be compacted. .
. Place all Fine and Coarse Granular Fill in maximum 12-inch loose lifts and compact to 95%
relative compaction according to ASTM D698. Material used as retaining wall backfill
should be compacted using hand-operated equipment only within 5 ft of any wall face.
. Place Drain Rock and Buttress Fill in maximum 18-inch loose lifts and compact (vibrate or
seat) using vibratory or tamping equipment. For materials that are mostly open-graded, a
dozer should be sufficiently to adequately seat the material.
. Place Native Structural Fill (as approved for general grading and reuse as structural fill
under buildings and pavements), in maximum 8-inch loose lifts and compact to 98% relative
compaction (ASTM D698) within :1:2% of the optimum water content. Adequate and efficient
compaction would require a sheepsfoot or padfoot roller.
. Provide density testing from a testing company approved by the geotechnical engineer. The
adequacy of compaction of material that is too variable or coarse for testing (i.e. native
material) will have to be evaluated by the geotechnical engineer in the field. The
geotechnical engineer should establish the frequency of material testing.
9,0 LIMITATIONS AND USE OF THIS REPORT
This report has been prepared for the exclusive use of the Frontier Land Company and their
design consultants for the proposed Mountain Gate subdivision project in Springfield, Oregon.
Information contained herein should not be construed as a warranty or guaranty of site or
subsurface conditions. Our explorations indicate soil conditions only at specific locations and
only to the depths penetrated. They do not necessarily reflect soil strata or water level
variations that may exist between or beyond exploration locations or limits. Soil and
groundwater conditions at other locations or times may differ. .
Mountain Gate Subdivision
Geotechnical Investigation
16
Project 201.037'
November 12, 2002
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Contractors using this report for bidqing or quantity estimates, or to determine construction
difficulties, do. so at their own risk. Homebuildersusing this information to plan foundation'
systems should realize subsurface conditions could vary from those described in Section 6.5.
The scope of our services does not include services related to construction safety precautions,
techniques, sequences or procedures, except as specifically described in our report for
consideration in design. Our work, at the time this report was prepared, have been conducted
in accordance with generally accepted principles and practices. No warranty or other
conditions, expressed or implied, is made.
I
I
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Mountain Gate Subdivision
Geotechnical Investigation
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Project 201.037
November 12, 2002
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APPENDIX A
(Figures)
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11.17 PLOTS AU ttALf<<ALE
NOTES:
I. TEST PrT LOCATJ::lfr(S ARf APPROXIMATE.
2.5 -INDICATES TEST P!T lOCATOl.
1. STREET lOCA~S DEPICTED ON nlls MAP lUt.Y Be OIFFERfNT
I'ROIII THOS! SHOIoH CN THE FNAL ......T.
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FIGURE 1<<).
"
MOUNTAGA TE SUBD/V/SION - PHASE 1 AND 2
SPR/NGFIELD, OREGON
TEST PIT LOCATIONS A-1
. (ENTIRE S/TE AREA)
,
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.
.
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.
~:I'.IO'FORD-SiEET
11.17PLOT'&AAEHALF...scAlE
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HOTES:
1. TEST PlTLOCAl'lOMSAltEAPPItOlUMAT!.
2.1!IiI.~D'CATESTEST PIT LOCATlCt"
3. IIT1tIEfT...O LOT L0CA1"ICN$ OEPlCTED a4 THIS MAP MAY Ie
OIfFfftEHT FROM Tl40SE SHOMI CN 1l1! FNAL PlAT.
".IEE SHEET A-3 FOR SECn:lN DUALS.
PHASE 1:
LOTS (0-@
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FIGURE t<<:l.
STP-10
MOUNT AGA TE SUBDIV/S/ON - PHASE 1 AND 2
SPR/NGF/ELD, OREGON
PLAN INFORMA TlON
(PHASES 1 AND 2)
A-2
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WA'EO
SECTION C ' C'
SCALf: t'_4O'
HaTES:
I.SECTlClI\I LOCAnc::NSARE SHOw"otoI CH SHEETA-2.
2. NOMJDAL OlU.1IVtIG SCAlES VARY.
3.11117 PlaTS ARE HALF..sIZED.
.
OOO<JNO
SUIlFACE
WATER
SECTION B, B'
SCA1.E:I"_<<r
C'
......0
SURFACE '"
....
MOUNT AGA TE SUBDIVIS/ON - PHASE 1 AND 2
SPRINGFIELD, OREGON
I""'" I
.
-
CROSS-SECTIONS
A - A', B - B', C - C'
"
B'
-
FIGURE hO.
A..3
-/
".
.
.
SPECITICA~
L "DRAIN ROCK' SHALL CONSIST or 2 TO 3-lNCi. IJPEH-GRADED, CLEAN, HARD, N<<ilJLAR. rRE:E:-DRAlNIHG. QUARRy ROO<.
2. "f"lNE GRAHlLAR nu.' SHAl.l a:tmST IF l-INC:H MINUS. a..EAN. HARD. ANGl.JLAA. WEl..L-aRADED. CRUSHED ROCK.
3. '"DRAIN PIPE' SHALL CONSIST IF SLOTTED OR PERFllRATtD, AlGID PIPE: NlPRCPRIATELY SIZED BY THE CIVIl. ENGINEER.
<t. ~ FABRIC" SHALl. ClJUIST IF AN AMOCD 454:! NJN-wvtN GEJJTDnnL
s. AU. RlXIC FlLL MATERIAL..S SHALL BE PlACED IN NAXlM.JM 24-INQ4 L.IJJSE: LIFTS AND COMPACTED COR SEATtID
USING HAHlI-{P[RATED. VIJRATDAY E.QUIPMDfr.
6. RErER TO REPORT F1lR ADDITlIJNAL SPECFlCA lIONS.
~
L EXPECT THAT TRENOi SIIEVALLS VILL BE UNSTABLE AND CI1l.D CAVE DR SLDUCiH. ESPEClALLY 'WITH
INrD..TRAT'IrfL ALL OCCAVATlDN$ SI-IJLLD BE SUF'EIl AHI1ItR SHJREII IN ACaIUIANC( \11TH OSHA GUIDELINEs.
2. Rl1IfII RDCC I:R PEA GRAvn. SHAl..1. NOT BE SUBSTITUTED f1lA DRAIN ROCK.
3. CRUSHtD GRAVEL stW..L NOT BE SUBSTITUTED F1lR CRUStE1I RDCK.
<I. tmJIVAlENT ........'-"'....E TYPES MAY IE SUBSTITUTED IF' N'PRDVtIl BY us.
S. Ai m..m CEXTIW PIPE IS SHD\iN IN THE: EVENT TO PRIJVIDE A I€AHS Of' REHDVOO VATER FROM 0THtR SOJRCE:S
SUCH AS nJ.JNJMTUJrt DRAINS. RI:IF DRAIHS. RETAlHIHl:i VAl..LS. OR DnER AR(A DRAUWiE. SUCH DRA!PWi( stD..LD
NOT DE: IlIS04ARG[D INTO TO nE PERrtRATED PIPE zmG:. A GR[(N TRACER VIR[ or VDmCAl. STUB-CUTS SIO.JL.D
BE 0.... .-... F1lR F11Tl..RE """"wo......... IN I:RIIER TO lJJCATt THE PIPt.
6. REFER TO REPORT F1lR ADllITUJriAL. NDTtS.
~ ~.:
- - - - - - - - - - -"'---=-"".-.
~ .,~"'~.
--6:10_
I
~
-+-
$CAlL I' . SO' FllR D-SHEET
.U Jl 17 PlDTS ARE HALF-SIZED
BASEUHE MAP PRCVUJED Err'
~ Branch Jln,cineeriD,c, In..
\e)l11II__
--......
(6U""""',JI 'M1~
.. BolRE
..AssOClArES
"
'. . .' .
. . '\
. - - MCKENZIE - - HrGHlfAY ~ ~ :-:-- - - - - - - ~ -
(U,S. /In', 11lt1)
8ACIlTILL \lITH "f1N[ GRNU..AR nu.'
/; LWDER STRUCTURES - USE NATIVE SOIl. AT
l.AHIl3CN"ING UlCA nONS .
_G<lDlJHn SURf''''''''-." ~_ _ _ _ _ 1; ~ ::~ AT TOP
o CTYPJ
~m PIPE' --it
ar NELDE:D) I'
"- son. ABOVE ROC< ..........
WI VATER DEPTH
\. <vARIES)
'IlRAIHAGE: F'~ l
EXCAVATED TRENl H
em: NOTES>
'DRAIN RDCK'
~;.
~, ,~,
~I-' \ ~,..
',,'-;\----~ - - - - - - --
.11 \. '~s~'~=------~' ", ..:j
----.....::. ",-~ ~ . .530~1
1---- . ;" ~. ---. I,.. ~,,~, ~
~~_\ ~- -~T-?q ,
~_ i '9~,~m ~ I, ~
-"~ ~
a.. SIt -600-./ . . ----'- _f!'-
(-3 m ,.- -"
-61Q~'-~~ __ ,L~
< ~~- .---.:... .~.~--........,
--" v./~
'~
'..,n
-DRAIN P .
"----- ------. i
,,:,:wtATHEREll RIlQC': L -!~ '
.---.-----------.------.---." 4' .
--;-.-.-.:-:-:-::-:-:-:.-.---. oaHJ TRDOI TO OCTEND
MINIMUM 1 F'T INTO RDOC
_ IETAIl. CTYPJ
SCALE l' . 5-
Q1 X 17 PlOT IS HALF' -SCALD
.' .9~
<-11m " _a,.;.. I. c-um/
.1....m .
~700 .
-.......... .' I I I
...........--L I , I
_ _ __. ,f.~ J_.7\ .
I ----r7'" '--l....... - - - -
I .~ I . I ~
"'S
I . r;:..7'
I <: c,F'-
I .' '\'l"'k~\"--'-
,') >l'"
---,;9']_.
..,/
DRAINAGE PLAN
(PHASES 1 AND 2)
MOUNTAGATE SUBDIVISION -PHASE 1 AND 2
SPR/NGFIELD, OREGON
A-4
/
.
.
APPENDIX B
(Exploration Methods and Logs)
!
.
.
APPENDIX B
FIELD EXPLORATION METHODS AND LOGS
. .
This appendix provides information about the subsurface explorations conducted to support
geotechnical design services for the Mountain Gate .Subdivision project located in Springfield,
Oregon.
Subsurface soil conditions within proposed development area were explored by excavating a
total of 39 exploratory test pits on February 18, 21, and March 28, 2002. Test pits TP-1 through
TP-7 were excavated using a rubber-tired backhoe. The remaining test pits were excavated
using a tracked hoe. The locations are illustrated on Figure A-1 of this report (Appendix B).
The field explorations were coordinated and monitored by a geotechnical engineer from our staff
who recorded the'subsurface conditions encountered, obtained representative soil samples, and
described the soil by visual and textural examinations. Field tests, (such as undrained soil'
shear strength'measurements made with a Torvane Shear device) were made where practical.
Disturbed (bag) samples were obtained from representative soil strata by hand. All soil
encountered was described using the Unified Soil Classification System (Standard
Recommended Practice for Description of Soil, Visual-Manual Procedures). Narrative
descriptions of the test pits and test holes are presented on the following pages in this appendix.
These logs represent our interpretation of subsurface conditions identified during the
geotechnical explorations.
The explorations were located in the field by pacing from approximate road alignments and field
stakes established by the surveyor. Ground surface elevations were estimated based on the
topographic contours shown on the map. The exploratory locations and elevations are
approximate.
Information presented on the summary logs depicts subsurface conditions only at the specified
locations and at the date designated on the logs.. Soil and groundwater conditions at other
locations or times may differ.
,-
,
Project Name:
Project Number:
~oject Location:
.
.
. TEST PIT LOGS
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: Tp-1
Elevation: 720 ft
Deoth 1ft) Soil Profile Description
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-1
1 - 2Y:.
2Y:. - 5
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6to 12 inches. Sample S-1-1taken at Y:. ft (WC = 34.4%).
Stiff SILT; clayey, light brown to rust (iron-stained), damp to moist, friable high
plasticity. Black mineral deposits and white sand noted within the soil.
Sample S-1-2 taken at 2 ft (WC=56.7%). The water content is relatively high
given its "damp to moist" appearance. This suggests the presence of tuff.
Weathered ROCK (siltstone); basically decomposed to the consistency of
tan/gray/yellow, moist, high plasticity, sandy, clayey silt (MH). Seepage at 4Y:.
ft. Excavation becomes harder immediately below this depth. The rock
appears to originate from pyroclastic sediment. Undrained shear strength
measured at 0.5 tsf for the material at 3Y:. ft using a Torvane device. Sample
S-1-3 taken at5 ft (WC = 51.8%). The high water content suggests tuff and/or
pyroclastic debris.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches,
2. Seeps noted at 4%.
3. The water/harder malerial below about 4Y2 may indicate a potential shear zone. The excavation might be extending
into an underlying volcanic rock.
Test Pit: Tp-2
Elevation; 705 ft
Death (ft). Soil Profile Description
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-1
1-4
4-9
9-9Y:.
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches.
Stiff SILT; slightly clayey, brown to rust-brown (iron-stained), damp to moist,
friable, medium plasticity. The soil contains sand, pebbles and other rock
fragments throughout and generally has a "jumbled" appearance. Undrained
shear strength> 1.0 tsf at3 ft. Sample S-2-1.laken at2Y, ft (WC=29.8%).
Weathered ROCK (siltstone); basically decomposed to the consistency of
brown and gray, moist, stiff, high plasticity, sandy, clayey silt (MH). Excavation
becomes harder below a depth of 9Y:. ft. The rock appears to originate from
pyroclastic sediment. Pebbles and gravels noted throughout. Undrained
shear strength> 0.85 tsf at 6Y:. ft.
Weathered ROCK (basalt): tan to brown and gray, damp, hard. The
weathered nature of the rock at its surface gives it a sandy appearance. The
rock likely represents and volcanic (igneous) rock that has intruded from
below.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered. However, tl1e soil from 4 to 9 shows evidence of past movement. The contact at 9 ft may
indicate a potential shear zone. The excavation appears to have encountered an underlying volcanic rock.
/
,
B-1
ProjeCt Name:
Project Number:
Project Location:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: Tp-3
Elevation: 645 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-1%
1% - 2%
2% - 10%
10%
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Stiff SILT; slightly clayey, brown to rust-brown (iron-stained), damp to moist,
friable, medium plasticity. The soil contains sand, pebbles and other rock
fragments throughout and generally has a "jumbled" appearance.
Weathered ROCK (siltstone); basically decomposed to the consistency of
yellow-brown, gray and rust (heavily iron-stained), moist to wet, stiff, high
plasticity silt (MH). The soil/rock is highly fractured ("jumbled" or mixed) and
contains water within the matrix. Sand, pebbles and gravel noted throughout.
Sample S-3-1taken at6 ft (WC=55.0%). The high water content suggests the
presence of tuff and/or pyroclastic debris.
Hard ROCK; tan to brown, basalt. The rock likely represents and volcanic
(igneous) rock that has intruded from below. Refusal encountered with the
excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Substantial water and rapid water infiltration encountered above the rock all0 ft.
3. The soil from 2Y2 to 10}-) shows evidence of past movement. The contact at 10% may represent a shear Zone.
Test Pit: TP-4
Elevation: 655 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-3
3-6
6-10
10-10%
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. Hard fragments of angular basalt rock contained throughout.
Substantial roots and other organic material within the upper 2 ft. The test pit
was dug on the edge of a suspect scarp and this upper.material may represent
debris from past slope movement.
Stiff SILT; clayey, red-brown and gray, iron-stained, damp to moist, friable,
medium to high plasticity. Black mineral deposits noted. The soil contains
sand, pebbles and other rock fragments throughout, and generally has a
"jumbled" appearance.
Weathered ROCK (siltstone); basically decomposed to the consistency of yell-
brown, gray and rust (heavily iron-stained), moist to wet, stiff, high plasticitY silt
(MH). The soil/rock is fractured but appears more stable than the material
above. Sample S-4-1 taken at 7 ft (WC=44.3%). The high water content
suggests the presence of tuff and/or pyroclastic debris.
Hard ROCK: tan to brown, slightly sandy, damp. The rock is more weathered
than found in test pit TP-3, but likely still likely represents a volcanic (igneous)
rock that has intruded from below.
Notes: .
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No subsurface water encountered. /
B-2
Project Name:
Project Number:
Project Location:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037
Sp.ringfield, Oregon
Test Pit: Tp-5
Elevation: 685 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
February '18, 2002
Case 580K Backhoe
0-1
1-2Y:z
2Y:z - 3
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Dense GRAVEL: some clay, slightly silly, sandy, light brown, moist.
Hard ROCK: tan to brown and buff-colored. The rock could represent very
hard sandstone, or a volcanic basalt (igneous) rock that has intruded from
below. The rock surface is smooth. Refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered.
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
Test Pit: TP-6
Elevation: 655 ft
Deoth 1ft) Soil Profile Descriotion
0-1
1 - 2Y:z
2Y:z - 3
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Dense GRAVEL; some clay, slightly silly, sandy, light brown, moist.
Hard ROCK; tan to brown and buff-colored. The rock could represent very
hard sandstone, or a volcanic basalt (igneous) rock that has intruded from
below. The rock surface is smooth. Refusal encountered with the excavator.
Notes:
1. The ground surface Is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered.
B-3
Project Name:
Project Number:
Project Location:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037
Sp~ingfie~d, Oregon
Test Pit: Tp-7
Elevation: 650 ft
Deoth (ft). Soil Profile Descriotion
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-3
3-SY:.
SY:. - 7Y:.
7Y:. - gy:'
9Y:. -10
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown in color and stiffer from 2 to 3 ft.
Medium stiff CLAY: gray, moist, high plasticity (CH).
Stiff SILT; slightly clayey, gray to yellow and buff, moist, friable, high plasticity
(MH). The soil contains sand, pebbles and other rock fragments throughout,
and generally has a "jumbled" appearance. May have weathered from rock.
Seeps noted at SY:.to 6Y:. fl.
Weathered ROCK (siltstone); basically decomposed to the consistency of
yellow, brown, gray, and rust (iron_stained), moist, stiff, high plasticity, sandy,
clayey silt (MH). The rock appears to o(iginate from pyroclastic sediment.
Pebbles and gravels noted throughout. The material appears more competent
than the overlying soil.
Weathered ROCK (siltstone or basalt); tan to brown and gray, damp, hard.
The weathered nature of the rock at its surface gives it a sandy appearance.
The rock could represent hard, sandy siltstone, or possibly volcanic basalt
(igneous rock) that has intruded from below.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2_ Seeps encountered at about 5% to BY; ft. The material in the depth range of SYZ to 7% ft may represent a zone of
previous soil shearing. The shearing (if currently present) could extend to a depth of 9Y2 ft.
Test Pit: TP-8
Elevation: 685 ft
Deoth (ft) Soil Profile Descriotion
Date:
Equipment:
February 21.. 2002
Cat 320 Excavator
0-2
2-6
6-14
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), moist,
friable, high plasticity (MH). The soil contains sand, pebbles, gravel and
cobble-sized rock fragments throughout. The profile generally has a mixed
appearance. Seeps noted at 5 to 6 ft.
Weathered ROCK (siltstone); basically decomposed to the consistency of
yellow, brown, gray, and rust (iron-stained), moist, stiff, high plasticity, sandy,
clayey silt (MH). The rock appears to originate from pyroclastic sediment.
Contains a substantial amount of pebbles and gravels throughout. The
material appears more competent than the overlying soil. Becomes harder
below 10 to 12 ft.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Seeps encountered at about 5 to 6 ft. The material in the depth range of 5 to 7 ft may represent a zone of previous
soil shearing. .
I
,
,
B-4
Project Name:
Project Number:
"proje_cll"ocation:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037 .
Springfield, Ore~. __
Test Pit: Tp-9
Elevation: 700 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
February 21, 2.002
Cat 320 Excavator
0-2
2-3)1,
3)1, - 4)1,
4)1,-6)1,-
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown and stiffer below 1)1, ft.
Medium Stiff CLAY: gray, moist, high plasticity.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), moist,
friable, high plasticity (MH). The soil contains sand, pebbles, gravel and
cobble-sized rock fragments throughout. The profile generally has a mixed
appearance. Seeps noted throughout. The soil structure and water suggest a
possible shear zone.
Weathered ROCK (siltstone): basically decomposed to the consistency of
yellow, brown, gray, and rust (iron-stained), moist, stiff, high plasticity, sandy,
clayey silt (MH). Contains a substantial amount of pebbles and gravels
throughout. The material appears more homogenous than the overlying soil.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. The seeps and ~jumbled. soli appearance between about 3'V2 and 41'2 may indicate a zone of soil shearing.
Test Pit: TP-10
Elevation: 670 ft
Deoth 1ft). Soil Profile Descriotion
Date: February 21,2002
Equipment: Cat 320 Excavator
0-2
2-3)1,
3)1, - 12
12-15
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown and stiffer below 1)1, ft.
Medium Stiff CLAY; gray, moist, high plasticity.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-statined), moist,
friable, high plasticity (MH). The soil contains sand, pebbles and gravel sized
rock fragments throughout. Black mineral deposits noted. The profile
generally has a mixed appearance. Substantial seepage noted throughout.
The test pit sidewalls cave and the soil is unstable. Undrained shear strength
measured at 0.9 tsf. Residual strength measured at 0.3 tsf. Sample 5-10-1
taken at 6)1, ft (WC = 46.2%).
Stiff SILT; slightly clayey, gray and blue, moist, friable, high plasticity (MH).
The soil may represent weathered rock and contains sand, pebbles and
rounded gravel throughout. The profile generally has a mixed appearance and
is unstable. Some continued seepage noted with depth (less severe than
above). Sample S-10-2taken at 13 ft (WC = 42.5%).
Notes:
1. The ground surtace is covered with short grass with roots extending downward approximately 4 inches.
2. The soil and rock appears -jumbled- throughout. A slip plane could be located a depth greater than 15 ft.
t
,
8-5
Project Name:
Project Number:
Project Location:
.
.
. TEST PIT LOGS
Mountaingate Subdivision
201.037
Springfield, Ore'gon
Test Pit: Tp-11
Elevation: 605 ft
Deoth (ft) , Soil Profile Descriotion
Date:
Equipment:
February 21,2002
Cat 320 Excavator
0-2
2-4
4-9
9-11
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown and stiffer below 1 Y:. ft.
Medium Stiff CLAY; gray, moist, high plasticity. Seeps noted above clay
(perched water). .
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-statined), moist,
friable, high plasticity (MH). The soil contains sand, pebbles, gravel and
cobble-sized rock fragments throughout. The profile generally has a mixed
appearance.
Weathered ROCK (siltstone); sandy and pebbly with some apparent tuff, gray,
white, rust (iron-stained), dry, hard. The .material appears relatively stable,
and could represent the surface of an underlying bedrock formation.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. The profile at this location appears more stable; however, previous soi.1 movement may have occurred above 9 ft.
Test Pit: TP-12
Elevation: 570 ft
Deoth (ft). Soil Profile Descriotion
Date: February 18, 2002
Equipment: Cat 320 Excavator
Weathered 51L TSTONE; blue and gray, damp, relatively hard, but can be
easily excavated. The material has a fractured or slick-en-sided appearance.
Weathered ROCK (siltstone): basically decomposed to the consistency of
yellow, brown, gray, and rust (iron-stained), moist, stiff, high plasticity, sandy,
clayey silt (MH). The rock appears to originate from pyroclastic sediment.
Pebbles and gravels noted throughout. The material has a "jumbled"
appearance and may represent a zone of shear. Sample 5-7-1 taken at 7 ft
(WC = 55.5%). The high water content suggests the presence of tuff.
Weathered ROCK; tan to brown, gray, rust, damp, hard. Black mineral
deposits noted. The weathered nature of the rock at its surface gives it a
sandy appearance. The rock could represent hard, sandy siltstone, or
possibly volcanic basalt (igneous) rock that has intruded from below.
Notes:
1. light seeps (perched water) above 2}s ft. The material in the depth range of 6 to 9 ft may' represent a zone of shear.
0-2Y:.
2Y, - 3Y:.
3Y:. - 5
5-6
6-9
9-11
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches. Lighter brown in color and stiffer from 2 to 3 ft.
Medium stiff CLAY; gray, moist, high plasticity (CH). Some organics noted.
Stiff SILT; slightly clayey, gray to yellow and buff, moist, friable, high plasticity
(MH). The soil contains sand, pebbles, and other rock fragments throughout
and generally has a "jumbled" appearance. May have weathered from rock,
Seeps noted at SY:. to 6Y:. ft.
8-6
Project Name:
Project Number:
Project Location:
"
.
.
. TEST PIT LOGS
Mountaingate Subdivision
201.037 .
Springfield, Oregon
Test Pit: Tp-13
Elevation: 650 ft
Deoth (ft) Soil Profile Description
Date: .
Equipment:
March 28: 2002
Cat 320 Excavator
0-1%
1 % - 2%
2%- 4
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic materialthroughoul.
Stiff CLAY; gray, moist, high plasticity.
Hard ROCK; tan to brown and buff-colored. The rock could represent very
.hard sandstone, or volcanic basalt (igneous) rock that has intruded from
below. The rock surface is smooth. Refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered. ..
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
Test Pit: Tp-14
Elevation: 710 ft
Deoth (ft). Soil Profile Descriotion
0-1
1 -1%
1% - 2
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic materialthroughoul.
Stiff CLAY: gray, moist, high plasticity.
Hard ROCK: tan to brown and buff-colored. The rock could represent very
hard sandstone, or volcanic basalt (igneous) rock that has intruded from
below. The rock surface is smooth. Refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered.
B-7
.
TEST PIT LOGS
.
Project Name:
Project Number:
Project Location:
Mountaingate Subdivision
201.037 .
Springfield, Oregon
Test Pit: Tp-15
Elevation: 740 ft
Deoth (ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
5-8
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic materialthroughoul.
Stiff SILT: slightly clayey, red-brown (iron-stained), damp to moist, friable, high
plasticity. The soil contains sand, pebbles, and other rock fragments
throughout and generally has a "jumbled" appearance.
Weathered ROCK (siltstone); basically decomposed to the consistency of red-
brown and gray (heavily iron-stained), moist, stiff, high plasticity clayey silt
(MH). The material is highly fractured ("jumbled" or mixed) and contains
fragments of harder rock throughout. A shear zone is evident between 6 and
8ft.
Hard ROCK; tan to brown, basalt. The rock likely represents and volcanic
(igneous) rock that has intruded from below. Refusal encountered with the
excavator.
0-2
2-5
8 -10
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered.
3. An old shear zone encountered from 6 to 8 ft suggests evidence of past movement.
Test Pit: Tp-16
Elevation: 745 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-1
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic materialthroughoul.
Hard ROCK; tan to brown and buff-colored. The rock could represent very
hard sandstone, or volcanic basalt (igneous) rock that has 'intruded from
below. The rock surface is smooth. Refusal encountered with the excavator.
1 - 1%
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered.
8-8
.
.
TEST PIT LOGS
Project Name:
Project Number:
Project Location:
.
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: Tp-17
Elevation: 720 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28: 2002
Cat 320 Excavator
0-1%
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches.
Stiff SILT: slightly clayey, brown to rust-brown (iron-stained), damp to moist,
friable, low to medium plasticity. The soil contains sand, pebbles and other
rock fragments throughout and generally has a "jumbled" appearance.
Weathered ROCK (siltstone); basically decomposed to the consistency of
brown, tan, red, gray, black, moist, stiff, high plasticity, sandy, clayey silt (MH)
with pebbles and gravel throughout. The rock appears to originate from
pyroclastic sediment. The material falls apart and ravels after excavation. The
mixed nature of the soil/rock and its apparent sensitivity to disturbance
suggest the material has been subject to shearing. Sample S-17-1taken from
15 ft (WC = 36.7%).
1%- 5
5-18
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered,"
3. Excavation difficulty increases below 13 ft, but then becomes softer from 17 to 18 ft. Maximum depth limit reached.
Test Pit: TP-18
Elevation: 735 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-1%
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches.
Stiff SILT (possibly weathered from rock): slightly clayey, brown to rust-brown
(iron-stained), damp to moist, friable, medium plasticity. The soil contains
sand, pebbles, and other rock fragments throughout and generally has a
"jumbled" appearance. '
Weathered ROCK (siltstone); sandy, rust-colored, fractured and sheared
(indicates a slip plane).
Weathered ROCK (basalt); tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. Practical refusal encountered with the excavator.
1 -10
10-10%
10-11
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered. However, the soil above 10 ft shows evidence of past movement. The contact at 10 to 10~
ft may indicate a potential shear zone. The excavation appears to have encountered the underlying volcanic rock.
8-9
Project Name:
Project Number:
Project Location:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037
Springfield, Ore'gon
Test Pit: Tp-19
Elevation: 680 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-2
2-5
5-7
7 -17
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Stiff SILT; slightly clayey, brown to rust-brown (iron-stained), damp to moist,
friable, medium plasticity. The soil contains sand, pebbles, and other rock
fragments throughout and generally has a "jumbled" appearance.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friabie (broken), high plasticity (MH). The soil contains sand, pebbles, gravel
and cobble-sized rock fragments 'throughout. The profile generally has a
mixed appearance and water can be found within the soil/rock fractures.
Weathered ROCK (siltstone): basically decomposed to the consistency of
brown, tan, red, gray, black, moist, stiff, high plasticity, sandy, clayey silt (MH)
with pebbles and gravel throughout. The rock appears to originate from
pyroclastic sediment. The material is more competent than at other locations
and has the appearance of conglomerate. Rockets of blue, dry, hard, siltstone
noted.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered.
3. Excavation difficulty increases with depth; however, it cannot be determined if a soft layer (andfor water zone) is
present below 17 ft as the depth limit was reached with equipment provided.
Test Pit: Tp-20
Elevation: 660 ft
Deoth (ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-2
2-15
15-17
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 fl.
Stiff SILT: slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles, gravel
and cobble-sized rock fragments throughout. The profile generally has a
mixed appearance and water can be found within the soil/rock fractures.
Weathered ROCK (siltstone); basically decomposed to the consistency of
brown, tan, red, gray, black, moist, stiff, high plasticity, sandy, clayey silt (MH)
with pebbles and gravellhroughout. Rapid seepage encountered at 16 fl. The
depth represents a zone of shear or sliding.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. A relatively definitive shear zone was encountered between 15 and 17 ft. The excavation could not continue as the
maximum depth of the excavator was reached.
8-10
Project Name:
Project Number:
Project Location:
.
.
. TEST PIT LOGS
Mountaingate Subdivision
201.037 .
Springfield, Oregon
Test Pit: Tp-21
Elevation: 645 ft
Deoth (ft). . Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-2
2-7%
7%
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles and
gravel sized rock fragments throughout. The profile generally has a mixed
appearance and may represent a weathered rock (siltstone).
Weathered ROCK (basalt); tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. Practical refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Ground water noted on rock surface.
Test Pit: Tp-22
Elevation: 615 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-1
1-3
3-4%
4% - 5
ORGANICS; leaves, woods, limbs, etc (duff).
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles, and
other gravel sized rock fragments throughout. The profile generally has a
mixed appearance and may represent a weathered rock (siltstone).
Weathered ROCK (basalt): tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. Practical refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Ground water noted on rock surface (above 4 ft).
8-11
.
. TEST PIT LOGS
.
Project Name:
Project Number:
Project Location:
Mountaingate Subdivision
201.037
Sp,ingfield, Or~gon
Test Pit: Tp-23
Elevation: 620 ft
Deoth (ft) Soil Profile Descriotion
Date: March 28, 2002
Equipment: Cat 320 Excavator
0-1
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Hard ROCK: tan to brown and buff-colored. The rock could represent very
hard sandstone, or possibly volcanic basalt (igneous) rock that has intruded
from below. The rock surface is smooth. Refusal encountered with the
excavator.
1 - 1 Yo
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No ground~ater encountered.
Test Pit: Tp-24
Elevation: 625 ft
Deoth (ft) Soil Profile Descriotion
Date:
Equipment:
Ma,ch 28, 2002
Cat 320 Excavator
2
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profiles become lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles, and
gravel sized rock fragments throughout. The profile generally has a mixed
appearance and may represent a weathered rock (siltstone).
Weathered ROCK (basalt); tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. P<actical refusal encountered with the excavator.
0-1
1-2
Notes:
1. The ground surface Is covered with short grass with roots extending downward approxImately 4 inches.
2. Substantial runoff (flow) encountered above rock surface.
,.
,
8-12
Project Name:
Project Number:
Project Location:
.
.
TEST PIT LOGS
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: TP-25
Elevation: 615 ft
Deoth lID Soil Profile Descriotion,
Date:
Equipment:
March 28, 2002
Cat 32.0 Excavator
0-1
1 - 2
2-3Y,
3Y, - 4 -
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Medium stiff CLAY: gray, moist, high plasticity.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles and
other gravel sized rock fragments throughout. The profile generally has a
mixed appearance a"nd may represent weathered rock (siltstone).
Weathered ROCK (basalt): tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. Practical refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Substantial runoff (flow) encountered above rock surface.
3. Evidence of soil shear present at rock surface interface.
Test Pit: TP-26
Elevation: 630 ft
Deoth lft\ Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-1
1 - 2
2-5
5-10
10 -12
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Medium stiff CLAY: gray, moist, high plasticity.
Stiff SILT; slightly clayey, gray to yellow, buff and rust (iron-stained), wet,
friable (broken), high plasticity (MH). The soil contains sand, pebbles and
gravel sized rock fragments throughout. The profile generally has a mixed
appearance and may represent weathered rock (siltstone).
Weathered ROCK (siltstone); basically decomposed to the consistency of
brown, tan, red, gray, black, moist, stiff, high plasticity, sandy, clayey silt (MH)
with pebbles and gravel throughout. The rock appears to originate from
pyroclastic sediment. The material falls apart and ravels after excavation. The
mixed nature of the soil/rock and its apparent sensitivity to disturbance
suggest the material has been subject to shearing.
Weathered ROCK (basalt); tan to brown and gray, damp, hard. The rock
surface is smooth and likely represents volcanic (igneous) rock that has
intruded from below. Practical refusal encountered with the excavator.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Substantial runoff (flow) from 2 to 5 ft. No water below 5 ft.
3. The soil above 5 ft is suspect for creep movement. Movement could extend to ~ depth of 10 ft.
8-13
. . TEST PIT LOGS
Project Name:
Project Number:
Project Location:
.
Mountaingate Subdivision
201.037
Springfield, Oregon
.
Dense sandy gravel (FILL); brown and gray, moist, well-graded, compacted.
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes. lighter brown and stiffer below 1 ft.
Medium stiff CLAY; gray, moist, high plasticity.
Stiff SILT: slightly clayey, brown and tan, iron-stained (mottled) moist.
Dense GRAVEL; sandy, brown and gray, wet.
Test Pit: Tp-27
Elevation: 510 ft
Deoth I.ftl Soil Profile Descriotion
Date:
Equipment:
0-1
1-2
2-3
3-SY:z
SY:z - 6Y:z
March 28, 2002
Cat 320 Excavator
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Seeps encountered at 3 ft.
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Medium stiff SILT; clayey, brown and tan, iron-stained (mottled) saturated.
Extremely rapid infiltration from 2 to 5 ft
Medium stiff to stiff CLAY; gray, moist, high plasticity. Little water within this
zone.
Test Pit: Tp-28
Elevation: 515 ft
Deoth Ift\ . Soil Profile Descriolion
Date:
Equipment:
0-2
2-5
5-9
9 -10
Dense GRAVEL: sandy, brown and gray, wet.
March 28, 2002
Cat 320 Excavator
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. The rate of seepage encountered indicates this area represents a terminal drainage location.
i
,
8-14
Project Name:
Project Number:
Project Location:
.~
,
TEST PIT LOGS
Mountaingate Subdivision
201.037 .
Springfield, Oregon
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
Test Pit: Tp-29
Elevation: 540 ft
Deoth (ft) Soil Profile Descriotion
0-2%
2% - 10
10 - 16
16 - 18
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, 'yellow to brown, moist, friable, high plasticity (MH).
The soil contains fragments of siltstone and sandstone throughout. The profile
generally has a mixed appearance and may represent a sheared material.
Same as above, except that lhe larger rock fragment can be found.
Stiff SILT; clayey, gray, damp to moist, high plasticity. The silt has a fractured
or slick-en-sided appearance.
Notes:
'1. The ground sulface is covered with short grass with roots extending downward approximately 4 inches.
2. No water encountered. .
3. Maximum depth of excavator reached at 18 ft.
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
Test Pit: TP-30
Elevation: 520 ft
Deoth (ill Soil Profile Descriotion
0-2
2-6
6-9%
9% - 12%
12% - 13%
13%- 14
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 ft.
Stiff SILT; slightly clayey, yellow to brown, moist, friable, high plasticity (MH).
The soil contains fragments of siltstone and sandstone throughout. The profile
generally has a mixed appearance and may represent a sheared material.
Sample S-30-1taken at about 5 ft (WC = 37.7%).
Stiff SILT; slightly clayey, gray, moist, friable, high plasticity (MH). The soil
contains fragments of siltstone and sandstone throughout. The soil is less
mixed that the overlying material.
Stiff SILT; some clay, blue-green, damp to moist, high plasticity (MH). Sample
S-30-2 obtained from about 11 ft (WC = 53.50/0).
Medium stiff SILT; sandy, moist to wet, contains organics (i.e., wood
branches). Sample S-30-3taken at about 13 ft (WC = 74.0%). The high water
content results from the significant amount of organic material present.
Dense GRAVEL; sandy, brown and gray, wet.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Rapid water infiltration encountered at 6 ft.
,.
,
8-15
.
. TEST PIT LOGS
.
Project Name:
Project Number:
Project ~ocation:
Mountain9ate Subdivision
201.037
Springfield, Oregon
Test Pit: TP-31
Elevation: 740 ft
Deoth (ft) Soil Profile Descriotion
Date:
Equipment:
March 28: 2002
Cat 320 Excavator
0-1
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 fl.
Weathered ROCK (siltstone, sandstone or basalt): basically decomposed to
the consistency of tan, damp, dense, silty sandy. The material is more
homogenous and more competent than at other locations. Practical refusal
encountered with the excavator.
1 -10
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Some slight evidence of soil creep (i.e" a thin shear zone may be present) at 5 ft.
Test Pit: TP-32
Elevation; 710 ft
Deoth (ft). Soil Profile Descriotion
Date;
Equipment:
March 28, 2002
Cat 320 Excavator
1-4
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 fl.
Very stiff SILT: some sand, brown to tan, with isolated seeps. May represent a
weathered siltstone.
Weathered ROCK (siltstone); tan, dry, hard. Excavation is slow and hard but
continued digging is possible.
0-1
4-10
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Seepage encountered above rock surface.
3. Evidence of soli shea~ at 4 ft.
t
,
8-16
Project Name:
Project Number:
Project Location:
.
TEST PIT LOGS
.
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: Tp-33
Elevation: 685 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28:2002
Cat 320 Excavator
o -1Y,
1)1, - 6
6-8Y,
8Y, - 11
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The profile becomes lighter brown and stiffer below 1 ft.
Very stiff SILT; some sand, brown to tan, with isolated seeps. May represent a
weathered siltstone.
Stiff SILT; bark brown, damp, high plasticity. Possible evidence of previous
shear between 7Y, and 8Y, ft.
Weathered ROCK (siltstone): tan, dry, hard. Excavation is slow and hard but
continued digging is possible. The rock could possibly represent highly
weathered basalt (igneous intrusive) that is indicative of the underlying
volcanic series.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Substantial runoff (flow) encountered above rock surface.
3. Evidence of soil shear above 8% ft (specifically between 7% and 8% ft)
Test Pit: TP-34
Elevation: 680 ft
Deoth 1ft) Soil Profile Description
Date:
Equipment:
February 18, 2002
Case 580K Backhoe
0-1
1 -14
14-15
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material within the
upper 6 to 12 inches.
Soft SILT; clayey, brown to rust-brown (iron-stained), moist, friable high
plasticity. Mixed pebbles, gravel and topsoil layers present. Substantial water
below 3 ft.
Weathered ROCK (siltstone): somewhat decomposed to blue, high plasticity,
silt (MH). Fragments of harder rock noted throughout.
Notes:
1. The ground surface is covered with short grass with roots-extending downward approximately 4 inches.
2. Rapid seepage below 3 ft.
3. The test pit sidewalls are highly unstable. The area dearly defines an area and depth of instability.
8-17
Project Name:
Project Number:
Project Location:
.
. TEST PIT LOGS
.
Mountaingate Subdivision
201.037
Springfield, Oregon
Test Pit: Tp-35
Elevation: 700 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-2
2-4
4-7
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains substantial roots and other organic material
throughout.
Medium stiff SILT; some sand and pebbles and harder siltstone rock
fragments noted, brown to tan, high plasticity. The soil has a "jumbled"
appearance.
Weathered ROCK (siltstone); tan, dry, hard. Excavation is slow and hard but
continued digging is possible. The rock could possibly represent highly
weathered basalt (igneous intrusive) that is indicative of the underlying
volcanic series.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Substantial runoff (flow) encountered above rock surface.
3. Evidence of soil shear between 2 and ft.
Test Pit: TP-36
Elevation: 795 ft
Deoth 1ft) Soil Profile Descriotion
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
0-1
1-6
6-13
13-14
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Stiff SILT; slightly clayey, brown to rust-brown (iron-stained), damp to moist,
friable, medium plasticity. The soil contains sand, pebbles and other rock
fragments throughout and generally has a "jumbled" appearance.
Weathered ROCK (siltstone); basically decomposed to the consistency of yell-
brown, gray and rust (heavily iron-stained), moist to wet, stiff, high plasticity silt
(MH). The soil/rock is highly fractured ("jumbled" or mixed) and contains water
'within the matrix. Sand, pebbles, and gravel noted throughout. The material
appear more homogenous below a depth of 13 ft.
Hard ROCK; tan to brown, basalt. The rock likely represents and volcanic
(igneous) rock that has intruded from below. Refusal encountered with the
excavator. Rapid seepage at13Y, ft.
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
;
,
8-18
.
TEST PIT lOGS
Project Name:
Project Number:
Project Location:
Mountaingate Subdivision
201.037
Springfield, Oregon
.
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Medium stiff SILT: clayey, brown, moist, angular rock fragments scattered
throughout.
Hard ROCK; tan to brown and buff-colored.. The rock likely represents a
volcanic basalt (igneous) rock that has intruded from below. The rock surface
is smooth. Refusal encountered with the excavator.
Test Pit: Tp-37
Elevation: 875 ft
Deoth (ft) Soil Profile Descriotion
0-1Y:.
1Y:.- 3
3-4
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No groundwater encountered.
Loosely structured SILT (topsoil): some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
The soil becomes lighter brown and stiffer below 1 ft.
Medium stiff, CLAY: gray, moist, high plasticity.
Very stiff SILT; sandy, brown to tan with black mineral deposits, dry fractured.
May represent weathered siltstone.
Weathered ROCK (siltstone); tan, dry, hard. Excavation is slow and hard but
continued digging is possible. The rock could possibly represent highly
weathered basalt (igneous intrusive) indicative of the underlying volcanic
series. Hard digging below 9 ft.
Test Pit: TP-38
Elevation: 900 ft
Deoth 1ft) , Soil Profile Descriotion
0-1
1-3
3-7
7 -10
Date:
Equipment:
March 28, 2002
Cat 320 Excavator
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. No subsurface water encountered. .
,
,
,
8-19
.
. TEST PIT LOGS
.
Project Name:
Project Number:
.Project Location:
Mountaingate Subdivision
201.037 .
Springfield, Oregon
Test Pit: Tp-39
Elevation: 715 ft
Deoth (ft). Soil Profile Descriotion
Date:
Equipment:
March 28: 2002
Cat 320 Excavator
0-1
Loosely structured SILT (topsoil); some clay, dark brown, moist, low plasticity,
very friable. The soil contains roots and other organic material throughout.
Medium stiff CLAY; gray, moist, high plasticity.
Weathered ROCK (siltstone); basically decomposed to the consistency of red-
brown and gray (heavily iron-stained), moist, stiff, high plasticity clayey silt
(MH). The material is highly fractured ("jumbled" or mixed) and contains
fragments of harder rock throughout.
Haft! ROCK; tan to brown, basalt. The rock likely represents volcanic
(igneous) rock that has intruded from below. Refusal encountered with the
excavator. Water at SY> ft.
1-2
2-5
5 - SY>
Notes:
1. The ground surface is covered with short grass with roots extending downward approximately 4 inches.
2. Water encountered at a depth of 5~ ft.
3. Some evidence of minor soil shear above 5 ft.
8-20
.
.
APPENDIX C
(Laboratory Test Results)
.
.
APPENDIX C
LABORATORY TESTING
This appendix provides information about the 'Iaboratory testing conducted. to support
geotechnical design services for the Mountain Gate Subdivision project located in Springfield,
Oregon.
Laboratory tests were performed on representative samples 'of soil encountered to evaluate
pertinent physical characteristics. The laboratory testing program consisted of visual inspection,
Atterberg limits, moisture content determinations, and organic (ash) contents to classify the
native soils in general accordance with ASTM D2488, ASTM D4318, ASTM D2216, and ASTM
D2974, respectively. The results from these tests are summarized in this appendix (Figure C-1
and Table C-1), in the report text, and on the test pit logs (Appendix B).
The results of the laboratory tests are indicative of certain general soil properties. Where
practical, ASTM procedures have been followed as standard practice. However, it should be
understood that actual soil properties might differ dependir]g on specific material variations,
handling procedures, and testing conditions.
i
,
FIGURE B-1
ATTERBERG LIMITS /
60, , 1-1-1--1----'.1.., .1 ____..._[-.1..1...++ --+HjJ,,' ---.tll 11_/ / /0
I[ II L_ . I _nt . LJ--1'1 __-:l,,~~Q)~vl"! I, ~ ~~~1
I '+1 + . ~ ~ I ,~ -I
50 -I I! 1- - I I .. - - ~ q', I I "' - I $-
:=1= =:nl 1- - _ J i- += 1: = ytl- -I II , ~...... *.. -.Iv~~r~ :=1=1=
I --'--,-- L L __I j Lr---- I ~ ~')l- ---
--.1.." J. - __L... -.. -'1-- -+.. - .. -, .l..l. _IL T Iln~rgancclays or'-T1 .1 ~~~'r ' -- - -
! I I I : I 1: I I t ~ t I. 1 ~\ I I
~ 40 ll.~_ FF~ll=::.ttT -H=r=-jj--H- tl : :r-i'~"c'll;~1 ~~~'fH-+--t
~ -i-tt; - ,- .J..+_, ,L, - Ti+ ...L.+_j-i., +i;(itF+~~-U+-i-;~ -1-++11'-: i i I +1-1+
.5 ..L_ -.--4-,.1-. ,....,-". '''I++-f'''' '.. . J...,...L,. ,......-......-~- 1
~ 30 --'-1_1_ I U~_l_ .J~_l: 1_1__'_ 1'1 1 J_ J I ! I i..."..! I Micaceous or dIatomaceous, I !
:2 ! ~ I~' '. ~' .'! J ! ,I I i I ~'~ ' I I ,'1-.LJ .."i ; I I fine sandy and silty soils: 1$
Vi ! I Low ~Iastlc Inorgamc 1--t-,-- --1- r,J' - ~edlum -r-i i t'1--;-1-TT elastic silts: organic silts.
. Tr' clays, sandy and L ..I..... ". ~. ... plostlc -j-t;'1'" "+-;1-['1'" clays, and silty Clay,S '
n: I 'I slilty CI~y~ XI-i' T~' +1)1/1"1" -1 ~:~onlc ;?'~PI. 7t'~r I T'11"i~OH'-t'-' J I i 'I -+--
20 J:"" -I_L 1'.,,-"1.::;2, 'I-IT_JI~ US-1Q-,-ni'-' I'U:''='III i . I
-1..J-+-I- -H$t=,. - _I +-1:.; - _~sompl. .. -8 2'...L :J.l.1J.. ,-1-++,1,,1-1-, -!-t' --I+':~ -- _...J-
'''!-. 'Siltycla~s: '1 -+ - :-[' ..,. "I'''''I~':-J2,-,!. ~ -Yi-H'I-i"'I"'H'H"'i-j-i,,+ 'Ti"I-'MH'-r+-' - - ..-+
T ~~J~~~~~ l 'I B-; , 'l"io..LD Ii: 'IT;+i.J-- j"=t+'-J'Tl Il'+' l-
ID I, " '_=U'. ~ 1 CO::: ~- Z('C ~.=c.IT1 I I I 'l; :.J..L....! I__~-'-'-L -- T
-H-+---8-Jt:~111 I I kJ~,J_j'.lnor9anjCandOr9anlcsilts '_1..I...i.-I++' =rJ..LL I__IJ$
1 r-:. ,. " UL -t' I and silty clays of row : ~: ii' '...1-' ' I
- CL;-ML- ". - ,r'w///3f!P/W' ......R' ' ::1 ( plasticity; rock; flour: . -i'-, 'TTT" - "', I t- - ,-
-W-l-- ~H+""'" U:"?H-t~.- - -I "I silty or, clayey fine sands . -:-C _1_ I I 1- -flT::::-
o I I , 1.1. 1 I 1"....,' . t . , l l i I I I I j I I j I I I , I, I It:
o 10 W ~ 40 ~ W ro 00 00 100
Liquid Limit (LL)
.
.
",
TABLE B-1
WC's and % FINES
Sample Depth (ft) Water Content (%) Atterberg Limits
LL PL PI USC5
5-1-1 0.5 34.4
5-1-2 2 58.7
S-1-3 5' 51.8
5-2-1 2.5 29.8 45 32 26 ML
S-2-2 6.5 36.6
5-3-1 6 55.0 79 46 33 MH
S-4-1 7 44.3
5-10-1 6.5 46.2 63 38 25 MH
S-10-2 13 42.5
S-12-1 7 55.5 111 50 61 MH
S-17-1 15 36.7
S-30-1 5 37.7 59 31 28 MH
S-30-2 11 53.5 74 39 35 MH
S-30-3 13 74.0
(10% Organics)
.'
.Ii SOlRE MountainGate Subdivision -
Phases 1 and 2 Laboratory Test Resll/ts C-1
.!!if ASSOCIATES Springfield, Oregon