Geotechnical and Pavements Technical Memo.pdf

Technical Memorandum 2525 Airpark Drive Redding, California 96001 T +1.530.243.5831 F +1.530.339.3323 www.jacobs.com

BI0930191508RDD 1

Subject Geotechnical Investigation for Sacramento Island Trail

Project Name Sacramento Island Trail, CA FLAP RED 2017(3)

Prepared for Federal Highway Administration, Central Federal Lands Highway Division

From Mark Twede, Jacobs

Date October 13, 2020

1. Introduction

Jacobs has been retained by Central Federal Lands Highway Division to prepare design documents for a paved recreational trail along the north bank of the Sacramento River across from Sacramento Island in Redding, California. A geotechnical investigation was conducted in support of the trail design. The paved trail will replace an existing unpaved trail. This technical memorandum summarizes activities and pertinent findings of the geotechnical investigation, and recommended design criteria for the proposed improvements to the trail.

The purpose of this geotechnical investigation was to evaluate the subgrade conditions and provide design criteria for asphalt pavement and grading. To accomplish this, the scope of services included the following:

Advancing boreholes in the parking area and along the trail alignment Collecting samples of soil materials Performing laboratory testing of soil materials Conducting engineering analysis of geotechnical data for pavement section design Preparing this technical memorandum to summarize design criteria for the trail improvements

The scope of services was performed in general accordance with the scope presented in the Jacobs proposal, January 9, 2019, and incorporated into a contract with Central Federal Lands Highway Division, dated March 7, 2019.

2. Project Description

The project consists of constructing a new recreational trail and parking area in the Riverland Open Space along the Sacramento River in Shasta County, California, approximately 3 miles south of the city of Redding. A vicinity map is included on Figure 1. Construction activity and improvements will include site preparation, clearing, grading and compacting, drainage improvements in the parking area, and paving the parking lot and trail with asphalt concrete. The proposed parking amenities will include a precast restroom facility, parking delineations, signage, striping, and other typical items.

3. Subsurface Exploration

The fieldwork was conducted on April 23, 2019, and included hand-auger drilling and soil sampling.

Borings were advanced at eight locations with a 4-inch-diameter hand auger to 5 feet depth below the ground surface, or until refusal occurred. The boring locations are shown on Figure 1. Multiple borings

Geotechnical Investigation for Sacramento Island Trail

2 BI0930191508RDD

were drilled at each designated borehole location to obtain sufficient soil materials for testing. The boring logs are included in Attachment 1.

4. Soil Laboratory Testing

Soil samples were collected from the hand auger borings for laboratory testing. Testing included gradation tests, Atterberg Limits tests, and resistance value (R-value) tests. Testing was performed by Materials Testing, Inc., of Redding, California. Index and R-value laboratory test results are summarized in Table 1. Laboratory test reports are included in Attachment 2.

Table 1. Summary of Laboratory Test Results Geotechnical Investigation for Sacramento Island Trail

Borehole Depth (feet)

Percent Passing No. 200

Sieve ASTM D1140

Liquid Limit

ASTM D4318

Plasticity Index

ASTM D4318

USCS

Classification

ASTM D2487

R-Value

CTM 301

B-1 0.75 to 3.0 38 NP NP SM 28

B-2 0.75 to 3.0 28 SM 48

B-3 0.5 to 2.5 53 35 6 ML 18

B-4 & B-6a 0.5 to 3.0 42 SM 47

B-7 & B-8a 0.5 to 2.5 22 NP NP SM 67 a Samples from two boreholes were visually identical and were combined into one sample for testing.

Notes:

ASTM = American Society of Testing and Materials CTM = California Test Method ML = silt NP = non-plastic SM = silty sand USCS = Unified Soil Classification System

5. Local Geology

The project area is underlain by Holocene age alluvium (Fraticelli et al., 1987). The alluvium consists of unconsolidated silt, sand, and gravel along stream channels and on associated low terraces.

6. Geotechnical Conditions

At the parking area, a mantle of fill material up to approximately 1 foot thick was observed, consisting of gravel, silt, sand, and cobbles. The fill was underlain by alluvial silty sand with varying amount of gravel.

Along the trail alignment, the soil generally consisted of silty sand. The sand was fine-grained, and the soil was generally non-plastic. The silt content of the silty sand varied from an estimated 15 to 45 percent.

Near the start of the trail parallel to Riverland Drive, in the vicinity of boring B-3, the upper 1 to 2 feet of soil consisted of soft silt material with apparent organics. The silt was of low plasticity and appeared to be possible fill materials based on the grading along this stretch of the trail. The fill appeared to be approximately 130 feet in length. A gravel surfaced path currently exists along this stretch of the trail alignment, and boring B-3 was drilled on the western edge of the gravel surfacing. The R-value of the silt is relatively low in comparison to other locations along the trail.

Groundwater was encountered in some of the borings, generally at depths of approximately 3 feet below the ground surface. The proposed grading for the trail is mostly fill, and groundwater is unlikely to affect the project design.

BI0930191508RDD 3

7. Recommendations

7.1 Earthworks and Grading

All embankment fill materials should be free of deleterious debris, trash, organics, or cobbles larger than 4 inches in dimension. The native soil does not appear to contain these deleterious materials but may contain an excessive amount of silt, which is difficult to work with due to its moisture sensitivity. Silt soil begins to pump excessively at moisture contents above the optimum moisture content, limiting compaction effectiveness. Native soil should be selectively segregated during excavation or borrow, disposing of soil with greater than 50 percent fines content. Only native material classified as sand or silty sand in accordance with the USCS should be used as embankment fill beneath surface improvements. If fill materials are imported, fill should consist of low-plasticity material (that is, plasticity index less than 12) with less than 35 percent fines content [percent passing No. 200 (0.075 millimeter) sieve].

The ground surface should be graded to drain away from pavement toward drainage features. Cut and fill slopes should be no steeper than 2 horizontal to 1 vertical (2H:1V).

All embankment fill should be compacted to at least 90 percent relative compaction at a moisture content within 2 percent of the optimum moisture content, in accordance with American Society of State Highway and Transportation Officials (AASHTO) Test Method T-180 or ASTM Test Method D1557. Fill material should be placed in thin lifts with a maximum loose thickness of 8 inches.

The native alluvial soil is likely to be looser than the soil when compacted to the recommended density.

Undisturbed samples of the native soil were not obtained in the field investigation to evaluate the existing moisture and density of the soil. However, from experience with similar alluvial environments, the volume of the compacted soil is estimated to be 90 percent of the volume of the excavated loose native soil.

7.2 Subgrade Preparation

All finish subgrade soil, or soil within 6 inches below the aggregate base rock of the pavement section, should be moisture-conditioned as necessary to near optimum moisture conditions and compacted to a minimum of 95 percent of the maximum dry density as determined by AASHTO T-180 or ASTM D-1557.

The subgrade should be smooth and unyielding prior to placing aggregate base rock. Proof rolling of the subgrade should be performed using a loaded water truck or similarly heavy equipment and observed by the engineer representative to verify the subgrade is firm and unyielding prior to placing the aggregate base rock. If the subgrade condition degrades due to inclement weather or construction traffic, the subgrade should be moisture-conditioned and recompacted.

7.3 Pavement Section Design

The trail will be paved with asphalt concrete overlying aggregate base rock. The recommended thickness of aggregate base and asphalt concrete surfacing is dependent on the design traffic loading, which is quantified using a traffic index in accordance with the California Department of Transportation (Caltrans) Highway Design Manual. For a recreational trail that will experience little vehicle traffic, the traffic index is somewhat more of a standard minimum value rather than being related to number of axle loads passing across the pavement. The City of Redding uses a minimum traffic index of 5.5 for asphalt concrete-paved trails. However, this corresponds to between approximately 10 to 20 thousand 18-kip Equivalent Single Axle Loads (ESALs), much more than the Sacramento Trail pavement will be exposed to. A traffic index of 5.0 is considered sufficient for the design, corresponding to approximately 5 to 10 thousand 18-kip ESALs. A traffic index of 5.0 is the minimum traffic index used by Caltrans for auto parking areas at roadside rest areas.

The R-value for most of the trail and parking area was greater than 28, and this is the recommended value for design use. The short section of trail through the area around boring B-3, where silt soil with a lower R-value was encountered, will be constructed on at least 12 inches of compacted fill material.

Based on the recommendation for fill with less than 50 percent silt, the weaker silt soil material can therefore be excluded from the design.

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The recommended pavement section for the proposed asphalt flexible paving is based on design methods presented in the Caltrans Highway Design Manual, Section 630. The recommended design pavement section for the proposed trail and parking area pavement are summarized in Table 2.

Table 2. Recommended Pavement Section Design for Trail and Parking Area Geotechnical Investigation for Sacramento Island Trail

Traffic Index Asphalt Concrete

(inches) Aggregate Base Rock

(inches)

5.0 3.0 6

Note: Design is based on an overall R-value of 28.

The aggregate base rock should meet the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects for Grading Designation E and have a minimum R-value of 75. The aggregate base rock should be spread in a lift restricted to 8 inches in loose thickness or less, moisture-conditioned to within 2 percent of the optimum moisture content, and compacted to a minimum of 95 percent of the maximum dry density as determined by AASHTO T-180 or ASTM D1557. Density testing should be performed prior to placing the asphalt paving.

Asphalt paving materials should meet or exceed requirements for materials and construction as specified in the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects. The pavement coarse thickness should be at least 3 inches for a Traffic Index of 5.

7.4 Aggregate-Surfaced Access Road

A new unpaved access road is proposed from the north end of the trailhead parking area into the adjacent Providence International property. The access driveway will be constructed with aggregate base rock as described in Section 7.3. The access road design section was evaluated in accordance with the low-volume road design (AASHTO, 1993). The parameters assumed in the design are summarized in Table 3.

Table 3. Design Parameters for Aggregate-Surfaced Road Geotechnical Investigation for Sacramento Island Trail

Parameter Value

Soil Type 3.0

R-Value of Subgrade 28

Relative Quality of Roadbed Soil Good

Climatic Region IV

Traffic Level Low

The minimum recommended thickness of aggregate base rock is 6 inches.

8. Construction and Performance Considerations

The largest risk of damage to the trail is from uplift caused by roots growing underneath the pavement and erosion of the subgrade during flooding. Coarse gravel material along the sides of the pavement section may help to reduce, but not eliminate, these risks.

The native alluvial soil is non-expansive, coarse-grained material and is unlikely to have significant expansion or shrinkage with changes in moisture over time. Post-construction settlement of the trail due to consolidation of the native soil under the weight of embankment fills is estimated to be less than

0.5 inch.

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The silt content of the native soil requires vigilance during construction to maintain the moisture condition of the soil very near the optimum moisture content. If the soil is over optimum moisture by a couple percent, it will begin to pump under the compaction equipment load, and it will not be possible to achieve the required compaction.

9. References

AASHTO Guide for Design of Pavement Structures, 1993.

Fraticelli, L.A., Albers, J.P, Irwin, W.P., and Blake, M.C. 1987. Geologic Map of the Redding 1x2 Degree Quadrangle, Shasta, Tehama, Humboldt, and Trinity Counties, California. U.S. Geological Survey, Open File Report 87-257.

N

©2018 Google Earth, Modifications by Jacobs

FIGURE 1

Boring Locations Geotechnical Investigation for Sacramento Island Trail

CA FLAP RED 2017(3)

Central Federal Lands Highway Division

Attachment 1 Boring Logs

KEY TO SOIL BORING LOGS

SAMPLE TYPES AND ABBREVIATIONS

TERM EXPLANATION

BU Bulk Sample

USCS UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM D2487)

LL, PI LIQUID LIMIT, PLASTICITY INDEX (ASTM D4318)

DD DRY DENSITY (pounds per cubic foot) wc WATER CONTENT (%)

GENERAL NOTES

1) THE BORING LOGS AND RELATED INFORMATION DEPICT SUBSURFACE CONDITIONS AND WATER LEVELS ONLY AT THE

SPECIFIC LOCATIONS AND DATES INDICATED. SOIL CONDITIONS AND WATER LEVELS OCCURRING AT OTHER LOCATIONS MAY DIFFER FROM THE CONDITIONS OCCURRING AT THESE BORING LOCATIONS. THE PASSAGE OF TIME MAY RESULT IN A CHANGE IN THE CONDITIONS AT THESE LOCATIONS. MATERIAL BOUNDARIES ARE ESTIMATED FROM

NON‐CONTINUOUS SAMPLING AND ARE APPROXIMATE.

2) DRILLING OF SOIL BORINGS WAS DIRECTED BY JACOBS GEOTECHNICAL PERSONNEL. THE SUBSURFACE MATERIALS FROM THE BORINGS WERE CLASSIFIED IN APPROXIMATE ACCORDANCE WITH ASTM D4288 (VISUAL‐MANUAL PROCEDURE FOR DESCRIPTION OF SOILS, AND ADJUSTED BASED ON LABORATORY TEST RESULTS WHERE NECESSARY.

3) DEPTH TO WATER LISTED ON THE BORING LOGS IS ESTIMATED BASED ON MOISTURE CONDITIONS OBSERVED WITHIN THE SOIL SAMPLES. A STABILIZED GROUNDWATER LEVEL WAS NOT MEASURED IN THE BORINGS, AND THE ACTUAL

DEPTH TO WATER MAY BE SEVERAL FEET ABOVE OR BELOW THE REPORTED WATER LEVEL.

GRAVEL

AND

GRAVELLY

SOILS

CLAYEY GRAVELS, GRAVEL - SAND -

CLAY MIXTURES

WELL-GRADED SANDS, GRAVELLY

SANDS, LITTLE OR NO FINES

POORLY-GRADED SANDS,

GRAVELLY SAND, LITTLE OR NO

FINES

SILTY SANDS, SAND - SILT

MIXTURES

CLAYEY SANDS, SAND - CLAY

MIXTURES

INORGANIC SILTS AND VERY FINE

SANDS, ROCK FLOUR, SILTY OR

CLAYEY FINE SANDS OR CLAYEY

SILTS WITH SLIGHT PLASTICITY

INORGANIC CLAYS OF LOW TO

MEDIUM PLASTICITY, GRAVELLY

CLAYS, SANDY CLAYS, SILTY

CLAYS, LEAN CLAYS

ORGANIC SILTS AND ORGANIC

SILTY CLAYS OF LOW PLASTICITY

INORGANIC SILTS, MICACEOUS OR

DIATOMACEOUS FINE SAND OR

SILTY SOILS

INORGANIC CLAYS OF HIGH

PLASTICITY

SILTS

AND

CLAYS

MORE THAN 50%

OF MATERIAL IS

LARGER THAN

NO. 200 SIEVE

SIZE

MORE THAN 50%

OF MATERIAL IS

SMALLER THAN

NO. 200 SIEVE

SIZE

MORE THAN 50%

OF COARSE

FRACTION

PASSING ON NO.

4 SIEVE

MORE THAN 50%

OF COARSE

FRACTION

RETAINED ON NO.

4 SIEVE

SOIL CLASSIFICATION CHART

(APPRECIABLE

AMOUNT OF FINES)

(APPRECIABLE

AMOUNT OF FINES)

(LITTLE OR NO FINES)

FINE

GRAINED

SOILS

SAND

AND

SANDY

SOILS

SILTS

AND

CLAYS

ORGANIC CLAYS OF MEDIUM TO

HIGH PLASTICITY, ORGANIC SILTS

PEAT, HUMUS, SWAMP SOILS WITH

HIGH ORGANIC CONTENTS

LETTER

SYMBOLS

MAJOR DIVISIONS

COARSE

GRAINED

SOILS

TYPICAL

DESCRIPTIONS

WELL-GRADED GRAVELS, GRAVEL -

SAND MIXTURES, LITTLE OR NO

FINES

POORLY-GRADED GRAVELS,

GRAVEL - SAND MIXTURES, LITTLE

OR NO FINES

SILTY GRAVELS, GRAVEL - SAND -

SILT MIXTURES

CLEAN

GRAVELS

GRAVELS WITH

FINES

CLEAN SANDS

(LITTLE OR NO FINES)

SANDS WITH

FINES

LIQUID LIMIT

LESS THAN 50

LIQUID LIMIT

GREATER THAN 50

HIGHLY ORGANIC SOILS

NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

GRAPHIC

BU

Abundant roots in upper 6 inches.

@3': Becomes wet.

Silty Sand with gravel and cobbles (SM): brown, moist, loose, fine to coarse sand, subrounded gravel and cobbles, maximum size 6 inches, non-plastic fines.

Silty Sand (SM): brown, moist, loose, fine to medium sand, low plasticity, 1 percent fine gravel.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-1 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

CONSISTENCY, SOIL STRUCTURE, MINERALOGY

EXCAVATION CONTRACTOR: Jacobs

No Free Water Encountered

@3.5': Refusal in gravel

Silty Sand with gravel (SM): brown, moist, loose, non-plastic, subrounded.

Silty Sand (SM): brown, moist, loose, fine to medium sand, low plasticity, 1 percent fine gravel.

Silty Sand (SM): brown, moist, loose, fine to medium sand, low plasticity, 5 percent gravel, subrounded to subangular, maximum size 1.5 inches.

Bottom of Hole at 3.5 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 3.5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-2 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

@2.75': Becomes wet.

@4': Becomes very loose/soft.

Silt (ML): dark brown, moist, medium stiff, low plasticity.

Silty Sand (SM): brown, moist, loose, fine to medium sand, low plasticity.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-3 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

Silty Sand (SM): brown, moist, loose, fine sand, non-plastic fines.

Silt (ML): brown, moist, medium stiff, low plasticity.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-4 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

Similar to soil from B-4, combined for laboratory testing.

@4': Becomes slightly coarser, but still fine sand.

@4.75': Becomes wet.

Silty Sand (SM): brown, moist, medium dense, non-plastic, fine sand.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-5 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

Silty Sand (SM): brown, moist, medium dense, non-plastic, approximately 45 percent silt.

Poorly-graded Sand with Silt (SP-SM): brown, moist, medium dense, fine sand, approximately 15 percent silt, non-plastic.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-6 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

@4.7': refusal on gravel

Silty Sand (SM): brown, moist, medium dense, non-plastic, approximately 25 percent silt.

Silty Sand (SM): brown, moist, medium dense, non-plastic, approximately 15 percent silt.

Poorly-graded Sand with Silt and Gravel (SP-SM): brown, moist, medium dense, fine to medium sand, approximately 15 percent fine gravel, maximum size 1.5 inches, subrounded, non-plastic.

Bottom of Hole at 4.7 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 4.7

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-7 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

Silty Sand (SM): brown, moist, loose, non-plastic, fine sand, approximately 25 percent silt.

Poorly-graded Sand with Silt (SP-SM): dark brown, moist, medium dense, fine to medium sand, approximately 5 to 10 percent silt, non-plastic.

Sandy Silt (ML): brown, moist, medium stiff, fine sand, approximately 50 percent silt, low plasticity.

Bottom of Hole at 5.0 ft below ground surface 4/23/2019

SOIL BORING LOG

DRILLING METHOD AND EQUIPMENT: Hand Auger DATE DRILLED: 4/23/2019

TOTAL DEPTH: 5

PROJECT: Sac Island Trail - Central Federal Lands, Redding, CA LOCATION:

BELOW

PROJECT NUMBER:

SURFACE

WATER LEVELS: ---

LOGGER: M. Twede

OBJECTS, DEBRIS, ROOTS, ETC.

APPROXIMATE ELEVATION:

DEPTH

S A

M P

LE

T

Y P

E

G R

A P

H

IC

LO

G

TEST PIT NUMBER:

WXXY1600 B-8 SHEET 1 OF 1

SOIL DESCRIPTION COMMENTS

SOIL NAME, USCS GROUP SYMBOL, COLOR,

MOISTURE CONTENT, RELATIVE DENSITY OR

Attachment 2 Soil Laboratory Test Results