Geotechnical Letter Report.pdf

Project No. - 23-1-01458-060_L1.docx

1321 Bannock Street Suite 200 Denver, Colorado 80204-2718 303 825-3800 Fax 206 695-6777 www.shannonwilson.com

March 24, 2020

Aaron Swafford, PE Jacobs Engineering Group 717 17th Street Denver, Colorado 80202

RE: BRUSH CREEK TRANSIT CENTER, CO FLAP PIT 82(1), PITKIN COUNTY, COLORADO

Dear Mr. Swafford:

This geotechnical letter report summarizes the results of our subsurface exploration program and presents geotechnical engineering recommendations and construction considerations for the proposed Brush Creek Transit Center (the Center) in Pitkin County, Colorado.

Our services were conducted in general accordance with our Subconsultant Agreement with Jacobs Engineering (Jacobs). We completed the following tasks for the project:

Coordination of utility locates and subcontractors for drilling borings, Observation, logging, and sample collection from borings at two locations, Geotechnical engineering analyses to develop foundation recommendations for design and construction of the proposed restroom facility, and

Preparation of this letter report.

PROJECT AND SITE DESCRIPTION

The proposed Center improvements are located at the existing Brush Creek Transit Center north of Aspen, Colorado near the intersection of Brush Creek Road and Colorado State Highway 82 (see Figure 1). The current transit site contains a bus loop configuration with the passenger pick-up/drop-off island consisting of a station platform, restroom facilities and various passenger amenity features located within the loop. To the east of the passenger and bus area, the existing parking lot consists of paved and un-paved parking with traffic islands.

http://www.shannonwilson.com/

March 24, 2020

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Based on the Brush Creek Park and Ride Mid-Station Alternative drawings provided by Jacobs, the proposed expansion area east of the existing passenger island will consist of a restroom facility and future information/special events building (to be designed by others).

GEOLOGIC CONDITIONS

Regional Geology

The Center lies in the Roaring Fork Valley in an area near Roaring Fork River, which is underlain by Upper Cretaceous (100-66 million years ago) sedimentary rocks. The surficial soils along the Roaring Fork River consist of alluvial and glacial deposits of the Pleistocene to upper Holocene age (deposited from approximately 2.6 million years ago to present day).

The gravel unit within the project area is described as poorly sorted gravel and sand; largely of glaciofluvial origin.1

Existing Data

A geotechnical investigation report by RockSol completed for the current Center2 was provided by Jacobs. The report included three geotechnical borings approximately 100 to 180 feet of the proposed restroom facility, designated BC-1 through BC-3. These borings generally encountered surficial medium dense to dense (native) sand overlying very stiff (native) clay with varying amounts of sand (prior to the construction of the Center).

Underlying the clays, at a depth ranging from 7 to 15 feet, the borings encountered dense to very dense, (native) gravel, which was “silty to sandy with cobbles…”.

Field Explorations

Shannon & Wilson conducted a field exploration program on February 14 and 21, 2020, to explore subsurface conditions at the Center. Three geotechnical borings, designated as SW- 01, SW-01A, and SW-02 were drilled at or near the proposed restroom facility and future information/special events building. At boring location SW-01, shallow auger refusal halted drilling efforts beyond a depth of 5.5 feet with hollow stem augers. Additional offset boring

1 Freeman, 1970, Geologic map of the Woody Creek and southwest part of the Ruedi quadrangles, Pitkin County, Colorado: U.S. Geological Survey, Open-File Report OF-70-130, scale 1:20,000.

2 RockSol, 2011, Geotechnical Investigation Report: 90 Percent Submittal, VelociRFTA Bus Rapid Transit Colorado Highway 82 Glenwood Springs to Aspen, Colorado, RockSol Project No. 251.01.

https://ngmdb.usgs.gov/Prodesc/proddesc_8471.htm https://ngmdb.usgs.gov/Prodesc/proddesc_8471.htm

March 24, 2020

23-1-01458-060_L1.docx 23-1-01458-060 locations were attempted but auger refusal was encountered at depths less than 2 feet. A second mobilization with ODEX drilling methods (consisting of a down-hole air hammer system) was used to advance borings SW-01A and SW-02 to a depth of 15.4 and 10.4 feet, respectively. All borings were drilled by Vine Laboratories, Inc. under subcontract to us.

The approximate locations of the borings are shown in Figure 2. Photographs of the boring locations are provided in Figure 7.

During exploration, representative soil samples were obtained in the borings in general accordance with the standard penetration test (SPT) procedures in ASTM D1586. The collected soil samples were observed by Shannon & Wilson representatives, classified based on the Unified Soil Classification System in accordance with ASTM D2487 (Figure 3), and a log of the subsurface conditions at each boring location was prepared in accordance with ASTM D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). Refer to Figures 4 through 6 for boring logs.

Subsurface Conditions

Each of our borings encountered surficial deposits, generally consisting of very dense sand, gravel, and cobbles (inferred by drill action) with varying constituent amounts of silt and clay. Boring SW-02 encountered a stratum of cobbles and boulders at a depth of 7 feet. The clay subgrade observed in the borings completed by RockSol was not encountered in our borings.

During drilling, groundwater was not encountered in any of our borings. However, fluctuations of groundwater levels at the site are possible and will depend on many factors, including seasonal variations, local precipitation and runoff, and the nearby Roaring Fork River flood events.

The explorations were performed to evaluate geotechnical soil conditions at the Center. Our observations are specific to the locations, depths, and times noted on our boring logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions. Potential variation includes, but is not limited to:

The conditions between explorations may be different.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

March 24, 2020

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Penetration test results in gravelly soils may be unrealistic. Actual soil density may be lower than estimated if the test was performed on a gravel or cobble.

If conditions that are different from those described herein are encountered during construction, we should review our description of the subsurface conditions and reconsider our conclusions and recommendations.

GEOTECHNICAL RECOMMENDATIONS

Restroom Foundations

We understand that the proposed structure will be single story, constructed near existing grades and supported by shallow foundations. A slab on grade will be utilized for the floor of the structure. Foundation loads are anticipated to be relatively light.

Based on the subsurface explorations, the anticipated foundation subgrade will consist of granular soil (very dense, poorly graded sand and gravel with varying amounts of silt and clay and cobbles and boulders). In our opinion, shallow spread and strip footings are a suitable foundation option for the proposed structure. We recommend designing the footings for a nominal bearing resistance value of 10,000 pounds per square foot (psf) and a resistance factor of 0.45. At a service load 4,000 psf, we estimate less than 1-inch of total settlement. Differential settlement over the length or width of the structure is anticipated to be less than ¾ inch. In addition, we recommend a minimum footing width of 24 inches and an embedment of 36 inches for strip footings supporting the perimeter walls of the proposed structures. Any spread footings supporting columns should have a minimum width of 36 inches and an embedment of 36 inches (unless the building is heated, wherein interior strip or spread footings could be embedded 24 inches). The settlement is anticipated to occur as the footings are loaded.

Horizontal seismic or wind loads on the structure may be resisted by friction along the base of the foundation and by passive soil resistance against the buried portion of the foundation.

Passive soil resistance can be calculated based on a nominal equivalent fluid density of 550 pounds per cubic foot with a resistance factor of 0.50. This value reflects limited lateral deformations (less than 1% of the embedment depth). This value also assumes no groundwater is below the base of the footing and that a horizontal ground surface exists beyond the footing at least two times the depth of embedment in the direction of movement.

Passive resistance should be ignored above the frost depth (3 feet). Footings cast on

March 24, 2020

23-1-01458-060_L1.docx 23-1-01458-060 properly prepared material (as described in this report) may be designed using a nominal coefficient of base friction of 0.55 and a resistance factor of 0.80.

We anticipate that the native subgrade soils will provide adequate support for slabs on grade, but we recommend that the upper 12 inches of native subgrade be scarified, and either (a) screened to remove oversized material (boulders or cobbles greater than 3 inches in diameter) to prevent point loading on a boulder or cobble, or (b) overexcavated and backfilled with imported granular material that is 3 inch minus. The footing subgrade should be compacted to at least 95% of the modified Proctor maximum dry density (MDD) and within 2% of the optimum moisture content (OMC) in accordance with ASTM D1557.

Restroom Floor Slab

We recommend slab on grade floors be supported by at least 6 inches of granular base to act as a capillary break and provide additional support (or to the frost depth if the interior is not heated). The base should consist of clean crushed gravel. The maximum particle size should be 1½ inches with no more than 2% passing the No. 4 sieve. The subbase should be compacted to a dense and unyielding condition and to at least 95% of the modified Proctor MDD (ASTM D1557) and within 2% of OMC. We estimate slab movement (differential with respect to the footings) will be on the order of ½ inch or less.

Seismic Ground Motion Design Parameters

Colorado is comprised of areas of very low to moderate potential for damaging earthquakes. Based on a geologic map by the U.S. Geological Survey3, the nearest fault to the Center is the late Quaternary Sawatch Fault, located approximately 26 miles to the east (near Leadville, Colorado). Based on this distance, it is our opinion that the risk of fault rupture is low at the site.

Our geotechnical borings at the site did not provide sufficient penetration to determine the site classification in accordance with IBC design guidelines. While we believe that Site Class C is possible, because of the lack of depth of the borings, we recommend assuming a Site Class D for the site unless additional testing is performed. Ground motion parameters

3 USGS, 2020a, Earthquake Hazards, Faults, Quaternary Fault and Fold Database of the United States, accessed March 10, 2019. Available from: https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-science_support_page_related_con=4#qt-science_support_page_related_con https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-science_support_page_related_con=4#qt-science_support_page_related_con https://www.usgs.gov/natural-hazards/earthquake-hazards/faults?qt-science_support_page_related_con=4#qt-science_support_page_related_con

March 24, 2020

23-1-01458-060_L1.docx 23-1-01458-060 provided in the below table were determined for the site using the U.S. Geological Survey (USGS) Seismic Design Map Web Application4 with the 2015 International Building Code (IBC) design criteria.

Exhibit 1: Seismic Design Ground Motion Parameters

Design Parameter Value

Site Class D

Short-period Spectral Acceleration, SS 0.32 g

Long-period Spectral Acceleration, S1 0.082 g

Site Factor, Fa 1.544

Site Factor, FV 2.4

Short-period Design Spectral Acceleration, SDS 0.33 g

Long-period Design Spectral Acceleration, SD1 0.13 g

NOTE:

g = gravity

CONSTRUCTION CONSIDERATIONS

The applicability of the above design parameters is contingent on good construction practice. Poor construction techniques may alter conditions from those upon which our recommendations are based, and therefore result in poor performance.

Site Preparation

Prior to site grading, existing pavement, brush and other vegetation should be cleared from all areas to be graded. Any existing surficial topsoil and any soil containing organics should be stripped and removed from all areas. The depth of this removal is anticipated to vary, but generally be relatively thin. Pavement, topsoil, and organic-rich soils are not considered suitable for reuse as fill and should be removed from the site. Care should be taken to avoid disturbing subgrade soils and supporting soils that will remain in place, as they can rut and pump under repeated construction traffic. The final subgrade surface should be sloped to promote positive drainage.

4 USGS, 2020b, IBC-2015 Web Service Documentation, accessed on March 10 from USGS website:

https://earthquake.usgs.gov/ws/designmaps/ibc-2015.html https://earthquake.usgs.gov/ws/designmaps/ibc-2015.html

March 24, 2020

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Subgrade Preparation and Proof Roll

Proper subgrade preparation is required for adequate foundation and pavement performance. Excavations for foundations should be observed by a geotechnical engineering representative familiar with the subsurface conditions to evaluate the adequacy of the bearing stratum and check that the subsurface conditions at and below the bearing elevations are suitable for the design values presented in this report. Subgrade excavations should be cleaned of all fill, debris, or loose material prior to concrete placement and should be kept free of water at all times. We recommend that the foundation subgrade be proof rolled (where feasible) or probed to identify soft or loose zones.

Proof-rolls should be conducted using a fully-loaded, tandem-axle dump truck or equivalent. Any areas that are delineated to be soft, loose, or yielding during proof-rolling should be removed and reconditioned, or replaced with granular fill.

Fill Placement and Compaction

All fill should consist of either on-site or other granular material with less than 30% fines (material passing the U.S. Standard No. 200 sieve). The onsite soils can be re-used as fill provided the soil does not contain organics, any other deleterious material, or if silt or clay soils are encountered. In addition, we recommend screening the onsite material to remove oversized material (material larger than 3 inches). The onsite material was observed to contain numerous cobbles and reusing this material can be difficult to compact.

Fill materials should be placed in horizontal lifts, with the loose lift thickness not to exceed 10 inches for heavy equipment compactors and 6 inches for hand-operated compactors.

Thinner lifts may be required, depending on the size of the contractor’s equipment. All fill should be compacted to at least 95% of its modified Proctor (ASTM D1557) MDD and within 2% of OMC. If the oversized material fraction (material larger than ¾ inch) exceeds 30%, then the compaction criteria determined from ASTM D1557 is not valid. For these fill soils, we recommend that the fill placement be monitored on a full-time basis to observe and document the compaction process.

PLAN REVIEW AND CONSTRUCTION OBSERVATION SERVICES

We recommend that we be retained to review the geotechnical aspects of the plans and specifications before construction begins to confirm that they are in accordance with our recommendations.

March 24, 2020

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The geotechnical design recommendations included herein were developed from a limited number of explorations and tests. Geotechnical recommendations may need to be adjusted in the field based on conditions encountered during construction. Therefore, we recommend that a construction observation and monitoring program be implemented for the project and that Shannon & Wilson be retained to monitor the geotechnical aspects of construction, particularly earthwork activities. This monitoring would allow us to confirm that conditions encountered are consistent with those indicated by the explorations. A site representative will also be able to quickly provide changes to recommendations in the event that conditions revealed during construction are different from those anticipated.

CLOSURE

The analyses, conclusions, and recommendations presented in this report are based on our understanding of the project and a limited number and limited depth of subsurface explorations and laboratory test results. We assume that these explorations are representative of the subsurface conditions beneath the site; that is, the subsurface conditions everywhere are not significantly different from those disclosed by the explorations. This geotechnical design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analyses and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule and budget, the analyses, conclusions and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

The scope of our services did not include an evaluation regarding the presence or absence of hazardous or toxic materials in the soil, surface water, groundwater, or air, on or below or around this site. If such contamination exists, it would not be possible to determine it within this limited scope of work.

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

23-1-01458-060

F i l e n a m e

I E

F

D

E N s

J a c o b s

C

F L

B r u s h

C r e e k

P a r k i n g D r a f t i n g

F i g d w g t e

L o g i n r d d

MT

0 2 4

Approximate Scale in Miles

VICINITY MAP

FIG. 1

PROJECT

LOCATION

March 2020

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

Denver

Colorado

Aspen

To Twin Lakes

To Basalt

Project

Location

Aspen

Snowmass Village

Brush Creek Road

Landscape overlay adapted from Brush Creek Parking: Preliminary

30% Plans provided by Jacobs on November 14, 2019.

NOTE

F i l e n a m e

I E

F

D

E N s

J a c o b s

C

F L

B r u s h

C r e e k

P a r k i n g D r a f t i n g F i g d w g t e

L o g i n r d d

60 120

Approximate Scale in Feet SITE AND EXPLORATION PLAN

23-1-01458-060March 2020

FIG. 2

LEGEND

Boring Designation and

Approximate Location

SW-01

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

SW-01A

Proposed Restroom

Facility

SW-02

To Aspen

VIA US 82

To Basalt

VIA US 82

To US 82 and

Brush Creek Road

SW-01

Future Information/

Special Events

Building

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

23-1-01458-060March 2020

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

S&W INORGANIC SOIL CONSTITUENT DEFINITIONS

CONSTITUENT2

COHESIONLESS SOILS

Silt, Lean Clay, Elastic Silt, or

Fat Clay 3

PERCENTAGES TERMS 1, 2

Trace

Few

Little

Some

Mostly

WELL AND BACKFILL SYMBOLS

Bentonite Cement Grout

Bentonite Grout

Bentonite Chips

Silica Sand

Perforated or Screened Casing

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. 3

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All percentages are by weight of total specimen passing a 3-inch sieve.

2The order of terms is: Modifying Major with Minor.

3Determined based on behavior.

4Determined based on which constituent comprises a larger percentage.

5Whichever is the lesser constituent.

COARSE-GRAINED

SOILS

(less than 50% fines)1

NOTE: Penetration resistances (N-values) shown on boring logs are as recorded in the field and have not been corrected for hammer efficiency, overburden, or other factors.

PARTICLE SIZE DEFINITIONS

RELATIVE DENSITY / CONSISTENCY

Sand or Gravel 4

30% or more coarse-grained:

Sandy or Gravelly 4

More than 12% fine-grained:

Silty or Clayey 3

15% to 30% coarse-grained:

with Sand or with Gravel 4

30% or more total coarse-grained and lesser coarse-grained constituent is 15% or more:

with Sand or with Gravel 5

Very soft Soft Medium stiff Stiff Very stiff Hard

Very loose Loose Medium dense Dense Very dense

RELATIVE

DENSITY

FINE-GRAINED SOILS

(50% or more fines)1

COHESIVE SOILS

< 2 2 - 4 4 - 8

8 - 15 15 - 30

> 30

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

S

S

-1 -0

-0

B

R U

S H

C R

E E

K P

A R

K

IN

G .G

P J

S W

N E

W .G

D T

/1

0/

23-1-01458-060

CO FLAP PIT 82(1)

Pitkin County, Colorado

March 2020

GC

SC

Inorganic

Organic

(more than 50% of coarse fraction retained on No. 4 sieve)

MAJOR DIVISIONS GROUP/GRAPHIC

SYMBOL

CH

OH

ML

CL

TYPICAL IDENTIFICATIONS

Gravel

Sand

Silty Sand; Silty Sand with Gravel

Clayey Sand; Clayey Sand with Gravel

Clayey Gravel; Clayey Gravel with Sand

Sheet 2 of 3

Gravels

Primarily organic matter, dark in color, and organic odor

SW

(more than 12% fines)

Silts and Clays

Silts and Clays

(more than 50% retained on No.

200 sieve)

(50% or more of coarse fraction passes the No. 4 sieve)

(liquid limit less than 50)

(liquid limit 50 or more)

Organic

Inorganic

FINE-GRAINED

SOILS

SM

Sands

Silty or Clayey Gravel

Silt; Silt with Sand or Gravel; Sandy or Gravelly Silt

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

HIGHLY-

ORGANIC

SOILS

COARSE-

GRAINED

SOILS

GW

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

(less than 5% fines)

PT

(more than 12% fines)

MH

SP

GP

GM

Silty or Clayey Sand

Silty Gravel; Silty Gravel with Sand

(50% or more passes the No.

200 sieve) Elastic Silt; Elastic Silt with Sand or Gravel; Sandy or Gravelly Elastic Silt

Fat Clay; Fat Clay with Sand or Gravel;

Sandy or Gravelly Fat Clay

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

Poorly Graded Sand; Poorly Graded Sand with Gravel

Well-Graded Sand; Well-Graded Sand with Gravel

Well-Graded Gravel; Well-Graded Gravel with Sand

Poorly Graded Gravel; Poorly Graded Gravel with Sand

Lean Clay; Lean Clay with Sand or Gravel; Sandy or Gravelly Lean Clay

Peat or other highly organic soils (see

ASTM D4427)

FIG. 3

OL

(less than 5% fines)

NOTES

1. Dual symbols (symbols separated by a hyphen, i.e., SP-SM, Sand with Silt) are used for soils with between 5% and 12% fines or when the liquid limit and plasticity index values plot in the CL-ML area of the plasticity chart. Graphics shown on the logs for these soil types are a combination of the two graphic symbols (e.g., SP and SM).

2. Borderline symbols (symbols separated by a slash, i.e., CL/ML, Lean Clay to Silt; SP-SM/SM, Sand with Silt to Silty Sand) indicate that the soil properties are close to the defining boundary between two groups.

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

S

S

-1 -0

-0

B

R U

S H

C R

E E

K P

A R

K

IN

G .G

P J

S W

N E

W .G

D T

/1

0/

NOTE: No. 4 size = 4.75 mm = 0.187 in.; No. 200 size = 0.075 mm = 0.003 in.

UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)

(Modified From USACE Tech Memo 3-357, ASTM D2487, and ASTM D2488)

23-1-01458-060

CO FLAP PIT 82(1)

Pitkin County, Colorado

March 2020

Angular

Subangular

Subrounded

Rounded

Flat

Elongated

Sharp edges and unpolished planar surfaces.

Similar to angular, but with rounded edges.

Nearly planar sides with well-rounded edges.

Smoothly curved sides with no edges.

Width/thickness ratio > 3.

Length/width ratio > 3.

Narrow range of grain sizes present or, within the range of grain sizes present, one or more sizes are missing (Gap Graded). Meets criteria in ASTM D2487, if tested.

Full range and even distribution of grain sizes present. Meets criteria in ASTM D2487, if tested.

Crumbles or breaks with handling or slight finger pressure Crumbles or breaks with considerable finger pressure Will not crumble or break with finger pressure

Weak

Moderate

Strong

VISUAL-MANUAL CRITERIA

A 1/8-in. thread cannot be rolled at any water content.

A thread can barely be rolled and a lump cannot be formed when drier than the plastic limit.

A thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. A lump crumbles when drier than the plastic limit.

It take considerable time rolling and kneading to reach the plastic limit. A thread can be rerolled several times after reaching the plastic limit. A lump can be formed without crumbling when drier than the plastic limit.

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants Sheet 3 of 3

Interbedded

Laminated

Fissured

Slickensided

Blocky

Lensed

Homogeneous

Alternating layers of varying material or color with layers at least 1/4-inch thick; singular: bed.

Alternating layers of varying material or color with layers less than 1/4-inch thick; singular:

lamination.

Breaks along definite planes or fractures with little resistance.

Fracture planes appear polished or glossy;

sometimes striated.

Cohesive soil that can be broken down into small angular lumps that resist further breakdown.

Inclusion of small pockets of different soils, such as small lenses of sand scattered through a mass of clay.

Same color and appearance throughout.

At Time of Drilling Diameter Elevation Feet Iron Oxide Gallons Horizontal Hollow Stem Auger Inside Diameter Inches Pounds Magnesium Oxide Millimeter Manganese Oxide Not Applicable or Not Available Nonplastic Outside Diameter Observation Well Pounds per Cubic Foot Photo-Ionization Detector Pressuremeter Test Parts per Million Pounds per Square Inch Polyvinyl Chloride Rotations per Minute Standard Penetration Test Unified Soil Classification System Unconfined Compressive Strength Vibrating Wire Piezometer Vertical Weight of Hammer Weight of Rods Weight

ATD

Diam.

Elev.

ft.

FeO gal.

Horiz.

HSA

I.D.

in.

lbs.

MgO mm

MnO

NA

NP

O.D.

OW

pcf

PID

PMT

ppm psi

PVC

rpm

SPT

USCS

qu

VWP

Vert.

WOH

WOR

Wt.

STRUCTURE TERMS1

1Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be obtained from ASTM International, www.astm.org.

2Adapted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be obtained from ASTM International, www.astm.org.

ACRONYMS AND ABBREVIATIONS

Poorly Graded

Well-Graded

Irregular patches of different colors.

Soil disturbance or mixing by plants or animals.

Nonsorted sediment; sand and gravel in silt and/or clay matrix.

Material brought to surface by drilling.

Material that caved from sides of borehole.

Disturbed texture, mix of strengths.

Mottled

Bioturbated

Diamict

Cuttings

Slough

Sheared

DESCRIPTION

Nonplastic

Low

Medium

High

ADDITIONAL TERMS

PLASTICITY2

CEMENTATION TERMS1

GRADATION TERMS

APPROX.

PLASITICTY

INDEX

RANGE

< 4

4 to 10

10 to 20

> 20

PARTICLE ANGULARITY AND SHAPE TERMS1

FIG. 3

SOIL CLASSIFICATION

AND LOG KEY

_B O

R

IN

G _C

LA

S

S

-1 -0

-0

B

R U

S H

C R

E E

K P

A R

K

IN

G .G

P J

S W

N E

W .G

D T

/1

0/

S -1

S -2

5 inches of asphalt.

Very dense, red-brown, Clayey Gravel with Sand and Cobbles (GC) to Silty Gravel with Sand and Cobbles (GM); moist; cobbles inferred from drill action.

Alluvium

- Auger refusal at 5.5 feet.

BOTTOM OF BORING

COMPLETED ON 02/14/2020 G

ro un dw at er N ot E nc ou nt er ed D ur in g D ril lin g

0.4

5.5

March 2020

Sample Not Recovered

Hole Diam.:

Rod Type.:

Hammer Type:

SHANNON & WILSON, INC.

5.5 ft.

FIG. A-4

S am pl es

LOG OF BORING SW-01

7 in.

AWJ

Automatic

S ym bo l

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between material types, and the transition may be gradual.

SOIL DESCRIPTION

NOTES

1. Refer to Figure A-1 for explanation of symbols, codes, abbreviations and definitions.

2. The discussion in the text of this report is necessary for a proper understanding of the nature of the subsurface materials.

3. Groundwater level, if indicated above, is for the date specified and may vary.

4. USCS designation is based on visual-manual classification and selected lab testing.

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

0 60

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

20 40

Geotechnical and Environmental Consultants

23-1-01458-060

Hollow-Stem Auger Vine Laboratories CME 55 Truck Offsets attempted 2' and and 4 ' North

LEGEND

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

G ro un d

W at er

D ep th , f t.

Standard Penetration Test

D ep th , f t.

Latitude:

Longitude:

Station:

Offset:

20 40

QCL 3

M A

S T

E R

_L O

G _E

_P O

C K

E T

P E

N _L

A T

LO

N G

3-

1-

-0

B R

U S

H C

R E

E K

P A

R K

IN

G

.G P

J

/1 0/

(blows/foot)PENETRATION RESISTANCE Hammer Wt. & Drop: 140 lbs / 30 inches

50/5"

50/4"

S -2

S -3

S -4

S -5

S -6

5 inches of asphalt.

Very dense, brown to red-brown, Clayey Gravel with Sand and Cobbles (GC) to Silty Gravel with Sand and Cobbles (GM); moist; cobbles inferred from drill action.

Alluvium

Very dense, brown to red-brown, Clayey Gravel with Sand and Cobbles (GC); moist; cobbles inferred from drill action.

Alluvium

Very dense, brown to red-brown, Poorly Graded Sand with Silt and Gravel and Cobbles (SP-SM); moist; cobbles inferred from drill action.

Alluvium

Very dense, brown to gray, Poorly Graded Sand with Gravel and Cobbles (SP); moist;

trace silt; cobbles inferred from drill action.

Alluvium

Very dense, brown to white, Poorly Graded Gravel with Silt and Sand and Cobbles (GP-GM); moist; cobbles inferred from drill action, occasional gypsum nodules.

Alluvium

Very dense, red-brown, Poorly Graded Gravel with Sand and Cobbles (GP); moist; cobbles inferred from drill action.

Alluvium

BOTTOM OF BORING

COMPLETED ON 02/21/2020

G ro un dw at er

N ot

E nc ou nt er ed

D ur in g

D ril lin g

0.4

4.5

7.0

9.4

11.7

14.2

15.4

March 2020

Sample Not Recovered

Hole Diam.:

Rod Type.:

Hammer Type:

SHANNON & WILSON, INC.

15.4 ft.

FIG. A-5

S am pl es

LOG OF BORING SW-01A

5 in.

AWJ

Automatic

S ym bo l

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between material types, and the transition may be gradual.

SOIL DESCRIPTION

NOTES

1. Refer to Figure A-1 for explanation of symbols, codes, abbreviations and definitions.

2. The discussion in the text of this report is necessary for a proper understanding of the nature of the subsurface materials.

3. Groundwater level, if indicated above, is for the date specified and may vary.

4. USCS designation is based on visual-manual classification and selected lab testing.

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

0 60

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

20 40

Geotechnical and Environmental Consultants

23-1-01458-060

ODEX

Vine Laboratories CME 55 Truck Located 2' south of boring SW-01

LEGEND

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

G ro un d

W at er

D ep th , f t.

Standard Penetration Test

D ep th , f t.

Latitude:

Longitude:

Station:

Offset:

20 40

QCL 3

M A

S T

E R

_L O

G _E

_P O

C K

E T

P E

N _L

A T

LO

N G

3-

1-

-0

B R

U S

H C

R E

E K

P A

R K

IN

G

.G P

J

/1 0/

(blows/foot)PENETRATION RESISTANCE Hammer Wt. & Drop: 140 lbs / 30 inches

76/11"

50/3"

50/4"

50/5.5"

S -2

S -3

S -4

5 inches of asphalt.

Very dense, brown to red-brown, Clayey Gravel with Sand and Cobbles (GC); moist; cobbles inferred from drill action, occasional iron oxide staining.

Alluvium

Cobbles and Boulder; inferred from drill action.

BOTTOM OF BORING

COMPLETED ON 02/21/2020

G ro un dw at er N ot E nc ou nt er ed D ur in g D ril lin g

0.4

7.0

10.4

March 2020

Sample Not Recovered

Hole Diam.:

Rod Type.:

Hammer Type:

SHANNON & WILSON, INC.

10.4 ft.

FIG. A-6

S am pl es

LOG OF BORING SW-02

5 in.

AWJ

Automatic

S ym bo l

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between material types, and the transition may be gradual.

SOIL DESCRIPTION

NOTES

1. Refer to Figure A-1 for explanation of symbols, codes, abbreviations and definitions.

2. The discussion in the text of this report is necessary for a proper understanding of the nature of the subsurface materials.

3. Groundwater level, if indicated above, is for the date specified and may vary.

4. USCS designation is based on visual-manual classification and selected lab testing.

Brush Creek Transit Center

CO FLAP PIT 82(1)

Pitkin County, Colorado

0 60

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

20 40

Geotechnical and Environmental Consultants

23-1-01458-060

ODEX

Vine Laboratories CME 55 Truck Boring SW-02 and 2 offsets attempted on 02/14/2020

LEGEND

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

G ro un d

W at er

D ep th , f t.

Standard Penetration Test

D ep th , f t.

Latitude:

Longitude:

Station:

Offset:

20 40

QCL 3

M A

S T

E R

_L O

G _E

_P O

C K

E T

P E

N _L

A T

LO

N G

3-

1-

-0

B R

U S

H C

R E

E K

P A

R K

IN

G

.G P

J

/1 0/

(blows/foot)PENETRATION RESISTANCE Hammer Wt. & Drop: 140 lbs / 30 inches

77/11"

50/6"

50/0"

50/5.5"

March 2020

Sheet 1 of 3

Brush Creek Transit Cient

CO FLAP PIT 82(1)

Pitkin County, Colorado Boring Location SW-01

BORING LOCATION PHOTOGRAPHS

23-1-01458-060

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

View looking south.

FIG. 7

Sheet 2 of 3

Brush Creek Transit Cient

CO FLAP PIT 82(1)

Pitkin County, Colorado Boring Location SW-01A

BORING LOCATION PHOTOGRAPHS

23-1-01458-060

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Sheet 3 of 3

Brush Creek Transit Cient

CO FLAP PIT 82(1)

Pitkin County, Colorado Boring Location SW-02

BORING LOCATION PHOTOGRAPHS

23-1-01458-060

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants