5020 County Road 154 Email: …townofgypsum.com/sites/default/files/Appendix J_ Prelim. Subsoil... · ENGINEERING ANALYSIS ... soils and Evaporite with auger equipment was occasionally

5020 County Road 154

Glenwood Springs, CO 81601

Phone: (970) 945-7988

Fax: (970) 945-8454

Email: [email protected]

Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado

PRELIMINARY SUBSOIL STUDY PROPOSED SIENA LAKE PUD – PHASE I

COOLEY MESA ROAD GYPSUM, COLORADO

PROJECT NO. 17-7-431.01

MARCH 28, 2018

PREPARED FOR:

RED TABLE VENTURES, LLC ATTN: GEORGE ROBERTS

P. O. DRAWER 4930 EAGLE, COLORADO 81631

[email protected]

mailto:[email protected]

Project No. 17-7-431.01

TABLE OF CONTENTS

PURPOSE AND SCOPE OF STUDY ....................................................................................... - 1 -

PROPOSED CONSTRUCTION ................................................................................................ - 1 -

SITE CONDITIONS ................................................................................................................... - 2 -

POTENTIAL GEOLOGIC HAZARDS ..................................................................................... - 2 -

FIELD EXPLORATION ............................................................................................................ - 3 -

SUBSURFACE CONDITIONS ................................................................................................. - 4 -

ENGINEERING ANALYSIS ..................................................................................................... - 5 -

DESIGN RECOMMENDATIONS ............................................................................................ - 6 - SITE GRADING ..................................................................................................................... - 6 -

PAVEMENT SECTION THICKNESS .................................................................................. - 6 - PRELIMINARY FOUNDATION RECOMMENDATIONS .................................................... - 9 -

FOUNDATIONS .................................................................................................................... - 9 - FLOOR SLABS .................................................................................................................... - 10 -

UNDERDRAIN SYSTEM ................................................................................................... - 11 -

SURFACE DRAINAGE ....................................................................................................... - 11 - LIMITATIONS ......................................................................................................................... - 11 -

FIGURE 1 - LOCATION OF EXPLORATORY BORINGS

FIGURE 1A – OVERALL DEVELOPMENT PLAN

FIGURES 2 and 3 - LOGS OF EXPLORATORY BORINGS

FIGURE 4 through 16 - SWELL-CONSOLIDATION TEST RESULTS

TABLE 1- SUMMARY OF LABORATORY TEST RESULTS

Project No. 17-7-431.01

PURPOSE AND SCOPE OF STUDY

This report presents the results of a preliminary subsoil study for Phase I of the proposed Siena

Lake PUD, south of Cooley Mesa Road, Gypsum, Colorado. The project site is shown on

Figures 1 and 1A. The purpose of the study was to develop recommendations for the site

grading and roadway pavement sections as well as preliminary recommendations for building

foundations. The study was conducted as supplemental services to our agreement for

geotechnical engineering services to Red Table Ventures, LLC dated May 26, 2017. We

previously reviewed the geologic conditions at the site for sketch plan submittal of the project

and presented our findings in a report dated July 28, 2017, Project No. 17-7-431.

A field exploration program consisting of exploratory borings was conducted to obtain

information on the general subsurface conditions. Samples of the subsoils and bedrock obtained

during the field exploration were tested in the laboratory to determine their classification,

compressibility or swell and other engineering characteristics. The results of the field

exploration and laboratory testing were analyzed to develop recommendations for the site

grading and roadway pavements section thicknesses, as well as preliminary foundation design

recommendations for the proposed buildings. This report summarizes the data obtained during

this study and presents our conclusions, design recommendations and other geotechnical

engineering considerations based on the proposed construction and the subsurface conditions

encountered.

PROPOSED CONSTRUCTION

The planned Phase I area is located in the north and northeast portion of the development as

shown on Figure 1A. The development will consist primarily of smaller, single family

residences (mountain cottages) as well as pads for recreational vehicle (RV) parking. There will

also be a clubhouse building in the middle portion of the site on the north side of the larger lake.

The larger lake near the proposed clubhouse has been mostly graded but does not contain water.

There will also be a smaller lake in the north-central part of the Phase I area. The lakes will be

lined to prevent leakage. The future development will include mixed use residential and

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Project No. 17-7-431.01

commercial in the northwestern part of the site and additional residential construction in the

central, western and southern portions of the site. The infrastructure will include asphalt paved

roadways and deep (water and sewer) and shallow utilities.

The Phase I residences will be one to possibly two story structures typically constructed over

crawlspace. Based on the sloping terrain, some of the residences may have walkout basement

levels. The buildings are desired to be founded on helical piers and/or micro-piles, as feasible,

due to the sloping terrain in areas. We assume relatively light foundations loadings for the

residential buildings. The clubhouse will be a larger structure and may have moderate

foundation loadings.

When building plans, grading design and traffic loading information have been developed, we

should be notified to re-evaluate the recommendations presented in this report and perform

additional analyses as needed.

SITE CONDITIONS

The site is vacant and has undergone extensive previous grading primarily in the central and

northern portions of the site mainly consisting of down cutting the natural terrain. There are

some minor fill areas in the central and northeastern parts of the site. A debris flow mitigation

fill berm and associated basin storage area is located in the southeastern portion. There are two

relatively large fill piles that include vegetation and topsoil located to the west of the larger lake

area. The natural areas in the eastern, northeastern, western and extreme southern parts of the

site are gently rolling to hilly terrain with slope grades of typically 5 to 10% with steeper hillside

areas of about 20 to 35%. The graded cut slopes are steep and non-vegetated. The natural

vegetation consists of grasses, weeds and brush with scattered juniper trees. Eagle Valley

Evaporite is exposed in several of the cut areas on the site and on the nearby hillside terrain.

POTENTIAL GEOLOGIC HAZARDS

Potential geologic hazards that may impact the development include the potential for sinkhole

development, debris flows and moisture sensitive soils. The sinkhole potential is discussed

further below. The debris flow hazard in the southeastern part of the site has apparently been

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Project No. 17-7-431.01

mitigated by a catchment basin designed by the civil engineer. The moisture sensitive soils are

discussed further in the “Preliminary Foundation Recommendations” section of this report.

Bedrock of the Pennsylvanian age Eagle Valley Evaporite underlies the site. These rocks are a

sequence of gypsiferous shale, fine-grained sandstone and siltstone with some massive beds of

gypsum and limestone. Based on our boring information, there are areas of massive gypsum

deposits associated with the Eagle Valley Evaporite underlying portions of the site. Dissolution

of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of

localized subsidence. During previous work in the area, several sinkholes were observed

scattered throughout the Gypsum area and to the south of the Siena Lake planned development.

These sinkholes appear similar to others associated with the Eagle Valley Evaporite in other

areas of the Eagle River valley underlain by the Evaporite.

Sinkholes were not observed on the subject property. No evidence of cavities was encountered

in the subsurface materials; however, the exploratory borings were relatively shallow, for

grading and preliminary foundation designs. Based on our present knowledge of the subsurface

conditions at the site, it cannot be said for certain that sinkholes will not develop. The risk of

future ground subsidence on Phase I of the Siena Lake PUD throughout the service life of the

proposed development, in our opinion, is low; however, the owners should be made aware of the

potential for sinkhole development. If further investigation of possible cavities in the bedrock

below the site is desired, we should be contacted.

FIELD EXPLORATION

The field exploration for the project was conducted between December 29, 2017 and January 9,

2018. Fifteen exploratory borings were drilled at the locations shown on Figures 1 and 1A to

evaluate the general subsurface conditions. The borings were advanced with 4 inch diameter

continuous flight augers powered by a truck-mounted CME-45B drill rig. The borings were

logged by a representative of H-P/Kumar. The locations and ground elevations of the borings

were surveyed and provided by Boundaries Unlimited.

Samples of the subsoils and bedrock were taken with 1⅜ inch and 2 inch I.D. spoon samplers.

The samplers were driven into the subsoils and bedrock at various depths with blows from a 140-

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Project No. 17-7-431.01

pound hammer falling 30 inches. This test is similar to the standard penetration test described by

ASTM Method D-1586. The penetration resistance values are an indication of the relative

density or consistency of the subsoils and hardness of the bedrock. Depths at which the samples

were taken and the penetration resistance values are shown on the Logs of Exploratory Borings,

Figures 2 and 3. The samples were returned to our laboratory for review by the project engineer

and testing.

SUBSURFACE CONDITIONS

Graphic logs of the subsurface conditions encountered at the site are shown on Figures 2 and 3.

The subsoils encountered consisted of nil to 15 feet of man-placed fill overlying sandy to very

sandy clay and silt, intermixed sand and clay, silty clayey sand or clayey sand and gravel. These

soils extended to the depths drilled of 26 to 31 feet at Borings 2, 3, 4 and 8. With depth, two of

the borings located in the lower, northern part of the site (Borings 1 and 4) encountered relatively

dense, silty sandy gravel and cobble with probable small boulders (below depths of 30 feet) that

are river deposited alluvium. Eagle Valley Evaporite bedrock was encountered in several of the

borings (Borings 6, 7 and 9 through 15) below depths from 3 to 28 feet. The fill soils were

generally very stiff to medium dense and included some topsoil, and an organic layer of topsoil

and vegetation from about 12 to 15 feet depth at Boring 14. The sandy to very sandy clay and

silt, intermixed sand and clay, silty clayey sand or clayey sand and gravel soils were stiff to very

stiff and medium dense to occasionally dense, contained scattered cobbles and possible small

boulders consisting primarily of shale fragments, and were occasionally gypsiferous. The

Evaporite consisted of claystone/siltstone with gypsum in areas and between various depths, was

generally weathered and hard becoming less weathered and very hard with depth. Drilling in the

soils and Evaporite with auger equipment was occasionally difficult due to cobbles and boulders

and bedrock hardness, however, drilling refusal was not encountered to the depths drilled.

Laboratory testing performed on samples obtained from the borings included natural moisture

content and density, percent finer than sand size gradation analyses, and Atterberg limits.

Results of swell-consolidation testing performed on relatively undisturbed drive samples,

presented on Figures 4 through 16, indicate generally low to moderate compressibility under

conditions of loading and wetting. Several of the lower density and gravelly soil samples

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Project No. 17-7-431.01

showed a low to moderate collapse potential when wetted under a constant light surcharge and

moderately high compressibility when loaded after wetting, and some of these samples may have

been partly disturbed due to the rock content. Several other of the more clayey soil and

weathered claystone/siltstone samples showed a low swell potential when wetted under a

constant light surcharge. The laboratory testing is summarized in Table 1.

No free water was encountered in the borings at the time of drilling or when checked 1 or more

days later. The subsoils and bedrock were slightly moist.

ENGINEERING ANALYSIS

The subsoil and bedrock conditions at the site are variable with respect to type, depths and

engineering characteristics. The existing fill appears generally well compacted and fair quality

with the except of the “slash pile” at Boring 14 which includes some topsoil and an organic

topsoil/vegetation layer in the bottom 3 feet. Difficult excavation for the deeper utilities should

be expected in areas due to the very hard bedrock and gypsum. Based on the primarily fine

grained soils near the surface and some fill areas, comparatively thick pavement sections,

desirably with a granular sub-base, will be needed for better long term performance of the

pavement areas.

Foundations for most of the lightly loaded structures can probably consist of spread footings.

For alternate foundation types, helical piers should also be feasible in deeper soil and fill areas,

and in shallow bedrock areas micro-piles or drilled piers are more feasible to penetrate the

bedrock. For the commercial development area, the upper soils are typically hydro-compressive

and relatively deep, and removal and replacement of a depth of the soils as structural fill below

the buildings and/or use of relatively deep foundation system such as driven piles may be

needed.

Provided below are recommendations for site grading and pavement section thickness designs, as

well as preliminary recommendations for the building foundation, floor slab and subsurface and

surface drainage.

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Project No. 17-7-431.01

DESIGN RECOMMENDATIONS

SITE GRADING The on-site soils and well broken bedrock, excluding topsoil, can be used for roadway

construction and utility trench backfill with proper processing and placement. Most of the “slash

pile” (Boring 14 area) contains vegetation and topsoil and is probably not suitable as structural

fill. Structural fill, such as for roadway embankment and below other pavement areas, should be

compacted to at least 95% of the maximum standard Proctor density (SPD) at a moisture content

within about 2% of optimum. This will likely require moistening and mixing the materials prior

to use as structural fill. We estimate the onsite soils and well broken bedrock will have long

term settlements of about 1 to 1½% of their fill depth when placed to 95% SPD. Higher degree

of compaction for fills greater than about 8 to 10 feet deep is desirable to limit fill settlement and

distress to facilities constructed on the fill. Miscellaneous fill can consist of the on-site soils and

well broken bedrock and should be compacted to at least 90% SPD. We should review the site

grading plans when developed.

Prior to the fill placement, the subgrade should be carefully prepared by removing all vegetation

and topsoil, scarifying to a depth of about 8 inches, adjusting to near optimum moisture content

and compacting to at least 95% of the maximum standard Proctor density. Soft subgrade or

existing fill areas may require stabilization prior to fill placement. Stabilization can probably be

accomplished by sub-excavating around 1 to 2 feet and placing coarse granular soils. Providing

a geo-grid on the subgrade, such as Tensar TX140 or TX160, would help to decrease the amount

of coarse granular soils needed for stabilization. Crushed and processed base course (angular)

material, such as CDOT Class 2 road base, is more compatible with the tri-axial geogrid to

reduce the depth of coarse granular soils for stabilization. We should review the field conditions

exposed to determine need for sub-excavation of unsuitable soils and/or placement of a geo-grid

on the subgrade prior to fill placement for pavement section construction.

PAVEMENT SECTION THICKNESS We understand asphalt pavement is planned for the access and subdivision roads. Traffic

loadings for the roads have not been provided. Based on our experience, we expect the primary

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Project No. 17-7-431.01

access roads will classify as collector streets with moderate traffic, and the neighborhood roads

will have low traffic volume typical of residential streets. The traffic will likely include

construction traffic. There will also likely be some concrete pavement areas.

Subgrade Materials: Pavement design procedures are based on strength properties of the

subgrade and pavement materials assuming stable, uniform subgrade conditions. Certain soils

such as the upper, fine-grained soils encountered on this site, are frost susceptible and could

impact pavement performance. The soils at the site are considered moderately to highly

susceptible to frost action. Frost susceptible soils are problematic when there is a free water

source. If those soils are wetted, the resulting frost heave movements can be large and erratic.

Therefore, pavement design procedures assume dry subgrade conditions by providing proper

surface and subsurface drainage. A granular sub-base (12 to 18-inch depth) below the pavement

section would reduce the frost heave potential and increase the support capacity of the subgrade

for pavement sections.

The near surface fine-grained soils encountered at the site are mainly low to non-plastic sandy

silts and clays and sandy silts which classify as AASHTO A-4 with Group Indices of 0 to 4 on

the samples tested. These soils are considered a poor support for pavement materials. From the

soil classifications and our experience in the area, we estimate a Hveem stabilometer 'R' value in

the range of 8 to 12 for these soils. For design purposes, the soil support value of the subgrade

was selected based on an Hveem 'R' value of 8 for flexible (asphalt) pavements and a modulus of

subgrade reaction of 50 pci was selected for rigid (portland cement) pavements.

Pavement Section: Since anticipated traffic loading information was not available at the time of

report preparation, an 18-kip equivalent daily load application (EDLA) of about 40 was assumed

for the main access road and about 15 for the neighborhood roads of the subdivision. These

loadings assume some construction traffic and should be reviewed by the project civil engineer.

A Regional Factor of 2.0 was also assumed for this site based on the site terrain, drainage and

climatic conditions. Serviceability Indices of 2.5 and 2.0 were used for the main access road and

the subdivision streets, respectively.

Based on the assumed parameters, the following alternate asphalt surface pavement thickness

sections are recommended.

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Project No. 17-7-431.01

Roadway

Location

Alternative

Number

Asphalt

Depth

(inches)

Base Course

Depth

Inches

Sub-Base

Depth *

(inches)

Main

Road(s)

1 4 12 0

Main

Road(s)

2 5 8 0

Main

Road(s)

3 4 6 12

Subdivision

Streets

1 4 8 0

Subdivision

Streets

2 4 6 12

Subdivision

Streets

3 3 8 12

*CDOT Class 2 Aggregate Base Course (minus 4 inch road base)

As an alternative to asphalt pavement and in areas where truck turning movements are

concentrated, or for roadway drainage pans, the pavement section can consist of 6 inches of

portland cement concrete on 6 inches of base course. We can review the pavement section

recommendations if desired and when additional information is available.

Pavement Materials: The section thicknesses assume a structural coefficient of 0.44 for the

asphalt surface. The base course should meet CDOT Class 6 specifications. The granular sub-

base material should meet CDOT Class 2 specifications. The concrete should meet CDOT Class

D or P specifications and be air entrained. The material properties and compaction should be in

accordance with the project specifications.

Subgrade Preparation: Recommendations for placing roadway fill were provided above in the

“Site Grading” section of the report. The subgrade in cut and existing grade areas should be

scarified to a depth of 8 inches, adjusted to a moisture content near optimum and compacted to at

least 95% of the maximum standard Proctor density. Prior to placing the pavement section, the

subgrade should be proof-rolled with a heavily loaded pneumatic-tired vehicle. Pavement design

procedures assume a stable subgrade. Areas which deform excessively under heavy wheel loads

are not stable and should be removed and replaced to achieve a stable subgrade prior to paving.

Partial subexcavation of a depth (typically 2 to 3 feet) and replacement with coarse granular soils

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Project No. 17-7-431.01

and/or Tensar TX-140 or TX-160 geo-grid may be needed in existing fill areas and should be

further evaluated at the time of construction.

Drainage: The collection and diversion of surface drainage away from paved areas is extremely

important to the satisfactory performance of pavement. Drainage design should provide for the

removal of water from paved areas and prevent wetting of the subgrade soils. Uphill roadside

ditches should have an invert level at least 1 foot below the road base and sub-base, or be a

minimum 1 foot depth with a minimum 12 inch thick clay soil cover over the roadside ditch

slope. We should review the ditch detail if a clay soil cover over the base course and sub-base is

planned.

PRELIMINARY FOUNDATION RECOMMENDATIONS

Provided below is a discussion of preliminary recommendations for building foundation, floor

slab and, subsurface and surface drainage for the residences and club house. Site specific studies

should be conducted to provide more detailed design recommendations for the individual

buildings.

FOUNDATIONS

Spread Footings: Bearing conditions will vary depending on the specific location of the

building on the property. Based on the nature of the proposed construction, spread footings

bearing on the natural subsoils or bedrock should be suitable at most of the Phase I residential

building sites and probably the club house. The soils and bedrock have variable compressibility/

expansion potential which could result in differential movement of the foundation especially in

areas where the footings transition soil to bedrock and/or the bearing materials become wetted.

We expect the footings can be sized for an allowable bearing pressure in the range of 1,000 psf

to 1,500 psf for the neutral soils and 2,000 psf to 3,000 psf for the bedrock. Expansive clays and

bedrock encountered in building areas may need to be removed or the footings designed to

impose a minimum dead load pressure to limit potential heave. Foundation walls should be

designed to span local anomalies and to resist lateral earth loadings when acting as retaining

structures. Below grade areas and retaining walls should be protected from wetting and

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Project No. 17-7-431.01

hydrostatic loading by use of an underdrain system. The footings should have a minimum depth

of 42 inches for frost protection.

Deep Foundations: Several options are feasible for a relatively deep foundation system at the

site. Helical piers should be feasible to support the light residential buildings in areas where soil

is deeper than about 12 to 15 feet. Light duty helical piers typically develop a downward

working capacities in the range of 20 to 25 kips. The piers should have a minimum embedded

length of about 15 feet.

In areas where bedrock is shallow, helical piers are not considered feasible due to assumed

shallow refusal and micro-piles would be more desirable. Micro-piles should develop downward

working capacities in the range of 30 to 50 kips depending on the bedrock conditions and their

installation depth. Micro-piles are typically design/build by qualified contractors with

experience in the area. Straight-Shaft drilled piers may also be feasible in most areas of the site

where underlain by bedrock.

In the commercial development area, steel H-piles, heavy duty screw piles or possibly concrete

filled pipe piles driven to refusal in the underlying coarse granular soils are feasible as a

relatively deep foundation system. The piles should develop their structural capacity when

properly installed to refusal.

FLOOR SLABS

Slab-on-grade construction should be feasible for bearing on the natural soils or the weathered

bedrock for subgrade with low or no potential for movement. There could be some post

construction slab movement at sites with collapsible matrix or expansive clays especially if the

subgrade becomes wetted. In areas where gypsum or moisture sensitive soils are exposed at slab

subgrade, it may be necessary to sub-excavate a few feet and replace the material with

compacted structural fill such as road base. To reduce the effects of some differential

movement, floor slabs should be separated from all bearing walls and columns with expansion

joints. Floor slab control joints should be used to reduce damage due to shrinkage cracking. A

minimum 4-inch-thick layer of free-draining gravel should underlie basement level slabs to

facilitate drainage.

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Project No. 17-7-431.01

UNDERDRAIN SYSTEM

Although free water was not encountered in the exploratory borings, it has been our experience

in the area where clayey soils are present and/or bedrock is shallows that local perched

groundwater can develop during times of heavy precipitation or seasonal runoff. An underdrain

system should be provided to protect below-grade construction, such as retaining walls,

crawlspace and basement areas from wetting and hydrostatic pressure buildup. The drains

should consist of drainpipe surrounded above the invert level with free-draining granular

material. The drain should be placed at each level of excavation and at least 1 foot below lowest

adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet. An impervious

membrane such as 20 or 30 mil PVC should typically be placed beneath the drain gravel in a

trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing

soils or bedrock.

SURFACE DRAINAGE

The grading plan for the subdivision should consider runoff from uphill slopes through the

project and at individual sites. Water should not be allowed to pond which could impact slope

stability, pavements and foundations. To limit infiltration into the bearing soils next to

buildings, exterior backfill should be well compacted and have a positive slope away from the

building for a distance of at least 10 feet. Roof downspouts and drains should discharge well

beyond the limits of all backfill and landscape irrigation should be restricted.

LIMITATIONS

This study has been conducted in accordance with generally accepted geotechnical engineering

principles and practices in this area at this time. We make no warranty either express or implied.

The conclusions and recommendations submitted in this report are based upon the data obtained

from the exploratory borings drilled at the locations indicated on Figures 1 and 1A, the proposed

type of construction and our experience in the area. Our services do not include determining the

presence, prevention or possibility of mold or other biological contaminants (MOBC) developing

in the future. If the client is concerned about MOBC, then a professional in this special field of

TABLE 1 SUMMARY OF LABORATORY TEST RESULTS

Project No. 17-7-431.01 Page 1 of 4

SAMPLE LOCATION NATURAL MOISTURE CONTENT

NATURAL DRY

DENSITY

GRADATION PERCENT PASSING NO. 200 SIEVE

ATTERBERG LIMITS AASHTO

CLASSIFICATION SOIL TYPE BORING DEPTH GRAVEL SAND LIQUID

LIMIT PLASTIC

INDEX (%) (%)

(ft) (%) (pcf) (%) (%)

1 2½ 7.2 99 Very Sandy Silt and Clay

5 9.8 111 77 Sandy Clayey Silt

10 15.8 106 Sandy Silt and Clay

15 15.0 105 88 Sandy Silt and Clay


2 5 7.4 126 Clayey Silty Sand with Gravel

10 7.8 124 Clayey Silty Sand with Gravel


3 2½ 5.8 113 71 NP* A-4 (0) Sandy Silt

10 6.3 107 Sandy Silt and Clay with Gravel

20 5.0 118 Sandy Silty Clay


4 2½ 13.8 106 Sandy Silt and Clay


15 10.9 122 Very Sandy Silty Clay with

Gravel

*NP=Non-Plastic

TABLE 1

SUMMARY OF LABORATORY TEST RESULTS Project No. 17-7-431.01

Page 2 of 4


NATURAL DRY

DENSITY




LIMIT PLASTIC

INDEX (%) (%)

(ft) (%) (pcf) (%) (%)

5 2½ 10.6 114 85 NP* A-4 (0) Sandy Silt


20 5.8 124 47 Very Clayey Silty Sand with

Gravel

6 2½ 4.7 126 Gypsum

7 2½ 4.5 109 66 NP* A-4 (0) Sandy Silt


8 2½ 8.6 122 69 Sandy Silt and Clay (Fill)


(Fill)


(Fill)

20 8.0 126 Clayey Silty Sand and Gravel

9 2½ 7.0 114 89 24 6 A-4 (4) Sandy Silt and Clay

5 8.8 109 Very Sandy Silt and Clay



*NP-Non-Plastic

TABLE 1


Page 3 of 4


NATURAL DRY

DENSITY




LIMIT PLASTIC

INDEX (%) (%)

(ft) (%) (pcf) (%) (%)

10 1 8.3 124 76 NP* A-4 (0) Sandy Silt with Gravel

5 0.5 110 Gypsum

15 11.4 118 Weathered Claystone/Siltstone

with Gypsum

11 2½ 7.2 123 Sandy Silt and Clay with Gravel




12 2½ 6.8 115 66 29 7 A-4 (3) Sandy Silt and Clay with Gravel


13 5 7.0 117 Sandy Silt and Clay with Gravel

10 7.5 118 78 Sandy Silt and Clay with Gravel


*NP=Non-Plastic

TABLE 1


Page 4 of 4


NATURAL DRY

DENSITY




LIMIT PLASTIC

INDEX (%) (%)

(ft) (%) (pcf) (%) (%)

14 10 14.0 104 66 Sandy Silty Clay with Gravel

(Fill)

15 8.0 115 Silty Clayey Sand with Gravel

15 2½ 5.9 118 44 23 4 A-4 (0) Very Sandy Silt and Clay with

Gravel

5 5.7 109 Silty Clayey Sand with Gravel


Documents

5020 County Road 154 Email: …townofgypsum.com/sites/default/files/Appendix J_ Prelim. Subsoil... · ENGINEERING ANALYSIS ... soils and Evaporite with auger equipment was occasionally