geotechnical engineering design report for the...

GEOTECHNICAL ENGINEERING

DESIGN REPORT For The

Montezuma-Cortez High School Project

Prepared For: Mr. Alex Carter, Superintendent

Montezuma County School District RE-1, and, Mr. Jim Ketter, PE, KPMC

Project Number: 53088GE November 7, 2013

PN: 53088GE Design Level Geotechnical Engineering Report

November 7, 2013

1

1.0 REPORT INTRODUCTION ................................................................................................ 2

1.1 Scope of Project ................................................................................................................... 3

2.0 GEOTECHNICAL ENGINEERING STUDY .................................................................... 4

2.1 Geotechnical Engineering Study Scope of Service .............................................................. 4

3.0 FIELD STUDY....................................................................................................................... 6

3.1 Project location ................................................................................................................ 6

3.2 Site Description and Geomorphology.................................................................................. 6

3.3 Subsurface Soil and Water Conditions ................................................................................ 6

3.4 Site Seismic Classification .................................................................................................. 12

4.0 LABORATORY STUDY .................................................................................................... 12

5.0 FOUNDATION RECOMMENDATIONS ........................................................................ 14

5.1 Spread Footings ................................................................................................................. 14

5.2 General Shallow Foundation Considerations ................................................................... 17

5.3 Drilled Piers....................................................................................................................... 17

5.4 Grade Beams...................................................................................................................... 20

6.0 RETAINING STRUCTURES............................................................................................. 20

7.0 SUBSURFACE DRAIN SYSTEM ...................................................................................... 22

8.0 CONCRETE FLATWORK ................................................................................................. 24

8.1 Interior Concrete Slab-on-Grade Floors............................................................................ 24

8.2 Exterior Concrete Flatwork Considerations ...................................................................... 27

8.3 General Concrete Flatwork Comments ............................................................................. 28

9.0 PAVEMENT SECTION THICKNESS DESIGN RECOMMENDATIONS .................. 28

10.0 CONSTRUCTION CONSIDERATIONS ........................................................................ 30

10.1 Fill Placement Recommendations..................................................................................... 31

10.1.1 Embankment Fill on Slopes ....................................................................................... 31

10.1.2 Natural Soil Fill ........................................................................................................ 32

10.1.3 Granular Compacted Structural Fill ......................................................................... 33

10.2 Excavation Considerations ............................................................................................... 34

10.2.1 Excavation Cut Slopes ............................................................................................... 35

10.3 Utility Considerations....................................................................................................... 35

10.4 Landscaping Considerations ............................................................................................ 35

10.5 Soil Sulfate Content, Corrosion Issues ............................................................................. 38

10.6 Radon Issues ..................................................................................................................... 38

11.0 CONSTRUCTION MONITORING AND TESTING .................................................... 38

12.0 CONCLUSIONS AND CONSIDERATIONS ................................................................. 39

FIELD STUDY RESULTS…………………………………………………….……Appendix A

Log of Test Borings

LABORATORY TEST RESULTS……………………………………………….. Appendix B

Swell Consolidation Test Results

Moisture Content/Dry Density (Proctor)

California Baring Ratio Test


November 7, 2013

2

1.0 REPORT INTRODUCTION

This report presents our geotechnical engineering recommendations for the new Montezuma-

Cortez High School Project. Our data report was presented on May 6, 2013. This report was

requested by Mr. Alex Carter, Superintendent, Montezuma School District RE-1, and Mr. Jim

Ketter, PE, KPMC. The field study was completed on June 19, 2013. The laboratory study was

completed on July 12, 2013. This November 7, 2013 report is a re-issue of our July 15, 2013

report with the addition of the subsurface logs and tables from our Phase I report

Geotechnical engineering is a discipline which provides insight into natural conditions and site

characteristics such as; subsurface soil and water conditions, soil strength, swell (expansion)

potential, consolidation (settlement) potential, and often slope stability considerations. Typically

the information provided by the geotechnical engineer is utilized by many people including the

project owner, architect or designer, structural engineer, civil engineer, the project builder and

others. The information is used to help develop a design and subsequently implement

construction strategies that are appropriate for the subsurface soil and water conditions, and slope

stability considerations. It is important that the geotechnical engineer be consulted throughout

the design and construction process to verify the implementation of the geotechnical engineering

recommendations provided in this report. Generally the recommendations and technical aspects

of this report are intended for design and construction personnel who are familiar construction

concepts and techniques, and understand the terminology presented below. We should be

contacted if any questions or comments arise as a result of the information presented below.

The following outline provides a synopsis of the various portions of this report;

� Sections 1.0 and 2.0 provide an introduction and an establishment of our scope of

service.

� Sections 3.0 and 4.0 of this report present our geotechnical engineering field and

laboratory studies

� Sections 5.0 through 10.0 presents our geotechnical engineering design parameters and

recommendations which are based on our engineering analysis of the data obtained.

� Section 10.0 provides a brief discussion of construction sequencing and strategies which

may influence the geotechnical engineering characteristics of the site.

The discussion and construction recommendations presented in Section 10.0 are intended to

help develop site soil conditions that are consistent with the geotechnical engineering

recommendations presented previously in the report. Ancillary information such as some

background information regarding soil corrosion and radon considerations is presented as

general reference. The construction considerations section is not intended to address all of the


November 7, 2013

3

construction planning and needs for the project site, but is intended to provide an overview to

aid the owner, design team, and contractor in understanding some construction concepts that

may influence some of the geotechnical engineering aspects of the site and proposed

development.

In the interest of developing a concise and brief discussion of the geotechnical engineering

conditions and associated design recommendations this report does not contain significant

tutorial information. The intent of this report is for the architect, structural engineer, contractor

and others that are familiar with design and construction terminology. We are available to

discuss and provide additional explanation for those who are not familiar with the terminology,

as needed.

We have not included significant information from our data report for this project. This

information was utilized, however, as part of the development of the recommendation is within

this report. We included some of the previous discussions from the data report within the text

of this report, where appropriate.

The data used to generate our recommendations are presented throughout this report and in the

attached figures.

1.1 Scope of Project

The project development will include construction of a new high school campus. The

proposed main high school structure is located along the northern, higher elevation, portion of

the project site. Athletic fields, tennis courts and other improvements are proposed for the

southern portion of the project site. The proposed entrance and parking areas are located

primarily in the northwest quadrant of the (approximate) 35 acre site.

The structures will include design and construction of steel reinforced concrete foundations

systems and floors, reinforced masonry (veneer and structural) and retaining walls. The proposed

parking area will most likely be constructed of flexible asphalt concrete pavement. The athletic

field will include a track and playing fields with associated bleachers and infrastructure.

The entire project site will likely include relatively extensive earthwork including excavation

cut of portions of the site and fill placement. We suspect that the earthwork portion of the site

will include mass excavation and fill placement utilizing large earth working equipment such as

scrapers and large compaction equipment.


November 7, 2013

4

2.0 GEOTECHNICAL ENGINEERING STUDY

This section of this report presents the results of our field and laboratory study and our

geotechnical engineering recommendations based on the data obtained.

Our services include a geotechnical engineering study of the subsurface soil and water

conditions for development of this site for the proposed high school structure.

2.1 Geotechnical Engineering Study Scope of Service

The scope of our study which was delineated in our proposal for services, and the order of

presentation of the information within this report, is outlined below.

Field Study

• We advanced twenty-eight (28) test borings on the project site for the data report and

advanced an additional eight (8) test borings on the project site for this portion of our

contribution to this project.

• The field study for the design level report included advancing three (3) NWL core borings

and five (5) continuous flight auger test borings.

• Select NWL core, driven sleeve and bulk soil samples were obtained from the test borings

and returned to our laboratory for testing.

Laboratory Study

• The laboratory testing and analysis of the samples obtained included;

� Moisture content and dry density,

� Estimates of soil and rock strength based on unconfined compressive strength

tests and direct shear strength tests, to help establish a basis for development of

soil bearing capacity and lateral earth pressure values,

� Swell/consolidation tests to help assess the expansion and consolidation potential

of the support soils on this site to help estimate potential uplift associated with

expansive soils and to help estimate settlement of the foundation system, and,

� Sulfate content testing of select soil samples to help assess the potential for

corrosion due to sulfates on Portland cement concrete,

� Moisture content/dry density relationship (Proctor) tests, and,

� California Bearing Ratio (CBR) tests


November 7, 2013

5

Geotechnical Engineering Recommendations

• This report addresses the geotechnical engineering aspects of the site and provides

recommendations including;

Geotechnical Engineering Section(s)

� Subsurface soil and water conditions that may influence the project design

and construction considerations

� Geotechnical engineering design parameters including;

� Viable foundation system concepts including soil bearing capacity

values,

� settlement considerations for the foundation system concepts that are

viable for this project, and,

� Lateral Earth Pressure values for design of retaining structures,

� Flexible asphalt concrete pavement thickness considerations

� Soil support considerations for interior and exterior concrete flatwork,

Construction Consideration Section

� Fill placement considerations including cursory comments regarding site

preparation and grubbing operations,

� Comments for placement and compaction of fill on sloped areas,

� Considerations for excavation cut slopes,

� Natural soil preparation considerations for use as backfill on the site,

� Compaction recommendations for various types of backfill proposed at the

site,

� Utility trench considerations, and,

� Cursory exterior grading considerations

• This report provides design parameters, but does not provide foundation design or

design of structure components. The project architect, designer, structural engineer or

builder may be contacted to provide a design based on the information presented in

this report.

• Our subsurface exploration, laboratory study and engineering analysis do not address

environmental or geologic hazard issues


November 7, 2013

6

3.0 FIELD STUDY

3.1 Project location

The project site is located at the southwest corner of the intersection of Sligo and 3rd Street in

Cortez, Colorado. The project site is located on previously undeveloped property that is located

immediately south of the Cortez Wal-Mart.

3.2 Site Description and Geomorphology

The project site is located on a gently sloping surface with the general inclination of the site

being down to the south with inclination generally flatter than about twenty (20) percent. There

are small intermittent ephemeral drainages on the site. The surface soil consists of eolian (wind

blown) loess deposits. The underlying geologic material is the Dakota Formation which consists

of sandstone and claystone and areas of interbedded sandstone and claystone. There are outcrops

of the Dakota in the northeast section of the property.

We observed evidence of previous excavations near the northwest-central portion of the site and

near the northeast corner of the site. We understand that these excavations may be related to

archeological sites on the property. Other portions of the site have had removal of vegetation,

which may have been related to construction activities associated to the previous Wal-Mart

project construction on the adjacent property located north of the site.

Vegetation on the site consists primarily of sage brush with sparse grass.

3.3 Subsurface Soil and Water Conditions

We advanced three (3) NWL rock core borings within the proposed structure and advanced five

(5) continuous flight auger test borings at the project site in addition to the twenty-eight (28) test

borings that were advanced as part of the geotechnical engineering data report for this site.

We have included the test boring location map from Phase 1 below in Figure 1 for reference. We

have shown the outline of the proposed structure locations that was provided to us with the

locations of the test borings that were advanced as part of this study, below on Figure 2. The logs

of the soils encountered in our test borings are presented in Appendix A.


November 7, 2013

7

Figure 1. Phase 1 Test boring location map from Phase 1 report. Red dots indicate auger test

borings (TB-1). Target symbols represent NQ Test Core locations (TC-1).

TC-1

TC-2

TC-4

TC-3


November 7, 2013

8

Figure 2. Test boring and test core location map for Phase II. TB refers to auger advanced

test borings. TC refers to test cores advanced with NWL rock core. “Ph-II” refers to the design

level Phase two study borings.

TC-2, Ph-II

TB-4, Ph-II

TB-5, Ph-II

TB-7, Ph-II

TB-6, Ph-II

TC-1, Ph-II

TC-3, Ph-II

TB-8, Ph-II


November 7, 2013

9

The figure presented above was prepared using plans provided to us and notes taken during the

field work. The intent of the figure is only to show the approximate test boring locations for

reference purposes only. The test borings were marked with survey lath upon their completion.

We recommend that the project surveyor located and establish the elevations of the ground

surface at each test boring location so that the subsurface information provided can better be

correlated to the proposed building and foundation elevations.

We have tailored our subsurface conditions discussion presented in our data report by

incorporating the information obtained from our June 16-19, 2013 subsurface exploration below.

We encountered about one and one-half (1½) to two and one-half (2½) feet of a loess soil

deposit in our test borings. The upper few inches of this material has more organic content than

deeper layers. The material is essentially very fine sand and silt materials with a minor amount

of clay. Though this material may be considered as generally suitable for site fill and

establishing grade, it is less desirable for use as-is for fill material for support of flatwork and

structural components. Though this material is not “topsoil” in the strict sense, it should be

considered for stockpiling and subsequent use as final surface soils in area of the site where

structural components will not be placed. For estimating and budgeting the amount of the more

organic portion of this soil for final surface vegetative planting material we suggest using

between 6 to 9 inches of depth across most of the project site. There are two (2) areas within the

building foot print and parking area where surface vegetation has been recently stripped, and

therefore the depth of this material is generally less within these areas. The recently stripped

areas are easily identifiable on aerial photographs of the site. The upper 6 to 9 inches of the loess

soil material have organic materials and should therefore be stockpiled for use as surface planting

soil and preparation for landscaping and establishment of surface vegetation after the

construction, if the landscape architect or landscape professional determines that they are suitable

for that use.

We encountered clayey sand in our borings to variable depths. This material ranged from

clayey and silty sand, to clay with lesser amounts of sand. Generally this soil layer may be

considered as existing from about two (2) to five (5) feet below the surface within the test

borings advanced for this study.

We encountered lean clay with sandstone fragments in some of our test borings primarily in the

southwest quadrant of the site as part of the data report study. We did not encounter this material

within the test borings for this study; however we have included the previous discussion since it

is possible that this soil will be encountered in the excavation phase of the project. This material

is somewhat anomalous in that it consists of a lean clay with angular clasts of sandstone and


November 7, 2013

10

actually exists within the formational materials as observed in some of our core borings. It is

very atypical for a soil deposit to exist within a formational materials deposit, however it is

possible if there is a sudden climatic change during the depositional period of the formation. In

this case we suspect that the well indurated soil is a result of short term localized erosion and

subsequent deposition of detritus from areas close to the site. As more normal climatic and

depositional characteristics were re-established, additional deposition of the sandstone materials

occurred. The Molas formation is one such mapped geologic unit in the Four Corners region that

was formed in such a fashion. The Molas formation may be observed in outcroppings and

roadway cuts near the Durango Mountain Report and other locations in the San Juan Mountains,

The swell tests performed on samples of the clay and sandstone clast material included in our

data report indicates that it has a very high to extreme swell pressure and potential when wetted

and may consolidate under high loads. If this material is encountered within areas of the

proposed structure or within areas where structural components for ancillary buildings we

recommend that it be removed, if feasible as part of the site preparation. If the depth is such that

removal is not realistic, mitigative measures will need to be developed based on the nature of the

structure or flatwork being supported by this material.

The site is underlain by the Cretaceous Dakota Sandstone. It should be noted that the name of

this geologic unit is somewhat misleading in that the unit contains more than just sandstone.

Carbonaceous shale, lignite and coal are all found within the Dakota Sandstone unit in the Four

Corners region. The generally hard, cliff-forming quartzitic sandstone exposures of this unit are

noted throughout Colorado, thus the name of the unit reflects these omnipresent sandstone beds.

We have had experience in the Cortez area, including recent exploration within a quarter mile

of this site where the sandstone beds of the Dakota are extremely hard and are suitable for

processing and use as rock products. Mesa Sandstone, a local quarry, utilizes sandstone

materials from the Dakota for production of commercial rock products. Although we did find

relatively hard sandstone layers in our core borings, the relatively thin layers of these hard layers

may reduce the viability for utilization of this material for rock products produced on-site. The

additional core and auger borings conducted for this design level report have confirmed that the

site materials that are potentially suitable for on-site crushing and processing do not have

sufficient lateral or vertical extent to be considered for this type of on-site processing.

We encountered a sandy claystone layer that has a medium dark to buff-green color. This

material was encountered within both Ph-II-TC-3 and the immediately adjacent Ph-II-TB-8 from

about five (5) to fifteen (15) feet below the ground surface. We estimate that the ground surface

elevation at these test borings is nominally 6,157 to 6,158 feet, but should be confirmed. We

understand that the current proposed finished floor elevation is 6,155, therefore the estimated


November 7, 2013

11

spread footing foundation system, if used, will be at nominally 6,152 and within this zone of

weathered sandy claystone material. The sandy claystone material generally consists of thin

(generally less than about one (1) inch thick) layers of friable clayey sandstone, interlaminated

with layers of a sandy claystone. The sandy claystone to claystone layers washed out of our core

barrel at some elevations, and expanded extensively and rapidly in others and became lodged in

our core equipment. Due to the friable and delicate nature of the claystone encountered in Ph-II-

TC-3, we advanced a continuous flight auger test boring (Ph-II-TB-8) immediately adjacent to

this core boring so that we could obtain a driven sample of the material for laboratory testing.

The sample tested, Ph-II-TB-8 @ 9 feet, had a measured swell pressure of approximately 7,620

pounds per square foot with a swell potential of about nine (9) percent under a 100 pound per

square foot surcharge load. The sample obtained from Ph-II-TC-3 @ 9 feet had a measured swell

pressure of bout 2,940 pounds per square foot with a slightly less swell potential of about eight

(8) percent.

The elevations of the two samples discussed above are nominally about two (2) feet below the

estimated footing support elevation discussed above, but are within the zone of influence of the

spread footing elevation. Unlike a soil sample where the measured swell potential will constitute

an estimate of volume increase (and associated uplift) that is directly proportional to the

thickness of material wetted, the interlaminated nature of the material encountered suggests that

the actual volume increase will be proportional only to the percentage of the expansive material

within this layer. It is not possible to accurately estimate the proportion of the expansive material

within this layer throughout the proposed building site, but a cursory estimate is between 50 to 75

percent. We have provided additional discussion of this layer relative to a spread footing

foundation design and associated mitigative concepts in Section 5.0 of this report below.

We did not encounter free subsurface water in our test borings at the time of our field work.

Although we do not feel that it is likely that subsurface water will be encountered during the

project construction, it has been our experience on sites with shallow formational materials that

due to a lack of significant a soil mantle that subsurface water migration and temporary perched

areas of subsurface water may occur as a result of heavy precipitation.

The logs of the subsurface soil conditions encountered in our test borings are presented in

Appendix A. The logs present our interpretation of the subsurface conditions encountered

exposed in the test borings at the time of our field work. Subsurface soil and water conditions

are often variable across relatively short distances. It is likely that variable subsurface soil and

water conditions will be encountered during construction. Laboratory soil classifications of

samples obtained may differ from field classifications.


November 7, 2013

12

3.4 Site Seismic Classification

The seismic site class as defined by the 2006 International Building Code is based on some

average values of select soil characteristics such as shear wave velocity, standard penetration test

result values, undrained shear strength, and plasticity index.

We encountered weathered formational material soils in our test borings at and below the

anticipated footing support elevations. Based on our standard penetration test results at this site

and on laboratory test results of the soils tested we feel that the Site Class as outlined in the 2006

international Building Code, Table 1613.5.2 is Site Class C

4.0 LABORATORY STUDY

The laboratory study included tests to estimate the strength, swell and consolidation potential of

the soils tested. We performed the following tests on select samples obtained from the test

borings.

Moisture content and dry density; the moisture content and in-situ dry density of some of the

soil samples were assessed in general accordance with ASTM D2216

Atterberg Limits; the plastic limit, liquid limit and plasticity index of some of the soil samples

was determined in general accordance with ASTM D4318

Swell-Consolidation Tests; the one dimensional swell-consolidation potential of some of the

soil samples obtained was determined in general accordance with ASTM D2435. The soil

sample tested is exposed to varying loads and usually the addition of water. The one-

dimensional swell-consolidation response of the soil sample to the loads and/or water is

represented graphically on Figures 4.1 through 4.6.


November 7, 2013

13

A synopsis of some of our laboratory swell-consolidation data for the samples tested is

tabulated below.

Sample

Designation,

PHII Borings

Moisture Content

(percent)

Dry Density

(PCF)

Swell Pressure

(PSF) Swell Potential

(% under 100 psf load)

TB4 @ 2’ 8.0 108.0 1,030 0.5

TB5 @ 2’ 6.2 102.1 510 < 0.5

TB6 @ 7’ 4.2 133.8 1,410 1.0

TB7 @ 4’ 4.9 121.8 1,120 1.0

TB8 @ 9’ 7.5 123.2 7,620 9.2

TC3 @ 9’ 7.8 123.8 2,940 8.0

Moisture content-dry density relationship (Proctor) tests; We performed laboratory moisture

content-dry density tests to assess the relationship between the soil moisture content and dry

density. The Proctor tests were performed in general accordance with ASTM D1557. The

results of the laboratory Proctor tests are presented on Figure 4.7.

California Bearing Ratio (CBR) Tests; We assessed the pavement section support characteristics

of select composite soil samples in general accordance with ASTM D1883. The results of the

CBR tests are presented on Figure 4.8.

Unconfined Compressive Strength of Rock Core Samples; the unconfined compressive strength

of select in-situ core samples were performed was obtained in general accordance with ASTM

D2166-06. The tests were performed on NWL Core Samples, approximately 1.875 inch

diameter by approximate four (4) inch long. The results of the unconfined compressive strength

samples are presented below

Sample Designation PHII-TC-2@5’ PHII-TC-2@7’

Sample Density (PCF) 134.9 148.7

Unconfined Compressive

Strength (PSI) 2,920 3,880


November 7, 2013

14

Soluble Sulfate Tests: We performed soluble sulfate tests on soil samples obtained during our

field work. The soluble sulfate tests indicate100 parts per million soluble sulfates in the samples

tested. Soluble sulfate considerations are discussed in Section 10.6 of this report.

5.0 FOUNDATION RECOMMENDATIONS

We have provided recommendations for both conventional spread footings and drilled piers

below. Generally we feel that conventional spread footings are a viable foundation system for

the proposed structure based on our subsurface exploration and laboratory testing, however as

discussed in Section 3.3 above, the sandy claystone layer encountered in Ph-II-TC-3 and Ph-

II_TB-8 was determined to have expansive layers, therefore we have provided drilled piers as an

alternative foundation system design for consideration.

5.1 Spread Footings

Generally we encountered materials with a low swell potential in our test borings as shown in

the tabulation presented in Section 4.0 above. We encountered a sandy claystone with a high

swell pressure and swell potential in Ph-II-TC-3 and Ph-II-TB-8. It is not possible to fully

mitigate the potential for uplift of soils with swell pressures on the order of 2,940 to 7,620

pounds per square foot with swell potentials of 8 to 9 percent solely by developing a footing with

a high dead load, since it is not realistic to achieve a design dead load of these magnitudes. The

mitigation of the influence for these swelling soils should include the following;

� Our geotechnical engineer must observe the characteristics of the materials exposed in the

excavation.

� If non-expansive material are encountered the footings may be placed either on the clean,

competent formational material or on a leveling course of compacted granular fill placed

on the competent formational material.

� If the material exposed in the foundation excavation (or portions thereof) is suspected of

being the expansive claystone the following options may be considered:

� Fully excavate expansive materials, if feasible, and support footings on deeper

sandstone,

� If two (2) feet of excavation occurs and expansive materials are still encountered,

compacted structural fill composed of CDOT Class 6, ¾ inch minus aggregate

base course should be placed and compacted as discussed in Section 10 of this

report.

� CDOT Class 6 specifies a range of 3-12 percent passing the #200. For the

purposes of this project the minimum amount passing the #200 sieve should be 6

percent


November 7, 2013

15

It may not be fully possible to identify all expansive layers within the zone of influence below

the footing particularly since the material can only be observed at the bottom of the excavations

at the time of construction, therefore it is imperative that this project include an aggressive effort

to prevent the support material from being wetted after construction. We recommend that a

subsurface drain system be placed around the perimeter footings and adjacent to any areas that

may be influenced by future water leaks in the structure. The subsurface drain system should be

underlain by a 40 mil PVC impervious geotextile material to further reduce the potential for

subsurface water migration as shown below.

It should be noted that based on our understanding if the current finished elevations of 6,155

and the minimum depth required for frost depth that the nominal footing support elevation will

be about 6,152. Based on the topographic map provided that shows the building location,

portions of the building will be located in areas where the current ground surface elevation is

about 6,148. Due to the variable surface topography and the location of the building it will be

necessary to adjust the footing support elevation in portion of the building so that all footings are

either supported directly by the competent sandstone formation, or a layer of structural fill placed

on the formational material.

Compacted backfill of

foundation excavation

Exterior grade sloped to

promote surface drainage

Impervious geotextile

liner, 40 mil PVC or

similar

Subsurface drain –

discussed in Section 7.0

of this report

Landscape drain

discussed din Section

10.5 of this report


November 7, 2013

16

All footings should have a minimum depth of embedment of at least one (1) foot. The

embedment concept is shown below.

The footings may be supported directly by the clean, competent formational material or on a

blanket of compacted structural fill which is supported by the formational material. Footings

supported directly on the formational material may be designed using a bearing capacity of 5,000

pounds per square foot. Footings supported by a blanket of compacted structural fill placed on

the formational material may be designed using a soil bearing capacity of 3,000 pounds per

square foot with a minimum depth of embedment of at least one (1) foot. The bearing capacity

may be increased by twenty (20) percent due to transient loads.

We estimate that the footings designed and constructed above will have a total post construction

settlement of about 1/4 - 1/3 inch. We estimate that the differential settlement may be about ¼

inch.

All footings should be support at an elevation deeper than the maximum depth of frost

penetration for the area. It is our understanding that the current building code for Cortez includes

a minimum depth for frost protection of thirty-six (36) inches. This recommendation includes

exterior isolated footings and column supports. Please contact the local building department for

specific frost depth requirements.

Minimum depth

of embedment Footing

Footing Embedment Concept

No Scale


November 7, 2013

17

The post construction differential settlement may be limited and reduced by designing footings

that will apply relatively uniform loads on the support soils. Concentrated loads should be

supported by footings that have been designed to impose similar loads as those imposed by

adjacent footings.

Under no circumstances should any footing be supported by more than three (3) feet of

compacted structural fill material unless we are contacted to review the specific conditions

supporting these footing locations.

The design concepts and parameters presented above are based on the soil conditions

encountered in our test borings. We should be contacted during the initial phases of the

foundation excavation at the site to assess the soil support conditions and to verify our

recommendations.

5.2 General Shallow Foundation Considerations

Some movement and settlement of any shallow foundation system will occur after construction.

Movement associated with swelling soils also occurs occasionally. Utility line connections

through and foundation or structural component should be appropriately sleeved to reduce the

potential for damage to the utility line. Flexible utility line connections will further reduce the

potential for damage associated with movement of the structure.

5.3 Drilled Piers

Drilled piers which are designed as end bearing and supported by the clean competent

unweathered formational material underlying the site are a viable foundation system option. The

drilled pier borings should be advanced a minimum of two (2) pier diameters into the hard

sandstone formational material which we anticipate will be encountered at a nominal depth of

about ten (10) to fifteen (15) feet below finished floor elevation, however the elevation of this

material encountered in our test borings ranged from at the ground surface to depths of fifteen

(15) feet, therefore we suspect that the depth encountered during construction will be highly

variable.

If refusal of the equipment occurs prior to establishing the appropriate embedment of the

bottom of the pier into the formational material it may be necessary for the pier drilling

contractor to establish the best type of cutting head for maximum advancement of the pier into

the formational material. Drilled piers supported by the clean, competent formational material

may be designed using a bearing capacity of 30,000 pounds per square foot. The portion of the

pier in the unweathered formational material may be designed using a side friction of 2,000


November 7, 2013

18

pounds per square foot. The drilled piers should be designed to resist uplift associated with

swelling of the support soils. The top of the piers should not be flared, which can allow the soils

to “grab” the pier and cause uplift. Our experience has been that the claystone and shale

formational material in the area may exert swell pressures in the range of about 4,000 to 6,000

pounds per square foot.

The site sandy claystone had a measured swell pressure of as high as about 7,220 pounds per

square foot with a swell potential of about 9.2 percent under a 100 pound per square foot

surcharge load. The swelling soils will tend to grab the piers which will cause tensional forces to

develop in the drilled pier. The total uplift force imposed on the drilled piers by the swelling

sandy claystone may be estimated based on the surface area of the pier that is exposed to the

active depth of the swelling soils. We estimate that the site soils may imposed an uplift force of

about 3,500 pounds per square foot of pier circumference surface area for portion of each pier

where the sandy claystone is encountered. For estimating purposes we suggest that about ten

(10) feet of each pier be considered as being exposed to this uplift force where the claystone is

encountered.

The required depth of the drilled piers to resist movement must be determined to help resist

uplift of the piers from the swelling soils. The required depth of the piers to resist movement is

estimated based on; the soil characteristics and active zone depth, loads from the structure that

will be exerted on the piers, and the diameter of the piers used on the site. We are available to

provide recommendations for minimum pier depths based on the parameters above. We will

need estimates of the imposed structure loads and the chosen pier diameters to perform our

drilled pier depth analysis. Please contact us with this information when it becomes available.

Many geotechnical engineers feel that some mobilization and movement of the pier may be

needed to develop side shear strength and associated skin friction within the soil mantle which

overlies the formational material. Mobilization of the pier can only develop if settlement or

failure of the support materials of the pier occurs. Movement of pier is obviously undesirable

regardless of the mode of movement. If it is desirable to establish design values for additional

side friction from the portion of the piers in the soil mantle, we should be contacted to discuss

this topic and provide additional information, if needed.

The piers should be installed using drilling equipment which is good working order and intended

for advancing large diameter borings. Proper performance of the drilled piers requires

appropriate drilling and installation techniques. All drilled piers must be installed by a contractor

who is familiar with pier construction. The piers should be cased, as required by the site soil

conditions so that no flares or “mushrooms” exist at the tops of the piers. Flares allow for

increased uplift forces to develop in the piers and subsequent movement which may cause

damage to the structure.


November 7, 2013

19

Proper performance of the drilled pier is partially influenced by the character and quality of the

concrete used to construct the pier. The pier concrete should not be too stiff, which may prevent

proper consolidation of the concrete, or too fluid, which may adversely effect the strength of the

concrete. Generally the concrete should have a slump between about three (3) to six (6) inches.

It may be necessary to use mid- or high-range water reducing concrete admixtures to obtain

concrete with both a suitable slump and acceptable concrete compressive strength characteristics.

We generally recommend use of a tremmie and/or pumping equipment should be used to place

concrete in drilled pier borings deeper than about ten (10) feet, however recent studies have

shown that the characteristics of the concrete dropped to this and greater heights has not been

significantly influenced, therefore the structural engineer should be consulted in regard to use of

tremmie, or pump-placed concrete for this project.

We did not encounter free subsurface water in our test borings at the time of our field work. It

has been our experience that subsurface water is often encountered along fractures, fissures and

joints within the formational material. Occasionally the drilling operations will increase the pore

pressures within the adjacent material to produce a small amount of water access to the drilled

pier excavation. If water and/or caving soils are encountered during the pier installation

operation it may be necessary to dewater the pier excavations and remove any caved soils. Pier

concrete should not be conventionally placed if more than a few inches of water exists in the

bottom of the pier boring. If more than a few inches of water exists in the bottom of the boring

the concrete should be placed using a tremmie, or pump, so that the concrete displaces any water

during the pier foundation construction operation.

The support elevation of the pier must be thoroughly cleaned prior to placement of the pier

concrete. Loose material in the bottom of the pier borings will cause settlement of the pier. The

pier support elevation may be cleaned using clean-out tools attached to the drill rig, hand

equipment, excavation suction equipment, or a combination of these. Under no circumstances

should the pier foundation concrete be placed when loose material exists in the bottom of the

borings.

The interface between the weathered formational and the underlying competent formational

material was relatively obscure in some of our test borings and was a transitional contact in other

borings. We should be contacted during construction to aid in determining the appropriate pier

support elevation.

We should be contacted to measure the depth of the piers, verify the competency of the support

materials, and check the plumbness of the piers. We are available provide an as-built record of

the installed drilled pier foundation system. Please contact us if this service is desired.


November 7, 2013

20

5.4 Grade Beams

Grade beams are utilized in a pier and grade beam foundation system to distribute the structure

loads to each of the piers. The grade beam reinforcement and associated span distance is

developed by the project structural engineer. The structural considerations of the grade beam in

association with an assessment of the structure being supported by them will, in part determine

the spacing between each of the deep foundation components, such as drilled piers (or drilled

shafts), helical piers, micropiles and driven piles. Regardless of the type of deep foundation

being considered, it is imperative that an appropriate void be developed below the grade beam so

that swelling soils do not create uplift of the supported structure.

Voids are most commonly developed with commercially available cardboard “void forms” that

are placed at the bottom of the concrete forms prior to placement of reinforcement steel and the

grade beam concrete. If the soils below the grade beam become moistened and expand, the

cardboard void form will collapse without the soils having the ability to impose uplift forces on

the bottom of the grade beam. The height of the void is often related to the expansion potential

of the site soils and anticipated depth of wetting that will develop within the soils below the

grade beam. We generally recommend that a minimum of four (4) inches of void be established.

Thicker voids, such as six (6) inches are common in the areas where more expansive soils are

encountered. We recommend that minimum void height of six (6) inches established for this

project.

We are available to provide additional information in regard to void forms and associated

conditions if additional information is needed.

6.0 RETAINING STRUCTURES

We understand that laterally loaded walls will be constructed as part of this site development.

Lateral loads will be imposed on the retaining structures by the adjacent soils and, in some cases,

surcharge loads on the retained soils. The loads imposed by the soil are commonly referred to as

lateral earth pressures. The magnitude of the lateral earth pressure forces is partially dependent

on the soil strength characteristics, the geometry of the ground surface adjacent to the retaining

structure, the subsurface water conditions and on surcharge loads.


November 7, 2013

21

The retaining structures may be designed using the values tabulated below.

Lateral Earth Pressure Values

Type of Lateral Earth Pressure Level Non-Expansive Native

Soil Backfill

(pounds per cubic foot/foot)*

Level Granular Soil Backfill

(pounds per cubic foot/foot)

Active 50 35

At-rest 70 55

Passive 295 460

Allowable Coefficient of Friction 0.31 0.45

Some of the site soils have measured swell pressures of nominally 500 to 1,000 pounds per

square foot which may be exerted on the retaining wall should the backfill soils become

moistened. If the site clay soils are used as backfill they must be moisture conditioned to above

optimum moisture content during the backfill placement. We should be consulted during

construction to verify the characteristics of any native soil backfill for walls taller than five (5)

feet.

The granular soil that is used for the retaining wall backfill may be permeable and may allow

water migration to the foundation support soils. There are several options available to help

reduce water migration to the foundation soils, two of which are discussed here. An impervious

geotextile layer and shallow drain system may be incorporated into the backfill, as discussed in

Section 9.5, Landscaping Considerations, below. A second option is to place a geotextile filter

material on top of the granular soils and above that place about one and one-half (1½) to two (2)

feet of moisture conditioned and compacted site clay soils. It should be noted that if the site clay

soils are used volume changes may occur which will influence the performance of overlying

concrete flatwork or structural components.

The values tabulated above are for well drained backfill soils. The values provided above do

not include any forces due to adjacent surcharge loads or sloped soils. If the backfill soils

become saturated the imposed lateral earth pressures will be significantly higher than those

tabulated above.

The granular imported soil backfill values tabulated above are appropriate for material with an

angle of internal friction of thirty-five (35) degrees, or greater. The granular backfill must be

placed within the retaining structure zone of influence as shown below in order for the lateral

earth pressure values tabulated above for the granular material to be appropriate.


November 7, 2013

22

If a granular backfill is chosen it should not extend to the ground surface. Some granular soils

allow ready water migration which may result in increased water access to the foundation soils.

The upper few feet of the backfill should be constructed using an impervious soil such as silty-

clay and clay soils from the project site, if these soils are available.

Backfill should not be placed and compacted behind the retaining structure unless approved by

the project structural engineer. Backfill placed prior to construction of all appropriate structural

members such as floors, or prior to appropriate curing of the retaining wall concrete (if used) may

result in severe damage and/or failure of the retaining structure.

7.0 SUBSURFACE DRAIN SYSTEM

A subsurface drain system and/or weep holes should be included in the retaining structure

design. Exterior retaining structures may be constructed with weep holes to allow subsurface

water migration through the retaining structures. A drain system constructed with a free draining

aggregate material and a perforated pipe should be constructed adjacent to retaining structures or

adjacent to foundation walls on sites with expansive soil conditions. We suggest that the system

consist of a fabric-wrapped aggregate, or a sand material (some sands may not need fabric, we

are available to discuss this with you) which surrounds a rigid perforated pipe. We typically do

not recommend use of flexible corrugated perforated pipe since it is not readily possible to

establish a uniform gradient of the flexible pipe throughout the drain system alignment.

55 Degrees

Retaining wall zone

of influence

Retaining

Structure

Retaining Structure Zone of

Influence Concept, No Scale

Impervious soil

backfill for

upper 2 feet


November 7, 2013

23

Corrugated drain tile is perforated throughout the entire circumference of the pipe and therefore

water can escape from the perforations at undesirable locations after being collected. The nature

of the perforations of the corrugated material further decreases its effectiveness as a subsurface

drain conduit.

The drain system pipe should be graded to surface outlets or a sump vault. Typically a

minimum gradient of about two (2) percent is preferred for subsurface drain systems, but site

geometry and topography may influence the actual installed pipe gradient. Water must not be

allowed to pool along any portion of the subsurface drain system. An improperly constructed

subsurface drain system may actually promote water access to undesirable locations. The drain

system pipe should be surrounded by about two (2) to four (4) cubic feet per lineal foot of free

draining aggregate or sand. If a sump vault and pump are incorporated into the subsurface drain

system, care should be take so that the water pumped from the vault does not recirculate through

pervious soils and obtain access to the basement or crawl space areas. A generalized subsurface

drain system concept is shown below.

Perforated pipe surrounded by

fabric wrapped free-draining

material. Note: The elevation

of the pipe will depend on the

location in the system at which

the cross section is considered.

Impervious backfill for

upper 2 feet

Compacted backfill that

meets lateral earth pressure

design criteria.

Retaining or

foundation wall

Water proof

membrane or

similar placed on

the foundation wall

and extending

below outer face of

footing

Pervious drain board or

fabric (optional)

Footing

Subsurface Drain System Concept No Scale

Geotextile filter fabric, if appropriate


November 7, 2013

24

There are often aspects of each site and structure which require some tailoring of the subsurface

drain system to meet the needs of individual projects. We are available to provide consultation

for the subsurface drain system for this project, if desired.

Water often will migrate along utility trench excavations in formational material. If the utility

trench extends from areas above the site, this trench may be a source for subsurface water within

the proposed basements. We suggest that the utility trench backfill be thoroughly compacted to

help reduce the amount of water migration. The subsurface drain system should be designed to

collect subsurface water from the utility trench and fractures within the formational material and

direct it to surface discharge points.

8.0 CONCRETE FLATWORK

We understand that both interior and exterior concrete flatwork will be included in the project

design. Concrete flatwork is typically lightly loaded and has a limited capability to resist shear

forces associated with uplift from swelling soils and/or frost heave. It is prudent for the design

and construction of concrete flatwork on this project to be able to accommodate some movement

associated with swelling soil conditions, if possible.

The soil samples tested have a measured swell pressure of 500 to 1,000 pounds per square foot

and a negligible volume increase under a 100 pound per square foot surcharge load. The

formational sandy claystone has swell pressures of as high as 7,620, however based on the

locations and elevations where the formational sandy claystone was encountered we suspect that

this expansive layer will not be encountered at the slab-on-grade support elevations throughout

the site. As with the footing support considerations we have provided an outline regarding

observations of the slab-support materials with associated recommended actions in the following

section of this report.

8.1 Interior Concrete Slab-on-Grade Floors

Generally the interior floor support materials will be less susceptible to water intrusion and

subsequent moisture migration, however care should be taken during the construction operations

to verify that the sandy claystone with expansive characteristics does not exist in support areas

for interior floors. If the expansive claystone is encountered under portions of the floor slab we

recommend that the following be conducted, which is the same outline as presented in Section

5.1, above.


November 7, 2013

25

� Our geotechnical engineer must observe the characteristics of the materials exposed in the

excavation.

� If non-expansive material are encountered the footings may be placed either on the clean,

competent formational material or on a leveling course of compacted granular fill placed

on the competent formational material.

� If the material exposed in the foundation excavation (or portions thereof) is suspected of

being the expansive claystone the following options may be considered:

� Fully excavate expansive materials, if feasible, and support footings on deeper

sandstone,

� If two (2) feet of excavation occurs and expansive materials are still encountered,

compacted structural fill composed of CDOT Class 6, ¾ inch minus aggregate

base course should be placed and compacted as discussed in Section 10 of this

report.

� CDOT Class 6 specifies a range of 3-12 percent passing the #200. For the

purposes of this project the minimum amount passing the #200 sieve should be 6

percent

Regardless of support materials encountered on this site we recommend that they be supported

by a one (1) foot thick layer of compacted structural fill. This will help mitigate soils or other

materials that have a lesser swell potential than the claystone materials discussed throughout this

report.

If drilled piers are utilized for this project, it may be desirable to structurally support the floor

slabs to take full advantage of the more robust drilled pier foundation design. The only means to

completely mitigate the influence of volume changes on the performance of interior floors is to

structurally support the floors. Floors that are suspended by the foundation system will not be

influenced by volume changes in the site soils. The suggestions and recommendations presented

below are intended to help reduce the influence of swelling soils on the performance of the

concrete slab-on-grade floors.

Capillary and vapor moisture rise through the slab support soil may provide a source for

moisture in the concrete slab-on-grade floor. This moisture may promote development of mold

or mildew in poorly ventilated areas and may influence the performance of floor coverings and

mastic placed directly on the floor slabs. There are a few options available to help reduce the

migration of capillary moisture and vapor rise into the floor slab.


November 7, 2013

26

Comments for Reduction of Capillary Rise

One option to stop capillary rise through the floor slab is to place a layer of clean aggregate

material, such as washed concrete aggregate for the upper four (4) to six (6) inches of fill

material supporting the concrete slabs.

Comments for Reduction of Vapor Rise

To reduce vapor rise through the floors slab a moisture barrier such as a 6 mil (or thicker)

plastic, or similar impervious geotextile material may be placed below the floor slab. The

American Concrete Institute (ACI) recommends that four (4) inches of “trimmable material” (not

sand) conforming to ASTM D448, No.10 grading be used between the vapor barrier and the

overlying concrete for support of concrete slab-on-grade floors. We have provided the

specifications for ASTM D48 No.10 Sand below.

Grading of ASTM D448 No. 10 Material

Sieve Size Percent Passing Each Sieve

3/8 inch 100

#4 85-100

#100 10 - 30

This type of material may not be locally available therefore we suggest that if an impervious

barrier is used that it should be placed on at two (2) to three (3) inches fine-grained granular

material, such as crusher reject material to protect it from punctures from the underlying

substrate materials with at least four (4) of trimmable material closely conforming to the D448

No. 10 grading, such as appropriately graded crusher reject material, on top of the barrier to

support the concrete floor slab. This will help reduce the influence of the barrier on migration of

concrete bleed water and associated concrete curing conditions during construction of the slab.

There are proprietary barriers that are puncture resistant that may not need the underlying layer of

protective material. We do not recommend placement of the concrete directly on a moisture

barrier unless the concrete contractor has had previous experience with curing of concrete placed

in this manner. The granular materials utilized for vapor or capillary considerations may be

considered as contributing to the compacted structural fill thickness discussed above. The

project architect, designer and/or builder should be contacted for the best capillary break for this

project.

The project architect, designer and/or builder should be contacted for the best capillary break for

this project. It is not necessary, from a geotechnical engineering perspective, to install capillary

breaks under garage floors unless it is possible that future conversion of the garage into interior

rooms is planned.


November 7, 2013

27

The project structural engineer should be contacted to provide steel reinforcement design

considerations for the proposed floor slabs. Any steel reinforcement placed in the slab should be

placed at the appropriate elevations to allow for proper interaction of the reinforcement with

tensile stresses in the slab. Reinforcement steel that is allowed to cure at the bottom of the slab

will not provide adequate reinforcement.

8.2 Exterior Concrete Flatwork Considerations

Exterior concrete flatwork includes concrete driveway slabs, aprons, patios, and walkways. The

desired performance of exterior flatwork typically varies depending on the proposed use of the

site and each owner’s individual expectations. As with interior flatwork, exterior flatwork is

particularly prone to movement and potential damage due to movement of the support soils. This

movement and associated damage may be reduced by following the recommendations discussed

under interior flatwork, above. Unlike interior flatwork, exterior flatwork may be exposed to

frost heave, particularly on sites with high silt-content soils. Without complete removal of soils

susceptible to frost heave, all exterior flatwork will be exposed to some potential for frost heave.

Since there is no subsurface water on the project site, any frost heave that occurs will be

associated with precipitation, snow melt, or irrigation. Proper surface drainage and eliminating

areas near exterior concrete flatwork where water may pond will greatly reduce the potential for

frost heave.

For exterior concrete flatwork that is placed immediately adjacent to the structure or other

critical structural components it is prudent to consider a thick granular compacted structural fill

layer of about two (2) feet and to isolate this flatwork from the structure or exterior finishes to

that uplift associated with frost heave does not influence exterior components or veneer.

If some movement of exterior flatwork is acceptable, we suggest that the support areas be

prepared by scarification, moisture conditioning and re-compaction of about six (6) to eight (8)

inches of the natural soils followed by placement of about four (4) to six (6) inches of compacted

granular fill material. The scarified material and granular fill materials should be placed as

discussed under the Construction Considerations, “Fill Placement Recommendations” section of

this report, below.

It is important that exterior flatwork be separated from exterior column supports, masonry

veneer, finishes and siding. No support columns, for the structure or exterior decks, should be

placed on exterior concrete unless movement of the columns will not adversely affect the

supported structural components. Movement of exterior flatwork may cause damage if it is in

contact with portions of the structure exterior.


November 7, 2013

28

8.3 General Concrete Flatwork Comments

It is relatively common that both interior and exterior concrete flatwork is supported by areas of

fill adjacent to either shallow foundation walls or basement retaining walls. A typical sketch of

this condition is shown below.

Settlement of the backfill shown above will create a void and lack of soil support for the

portions of the slab over the backfill. Settlement of the fill supporting the concrete flatwork is

likely to cause damage to the slab-on-grade. Settlement and associated damage to the concrete

flatwork may occur when the backfill is relatively deep, even if the backfill is compacted.

If this condition is likely to exist on this site it may be prudent to design the slab to be

structurally supported on the retaining or foundation wall and designed to span to areas away

from the backfill area as designed by the project structural engineer. We are available to discuss

this with you.

9.0 PAVEMENT SECTION THICKNESS DESIGN RECOMMENDATIONS

We performed a California Bearing Ratio (CBR) test on a composite sample of soil obtained

from the project site. Based on the results of the CBR test we used an R-Value of 15 in our

analysis for the pavement section thickness design.

Limit of construction

excavation

Foundation or

retaining wall

Concrete Slab-on-grade

Wall backfill area

Wall Backfill and Slab Support

Sketch No Scale


November 7, 2013

29

We recommend that the subgrade soils be proof-rolled prior to the scarification and processing

operations. Any soft areas observed during the proof-rolling operations should be removed and

replaced with properly processed materials and/or granular aggregate materials as part of the

subgrade preparation.

The site subgrade pavement section support soils must be scarified to a depth of twelve (12)

inches, moisture conditioned and compacted prior to placement of the overlying aggregate

pavement section materials. The material should be moisture conditioned to within about two (2)

percent of the optimum moisture content and compacted to at least ninety (90) percent of

maximum dry density as determined by the modified Proctor test, ASTM D1557.

The surface of the subgrade soil should be graded and contoured to be approximately parallel to

the finished grade of the asphalt surface.

The aggregate materials used within the pavement section should conform to the requirements

outlined in the current Specifications for Road and Bridge Construction, Colorado Department of

Transportation (CDOT). The aggregate base material should be a three-quarter (3/4) inch minus

material that conforms to the CDOT Class 6 aggregate base course specifications and have an R-

value of at least 78. The aggregate sub-base course should conform to the CDOT specifications

for Class 2 material and should have a minimum R-value 70. Other material may be suitable for

use in the pavement section, but materials different than those listed above should be tested and

observed by us prior to inclusion in the project design or construction. Aggregate sub-base and

base-course materials should be compacted to at least ninety-five (95) percent of maximum dry

density as defined by the modified Proctor test, ASTM D1557.

We recommend that the asphalt concrete used on this project be mixed in accordance with a

design prepared by a licensed professional engineer, or a asphalt concrete specialist. We should

be contacted to review the mix design prior to placement at the project site. We recommend that

the asphalt concrete be compacted to between ninety-two (92) and ninety-six (96) percent of the

maximum theoretical density.

We have provided several pavement section design thicknesses below. The structural support

characteristics of each section are approximately equal. The project civil engineer, or contractor

can evaluate the best combination of materials for economic considerations.

We have provided pavement section thicknesses for both 50,000 and 75,000 - 18,000 pound

equivalent single axle loads (18k ESAL). We are available to provide additional design sections,

if these are desired.


November 7, 2013

30

Pavement Section Design Thickness

50,000 18k ESAL

Pavement Section Component Alternative Thicknesses of Each Component

(inches)

Asphalt Concrete 3 3 3 4 6

Class 6 4 6 10 6 0

Class 2 8 5 0 0 0

Reconditioned Subgrade 12 12 12 12 12

Pavement Section Design Thickness

75,000 18k ESAL

Pavement Section Component Alternative Thicknesses of Each Component

(inches)

Asphalt Concrete 3 3 3 4 4 5 6.5

Class 6 4 6 11 4 8 5 0

Class 2 10 7 0 5 0 0 0

Reconditioned Subgrade 12 12 12 12 12 12 12

The pavement section thicknesses tabulated above are appropriate for the post-construction

residential traffic use. Heavy construction equipment traffic will have a significant influence on

the quality, character, and design life of the pavement sections tabulated above. If possible we

recommend that a partial section be constructed followed by construction of an overlay after

completion of the construction operations. We are available to discuss this with you as the

project progresses.

10.0 CONSTRUCTION CONSIDERATIONS

This section of the report provides more tutorial information than previous section and includes

comments, considerations and recommendations for aspects of the site construction which may

influence, or be influenced by the geotechnical engineering considerations discussed above. The

information presented below is not intended to discuss all aspects of the site construction

conditions and considerations that may be encountered as the project progresses. If any questions

arise as a result of our recommendations presented above, or if unexpected subsurface conditions

are encountered during construction we should be contacted immediately.


November 7, 2013

31

10.1 Fill Placement Recommendations

There are several references throughout this report regarding both natural soil and compacted

structural fill recommendations. The recommendations presented below are appropriate for the

fill placement considerations discussed throughout the report above.

All areas to receive fill, structural components, or other site improvements should be properly

prepared and grubbed at the initiation of the project construction. The grubbing operations

should include scarification and removal of organic material and soil. No fill material or

concrete should be placed in areas where existing vegetation or fill material exist.

We observed evidence of previous site use and excavations associated with archeological sites.

We suspect that man-placed fill or subsurface disturbance may be encountered as the project

construction progresses. All existing fill material should be removed from areas planned for

support of structural components. Excavated areas and subterranean voids should be backfilled

with properly compacted fill material as discussed below.

10.1.1 Embankment Fill on Slopes

Embankment fill placed on slopes must be placed in areas that have been properly prepared

prior to placement of the fill material. The fill should be placed in a toe key and benches

constructed into the slope. The concept is shown below.

New Embankment Fill

Bench Drain-

optional, as needed

Toe Key Drain, optional,

as needed

Benches

Toe Key

Pre-construction ground

surface

Toe Key and Bench Concept No Scale


November 7, 2013

32

The width of the toe key should be at least one-fourth (1/4) of the height of the fill. The

elevation difference between each bench, width, and geometry of each bench is not critical,

but generally the elevation difference between each lift should not exceed about three (3) to four

(4) feet. The benches should be of sufficient width to allow for placement of horizontal lifts of

fill material, therefore the size of the compaction equipment used will influence the bench

widths.

Embankment fill material thicker than five (5) feet should be analyzed on a site specific basis.

The fill mass may impose significant loads on, and influence the stability of the underlying slope.

We suggest that no fill slopes steeper than two and one-half to one (2½:1, horizontal to vertical)

be constructed unless a slope stability analysis of the site is conducted.

The toe key and bench drains shown above should be placed to reduce the potential for water

accumulation in the embankment fill and in the soils adjacent to the embankment fill. The

placement of these drains is more critical on larger fill areas, areas where subsurface water exists

and in areas where the slopes are marginally stable.

The toe key and bench drains may consist of a perforated pipe which is surrounded by a free

draining material which is wrapped by a geotextile filter fabric. The pipe should be surrounded

by four (4) to six (6) cubic feet of free draining material per lineal foot of drain pipe.

10.1.2 Natural Soil Fill

Any natural soil used for any fill purpose should be free of all deleterious material, such as

organic material and construction debris. Natural soil fill includes excavated and replaced

material or in-place scarified material.

Due to the expansive characteristics of the natural soil encountered on portions of the site,

particularly during the data report preparation, we recommend that any native soil proposed for

use as fill be evaluated during the construction operation to determine the suitability of specific

soil for use as fill within areas where structural components will be placed. All natural soils may

be used to establish general site elevation where not structural components or other improvement

features are constructed.

The natural soils should be moisture conditioned, either by addition of water to dry soils, or by

processing to allow drying of wet soils. The proposed fill materials should be moisture

conditioned to between about optimum and about two (2) percent above optimum soil moisture

content. This moisture content can be estimated in the field by squeezing a sample of the soil in

the palm of the hand. If the material easily makes a cast of soil which remains in-tact, and a


November 7, 2013

33

minor amount of surface moisture develops on the cast, the material is close to the desired

moisture content. Material testing during construction is the best means to assess the soil

moisture content.

Moisture conditioning of clay or silt soils may require many hours of processing. If possible,

water should be added and thoroughly mixed into fine grained soil such as clay or silt the day

prior to use of the material. This technique will allow for development of a more uniform

moisture content and will allow for better compaction of the moisture conditioned materials.

The moisture conditioned soil should be placed in lifts that do not exceed the capabilities of the

compaction equipment used and compacted to at least ninety (90) percent of maximum dry

density as defined by ASTM D1557, modified Proctor test. We typically recommend a

maximum fill lift thickness of six (6) inches for hand operated equipment and eight (8) to ten

(10) inches for larger equipment. Care should be exercised in placement of utility trench backfill

so that the compaction operations do not damage the underlying utilities.

Typically the maximum lift thickness is about six (6) to eight (8) inches, therefore the

maximum allowable rock size for natural soil fill is about six (6) inches. If smaller compaction

equipment is being used, such as walk behind compactors in trenches, the maximum rock size

should be less than about three (3) inches.

10.1.3 Granular Compacted Structural Fill

Granular compacted structural fill is referenced in numerous locations throughout the text of

this report. Granular compacted structural fill should be constructed using an imported

commercially produced rock product such as aggregate road base. Many products other than

road base, such as clean aggregate or select crusher fines may be suitable, depending on the

intended use. If a specification is needed by the design professional for development of project

specifications, a material conforming to the Colorado Department of Transportation (CDOT)

“Class 6” aggregate road base material can be specified. This specification can include an option

for testing and approval in the event the contractor’s desired material does not conform to the

Class 6 aggregate specifications. We have provided modification to the CDOT Specifications for

Class 6 material, in regard to the minimum recommended percent passing the #200 sieve below


November 7, 2013

34

Grading of CDOT Class 6 Aggregate Base-Course Material*

Sieve Size Percent Passing Each Sieve

¾ inch 100

#4 30 – 65

#8 25 – 55

#200 6 – 15

* Modified from CDOT Specifications in regard to -#200 specifications.

Liquid Limit of this material should be less than 30

All compacted structural fill should be moisture conditioned and compacted to at least ninety

(90) percent of maximum dry density as defined by ASTM D1557, modified Proctor test. Areas

where the structural fill will support traffic loads under concrete slabs or asphalt concrete should

be compacted to at least ninety-five (95) percent of maximum dry density as defined by ASTM

D1557, modified Proctor test.

Clean crushed aggregate fill should not be used on this project site due to the potentially

expansive nature of some of the materials that may be encountered below the footing support

elevations.

10.2 Excavation Considerations

Unless a specific classification is performed, the site soils should be considered as an

Occupational Safety and Health Administration (OSHA) Type C soil and should be sloped and/or

benched according to the current OSHA regulations. Excavations should be sloped and benched

to prevent wall collapse. Any soil can release suddenly and cave unexpectedly from excavation

walls, particularly if the soils are very moist, or if fractures within the soil are present. Daily

observations of the excavations should be conducted by OSHA competent site personnel to

assess safety considerations.

We did not encounter free subsurface water in our test borings. If water is encountered during

construction, it may be necessary to dewater excavations to provide for suitable working

conditions.

If possible excavations should be constructed to allow for water flow from the excavation the

event of precipitation during construction. If this is not possible it may be necessary to remove

water from snowmelt or precipitation from the foundation excavations to help reduce the

influence of this water on the soil support conditions and the site construction characteristics.


November 7, 2013

35

We encountered formational material in our test borings. We suspect that it may be difficult to

excavate this material using conventional techniques. If blasting is planned it must be conducted

strategically to reduce the affect of the blasting on the support characteristics of the site materials

and the stability of adjacent slopes.

10.2.1 Excavation Cut Slopes

We anticipate that some permanent excavation cut slopes may be included in the site

development. Temporary cut slopes should not exceed five (5) feet in height and should not be

steeper than about one to one (1:1, horizontal to vertical) for most soils. Permanent cut slopes of

greater than five (5) feet or steeper than two and one-half to one (2½:1, h:v) must be analyzed on

a site specific basis.

We did not observe evidence of existing unstable slope areas influencing the site, but due to the

steepness and extent of the slopes in the area we suggest that the magnitude of the proposed

excavation slopes be minimized and/or supported by retaining structures.

10.3 Utility Considerations

Subsurface utility trenches will be constructed as part of the site development. Utility line

backfill often becomes a conduit for post construction water migration. If utility line trenches

approach the proposed project site from above, water migrating along the utility line and/or

backfill may have direct access to the portions of the proposed structure where the utility line

penetrations are made through the foundation system. The foundation soils in the vicinity of the

utility line penetration may be influenced by the additional subsurface water. There are a few

options to help mitigate water migration along utility line backfill. Backfill bulkheads

constructed with high clay content soils and/or placement of subsurface drains to promote utility

line water discharge through the foundation drain system.

Some movement of all structural components is normal and expected. The amount of

movement may be greater on sites with problematic soil conditions. Utility line penetrations

through any walls or floor slabs should be sleeved so that movement of the walls or slabs does

not induce movement or stress in the utility line. Utility connections should be flexible to allow

for some movement of the floor slab.

10.4 Landscaping Considerations

We recommend against construction of landscaping which requires excessive irrigation.

Generally landscaping which uses abundant water requires that the landscaping contractor install

topsoil which will retain moisture. The topsoil is often placed in flattened areas near the

structure to further trap water and reduce water migration from away from the landscaped areas.


November 7, 2013

36

Unfortunately almost all aspects of landscape construction and development of lush vegetation

are contrary to the establishment of a relatively dry area adjacent to the foundation walls. Excess

water from landscaped areas near the structure can migrate to the foundation system or flatwork

support soils, which can result in volume changes in these soils.

A relatively common concept used to collect and subsequently reduce the amount of excess

irrigation water is to glue or attach an impermeable geotextile fabric or heavy mill plastic to the

foundation wall and extend it below the topsoil which is used to establish the landscape

vegetation. A thin layer of sand can be placed on top of the geotextile material to both protect

the geotextile from punctures and to serve as a medium to promote water migration to the

collection trench and perforated pipe. The landscape architect or contractor should be contacted

for additional information regarding specific construction considerations for this concept which

is shown in the sketch below.


November 7, 2013

37

A free draining aggregate or sand may be placed in the collection trench around the perforated

pipe. The perforated pipe should be graded to allow for positive flow of excess irrigation water

away from the structure or other area where additional subsurface water is undesired. Preferably

the geotextile material should extend at least ten (10) or more feet from the foundation system.

Shallow Landscaping Drain Concept No Scale

Foundation Wall

Approximate

limit

foundation

excavation

backfill

Impermeable geotextile

material, lapped and

glued to the foundation

wall above grade

Perforated pipe

surrounded by free-

draining material

Filter Fabric


November 7, 2013

38

Care should be taken to not place exterior flatwork such as sidewalks or driveways on soils that

have been tilled and prepared for landscaping. Tilled soils will settle which can cause damage to

the overlying flatwork. Tilled soils placed on sloped areas often “creep” down-slope. Any

structure or structural component placed on this material will move down-slope with the tilled

soil and may become damaged.

The landscape drain system concept provided above as an additional mitigative effort in the

event that spread footings are use to support the structure We are available to help tailor this

concept as needed to best suit the needs of this project. Often this concept is implemented only

on the northern sides of structures and/or where snow may accumulate and melt water may

migrate toward subsurface areas under the structure.

10.5 Soil Sulfate Content, Corrosion Issues

We performed soluble sulfate content tests on select soil samples obtained during our field

study. The soluble sulfate content was 100 parts per million. The American Concrete Institute

(ACI) indicates that soil with a soluble sulfate content of 100 parts per million constitutes a

negligible exposure of sulfate corrosion to concrete.

The ACI does not provide specific design or concrete constituent recommendations for

concrete exposed to soil with a negligible corrosion potential.

10.6 Radon Issues

The requested scope of service of this report did not include assessment of the site soils for

radon production. We have provided radon test results separately from this report.

11.0 CONSTRUCTION MONITORING AND TESTING

Construction monitoring including engineering observations and materials testing during

construction is a critical aspect of the geotechnical engineering contribution to any project.

Unexpected subsurface conditions are often encountered during construction. The site foundation

excavation should be observed by the geotechnical engineer or a representative during the early

stages of the site construction to verify that the actual subsurface soil and water conditions were

properly characterized as part of field exploration, laboratory testing and engineering analysis. If

the subsurface conditions encountered during construction are different than those that were the

basis of the geotechnical engineering report then modifications to the design may be

implemented prior to placement of fill materials or foundation concrete.


November 7, 2013

39

Compaction testing of fill material should be performed throughout the project construction so

that the engineer and contractor may monitor the quality of the fill placement techniques being

used at the site. Generally we recommend that compaction testing be performed for any fill

material that is placed as part of the site development. Compaction tests should be performed on

each lift of material placed in areas proposed for support of structural components. In addition to

compaction testing we recommend that the grain size distribution, clay content and swell

potential be evaluated for any imported materials that are planned for use on the site. Concrete

tests should be performed on foundation concrete and flatwork. If asphaltic concrete is placed

for driveways or aprons near the structure we are available to provide testing of these materials

during placement. We are available to develop a testing program for soil, aggregate materials,

concrete and asphaltic concrete for this project.

12.0 CONCLUSIONS AND CONSIDERATIONS

The information presented in this report is based on our understanding of the proposed

construction that was provided to us and on the data obtained from our field and laboratory

studies. We recommend that we be contacted during the design and construction phase of this

project to aid in the implementation of our recommendations. Please contact us immediately if

you have any questions, or if any of the information presented above is not appropriate for the

proposed site construction.

The recommendations presented above are intended to be used only for this project site and the

proposed construction which was provided to us. The recommendations presented above are not

suitable for adjacent project sites, or for proposed construction that is different than that outlined

for this study.


November 7, 2013

40

Our recommendations are based on limited field and laboratory sampling and testing.

Unexpected subsurface conditions encountered during construction may alter our

recommendations. We should be contacted during construction to observe the exposed

subsurface soil conditions to provide comments and verification of our recommendations.

We are available to review and tailor our recommendations as the project progresses and

additional information which may influence our recommendations becomes available.

Please contact us if you have any questions, or if we may be of additional service.

Respectfully submitted, TRAUTNER GEOTECHTRAUTNER GEOTECHTRAUTNER GEOTECHTRAUTNER GEOTECH LLC LLC LLC LLC

David L. Trautner, P.E., CPG

Principal Geotechnical Engineer

PN: 53088GE May 6, 2013

APPENDIX A

Field Study Results

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TC-1

.bor

Field Engineer : J. ButlerHole Diameter : NQDrilling Method : Wireline CoreSampling Method : NQ CoreDate Drilled : June 16, 2013Total Depth : 22 feetLocation : See Figure in Report

LOG OF BORING PH. II, TC-1

PN: 53088GEMr. Jim Ketter, PE, KPMC

Mr. Alex Carter, SuperintendentPhase II , Design Level

Montezuma-Cortez High School

Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

DESCRIPTION

NQ Core

US

CS

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Clay, sandy, medium stiff, slightly moist to moist, tan to red (CL)

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, weathered sandstone with thin interbedded layers of clayey sandstone, highly fractured, stiff/hard, tan to white

CLAYEY SANDSTONE, highly fractured

SANDSTONE, highly fractured, white

Bottom of test core run at twenty-two (22) feet

CL

Top of First Run at four and one-half (4.5) feet

Recovery= 100% R.Q.D= 0%

Bottom of First Run at seven (7) feetTop of Second Run at seven (7) feet

Recovery= 100%R.Q.D.= 0%

Bottom of Second Run at twelve (12) feet Top of Third Run at twelve (12) feet


Bottom of Third Run at seventeen (17) feetTop of Fourth Run at seventeen (17) feet

Recovery=100%R.Q.D.= 15%

Bottom of Fourth Run at twenty-two (22) feet

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TC-2

.bor






Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

DESCRIPTION

NQ Core

US

CS

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at four (4) feet








Bottom of Fourth Run at twenty-two (22) feet

Clay, sandy, medium stiff, slightly moist, red (CL)

FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandstone, white to tan, moderate to low fracturing, black layer at five (5) to six (6) feet

SANDSTONE, white to tan, highly fractured

Bottom of test core run at twenty-two (22) feet

CL

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TC-3

.bor






Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

DESCRIPTION

NQ Core

Clay, sandy, medium stiff, slightly moist, red (CL)

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandstone layer at five (5) to five and one-half (5.5) feet, sandy claystone, white to tan, highly fractured

SANDSTONE, white to tan, fractured

Bottom of test core run at sixteen (16) feet

US

CS

CL

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at three and one-half (3.5) feet





Core water washed coreNo recovery

Bottom of Third Run at sixteen (16) feet

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TB-4

.bor

Field Engineer : J. ButlerHole Diameter : 4" solidDrilling Method : Continuous Flight AugerSampling Method : Mod. California SamplerDate Drilled : 06/19/2013Total Depth (approx.) : 6.5 feetLocation : See Figure in Report

LOG OF BORING PH. II TB-4

PN:53088GEMr. Jim Ketter, PE, KPMC

Mr. Alex Carter, SuperintendentPhase II, Design Level


Depthin

feet

0

1

2

3

4

5

6

7

8

DESCRIPTION

Sample TypeMod. California Sampler

Bag Sample

Standard Split Spoon

Water LevelWater Level During Drilling

Water Level After Drilling

CLAY, sandy, medium stiff, dry, red

CLAY, sandy, very stiff, slightly moist, red to white, white chemical deposits

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandy claystone, hard/stiff, slightly moist, tan

SANDSTONE, very hard, slightly moist, tan

Auger refusal at six and one-half (6.5) feet

US

CS

CL

CL

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

18/6

50/5

17/6

19/6

22/6

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TB-5

.bor

Field Engineer : J. ButlerHole Diameter : 4" solidDrilling Method : Continuous Flight AugerSampling Method : Mod. California SamplerDate Drilled : 06/19/2013Total Depth (approx.) : 12 feetLocation : See Figure in Report





Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

DESCRIPTION


Bag Sample





WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandy claystone, hard/stiff, moist, tan, very hard sandstone layer at six and one-half (6.5) feet to eight (8) feet

Auger refusal at twelve (12) feet

US

CS

CL

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

10/6

10/5

50/6

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TB-5

.bor






Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

CLAY, sandy, medium stiff, moist, red

FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandstone, very hard, white to tan

SANDY CLAYSTONE, hard to very hard, thin interbedded sandstone lenses

SANDSTONE, very hard, white to tan

Auger refusal at twelve (12) feet

CL

12/6

50/4

23/6

50/5

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TB-7

.bor






Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

DESCRIPTION


Bag Sample





WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandy claystone, hard/stiff, slightly moist, white to gray

CLAYEY SANDSTONE, hard to very hard, slightly moist, tan

Auger refusal at fourteen (14) feet

US

CS

CL

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

14/6

50/5

12/6

50/4

07-1

2-20

13 T

:\Cur

rent

GE

\530

04G

E th

ru 5

3096

GE\

5308

8GE,

MC

HS

Mon

tezu

ma

Cor

tez

Hig

h Sc

hool

\PH

ASE

II Te

st B

orin

g Lo

gs\M

CH

S PH

. II,

TB-8

.bor






Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

DESCRIPTION


Bag Sample




CLAY, sandy, medium stiff, slightly moist, red

CLAY, sandy, medium stiff, moist, tan

FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandstone, very hard, white

SANDY CLAYSTONE, interbedded sandstone lenses, very hard with weathered layers

Bottom of test boring at fourteen and one-half (14.5) feet

US

CS

CL

CL

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

6/6

12/6

50/6

50/6

PN: 53088GE May 6, 2013

APPENDIX B

Laboratory Test Results

Sample SourceSoil DescriptionSwell Pressure (P.S.F)

Initial FinalMoisture Content (%) 8.0 18.3Dry Density (P.C.F) 108.0 112.9Height (in.) 1.000 0.957Diameter (in.) 1.94 1.94

Project NumberDateFigure

SWELL - CONSOLIDATION TEST

SUMMARY OF TEST RESULTS PH II, TB-4@2'

4.1

Sandy Clay (CL)1,030

53088GEJune 20, 2013

-5-4.5

-4-3.5

-3-2.5

-2-1.5

-1-0.5

00.5

10 100 1000 10000Pressure (Pounds per Square Foot)

Con

solid

atio

n %

Sw

ell

Swell/Consolidation due to wetting under constant load

Water added to sample





SUMMARY OF TEST RESULTS PH. II, TB-5@2'

4.2

Sandy Clay (CL)510

53088GEJune 20, 2013

-12

-10

-8

-6

-4

-2

010 100 1000 10000

Pressure (Pounds per Square Foot)

Con

solid

atio

n %

Sw

ell








4.3

Sandstone1,410

53088GEJune 20, 2013

-2

-1.5

-1

-0.5

0

0.5

110 100 1000 10000


Con

solid

atio

n %

Sw

ell








4.4

Sandstone1,120

53088GEJune 20, 2013

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.510 100 1000 10000


Con

solid

atio

n %

Sw

ell








4.5

Sandstone7,620

53088GEJune 20, 2013

-2

0

2

4

6

8

1010 100 1000 10000


Con

solid

atio

n %

Sw

ell

Swell/Consolidation due to wetting under constant loadWater added to sample





SUMMARY OF TEST RESULTS PH. II, TC-3@9'

4.6

Sandy Claystone2,940

53088GEJune 21, 2013

-4

-2

0

2

4

6

8

1010 100 1000 10000


Con

solid

atio

n %

Sw

ell



PN: 53088GE

November 7, 2013

Appendix C

1

APPENDIX C

November 7, 2013 Design Level Report

This Appendix provides excerpts and a tabulation of the shallow test borings (TB1-TB20)

that were advanced as part of the Data Report (Phase I Study) for this project and the test

boring Logs from the Data Report.

PN: 53088GE

November 7, 2013

Appendix C

2

3.3 Subsurface Soil and Water Conditions-Excerpt from May 6, 2013 Data Report

We advanced twenty (20) shallow depth auger test borings in a grid pattern across the

site with an additional eight (8) deeper depth continuous flight auger test borings and four

(4) NQ-Wireline rock core borings advanced with an emphasis on obtaining information

within the northwest and southeast quadrants of the site. The approximate locations of

the test borings are shown on Figure 1. The subsurface conditions encountered in our

shallow test borings are tabulated below with the logs of the remaining test borings

shown presented in Appendix A.

We have provided a tabulation of the soil conditions encountered in our shallow depth

test borings that were advanced for the primary purposed of gathering bulk soil samples.

It should be noted that the soil classification information obtained from these test borings

is based solely on our observations of the auger cuttings, therefore the depths of the soils

and the classifications of the materials encountered should be considered as approximate.

The description of the soil materials are shown below the tabulation of the subsurface

conditions. Test boring designation numbers correspond to Figure 1, presented in Section

3.2 above.

Test Boring

Designation

Depth range of

loess soil (Feet)

Depth range of

slightly sandy

clay soil (Feet)

Depth range to

formation (feet)

Bottom of Test

Boring (feet)

1 0-1½ -- 1½ 2 refusal

2 0-2 2-3½ 3½ weathered 4½ refusal

3 0-2½ 2½-4 4-5 weathered 5

4 -- -- 0-4½ 4½

5 0-3 3-4 4-6½ 6½ refusal

6 0-2½ 2½-4 4-5 5

7 0-2½ 2½-4 4-4½ 4½ refusal

8 0-2 2-4½ -- 4½

9 0-3½ 3½-5 5-6½ weathered 6½ refusal

10 0-2½ 2½--3½ 3½ 3½ refusal

11 0-2 -- 2-2½ weathered 2½ refusal

12 0-3 3-6 ½ -- 6½

13 0-4 4-9 -- 9

14 0-3 -- 3-3½ weathered 3½ refusal

15 0-1 1-2½ 2½-5 weathered 5

16 0-2½ 2½-5 5-6 weathered 6

17 0-2 -- 2-3 weathered 3½ refusal

18 0-2½ 2½-3½ 4½-5 weathered 5

19 0-2 2-3 3-5 weathered 5

20 0-1 -- 1-4½ 4½

Please refer to Pages 7 and 8 of the 11-07-2013 report for the locations of these borings

PN: 53088GE

November 7, 2013

Appendix C

3

The Loess soil was encountered in all of the test borings at the depths shown, the

classification of this soil is Clay and sand, slightly silty, scattered sandstone clasts, soft to

medium stiff, slightly moist, red-brown (CL-SC)

The slightly sandy clay soil may be either a thin soil material or highly weathered

formational material, but it was not discernible in these borings. The soil classification is

as follows: Clay, sandy, sandstone clasts, stiff, slightly moist, gray-brown, (CL)

We logged weathered formational material as noted in the tabulation above. Generally

this material was similar to, but slightly harder than the overlying soil mantle.

We noted where auger refusal was encountered in the borings above. The auger used

for the bulk sampling effort was a 6 inch diameter continuous flight auger. Though we

encountered refusal in some of the borings with this auger, we generally were able to

advance a four (4) inch diameter borings into the harder sandstone formation at the site.

Generally we feel that an estimated blow count for the materials in these test borings

where refusal occurred is about 50/2 to 50/4 based on the information obtained from the

deeper test borings where driven samples were taken after these borings had been

completed.

Please refer to the logs of the deeper continuous flight auger borings where driven

samples were taken and the logs of the core borings presented in Appendix A for

additional information.

We encountered about one and one-half (1½) to two and one-half (2½) feet of a loess

soil deposit in our test borings. The upper few inches of this material has more organic

content than deeper layers. The material is essentially very fine sand and silt materials

with a minor amount of clay. Though this material may be considered as generally

suitable for site fill and establishing grade, it is less desirable for use as-is for fill material

for support of flatwork and structural components. We encountered clayey sand in our

borings to variable depths. This material ranged from clayey and silty sand, to clay with

lesser amounts of sand. Generally this soil layer may be considered as existing from

about two (2) to four (4) feet below the surface over about ¾ of the project site for

general planning considerations and volume estimates.

However it should be noted that we did encounter formational material at depths as

shallow as about one and one-half (1½) feet below the ground surface in several testing

borings. If it is desirable to utilize the loess materials for processing and compaction we

suggest that only the lower 12 inches of this material be considered, since the upper

nominally 12 inches of this material contained significant organic material. The lower 12

inches of the loess materials are only suitable or use as fill if they are mixed and blended

with the underlying sandy clay and clay-sand soil. Formational material may be

observed at the ground surface in some areas of the site. The loess soils are more red-

brown in color than are the tan to gray-brown soil below. Generally both of these

shallow soils may be considered as having a low swell potential when wetted and may

PN: 53088GE

November 7, 2013

Appendix C

4

consolidate under light loads. The upper 6 to 12 inches of the loess soil material have

organic materials and should therefore be stockpiled for use as surface planting and

preparation for landscaping and establishment of surface vegetation after the

construction, if the landscape architect or landscape professional determines that they are

suitable for that use.

We encountered lean clay with sandstone fragments in some of our test borings. This

material is somewhat anomalous in that it consist of a lean clay with angular clasts of

sandstone and actually exists within the formational materials as observed in some of our

core borings. It is very atypical for a soil deposit to exist within a formational materials

deposit, however it is possible if there is a sudden climatic change during the depositional

period of the formation. In this case we suspect that the well indurated soil is a result of

short term localized erosion and subsequent deposition of detritus from areas close to the

site. As more normal climatic and depositional characteristics were re-established

additional deposition of the sandstone materials occurred. The Molas formation is one

such map able geologic unit in the Four Corners region that was formed in such a

fashion. The Molas formation may be observed in outcroppings and roadway cuts near

the Durango Mountain Report and other locations in the San Juan Mountains,

The swell tests performed on samples of the clay and sandstone clast material indicates

that it has a very high to extreme swell pressure and potential when wetted and may

consolidate under high loads. The significance of this soil deposit is discussed

additionally under the foundation discussion of this report below.

The site is underlain by the Cretaceous Dakota Sandstone. It should be noted that the

name of this geologic unit is somewhat misleading in that the unit contains more than just

sandstone. Carbonaceaous shale, lignite and coal are all found within the Dakota

Sandstone unit in the Four Corners region. The generally hard, cliff-forming quartzitic

sandstone exposures of this unit are noted throughout Colorado, thus the name of the unit

reflects these omnipresent sandstone beds.

We have had experience in the Cortez area, including recent exploration within a quarter

mile of this site where the sandstone beds of the Dakota are extremely hard and are

suitable for processing and use as rock products. Mesa Sandstone, a local quarry utilizes

sandstone materials

from the Dakota for production of commercial rock products. Although we did find

relatively hard sandstone layers in our core borings, the relatively thin layers of these

hard layers may reduce the viability for utilization of this material on site for rock

products produced on-site.

We did not encounter free subsurface water in our test borings at the time of our field

work. Although we do not feel that it is likely that subsurface water will be encountered

during the project construction, it has been our experience on sites with shallow

formational materials that due to a lack of significant a soil mantle that subsurface water

PN: 53088GE

November 7, 2013

Appendix C

5

migration and temporary perched areas of subsurface water may occur as a result of

heavy precipitation.

The tabulation of the subsurface conditions encountered in our shallow test borings

above and the logs of the test borings presented in Appendix A represent our

interpretation of the subsurface conditions encountered exposed in the test borings at the

time of our field work. Subsurface soil and water conditions are often variable across

relatively short distances. It is likely that variable subsurface soil and water conditions

will be encountered during construction. Laboratory soil classifications of samples

obtained may differ from field classifications.

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-21

.bor

Field Engineer : D. TrautnerHole Diameter : 4" solidDrilling Method : Continuous Flight AugerSampling Method : Mod. California SamplerDate Drilled : 04/24/2013Total Depth (approx.) : 14 feetLocation : SW Quadrant

: See Figure in Report

LOG OF BORING TB-21


Mr. Alex Carter, SuperintendentMontezuma-Cortez High School

Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

8/6

10/6

30/6

42/6

Wat

er L

evel

REMARKS

6 inches organicsCLAY, sandy, medium stiff, slightly moist, brown to red

Clay and sandstone clasts, very stiff, slightly moist, variegated color

FORMATIONAL MATERIAL, Dakota Sandstone Formation, very hard, dry, tan

Auger refusal at fourteen (14) feet

CL

CL-GC

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-22

.bor

Field Engineer : D. TrautnerHole Diameter : 4" solidDrilling Method : Continuous Flight AugerSampling Method : Mod. California SamplerDate Drilled : 04/24/2013Total Depth (approx.) : 6 feetLocation : See Figure in Report

LOG OF BORING TB-22



Depthin

feet

0

1

2

3

4

5

6

7

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

10/6

19/6

Wat

er L

evel

REMARKS

Loess

CLAY, sandy, medium stiff, slightly moist, brown to red

CLAY, GRAVEL, sandstone clasts, stiff, slightly moist, brown to gray


Auger refusal at six (6) feet

CL

CL-GC

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-23

.bor


LOG OF BORING TB-23



Depthin

feet

0

1

2

3

4

5

6

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

50/4

Wat

er L

evel

REMARKS

Loess

CLAY, sandy, medium stiff, moist, brown to red

WEATHERED FORMATIONAL MATERIAL, sandstone, medium dense, slightly moist, tan


Auger refusal at five (5) feet

CL

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-24

.bor


LOG OF BORING TB-24



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

50/6

Wat

er L

evel

REMARKS

LoessCLAY, silty, sandy, few sandstone cobbles, medium soft, slightly moist, brown to red

WEATHERED FORMATIONAL MATERIAL, interbedded sandstone and claystone, medium dense, slightly moist, tan

FORMATIONAL MATERIAL, interbedded claystone and sandstone, hard, dry, tan

Sandstone lenses 3 to 6 inches in thickness

Auger refusal at eighteen (18) feet

CL-ML

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-25

.bor


LOG OF BORING TB-25



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

21/6

29/6

Wat

er L

evel

REMARKS

Loess

CLAY, silty, sandy, medium stiff to soft, slightly moist, brown to red

CLAY, GRAVEL, scattered sandstone fragments, medium stiff to stiff, slightly moist, brown to gray

Bottom of test boring at nine (9) feet

CL

CL-SC

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-26

.bor


LOG OF BORING TB-26



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

16/6

36/6

50/6

Wat

er L

evel

REMARKS

Disturbed ground surface

Lost sampler

CLAY, silty, sandy, medium stiff to soft, slightly moist, brown

FORMATIONAL MATERIAL, sandy claystone, firm to medium hard, dry, gray to brown

Bottom of test boring at ten (10) feet

CL

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-27

.bor

Field Engineer : D. TrautnerHole Diameter : 4" solidDrilling Method : Continuous Flight AugerSampling Method : Mod. California SamplerDate Drilled : 04/24/2013Total Depth (approx.) : 15 feetLocation : North Central

: See Figure in Report

LOG OF BORING TB-27



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

50/3

Wat

er L

evel

REMARKS

CLAY, silty, sandy, medium stiff to soft, slightly moist, brown

WEATHERED FORMATIONAL MATERIAL, interbedded claystone and sandstone, friable, medium dense, dry, tan to brown

Sandstone layers to 12 inches thick

Bottom of test boring at fifteen (15) feet

CL

05-0

6-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

B-28

.bor


LOG OF BORING TB-28



Depthin

feet

0

1

2

3

4

5

6

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

22/6

21/6

Wat

er L

evel

REMARKS

CLAY, silty, sandy, few cobbles, clasts of sandstone, medium stiff, slightly moist, brown

WEATHERED FORMATIONAL MATERIAL, claystone and sandstone, firm, dry, tan

Bottom of test boring at five (5) feet

CL

05-0

2-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

C-1

.bor

Field Engineer : J. ButlerHole Diameter : NQDrilling Method : Wireline CoreSampling Method : NQ CoreDate Drilled : April 29,2013Total Depth : 21.5 feetLocation : See Figure in Report

LOG OF BORING TC-1



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

DESCRIPTION

NQ Core

Clay, sandy, medium stiff, slightly moist to moist, red (CL)

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, weathered claystone with thin interbedded sandstone, tan, little return in core

SANDY CLAYSTONE, interbedded sandstone lenses with clay infilling, highly fractured, brown/gray

SANDY CLAYSTONE, highly fractured, brown/gray

CLAYEY SANDSTONE, highly fractured, tan/brown

SANDSTONE, improved competency, white

Bottom of Core Run at twenty one and one-half (21-1/2) feet

US

CS

CL

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at five (5) feetRecovery= 11% R.Q.D= 0%

Bottom of First Run at six and one-half (6.5) feetTop of Second Run at six and one-half (6.5) feet


Bottom of Second Run at eleven and one-half (11.5) feet Top of Third Run at eleven and one-half (11.5) feet


Bottom of Third Run at sixteen and one-half (16.5) feetTop of Fourth Run at sixteen and one-half (16.5) feet


Bottom of Fourth Run at twenty one and one-half (21.5) feet

05-0

2-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

C-2

.bor

Field Engineer : J. ButlerHole Diameter : NQDrilling Method : Wireline CoreSampling Method : NQ CoreDate Drilled : April 29,2013Total Depth : 27 feetLocation : See Figure in Report

LOG OF BORING TC-2



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

DESCRIPTION

NQ Core


WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, sandstone, hard, dry, tan/whiteSANDSTONE, minor fractures, very hard, tan/brown

SANDSTONE, minor fractures, tan/white

SANDSTONE, highly fractured, tan

CLAYEY SANDSTONE, highly fractured, tan/brown

SANDY CLAYSTONE, highly fractured, tan/brown

Bottom of Core Run at twenty-seven (27) feet

US

CS

CL

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at two (2) feet








Bottom of Fourth Run at twenty-two (22) feetTop of Fifth Run at twenty-two (22) feet


Bottom of Fifth Run at twenty-seven (27) feet

05-0

2-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

C-3

.bor


LOG OF BORING TC-3



Depthin

feet

0123456789

10111213141516171819202122232425262728293031323334353637383940

DESCRIPTION

NQ Core

Clay, sandy, medium stiff, dry, red (CL)

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, interbedded claystone and sandstone, hard, moist, tan

SANDSTONE, interbedded claystone, highly fractured, tan

SANDY CLAYSTONE, interbedded shale, hgihly fractured, tan/brown

SANDSTONE, moderately fractured, tan/white

SANDY CLAYSTONE, interbedded shale, highly fractured, tan/brown

SANDSTONE, gypsum veins, moderately fractured, tan/white

LIGNITE LAYER

SANDSTONE, moderately fractured, tan

Bottom of Core Run at thirty six and one-half (36.5) feet

US

CS

CL

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at three (3) feet

Recovery= 100% R.Q.D= 0% Bottom of First Run at six and one-half (6.5) feetTop of Second Run at six and one-half (6.5) feet


Bottom of Second Run at eleven and one-half (11.5) feet Top of Third Run at eleven and one-half (11.5) feet


Bottom of Third Run at sixteen and one-half (16.5) feetTop of Fourth Run at sixteen and one-half (16.5) feet


Bottom of Fourth Run at twenty one & one-half (21.5) feetTop of Fifth Run at twenty one and one-half (21.5) feet


Bottom of Fifth Run at twenty six and one-half (26.5) feetTop of Sixth Run at twenty six and one-half (26.5) feet


Bottom of Seventh Run thirty one and one-half (31.5) feetTop of Eighth Run at thirty one and one-half (31.5) feet


Bottom of Eighth Run at thrity six and one-half (36.5) feet

05-0

2-20

13 T

:\Cur

rent

GE

\530

88G

E, M

CH

S M

onte

zum

a C

orte

z H

igh

Scho

ol\L

ogs

of T

est B

orin

gs\M

CH

S T

C-4

.bor


LOG OF BORING TC-4



Depthin

feet

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

DESCRIPTION

NQ Core


WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, highly fractured

CLAYEY SANDSTONE, highly fractured, tan

SANDY CLAYSTONE, highly fractured, tan/brown

SANDSTONE, highly fractured, tan/white

Bottom of Core Run at twenty two and one-half (22.5) feet

US

CS

CL

GR

AP

HIC

Run

dep

th

Recovery and R.Q.D.

Top of First Run at four (4) feet


Bottom of First Run at seven and one-half (7.5) feetTop of Second Run at seven and one-half (7.5) feet


Bottom of Second Run at twelve and one-half (12.5) feet Top of Third Run at twelve and one-half (12.5) feet


Bottom of Third Run at seventeen and one-half (17.5) feetTop of Fourth Run at seventeen and one-half (17.5) feet


Bottom of Fourth Run at twenty two and one-half (22.5) feet

geotechnical engineering design report for the...

Documents