GJ Geotech Report 2019.pdf

GEOTECHNICAL INVESTIGATION

BOILER FACILITY EXPANSION

VA HOSPITAL AND MEDICAL CENTER

GRAND JUNCTION, COLORADO

PROJECT#01886-0001

ENGINEERED WITH LAYTON

1490 SOUTH PRICE ROAD, SUITE 215

CHANDLER, ARIZONA 85286

JANUARY 10, 2019

Huddleston-Berry Engineering and Testing, LLC 640 White Avenue, Grand Junction, Colorado 81501

SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS

A geologic hazards and geotechnical investigation was conducted for an addition to the boiler building at the VA Medical Center in Grand Junction, Colorado. The project location is shown on Figure 1 – Site Location Map. The purpose of the investigation was to evaluate the surface and subsurface conditions at the site with respect to foundation design and earthwork for the proposed construction. This summary has been prepared to include the information required by civil engineers, structural engineers, and contractors involved in the project.

Subsurface Conditions (p. 2)

The subsurface investigation consisted of one boring, drilled on November 15th, 2018. The location of the boring is shown on Figure 2 – Site Plan. The boring encountered native clay soils above dense gravel and cobble soils. Groundwater was encountered in the boring at a depth of 7.5 feet at the time of the investigation. The native clay soils are moderately plastic and are anticipated to range from slightly collapsible to slightly expansive.

Summary of Foundation Recommendations

Shallow Foundations Foundation Type – Spread footings or monolithic structural slabs (p. 3) Structural Fill – Minimum of 24-inches below foundations. The native soils are not suitable for re-use as structural fill. Imported structural fill should consist of crusher fines, CDOT Class 6 base course, or other granular material approved by the engineer. (p. 3)

Maximum Allowable Bearing Capacity – 1,250 psf. (p. 3) Subgrade Modulus – 250 pci for imported granular materials. (p. 3)

Deep Foundations Foundation Type – Helical Piles (p .4) Anticipated Length – 42 to 54 feet (measured from existing grade) (p. 4) Axial Capacity – Dependent upon pile load testing; however, 20 to 40 tons likely. (p. 4)

Other Design Criteria Seismic Design – Site Class E for shallow foundations. Site Class D for deep foundations. (p. 4) Lateral Earth Pressure – 55 pcf active. 75 pcf at-rest. (p. 5)

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Scope

1.2 Site Location and Description

1.3 Proposed Construction

2.0 SUBSURFACE INVESTIGATION

3.0 LABORATORY TESTING

4.0 RECOMMENDATIONS

4.1 Foundations

4.2 Lateral Resistance for Seismic and Wind Loads

4.3 Seismic Design Criteria

4.4 Corrosion of Concrete and Steel

4.5 Non-Structural Floor Slabs and Exterior Flatwork

4.6 Lateral Earth Pressures

4.7 Drainage

4.8 Excavations

5.0 GENERAL

FIGURES

Figure 1 – Site Location Map Figure 2 – Site Plan

APPENDICES

Appendix A – Typed Boring Log

Appendix B – Laboratory Testing Results

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1.0 INTRODUCTION

As part of ongoing infrastructure improvements, the VA Hospital and Medical Center in Grand Junction, Colorado proposes to construct an addition to their existing boiler plant facility. As part of the design development process, Huddleston-Berry Engineering and Testing, LLC (HBET) was retained by Engineered With Layton to conduct a geologic hazards and geotechnical investigation at the site.

1.1 Scope

As discussed above, a geologic hazards and geotechnical investigation was conducted at the VA Hospital in Grand Junction, Colorado. The scope of the investigation included the following components:

Conducting a subsurface investigation to evaluate the subsurface conditions at the site.

Collecting soil samples and conducting laboratory testing to determine the engineering properties of the soils at the site.

Providing recommendations for foundation type and subgrade preparation.

Providing recommendations for bearing capacity.

Providing recommendations for lateral earth pressure.

Providing recommendations for drainage, grading, and general earthwork.

The investigation and report were completed by a Colorado registered professional engineer in accordance with generally accepted geotechnical engineering practices. This report has been prepared for the exclusive use of Engineered With Layton and the Owner.

1.2 Site Location and Description

The site is located at 2121 North Avenue in Grand Junction, Colorado. The project location is shown on Figure 1 – Site Location Map.

At the time of the investigation, the site was occupied by the existing VA Hospital building and several outbuildings. The area of the proposed new addition was located north of the existing boiler building. The vicinity of the addition was fairly flat.

1.3 Proposed Construction

The proposed construction is anticipated to include an addition to the existing boiler plant building.

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2.0 SUBSURFACE INVESTIGATION

The subsurface investigation was conducted on November 15th, 2018 and consisted of one boring drilled to a depth of 40.5 feet below the existing ground surface.

The location of the boring is shown on Figure 2 – Site Plan. A typed boring log is included in Appendix A. Samples of the native soils were collected during Standard Penetration Testing (SPT) and using bulk sampling methods at the locations shown on the log.

The boring encountered a thin layer of topsoil above brown, moist to wet, very stiff to very soft sandy lean clay with gravel to lean clay soils to a depth of 39.0 feet. The clay was underlain by brown, wet, dense sandy gravel and cobbles to the bottom of the boring. Groundwater was encountered in the subsurface at a depth of 7.5 feet at the time of the investigation.

3.0 LABORATORY TESTING

Selected native soil samples collected from the boring were tested in the Huddleston-Berry Engineering and Testing LLC geotechnical laboratory for natural moisture content determination, grain size analysis, maximum dry density and optimum moisture (Proctor) determination, Atterberg limits determination, and soluble sulfates content. The laboratory testing results are included in Appendix B.

The laboratory testing results indicate that the native clay soils are moderately plastic. Based upon our experience with the clay soils at the VA Hospital site, the native clay soils are anticipated to be slightly collapsible at their existing density. However, based upon the Atterberg limits of the materials and upon our experience in the vicinity of the subject site, the native clay soils may have a slight potential for expansion when compacted and introduced to excess moisture. Water soluble sulfates were detected in the site soils in a concentration of 0.2%.

4.0 RECOMMENDATIONS

4.1 Foundations

Based upon the results of the subsurface investigation and nature of the proposed construction, shallow foundations may be considered for the structural addition.

However, due to the presence of shallow groundwater and soft soil conditions, shallow foundation construction could be difficult. Alternatively, deep foundations could be used. The recommended foundation alternatives are discussed in the following sections.

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Shallow Foundations

In general, the recommended shallow foundation alternatives include spread footings and monolithic structural slabs. However, as discussed previously, the native soils are moisture sensitive. Therefore, in order to limit the potential for excessive differential movements, it is recommended that shallow foundations be constructed above a minimum of 24-inches of structural fill.

Due to the plasticity of the material, the native soils are not suitable for reuse as structural fill. Imported structural fill should consist of a granular, non-expansive, non-free draining material such as ¼-inch minus crusher fines or CDOT Class 6 base course.

Unless it can be demonstrated that they are not free draining, pit-run materials should not be used as structural fill.

For spread footing foundations, the footing areas may be trenched. However, for monolithic slab foundations, the structural fill should extend across the entire building pad area to a depth of 24-inches below the turndown edges. Structural fill should extend laterally beyond the edges of the foundations a distance equal to the thickness of structural fill for both foundation types; except where this is not possible adjacent to the existing building.

Prior to placement of structural fill, it is recommended that the bottoms of the foundation excavations be scarified to a depth of 6 to 9-inches, moisture conditioned, and re-compacted to a minimum of 95% of the standard Proctor maximum dry density, within ±2% of the optimum moisture content as determined in accordance with ASTM D698.

However, soft soils were encountered at the site and this may make compaction of the subgrade difficult. It may be necessary to utilize geotextile and/or geogrid in conjunction with up to 30-inches of additional granular fill to stabilize the subgrade. HBET should be contacted to develop specific recommendations for subgrade stabilization based upon the actual conditions encountered during construction.

Structural fill should be moisture conditioned, placed in maximum 8-inch loose lifts, and compacted to a minimum of 95% of the standard Proctor maximum dry density for fine grained soils or modified Proctor maximum dry density for coarse grained soils, within ±2% of the optimum moisture content as determined in accordance with ASTM D698 or D1557, respectively. Structural fill should be extended to within 0.1-feet of the bottom of the foundation. No more than 0.1-feet of gravel should be placed below the footings or turndown edge as a leveling course.

For foundation building pads prepared as recommended with structural fill consisting of imported granular materials, a maximum allowable bearing capacity of 1,250 psf may be used. In addition, a modulus of subgrade reaction of 250 pci may be used for structural fill consisting of crusher fines or base course. Foundations subject to frost should be at least 24-inches below the final grade.

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Deep Foundations

In general, HBET believes that helical piles are the most appropriate deep foundation alternative. Helical piles consist of circular or square steel shafts with load carrying helices attached to them. Helical piles are installed by screwing them into the ground which avoids the noise and vibration associated with driven pile foundations.

Most helical pile systems are proprietary. In general, the precise type, size, and quantity of piles should be established by the contractor in conjunction with the structural engineer. However, HBET provides the following design comments.

In general, helical piles should be designed to penetrate the native clay soils and bear into the dense gravel soils. It is anticipated that the helical piles will reach refusal within 3 to 15 feet of the top of the gravel and cobble soils. Therefore, pile lengths of up to approximately 54 feet may be possible (measured from existing grade).

In general, for helical piles installed to refusal, the allowable structural capacity is used. Based upon our experience with other projects utilizing helical piles, allowable axial capacities of between approximately 20 and 40 tons are anticipated for helical piles, depending upon the shaft diameter. However, higher capacities are possible, if necessary.

The actual allowable capacity should be determined based upon the results of load testing conducted on the project site. To eliminate reductions in capacity from group effects, the piles should be spaced a distance equal to three times the diameter of the largest helix.

4.2 Lateral Resistance for Seismic and Wind Loads

Based upon the results of the subsurface investigation, the following soil parameters are recommended for use in lateral pile capacity analyses:

Depth from Grade (in). 0 to 90 90+ Soil Type Soft Clay Soft Clay Density (pci) 0.0637 0.0318 Cohesion (psi) 3 3 Friction Angle (φ) 0 0 ε50 (in/in) 0.02 0.02 K (pci) 200 200 Modulus – Kh (tcf) 15 15

In addition to lateral resistance of the piles, lateral resistance can be developed from sliding friction between the floor slab and the ground. A sliding friction angle of 18° is recommended. This corresponds to a friction factor of 0.32.

4.3 Seismic Design Criteria

In general, based upon the results of the subsurface investigation, the site generally classifies as Site Class E for a soft soil profile. However, if deep foundations are used, Site Class D is appropriate.

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4.4 Corrosion of Concrete and Steel

As indicated previously, water soluble sulfates were detected in the site soils in a concentration of 0.2% which indicates a severe potential for sulfate attack on concrete.

The International Building Code (IBC) specifies Type V cement for this concentration of sulfates. However, Type V cement can be difficult to obtain in Western Colorado.

Where Type V cement is unavailable, Type I-II sulfate resistant cement is recommended.

Based upon our experience in the vicinity of the subject site, the native clay soils are anticipated to have a resistivity of less than 1,000 ohm-cm. Therefore, the deep foundation elements should consider corrosion in their design either through the use of galvanization or by accounting for section loss.

4.5 Non-Structural Floor Slabs and Exterior Flatwork

In order to reduce the potential for and/or magnitude of movement of slabs-on-grade, it is recommended that non-structural floating floor slabs be constructed above a minimum of 24-inches of structural fill with subgrade preparation, structural fill materials, and structural fill placement in accordance with the Shallow Foundations section of this report. It is recommended that exterior flatwork be constructed above a minimum of 18-inches of structural fill.

4.6 Lateral Earth Pressures

Stemwalls, grade beams, and/or retaining walls should be designed to resist lateral earth pressures. For backfill consisting of the native soils or imported granular, non-free draining, non-expansive material, we recommend that the walls be designed for an active equivalent fluid unit weight of 55 pcf in areas where no surcharge loads are present. An at-rest equivalent fluid unit weight of 75 pcf is recommended for braced walls. Lateral earth pressures should be increased as necessary to reflect any surcharge loading behind the walls.

4.7 Drainage

In order to improve the long-term performance of the foundations and slabs-on-grade, grading around the structure should be designed to carry precipitation and runoff away from the structure. It is recommended that the finished ground surface drop at least twelve inches within the first ten feet away from the structure. However, where impermeable surfaces (i.e. sidewalks, pavements, etc.) are adjacent to the structures the grade can be reduced to approximately 2.5-inches (ADA grade) within the first ten feet away from the structure. It is recommended that landscaping within five feet of the structures include primarily desert plants with low water requirements.

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As discussed previously, shallow groundwater was encountered at the site.

Therefore, a perimeter foundation drain is recommended where below grade construction and/or a crawlspace are proposed. In general, the perimeter foundation drain should consist of prefabricated drain materials or a perforated pipe and gravel system with the flowline of the drain at the bottom of the foundation (at the highest point). The perimeter drain should slope at a minimum of 1.0% to a sump with pump.

4.8 Excavations

Excavations in the soils at the site may stand for short periods of time but should not be considered to be stable. Trenching and excavations should be sloped back, shored, or shielded for worker protection in accordance with applicable OSHA standards. The soils generally classify as Type C soil with regard to OSHA’s Construction Standards for Excavations. For Type C soils, the maximum allowable slope in temporary cuts is 1.5H:1V. However, the soil classification is based solely on the boring data and may not represent the actual soil conditions. HBET should be contacted to re-evaluate the soil classification during construction to determine the appropriate classification of the native soils.

5.0 GENERAL

The recommendations included above are based upon the results of the subsurface investigation and on our local experience. These conclusions and recommendations are valid only for the proposed construction.

As discussed previously, only one boring was conducted at the site. Therefore, the precise nature and extent of subsurface variability may not become evident until construction. The recommendations contained herein are designed to reduce the risk and magnitude of any structure movements and it is extremely critical that ALL of the recommendations herein be applied to the design and construction.

In addition, the success of the structure foundations, slabs, etc. is critically dependent upon proper construction. Therefore, HBET should be retained to provide materials testing, special inspections, and engineering oversight during ALL phases of the construction to ensure conformance with the recommendations herein.

Huddleston-Berry Engineering and Testing, LLC is pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report.

Respectfully Submitted:

Huddleston-Berry Engineering and Testing, LLC

Michael A. Berry, P.E.

Vice President of Engineering

01/10/19

FIGURES

Cr e dit s :

Mesa County Map Print Date: January 2, 2019

The Geographic Information System (GIS) and its com ponents are des igned as a source of reference for answering inquiries, for planning and for modeli ng. GIS is not intended or does not replace legal description information in the chain of title and other inform ati on contained in offici al government records s uch as the County Clerk and Recorders office or the courts. In addition, the repres entations of locati on in this G IS cannot be substitute for actual legal surveys.

The information contained herein is believed accurate and sui table for the li mited uses, and subject to the limitations, set forth above. Mesa County makes no warranty as to the accuracy or suitability of any information contained herein. Users assume al l ri sk and res ponsibil ity for any and al l dam ages , inc luding consequential dam ages, which may flow from the user's use of this information.

0 0.5 10.25 mi

0 0.6 1.20.3 km

I millerc Polygon millerc Text Box Site Location millerc Text Box

FIGURE 1

Site Location Map

± 1 inch = 24 feet 0 0.010.005 mi

City of Grand Junction

Printed: 1/2/2019 millerc Text Box B-1 millerc Oval millerc Text Box

FIGURE 2

Site Plan

APPENDIX A

Typed Boring Log

Lean CLAY with organics (TOPSOIL)

Sandy Lean CLAY with Gravel to Lean CLAY (CL), brown, moist to wet, very stiff to very soft

*** Lab Classified GB1

*** Lab Classified SS2

*** Lab Classified SS4

Sandy GRAVEL and COBBLES (gw), brown, wet, dense

Bottom of hole at 40.5 feet.

SS

GB

SS

SS

SS

4-4-3 (7)

0-0-1 (1)

1-0-1 (1)

1-2-1 (3)

NOTES

GROUND ELEVATION

LOGGED BY SD

DRILLING METHOD Simco 2000 Track Rig AT TIME OF DRILLING 7.5 ft

AT END OF DRILLING 7.5 ft

AFTER DRILLING ---

HOLE SIZE 4-inches

DRILLING CONTRACTOR S. McKracken GROUND WATER LEVELS:

CHECKED BY MAB

DATE STARTED 11/15/18 COMPLETED 11/15/18

D E

P T

H (f t)

G R

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H

IC

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ATTERBERG

LIMITS

MATERIAL DESCRIPTION

S A

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V A

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(t sf

D R

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(p cf

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BORING NUMBER B-1

CLIENT Engineered With Layton

PROJECT NUMBER 01886-0001

PROJECT NAME VAMC Boiler Expansion

PROJECT LOCATION Grand Junction, CO

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APPENDIX B

Laboratory Testing Results

0.0010.010.1110100

PI Cc

CuLL PL

GRAIN SIZE DISTRIBUTION

COBBLES

GRAVEL

62.9

93.1

98.8

0.3

0.3

P E

R C

E N

T F

IN

E

R B

Y W

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3 10024 16 301 2006 10 501/2

HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS

1403 4 20 406 601.5 8 143/4 3/8

SAND

GRAIN SIZE IN MILLIMETERS

coarse fine

SANDY LEAN CLAY with GRAVEL(CL)

LEAN CLAY(CL)

LEAN CLAY(CL)

ClassificationSpecimen Identification

Specimen Identification D100 D60 D30 D10 %Gravel coarse

SILT OR CLAY

finemedium

%Sand %Silt %Clay

17.0

0.0

0.0

20.1

6.9

1.2

B-1, GB1

B-1, SS2

B-1, SS4

B-1, GB1

B-1, SS2

B-1, SS4

11/18

11/18

11/18

11/18

11/18

11/18

CLIENT Engineered With Layton

PROJECT NUMBER 01886-0001

PROJECT NAME VAMC Boiler Expansion

PROJECT LOCATION Grand Junction, CO

G R

A

IN

S

IZ

E

-0

V

A M

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0 20 40 60 80 100

ML

CL

MH

CH

Specimen Identification

CL-ML

P L A S T I C I T Y

I N D E X

LIQUID LIMIT

Classification

SANDY LEAN CLAY with GRAVEL(CL)

LEAN CLAY(CL)

LEAN CLAY(CL)

LL PL PI

ATTERBERG LIMITS' RESULTS

11/15/2018

11/15/2018

11/15/2018

#200

B-1, GB1

B-1, SS2

B-1, SS4

CLIENT Engineered With Layton

PROJECT NUMBER 01886-0001

PROJECT NAME VAMC Boiler Expansion

PROJECT LOCATION Grand Junction, CO

A T

T E

R B

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G L

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Huddleston-Berry Engineering & Testing, LLC 640 White Avenue, Unit B Grand Junction, CO 81501

0 5 10 15 20 25 30

SANDY LEAN CLAY with

GRAVEL(CL)

B-1 Sample No.:

ASTM D698A

PL PI

11D

R Y

D E

N S

IT

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, p cf

3/4"

WATER CONTENT, %

Test Method:

MOISTURE-DENSITY RELATIONSHIP

LL

GRADATION RESULTS (% PASSING)

ATTERBERG LIMITS

Curves of 100% Saturation for Specific Gravity Equal to:

2.80

2.70

2.60

120.0

12.5

Sample Date: 11/15/2018

GB1

Source of Material:

Description of Material:

TEST RESULTS

Optimum Water Content %

#200

Maximum Dry Density PCF

#4

63 83 100

CLIENT Engineered With Layton

PROJECT NUMBER 01886-0001

PROJECT NAME VAMC Boiler Expansion

PROJECT LOCATION Grand Junction, CO

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Huddleston-Berry Engineering & Testing, LLC 640 White Avenue, Unit B Grand Junction, CO 81501