Soils Report NCSRC.pdf

110979-5/CSP10R137 Page ii of ii September 24, 2010 Copyright 2010 Kleinfelder

TABLE OF CONTENTS

PAGE

1 INTRODUCTION

1.1 GENERAL

1.2 PROJECT DESCRIPTION

1.3 PURPOSE AND SCOPE

2 FIELD EXPLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

2.2 LABORATORY TESTING

2.2.1 Geotechnical Laboratory Tests

2.2.2 Analytical Laboratory Testing

3 SITE CONDITIONS

3.1 SURFACE

3.2 GEOLOGY

3.2.1 Seismicity

3.3 SUBSURFACE

3.3.1 Groundwater

4.1 GEOTECHNICAL FEASIBILITY OF PROPOSED CONSTRUCTION

4.2 CONSTRUCTION CONSIDERATIONS

4.2.1 Site Preparation & Grading

4.2.2 Excavation Characteristics

4.2.3 Structural Fill

4.2.4 Structural Fill Placement and Compaction

4.2.5 Utility Trench Backfill

4.2.6 Construction in Wet or Cold Weather

4.2.7 Construction Testing and Observation

4.2.8 Drainage and Landscaping

4.3 FOUNDATION RECOMMENDATIONS

4.4 CONCRETE FLOOR SLAB CONSTRUCTION RECOMMENDATIONS

4.5 EXTERIOR CONCRETE FLATWORKS

4.6 CONCRETE TYPE

4.6.1 Corrosion Potential

4.7 PAVEMENT RECOMMENDATIONS

4.7.1 Anticipated Pavement Subgrade Material

4.7.2 Pavement Subgrade Preparation

4.7.3 Drainage

4.7.4 Pavement Maintenance

4.7.5 Design Traffic Loadings

4.7.6 Design Sections

4.7.7 Pavement Material Specifications

5 ADDITIONAL SERVICES

5.1 REQUIREMENTS FOR ADDITIONAL SERVICES

5.2 REVIEW OF PLANS AND SPECIFICATIONS

5.3 PRE-BID AND PRE-CONSTRUCTION MEETINGS

6 LIMITATIONS

APPENDICES

A Vicinity Map and Boring Location Plan B Logs of Exploratory Borings C Geotechnical Laboratory Test Results D Analytical Laboratory Test Results E Geothermal Conductivity Test Results (To Be Provided at a Later Date) F Important Information about your Geotechnical Engineering Report

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1 INTRODUCTION

1.1 GENERAL

This report presents the results of Kleinfelder’s Final Geotechnical Investigation performed for the proposed North Colorado Springs Readiness Center in Colorado Springs, Colorado.

Preliminary geotechnical engineering exploration, laboratory testing, and analysis was submitted under a separate cover (Kleinfelder Project Number 110979), dated June 3, 2010.

An attached Vicinity Map (Figure A-1) shows the general location of the project.

This report includes our recommendations relating to the geotechnical aspects of project design and construction. The conclusions and recommendations stated in this report are based on the subsurface conditions found at the locations of our exploratory borings at the time our exploration was performed. They also are subject to the provisions stated in the report sections titled Additional Services and Limitations. Our findings, conclusions, and recommendations should not be extrapolated to other areas or used for other projects without our prior review.

Furthermore, they should not be used if the site has been altered, or if a prolonged period has elapsed since the date of the report, without Kleinfelder’s prior review to determine if they remain valid.

1.2 PROJECT DESCRIPTION

We understand that the proposed project includes the construction of the North Colorado Springs Readiness Center northwest of the intersection of Briargate Parkway and Highway 83 in Colorado Springs, Colorado. We understand the size of the proposed structure is planned to be approximately 88,663 square feet (SF). We understand the building will be partially two-stories in height and constructed of either pre-cast concrete or steel-frame with a brick veneer.

Associated flexible and rigid pavement will be constructed for parking and drive access. We understand that column loads for the one-story portions of the structure will have an average load of approximately 110 kips. Two-Story portions of the structure will have column loads averaging 200-250 kips, with a maximum column load of approximately 400 kips. Perimeter walls will have a load of approximately 3 kips per lineal foot.

We anticipate additional construction activities will include general site grading, installation of utilities, and landscaping. No grading plans were available for our review when this report was prepared; however, we estimate general site grading will be limited to providing proper drainage away from the structure and site improvements, and preparing the foundation excavations for the new structure. If actual building configurations or loads vary significantly from those

110979-5/CSP10R137 Page 2 of 21 September 24, 2010 assumed above, Kleinfelder should be notified immediately in order to revise our recommendations, if required.

1.3 PURPOSE AND SCOPE

The purpose of our investigation was to explore and evaluate subsurface conditions specifically within the proposed structure area on the site and, based on the conditions found, to develop recommendations relating to the geotechnical aspects of project design and construction. Our conclusions and recommendations in this report are based on analysis of the data from our field exploration, laboratory tests, and on our experience with similar soil and geologic conditions in the area.

Kleinfelder’s scope of services included:

A visual reconnaissance to observe surface and geologic conditions at the project site and to locate the exploratory borings;

Notifying the Utility Notification Center of Colorado and working with USAFA Civil

Engineering personnel to identify underground utility lines at the boring locations;

The drilling of twelve (12) exploratory borings at the approximate location of the proposed structure and parking/drive areas, selected based on the proposed site plans, access, and location of existing utilities;

Laboratory testing of selected samples obtained during the field exploration to evaluate relevant physical and engineering properties of the soil;

Evaluation and engineering analysis of the field and laboratory data to develop our geotechnical conclusions and recommendations;

Geothermal Conductivity testing associated with the drilling of one (1) boring to a depth of approximately 400-feet, and;

Preparation of this report, which includes a description of the proposed project, a description of the surface and subsurface site conditions found during our investigation, our conclusions and recommendations as to foundation design, other related geotechnical issues, and appendices which summarize our field and laboratory investigations.

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2 FIELD EXPLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

Our geotechnical and geothermal exploration programs were performed on September 2, 2010 and September 13, 2010, respectively, and included advancing the following borings at the locations indicated on the attached Figure A-1:

Table 1 – Summary of Field Exploration Program

Boring Designation Approximate Depths of

Total Exploration

[Feet, bgs]*

Surface Elevation of Boring

[Feet]**

B-4 10½ 6612.2 B-5 10 6606.1 B-6 30½ 6602.4 B-7 30 6600.7 B-8 30 6604.3 B-9 30 6602.3

B-10 29½ 6601.4 B-11 29½ 6601.4 B-12 29½ 6602.0 B-13 29 6600.5 B-14 29½ 6602.2 B-15 10 6599.0 B-16 402 6607.4

*All depths referenced to existing ground surface.

**Surface elevations of borings surveyed and provided by Farnsworth Group, Inc.

The geotechnical borings were advanced using a truck-mounted CME-55 drill rig equipped with 4-inch diameter, continuous-flight, solid-stem augers. Samples were taken with a standard split-spoon sampler and modified California sampler. The geothermal boring was advanced using a GEFCO Model SD-300 drill rig equipped with a 5¼ -inch diameter mud rotary drilling system. Appendix B to this report includes the individual boring logs describing the subsurface conditions encountered within our borings at the site. The lines defining boundaries between soil and rock types on the logs are based upon drill behavior and interpolation between samples and are approximate. Therefore, the transition between soil and rock types may be abrupt or may be gradual.

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2.2 LABORATORY TESTING

2.2.1 Geotechnical Laboratory Tests

Laboratory tests were performed on select soil samples to estimate their relative engineering properties. The following tests were performed in general accordance with recognized standards:

Description and Identification of Soils (Visual-Manual Procedure);

Classification of Soils for Engineering Purposes;

Sieve Analysis of Fine and Coarse Aggregates Test;

Liquid Limit, Plastic Limit, and Plasticity Index Test Natural Density and Moisture Content Test;

Swell/Consolidation Test; and, Determination of Resistance R-Value of Compacted Soils.

Results of the geotechnical laboratory tests are included in Appendix C of this report. Selected geotechnical test results are also shown on the boring logs contained in Appendix B.

2.2.2 Analytical Laboratory Testing

A summary of test methods and results of the analytical laboratory testing are presented in Appendix D of this report. Analytical testing included:

pH;

Resistivity; and Water Soluble Sulfates.

Results of the Analytical testing are summarized below:

Table 2 – pH value, Resistivity, & Soluble Sulfate Tests Results

Sample Location and Depth (Feet) pH Value Resistivity (ohm-cm)

Water Soluble Sulfates (percent)

B-10 @ 2 7.12 250,000 Not Detectable

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3 SITE CONDITIONS

3.1 SURFACE

The proposed North Colorado Springs Readiness Center is to be located east of Interstate 25, west of Highway 83, and north of Briargate Parkway as shown on Figure A-1. The existing ground surface at the site comprises areas of grass, weeds, and trees. The site slopes gently to the south towards man-made drainage controls.

3.2 GEOLOGY

Prior to drilling, the geology of the site was evaluated by reviewing published geologic maps, including:

USGS Geologic Map of the Colorado Springs-Castle Rock area, Front Range Urban Corridor, Colorado (Trimble and Machette, 1979)

Colorado Geologic Survey Geologic Map of the Pikeview Quadrangle, El Paso County, Colorado (Thorson, Carroll, & Morgan, 2001)

The mapping indicates that the surface soils consist primarily of alluvial deposits comprising sand and gravels with varying amounts of silt and clay overlying Dawson Formation bedrock.

Samples collected during the subsurface investigation generally agree with the published geologic mapping.

3.2.1 Seismicity

The subsurface soil profiles correspond with Site Class C of the 2006 International Building Code (IBC). We recommend the following site coefficients be used at this site.

Table 3 – Design Acceleration for Short Period SS Fa

0.212 1.2 SS = The mapped spectral accelerations for short periods (U.S. Geological Survey Web Page, 2010) Fa = Site coefficient from Table 1615.1.2(1), 2006 IBC

Table 4 – Design Acceleration for 1-Second Period S1 Fv

0.058 1.7 S1 = The mapped spectral accelerations for 1-second period (U.S. Geological Survey Web Page, 2010)

Fv = Site coefficient from Table 1615.1.2(2), 2006 IBC

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3.3 SUBSURFACE

From the ground surface down, the general profile encountered in our borings consisted of sandy alluvial layers overlying weathered to formational bedrock of the Dawson Formation, as described in more detail in Table 5:

Table 5 – Summary of Geologic Units

Geologic Unit

Ranges of Soil/Rock Type

Borings Encountered

Depths Encountered

[Feet]* Color Moisture Density

Alluvium

Silty Sand (SM) with gravel, Poorly to Well Graded SAND

(SP-SM,

SW-SM)

B-4 through B-16

Variable—see Boring Logs

Dark Brown, Light

Brown

Slightly Moist to

Wet

Loose to Medium Dense

(Generally Loose Near- Surface soils)

Weathered Dawson Bedrock

Silty to Clayey Sandstone and

Sandy Claystone

B-6 B-7 B-8 B-9

B-10 B-11 B-12 B-13 B-14

24½ to BOH** 22 to BOH** 24 to BOH** 28 to BOH** 16 to 24½ 22 to 25 22 to 29

22 to BOH** 26 to BOH**

Dark Gray to

Reddish- Brown

Slightly Moist to

Moist

Moderately Hard to Hard

Formational Dawson Bedrock

Clayey Sandstone and

Sandy Claystone

B-10 B-11 B-12 B-16

24½ to BOH** 25 to BOH** 29 to BOH** 25 to BOH**

Dark Gray to

Reddish- Brown

Slightly Moist to

Moist

Hard to Very hard

*All depths referenced to below existing ground surface.

**BOH = Bottom of Hole.

The boring logs in Appendix B should be reviewed for more detailed descriptions of the subsurface conditions at the boring locations explored.

3.3.1 Groundwater

Groundwater was encountered in 7 of the 12 geotechnical borings advanced during our field investigation, at the depths presented in Table 6. It is not anticipated that groundwater will affect construction of the proposed structure.

Soil moisture levels and groundwater levels commonly vary over time and space depending on seasonal precipitation, irrigation practices, land use, and runoff conditions. These conditions and the variations that they create often are not apparent at the time of field investigation.

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Accordingly, the soil moisture and groundwater data in this report pertain only to the locations and times at which exploration was performed. They can be extrapolated to other locations and times only with caution. It should also be noted that Kleinfelder has not performed a hydrologic study to verify the seasonal high water level.

Table 6 – Approximate Elevation of Groundwater Encountered at Boring Location*

Boring Designation

Groundwater Depth (bgs) [feet]

Approx. Relative Groundwater Elevation

[feet]

B-4 None Encountered --

B-5 None Encountered --

B-6 23½ 6578.5

B-7 21½ 6579.0

B-8 None Encountered --

B-9 27½ 6575.0

B-10 28 6573.5

B-11 21 6580.5

B-12 None Encountered --

B-13 21 6579.5

B-14 25 6577.0

B-15 None Encountered --

*All depths referenced to below existing ground surface. Surface elevations of borings provided by Farnsworth Group, Inc. Groundwater elevations may vary and apply to the boring location only.

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4 CONCLUSIONS AND RECOMMENDATIONS

4.1 GEOTECHNICAL FEASIBILITY OF PROPOSED CONSTRUCTION

Based on the information presented herein, it is Kleinfelder’s opinion that construction of the proposed North Colorado Springs Readiness Center on the site as planned is feasible, provided that the recommendations in this report are incorporated into the planning and design of the project. We believe that utilizing a spread footing foundation and slab-on-grade floor system to support the new structure is appropriate.

Foundation & Slab-on-grade Floor System Our investigation found variable density sand deposits in our borings extending to depths of approximately 10- to 28-feet below the ground surface. Near-surface soils were generally loose. In order to create a firm and more uniform bearing surface and reduce the potential for differential movement of structural elements, we anticipate removal of at least 2-feet of the alluvial soils from beneath the proposed footing and floor slab elevation and replacement with properly compacted structural fill (on-site sand soils or imported granular material) that meets the recommendations in this report. Further detail and recommendations are provided in the following sections of this report. Prior to placement of structural fill, the native subgrade should be scarified at least 12-inches, moisture conditioned, and re-compacted in accordance with this report.

4.2 CONSTRUCTION CONSIDERATIONS

4.2.1 Site Preparation & Grading

Begin site work by stripping the vegetation and other deleterious materials now present at the ground surface within the proposed structure and site improvements. Remove the stripped materials for offsite disposal in accordance with local laws and regulations or, if appropriate, stockpile them for later use in landscaped areas. If any abandoned utilities exist within the excavation zone, they should be completely removed and backfilled with compacted structural fill. Materials removed from the construction areas that contain significant amounts of organics or other deleterious materials should be set aside for offsite disposal in accordance with applicable codes, safety regulations and other Local, State or Federal guidelines.

After performing the required over-excavations and prior to the placement of any structural fill, processing of the subgrade should be performed. The subgrade should be scarified to a depth

110979-5/CSP10R137 Page 9 of 21 September 24, 2010 of at least 12-inches, and compacted as recommended in this report, prior to placement of structural fill.

4.2.2 Excavation Characteristics

Based on our subsurface drilling information, we anticipate that excavations on the order of approximately 5-feet will be required to construct shallow foundations on at least 2-feet of structural fill, with considerations for frost depth. Excavation of the on-site soil may be accomplished utilizing conventional excavation equipment.

All excavations must comply with the applicable Local, State, and Federal safety regulations, and particularly with the excavation standards of the Occupational Safety and Health Administration (OSHA). Construction site safety, including excavation safety, is the sole responsibility of the Contractor as part of its overall responsibility for the means, methods, and sequencing of construction operations. Kleinfelder’s recommendations for excavation support are intended for the Client’s use in planning the project, and in no way relieve the Contractor of its responsibility to construct, support, and maintain safe slopes. Under no circumstances should the following recommendations be interpreted to mean that Kleinfelder is assuming responsibility for either construction site safety or the Contractor’s activities.

We believe that the sand soils on this site will classify as Type C materials using OSHA criteria.

OSHA requires that unsupported cuts be laid back to ratios no steeper than 1.5H:1V (horizontal to vertical) up to 20-feet in height. In general, we believe that these slope ratios will be temporarily stable under unsaturated conditions. Where groundwater seepage occurs, flatter slopes may be appropriate. Please note that the actual determination of soil type and allowable sloping must be made in the field by an OSHA-qualified “competent person.”

4.2.3 Structural Fill

The on-site sand soils are suitable for use as structural fill beneath the proposed site improvements. Imported material (if required) should consist of a non-expansive granular material meeting the following criteria:

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Table 7 – Imported Structural Fill Criteria Gradation Requirements

Standard Sieve Size Percent Passing

2-inch 100

No. 200 10-30

Plasticity Requirements (Atterberg Limits)

Liquid Limit Non-plastic

Plasticity Index Non-plastic

Prior to placement of the fill, it should be moisture conditioned as described in this report. A sample of any imported fill material should be submitted to our office for approval and testing at least one week prior to stockpiling at the site. Structural fill should be compacted according to the recommendations in Section 4.2.4 of this report.

4.2.4 Structural Fill Placement and Compaction

Fill materials should be placed in horizontal lifts compatible with the type of compaction equipment being used, moisture-conditioned, and compacted in accordance with following criteria:

Table 8 – Compaction Specifications

FILL LOCATION MATERIAL TYPE

PERCENT

COMPACTION*

MOISTURE

CONTENT

Building Subgrade Preparation (after clearing, grubbing, excavation, and prior to fill placement)

On-site Sand Soils 92 minimum

(ASTM D 1557)

-2% to +2% of optimum

Foundation/Floor Slab Structural Fill

On-site Sand Soils/Import Structural Fill

95 minimum

(ASTM D 1557)

-2% to +2% of optimum

Foundation/Retaining Walls Backfill

On-site Sand Soils/Import Structural Fill

95 minimum

(ASTM D 1557)

-2% to +2% of optimum

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FILL LOCATION MATERIAL TYPE

PERCENT

COMPACTION*

MOISTURE

CONTENT

Pavement Subgrade On-site Sand Soils/Import Structural Fill

95 minimum

(ASTM D 1557)

-2% to +2% of optimum

Pavement Base Course Imported

Aggregate Base Course

100 minimum

(ASTM D 1557)

-2% to +2% of optimum

Utility Trenches On-Site Soil 95 minimum

(ASTM D 1557)

-2% to +2% of optimum

* In non-structural or landscaped areas, the compaction specification may be reduced to 90 percent, ASTM D 1557.

Structural fill should be placed in level lifts not exceeding 8-inches in loose thickness, and compacted to the specified percent compaction to produce a firm and unyielding surface. If field density tests indicate the required percent compaction has not been obtained, the fill material should be reconditioned as necessary and re-compacted to the required percent compaction before placing any additional material.

4.2.5 Utility Trench Backfill

Backfill material for utility trenches should be essentially free of plant matter, organic soil, debris, trash, other deleterious matter and rock particles larger than 2-inches. However, backfill material in the “pipe zone” (from the trench floor to 1-foot above the top of pipe) should not contain rock particles larger than 1-inch. Strictly observe any requirements specified by the utility agency for bedding and pipe-zone fill. In general, backfill above the pipe zone in utility trenches should be placed in lifts of 6- to 8-inches, and compacted using power equipment designed for trench work. Compact trench backfill as recommended in Section 4.2.4 of this report.

4.2.6 Construction in Wet or Cold Weather

No grading fill, structural fill or other fill should be placed on frosted or frozen ground, nor should frozen material be placed as fill. Frozen ground should be allowed to thaw or be completely removed prior to placement of fill. If earthwork is performed during the winter months when freezing is a factor, a good practice is to cover the compacted fill with a “blanket” of loose fill to help prevent the compacted fill from freezing.

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During construction, grade the site so that surface water can drain readily away from the excavation areas. With the given subgrade conditions, and the close proximity of the existing building, it is very important to avoid ponding of water in or near excavations. Promptly pump out or otherwise remove water that accumulates in excavations or on subgrades, and allow these areas to dry out before resuming construction. Use berms, ditches, and similar means to prevent stormwater from entering the work area and to convey it off site efficiently.

If the structure is erected during cold weather, do not install concrete elements on frozen soil.

Frozen soil should either be removed from beneath the concrete elements altogether, or thawed and re-compacted. To avoid soil freezing, minimize the amount of time passing between excavation/subgrade preparation and pouring concrete. Use blankets, soil cover, or heating as required to prevent the footing subgrade from freezing.

4.2.7 Construction Testing and Observation

Enough field testing and construction observation should take place under the direction of a qualified geotechnical engineer to support that engineer’s professional opinion as to whether the earthwork does or does not substantially conform to the recommendations in this report.

Furthermore, the opinions and conclusions of a geotechnical report are based on interpretation of a limited amount of information obtained from the field exploration. It is therefore not uncommon to find that actual site conditions differ somewhat from those indicated in the report.

The geotechnical engineer should remain involved throughout the project to evaluate such differing conditions as they appear, and to modify or add to the geotechnical recommendations as necessary.

4.2.8 Drainage and Landscaping

Proper grading and drainage is essential to the performance of foundations and flatwork. Grade the ground surface around the structure so that surface water will quickly flow away from the perimeter walls. Landscaped areas should have minimum gradients of 8-percent away from the foundations. Areas with flatwork present immediately adjacent to foundations should have a minimum gradient of 2-percent away from the foundations. Carry the downspouts from roof drains across all backfilled areas so that they discharge well clear of the backfill zone and structures. Water should drain away from structures as rapidly as possible and not be allowed to stand or pond near the building. Water removed from one building area should not be directed onto the backfill areas of adjacent building areas. We recommend avoiding irrigating adjacent to improved areas.

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We believe any permanent cut and fill slopes exposing the materials encountered in our boring will be stable at slope ratios as steep as 3H:1V (horizontal to vertical) under dry conditions.

New slopes should be re-vegetated as soon as possible after completion to reduce erosion problems.

4.3 FOUNDATION RECOMMENDATIONS

As discussed in Section 4.1, to help reduce the potential for differential settlement we recommend the new structure be supported on shallow foundations bearing on at least 2-feet of structural fill overlying a properly prepared subgrade as described above. Acceptable structural fill material and compaction requirements are provided in Sections 4.2.3 and 4.2.4, respectively.

The lateral extents of the excavation should extend beyond the edge of the footing the same amount as the depth of the recommended over-excavation.

1. Footings placed on at least 2-feet of structural fill overlying properly prepared subgrade soils as described above may be designed for a maximum allowable soil bearing capacity of 2,500 pounds per square foot (psf). This bearing pressure may be increased by one-third for transient loading.

2. Lateral loads may be resisted using a coefficient of friction for sliding of 0.40 and an unfactored passive earth pressure of 360 pounds per cubic foot (pcf) for the foundation wall backfill consisting of compacted on-site sand soils or imported granular structural fill. As large movements are generally required to mobilize the full passive earth pressure, we recommend a factor of safety of 2 be applied to the above passive earth pressure value.

3. Continuous footings should have a minimum width of 18-inches and isolated column footings should have a minimum width of 24-inches. The actual footing sizes should be determined by a qualified structural engineer based on the soil bearing capacity and actual structural loads.

4. We estimated post-construction total settlement for new footings placed on structural fill as described above would be about 1-inch or less.

5. Stem walls for a shallow spread footing foundation system should be designed as grade beams capable of spanning at least 8-feet. These “grade beams” should be horizontally reinforced both near the top and near the bottom. The horizontal reinforcement required shall be placed continuously around the structure with no gaps or breaks. A foundation

110979-5/CSP10R137 Page 14 of 21 September 24, 2010 system designed in this manner will properly spread loads and will be better able to tolerate differential movements.

6. Exterior footings or footings in unheated areas should have at least 36-inches of cover above the bottom of the footing for frost protection, or that required by the local building code, whichever is greater.

7. The foundation subgrade and compacted structural fill should be protected from wetting and drying prior to and after concrete placement. Footings should be backfilled as soon as practical after concrete placement.

8. A representative of Kleinfelder should observe all foundation excavations prior to placement of concrete and/or fill. Additionally, the placement and compaction of structural fill should be observed and tested by a representative of our firm.

4.4 CONCRETE FLOOR SLAB CONSTRUCTION RECOMMENDATIONS

As discussed in Section 4.1 of this report, we recommend that the floor slab subgrade for the proposed floor bear on at least 2-feet of structural fill. Preparation of the subgrade shall include scarifying or excavating a minimum of 8-inches of the existing site soils followed by proper moisture conditioning and compaction of imported fill as recommended in Sections 4.2.1 and

4.2.4 of this report. The design and construction criteria presented below should be observed for floor slabs constructed on grade.

1. For design of floor slabs, a modulus of subgrade reaction of 200 pounds per cubic inch (pci) may be used in design of slabs placed on at least 2-feet of structural fill, as described above.

2. Floor slabs should be separated from all bearing walls and columns with expansion joints that allow unrestrained vertical movement.

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

Control joint spacing is a function of slab thickness, aggregate size, slump and curing conditions. The requirements for concrete slab thickness, joint spacing, and reinforcement should be established by the designer, based on experience, recognized design guidelines and the intended slab use. Placement and curing conditions will have a strong impact on the final concrete slab integrity.

4. Utility lines should be provided with flexible joints or oversized sleeves where they penetrate floor slabs to prevent breakage caused by differential slab movement.

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If vibrating machinery will be installed in the building, the machine foundations should be physically isolated from other foundations and slabs to reduce vibration damage. The design of such foundations requires special analysis that is beyond the scope of this investigation.

Please contact Kleinfelder for additional analysis and recommendations if machine vibrations will be an issue at this building.

4.5 EXTERIOR CONCRETE FLATWORKS

Exterior concrete flatwork typically refers to the concrete sidewalks around the proposed structure. Some potential for differential movement and cracking of these flatworks is possible.

While it is not likely that the exterior flatworks can be economically protected from distress, several techniques are available to reduce the potential long-term movement of the slabs, including:

Replacing at least 2-feet of subgrade material located immediately beneath the slabs in accordance with Section 4.2.1 and 4.2.4 of this report.

Avoidance of landscape irrigation watering adjacent to slabs.

Thickening or structurally reinforcing slabs.

4.6 CONCRETE TYPE

The concentration of water-soluble sulfates measured on subsurface soil submitted for testing was found to be not detectable. In accordance with ACI Building Code 318, the requirements for concrete exposed to sulfate – containing soils are presented in following table.

Table 9 – Requirements for Concrete Exposed to Sulfate-Containing Soils

Sulfate Exposure Water-Soluble Sulfates (SO4) in

Soil [percent by weight] Cement Type

Negligible 0.00 to 0.10 --------

Moderate 0.10 to 0.20

II, IP(MS), IS(MS),

P(MS), I(PM)(MS),

I(SM)(MS)

Severe 0.20 to 2.00 V

Very Severe Over 2.00 V plus Pozzolan

The concentration of water-soluble sulfates measured on subsurface soils submitted for testing represents a negligible degree of sulfate attack on concrete exposed to the on-site sand soils.

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These results indicate that a locally available Type I/II cement should be used for concrete in contact with the on-site sand soils or imported structural fill meeting the requirements presented in this report.

4.6.1 Corrosion Potential

The pH and electrical resistivity were determined for a selected sample. Test results measured a pH value of 7.12 and resistivity measurements had a value of 250,000 ohm-centimeters for the existing on-site sand soils. The primary physical property for evaluating corrosivity in soil is electrical resistivity. Electrical resistivity is a measure of resistance to the flow of electrical current. Corrosion of buried metal is an electrochemical process in which the amount of metal loss due to corrosion is directly proportional to the flow of electrical current (DC) from metal into the soil. As resistivity decreases, the corrosivity of the soil increases. The following table provides a correlation between soil resistivity and corrosivity towards ferrous metal.

Table 10 – Corrosivity Classification Resistivity in Ohm-centimeters Corrosivity Category

0 to 1,000 Severely Corrosive

1,000 to 2,000 Corrosive

2,000 to 10,000 Moderately Corrosive

Greater than 10,000 Mildly Corrosive

Based on the resistivity measurements discussed above, the native soils are expected to be mildly corrosive. A qualified corrosion engineer should review this data to determine the appropriate corrosion protection measures at the site.

4.7 PAVEMENT RECOMMENDATIONS

A pavement section is a layered system designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and traffic loadings. Soils are represented for pavement design purposes by means of a soil support value for flexible pavements and a modulus of subgrade reaction for rigid pavements. Both values are empirically related to strength. Pavement design procedures are based on strength properties of the subgrade and pavement materials, along with the design traffic conditions. Proper surface drainage is essential for adequate performance of pavement on these soils.

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The pavement sections for the proposed North Colorado Springs Readiness Center development were calculated using the Departments of the Army and the Air Force June 1992 Pavement Design for Roads, Streets, Walks and Open Storage Areas (TM 5-822-5/AFM 88-7).

Based on some provided traffic conditions, we anticipate pavements will consist of asphaltic concrete (AC) overlying an aggregate base course (ABC) as well as areas of Portland cement concrete (PCC) overlying ABC.

4.7.1 Anticipated Pavement Subgrade Material

The anticipated pavement subgrade soils at this site consist mainly of silty to clayey sand soils.

An Hveem stabilometer test (R-Value) was performed on a bulk soil sample comprising the upper 10-feet of soil obtained in borings B-4, B-5, and B-15. The resulting R-value was 56, or approximate equivalent CBR of 20.

4.7.2 Pavement Subgrade Preparation

To create a uniform subgrade, all pavement subgrade material should be scarified to a depth of at least 12-inches and moisture-treated and compacted in accordance with this report. Prior to placing the pavement section including aggregate base course, the pavement subgrade should be proof-rolled with a heavily loaded pneumatic-tired vehicle (such fully loaded water truck) after preparation. Areas that deform under heavy wheel loads are not stable and should be removed and replaced to achieve a stable subgrade prior to paving. Care should be taken to ensure areas around manholes or other utility protrusions are proof-rolled adequately.

4.7.3 Drainage

The collection and diversion of surface drainage away from paved areas is extremely important to the satisfactory performance of pavement. Drainage design should provide for the removal of water and snow from paved areas and prevent the wetting of the subgrade soils. Possible water sources include but are not limited to storm runoff, irrigation of landscaping adjacent to the pavement, and localized groundwater seepage. Landscaping adjacent to the pavements should be avoided.

4.7.4 Pavement Maintenance

Annual maintenance generally refers to crack filling and general surface sealers. We recommend implementation of an at least annual if not more frequent flatwork/pavement crack sealing program. This is very important to prevent surface water (especially from slow infiltration from sources such as snow melt) from entering cracks and wetting the subgrade.

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Due to temperature fluctuations in Colorado significant separations can also occur at interfaces between the asphalt pavement and curbs, concrete flatwork, building structures, and other features. These areas generally result in a high rate of premature distress and failure that can propagate well beyond the original problem area.

4.7.5 Design Traffic Loadings

No specific traffic volume estimates were available for our use at the time this report was written. However, we expect the pavement will be subjected to high volumes of automobile traffic as well as frequent trucks, commercial vehicles, and military vehicles. We understand that the largest vehicle expected to be onsite will be a City of Colorado Springs Fire Truck, and that the pavement sections will need to be designed for an 80,000 pound GVW capacity. For design purposes, we have utilized a Road Classification equivalent to Class D, a Category III Traffic Level, and a Design Index of 3 in our design for the parking areas and access drives. If traffic estimates vary significantly from those described above, we should be contacted to re-evaluate our recommendations.

4.7.6 Design Sections

Based on laboratory test results, the provided design traffic parameters, experience, and the referenced design procedures, we recommend the following pavement sections:

Table 11 – Pavement Section Thickness

Location

Asphalt Concrete (AC) [inches] over

Concrete Pavement (PCC) [inches] over

Aggregate Base Course (ABC) [inches]

Aggregate Base Course (ABC) [inches]

Drive Areas/ Parking Areas

5-inches AC 6-inches PCC 9-inches ABC 8-inches ABC

12-inches of Scarified/Moisture Conditioned On-site Sand Soils

12-inches of Scarified/Moisture Conditioned On-site Sand Soils

4.7.7 Pavement Material Specifications

Based on the anticipated soil type, classification, R-value testing, and on our experience with similar soils in the area, we assumed a California Bearing Ratio (CBR) design value of 24 for

110979-5/CSP10R137 Page 19 of 21 September 24, 2010 the on-site sand soils and a CBR design value of 100 for Aggregate Base Course (ABC) equivalent to a Graded Crushed Aggregate according to the Departments of the Army and the Air Force June 2992 Pavement Design for Roads, Streets, Walks and Open Storage Areas (TM 5-822-5/AFM 88-7) placed and compacted as specified herein. Asphalt specifications are listed in Chapter 9 of TM 5-822-8/AFM 88-6.

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5 ADDITIONAL SERVICES

5.1 REQUIREMENTS FOR ADDITIONAL SERVICES

In most cases, other services beyond completion of a geotechnical report are necessary or desirable to complete a project satisfactorily. It also sometimes happens that, while performing our services, we discover conditions or circumstances that require the performance of additional work that was not anticipated when the geotechnical report was written. Kleinfelder offers a range of environmental, geological, geotechnical, and construction services to suit the varying needs of our clients. This section outlines some of those services that may pertain to this project. Kleinfelder will be happy to submit a proposal for performing any such services upon request.

5.2 REVIEW OF PLANS AND SPECIFICATIONS

We strongly recommend that Kleinfelder be given an opportunity to review the plans and specifications for this project before they are finalized. Such a review allows us to verify that our recommendations and concerns have been adequately incorporated in the design. It also gives us an opportunity to discuss those recommendations and concerns with other members of the design team so that we can clear up misunderstandings or ambiguities before the project reaches the construction stage.

5.3 PRE-BID AND PRE-CONSTRUCTION MEETINGS

Contractors often contact us during the bidding process to discuss the geotechnical aspects of projects. Informal contacts between Kleinfelder and individual contractors can result in incorrect or incomplete information being provided to the contractor. Therefore, we recommend that a pre-bid meeting be held to answer any questions about the report prior to submittal of bids. If this is not possible, questions or requests for clarifications regarding this report should be directed to the Owner or his designated representative. After consultation with Kleinfelder, the Owner (or his representative) should provide clarifications or additional information to all contractors bidding the job. After award of a construction contract for this project, we recommend that the Owner, the Contractor, and the other members of the design team hold a pre-construction meeting with Kleinfelder’s project engineer. The purpose of this meeting is to go over geotechnical aspects of the project so that all parties have a clear understanding of the geotechnical issues that affect the Contractor’s work and how they will be handled. The meeting also allows us to set up the communication and coordination needed for construction observation and testing, and to identify points of confusion or disagreement that need to be resolved.

APPENDIX A

Vicinity Map and Boring Location Plan

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6 LIMITATIONS

The recommendations in this report are based on our field observations, laboratory testing, and our present understanding of the proposed construction. It is possible that subsurface conditions can vary between or beyond the points explored. If the conditions found during construction differ from those described in this report, please notify us immediately so that we can review our report in light of those conditions and provide supplemental recommendations as necessary. We should also review the report if the scope of the proposed construction, including the proposed loads or structure locations, changes from that described in this report.

Kleinfelder has prepared this report for the exclusive use of HB&A for the proposed North Colorado Springs Readiness Center in Colorado Springs, Colorado. The report was prepared in substantial accordance with the generally accepted standards of practice for geotechnical engineering as exist in the site area at the time of our investigation. No warranty is expressed or implied. The recommendations in this report are based on the assumption that Kleinfelder will conduct an adequate program of construction testing and observation to evaluate compliance with our recommendations.

This report may be used only by the Client, and only for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both on- and off-site), or other factors may change over time, so that additional investigation or revision of our recommendations may be required with the passage of time. It is the Client’s responsibility to see that all parties to the project including the designer, contractor, and subcontractors, are made aware of this report in its entirety. The use of information contained in this report for bidding purposes shall be at the Contractor’s option and risk. Any party other than the Client who wishes to use this report must notify Kleinfelder of such intended use. Based on that intended use of the report, Kleinfelder may require that additional work be performed and that an updated report be issued. Noncompliance with these requirements by the Client or anyone else will release Kleinfelder from any liability resulting from the use of this report by an unauthorized party.

APPENDIX B

Logs of Exploratory Borings

Geothermal Boring B-16 (To Be Supplied at a Later Date with the Geothermal Test Results)

APPENDIX C

Geotechnical Laboratory Test Results

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APPENDIX D

Analytical Laboratory Test Results

APPENDIX E

Geothermal Conductivity Test Results (To Be Provided at a Later Date)

APPENDIX F

Important Information About Your Geotechnical Engineering Report

Geotechnical Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi-neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solely for the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one

— not even you — should apply the report for any purpose or project except the one originally contemplated.

Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary.

Do not read selected elements only.

A Geotechnical Engineering Report Is Based on A Unique Set of Project-Specific Factors Geotechnical engineers consider a number of unique, project-specific fac-tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth-erwise, do not rely on a geotechnical engineering report that was:

• not prepared for you,

• not prepared for your project,

• not prepared for the specific site explored, or

• completed before important project changes were made.

Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect:

• the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse,

• elevation, configuration, location, orientation, or weight of the proposed structure,

• composition of the design team, or

• project ownership.

As a general rule, always inform your geotechnical engineer of project changes—even minor ones—and request an assessment of their impact.

Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed.

Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineer-ing report whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site;

or by natural events, such as floods, earthquakes, or groundwater fluctua-tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems.

Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi-neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ—sometimes significantly— from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions.

A Report's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those recommendations are not final, because geotechnical engi-neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual

Important Information About Your

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

Geotechnical Engineering Report The following information is provided to help you manage your risks.

subsurface conditions revealed during construction. The geotechnical engineer who developed your report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation.

A Geotechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo-technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti-nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation.

Do Not Redraw the Engineer's Logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings.

Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk.

Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con-tractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac-tors have sufficient time to perform additional study.