05 - Geotechnical Report GLEN 20-2005.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report Proposed Design Addition to Building 20

Schriever AFB, Colorado

November 29, 2017

Terracon Project No. 23175083

Prepared for:

HB&A, LLC

Colorado Springs, Colorado

Prepared by:

Terracon Consultants, Inc.

Colorado Springs, Colorado

Terracon Consultants, Inc. 4172 Center Park Drive Colorado Springs, Colorado 80916

P (719) 597 2116 F (719) 597 2117 terracon.com

REPORT C OVER LETTER TO SIGN

HB&A, LLC

102 East Moreno Ave

Colorado Springs, Colorado 80903

Attn: Ms. Carrie Ann Higgs, AIA, AICP, LEED BD+C

P: (719) 473-7063

E: carrie.higgs@hbaa.com

Re: Geotechnical Engineering Report

Proposed Design Addition to Building 20

Southeast of Enoch Road and Falcon Parkway

Schriever AFB, Colorado

Dear Ms. Higgs:

We have completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with our proposal number P23175083R dated August

31, 2017.

This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

Tyler A. Compton, E.I. Robert M. Hernandez, P.E.

Staff Engineer Geotechnical Services Manager mailto:carrie.higgs@hbaa.com

REPORT TOPICS

REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

SEISMIC CONSIDERATIONS

FLOOR SLABS

CORROSIVITY

GENERAL COMMENTS

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced heading. The PDF version also includes hyperlinks which direct the reader to that section. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLAN

EXPLORATION RESULTS (Boring Logs and Laboratory Data)

SUPPORTING INFORMATION (General Notes and USCS) http://client.terracon.com/

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INTRODUCTION

Geotechnical Engineering Report

Proposed Design Addition to Building 20

Southeast of Enoch Road and Falcon Parkway

Schriever AFB, Colorado

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed Design Addition to Building 20 to be located Southeast of

Enoch Road and Falcon Parkway in Schriever AFB, Colorado. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ subsurface soil conditions ■ foundation design and construction

■ groundwater conditions ■ floor slab design and construction

■ site preparation and earthwork ■ seismic site classification per IBC

■ excavation considerations ■ lateral earth pressures

The geotechnical engineering scope of work for this project included the advancement of two test borings to depths ranging from approximately 20.5 to 30.5 feet below existing site grades.

Maps showing the site and boring locations are shown in the Site Location and Exploration

Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the boring logs and as separate graphs in the Exploration Results section of this report.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel information

The project is located Southeast of Enoch Road and Falcon Parkway in

Schriever AFB, Colorado.

See Site Location

Proposed Design Addition to Building 20 ■ Schriever AFB, Colorado

November 29, 2017 ■ Terracon Project No. 23175083

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Existing improvements

The site is located in a landscaped area adjacent to the northeast side of

Building 20. An asphalt paved parking lot is located immediately southeast of the site, and the remaining areas adjacent to the site are landscaped.

Current ground cover At the time of our exploration the site was vegetated by grass and a sparse growth of trees.

Existing topography

The ground surface across the addition footprint is relatively flat with less than about 1 foot of relief. Areas north of the site are hilly and the terrain slopes gently down to the south away from the site.

Geology Clay and sand deposits with varying clay and silt contents extending to the total depths explored.

PHOTOGRAPHY LOG

Site Photo Facing Northeast

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Site Photo Facing Southwest

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed in the project planning stage. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Information provided

Our understanding of this project comes from an email with the client dated August 25, 2017, the Statement of Work dated September 20, 2017, and the undated Preliminary Concept Plan for Building 20 Pavilion

Proposed structure

The project includes a pavilion structure on the east side of Building 20 occupying a footprint of about 2,500 square feet. The Design is to be site specific and take advantage of the existing trees as a visual back ground and extension for the facility. The pavilion will be connected to Building 20 with a covered walkway accessible from the Bar and Coat Room area and will not include any below grade structures such as basements.

Building construction Structure to be steel framing, steel roof deck with EDPM roof system, external drainage, steel fascia and concrete slab. Low masonry walls.

Finished floor elevation Not known at this time, expected to be near existing grade.

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Maximum loads

■ Columns: 50 kips maximum

■ Walls: 2 kips per linear foot maximum

Slabs: 150 pounds per square foot maximum

Grading/slopes

Up to 1 foot of cut and 1 foot of fill will be required to develop final grade.

Final slope angles of as steep as 3H:1V (Horizontal:Vertical) are expected.

Below grade structures None anticipated.

Free-standing retaining walls

Retaining walls are not expected to be constructed as part of site development.

Pavements None anticipated

Estimated start of construction Fall 2018

GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

Based on the results of the borings, subsurface conditions at the boring locations can be generalized as follows:

Stratum Approximate Depth to

Bottom of Stratum (feet) Material Description Consistency/Density

1 6 to 7.5 Clay soils Stiff to very stiff

2 20.5 to 30.5 Sand soils with varying silt and clay contents

Loose to medium dense

1. Both Boring B-1 and B-2 terminated in Stratum 2

Conditions encountered at each boring location are indicated on the individual boring logs shown in the Exploration Results section and are attached to this report. Stratification boundaries on the boring logs represent the approximate location of changes in native soil types; in situ, the transition between materials may be gradual.

Laboratory test results indicate that the clay soil samples tested exhibit low compression at in-situ water contents. When exposed to increases in moisture content, the clay soils tested exhibit negligible to low expansion potential followed by low to moderate compression at increased loadings.

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Groundwater Conditions

Groundwater was not encountered in the borings at the time of our field study. The borings were observed for the presence of groundwater during and after completion of drilling. Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

GEOTECHNICAL OVERVIEW

Based on the results of our field investigation, laboratory testing program and geotechnical analyses, development of the site is considered feasible from a geotechnical viewpoint provided that the conclusions and considerations provided herein are incorporated into the project.

Low density, compressible, and potentially expansive soils are present on this site. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement in the structure should be anticipated.

The severity of cracking and other damage will probably increase if modification of the site results in excessive wetting or drying of the expansive material. We recommend the proposed structure be supported on shallow spread footings bearing on compacted structural fill. Floor slabs should also bear on compacted structural fill.

Based on our field exploration and laboratory testing, it is our opinion the existing clay soils could be re-used as structural fill provided they meet the requirements for imported soils recommended in the Earthwork section of this report. Our scope of services for the geotechnical engineering phase of this project included gradation and Atterberg limit laboratory testing that indicated the clay soils may be suitable for re-use as structural fill. Before being re-used as structural fill a representative sample of the clay soils excavated from the building site should be tested to confirm that the soils meet the remolded swell potential and other recommended materials requirements.

We recommend a contingency cost/plan be in place for imported soils for support of the proposed structure should the on-site soils not meet the remolded swell potential criteria.

The on-site clay soils are susceptible to becoming unstable when exposed to increased moisture conditions. These soils are highly susceptible to pumping, even during fill placement, when subjected to dynamic loading, such as construction equipment and vehicle traffic. A contractor experienced with these soils should be retained for construction.

Lightweight or tracked excavation and compaction equipment may be required. Mitigation of subgrade soils prior to placement of fill may also be required if the subgrade soils are subjected to

Responsive ■ Resourceful ■ Reliable 6 construction traffic. Mitigation will depend on the extent of unstable material and will likely require removal and replacement with approved soils.

Existing utilities are present on the site. Sanitary utilities, water lines, and electric lines are located within the proposed pavilion footprint. It has been our experience that backfill associated with old utilities may not have been compacted sufficiently to support building foundations. The old backfill may need to be removed and replaced in order to reduce the risk of excessive settlement within the zone of influence (1:1 projection) of foundations. As an alternative, the foundations can be lowered such that the outside edge of footings are laterally no closer than a 1:1 slope to the bottom of the existing utilities.

Additional floor slab and foundation information pertaining to the building can be found in the

Floor Slabs and Shallow Foundations sections of this report.

The General Comments section provides an understanding of the report limitations.

EARTHWORK

Earthwork will include clearing and grubbing, excavations and fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. These recommendations include critical quality criteria as necessary to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Site Preparation

Prior to placing fill, existing vegetation and root mat should be removed. Complete stripping of the topsoil should be performed in any of the proposed building and parking/driveway areas.

The subgrade should be proof-rolled. Proof-rolling can be performed with an adequately loaded vehicle such as a fully loaded tandem axle dump truck. The proof-rolling should be performed under the direction of the Geotechnical Engineer. Areas which excessively deflect under the proof-roll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should either be removed or modified by stabilizing with geotextile. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill is that material used below, or within 5 feet of structures or constructed slopes.

General fill is that material used to achieve grade outside of these areas. Earthen materials used for structural and general fill should meet the following material property requirements:

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Soil Type

USCS Classification Acceptable Locations for Placement

On-site soils CL

The on-site clay soils are considered acceptable for use as general fill, and are suitable for use as structural fill provided they meet the requirements for imported soils provided on the following page.

Imported soils Varies

Imported soils meeting the gradation outlined herein can be considered suitable for use as structural and/or general fill. We recommend a contingency cost/plan be in place for the use of imported soils, if needed, provided the on-site soils do not meet the recommended criteria for imported soils.

1. Structural and general fill should consist of approved materials free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

Imported soils for use as structural and/or general fill should conform to the following:

Gradation Percent finer by weight (ASTM C136)

3” 100

No. 4 Sieve 50-100

No. 200 Sieve 20-65

Liquid Limit…………………………………………………....35 (max)

Plastic Index…………………………………………………..15 (max)

Maximum Expansive Potential (%)…………………………1.5*

*Measured on a sample compacted to approximately 95 percent of the ASTM D698 maximum dry density at one percent below optimum water content. The sample is confined under a 150 psf surcharge and submerged.

Fill Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill

Maximum lift thickness

8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack, plate compactor) is used

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Item Structural Fill

Minimum compaction requirements 1, 2, 3

95% of the materials maximum dry density for foundations and slabs

90% of the materials maximum dry density for general fill outside of structural areas

Water content range

Optimum to three percent above optimum water content (cohesive soils)

Within three percent of optimum water content (granular soils)

1. We recommend that engineered fill be tested for water content and compaction during placement. Should the results of the in-place density tests indicate the specified water or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified water and compaction requirements are achieved.

2. Maximum dry density and optimum water content as determined by the Standard Proctor test (D698).

3. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least 70% relative density (ASTM D 4253 and D 4254).

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. These greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5 percent away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary as part of the structure’s maintenance program. Where paving or flatwork abuts the structure a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations, for the proposed structure, are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of floor slabs. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Any water that collects over, or adjacent to, construction areas should be promptly removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or these materials

Responsive ■ Resourceful ■ Reliable 9 should be scarified, moisture conditioned, and recompacted, prior to floor slab construction. All these processes should be observed by Terracon.

As mentioned, the on-site clay soils are susceptible to becoming unstable when exposed to increased moisture conditions. These soils are highly susceptible to pumping, even during fill placement, when subjected to dynamic loading, such as construction equipment and vehicle traffic. A contractor experienced with these soils should be retained for construction.

Lightweight or tracked excavation and compaction equipment may be required. Mitigation of subgrade soils prior to placement of fill may also be required if the subgrade soils are subjected to construction traffic. Mitigation will depend on the extent of unstable material and will likely require removal and replacement with approved soils.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local, and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming any responsibility for construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer. This monitoring should include documentation of adequate removal of vegetation and top soil, proof-rolling and mitigation of areas delineated by the proof-roll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked as necessary until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,000 square feet of compacted fill in the building areas. One density and water content test for every 50 linear feet of compacted utility trench backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. In the event unanticipated conditions are encountered, the

Geotechnical Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the

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SHALLOW FOUNDATIONS

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Maximum net allowable bearing pressure 1, 2 2,000 psf (foundations bearing on structural fill)

Required bearing stratum 3 Minimum of 2 feet of compacted structural fill

Minimum foundation dimensions

Columns: Min 24 inches

Max 6 feet

Continuous: Min 16 inches

Max 3 feet

Ultimate passive resistance 4

(equivalent fluid pressures) 205 pcf (on-site soil backfill)

Ultimate coefficient of sliding friction 5 0.30 (on-site soils)

Minimum embedment below finished grade 6, Exterior footings: 36 inches

Interior footings: 36 inches

Estimated total settlement from structural loads 2 About 1 inch

Estimated differential settlement 2, 7 About ½ to ¾ of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied. These bearing pressures can be increased by 1/3 for transient loads unless those loads have been factored to account for transient conditions. Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description.

3. Unsuitable or soft soils should be over-excavated and replaced according to the recommendations presented in the Earthwork.

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations, and develop the recommended allowable bearing pressure. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

7. Differential settlements are as measured over a span of 50 feet.

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Construction Adjacent to Existing Building

Differential settlement between the addition and the existing building is expected to approach the magnitude of the total settlement of the addition. Expansion joints should be provided between the existing building and the proposed addition to accommodate differential movements between the two structures. Underground piping between the two structures should be designed with flexible couplings and utility knockouts in foundation walls should be oversized, so minor deflections in alignment do not result in breakage or distress. Care should be taken during any excavation adjacent to existing foundations, so as not to disturb any existing foundation bearing soils.

New footings should bear at or near the bearing elevation of any immediately adjacent existing foundation. Depending upon their locations and current loads on the existing footings, footings for the new addition could cause settlements of adjacent walls. To reduce this concern and risk, clear distances at least equal to the new footing widths should be maintained between the addition’s footings and footings supporting the existing building. Construction of new foundations may also require shoring of excavations adjacent to existing foundations

We understand existing foundations could possibly support additional load from the new addition.

It is possible additional loads on the existing foundations could cause other building settlements and existing foundations may experience similar movements to those described in this report. The structural capacity of existing foundations should be evaluated by a licensed structural engineer, where these increases in loading are planned.

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Design Parameters - Uplift Loads

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils. As illustrated on the subsequent figure, the effective weight of the soil prism defined by diagonal planes extending up from the top of the perimeter of the foundation to the ground surface at an angle,, of 30 degrees from the vertical can be included in uplift resistance. The maximum allowable uplift capacity should be taken as a sum of the effective weight of soil plus the dead weight of the foundation, divided by an appropriate factor of safety. A maximum total unit weight of 110 pcf should be used for the backfill.

Foundation Construction

Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction of the

Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable bearing soils are encountered at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. This is illustrated on the sketch below.

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Over-excavation for structural fill placement below footings should be conducted as shown below.

The over-excavation should be backfilled up to the footing base elevation with structural fill placed as recommended in the Earthwork section.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design

Category. Site Classification is required to determine the Seismic Design Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7-10.

Description Value

2015 International Building Code Site Classification (IBC) 1 D 2

Site Latitude 38.8086

Site Longitude -104.5337

SDS Spectral Acceleration for a Short Period 3 0.173g

SD1 Spectral Acceleration for a 1-Second Period 3 0.092g

1. Seismic site classification in general accordance with the 2015 International Building Code, which refers to

ASCE 7-10.

2. The 2015 International Building Code (IBC) uses a site profile extending to a depth of 100 feet for seismic site classification. Borings at this site were extended to a maximum depth of 30.5 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

3. These values were obtained using online seismic design maps and tools provided by the USGS

(http://earthquake.usgs.gov/hazards/designmaps/).

http://earthquake.usgs.gov/hazards/designmaps/

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FLOOR SLABS

Design parameters for floor slabs assume the requirements for Earthwork have been followed.

Specific attention should be given to positive drainage away from the structure.

Floor Slab Design Parameters

Floor Slab Support

A minimum of 3 feet of compacted structural fill.

Estimated Modulus of

Subgrade Reaction

100 pounds per square inch per inch (psi/in) for point loads

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

The use of a vapor retarder should be considered beneath concrete slabs on grade that will be covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or any cracks that develop should be sealed with a water-proof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates that any differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks that occur beyond the length of the structural dowels. The structural engineer should account for this potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

Floor Slab Construction Considerations

Finished subgrade within and for at least 10 feet beyond the floor slab should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed and structural fill should be added to replace the

Responsive ■ Resourceful ■ Reliable 15 resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should approve the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

CORROSIVITY

The table below lists the results of laboratory soluble sulfate, soluble chloride, electrical resistivity, and pH testing. These values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction.

Corrosivity Test Results Summary

Boring Sample Depth

(feet)

Soluble

Sulfate

(percent)

Soluble

Chloride

(percent)

Electrical

Resistivity (Ω-cm) pH

B-1 1-10 0.004 0.0005 2317 7.8

Results of soluble sulfate testing indicate that samples of the on-site soils tested possess negligible sulfate concentrations when classified in accordance with Table 4.3.1 of the ACI Design

Manual. Concrete should be designed in accordance with the provisions of the ACI Design

Manual, Section 318, Chapter 4.

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GENERAL COMMENTS

Our work is conducted with the understanding of the project as described in the proposal, and will incorporate collaboration with the design team as we complete our services to verify assumptions.

Revision of our understanding to reflect actual conditions important to our work will be based on these verifications and will be reflected in the final report. The design team should collaborate with

Terracon to confirm these assumptions and to prepare the final design plans and specifications.

This facilitates the incorporation of our opinions related to implementation of our geotechnical recommendations. Any information conveyed prior to the final report is for informational purposes only and should not be considered or used for decision-making purposes.

Our analysis and opinions are based upon our understanding of the geotechnical conditions in the area, the data obtained from our site exploration and from our understanding of the project.

Variations will occur between exploration point locations, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the Geotechnical

Engineer, where noted in the final report, to provide observation and testing services during grading, excavation, foundation construction and other earth-related construction phases of the project. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our scope of services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third party beneficiaries intended.

Any third party access to services or correspondence is solely for information purposes only.

Reliance upon the services and any work product is limited to our client, and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly impact excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing.

Site safety, and cost estimating including, excavation support, and dewatering

Responsive ■ Resourceful ■ Reliable 17 requirements/design are the responsibility of others. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

ATTACHM ENTS

ATTACHMENTS

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EXPLORATION AND TESTING PROCEDURES

Field Exploration

Number of Borings Planned Boring Depth (feet) 1 Planned Location

2 20 to 30 or auger refusal Planned building area

1. Below ground surface

Boring Layout and Elevations: We use handheld GPS equipment to locate borings with an estimated horizontal accuracy of +/-20 feet. Approximate elevations were obtained by interpolation from the topographic survey provided by HB&A, LLC on 10/11/2017.

Subsurface Exploration Procedures: We advance soil borings with a truck-mounted drill rig using continuous flight augers (solid stem and/or hollow stem, as necessary, depending on soil conditions). Four samples are obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. Soil sampling is typically performed using thin-wall tube and/or split-barrel sampling procedures. The samples are placed in appropriate containers, taken to our soil laboratory for testing, and classified by a geotechnical engineer. In addition, we observe and record groundwater levels during drilling and sampling.

Upon encountering bedrock or refusal-to-drilling conditions the borings will be terminated.

Our exploration team prepares field boring logs as part of standard drilling operations, these include sampling depths, penetration distances, and other relevant sampling information. Field logs include visual classifications of materials encountered during drilling, and our interpretation of subsurface conditions between samples. Final boring logs, prepared from field logs, represent the geotechnical engineer's interpretation, and include modifications based on observations and laboratory tests.

Laboratory Testing

The project engineer reviews the field data and assigns various laboratory tests to better understand the engineering properties of the various soil strata as necessary for this project.

Procedural standards noted below are for reference to methodology in general. In some cases, variations to methods are applied because of local practice or professional judgment. Standards noted below include reference to other, related standards. Such references are not necessarily applicable to describe the specific test performed.

■ ASTM D2216 Standard Test Methods for Laboratory Determination of Water (Moisture)

Content of Soil and Rock by Mass

Responsive ■ Resourceful ■ Reliable

■ ASTM D4318 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of

Soils

■ ASTM D422 Standard Test Method for Particle-Size Analysis of Soils

■ ASTM D2435/D2435M Standard Test Methods for One-Dimensional Consolidation

Properties of Soils Using Incremental Loading

■ ASTM D4327 Standard Test Methods for Water Soluble Chloride and Sulfate Content

■ AASHTO T289-91 Standard Test Methods for Determination of pH and Resistivity

The laboratory testing program often includes examination of soil samples by an engineer. Based on the material’s texture and plasticity, we describe and classify the soil samples in accordance with the Unified Soil Classification System.

SITE LOC ATION AND EXPLOR ATION PLAN S

SITE LOCATION AND EXPLORATION PLANS

SITE LOCATION

Schriever AFB - Design Addition to Building 20 ■ Schriever AFB, Colorado

November 27, 2017 ■ Terracon Project No. 23175083

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT

INTENDED FOR CONSTRUCTION PURPOSES

EXPLORATION PLAN

Schriever AFB - Design Addition to Building 20 ■ Schriever AFB, Colorado

November 27, 2017 ■ Terracon Project No. 23175083

AERIAL PHOTOGRAPHY PROVIDED BY

MICROSOFT BING MAPS

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT

INTENDED FOR CONSTRUCTION PURPOSES

EXPLOR ATION RESULTS

EXPLORATION RESULTS

32-19-13

6301.5

6295.5

6286.5

7-8

6-7

8-9

9-11

8-13

8-11-11 N=22

11-12-15 N=27

12-11-17 N=28

6.0

12.0

21.0

30.5

SANDY LEAN CLAY (CL), light brown, stiff, with calcium deposits and rootlets to 5 feet

SILTY SAND (SM), fine to medium grained, light brown, medium dense

CLAYEY SAND (SC), fine to medium grained, light brown, medium dense

POORLY GRADED SAND (SP), fine to medium grained, brown, medium dense

Boring Terminated at 30.5 Feet

G R

A P

H

IC

L O

G

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

T V

A

LI

D

IF

S E

P A

R A

T E

D F

R O

M O

R

IG

IN

A

L R

E P

O R

T

G

E O

S M

A R

T L

O G

-N O

W E

LL

S

C H

R

IE

V E

R A

F B

D

.G P

J T

E R

R A

C O

N _D

A T

A T

E M

P

LA

T E

.G D

T

1/

7/

P E

R C

E N

T F

IN

E

S

W A

T E

R C

O N

T E

N T

D R

Y U

N

IT

W E

IG

H

T pc f)

LL-PL-PI

ATTERBERG

LIMITS

ELEVATION (Ft.)

Surface Elev: 6312.5 (Ft.)

W A

T E

R L

E V

E L

O B

S E

R V

A T

IO

N

S

D E

P T

H

F t.)

S A

M P

LE

T

Y P

E

F

IE

LD

T

E S

T R

E S

U

LT

S

DEPTH

LOCATION

Latitude: 38.8086° Longitude: -104.5337°

See Exploration Plan

Advancement Method:

4-inch solid stem auger

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

4172 Center Park Dr Colorado Springs, CO

Notes:

Project No.: 23175083

Drill Rig: BK 51

Boring Started: 11-06-2017

BORING LOG NO. B-1

HB&A, LLCCLIENT:

Colorado Springs, CO

Driller: Unlimited Access

Boring Completed: 11-06-2017

PROJECT: Schriever AFB - Design Addition to Building

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Enoch Road and Falcon Parkway Schriever AFB, CO

SITE:

No free water observed

WATER LEVEL OBSERVATIONS

NP6300

6295.5

13-17

6-8

6-11

6-8

9-18

8-10-11 N=21

7.5

12.0

20.5

SANDY LEAN CLAY (CL), brown, stiff to very stiff

SILTY SAND (SM), fine to medium grained, light brown, loose

CLAYEY SAND (SC), fine to medium grained, light brown, medium dense

Boring Terminated at 20.5 Feet

G R

A P

H

IC

L O

G

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

T V

A

LI

D

IF

S E

P A

R A

T E

D F

R O

M O

R

IG

IN

A

L R

E P

O R

E O

S M

A R

T L

O G

-N O

W E

LL

S

C H

R

IE

V E

R A

F B

D

.G P

J T

E R

R A

C O

N _D

A T

A T

E M

P

LA

T E

.G D

T

1/

7/

P E

R C

E N

T F

IN

E

S

W A

T E

R C

O N

T E

N T

D R

Y U

N

IT

W E

IG

H

T pc f)

LL-PL-PI

ATTERBERG

LIMITS

ELEVATION (Ft.)

Surface Elev: 6312.5 (Ft.)

W A

T E

R L

E V

E L

O B

S E

R V

A T

IO

N

S

D E

P T

H

F t.)

S A

M P

LE

T

Y P

E

F

IE

LD

T

E S

T R

E S

U

LT

S

DEPTH

LOCATION

Latitude: 38.8086° Longitude: -104.5335°

See Exploration Plan

Advancement Method:

4-inch solid stem auger

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

4172 Center Park Dr Colorado Springs, CO

Notes:

Project No.: 23175083

Drill Rig: BK 51

Boring Started: 11-06-2017

BORING LOG NO. B-2

HB&A, LLCCLIENT:

Colorado Springs, CO

Driller: Unlimited Access

Boring Completed: 11-06-2017

PROJECT: Schriever AFB - Design Addition to Building

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

Enoch Road and Falcon Parkway Schriever AFB, CO

SITE:

No free water observed

WATER LEVEL OBSERVATIONS

0 20 40 60 80 100

CH

o r

OH

CL

o r

OL

ML or OL

MH or OH

"U " L ine

"A " L ine

ATTERBERG LIMITS RESULTS

ASTM D4318

P L A S T I C I T Y

I N D E X

LIQUID LIMIT

4172 Center Park Dr Colorado Springs, CO

PROJECT NUMBER: 23175083

SITE: Enoch Road and Falcon Parkway Schriever AFB, CO

CLIENT: HB&A, LLC

Colorado Springs, CO

PROJECT: Schriever AFB - Design Addition to Building 20

LA

B

O R

A T

O R

Y T

E S

T S

A R

E N

O T

V A

LI

D

IF

S

E P

A R

A T

E D

F R

O M

O R

IG

IN

A L

R E

P O

R

A

T E

R B

E R

G L

IM

IT

S

S C

H R

IE

V

E R

A F

B

D .G

P J

T E

R R

A C

O N

_D A

T A

T E

M P

LA

T

E .G

D T

1/

/1

4 - 5

7 - 8

NP

NP

NP

CL

SM

SANDY LEAN CLAY

SILTY SAND

DescriptionUSCSFinesPIPLLLBoring ID Depth

B-1

B-2

CL-ML

0.0010.010.1110100

30 40 501.5 2006 810 1441 3/4 1/2 60

GRAIN SIZE IN MILLIMETERS

P E

R C

E N

T F

IN

E

R B

Y W

E

IG

H T

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

4 3/8 3 100 1403 2

GRAIN SIZE DISTRIBUTION

ASTM D422 / ASTM C136

6 16 20

4172 Center Park Dr Colorado Springs, CO

PROJECT NUMBER: 23175083

SITE: Enoch Road and Falcon Parkway Schriever AFB, CO

CLIENT: HB&A, LLC

Colorado Springs, CO

PROJECT: Schriever AFB - Design Addition to Building 20

LA

B

O R

A T

O R

Y T

E S

T S

A R

E N

O T

V A

LI

D

IF

S

E P

A R

A T

E D

F R

O M

O R

IG

IN

A L

R E

P O

R

R

A

IN

S

IZ

E : U

S C

S -2

S

C H

R

IE

V E

R A

F B

D

.G P

J T

E R

R A

C O

N _D

A T

A T

E M

P

LA

T E

.G D

T

1/

7/

SANDY LEAN CLAY (CL)

SILTY SAND (SM)

0.087

0.143

2.36

9.5

NP

54.8

34.2

0.0

0.1

45.2

65.7

4 - 5

7 - 8

4 - 5

7 - 8

WC (%) LL

D30 D10 %Gravel %Fines %Clay

B-1

B-2

NP

NP

Boring ID Depth USCS Classification PL PI Cc Cu

D100 D60 Boring ID Depth %Sand %Silt medium

B-1

B-2 coarse coarsefine fine

COBBLES

GRAVEL SAND

SILT OR CLAY

-10

-8

-6

-4

-2

100 1,000 10,000

A X

IA

L

S T

R A

IN

PRESSURE, psf

SWELL CONSOLIDATION TEST

ASTM D4546

NOTES: Sample inundated with water at 500 pounds per square foot (psf).

PROJECT NUMBER: 23175083

PROJECT: Schriever AFB - Design

Addition to Building 20 SITE: Enoch Road and Falcon

Parkway Schriever AFB, CO

CLIENT: HB&A, LLC

Colorado Springs, CO

4172 Center Park Dr Colorado Springs, CO

Specimen Identification Classification , pcf

91B-1 8

WC, %

SANDY LEAN CLAY(CL)4 - 5 ft

LA

B

O R

A T

O R

Y T

E S

T S

A R

E N

O T

V A

LI

D

IF

S

E P

A R

A T

E D

F R

O M

O R

IG

IN

A L

R E

P O

R

C

_C O

N S

O L_

S T

R A

IN

-U

S C

S

S C

H R

IE

V

E R

A F

B

D .G

P J

T E

R R

A C

O N

_D A

T A

T E

M P

LA

T

E .G

D T

1/

7/

-10

-8

-6

-4

-2

100 1,000 10,000

A X

IA

L

S T

R A

IN

PRESSURE, psf

SWELL CONSOLIDATION TEST

ASTM D4546

NOTES: Sample inundated with water at 500 pounds per square foot (psf).

PROJECT NUMBER: 23175083

PROJECT: Schriever AFB - Design

Addition to Building 20 SITE: Enoch Road and Falcon

Parkway Schriever AFB, CO

CLIENT: HB&A, LLC

Colorado Springs, CO

4172 Center Park Dr Colorado Springs, CO

Specimen Identification Classification , pcf

106B-2 5

WC, %

SANDY LEAN CLAY (CL)7 - 8 ft

LA

B

O R

A T

O R

Y T

E S

T S

A R

E N

O T

V A

LI

D

IF

S

E P

A R

A T

E D

F R

O M

O R

IG

IN

A L

R E

P O

R

C

_C O

N S

O L_

S T

R A

IN

-U

S C

S

S C

H R

IE

V

E R

A F

B

D .G

P J

T E

R R

A C

O N

_D A

T A

T E

M P

LA

T

E .G

D T

1/

7/

171113026TASK NO:

Analytical Results

Terracon, Inc. - Colo Springs

Tyler Compton

Company:

Report To:

Company:

Bill To:

4172 Center Park Drive Colo. Springs CO 80916

Tyler Compton

Terracon, Inc. - Accounts Payable 18001 W. 106th St Suite 300 Olathe KS 66061

Schriever AFB Design 23175083 Date Reported: 11/20/17

Task No.: 171113026

Matrix: Soil - Geotech

Date Received: 11/13/17

Client Project:

Client PO:

B-1 @ 1-10 FtCustomer Sample ID

Test Method

171113026-01Lab Number:

Result

Chloride - Water Soluble AASHTO T291-91/ ASTM D4327 0.0005 % pH AASHTO T289-91 7.8 units

Resistivity AASHTO T288-91 2317 ohm.cm

Sulfate - Water Soluble AASHTO T290-91/ ASTM D4327 0.004 %

240 South Main Street / Brighton, CO 80601-0507 / 303-659-2313 Mailing Address: P.O. Box 507 / Brighton, CO 80601-0507 / Fax: 303-659-2315

DATA APPROVED FOR RELEASE BY

Abbreviations/ References:

171113026

AASHTO - American Association of State Highway and Transportation Officials.

ASTM - American Society for Testing and Materials.

ASA - American Society of Agronomy.

DIPRA - Ductile Iron Pipe Research Association Handbook of Ductile Iron Pipe.

SUPPORTING INFORM ATION

SUPPORTING INFORMATION

Schriever AFB - Design Addition to Building 20 Schriever AFB, CO

11/27/2017 Terracon Project No. 23175083

3.5 to 7.0

> 55.5

28.0 to 55.5

14.0 to 28.0

7.0 to 14.0 less than 3.50

Unconfined Compressive Strength Qu, (psi)

Modified Dames & Moore Ring Sampler

Grab Sample

Standard Penetration Test

Trace

PLASTICITY DESCRIPTION

Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations.

DESCRIPTION OF SYMBOLS AND ABBREVIATIONS

GENERAL NOTES

> 30

11 - 30

1 - 10Low

Non-plastic

Plasticity Index

#4 to #200 sieve (4.75mm to 0.075mm

Boulders

12 in. to 3 in. (300mm to 75mm)Cobbles

3 in. to #4 sieve (75mm to 4.75 mm)Gravel

Sand

Passing #200 sieve (0.075mm)Silt or Clay

Particle Size

Water Level After a Specified Period of Time

Water Level After a Specified Period of Time

Water Initially Encountered

Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

GRAIN SIZE TERMINOLOGY

RELATIVE PROPORTIONS OF FINESRELATIVE PROPORTIONS OF SAND AND GRAVEL

DESCRIPTIVE SOIL CLASSIFICATION

LOCATION AND ELEVATION NOTES

SAMPLING WATER LEVEL FIELD TESTS

N

(HP)

(T)

(DCP)

UC

(PID)

(OVA)

Standard Penetration Test Resistance (Blows/Ft.)

Hand Penetrometer

Torvane

Dynamic Cone Penetrometer

Unconfined Compressive Strength

Photo-Ionization Detector

Organic Vapor Analyzer

Medium

0Over 12 in. (300 mm)

>12

5-12

<5

Percent of Dry Weight

TermMajor Component of Sample

Modifier

With

Trace

Descriptive Term(s) of other constituents

>30Modifier

<15

Percent of Dry Weight

Descriptive Term(s) of other constituents

With 15-29

High

Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

Descriptive Term (Consistency)

0 - 6

Standard Penetration or N-Value

Blows/Ft.

CONSISTENCY OF FINE-GRAINED SOILS

Hard

Very Loose

Loose

Medium Dense

Dense

Very Dense

Descriptive Term (Density)

Standard Penetration or N-Value Blows/Ft.

Ring Sampler Blows/Ft.

0 - 3

4 - 9 7 - 18

10 - 29 19 - 58

30 - 50 59 - 98

> 30

> 50 > 99 Very Stiff

Stiff

Medium Stiff

Soft

Very Soft

(50% or more passing the No. 200 sieve.)

Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance

STRENGTH TERMS

RELATIVE DENSITY OF COARSE-GRAINED SOILS

(More than 50% retained on No. 200 sieve.)

Density determined by Standard Penetration Resistance

0 - 1

2 - 4

4 - 8

8 - 15

15 - 30

UNIFIED…