Attachment_7_-_Geotechnical_Report_-_Cedar_Pass_Visitor_Center_0001.pdf

Geotechnical ● Materials Forensic ● Environmental

Building Technology Petrography/Chemistry

American Engineering Testing 1745 Samco Road Rapid City, South Dakota 57702 TeamAET.com • 605.388.0029

Report of Geotechnical Exploration Proposed Cedar Pass Visitor Center South Dakota Highway 240 Badlands National Park near Interior, South Dakota

AET Project No. P-0015733

Date:

January 25, 2023

Prepared for:

Kenneth Hahn Architects 1343 South 75th Street Omaha, Nebraska 68124

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1745 Samco Road | Rapid City, SD 57702 Phone (605) 388-0029 | teamAET.com | AA/EEO

This document shall not be reproduced, except in full, without written approval from American Engineering Testing, Inc.

Kenneth Hahn Architects 1343 South 75th Street Omaha, Nebraska 68124

Attn: Mr. Ken Hahn, AIA

RE: Report of Geotechnical Exploration Proposed Cedar Pass Visitor Center South Dakota Highway 240 Badlands National Park Near Interior, South Dakota AET Project No. P-0015733

Dear Mr. Hahn, American Engineering Testing, Inc. (AET) is pleased to present the results of our subsurface exploration program and geotechnical engineering review for the above referenced project to be constructed within the Badlands National Park, near Interior, South Dakota. These services were performed in general accordance with our proposal dated June 16, 2022, and your written authorization to proceed provided on August 9, 2022. We are submitting one (1) electronic copy of the report to you.

Please contact me if you have any questions about the report. I can also be contacted to arrange observation and testing services during construction of the project.

Sincerely, American Engineering Testing, Inc.

Walt Feeger, PE Senior Geotechnical Engineer wfeeger@teamaet.com Phone: (605) 388-0029 mailto:wfeeger@teamaet.com

Proposed Cedar Pass Visitor Center – Badlands National Park, South Dakota

Copyright 2023 American Engineering Testing, Inc.

All Rights Reserved

Unauthorized use or copying of this document is strictly prohibited by anyone other than the client for the specific project.

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SIGNATURE PAGE

Prepared for: Prepared by:

Kenneth Hahn Architects American Engineering Testing, Inc.

1343 South 75th Street 1745 Samco Road Omaha, Nebraska 68124 Rapid City, South Dakota 57702

(605) 388-0029 Attn: Mr. Ken Hahn, AIA www.teamAET.com

Authored by: Reviewed by:

Walt Feeger, PE Robert Temme, PE Senior Geotechnical Engineer Vice President – Western Region http://www.teamaet.com/

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TABLE OF CONTENTS

Transmittal Letter ............................................................................................................. i Signature Page ................................................................................................................ ii

1.0 INTRODUCTION

2.0 SCOPE OF SERVICES

3.0 PROJECT INFORMATION

4.0 SUBSURFACE EXPLORATION AND TESTING

4.1 Field Exploration Program

4.2 Laboratory Testing

5.0 SITE CONDITIONS

5.1 Surface Observations

5.2 Subsurface Soils/Geology

5.3 Groundwater

6.0 RECOMMENDATIONS

6.1 Discussion

6.2 Site Preparation

6.3 Foundation Design Recommendations

6.4 Interior Concrete Floor Slabs

6.5 Exterior Concrete Flatwork

6.6 Exterior Backfill Considerations

6.7 Trench Excavation

6.8 Pavements

7.0 CONSTRUCTION CONSIDERATIONS

7.1 Potential Difficulties

7.2 Excavation Backsloping

7.3 Observation and Testing

8.0 LIMITATIONS

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TABLE OF CONTENTS

STANDARD SHEETS

Floor Slab Moisture/Vapor Protection Freezing Weather Effects on Building Construction Excavation and Refilling for Structural Support

APPENDIX A

Geotechnical Field Exploration and Testing Boring Log Notes Unified Soil Classification System Figure 1: Site Location Map Figure 2: Boring Location Map Subsurface Boring Logs Swell/Consolidation Test Moisture-Density Relationship (Proctor) Test Report California Bearing Ratio (CBR) Test Report

APPENDIX B

Geotechnical Report Limitations and Guidelines for Use

1.0 INTRODUCTION

We understand a new visitor center has been proposed near the Cedar Pass Campground within the Badlands National Park, near Interior, South Dakota. Please refer to Figure 1: Site Location Map within Appendix A for the location of the site. To assist with the planning and design, American Engineering Testing, Inc. (AET) has been authorized to conduct a subsurface exploration program at the site, conduct soil laboratory testing, and perform a geotechnical engineering review for the project. This report presents the results of the above services and provides our engineering recommendations based on this data.

2.0 SCOPE OF SERVICES

AET's services were performed in general accordance with our proposal dated June 16, 2022. The authorized scope consists of the following:

• Nine (9) Standard Penetration Test (SPT) borings at the site to depths of about 5 to 15 feet below existing grade.

• Soil laboratory testing.

• Geotechnical engineering analysis based on the gained data and preparation of this report.

These services are intended for geotechnical purposes only. The scope is not intended to explore for the presence or extent of environmental contamination in the soil or groundwater.

3.0 PROJECT INFORMATION

Although the project is currently in the conceptual phase, we understand the new Visitor Center will likely be a predominately single-story, concrete slab-on-grade structure, constructed between the existing Ben Reifel Visitor Center and the Cedar Pass Campground, on the south side of SD Highway 240. Site infrastructure will include paved access drives off SD Highway 240 as well as additional paved parking lots, likely constructed to the south of the new structure.

The purpose of the geotechnical study was to determine the subsurface conditions at the site and to evaluate the suitability of the site soils for their use in constructing the proposed additions and associated paved parking areas/access drives.

The previously stated information represents our understanding of the proposed construction. This information is an integral part of our engineering review. It is important that you contact us if there are changes from that described so that we can evaluate whether modifications to our recommendations are appropriate.

4.0 SUBSURFACE EXPLORATION AND TESTING

4.1 Field Exploration Program

The subsurface exploration program conducted for the project consisted of nine (9) standard penetration test (SPT) borings drilled on January 5, 2023. The borings were drilled at locations selected by AET personnel based on a conceptual site plan provided by Kenneth Hahn Architecture. The logs of the borings and details of the methods used appear in Appendix A. The logs contain information concerning soil layering, soil classification, geologic origins, and moisture condition. A density description or consistency is also noted for the natural soils, which is based on the standard penetration resistance (N-value).

The boring locations are shown on Figure 2: Boring Location Map included in Appendix A. Surface elevations at the boring locations were interpolated from a Google Earthtm image of the site.

4.2 Laboratory Testing

The laboratory test program included natural moisture content, dry density, Atterberg Limits, percent passing the #200 sieve, swell/consolidation, moisture-density relationship (Proctor), and California Bearing Ratio (CBR). The test results appear in Appendix A on the individual boring logs adjacent to the samples upon which they were performed or on the data sheets following the logs.

The swell/consolidation test is commonly performed to evaluate the swell or consolidation potential of soils or bedrock for determining foundation and concrete slab-on-grade design criteria. In this test, relatively undisturbed samples obtained directly from the ring barrel sampler are placed in a laboratory device and saturated under a predetermined load. The swell-index is the resulting amount of swell (+) as a percent of the sample’s thickness after the saturation period. Conversely, the consolidation index is the amount of consolidation (-) as a percent of the sample’s thickness after consolidation under the confining load.

Test results are summarized as follows:

Boring Depth, ft Soil Type Swell (+) or Consolidation (-) Potential, %

Swell Pressure, psf

B-2 5-6.5 Claystone (Fat Clay) 3.1 4,600

B-4 10-11.5 Claystone (Fat Clay) 5.4 6,500

Based on the laboratory test results, the claystone (fat clay) bedrock at this site has moderate swell potentials with moderate to high swell pressures. The results for the swell-consolidation test are included within Appendix A of this report.

The CBR test was remolded to approximately 95% of maximum dry density at the optimum moisture content for the specific boring/material. Results are summarized as follows:

Boring Soil Classification Optimum Moisture Content, % 1

Maximum Dry Density, pcf 1

CBR

Value2

B-5 W. Claystone (Fat Clay) 19.9 98.7 1.7 1 Based on ASTM D 698 (standard Proctor) 2Remolded to 95%

It should be noted the bulk soil sample represents a mixture of the soils encountered within the upper 5 foot interval of the borehole. As such, the soil classification as presented on the Moisture-Density Relationship and CBR data sheets may differ from the classifications of the individual soil layers identified on the respective Subsurface Boring Log.

5.0 SITE CONDITIONS

5.1 Surface Observations

The project site is located on the south side of SD Highway 240, between the Cedar Pass Campground and the Ben Reifel Visitor Center, just east of Interior. At the time of our field work, the site consisted of a vacant parcel of property vegetated with native grasses and weeds.

In general, the area within the proposed building footprint is relatively flat with about 1 foot or less of elevation difference noted between the borings.

5.2 Subsurface Soils/Geology

Underlying a layer of topsoil/vegetative material, the subsurface soils encountered in the borings consisted of very stiff to hard weathered claystone, associated with the White River Group, which extended to the total depths explored in Borings B-6 through B-9. Within Borings B-1 through B-5, the weathered claystone is underlain by competent claystone at depths of about 3½ to 10½ feet below grade. The competent claystone extended to the total depths explored in these borings.

Please note that determining the thickness of “topsoil” layers is usually limited, due to variations in topsoil definition, sample recovery, and other factors. Visual-manual description often relies on color for determination, and transitioning changes can account for significant variation in thickness judgment. Accordingly, the topsoil thickness presented on the logs should not be the sole basis for calculating topsoil stripping depths and volumes (where applicable). If more accurate information is needed relating to thickness and topsoil quality definition, alternate methods of sample retrieval and testing should be employed.

The Subsurface Boring Logs included in Appendix A give a more detailed description of the soils encountered within the borings.

5.3 Groundwater

At the time of our field work, groundwater was not encountered in the borings drilled at the site. The lack of groundwater noted at the boring locations should not be taken as an accurate representation of the actual groundwater levels. Groundwater levels can fluctuate due to varying seasonal and annual rainfall and snow melt amounts, as well as other factors including local irrigation practices. A long period of time may be required for groundwater to stabilize in the soils present at the site; this period of time is generally not available during a typical subsurface exploration program.

6.0 RECOMMENDATIONS

6.1 Discussion

Our recommendations in the following sections are based on our understanding of the project details at this time. The geotechnical engineer should be allowed to review the final project plans to verify the following recommendations remain applicable for construction.

The area within the proposed building footprint is relatively flat and therefore, we anticipate only minor grading on the order of about 1-foot or less will be required. Based on our borings and laboratory test data, the site weathered to competent claystone bedrock should be considered moderately to highly expansive depending on the moisture content of the material.

Therefore, we recommend the structure be founded on a reinforced concrete drilled pier foundation system utilizing grade beams for wall support. In lieu of a drilled pier foundation system, the structure may be placed on a conventional spread footing foundation system bearing on imported granular engineered fill provided the Owner is willing to accept the risk that movements on the order of about 1-inch could occur due to future moisture variations within the claystone bedrock.

To address the moderate to high swell potential of the site claystone below the interior concrete slab-on-grade floor, we recommend the claystone material be over excavated to allow for the placement of at least four (4) feet of imported granular engineered fill below the concrete slab. Based on our experience, we believe slabs-on-grade can be supported as outlined and will perform with a reduced potential of significant movement. The Owner should recognize that concrete slabs constructed on engineered fill could experience some differential movement under normal loads or should the sub-soils become wetted. If no movement of the floor system can be tolerated, a structural floor should be considered.

In addition, strict moisture control will be required during placement and compaction of the site soils and/or imported engineered fill to minimize the potential of damaging differential movements due to moisture variations in the subsurface soils.

To reduce the risk of future movement, good drainage must be maintained during and after construction. For this reason, we recommend that the excavations be left open a minimal amount of time. Additionally, the concrete slab-on-grade floor should be structurally independent of walls and columns.

Our recommendations in the following sections are intended to minimize, to varying degrees, swell related problems for the proposed foundations and floor slabs. Even if our recommendations are followed, we cannot guarantee that some movement will not occur.

The present state of the art is such that the risk of movement cannot be accurately assessed.

It depends on a number of uncontrolled variables such as climatic conditions during and after construction, long term fluctuations of the groundwater level, utility line leakage, landscaping, and other similar aspects. The risk of detrimental movement must be assumed by the project owner.

6.2 Site Preparation

We recommend all topsoil, organics, abandoned utility lines, and construction-manmade debris (if encountered) be removed in their entirety from within the proposed building footprint, and areas to receive pavement. The stripped topsoil may be stockpiled on-site and re-used in landscaping areas. Grading should then continue to the design site grades.

If the spread footing foundation system is selected, excavations within the proposed building footprint should continue to allow for the placement of at least four (4) feet of imported granular engineered fill below footings and below interior concrete slab-on-grade floors. The footing excavations should be laterally oversized at a 1H:1V ratio as necessary to accommodate the four (4) feet of granular engineered fill material. The excavated site clays may be stockpiled on-site and used as overlot fill outside of the building limits. Based on the results of the laboratory testing, moisture conditioning and processing of the site soils will be required prior to re-use.

Once the over excavation is complete, and in areas to received overlot fill, we recommend the exposed subgrade be scarified to a depth of at least 8-inches, the moisture content of the scarified soils adjusted to near optimum and the material compacted to at least 95% of maximum standard Proctor dry density (ASTM D698).

Imported granular engineered fill can then be placed within the over-excavations required below the foundations and floor slabs. The granular engineered fill should be pre-approved by the geotechnical engineer prior to use. The granular engineered fill should be a pit run or crushed/screened material with a maximum aggregate size of 2-inches, 40-85% passing the #4 sieve, and no more than 15% passing the #200 sieve with a Liquid Limit less than

25. Engineered fill should be placed in 8-inch thick maximum loose lifts; the moisture content conditioned to within ±3% of optimum moisture content and compacted to at least 98% of maximum standard Proctor (ASTM D698) dry density.

As noted, groundwater was not encountered in the borings drilled at the site, and we do not anticipate groundwater will be encountered within the shallow excavations required for this project. However, if encountered, the earthwork contractor should have the necessary equipment on-site to remove and maintain any groundwater levels below the base of the excavation.

6.3 Foundation Design Recommendations

Reinforced Concrete Drilled Piers – As noted, it is our primary recommendation that the structure be founded on a reinforced concrete drilled pier foundation system utilizing concrete grade beams for wall support. We recommend all drilled piers bear at least 3 feet into the hard competent claystone bedrock and have a minimum length of 15 feet.

The drilled pier recommendations should provide a theoretical factor of safety of 2 or more. Total and differential movements should not exceed 1/2-inch and 1/4-inch, respectively.

Based on the results of the borings, laboratory testing, and our analysis, we have developed the following design parameters:

Soil Type Allowable Skin Friction (psf)

Allowable End Bearing Pressure (psf)

Frost Zone

0 – 5’ Ignore Ignore

Weathered Claystone 500 na

Competent Claystone 1,000 20,000

In designing to resist uplift, ⅔ of the allowable side friction values provided for compressive loading could be used along with the effective weight of the drilled shafts.

Straight shaft piers with a minimum diameter of 18-inches are recommended. Proper reinforcing steel should be included in the drilled shaft designs.

Lateral deflections of drilled shafts should be evaluated using an appropriate design procedure, and would be dependent on shaft diameter, length, configuration, stiffness and “fixed head” or “free head” conditions.

Single pier lateral load capacity can be estimated using the following design parameters for the soil profile in a p-y analysis such as conducted using the computer program LPILE:

Drilling to design depths should be possible with conventional large drilled pier equipment.

Care should be taken so that the sides and bottom of the shaft excavations are not disturbed during drilling. The bottom of the shaft excavations should be free of loose material and water when concrete is placed. Concrete should be placed as soon as possible after the foundation excavation is completed to reduce the potential for disturbance of the bearing surface.

Groundwater was not encountered at the time of our field work within the borings drilled at the site. However, the use of temporary casing should be anticipated and the drilled pier contractor should have the appropriate casing and dewatering equipment on-site prior to commencing the drilling operations. The need for casing will depend on the conditions encountered at the time the pier excavations are made. A sufficient head of plastic concrete having a minimum slump on the order of 6-8 inches should be maintained inside the casing as it is withdrawn to prevent concrete arching and the influx of soil and water (if encountered) and creation of voids in the pier shaft.

Drilled shaft construction should be constructed in accordance with applicable portions of ACI 336.3R-93 or other similar, approved specification. Concrete mix should be designed utilizing cement to have a minimum 28-day compressive strength of 4,000 psi and a maximum water cement ratio of 0.45. A super plasticizer may be necessary to increase concrete slump/flow temporarily for drilled shaft placement.

Design Parameter Weathered Shale Competent Shale

Moist Unit Weight (pcf) 105 110

Undrained Shear Strength (psf)

2,000 4,000

Friction Angle (degrees) 10 10

Static Soil Modulus Parameter, k (pci) 1,000 2,000

Strain, ε50 (in/in) 0.005 0.004

Concrete should be on-site and ready for placement as soon as practical after each pier excavation is completed. Concrete placement in pier excavations should occur on the same day as pier excavation is completed. We do not recommend free-fall concrete placement in piers. The use of a bottom-dump hopper, tremie, or pump, discharging near the bottom of the hole where concrete segregation will be minimized, is recommended.

A representative from AET should observe all drilled shaft excavations to evaluate the suitability of the bearing materials and to verify that conditions in the drilled shaft excavations are consistent with those encountered in the test borings. If unsuitable materials are encountered at planned depths, it may be necessary to deepen the shaft.

Conventional Spread Footing Foundation System – Provided the Owner is willing to accept the risk that movement to the completed structure may occur if the subsurface claystone bedrock becomes wetted, the structure may be founded on a conventional spread footing foundation system bearing on a minimum of four (4) feet of imported granular engineered fill as previously described.

Exterior footings, interior footings in unheated portions of the building, or footings placed during freezing conditions should be placed at least 4 feet below final grades for frost protection. Interior footings in heated areas may be placed directly below the floor slab. For additional information please refer to the attached Standard Sheet “Freezing Weather Effects on Building Construction”. We recommend the base of the footing and floor slab excavations be observed and properly compacted to verify a firm and unyielding subgrade has been obtained on which to place the granular engineered fill and structural elements.

The spread footing foundation system may be designed for an allowable bearing capacity of 3,000 pounds per square foot (psf). As designed, loadings should provide a theoretical safety factor of three or more with respect to a general shear or base failure of the footings.

If properly constructed and the subsurface claystone does not become saturated over the life of the structure, total and differential movements should not exceed 1 inch and 1/2-inch, respectively.

To intercept potential water infiltration, an exterior foundation drain should be installed. A perforated PVC drain pipe, typically 4-inches in diameter, with a filter sock, should be placed at the outside base of the over-excavation perimeter. Additionally, the pipe should be embedded in free draining gravel. For drainage, the pipe should be properly sloped and connected to a collection pipe that discharges to a sump and pump system, storm sewer, or to a daylight point beyond the footprint of the structure.

6.4 Interior Concrete Floor Slabs

As discussed, we recommend the interior concrete slab-on-grade floor be placed on a minimum of four (4) feet of imported granular engineered fill. Prior to placement of the engineered fill, we recommend the exposed subgrade be scarified to a depth of at least 8-inches, the moisture content of the clay soils adjusted to within -1% to +3% of the optimum moisture content and the material compacted to at least 95% of maximum standard Proctor (ASTM D698) dry density.

A leveling course, typically 4 to 6 inches of a granular material provided below the concrete slab, is placed to prevent capillary moisture rise to the slab. This granular fill should contain less than 12% by weight passing the #200 sieve, and less than 40% passing the #40 sieve. This sand/gravel cushion layer may be considered as part of the four (4) feet of granular engineered fill recommended below the floor slab. Please refer to the “Floor Slab Moisture/Vapor Protection” document in the Standard Sheets section at the back of this report for additional information.

6.5 Exterior Concrete Flatwork

Exterior concrete flatwork typically consists of 4 to 6-inches of concrete placed on aggregate base course. Increased moisture contents of the clay soils present on site, due to drainage and/or seasonal weather, may result in upward movement of these slabs and sidewalks especially during colder weather.

While this upward movement may not immediately or directly affect the integrity of the building foundations and interior slabs, over time positive drainage away from the building may be lost. In addition, upward movement tends to cause distress cracks and potential tripping hazards. To minimize these potential issues, we recommend placement of these exterior slabs and sidewalks directly adjacent to the structure on at least 18-inches of imported low frost susceptible granular engineered fill.

6.6 Exterior Backfill Considerations

We recommend imported granular engineered fill be used as exterior wall backfill. The site clay soils may be used as overlot fill material outside the building limits, as utility trench backfill, and as a cap for wall backfill in landscape areas. Backfill should be placed as follows. All recommendations are based on the standard Proctor method (ASTM D 698).

1. All backfill should be free of deleterious/frozen material and have a maximum nominal size of 2-inches.

2. Clay backfill should be moisture conditioned to within -1% to +3% of optimum moisture content prior to being placed. Granular material should be moisture conditioned to within ±3% of optimum prior to re-use.

3. All backfill should be placed in loose lift thicknesses of 8-inches or less. If hand-operated compaction equipment is used, the loose lift thickness should be reduced to 4-inches or less.

4. Each lift should be compacted to at least 95% of maximum proctor density. Where utilities will be present within paved areas, we recommend the final lift of backfill be compacted to at least 98% of the maximum dry density.

5. Compaction density tests should be performed on alternating lifts to ensure the minimum density is maintained.

6. Utility lines entering or exiting the structure should be leak tested prior to the placement of the slab.

6.7 Trench Excavation

If excavation faces are not retained, the excavations should maintain maximum allowable slopes in accordance with OSHA Regulations (Standards 29 CFR), Part 1926, Subpart P, “Excavations” (can be found on www.osha.gov). Even with the required OSHA sloping, water seepage or surface runoff can potentially induce side slope erosion or running which could require slope maintenance.

For trench excavations, it is our opinion the site claystone can be classified as Type B soils with recommended slope laybacks of 1H:1V. This classification should be considered preliminary and should be verified in the field on a daily basis by the contractor and/or geotechnical engineer.

Excavations deeper than 20 feet and/or in saturated soils or below the ground water table should be considered on an individual basis. Water levels, due to climatic conditions, should be evaluated at the time of construction. If the above trench layback recommendations are not feasible, due to space limitations or other factors, the OSHA rules should be consulted for alternative trench stabilization methods. Trench boxes or shoring in compliance with OSHA rules may be acceptable alternatives.

http://www.osha.gov/

6.8 Pavements

6.8.1 Considerations

The following pavement section was designed based on the procedures outlined in the 1993 AASHTO Empirical Equation for Flexible Pavements and Rigid Pavements.

It is anticipated that pavement subgrade soils will consist of the site weathered claystone (fat clay), and based on the laboratory test results, a California Bearing Ratio (CBR) value of 1.7 was used in the pavement design analysis. In addition to the calculated laboratory CBR value, we have used the following design parameters:

Design Criteria Asphalt Portland Cement Concrete

Overall Design Standard Deviation 0.45 0.35

Soil Resilient Modulus CBR x 1500 100 pci

Initial Serviceability 4.2 4.5

Terminal Serviceability 2.0 2.5

Reliability, % 85 85

Drainage Coefficient 0.75 0.75

No anticipated traffic volumes or ESAL values have been provided to us at this time.

However, based on our understanding of the project, we have assumed mainly passenger cars and pickup trucks within general use parking areas with additional parcel/delivery trucks, busses, and RVs within the access drives, pickup/drop off loops, and in designated bus/RV parking areas. Therefore, we have assumed a 20 year traffic count of 65,000 for standard duty pavement sections (general use parking lots) and an ESAL of 130,000 for heavy duty pavement sections (access lanes, drop loops, and RV/bus lots). Please notify us if any of the parameters used in the pavement design do not adequately define the anticipated conditions.

The 20-year design period is considered to be the interval over which, with proper maintenance, the pavement will not require major repairs. A continuing regular maintenance program should be implemented to maintain satisfactory serviceability over the design life. The maintenance program should include sealing cracks and repairing minor deficiencies. Please notify us if any of the parameters used in the pavement design do not adequately define the anticipated conditions.

6.8.2 Subgrade Preparation

Prior to placement of base course/new pavement or any fill to obtain final subgrade elevations, the exposed subgrade soils should be scarified to a depth of 8-inches, the moisture content of the scarified soils adjusted to near optimum moisture content and the material compacted to at least 95% of maximum standard Proctor dry density (ASTM D698). All prepared subgrades should be proof rolled to verify a firm and unyielding subgrade has been obtained prior to the placement of new fill and/or base course materials.

To obtain a firm and unyielding subgrade, on which to construct the new pavement section, scarification and drying of the subgrade soils should be anticipated. This scarification process may need to be repeated over several days in order to allow the soils to dry back to an acceptable moisture content. The earthwork contractor should be made aware of the soil conditions at the site and account for the anticipated subgrade preparation work.

If project schedules do not allow for sufficient time to dry the soil back to acceptable levels, use of a geo-textile stabilization/separation material can be incorporated in the design. The geo-textile should be placed on top of the graded subgrade and below the aggregate base course layer. Please note the pavement section, including base course thickness, may be subject to change if incorporating a geo-textile stabilization material into the design.

Any areas that "pump" under the proof rolling program should be evaluated by the geotechnical engineer to determine whether additional excavation and replacement with a coarse, clean rock or the use of a geo-textile fabric should be used to stabilize the subgrade. Once the subgrade has been proof rolled and approved by the geotechnical engineer, base course may be placed.

If additional fill is required, the proposed import backfill should be submitted to the geotechnical engineer for approval prior to use.

6.8.3 Aggregate Base Course

Aggregate base course gravel should be moisture conditioned to within ±3% of optimum and compacted to a minimum of 95% of maximum density as determined by the standard Proctor method (ASTM D698) and should meet the requirements as outlined in Section 882 “Aggregates for Granular Bases and Surfacing” of the SDDOT specifications, current edition.

6.8.4 Pavement Section Recommendations

Based on the above stated information, our calculations indicate the following pavement sections should be considered for this project:

If a high modulus geotextile, such as Mirafi RS380i, or approved equivalent, is placed on the prepared subgrade, for separation and reinforcement purposes, the thickness of basecourse within the recommended asphalt pavement section can typically be reduced by about 25 percent.

We recommend the asphalt be obtained from an approved mix design conforming to the South Dakota Department of Transportation (SDDOT) Specifications as defined in Sections 320 and 321 of the “Standard Specifications for Road and Bridges”, current edition.

Where rigid pavements are used, the concrete should be obtained from an approved mix design conforming to Section 380 “Portland Cement Concrete Pavement” and Section 460 “Structural Concrete” of the SDDOT Specifications, current edition. Mix designs should be submitted prior to construction to verify their adequacy.

Longitudinal and transverse joints should be provided as needed in concrete pavements for expansion/contraction and isolation. The location and extent of joints should be based upon the final pavement geometry. Sawed joints should be cut within 24-hours of concrete placement. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer.

6.8.5 Pavement Maintenance

The pavement sections provided in this report represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore, preventive maintenance should be planned and provided for through an on-going pavement management program.

Typical Pavement Section Thickness (Inches)

Traffic Area Asphalt Concrete Portland Cement Concrete Base Course Total

Standard Duty 5 -- 9 14

-- 6 6 12

Heavy Duty 5 -- 12 17

-- 7 6 13

Preventive maintenance activities are intended to slow the rate of pavement deterioration.

Pavement maintenance consists of both localized maintenance (crack and joint sealing and patching) and global maintenance (surface sealing).

Preventive maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Prior to implementing any maintenance program, additional engineering input is recommended to determine the type and extent of preventive maintenance appropriate. Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required.

7.0 CONSTRUCTION CONSIDERATIONS

7.1 Potential Difficulties

7.1.1 Soft Subgrade Soils

Depending on the time of year in which construction takes place, unstable subgrade soils could be encountered during the site and building grading operations. If encountered, additional conditioning of the soils may be required to obtain moisture contents which allow for firm and unyielding subgrade and/or compaction.

Localized areas of soft wet subgrades can be remedied with additional excavation to expose firmer soils, placement of coarse rock to provide a solid base on which to place additional fill and/or the use of geotextiles between the soft soils and the overlying fill and/or pavement sections. The appropriate means of subgrade stabilization should be evaluated by the geotechnical engineer at the time of construction.

7.1.2 Runoff Water in Excavation

Water can be expected to collect in the excavation bottom during times of inclement weather or snow melt. To allow observation of the excavation bottom, to reduce the potential for soil disturbance, and to facilitate filling operations, we recommend water be removed from within the excavation during construction. Based on the soils encountered, we anticipate the groundwater can be handled with conventional sump pumping.

7.1.3 Disturbance of Soils

The on-site soils can be disturbed under construction traffic, especially if the soils are wet.

If soils become disturbed, they should be subcut to the underlying undisturbed soils. The subcut soils can then be dried and recompacted back into place, or they should be removed and replaced with drier imported fill.

7.2 Excavation Backsloping

If excavation faces are not retained, the excavations should maintain maximum allowable slopes in accordance with OSHA Regulations (Standards 29 CFR), Part 1926, Subpart P, “Excavations” (can be found on www.osha.gov). Even with the required OSHA sloping, water seepage or surface runoff can potentially induce sideslope erosion or sloughing which could require slope maintenance.

7.3 Observation and Testing

The recommendations in this report are based on the subsurface conditions found at our test boring locations. Since the soil conditions can be expected to vary away from the soil boring locations, we recommend on-site observation by a geotechnical engineer/technician during construction to evaluate these potential changes. Soil density testing should also be performed on new fill placed in order to document that project specifications for compaction have been satisfied.

8.0 LIMITATIONS

Within the limitations of scope, budget, and schedule, we have endeavored to provide our services according to generally accepted geotechnical engineering practices at this time and location. Other than this, no warranty, expressed or implied, is intended. Important information regarding risk management and proper use of this report is given in Appendix B entitled “Geotechnical Report Limitations and Guidelines for Use.”

Standard Sheets

01REP013(2/01) AMERICAN ENGINEERING TESTING, INC.

FLOOR SLAB MOISTURE/VAPOR PROTECTION

Floor slab design relative to moisture/vapor protection should consider the type and location of two elements, a granular layer and a vapor membrane (vapor retarder, water resistant barrier or vapor barrier). In the following sections, the pros and cons of the possible options regarding these elements will be presented, such that you and your specifier can make an engineering decision based on the benefits and costs of the choices.

GRANULAR LAYER

In American Concrete Institute (ACI) 302.1-96, a “base material” is recommended, rather than the conventional cleaner “sand cushion” material. The manual maintains that clean sand (common “cushion” sand) is difficult to compact and maintain until concrete placement is complete. ACI recommends a clean, fine graded material (with at least 10% to 30% of particles passing a #100 sieve) which is not contaminated with clay, silt or organic material. We refer you to ACI 302.1-96 for additional details regarding the requirements for the base material.

In cases where potential static water levels or significant perched water sources appear near or above the floor slab, an underfloor drainage system may be needed wherein a draintile system is placed within a thicker clean sand or gravel layer. Such a system should be properly engineered depending on subgrade soil types and rate/head of water inflow.

VAPOR MEMBRANE

The need for a vapor membrane depends on whether the floor slab will have a vapor sensitive covering, will have vapor sensitive items stored on the slab, or if the space above the slab will be a humidity controlled area. If the project does not have this vapor sensitivity or moisture control need, placement of a vapor membrane may not be necessary. Your decision will then relate to whether to use the ACI base material or a conventional sand cushion layer. However, if any of the above sensitivity issues apply, placement of a vapor membrane is recommended. Some floor covering systems (adhesives and flooring materials) require a vapor membrane to maintain a specified maximum slab moisture content as a condition of their warranty.

VAPOR MEMBRANE/GRANULAR LAYER PLACEMENT

A number of issues should be considered when deciding whether to place the vapor membrane above or below the granular layer.

The benefits of placing the slab on a granular layer, with the vapor membrane placed below the granular layer, include reduction of the following:

• Slab curling during the curing and drying process.

• Time of bleeding, which allows for quicker finishing.

• Vapor membrane puncturing.

• Surface blistering or delamination caused by an extended bleeding period.

• Cracking caused by plastic or drying shrinkage.

The benefits of placing the vapor membrane over the granular layer include the following:

• The moisture emission rate is achieved faster.

• Eliminates a potential water reservoir within the granular layer above the membrane.

• Provides a “slip surface”, thereby reducing slab restraint and the associated random cracking.

If a membrane is to be used in conjunction with a granular layer, the approach recommended depends on slab usage and the construction schedule. The vapor membrane should be placed above the granular layer when:

• Vapor sensitive floor covering systems are used or vapor sensitive items will be directly placed on the slab.

• The area will be humidity controlled, but the slab will be placed before the building is enclosed and sealed from rain.

• Required by a floor covering manufacturer’s system warranty.

The vapor membrane should be placed below the granular layer when:

• Used in humidity controlled areas (without vapor sensitive coverings/stored items), with the roof membrane in place, and the building enclosed to the point where precipitation will not intrude into the slab area. Consideration should be given to slight sloping of the membrane to edges where draintile or other disposal methods can alleviate potential water sources, such as pipe or roof leaks, foundation wall damp proofing failure, fire sprinkler system activation, etc.

There may be cases where membrane placement may have a detrimental effect on the subgrade support system (e.g., expansive soils). In these cases, your decision will need to weigh the cost of subgrade options and the performance risks.

AMERICAN ENGINEERING TESTING, INC.

FREEZING WEATHER EFFECTS ON BUILDING CONSTRUCTION

GENERAL

Because water expands upon freezing and soils contain water, soils which are allowed to freeze will heave and loose density. Upon thawing, these soils will not regain their original strength and density. The extent of heave and density/strength loss depends on the soil type and moisture condition. Heave is greater in soils with higher percentages of fines (silts/clays). High silt content soils are most susceptible, due to their high capillary rise potential which can create ice lenses. Fine grained soils generally heave about 1/4" to 3/8" for each foot of frost penetration. This can translate to 1" to 2" of total frost heave. This total amount can be significantly greater if ice lensing occurs.

DESIGN CONSIDERATIONS

Clayey and silty soils can be used as perimeter backfill, although the effect of their poor drainage and frost properties should be considered. Basement areas will have special drainage and lateral load requirements which are not discussed here. Frost heave may be critical in doorway areas. Stoops or sidewalks adjacent to doorways could be designed as structural slabs supported on frost footings with void spaces below. With this design, movements may then occur between the structural slab and the adjacent on-grade slabs. Non-frost susceptible granular soils (with less than 12% passing a #200 sieve) can be used below such areas.

Depending on the function of surrounding areas, the granular soil layer may need a thickness transition away from the area where movement is critical. With granular soil placement over slower draining soils, subsurface drainage would be needed for the granular layer. High density extruded insulation could be used within the granular soils to reduce frost penetration, thereby reducing the granular soil thickness needed. We caution that insulation placed near the surface can increate the potential for ice glazing of the surface.

The possible effects of adfreezing should be considered if clayey or silty soils are used as backfill.

Adfreezing occurs when backfill adheres to rough surfaced foundation walls and lifts the wall as it freezes and heaves. This occurrence is most common with masonry block walls, unheated or poorly heated building situations and clay backfill. The potential is also increased where backfill soils are poorly compacted and become saturated. The risk of adfreezing can be decreased by placing a low friction separating layer between the wall and backfill.

Adfreezing can occur on exterior piers (such as deck, fence or other similar pier footings), even if a smooth surface is provided. This is more likely in poor drainage situations where soils become saturated. Additional footing embedment and/or widened footings below the frost zones (which include tensile reinforcement) can be used to resist uplift forces. Specific designs would require individual analysis.

CONSTRUCTION CONSIDERATIONS

Foundations, slabs, and other improvements which may be affected by frost movements should be insulated from frost penetration during freezing weather. If filling takes place during freezing weather, all frozen soils, snow, and ice should be stripped from areas to be filled prior to new fill placement. The new fill should not be allowed to freeze during transit, placement, or compaction. This should be considered in the project scheduling, budgeting, and quantity estimating. It is usually beneficial to perform cold weather earthwork operations in small areas where grade can be attained quickly rather than working large areas where a greater amount of frost stripping may be needed. If slab subgrade areas freeze, we recommend the subgrade be thawed prior to floor slab placement. The frost action may also require reworking and recompaction of the thawed subgrade.

01REP011(12/09) AMERICAN ENGINEERING TESTING, INC.

EXCAVATION AND REFILLING FOR STRUCTURAL SUPPORT

EXCAVATION

Excavations for structural support at soil boring locations should be taken to depths recommended in the geotechnical report. Since conditions can vary, recommended excavation depths between and beyond the boring location should be evaluated by geotechnical field personnel. If groundwater is present, the excavation should be dewatered to avoid the risk of unobservable poor soils being left in-place. Excavation base soils may become disturbed due to construction traffic, groundwater or other reasons. Such soils should be subcut to underlying undisturbed soils. Where the excavation base slopes steeper than 4:1, the excavation bottom should be benched across the slope parallel to the excavation contour.

Soil stresses under footings spread out with depth. Therefore, the excavation bottom and subsequent fill system should be laterally oversized beyond footing edges to support the footing stresses. A lateral oversize equal to the depth of fill below the footing (i.e., 1:1 oversize) is usually recommended.

Unless the excavation is retained, the backslopes should be maintained in accordance with OSHA Regulations (Standards-29 CFR), Part 1926, Subpart P, "Excavations" (found on www.osha.gov). Even with the required OSHA sloping, groundwater can induce sideslope raveling or running which could require that flatter slopes or other approaches be used.

FILLING

Filling should proceed only after the excavation bottom has been approved by the geotechnical engineer/technician. Approved fill material should be uniformly compacted in thin lifts to the compaction levels specified in the geotechnical report. The lift thickness should be thin enough to achieve specified compaction through the full lift thickness with the compaction equipment utilized.

Typical thicknesses are 6" to 8". Fine grained soils are moisture sensitive and are often wet (water content exceeds the "optimum moisture content" defined by a Proctor test). In this case, the soils should be scarified and dried to achieve a water content suitable for compaction. This drying process can be time consuming, labor intensive, and requires favorable weather.

Filling operations for structural support should be closely monitored for fill type and compaction by a geotechnical technician. Monitoring should be on a full-time basis in cases where vertical fill placement is rapid; during freezing weather conditions; where groundwater is present; or where sensitive bottom conditions are present.

EXCAVATION/REFILLING DURING FREEZING TEMPERATURES

Soils that freeze will heave and lose density. Upon thawing, these soils will not regain their original strength and density. The extent of heave and density loss depends on the soil type and moisture condition; and is most pronounced in clays and silts. Foundations, slabs, and other improvements should be protected from frost intrusion during freezing weather. For earthwork during freezing weather, the areas to be filled should be stripped of frozen soil, snow and ice prior to new fill placement. In addition, new fill should not be allowed to freeze during or after placement. For this reason, it may be preferable to do earthwork operations in small plan areas so grade can be quickly attained instead of large areas where much frost stripping may be needed.

Appendix A

Geotechnical Field Exploration and Testing Boring Log Notes

Unified Soil Classification System Figure 1: Site Location Map

Figure 2: Boring Location Map Subsurface Boring Logs

Swell/Consolidation Test Moisture-Density Relationship (Proctor) Report

California Bearing Ratio (CBR) Test Report

Appendix A - Page 1 of 2 AMERICAN ENGINEERING TESTING, INC.

A.1 FIELD EXPLORATION

The subsurface conditions at the site were explored by drilling and sampling standard penetration test (SPT) borings. The locations of the borings appear on Figure 2, preceding the Subsurface Boring Logs in this appendix.

A.2 SAMPLING METHODS

A.2.1 Split-Spoon Samples (SS) - Calibrated to N60 Values Standard penetration (split-spoon) samples were collected in general accordance with ASTM: D1586 with one primary modification. The ASTM test method consists of driving a 2-inch O.D. split-barrel sampler into the in-situ soil with a 140-pound hammer dropped from a height of 30 inches.

The sampler is driven a total of 18 inches into the soil.