M2215045 - USFS Northern Hills Office Geotechnical-Revised.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report

USFS Northern Hills Office

Spearfish, South Dakota

September 9, 2021

Terracon Project No. M2215045

Prepared for:

Chamberlin Architects, P.C.

Grand Junction, CO

Prepared by:

Terracon Consultants, Inc.

Bismarck, ND

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SEISMIC CONSIDERATIONS

PAVEMENTS

GENERAL COMMENTS

FIGURES

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the

GeoReport logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

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INTRODUCTION

Geotechnical Engineering Report

USFS Northern Hills Office

2014 N Main Street

Spearfish, South Dakota

September 9, 2021

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed parking lot reconstruction to be located at 2014 N Main Street in Spearfish, South Dakota. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Site preparation and earthwork

■ Groundwater conditions ■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of four test borings to a depth of approximately 11 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/or as separate graphs in the Exploration Results section.

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 at 2014 N Main Street in Spearfish, South Dakota

Latitude: 44.5048° N, Longitude: 103.8596° W (approximate)

See Site Location

Existing

Improvements Parking lot and USFS building

Current Ground

Cover Asphalt paved parking lot

Existing Topography The site slopes east to west.

USFS Northern Hills Office ■ Spearfish, South Dakota

September 9, 2021 ■ Terracon Project No. M2215045

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PROJECT DESCRIPTION

Our understanding of the project conditions is as follows:

Item Description

Information Provided

Information used to develop our project understanding was initially provided to us through phone and email correspondence with

Chamberlin.

Project Description The project includes the reconstruction of the existing parking lot.

Grading We anticipate up to 2 to 3 feet of cut and fill will be required to develop final grade.

Pavements

We anticipate both rigid (concrete) and flexible (asphalt) pavement sections are being considered.

Anticipated traffic is as follows:

■ Autos/light trucks: 1,000 vehicles per day

■ Light delivery and trash collection vehicles: 10 vehicles per week

■ Tractor-trailer trucks: <1 vehicle per week

The pavement design period is 20 years.

GEOTECHNICAL CHARACTERIZATION

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs can be found in the

Exploration Results section and the GeoModel can be found in the Figures section of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model Layer Layer Name General Description

1 Surface 4 inches of Asphalt followed by 1 to 2 inches of aggregate base

2 Fill Sandy Lean Clay – trace gravel, brown (B-3 only)

3 Clay 1 Fat Clay – dark brown, medium stiff

4 Clay 2 Lean Clay with various amounts of Sand – brown to reddish brown, soft to stiff

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The boreholes were observed while drilling and after completion for the presence and level of groundwater. Groundwater was not observed in the borings while drilling, or for the short duration the borings could remain open. However, this does not necessarily mean the borings terminated above groundwater. Due to the low permeability of the clays encountered in the borings, a relatively long period may be necessary for a groundwater level to develop and stabilize in a borehole. Long term observations in piezometers or observation wells sealed from the influence of surface water are often required to define groundwater levels in materials of this type.

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

As discussed in the Geotechnical Characterization, undocumented fill was encountered in boring B-3 to an approximate depth of two feet. This undocumented fill was placed during the original grading of the site and prior to paving. Theses clay fill soils should adequately support the parking lot pavements if they are prepared as recommended in this report. We recommend close observation of the subgrade soils during removal of the existing pavement in the parking lot.

The clays encountered at the site have a potential for volume change with seasonal and yearly variations in moisture content. These soils swell upon wetting and shrink upon drying. Moisture content changes in clays beneath the pavement should be expected over the life of the pavement.

This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these recommendations are followed, some movement and minor cracking of pavements may occur. The possibility of cracking and pavement movement may increase with modifications of the site which result in excessive wetting and drying of the clays.

Eliminating the risk of movement and cracking is not normally economically feasible.

The clays encountered at the project site are also susceptible to movement from frost action.

Pavements will be subject to post-construction movement associated with frost heaving.

Maximum grades practical should be used for paving and flatwork to prevent water from ponding.

Allowances in final grades should also consider post-construction movement of flatwork, particularly if such movement would be critical. Pavement cracking should also be expected due to the extreme temperature variations which will occur in the pavement between winter and summer months. In order to prevent movement from frost, existing soils would need to be subcut to a depth of 5 feet and replaced with a non-frost susceptible soil. This practice is typically cost

Responsive ■ Resourceful ■ Reliable 4 prohibitive. After discussions with the Forest Service, it was decided that an intermediate option for a 24-inch subcut be discussed. This option, as discussed in the meeting, is presented in the

Earthwork section.

The Pavements section addresses the design of pavement systems.

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

EARTHWORK

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

Site Preparation

As previously discussed, undocumented fill was encountered in Boring B-3 within the upper 2 feet of the pavement subgrade. The clay fill, if prepared as recommended in this section, should be suitable for pavement support as long as the fill does not contain organics or debris. Prior to reconstruction of the parking lot, we recommend the existing pavements and any underlying debris containing soils be removed from the parking lot area. We recommend Terracon be contacted to observe the subgrade soils if any unexpected soil conditions are encountered upon removal of the existing pavements. After excavating to the desired depth to allow for construction of the parking lot, we recommend the exposed subgrade soils be scarified to a depth of 12 inches and recompacted as specified in Fill Compaction Requirements. All structural fill materials imported to the site should meet the requirements specified in Fill Material Types.

As an alternative to a 60-inch subcut as provided above, the existing soils can be removed to a minimum of 24 inches beneath the proposed pavement section. The exposed subgrade should then be scarified and recompacted to a minimum depth of 12 inches. A granular subbase meeting the material requirements outlined below should then be placed up to the aggregate base section.

The subgrade should be proofrolled with an adequately loaded vehicle such as a fully-loaded tandem-axle dump truck. The proofrolling should be performed under the direction of the

Geotechnical Engineer. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should either be removed or modified. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

After completing the proofroll and any necessary subgrade improvements, we recommend the pavement subgrade be graded to provide positive drainage within the granular base section. Prior

Responsive ■ Resourceful ■ Reliable 5 to the placement and compaction of the granular base material, we recommend installing an appropriate woven geotextile separation fabric, that is locally available, over the clay subgrade to serve as a separation barrier during wet seasonal conditions and promote long-term pavement performance.

Fill Material Types

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

Structural fill is material used below, or within 10 feet of structures, pavements or constructed slopes. General fill is material used to achieve grade outside of these areas. Earthen materials used for structural fill should meet the following material property requirements:

Fill Type USCS Classification Acceptable Parameters

Cohesive Soils CL, CH 100% Passing 2-inch sieve

Granular Soils

SW, SW-SM, SW-SC,

SP, SP-SM, SP-SC,

SM, SC

All: 100% Passing 2-inch sieve

Granular Subbase

SW, SW-SM, SW-SC,

SP, SP-SM, SP-SC,

SM, SC

100% Passing 2-inch sieve

Less than 15% passing the #200

1. The on-site soils typically appear suitable for use as fill, however they should be tested prior to placement to ensure they meet the recommendations for structural fill as outlined above.

Fill Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Structural Fill General Fill

Maximum Lift

Thickness

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

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

Same as Structural fill

Minimum

Compaction

Requirements 1, 2

95% of max. 90% of max.

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Item Structural Fill General Fill

Water Content

Range

Granular: As required to work the material and achieve minimum compaction requirements

Low plasticity cohesive: -3% to +3% of optimum

On-site high plasticity cohesive: -1% to +4% of optimum

As required to achieve min.

compaction requirements

Same as Structural fill

High plasticity cohesive:

0 to +4% of optimum

1. Maximum density and optimum water content as determined by the standard Proctor test (ASTM D 698).

2. High plasticity cohesive fill should not be compacted to more than 100% of standard Proctor maximum dry density.

Earthwork Construction Considerations

Subgrade preparation for pavement construction should be scheduled during favorable weather conditions. If attempts are made to moisture-condition subgrade soils during west spring or fall months or during freezing conditions, construction difficulties should be expected.

Subgrade preparation is 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 pavements. 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. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

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 responsibility for construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred.

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Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer.

Monitoring should include documentation of adequate removal of vegetation and topsoil (if any), proofrolling, and mitigation of areas delineated by the proofroll 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 5,000 square feet in pavement areas. One density and water content test should be performed for every 50 linear feet of compacted utility trench backfill.

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 continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

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 and the International Building Code (IBC).

Based on the soil properties encountered at the site and as described on the exploration logs and results, it is our professional opinion that the Seismic Site Classification is E. Subsurface explorations at this site were extended to a maximum depth of 11 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.

PAVEMENTS

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in

Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs, noted in this section, must be applied to the site, which has been prepared as recommended in the Earthwork section.

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Based on the planned grading, we anticipate the onsite soils will be utilized in subgrade construction. A California Bearing Ratio (CBR) has been determined on a composite blend of material encountered in borings B-2 and B-4 from an approximate depth of one to five feet below existing grade. This material was compacted at about 95 percent of the standard Proctor maximum dry density at about optimum moisture. The moisture-density relationship test and CBR test is presented in the Exploration Results section.

Pavement Design Parameters

A subgrade CBR of 3.5 was used for the AC pavement designs, and a modulus of subgrade reaction of 110 pci was used for the PCC pavement designs. The values were empirically derived based upon our experience with the described soil type subgrade soils and our understanding of the quality of the subgrade as prescribed by the Site Preparation conditions as outlined in Earthwork. A modulus of rupture of 580 psi was used for pavement concrete.

Pavement design recommendations for this project have been based on procedures outlined in the AASHTO Guide for Design of Pavement Structures, 1993, coupled with publications by the

Asphalt Institute and the American Concrete Institute on the design of parking lots and our local experience. Pavement design input parameters and resulting pavement sections are provided in the following table:

Pavement Thickness Design Parameters

Input Parameter Flexible (asphalt) Rigid (concrete)

Reliability 85% 85%

Initial Serviceability 4.2 4.5

Terminal Serviceability 2.0 2.5

Standard Deviation 0.45 0.35

Drainage 1.0 1.0

Design ESAL Value:

Anticipated Traffic 52,000 60,000

Pavement Section Thicknesses

The following table provides options for AC and PCC Sections:

Asphaltic Concrete Design Thickness (inches)

Traffic Area Asphalt Surface 1, 2

Asphalt Base 1, 2

Aggregate Base Total Thickness

Parking and

Drive Areas

2.0 2.0 6.0 10.0

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Asphaltic Concrete Design Thickness (inches)

Traffic Area Asphalt Surface 1, 2

Asphalt Base 1, 2

Aggregate Base Total Thickness

1. Asphalt binder shall conform to PG 58-28 per SDDOT Standard Specifications for Roads and Bridges, Section

2. Aggregates shall conform to Class E (Type 1) per SDDOT Standard Specifications for Roads and Bridges, Section 880

3. SDDOT Aggregate Base Course in accordance with SDDOT Standard Specifiactions for Roads and Bridges, Section 882.

Portland Cement Concrete Design Thickness (inches)

Traffic Area Portland Cement

Concrete

Aggregate Base Total Thickness

Parking and Drive

Areas

5.0 6.0 11.0

Dumpster Pad 3 6.0 8.0 14.0

1. Type II cement with 20 to 25% fly ash, 4000 psi at 28 days, four-inch maximum slump and 5.0% to 7.5% air-entrained, 6 sack minimum mix. PCC pavements are recommended for trash container pads and any other areas subjected to heavy wheel loads and/or turning traffic.

2. SDDOT Aggregate Base Course in accordance with SDDOT Standard Specifications for Roads and Bridges, Section 882.

3. The trash container pad should be large enough to support the container and the tipping axle of the collection truck.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet could be provided to remove water from the granular subbase.

Due to frost susceptible soils and the possibility of perched groundwater, consideration could be given to installing a pavement subdrain system to control subgrade moisture, improve stability, and improve long term pavement performance.

We recommend minimum thicknesses of free-draining granular material (aggregate base) be placed beneath the pavements as outlined in the Pavement Section Thicknesses section. The use of a free draining granular base will also reduce the potential for frost action. We recommend pavement subgrades be crowned at least 2 percent, to promote the flow of water towards the subdrains, and to reduce the potential for ponding of water on the subgrade.

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If installed, the subdrains should be hydraulically connected to the subbase granular layer.

Subdrains should be sloped to provide positive gravity drainage to reliable discharge points.

Periodic maintenance of subdrains is required for long-term proper performance.

The pavement surfacing and any adjacent sidewalks should be sloped to provide rapid drainage of surface water. Water should not be allowed to pond on or adjacent to these grade supported slabs, since this could saturate the subgrade and contribute to premature pavement or slab deterioration.

Pavement Maintenance

The pavement sections 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. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment.

Maintenance consists of both localized maintenance (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Preventive maintenance is usually the priority when implementing a pavement maintenance program. Additional engineering observation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required.

Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2%.

■ Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage.

■ Install below pavement drainage systems surrounding areas anticipated for frequent wetting.

■ Install joint sealant and seal cracks immediately.

■ Seal all landscaped areas in or adjacent to pavements through the reuse of on-site clays to reduce moisture migration to subgrade soils.

■ Place compacted, low permeability backfill against the exterior side of curb and gutter.

On-site clays would be suitable for this purpose.

■ Place curb, gutter and/or sidewalk directly on clay subgrade soils rather than on unbound granular base course materials.

GENERAL COMMENTS

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

Responsive ■ Resourceful ■ Reliable 11 between exploration point locations 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 this report, to provide observation and testing services during pertinent construction phases. 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 or collaboration through this system 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 to support the services provided by Terracon to our client.

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 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.

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FIGURES

Contents:

GeoModel

Note: All attachments are one page unless noted above.

3,570

3,572

3,574

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3,580

3,582

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3,588

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(f ee t)

USFS Northern Hills Office Spearfish, South Dakota Terracon Project No. M2215045

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1

B-2

B-3

B-4

GEOMODEL

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

Fat Clay - dark brown, medium stiff3

Lean Clay with various amounts of sand - brown to reddish brown, soft to stiff4

LEGEND

Asphalt

Aggregate Base Course

Fat Clay

Lean Clay

Lean Clay with Sand

Fill

Model Layer General DescriptionLayer Name

4 inches of Asphalt followed by 1 to 2 inches of aggregate base1

Sandy Lean Clay - trace gravel, brown (B-3 only)2

Clay 1

Clay 2

Surface

Fill

0.4

0.4

0.4

4 0.4

ATTACHMENTS

Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2

EXPLORATION AND TESTING PROCEDURES

Field Exploration

Number of Borings Boring Depth (feet) Location

4 11 Pavement area

Boring Layout and Elevations: Terracon personnel provided the boring layout. Coordinates were obtained with a handheld GPS unit (estimated horizontal accuracy of about ±10 feet).

Elevations of our boring locations were provided by others.

Subsurface Exploration Procedures: We advanced the borings with a track-mounted rotary drill rig using continuous flight augers. Samples were obtained at 2½-foot intervals in each boring using split-barrel sampling procedures. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, all borings were backfilled with auger cuttings after their completion. Pavements were patched with cold-mix asphalt.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials encountered during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the

Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests to 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 were 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.

Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2

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

Content of Soil and Rock by Mass

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

Soils

■ ASTM D1140 Standard Test Methods for Determining the Amount of Material Finer than

No. 200 Sieve in Soils by Washing

■ ASTM D698 Standard Test Methods for Laboratory Compaction Characteristics of Soil

Using Standard Effort

■ ASTM D1883 Standard Test Method for California Bearing Ratio (CBR) of Laboratory-

Compacted Soils

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

SITE LOCATION AND EXPLORATION PLANS

Site Location

Exploration Plan

SITE LOCATION

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SITE LOC ATION

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

EXPLORATION PLAN

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EXPLOR ATION PLAN

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

EXPLORATION RESULTS

Boring Logs (B-1 through B-4)

Moisture Density Relationship

Report of California Bearing Ratio (CBR)

2-3-3 N=6

4-4-5 N=9

2-3-3 N=6

2-2-2 N=4

2-3-4 N=7

25.0

14.6

15.3

20.6

17.7

ASPHALT

FILL - AGGREGATE BASE COURSE

FAT CLAY (CH), dark brown, medium stiff

LEAN CLAY (CL), brown to reddish brown, stiff to medium stiff seam of scoria at 7.5'

Boring Terminated at 11 Feet

0.3 0.4

2.0

11.0

3586.5 3586.5

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

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)LOCATION See Exploration Plan

Latitude: 44.5048° Longitude: -103.8596°

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DEPTH ELEVATION (Ft.)

Surface Elev.: 3586.8 (Ft.)

Advancement Method:

3¼" HSA, 0-9½'

Abandonment Method:

Boring backfilled with Auger Cuttings Surface capped with asphalt

Notes:

Project No.: M2215045

Drill Rig: Mobile B-57

BORING LOG NO. B-1

Chamberlin Architects, P.C.CLIENT:

Grand Junction, Colorado

Driller: Mike R

Boring Completed: 06-28-2021

PROJECT: USFS Northern Hills Office

Elevations not obtained

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.

2014 N Main Street Spearfish, South Dakota

SITE:

Boring Started: 06-28-2021

1805 Hancock Dr PO Box 2084 Bismarck, NDCave in at 8'Cave in at 8'

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y P

E

2-2-2 N=4

2-2-2 N=4

2-2-2 N=4

2-2-3 N=5

2-2-2 N=4

17.2

14.4

20.6

16.9

20.1

ASPHALT

FILL - AGGREGATE BASE COURSE

LEAN CLAY WITH SAND (CL), brown to reddish brown, soft

LEAN CLAY (CL), brown to reddish brown, soft

LEAN CLAY WITH SAND (CL), brown to reddish brown, medium stiff to soft

Boring Terminated at 11 Feet

0.3 0.4

4.0

7.0

11.0

3579.5

3576.5

3572.5

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

M

U

S F

S N

O R

T H

E R

N H

IL

.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

/2

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.)

F

IE

LD

T

E S

T R

E S

U

LT

S

R E

C O

V E

R Y

In

W A

T E

R C

O N

T E

N T

)LOCATION See Exploration Plan

Latitude: 44.5046° Longitude: -103.8598°

G R

A P

H

IC

L O

G

M O

D E

L

LA

Y E

R

DEPTH ELEVATION (Ft.)

Surface Elev.: 3583.5 (Ft.)

Advancement Method:

3¼" HSA, 0-9½'

Abandonment Method:

Boring backfilled with Auger Cuttings Surface capped with asphalt

Notes:

Project No.: M2215045

Drill Rig: Mobile B-57

BORING LOG NO. B-2

Chamberlin Architects, P.C.CLIENT:

Grand Junction, Colorado

Driller: Mike R

Boring Completed: 06-28-2021

PROJECT: USFS Northern Hills Office

Elevations not obtained

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.

2014 N Main Street Spearfish, South Dakota

SITE:

Boring Started: 06-28-2021

1805 Hancock Dr PO Box 2084 Bismarck, NDCave in at 8'Cave in at 8'

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y

2-4-3 N=7

2-3-2 N=5

1-2-2 N=4

2-2-2 N=4

2-3-2 N=5

17.0

17.1

15.9

15.5

18.6

ASPHALT

FILL - AGGREGATE BASE COURSE

FILL - SANDY LEAN CLAY (CL), trace gravel, brown

LEAN CLAY (CL), reddish brown, medium stiff

LEAN CLAY WITH SAND (CL), brown to reddish brown, soft to medium stiff

Boring Terminated at 11 Feet

0.3 0.4

2.0

4.5

11.0

3587.5 3587.5

3583.5

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

M

U

S F

S N

O R

T H

E R

N H

IL

.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

/2

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.)

F

IE

LD

T

E S

T R

E S

U

LT

S

R E

C O

V E

R Y

In

W A

T E

R C

O N

T E

N T

)LOCATION See Exploration Plan

Latitude: 44.5043° Longitude: -103.8596°

G R

A P

H

IC

L O

G

M O

D E

L

LA

Y E

R

DEPTH ELEVATION (Ft.)

Surface Elev.: 3587.9 (Ft.)

Advancement Method:

3¼" HSA, 0-9½'

Abandonment Method:

Boring backfilled with Auger Cuttings Surface capped with asphalt

Notes:

Project No.: M2215045

Drill Rig: Mobile B-57

BORING LOG NO. B-3

Chamberlin Architects, P.C.CLIENT:

Grand Junction, Colorado

Driller: Mike R

Boring Completed: 06-28-2021

PROJECT: USFS Northern Hills Office

Elevations not obtained

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.

2014 N Main Street Spearfish, South Dakota

SITE:

Boring Started: 06-28-2021

1805 Hancock Dr PO Box 2084 Bismarck, NDCave in at 8'Cave in at 8'

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y

2-3-4 N=7

3-2-2 N=4

2-2-2 N=4

2-1-3 N=4

2-3-3 N=6

16.5

13.4

17.7

19.8

13.5

ASPHALT

FILL - AGGREGATE BASE COURSE , brown LEAN CLAY (CL), brown, medium stiff

LEAN CLAY WITH SAND (CL), brown to reddish brown, soft

LEAN CLAY (CL), trace gravel, trace scoria, brown to reddish brown, soft to medium stiff

Boring Terminated at 11 Feet

0.3 0.4

2.0

7.0

11.0

3581.5

3579.5

3574.5

3570.5

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

M

U

S F

S N

O R

T H

E R

N H

IL

.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

/2

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.)

F

IE

LD

T

E S

T R

E S

U

LT

S

R E

C O

V E

R Y

In

W A

T E

R C

O N

T E

N T

)LOCATION See Exploration Plan

Latitude: 44.5043° Longitude: -103.8603°

G R

A P

H

IC

L O

G

M O

D E

L

LA

Y E

R

DEPTH ELEVATION (Ft.)

Surface Elev.: 3581.6 (Ft.)

Advancement Method:

3¼" HSA, 0-9½'

Abandonment Method:

Boring backfilled with Auger Cuttings Surface capped with asphalt

Notes:

Project No.: M2215045

Drill Rig: Mobile B-57

BORING LOG NO. B-4

Chamberlin Architects, P.C.CLIENT:

Grand Junction, Colorado

Driller: Mike R

Boring Completed: 06-28-2021

PROJECT: USFS Northern Hills Office

Elevations not obtained

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.

2014 N Main Street Spearfish, South Dakota

SITE:

Boring Started: 06-28-2021

1805 Hancock Dr PO Box 2084 Bismarck, NDCave in at 8'Cave in at 8'

WATER LEVEL OBSERVATIONS

S A

M P

LE

T

Y

0 5 10 15 20 25 30 35 40 45

D R

Y D

E N

S

IT

Y pc f

WATER CONTENT, %

ZAV for G s = 2.8

ZAV for G s = 2.7

ZAV for G s = 2.6

MOISTURE-DENSITY RELATIONSHIP

ASTM D698/D1557

PROJECT NUMBER: M2215045

SITE: 2014 N Main Street Spearfish, South Dakota

PROJECT: USFS Northern Hills Office

CLIENT: Chamberlin Architects, P.C.

Grand Junction, Colorado

1805 Hancock Dr PO Box 2084 Bismarck, ND

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 T

C O

M P

A C

T

IO

N

V

M

U

S F

S N

O R

T H

E R

N H

IL

.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

/2

ASTM D698 Method A

B-2 & B-4 Composite @ 1 - 5 feetSource of Material

Description of Material

Remarks:

Test Method

PCF

TEST RESULTS

LEAN CLAY with SAND(CL)

Maximum Dry Density

LL

109.7

73.7 Optimum Water Content

PIPL

16 21

ATTERBERG LIMITS

17.1

Percent Fines

0 5 10 15 20 25 30 35 40 45

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

104.0 104.2 104.4 104.6 104.8 105.0

Percent Fines

LEAN CLAY with

SAND(CL)

16 21

PIPL

Atterberg Limits

B-2 & B-4 Composite 1.0

ASTM D1883-072

CALIFORNIA BEARING RATIO

P en et ra tio n

R es is ta nc e

(p si

LL

DRY DENSITY (PCF)

Penetration (in)

Source of Material

Description of Material

Remarks:

%73.7

S O

A K

E D

C B

R

(C O

R R

E C

T E

D

PROJECT NUMBER: M2215045

SITE: 2014 N Main Street Spearfish, South Dakota

PROJECT: USFS Northern Hills Office

CLIENT: Chamberlin Architects, P.C.

Grand Junction, Colorado

1805 Hancock Dr PO Box 2084 Bismarck, ND

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 T

C B

R

P T

R E

P O

R T

M

U

S F

S N

O R

T H

E R

N H

IL

.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

2/

0 0.25 0.50

Sample No.

Dry Density before Soaking, (pcf)

Sample Condition

Moisture Content, (%)

Surcharge,. (lbs)

Swell, (%)

Bearing Ratio, (%)

Optimum Moisture Content, (%)

Maximum Dry Density, (pcf)

Compaction Method

Top 1" After Soaking

After Compaction

10.00

1.49

ASTM 698A

Soaked

22.3

3.7

104.78

109.7

17.1

SUPPORTING INFORMATION

General Notes

Unified Soil Classification System

USFS Northern Hills Office Spearfish, South Dakota

500 to 1,000

> 8,000

4,000 to 8,000

2,000 to 4,000

1,000 to 2,000 less than 500

Unconfined Compressive Strength Qu, (psf)

Auger Cuttings Split Spoon

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

SAMPLING WATER LEVEL FIELD TESTS

GENERAL NOTES

DESCRIPTION OF SYMBOLS AND ABBREVIATIONS

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.

Water Initially Encountered

Water Level After a Specified Period of Time

Water Level After a Specified Period of Time

Cave In Encountered

Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude and Longitude are approximate. See Exploration and Testing Procedures in the report for the methods used to locate the exploration points for this project. 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.

LOCATION AND ELEVATION NOTES

Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory data exist to classify the soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this procedure is used. ASTM D2488 "Description and Identification of Soils (Visual-Manual Procedure)" is also used to classify the soils, particularly where insufficient laboratory data exist to classify the soils in accordance with ASTM D2487.

In addition to USCS classification, coarse grained soils are classified on the basis of their in-place relative density, and fine-grained soils are classified on the basis of their consistency. See "Strength Terms" table below for details. The ASTM standards noted above are for reference to methodology in general. In some cases, variations to methods are applied as a result of local practice or professional judgment.

DESCRIPTIVE SOIL CLASSIFICATION

The soil boring logs contained within this document are intended for application to the project as described in this document. Use of these soil boring logs for any other purpose may not be appropriate.

RELEVANCE OF SOIL BORING LOG

STRENGTH TERMS

Standard Penetration or N-Value

Blows/Ft.

Descriptive Term (Density)

Hard

15 - 30Very Stiff> 50Very Dense

8 - 15Stiff30 - 50Dense

4 - 8Medium Stiff10 - 29Medium Dense

2 - 4Soft4 - 9Loose

0 - 1Very Soft0 - 3Very Loose

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

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

> 30

Descriptive Term (Consistency)

Standard Penetration or N-Value

Blows/Ft.

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

Density determined by Standard Penetration Resistance

CONSISTENCY OF FINE-GRAINED SOILSRELATIVE DENSITY OF COARSE-GRAINED SOILS

UNIFIED SOIL CLASSIFICATION SYSTEM

UNIFIED SOIL C LASSIFIC AT ION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification

Group Symbol

Group Name B

Coarse-Grained Soils:

More than 50% retained on No. 200 sieve

Gravels:

More than 50% of coarse fraction retained on No. 4 sieve

Clean Gravels:

Less than 5% fines C

Cu 4 and 1 Cc 3 E GW Well-graded gravel F

Cu 4 and/or [Cc<1 or Cc>3.0] E GP Poorly graded gravel F

Gravels with Fines:

More than 12% fines C

Fines classify as ML or MH GM Silty gravel F, G, H

Fines classify as CL or CH GC Clayey gravel F, G, H

Sands:

50% or more of coarse fraction passes No. 4 sieve

Clean Sands:

Less than 5% fines D

Cu 6 and 1 Cc 3 E SW Well-graded sand I

Cu 6 and/or [Cc<1 or Cc>3.0] E SP Poorly graded sand I

Sands with Fines:

More than 12% fines D

Fines classify as ML or MH SM Silty sand G, H, I

Fines classify as CL or CH SC Clayey sand G, H, I

Fine-Grained Soils:

50% or more passes the No. 200 sieve

Silts and Clays:

Liquid limit less than 50

Inorganic:

PI 7 and plots on or above “A” line J

CL Lean clay K, L, M

PI 4 or plots below “A” line J ML Silt K, L, M

Organic:

Liquid limit - oven dried

0.75 OL

Organic clay K, L, M, N

Liquid limit - not dried Organic silt K, L, M, O

Silts and Clays:

Liquid limit 50 or more

Inorganic:

PI plots on or above “A” line CH Fat clay K, L, M

PI plots below “A” line MH Elastic Silt K, L, M

Organic:

Liquid limit - oven dried

0.75 OH

Organic clay K, L, M, P

Liquid limit - not dried Organic silt K, L, M, Q

Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-inch (75-mm) sieve.

B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name.

C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay.

E Cu = D60/D10 Cc =

DxD

)(D

F If soil contains 15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H If fines are organic, add “with organic fines” to group name.

I If soil contains 15% gravel, add “with gravel” to group name.

J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant.

L If soil contains 30% plus No. 200 predominantly sand, add

“sandy” to group name.

M If soil contains 30% plus No. 200, predominantly gravel, add

“gravelly” to group name.

N PI 4 and plots on or above “A” line.

O PI 4 or plots below “A” line.

P PI plots on or above “A” line.

Q PI plots below “A” line.

ROCK VER SION 2