S06 - Geotechnical Report - ADDED.pdf

REPORT COVER PAGE

Geotechnical Engineering Report Proposed Addition to Building 112

Milwaukee, Wisconsin March 10, 2021

Terracon Project No. 58215015

Prepared for:

Foresite Group LLC

Bloomington, Alabama

Prepared by:

Terracon Consultants, Inc.

Franklin, Wisconsin

ACCOMPANYING 36C25222B0030 0003

Terracon Consultants, Inc. 9856 South 57 th Street Frankl in, Wisconsin P [414] 423 0255 F [414] 423 0566 terracon.com

REPORT COVER LETTER TO SIGN

March 10, 2021

Foresite Group LLC 2101 Magnolia Avenue, Suite 100 Bloomington, Alabama 35205

Attn: Mr. Nathan Spence, P.E.

P: (205) 397-0370 E: nspence@fg-inc.net

Re: Geotechnical Engineering Report Proposed Addition to Building 112 5000 West National Avenue Milwaukee, Wisconsin Terracon Project No. 58215015

Dear Mr. Spence:

We have completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with Terracon Proposal No. P58215015 dated January 26, 2021. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

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

Sincerely, Terracon Consultants, Inc.

Tyler J. Fugar, E.I.T. Paul J. Koszarek, P.E.

Field Engineer Department Manager Geotechnical Services Geotechnical Services

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REPORT TOPICS

REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

INTERMEDIATE FOUNDATIONS

FLOOR SLABS

FROST CONSIDERATIONS

SEISMIC CONSIDERATIONS

GENERAL COMMENTS

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 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 (Boring Log) SUPPORTING INFORMATION (General Notes and Unified Soil Classification System)

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INTRODUCTION

Geotechnical Engineering Report Proposed Addition to Building 112

5000 West National Avenue Milwaukee, Wisconsin

Terracon Project No. 58215015 March 10, 2021

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed building addition to Building 112 at the VA Medical Center located at 5000 West National Avenue in Milwaukee, Wisconsin. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Foundation design and construction

■ Groundwater conditions ■ Floor slab design and construction

■ Site preparation and earthwork

■ Seismic site classification per IBC

■ Frost considerations

The geotechnical engineering scope of services for this project included the advancement of one

(1) test boring to a depth of 20 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 log in the Exploration Results section of this report.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration.

Item Description

Parcel Information The project is on the east side of Building 112 of the VA Medical Center located at 5000 West National Avenue in Milwaukee, Wisconsin. The site Latitude and Longitude is 43.0477 and -87.9783, respectively

Existing Improvements The project site has an existing building with a concrete driveway and asphalt parking lots.

Proposed Addition to Building 112 ■ Milwaukee, Wisconsin March 10, 2021 ■ Terracon Project No. 58215015

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Item Description

Existing Topography A topographic map has not been provided; the site appears to be relatively flat.

PROJECT DESCRIPTION

Our understanding of the project is as follows:

Item Description Information Provided A request for proposal.

Project Description It is understood the project includes a 6-foot-wide addition to Building 112.

The addition will be a slab on grade structure without a basement.

Finished Floor Elevation The finished floor elevation of the building addition is anticipated to match that of the existing structure.

Maximum Loads ■ Walls: 2 to 3 kips per linear foot (klf) (anticipated)

■ Slabs: 150 pounds per square foot (psf) (anticipated)

Grading/Slopes A site grading plan has not been provided at this time; however, it is anticipated that cut and fills will be minimal

Below Grade Structures It is understood that no below grade structures are planned for this project.

GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

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 forms the basis for our geotechnical calculations and evalution of site preparation and foundation options. Conditions encountered are indicated on the boring log as well as found in the Exploration Results section of the report.

The general characterization of the subsurface conditions below the surficial concrete consisted of existing fill materials to a depth of 13.5 feet underlain by native clay soils. The existing fill materials consisted of sand with varying amounts of gravel and silt. The Standard Penetration Test SPT N Values of the existing fill varied from 2 to 5 blows per foot, indicating very loose relative densities.

Below the fill materials, native cohesive soils were encountered to the boring termination depth.

These soils typically consisted of lean clay with varying amounts of gravel and were typically observed to be in a very stiff to hard condition with hand penetrometers varying from 3.5 to 4.5 tons per square foot.

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

Groundwater Conditions

The boreholes were observed while drilling and immediately after completion for the presence and level of groundwater. Groundwater was observed at about 8 feet below existing grade during drilling operations. It is likely that the groundwater observed within the boring is perched within the more permeable sandy fill soils by the underlying less permeable clay soils. Due to the presence of low permeability soils, 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

The results of this exploration indicate that there is a thick layer of existing fill within the area of the new building addition. This existing fill material is likely backfill for the basement of the existing building. These fill soils are not considered suitable for support of new foundations or floor slab.

Based on the depth of the existing fill (about 13.5 feet), the existing building would be required to be underpinned in order to allow for the over excavation of the existing fill. Additionally, due to the granular nature of the fill materials, the lateral extents of these excavations could create significant cave in issues and therefore an over excavation and backfill is not the most cost-effective approach. If over excavation is the preferred method of remediating the fill material, we would recommend additional borings to locate the lateral extents of the existing fill. Alternatively, it may be more cost beneficial to support the floor slab (designed as a structural slab) and grade beam foundations on helical piers that are bearing in the very stiff to hard native clay soils.

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

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EARTHWORK

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 foundations and floor slabs.

Site Preparation

Prior to placing fill (if necessary), existing pavement sections should be removed. The subgrade should be compacted using a heavy diesel plate compactor. Care should be taken driving heavy equipment within 10 feet of the existing building so as not to impart additional load on the adjacent basement structure. Excessively wet or dry material should either be removed, or moisture conditioned and recompacted.

Fill Material Types

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

Engineered 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 engineered and general fill should meet the following material property requirements:

Fill Type 1, 2 USCS Classification Acceptable Locations for Placement

Cohesive

CL 3, CL/ML3,

(LL ≤ 45 and PI ≤ 20) non-structural locations

Granular GW, GM, GC SW, SP, SM, SC Below/adjacent to footings, floor slabs, and pavement

Unsuitable

CL/CH4, CH4, ML3

MH4, OL, OH4, PT

non-structural locations

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

2. Any organic materials, rock fragments larger than 3 inches, and other unsuitable materials should be removed prior to use as engineered fill.

3. Highly susceptible to frost; unstable when wet, are commonly used for pavement support with the knowledge that additional maintenance and/or shorter pavement life are likely

4. High plasticity. Not recommended beneath movement sensitive features such as foundations, floor slabs, or directly below pavements.

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Fill Compaction Requirements

Engineered fill should meet the following compaction requirements.

Item Description

Maximum fill lift thickness

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

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

Minimum compaction requirements 1, 2

■ 95% of the modified Proctor maximum dry density below foundations; the compaction effort should extend laterally beyond the foundations at least 8 inches for every foot of fill placed below the foundation elevation

■ 92% of the modified Proctor maximum dry density below floor slabs and pavement subgrade

Moisture content range 3

■ within 2% below to 3% above the modified Proctor optimum moisture content at the time of placement and compaction

■ granular materials should be compacted within workable moisture levels

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

2. If the granular material is a coarse sand, crushed limestone, or gravel, is of a uniform size, or has a low fines content, compaction comparison to relative density (ASTM D 4253 and D 4254) may be more appropriate. In this case, granular materials should be compacted to at least 60% and 65% of the material’s maximum relative density for the 92% and 95% modified Proctor recommendations, respectively.

3. Specifically, moisture levels should be maintained to achieved compaction without bulking during placement or pumping when proofrolled.

Grading and Drainage

During construction, grades should be developed to direct surface water flow away from or around the site. Exposed subgrades should be sloped to provide positive drainage so that saturation of subgrade is avoided. Surface water should not be permitted to accumulate on the site.

Final grades should slope away from the structure to promote rapid surface drainage.

Accumulation of water adjacent to the structure could contribute to significant moisture increases in the subgrade soils and subsequent softening/settlement. Roof drains should discharge into a storm sewer or several feet away from the building.

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Earthwork Construction Considerations

Terracon should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation, and placement and compaction of engineered fills.

Upon completion of filling and grading, care should be taken to maintain the moisture content of the subgrade soils prior to construction of floor slabs. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Any water that collects over or adjacent to construction areas should be promptly removed. If the subgrade should become frozen, desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction and observed by Terracon.

Care should be taken to avoid disturbance of prepared subgrade soils. The existing fill and native soils can be easily disturbed, especially by construction traffic. Construction traffic should not operate directly on saturated or low strength soils. If the subgrade becomes saturated, desiccated, or disturbed, the affected materials should either be scarified and compacted, or be removed and replaced as previously discussed. Subgrades should be observed and tested by Terracon prior to construction.

Based on conditions encountered at the boring locations, excavations for the building area are expected to encounter free water at about 8 feet below existing grade. If water is encountered, the contractor is responsible for employing appropriate dewatering methods to control seepage and facilitate construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, as well as other applicable codes, and in accordance with any applicable local, state, and federal safety regulations. The contractor should be aware that slope height, slope inclination, and excavation depth should in no instance exceed those specified by these safety regulations. The granular fill soils above the water level are considered Type “C” soils under the OSHA regulations, and the native stiff clays Type “B” soils.

Maximum slope inclinations for Type “C” and Type “B” soils under the OSHA regulations are 1.5H:1V and 1H:1V, respectively.

Flatter slopes than those dictated by these regulations may be required depending upon the soil conditions encountered and other external factors. These regulations are strictly enforced and if they are not followed, the owner, the contractor, and/or earthwork and utility subcontractor could be liable and subject to substantial penalties. Under no circumstances should the information provided in this report be interpreted to mean that Terracon is responsible for construction site safety or the contractor’s activities. Construction site safety is the sole responsibility of the

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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, proof-rolling and mitigation of areas delineated by the proof-roll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked as necessary until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,500 square feet of compacted fill in the building areas and 5,000 square feet in pavement areas. One density and water content test for every 50 linear feet of compacted utility trench backfill.

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

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

INTERMEDIATE FOUNDATIONS

At boring B-1, existing fills were observed to a depth of about 13.5 feet. In order to remove these fills adjacent to the building, the existing building would require underpinning and the overexcavation would have a high potential for uncontrollable cave in to occur. Therefore, we recommend to support the building addition on grade beams and helical piers. The helical piers would extend through the upper existing fill soils to bear a minimum of 5 feet into the very stiff to hard clay soils below approximately 18.5 feet.

The following sections outline recommendations for design and construction of the intermediate foundation option described above that can be used to support the structural improvements.

Helical Pier Foundations

Based on the anticipated structural loads and the soil conditions encountered in the planned building addition, we anticipate that helical piers could also be utilized to support the new building addition’s foundations. Helical piers are an intermediate foundation system consisting of helical-

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Responsive ■ Resourceful ■ Reliable 8 shaped circular steel plates welded to a steel bar or steel pipe at a predetermined spacing. The piers are advanced into the ground using standard truck or trailer mounted auguring equipment until a suitable bearing strata is reached. Threaded or bolted extension bars can be connected to the lead anchor bar in order to reach greater depths. An eye or suitable termination device is attached to the top end of the final extension bar to provide an attachment point for the axial load.

Depending on the soil conditions, helical piers can be a cost-effective means of providing both tension and compression anchorage for foundations subjected to compressive, uplift and overturning loads. Typically, the torque required to install the piers is measured and is used to evaluate the pier capacity. Helical piers are typically designed and installed by specialty design build contractors. Preliminary helical pier design recommendations are provided below. Terracon can provide contact information for specialty contractors who provide full design and installation services, if requested.

Helical pier systems can be installed with one or multiple helices. The bearing capacity of an individual foundation pier is equal to the sum of the capacities of the individual helices. The individual helix capacity is estimated by calculating the unit bearing capacity of the soil and applying it to the individual helix areas. Friction along the lead and extension shafts is not normally used when determining the ultimate capacity of the foundation pier unless the extension bars are grouted in place. Friction may be considered where cylindrical pipe sections are used.

The helices should be spaced far enough apart to avoid overlapping of the stress zones at each helix. Most helical pier manufacturers produce piers with a minimum three-helix-diameter spacing, which has historically been sufficient to prevent one helix from significantly affecting the performance of another. A maximum of 6 helices is typically recommended for an individual anchor.

Based on the subsurface profile, we recommend that the helical pier foundations be extended through the upper existing fill soils encountered to a depth of approximately 13.5 feet and be designed to bear in the very stiff to hard lean clays below a depth of about 18.5 feet. The depth to the bearing stratum is estimated based on the new and historic soil boring logs.

Helical piers can preliminarily be designed for an ultimate unit end bearing pressure of 9,000 psf if extended into the recommended bearing stratum. The top helix should project a minimum distance of three helix diameters into the prescribed bearing layer. We recommend that a minimum factor of safety (FOS) of 2.0 be used to calculate allowable design capacities provided that the actual capacities of the piers are verified in the field using torque measurement methods or load tests. If load testing cannot be performed, this minimum factor of safety should be increased to 3.0.

The designer should check that the manufacturer rated structural capacity of the individual helices and anchor bar is not exceeded. Additionally, the designer should check that the installation

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For helical piers intended to work in compression we recommend that only threaded pipe sections be used for extension bars. Square bar stock extensions which are connected with bolted couplers allow too much elastic settlement. Square bar extensions may only be used where the bars are grouted in place through the “pull down pile” or other method that results in a cylindrical grout column of at least 4 inches in diameter that encases the extension bars. Expansive grout should be used in this application. Grouted square extension bars should not be used where both compression and net tension is applied to the foundations since cycling between compression and net tension could result in cracking of the grout.

We anticipate that the helical piers will be loaded predominantly in compression. However, if needed, resistance to uplift is generally provided by the soil shear resistance along a cylinder defined by the helix diameter(s) and the shear strength of the soil above the top helix (bearing capacity). We recommend that a minimum factor of safety of 2 (or 3 if field verification is not performed) be used to calculate allowable design uplift capacities provided that the actual capacities are verified in the field using torque measurements or load tests.

The installation torque should be monitored during construction to confirm that the installed piers have achieved the required vertical capacity at the proposed installation depth. The ultimate pier capacity (Qu), based on average installation torque, can be estimated by the following equation.

where Kt = Manufacturer’s empirical torque factor [ft-1]. The value of Kt may range from 3 to 20 ft-1 depending on soil conditions and pier design (principally shaft size).

T = Torque strength rating [lb-ft]

Lateral loads and bending moments are resisted more effectively by two or three helical piers.

Battered piers could also be used to resist lateral loads. Lateral load capacity of battered helical piers can be computed by multiplying the individual allowable vertical capacity by the sine of the angle of the batter from the vertical. The minimum center to center spacing between individual helical piers should not be less than three times the maximum helix diameter, or 3 feet, whichever is greater, to avoid group effects.

Exterior pier caps or grade beams should extend at least 4 feet below grade for heated structures to protect against frost heave. The connections to the grade beam or pier cap should be designed by a licensed Professional Engineer in the State of Wisconsin.

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FLOOR SLABS

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

Specific attention should be given to positive drainage away from the structure and. positive drainage of the aggregate base beneath the floor slab. It is recommended that the floor slab be designed as a structural slab that will span over the existing fill soils to grade beams that are supported by helical piers.

Floor Slab Design Parameters

Item Description Structural Floor slab support

Existing fill, or new engineered fill materials that have been prepared in accordance with the Earthwork section and tested/ approved by Terracon

Granular leveling course 2 6 inches of well-graded granular material

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

2. The floor slab should be placed on a leveling course comprised of well-graded crushed stone (less than 3 percent fines) compacted to at least 95% of the modified Proctor maximum dry density (ASTM D 1557).

3. The recommended modulus value is based on a 12-inch square plate. The modulus value used in design should be adjusted based on the actual size of the floor slab according to the Naval Facilities Engineering Design Manual 7.2, page 7.2-155, Table 4.

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

Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual.

Floor Slab Construction Considerations

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

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Responsive ■ Resourceful ■ Reliable 11 resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

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

FROST CONSIDERATIONS

The soils on this site are frost susceptible, and water present or migrating beneath structures in non-climate controlled areas can affect the performance of the slabs on-grade, sidewalks and pavements. Exterior slabs should be anticipated to heave during winter months. If frost action needs to be eliminated in critical areas, we recommend the use of non-frost susceptible (NFS) fill or structural slabs (for instance, structural stoops in front of building doors). Placement of NFS material in large areas may not be feasible; however, the following recommendations are provided to help reduce potential frost heave:

■ Provide surface drainage away from the building and slabs.

■ Install drains around the perimeter of the building, stoops, below exterior slabs and pavements, and connect them to the storm drainage system.

■ Grade clayey subgrades, so groundwater potentially perched in overlying more permeable subgrades, such as sand or aggregate base, slope toward a site drainage system.

■ Place NFS fill as backfill beneath slabs and pavements critical to the project.

■ Place a 3 horizontal to 1 vertical (3H:1V) transition zone between NFS fill and other soils.

■ Place NFS materials in critical sidewalk areas.

As an alternative to extending NFS fill to the full frost depth, consideration can be made to placing extruded polystyrene or cellular concrete under a buffer of at least 2 feet of NFS material.

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 D. Subsurface explorations at this site were extended to a maximum depth of 20 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic

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GENERAL COMMENTS

As the project progresses, we address assumptions by incorporating information provided by the design team, if any. Revised project information that reflects actual conditions important to our services is reflected in the final report. The design team should collaborate with Terracon to confirm these assumptions and to prepare the final design plans and specifications. This facilitates the incorporation of our opinions related to implementation of our geotechnical recommendations.

Any information conveyed prior to the final report is for informational purposes only and should not be considered or used for decision-making purposes.

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

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ATTACH MENTS

ATTACHMENTS

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EXPLORATION AND TESTING PROCEDURES

Field Exploration

Number of Borings Boring Depth (feet) Planned Location

1 20 Building Addition Footprint

Boring Layout and Elevations: Unless otherwise noted, Terracon personnel provided the boring layout. Coordinates were obtained with a handheld GPS unit (estimated horizontal accuracy of about ±20 feet) and approximate elevations were obtained by interpolation from the provided site survey. If elevations and a more precise boring layout are desired, we recommend borings be surveyed following completion of fieldwork.

Subsurface Exploration Procedures: We advanced the borings with an ATV-mounted, rotary drill rig using continuous flight hollow-stem. Four samples at 2.5-foot intervals were obtained in the upper 10 feet of each boring and at 5-foot intervals thereafter. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon is 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 (if present) during drilling and sampling. For safety purposes, all borings were backfilled with auger cuttings and/or bentonite chips after their completion.

The sampling depths, penetration distances, and other sampling information were 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 various laboratory tests to better understand the engineering properties of the various soil strata as necessary for this project.

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

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■ Water (Moisture) Content

■ Hand Penetrometer

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

SITE LOCA TION AND EXPLORATI ON PLANS

SITE LOCATION AND EXPLORATION PLANS

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EXPLORATION RESULTS

EXPLORATION RESULTS

SUPPORTING INFORMA TION

SUPPORTING INFORMATION

UNIFIED SOIL CLASSIFICATION SYSTEM

March 10, 2021 ■ Terracon Project No. 58215015

UNIFIED SOIL C LASSIFICATI ON 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 1 Cc 3 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 1 Cc 3 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”

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.

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

“gravelly” to group name.

NPI 4 and plots on or above “A” line.

OPI 4 or plots below “A” line.

P PI plots on or above “A” line.

QPI plots below “A” line.

Exhibit D-1