Geotechnical_Engineering_Report_0002.pdf

REPORT COVER PAGE

Geotechnical Engineering Report

Proposed Oak Grove Administration Site Improvements Grand Canyon Parashant National Monument

Oak Grove, Arizona February 19, 2020

Terracon Project No. 65195067

Prepared for:

SEH, Inc.

Pueblo, Colorado

Prepared by:

Terracon Consultants, Inc.

Tempe, Arizona

Terracon Consul tants, Inc. 4685 S. Ash Avenue, Ste. H-4 Tempe, AZ 85282 P (480) 897 8200 F (480) 897 1133 terracon.com

REPORT COVER LET TER T O SIGN

February 19, 2020

SEH, Inc.

503 N. Main Street Suite 225 Pueblo, Colorado 81003

Attn: Mr. Jimmie Hayson P: (719) 423-7403 E: jhayson@sehinc.com

Re: Geotechnical Engineering Report Proposed Oak Grove Administration Site Improvements Grand Canyon Parashant National Monument Oak Grove, Arizona Terracon Project No. 65195067

Dear Mr. Hayson:

Terracon Consultants, Inc. (Terracon) has completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with Terracon Proposal No. P65195067 dated December 13, 2019. This revised geotechnical engineering report presents the findings of the subsurface exploration and provides geotechnical engineering 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.

Eddy F. Ramirez, P.E. Donald R. Clark, P.E.

Geotechnical Project Manager Sr. Consultant/Sr. Principal

Proposed Oak Grove Administration Site Improvements ■ Oak Grove, Arizona February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 1

REPORT TOPICS

Page No.

REPORT SUMMARY ....................................................................................................... I

INTRODUCTION

PROJECT DESCRIPTION

SITE CONDITIONS

EXPLORATION AND TESTING PROCEDURES

GEOTECHNICAL CHARACTERIZATION

FROST CONSIDERATIONS

CORROSIVITY

SEISMIC CONSIDERATIONS

GEOTECHNICAL OVERVIEW

SHALLOW FOUNDATIONS

LATERAL EARTH PRESSURES

EARTHWORK

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

ATTACHMENTS

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

(Unified Soil Classification System, P-Wave Velocity Profiles, Boring Logs, and Laboratory Testing Results)

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

http://client.terracon.com/

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable i

REPORT SUMMARY

Topic 1 Overview Statement 2

Project Description

We understand the proposed project will consist of a renovation to the existing administration building and new concrete patio, well pump, water storage tanks, and a 2-kw solar system with a 7-kw backup generator. The existing patio, water well and water storage tank will be razed.

Geotechnical Characterization

The subsurface conditions at the site generally consist of lean clay with sand and fat clay with sand to a depth of approximately 6 to 10 feet and underlain by decomposed to highly weathered sandstone bedrock.

The near surface sandy lean clay exhibits medium plasticity characteristics and the near surface sandy fat clay soils exhibit high plasticity characteristics.

Shallow Foundations

Shallow foundations can be utilized for the new patio canopy.

■ Maximum allowable bearing pressure = 1,500 psf with a minimum 2-foot embedment depth is recommended.

■ Expected settlements: 1 inch or less total, ¾ inch or less differential

■ Shallow foundations should be supported on undisturbed native soils.

Mat/slab foundations can be utilized for the project

■ Maximum allowable bearing pressure = 2,000 psf with a minimum 2-foot embedment depth is recommended.

■ Expected settlements: 1 inch or less total, ¾ inch or less differential

■ Mat/slab foundations should be supported on a minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Earthwork section of the report. The requirement for the 2 feet of low volume change materials can be waived if the contact stress at the base of the foundation is greater than 1,000 psf.

Earthwork

■ No site preparation is required below shallow foundations. If disturbed soils from demolition activities are encountered at the base of the planned foundation excavation, the disturbed subgrade soils should be removed. The proposed foundations could either bear directly on deeper approved native undisturbed soils or the deepened excavations could be backfilled to planned foundation bearing depth with lean concrete placed in the excavations.

■ Because of expansive characteristics of the near surface soils, mat/slab foundations and new slabs for the new patio should be supported on a minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Earthwork section of the report. The requirement for the 2 feet of low volume change materials can be waived if the contact stress at the base of the foundation is greater than 1,000 psf.

Seismic Considerations

Based on the site soil properties, the site is classified as Site Class B in accordance with Chapter 20 of ASCE 7 as required by the 2012/2015 IBC

Pavements None are planned.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable ii

Topic 1 Overview Statement 2

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

Responsive ■ Resourceful ■ Reliable 1

INTRODUC TION

Geotechnical Engineering Report Proposed Oak Grove Administration Site Improvements

Grand Canyon Parashant National Monument Oak Grove, Arizona

Terracon Project No. 65195067 February 19, 2020

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed Oak Grove Administration Site Improvements project to be located at Grand Canyon Parashant National Monument in Oak Grove, Arizona. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil/bedrock conditions ■ Seismic site classification per IBC

■ Groundwater conditions ■ Foundation design and construction

■ Lateral earth pressures ■ Excavation considerations

■ Site preparation and earthwork

The geotechnical engineering scope of services for this project included the advancement of three hand excavated borings to a depth of approximately 4 feet below the existing ground surface, collection of compression wave (p-wave) velocity data performed at 2 locations, laboratory testing from bulk samples collected from our field exploration, geotechnical engineering analysis, and preparation of this report.

A map showing the site is shown on the attached Site Location. A map showing the boring and seismic refraction survey line locations are shown on the attached Exploration Plan. A log of each boring is included in the Exploration Results section of this report. The seismic compression wave velocity profiles interpreted along the seismic refraction survey lines during the field exploration are included in the attached Exploration Results section of this report. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included as separate graphs in the Exploration Results section of this report.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 2

PROJECT DESCRIPTION

Item Description

Project Description

We understand the proposed project will consist of a renovation to the existing administration building and constructing a new concrete patio, well pump, 8-foot diameter water storage tank, and a 2-kw solar system with a 7-kw backup generator. The existing patio, water well and water storage tank will be razed.

Proposed Construction

We anticipate the new patio will be wood or metal frame structure supported on shallow spread footings. We understand the new water storage will be fully buried supported by aggregate base course material bedding. We anticipate the new water pump and backup generator will be supported by mat/slab foundations.

Maximum Loads (Assumed)

Load information was not provided for the proposed project. The expected bearing load beneath the concrete shallow spread footings and mat/slab foundations is anticipated to be less than 1,500 psf.

Grading/Slopes Grading operations are anticipated to include relatively minor amounts of cuts and fills on the order of up to two feet.

Below-Grade Structures No basements are planned.

Free-Standing Retaining Walls None are planned.

Pavements No pavements are planned.

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 topographic maps.

Item Description

Parcel/Site Information

The project is located at the existing Oak Grove Administration building located Grand Canyon Parashant National Monument in Oak Grove, Arizona. See the attached Site Location and Exploration Plan for additional site information.

Existing Improvements

The site is presently occupied by the existing administration building with a covered patio. There is an existing water storage tank located 1,900 feet northeast of the existing building.

Current Ground Cover

Current ground cover consists of bare soil, a light growth of vegetation, and a moderate growth of native trees.

Existing Topography

The area of the existing building appears to be relatively flat. The area of the existing water storage tank consists of a gentle slope from the south down to the north. Based on the review of available topographic conditions indicated from Google Earth, there is approximately 2 feet of topographic relief across the existing water storage tank area.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 3

EXPLORATION AND TESTING PROCEDURES

Field Exploration

A total of three hand excavated borings were augered to a depth of approximately 4 feet below the exiting ground surface at the project site on January 6, 2020. The approximate boring locations at the project site are shown on the Exploration Plan.

Boring Layout and Elevations: Terracon personnel provided the boring layout. Coordinates were obtained by Terracon with a handheld GPS unit (estimated horizontal accuracy of about ±20 feet). Ground surface elevations at the location of the borings were estimated from Google Earth.

If a more precise boring layout and elevation data are desired, we recommend the borings be surveyed.

Subsurface Exploration Procedures: The borings were advanced with hand augering equipment utilizing a 4-inch outside diameter auger. One bulk sample of subsurface materials was obtained from the hand auger cuttings at the boring locations. Groundwater was not encountered during drilling and sampling. For safety purposes, all borings were backfilled with auger cuttings after their completion.

Our exploration team prepared field boring logs as part of the drilling operations. The sampling depths and other sampling information were recorded on the field boring logs. These field logs included visual classifications of the materials encountered during drilling, and our interpretation of the subsurface conditions between samples. The bulk samples were taken to our soil laboratory for testing and classification by a geotechnical engineer. 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 the results of tests of the samples in our laboratory.

Seismic Refraction Survey

Two seismic refraction test lines were performed at the project site on January 6, 2020. One seismic refraction test line was performed adjacent to the existing building and the second line was performed adjacent to the existing water storage tank. The seismic refraction test line locations are shown on the attached Exploration Plan. The compressional p-wave velocity profile interpreted along each survey test line are presented in the Exploration Results section of this report. The compressional wave velocities are indicated on each layer within the profiles.

The seismic refraction testing was completed with a two-man crew equipped with a 24-channel seismograph, 24 geophones and a computer to record and to store field data. The seismograph equipment used for the seismic refraction survey was an ES-3000 manufactured by Geometrics.

The seismic refraction method of field exploration consists of measuring (at known points along the surface of the ground) the travel time of compressional waves (p-waves) generated by an impulse

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 4 energy source, recorded by a detector (geophone). The field data recorded consists of the time it takes the compressional wave to travel from the source to the detectors, and the distance between the detector and the source. Depending upon the hardness and depth of subsurface materials, the travel time of the compressional waves are shortened and refracted quicker as the material becomes harder with depth.

For seismic line SL-1, a geophone spacing of 2 feet was used, resulting in the total line length of 48 feet between the first and last geophone. For the seismic refraction survey SL-2, a geophone spacing of 3.5 feet was used, resulting in the total line length of 87.5 feet between the first and last geophone. Off-end shot points were completed for the test line at a distance equal to the geophone spacing. A total of four shot points was performed along each test line. All field data obtained was processed with the SeisImager software program to generate appropriate time-distance curves. The data obtained from our field explorations were evaluated and interpreted using Snell's law to determine the compressional wave velocities of each stratum.

Laboratory Testing

Samples retrieved during the field exploration were taken to the laboratory for further observation by the project geotechnical engineer and were classified in accordance with the Unified Soil Classification System (USCS) as described in the Exploration Results section of this report. At that time, the field descriptions were confirmed or modified as necessary and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials.

General laboratory tests were conducted on selected soil samples and the test results are presented in the Exploration Results section of this report. These results were used for the geotechnical engineering analyses, and the development of foundation and exterior floor slab recommendations. Laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards.

Selected soil samples obtained from the site were tested for the following engineering properties:

n Atterberg Limits n Sieve Analysis n Remolded Swell n Moisture Density Relationship n Soluble Sulfate n pH n Soluble Chloride n Minimum Resistivity

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 5

GEOTECHNICAL CHARACTERIZATION

Geology

The project area is located in the Colorado Plateau physiographic province of the (1Cooley, 1967) North American Cordillera (2Stern, et al, 1979) of the southwestern United States. The Colorado Plateau province is situated between the Rocky Mountains to the east, and the Basin and Range physiographic province to the southwest. Formed during middle and late Tertiary time (100 to 15 m.y. ago), the Colorado Plateau is characterized by alternating cliffs and slopes formed as a result of different rates of erosion on resistant and weak sedimentary rocks. Ledges, cliffs or rock benches formed of resistant beds of sandstone and limestone are separated by slopes, valleys, and badlands carved on the weaker intervening shale strata. The entire province has similar rock formations, which have nearly horizontal bedding, or which are inclined slightly to the southwest.

The entire plateau drains to the Colorado River.

The physiographic features within the province are related to their distance from the Colorado River and to the amount of downcutting caused by erosional processes. In areas adjacent to the Colorado River, canyon lands are developed extensively. In the areas surrounding the canyon lands and in part of the uplands adjoining the canyon rims, rock terraces form a series of platforms and high cliffs that include Marble Platform, Coconino Plateau, Echo Cliffs, Black Mesa, and Defiance Plateau. In the southern part of the province beyond the belt of rock terraces, the relief is rather subdued and broad slopes and low mesa-like features predominate.

Surficial geologic conditions mapped at the site (3Richard, et al, 2000) consist of Permian Sedimentary Rocks. This unit is described as gray to tan, cherty limestone of Kaibab and Toroweap Formations, and underlying white to tan, fine-grained Coconino Sandstone. Limestone was deposited in a shallow sea, and sandstone was deposited in near-shore dunes and beach settings.

Subsurface Profile

The relative surface elevation along each seismic refraction survey test line was measured in the field and incorporated in the respective velocity profiles. The compressional p-wave velocity profile interpreted along each survey test line are presented in the Exploration Results section of this

1Cooley, M.E., 1967, Arizona Highway Geologic Map, Arizona Geological Society.

2Stern, C.W., et al, 1979, Geological Evolution of North America, John Wiley & Sons, Santa Barbara, California.

3 Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 6 report. Based on interpretation of the seismic refraction data, the depth to various strata was determined along each test line and is summarized in the following table:

Subsurface Layer

Approximate Bottom Depth (feet) Anticipated Material Type Compressional Wave

Velocity (feet/second)

1 6 to 10 Lean Clay with Sand, Fat Clay with Sand 536 to 1,909

14 to 18

(maximum depth explored by seismic refraction)

Decomposed to Highly Weathered Bedrock - Sandstone 2818 to 4,700

Laboratory tests were conducted on selected bulk soil samples collected during our field exploration and the test results are presented in the Exploration Results section of this report.

Test results indicate the near surface lean clay with sand soils exhibit medium plasticity characteristics and the near surface fat clay with sand soils exhibit high plasticity characteristics.

When water was added to a sample of laboratory compacted on-site near surface fat clay with sand soils, the compacted soils exhibited high expansive potential when subjected to light loading conditions such as those imposed by lightly loaded slabs and mat/slab foundations.

Groundwater Conditions

Based on information obtained from the Arizona Department of Water Resources – Groundwater Data website (https://gisweb.azwater.gov/waterresourcedata/GWSI.aspx), the depth to groundwater was measured in March of 1976 to be approximately 12 feet below the ground surface at an Arizona Department of Water Resources (ADWR) monitored well site (Local I.D.:

B-34-12 24DDA) located near the existing water storage tank at the project site. However, perched water development may occur on the top or in the fractures of the bedrock during certain seasonal times of the year and weather conditions.

FROST CONSIDERATIONS

Based on data obtained from the National Resources Conservation Service (NRCS) reported frost depth at the project site is approximately 12 to 24 inches.

CORROSIVITY

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

https://gisweb.azwater.gov/waterresourcedata/GWSI.aspx

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 7

Corrosivity Test Results Summary

Location Sample Depth (feet)

Soil Description pH Electrical Resistivity

(Ω-cm)

Soluble Sulfate Content (ppm)

Soluble Chloride Content (ppm)

B-3 0 – 4 Fat Clay with Sand 8.1 936 5 5

Results of soluble sulfate testing indicate that samples of the near surface soils tested classify as S0 according to Table 19.3.1.1 of Section 318 of the American Concrete Institute (ACI) Building Code Requirements for Structural Concrete. Concrete should be designed in accordance with the provisions of the ACI Building Code Requirements for Structural Concrete, Section 318, Chapter 19.

These values should be used to help determine potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction. Refer to Summary of Laboratory Results contained in Exploration Results section for the complete results of the corrosivity testing performed on the site soils in conjunction with this geotechnical exploration. The corrosion information presented is specific to the sample tested. If the actual soils that will be in contact with the structures at the site are different than those tested, then additional corrosion testing should be performed. Terracon is not a corrosion engineer, and our scope of work was limited to performing corrosion laboratory tests on selected samples, presenting these results, and providing a brief comparison of the results to selected criteria. A qualified corrosion engineer should be consulted if corrosion of underground utilities and structures is a concern.

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 seismic refraction survey completed for the project, it is our professional opinion that the Seismic Site Classification is B. The seismic refraction survey velocity profiles completed for this project extended to a maximum depth of approximately 18 feet. The site properties to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional exploration to deeper depths or geophysical testing may be performed to confirm the conditions below the current seismic refraction survey profile depth.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 8

GEOTECHNICAL OVERVIEW

The site appears suitable for the proposed construction based upon geotechnical conditions encountered, and provided our recommendations contained in this report are properly implemented in the design and construction.

n The subsurface conditions at the site generally consist of lean clay with sand to fat clay with sand to a depth of approximately 6 to 10 feet and is underlain by decomposed to highly weathered sedimentary sandstone bedrock.

n Based on the subsurface conditions at the project site, we recommend shallow spread footings be used for support of the new patio canopy. The footing can be supported on undisturbed native soils with a minimum embedment depth of 2 feet below finished grade.

n The new water pump, backup generator, and any other slab mounted equipment can be supported on mat/slab foundations. Because of expansive characteristics of the near surface soils, mat/slab foundations should be supported on a minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Earthwork section of the report. The requirement for the 2 feet of low volume change materials can be waived if the contact stress at the base of the foundation is greater than 1,000 psf.

n Expansive soils are present on this site. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and (at least minor) cracking in the structure should be anticipated. The severity of cracking and other (cosmetic) damage such as uneven slabs will probably increase if any modification of the site results in excessive wetting or drying of the expansive soils.

n All grades must provide effective drainage away from the building during and after construction. Water permitted to pond next to the building can result in greater soil movements than those discussed in this report. These greater movements can result in unacceptable differential slab movements, cracked slabs and walls, and roof leaks.

Estimated movements described in this report are based on effective drainage for the life of the structure and cannot be relied upon if effective drainage is not maintained.

n Exposed ground should be sloped at a minimum 5 percent away from the building for at least 10 feet beyond the perimeter of the building. After building construction and landscaping, we recommend verifying final grades to document that effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary, as part of the structure’s maintenance program.

n Based on the site soil properties, the site is classified as Site Class B in accordance with Chapter 20 of ASCE 7 as required by the 2012 International Building Code.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 9

Geotechnical engineering recommendations for foundation systems and other earth connected phases of the project are outlined below. The recommendations contained in this report are based upon the results of field and laboratory testing (included in the Exploration Results section), engineering analyses, and our current understanding of the proposed project.

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

SHALLOW FOUNDATIONS

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

Design Parameters – Spread Footings for Compressive Loads

The new patio canopy should be supported by a shallow spread footing foundation system.

Foundation excavations and bearing soils should be observed by the geotechnical engineer.

Design recommendations for foundations for the new patio canopy are presented as follows:

Design Item Description/Recommendations

Maximum Net Allowable

Bearing Pressure 1 1,500 psf

Minimum Embedment Depth Below finished grade 2 A minimum of 2 feet for frost protection

Bearing Material Spread footings may be supported on undisturbed native soils.

Minimum footing dimensions

Isolated Column Footings: 24 inches Continuous Wall Footings: 18 inches

Estimated total settlement

1 inch or less

Estimated differential settlement

¾ of the total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. The allowable bearing pressure may be increased by one-third when considering the alternative load combinations of Section 1605.3.2 of the 2012 International Building Code, however, it should not be increased when loads are determined by the basic allowable stress design load combinations of Section 1605.3.1.

2. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 10

Footings, foundations, and walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in walls is recommended.

Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required.

Footings Subject to Uplift

Reinforced concrete dead-man foundations, cast-in excavations against undisturbed subsoils are recommended for resistance to uplift. Footing or dead-man foundations may be designed using the cone method. The equation for determining the ultimate uplift capacity as a function of footing or dead-man foundation dimension, foundation depth, and soil weight is presented below:

Tu = 0.5g x D2 x (B + L) + W

Where: Tu = Ultimate uplift capacity (lbs) g = Unit weight of soil (lbs/ft3)* D = Depth to base of footing/dead-man foundation below final grade (ft) B = Width of footing/dead-man foundation (ft) L = Length of footing/dead-man foundation (ft) W = Weight of footing/dead-man + weight of soil directly over the top of the footing/block (lbs)

*A unit weight (g) of 110 pcf is recommended for soil (either undisturbed or compacted backfill) at this site.

The design uplift resistance should be calculated by dividing the ultimate resistance obtained from the equation above by an appropriate factor of safety. A factor of safety of at least 2 is recommended for live uplift loads in the analysis.

Mat Foundation Design Recommendations

The new water storage tank (if required), water pump, backup generator, and any other slab mounted equipment may be supported by reinforced mat/slab foundations on the project.

Mat/slab foundations should be designed based on the criteria outlined below:

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 11

Design Item Description/Recommendations

Foundation Type Mat/slab foundations

Maximum Design Contact Stress1 Any practical value up to a maximum of 2,000 psf

Minimum Embedment Depth for Frost Penetration 2 2 feet

Bearing Material

Mat/slab foundations should be supported on a minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Earthwork section of the report. The requirement for the 2 feet of low volume change materials can be waived if the contact stress at the base of the foundation is greater than 1,000 psf.

Design Modulus of Subgrade Reaction, k 100 pci Minimum Width 4 feet

Modulus Correction Factor3 kc=k/b

Total Estimated Settlement 1 inch or less Differential Settlement ¾-inch over 4 feet

Minimum Embedment for Frost Penetration 2 feet

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the foundation base elevation. The allowable bearing pressure may be increased by one-third when considering the alternative load combinations of Section 1605.3.2 of the 2012 International Building Code, however, it should not be increased when loads are determined by the basic allowable stress design load combinations of Section 1605.3.1.

2. Finished grade is defined as the lowest adjacent grade within 5 feet of the mat foundation.

3. It is common to reduce the k-value to account for dimensional effects of large loaded areas. Where k c is the corrected or design modulus value and b is the mat width (short dimension) or tributary loaded area

Mat/slab foundations should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, proper drainage should be provided in the final design and during construction.

Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 12

Foundation Construction Considerations

As noted in Earthwork section of this report, the foundation excavations should be evaluated and approved under the direction of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Extremely wet, loose or disturbed material in the bottom of the foundation excavations should be removed before foundation concrete is placed. Should the soils at bearing level become excessively disturbed or saturated, the affected soil should be removed prior to placing concrete.

LATERAL EARTH PRESSURES

Design Parameters

The lateral earth pressure recommendations herein are applicable to the design of footings.

Material Type Design Parameter Design Value1

On-Site Soils

Active Case 55 psf/ft

Passive Case 235 psf/ft

At-Rest Case 70 psf/ft

Total Unit Weight 100 pcf

Coefficient of Base Friction 0.352

1. The values are based on the on-site soils used as backfill.

2. The coefficient of base sliding should be reduced to 0.30 when used in conjunction with passive pressure.

Fill against foundations should be compacted to densities specified in the Earthwork section of this report.

EARTHWORK

The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project. The recommendations presented for design and construction of earth supported elements including foundations are contingent upon following the recommendations outlined in this section.

Earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 13 foundation bearing soils, and other geotechnical conditions exposed during the construction of the project.

Site Preparation

Strip and remove all existing vegetation, demolition debris, and any deleterious materials from the new patio canopy, water storage tank, and backup generator areas. Exposed surfaces should be free of mounds and depressions which could prevent uniform compaction. The site should be initially graded to create a relatively flat surface to receive fill.

Although evidence of fills or underground facilities such as septic tanks, cesspools, basements, and utilities was not observed during the site reconnaissance, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction

Subgrade Preparation

Shallow foundations bearing entirely upon undisturbed native soils are recommended for support of the new patio canopy. Areas of loose soils from demolition activities of the existing patio may be encountered at foundation bearing depth after excavation is completed for foundations. When such conditions exist beneath planned footing areas, the subgrade soils should be removed. The proposed footings could either bear directly on deeper approved native undisturbed soils or the deepened excavations could be backfilled to planned foundation bearing depth with lean concrete placed in the excavations.

The water storage tanks (if required), backup generate, and any other slab mounted equipment can be supported on mat/slab foundations. Because of expansive characteristics of the near surface soils, mat/slab foundations should be supported on a minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Fill Compaction Requirements in this report. The requirement for the 2 feet of low volume change materials can be waived if the contact stress at the base of the foundation is greater than 1,000 psf.

Patio Canopy Slab Subgrade Preparation

Compacted subgrade of existing clay soils will expand with increasing moisture content; therefore, exterior concrete grade slabs for the patio canopy could heave, resulting in cracking or vertical offsets. The potential for damage would be greatest where slabs are constructed adjacent to the building or other structural elements. To reduce the potential for damage caused by movement, we recommend the following:

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 14 n New patio canopy slabs should be minimum of 2 feet of suitable low volume change materials placed as engineered fill in accordance with the Fill Compaction Requirements in this report n Strict moisture-density control during placement of subgrade fills n Placement of effective control joints on relatively close centers and isolation joints between slabs and other structural elements n Provision for adequate drainage in areas adjoining the slabs n Use of designs which allow vertical movement between the slabs and adjoining structural elements

Fill Material Types

All fill materials should be inorganic soils free of vegetation, debris, and fragments larger than four inches in size. Pea gravel or other similar non-cementitious, poorly-graded materials should not be used as fill or backfill without the prior approval of the geotechnical engineer.

Clean on-site soils or approved imported materials may be used as fill material for the following:

Fill Type 1 USCS Classification Acceptable Location for Placement

On-Site Soils for Mat/Slab Foundations CL, CH

The on-site soils are considered suitable for use as engineered fill with the exception of within the upper 2 feet of finished subgrade beneath mat/slab foundations.

On-Site Soils for Shallow Spread Footings CL, CH

The near-surface on-site soils are not considered suitable for use as engineered fill beneath shallow spread footings.

Imported Material Varies All locations and elevations

1. Controlled, compacted fill should consist of approved materials that are free of organic matter, debris, and oversized materials. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

Imported soils (if required) for use as fill material on the project should conform to low volume change materials as indicated in the following specifications:

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 15

Percent Finer by Weight Gradation (ASTM C 136)

4" No. 4 Sieve ..................................................................................... 50-100 No. 200 Sieve ............................................................ 15 (min) to 45 (max) n Liquid Limit ....................................................................... 30 (max) n Plasticity Index ................................................................. 12 (max) n Maximum expansive potential (%)* ............................................ 1.5

*Measured on a sample compacted to approximately 95 percent of the ASTM D698 maximum dry density at about 3 percent below optimum water content. The sample is confined under a 100 psf surcharge and submerged/inundated.

Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift.

Fill lifts should not exceed 10 inches loose thickness.

Fill Compaction Requirements

Engineered fill should meet the following compaction and moisture requirements:

Material Type and Location

Per the Standard Proctor Test (ASTM D 698)

Minimum Compaction Requirement

Range of Moisture Contents for Compaction (referenced from optimum moisture content) Minimum Maximum

On-site soils Beneath shallow spread footings 95 -1% +3%

Beneath mat/slab foundations and patio slabs (except the upper 24 inches) 95 At optimum +3%

Imported soils

Beneath shallow spread footings 95 -3% +3%

Beneath mat/slab foundations and patio slabs 95 -2% +2%

Aggregate base 95 -3% +3%

Miscellaneous backfill 95 -2% +3%

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 16

Material Type and Location

Per the Standard Proctor Test (ASTM D 698)

Minimum Compaction Requirement

Range of Moisture Contents for Compaction (referenced from optimum moisture content) Minimum Maximum

1. The moisture content and compaction should be measured for each lift of engineered fill 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.

Utility Trench Backfill

Utility trenches are a common source of water infiltration and migration. Utility trenches penetrating beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

Positive drainage should be provided during construction and maintained throughout the life of the development. Infiltration of water into utility trenches or foundation excavations should be prevented during construction. Planters and other surface features which could retain water in areas adjacent to the building should be sealed or eliminated. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of approximately 5 percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility trenches should be compacted to the densities outlined herein and be free of all construction debris to reduce the possibility of moisture infiltration.

Earthwork Construction Considerations

It is anticipated that shallow excavations in soils for the proposed construction can be accomplished with conventional earthmoving equipment. Excavations penetrating the weathered bedrock may require additional effort or the use of specialized heavy-duty equipment.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 17 surface water on the prepared subgrades or in excavations. If the subgrade should become desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture

Surface water should not be allowed to pond on the site and soak into the soil during construction.

Construction staging should provide drainage of surface water and precipitation away from the building and other structure areas. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils. Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage.

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, 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.

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, contractor, and/or earthwork and utility subcontractor could be liable and subject to substantial penalties.

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 that Terracon is assuming any responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Construction Observation and Testing

The exposed subgrade and each lift of compacted fill should be tested, evaluated and reworked, as necessary, until approved by the geotechnical engineer’s representative prior to placement of additional lifts of fill. We recommend that each lift of fill be tested for density and moisture content at a minimum frequency of one test for every 5,000 square feet of compacted fill in the structure areas or a minimum of 3 density tests per lift (with the greater number of density tests to govern).

We recommend one density and moisture content test for every 300 linear feet of compacted utility trench backfill. If engineered fill is placed beneath individual structures, we recommend at least one density and moisture content test per each vertical lift per structure.

Terracon should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation; proofrolling;

placement and compaction of controlled compacted fills; backfilling of excavations into the completed subgrade, and just prior to construction of building floor slabs.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable 18

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 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.

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable

ATTACHMENTS

February 19, 2020 ■ Terracon Project No. 65195067

Responsive ■ Resourceful ■ Reliable

SITE LOCATION AND EXPLORATION PLANS

Contents:

Site…