ATTACHMENT 4 - Geotechnical Report.pdf

Geotechnical Evaluation

Southern Arizona Veteran Affairs Medical Center

Consolidated Mail Outpatient Pharmacy

3675 East Britannia Drive

Tucson, Arizona

H2B Engineers, Inc.

1225 North Loop West, Suite 800 | Houston, Texas 77008

November 24, 2021 | Project No. 607004001

Geotechnical | Environmental | Construction Inspection & Testing | Forensic Engineering & Expert Witness

Geophysics | Engineering Geology | Laboratory Testing | Industrial Hygiene | Occupational Safety | Air Quality | GIS

1991 East Ajo Way, Suite 145 | Tucson, Arizona 85713 | p. 520.577.7600 | www.ninyoandmoore.com

Geotechnical Evaluation

Southern Arizona Veteran Affairs Medical Center

Consolidated Mail Outpatient Pharmacy

3675 East Britannia Drive

Tucson, Arizona

Mr. Frank Espinal, PE

H2B Engineers, Inc.

1225 North Loop West, Suite 800 | Houston, Texas 77008

November 24, 2021 | Project No. 607004001

MJK/SDN/FFN/jom

Marek J. Kasztalski, PE Senior Geotechnical Engineer

Fred F. Narcaroti Principal/Tucson Office Manager http://www.ninyoandmoore.com/

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 i

CONTENTS

1 INTRODUCTION 1

2 SCOPE OF SERVICES 1

3 SITE DESCRIPTION 1

4 TOPOGRAPHIC MAP AND AERIAL PHOTOGRAPH REVIEW 2

5 PROPOSED CONSTRUCTION 2

6 FIELD EXPLORATION AND LABORATORY TESTING 2

7 MICRO-TREMOR ARRAY MEASUREMENTS 3

7.1 Field Methods 3

7.2 Data Processing and Modeling 3

8 GEOLOGY AND SUBSURFACE CONDITIONS 4

8.1 Subsurface Conditions 5

8.2 Groundwater 5

9 GEOLOGIC HAZARDS 5

9.1 Land Subsidence and Earth Fissures 6

9.2 Faulting and Seismicity 6

9.3 Seismic Design Considerations 7

10 CONCLUSIONS 8

11 RECOMMENDATIONS 9

11.1 Earthwork 9

11.1.1 Site Preparation 9

11.1.2 Excavations 9

11.1.3 Temporary Slopes 10

11.1.4 Fill Materials and Reuse of On-site Soils 10

11.1.5 Subgrade Preparation 10

11.1.6 Fill Placement and Compaction 11

11.1.7 Pipe Bedding 12

11.1.8 Trench Backfill 12

11.2 Foundations, Slab-on-Grade and Flatwork 12

11.2.1 Spread or Continuous Footings 12

11.2.2 Slab-On-Grade 13

11.2.3 Flatwork 14

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11.3 Pavements 14

11.3.1 Traffic 14

11.3.2 Subgrade 14

11.3.3 Asphalt Concrete Pavement Sections 15

11.3.4 PCC Pavement Section 15

11.4 Corrosion 16

11.5 Concrete 17

12 SITE DRAINAGE 17

13 PRE-CONSTRUCTION CONFERENCE 18

14 CONSTRUCTION OBSERVATION AND TESTING 18

15 LIMITATIONS 18

16 REFERENCES 20

TABLES

1 – IBC Seismic Design Criteria 8

2 – Compaction Recommendations 11

3 – Subgrade Soil Correlated R-value Summary 15

4 – Recommended AC Structural Pavement Sections 15

5 – Rigid Pavement Sections 15

FIGURES

1 – Site Location

2 – Exploration Locations

3 – Shear Wave Velocity Profile

APPENDICES

A – Boring Logs

B – Laboratory Testing

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 1

1 INTRODUCTION

In accordance with our proposal dated October 29, 2021, and your authorization, we have performed a geotechnical evaluation for the design and construction for the new Veteran Affairs

(VA) Consolidated Mail Outpatient Pharmacy project in Tucson, Arizona (Figure 1). The purpose of our evaluation was to assess the subsurface conditions at the project site in order to provide geotechnical recommendations for design and construction. This report presents the results of our evaluation and our geotechnical conclusions and recommendations regarding the proposed construction.

2 SCOPE OF SERVICES

The scope of our services for this project generally included:

Reviewing available topographic information, soil surveys, geologic literature, and aerial photographs of the project area.

Conducting a visual reconnaissance of the project area and marking out the boring locations.

Notifying Arizona 811 of the proposed exploration locations prior to conducting our field work.

Drilling, logging, and sampling two exploratory soil borings to an approximate depth of 25 feet below ground surface (bgs). The boring logs are presented in Appendix A.

Performing laboratory tests on selected samples collected from our borings to evaluate the in-situ moisture content and dry density, gradation, Atterberg limits, consolidation, and corrosivity characteristics (including pH, minimum electrical resistivity, and soluble sulfate and chloride contents). The results of the laboratory tests are included in Appendix B.

Conducting Micro-Tremor Array Measurements (MAM) that consisted of a single linear profile of seismic data collection within the project site (Figure 2).

Preparing this report presenting our findings, conclusions, and recommendations regarding the proposed design and construction.

Our scope of services did not include environmental consulting services such as hazardous waste sampling or analytical testing at the site. A detailed scope of services and estimated fee for such services can be provided upon request.

3 SITE DESCRIPTION

The project site is located at 3675 East Britannia Drive in Tucson, Arizona. At the time of our evaluation, the project site was a relatively flat, undeveloped parcel with sparse desert vegetation. Existing commercial and public facilities were located to the south, north, and west

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 2 of the project site. A residential, single-family subdivision was located to the east of the project site.

4 TOPOGRAPHIC MAP AND AERIAL PHOTOGRAPH REVIEW

According to the Tucson, Arizona-Pima County, 7.5-Minute United States Geological Survey

(USGS) Topographic Quadrangle Map (2018), the average site elevation is approximately 2,625 feet relative to mean sea level (MSL). Based on the information from this quadrangle map, the ground surface in the project vicinity generally slopes from southeast down to northwest.

Several historical aerial photographs from Historicaerials.com (Nationwide Environmental Title

Research [NETR]) and from Google Earth™ were reviewed for this project. Aerial images dated

1958 through 1998 depicted the project site and adjacent parcels as undeveloped desert land.

An aerial image dated 2002 depicted a commercial development to the west of the site. An aerial photograph dated 2005 depicted development of the residential subdivision to the east of the project site and the public building to the north. Aerial images dated 2009 through 2020 depicted the project site and adjacent areas as being similar to their present condition.

5 PROPOSED CONSTRUCTION

We understand that the project will include the design and construction of an approximately

30,000 square feet (sf) parking lot and a 30,000 sf single-story building to serve as the VA

Consolidated Mail Outpatient Pharmacy.

Engineering plans for the project were not available for our review. We understand that the new building will be supported on shallow foundations and a slab on grade. We further understand that the new construction will include excavations for new utilities. However, no significant grading operations are anticipated.

6 FIELD EXPLORATION AND LABORATORY TESTING

On November 111h, 2021, Ninyo & Moore conducted a subsurface exploration at the site in order to evaluate the subsurface conditions and to collect soil samples for laboratory testing.

Our evaluation consisted of drilling, logging, and sampling of two exploratory borings (denoted as B-1 and B-2) using a CME 75 truck mounted drill rig equipped with hollow-stem augers

(Figure 2). The borings extended to an approximate depth of 25 feet below ground surface

(bgs). Bulk and relatively undisturbed soil samples were collected at selected depth intervals in our borings.

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Ninyo & Moore personnel logged the borings in general accordance with the Unified Soil

Classification System (USCS) and American Society for Testing and Materials (ASTM) test method D 2488 by observing cuttings and drive samples. Collected ring samples were trimmed in the field, wrapped in plastic bags, and placed in cylindrical plastic containers to retain in-place moisture conditions. Similarly, Standard Penetration Test (SPT) and bulk samples were sealed in plastic bags to retain their approximate in-place moisture. Detailed descriptions of the soils encountered are presented on the boring log in Appendix A.

The soil samples collected from our exploratory activities were transported to the Ninyo & Moore laboratory in Tucson, Arizona for geotechnical laboratory testing. The testing included in-situ moisture content and dry density, gradation, Atterberg limits, consolidation, and corrosivity characteristics (including pH, minimum electrical resistivity, and soluble sulfate and chloride contents). The results of the in-situ moisture content and dry density testing are presented on the boring logs in Appendix A and a description of each laboratory test method and the remainder of the test results is presented in Appendix B.

7 MICRO-TREMOR ARRAY MEASUREMENTS

A seismic survey using passive surface wave techniques was performed at the project site on

November 8, 2021. The purpose of the study was to evaluate the subsurface shear-wave velocity at a representative location (Figure 2). The passive seismic method carried out included

Micro-Tremor Array Measurements (MAM) and consisted of a single linear profile of seismic data collection. The method provided a shear wave velocity profile to a depth of approximately

100 feet below the ground surface (bgs) and Vs100 for seismic site classification (IBC, 2012).

The following sections provide a summary of the methods and analyses used in our study. The seismic model results are presented on Figure 3.

7.1 Field Methods

A Geode 24–Channel Seismograph (Geometrics Inc., San Jose, CA) was used for MAM surveying, with 4.5 Hertz (Hz) vertical component geophone placement every 10 feet for a total profile length of 230 feet. Approximately twenty-five records were collected, with a record length of 30 seconds (s) and 2 millisecond (ms) sample interval. The field data were digitally recorded in SEG2 format, reviewed in the field for data quality, saved to a hard disk, and documented.

7.2 Data Processing and Modeling

The MAM seismic data were processed using SeisImager seismic processing software

(Geometrics Inc., San Jose, CA). The dispersive characteristics of surface waves are used to

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 4 evaluate the subsurface velocity at depth. Longer wavelength (that is, longer-period and lower-frequency) surface waves travel deeper and thus contain more information about deeper velocity structure. Shorter wavelength (that is, shorter-period and higher-frequency) surface waves travel shallower and thus contain more information about shallower velocity structure.

The dispersion is dependent on the material properties, such as surface wave velocity, relative material densities, and Poisson's ratio. An inversion is performed on the collected passive seismic shear wave records within SeisImager to produce a model of the variation in shear wave velocities with depth. The following data processing flow was used to calculate Average

Shear-wave Velocities (AVS) to a depth of approximately 100 feet (Vs100):

Collate records into list file and edited any bad channels or records;

Apply 2D Spatial Auto Correlation (SPAC); using a linear array and 24 geophones at 10 feet spacing;

Phase velocity frequency transformation from 2 to 20 Hz;

Automated velocity picks of raw phase velocity were calculated and updated manually;

Create an initial model and carry out a non-linear Least Squares Method (LSM) inversion to produce a final shear wave velocity model; convergence of the inversion was evaluated to assure the model achieved an RMS <5% within 5-7 iterations, Calculate Vs100 using the final shear wave velocity model.

8 GEOLOGY AND SUBSURFACE CONDITIONS

The project site is located in the Sonoran Desert Section of the Basin and Range physiographic province, which is typified by broad alluvial valleys separated by steep, discontinuous, subparallel mountain ranges. The mountain ranges generally trend north-south and northwest-southeast. The basin floors consist of alluvium with thickness extending to several thousands of feet.

The basins and surrounding mountains were formed approximately 18 million years ago during the mid- to late-Tertiary age. Extensional tectonics resulted in the formation of horsts

(mountains) and grabens (basins) with vertical displacement along high-angle normal faults.

Intermittent volcanic activity also occurred during this time. The surrounding basins were filled with alluvium from the erosion of the surrounding mountains as well as from deposition from rivers. Coarser-grained alluvial material was deposited at the margins of the basins near the mountains.

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The surficial geology of the site is described as being Quaternary age (0.79 Ma to 10,000 years) basin-fill deposits composed of active stream channels, low stream terraces, and relatively un-dissected alluvial fans (Pearthree, 1998). Our review of the United States Department of

Agriculture (USDA), Natural Resource Conservation Service (NRCS) online Web Soil Survey, indicates that the soils at this site are described as the Cave soils and urban land complex. This unit consists of gravelly fine sandy loam. cemented material, and gravelly loamy sand. Loam is an agricultural soil classification that refers to a soil comprised of a mixture of clay, silt, and sand.

8.1 Subsurface Conditions

The boring logs contain our field and laboratory test results, as well as our interpretation of conditions believed to exist between actual samples retrieved. Therefore, these boring logs contain both factual and interpretive information. Lines delineating subsurface strata on the boring logs are intended to group soils having similar engineering properties and characteristics.

They should be considered approximate, as the actual transition between soil types (strata) may be gradual. Detailed stratigraphic information as well as a key to the soil symbols and terms used on the boring logs are provided in Appendix A.

Native alluvial soils were encountered at the surface of our borings, and extended to the boring termination depths. In general, the alluvium in our borings consisted of medium dense to dense clayey sand extending to an approximate depth of 8 feet bgs underlain by very dense well-graded sand with clay and varying percentages of gravel. Zones of carbonate cementation

(caliche) were encountered at different depths.

8.2 Groundwater

Groundwater was not encountered in our exploratory boring. Based on well data provided by the

Arizona Department of Water Resources (ADWR), groundwater has been historically measured at a depth on the order of 140 feet bgs. However, it should be noted that groundwater levels near the site can fluctuate due to seasonal variations, flows in nearby washes, irrigation, groundwater withdrawal or injection, and other factors.

9 GEOLOGIC HAZARDS

The following section provides a discussion regarding potential geologic hazards such as land subsidence, earth fissures, faulting and seismicity.

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9.1 Land Subsidence and Earth Fissures

Groundwater depletion, due to groundwater pumping, has caused land subsidence and earth fissures in numerous alluvial basins in Arizona. It has been estimated that subsidence has affected more than 3,000 square miles and has caused damage to a variety of engineered structures and agricultural land. From 1948 to 1983, excessive groundwater withdrawal has been documented in several alluvial valleys where groundwater levels have been reportedly lowered by up to about 500 feet. With such large depletions of groundwater, the alluvium has undergone consolidation resulting in large areas of land subsidence (Schumann and Genualdi, 1986).

In Arizona, earth fissures are generally associated with land subsidence and pose an on-going geologic hazard. Earth fissures generally form near the margins of geomorphic basins where significant amounts of groundwater depletion have occurred. Reportedly, earth fissures have also formed due to tensional stress caused by differential subsidence of the unconsolidated alluvial materials over buried bedrock ridges and irregular bedrock surfaces (Schumann and

Genualdi, 1986).

According to the information from ADWR, the project site lies within the Tucson Land

Subsidence Feature. The InSAR data that compared satellite passes on various dates between

November 9, 1993 and March 18, 2021 indicated that up to about 1.8 inches of subsidence had occurred in the vicinity of the project site location within the past approximately 25 years of recorded history. Historic subsidence may have also occurred prior to ADWR’s 1993 measurements.

Based on our field reconnaissance and review of the referenced material, there are no known earth fissures at the surface of the subject site. Based on fissure maps published by the Arizona

Geological Survey (AZGS), the closest reported unconfirmed earth fissures to the site are located approximately 26 miles to the west of the project site near the Town of Marana

(Shipman, 2007). Continued groundwater withdrawal in the area may result in subsidence and the formation of new fissures or the extension of existing fissures. While the future occurrence of land subsidence and earth fissures cannot accurately be predicted, these phenomena are not expected to be a constraint to the construction of this project.

9.2 Faulting and Seismicity

The site lies within the Sonoran zone, which is a relatively stable tectonic region located in southwestern Arizona, southeastern California, southern Nevada, and northern Mexico (Euge et

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 7 al., 1992). This zone is characterized by sparse seismicity and few Quaternary faults. Based on our field observations and on our review of readily available published geologic maps and literature, there are no known active faults underlying the subject site or adjacent areas.

The closest known Quaternary fault to the site is the Santa Rita Fault Zone, located approximately 15 miles southeast of the site. The Santa Rita Fault Zone is situated along the western piedmont of the Santa Rita Mountains. The fault zone is a series of northeast-striking normal faults that dip to the northwest. The most recent movement along this fault was approximately 130,000 years ago during the Middle to Late Pleistocene epoch. The slip-rate category of this fault is less than 0.2 millimeters per year (Pearthree, 1998).

9.3 Seismic Design Considerations

The results of our MAM survey indicate that the average shear-wave velocity in the upper approximately 100 feet bgs (Vs100) is approximately 1,347 feet per second (fps) indicating that the site falls under Seismic Site Class C per the current IBC.

The current IBC specifies that the Risk-Targeted, Maximum Considered Earthquake (MCER) ground motion response accelerations be used to evaluate seismic loads for design of buildings and other structures. The MCER ground motion response accelerations are based on the spectral response accelerations for 5 percent damping in the direction of maximum horizontal response and incorporate a target risk for structural collapse equivalent to 1 percent in 50 years with deterministic limits for near-source effects. The horizontal PGA that corresponds to the

MCER for the site was calculated as 0.118g. The MCEG PGA, based on the geometric mean

PGA with a 2 percent probability of exceedance in 50 years, with adjustment for site class effects (PGAM) was calculated as 0.152g. Seismic design parameters were calculated using the

ATC Hazards by Location website seismic design tool.

Table 1 presents the seismic design parameters for the site in accordance with IBC guidelines and mapped spectral acceleration parameters. In accordance with the results of our MAM scan, (Figure 3) these ground motion values are calculated for "very dense soil and soft rock" sites, which correspond to a shear-wave velocity of approximately 1,200 to 2,500 fps in approximately the top 100 feet bgs. Different soil or rock types may amplify or de-amplify these values. The proposed improvements should be designed in accordance with the requirements of governing jurisdictions and applicable building codes.

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Table 1 – IBC Seismic Design Criteria

Seismic Design Factors Value

Site Class C

Site Coefficient, Fa 1.3

Site Coefficient, Fv 1.5

Mapped Spectral Acceleration at 0.2-second Period, Ss 0.267 g

Mapped Spectral Acceleration at 1.0-second Period, S1 0.083 g

Spectral Acceleration at 0.2-second Period Adjusted for Site Class, SMS 0.348 g

Spectral Acceleration at 1.0-second Period Adjusted for Site Class, SM1 0.124 g

Design Spectral Response Acceleration at 0.2-second Period, SDS 0.232 g

Design Spectral Response Acceleration at 1.0-second Period, SD1 0.083 g

10 CONCLUSIONS

Based on the results of our subsurface evaluation, laboratory testing, and data analysis, the proposed construction is feasible from a geotechnical standpoint, provided the recommendations of this report are incorporated into the design of the project, as appropriate.

Geotechnical considerations include the following:

The site soils can generally be excavated or ripped using heavy-duty earthmoving or excavation equipment. However, zones of carbonate cementation and gravel should be anticipated, which may result in difficult and/or slower excavation rates.

Soils of variable relative densities encountered in our borings may be compressible upon saturation.

Imported soils and soils generated from on-site excavation activities, that exhibit a relatively low plasticity index (PI) can generally be used for engineered fill. Based on the results of our study, many of the on-site soils are suitable for re-use as engineered fill.

Groundwater was not observed in our borings. Based on ADWR well data, the regional groundwater table has been historically measured at depths on the order of 140 feet bgs. In general, groundwater is not expected to be a constraint to the design and construction of this project.

No documented geologic hazards are present underlying or immediately adjacent to the site.

However, the project site lies within the Tucson Land Subsidence Feature. Based on the InSAR data, within the past approximately 25 years of recorded history, up to approximately

1.8 inches of subsidence has occurred within portions of the project area.

Corrosivity test results indicate that on-site soils may be corrosive to ferrous materials and the sulfate content of the soils presents a negligible sulfate exposure to concrete.

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11 RECOMMENDATIONS

The following sections present our geotechnical recommendations for the project design and construction. If the proposed construction is changed from that discussed in this report, Ninyo & Moore should be contacted for additional recommendations.

11.1 Earthwork

The following sections provide our earthwork recommendations for this project. In general, the earthwork specifications contained in the Pima Association of Governments (PAG) Standard

Specifications for Public Improvements (Standard Specifications) are expected to apply unless specifically noted.

11.1.1 Site Preparation

Construction areas should be cleared of deleterious materials, if any are present, construction debris, vegetation, and any other material that might interfere with the performance or progress of the work. These materials should be disposed of at a legal dumpsite. Existing features that call for relocation or removal and extend below finished grade, if present, should be removed, and the resulting excavations backfilled with compacted engineered fill as discussed in this report.

11.1.2 Excavations

Our evaluation of the excavation characteristics of the on-site soils is based on the results of our exploratory borings, site observations, and experience with similar soils. The on-site soils include medium dense to very dense clayey sand and well graded sand with clay which can generally be excavated or ripped using heavy-duty earthmoving or excavation equipment. However, ones of carbonate cementation and gravel should be anticipated, which could be more difficult to excavate and could slow the excavation rate.

Equipment and procedures should be used that do not cause significant disturbance to the excavation bottoms. Excavators and backhoes with buckets having large claws to loosen the soil should be avoided when excavating the last 6 to 12 inches. Such equipment will probably disturb the excavation bases. If wet or saturated soils are found at the excavation bases, these soils may soften under the action of light equipment and foot traffic. If the subgrade becomes disturbed, it should be compacted before placing the backfill material.

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11.1.3 Temporary Slopes

Sidewalls for temporary excavations should not be anticipated to stand near-vertical without sloughing. Therefore, the contractor should provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with Occupational Safety and Health Administration (OSHA) regulations, for employees working in an excavation that may expose them to the danger of moving ground. For planning purposes and according to

OSHA soil classifications, a "Type C" soil should be considered for this project. This corresponds to a temporary slope inclination no steeper than 1.5:1 (horizontal to vertical

[H:V]) up to a height of 20 feet. During excavation, soil classification and excavation performance should be evaluated in the field by Ninyo & Moore in accordance with the

OSHA regulations.

11.1.4 Fill Materials and Reuse of On-site Soils

On-site and imported soils that exhibit relatively low plasticity indices and very low to low expansive potential are generally suitable for re-use as engineered fill. Relatively low plasticity indices are defined as a PI value of 15, or less, as evaluated by ASTM D 4318.

Based on laboratory test results, the near-surface on-site soils are characterized by PI values of 9 to 11. As such, it is our opinion that many of the on-site soils will be suitable for re-use as engineered fill during construction. The Contractor should perform additional testing either prior to or during construction to better understand the soil conditions. Fill soils not suitable for re-use as engineered fill can be re-used in non-structural areas (e.g.

landscaping, etc.).

In addition, suitable fill should not include organic material, construction debris, or other non-soil fill materials. Clay lumps and rock particles should not be larger than 4 inches in dimension. This material should be disposed of off-site or in non-structural areas. In addition, the subgrade under new pavements should meet the design R-value recommendation in Section 11.3.2 of this report.

Engineered fill materials in contact with ferrous metals should also have low corrosion potential (minimum resistivity more than 2,000 ohm-cm, chloride content less than 25 parts per million [ppm]). Engineered fill material in contact with concrete should have a soluble sulfate content of less than 0.1 percent.

11.1.5 Subgrade Preparation

As stated previously, our borings disclosed near-surface alluvial soils generally consisting of clayey sand. Based on the results of our explorations and laboratory testing, the on-site

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 11 soils exhibit potential for volume changes upon inundation with water and may be compressible. Accordingly, we recommend that new shallow foundations be supported on a zone of engineered fill that extends 2 feet below the footing base. The engineered fill placed in this zone should be moisture-conditioned and compacted as discussed in Section 11.1.6.

This overexcavation zone should extend a horizontal distance from the edge of the foundation footprint that is equal to the depth of the overexcavation.

In addition, we recommend that new slab-on-grade, flatwork and pavement be supported on 8 inches of moisture-conditioned and compacted engineered fill, as discussed in Section

11.1.6. This can be achieved by overexcavation or in-place scarification. The fill thickness should be measured from the bottom of the aggregate base (AB) layer, where applicable.

This subgrade improvement should extend laterally 1 foot beyond the slab/pavement footprint.

After the overexcavation described above is finished and prior to the placement of engineered fill, exposed surfaces from excavations should be carefully evaluated by Ninyo

& Moore for the presence of soft, loose, or wet soils that were not removed as part of the improvement process. This evaluation should consist of probing and visual observation of the excavation bottom. Based on this evaluation, additional remediation may be needed.

This could include further scarification of the exposed surface. This additional remediation, if needed, should be addressed by the geotechnical consultant during the earthwork operations.

11.1.6 Fill Placement and Compaction

Engineered fill soils should be moisture-conditioned within the moisture range shown below in Table 2 and mechanically compacted to the percent compaction shown. Engineered fill should generally be placed in 8-inch-thick loose lifts such that each lift is firm and non-yielding under the weight of construction equipment.

Table 2 – Compaction Recommendations

Engineered Fill Description Percent Compaction per ASTM D698 Moisture Content

Below foundations, floor slabs, exterior flatwork, and pavement

95 percent ±2 percent of optimum

Aggregate Base (AB) 100 percent ±2 percent of optimum Trench Backfill – within 2 feet below pavements

100 percent ±2 percent of optimum

Trench Backfill – deeper than 2 feet below pavement

95 percent ±2 percent of optimum

Pipe Bedding/Pipe Zone 95 percent ±2 percent of optimum

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An earthwork (shrinkage) factor of 10 to 20 percent is estimated. This shrinkage factor range represents an average of the material tested and assumes that materials excavated from the site will be placed as fill. Potential bidders should consider this in preparing estimates and should review the available data to make their own conclusions regarding excavation conditions.

11.1.7 Pipe Bedding

We recommend that new pipelines be supported on 6 inches or more of graded granular bedding material meeting the Standard Specifications. This bedding/pipe-zone backfill should extend 1 foot above the pipe crown. Care should be taken not to allow voids to form beneath the pipe (i.e., the pipe haunches should be continuously supported) to avoid damaging the pipeline. This may involve fill placement by hand or small compaction equipment. When backfilling, care should be taken to fill voids with compacted material so that excessive settlement of the backfill will not occur.

The bedding/pipe-zone should be placed in lifts of approximately 8 inches in loose thickness and compacted as detailed in Section 11.1.6 above.

11.1.8 Trench Backfill

Trench backfill should be mechanically compacted to a relative compaction as detailed in

Section 11.1.6 above. Lift thickness for backfill will be dependent upon the type of compaction equipment utilized, but should generally be placed in lifts not exceeding

8 inches in loose thickness. Special care should be exercised to avoid damaging the pipe or other structures during the compaction of the backfill. In addition, the underside (or haunches) of the buried pipe should be supported on a well-graded, compacted bedding material. This area may need placement by hand or small-scale compaction equipment.

11.2 Foundations, Slab-on-Grade and Flatwork

Based upon our review of field exploration and laboratory test results, we are providing recommendations for shallow foundations, slab-on-grade, and flatwork. We understand that the foundation system used will be selected by others based on loading conditions, settlement tolerances of the structures, as well as associated costs and constructability.

11.2.1 Spread or Continuous Footings

Spread or continuous footings may be used for this project and should be supported at a depth of 18 inches or more below finished grade, bearing on engineered fill in accordance

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 13 with recommendations presented in Section 11.1.5. Continuous footings should have a width of 16 inches or more, and isolated column footings should have a width of 24 inches or more. Footings may be designed using the allowable net bearing pressures for static conditions of 2,500 pounds per square foot. The allowable soil bearing pressure may be increased by one-third when considering total loads including loads of short duration such as wind or seismic forces.

Total and differential settlement of 1-inch and 1/2-inch over a horizontal distance of 40 feet, respectively, may occur. These settlement estimates are based on the estimated loading conditions, the available soil boring information, and our experience with similar soils.

These settlements are contingent on the preparation of soils underlying the foundations in accordance with the recommendations contained in Section 11.1.5 of this report and in compliance with the drainage recommendations presented in Section 12 of this report.

Foundations bearing on engineered fill and subject to lateral loadings may be designed using an ultimate coefficient of friction of approximately 0.35 (total frictional resistance equals the coefficient of friction multiplied by the dead load).

An ultimate passive resistance value of 360 psf per foot of depth may be used up to a value of 3,600 psf. The ultimate lateral resistance can be taken as the sum of the frictional resistance and passive resistance, provided that the passive resistance does not exceed one-half of the total allowable resistance.

The passive resistance may be increased by one-third when considering loads of short duration such as wind or seismic forces. The foundations should preferably be proportioned such that the resultant force from lateral loadings falls within its kern (i.e., middle one-third).

11.2.2 Slab-On-Grade

The design of the slabs-on-grade (floor slabs) is the responsibility of the structural engineer.

However, from a geotechnical standpoint, we recommend that floor slabs have a thickness of 4 inches or more and be reinforced. Placement of the reinforcement in the slab is vital for satisfactory performance. The slabs should be underlain by 4 or more inches of moist clean sand (ASTM 448 or similar) or compacted AB, which should be underlain by engineered fill as described in Section 11.1.5. The need for a moisture-retarding system and/or vapor retarder should be considered by the structural engineer or architect based on the moisture sensitivity of the anticipated flooring.

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In addition, the floor slab should either be constructed so that it “floats” independent of the foundations or be designed to be structurally connected to the foundations. Joints should be constructed in accordance with the relevant Technical Manual and at intervals designed by the structural engineer to help reduce random cracking of the slab. Doweled construction joints should be provided as deemed appropriate by the structural engineer.

11.2.3 Flatwork

To reduce the potential manifestation of distress to any concrete flatwork due to movement of the underlying soil, we recommend that such flatwork be installed with crack-control joints at appropriate spacing as designed by the structural engineer. We recommend that concrete flatwork be supported on engineered fill as described in Section 11.1.5. Positive drainage should be established and maintained adjacent to flatwork. We also recommend that a flexible sealant be applied in control joints that exhibit post-construction cracking to reduce the introduction of moisture into the subgrade. The flexible sealant should be installed and maintained in accordance with the manufacturer’s recommendations.

11.3 Pavements

The new pavements design were developed in accordance with the Pima County Roadway

Design Manual, 2013 Edition with June 2016 updates (Manual). The sections below present our main design assumptions and recommended new asphaltic concrete (AC) and Portland cement concrete (PCC) pavement sections. We assumed that the subgrade preparation recommendations outlined in this report will be employed.

11.3.1 Traffic

Traffic information for this project was not available as of the date of this study. However, we anticipate that the driveways will be used by passenger car traffic, delivery trucks and maintenance trucks while the parking areas will be subjected mainly to passenger car traffic.

11.3.2 Subgrade

The subsurface soils encountered in our borings generally consisted of clayey sand with variable percentages of gravel. Table 3 summarizes the correlated R-values evaluated in accordance with the Manual.

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Table 3 – Subgrade Soil Correlated R-value Summary

Boring No. Sample Depth (feet) Pima County Correlated

R-value

B-1 0.0 – 5.0 30

B-2 0.0 – 5.0 32

The mean R-value calculated for this project is 31. However, in the interest of conservatism, we recommend that R-value of 25 be adopted as the pavement design and construction control R-value. In addition, we recommend that any imported material used within 2 feet of the finished subgrade have a correlated or laboratory tested R-value of 25 or more.

11.3.3 Asphalt Concrete Pavement Sections

AC pavements are recommended for areas where relatively light vehicle traffic is anticipated. The recommended structural pavement sections are presented in Table 4 below.

Table 4 – Recommended AC Structural Pavement Sections

Pavement Section Subgrade Aggregate

Base1 (inches) Asphaltic Concrete2

Entrance/Exit Driveways

Per Sections

11.1.5 and 11.1.6

3 ½ inches of 3/4 inch mix

Parking Area Per Sections

11.1.5 and 11.1.6

2 ½ inches of 1/2 inch mix

1 Per Standard Specification No. 303;

2 Per Standard Specification No. 406.

The service life for the above-specified new pavement sections is estimated to be on the order of 20 years. The above pavement sections may need to be revised if future traffic projects become available.

11.3.4 PCC Pavement Section

PCC pavements are recommended for areas where vehicles will be turning or loading (e.g., adjacent to trash dumpsters). The recommended PCC pavement section is presented in

Table 5 below.

Table 5 – Rigid Pavement Sections

Pavement Section Aggregate Base (in) PCC Slab (in)

Truck turning/loading areas 4 6

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11.4 Corrosion

The corrosion potential of the on-site materials was analyzed to evaluate its potential effect on the foundations and structures. Corrosion potential was evaluated using the results of laboratory testing of a soil sample obtained during our subsurface evaluation that was considered representative of soils at the subject site.

Laboratory testing consisted of pH, minimum electrical resistivity, and chloride and soluble sulfate contents. The pH and minimum electrical resistivity tests were performed in general accordance with Arizona Test 236c, while sulfate and chloride tests were performed in accordance with Arizona Test 733 and 736, respectively. The results of the corrosivity tests are presented in Appendix B.

The soil pH value of the tested sample was 7.6, which is considered to be alkaline. The minimum electrical resistivity measured in the laboratory was 2,210 ohm-cm, which is considered to be non-corrosive to ferrous metals. The chloride content of the sample tested was

30 parts per million (ppm), which is considered to be corrosive environment to ferrous metals.

The soluble sulfate content of the soil samples tested was 0.005 percent by weight, which is considered to represent negligible sulfate exposure for concrete.

The results of the laboratory testing indicate that the on-site materials may be corrosive to ferrous materials. It is possible that soils with variable corrosivity characteristics may be encountered at the site and should be evaluated during construction. Special consideration should be given to the use of heavy-gauge, corrosion-protected, underground steel pipe or culverts, if any are planned. As an alternative, plastic pipe or reinforced concrete pipe could be considered. To minimize corrosion of buried metallic utilities, we recommend that topsoil, organic soils, existing fill soils, and mixtures of sand and clay not be placed adjacent to buried metallic utilities. Rather, we suggest that sand or gravel be placed around buried metal piping.

Also, buried utilities of different metallic construction or operating temperatures should be electrically isolated from each other to minimize galvanic corrosion problems. In addition, new piping should be electrically isolated from old piping, if any, so that the old metal will not increase the corrosion rate of the new metal. A corrosion specialist should be consulted for further recommendations.

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11.5 Concrete

Laboratory chemical tests performed on the soil sample indicated sulfate content of approximately 0.005 percent by weight. Based on American Concrete Institute (ACI), the on-site soils should be considered to represent negligible sulfate exposure to concrete.

We recommend the use of Type II cement for construction of concrete structures at this site.

Due to potential uncertainties as to the use of reclaimed irrigation water, or topsoil that may contain higher sulfate contents, pozzolan or admixtures designed to increase sulfate resistance may be considered.

The concrete should have a water-cementitious materials ratio of no more than 0.50 by weight for normal weight aggregate concrete. The structural engineer should select the concrete design strength based on the project specific loading conditions. Higher strength concrete may be selected for increased durability and resistance to slab curling and shrinkage cracking.

We recommend that concrete cover over reinforcing steel for foundations be in accordance with the recommendations of the structural engineer. The structural engineer should be consulted for additional concrete specifications.

12 SITE DRAINAGE

Surface drainage should be provided to divert water away from the structures and off of paved surfaces. Surface water should not be permitted to drain toward the structures or to pond adjacent to footings or on flatwork or pavement areas. Positive drainage for this project is defined as a slope of 2 or more percent for a distance of 5 or more feet away from the structures. Roof gutters should be installed on structures. Downspouts should discharge to drainage systems away from structures, pavements, and flatwork.

Further drainage recommendations include the following:

Roof drain downspouts should be tight-lined to an appropriate outlet such as a storm drain or the street. If tight-lining of the roof drains is not practicable, they should discharge approximately 5 feet away from the structure or onto flatwork (with flexible sealant in its joints), which slopes away from the structure. Roof drains should not be allowed to discharge onto the ground surface near the building foundations.

If planters are constructed adjacent to the building, we recommend that these planters be waterproofed and equipped with drains tight-lined to an appropriate drainage outlet.

We recommend that low-water-use (desert-type) landscaping be utilized on site, particularly within 5 feet of the building and hardscaped areas.

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Beneath the perimeter of any structure, utility trenches should be backfilled with either compacted non-pervious fill material (pea gravel or clean sand backfill should be avoided in these areas) or lean concrete to reduce water infiltration into the interior of the building. Special care should be taken during installation of sub-floor water and sewer lines to reduce the possibility of leaks.

13 PRE-CONSTRUCTION CONFERENCE

We recommend that a pre-construction conference be held. Representatives of the owner, the civil engineer, Ninyo & Moore, and the contractor should be in attendance to discuss the project plans and schedule. Our office should be notified if the project description included herein is incorrect or if the project characteristics are significantly changed

14 CONSTRUCTION OBSERVATION AND TESTING

During construction operations, we recommend that Ninyo & Moore perform observation and testing services for the project. These services should be performed to evaluate exposed subgrade conditions, including the extent and depth of overexcavation, to evaluate the suitability of the on-site materials for use as fill, and to observe placement and test compaction of fill soils.

Qualified subcontractors utilizing appropriate techniques and construction materials should perform construction of the proposed improvements.

15 LIMITATIONS

The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care exercised by geotechnical consultants performing similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore

Ninyo & Moore | VA Consolidated Mail Outpatient Pharmacy, Tucson, Arizona | 607004001 | November 24, 2021 19 should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document.

This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant perform an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing.

Our conclusions, recommendations, and opinions are based on an analysis of the observed site conditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified and additional recommendations, if warranted, will be provided upon request. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites.

In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control.

This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

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16 REFERENCES

American Concrete Institute, Guidelines for Concrete Floor and Slab Construction (ACI 302.1R).

American Concrete Institute, Guidelines for Residential Cast-in-Place Concrete Construction

(ACI 332R).

Arizona Department of Water Resources, Well Registry Application, https://gisweb.azwater.gov/waterresourcedata/.

Arizona Department of Water Resources (ADWR), 2000, Total Land Subsidence in the Tucson Metropolitan Area, 11/09/1993 to 09/20/2000;

Arizona Department of Water Resources (ADWR), 2010, Total Land Subsidence in the Tucson Metropolitan Area, 02/14/2003 to 01/08/2010;

Arizona Department of Water Resources (ADWR), 2020, Total Land Subsidence in the Tucson Metropolitan Area, 05/15/2010 to 04/16/2020;

Arizona Department of Water Resources (ADWR), 2020, Total Land Subsidence in the Tucson Metropolitan Area, 04/16/2020 to 03/18/2021;

American Society for Testing and Materials (ASTM), Annual Book of ASTM Standards.

Arizona Geological Survey (AZGS), Natural…