AMENDMENT 0001-W912PL21R0015.pdf

AMENDMENT OF SOLICITATION/MODIFICATION OF CONTRACT

Except as provided herein, all terms and conditions of the document referenced in Item 9A or 10A, as heretofore changed, remains unchanged and in full force and effect.

15A. NAME AND TITLE OF SIGNER (Type or print)

30-105-04EXCEPTION TO SF 30

APPROVED BY OIRM 11-84

STANDARD FORM 30 (Rev. 10-83) Prescribed by GSA

FAR (48 CFR) 53.243

High Water Crossing at Vamori Wash: The purpose of this Amendment 0001 is to add the Geotechnical report that w as developed as a supporting document. See Enclosure 1 dated March 11, 2016.

1. CONTRACT ID CODE PAGE OF PAGES

J 1 490

16A. NAME AND TITLE OF CONTRACTING OFFICER (Type or print)

16C. DATE SIGNED

BY 08-Jun-2021

16B. UNITED STATES OF AMERICA15C. DATE SIGNED15B. CONTRACTOR/OFFEROR

(Signature of Contracting Officer)(Signature of person authorized to sign)

8. NAME AND ADDRESS OF CONTRACTOR (No., Street , County, State and Zip Code) X W912PL21R0015

X 9B. DATED (SEE ITEM 11)

28-May-2021

10B. DATED (SEE ITEM 13)

9A. AMENDMENT OF SOLICITATION NO.

11. THIS ITEM ONLY APPLIES TO AMENDMENTS OF SOLICITATIONS

X The above numbered solicitation is amended as set forth in Item 14. The hour and date specified for receipt of Offer is extended, X is not extended.

Offer must acknowledge receipt of this amendment prior to the hour and date specified in the solicitation or as amended by one of the following methods:

(a) By completing Items 8 and 15, and returning 1 copies of the amendment; (b) By acknowledging receipt of this amendment on each copy of the offer submitted;

or (c) By separate letter or telegram which includes a reference to the solicitation and amendment numbers. FAILURE OF YOUR ACKNOWLEDGMENT TO BE RECEIVED AT THE PLACE DESIGNATED FOR THE RECEIPT OF OFFERS PRIOR TO THE HOUR AND DATE SPECIFIED MAY RESULT IN

REJECTION OF YOUR OFFER. If by virtue of this amendment you desire to change an offer already submitted, such change may be made by telegram or letter, provided each telegram or letter makes reference to the solicitation and this amendment, and is received prior to the opening hour and date specified.

12. ACCOUNTING AND APPROPRIATION DATA (If required)

13. THIS ITEM APPLIES ONLY TO MODIFICATIONS OF CONTRACTS/ORDERS.

IT MODIFIES THE CONTRACT/ORDER NO. AS DESCRIBED IN ITEM 14.

A. THIS CHANGE ORDER IS ISSUED PURSUANT TO: (Specify authority) THE CHANGES SET FORTH IN ITEM 14 ARE MADE IN THE

CONTRACT ORDER NO. IN ITEM 10A.

B. THE ABOVE NUMBERED CONTRACT/ORDER IS MODIFIED TO REFLECT THE ADMINISTRATIVE CHANGES (such as changes in paying office, appropriation date, etc.) SET FORTH IN ITEM 14, PURSUANT TO THE AUTHORITY OF FAR 43.103(B).

C. THIS SUPPLEMENTAL AGREEMENT IS ENTERED INTO PURSUANT TO AUTHORITY OF:

D. OTHER (Specify type of modification and authority)

E. IMPORTANT: Contractor is not, is required to sign this document and return copies to the issuing office.

14. DESCRIPTION OF AMENDMENT/MODIFICATION (Organized by UCF section headings, including solicitation/contract subject matter where feasible.)

10A. MOD. OF CONTRACT/ORDER NO.

2. AMENDMENT/MODIFICATION NO. 5. PROJECT NO.(If applicable)

6. ISSUED BY

3. EFFECTIVE DATE

08-Jun-2021

CODE

USACE, LOS ANGELES DISTRICT

CONTRACTING DIVISION

915 WILSHIRE BLVD, SUITE 930

LOS ANGELES CA 90017

W912PL 7. ADMINISTERED BY (If other than item 6)

4. REQUISITION/PURCHASE REQ. NO.

CODE

See Item 6

FACILITY CODECODE

EMAIL:TEL:

W912PL21R0015

SECTION SF 30 BLOCK 14 CONTINUATION PAGE

SUMMARY OF CHANGES

SECTION 00 01 10 - TABLE OF CONTENTS

The below Table of Contents has been added

Exhibit/Attachment Table of Contents

DOCUMENT TYPE DESCRIPTION PAGES DATE

Attachment 1 Geotechnical Report 488

(End of Summary of Changes)

ENCLOSURE 1

Geotechnical Report Vamori Wash Bridge Tucson Sector, Ajo and Casa Grande Stations Tohono O’odham Nation Lands, Pima County, Arizona

March 11, 2016

Prepared for

U.S. Army Corps of Engineers P.O. Box 532711

Los Angeles, CA 90053-2325

Prepared by

Diaz•Yourman – GeoPentech – Kinnetic Laboratories / Joint Venture 1616 E. 17th Street

Santa Ana, CA 92705-8509

(714) 245-2920

DY Project No. 2011-026.07, GP Project No. 09021C

Solicitation Number W912PL21R0015 High Water Crossing at Vamori Wash ENCLOSURE 1

Geote Vamo Tucso Tohon

DY Proje

Prepared

Steve Du Geologic

Allen M.

Civil Eng

Diaz•You 1616 Eas Santa An

(714) 245

March 11 echnical ori Wash on Secto no O’od ect No. 2011 d by uke cal Engineer

Yourman, J gineer 28777 urman – Geo st 17th Stree na, CA 9270 5-2920

1, 2016

Report h Bridge or, Ajo a ham Na

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60072 r.

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P Project No

Kinnetic Lab a Grand nds, Pim

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Joint Venture ons nty, Arizo e ona

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TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 GENERAL

1.2 PROJECT DESCRIPTION

1.3 SCOPE OF SERVICES

2.0 FIELD INVESTIGATION AND LABORATORY TESTING

2.1 HOLLOW STEM AUGER AND ROTARY WASH BORINGS

2.2 GEOPHYSICAL SURVEYS

2.3 LABORATORY TESTING

3.0 GEOLOGIC CONDITIONS

3.1 REGIONAL GEOLOGY

3.2 SITE TOPOGRAPHY AND SURFACE CONDITIONS

3.3 LOCAL GEOLOGIC CONDITIONS

3.3.1 Alluvium

3.3.2 Coarse-Grained Alluvium

3.3.3 Fine-Grained Alluvium

3.4 GROUNDWATER

4.0 POTENTIAL GEOLOGIC HAZARDS

4.1 FAULT SURFACE RUPTURE

4.2 SEISMIC SHAKING

4.3 LIQUEFACTION POTENTIAL

4.4 SEISMICALLY INDUCED SETTLEMENT

4.5 SEISMICALLY INDUCED FLOODING

4.6 EROSION, FLASH FLOODS, AND DEBRIS FLOWS

4.7 EARTH FISSURES

4.8 SLOPE INSTABILITY

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 EARTHWORK

5.1.1 Site Preparation and Grading

5.1.2 Material for Fill

5.1.3 Excavations and Temporary and Permanent Slopes in Alluvial and Fill Soils

5.2 ACCESS ROADWAYS

5.2.1 Drainage

5.2.2 Culvert Design

5.3 SOIL CORROSION POTENTIAL

5.4 RESISTANCE TO LATERAL LOADS AND LATERAL EARTH PRESSURES

5.5 UTILITY TRENCHES

5.6 EROSION AND EMBANKMENT ARMORING

6.0 PLAN REVIEW, CONSTRUCTION OBSERVATION, AND TESTING

7.0 LIMITATIONS

8.0 REFERENCES

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LIST OF TABLES

Table 1 – GROUNDWATER SUMMARY Table 2 – IMPORT FILL AND SELECT BACKFILL CRITERIA Table 3 – AGGREGATE BASE GRADATION

LIST OF FIGURES

Figure 1 – VICINITY MAP Figure 2 – SITE PLAN Figure 3a – SITE GEOLOGIC MAP Figure 3b – LEGEND TO ACCOMPANY GEOLOGIC MAP Figure 4a – SITE SUBSURFACE PROFILE Figure 4b – SITE SUBSURFACE PROFILE (NEAR SURFACE PORTION) Figure 5 – LATERAL EARTH PRESSURES Figure 6 – RETAINING WALL DRAINAGE Figure 7 – PIPELINE BACKFILL SCHEMATIC

LIST OF APPENDICES

APPENDIX A - HIGH WATER CROSSING, PRELIMINARY PLANS

APPENDIX B - BORING INVESTIGATION

APPENDIX C - GEOPHYSICAL INVESTIGATION

APPENDIX D - LABORATORY TESTING

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LIST OF ACRONYMS AND ABBREVIATIONS

ACB Articulated Concrete Block ADOT Arizona Department of Transportation ASCE American Society of Civil Engineers ASTM ASTM International AZGS Arizona Geological Survey bgs below ground surface BMP best management practices bpf blows per foot CBP U.S. Customs and Border Protection Service CBR California Bearing Ratio CH clay of high plasticity, fat clay CIP cast-in-place CL Clay DI design index DY-GP-KL Diaz Yourman–GeoPentech–Kinnetic Laboratories, /JV EPA U.S. Environmental Protection Agency ER efficiency rating FS factor of safety ft feet GC clayey gravel GM silty gravel

GPS

GSRC

global positioning system Gulf South Research Corporation

H:V horizontal:vertical IBC International Building Code IFT Integrated Fixed Tower ISRM International Society for Rock Mechanics ksf Kip per square foot LL liquid limit MASW Multi-spectral analysis of surface waves ML Silt NAD North American Datum OSHA Occupational Safety and Health Administration

-iv- Geotechnical Report v3.docx p-wave pressure-wave pcf pounds per cubic foot PL plastic limit ppm parts per million psf pounds per square foot psi pounds per square inch s-wave shear-wave SC clayey sand SM silty sand SP poorly graded sand SPT standard penetration test T.O.N. Tohono O’odham Nation UCS unconfined compressive strength UFC Unified Facilities Criteria USACE U.S. Army Corps of Engineers USGS U.S. Geological Survey YJD Yellow Jacket Drilling Services

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1.0 INTRODUCTION

1.1 GENERAL

This report presents the results of the geotechnical investigation for the Vamori Wash Crossing within the U.S. Customs and Border Protection Service (CBP) Tucson Sector. The project site is located along the U.S.-Mexico border within the main reservation of the Tohono O’odham

Nation (T.O.N.) in Pima County, Arizona.

This report was prepared by Diaz•Yourman–GeoPentech–Kinnetic Laboratories, Joint Venture

(DY-GP-KL) for the U.S. Army Corps of Engineers (USACE) for the Vamori Wash Crossing project. This work was completed in accordance with Agreement No. W912PL-11-D-0015, Delivery Order 0007, dated March 24, 2015, between USACE and DY-GP-KL.

1.2 PROJECT DESCRIPTION

In support of the CBP, the USACE originally planned to construct a two-lane, all-weather bridge across Vamori Wash along the US-Mexico border in south-central Arizona on T.O.N. lands, as shown on the Vicinity Map, Figure 1. The bridge was originally envisioned to be approximately

720 feet long and 14 feet wide supported by 11 interior pier foundations and elevated bridge abutment foundations on both sides of the wash. Approach earthfills were expected to lead to the elevated bridge abutments. Accordingly, the field investigation was established for this original bridge layout, and borings were labeled based on the originally proposed bridge structure.

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Figure 1 - VICINITY MAP

Project Location

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After DY-GP-KL completed the field investigation, the project team decided that a high-water crossing was a more efficient solution than the originally planned bridge. Preliminary (30%) plans for the proposed high-water crossing (Option 3) dated January 15, 2015 are presented in

Appendix A.

As shown in Appendix A, the proposed crossing consists of a series of box culverts and armored mats/aprons that span the main channel of the Vamori Wash and two ancillary channels (east and west), and also includes approach embankments with surface paving and rip-rap armoring. The proposed road system will serve to redirect high drainage water experienced during flooding events through culverts and toward the armored portions of the crossing, rather than allowing floodwaters to scour the natural channels and degrade the existing border road. Features of the proposed high-water crossing include:

Approximately 1,700-foot-long improvements that will tie-in to the existing border road.

Embankment fill with culverts in the wash.

Cuts and fills less than 10 feet.

Relocating the existing border fence.

Box culverts and drainage improvements.

Rip rap on upstream and downstream sides of fills.

Asphalt cap/road at the crest of the crossing.

25-year flood is estimated to overtop the proposed high water crossing for its entire length.

1.3 SCOPE OF SERVICES

The objective of this assignment was to collect surface and subsurface geological/geotechnical data and provide geological/geotechnical recommendations for the design of the Vamori Wash

Crossing.

In order to complete this preliminary investigation, the following tasks were performed by DY-

GP-KL:

Coordinated with T.O.N., USACE, and CBP for access to the project site.

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Compiled and reviewed available and relevant planning documents provided by USACE and geologic and geotechnical information from existing publications completed in the vicinity of the project area.

Prepared an Exploration Plan (DY-GP-KL, 2015).

Conducted a site reconnaissance at the Vamori Wash. This task included performing a geophysical investigation, consisting of both seismic refraction and Multi-spectral

Analysis of Surface Waves (MASW) methods.

Performed subsurface investigations, which included drilling, logging, and sampling

19 borings using both hollow-stem-auger and mud-rotary methods.

Performed laboratory testing on selected soil samples collected from the borings to evaluate pertinent geotechnical properties.

Performed engineering analyses and evaluations to develop recommendations.

Prepared this report.

Scour and erosion evaluations were not a part of this scope of work and will be provided by others.

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2.0 FIELD INVESTIGATION AND LABORATORY TESTING

The field investigation program for the Vamori Wash Crossing study consisted of (1) collecting geophysical measurements (surface wave and seismic refraction) and (2) completing borings using hollow-stem-auger and rotary wash methods. The locations of the investigations are shown on Figure 2. Appendices A through D provide details of the field investigation and laboratory testing.

2.1 HOLLOW STEM AUGER AND ROTARY WASH BORINGS

A total of 19 borings were drilled, sampled, and logged along the existing border patrol road and the Vamori wash area as part of this investigation. The depths of the borings ranged from approximately 37.5 feet to 121.5 feet. The borings were advanced using hollow-stem-auger drilling methods, except for four borings (ABUT-1, BENT-1, BENT-5, and BENT-6) which were drilled using a combination of hollow-stem-auger and rotary-wash drilling methods. These four borings were started using hollow-stem-auger drilling methods and switched over to rotary-wash methods once groundwater was encountered. The primary purpose of the boring investigation was to characterize soil and groundwater conditions and collect soil samples for laboratory testing. Additional details of the drilling program, including the boring logs, are included in

Appendix B.

2.2 GEOPHYSICAL SURVEYS

Surface wave and refraction geophysical measurements were collected along a 1,670-foot-long line along the existing border patrol road across Vamori Wash. The surface wave geophysical data were analyzed using MASW methods. The primary purpose of the geophysical measurements was to measure seismic pressure-wave (p-wave) and shear-wave (s-wave) velocities beneath the proposed crossing extents to evaluate existing soil and groundwater conditions. The results of the geophysical surveys along with other pertinent details are presented in Appendix C.

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Figure 2 - SITE PLAN

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2.3 LABORATORY TESTING

Selected soil samples recovered from the borings were tested at the geotechnical laboratories of Kleinfelder, in Phoenix, Arizona, to evaluate their physical and engineering properties. The laboratory tests performed consisted of dry density, moisture content, sieve analysis, Atterberg limits, compaction, expansion index, one-dimensional consolidation, direct shear strength, and a suite of corrosion tests (pH, chloride, minimum resistivity, soluble salts, and sulfate). Testing was performed in general accordance with ASTM International (ASTM) and U.S. Environmental

Protection Agency (EPA) standards. The results of the laboratory testing are included in

Appendix D.

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3.0 GEOLOGIC CONDITIONS

3.1 REGIONAL GEOLOGY

The project is located in the Basin and Range Physiographic and Tectonic Province of southern Arizona, which is characterized by low to mid-elevation mountain ranges and intervening broad basins or valleys. The basins and ranges are typically separated by inactive, buried normal faults. The late Cenozoic age basins are filled with alluvial material, generally consisting of sand and gravel, but also including silt and clay. Bedrock in the project area consists of Tertiary-, Mesozoic-, and Precambrian-age igneous rocks (generally of granitic composition), metamorphic rocks (mostly schist and phyllite), sedimentary rocks (generally sandstone and conglomerate), and Cenozoic-age volcanic rocks.

Figure 3a shows the Vamori Wash Crossing study area overlain on a regional geologic map of the area (Beikman, et al., 1995). The legend for Figure 3a is presented on Figure 3b. As shown on this geologic map, the Vamori Wash Crossing site is underlain by Quaternary surficial sediments (Qs) [herein referred to as alluvium].

The project site is not located within a seismically active region. The U.S. Geological Survey (USGS) Quaternary Fault and Fold Database (USGS, 2006) shows that there are no active faults within the study area. Also, the project area is not located near any mapped significant faults based on a review of the 2014 (USGS) National Seismic Hazard Maps. Additionally, the USGS Arizona Seismic Hazard Map (USGS, 2014) shows that the study area has a relatively low seismic hazard potential.

3.2 SITE TOPOGRAPHY AND SURFACE CONDITIONS

The project area generally consists of the main Vamori Wash stream channel and the smaller easterly and westerly draining channels that empty back into the main channel downstream of their existing road crossing. These channels are ephemeral and generally drain from south to north. The existing ground surface at the Vamori Wash Crossing site currently varies in elevation from about 2,525 to 2,530 feet.

The site is accessible by an existing dirt road that parallels the US-Mexico border fence.

Vegetation across the project area is generally dense outside the dirt road and drainage channels. The vegetation includes various cacti species, notably saguaro cacti, which are considered sacred by the T.O.N. A few outlying cattle stock ponds and cattle pens are also located near the study area.

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Figure 3a - SITE GEOLOGIC MAP

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Figure 3b - LEGEND TO ACCOMPANY GEOLOGIC MAP

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3.3 LOCAL GEOLOGIC CONDITIONS

The geotechnical investigation completed for this project encountered alluvium. Additionally, it is noted that an approximately 1-foot-thick layer of surficial gravel road base was encountered on top of the alluvial sediments in borings Bent-8 through Bent-10. A geologic profile of subsurface materials encountered in the borings is shown on Figure 4a overlain on the preliminary civil profile of the proposed high-water crossing. Details of the near surface portion (the uppermost

30 to 35 feet below the existing ground surface) are shown on Figure 4b. The geologic properties and descriptions of the alluvium observed during our investigation are discussed below.

3.3.1 Alluvium

Alluvium soil deposits were encountered extending from the existing ground surface to the full depth at all the drilling sites (121.5 feet below ground surface). Bedrock was not encountered within any of the boreholes. The alluvium observed in the investigation was predominantly sands and silty to clayey sands occasionally interbedded with a lesser amount of clay layers, as shown on the geologic profile in Figures 4a and 4bf. One location, Box-2 encountered clay throughout the upper 30 feet of the borehole. For purposes of discussion, we have classified the alluvium as either coarse-grained (i.e. sand, silty sand, clayey sand, etc.) or fine-grained (i.e.

clay, sandy clay, etc.). The characteristics of the coarse- and fine-grained alluvium are described below.

3.3.2 Coarse-Grained Alluvium

The coarse-grained alluvium primarily consisted of sand with occasional gravelly zones

(predominantly SC with lesser SM and SP) and occasional gravel layers (GC and GP). The coarse-grained alluvium was generally loose to dense (generally 5 to 40 blows per foot) in the upper 15 to 25 feet below ground surface (bgs), and below this depth, the coarse-grained alluvium was predominantly very dense (generally greater than 50 blows per foot). Direct shear tests performed on coarse-grained alluvium samples (31 tests) had an average friction angle of approximately 43 degrees (standard deviation = 8 degrees) and an average cohesion of approximately 1.0 kip pounds per square foot (ksf) (standard deviation = 0.7 ksf). The consolidation test results for samples collected within the upper 21 feet (2 total) indicated that the coarse-grained alluvium was relatively incompressible under static loading. The measured

12 Geotechnical Report v3.docx initial void ratios of these samples were both 0.4, and their change in height upon wetting ranged from 0% to 1.8% upon saturation (i.e. hydrocollapse).

3.3.3 Fine-Grained Alluvium

The fine-grained alluvium primarily consisted of clay (predominantly CL and rarely CH) with varying percentages of sand. The fine-grained alluvium encountered in the upper 5 to 10 feet bgs was generally medium stiff to stiff (generally 5 to 15 blows per foot), and the fine-grained alluvium encountered below this depth was predominantly very stiff to hard (generally 20 to greater than 30 blows per foot). The fine-grained alluvium was predominantly medium plastic with some highly plastic layers. The plasticity indices for the 39 tested fine-grained alluvium samples ranged from 16 to 49 and averaged 25. The direct shear tests performed on fine-grained alluvium samples (13 tests total) had an average friction angle of approximately 33 degrees (standard deviation = 8 degrees) and an average cohesion of approximately 1.3 ksf

(standard deviation = 0.4 ksf). The consolidation test results indicated the fine-grained alluvium was relatively incompressible under static loading. The initial void ratios of these samples (15 total) ranged between approximately 0.4 and 1.1. Additionally, laboratory tests within the upper

15 feet (2 total) indicated the fine-grained alluvium change in height upon wetting (i.e.

hydrocollapse) ranged from 0.1% to 0.5%. The average hydrocollapse for all fine-grained alluvium samples tested (15 total) was approximately 0.3% with the sample within Bent-8 at a depth of 46 feet swelling 0.1%.

Additionally, occasional caliche (also referred to as “hardpan”) layers composed of calcium-carbonate-cemented sediments were encountered in our subsurface investigation. The caliche layers encountered were generally white or white and brown in color, very hard, well cemented, and composed of carbonate-veined silty sand, sand, and gravel. The caliche layers were difficult to drill through, and refusal was encountered within a caliche layer at a depth of 36 feet bgs at boring Fill-2 using the CME-850 drilling rig and hollow-stem-auger drilling methods.

3.4 GROUNDWATER

In general, the project site which is located within the Lower Colorado River Planning Area, is relatively dry and receives little precipitation. The San Simon Wash Area, where the proposed

Vamori Wash Crossing is located, receives on average about 5 inches/year (ADWR, 2009).

Heavy rainfall in the site area is typically associated with the summer monsoon season with most of the rain in southern Arizona falling during July, August, and September, but overall

13 Geotechnical Report v3.docx rainfall is highly variable. Accordingly, the local streams and creeks are ephemeral, generally flowing only temporarily when storms occur or occasionally during winter months. For these reasons, it is expected that the regional static groundwater level at the project site is likely relatively deep below the existing ground surface. However, localized shallow perched zones likely persist as some of the surface water accumulated during flood events and other precipitation percolates through the highly variable alluvial layers.

Consistent with this regional context, groundwater at the site was observed during drilling at varying elevations and was primarily perched in thin, discontinuous saturated layers that generally occurred above relatively impermeable clay or clayey sand layers. Individual samples that appeared wet or saturated were noted, and in some cases, groundwater was measured directly through the hollow-stem augers, typically after leaving the borehole open overnight.

However, it should be noted that water levels measured in the hollow stem borings may not represent static groundwater levels, and may instead be associated with groundwater accumulating in the boring from the localized perched conditions. As summarized in Table 2, groundwater was observed in 11 of the 19 borings (Bent-1 through Bent-11) at depths ranging from approximately 5½ to 111 feet bgs. Groundwater observations in the borings are also shown on the geologic profile in Figures 4a and 4b. The layers where perched saturated conditions were observed during drilling were generally less than 10 feet thick.

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Figure 4a - SITE SUBSURFACE PROFILE

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Figure 4b -– SITE SUBSURFACE PROFILE (NEAR SURFACE PORTION)

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Table 1 - GROUNDWATER SUMMARY

BORING ID

SATURATED OR WET

MATERIAL OBSERVED

IN SAMPLES DURING

DRILLING

(feet bgs)

GROUNDWATER LEVEL

MEASURED DURING

DRILLING

(feet bgs)

Abut-1 -- -- Abut -2 -- -- Bent-1 10 to 20 -- Bent-2 5.5 to 10 52 Bent-3 10.2 to 10.3; 50 to 55 -- Bent-4 12.5 to 17.5 92 Bent-5 38.5 to 45 15.5 Bent-6 20 to 25 14 Bent-7 20 to 25 -- Bent-8 25 to 30; 110.5 to 111 36.6 Bent-9 15 to 19 12 Bent-10 22 to 25 63 Bent-11 -- 38.5 Box-1 -- -- Box-2 -- -- Fill-1 -- -- Fill-2 -- -- Fill-3 -- -- Fill-4 -- --

Notes

1. Samples appeared to be saturated upon removal from the sampler during drilling with hollow-stem augers.

2. Where the groundwater level was directly observed, it was measured within hollow-stem augers typically after leaving the borehole open overnight.

-- Saturated material or groundwater not observed.

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4.0 POTENTIAL GEOLOGIC HAZARDS

The following sections describe the potential for various geologic hazards at the Vamori Wash.

4.1 FAULT SURFACE RUPTURE

Large earthquakes in Arizona are rare, and no earthquakes in Arizona have ruptured the ground surface in historic time. As discussed above, the USGS Quaternary Fault and Fold Database

(USGS, 2006) shows that there are no known active faults within the project area, and the 2014

USGS National Seismic Hazard Maps show the project area is not located near any mapped significant faults. Therefore, potential for fault surface rupture at Vamori Wash is considered negligible.

4.2 SEISMIC SHAKING

The area of the site is not prone to significant earthquakes. As discussed above, the USGS

Arizona Seismic Hazard Map (USGS, 2014) shows that the study area has a relatively low seismic hazard potential (i.e. less than 0.10g expected for 2% in 50 years hazard level). Note that this geotechnical investigation did not include a project-specific evaluation of ground motions.

4.3 LIQUEFACTION POTENTIAL

Liquefaction can be defined as significant and relatively sudden reduction in stiffness and shear strength of saturated sandy soils caused by a seismically or statically induced increase in pore water pressure. The potential for seismically induced liquefaction exists whenever saturated, relatively loose, sandy soils exist with a high groundwater level and/or a potential for long duration high seismic shaking exists. Typically, liquefaction potential is greatest where submerged, loose fine sands occur within a depth of approximately 50 feet.

As discussed in Section 3.3.1 (Alluvium), the soils beneath the proposed improvements are predominantly sands, silty sands, and clayey sands. The sandy material in the upper 50 feet of the profile varies from loose to dense and the shallower portions of it could be considered susceptible to liquefaction.

However, shallow static groundwater was not encountered beneath the site and only occasional perched water conditions were observed within thin, discontinuous saturated layers generally

18 Geotechnical Report v3.docx less than 10 feet thick. Considering the relatively low probability for strong shaking at the site, and the predominantly dry unsaturated conditions, the potential for liquefaction at the site is considered low.

4.4 SEISMICALLY INDUCED SETTLEMENT

Seismically induced settlement is often caused when unsaturated loose to medium-dense granular soils are densified during ground shaking. Loose to medium-dense granular soils were observed near the ground surface at the site; however, due to the very low probability of strong seismic shaking in this area, the potential for seismically induced settlement is considered to be negligible.

4.5 SEISMICALLY INDUCED FLOODING

The potential hazard for seismically induced flooding is generally associated with a body of water located adjacent to the site or from seismically induced failure of a reservoir located on a drainage upstream of the site. Because there are no standing bodies of water located upstream of the project site and the hazard for seismic shaking in the vicinity of the site is very low, the potential for seismically induced flooding is considered to be negligible.

4.6 EROSION, FLASH FLOODS, AND DEBRIS FLOWS

The main Vamori Wash drainage and its smaller tributary channels cross the project area.

These channels show evidence of the seasonal occurrence of flash floods (water-deposited debris and brush), surficial runoff, and erosion from periodic storms that occur during Arizona’s late summer monsoonal season. Erosion is a concern within the project area, and the potential for erosion is high in the areas located within or close to the Vamori Wash channels.

Flooding during heavy rainfall is also a concern, with the most vulnerable areas located adjacent to the Vamori Wash channels. The potential for erosion can be reduced by covering critical surfaces with concrete, asphalt, rip-rap, or vegetation. The potential for flooding and erosion can be additionally reduced by controlling/diverting surface runoff (e.g., with a drainage channel) to carry water away from critical areas.

Debris flows are mixtures of water and debris that move downslope under the influence of gravity. They entrain and transport particles ranging from clays, silt, and sand to boulders tens of feet in maximum dimension. In Arizona, debris flows are particularly prevalent during

19 Geotechnical Report v3.docx monsoonal storms in recently burned terrain. Steep, mountainous topography with abundant poorly consolidated alluvial material is generally necessary to generate debris flows during a heavy rainstorm. This type of topography and deposits are not generally present in the project area; therefore, the debris flow potential is considered to be low.

4.7 EARTH FISSURES

Earth fissures generally form in deeper alluvial basins as a result of land subsidence driven by groundwater withdrawal. The Arizona Geological Survey (AZGS) has published earth fissure maps (AZGS, 2014), and their online Earth Fissure Map Viewer shows that no earth fissures have been identified in the study area (AZGS, 2014), although it appears that their mapping effort is ongoing. No earth fissures were observed during our work, and since there is no known extraction of fluid in the project area, the potential for earth fissures is considered negligible.

4.8 SLOPE INSTABILITY

Overall, the topography in the vicinity of the Vamori Wash project site is relatively flat and large landslides are not a potential hazard for the project. However, local sloughing and minor slides can potentially form where the natural banks of the wash and its tributaries are oversteepened or undermined and small pop-out slides and areas of minor sloughing were visible at the site along portions of the channel during our field investigation. These limited areas should not present a hazard to the project.

Where the project will introduce new slopes, provided that the new slopes are constructed according to the recommendations in this report and are protected from erosion and scour and their effects, these new slopes should remain stable.

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5.0 CONCLUSIONS AND RECOMMENDATIONS

Based on geotechnical and geologic considerations, the site is suitable for the proposed project.

Based on the maps and cross sections provided, there does not appear to be any significant areas of the high water crossing road that will act like a dam and retain water. The projected 25-year flood event will overtop the entire road length. It appears that scour will be the major issue, as well as durability of proposed asphalt road subjected to water flowing over it during high water events. Based on geotechnical and geologic considerations, the site is suitable for the proposed project. Based on the maps and cross sections provided, there does not appear to be any significant portions of the proposed high water crossing road and associated approach fills that will act like a dam and retain water during high-water events. The projected 25-year flood event will overtop the entire road length. It appears that scour and erosion will be a key issue, as well as durability of the proposed asphalt road subjected to water flowing over it during high water events.

Scour and erosion can generally be addressed with appropriate armoring such as the use of articulated block mats, rip-rap, revetments or other items and would include the sizing and selection of these elements (i.e. rip-rap size, etc.). However, note that we have not performed any scour or erosion evaluation specific to the proposed design. In order to perform such an evaluation, estimates of the anticipated flows are necessary. We understand that the 30% plans provided to us are preliminary and do not include such detailed estimates. Accordingly, once estimates of anticipated flows are completed, a scour and erosion evaluation should be completed to determine whether the proposed embankment and structure armoring is sufficient.

Also, note that based on the flood levels shown on the 30% design plans in Appendix A, water over-topping of the proposed crossing is anticipated within the lifetime of the project (i.e. less than 25 years). The extent of asphalt road maintenance and repair will depend on the severity and duration of the over-topping event and would require estimates of the anticipated flows.

However, it should be anticipated that minor overtopping (less than 1 foot above road level with duration less than an hour) might result in localized repairs and maintenance, whereas major overtopping (several feet above road level for several hours) might result in extensive damage.

Box culverts can be either segmented pre-cast, or cast-in-place (CIP). CIP box culverts can follow the Arizona Department of Transportation (ADOT) Structure Detail Drawings for

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Reinforced Concrete Box Culverts (ADOT, 2015) The following sections give our recommendations for design and construction.

5.1 EARTHWORK

Minor earthwork (cuts and fills less than approximately 10 feet) are anticipated to be required.

Based on the plans provided, most of the roadway alignment will consist of placement of fill to construct the roadway embankment.

5.1.1 Site Preparation and Grading

Areas excavated to receive fill should be cleared and stripped of all debris, deleterious matter, organic material and vegetation, and remnants resulting from demolition of any existing foundations or facilities. Cleared and grubbed material should be removed from the site for disposal.

After clearing the site of existing debris, the exposed subgrade should be observed for organic material or other undesirable materials. All loose or soft materials should be removed to firm subsurface layers. Compacted fill should be placed immediately upon approval of the prepared subgrade by the geotechnical engineer of record.

Prior to placement of the first lift of fill, the bottom of the excavation should be:

Scarified to a depth of 8 inches.

Moisture-conditioned to above optimum moisture content.

Compacted to at least 95% relative compaction.1

The bottom of the excavation should be firm, hard, and unyielding.

Where the soils at the bottom of the excavation preclude compaction, they should be excavated to a sufficient depth such that a firm and unyielding surface is achieved at the planned bottom of excavation or the base of fill. Generally, an overexcavation depth of 1 to 3 feet is sufficient.

Using geogrids and/or easily compactable material such as crushed rock can reduce the depth

1 Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same material, as determined by CE 55, MIL-STD-621Test Method 100. Optimum moisture content is the moisture content corresponding to the maximum dry density, as determined by the CE 55, MIL-STD-621Test Method 100. MIL-STE-621 Test Method 100 test procedure is similar to ASTM D1557 test procedure.

22 Geotechnical Report v3.docx of excavation. Geogrids, if necessary, should satisfy the requirements of the Uniform Facilities

Criteria (UFC).

Roadway embankment fill and backfill should be compacted by:

Placing in loose layers less than 8 to 12 inches thick.

Moisture-conditioning to within 2% of optimum.

Compacting to at least 95% relative compaction for subgrades below mat foundations and roadways.

The roadway aggregate layer over the embankment should be compacted to at least

100% relative compaction for access roadway surface aggregates.

Any compacted subgrade soils should be firm, hard, and unyielding.

Concrete flatwork (i.e., slabs-on-grade, sidewalks, hardscape, curbs, and gutters) should be underlain by a minimum of 12 inches of engineered soil compacted to at least 95% relative compaction and at least 2% above optimum moisture content.

Site grading may be accomplished with conventional heavy-duty construction equipment (see

Caterpillar Performance Handbook, 2014). Examples of conventional heavy-duty construction equipment are Caterpillar 815 to 825 series compactors or Caterpillar 816 to 850 series front-end loaders (see Caterpillar Performance Handbook, 2014). The compactors total weights range from 45,000 to 72,000 pounds. The axle weights for the compactors range from approximately 21,000 to 37,000 pounds. The front-end loader axle weights vary depending on the load in the bucket, but are in a similar range. Ground contact pressures can vary from 20 to over 1,000 pounds per square inch (psi) depending on the compactor wheel tip penetration.

The ground contact pressures for the front-end loaders also vary significantly. Therefore, we do not recommend that ground contact pressures be used to select compaction equipment. If compaction equipment is specified, the equipment type, vehicle weight, and/or axle weight should be used. To avoid overstressing retaining walls, backfill behind walls should be compacted using lightweight compaction equipment, or the walls should be braced. Note that the choice of equipment should be left to the contractor as a part of their means and methods.

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5.1.2 Material for Fill

The on-site granular soils (sands, silty sands with gravel) can be used as engineered fill. The clay soils encountered are not considered suitable for use as compacted fill beneath concrete sidewalks and paving. Oversize material (larger than 6 inches in diameter) should not be used in the fill. Any required import material should be approved by the geotechnical engineer of record prior to being placed at the site. Requirements for imported fill material or select backfill taken from on-site materials are summarized in Table 2 below. Select backfill is material placed within a horizontal distance of 5 feet or one-half of the wall height, whichever is greater, behind retaining/basement walls.

Table 2 - IMPORT FILL AND SELECT BACKFILL CRITERIA

CRITERIA IMPORT FILL SELECT BACKFILL

Maximum particle size (inches) 4 1 Maximum liquid limit (%) 10 5 Maximum plasticity index (%) 5 0 Maximum percentage passing the No. 200 sieve (%) 40 15 Minimum sand equivalent 10 20

The field density of fill should be measured in accordance with the sand cone method (ASTM

D1556) or the nuclear method (ASTM D6938).

5.1.3 Excavations and Temporary and Permanent Slopes in Alluvial and Fill Soils

The stability of temporary excavations is a function of several factors, including the total time the excavation is exposed, moisture condition, soil type and consistency, and contractor's operations. The contractor is responsible for excavation safety. As a guideline, temporary construction excavations greater than 3 feet but less than 15 feet deep in alluvial soils should be planned with slopes no steeper than 1 1/2H:1V (horizontal to vertical). For steeper temporary construction slopes or deeper excavations in alluvium, shoring should be provided for stability and protection. The contractor should strictly adhere to grading requirements of Pima County and applicable health and safety regulations, including those of the Occupational Safety and

Health Administration (OSHA).

Planned excavations are not expected to encounter rock. Permanent compacted fill slopes should be planned no steeper than 2H:1V. The slopes should be protected with rip-rap to reduce surface erosion. Static groundwater is not anticipated within the proposed depths of

24 Geotechnical Report v3.docx excavation (generally less than about 10 feet below existing ground surface). However, note that groundwater levels can fluctuate over time, and excavation or grading during the summer monsoon season may encounter temporarily elevated groundwater levels if operations follow shortly after heavy storms. In such a case, groundwater encountered in the excavations can likely be controlled by the contractor using sumps and pumps, but in general, construction should be scheduled for the dry season if possible.

5.2 ACCESS ROADWAYS

Access roads should be based on UFC design standards. Design indices (DI) or road classes were not provided by the design team. However, we have assumed for design purposes that that the proposed relocated road will sustain generally light traffic, handling mostly border patrol and maintenance vehicles, with occasional heavy vehicles such as tractor trailers, or large equipment on an infrequent basis. Based on visual classifications of the near surface soils at the boring locations and published correlations, a CBR value of 20 can be used for design of the proposed roadway, provided that the subgrade is prepared according to the recommendations in this report.

The roadway subgrade should be prepared prior to placing road base material. The existing subgrade should be proof rolled and locations where the native material is discovered to be soft or loose identified. The loose and/or soft soils should be removed, compacted, or replaced.

This may consist of reworking the upper portion of native soil and placing it as engineered fill.

The depth of rework can generally be limited to 12 inches; however, additional depth could be required based on observation in the field.

Any existing aggregate base can be recycled provided it meets the requirements in Table 3

(UFC, 2004c).

Table 3 - AGGREGATE BASE GRADATION

SIEVE SIZES PERCENT PASSING

1" 100

3/4" 87–100

No. 4 30–65

No. 30 5–35

No. 200 0–12

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For unpaved roads, the upper wearing course should consist of a minimum of 6 inches aggregate surface; the underlying subgrade can consist of in-place compacted native materials or fills. The aggregate surface course should be compacted to 100% relative compaction and moisture conditioned to within 2% of optimum moisture content. Underlying fills and native material should be compacted to 95% relative compaction and moisture conditioned to within

2% of optimum to a minimum depth of 1 foot. Individual lifts of base should be limited to 8-inches in loose thickness.

For asphalt paved roads, the asphalt thickness should be a minimum of 2½ inches and the underlying aggregate base should be a minimum of 6 inches. Depending on the desired resistance to erosion under heavy water overtopping, the actual required thickness of asphalt could be higher and once the road design criteria and estimated design flows are available, these recommendations should be updated.

The subgrade soils should be firm, hard, and unyielding, and not “pumping” prior to placing the aggregate surface course. If the subgrade soil cannot be compacted, the soil should be overexcavated as noted in Section 5.1.1.

The roadway should be designed and maintained to provide positive drainage and not allow ponding. Drainage ditches should lead to appropriate discharge points where ponding will not accumulate near the road base.

5.2.1 Drainage

Drainage Best management practices (BMP) should be used and maintained both during construction and over the entire life of the project.

The ground surface around structures should be graded so that water drains rapidly away from structures without ponding to reduce the potential for hydrocollapse. The surface gradient needed to accomplish this depends on the landscaping type, soil type, surrounding topography, and expected precipitation. Positive drainage should be established away from foundations and other structures. In general, positive drainage is established herein as a minimum slope of 5% extending 10 feet, if practical, away from structures. For areas covered with concrete or asphalt, the minimum slope may be reduced to 2%.

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5.2.2 Culvert Design

Box culverts can be either segmented pre-cast, or cast-in-place (CIP). CIP box culverts can follow the Arizona Department of Transportation (ADOT) Structure Detail Drawings for

Reinforced Concrete Box Culverts (ADOT, 2015)

CIP box culverts would tend to experience less differential settlement and associated surficial road cracking and maintenance than pre-cast unconnected segmental culverts.

In either case, a minimum of 3 feet of overexcavation and recompaction below the culvert foundations is required.

Bedding Requirements – Pipe bedding for pre-cast culverts should extend laterally a minimum of 6 inches below the invert of the pipe and a minimum of 12 inches beyond the pipe on both sides. Pipe bedding material should conform to requirements of UFC 3-220-01 2012 and should be compacted to at least 90% relative compaction and moisture-conditioned within 2% of optimum.

Trench Backfill – Backfill material should consist of granular material and be compacted to at least 90% relative compaction and moisture-conditioned to within 2% of optimum. Pea gravel or aggregate base should be avoided for use as general trench backfill to prevent preferential groundwater flow in trenches and potential migration of finer material.

Minimum Cover – A minimum of 1 foot of soil cover above the top of the culvert or that recommended by the culvert manufacturers, whichever is greater, should be maintained for all culverts.

The depth of scour (calculated and addressed by others) should be considered in the culvert and embankment design as well as other constraints.

5.3 SOIL CORROSION POTENTIAL

The corrosion potential of the on-site soil/rock materials was evaluated for its effect on steel and concrete structural members. The corrosion potential was evaluated using the results of the laboratory tests on selected soil samples obtained during our investigation (see Appendix D).

Based on the laboratory tests within the upper 25 feet of the ground surface, the on-site soil varies from corrosive to mildly corrosive to ferrous metals. We recommend that a corrosion

27 Geotechnical Report v3.docx consultant be retained to evaluate these results and anticipated types of metals, and recommend specific protection.

Based on the sulfate contents, the site may be classified as having a negligible sulfate exposure potential (sulfate concentrations <150 parts per million [ppm]). PH values were greater than 7, and chloride concentrations were less than 25 ppm, both of which are indicative of non-aggressive sulfate exposure conditions.

5.4 RESISTANCE TO LATERAL LOADS AND LATERAL EARTH PRESSURES

Retaining and subterranean walls and mat foundations should be designed to resist lateral earth pressures with the equivalent fluid pressures as illustrated on Figure 5. Lateral earth pressures are presented for walls free to rotate and restrained walls. At-rest earth pressures (restrained walls) should be used where the top of the wall is not expected to move laterally more than

0.001 H1 (see Figure 5). The lateral earth pressures on Figure 5 are based on natural on-site granular recompacted soils. See Figure 6 for typical sections of wall drains.

The lateral resistance may be calculated using the following: 50% of passive resistance plus

50% of base friction, 100% passive resistance only, or 100% of the base friction only. Lateral loads can be resisted by an allowable passive soil pressure and base friction, as outlined on

Figure 5 for compacted fill, applied against below-grade walls and foundation elements.

The passive earth pressure and coefficient of sliding friction values presented on Figure 5 include an implicit FS of approximately 1.5 because of simplifying assumptions (e.g., neglecting wall friction, Coulomb earth pressure theory) and assumptions regarding soil slab interface, respectively. Active earth pressures on Figure 5 do not include an implicit FS.

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Drainage Backfill

P

H

H

Weep Drain Select Backfill 1

HH

P Pp

P Pq oa, q (Surcharge)

Pp = 350 H2 4,000 psf Cantilever Walls Restrained Walls µ = 0.4 P = Pa + Pq = 35 H3 + 0.4q P = Po + Pq = 50 H3 + 0.5q

Notes:

All values of height (H) in feet, pressure (P) and surcharge (q) in pounds per square foot (psf), and force (F) in pounds.

Pp, Pa, and Po are the passive, active, and at-rest earth pressures, respectively.

Pq is the incremental surcharge pressure; µ is the allowable friction coefficient applied to dead normal

(buoyant) loads. Below groundwater, in areas of potential pipeline rupture, or areas of potential surface water infiltration, active and at-rest pressure should be reduced by 50% and hydrostatic pressure should be added to active and at-rest pressures. Pp should be reduced by 50% below the groundwater.

For 2H:1V slopes above the wall, increase the active and at-rest pressures by 50%; for 1.5H:1V slope, increase the active and at-rest pressures by 100%.

Neglect the upper 1 foot for passive pressure unless the surface is contained by a pavement or slab.

For walls with heights greater than 6 feet, an incremental seismic force should be considered.

See Figure 6 for drainage details.

Figure 5 - LATERAL EARTH PRESSURES

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Tendrain, or EquivalentPervious Material

Granular Material Free-Draining

4-Inch-Diameter

Impervious Soil Minimum 12-Inch

12-Inch

4-Inch Minimum

Minimum

Drainpipe Perforated Minimum

Geocomposite, Miradrain Manufactured Drainage

FOOTING