J.12_Geotech_Hatch_Final_VI_S&B_8-4-2008.pdf

FINAL

TECHNICAL MEMORANDUM

VOLUME I

FOR

Geotechnical Explorations of Levee System Within the Rio Grande Canalization Project

HATCH-TONUCO LEVEE SEGMENT

Prepared for:

United States Section, International Boundary & Water Commission

Submitted / Prepared by:

Project Manager: Daniel O. Rios Deputy Project Manager: Sharlotte L. Teague Task Order Manager: James Sassin, PE

In Association With:

Raba-Kistner Consultants, Inc.

Contract No. IBM05D0001 Task Order No. IBM08T0009

August 4, 2008

XX

XX

FINAL TECHNICAL MEMORANDUM

Geotechnical Explorations of Levee System Within the Rio Grande Canalization Project

Contract No. IBM05D0001 Order No. IBM08T0009 i

ACKNOWLEDGEMENT / CERTIFICATION

The preparation of this document included the collaborative participation of the following parties:

US Section, International Boundary & Water Commission

• Colleen Jaye Elliott Contracting Officer El Paso

• Josè A. Nuñez, PE Principal Engineer El Paso

• Steve Lyell Technical Manager El Paso

Contractor Team

• Daniel O. Rios Project Manager S&B, McAllen

• Sharlotte L. Teague Deputy Project Manager S&B, McAllen

• James Sassin, PE Task Order Manager S&B, Austin

• Chris L. Schultz Project Manager (Geotech) R-K, San Antonio

• John A. Focht III Chief Geotechnical Engineer R-K, San Antonio

• John Cordova, PE Project Engineer R-K, El Paso

• Jerrell “Bo” Blackmon GIS Manager S&B, McAllen

• Victor Pena Engineering Assistant S&B, McAllen

• Hazel Herrera Lead GIS Technician S&B, McAllen

All geotechnical sampling, testing, evaluations, and analysis for this Technical Memorandum were developed under a geotechnical study by Rabal-Kistner Consultants, Inc. entitled, “Geotechnical Exploration And Engineering Evaluation Of Levee System, The Rio Grande Canalization Project - Hatch/Tonuco Segment” dated August 4, 2008”.

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This Page Intentionally Blank iii

TABLE OF CONTENTS

VOLUME I: Page

SECTION 1 PURPOSE OF TECHNICAL MEMORANDUM

1.1 Introduction / Background ……………………………………… 1 -1

1.2 Project Description ………………..………………….…………. 1 -1

1.3 Scope of Work ………………..…………………………………. 1 -2

1.4 Records / References / Acronyms……………………..………… 1 -4

SECTION 2 GEOTECHNICAL EXPLORATION / EVALUATION

2.1 Levee Segment Description……………………….……………… 2 -1

2.2 Previous Geotechnical Studies……..………………….…………. 2 -1

2.3 Risk …………………………………..………………….…………. 2 -3

2.4 Limitations…………………………..………………….…………. 2 -4

2.5 Field Exploration……………………..………………….…………. 2 -5

2.6 Laboratory Testing……………..…………………………………. 2 -6

2.7 General Site Conditions……………………..…………..………… 2 -8

2.8 Impact of Sampling / Testing Procedures on Measured and

Design Soil Properties………………..………………….…………. 2 -11

2.9 Design Considerations……………………..…………..………… 2 -13

2.10 Slope Stability………………………………..…………..………… 2 -16

2.11 Seepage Analysis……………………..…………………..………… 2 -21

2.12 Erosion Protection……………………….…..…………..………… 2 -23

2.13 Settlement Associated with the Proposed Raised Levee………… 2 -24

2.14 Trafficability……………………………...…..…………..………… 2 -26

2.15 Conclusions…………………….……………..…………..………… 2 -26

2.16 Recommendations…………….……………..…………..………… 2 -26

2.17 Notes / Bibliography……………….…….…..…………..………… 2 -32

SECTION 3 GIS PROJECT DATABASE

3.1 Inventory …………………………….…..………………………… 3 -1

3.2 Survey & Mapping………..…………….……………….…………. 3 -2

3.3 Three-Dimensional Geographic Information System Model……. 3 -2

TABLES:

Page Table 1-1 Definitions / Acronyms……………..………………….…………. 1 -4

Table 2-0 Hatch-Tonuco Segment Condition Assessment by USACE 2 -2 Table 2-1 Hatch-Tonuco Levee Segment, Samples Collected.…………. 2 -6

Table 2-2 Hatch-Tonuco Levee Segment, Laboratory Tests.…………. 2 -6 Table 2-3 Hatch-Tonuco Levee Segment, Direct Shear Test Results…. 2 -7 iv

Table 2-4 Hatch-Tonuco Levee Segment, CD Triaxial Compressions. 2 -8 Table 2-5 Required Factors of Safety…………………………………………. 2 -17 Table 2-6 Soil Parameters………………………………………………………. 2 -19 Table 2-7 Computed Factors of Safety…………………………………… 2 -19 ~ 21

Table 2-8 Summary of Steady-State Seepage Analysis …………………. 2 -22 Table 2-9 Maintenance Roadway Base Gradation ………………………. 2 -31

FIGURES:

Page Figure 2-1 Hatch-Tonuco Levee Segment, Hydraulic Conductivity Test Results…. 2 -9

Figure 2-2 Assumed Geometries of Steady-State Seepage Analysis..……. 2 -22 Figure 2-3 Remedial Repair Option 1…………………………………....……. 2 -27

Figure 2-4 Remedial Repair Option 2…………………………………....……. 2 -27 Figure 2-5 Reconstruction Option ……………………………………....……. 2 -28

APPENDIX A FIELD DATA

A.1 Bore Coordinates & Elevations A.2 Logs of Borings A.3 Key to Terms & Symbols A.4 Results of Soil Sample Analyses

VOLUME II:

APPENDIX A FIELD DATA, continued.

A.5 Field Photos

APPENDIX B LABORATORY TEST REPORTS

B.1 Grain Size Distribution B.2 Consolidated Drained Triaxial Compression B.3 Hydraulic Conductivity (Permeability) Test Reports B.4 Direct Shear Test Reports B.5 Consolidation Test Report B.6 Dial Reading Vs. Time B.7 Consolidation Test Data

APPENDIX C SLOPE STABILITY, ANALYSES, AND RESULTS

v

APPENDIX D EXISTING CROSS-SECTIONS

APPENDIX E DESIGN CROSS-SECTIONS

APPENDIX F REVISED EMBANKMENT MATERIAL SPECIFICATION

APPENDIX G OPINION OF PROBABLE COST / BACK-UP DATA

G.1 Earthwork Calculations G.2 Estimated Material Dry Unit Weights Near Site Location G.3 Structure List G.4 Opinion of Probable Construction Cost (Construction by Contractor) G.5 Location Maps – Borehole / Levee Fill Data

EXHIBIT I BORE LOCATION MAPS

(Separate Cover)

EXHIBIT II DIGITAL ELEVATION MAPS

(Separate Cover) vi

SECTION 1 -1

1.0 PURPOSE OF STUDY

1.1 Introduction / Background

The United States Section of the International Boundary and Water Commission (USIBWC) conducted hydraulic and aerial geophysical studies of the Rio Grande Canalization Project to assess the ability of the associated levees to safely contain flood flows in the Rio Grande:

“Condition Assessment of U.S. International Boundary & Water Commission, Texas and New Mexico Levees” by the US Army Corps of Engineers (USACE) dated June 2004, and the “Flood Simulation Study of Rio Grande Levees Near Las Cruces, New Mexico, Using Seismic and Electrical Geophysical Methods” dated May 2007. From these studies, the USIBWC determined that certain reaches of the levees require rehabilitation improvements in order to meet Federal Emergency Management Agency (FEMA) requirements for the safe containment of 100-year flood flows.

The Rio Grande Canalization Project was completed in 1943 pursuant to Public Resolution No. 4- 74th Congress, Approved February 13, 1935, Control and Canalization of the Rio Grande- Caballo Dam, New Mexico to El Paso, Texas. The Project extends for 105.6 miles along the Rio Grande from Percha Dam to the American Dam at El Paso. The Rio Grande Canalization Project consists of a normal flow channel and a leveed floodway. The normal channel carries the irrigation releases from Elephant Butte and Caballo Dams to the headworks of irrigation projects developed by the US Bureau of Reclamation in New Mexico and Texas and also carries waters released for delivery to Mexico under the Treaty of 1906. The normal flow channel has a depth of 3 to 5 feet, a width ranging from 110 to 500 feet, and a capacity of 2,500 cubic feet per second (cfs) above Leasburg Dam to 1,200 cfs at El Paso. The floodway varies from about 50 to 2,100 feet in width.

Its bordering levees are 3 to 15 feet in height and have a total length of 130 miles. The crowns of the levees are gravel surfaced to facilitate access during flood emergencies and maintenance.

Some of the floodway lands are used for recreational purposes and the remainder largely for grazing and agriculture.

On February 13, 2008 a unilateral task order was issued by the USIBWC to S&B Infrastructure, Ltd. (S&B), as Contractor, to prepare a technical memorandum for geotechnical explorations and analysis of the existing levee system within the Rio Grande Canalization Project. S&B subcontracted the geotechnical exploration, laboratory testing, and evaluations to Raba-Kistner Consultants, Inc. The following information, along with a Borehole Location Map under separate cover, comprises the Technical Memorandum – Geotechnical Explorations of Levee System within the Rio Grande Canalization Project for the Hatch-Tonuco Levee Segment.

1.2 Project Description: Hatch-Tonuco Levee Segment

The Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project is approximately 26 miles in length (from River Mile 72 to River Mile 98) along the Rio Grande in Dona Ana County, New Mexico; the eastern levee extends from about River Mile 72 to a point near River Mile 98.

Whereas the eastern levee is contiguous along the entire alignment, the western levee only extends from about River Mile 76 to Mile 90. The average existing height of the east and west levee of the

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Hatch-Tonuco Levee Segment is approximately 7.2 feet and 6.0 feet, respectively. As a result of the previously referenced studies mentioned in Section 1.1, paragraph 1, and the determinations made by the USIBWC, it is also understood that the proposed levee will remain at its existing height in some areas, and up to 8 feet may be added in other areas of the alignment. For a majority of this section, additional heights of 5 feet or less are anticipated.

1.3 Scope of Work

The work to be performed included geotechnical investigations and evaluations along the alignment of the levee reach. Field work was coordinated with the USIBWC American Dam and Las Cruces Field Offices. The technical memorandum contains the findings of the geotechnical investigations and evaluations, and also includes a set of location maps (24 inch x 36 inch, scale1 inch = 1,000 feet) under separate cover.

The Contractor provided personnel and equipment necessary to perform geotechnical investigations and engineering evaluations, incorporating existing geotechnical studies provided by the USIBWC, and took into account slope stability, levee settlement, through-seepage, under-seepage, and trafficability of levees located in and around the Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project. The engineering evaluations conform to current engineering practices as defined by the US Army Corps of Engineers Engineering Manual 1110-2-1913, Design and Construction of Levees and 44 CFR 65.10. All samples were classified and recorded using standard reporting procedures.

Specific activities and requirements that were performed by the Contractor included the following:

1.3.1 Site Exploration – Borings.

1.3.1(a) The proposed boring locations were identified on project maps and submitted to the USIBWC for review prior to mobilization to the site. The boring spacings are approximately 1000 linear feet intervals. The Contractor provided recommendations with regards to other areas where additional borings were required to address associated previous meanders or areas of known highly variable soils identified by previous studies.

1.3.1(b) The borings were located and staked in the field by an engineer and geologist prior to drilling utilizing tape and right angle measurements from existing benchmarks.

Final boring locations were surveyed in the field by the USIBWC, and are included in Appendix A-1. Screening of locations were coordinated with the American Dam and Las Cruces USIBWC Field Offices.

1.3.1(c) The field drilling included borings at a spacing of no more than 1000 linear feet, altering the spacing where required to drill in identified anomalies discovered during the geophysical study and in areas defined by the Contractor. The spacing of borings were not arbitrarily uniform but rather based upon available geologic information. Boring depths were deep enough to provide data for stability analyses of

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the levee and foundation (at least equal to the height of proposed levee at its highest point but not less than 10 feet with distinctions made between borings for the preliminary stage and final-design stage). The boring depths identified below were based on a levee height of 7.5 feet or less combined with the additional height to be added identified in the USIBWC documents, taken to the next 5-foot increment. If auger refusal was encountered in these borings prior to achieving their intended depths, the borings would be terminated 10 feet into rock. The following outlines the depths and total linear footage of drilling for the Mesilla Levee Segment:

• Average Height of East Levee = 7.2 feet

• Average Height of West Levee = 6.0 feet

• Number of borings = 138

• Depth of Bores = 20 feet

1.3.1(d) All drilling activities were logged by the Contractor to include samples taken, major stratum changes, and general conditions of drilling and any unusual aspects of the boring location or drilling and sampling procedures.

1.3.1(e) Where auger refusal wass encountered, air-rotary and/or mud-rotary drilling techniques were utilized to advance the borings to their final depths, and grab samples were collected from the cuttings. Representative portions of all samples were sealed and packaged for transportation to the Contractor’s laboratory.

1.3.1(f) Standard geotechnical drilling techniques were utilized for all borings. The borings were backfilled utilizing bentonite grout. No containerizing and/or off-site disposal of the soil cuttings were required.

1.3.1(g) In all test borings, ground water level readings were taken upon completion of drilling activities, and the borings were backfilled in accordance with USIBWC’s Realty Office requirements.

1.3.2 Site Exploration – Soil Sampling.

1.3.2(a) All soil borings were sampled at 2.5-foot intervals in the first 5 feet, and at 5-foot intervals thereafter.

1.3.2(b) In sandy soils, Standard Penetration Test samples were collected. In cohesive soils, sampling was alternated between Shelby tube and Standard Penetration Test samples.

1.3.3 Site Exploration – Laboratory Testing.

1.3.3(a) In each boring, standard strength and classification testing were performed:

moisture content tests, Atterberg Limits (plasticity tests), gradation, and unconfined

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compression tests. In addition to the standard testing program, the following tests were performed on the basis of conditions encountered in the field:

• Consolidation Test = 1 per 4 miles (anticipating predominately sandy soils).

• Permeability Test = 1 per mile

• Double Hydrometer Test (dispersivity) = 1 per 2 miles

• Moisture Density Test = 1 per five miles

• Direct Shear or Consolidated-Drained Triaxials = 1 per 5 miles

1.3.3(b) All samples were classified and recorded using standard reporting procedures.

1.3.4 GIS Inventory, Database, and Mapping.

The Contractor developed a Geographic Information System (GIS) project inventory and database, as well as a three-dimensional (3D) model in both Environmental Systems Research Institute (ESRI) GIS format and AutoCAD Civil 3D 2008 format which captures all levee elevation information as well as soil boring locations and depths. The Contractor also produced location and analysis maps. A site visit was also performed where photographs and data was collected regarding physical features (cross-drainage structures, access roads, etc.) of the Hatch-Tonuco Levee Segment.

1.4 References and Definition of Acronyms

The following records and information were provided by the USIBWC and reviewed by the Contractor as background information:

• The USACE report “Condition Assessment of U.S. International Boundary & Water

Commission, Texas and New Mexico Levees” dated June 2004, with associated GIS, pdf, and other files.

• The report “Flood Simulation Study of Rio Grande Levees Near Las Cruces, New

Mexico, Using Seismic and Electrical Geophysical Methods” dated May 2007.

• Water surface profile for 100-year flood fully contained.

• Technical Memorandum: Conceptual Design Study of Replacement Canal Lining American Canal, American Dam to International Dam, Oct 2001.

• Environmental “Final Assessment, Flood Control Improvements to the Rio Grande

Canalization Project,” dated December 2007.

• Lidar Data.

• “Technica l Memorandum: Environmental Issues and Concerns, Conceptual Design Study of Replacement Canal Lining, American Canal, American Dam to International Dam,” Prepared for the USIBWC by Montgomery Watson Harza, June 7, 2002.

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• “Analysis of Contamination on the USIBWC Property in Relation to the ASARCO El

Paso Smelter,” prepared by Allen J. Medine, July 27, 2007.

• Old River Meander Schedule

Although some acronyms have been defined above, Table 1-1 below provides a consolidated summary of terms used throughout this Technical Memorandum.

Acronym Definition

3D three-dimensional CD consolidated drained CU consolidated undrained cfs cubic feet per second DEM Digital Elevation Model DLG Digital Line Graph EPA Environmental Protection Agency ERDC Engineer Research and Development Center ESRI Environmental Systems Research Institute FEMA Federal Emergency Management Agency GIS Geographic Information System (H:V) Slope, horizontal to vertical Hz Hertz IBC International Building Code kHz Kilohertz (1,000 Hertz) NED National Elevation Datasets R-K Raba-Kistner Consultants, Inc.

S&B S&B Infrastructure, Ltd.

SCAPS Site Characterization and Analysis Penetrometer System SPT Standard Penetration Tests TDS Total Dissolved Solids TxDOT Texas Department of Transportation USCS Unified Soil Classification System USIBWC United States Section, International Boundary and Water Commission USACE US Army Corps of Engineers USACE EM US Army Corps of Engineers Engineering Manual

Table 1-1: Definition of Terms

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SECTION 2 -1

2.0 GEOTECHNICAL EXPLORATION / EVALUATION

Raba-Kistner Consultants, Inc. (R-K) completed the authorized subsurface exploration and engineering analyses of the Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project located in south central New Mexico. The following briefly describes the procedures utilized during this study and presents R-K’s findings along with their geotechnical analyses of the levee which was performed in general accordance with the US Army Corps of Engineers (USACE) Engineering Manual (EM) 1110-2-1913 Design and Construction of Levees as it pertains to geotechnical evaluations.

2.1 Levee Segment Description

The Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project consists of approximately 26 miles of existing levees, all of which run parallel to the Rio Grande in New Mexico.

Whereas the eastern levee is contiguous along the entire alignment discussed above, the western levee has one gap which begins at the Mesilla Dam and extends to approximately Mile 41.5. In addition, the western levee terminates at approximately Mile 51.5, several miles south of the eastern levee.

On the basis of information provided by the USIBWC, it is understood that the average existing height of the east and west levee of the Hatch-Tonuco Levee Segment is approximately 5.4 feet and 6.1 feet, respectively. As a result of the previously referenced study, it is also understood that the proposed levee will remain at its existing height in some areas, while grade changes of up to 8 feet may be added in other areas of the alignment. For a majority of this section, additional heights of 5 ft or less are anticipated.

2.2 Previous Geotechnical Studies

The USACE Engineer Research and Development Center (ERDC) in Vicksburg, MS performed a condition assessment1 in 2004 of a portion of the levees along the Rio Grande in Texas and New Mexico. This document (USACE ERDC-TR-03-04) included the results of geophysical testing of the Hatch-Tonuco Levee Segment; it also subdivided the Hatch-Tonuco Levee Segment into sixteen (16) subsections identified as SRALT-01, RINCN-01, RINCN-02, RINCN-03, RINCN-04, RINCN-05, RINCN-06, HATCH-01, HATCH-02, HATCH-03, HATCH-04, HATCH-05, HATCH-06, ARCVO-01, ARCVO-02, and GRFLD-01, and outlined (in Table 2.2), the values and overall scores for the levee condition assessment for each subsection. An excerpt of this table is shown in Table 2-0 on the next page. The USACE ERDC study also included some limited soil sampling in specific areas using a Site Characterization and Analysis Penetrometer System (SCAPS). Six SCAPS probe locations were within the Hatch-Tonuco Levee Segment (HA01-01, RC03-01, RC05-01, RC01-01, SA01-01 and SA01-02.) The SCAPS probe findings are discussed on pages 6-41 and 6-43 of the report, and an enlarged image of the ‘EM signature’ of this section of the levee is presented on page 6-42. The specific frequencies used in developing this ‘EM signature’ are unclear, but are presumed to be a combination of 25 kHz and 115 kHz survey measurements.

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Table 2-0: Hatch-Tonuco Levee Segment Condition Assessment by USACE1

Segment ID Quad

Perfor-mance

Constr History

Visual Insp

Mat’l Type

Topo Irreg

Slope Stab

Man Inrt Geology

Borrow Areas Anom SCORE

Avg Score

Condition Assessment

SRALT-

01 Sierra Alta 3.0 2.0 3.0 0.5 3.0 0.0 3.0 0.5 4.0 3.0 59.0 5.90 Marginal

RINCN-

01 Rincon 3.0 2.0 3.0 0.5 2.0 0.0 4.0 1.0 4.0 4.0 62.5 6.25 Marginal

RINCN -

02 Rincon 3.0 2.0 3.0 0.5 3.0 1.0 4.0 1.0 4.0 4.0 68.5 6.85 Marginal

RINCN -

03 Rincon 3.0 2.0 3.0 0.5 3.0 1.0 3.0 0.5 4.0 4.0 64.0 6.40 Marginal

RINCN -

04 Rincon 3.0 2.0 3.0 0.5 3.0 1.5 4.0 1.0 4.0 4.0 70.0 7.00 Acceptable

RINCN -

05 Rincon 3.0 2.0 3.0 0.5 0.0 0.0 4.0 0.5 4.0 4.0 55.0 5.50 Marginal

RINCN -

06 Rincon 3.0 2.0 3.0 0.5 3.0 0.0 3.0 1.0 4.0 4.0 62.5 6.25 Marginal

HATCH-

01 Hatch 3.0 2.0 3.0 0.5 3.0 1.5 4.0 0.5 4.0 4.0 68.5 6.85 Marginal

HATCH-

02 Hatch 3.0 2.0 3.0 0.5 3.0 1.0 4.0 0.5 4.0 4.0 67.0 6.70 Marginal

HATCH-

03 Hatch 3.0 2.0 3.0 0.5 3.0 1.0 4.0 0.5 4.0 4.0 67.0 6.70 Marginal

HATCH-

04 Hatch 3.0 2.0 3.0 0.5 0.0 3.0 4.0 0.5 4.0 4.0 64.0 6.40 Marginal

HATCH-

05 Hatch 3.0 2.0 3.0 0.5 3.0 1.5 4.0 0.5 4.0 4.0 68.5 6.85 Marginal

HATCH-

06 Hatch 3.0 2.0 3.0 0.5 3.0 2.5 4.0 0.5 4.0 4.0 71.5 7.15 Acceptable

ARCVO-

01 Arroyo Cuerv 3.0 2.0 3.0 0.5 3.0 1.5 4.0 0.5 3.0 4.0 66.5 6.65 Marginal

ARCV0-

02 Arroyo Cuerv 3.0 2.0 3.0 0.5 4.0 2.5 4.0 0.5 1.0 4.0 68.5 6.85 Marginal

GRFLD-

01 Garfield 3.0 2.0 3.0 0.5 3.0 0.0 4.0 0.5 4.0 4.0 64.0 6.40 Marginal

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Under the USACE ERDC study, remote sensing of the alignment primarily consisted of an airborne electromagnetic survey using sampling frequencies of 400 Hertz (Hz), 1.5 kilohertz (kHz), 6.2 kHz, 25 kHz and 115 kHz. (Please note that the report text and plates do not agree on the highest frequency employed in this study. R-K has referred to the frequency shown on the plates.) The following statements are found on page 4-12 of the USACE ERDC study:

• Airborne electro-magnetic results for the entire condition assessment study area are perhaps best discussed with reference to the 102 (sic) and 25 kHz frequency data.

Effective depth of investigation at these frequencies is within the body of the levee and immediately below the base of the levees roughly 15 to 20 feet in depth.

• The levees and their shallow foundations on both sides of the Rio Grande from

Garfield, NM to near Fabens, TX (about 30 miles southeast (SE) of El Paso) consist almost entirely of dry, fine-grained sands and silts (with predominantly blue and dark blue airborne EM signatures). These reaches comprise all of the Canalization and a portion of the Rectification levees.

R-K did find some locations with significant thicknesses of clay (e.g. HT-61, HT-115, HT-181.)

However, the erratic and discontinuous nature of the encountered clays appears to be consistent with the findings of the EM survey. R-K confirmed the presence of deep gravels at discontinuous locations (HT-54) like those encountered at SCAPS probe SA01-01. R-K concurs with the ERDC report conclusion that the subsurface soils consist largely of fine-grained sands and silts.

2.3 Risk

The geotechnical engineering design recommendations contained in this report are intended to provide the USIBWC with final design information. R-K has attempted to provide guidance regarding the impact of various design choices on calculated factors of safety with respect to calculated slope stability. The design factors of safety used for this study were taken from USACE EM 1110-2-1913 dated April 30, 2000. The selection of a given design factor of safety implicitly includes a decision regarding the level of acceptable risk for a project. The geotechnical study for this Technical Memorandum did not include an independent evaluation of risk with respect to levee performance, and adopted the published USACE design factors of safety as the current performance standards for these types of structures. Levees are only designed to provide protection to a certain flood level; R-K did not determine the chosen design flood level, and the selection of this parameter is outside R-K’s area of expertise. R-K understands that the USIBWC used the computer program FLO-2D to evaluate the water surface profile for the 100-year design flood in accordance with the current FEMA Levee Certification criteria. Furthermore, for the purposes of this Technical Memorandum, it has been assumed that the maximum time that the levee would be subjected to the design flood level is 48 hours or less.

It is important to note that the levee systems are being designed to perform a required function (retain flood waters) under stated conditions (during a 100-year flood event) for a specified period of time (assumed to be 48 hours or less.) The design may not be adequate for a different storm event or longer performance period, and unexpected damage to the levees may result in the need for repairs to the levee and/or levee improvements over time. The enclosed design

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recommendations inherently assume that the levee will be properly maintained and regularly inspected by trained and qualified personnel. The design recommendations also assume that any identified repairs will be made promptly, and the adequacy of the levee system will be regularly assessed, fully taking into account changes in weather, land use and evolving design and performance standards, with changes made as appropriate.

The geotechnical properties of the soils encountered in this study involve significant variability.

This variability includes some spatial variability; however, the spatial variability appears to occur over relatively short distances. R-K did not observe geological sections along the Hatch-Tonuco Levee Segment alignment distinct enough to justify subdividing the alignment into subsections for analysis. The basis for this statement is substantiated by findings presented in USACE ERDC /GSL TR-03-04, Report 2, June 2004, as discussed in the Section 2.2 herein, and where Table 2-0 identifies the same material type and geological references for all sixteen (16) Segment IDs of the Hatch-Tonuco Levee Segment. As such, R-K treated the entire alignment as a single unit. It is important to note that levees differ from other types of structures, such as drilled piers or driven piles, in that the performance of the levee involves local, not average, soil conditions.2 The selection of design parameters for this project was based on a review of the available geotechnical data, R-K’s knowledge of the project area, design calculations using idealized geometries and the assumption that the soils are relatively uniform with depth and position on the basis of conditions encountered in R-K’s borings. The results of R-K’s analyses were then reviewed with respect to important trends and general design concepts, keeping these conditions and limitations in mind.

R-K’s recommendations are based on a conservative approach to design as is warranted for all levee structures. R-K believes that the combination of observed conditions and probable failure modes justifies this approach.

2.4 Limitations

The geotechnical engineering information within this Technical Memorandum has been prepared in accordance with accepted Geotechnical Engineering practices in the region of southeast New Mexico for the use of the USIBWC, and its representatives for design purposes. This Technical Memorandum may not contain sufficient information for purposes of other parties or other uses.

The recommendations submitted in this Technical Memorandum are based on the data obtained from 216 borings drilled along the alignment of the Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project; R-K’s understanding of the project information provided by the USIBWC, and the assumptions with regard to water elevations and durations that are discussed in greater detail herein. If the project information described in this report is incorrect, is altered, or if new information is available, R-K should be retained to review and modify recommendations contained herein.

The geotechnical engineering information within this Technical Memorandum may not reflect the actual variations of the subsurface conditions across the site. This is particularly true with regard to existing groundwater levels that are likely to be highly variable based on precipitation events and the percent of sands versus fine grained materials. The nature and extent of variations along the levee may not become evident until construction commences. The construction process itself

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may also alter subsurface conditions. If variations appear evident at the time of construction, it may be necessary for R-K to reevaluate these recommendations after performing on-site observations and tests to establish the engineering impact of the variations.

The scope of this geotechnical exploration / evaluation of the Hatch-Tonuco Levee Segment does not include an environmental assessment of the air, soil, rock, or water conditions either on or adjacent to the site. No environmental opinions are presented in this Technical Memorandum.

If final added heights along the levee are significantly different from those provided by the USIBWC (more than plus or minus 12-inches), R-K should be informed about these changes. If needed and/or if desired, R-K will reexamine these analyses and make supplemental recommendations.

2.5 Field Exploration

Representatives of R-K made visual observations of the existing levee conditions in conjunction with marking the boring locations in the field. General observations were made of the existing levee configuration including side slopes and vegetative cover.

Subsurface conditions along the Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project were evaluated by 216 borings. The borings were spaced at approximately every 1,000 feet along the Hatch-Tonuco Levee Segment alignment, and were drilled to a minimum depth of about 20 to 35 feet. Given the conditions encountered in the project borings and the design recommendations contained in this Technical Memorandum, R-K believes that the number and depth of borings is sufficient for the intended purpose.

The borings were drilled at the locations shown on the Boring Location Map in Exhibit I. The borings are designated HT-1 through HT-216 and the drilling logs are presented as Figures 2 through 217, of Appendix A-2. The locations shown on the Boring Location Map in Exhibit I and described on the boring logs were provided by S&B. The boring locations were estimated from the boring location maps provided by S&B on February 25, 2008; final locations (after drilling) were field surveyed by the USIBWC, and the results (boring coordinates and elevations), in tabular form, are included in Appendix A-1.

The borings were drilled to depths of about 20 to 35 feet below the existing top of levee using truck-mounted drilling rigs. The borings were advanced using a modified hollow-stem auger procedure. Upon completion of drilling, cement-grout was used to backfill holes. During drilling operations, samples were collected as shown in Table 2-1 on the next page.

The Shelby tube samples and the Standard Penetration Tests (SPT) were obtained in general accordance with accepted standard practices. Selected portions of the samples were sealed in containers to reduce moisture loss, labeled, packaged, and transported to R-K’s laboratory for subsequent testing and classification.

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2.6 Laboratory Testing

In the laboratory, each sample was evaluated and visually classified by a member of R-K’s Geotechnical Engineering staff in general accordance with the Unified Soil Classification System (USCS). The geotechnical engineering properties of the strata were evaluated by the laboratory tests tabulated in Table 2-2 below.

With the exception of the laboratory consolidated undrained (CU) triaxial tests, hydraulic conductivity tests, and direct shear tests, the results of the field and laboratory tests are presented in graphical or numerical form on the boring logs illustrated on Figures 2 through 238 of Appendix A-2. A key to the classification of terms and symbols used on the logs is presented on Figure 218 of Appendix A-3. The results of the laboratory and field testing are also tabulated on Figure 219 of Appendix A-4 for ease of reference.

Type of Sample Number Collected

Hatch-Tonuco Levee Segment Borings:

Split-Spoon (with SPT) 1556

Shelby Tubes 11

Grab Samples 1

Bulk Samples (from auger cuttings) 45

Table 2-1: Hatch-Tonuco Levee Segment, Samples Collected

Type of Test Number Conducted

Natural Moisture Content 1388

Atterberg Limits 198

Sieve Analysis 607

Percent Passing No. 200 Sieve 383

Hydrometer* 22

Unconfined Compressive Strength 1

Dry Unit Weight 2

Consolidated Undrained Triaxial Test* 5

Multi-Stage Direct Shear* 23

Hydraulic Conductivity (Permeability)* 45

* Additional testing is currently being performed

Table 2-2: Hatch-Tonuco Levee Segment, Laboratory Tests

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SPT results are noted as “blows per foot” on the boring logs and on Figure 219 of Appendix A-3, where “blows per foot” refers to the number of blows required for a falling 140-pound hammer to penetrate 12 inches into the subsurface materials. Where hard and/or very dense materials were encountered, the tests were terminated at 50 blows even if one foot of penetration had not been achieved.

Samples will be retained in the R-K laboratory for 30 days after submittal of the Final Technical Memorandum.

2.6.1 Strength Tests. Multi-stage direct shear tests were performed on 23 selected samples.

These samples were subjected to various normal loads and sheared at a rate of 0.007 inches per minute. Samples tested are composite in nature and were obtained as grab samples from auger cuttings along the depth interval shown. The samples were reconstituted in the lab to simulate in-situ densities in the field. The results of the multi-stage direct shear tests presented graphically and numerically in Appendix B-3, are also summarized in the table below.

Peak Conditions Residual Conditions

Boring

No.

Depth

(ft)

Length

Sample Type Friction

Angle, φ deg

Apparent Cohesion tsf

Friction Angle, φ deg

Apparent Cohesion tsf

Visual

Classification

HT-10 10 5 Grab 32.0 0.286 32.0 0 ML HT-20 5 10 Grab 33.6 0.166 32.4 0.112 SP HT-25 5 10 Grab 34.1 0.101 32.5 0.048 SP HT-35 5 10 Grab 35.3 0 34.6 0 CL HT-40 7 3 Grab 37.3 0.049 36.7 0.033 SM HT-45 5 10 Grab 35.5 0.022 35.9 0 SM HT-62 10 5 Grab 26.2 0.237 26.1 0.220 CL HT-67 0 5 Grab 33.7 0.067 31.9 0.057 SM HT-70 10 4 Grab 36.6 0.286 35.3 0.050 SP HT-75 7.5 2.5 Grab 32.9 0.173 32.3 0.155 SP HT-80 10 5 Grab 33.3 0.222 31.0 0.178 SP-SM HT-85 10 5 Grab 34.4 0.112 32.4 0.088 SP-SM

HT-100 0 5 Grab 37.1 0.105 37.3 0.063 SP-SM HT-116 10 5 Grab 30.8 0.195 29.2 0.177 SP-SM HT-134 10 5 Grab 36.9 0.162 33.6 0.112 SP-SM HT-143 10 5 Grab 38.1 0.018 37.9 0 SP HT-150 15 5 Grab 33.9 0.205 33.8 0.199 SP HT-155 10 5 Grab 33.6 0.198 31.2 0.180 SP HT-160 10 5 Grab 35.2 0.175 32.6 0.173 SP-SM HT-170 15 5 Grab 30.3 0.212 28.8 0.202 SP HT-180 5 10 Grab 31.7 0.122 31.4 0.077 SP HT-185 15 5 Grab 36.2 0.107 34.4 0.077 SM HT-205 10 5 Grab 31.3 0.146 30.5 0.142 SP

Table 2-3: Hatch-Tonuco Levee Segment, Direct Shear Test Results

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The drained shear strengths of 5 selected soil samples were determined using consolidated drained (CD) triaxial compression tests. These samples were subjected to four stages of increasing normal loads and sheared at a rate of 0.01 inches per minute.

Samples tested are composite in nature and were obtained as grab samples from auger cuttings anlong the depth internval shown. The samples were reconstituted in the lab to simulate in-situ densities in the field. The results of the CD triaxial tests are presented in graphical / numerical form in Appendix B-2; they are also summarized in Table 2-4 below.

Boring

No.

Depth

Length

Sample Type

Friction Angle, φ deg

Apparent Cohesion tsf

Visual Classification

HT-110 10 5 Grab 34.8 0 SP-SM HT-125 5 10 Grab 30.8 0 CL-ML HT-190 0 5 Grab 33.7 0 SP-SM HT-195 0 5 Grab 35.1 0 SP HT-215 15 2 Grab 34.5 0 SP-SM

Table 2-4: Hatch-Tonuco Levee Segment, CD Triaxial Compression Results

2.6.2 Hydraulic Conductivity (Permeability) Tests. Hydraulic conductivity (permeability) tests were performed on remolded, composite samples obtained from 27 borings along the Hatch-Tonuco Levee Segment. These samples were remolded to simulate in-situ conditions. The remolded specimens were tested for vertical hydraulic conductivity to assess the seepage velocities of the subsurface soils. The results of the hydraulic conductivity (permeability) tests are presented numerically in Appendix B-3, and are also summarized below.

Based on the USACE EM 1110-2-1901 Seepage Analysis and Control for Dams, indirect methods for determining hydraulic conductivity may also be used. For uniform, loose clean sands classified as SP (poorly graded sand), the Hazen equation (Taylor, 1948) is suggested for use. Figure 2-1 on the next page graphically presents the results of hydraulic conductivity testing as well as results calculated using the Hazen equation.

2.7 General Site Conditions

The following outlines the general site conditions of the Hatch-Tonuco Levee Segment of the Rio Grande Canalization Project.

2.7.1 Site Description. The existing levee system along the project alignment was observed to have heights ranging from 0 to 15 feet and crest widths between 7 to 20 feet. The top of the levees were relatively level and were free of vegetation. The side slopes were sparsely covered with some grass and small bushes. Overhead electrical power lines, a few gas lines and several bridges transverse the project alignment at different points along the Rio Grande.

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0 50 100 150 200 250 300

Samples Tested

0.0001

0.001

0.01

0.1 H

yd ra ul ic

C on du ct iv ity

, c m

/s ec

K values calculated using Hazen formula K values from laboratory testing on reconstituted soil samples

Figure 2-1: Hatch-Tonuco Levee Segment, Hydraulic Conductivity Test Results

Numerous pecan tree orchards, farm fields, and various residential structures were observed along the both sides of the project alignment. In particular, the number of residential structures increased significantly within the area near Hatch, New Mexico.

New Mexico State Highway 185 and Interstate Highway 25 run roughly parallel to the project alignment.

Sections of hilly and mountain terrains were observed along various sections of the project alignment. Houses were observed on the top and/or sides of the hilly terrain as well as within the river valley.

2.7.2 Site Geology. The Hatch-Tonuco Levee Segment is located within the confines of the Rio Grande Rift, a continental rift belt comprised of echelon extensional basins that originate in central Colorado and extend through New Mexico, and possibly into northern Chihuahua Mexico and west Texas. The Rio Grande Rift is characterized by deep asymmetrical, sedimentary basins, high heat flow from volcanic activity, and Quaternary-age faulting causing basin subsidence and infilling with sediments.3 The sediments have been informally divided into the upper, middle, and lower Santa Fe units which are underlain by Cretaceous age limestones in the southern New Mexico basins, i.e. Hatch / Tonuco basin.

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The upper Santa Fe sediments are subdivided into the overlying Camp Rice and underlying Fort Hancock Formations which are found within the Mesilla basin of New Mexico and the Hueco Basin of Texas and extend to depths of up to 10,000 feet. The Fort Hancock Formation generally consists of silt and clay basin floor sediments that inter-finger into ephemeral streams originating in the surrounding highlands.3 The sediments were primarily deposited in closed basin lacustrine playas that were fed from ephemeral streams. Exotic clasts are minimal throughout the Fort Hancock formation implying a non-through flowing Rio Grande existed during deposition of the Fort Hancock Formation.3

The Camp Rice Formation consists of fluvial deposited gray coarse-grained, cross-bedded sand and gravel that has incised unconformably into the Camp Rice Formation.4,5,3 Gravel clasts within the Camp Rice Formation comprise a wide variety of distant and local resistant rock type sources.

The specific project setting is located along the levee of the Rio Grande which was channelized in the 1930’s as part of a valley-wide flood control and irrigation project.

The Rio Grande Floodplain deposits represent the most recent incision of the Rio Grande into the Camp Rice formation and were deposited during the late Pleistocene through the Holocene Epochs.4,5 The thickness of the Rio Grande Floodplain deposits are up to 200 feet thick comprised of distant and local source sediments ranging from gravel to silt size. Crevasse splays are the typical deposition pattern encountered on the Rio Grande floodplains and are comprised of thin fans of sand and silt.4,5 These sediments are spread across the floodplain during a break in a natural or artificial levee caused by a flood event. The splay grows uniformly progressively coarser and sandier until channels are cut into the top of the splay. These channels are then filled with coarse sediment that becomes progressively finer-grained upward, opposite the majority of the splay deposition.4,5 These channels are discontinuous, often become commingled, and are difficult to correlate across short distances.

2.7.3 Seismic Coefficients. Based upon a review of Section 1615 Earthquake Loads – Site Ground Motion of the 2006 International Building Code (IBC), the following information has been summarized for seismic considerations associated with this site.

Note that the project covers a substantial geographic range. As such, the values taken from the IBC charts also vary across the project. The following parameters are presented as a range and represent the south-eastern most boring (HT-1) to the north-western most boring (HT-138); these values presented are for Boring HT-1 and Boring HT-106138, respectively.

• Mapped Maximum Considered Earthquake Ground Motion for a 0.2 sec., Spectral

Response Acceleration (Figure 1613.5(1)): Ss = 0.273 to 0.271g.

• Mapped Maximum Considered Earthquake Ground Motion for a 1 sec., Spectral Response Acceleration (Figure 1613.5(2)): S1 = 0.088 to 0.085g.

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2.7.4 Stratigraphy. The subsurface conditions observed in the borings performed for this study were relatively consistent along the entire length of levee. In general, the fill soils consisting of locally available soils were observed at the levee crest, extending to the natural ground elevations. These fill soils were observed at depths ranging from about 15 ft to areas without any existing levee structure. Beneath the fill soils, predominately naturally deposited sands were observed to depths of about 20 to 35 ft, the maximum depths explored.

As with any linear project that crosses spatially diverse conditions, a number of thin cohesive soil layers and layers with varying silt fractions were observed at different depths and thicknesses. A detailed exposition of these minor variances is not addressed in this text. However, a detailed description of the soil conditions observed at each boring location has been presented in the boring logs, Figures 2 through 217 of Appendix A-1. The lines designating the interfaces between strata on the boring logs represent approximate boundaries. Transitions between strata may be gradual.

The predominate soils observed in the borings were classified as poorly graded sands (SP), poorly graded sands with silt (SP-SM), and silty sands (SM). However, areas of well graded gravels (GW), well graded sands with silt (SW-SM), clayey sands (SC), lean clays with sand (CL), fat clays with sand (CH), silts with sand (ML), and sandy silty clays (CL-ML) were also observed.

2.8 Impact of Sampling / Testing Procedures on Measured and Design Soil Properties

2.8.1 Permeability. Soils were deposited along the Rio Grande floodplain through a series of natural processes, primarily by transport by water and wind. The soils beneath the levee embankments are primarily sands and were generally deposited by the Rio Grande river system, with some relatively thin, fine layers of sand and silt deposited by wind during dust storms. The soil deposits exhibit spatial variability, with resulting anisotropy inherent in the gradation and permeability of the natural deposits. In general, the horizontal permeability of the soil strata are expected to be at least 2 to 5 times greater than their vertical permeability.

The man-made sand embankments also expected to exhibit some spatial variability, although the variations would not seem to be as great as the variations within the natural soil deposits. However, the process of constructing the levees by compacting soils in relatively thin lifts can also result in significantly greater horizontal permeability compared to vertical permeability. Each lift required a finite amount of time to construct; the interfaces between lifts often dry out and develop a thin layer of loose surficial soils, which exhibit a higher permeability than the soils in the middle of the lift. It is also likely that the sands were compacted dry of their optimum moisture content using non-vibratory smooth drum compaction equipment. Soils compacted dry of optimum moisture content exhibit significantly higher field permeability than the

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same soils compacted to the same density, but wet of optimum moisture content.

Smooth drums on compaction equipment are not capable of generating the kneading action needed to mechanically destroy the inter-lift discontinuity in the compacted soil lifts. All of these factors permit the development of higher horizontal permeability than might be expected. These factors are exacerbated if the construction contractor also used fairly thick compaction lifts.

The potential impacts of natural soil and compacted soil fill layering on permeability are significant. Under ideal conditions, the field exploration and laboratory testing programs would be aimed at harvesting and testing undisturbed soil samples so that the in-place soil permeability could be measured. Unfortunately, the predominate soil types encountered in this study are very difficult to sample and test in an undisturbed condition. As a result, conventional practice is to obtain disturbed soil samples and perform the various laboratory tests on reconstituted, or remolded, samples, and to make adjustments to the measured values when evaluating their probable behavior in the field. The sampling process destroys the structure and orientation of layers of differing characteristics, and distributes the fine-grained silt and clay fraction throughout the bulk sample. The process of harvesting large volumes of soil and remolding samples has the effect of homogenizing the samples, generally resulting in lower tested permeability. The impact on tested permeability can be significant.

Laboratory measured permeability can be several orders of magnitude lower than the actual maximum field permeability.

The laboratory permeability tests were conducted using ordinary tap water as the permeate in accordance with industry practice. This choice can affect the tested permeability where the soils contain significant amounts of soluble salts, or the tap water contains unusually high amounts of total dissolved solids (TDS). R-K does not believe that the tested samples contained significant amounts of TDS, and the tap water used in the tests meets current Environmental Protection Agency’s (EPA) drinking water standards. Given the soil types tested for this study, R-K does not believe that changes in the tested samples’ TDS, if any, had a significant impact on the measured results.

The laboratory permeability tests were performed using hydraulic gradients as high as

30. This test condition is much higher than the typical expected field gradient of less than 0.5. Excessive laboratory hydraulic gradients can cause migration of silt and clay particles within the sample, significantly reducing the measured permeability.

However, R-K does not believe that particle migration significantly affected the test results. Particle migration often occurs when the gradient is applied instantaneously.

The test gradient was gradually applied over several minutes in an effort to avoid this problem.

2.8.2 Inferred Permeability. The laboratory grain size analyses were used in conjunction with the Hazen6 formula to provide an estimate of permeability. The Hazen formula

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was developed using filter sands with effective sizes between 0.1 and 3 millimeters and uniformity coefficients of less than 5. For this limited range of clean sands, permeability estimates computed using the formula generally was within 20 percent (20%) of the measured values.

The soils tested for this study generally do not meet the effective size or fines fraction requirements of the soils Allen Hazen used to develop his correlation. However, in many cases, the effective sizes of the tested sands are close enough to the sands tested by Hazen that the equation can be used to provide some indication of the variability of permeability of the soils. In general, we would expect that the laboratory permeability will be lower than the value calculated using Hazen’s correlation.

2.8.3 Depth-To-Water. Free water was encountered in the majority of exploratory borings conducted for this project. The depth-to-water levels recorded during drilling are considered short-term water level readings.