J.10_TR-03-04_Rpt2_VI_Cond_Ass_USIBWC_Levees_TX_ _NM_6-2004_USACE.pdf

Condition Assessment of U.S. International Boundary & Water Commission, Texas and New Mexico Levees, Volume I, Main Text

Joseph B. Dunbar, William L. Murphy, June 2004 Robert F. Ballard, Thomas E. McGill, Linda D. Peyman-Dove, and Micheal J. Bishop

ERDC

Distribution is authorized to U.S. Government agencies only; administrative or operational use; June 2004. Other requests for this document shall be referred to Geotechnical and Structures Laboratory, ATTN: CEERD-GS-G, U.S. Army Engineering Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199.

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ERDC TR-03-4 Report 2 June 2004

Condition Assessment of U.S. International Boundary & Water Commission, Texas and New Mexico

Volume I, Main Text and Appendices

Joseph B. Dunbar, William L. Murphy, Robert F. Ballard, Thomas McGill

Geotechnical and Structures Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199

Linda D. Peyman-Dove, Michael J. Bishop

Environmental Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199

Final report

Distribution authorized to U.S. Government agencies only;

administrative or operational use; June 2004. Other requests for this document shall be referred to Geotechnical and Structures Laboratory, ATTN: CEERD-GS-G, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199.

Prepared for U.S. Army Corps of Engineers

Washington, DC 20314-1000

ABSTRACT:

The U.S. Army Engineer Research and Development Center (ERDC) performed a condition assessment of the U.S. section of the International Boundary and Water Commision (IBWC) levees along the Upper Rio Grande Valley (URGV) in Central New Mexico and West Texas. ERDC and the IBWC conducted the condition assessment using airborne geophysics, geologic studies, groudtruth investigations, and an Enterprise Geographic Information System (eGIS). The assessment encompassed 231 miles of levee in Donna Anna and Sierra Counties, New Mexico, and El Paso, Hudspeth, and Presidio Counties, Texas. The goal of the assessment was to detect, identify, and map potentially unstable levee reaches that require repair or replacement. The condition assessment will enablae levee managers to priortize embankment reaches for preventive and remedial measures based on best engineering practice.

Airborne or overhead geophysical surveying was the primary method used to assess the condition of IBWC levees in New Mexico and Texas. Airborne methods include multifrequency electromagnetic (EM), digital video, magnetic (magnetometer), and high-resolution topgraphy using LIDAR (acronym for Light Detection and Ranging) technology. Results of the study indicated the soil conductivities measured by the EM system and their spatial signatures accurately identified levee composition and predicted foundation geology. The 231 miles of levees were divided into segments based on their EM signatures. A levee condition rating system based on 10 factors was used to numerically score and rank the levee segments. Of the 102 levee segments scored, 14 percent, rated “Acceptable,” and 86 percent, rated “Marginal.” No levee segment was rated "Good" or "Poor" for overall condition.

DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

DESTRUCTION NOTICE: For classified documents, follow the procedures in DOD 5200.22-M, Industrial Security Manual, Section II-19, or DOD 5200.1-R, Information Security Program Regulation, Chapter IX. For unclassified, limited documents, destroy by any method that will prevent disclosure of contents or reconstruction of the document.

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Contents

Conversion Factors, Non-SI and SI Units of Measurement ................................ vii

Preface................................................................................................................ viii

Executive Summary ...............................................................................................x

Acronyms and Abbreviations ............................................................................. xiii

1 Introduction ................................................................................................. 1-1

Purpose ............................................................................................................ 1-1

Scope ............................................................................................................... 1-1

Background and study area ............................................................................. 1-1

Approach ......................................................................................................... 1-4

2 Development of Condition Assessment Criteria ....................................... 2-1

Levee condition assessment design considerations ......................................... 2-1

Ten-point criteria............................................................................................. 2-4

Condition assessment results......................................................................... 2-10

3 Geographical Information System ............................................................. 3-1

Purpose and scope ........................................................................................... 3-1

Physical requirements and standards............................................................... 3-1

GIS database development .............................................................................. 3-2

Technology transfer......................................................................................... 3-9

4 Airborne Reconnaissance and Surveying.................................................. 4-1

Introduction ..................................................................................................... 4-1

LiDAR............................................................................................................. 4-1

Electromagnetic and magnetic ........................................................................ 4-2

Airborne survey results ................................................................................... 4-7

5 Geologic Investigation ................................................................................. 5-1

Introduction ...................................................................................................... 5-1

Regional and local geologic settings ................................................................ 5-1

Geologic mapping of levee areas ..................................................................... 5-3

6 Ground Truth Procedures and Results ..................................................... 6-1

Purpose ............................................................................................................. 6-1

Data acquisition procedures ............................................................................. 6-1

Results of field investigations ........................................................................ 6-12

7 Conclusions and Recommendations .......................................................... 7-1

Conclusions ...................................................................................................... 7-1

Recommendations ............................................................................................ 7-2

References .........................................................................................................R-1

Appendix A: Levee Condition Survey Scores................................................... A-1

Appendix B: GIS Data Dictionary ....................................................................B-1

Appendix C: Report: Furgo Resolve Survey Phases

III and IV IBWC Levees, December 2002 ....................................C-1

Appendix D: SCAPS Logs IBWC Phase III and IV ......................................... D-1

Appendix E: Laboratory soils test data ..............................................................E-1

List of Figures

Figure 1-1. Location of topographic quadrangles surveyed for

Canalization, Rectification, and Presidio levee assessment ............ 1-3

Figure 2-1. Example of segment numbering, showing segments for Presidio West and Presidio East quadrangles ............................. 2-2

Figure 2-2. Example of completed condition assessment form for levee segment 5 of Hatch (NM) quadrangle .............................. 2-3

Figure 2-3. Statistical distribution of levee condition assessment scores, 103 levee segments, all criteria, URGV levees ............................. 2-12

Figure 4-1. “Fli-Map” system deployment, John Chance Land

Survey, Inc....................................................................................... 4-3

Figure 4-2. Helicopter-deployed EM and magnetometer similar to the RESOLVE system flown for Phase III and IV levee condition surveys ................................................................... 4-5

Figure 4-3. Cross section through levee showing flight paths of airborne EM/magnetometer survey sonde....................................... 4-6

Figure 4-4. Color contour map of conductivity from 25 kHz-frequency airborne EM system, Presidio, Texas area ...................................... 4-8

Figure 4-5. Sengpiel section for a segment of levee........................................... 4-9 iv v

Figure 4-6. Airborne EM color table maps for frequencies

400 Hz, top, and 1.5 kHz, bottom, Presidio, TX ............................ 4-10

Figure 4-7. Airborne EM color table maps for frequencies 6.2 kHz, top

And 100kHz, bottom, San Juan SE quadrangle............................. 4-11

Figure 5-1. Cross-section through Rio Grande Rift and valley fill at Albuquerque, NM .................................................................. 5-2

Figure 5-2. View of Rio Grande looking upstream toward El Paso, around 1934.Oblique photograph is in vicinity of San Jose, TX, during Rectification process.................................................... 5-5

Figure 5-3. Same view of Rio Grande without annotation looking upstream toward El Paso around 1934. ........................................... 5-6

Figure 5-4. Close-up view of meander loop in Figure 5-2 showing borrow pits used to build up the levee............................................. 5-6

Figure 5-5. Plan view of the are of Figure 5-2 through 5-4 in 1940 .................. 5-7

Figure 5-6. Plan view of the area of Figure 5-5 in 1996 .................................... 5-8

Figure 5-7. Plan view of the area of Figures 5-5 and 5-6 in 1996...................... 5-9

Figure 6-1. Areas of USIBWC levees surveyed in URGV and LRGV.............. 6-2

Figure 6-2. SCAPS vehicle ................................................................................ 6-4

Figure 6-3. Configuration of SCAPS truck ........................................................ 6-5

Figure 6-4a. SCAPS soil sampler retrieved from sample depth......................... 6-6

Figure 6-4b. Soil sample retrieved with SCAPS ................................................ 6-6

Figure 6-5. Configuration of cone penetrometer tip and sleeve ......................... 6-7

Figure 6-6. Plot corrected sleeve friction versus corrected cone resistance for cone penetrometer soil classification................ 6-9

Figure 6-7. Cone penetrometer and equivalent USCS soil

Classification (below) derived from friction ratio column of real time record (above) ............................................................ 6-10

Figure 6-8. SCAPS probe showing resistivity bands ....................................... 6-11

Figure 6-9. SCAPS probe log for probe site PE 03-02, Presidio Reach, IBWC levees........................................................ 6-13

Figure 6-10. Plasticity chart of fine-grained soils from Phase III and IV levee investigation ........................................................... 6-15

Figure 6-11. SCAPS probe locations, Presidio Reach...................................... 6-17

Figure 6-12. SCAPS probe locations, Rectification Reach .............................. 6-18

Figure 6-13. SCAPS probe locations, Canalization Reach .............................. 6-19

Figure 6-14. EM color spectrum for electrical conductivity (right).

On left is a segment of surveyed levee showing variations in EM encountered ...................................................................... 6-20

Figure 6-15. SCAPS boring locations, Presidio Reach .................................... 6-21

Figure 6-16. SCAPS boring locations, Rectification Reach, south .................. 6-22

Figure 6-17. SCAPS boring locations, Rectification Reach, north .................. 6-23

Figure 6-18. SCAPS boring locations, Canalization Reach, south .................. 6-24

Figure 6-19. SCAPS boring locations, Canalization Reach, north................... 6-25

Figure 6-20. Airborne EM signatures, Presidio Reach..................................... 6-26

Figure 6-21. Airborne EM signatures, Rectification Reach, Esperanza........... 6-29

Figure 6-22. Airborne EM signatures, Rectification Reach, McNary.............. 6-31

Figure 6-23. Airborne EM signatures, Rectification Reach, Acala.................. 6-33

Figure 6-24. Airborne EM signatures, Rectification Reach, Isla, TX .............. 6-35

Figure 6-25. Airborne EM signatures, Rectification Reach, Ysleta, TX.......... 6-36

Figure 6-26. Airborne EM signatures, Canalization Reach, south ................... 6-38

Figure 6-27. Airborne EM signatures, Canalization Reach, central................. 6-40

Figure 6-28. Airborne EM signatures, Canalization Reach, north ................... 6-42

List of Tables

Table 2-1. Condition factors for rating levee condition ................................... 2-13

Table 2-2. Values and overall scores for levee condition assessment, USIBWC Phase III and IV levees .................................................. 2-14

Table 3-1. Model components and related GIS database files ......................... 3-11

Table 3-2. Hierarchical directories and subdirectories for

USIBWC Upper Rio Grande Valley (URGV) GIS database .......... 3-12

Table 4-1. RESOLVE-delivered products and maps, USIBWC

Texas Levee Survey ........................................................................ 4-13

Table 6-1. Data summary, USIBWC URGV SCAPS probes........................... 6-44

Table 6-2. Laboratory soils tests, USIBWC levees URGV.............................. 6-46

Table 6-3. Summary of laboratory soil-test results on samples from Presidio, TX to Hatch, NM..................................................... 6-47

Table 6-4. USIBWC URGV levees, possible anomalies.................................. 6-48 vi vii

Conversion Factors, Non-SI and SI Units of Measurement

Non-SI units of measurement used in this report can be converted to SI units as follows:

Multiply By To Obtain cubic feet 0.02832 cubic meters cubic feet per day 28.32 liters per day degrees 0.01745 radians degrees Fahrenheit (F-32) 5/9 degrees Centigrade feet 0.3048 meters feet per day 0.0003528 centimeters per second gallon 3.785 liter gallons per day 3.785 liters per day gallons per day per foot 12.42 liters per day per meter gallons per minute per foot 12.42 liters per minute per meter cubic feet per minute 28.32 liters per minute feet per minute 0.508 centimeters/second inches 2.54 centimeters inches 25.4 mm inches 25,400 microns mile 1.609 kilometer parts per billion 1.0 micrograms per liter parts per million 1.0 milligrams per liter square miles 2.590 square kilometers square feet 0.0929 square meters square feet per day 0.0929 square meters per day pounds force per square inch 6894.757 pascals pounds (force) 4.448222 newtons

Preface

This report documents field airborne electromagnetic and LiDAR surveying, ground-truthing, soil sampling, soils analysis, and geologic analysis of Upper Rio Grande Valley (URGV) U.S.

International Boundary and Water Commission (USIBWC) levees between Presidio, Texas and Garfield, New Mexico. This report, Report 2, documents follow-up investigations to levee condition surveys described in a report published in 2003 by the US Army Corps of Engineers Engineer Research and Development Center (ERDC) entitled “Condition Assessment of U.S.

International Boundary and Water Commission, Lower Rio Grande Valley Levees, South Texas”, ERDC TR-03-4, October 2003. Funding for the URGV work was authorized by a Memorandum of Understanding IBM-01-12 between the USIBWC and ERDC, and by subsequent Individual Work Orders (IWO). Mssrs. James Stefanov and James Robinson of USIBWC, El Paso, TX, were the program managers for this study and monitored the work.

The report was written by Mr Joseph B. Dunbar, geologist and program manager, Geotechnical and Structures Laboratory (GSL), Mr. William L. Murphy, geologist, GSL, Mr.

Robert F. Ballard, geophysical contractor, Soils Engineering & Geophysics, Inc., Mr Thomas E.

McGill, geologist, GSL, Mr. Michael J. Bishop, physical scientist, EL, and Dr. Linda P. Peyman- Dove, landscape architect, Environmental Laboratory (EL).

This investigation and report were a joint effort of two ERDC laboratories and private industry. The GSL provided technical oversight of airborne geophysical surveying and performed technical and geological analysis of data. GSL performed ground-truth field investigations, including soil sampling and analysis, to corroborate the airborne survey results.

The EL developed and documented a Geographical Information System (GIS) to store and present the data.

SCAPS system field operations and data acquisition were performed by Mssrs Karl F.Konecny, EP-E under the direct supervision of Mr. John H. Ballard, EM-J, Fred D. Shirley, Instrumentation Engineering Branch (IE-A), and Marvin E. Hadley, Public Works (PW-C).

Messrs Murphy and Thomas E. McGill of GSL provided inspection during ground-truthing operations. Airborne geophysical surveying of the levees was performed by Fugro Airborne Surveys, Mississauga, Ontario, Canada. Complementary airborne LiDAR surveys were performed by John Chance Land Surveys, Inc., Lafayette, LA, a Fugro subsidiary.

The authors gratefully acknowledge the support and assistance of USIBWC personnel in several field offices, particularly Mssrs. John Lee and Hector Hernandez, Presidio Area Project Manager and Assistant Project Manager, respectively; and Mr. Hector Maynes, Project Manager at American Dam. Ms Julie Kelley, GSL, prepared many of the plates presented in Volumes II, III, and IV of this report.

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GSL work was performed under the direct supervision of Dr. Lillian Wakeley, Chief, Engineering Geology and Geophysics Branch, Dr. Robert Hall, Chief, Geosciences and Structures Division, GSL. Dr. David W. Pittman was acting Director, GSL during the period of this investigation. Dr. James R. Houston was Director, ERDC and COL James R. Rowan was Commander, ERDC.

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Executive Summary

The U.S. Army Engineer Research and Development Center (ERDC) performed a condition assessment of levees along the Middle Rio Grande River Valley (URGV) in Central New Mexico and West Texas for the U.S. section of the International Boundary and Water Commission (IBWC). This is the second report of a series involving the condition assessment of IBWC levees. ERDC performed a similar condition assessment of 270 miles of IBWC levees in the Lower Rio Grande Valley (LRGV) in Fiscal Year 2001 and 2002 (Dunbar and others, 2003). Both studies involved an assessment of IBWC levees using airborne geophysics, geologic studies, and ground truth investigations.

The condition assessment described herein encompassed approximately 231 miles of levee in Donna Anna and Sierra Counties, New Mexico, and El Paso, Hudspeth, and Presidio Counties, Texas. The condition assessment study involved three areas: Canalization, Rectification, and Presidio. An Enterprise Geographic Information system (eGIS) was developed to manage the digital data and assist with the condition assessment process in each area. The goal of the assessment was to detect, identify, and map potentially unstable levee reaches that require repair or replacement. In addition, the condition assessment will enable managers to prioritize and identify preventive and remedial measures for embankments based on best engineering practice.

A basic understanding of the processes of levee failure along the Mississippi River Valley System exists from historical experience and documented study by USACE Districts and Divisions. ERDC investigators recognized, however, that geology, construction techniques, and material properties unique to New Mexico and Texas levees may cause the levees to exhibit failure mechanisms different from those of the Mississippi system. It was necessary, therefore, to establish an understanding of URGV levee and foundation characteristics before appropriate geophysical techniques could be effectively applied and understood for condition assessment.

Levee failures are governed in large part by the soils that form the embankments and their foundations. Water seepage through the levee embankment can produce internal erosion of the levee soils. Foundation problems in levees usually are caused by under-seepage and are related to geologic conditions at the site. Because levees are underlain by floodplain deposits, knowledge of the geology of local floodplain deposits is an important consideration in flood control management. Levee systems are often built on highly permeable, relatively coarse-grained river deposits representing point bars, old channels, and courses of the river system abandoned during its history of meandering over the floodplain. Sandy sediments associated with these deposits xi represent the most likely locations for under-seepage in levee systems. Similar conditions exist on the URGV system.

Thus, it was imperative that geologic features be identified in the earliest stages of a levee condition assessment so that other exploratory methods could be used to map their distribution. Knowledge of fluvial processes and the ability to recognize depositional environments in the geologic record are the key to identifying locations along modern levees where under-seepage has the greatest potential to occur. Development of a comprehensive GIS to effectively manage long-term levee condition assessment and flood-control data was also essential.

Developing of the condition assessment model involved a one-day workshop by ERDC with U.S. Army Corps of Engineers (USACE) geotechnical experts in flood control to develop procedures for performing numerical levee condition assessments using quantitative and qualitative descriptors. As a result of the workshop, ERDC produced a levee condition tabulation form with ten criteria.

Important criteria discussed in the workshop included construction history, past performance, material type, floodplain geology, anomalous conductivity zones, and river migration rates. In this rating system, a higher rating number or score always represents a better condition. Of the 102 levee segments scored, 14 percent, rated “Acceptable”; and 86 percent, rated “Marginal”. No levee segment was “Good” or “Poor” when rated using the mean of all ten criteria.

A comprehensive GIS database was developed for the URGV levee condition assessment study area. GIS technology was used to develop and analyze the database to address levee condition assessment factors. The GIS also functioned as one of the project’s primary data management tools. The GIS data management tool consisted of a functional, integrated geospatial information base containing available baseline data, engineering geology data, and geophysical data acquired from existing sources or collected specifically for this project. It was designed to provide support for geo-information integration, storage, access, retrieval, and sharing to all study partners. The GIS can be used to fully integrate, analyze, and display data in such a way that up-to-date levee conditions are readily available. In the future, preventive and remediation efforts can be reliably planned and prioritized based upon the best information available.

Airborne, or overhead, geophysical surveying was the primary method used to assess the condition of IBWC levees in Central New Mexico and West Texas.

Airborne methods included multi-frequency electromagnetic (EM), digital video, magnetic (magnetometer), and high-resolution topography using LiDAR (an acronym for Light Detection and Ranging) technology. Airborne surveys were flown in September 2003 in an integrated fashion to perform levee condition assessments. Fugro Airborne Surveys, Mississauga, Canada, conducted an airborne, multi-frequency electromagnetic survey using a helicopter-borne digital helicopter electromagnetic system (i.e., RESOLVE system) to collect resistivity and conductivity measurements for the levee surveys in five discreet frequencies.

Three survey lines were flown over the levees to adequately describe the levee electrical and magnetic characteristics. One line was flown down the levee centerline and one each along the toes of the levee about 160 ft from the centerline. The total width of survey was about 320 ft. The towed bird sensor operated at a nominal survey altitude of 100 ft with an average aircraft speed of about 50 knots. Sample rate was equivalent to 1 sample every 10 ft at a survey speed of 60 knots. GPS data were collected simultaneously.

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Airborne EM results for the entire condition assessment study area are based on the 102 and 25 kHz frequency data. Effective depth of investigation for these two frequencies is approximately 15 to 20 ft depending on the floodplain soils.

Conductivities reflect material type and physical condition of soils primarily within the levees and in the upper 5 to 10 feet of foundation. Field verification studies indicate that low conductivity signatures identify sand and/or more porous levee soils and high conductivity identifies clayey soils, one can predict or estimate composition of the levees and underlying foundations. Levees along and parallel to the Middle Rio Grande are constructed and underlain by primarily low conductivity or sandy soils. This picture is consistent with the varied depositional facies that typify the floodplain environment in the URGV from geologic studies.

Airborne geophysical investigations provided remotely sensed data relating to the electrical and magnetic properties of the ground surface and the subsurface soils. ERDC performed confirmation of airborne geophysical signatures and material properties (called ground-truthing) by conducting Site Characterization and Penetrometer System (SCAPS) borings. The SCAPS probed the levees and the levee foundations (to a depth of at least twice the levee height) and produced logs of soil physical properties and soil samples for laboratory testing. Results of boring investigations indicated the airborne methods would accurately predict soils used in levee construction and underlying foundations.

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Acronyms and Abbreviations

ArcIMS – Arc Internet Mapping Service ASCII – American Standard Code for Information Interchange BIL – Band Interleaved by Line (a data format) CD – compact disc CD-ROM – compact disc, read-only memory cm – centimeter(s) CPT – Cone penetrometer technology DEM – Digital Elevation Model DIGHEM – Digital Helicopter Electromagnetic DOQQ – digital orthophoto quarter quadrangle DRG – Digital Raster Graphics EM – electromagnetic EMI – electromagnetic induction ERDC – Engineer Research and Development Center ESRI – Environmental Systems Research Institute FDEM – Frequency-domain electromagnetic FGDC – Federal Geographic Data Commmitee Fli-Map –software and hardware in support of airborne surveying system ft – feet FY – fiscal year GIS – geographic information system GPS – global positioning system Hz – Hertz (unit of electromagnetic frequency) USIBWC – International Boundary and Water Commission – U.S. Section JCLS – John Chance Land Surveys K – hydraulic conductivity Klab – Laboratory measured hydraulic conductivity LiDAR – light detection and ranging LRGFCP – Lower Rio Grande Flood Control Project LRGV – Lower Rio Grande Valley M - million MrSID – Multi-resolution Seamless Image database NAD – North American Datum NED – National Elevation Dataset NIM – Nuclear Research Instrument NLCD – National Land Cover Dataset NRCS – Natural Resources Conservation Service OD or O.D. – outside diameter PTO – power take-off QA – quality assurance RTCM – Radio Technical Commission for Maritime services xiv

SARIS – Scintrix automated electrical resistivity system SCAPS – Site Characterization and Analysis Penetrometer System SDSFIE – Spatial Data Standard for Facilities, Infrastructure and Environment sec – second(s) SSURGO – Soil Survey Geographic Database S-VHS – Super Video Home System TDEM – Time-domain electromagnetic TIFF – Tagged Image File Format TOWNS – Technologies and Innovations for Urban Watershed Networks URGV Upper Rio Grande Valley USCS – Unified Soil Classification System USGS – United States Geological Survey UTC – Universal Coordinated Time XYZ - A three-coordinate data point or file.

µm – micron (one millionth of a meter)

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1 Introduction

Purpose This report documents a condition assessment of the U.S. section of International Boundary and Water Commission (USIBWC) levees along the Upper Rio Grande River Valley (URGV) and its floodways in southwest Texas and New Mexico. This section of the Rio Grande valley is known as the Canalization and Rectification area and includes a short segment near Presidio, TX. The U.S. Army Engineer Research and Development Center (ERDC) and the USIBWC carried out the integrated condition assessment using airborne and surface geophysics, geologic studies, ground truth investigations, and an Enterprise Geographic Information System (eGIS). The assessment encompassed approximately 231 miles of river levees. The goal of the assessment was to detect, identify, and map potentially unstable levee reaches that require repair or replacement. In addition, the products of the condition assessment will enable managers to prioritize levee reaches and identify preventive and remedial measures for embankments based on best engineering practice.

Scope The work documented in this report comprises Phases III and IV of the USIBWC levee condition assessment. Phases I and II, which covered levees in the Lower Rio Grande Valley (LGRV, were accomplished in 2001 through 2003.

Airborne surveys for Phases III and IV were completed in 2002 and ground surveys and ground-truthing in 2003. Geologic mapping, laboratory soils testing, condition assessment, data reduction, and report preparation were performed in 2003 and 2004. The study was limited to United States levees; levees under Mexican jurisdiction were not included.

The methodology described in this report is considered to be applicable at a research and development level nationally and globally for other areas that might require rapid assessment of levee condition.

Background and study area USIBWC program engineers recognized a potential need for assessment of its levees in the late 1990’s. Considering the threat from major hurricanes, engineers foresaw potential levee instability from movement of river water through or under the levees, removing soil in the foundation or levee by piping.

Representatives from the USIBWC’s El Paso office approached the U. S. Army

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Corps of Engineers, Galveston District for assistance. Galveston District personnel referred USIBWC to ERDC, where a proposal for condition assessment was presented to USIBWC in October 2000. The ERDC is a world leader in flood control research.

USIBWC subsequently funded ERDC for a 4-Phase condition assessment of LRGV and URGV levees. Phases I and II incorporated 25 U.S.G.S. 7-1/2 minute topographic quadrangles near the mouth of the Rio Grande, which comprised the study area and formed the basis for the condition assessment evaluation. Phase I work was documented in Dunbar et al 2003. Phases III and IV included geophysical and geological investigations to assess the structural integrity of levees in the Presidio Flood Control and Rio Grande Rectification (Texas), and Rio Grande Canalization (New Mexico) projects, a total of 30 topographic quadrangles. Figure 1-1 shows the surveyed area represented by the 30 topographic quadrangles. This report documents Phases III and IV work, which was divided into two phases because of multiyear funding by USIBWC. Phase III involved data collection, data formatting, and airborne surveying in the three project areas. Phase IV work consisted of geologic mapping, data reduction, interviews with USIBWC project personnel, condition assessment of the levees, and preparation of this report.

Canalization and Rectification are part of the Upper Rio Grande Project (URGP) of USIBWC. The URGP extends along the Rio Grande from Percha Diversion Dam, located 27 miles downstream of Elephant Butte Dam in New Mexico, downstream to the southern end of Hudspeth County, Texas, a distance of some 204 river miles (USIBWC 2004). The Canalization project carries out the delivery of waters of the Rio Grande, under provisions of the 1906 Water Treaty with Mexico. Under the treaty, responsibilities include protecting valley lands in the United States from floods, stabilizing the river channel, and improving drainage of adjacent lands.

The Canalization Project was completed in 1943 pursuant to the Act of June 4, 1936. The Project extends for 105.6 miles along the Rio Grande from Rio Percha to the American Dam at El Paso. The 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 U.S. Bureau of Reclamation in New Mexico and Texas and also carries waters released for delivery to Mexico under the 1906 convention. The normal flow channel has a depth of 3 to 5 ft, 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 floodway lands are used for recreational purposes and the remainder largely for grazing and agriculture.

The Rio Grande Rectification Project is largely a result of sedimentation problems created by the completion of Elephant Butte Dam in New Mexico in 1916 (TSHA 2004). The Federal Government decided to straighten and trench the Rio Grande from the lower limit of Cordova Island at El Paso downstream to Box Canyon, below Fort Quitman, Texas. The United States and Mexico signed the Rio Grande Rectification Treaty in 1933. The agreement called for

0 125 25062.5 Miles

Figure 1-1. Location of topographic quadrangles surveyed for Canalization, Rectification, and Presidio levee assessment.

New Mexico

Texas

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1-4 construction of a levee-protected floodway 590 feet wide and a normal flow channel with a bottom width of 66 ft. Levees would average 7 ½ feet in height.

Engineers shortened the river from 155 miles to 85 miles.

However, “straightening the river channel” has created a new potential threat

– that of underseepage that might occur where levees were constructed directly over the old riverbed. In most instances, the old riverbed is filled with pervious materials that permit passage of flood waters beneath the levee to the land side.

This potential problem is recognized and treated in this report in the geologic analysis of each levee segment of all three projects.

The three USIBWC projects investigated in Phases III and IV have approximately 231 miles of levees. Levee widths range from 40 ft on the low levees to 120 ft on the high levees.

Approach A basic understanding of the processes of levee failure along the Mississippi River exists from historical experience and documented study (Wolff, 2001, USACE, 1956a and 1956b). ERDC investigators recognized, however, that geology, construction techniques, and material properties unique to Texas levees may cause the levees to exhibit failure mechanisms different from those of the Mississippi system. It was necessary, therefore, to establish an understanding of Texas levee and foundation characteristics before appropriate geophysical techniques could be effectively applied for condition assessment. Levee failures are governed in large part by the soils that form the embankments and their foundations. Failure of the levee occurs as a result of the river scouring the toe of the levee, resulting in failure of the embankment into the channel, by overtopping of the embankment, and by seepage and piping. Water seepage through the levee embankment (through-seepage) can produce internal erosion of the levee soils. Foundation problems in levees usually are caused by under-seepage and are related to geologic conditions at the site.

Through-seepage is not normally a major concern for levees constructed of clay soils unless flood stage is long enough that the embankment becomes saturated, or when defects in the levee, such as animal burrows or desiccation cracks, produce concentrated flows. Seepage through levees consisting of silt and sand can produce boils and piping of levee materials, erosion at the land-side slope, and can lead to breaching of the levee if the seepage remains uncontrolled.

Seepage of water beneath a levee constructed on a highly erodible foundation of silt or sand is more critical than through-seepage. Identifying erodible foundation soils is an important step in preventing bank failures. Because floodplain deposits underlie levees, knowledge of the geology of local floodplain deposits is an important consideration in flood control management. Topstratum thickness, desiccation potential, and bulk permeabilities of the fine-grained materials are important factors in determining whether uncontrolled seepage is possible. A greater topstratum thickness reduces the potential for uncontrolled seepage. Levee systems are often built atop highly permeable, relatively coarse-grained river deposits representing point bars, old channels, and courses of the river system abandoned during its history of meandering over the floodplain.

Sandy sediments associated with the deposits represent the most likely locations

1-5 for under-seepage in levee systems (USACE, 1956a and 1956b); Wolff, 2002).

Similar conditions exist on the Rio Grande system (Brown et al, 1980, University of Texas, 1965 and 1983, and Seager et al, 1982 and 1987). It was imperative that geologic features be identified in the earliest stages of a levee condition assessment so that other exploratory methods could be used to confirm their existence and map their distribution. Knowledge of fluvial processes and the ability to recognize depositional environments in the geologic record are the key to identifying locations along modern levees where under–seepage has the greatest potential to occur. Development of a comprehensive GIS to effectively manage long-term levee condition assessment and flood-control data was also essential.

ERDC and USIBWC identified four task areas with specific sub-tasks required to accomplish the levee condition assessment:

Task 1 – Data Management. Develop a comprehensive eGIS data management tool:

▪ Define functional and content requirements

▪ Define physical requirements and standards

▪ Locate and compile existing base, geologic engineering, and historic data

▪ Provide guidelines for new data products

▪ Establish protocol for data access

▪ Maintain, update, and provide quality assurance (QA)

▪ Provide study partner support

▪ Document, archive

▪ Develop plan for technology transfer to USIBWC site and long-term maintenance

▪ Store GIS data on an ERDC server accessible to the USIBWC (with an ultimate goal of transferring all data to USIBWC servers)

Task 2 – Conduct geologic studies of the area to prioritize problem zones and river reaches:

▪ Locate and compile existing geologic and related data

▪ Describe the geology underlying the levees

▪ Identify specific floodplain depositional environments

▪ Map on topographic bases the depositional environments and, specifically, the distribution of abandoned river channels and courses

▪ Produce representative geologic cross sections from boring and other data

Task 3 – Conduct airborne geophysical/photographic surveys using the following methods/technologies:

▪ Multi-frequency electromagnetic (EM) induction

▪ Magnetometry

▪ Aerial photography

▪ Digital flight line video

▪ High-resolution topographic mapping using Light Detection and Ranging (LiDAR)

▪ On-board differential GPS for position referencing of airborne data

▪ Process data and provide interpretation

Task 4 – Perform ground truth investigations using ground surface geophysical surveys and cone-penetrometer technology.

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▪ Cone-penetrometer and in-place resistivity/conductivity using the Site Characterization and Analysis Penetrometer System (SCAPS)

▪ Soil sampling with SCAPS and field logging of soils

▪ Laboratory testing of selected soil samples

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2 Development of Condition Assessment Criteria

Levee condition assessment design considerations Levee segments

An immediate objective of the levee condition assessment was to identify and quantify those factors that influence the stability and performance of USIBWC levees. Using these factors as criteria for assessing levee condition, a numeric score could then be applied to levee segments. A numeric score would allow USIBWC managers to more effectively monitor those levee segments that are distressed or have the potential to become unstable. The first step in developing a rating system was to create a workable catalog of levee reaches, or segments. After reviewing the results of the airborne geophysical surveys and the color-coded EM conductivity1 maps that the surveys produced, it became apparent that segmenting levee reaches by EM conductivity would be a logical approach.

ERDC divided the Phase III and IV levees into segments based on uniform EM airborne conductivity and assigned a number to each segment sequentially on topographic quadrangle base maps (see Plate 1 of Volumes II, III, and IV for locations of levee segments in the Canalization, Rectification, and Presidio areas). ERDC assigned and rated 102 levee segments on 29 topographic quadrangles mapped in Phase III and IV areas. Figure 2-1 is an example showing numbered levee segments for the Presidio West and Presidio East quadrangles.

Condition assessment criteria

ERDC held a one-day workshop on 17 July, 2001 to develop procedures for performing numerical levee condition assessments using quantitative and qualitative descriptors. As a result of feedback from workshop attendees, ERDC produced a levee condition tabulation form with ten criteria, or factors (Table 2- 1, Tables presented at the end of each chapter). Figure 2-2 is an example of a completed rating form for levee segment 5 of the Hatch (NM) quadrangle.

1 Unless otherwise stated, the term “conductivity” used throughout this report refers to electrical conductivity.

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PE-03 PE-06

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0 1 20.5 Miles

Figure 2-1. Example of segment numbering, showing segments for Presidio West and Presidio East quadrangles.

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Figure 2-2. Example of completed condition assessment form (rating sheet) for levee segment 5 of Hatch (NM) quadrangle.

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In this rating system, a higher rating number or score always represents a better condition. The workshop established the following definitions for use in the ten-point criteria condition assessment of levees:

Descriptor – term describing factors related to a levee segment’s past and probable future performance.

Weight – number relating the degree of importance of the descriptor to levee performance, assigned to a descriptor on a scale of 0 to 3, where 0 = not important, 1 = somewhat important, 2 = important, 3 = very important.

Value – number relating how well a levee segment performs relative to the descriptor without regard to the weight assigned the descriptor (i.e. the score before adjusting for weight). Values range from 0 (worst performance) to 4 (best performance).

Score – a number representing the levee segment’s condition relative to that descriptor, or criterion, taken as the product of the “weight” and the “value”, and ranging from 0 to 12.

Condition – numerical expression of levee condition based on the average (mean) scores of all 10 descriptors (fewer than 10 in some cases), where 0-3.99 = Poor, 4-6.99 = Marginal, 7-9.99 = Acceptable, and 10-12 = Good.

It was recognized that even if a levee segment scored “Acceptable” or “Good” on Condition, a low score in any one of the ten descriptors (criteria) could result in poor performance and possibly levee failure under flood conditions. Thus, each descriptor was scored individually. ERDC presented segment rankings to USIBWC as a series of maps depicting levee segments and representing scores for all ten individual descriptors and a cumulative ranking of overall levee condition (see Plates 8-18 of Volumes II, III, and IV).

Plates 18 of Volumes II, III, and IV (Canalization, Rectification, and Presidio areas, respectively) show the overall levee condition score as the mean of scores for all 10 criteria for all levee segments (numbers carried to 2 decimal places).

Ten-point criteria Ten condition criteria developed during the July 2001 workshop enabled an evaluation of levee condition for each segment based on design, performance during past floods, material properties, and other factors. USIBWC personnel assigned ratings for the first three criteria - performance history, construction history, and visual inspection of apparent condition. USIBWC provided a rating for each quadrangle of the study area with, generally, all levee segments contained in a given quadrangle receiving the same rating for each of the three criteria.

Table 2-2 is a spreadsheet of values, scores, and condition assessment ratings for all criteria and all levee segments of the Phase III and IV study area. Data are grouped by Canalization, Rectification, and Presidio reaches. The last row of data in Table 2.2 presents the means of all levees for all criteria. Means for each reach (Canalization, Rectification, and Presidio) are also provided.

ERDC assigned ratings for the remaining seven criteria. Criteria ratings ranged from 0 for worst condition to 4 (best condition). Ratings were applied qualitatively for some criteria and quantitatively for others. The following

2-5 sections explain the philosophy and approach used in developing the ratings.

Ratings were assigned to each of the ten criteria and entered into the condition-rating form (Figure 2-2) as a “Value”. Data from the airborne EM survey were the primary tool for segmenting the levees and were used by ERDC analysts to derive ranking values for six criteria. The “topographic irregularity” criterion was based on the LiDAR survey and ranked segment elevations based on deviations in levee height.

Volumes II, III, and IV of this report presents large-format colored maps of the levees showing conductivity for each frequency, magnetometer data, and weighted scores for each of the ten criteria for all levee segments. Plate 18 (Volumes II, III, and IV) shows the mean scores for all criteria (the condition assessment) for all levee segments for each respective reach. The reader can rapidly assess the locations and distribution of potential trouble spots by studying this collection of maps.

Performance history under flood stage (Criterion 1)

USIBWC subjectively rated each quadrangle’s levees by how they performed under past flood events. Levees that “had never been tested” by flood received no rating. The mean of all levees was 2.4 (last row of data in Table 2-2). Only levee segments 3, 4, and 5 of Presidio East quadrangle received values lower than 2 for performance history. The Presidio reach was subjected to severe flooding in the early 1990’s and these segments required emergency measures to prevent breaching (Dunbar 2003).

Construction History (Criterion 2)

USIBWC subjectively rated URGV levees based on their construction history, which is as much a factor of age (when they were built) as how they were built. It was assumed that levee construction practices were less rigorous during early construction periods. The mean value for all levees was 2.0. Only segments 4 and 5 of Presidio East rated lower than 2. These segments were raised and armored with cobbles and boulders after the 1990’s flooding because of poor performance during the flooding (Dunbar 2003).

Visual Inspection (Criterion 3)

USIBWC personnel subjectively assigned condition values for the levee condition assessment from their annual levee inspection. Typical conditions observed and noted in the visual inspection were rills and cracks on levee slopes, depressed levee crests, vehicle ruts on levee slopes and crest roadway, and eroded toes. The mean value for all levees was 2.5. Only segments 4 and 5 of Presidio East rated lower than 2. These segments were raised and armored with cobbles and boulders after the 1990’s flooding because of poor performance (Dunbar 2003).

Material type (Criterion 4)

The material type criterion quantitatively assessed the relative suitability of soils used in levee construction. The assessment assumed that materials in the top stratum soils adjacent to the levees were used as borrow (based…