psi_report_322-95001_-_volume_iii.pdf

GEOTECHNICAL ENGINEERING SERVICES REPORT

UNITED STATES SECTION, INTERNATIONAL BOUNDARY & WATER COMMISSION

LOWER RIO GRANDE PROJECT – INTERIOR LEVEES

REHABILITATION OF MAIN FLOODWAY, FROM 23RD STREET TO FM 1015

HIDALGO COUNTY, TEXAS

PSI REPORT NO. 322-95001 - VOLUME III (SOUTH LEVEE)

PREPARED FOR S&B INFRASTRUCTURE, LTD.

MAY 2009

PSI REPORT 322-95001

VOLUME III (SOUTH LEVEE)

MAIN FLOODWAY SOUTH LEVEE

Levee Section Levee Section Levee Section Levee Section

Section 1 246+59 to 300+00 MFS1-1 to MFS1-5 278+78.63

Section 2 300+00 to 349+00 MFS1-6 to MFS1-10 310+43.00

Section 3 349+00 to 400+00 MFS1-11 to MFS1-15 350+32.70

Section 4 400+00 to 452+00 MFS1-16 to MFS1-20 433+43.26

Section 5 452+00 to 503+00 MFS1-21 to MFS1-25 493+80.33

Section 6 503+00 to 548+00 MFS1-26 to MFS1-30 514+09.59

Section 7 548+00 to 598+00 MFS1-31 to MFS1-35 548+96.86

Section 8 598+00 to 650+00 MFS1-36 to MFS1-40 620+62.17

Section 9 650+00 to 701+00 MFS1-41 to MFS1-46 692.47.73

Section 10 701+00 to 741+00 MFS1-47 to MFS1-50 712+79.95

Section 11 741+00 to 791+00 MFS1-51 to MFS1-55 743+20.22

Section 12 791+00 to 841+00 MFS1-56 to MFS1-60 793.08.38

Section 13 841+00 to 892+00 MFS1-61 to MFS1-65 883+32.34

Section 14 892+00 to 942+00 MFS1-66 to MFS1-70 923+75.40

Section 15 942+00 to 995+00 MFS1-71 to MFS1-75 965+69.91

Section 16 995+00 to 1047+00 MFS1-76 to MFS1-80 1038+43.89

Section 17 1047+00 to 1100+00 MFS1-81 to MFS1-85 1089+69.05

Section 18 1100+00 to 1154+00 MFS1-86 to MFS1-91 1135+56.07

Section 19 1154+00 to 1204+00 MFS1-92 to MFS1-95 1180+96.23

Section 20 1204+00 to 1245+00 MFS1-96 to MFS1-100 1226+35.34

Section 21 1245+00 to 1297+00 MFS1-101 to MFS1-105 1288.28.02

Section 22 1297+00 to 1345+00 MFS1-106 to MFS1-110 1297+41.67

Section 23 1345+00 to 1389+36 MFS1-111 to MFS1-115 1356+49.34

VOLUME III, SECTION 1 - PAGE NO. 1

SECTION 1.0: STA. 246+59.91 TO STA. 300+00 (MFS1-1 TO MFS1-5)

This section describes the subsurface conditions and the geotechnical engineering analyses for the Main Floodway South levee extending between Sta. 246+59.91 and Sta. 300+00. The subsurface conditions in this area of the project site were explored with five (5) soil borings (i.e., MFS1-1 through MFS1-5).

1.1 CROSS-SECTIONAL INFORMATION

The cross-sectional drawings of the levee system were provided by S & B Infrastructure, LTD on May 6, 2009. The existing cross-sectional information in conjunction with the proposed levee crown elevations was reviewed to identify the maximum height (most critical) for the proposed levee geometry and a design levee cross-section was selected.

The cross section at Sta. 278+78.63 was used for the analyses. Please note that the dimensions are rounded to the nearest foot for calculation purposes.

Key information pertaining to the design cross-section for this segment of levee includes the following:

1. Proposed Crown Width: 16 feet

2. Proposed Side Slope Inclination (Enlargement): 3H:1V on both sides

3. Flood Water Elevation: Three (3) feet below levee crown (freeboard)

4. Existing Levee Height: 13.5 feet

5. Maximum final Levee Height: 16 feet

6. Maximum Additional Fill to Raise the Levee: 2.5 feet

1.2 SUBSURFACE CONDITIONS

The subsurface conditions within this portion of the levee were explored with five soil borings (i.e., Borings MFS1-1 through MFS1-5) drilled to depths of 50 feet below the existing ground surface.

Laboratory test data along with detailed descriptions of the soils found within this portion of the levee system can be found on the logs of Borings MFS1-1 through MFS1-5 included in Appendix 1.1. Appendix 1.1 also contains portions of the laboratory test data (if any) including the results of the consolidated undrained triaxial tests with pore pressure measurements (CU test), consolidation tests, permeability tests and other tests.

Based on the soils found in the aforementioned test borings and the results obtained from the laboratory tests, a generalized soil profile was developed to evaluate the soil conditions along this section of the levee alignment. The soil types encountered and a range of the laboratory test results is presented below in Table 8.2.

Existing levee materials consisted predominantly of firm to very stiff lean to fat clay.

Native soils beneath the levee generally consist of firm to very stiff lean clay and fat clay

VOLUME III, SECTION 1 - PAGE NO. 2

with interbedded sandy lean clay layers. The range of the laboratory test results is presented below in Table 1.1.

Table 1.1: Summary of Laboratory Test Results (Borings MFS1-1 through MFS1-5)

Stratum Description

Moisture Content (%)

Atterberg Limits

Shear Strength (tsf)

Percent Passing No.

200 (%)

SPT – N

Values

(blows/ft)

Levee (CL, CH) 2 to 22 LL = 40 to 60

PI = 25 to 40 - 92 to 99 4 to 32

Fat Clay (CH), Lean Clay (CL)

15 to 32 LL = 27 to 60 PI = 11 to 35 0.1 to 1.61 55 to 100 WOH (o) to

Notes: LL: Liquid Limit; PI: Plasticity Index; WOH: Weigh of Hammer

1.3 DESIGN SOIL STRENGTH PROFILE

The soil strength parameters selected for the design profile are based on: 1) the results of our field and laboratory test data on selected soil samples, 2) prudent engineering judgment based on experience with similar soils, and 3) published correlations.

The selection process for obtaining soil strength parameters used in the stability analyses for the 1) Short-Term Condition, 2) Long-Term Condition, and 3) Rapid Draw- Down Condition (upstream slope) are described below:

• As previously mentioned, average undrained strength of the soil as measured by the Unconfined Compression tests and Unconsolidated Undrained tests were used to analyze the slopes in “short-term” conditions. For clay layers (at a given cross-sectional location), the strength test results obtained on the soils of the nearest boring locations were averaged to obtain the undrained shear strength parameters.

The values were obtained utilizing various correlations available in the geotechnical literature, our engineering judgment and well-established local experience.

• To analyze the slopes in “long-term and rapid draw-down conditions” (for a clay layer), the effective cohesion (c’) value and the effective angle of internal friction (φ’) were utilized. The phreatic surface developed during a theoretical steady-state seepage condition was utilized for both of these stability scenarios. These parameters were obtained from the CU tests performed, as well as published correlations.

VOLUME III, SECTION 1 - PAGE NO. 3

The design soil strength parameters used in the slope stability analyses for this section are presented below in Table 1.2.

Table 1.2 Design Soil Strength Parameters

Soil Strength Parameter(s) Stratum

(Elev. Range, feet) Undrained (Short-Term)

Effective (Long-Term & Rapid Draw-down) Levee (CL, CH) (+112 to +95 ft.) Su = 1,000 psf c’ = 250 psf φ’ = 27o

Fat Clay (CH) (+95 to +80 ft.) Su = 2,000 psf c’ = 200 psf φ’ = 20o

Lean Clay (CL) (Below +80 ft.) Su = 1,500 psf c’ = 150 psf φ’ = 25o

Notes: Su - Undrained Shear Strength, c’ - effective cohesion, φ’ - effective angle of internal friction

1.4 DISCUSSION OF RESULTS AND RECOMMENDATIONS

Using the soil strength parameters shown in Table 1.2, slope stability analyses were performed for the design (critical) cross-section previously mentioned in this section. The proposed side slopes of the levee enlargement at this location are 3H:1V with a maximum slope height of about 17 feet. The results of the stability analyses are shown graphically in Appendix 1.2.

• Based on the results of the slope stability analyses for 3H:1V slopes, the minimum calculated factor-of-safety for the short-term condition using undrained soil strength parameters is 4.71 (see Figure 1.1), thereby indicating stable slopes. The computed factor-of-safety for this condition exceeds the minimum acceptable value of 1.3, as recommended in the USACE publication Slope Stability Manual (EM 1110-2-1902), and USACE publication Design & Construction of Levees Manual (EM 1110-2-1913).

• Based on the stability analysis for the long-term condition using effective soil strength parameters, the minimum calculated factor-of-safety is 1.89 (see Figure 1.2), thereby indicating stable slopes. The computed factor-of-safety for this condition exceeds the minimum acceptable value of 1.5, as recommended in the USACE publication Slope Stability Manual (EM 1110-2-1902), and USACE publication Design & Construction of Levees Manual (EM 1110-2-1913).

• For the rapid draw-down condition using effective soil strength parameters, the minimum calculated factor-of-safety is 1.71 (see Figure 1.3) and the slopes are considered to be stable. The computed factor-of-safety for this condition exceeds the minimum acceptable value of 1.0, as recommended in the USACE publication Slope Stability Manual (EM 1110-2-1902), and USACE publication Design & Construction of Levees Manual (EM 1110-2-1913).

VOLUME III, SECTION 1 - PAGE NO. 4

In addition, the near-surface clay soils along the project alignment are subject to weathering (aging) in response to wetting and drying cycles, thereby resulting in a decrease in soil strength over time. A rapid draw-down condition in conjunction with soil weathering may result in sloughing of the riverside levee slope following a flood event.

These shallow failures should be regarded as a maintenance issue and it is recommended that they be repaired soon after they occur to maintain the integrity of the levee.

1.5 LEVEE SETTLEMENT ANALYSES

Within this segment of the levee (i.e., between Sta. 246+59.91 and Sta. 300+00), the levee is planned to be raised by approximately two (2) feet. Based on our analyses, the long-term settlement induced by the proposed levee enlargement is estimated to be less than one (1) inch.

1.6 SEEPAGE ANALYSES

PSI’s review of piping and seepage analyses were performed in accordance with USACE EM 1110-2-1901. A steady-state seepage analysis was performed for this section of levee using the finite-element computer program SEEP/W (see Figure 1.4).

Hydraulic gradients were calculated for the design cross-section and compared to established criteria. Based on this analysis, the exit gradient at the landside toe was calculated to be about 0.35. The ratio of the critical gradient (the gradient at which piping can occur) to the calculated gradient results in a factor-of-safety against piping.

Based on a critical gradient of 0.8, the resulting factor-of-safety exceeds the minimum value of 1.6, as recommended by the USACE. The seepage rate for this section of levee is estimated to be less than one (1) gallon per day, which is low. Therefore, mitigation measures for seepage are not warranted. Results of the seepage analyses are presented on Figure 1.4.

1.7 CONSTRUCTION RECOMMENDATIONS

As previously mentioned, the levee will be raised by a maximum of about 2.5 feet in this section (Sta. 255+31 to Sta. 300+00). Borrow materials for levee construction can be clays, sandy clays classified as CL, and fat clays (CH). Silts, sands and organic soils are unsuitable for levee construction. The borrow materials must be selected and placed in strict accordance with Section 4 of USACE Publication EM 1110-2-1913.

The borrow materials should be placed in maximum lifts of 12 inches of loose material and should be compacted to at least 95 percent of standard Proctor maximum dry density as determined by ASTM D 698 with the range of two percentage (+1% to +3%) points of the optimum moisture content value. The first layer of fill should be placed in a relatively uniform horizontal lift and be adequately keyed into the existing levee soils.

Please refer to Volume 1of this report for additional recommendations.

VOLUME III, SECTION 1 - PAGE NO. 5

Any structures or other special features within the levee (such as pipe penetrations) should be designed and constructed in accordance with Section 8 of USACE Publication

EM 1110-2-1913.

1.8 CONCLUSIONS

Based on our analyses of this section (Sta. 246+59.91 to Sta. 300+00), the levee can be raised by a maximum of about 2.5 feet with a side slope inclination of 3H:1V. The slope stability, seepage and settlement of the new levee system are acceptable and satisfy prudent and well-accepted USACE engineering criteria for the stability of levees.

VOLUME III, SECTION 1 - PAGE NO. 6

APPENDIX 1.1

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Fat Clay (CH), Firm to Stiff, Dark Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

FAT CLAY (CH), Firm to Very Stiff, Brown, Moist

LEAN CLAY (CL), Soft, Brown, Moist to Wet

SILTY CLAY (CL-ML), Stiff, Brown, Wet

CH

CH

CL

CL-ML

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS-1

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

E C

O N

T E

N T

LI

Q

U

ID

LI

M

IT

P

LA

S T

IC

LI

M

IT

N -B

LO

W

S /F

T

S A

M P

LE

S

U N

IT

W

E

IG

H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/13/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 248+12.42

INITIAL GROUND WATER (FT) 30 Feet

GROUND WATER

FINAL GROUND WATER (FT): Dry

TYPE OF BORING: HOLLOW STEM AUGER TO 27 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 111.07 feet

COORODINATE (X) OR EASTING: 1064696

COORDINATE (Y) OR NORTHING: 16576580

B L_

A U

S T

IN

G

IN

T S

T D

U S

L A

B .G

D T

/7 /0

:3

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

47.5

50.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Lean Clay (CL), Firm to Stiff, Dark Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

LEAN CLAY (CL), Firm to Stiff, Brown, Moist

Sandy at 45 Feet

CL

CL

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS-2

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

E C

O N

T E

N T

LI

Q

U

ID

LI

M

IT

P

LA

S T

IC

LI

M

IT

N -B

LO

W

S /F

T

S A

M P

LE

S

U N

IT

W

E

IG

H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/13/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 257+59.27

INITIAL GROUND WATER (FT) 34.5 Feet

GROUND WATER

FINAL GROUND WATER (FT): 20 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 40 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 110.46 feet

COORODINATE (X) OR EASTING: 1065632

COORDINATE (Y) OR NORTHING: 16576437

B L_

A U

S T

IN

G

IN

T S

T D

U S

L A

B .G

D T

/7 /0

:3

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: LEAN CLAY (CL), Firm to Stiff, Dark Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

SANDY LEAN CLAY (CL), Stiff to Very Stiff, Brown, Moist

LEAN CLAY (CL), Very Stiff, Brown, Moist Shear Strength = 1.06 tsf

SANDY LEAN CLAY (CL), Firm, Brown, Moist

LEAN CLAY (CL), Soft, Brown, Moist

Sandy at 48 Feet

CL

CL

CL

CL

CL

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS-3

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

E C

O N

T E

N T

LI

Q

U

ID

LI

M

IT

P

LA

S T

IC

LI

M

IT

N -B

LO

W

S /F

T

S A

M P

LE

S

U N

IT

W

E

IG

H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/13/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 267+85.04

INITIAL GROUND WATER (FT) 30 Feet

GROUND WATER

FINAL GROUND WATER (FT): 25 Feet

TYPE OF BORING: HOLLOW STEM AUGER

APPROXIMATE SURFACE ELEVATION: 110.11 feet

COORODINATE (X) OR EASTING: 1066641

COORDINATE (Y) OR NORTHING: 16576257

B L_

A U

S T

IN

G

IN

T S

T D

U S

L A

B .G

D T

/7 /0

:3

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL; Fat Clay (CH), Stiff to Very Stiff, Dark Brown, Moist

LEVEE MATERIAL; Lean Clay (CL), Very Stiff, Dark Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

LEAN CLAY (CL), Firm to Very Stiff, Brown, Moist

Shear Strength = 1.61 tsf

SANDY LEAN CLAY, Very Soft to Firm, Brown, Moist

LEAN CLAY (CL), Firm, Brown, Moist, With Sand Seams

SANDY LEAN CLAY, Very Stiff, Brown, Moist

CH

CL

CL

CL

CL

CL

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS-4

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

E C

O N

T E

N T

LI

Q

U

ID

LI

M

IT

P

LA

S T

IC

LI

M

IT

N -B

LO

W

S /F

T

S A

M P

LE

S

U N

IT

W

E

IG

H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/14/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 278+78.63

INITIAL GROUND WATER (FT) 30 Feet

GROUND WATER

FINAL GROUND WATER (FT): 23 Feet

TYPE OF BORING: HOLLOW STEM AUGER

APPROXIMATE SURFACE ELEVATION: 109.7 feet

COORODINATE (X) OR EASTING: 1067707

COORDINATE (Y) OR NORTHING: 16576010

B L_

A U

S T

IN

G

IN

T S

T D

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L A

B .G

D T

/7 /0

:3

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: FAT CLAY (CH), Stiff to Very Stiff, Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

FAT CLAY (CH), Stiff to Very Stiff, Brown, Moist

Sheat Strength = 1.47 tsf

Clayey Sand Layer at 30 feet

LEAN CLAY (CL), Stiff to Very Stiff, Brown, Wet

Clayey Sand Layer at 45 feet

CH

CH

CL

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS1-5

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

E C

O N

T E

N T

LI

Q

U

ID

LI

M

IT

P

LA

S T

IC

LI

M

IT

N -B

LO

W

S /F

T

S A

M P

LE

S

U N

IT

W

E

IG

H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/14/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 289+38.87

INITIAL GROUND WATER (FT) 25 Feet

GROUND WATER

FINAL GROUND WATER (FT): 27.5 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 30 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 109.29 feet

COORODINATE (X) OR EASTING: 1068741

COORDINATE (Y) OR NORTHING: 16575775

B L_

A U

S T

IN

G

IN

T S

T D

U S

L A

B .G

D T

/9 /0

:1

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

CH

CH

CL

CL

ML

MFS-1

CL

CL

MFS-2

CL

CL

CL

CL

CL

MFS-3

CH

CL

CL

CL

CL

CL

MFS-4

CH

CH

CL

MFS-5

E le va tio n

1064696 1065632 1066641 1067707 1068741

111.1 110.5 110.1 109.7 109.3

50.0 50.0 50.0 50.0 50.0

Varying soil deposits, including fill materials may exist between the sampling intervals and between boring locations.

PROJECT #

Borehole North East Elev. Depth

MFS-1

MFS-2

MFS-3

MFS-4

MFS-5

16576580 16576437 16576257 16576010 16575775

Distance Along Baseline

DATE PLATE

322-95001 1

SUBSURFACE FENCE DIAGRAM

MFS-1 through MFS-5

IBWC South Levee

Hidalgo County

May 2009

F E

N C

E _P

S I -

F A

G W

G N

.G

D T

/7 /0

:3

P

U

S

IB

W C

L E

V E

E \0

S

O U

T H

L O

G S

\F

IN

A L

LO

G

S \M

F S

-5

\M F

S

-5 R

E V

-1 .G

P J

3/4" #4 #10 #40 #200

2.0 0.075

US IBWC Levee mm mm

Boring No.: MFS-2 mm mm

Sample Depth: 45 to 47

GRADATION CURVE

US STANDARD SIEVE SIZE

6" 3"

BOULDERS COBBLES

GRAVEL SAND

SILT OR CLAY CLAY

FINECOARSE FINE COARSE MEDIUM

SERIES NO. SAMPLE IDENTIFICATION GRADATION INFORMATION

152 76.2 19.1 4.75 0.42 0.002

PARTICLE SIZE IN MM

D10: 0.00 D30: 0.00 D50: 0.00 D60: 0.00 Cc: 0.00 Cu: 0.00

# ##3

SILT

OR

CLAY

0.0010.010.1110100 Grain Size, mm

Pe rc en t P as si ng

US IBWC Levee mm mm

Boring No.: MFS-3 mm mm

Sample Depth: 15 to 17

GRADATION CURVE

US STANDARD SIEVE SIZE

6" 3"

BOULDERS COBBLES

GRAVEL SAND

SILT OR CLAY CLAY

FINECOARSE FINE COARSE MEDIUM

SERIES NO. SAMPLE IDENTIFICATION GRADATION INFORMATION

152 76.2 19.1 4.75 0.42 0.002

PARTICLE SIZE IN MM

D10: 0.00 D30: 0.00 D50: 0.00 D60: 0.09 Cc: 0.00 Cu: 0.00

# ##3

SILT

OR

CLAY

0.0010.010.1110100 Grain Size, mm

Pe rc en t P as

US IBWC Levee mm mm

Boring No.: MFS-4 mm mm

Sample Depth: 32 to 34

GRADATION CURVE

US STANDARD SIEVE SIZE

6" 3"

BOULDERS COBBLES

GRAVEL SAND

SILT OR CLAY CLAY

FINECOARSE FINE COARSE MEDIUM

SERIES NO. SAMPLE IDENTIFICATION GRADATION INFORMATION

152 76.2 19.1 4.75 0.42 0.002

PARTICLE SIZE IN MM

D10: 0.00 D30: 0.00 D50: 0.00 D60: 0.00 Cc: 0.00 Cu: 0.00

# ##3

SILT

OR

CLAY

0.0010.010.1110100 Grain Size, mm

Pe rc en t P as

US IBWC Levee mm mm

Boring No.: MFS-4 mm mm

Sample Depth: 45 to 47

GRADATION CURVE

US STANDARD SIEVE SIZE

6" 3"

BOULDERS COBBLES

GRAVEL SAND

SILT OR CLAY CLAY

FINECOARSE FINE COARSE MEDIUM

SERIES NO. SAMPLE IDENTIFICATION GRADATION INFORMATION

152 76.2 19.1 4.75 0.42 0.002

PARTICLE SIZE IN MM

D10: 0.00 D30: 0.00 D50: 0.00 D60: 0.08 Cc: 0.00 Cu: 0.00

# ##3

SILT

OR

CLAY

0.0010.010.1110100 Grain Size, mm

Pe rc en t P as g

1 of 10MFNI-5, 8-10, 13-15, 18-20

Consolidated Undrained Triaxial Test with Pore Pressure Measurements (ASTM D 4767)

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFS-5 Depth, feet: See Remarks Sample No./ID: NA

Liquid Limit: NA Plastic Limit: NA Plasticity Index: NA Percent Passing No. 200: NA

Specimen/Stage Data Before Test After Consolidation & Shear Description Saturation/Consolidation Specimen/Stage No. 1 2 3 1 2 3 Specimen/Stage No. 1 2 3

Diameter (D),in.: 2.84 2.86 2.84 - - - Method Wet Mounting Method Height (H), in.: 5.61 5.55 5.55 - - - Cell Pressure, lbs/in2 50.2 60.3 80.1 Volume (Vo, Vf = Vo -Δ 3:V), cm 583.2 585.5 574.9 568.9 563.0 547.8 Back Pressure, lbs/in2 40.1 40.1 40.3 Moisture, {Wo, Wf} %: 20.7% 21.7% 24.1% 24.7% 22.9% 23.7% B-Parameter 0.95 0.95 0.96 Wet Soil Wt. {Mo, Mf}, ,gm: 1177.10 1145.33 1150.27 1206.80 1171.65 1149.21 Consolidation Pressure, lbs/in2 10.1 20.1 39.8 Wet Unit Weight, pcf: 125.9 122.06 124.8 129.1 124.87 124.7 Volume Change After (Δ 3V), cm 14.3 22.5 27.1 Dry Unit Weight, pcf: 104.4 100.3 100.6 103.6 101.6 100.8 Time for Consolidation, min. 2830 2815 2825 Specific Gravity (Assumed): 2.7 2.7 2.7 2.7 2.7 2.7 Failure Type: Bulge-Fractures Void Ratio, eo, ef: 0.63 0.66 0.67 0.59 0.59 0.59 Bulge-Fractures Degree of Saturation, So, Sf: 0.89 0.89 0.89 1.14 1.04 1.08 Bulge-Fractures

Shear Data Specimen/Stage

1 2 3 Strain Rate, %/hr 0.5 0.5 0.5 Axial Strain at Failure, % 11.11 14.12 9.84 Deviator Stress, lbs/in2 (Δσ) 23.16 28.96 38.71 Excess Pore Pressure, lbs/in2 (u) 6.33 9.64 23.87 A-Parameter, (u/Δσ) 0.27 0.33 0.62 Total Major Pincipal Stress, lbs/in2 (σ1 = σ3 + Δσ) 33.23 49.03 78.43 Total Minor Pincipal Stress, lbs/in2 (σ3) 10.07 20.07 39.73 Effectivel Major Pincipal Stress, lbs/in2 (⎯σ⎯1 = σ1 − u) 26.89 39.39 54.57 Effectivel Minor Pincipal Stress, lbs/in2 (⎯σ⎯3 = σ3 − u) 3.73 10.43 15.86

Remarks: Speciment 1: MFS-5, 8-10 ft.; Specimen 2: MFS-5, 13-15 ft.; Specimen 3: MFS-5, 18-20 ft.

Consolidated Undrained Triaxial Test with Pore Pressure Measurements (ASTM D 4767)

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Boring Number: MFSI-5 Depth, feet: See Remarks Sample No./ID: 0

Cohesion (C T ), ksf: 1.14 Friction Angle( φ T ), deg: 11.3 Cohesion (C d ), ksf: 0.51 Friction Angle( φ d ), deg: 27.4

Remarks: Speciment 1: MFS-5, 8-10 ft.; Specimen 2: MFS-5, 13-15 ft.; Specimen 3: MFS-5, 18-20 ft.

0 20 40 60 80 100 Normal Stress,psi

Sh ea r S tr es s, p si

Specimen 1 - Total Stress Circle Specimen 1 - Effective Stress Circle Specimen 2 - Total Stress Circle Specimen 2 - Effective Stress Circle Specimen 3 - Total Stress Circle Specimen 3 - Effective Stress Circle Total Stress Envelope Effective Stress Envelope

MFNI-5, 8-10, 13-15, 18-20 2 of 10

(n

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Boring Number: MFSI-5 Depth, feet: See Remarks Sample No./ID: 0

Cohesion (C d ), ksf: 0.60 Friction Angle( φ d ), deg: 22.5

Remarks: Speciment 1: MFS-5, 8-10 ft.; Specimen 2: MFS-5, 13-15 ft.; Specimen 3: MFS-5, 18-20 ft.

0 10 20 30 40 50 60 70 80 90 100 p' = {Sig 1' + Sig 3'/2}, psi q'

{S ig

S ig

2, p si

Specimen 1 Specimen 2 Specimen 3

MFNI-5, 8-10, 13-15, 18-20 3 of 10

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Boring Number: MFSI-5 Depth, feet: See Remarks Sample No./ID: 0

Remarks: Speciment 1: MFS-5, 8-10 ft.; Specimen 2: MFS-5, 13-15 ft.; Specimen 3: MFS-5, 18-20 ft.

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Axial Strain, %

St re ss /P re ss ur e, p si

Delta Sigma of 1 Delta Sigma of 2 Delta Sigma of 3 Pore Pressure of 1 Pore Pressure of 2 Pore Pressure of 3

MFNI-5, 8-10, 13-15, 18-20 4 of 10

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFSI-5 Depth, feet: 8-10 ft Sample No./ID: 0

Specimen/Stage: Stage 1 gEffective Confinin Pressure, psi: 10.1 Failure Type: Bulge-Fractures Remarks:

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0

Axial Strain (%)

St re ss o r P re ss ur e (p si σ 1 σ 3

⎯σ⎯1 ⎯σ⎯3

Cell Pressure Back Pressure

Δσ Pore Pressure

MFNI-5, 8-10, 13-15, 18-20 5 of 10

MFNI-5, 8-10, 13-15, 18-20 6 of 10

Consolidated Undrained Triaxial Test with Pore Pressure Measurements (ASTM D 4767)

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFSI-5 Depth, feet: 8-10 ft Sample No./ID: 0

Specimen/Stage: Stage 1 gEffective Confinin Pressure, psi: 10.1 Remarks:

Clock Elaspsed Burrette Volume Date Time Time, min. Readings cm3

7/23/2008 8:05:00 AM 0.0 24.0 0.0

7/23/2008 8:05:06 AM 0.1 23.5 0.5

7/23/2008 8:05:15 AM 0.2 23.0 1.0

7/23/2008 8:05:30 AM 0.5 23.0 1.0

7/23/2008 8:06:00 AM 1.0 22.9 1.1

7/23/2008 8:07:00 AM 2.0 22.8 1.2

7/23/2008 8:09:00 AM 4.0 22.5 1.5

7/23/2008 8:13:00 AM 8.0 22.1 1.9

7/23/2008 8:20:00 AM 15.0 21.5 2.5

7/23/2008 8:35:00 AM 30.0 21.0 3.0

7/23/2008 9:05:00 AM 60.0 19.8 4.2

7/23/2008 10:05:00 AM 120.0 17.2 6.9

7/23/2008 1:25:00 PM 320.0 16.0 8.0

7/24/2008 11:41:00 AM 1656.0 14.8 9.2

7/25/2008 7:15:00 AM 2830.0 14.7 9.3

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0.01 0.1 1 10 100 1000 10000 Elapsed Time, min.

C ha ng e in V ol um e, c m 3 .

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFNI-5 Depth, feet: 13-15 ft Sample No./ID: 0

Specimen/Stage: Stage 2 gEffective Confinin Pressure, psi: 20.1 Failure Type: Bulge-Fractures

Remarks:

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0

Axial Strain (%)

St re ss o r P re ss ur e (p si σ 1 σ 3 ⎯σ⎯1 ⎯σ⎯3 Cell Pressure Back Pressure

MFNI-5, 8-10, 13-15, 18-20 7 of 10

MFNI-5, 8-10, 13-15, 18-20 8 of 10

Consolidated Undrained Triaxial Test with Pore Pressure Measurements (ASTM D 4767)

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFNI-5 Depth, feet: 13-15 ft Sample No./ID: 0

Specimen/Stage: Stage 2 gEffective Confinin Pressure, psi: 20.1 Remarks:

Clock Elaspsed Burrette Volume Date Time Time, min. Readings Cm3

7/23/2008 8:20:00 AM 0.0 24.5 0.0

7/23/2008 8:20:06 AM 0.1 23.5 1.0

7/23/2008 8:20:15 AM 0.2 23.2 1.3

7/23/2008 8:20:30 AM 0.5 23.1 1.4

7/23/2008 8:21:00 AM 1.0 23.0 1.5

7/23/2008 8:22:00 AM 2.0 22.9 1.7

7/23/2008 8:24:00 AM 4.0 22.0 2.5

7/23/2008 8:28:00 AM 8.0 21.5 3.0

7/23/2008 8:35:00 AM 15.0 21.0 3.5

7/23/2008 8:50:00 AM 30.0 20.0 4.5

7/23/2008 9:20:00 AM 60.0 18.3 6.2

7/23/2008 10:20:00 AM 120.0 16.1 8.4

7/23/2008 1:25:00 PM 305.0 13.3 11.3

7/23/2008 2:45:00 PM 385.0 12.5 12.0

7/24/2008 11:40:00 AM 1640.0 6.5 22.0

7/25/2008 7:15:00 AM 2815.0 6.1000 22.5

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0.01 0.1 1 10 100 1000 10000 Elapsed Time, min.

C ha ng e in V ol um e, c

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFNI-5 Depth, feet: 18-20 ft Sample No./ID: 0

Specimen/Stage: Stage 3 gEffective Confinin Pressure, psi: 39.8 Failure Type: Bulge-Fractures

Remarks:

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0

Axial Strain (%)

St re ss o r P re ss ur e (p si σ 1 σ 3

⎯σ⎯1 ⎯σ⎯3

Cell Pressure Back Pressure

MFNI-5, 8-10, 13-15, 18-20 9 of 10

MFNI-5, 8-10, 13-15, 18-20 10 of 10

Consolidated Undrained Triaxial Test with Pore Pressure Measurements (ASTM D 4767)

Project Name: IDWC-Main Floodway South Classification: Sandy Clay, Brown

Project Number: 322-95001 Borin Number: MFNI-5 Depth, feet: 18-20 ft Sample No./ID: 0

Specimen/Stage: Stage 3 gEffective Confinin Pressure, psi: 39.8 Remarks: 39.8143

Clock Elaspsed Burrette Volume Date Time Time, min. Readings cm3

7/23/2008 8:10:00 AM 0.0 24.0 0.0

7/23/2008 8:10:06 AM 0.1 23.2 0.8

7/23/2008 8:10:15 AM 0.3 22.5 1.5

7/23/2008 8:10:30 AM 0.5 22.1 1.9

7/23/2008 8:11:00 AM 1.0 21.5 2.5

7/23/2008 8:12:00 AM 2.0 20.6 3.4

7/23/2008 8:14:00 AM 4.0 19.9 4.1

7/23/2008 8:18:00 AM 8.0 18.5 5.5

7/23/2008 8:25:00 AM 15.0 16.5 7.5

7/23/2008 8:40:00 AM 30.0 14.0 10.0

7/23/2008 9:10:00 AM 60.0 11.6 12.4

7/23/2008 10:10:00 AM 120.0 9.5 14.6

7/23/2008 1:25:00 PM 315.0 6.5 17.5

7/23/2008 2:45:00 PM 395.0 5.0 19.0

7/24/2008 11:39:00 AM 1649.0 3.4 26.8

7/25/2008 7:15:00 AM 2825.0 3.1 27.1

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

0.01 0.1 1 10 100 1000 10000 Elapsed Time, min.

C ha ng e in V ol um e, c

7.5 7.5

3815.2 2022.5 1792.7 118.1

207.5 167.3 40.2

207.5 37.5

3839.8 2022.5 1817.3 119.7

207.5 174.5

7.5

3834.1 2022.5 1811.6 119.3

3813.8 2022.5 1791.3 118.0

1632.7 107.6

97.3 94.4

X 207.5 177.2 30.3

25.2

2 3 4 5

Weight of Soil Wet Unit Weight, lbs/ft3

Pan No.

Wet Weight & Pan

M oi st ur e

Weight of Pan Weight of Soil Water Content %

Dry Weight & Pan Weight of Water lbs/ft3

WET=

DRY=

OMC=

119.7

99.80

20.05

MFS1-2

Other:

lbs/ft3

Project:

Test Lab Number:

322-95001Project No.IBWC Levee 21-Apr-09 Sampled by: B.G.

Soil Description:

D698 CBTest Method:

MOISTURE DENSITY RELATIONS OF SOILS

Mold Volume = 947.6 g/cm3

Med. Brown Sandy Clay

ADASTM

Location Sampled:

Date Sampled:

7.5 174.1

14.9 17.9

7.5 169.7

19.8 23.1

162.5 159.8167

Dry Unit Weight, lbs/ft3 93.6 100.1 99.7

BY

207.5 181.6 25.9

Wet Weight & Mold Triad Number

Weight of Mold

3655.2 2022.5

90.00

95.00

100.00

105.00

110.00

10.00 15.00 20.00 25.00 30.00

Moisture Content %

D ry

U ni t W ei gh t l bs /ft

VOLUME III, SECTION 1 - PAGE NO. 7

APPENDIX 1.2

Levee (Undrained)

Fat Clay (CH) (Undrained)

Lean Clay (CL) (Undrained)

Soil Properties Name: Levee (Undrained) Unit Weight: 125 pcf Cohesion: 1000 psf Name: Lean Clay (CL) (Undrained) Unit Weight: 125 pcf Cohesion: 1500 psf Name: Fat Clay (CH) (Undrained) Unit Weight: 125 pcf Cohesion: 2000 psf

South Levee - Section 1 (Sta. No. 246+59.91 to 300+00) Boring MFS1-1 to MFS1-5 Crown Width: 16 feet; Side Slopes: 3H:1V Crown Elevation: 112 feet; Flood Elevation: 109 feet

FIGURE 1.1

Short Term Condition Method: Spencer Minimum Factor-of-Safety: 4.71 Center: (38.897, 124.962) ft Radius: 51.18818 ft

Levee

Fat Clay (CH)

Lean Clay (CL)

Distance (feet) -150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

E le va tio n (fe et

Levee (Effective)

Fat Clay (CH) (Effective)

Lean Clay (CL) - (Effective)

Soil Properties Name: Levee (Effective) Unit Weight: 125 pcf Cohesion: 250 psf Phi: 27 ° Name: Lean Clay (CL) - (Effective) Unit Weight: 125 pcf Cohesion: 150 psf Phi: 25 ° Name: Fat Clay (CH) (Effective) Unit Weight: 125 pcf Cohesion: 200 psf Phi: 20 °

South Levee - Section 1 (Sta. No. 246+59.91 to 300+00) Boring MFS1-1 to MFS1-5 Crown Width: 16 feet; Side Slopes: 3H:1V Crown Elevation: 112 feet; Flood Elevation: 109 feet

Long Term Condition Method: Spencer Minimum Factor-of-Safety: 1.89 Center: (42.881, 137.546) ft Radius: 35.88126 ft

FIGURE 1.2

Levee

Fat Clay (CH)

Lean Clay (CL)

Distance (feet) -150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

E le va tio n (fe et

Levee (Effective)

Fat Clay (CH) (Effective)

Lean Clay (CL) - (Effective)

Soil Properties Name: Levee (Effective) Unit Weight: 125 pcf Cohesion: 250 psf Phi: 27 ° Name: Lean Clay (CL) - (Effective) Unit Weight: 125 pcf Cohesion: 150 psf Phi: 25 ° Name: Fat Clay (CH) (Effective) Unit Weight: 125 pcf Cohesion: 200 psf Phi: 20 °

South Levee - Section 1 (Sta. No. 246+59.91 to 300+00) Boring MFS1-1 to MFS1-5 Crown Width: 16 feet; Side Slopes: 3H:1V Crown Elevation: 112 feet; Flood Elevation: 109 feet

FIGURE 1.3

Rapid Draw-Down Condition Method: Spencer Minimum Factor-of-Safety: 1.71 Center: (-43.599, 137.64) ft Radius: 35.88191 ft

Levee

Fat Clay (CH)

Lean Clay (CL)

Distance (feet) -150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

E le va tio n (fe et

Levee

Fat Clay (CH)

Lean Clay (CL)

0.01

.0

0.01

0.02

.0

0.07 0.08

0.09

0.11

.1

0.14

0.15

0.15

.16

.28

0.29 0.34

0.36

Soil Properties Name: Levee Model: Saturated Only K-Sat: 1.18e-005 ft/hr Name: Fat Clay (CH) Model: Saturated Only K-Sat: 1.18e-005 ft/hr Name: Lean Clay (CL) Model: Saturated Only K-Sat: 1.18e-005 ft/hr

South Levee - Section 1 (Sta. No. 246+59.91 to 300+00) Boring MFS1-1 to MFS1-5 Crown Width: 16 feet; Side Slopes: 3H:1V Crown Elevation: 112 feet; Flood Elevation: 109 feet

Exit Gradient = 0.35

Steady-State Seepage Analysis Contours of Hydraulic Gradient

Fat Clay (CH)

Lean Clay (CL)

FIGURE 1.4

Levee

.3

1e

-0 ft ³/h r

.5

8e

-0 ft ³/h r Distance (feet)

-150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

E le va tio n (fe et

VOLUME III, SECTION 2 - PAGE NO. 1

SECTION 2.0: STA. 300+00 TO STA. 349+00 (MFS1-6 TO MFS1-10)

analyses for the Main Floodway South levee extending between Sta. 300+00 and Sta.

349+00. The subsurface conditions in this area of the project site were explored with five (5) soil borings (i.e., MFS1-6 through MFS1-10).

2.1 CROSS-SECTIONAL INFORMATION

The cross-sectional drawings of the levee system and the following information were provided by S & B Infrastructure, LTD on May 6, 2009. The existing cross-sectional information, in conjunction with the proposed levee crown elevations was reviewed to identify the maximum height (most critical) for the proposed levee geometry and a design levee cross-section was selected. The cross-section at STA. 310+43.00 was used for the analyses. Please note that the dimensions are rounded to the nearest foot for calculation purposes.

2. Proposed Side Slope Inclination (Flood Side): 2 to 2.5H:1V

3. Proposed Side Slope Inclination (Enlargement on Land Side): 3H:1V

4. Flood Water Elevation: Three (3) feet below levee crown (freeboard)

5. Existing Levee Height: 15 feet

6. Maximum Final Levee Height: 18 feet

7. Maximum Additional Fill to Raise the Levee: 3 feet

2.2 SUBSURFACE CONDITIONS

borings (i.e., Borings MFS1-6 through MFS1-10) drilled to depths between 50 and 100 feet below the existing ground surface.

Laboratory test data along with detailed descriptions of the soils found within this portion of the levee system can be found on the logs of Borings MFS1-6 through MFS1-10 included in Appendix 2.1. Appendix 2.1 also contains portions of the laboratory test data including the results of the consolidated undrained triaxial tests with pore pressure measurements (CU test), consolidation tests and permeability tests and other tests.

Existing levee materials consisted predominantly of soft to hard lean clay and fat clay.

Native soils beneath the levee generally consist of very soft to very stiff lean clay, lean clay with sand, sandy lean clay, silty clay, fat clay, and loose to very dense silty sand, silt with sand, sand with clay, clayey sand. The range of the laboratory test results is presented below in Table 2.1:

VOLUME III, SECTION 2 - PAGE NO. 2

Table 2.1: Summary of Laboratory Test Results (Borings MFS1-1 through MFS1-10)

Stratum Description

Moisture Content

Atterberg Limits

Shear Strength (tsf)

Percent Passing No.

200 (%)

SPT – N

Values

(blows/ft)

Levee (CH, CL) 12 to 38 LL = 44 to 62 PI = 24 to 41 0.2 to 2.52 81 to 98 6 to 39

Fat Clay (CH), Lean Clay (CL), Lean Clay with

Sand (CL), Sandy Lean Clay (CL), Silty Clay

(CL-ML)

18 to 41 LL = 25 to 58 PI = 8 to 36 0.1 to 1.78 51 to 99 0 to 23

Sand (SP), Silty Sand (SM), Sand with Clay (SP- SC), Clayey Sand (SC)

8 to 47 LL = 34 PI = 13 - 12 to 23 6 to 88

Notes: LL: Liquid Limit; PI: Plasticity Index

2.3 DESIGN SOIL STRENGTH PROFILE

of our field and laboratory test data on selected soil samples, 2) prudent engineering judgment based on experience with similar soils, and 3) published correlations.

The selection process for obtaining soil strength parameters used in the stability analyses for the 1) Short-Term Condition, 2) Long-Term Condition, and 3) Rapid Draw- Down Condition (upstream slope) are described below:

• As previously mentioned, average undrained strength of the soil as measured by the Unconfined Compression tests and Unconsolidated Undrained tests were used to analyze the slopes in “short-term” conditions. For a clay layer (at a given cross-sectional location), the strength test results obtained on the soils of the nearest boring locations were averaged to obtain the undrained shear strength parameters.

For a sand layer, the blow counts obtained from the field Standard Penetration Test (N-Values) were used to obtain the angle of internal friction. The values were obtained utilizing various correlations available in the geotechnical literature, our engineering judgment and well-established local experience.

were utilized. The phreatic surface developed during a theoretical steady-state seepage condition was utilized for both of these stability scenarios. These are presented below in Table 2.2.

VOLUME III, SECTION 2 - PAGE NO. 3

Table 2.2 Design Soil Strength Parameters Soil Strength Parameter(s)

Stratum (Elev. Range, feet) Undrained

(Short-Term)

Effective (Long-Term & Rapid Draw-down) Levee (CH, CL) (+111 to +93 ft.) Su = 1,000 psf c’ = 250 psf φ’= 27o

Fat Clay 1 (CH) (+93 to +85 ft.) Su = 1,500 psf c’ = 150 psf φ’= 20o

Clayey Sand (SC) (+85 to +65 ft.) Su = 500 psf c’ = 50 psf φ’= 27o

Sand 1 (SM) (+65 to +56 ft.) φ’ = 33o c’ = 0 psf φ’= 33o

Fat Clay 2 (CH) (+56 to +52 ft.) Su = 2,000 psf c’ = 200 psf φ’= 20o

Silty Sand 3 (SM) (+52 to +27 ft.) φ’ = 33o c’ = 0 psf φ’= 33o

Lean Clay (CL) (Below +27 ft.) Su = 1,500 psf c’ = 150 psf φ’= 25o

Notes: Su - Undrained Shear Strength, c’ - effective cohesion, φ’ - effective angle of internal friction

2.4 DISCUSSION OF RESULTS AND RECOMMENDATIONS

Using the soil strength parameters shown in Table 2.2, slope stability analyses were performed for the design (critical) cross-section previously mentioned in this section. The proposed side slopes of the levee enlargement at this location are 3H:1V with a maximum slope height of about 18 feet. The results of the stability analyses are shown graphically in Appendix 2.2.

• Based on the results of the slope stability analyses, the minimum calculated factor-of-safety for the short-term condition using undrained soil strength parameters is

1.78 (see Figure 2.1), thereby indicating stable slopes. The computed factor-of-safety for this condition exceeds the minimum acceptable value of 1.3, as parameters, the minimum calculated factor-of-safety is 1.66 (see Figure 2.2), thereby indicating stable slopes. The computed factor-of-safety for this condition exceeds the minimum acceptable value of 1.5, as recommended in the USACE publication Slope minimum calculated factor-of-safety is 1.56 (see Figure 2.3) and this condition is considered to be stable. The computed factor-of-safety for this condition exceeds

VOLUME III, SECTION 2 - PAGE NO. 4

the minimum acceptable value of 1.0, as recommended in the USACE publication weathering (aging) in response to wetting and drying cycles, thereby resulting in a decrease in soil strength over time. A rapid draw-down condition in conjunction with soil weathering may result in sloughing of the riverside levee slope following a flood event.

These shallow failures should be regarded as a maintenance issue and it is

2.5 LEVEE SETTLEMENT ANALYSES

Within this segment of the levee (i.e., between Sta. 300+00 and Sta. 349+00), the levee is planned to be raised by approximately three (3) feet. Based on our analyses, the long-term settlement induced by the proposed levee enlargement is estimated to be less than one (1) inch.

2.6 SEEPAGE ANALYSES

USACE EM 1110-2-1901. A steady-state seepage analysis was performed for this section of levee using the finite-element computer program SEEP/W (see Figure 2.4).

Hydraulic gradients were calculated for the design cross-section and compared to established criteria. Based on this analysis, the exit gradient at the landside toe was calculated to be about 0.49. The ratio of the critical gradient (the gradient at which piping can occur) to the calculated gradient results in a factor-of-safety against piping.

Based on a critical gradient of 0.8, the resulting factor-of-safety exceeds the minimum value of 1.6, as recommended by the USACE. In addition, the seepage rate for this section of levee is estimated to be less than one (1) gallon per day, which is considered to be low. Therefore, mitigation measures for seepage are not warranted. Results of the seepage analyses are presented on Figure 2.4.

2.7 CONSTRUCTION RECOMMENDATIONS

As previously mentioned, the levee will be raised by a maximum of about four (4) feet in this section (Sta. 300+00 to Sta. 349+00). Borrow materials for levee construction can be clays, sandy clays classified as CL, and fat clays (CH). Silts, sands and organic soils are unsuitable for levee construction. The borrow materials shall be selected and placed in strict accordance with Section 4 of USACE Publication EM 1110-2-1913.

The borrow materials shall be placed in maximum lifts of 12 inches of loose material and compacted to at least 95 percent of standard Proctor maximum dry density as determined by ASTM D 698 with the range of two percentage (+1% to +3%) points of the optimum moisture content value. The first layer of fill shall be placed in a relatively

VOLUME III, SECTION 2 - PAGE NO. 5

uniform horizontal lift and be adequately keyed into the existing levee soils. Please refer to Volume 1of this report for additional recommendations.

Any structures or other special features within the levee (such as pipe penetrations) shall be designed and constructed in accordance with Section 8 of USACE Publication EM 1110-2-1913.

2.8 CONCLUSIONS

Based on our analyses of this section (Sta. 300+00 to Sta. 349+00), the levee can be raised by a maximum of about three (3) feet with the side slope inclination of 2H:1V to 3H:1V. However, it is recommended that the levee should be constructed with the slope inclination of 3H:1V (or flatter) on both sides of the levee. The slope stability, seepage and settlement of the new levee system are acceptable and satisfy prudent and well-accepted USACE engineering criteria for the stability of levees.

VOLUME III, SECTION 2 - PAGE NO. 6

APPENDIX 2.1

LEAN CLAY WITH SAND (CL), Stiff, Brown, Moist

FAT CLAY (CH), Hard, Brown, Moist

SILTY SAND (SM), Medium Dense to very Dense, Brown, Wet

No recovery

SANDY LEAN CLAY (CL), Firm to Stiff, Brown, Moist

With Some Gravel from 95 to 100 Feet

CLAYEY SAND WITH GRAVEL (SC), Very Dense, Poorly Graded, Fine to Medium Grained Sand, Brown, Wet, Subangular Gravel

CH

SM

CL

SC

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 100 FEET

LOG OF BORING MFS1-6

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

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T

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(p cf

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UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/24/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 307+45.90

INITIAL GROUND WATER (FT)

GROUND WATER

FINAL GROUND WATER (FT): 25 Feet

TYPE OF BORING: HOLLOW STEM AUGER

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P J

52.5

55.0

57.5

60.0

62.5

65.0

67.5

70.0

72.5

75.0

77.5

80.0

82.5

85.0

87.5

90.0

92.5

95.0

97.5

100.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Lean Clay with Sand (CL), Very Stiff, Dark Brown, Moist

Shear Strength = 2.52 tsf

APPROXIMATE BOTTOM OF LEVEE

LEAN CLAY (CL), Stiff, Brown, Moist

FAT CLAY (CH), Stiff, Brown, Moist

Very Soft at 25 Feet

LEAN CLAY (CL), Firm, Brown, Moist to Wet

LEAN CLAY WITH SAND (CL), Stiff, Brown, Moist

CL

CL

CH

CL

CL

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

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SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 100 FEET

LOG OF BORING MFS1-6

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

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N T

LI

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LA

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(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/24/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 307+45.90

INITIAL GROUND WATER (FT)

GROUND WATER

FINAL GROUND WATER (FT): 25 Feet

TYPE OF BORING: HOLLOW STEM AUGER

APPROXIMATE SURFACE ELEVATION: 109.13 feet

COORODINATE (X) OR EASTING: 1069520

COORDINATE (Y) OR NORTHING: 16575713

B L_

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-1

0\ M

F S

-1

R

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-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Lean Clay (CL), Firm to Very Stiff, Dark Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

FAT CLAY (CH), Fat Clay (CH), Very Stiff, Brown, Moist

LEAN CLAY WITH SAND (CL), Very Soft to Stiff, Brown, Moist

Shear Strength = 0.68 tsf

LEAN CLAY (CL), Stiff, Brown, Moist

SILTY SAND (SM), Poorly Graded, Fine Grained, Loose to Medium Dense, Brown, Wet

CL

CH

CL

CL

SM

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS1-7

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

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(p cf

U S

C S

S Y

M B

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UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/14/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 310+43.00

INITIAL GROUND WATER (FT) 28 Feet

GROUND WATER

FINAL GROUND WATER (FT): 32 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 28 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 108.39 feet

COORODINATE (X) OR EASTING: 1070805

COORDINATE (Y) OR NORTHING: 16575932

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P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Lean Clay (CL), Very Stiff, Brown, Moist

LEVEE MATERIAL: Fat Clay (CH), Very Stiff, Brown, Moist..

APPROXIMATE BOTTOM OF LEVEE

LEAN CLAY WITH SAND (CL), Very Stiff, Brown, Fine Grained Sand, Moist...

Shear Strength = 1.78 tsf

SILT WITH SAND (ML), Firm, Brown, Fine Grained Sand, Moist

SAND WITH CLAY (SP), Poorly Graded, Fine Grained, Loose to Dense, Brown, Moist to Wet

CL

CH

CL

ML

SP

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

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SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS1-8

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

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O N

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(p cf

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C S

S Y

M B

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UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/13/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 319+19.91

INITIAL GROUND WATER (FT)

GROUND WATER

FINAL GROUND WATER (FT): 22 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 30 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 107.64 feet

COORODINATE (X) OR EASTING: 1071664

COORDINATE (Y) OR NORTHING: 16576108

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P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Fat Clay (CH), Very Stiff, Dark Brown, Moist

Lean Clay layer at 8 feet

APPROXIMATE BOTTOM OF LEVEE

LEAN CLAY (CL), Fat Clay (CH), Firm to Very Stiff, Brown, Moist

SILTY CLAY (CL-ML), Firm, Brown, Moist

SILTY SAND (SM), Poorly Graded, Fine Grained, Hard, Brown, Wet

CH

CL

CL-ML

SM

10151

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS1-9

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

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O N

T E

N T

LI

Q

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LI

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P

LA

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N -B

LO

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S /F

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S A

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H T

(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/14/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 329+70.43

INITIAL GROUND WATER (FT)

GROUND WATER

FINAL GROUND WATER (FT): 15 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 30 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 107 feet

COORODINATE (X) OR EASTING: 1072687

COORDINATE (Y) OR NORTHING: 16576236

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G

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-1

0\ M

F S

-1

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-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

4'' to 6'' GRAVEL BASE LEVEE MATERIAL: Fat Clay (CH), Very Stiff, Brown, Moist

APPROXIMATE BOTTOM OF LEVEE

FAT CLAY (CH), Very Stiff, Brown, Moist

Shear Strength = 0.55 tsf

CLAYEY SAND (SC), Poorly Graded, Fine Grained, Loose to Dense, Brown, Moist to Wet

SAND WITH CLAY (SP-SC), Poorly Graded, Fine Grained, Dense to Very Dense, Brown, Moist to Wet

CH

CH

SC

SP-SC

PL PI

P

LA

S T

IC

IT

Y

IN

D E

X

P

A S

S

IN

G N o.

S

IE

V

E

SHEAR STRENGTH

(tons/square foot)

0.0 0.5 1.0 1.5 2.0 2.5

S O

IL

T

Y P

E

HP UC TV

DEPTH OF BORING: 50 FEET

LOG OF BORING MFS1-10

Hidalgo County

D E

P T

H , F

T

IBWC South Levee

LL

M O

IS

T

U R

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O N

T E

N T

LI

Q

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M

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P

LA

S T

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LI

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N -B

LO

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S /F

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(p cf

U S

C S

S Y

M B

O L

UU

PSI Project No.: 322-95001

SOIL DESCRIPTION

DATE DRILLED: 4/14/09

NOTES:

Geotechnical Consulting Services 2020 North Loop 499, Suite 302 Harlingen, Texas 76548

STATION NO.: 340+19.38

INITIAL GROUND WATER (FT)

GROUND WATER

FINAL GROUND WATER (FT): 23.5 Feet

TYPE OF BORING: HOLLOW STEM AUGER TO 25 FEET/ WET ROTARY

APPROXIMATE SURFACE ELEVATION: 106.44 feet

COORODINATE (X) OR EASTING: 1073692

COORDINATE (Y) OR NORTHING: 16576522

B L_

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:4

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S

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L O

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\F

IN

A L

LO

G

S \M

F S

-1

0\ M

F S

-1

R

E V

-1 .G

P J

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

32.5

35.0

37.5

40.0

42.5

45.0

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

CH

CH

SC

SP

SC

MFS1-10

CL

CL

CH

CL

CL

CH

SM

CL

SC

MFS1-6

CL

CH

CL

CL

SM

MFS1-7

CL

CH

CL

ML

SP

MFS1-8

CH

CL

CL

ML

SM

MFS1-9

E le va tio n

1073692 1069520 1070805 1071664 1072687

106.4 109.1 108.4 107.6…