Report_GEO_AC-820579_HWY-310.pdf

P.O. Box 260370, San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

April 12, 2019

Enrique Ruiz & Associates PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Addendum No.1 Proposed Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-310 at State Road PR-181, KM 8.7 on Marín Ward of the Municipality of Patillas, Puerto Rico.

Reference No. DA/18O3775

Gentlemen:

Following the necessary approval of our revised proposal by the PRTHA’s Soils Engineering office, Despiau

Associates was engaged for the Geotechnical Engineering & Subsurface Exploratory Services on the referenced project. The scope of work and associated terms and conditions of our engagement were detailed in said revised proposal.

However, in order to verify the adequacy of the presented reconstruction alternatives, internal and external stability analyses for slopes within the project’s limits were performed. The degree of stability of a slope is expressed as the factor of safety, which is the ratio of the forces resisting failure to the driving forces causing instability.

The undersigned hereby certifies that the analyses contained in our geotechnical report were performed following the Puerto Rico Transportation and Highway Authority (PRTHA) Design guidelines, including internal and external stability. Moreover, the undersigned confirms that, provided the recommendations contained in the geotechnical report of reference are strictly followed and considered in the design, adequate safety factors for global stability against Static and Pseudo-Static conditions will be obtained. Furthermore, additional slope stability analyses may be performed to assure the global stability of the finally selected alternative.

Should you have any question regarding these matters, please do not hesitate to contact the undersigned.

Respectfully submitted, DESPIAU ASSOCIATES

Jose R. Despiau, P.E.

Geotechnical Engineer http://www.despiau.net/ mailto:e.ruiz@era-pr.com

P.O. Box 260370, San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

April 29, 2022

PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Addendum No.2 Proposed Geotechnical Engineering and Subsurface

Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-310 at State Road PR-181, KM 8.7 on Marín Ward of the Municipality of Patillas, Puerto Rico. Reference No. DA/18O3775

Gentlemen:

Please attached the revised boring logs with the revised soil description based on the classification column. The herein submitted revised Boring Logs shall supersede the previously submitted with the geotechnical report. Therefore, this Addendum No. 2 is an integral part of the already submitted geotechnical report.

Should you have any question regarding these matters, please do not hesitate to contact the undersigned.

Respectfully submitted, Jose R. Despiau, P.E.

Enclosure http://www.despiau.net/ mailto:e.ruiz@era-pr.com

PROJECT: REFERENCE NO.:

BORING NO.:

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v er y

R .Q

.D

W a te r

C o n te n t q u

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n d ex

S o il

C la ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-1

Patillas

246845.917 223925.418

12/27/18

351.61

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

UU

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

7-8-20

13-37-41

30-47-52

37-51-53

44-60/6"

76/3"

100/6"

100/3"

32-59-36

100/1"

100/3"

100/2"

Ground Surface

6" Asphalt 3" Base Course

Silty Sand (Fill) Light olive brown, white mottled silty sand.

Clayey Sand (R) Light olive brown, white and black mottled clayey sand, trace cemented weathered rock gravel fragments.

Silty Sand (WC) Light olive brown, white and black mottled silty sand, some consolidated sandstone fragments.

Clayey Sand (WH) Light olive brown and white mottled clayey sand with trace of weathered sandstone fragments, G ro un d w at er le ve l w as n ot fo un d w ith in th e ex te nt d ril le

NP

A-2-4 (0)/SC

A-1-b (0)/SC

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 2 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-1

Patillas

246845.917 223925.418

12/27/18

351.61

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS 14 100/2" -

Continue - Clayey Sand (WH) Same as above.

Note:

Weathered rock was broken by sampling device into the described constituents

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-2

Patillas

223919.675 246815.101

12/28/18

349.65

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

8-8-8

24-27-38

37-40-41

20-31-40

41-50-57

42/60/3"

60/4"

70/4"

51-60/4"

67/6"

54-80/3"

75/4"

Ground Surface

6" Asphalt 5" Base Course

Clayey Sand (Fill) Light olive brown; white, black and light olive brown mottled, clayey sand trace subangular gravel fragments.

Silty Sand (R) Light olive brown, white and black mottled silty sand, trace subangular gravel fragments.

Clayey Sand (WC)

Light olive brown, pale yellow and black mottled clayey sand, some sandstone gravel fragments.

un d w at er le ve l w as n ot fo un d w ith in th e ex te nt d ril le

26.1

6.1

A-2-4(0)/SC-SM

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 2 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-2

Patillas

223919.675 246815.101

12/28/18

349.65

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

90/3"

100/2"

Clayey Sand (WC)

Same as above.

Note:

Weathered rock was broken by sampling device into the described constituents.

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-3

Patillas

223924.676 246800.366

12/17/18

349.15

Mot. Cathead

Jose R. Bruno

Wash Boring

2-1/2" O.D.

300 30

30 N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

4-5-7

9-12-17

24-21-28

23-27-38

26-16-14

23-32-27

30-37-35

32-41-50

42-60/6"

63/6"

40-55-70

51-73/6"

75/4"

Ground Surface

Sandy Silt Light olive brown; white and black mottled sandy silt.

Clayey Sand (R) Light olive brown, white and black mottled clayey sand, trace (-) sandstone consolidated fragments.

Sandy Silt (WC) Brown; pale yellow and white mottled sandy silt, some weathered sandstone.

Clayey Sand (WH) Olive; pale yellow and blalck mottled clayey sand, trace weathered sandstone and siltstone fragments.

un d w at er le ve l w as n ot fo un d w ith in th e ex te nt d ril d.

29.6

9.3

A-4 (0)/SC

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 2 of 2

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-3

Patillas

223924.676 246800.366

12/17/18

349.15

Mot. Cathead

Jose R. Bruno

Wash Boring

2-1/2" O.D.

300 30

30 N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

70/6"

82/5"

78/6"

90/5"

Continue- Clayey Sand

Same as above.

Note:

Weathered rock was broken by sampling device into the described constituents.

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 1

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-310 Landslides and Road Damage Evaluation DA/18O3775

310-4

Patillas

223925.982 246823.424

12/29/18

344.44

Mot. Cathead

Jose R. Bruno

Wash Boring

2-1/2" O.D.

300 30

30 N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

UU

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

3-1-1

3-4-4

5-12-18

18-18-20

28-50-34

12-28-60

20-38-50

30-41-37

50-60/4"

70/5"

Ground Surface

Silty Sand (Fill/Slope-Wash) Brown, gray, white mottled silty sand, some clay, trace subangular gravel fragments, many roots.

Silty Sand (Fill/Slope-Wash) Reddish brown, white mottled silty sand, some clay, trace subangular gravel fragments.

Silty Sand (R) Reddish brown, white mottled silty sand, some clay, trace subangular gravel fragments.

Clayey Sand(WC) Light olive brown; white and black mottled clayey sand, trace weathered sandstone rock fragments.

Note:

Weathered rock was broken by sampling device into the described constituents.

un d w at er w as n ot fo un d w ith in th e ex te nt d ril d.

25.3

3.7

A-2-4 (0)/SM

CONSULTING GEOTECHNICAL ENGINEERS

PO BOX 260370

San Juan, PR 00926-2622 www.despiau.net

Report of Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project at State Road PR-181, KM 8.7, Marín Ward of the Municipality of Patillas, Puerto Rico.

Reference No. DA/18O3775

PROJECT ID: ER-HWY-310

January 17, 2019

Prepared for:

Enrique Ruiz & Associates, PSC PO Box 360977

San Juan, Puerto Rico 00936-0977

Jose R. Despiau, P.E., License #17343 Geotechnical Engineer, Despiau Associates – Consulting Geotechnical Engineers.

P.O. Box 260370 San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

January 17, 2019

PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Proposed Geotechnical Engineering and Subsurface Exploratory Services for the

Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-310 at State Road PR-181, KM 8.7 on Marín Ward of the Municipality of Patillas, Puerto Rico. Reference No. DA/18O3775

Dear Eng. Ruiz:

As requested, we have completed the Subsoil Exploration and Geotechnical Engineering Assessment for the review of the landslide(s) and/or road, which were affected post Hurricane María as part of the Landslide and Road Damage Evaluation and Reconstruction Project ER- HWY-310, at State Road PR-181, KM 8.7, Marín Ward of the Municipality of Patillas, Puerto Rico.

The work was undertaken at the request of Mr. Enrique Ruiz, PE, President of Enrique Ruiz & Associates, PSC. The work was made in accordance to Proposal No. DA/04-53-18R for the subsurface exploration dated May 15, 2018. The work was commenced after order to proceed for the work was received on November 11, 2018.

This report presents the results of the field exploratory drilling, laboratory tests performed on secured soil samples, engineering assessments from geotechnical standpoint, soil and foundation design parameters for the proposed improvements (i.e. retaining walls, cut and fill earthwork specifications) as required thereof.

It has been a pleasure to have been of your assistance in this project.

Respectfully Submitted, Jose R. Despiau, PE.

Project No.: DA/18O3775 Patillas, Puerto Rico January 17, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS i

TABLE OF CONTENTS

Page No.

I. INTRODUCTION

II. SITE AND PROJECT DESCRIPTION

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

3.2 Geological Notes

3.3 Stratigraphic Units

IV. OBSERVATIONS AND FINDINGS

V. ENGINEERING RECOMMENDATIONS

5.1 General Design Parameters for Retaining Structures

5.1.1 Additional Considerations for Retaining Structures

5.2 Additional Recommendations for a Sheet Pile Retaining System

5.2.1 Lateral Load Design Considerations

5.3 Additional Recommendation for a Reinforced Soil Wall

5.3.1 Steps for Geogrid Reinforcement Selection

5.3 Cantilever Retaining Structure Foundation Recommendations

5.4 General Slope Surfaces Recommendations

5.4.1 Summary of General Construction Guidelines for the Slope Improvements

5.5 Earthquake Design

5.6 Excavations

5.7 Earthwork Recommendations for Fill and Cut Sections

5.7.1 Fill Sections

5.7.2 Temporary Cut Sections

5.8 Additional Earthwork Recommendations

5.8.1 Recommended Fill Types and Compaction Specifications

5.9 Proposed Storm Water Run-off Control

5.10 Nearby Structures

5.11 Additional Recommendations

VI. LIMITATIONS OF THIS REPORT

Appendix (A) – Figures

1. US Geological Survey Service Topographical plan at a scale 1:20,000 1A. Geological Map

2. Boring Location Plan

Appendix (1) - Boring Logs Appendix (2) - Fill Specifications Appendix (2-A) - Benching Appendix (3) - Special Laboratory Tests

I. INTRODUCTION

This report covers the Subsoil Exploration and Geotechnical Engineering Assessment for the review of the landslide(s) and/or road, which were affected post Hurricane María as part of the

Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-310, at State Road

PR-181, KM 8.7, Marín Ward of the Municipality of Patillas, Puerto Rico.

The work was undertaken at the request of Mr. Enrique Ruiz, PE, President of Enrique Ruiz &

Associates, PSC. The work was made in accordance to Proposal No. DA/04-53-18R for the subsurface exploration dated May 15, 2018. The work was commenced after order to proceed for the work was received on November 5, 2018.

This report presents the results of the field exploratory drilling, laboratory tests performed on secured soil samples, geotechnical assessments, and summary of findings, and recommendations for required site improvements.

Presently, three (3) reconstruction alternatives to cope with the disclosed conditions at the Site can be considered by the A/E Design Team. However, should the A/E design team consider other(s) and/or additional design reconstruction alternatives these shall be forwarded to this office to evaluate them and provided the required geotechnical recommendation, if deemed necessary.

In the following sections of this report the soil and foundation design parameters for the proposed improvements (i.e. retaining structures, cut and fill earthwork specifications) are being provided.

The selected boring locations were used to establish the profile data at the specific explored locations for the present geotechnical engineering review. This report has been prepared for the exclusive use of the owner and the A/E Consultant Firm involved in the preparation of the site engineering design plans and specifications.

II. SITE AND PROJECT DESCRIPTION

The Site observation revealed a slide occurred on the northern edge of State Road PR-181, near

KM 8.7, after the passing of Hurricane Maria. The affected area from the slide is approximately

50 meters long and caused the partial rupture of State Road PR-181 some 3.0 to 5.0 meters north

Project No.: DA/18O3775 Patillas, Puerto Rico January 17, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 2

of the northern edge of the road. The observed slide is found near km 8.7 of State Road PR-181 at Marín Ward of the Municipality of Patillas, Puerto Rico.

Evaluation revealed the site carries storm water from the highland sectors of the south toward the lowland areas at the north through a natural drainage gully streams all the way to Quebrada De los Colones Creek. Based on the US Topographic map, two (2) drainage gullies, spaced at about

90 m., run almost perpendicular to State Road PR-181. Evaluation dictate these drainage gullies carry all surface runoff from Cerro La Torrecilla hilltop (at nearly 600 mts. in elevation) all the way to Quebrada de los Colones Creek, which has an approximate elevation of 300 mts. to the north of the Site. De Los Colones Creek flow towards de south-west toward Marín River, found on the

Patillas Quadrangle map.

In addition, additional surface runoff from the northeastern highland sector runs along State Road

PR-181 collected on an existing catch basin (approx. elev. 348.13 mts.) and discharging this additional runoff through a 36”-inch concrete pipe. This is an affluent, which drains surface flows from the highland sectors to the south-northeast toward the De Los Colones Creek found to the north of the project site.

Based on the topographic plans submitted for the present evaluation, disclose the invert elevation of the Storm Sewer Pipe outfall is at an approximate elevation equal to 346.79. It is near this area where a major scarp slide occurred as evidenced during our field visits.

Thus, it has been concluded the excessive storm water runoff gave way for the displacement and rupture of the original road alignment. Also, it is evident the 36”-inch drainage pipe was not enough to cope with the excess storm water runoff experienced during the hurricane event.

Moreover, this storm sewer pipe also contributed in adding additional surface flow to the eastern sloping grounds.

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

The subsurface soil conditions at the site were investigated four (4) standard penetration test borings performed to assess the existing subsoil conditions at the project site. The location of

Project No.: DA/18O3775 Patillas, Puerto Rico January 17, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 3

Boring No. 4 was established on the northern sloping grounds, some 4.5 meters north of PR-181 road edge. The location of borings is shown in the accompanying Boring Location Plans, in

Appendix A, Figure No. 2.

Sampling of soils was performed continuously in the upper 10 ft. and thereafter, at approximately five-foot intervals. All soil samples were taken with a 2"-O.D. split barrel sampler following the standard penetration test procedures in ASTM D-1586. Penetration resistance values from the standard penetration tests are recorded in the "N" column of the boring logs.

The procedures used for the laboratory tests, as well as the routine and special laboratory procedures used, for the determination of the index soil properties are contained in the Appendix

(1) to this report.

3.2 Geological Notes

Based on the US Geological Survey of the Yabucoa and Punta Quadrangles (Map I-1086), prepared by Mr. C.L. Rogers, C.M. Cram, M.H. Pease, Jr., and M.S. Tischer (1979), the geologic units that lie at or near the site are the following:

1. Tonalite Facies of Granodiorite of San Lorenzo (Upper Cretaceous) (Klt) - Described as similar in occurrence, general appearance and mineralogy to the Granodiorite of San

Lorenzo, and separately mapped on where it forms borders sufficiently large and well defined. In the eastern and southern parts of quadrangle mapping was based largely on petrography, boundaries are transitional and indefinite. In the west, tonalite facies is locally more distinctive and can be recognizes in the field. Average modal composition (35 analyses) is 57.5 percent plagioclase, 2 percent potassium feldspar (3.5 percent of total feldspar), 20.5 percent quartz, 13 percent hornblende, 0.5 percent augite, 4.5 percent biotite, 1.5 percent magnetite, minor myrmelkite, and accessory sphene, apatite, and zircon. The plagioclase is largely andesine.

2. Metavolcanic Rocks (Upper Cretaceous) (Kmv)– Described as weakly metamorphosed volcanic rocks derived from lava flows, with some flow breccia and tuff and tuffaceous siltstone and sandstone. Lava flows are dark-gray to greenish-gray, predominantly fine-

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grained., porphyritic and amygdaloidal in varying degrees, and characterized by subtrachytic to felted and granoblastic textures. Predominantly plagioclase (originally intermediate in composition but now extensively albitized) and green to bluish-green hornblende or actinolite. Minor clinopyroxene, minor sporadic quartz and potassium feldspar (obviously secondary, in large part), ubiquitous fine- to very fine-grained magnetite and pyrite, and common alteration products, including sericite, clay, epidote, clinozoisite, chlorite, and limonite stain. Tuffs are dark greenish-gray, composed of lithic and mafic-crustal fragments in aphanitic matrix spotted with light greenish-gray plagioclase-crystal fragments. Rocks near western margin of mapped area and north of Río Maunabo are predominantly siltstone and sandstone and are dark gray to greenish gray, fine-grained, massive to finely laminated, with granoblastic texture; locally show graded bedding.

Predominantly plagioclase, clinopyroxene and quartz in variable proportions, with some hornblende or actinolite, ubiquitous fine- to very fine-grained magnetite and pyrite, and usual alteration products, including clay, sericite, chlorite and epidote; grains generally angular to subangular, but locally subrounded.

The approximate fault (dashed), along the south-west alignment of Quebrada de los Colones

Creek was identified at about 115 meters, northwest of the site. It also intersects a well-defined

Unnamed Fault, with a near south trend; that intersects about 520 south-west of the site. Also, northeast continuing nearly the same alignment of Quebrada de los Colones Creek, several additional well-defined Faults lines are shown in the Geologic map, among which there is

Quebrada Guayabo a well-defined alignment with a north to south trend and intersecting at about

6800 ft. from the study area. The Quebrada Guayabo Fault line passes through the Geologic

Formation of the Granodiorite of San Lorenzo.

Refer to the US Geological Survey – Geologic Map which is included in Appendix A, Figure 1A.

3.3 Stratigraphic Units

Surface Section – Generally at the road surface, the results of the exploration disclosed a surface layer thickness of about 3.0 ft. in depth. It is composed of a mixture of silty sand and sandy silt, with traces of subangular gravel fragments, with varying colors: light olive brown, with mottles white and black. Evidence of asphalt residue from the pavement structure were disclosed on the

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upper secured samples. The thickness of pavement was established in the field as 6”-inches and in the base course varying from 3” to 5” inches [Borings 310-1 and 310-2]. Also, at [Boring 310-

4] of lower elevation on the sliding surface section, few to many roots were found. The standard resistance to penetration (N-values) of the surface layers varied from 12 to 29 blows/foot, at a medium State of Consistency. At the location of Boring No. 310-4, some 5.0 ft. thick, the surface layer corresponding to a fill and slope wash layer. The (N-values) vary from 2 to 8 blows/foot

[Boring 310-4]. The natural moisture content values range from 8 to 24 percent.

Underlying the above described layer, the virgin soils consists of surface soils are identified as

Pandura loam 40 – 69 percent slope, eroded (PaF2); based on the US Soil Conservation Manual

(Sheet 45), these were described to be on side slopes and ridgetops in the humid dissected uplands that are well drained and have a rapid permeability. These were formed in residuum derived from partly weathered plutonic rocks, mainly quartz diorite and granodiorite. They are described as friable sandy loam, and strongly acid. Most of the its original surface layers has been removed by erosion.

Random samples of this layer from [Boring 310-2- from 0.0’ to 1.5 ft.] disclosed AASHTO class type A-2-4 (0) AASHTO type soils (USSCS type SC-Clayey sand). On Boring 310-4 from 0’ to

10.5 ft., an A-2-4 (0) AASHTO type (USSCS type SM-Silty sand) Soil was encountered. These correspond to the surface fill section. The Standard Free Swell Determination tests performed on the fill samples disclosed values ranging between 10 at 15 percent.

Residual Material – Beneath the above described section the residual material was found, extending to about 7.0 to 15.0 ft. in depth. These were described as light olive brown, with mottles white and black silty sand with traces of subangular gravel fragments; and at Boring [310-3] as sandy silt and clayey sand. The standard resistance to penetration (N-values) of the surface layers varied from 30 to 107 blows/foot, at a dense to very dense State of Compactness. The natural moisture content values range from 5 to 20 percent. Random sample of the residual material disclosed AASHTO class type A-2-4 (0) and A-4 (0) soils (USSCS type SC).

Completely Weathered Rock - At the deeper explored depths, until the borings were bottomed a weathered rock was broken by the sampling device into light olive brown and white mottled and light olive brown, pale yellow with mottles black sandy silt fines with traces of sandstone rock fragments, product of the weathering of the parent geologic units was found. The standard

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penetration test attempts varied from 88 blows/foot to practical refusal to penetration with values greater 70 blows for a few inches of penetration. The natural moisture contents range from 6 to

13 percent. Random sample of this horizon disclosed AASHTO class type A-1-b (0) soils (USSCS type SC – Clayey sand); AASHTO class type A-2-4 (0) soils (USSCS type SC – Clayey sand).

Graphical representation of the soil profiles is illustrated in the boring logs included as Appendix

(1) to this report.

3.4 Groundwater Levels

In general, the permanent ground water level was not found within the extent of depth drilled, during the period of exploration. However, high moisture content was observed on several samples of the upper surface layer, identified as slope wash [Boring 310-4]. All depths were measured from the existing ground surface prevailing during the period of exploration.

All surface ground and underground water should flow from the higher sectors at the west toward the lowland areas to the south west, intersecting De los Barros Creek, and then follows the Marin

River and finally, as an affluent joining the Patillas Lake.

IV. OBSERVATIONS AND FINDINGS

The present exploratory program was conducted to establish the subsurface profile and to allow the presentation engineering assessment, from a geotechnical standpoint, in addition to providing the construction guidelines for the implementation of the proposed improvements to the northern sloping grounds, where landslides scarps have been experienced on the northern edge of State

Road PR-181, which was subjected to extensive degradation, erosional effects, and landslides causing the observed damages and rupture of the road embankment and pavement structure.

Based on the results of the subsurface exploration performed, evaluations and site observations, our engineering assessment is that the primary cause for the prevalent conditions were caused by the excessive surface runoff, which caused the oversaturation (reducing the shear strength), and erosion of the lower northern sloping ground subsurface silty sand and sandy silt soils. The

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oversaturation of the underlaying clayey soils triggered a reduction of the shearing strengths causing unbalance conditions causing slope failure. Also, the intense or above normal erosional conditions experienced during Hurricane Maria was another primary factor which caused the prevailing conditions.

Moreover, the excessive surface runoff toward and through the existing drainage gully stream, running perpendicular to State Road PR-181 and additional surface runoff from the northeastern highland sector along State Road PR-181 which discharged these additional runoffs through the

36”-inch concrete pipe, also triggered the surface slides of the uppermost sloping surface and embankment section.

Therefore, to cope with the presently disclosed subsoil conditions and to assure not further instability is experienced, the herein recommendation shall be applied along the northern edge of

PR-181 to establish stable grounds and road safety. The herein recommendation by themselves and/or a combination of them shall be applied to the presently affected area (northern sloping grounds) to render stable grounds at the study area. The following section will provide the required Site improvements and the foundation design recommendation for the proposed re-construction alternatives.

Considering the subsoil profile and slope ratio prevailing at the site the northern sloping grounds shall be reconstructed all-throughout the study sector. However, considering the extent of the repair process this alternative may not be cost effective. Therefore, three (3) re-construction approaches or a combination of them may be considered. These are the following:

1. A possible solution to be considered is the installation of a Combined System composed of

Pre-drilled Steel HP-Piles (with the same minimum length of 20 ft.) with precast or cast-in-place concrete lagging panels to retain and restrict the embankment soil, existing structures movement (i.e. Pavement Structure) and the soil in between the piles. Considering the subsurface conditions at the site, where the residual and saprolitic material was found as shallow as 5.0 ft., the pre-auguering to encase the Steel-HP Piles shall be required.

If the embankment movements are not restrained, additional earth movements may further affect State Road PR-181. It shall be noted that the final length, type and quantity of pre-

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drilled HP steel-pile sections and lagging panels shall depend on the expected lateral loads and final grading elevations of the project.

2. Another reconstruction approach to consider is the use of a Reinforced Earth Wall using biaxial or triaxial geogrids (i.e. Tensar Geogrids or equivalent). The final length of the geogrids is a function of design, however for cost estimate and preliminary design evaluations purposes a minimum embedment length of 0.75 to 0.80 times the height of the wall and a minimum anchorage length passing the failure plane of 5.0 ft. shall be considered.

The overall length from the face of the wall to the tail of the geogrids is assumed to be constant throughout the height of the wall structure.

3. A cantilever retaining structure to retain the northern soil embankment mass and any existing structures (i.e. State Road PR-181 pavement structure) can also be considered. The retaining wall shall be provided all-throughout the affected area parallel to the northern edge of State Road PR-181. Evaluation dictate this retaining structure shall be some 30 meters long, approximately. The total height of the wall will depend on the final wall alignment and grading elevations of the project, which is predicted to be the same as the existing road side elevation which varies between 349.0 and 352.0 approximately.

Regardless, of the final solution to be implemented the installation of adequate drainage facilities to divert the surface runoff away the sloping surfaces shall be MANDATORY. Drainage facilities of enough capacity shall be provided to carry all surface water away from the embankment slope mass all the way to the toe of the northern sloping grounds, at least 200 ft. past the proposed retaining structures. Also, the surface of the existing gullies shall be provided with coarse gravely materials or even rip rap, reno mattress or similar erosion protection to prevent further erosion.

Also, we also strongly recommend the installations of monitoring instruments to assess the lateral yielding of the soil embankment mass adjacent to the identified study zone until the complete reconstruction of the retaining wall system is completed.

The following section of this report will further discuss this alternative and will provided the foundation design parameters.

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V. ENGINEERING RECOMMENDATIONS

The present geotechnical review revealed the aforementioned re-construction alternatives can be implemented. Preliminary evaluations dictate the required retaining structures shall be about 30 meters in length and their bottom foundation base shall be at an elevation of approximately 344.0 to 345.0 (5.0 ft. below the existing grade prevailing during the field exploration near Boring 310-

4). However, the final location, configuration, length and height of the retaining structure(s) shall be determined once the final design scheme is selected by the A/E Design Team.

The following sections of this report shall be used for the design of the herein recommended retaining structures.

5.1 General Design Parameters for Retaining Structures

Evaluation indicate that provided the proposed retention structure unit(s) are adequately embedded, beneath the upper loose, slope-washed and eroded surface layer, into the dense gravelly silty sand residual and weathered saprolitic material, an adequate global stability of the proposed retaining system can be obtained.

Considering the soil profiles found at the investigated locations the following parameters of in-situ soils may be used for the design of the proposed retaining systems:

TABLE NO. 1 - SUMMARY OF IN-SITU SOIL PARAMETERS FOR DESIGN

Recommended Range of values in layers for Borings 310-4

Soil Description Unit

Weight (pcf.)

Angle of Internal Friction (degrees)

Cohesion (psf.)

Allowable Soil Bearing Pressure

(psf.)

New Fill (A-2-4) 125 27 Neglect 2.0 Ksf.

New Fill (Crushed-Stone) 133 33 Neglect

In-Situ fill / Slope-washed Material

(0’-4’) 95 22 300

Residual Material (5' -9') 123 27 - 2.5 Ksf. @ 8.0 ft.*

Weathered rock (>9’) 130 32 -

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ADDITIONAL NOTES:

1. Complete removal of unsuitable soil and/or slope washed shall be guaranteed. By no means should the bearing material be loose. However, any unsuitable material can be replaced with a well compacted engineering fill section, for which the allowable bearing capacity shall be not greater than 2.0 Ksf.

2. The minimum depth of foundation shall be measured from the existing grade.

3. Full hydrostatic conditions and surcharge loads imposed by the construction sequence and vehicular loadings, shall be considered by design.

Lateral earth pressure coefficients are given for the active and for the at-rest case, depending on whether the wall can rotate at the top or not. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top.

The coefficient for lateral earth pressure, based on Rankine’s Theory, can be determined using the following formulas, however other methods and/or theories may be used as well, depending on actual retaining wall configuration.

Lateral Pressure Coefficient at rest case:

Coefficient Active Earth Pressure for sloping backfill:

Coefficient Passive Earth Pressure for sloping backfill:

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Coefficient Active Earth Pressure for horizontal backfill for vertical face:

Coefficient Passive Earth Pressure for horizontal backfill for vertical face:

The depth of foundation (Df) shall be compatible with the minimum depth requirements previously described. However, a re-compaction of the in-situ soil to a minimum of 95 % of its maximum dry density shall be allowed prior to the foundation construction.

To reduce hydrostatic loading on retaining walls, a subsurface drain system should be placed behind the wall. The drain system should consist of free-draining granular soils containing less than five percent fines (by weight) passing a No. 200 sieve placed adjacent to the wall. The free-draining granular material should be graded to prevent the intrusion of fines or provided with a suitable filter fabric.

A drainage system consisting of either weep holes or perforated drain lines (placed near the base of the wall) should be used to intercept and discharge water which would tend to saturate the backfill. Where used, drain lines should be embedded in a uniformly graded filter material and provided with adequate cleanouts for periodic maintenance. As an alternative, a prefabricated drainage structure, such as geocomposite (Macaferri MacDrain or equivalent), may be used as a substitute for the granular backfill adjacent to the wall.

In addition, a perimeter drain shall be placed along the wall footings and drained away from the units to proper out falls. Underground water, if any, may flows beneath foundations, which are not adequately drained, creating unsuitable erosional effects on foundations. This aspect of the construction and design should not be overlooked.

Preferably, the backfill soil is to be clean, free draining coarse granular material (AASHTO A-1-a

Classification), placed in 2-inch to 3-inch layers, each compacted to at least 95% of the material's

Modified Proctor maximum density. However, under standard design criterion, the backfill for the wall should be granular (AASHTO A-2-4 or better), carefully placed and of good quality, above

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1.0 m. from the maximum flood level; otherwise, crushed stone compacted to a minimum of 83 % of its bulk density shall be used for the reinforced back fill material.

5.1.1 Additional Considerations for Retaining Structures

Prior to the construction of any retention structure, the complete removal of any soft/loose, unsuitable saturated soil, slope-wash and debris shall be allowed prior to the back filling, which shall be done in stages, considering the back-filling recommendations contained in this report.

Also, it is of upmost importance to take all precautions during the excavation procedures to assure slope stability during construction, especially during the excavation phase. To prevent further instability of existing slope surfaces the herein construction sequence shall be performed in alternate improvement (two-stage) sections of not more than 15.0 ft. wide.

The initial stage is to remove any unstable surface material in benches to create a level area on which to rest the proposed retaining structure alignment. Once the initial demucking operation is performed and the over excavation to prepare the foundation base is completed, then the retaining wall foundation can commence.

Also, considering the proposed retaining structure foundation unit may lie on sloping grounds surfaces, the depth of foundation on these circumstances shall be compatible with a minimum depth requirement such that a line drawn from the bottom edge of the foundation at an angle ( ) of 30⁰ and at a horizontal distance (t) of 15 ft. from the sloping surface do not intersect with the face of the slope. Refer to the following Figure A.

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FIGURE A: Footing in Sloping Grounds

NOTE: The footing depth on sloping grounds shall satisfy a minimum separation requirement such that a line drawn from the bottom edge of the foundation at an angle ( ) of 30⁰ and at a horizontal distance (t) of 15 ft. do not intersect with the face of the slope.

Should the proposed foundation do not meet the minimum separation requirement, deepening of the foundation shall be required. Also, a structural key or soil/rock anchors may be provided to the foundation to avoid the translation of the foundation stresses to the sloping grounds and provide an additional sliding retraining measure. However, the prevailing slopes to remain shall be protected against scour and erosional effects during an intensive rainfall and flooding events.

5.2 Additional Recommendations for a Sheet Pile Retaining System

A possible solution to be considered is the installation of a combined system composed of Pre-drilled Steel HP-Piles (with the same minimum length of 20 ft.) with precast or cast-in-place concrete lagging panels, at 8.0 ft. on center, can be considered to restrain and restrict the embankment soil, existing structures movement (i.e. Pavement Structure) and the soil in between the piles. Considering the subsurface conditions at the site, where the residual and saprolitic material was found as shallow as 5.0 ft., the pre-auguering to encase the Steel-HP Piles shall be required to encase the Steel HP piles section with poured with concrete.

The wall shall be located at a distance from the northern edge of PR-181 such that it encases the proposed southern fill embankment north of PR-181, perpendicular to the slope failure.

Evaluation dictate this retaining structure shall be some 30 meters long, installed some 3 to 5

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meters from the crest of the prevailing slide scarp. The foundation base shall be at an elevation of approximately 344.0 to 345.0 (5.0 ft. below the existing grade prevailing during the field exploration near Boring 310-4). However, the final location, configuration, length and height shall be determined once the final design scheme is selected by the A/E Design Team.

For piles to be effective they should extend at least 20 ft [Boring 310-4] into the residual and completely weathered rock found in the borings of exploration. A minimum unsupported length of 15 ft. shall be considered by the design for the pile units. The pile units shall develop the necessary lateral resistance to sustain the earth and structure loads, assuming full mobility of the soil shear strength. Therefore, the final length and type of the pre-drilled HP steel-pile sections shall depend on the expected lateral loads and final grading elevations of the project.

Also, the precast or cast-in-place lagging panels shall withstand the expected lateral earth pressures, assuming full hydrostatic conditions and surcharge forces imposed by the construction sequence and vehicular loadings.

Once the combined retaining system is installed, then the re-construction of the pavement structure components can commence

5.2.1 Lateral Load Design Considerations

The following design model shall be used in the foundation design for lateral load evaluations of the proposed Steel HP Piles. For lateral calculations, an unsupported length of the upper 15 ft.

shall be considered in the evaluation. Should the structural evaluation reveal the expected deflection at the top of the pile is too excessive, the larger pile sections, smaller spacing in between piles and/or providing Deadman, beneath the PR-181 Pavement Structure, may be considered to cope with the expected lateral loads.

Lateral load evaluations depend on the specific requirements of the structure. Often, a 1/4-inch allowable lateral deflection is used as a limit. In no case, the lateral load shall exceed 0.33 the ultimate load capacity. The normally consolidated to slightly over consolidated cohesive as well as for granular soils, the pile deformation can be estimated assuming that the coefficient of sub grade reaction Kh, increases linearly with depth in accordance with the expression:

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Kh = f * z / D

Where, Kh = coefficient of lateral subgrade reaction (tons/ft.3) f = coefficient of variation of lateral subgrade reaction (tons/ft.3) z = depth (ft.)

D = width/diameter of loaded area

Profile Design Model - Considering the field and laboratory test data, we can establish the soil parameter for lateral load design. The following table presents a summary of the soil parameters to be used in the lateral design evaluations.

TABLE 2 - SUMMARY OF SOIL PARAMETERS FOR LATERAL PILE DESIGN

Sector Covered By

Boring

Extend of Depth Below Existing

Ground Surface (ft.)

Shear Strength

Value (psf.)

Coefficient of Variation of Lateral Subgrade Reaction (f)

(tons/sq.-ft./ft.)

310-4 0’ to 4’ neglect Disregard (Consider unsupported)

4’ to 9’ neglect 30 Deeper than 9’ - 50

Compacted Engineered Fill

(A-2-4) - 500 25

Consideration of the loading conditions using the above design models is required to calculate the allowable deflection of the pile top or the pile stresses. The determination of the lateral capacity and deflection shall be based on actual finite element analyses of the rod element embedded in the above soil design model.

All estimated depths are measured from the existing ground surface, prevailing during the period of the field work. A minimum penetration of 20 ft. into the residual and completely weathered material is been required.

5.3 Additional Recommendation for a Reinforced Soil Wall

Depending on the project’s requirements the improvements of the northern sloping grounds and pavement structure may also consider the use of Reinforced Soil Wall. However, this alternative requires enough space to place the required geogrids behind the wall, thus prior to its selection definite assurance that enough space is available to place the minimum required lengths of

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geogrids shall be guaranteed. Depending on the final wall alignment it may be necessary the partial closure of State Road PR-181.

The final length of the geogrids is a function of design, however for cost estimate purposes a minimum embedment length of 0.75-0.80 times the height of the wall and a minimum anchorage length passing the failure plane of 5.0 ft. shall be considered. The overall length from the face of the wall to the tail of the geogrids is assumed to be constant throughout the height of the wall structure.

Geogrid reinforcements used in conjunction with the soil, enable the soil to perform better than it would in its unreinforced state. Geogrids enable soils to accommodate greater loads and stand at steeper angles. The geogrids are laid horizontally within the compacted soil mass during construction, reinforcing it due to their high tensile strength, low strain and good interaction with the inter-layered compacted soil. Soil reinforced slopes and structures can accommodate differential settlement far better than more rigid solutions.

This alternative entails the complete removal and replacement of any slope-wash and debris which may be found.