Report_GEO_AC-820579_HWY-424.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-424 at State Road PR-796, KM. 4.40 on Río Cañas Ward of the Municipality of Caguas, Puerto Rico.

Reference No. DA/18O3783

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-424 at State Road PR-796, KM. 4.40 on Río Cañas Ward of the Municipality of Caguas, Puerto Rico. Reference No.

DA/18O3783

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-424 DA/18O3783

424-1

Caguas

244762.338 248430.379

01/12/19

43.48

CME-45

M. Ferrer

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

33-20-16

13-30-37

27-31-44

21-19-23

25-30-39

28-42-44

66-75/3"

75/3"

75/3"

47-75/3"

28-40-75/6"

Ground Surface

6"-Inches Asphalt

Clayey Sand Yellowish brown, gray mottled clayey sand, trace subangular gravel fragments, some asphalt.

Clayey Sandy Silt Brownish yellow, brown, light gray, clayey sandy silt, trace subangular gravel fragments.

Clayey Sandy Silt Brownish yellow, brown, light gray, clayey sandy silt, trace subangular gravel fragments.

Silty Sand Grayish brown, brownish yellow and bluish gray silty sand, some clay, some weathered rock fragments.

26.3

36.5

22.9

7.6

11.2

3.7

A-2-4 (0) /SC

A-6/SM

A-1-b/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-424 DA/18O3783

424-1

Caguas

244762.338 248430.379

01/12/19

43.48

CME-45

M. Ferrer

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

75/4"

75/3"

Continue - Silty 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 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-424 DA/18O3783

424-2

Caguas

244760.363 248409.424

02/11/19

43.42

CME-45

J. 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

UU

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

20-15-23

17-10-20

24-45-51

50-60/6"

10-15-21

38-40-35

30-41-40

52-60/6"

80/5"

75/4"

65/6"

50-60/3"

Ground Surface

6"-Inches Asphalt

Silty Clayey Sand Yellowish brown and dark brownsilty clayey sand, trace subangular gravel fragments, some asphalt.

Clayey Sand Brownish yellow, brown, light gray, clayey sand, trace subangular gravel fragments.

Clayey Sandy Silt Yellowish brown and light gray clayey sandy silt, trace weathered rock fragments.

Silty Clayey Sand

Yellowish brown and light gray silty clayey sand, trace weathered rock fragments.

25.2

38.8

36.6

6.3

13.8

11.9

A-2-4/SC-SM

A-6 (3)/ SC

A-6 (2) / 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-424 DA/18O3783

424-2

Caguas

244760.363 248409.424

02/11/19

43.42

CME-45

J. 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

80/5"

100/6"

Silty Clayey Sand

Brownish yellow and grayish brown silty clayey sand, some weathered rock fragments.

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

24.0

4.9

A-1-b/ SC-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-796, KM. 4.40 on Río Cañas Ward of the

Municipality of Caguas, Puerto Rico.

PROJECT ID: ER-HWY-424

February 11, 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

February 11, 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 at State Road PR-796, KM. 4.40 on Río Cañas Ward of the Municipality of Caguas, Puerto Rico.

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-424, at State Road PR-796, KM. 4.40 on Río Cañas Ward of the Municipality of Caguas, 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/04-61-18R 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/18O3783 Caguas, Puerto Rico February 11, 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 Surface Soils and Geological Notes

3.2.1 Surface Soils

3.2.2 Geology

3.3 Stratigraphic Units

3.4 Groundwater Levels

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 Pre-Drilled Hp-Steel Piles with Pre-Cast Panels

5.2.1 Lateral Load Design Considerations

5.3 Additional Recommendations for Secant Piles Retaining Structures

5.3.1 Additional Drilled Shaft (Secant) Considerations

5.3.2 Lateral Load Design Considerations

5.4 Additional Recommendations for Cantilever Retaining Structures

5.5 Earthquake Design

5.6 General Earthwork Recommendations

5.6.1 Excavations

5.6.2 Temporary Cut Sections

5.6.3 Backfill Material

5.7 Proposed Storm Water Run-off Control

5.8 Nearby Structures

5.9 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) - Earthwork Specifications 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-424, at State Road

PR-796, KM. 4.40 on Río Cañas Ward of the Municipality of Caguas, 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/04-61-18R 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, 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 one (1) major landslide occurred along the eastern edge of State

Road PR-796, near Km. 4.40. The extent of road damage of the project extends some 30.0 meters in length [Borings 424-1 to 424-2], along the western bank of Rio Grande de Loiza where

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 2

a meander directs the river flows toward the study sector. Site observation revealed severe erosion effects of the river occurred during the floods of Hurricane causing the observed slides and partial collapse of State Road PR-796.

Based on the US Topographic map, the intersection of the Rio Gurabo River and Rio Grande de

Loiza lies about 725 ft., northeast of the Site. In addition, in the vicinity of the study area, one ephemeral gully stream was identified in the US topographical plan; where the surface flows, with a near east-west alignment carrying the surface storm water flows from upland sectors of Altos de San Luis ridge line and ending on the terrace flood plain, which crosses nearly perpendicularly to the road embankment mass.

The following sections of this geotechnical report will provide the required Site improvements and foundation design recommendation for the proposed improvements required at the Site.

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

The subsurface soil conditions at the site were investigated two (2) standard penetration test borings performed to assess the existing subsoil conditions at the project site. The borings of exploration had to be relocated several times due to the extensive amount of underground facilities (i.e. telephone, water, etc...) found and due to the space constraints (i.e. lane width, encroaching river, etc…). 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.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 3

3.2 Surface Soils and Geological Notes

3.2.1 Surface Soils

The US Soil Conservation Service Manual – Soil Survey of San Juan Area of Puerto Rico, Sheet

#27, prepared by the Soil Conservation Service identifies the surface soils of the area as follows:

Mabí clay, 5 to 12 percent slopes, eroded (MaC) – This is a sloping, somewhat poorly drained soil on alluvial fans and terraces above the river flood plains. These soils are deep and were formed in fine textured sediments derived from volcanic rocks. The permeability and the available water capacity are moderate. Runoff is slow and is difficult to work because of the stickiness and plasticity of the clay.

3.2.2 Geology

The units that outcrop at and in the vicinity of the site, as shown in the US Geological Survey Map

I-479, of the Aguas Buenas Quadrangle prepared by Maurice H. Pease, Jr. (1968) are as follows:

1. Terrace deposits (Qt) - described as unconsolidated sand, gravel, silt and clay in terrace deposits above the present flood level. It includes some colluvial and alluvial-fan deposits on south slopes of Altos de San Luis.

2. Santa Olaya Lava (Ks) - described as massive greenstone composed chiefly of albite, quartz, and chlorite, containing greenish-gray pumice fragments. Pervasively intruded by quartz diorite stocks and dikes.

3. Quartz diorite (TKd) - described as chiefly medium- to light-greenish-gray albitized quartz porphyry containing subhedral phenocrysts of quartz and plagioclase in a fine-grained matrix of albite, potassic feldspar, quartz, and black hornblende. Rock is medium grained and equigranular in center of large stocks and fine grained in the smaller dikes. Commonly, the quartz diorite is sericitized, and partly chloritized, and partly altered to clay; locally contains pyrite and base sulfides. Weathers to yellowish-gray sand containing flecks of mica.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 4

4. Los Negros Formation (Kn) - described as stratified rocks, chiefly dark-greenish-gray thick-bedded pyroxene-rich crystal tuff. This formation contains some sheared chloritic breccia and lava. The planes of the stratified rock show dip angles varying from 45- to 70-degrees, with a general trend to the north-northeast and overturned horizontal folds of 85 degrees.

The geologic map shows east of the site, the Cerro Mula Fault, with a near west to east alignment, is found at about 1600 ft. south of the site. An additional approximate (dashed) Unnamed fault lines are shown on the map crossing the displaced alignment of the Cerro Mula Fault close to the study area.

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

3.3 Stratigraphic Units

Upper Surface Section – Following the six 6”-inch asphalt overlay [respectively at Borings 424-

1 to 424-2], a surface layer thickness of about 1.5 to 3.0 ft. depth was found. It is composed of yellowish brown, with mottles gray sandy silt with variable amounts of clay, with traces of subangular gavel fragments. The standard resistance to penetration (N-values) of the surface layers varied from 36 to 38 blows/foot in a dense of Compactness for the fill section. The natural moisture content values range from 9 to 14 percent. Random samples of this layer disclosed

AASHTO class type A-2-4 (0) AASHTO type soils (USCS type SC-SM and SC). The Free Swell

Tests show percent values at 10 percent.

Terrace deposits - Beneath the above described layers, the terrace deposits which includes some colluvial and alluvial-fan deposits was found, extending to approximately 13.5 ft. (average) in depth, [Borings 424-2 and 424-1], respectively. They are formed as fine textured sediments derived from volcanic rocks. The samples from this described as of brown, yellowish brown, and light gray, clayey sandy silt, with traces of weathered rock fragments. The standard resistance to penetration (N-values) of the in-situ material varied from 36 to 96 blows/foot; to practical refusal to penetration with values in excess of 60 blows for a few inched to penetration at a dense to very dense of State of Relative Density. The natural moisture content values range from 10 to 27 percent. Random sample of the residual material from the borings of exploration disclosed

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 5

AASHTO class type A-6 (2) (SM and SC USCS type). The Free Swell Tests show percent values at 20 percent.

Residual Material – Deeper into the profile the completely weathered rock, broken by the sampling device into grayish brown, brownish yellow, bluish gray, completely weathered rock with silty sand, some clay fines, with traces of volcanic rock fragments. The standard penetration test attempts disclosed penetration (N-values) of the residual layers at practical refusal practical refusal to penetration, with values greater 60 blows for a few inches of penetration. The natural moisture contents range from 8 to 16 percent.

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 found at a depth varying from 15 to 35 ft., beneath the existing ground surface prevailing during the period of exploration. At the location of

Boring 424-1, at a depth of 15 ft. high moisture content was observed, however the next samples recovered were dry. It was at a depth of 35 ft., where the actual water level was found within the open borehole. At Boring 424 -2, after 24 hours the water level rose to 9.0 ft., in depth, which correspond to the hydraulic gradient of the Rio Grande de Loiza river. All depths were measured from the existing ground surface prevailing during the period of exploration.

All surface ground and underground water should flow through existing drainage gullies, from higher sectors of the west toward the lowland areas, towards the Rio Grande de Loiza to the east and adjacent to the road embankment. Groundwater levels fluctuate due to seasonal variations, adjacent surface water bodies, and precipitation. Also, all surface ground and underground water should be influence with tide variations of the adjacent body of water (Rio Grande de Loiza River).

Therefore, groundwater levels higher than observed can be expected due to seasonal effects due to the vicinity of the adjacent river, especially during high rainy seasons. All the ground water observations were done after the boring were completed and were measured from the existing ground surface prevailing during the period of the field work.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 6

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 Rio

Grande de Loiza river banks, where one (1) major landslide scarps were developed on the eastern edge of State Road PR-796, near Km 4.40, which was subjected to extensive degradation, erosional effects, and slides causing the observed damages and partial 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 severe erosion effects of the river occurred during the floods of Hurricane and the oversaturation of the undersoil causing the observed slides and partial collapse of State Road

PR-796.

Site observation revealed the extent of road damage of the project extends some 30.0 meters in length [Borings 424-1 to 424-2], along the western bank of Rio Grande de Loiza where a meander directs the river flows toward the study sector. Evaluation of available plans revealed, the roadside elevation is at approximate 43.45 meters in elevation some 2.75 meters higher than river’s water elevation at the time of the field exploration.

Also, field observations revealed the average total width of State Road PR-796 at the project sector is approximately 3.76 to 3.83 mts. wide, however, with the existing jersey barrier the lane width is reduce to approximately 3.25 mts. (10.5 ft.). This narrow road section limits the reconstruction alternatives to cope with the limited space available for the re-construction of PR-

796, however the ADT (average daily traffic) is not as high as other main highways. In addition, the western sloping grounds, toward private properties on the opposite side of PR-796 present steep slope ratios of approximately 42° degrees.

This specific project presents challenging circumstances, from the geotechnical standpoint, considering the narrow road width, closeness to the river, and the high-water table, which do not

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 7

allow conventional construction alternatives, without encroaching the western properties and/or the eastern body of water.

Therefore, to cope with the presently disclosed subsoil conditions and space constraints, the herein recommendation to be considered shall be applied along the eastern edge of PR-796 to render stable grounds and road safety. It shall be noted the following reconstruction alternatives presented, intention is not to make any construction within the eastern body of water (Rio Grande de Loiza). However, encroaching the western property lands, may have to be required to cope with the project’s requirements, although it is not presently contemplated.

The herein recommendation by themselves and/or any combination of them shall be applied to the presently affected area (eastern sloping grounds) to render stable grounds. The following sections of this report will provide the required Site improvements and foundation design recommendation for the proposed improvements required at the Site.

Considering the subsoil conditions and space constraints of the site, the improvement project may consider the following three (3) construction approaches or any combination of them. These are the following:

1. To avoid and construction within the eastern body of water and to cope with the project’s space constraints, a retaining structure composed HP-steel piles encased in a pre-drilled borehole in conjunction with pre-cast panels to restrain the soil in between the piles and the road embankment may be considered. Evaluations dictate the retaining structure of approximately 30 to 35 meters long shall be required. The pre-drill piles shall have a minimum embedment length of 20 to 25 ft. shall be considered with a minimum unsupported length of 10.0 ft. shall be considered by design.

It shall be noted that the final length and type of the HP steel-pile section will depend on the final wall alignment and grading elevations as well as the expected lateral loads, as the structural evaluation will reveal. However, for cost estimate purposes, solely, the piles section spaced at 4.0 ft. on center can be considered until the final design scheme is established. Also, the pre-cast panels shall be designed to withstand the expected lateral earth pressures (with full hydrostatic conditions) considering the in-situ soil parameters. Also, Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 8

a non-woven geotextile shall be provided behind (west side) the wall to prevent any migration of fines into the Rio Grande de Loiza river.

Considering the subsurface conditions at the site, where the very dense was found as shallow as 4.0 ft., pre-auguring shall be performed. Although very dense profile was encountered, which on other circumstances this alternative would not be considered, implementing a well-thought-out review of as considering the space constraints of the project, it is considered one of the few alternatives viable to assure the road safety during and after construction.

2. As a second alternative for the reconstruction of the eastern river bank which may be consider is the use of a Secant drilled shafts wall to restrain the road embankment can be considered. This alternative will also avoid any construction within the eastern body of water and considering the project’s space constraints. Evaluations dictate the retaining structure of approximately 30 to 35 meters long shall be required. The pre-drill piles shall have a minimum embedment length of 20 to 25 ft. shall be considered. A minimum unsupported length of 10.0 ft. shall be considered by design. It shall be noted that the final length and type of the Drilled Secant piles will depend on the final wall alignment and grading elevations as well as the expected lateral loads, as the structural evaluation will reveal.

The drilled shafts diameters shall be determined based on the actual loading conditions required to withstand the expected loading conditions (dead and live loads). However, for cost estimate purposes, solely, 24”-inch diameter Secant Piles can be considered until the final design scheme is established. They shall be installed parallel of PR-796 at the crest of the eastern river bank, along the edge of PR-796. Although, this alternative does not allow any space in between piles, a non-woven geotextile shall also be provided behind (west side) the wall to prevent any migration of fines into the Rio Grande de Loiza.

3. As a third alternative, a cantilever retaining structure to retain the western soil embankment mass and State Road PR-796 pavement structure may be considered. The retaining wall shall be provided all-throughout the affected areas (some 30 meters long) parallel to the eastern edge of State Road PR-796. Preliminary evaluation, dictate the cantilever wall of approximately 5 to 7 ft. in height will most probably be required, depending on its final alignment. Also, this cantilever wall shall be provided with a long heel slab (at least 1.0 times

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 9

the wall height) and a structural key (preferably on the toe side) shall be provided as an additional sliding restraining measure.

To prevent the possibility of any water seepage into the open excavation, the final wall alignment shall be displaced to the west, such that a clear distance from the retaining wall toe to the outer face of the river bank is at least equal to the its base. Therefore, should the space available to the western edge of PR-796 not be enough, then cutting into the west high land sectors and/or providing an additional retaining wall may be required.

Regardless of the final design alternative selected, new and/or additional drainage facilities of enough capacity shall be provided. All surface water shall drain freely towards the river through adequate outfalls.

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

V. ENGINEERING RECOMMENDATIONS

The present geotechnical review revealed the proposed re-construction alternatives can be implemented. Evaluation of the Site conditions revealed, one (1) major landslide occurred along the eastern edge of State Road PR-796, near Km. 4.40. The extent of road damage of the project extends some 30.0 meters in length, along the western bank of Rio Grande de Loiza where a meander directs the river flows toward the study sector.

Field observations revealed, the roadside elevation is at approximate 43.45 meters some 2.75 meters higher than river’s water elevation at the time of the field exploration. Also, field observations revealed the average total width of State Road PR-796 at the project sector is approximately 3.76 to 3.83 mts. wide. This narrow road section limits the reconstruction alternatives to cope with the limited space available for the reconstruction of PR-796.

As previously mentioned, this project presents challenging circumstances, from the geotechnical standpoint, considering the narrow road width, closeness to the river, and the high-water table, Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 10

which do not allow conventional construction alternatives, without encroaching the western properties and/or the eastern body of water.

As part of the herein evaluation, several alternatives to cope with the limited space and ground water were evaluated. Among the alternative considered were Sheet pile walls, Soldier Hp-piles with pre-cast lagging, and a Pile retaining wall.

There are three (3) main distinct bored Pile Retaining Walls (driven alternatives were discarded due to shallow hard span) used in the construction industry.

These are Contiguous wall, Tangent wall and Secant wall. Refer to the following figure, taken from “Contiguous Pile Wall as a Deep Excavation Supporting System”, 2011; Venkata Ramasubbarao Godavarthi, et al., for illustration purposes.

Contiguous piles are suitable in crowded urban areas, where traditional retaining methods would otherwise encroach the adjoining properties or structures, these piles restrict ground movements on the backfill side and they are constructed with small gaps (leading to water infiltration) between adjacent piles.

Tangent pile walls consist of a series of drilled shafts located such that the adjacent shafts touch each other, hence the name Tangent wall.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 11

The principal disadvantages of contiguous and tangent pile walls are the gaps between piles and the resulting problems of lack of water tightness and migration of soil particles have been effectively overcome by interlocking or secant piles.

Secant pile walls are stiffer than tangent piles walls and are more effective in keeping ground water out of the excavation.

Taking into consideration the hard pan encountered the use of a Sheet pile system was discarded.

The use of slurry walls concrete diaphragm walls was also evaluated; however, it was discarded considering the dense to very dense subsoil profile encountered, and predicted costs involved not making it a cost-effective solution for the present project.

After a thorough evaluation the three alternatives selected as the most adequate to cope with the project’s constraints were the following:

1. HP-steel piles encased in a pre-drilled borehole in conjunction with pre-cast panels

2. Secant Pile Wall (Drilled shafts)

3. Cantilever retaining structure, however this alternative requires several considerations, which shall be taken into account by design.

Thus, order to assure an adequate Global Slope Stability of the western river bank, the use of the previously described alternatives can be considered. The following sections of this report shall be used for the design of the herein recommended retaining structures to be considered by the

A/E Design Team.

5.1 General Design Parameters for Retaining Structures

Evaluation indicate that provided the proposed retention structure unit(s) are adequately embedded, into the dense gravelly sandy silt terrace deposits, 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:

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 12

SUMMARY OF IN-SITU SOIL PARAMETERS FOR DESIGN

RECOMMENDED RANGE OF VALUES PER LAYERS – BORINGS 424-1 & 424-2

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

Upper Fill Sandy Silt (0.0’-3.0’) 123 27 1000

Terrace Deposits (3.0’-13.5’) 128 31 - 3.5 Ksf. @ 5.0 ft.

Residual Material (13.5' -25') 130 33 -

Weathered rock (>25’) 134 36 -

ADDITIONAL NOTES:

1. Complete removal of any unsuitable soil and/or slope washed shall be guaranteed.

By no means should the bearing material be soft/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.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 13

Lateral Pressure Coefficient at rest case:

Coefficient Active Earth Pressure for sloping backfill:

Coefficient Passive Earth Pressure for sloping backfill:

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 and provided with a suitable nonwoven 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 geo-composite (Macaferri MacDrain or equivalent), may be used as a substitute for the granular backfill adjacent to the wall.

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 14

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, 1.0 m.

above 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/or 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 excavation and slope stability during construction, especially during the excavation phase. To prevent further instability 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(s) 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 subsoil conditions found a sand cushion shall be provided beneath the proposed retaining units to avoid any punching shear to the base of the wall, provoke by any pinnacles of the rock once the excavation (working platform) is made.

Should the proposed retaining structures foundation unit may lie on sloping grounds surfaces, the depth of foundation on these circumstances shall be compatible with a minimum depth

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 15

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 10 ft. from the sloping surface do not intersect with the face of the slope. Refer to the following Figure A.

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 10 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. In lieu, a structural key 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. Also, the prevailing slopes to remain shall be protected against scour and/or erosional effects during an intensive rainfall.

5.2 Additional Recommendations for Pre-Drilled Hp-Steel Piles with Pre-Cast Panels

Evaluations dictate the retaining structure of approximately 30 to 35 meters long shall be required along the eastern edge of PR-796. However, the project’s challenging circumstances (i.e. narrow road width, closeness to the river, and the high-water table), which do not permit conventional construction alternatives, without encroaching the western properties and/or the eastern body of water. Therefore, to avoid and construction within the eastern body of water and to cope with the project’s space constraints, a retaining structure composed HP-steel piles encased in a pre-

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 16

drilled borehole in conjunction with pre-cast panels to restrain the soil in between the piles and the road embankment may be considered.

The pre-drill piles shall have a minimum embedment length of 20 to 25 ft. into the terrace and residual found in the borings of exploration deeper into the profile. A minimum unsupported length of 10.0 ft. plus the height required to reach the roadside elevation (failure plane depth + H of grading) shall be considered by design. Thus, preliminary estimates revealed the total length of the pile sections shall be approximately 30 to 35 ft. (pile bottom tip elevation at approximately

33.2 mts.). Considering the subsurface conditions at the site, where the terrace and residual material was found as shallow as 4.0 ft. pre-augering to encase (with poured concrete) the Steel-

HP Piles shall be required. It shall be noted that the final length and type of the HP steel-pile section will depend on the final wall alignment and grading elevations as well as the expected lateral loads, as the structural evaluation will reveal. Therefore, the final location, configuration, length and height shall be determined once the final design scheme is selected by the A/E Design

Team.

For cost estimate purposes, solely, the piles section spaced at 4.0 ft. on center can be considered until the final design scheme is established. Also, the pre-cast panels shall be designed to withstand the expected lateral earth pressures (with full hydrostatic conditions) considering the in-situ soil parameters. Also, a non-woven geotextile shall be provided behind (west side) the wall to prevent any migration of fines into the Rio Grande de Loiza.

The pile units and pre-cast panels system shall be designed to withstand the expected lateral earth pressures (with full hydrostatic conditions), surcharge loads and structure load. Therefore, the final 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 total height of the pre-cast panel sections shall be determined based on the final grading elevations of the project. Also, a non-woven geotextile shall be provided behind (west side) the wall to prevent any migration of fines into the

Rio Grande de Loiza river.

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

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 17

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 10 ft.

plus the height required to reach the roadside elevation (failure plane depth + H of grading) 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-796 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:

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.

SUMMARY OF SOIL PARAMETERS FOR LATERAL PILE DESIGN

Sector Covered

By Borings

Extend of Depth Below Existing

Ground Surface (ft.)

Shear Strength

Value (psf.)

Coefficient of Variation of Lateral Subgrade Reaction (f)

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

424-1 & 424-2 0’ to 10’ neglect Disregard (Consider unsupported)

10’ to 13.5’ - 40 13.5’ to 25’ - 50 Deeper than 25’ - 55

Compacted Engineered Fill (A-2-4) - 500 25

Project No.: DA/18O3783 Caguas, Puerto Rico February 11, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 18

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 terrace and residual material is been required.

5.3 Additional Recommendations for Secant Piles Retaining Structures

As already mentioned, this site presents challenging circumstances, from the geotechnical standpoint, considering the narrow road width, closeness to the river, and the high-water table, which do not allow conventional construction alternatives, without encroaching the western properties and/or the eastern body of water. Therefore, as a second alternative for the reconstruction of the eastern river bank which may be consider is the use of a Secant drilled shafts to restrain the road embankment and provide erosion protection may be considered. This alternative will avoid any construction within the eastern body of water while permitting the re-construction of the eastern road embankment.

Evaluations dictate the retaining structure of approximately 30 to 35 meters long shall be required.

The Secant piles to be effective should extend sufficiently below the predicted scour depth, not less than 30 ft., and measured existing ground surface prevailing during the fieldwork. They shall have a minimum embedment length of 20 to 25 ft.