Report_GEO_AC-838579_HWY-308.pdf

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

April 10, 2019

Klein Engineering, PSC.

PO Box 12009 San Juan, Puerto Rico 00922-2009 Ph: 787.993.2071 E-mail: franciscoklein@klein-engneering.com

Attn.: Mr. Francisco Klein, 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-308 at State Road PR-179, KM 13.25 on Carite Ward of the Municipality of Guayama, Puerto Rico.

Reference No. DA/18O3746

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:franciscoklein@klein-engneering.com

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-179, KM 13.25 on Carite Ward of the Municipality of Guayama, Puerto Rico.

December 28, 2018

Prepared for:

PO Box 12009

San Juan, Puerto Rico 00922-2000

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

December 28, 2018

San Juan, Puerto Rico 00922-2009 Ph: 787.993.2071 E-mail: franciscoklein@klein-engneering.com

Attn.: Mr. Francisco R. Klein, PE., MECE, PTOE, President

Subject: Proposed Geotechnical Engineering and Subsurface Exploratory Services for the

Landslide and Road Damage Evaluation and Reconstruction Project at State Road PR-179, KM 13.25 on Carite Ward of the Municipality of Guayama, Puerto Rico.

Dear Eng. Klein:

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 at State Road PR-179, KM 13.25 on Carite Ward of the Municipality of Guayama, Puerto Rico.

The work was undertaken at the request of Mr. Francisco R. Klein, PE., MECE, PTOE, President of Klein Engineering, PSC. The work was made in accordance to Proposal No. DA/04-14-18R for the subsurface exploration dated May 22, 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, 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.

Geotechnical Engineer

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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 Improvement using a Reinforced Engineered Backfill to Satisfy Slope Stability

5.2 Cantilever Retaining Structure Foundation Recommendations

5.2.1 Retaining Wall Design Parameters

5.3 Sheet Pile Retaining System Recommendations

5.3.1 Lateral Load Design Considerations

5.4 Earthquake Design

5.5 Excavations

5.6 Earthwork Recommendations for Fill and Cut Sections

5.6.1 Fill Sections

5.6.2 Temporary Cut Sections

5.7 Additional Earthwork Recommendations

5.7.1 Recommended Fill Types and Compaction Specifications

5.8 Proposed Storm Water Run-off Control

5.9 Nearby Structures

5.10 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 at State Road PR-179, KM

13.25 on Carite Ward of the Municipality of Guayama, Puerto Rico.

The work was undertaken at the request of Mr. Francisco R. Klein, PE., MECE, PTOE, President of Klein Engineering, PSC. The work was made in accordance to Proposal No. DA/04-14-18R for the subsurface exploration dated May 22, 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 can be considered by the A/E Design Team. However, should the A/E design team consider other(s) and/or additional design alternative these shall be forwarded to this office to evaluate them and provided the required geotechnical recommendation, if any. 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 eastern edge of State Road PR-179 near

Km. 13.25 after the passing of Hurricane Maria. The observed slide is found at the intersection with a municipal road to several residential units found to the west of the identified longitudinal

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slide along the eastern edge of State Road PR-179 at Carite Ward of the Municipality of

Guayama, Puerto Rico.

Evaluation revealed the site carries storm water from the highland sectors of the west toward the lowland areas at the east to a natural drainage gully stream, running parallel to State Road PR-

179. Based on the US Topographic map this drainage gully runs at the toe of the eastern sloping ground, where the landslide occurred at an approximate elevation of 560 mts. This is an affluent, which drains surface flows from the highland sectors to the north-northeast toward the Carite Lake found southwest of the project site.

Observations disclosed, severe erosion pattern along the northern edge of State Road PR-179, where surface slide caused the settlement, displacement and rupture of the pavement structure.

At the time of our initial site visit the landslide sector had been backfilled (dumped) with slope-wash material gathered from the site’s vicinity.

Also, an existing 30”-inch diameter pipe, crossing nearly perpendicular to the State Road PR-179, was previously provided to divert the surface flows to the east. However, it is evident this 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 two (2) standard penetration test borings performed to assess the existing subsoil conditions at the site. 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.

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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 available US Geological Survey publications, the units in the site vicinity are shown in the US Geological Survey (Open File Report 52-82-1097, Plate 1 of 2) of the Patillas and

Guayama Quadrangles (Preliminary), prepared by Mr. Lynn Glover, III (1982). Thus, the geologic units that lie at or adjacent to the site are the following:

1. Formation A (Cretaceous) (Ka) - Described as pyroclastic breccia, tuff, and lava; locally with thin interbeds of mudstone. Clasts of feldspathic pyroxene andesite are abundant and clasts of dacite are common.

2. Formation A (Member) (Ka1) – Described as abundant dacitic and feldspathic andesite breccia and tuff, common feldspathic andesite lava and brecciated lava, common tuffaceous mudstone, feldspathic andesite lava.

3. Formation A (Member) (Ka2) - Described as abundant feldspathic andesite lava, pyroclastic breccia, rare thin- to medium-bedded tuff, feldspathic andesitic lava and brecciated lava.

4. Porphyritic Quartz Dacite (Cretaceous) (Kqp) – Described as small stocks throughout

Formation A.

Fault lines alignment are identified as Unnamed with approximate north-south alignment at about

3300 ft., south of the site. It also intersects an Unnamed Fault, with a near south-west trend; the faults have a defined alignment and approximate (dashed) on the map.

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

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3.3 Stratigraphic Units

Surface Section - Generally, the results of the exploration disclosed a surface layer to about 8.0

ft. It is composed of a mixture of silty clay and clayey silt, with traces of sand, with subangular gravel fragments, with varying colors: red, olive yellow, grayish brown and light brownish gray.

Evidence of asphalt from the pavement structure were disclosed on the upper samples obtained.

The standard resistance to penetration (N-values) of the surface layers varied from 11 to 62 blows/foot, at a medium to hard State of Consistency. The natural moisture content values range from 9 to 38 (saturated) percent. Random samples of this layer from [Boring 308-1- from 0.0’ to

2.0 ft.] disclosed AASHTO class type A-7-5 and A-7-6 AASHTO type soils (USSCS type ML, MH, and CL). On Boring 308-2 from 0’ to 2.0 ft. a A-2-4 AASHTO type (USSCS type SC-SM) of Soil was encountered. This correspond to the pavement base course. The Standard Free Swell

Determination tests performed disclosed values ranging between 25 at 35 percent.

Residual Material – Beneath the above described section the residual material was found, extending to depth of 28 ft., approximately. It is composed of brownish yellow, reddish yellow and brownish yellow with black joints sandy silt. The standard resistance to penetration (N-values) of the residual layers varied from 23 to 47 blows/foot, at a stiff to hard State of Consistency. The natural moisture content values range from 9 to 24 percent. Random sample of the residual material disclosed AASHTO class type A-4 soils (USSCS type SC).

Completely Weathered Rock - At the deeper explored depths [Boring 308-1 & 308-2] until the borings were bottomed a weathered rock into brownish yellow, black joints sandy silt fines, product of the weathering of the parent geologic units was found. The standard penetration test attempts varied from 78 blows/foot to practical refusal to penetration with values greater 75 blows for a few inches of penetration. The natural moisture contents range from 7 to 18 percent.

Random sample of this horizon disclosed AASHTO class type A-4 soils (USSCS type ML - Sandy

Silt).

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

(1) to this report.

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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 (> 30 %) was observed on several samples of the upper surface layer. All depths were measured from the existing ground surface prevailing during the period of exploration.

Although not evidenced, perched water condition may be encountered within the fill section because of the low permeability of the in-situ clayey silts. All surface ground and underground water should flow from the higher sectors at the west toward the lowland areas to the east finally joining the affluent of the Carite 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 along the eastern sloping grounds, where landslides scarps have experienced causing a landslide on the eastern edge of State Road PR-179, which was subjected to extensive degradation, erosional effects, and landslides causing the observed damage to the 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 eastern sloping ground subsurface clayey silty soils. The 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 the existing drainage gully stream, running parallel to State Road PR-179 also triggered the surface slides of the uppermost sloping surface.

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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 eastern edge of

PR-179 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 (eastern sloping grounds) to render stable grounds. The following section will provide the required Site improvements and the foundation design recommendation for the proposed structures.

Considering the subsoil profile and slope ratio prevailing at the site, three (3) construction approaches or a combination of them may be considered. These are the following:

1. The eastern sloping grounds shall be reconstructed all-throughout the study sector. The new reconstructed sloping grounds shall be constructed with a Reinforced Engineered Backfill using biaxial or triaxial geogrids (i.e. Tensar Geogrids or equivalent). However, considering the extent of the repair process this alternative may not be cost effective.

The final length of the geogrids is a function of design, however for cost estimate purposes a minimum embedment length of 0.75 times the height of the wall and a minimum anchorage length passing the failure plane of 3.0 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.

2. A cantilever retaining structure to retain the eastern soil embankment mass and any existing structures (i.e. State Road PR-179 pavement structure). The retaining wall shall be provided all-throughout the affected area parallel to the eastern edge of State Road PR-179.

Evaluation dictate this retaining structure shall be some 35 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 (598.55 mts.

approx.).

3. An alternate solution to be considered is the installation of a Sheet Pile foundation with a cap beam, placed along the crest of the eastern sloping grounds. This alternative will not require the retaining wall of the previous alternative since the Sheet Pile structure, itself, will restrain the soil embankment mass. Once the sheet-pile section is installed, then the pavement reconstruction can commence.

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Regardless, of the final solution to be implemented the installation of adequate drainage facilities to divert the surface runoff away the sloping surfaces and slopes 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 eastern sloping grounds to the lower drainage stream. 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.

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

V. ENGINEERING RECOMMENDATIONS

5.1 Improvement using a Reinforced Engineered Backfill to Satisfy Slope Stability.

Based on the results of the present slope stability review it was confirmed, under the prevailing soft and the oversaturation of the fill embankment soil at the slope’s crest of the study areas, the earth fill embankment surface section to about 8 ft. in thickness lies on unstable grounds, which require immediate improvements.

The prevailing sloping grounds east of State Road PR-179 have slope ratios ranging between 23 to 32 degrees. These marginal to steep slope ratios are too steep considering the in-situ clayey soil. Therefore, the reconstruction of the affected sloping grounds shall consider slope ratios not steeper than 2.25H:1V with intermediate benches every 10 meters. Therefore, this alternative entails the complete removal and replacement 8.0 ft. (minimum) plus any slope-wash and debris which may be found during the construction process.

Thus, the initial stage is to remove the unstable surface soft material from scarp surfaces, in addition to any loose slope washed material in benches, so as to create a level area on which to rest new backfill material up to the desired grade, until meeting the required crest of slope (edge of PR-179).

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The removal operation of the surface material shall be done under the direct supervision of a Soil

Engineer or approved representative, who would establish the vertical extension of removal at intermediate areas between borings.

Based on the present boring program, the depth of removal shall involve a minimum thickness of removal of 2.45 m. (8.0) ft., measured from the existing surface. After surface loose soil (slope-washed) removal, benches shall be provided with a surface stabilization fabric. Definite shall be assured that the improvement process does not alter the working surface on which the remaining backfill material shall be constructed. A Heavy-Duty Stabilization Fabric (i.e. TerraTex HD or similar), to prevent soil intrusion into the under soil shall be provided between the backfill material and the exposed clayey sit soil at each bench. Once the unsuitable material is removed, the new earth embankment mass shall be constructed with a reinforced engineered backfill using biaxial or triaxial geogrids (i.e. Tensar Geogrids or equivalent).

This alternative requires enough space to place the required geogrids. The final length of the geogrids is a function of design, however for cost estimate purposes a minimum embedment length of 0.75 times the height of the wall and a minimum anchorage length passing the failure plane of 3.0 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.

Under standard design criterion, the replacement fill shall be granular A-2-4 or better ASHTO type and compacted to not less than 95 % of its maximum proctor density test carefully placed (in 6-to 8-inch lifts). However, in areas where oversaturation is expected, if any, the backfill material is to be clean, free draining coarse crushed-stone material, compacted to at least 83% of the material's Maximum Bulk Density.

Once the complete replacement of the soil embankment is completed, surface erosion protection countermeasures shall be provided up to the crest of the new embankment slope, until meeting the northern edge of State Road PR-179. Thus, the exposed upper slope surface, if any, shall be protected using surface MacMat R, BioMAc, MacGrid T or similar.

Also, drainage facilities of enough capacity shall be provided, on every elevation contour to carry all surface water away from the embankment slope mass all the way to the toe of the proposed reinforced soil embankment mass to the lower drainage stream which carry surface flow toward

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the Carite Lake. Also, the surface of the existing gullies shall be provided with coarse gravely materials to prevent further erosion. Neglecting to provide these drainage facilities it is possible future slides will develop due to the oversaturation and surface erosion.

The eastern 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.

5.2 Cantilever Retaining Structure Foundation Recommendations

A cantilever retaining structure to retain the eastern soil embankment mass and any existing structures (i.e. State Road PR-179 pavement structure). The retaining wall shall be provided all-throughout the affected area parallel to the eastern edge of State Road PR-179. Evaluation dictate this retaining structure shall be some 35 meters long, approximately. The minimum depth of foundation (Df) shall be 8.0 ft., into the in-situ residual soil, however 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 (598.55 mts. approx.).

The initial stage is to remove the unsuitable surface material to create a level area on which to rest the base of the new retaining structure. The base of foundation of the proposed retaining structure system shall be located at a depth which complies with the following criteria:

1. Once the cuts are made and the desired foundation pad is prepared, the base of the retention structure shall be located at a minimum depth of 8.0 ft., beneath any loose/soft saturated material.

2. The base backfill material shall be placed above the level of the pre-worked foundation pad in the firm in-situ stiff residual material. For such purposes an inspection of the exposed material shall be allowed during the construction sequence.

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 ( )

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of 30⁰ and at a horizontal distance (t) of 20 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 20 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.

5.2.1 Retaining Wall Design Parameters

The retaining wall units shall retain the in-situ material, structure loads (Pavement section) and any new fill thickness required at the site.

Prior to the construction of any retention structure, the complete removal of any soft, unsuitable saturated soil 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.

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The initial stage is to remove any unstable surface material from the toe of the slope in benches to create a level area on which to rest the proposed retaining structure alingment. Once the initial demucking operation is performed and the over excavation to prepare the foundation base on the eastern slope surfaces. Also, as part of the construction process, to prevent further instability of the 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 soil parameters to be used in the design of the retaining walls are shown in Tables 1.

However, once the exact location of the selected structure is known a review of the final criterion of design shall be established. Considering the soil profiles found the following parameters of in-situ soils may be used for the design of the proposed retaining wall:

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

Recommended Range of values in layers for Borings 308-1 & 308-2

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

Fill Section Clayey Silt, trace sand

(0’-8’) 106 23 1,000 3.0 Ksf. @ 8.0 ft.*

Residual Material (8' -28') 110 26 - .

Weathered rock (>28’) 130 33 -

* NOTES: 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.

Lateral Pressure Coefficient at rest case (Ko) = 1-sin 0. The minimum depth of foundation shall be measured from the existing grade.

Lateral pressure coefficients are given for the active and for the at-rest case, depending on whether the wall is allowed to rotate at the top or not. The depth of foundation shall be compatible with the minimum depth requirements previously described. The depth of foundation shall be compatible with the minimum depth requirements previously described (Df and footings on sloping

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grounds requirements). 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.

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.

A prefabricated drainage composite and filter fabric, to prevent soil intrusion into the flow channels shall be provided between the backfill material and the selected facing structure. 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 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.

Also, 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.

5.3 Sheet Pile Retaining System Recommendations

Another solution which may be consider is the installation of a Sheet Pile retaining structure with a cap beam, placed along the crest of the eastern sloping grounds, along the edge of State Road

PR-179. The use of a sheet pile wall to restrict the induced stresses due to the traffic loads has been evaluated and can be considered to restrain PR-179 road embankment mass.

This alternative will not require the retaining wall of the previous alternative since the Sheet Pile structure, itself, will restrain the soil embankment mass. The minimum length of embedment of the sheet-pile sections shall be approximately 30 ft. (measured from the road side elevation,

598.55 mts. approximately), into the in-situ residual and weathered material. A minimum unsupported length of 8.0 ft. shall be considered by design.

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Once the sheet-pile section is installed, then the pavement reconstruction can commence. It shall be noted that the type of the steel-pile section shall depend on the expected lateral loads, as the structural evaluation will reveal and final grading elevations of the project, as previously mentioned.

Although it is estimated steel sheet piles sections will be used, alternate sheet pile materials such as vinyl and fiberglass composite synthetic sheet piles can be also considered at the designer discretion. The use of combined special arrangements of sheet piles wall sections to achieving great resistance to bending may be required at this project.

5.3.1 Lateral Load Design Considerations

The following design model shall be used in the foundation design for lateral load evaluations of the proposed sheet-pile retaining system. For lateral calculations, an unsupported length of the upper 8 ft. shall be considered in the evaluation. The final sheet pile section will depend on the expected loading conditions.

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 design of the proposed Sheet Pile Retaining System. Table 2 present a summary of the soil parameters to be used in the lateral design evaluations.

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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.)

308-1 & 308-2 0’ to 4’ neglect Disregard (Consider unsupported)

4’ to 8’ 1,000 Disregard (Consider unsupported) 8’ to 28’ 1,800 30

Deeper than 28’ - 50

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 30 ft. into the completely weathered material is been required.

Also, Considering the subsoil profile found at the site, the negative skin friction should be very small and an adequate allowance for residual settlements has been considered in the analyses.

5.4 Earthquake Design

Spectral Response Acceleration of 90% of g. (probability of exceedance of 2% in 50 years) is identified for the Municipality of Guayama. The site will behave as Site Class D, as described in

International Building Code 2009 Edition and the Puerto Rico Building Code 2011.

The Soil Profile Types shall be used for the determination of the base shear of the structure units’ and shall be as follows:

TABLE 2 - Soil Profile Types

Sector Covered Range of Depths (ft.)

Soil Type

308-1 & 308-2 0’ to 28’ SD Deeper than 28’ SC

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 15

5.5 Excavations

For most parts of the project, shallow excavations to remove the soft slope-wash material f can be performed using backhoe equipped with a short tip radius and narrow bucket. However, frequent occurrence of consolidated materials, cobbles and rock fragments within the profiles above the foundation excavation will increase both the time and cost of the operations. High resistance to penetration values were found at shallow levels, beneath existing grade within the upper horizon at the presently investigated locations. The extent of depth where the Standard

Resistance to Penetration (N-values) exceeds 40 blows/foot is where difficulty in the trench excavations is predicted.

A careful review of the geological plans with the herein enclosed profile information would assist the planners in the selection of the adequate cutting equipment of the project.

5.6 Earthwork Recommendations for Fill and Cut Sections

5.6.1 Fill Sections

From the Geotechnical Engineering point of view, it is recommended that fill embankment slopes be constructed to a slope ratio not steeper than 2 horizontal to 1 vertical, using A-2-4 or better

AASHTO Class Type material. Also, whenever high plastic clay soils are exposed in the upper profile sections, a cut slope ratio not steeper than 2.25H: 1V (Horizontal to Vertical) must be provided.

The following construction criteria shall also be considered to render stable slope section:

A. Any exposed virgin soil slope shall be cut with the maximum slope ratio for temporary slopes.

B. Any exposed embankment slope face shall be protected against erosion as recommended by the Consulting Hydrologist.

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 16

C. The engineering control of the fill section shall be also placed in accordance to Section

304-3 of the Standard Specification for Road and Bridge Construction, 1989 Edition.

5.6.2 Temporary Cut Sections

Temporary cut slopes shall through the upper fill material and alluvial soils shall be constructed with a 2.0H: 1.0V (Horizontal: Vertical) slope ratio. Cuts on residual soils may be constructed at a slope ratio not steeper than 1.5H: 1.0V ratio.

Should existing structures (i.e. roadways), special construction processes to prevent further instability of the existing slope surfaces shall be put into effect. The construction sequence shall be performed in alternating sections of not more than 15.0 ft. wide. This criterion shall be considered as the general case through the project, except where an existing structure, if any, lie at horizontal distances closer than 15.0 ft. Under such circumstance a geotechnical review shall be allowed to establish the impact the proposed temporary slope may have on the existing structure and its foundations.

To assure adequate construction of steeper cut sections, it is mandatory the verification of the site and topographic conditions at the proposed cut sector, to review stability analysis and the specific conditions of the proposed cut slope.

5.7 Additional Earthwork Recommendations

5.7.1 Recommended Fill Types and Compaction Specifications

The fill material shall be inorganic and shall not exhibit swelling characteristics. Under standard design criterion, the backfill for the wall should be granular (AASHTO A-2-4 or better), carefully placed and of good quality and compacted to a minimum of 95 % of its maximum dry density. In area prone to oversaturation, crushed stone compacted to a minimum of 83 % of its bulk density shall be used as back fill material.

Crushed-stone material (2-inch maximum size and not having more than 15 % passing the No.

200 sieve) shall be used to fill gullies and at sectors near streams. All fill material shall be compacted in layers not to exceeding six (6”) inches when compacted (8" to 10”-inches loose).

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 17

All undesirable soil material from the gullies or ravines, slope-wash and debris from previous earth moving operation shall be removed entirely under direct supervision of a representative from this office. Once the surface undesirable soils are removed, the exposed shall be proof rolled, and compacted to not less than 95% of the in-situ material maximum dry density (Modified Proctor

Compaction).

All borrow materials shall be taken to a soils laboratory for testing and approval prior to their use at the project.

5.8 Proposed Storm Water Run-off Control

Evaluation revealed the previous existing storm sewer facilities were not enough for the project development, especially during the past Hurricane event. Therefore, regardless of the final design alternative selected, new and additional drainage facilities of enough capacity shall be provided, based on hydrologic study. All surface water shall drain freely away from the embankment slope mass. Existing gullies shall be provided with coarse gravely materials to prevent further erosion.

Also, the existing storm sewer 30”-inch diameter pipe shall be extended all the way to the toe of the eastern sloping grounds with appropriate discharge outfall into the eastern gully stream. By no means, should surface flow be allowed to run freely over the exposed slope surfaces. The existing gullies surface shall be provided with coarse gravely materials to prevent further erosion.

Neglecting to provide these drainage facilities it is possible additional surface slides may develop.

Whenever large topographic changes are made, groundwater flows are usually found, which can be detected during the grading process. Such conditions shall be observed, and the flow diverted to proper outfall, through adequate drainage facilities.

However, as temporary mitigation measure, until the complete stabilization procedure is designed and completed, all surface runoff shall be diverted away from slopes to minimize the erosional effects which will yield further saturation causing additional slope failure at the site.

Project No.: DA/18O3746 Guayama, Puerto Rico December 28, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 18

5.9 Nearby Structures

Should nearby structures exist, the earthwork process and the installation of foundation units require special consideration regarding vibrations during the earthwork process. It is difficult to predict at this stage the magnitude and extend of vibrations to be produced by the equipment to be used during the construction sequence. Thus, this aspect of construction shall be evaluated with care.

Regardless of the vibration restrain process provided, the use of photographs prior to the construction sequence is very valuable to establish pre-existing conditions of nearby structures.

These are very valuable in court. A monitoring process of vibrations shall be in place during the construction sequence, as considered necessary by the contractor. Also, there is no way to predict the amount of settlement caused by lateral yielding while the excavations are opened.

Thus, it is mandatory to provide a temporary retention system to assure the existing adjacent structures are not subject to differential settlement while the excavation, if any, are completed.

Alternate sequence for construction at the sector close to the existing structure is one method to minimize effects of lateral yielding.

The surface clayey deposits have friction angles which do not permit permanent cut slopes steeper than 2.0H: 1V (Horizontal: Vertical). Therefore, if the site does not permit such slopes, a

Temporary Retaining System shall be provided.

5.10 Additional Recommendations

We urge that our firm be retained to review those portions of the plans and specifications that pertain to earthwork and foundations to determine whether they are consistent with our recommendations. In the event the undersigned is not selected to review this item of the project contracts, the designers and construction firm involved in the design shall assume full responsibility of such important phase of the works.

The recommended geotechnical design concepts must be complemented with a structural design, which include and is not limited to the preparation of plans and specifications. Geotechnical

Project No.: DA/18O3746 Guayama, Puerto Rico December 28, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 19

reports by themselves are not considered a structural report and do not make any recommendations in relation to any structural problems observed nor any solutions that maybe required. It may be used as an adjunct to a Structural Report, prepared by a suitably qualified registered structural engineer. For such purposes, we urge the structural designer to contact this office to clarify, review the designed process and to provide support in the preparation of the specifications for the required work, to meet the geotechnical requirements herein being presented.

In addition, the owner and/or design team shall be aware that stability of the existing slopes (cut and fill slopes), especially those to the northeastern property line were beyond the scope of the present work. Thus, it is highly recommended that an additional subsoil exploration shall be performed for such purposes on this sector of the lot.

Also, it is highly recommended that at least three (3) inclinometers be installed along the easternmost property line to monitor any lateral displacement of the earth embankment mass during and post construction of the proposed retaining structure is constructed.

VI. LIMITATIONS OF THIS REPORT

The above design parameters and recommendations are based in the information and interpretation of laboratory data of the test boring performed, and existing published correlations.

Actual conditions, especially at intermediate locations, may differ from the information obtained in this exploration. The owner or contractor are urged to contact this office if different conditions than those herein described are encountered.

The recommendations contained in this report may have to be varied to accommodate recommendations to cope with undisclosed conditions. Furthermore, the monitoring and inspection of earthwork related construction procedures, as well as the supervision of the implementation of the herein given recommendations shall be made by the writer or his approved representative. Otherwise, the inspecting engineer shall study this report, perform additional tests as he deems necessary, to submit his own recommendations or assume full responsibility of the herein given recommendations in their entirety.

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 20

In the event that any changes in the nature, design, or location of the proposed development planned, the conclusions and recommendations contained in this report should not be considered valid unless the changes are reviewed, and the recommendations contain herein are verified and/or modified in writing by the undersigned.

The undersigned will not be responsible for any claims, damages, or liability associated with interpretation of subsurface data or reuse of the subsurface data or engineering analysis contained herein without his written consent.

The provision of services by Despiau Associates is specific to only providing documentation in relation to geotechnical recommendations and specifications for this project. All other engineering or non-engineering specifications are not included in the service herein provided. The scheduled fee does not cover any provision of any services beyond the issue of this geotechnical report. All further documentation or inspections will be charged at a separate quoted fee.

Also, if the geotechnical report is used for construction and/or to obtain a Construction Permit it will be considered an acceptance by the client of all geotechnical specifications and recommendations contained.

Respectfully Submitted, Jose R. Despiau, PE Geotechnical Engineer

DA/18O3746

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

APPENDIX (A)

Figures

SITE PLAN

FROM US GEOLOGICAL SURVEY TOPOGRAPHIC MAP AT A SCALE 1:20,000

SITE

ER-HWY308

GEOTECHNICAL ENGINEERING AND SUBSURFACE EXPLORATORY SERVICES

FOR THE LANDSLIDE AND ROAD DAMAGE EVALUATION

AND RECONSTRUCTION PROJECT

AT STATE ROAD PR-179, KM 13.25 ON CARITE WARD

OF THE MUNICIPALITY OF GUAYAMA, PUERTO RICO.

REFERENCE NO. DA/18O3746

SOIL/GEOTECHNICAL ENGINEERING LABORATORIES

P.O. BOX 260370, San Juan, Puerto Rico 00926-2622 / (787) 281-0686

1a

SITE PLAN

FROM US GEOLOGICAL SURVEY GEOLOGICAL MAP (REPORT 52-82-1097, PLATE 1 OF 2)

NOTE:

THE GEOLOGICAL UNITS IDENTIFIED AT OR IN THE VICINITY OF THE PROJECT ARE INDICATED IN THE US GEOLOGICAL SURVEY (OPEN FILE REPORT 52-82-1097) OF THE PATILLAS (PRELIMINARY) QUADRANGLE PREPARED BY M.H. LYNN GLOVER, III (1982) FOR THE US DEPARTMENT OF INTERIOR.

SCALE: NOT TO SCALE.

SITE

ER-HWY308

GEOTECHNICAL ENGINEERING AND SUBSURFACE EXPLORATORY SERVICES

FOR THE LANDSLIDE AND ROAD DAMAGE EVALUATION

AND RECONSTRUCTION PROJECT

AT STATE ROAD PR-179, KM 13.25 ON CARITE WARD

OF THE MUNICIPALITY OF GUAYAMA, PUERTO RICO.

REFERENCE NO. DA/18O3746

ER-HWY308

GEOTECHNICAL ENGINEERING AND SUBSURFACE EXPLORATORY SERVICES

FOR THE LANDSLIDE AND ROAD DAMAGE EVALUATION

AND RECONSTRUCTION PROJECT

AT STATE ROAD PR-179, KM 13.25 ON CARITE WARD

OF THE MUNICIPALITY OF GUAYAMA, PUERTO RICO.

REFERENCE NO. DA/18O3746

NOTE:

THIS DRAWING WAS PROVIDED BY THE CLIENT AND

WAS USED TO ILLUSTRATE THE APPROXIMATE

BORING LOCATION.

SCALE:

NOT TO SCALE - REDUCE FROM ORIGINAL

APPENDIX (1)

Boring Logs

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…