Amendment 0001 - PR ER DOT PRMNT RPR(13).pdf

(x)

693C7322R000021 x x

1 copies of the amendment; (b) By acknowledging receipt of this amendment on each copy of the offer submitted ; or (c) By separate letter or electronic communication which includes a reference to the solicitation and amendment numbers. FAILURE OF YOUR ACKNOWLEDGEMENT TO BE

RECEIVED AT THE PLACE DESIGNATED FOR THE RECEIPT OF OFFERS PRIOR TO THE HOUR AND DATE SPECIFIED MAY RESULT IN REJECTION OF YOUR

OFFER. If by virtue of this amendment you desire to change an offer already submitted , such change may be made by letter or electronic communication, provided each letter or electronic communication makes reference to the solicitation and this amendment, and is received prior to the opening hour and date specified.

x

ASHBURN VA 20147

ATTN:CONSTRUCTION

693C73

SUITE E2-3-300

QUANTUM PARK, 22001 LOUDOUN COUNTY PKWY

EASTERN FEDERAL LANDS HIGHWAY DIVISION

FEDERAL HIGHWAY ADMINISTRATION

ASHBURN VA 20147

ATTN:ACQUISITIONS

693C73

SUITE E2-3-300

QUANTUM PARK, 22001 LOUDOUN COUNTY PKWY

EASTERN FEDERAL LANDS HIGHWAY DIVISION

FEDERAL HIGHWAY ADMINISTRATION

See Block 1407/17/20220001

13. THIS ITEM ONLY APPLIES TO MODIFICATION OF CONTRACTS/ORDERS. IT MODIFIES THE CONTRACT/ORDER NO. AS DESCRIBED IN ITEM 14.

12. ACCOUNTING AND APPROPRIATION DATA (If required) is not extended.is extended, Items 8 and 15, and returning

Offers must acknowledge receipt of this amendment prior to the hour and date specified in the solicitation or as amended , by one of the following methods: (a) By completing

The above numbered solicitation is amended as set forth in Item 14. The hour and date specified for receipt of Offers

11. THIS ITEM ONLY APPLIES TO AMENDMENTS OF SOLICITATIONS

FACILITY CODE CODE

10B. DATED (SEE ITEM 13)

10A. MODIFICATION OF CONTRACT/ORDER NO.

9B. DATED (SEE ITEM 11)

9A. AMENDMENT OF SOLICITATION NO.

CODE

8. NAME AND ADDRESS OF CONTRACTOR (No., street, county, State and ZIP Code)

7. ADMINISTERED BY (If other than Item 6)CODE 6. ISSUED BY

PAGE OF PAGES

4. REQUISITION/PURCHASE REQ. NO.3. EFFECTIVE DATE2. AMENDMENT/MODIFICATION NO. 5. PROJECT NO. (If applicable)

1. CONTRACT ID CODE

AMENDMENT OF SOLICITATION/MODIFICATION OF CONTRACT

06/22/2022

CHECK ONE A. THIS CHANGE ORDER IS ISSUED PURSUANT TO: (Specify authority) THE CHANGES SET FORTH IN ITEM 14 ARE MADE IN THE CONTRACT

B. THE ABOVE NUMBERED CONTRACT/ORDER IS MODIFIED TO REFLECT THE ADMINISTRATIVE CHANGES (such as changes in paying office, C. THIS SUPPLEMENTAL AGREEMENT IS ENTERED INTO PURSUANT TO AUTHORITY OF:

D. OTHER (Specify type of modification and authority) appropriation data, etc.) SET FORTH IN ITEM 14, PURSUANT TO THE AUTHORITY OF FAR 43.103(b).

E. IMPORTANT: Contractor is not is required to sign this document and return __________________ copies to the issuing office.

ORDER NO. IN ITEM 10A.

14. DESCRIPTION OF AMENDMENT/MODIFICATION (Organized by UCF section headings, including solicitation/contract subject matter where feasible.)

Project PR ER DOT PRMNT RPR(13):

The purpose of this Amendment is to:

1) Revise the Government Furnished Information as follows:

a) Replace the Geotech Report for project AC-841579, HWY-410.

b) See Amended Report_GEO_ AC-841579_HWY-410_Amendment_1.pdf

2) Revise the Plans as follows:

a) AC-820579: Replace Sheet UTT-A/1.

b) See Amended_Plans_AC-820579_Amendment 1.pdf for details.

Continued ...

15A. NAME AND TITLE OF SIGNER (Type or print)

15C. DATE SIGNED 16B. UNITED STATES OF AMERICA 15B. CONTRACTOR/OFFEROR 16C. DATE SIGNED

(Signature of person authorized to sign) (Signature of Contracting Officer)

16A. NAME AND TITLE OF CONTRACTING OFFICER (Type or print)

STANDARD FORM 30 (REV. 11/2016)

Prescribed by GSA FAR (48 CFR) 53.243

Previous edition unusable

Except as provided herein, all terms and conditions of the document referenced in Item 9 A or 10A, as heretofore changed, remains unchanged and in full force and effect .

ITEM NO. SUPPLIES/SERVICES QUANTITY UNIT UNIT PRICE AMOUNT

NAME OF OFFEROR OR CONTRACTOR

2 82

CONTINUATION SHEET

REFERENCE NO. OF DOCUMENT BEING CONTINUED PAGE OF

(A) (B) (C) (D) (E) (F)

693C7322R000021/0001

3) Revise the Utility Endorsements and

Coordination for project AC-838579, HWY-308, as follows:

a) Replace Utility Endorsements and Coordination to update LUMA OGPe¿s approval letter and LUMA¿s no objection letter.

b) See Amended_Utility_Endorsement &

Coordination_PRASA-PREPA-TelCom_AC-838579_HWY-308_

Amendment 1.pdf for details.

4) Revise the Utility Endorsements and

Coordination for project AC-841579, HWY-410, as follows:

a) Replace Utility Endorsements and Coordination to update PRASA OGPe¿s approval letter and to add

PRASA¿s approval letter.

b) See Amended_Utility_Endorsement &

Coordination_PRASA-TelCom_AC-841579_HWY-410_Amendm ent 1.pdf for details.

5) Provide a summary of responses to questions/clarifications asked by potential bidders.

The RFP Proposal Package (both Technical and

Price Proposals) due date of July 21, 2022 at

2:00 p.m. EDT will remain.

NSN 7540-01-152-8067 OPTIONAL FORM 336 (4-86)

Sponsored by GSA

FAR (48 CFR) 53.110

Amendment No. 0001

Info Page 1 of 1

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

Project PR ER DOT PRMNT RPR(13)

Landslide Repairs in Aibonito, Caguas, Guayama, Gurabo, and Patillas.

Solicitation: 693C73-22-R-000021

The purpose of this Amendment is to:

1) Revise the Government Furnished Information as follows:

a) Replace the Geotech Report for project AC-841579, HWY-410.

b) See Amended Report_GEO_ AC-841579_HWY-410_Amendment_1.pdf

2) Revise the Plans as follows:

a) AC-820579: Replace Sheet UTT-A/1.

b) See Amended_Plans_AC-820579_Amendment 1.pdf for details.

3) Revise the Utility Endorsements and Coordination for project AC-838579, HWY-308, as follows:

a) Replace Utility Endorsements and Coordination to update LUMA OGPe’s approval letter and LUMA’s no objection letter.

b) See Amended_Utility_Endorsement & Coordination_PRASA-PREPA-

TelCom_AC-838579_HWY-308_Amendment 1.pdf for details.

4) Revise the Utility Endorsements and Coordination for project AC-841579, HWY-410, as follows:

a) Replace Utility Endorsements and Coordination to update PRASA OGPe’s approval letter and to add PRASA’s approval letter.

b) See Amended_Utility_Endorsement & Coordination_PRASA-TelCom_AC- 841579_HWY-410_Amendment 1.pdf for details.

5) Provide a summary of responses to questions/clarifications asked by potential bidders.

The RFP Proposal Package (both Technical and Price Proposals) due date of July 21, 2022 at 2:00 p.m. EDT will remain.

Report Changes Summary

Report changes

Report_GEO_AC-841579_HWY-410.pdf

1. Delete Report_GEO_AC-841579_HWY-410 and substitute with the Amended Report_GEO_ AC-841579_HWY-410_Amendment 1:

a) Report_GEO_AC-841579_HWY-410 was the incorrect document and was replace with the Geotechnical Report for HWY-410.

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-410 State Road PR 722, KM. 5.70 on Robles Ward of the Municipality of Aibonito, Puerto Rico, Reference No. DA/18O3753

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

Amendment No. 0001 http://www.despiau.net/ mailto:franciscoklein@klein-engneering.com

DESPIAU ASSOCIATES

CONSULTING GEOTECHNICAL ENGINEERS

PO BOX 260370

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

CONSULTING GEOTECHNICAL ENGINEERS

Report of Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project at State Road PR-722, KM 5.70 on Robles Ward of the Municipality of Aibonito, 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

CONSULTING GEOTECHNICAL ENGINEERS

December 28, 2018

PO Box 12009 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-722, KM 5.70 on Robles Ward of the Municipality of Aibonito, 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-722, KM 5.70 on Robles Ward of the Municipality of Aibonito, 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/04-22-18R 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. The original and one copy of the geotechnical report are being submitted with this transmittal letter.

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

Respectfully Submitted, Jose R. Despiau, PE.

Geotechnical Engineer

Project No.: DA/18O3753 Aibonito, Puerto Rico December 28, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS i

TABLE OF CONTENTS

Page No.

I. INTRODUCTION

II. SITE AND PROJECT DESCRIPTION

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

3.2 Geological Notes

3.3 Stratigraphic Units

IV. OBSERVATIONS AND FINDINGS

V. ENGINEERING RECOMMENDATIONS

5.1 Improvement of the Earth Slope Section to Satisfy Slope Stability

5.1.1 Summary of General Construction Guidelines for the Slope Improvements

5.2 Foundation Recommendations and Design Parameters for Retaining Wall Units

5.2.1 Retaining Wall Design Parameters

5.3 Combined Alternative recommendations

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-722, KM

5.70 on Robles Ward of the Municipality of Aibonito, 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/04-22-18R 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. It also includes the engineering assessments, from the geotechnical standpoint, to be used in the engineering evaluation and design for the reconstruction of the referenced sector.

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 walls, 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.

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 2

II. SITE AND PROJECT DESCRIPTION

The Site observation revealed a slide occurred on the northern edge of State Road PR-722 near

Km.5.70 after the passing of Hurricane Maria. The observed slide is found just north of the intersection with a private access road to existing residential units, south of the identified longitudinal slide along the northern edge of State Road PR-722 at Robles Ward of the

Municipality of Aibonito, Puerto Rico.

Evaluation revealed the site carries storm water from the highland sectors of the south toward the lowland areas at the north through an existing drainage gully toward the north-northwest, finally meeting the Rio de Aibonito river, found further northwest of the Site. This ephemeral gully streams runs almost parallel to PR-722 on the neighboring cattle pasture lands found at the north.

Excess surface runoff higher grounds from private properties drains toward the north toward the neighboring lands. An existing 24”-inch diameter pipe, crossing nearly perpendicular to the State

Road PR-722, was previously provided to divert the surface flows to the north. However, it is evident this drainage pipe was not enough to cope with the excess storm water runoff experienced during the hurricane event.

Observations disclosed, severe erosion pattern along the northern edge of State Road PR-722, where surface slide caused the settlement of the pavement and the rupture/displacement of the curb structure and the observed tension cracks on the wearing surface course of State Road PR-

722. Also, erosional scars at the crest of the northern sloping grounds along the edge of PR-722.

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

The subsurface soil conditions at the site were investigated three (3) 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.

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 3

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

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

(1) to this report.

3.2 Geological Notes

Based on available US Geological Survey publications, the units in the site vicinity are shown in the US Geological Survey of the Comerio Quadrangle (Map I-320), prepared by Messrs. Maurice

H. Pease, and Reginald P. Briggs (1960). Thus, the geologic unit descriptions that lie at or adjacent southwestern corner of the Quadrangle and to the site are the following:

1. Robles Formation (kt) – Described as chiefly thinly stratified fine-grained sedimentary rocks, Kr, but includes fine-grained volcanic breccia, Krb, and Krb2, and a lava flow, Krf. Also includes the Las Tetas lava member, Krt; the Lapa lava member, lower flow, Krl, and upper flow, Krl2;

and the Río Matón limestone member, Krr, a thin discontinuous unit at the base of the formation. The most prominent dip angles of the bedding planes in this formation adjacent to the site are at 31- and 55-degrees with the horizontal, trending toward the southeast.

The Robles formation consists chiefly of thinly bedded, fine to very fine-grained volcanic sandstone and water-laid tuff. These rocks are medium dark gray to medium bluish gray when fresh, but weather to pale shades of brown and to reddish brown soil. Calcite is the common cementing agent except in the southwestern corner of the quadrangle where laminated very fine-grained rocks of this member are cemented by silica.

2. Terrace deposits (Qt) - Described as unconsolidated sand, gravel, and silt including large cobbles and boulders of volcanic rock; restricted to deposits generally above the level of present stream action.

Project No.: DA/18O3753 Aibonito, Puerto Rico December 20, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 4

An Unnamed Fault, with an approximate (dashed) alignment, running with a semi-circular alignment is shown in the southwestern corner of the Quadrangle map. The Unnamed Fault is found northeast from the site, at about 1100 ft. Also, several Unnamed Fault lines, with approximate (dashed) alignments were identified, intersecting the above described Main Fault, running nearly perpendicular to each other meeting at about 1300 ft. from the site within the same described Robles Formation. These Unnamed Faults alignments have been identified with a near south-east, north-east and west alignments, located, to both south and north of the site. Refer to the US Geological Survey – Geologi c Map, which is included in Appendix A, Figure 1A.

3.3 Stratigraphic Units

Surface Section - Generally, the results of the exploration disclosed a surface fill layer about 2.0 to 3.0 ft. It is composed of a mixture of silty clay, with traces of sand, with subangular gravel fragments, with varying colors: yellowish red, olive yellow, olive gray, and brownish gray.

Evidence of asphalt pieces and residue were disclosed. Some asphalt fragments were secured from the surface samples [Borings 1 and 2]. It is on this sector, along the crest of the prevailing slope, where most of the fill section was deposited during the construction of State Road PR-722 embankment road section.

At the drilled location on the embankment slope of lower elevation [Boring 410-3], the fill section from the surface layer was described as brown, reddish brown silty clay, some sand and some subangular graver fragments with few roots and plastic debris. The standard resistance to penetration (N-values) of the surface layers varied from 7 to 11 blows/foot, at a loose to stiff State of Consistency. The natural moisture content values range from 17 to 19 percent. Random samples of this layer from [Boring 410-1- from 0.0’ to 3.0 ft.] disclosed AASHTO class type A-7-6

(18) (USSCS type CH- Sandy fat Clayey); and from [Boring 410-2- from 0.0’ to 1.5 ft.] disclosed

AASHTO class type A-7-6 (18) (USSCS type CH- Sandy fat Clayey); The Standard Free Swell

Determination tests performed disclosed values at 30 percent.

Intermediate Fill Section - The undersoil material is identified as the additional fill, respectively extending to depths varying from 13, 13.5 to 8 ft. [Borings 1, 2 and 3, respectively]. The profile layers consist of yellowish red, red and very dark grayish brown]. The samples from these layers

Project No.: DA/18O3753 Aibonito, Puerto Rico December 20, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 5

were described silty clay, trace sand. The standard resistance to penetration (N-values) of upper fill section varied from 10 to 30 blows/foot at a medium to densely compacted state. The natural moisture content values range from 33 to 44 percent. Random sample of this layer [Boring 410-

1 from 3’ to 10.5 ft.] disclosed AASHTO class type A-7-5 (42) (USSCS type CH - Sandy fat

Clayey); layer [Boring 410-2 from 1.5’ to 10.5 ft.] disclosed AASHTO class type A-7-5 (38)

(USSCS type CH - Sandy fat Clayey). The Standard Free Swell Determination test performed disclosed values at 40 percent.

Residual Material – Beneath the above described section [Borings 410-1 to 410-3] and below the modified fill section the residual and completely weathered material was found, extending to depth varying from 18 to 25 ft., respectively. It is composed of brownish yellow, yellowish red, and light gray with mottles yellow clayey sandy silt. At Boring 410-3, extending to depth 25.0 ft., a red, olive yellow and light gray sandy silt was found. The standard resistance to penetration

(N-values) of the residual layers varied from 23 to 73 blows/foot, at a stiff to hard State of

Consistency. The natural moisture content values range from 15 to 38 percent. Random sample of the residual material disclosed AASHTO class type A-6 and A-7-5 soils (USSCS type ML -

Sandy Silt and ML – Sandy elastic Silts, respectively).

Completely Weathered Rock - At the deeper explored depths [Boring 410-1, 410-2 & 410-3] until the borings were bottomed, reddish yellow, red, yellow and brown mottled weathered rock into clayey sandy silt fines and completely weathered rock fragments, product of the weathering of the parent geologic units was found. The standard penetration test attempts varied from 69 blows/foot to practical refusal to penetration with values greater 70 blows for a few inches of penetration. The natural moisture contents range from 16 to 22 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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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 6

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. 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 clay soils. All surface ground and underground water should flow from the higher sectors at the south-east toward the lowland areas toward lowland to the north and northwest.

IV. OBSERVATIONS AND FINDINGS

The present exploratory program along the Sloping Grounds Improvement Project was conducted to establish the subsurface profile section to allow the presentation of construction guidelines and design alternatives for the stabilization of the northern sloping grounds along the edge of State

Road PR-722, which has been subjected to continuing degradation, erosional effects, and landslides causing the observed damage to the pavement structure.

Evidence of unstable conditions, failure planes and the occurrence of erosional slides have been confirmed in the present evaluations, considering the profile sections submitted, subsoil conditions and laboratory tests performed for the present Geotechnical Engineering review.

Moreover, the conditions may be aggravated whenever additional mean of oversaturation to the undersoil is present, diminishing the shear strength of the undersoil, hence increasing the probability of a slope failure. In addition, the surface water runoff also triggered the surface slides of the uppermost sloping surface.

Therefore, the herein recommendations for the proposed improvement for the unstable sloping grounds are considered necessary to render stable grounds preventing future erosional related consequences and slope failure, hence assuring the complete stabilization of PR-722 pavement distressed sector. The following recommendations shall be applied to the presently affected

Project No.: DA/18O3753 Aibonito, Puerto Rico December 20, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 7

areas; however, it is highly recommended that the herein recommendation shall be applied to the complete study sector.

Therefore, to cope with the presently disclosed subsoil conditions and to assure not further instability is experienced, the herein recommendation shall be applied to establish stable grounds.

The herein recommendation by themselves and/or a combination of them shall be applied to the presently affected area (northern sloping grounds), along the edge of PR-722, 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 complete replacement of the northern sloping grounds shall be reconstructed all-throughout the study sector. However, depending on the actual available space for such improvement, it may be required to us retaining structures (i.e. retaining walls) to avoid the adjacent land acquisition of the neighboring lands past the PRTHA right of way.

The prevailing sloping grounds north of State Road PR-722 have slope ratios ranging between 23 to 33 degrees. Although it may seem this slope rations are marginal to adequate the slope reconstruction shall consider slope ratios not steeper than 2.25H:1V. Therefore, this alternative entails the complete removal and replacement of the upper 3.0 to 8.0 ft. 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. Once the backfilling operations are completed, surface erosion protection countermeasures shall be provided.

Also, drainage facilities of enough capacity shall be provided, to carry all surface water away from the embankment slope mass. Neglecting to provide these drainage facilities it is possible additional slides will continue to be experienced due to the oversaturation and surface erosion.

2. A cantilever retaining structure to retain the northern soil embankment mass and any existing structures (i.e. State Road PR-722 pavement structure) may also be considered. The retaining wall shall be provided all-throughout the affected area parallel to the northern edge

Project No.: DA/18O3753 Aibonito, Puerto Rico December 20, 2018

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 8

of State Road PR-722. Evaluation dictate this retaining structure shall be some 65 meters long, approximately. The minimum depth of foundation (Df) shall vary between 5.0 ft. and

8.0 ft., (Borings 410-1 & 410-2, respectively).

3. A combination of a retaining structure (Gabion or Cantilever type) with a new improved slope section (2.25 H: 1V) on top can also be considered by design. Therefore, a shorted retaining can be provided at a lower elevation parallel to State Road PR-722 and provided with a new slope section until meeting the desired road side elevation with slope ratio 2.25H:1V, protected with MacMat R (or similar), as an Erosion Protection to the exposed upper slope surface.

The retaining wall shall also be provided all-throughout the affected area parallel to the northern edge of State Road PR-722, but at a lower elevation (i.e. 469 mts.) resulting in a shorter retaining wall. The length of the wall shall be the same as alternative two (2), above

(65 meters), and the minimum depth of foundation (Df) shall be 5.0 ft. (Borings 410-3).

Therefore, this alternative entails the removal of the upper 5.0 ft. to allow the base of the wall.

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.

V. ENGINEERING RECOMMENDATIONS

5.1 Improvement of the Earth Slope Section to Satisfy Slope Stability.

Based on the results of the present slope stability review it was confirmed, under the prevailing loose and the oversaturation of the fill embankment soil at the slope crest of the study areas, the earth fill embankment surface section to about 3 to 8 ft. in thickness lies on unstable grounds, which require immediate improvements.

The unstable material was identified at the upper fill slope section, which correlates with the loose compacted fill material, which may have experienced erosional scarps at the study area.

Consequently, additional slope slides of the embankment mass could develop. Therefore, the

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DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 9

complete reconstruction of the northern sloping grounds can be considered to render stable grounds at the Site.

The geotechnical review disclosed the following deficiencies at the study area and shall be considered in the new embankment design and construction.

1. Inadequate control of surface run-off at the site; the improper deposition of the fill beneath the sloping grounds.

2. Not providing an adequate under-drain system, designed for additional water flows from alteration of the topography, as stream water shed analysis could have revealed.

3. Disregard of the fill construction benches at new fill sectors, along contour levels, causing lateral spreading or creep of the embankment mass along the original slope surfaces.

4. Inadequate stripping and demucking of unsuitable organic matter, beneath the original fill section underlying the embankment slope alignment, prior to earthwork operations at the site.

The following soil stabilization improvements recommendations are necessary for the present study area. Although it may seem the prevalent slope rations are marginal to adequate the slope reconstruction shall consider slope ratios not steeper than 2. 25H:1V. Therefore, this alternative entails the complete removal and replacement of the upper 3.0 to 8.0 ft. and provided with surface slope ration not greater than 2.25H:1V.

Under the presently proposed earth stabilizing improvements adequate slope stability shall be assured. Thus, the initial stage is to remove the unstable surface loose material from scarp surfaces and from the toe of the slope, 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-722.

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

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intermediate areas between borings. Based on the present boring program, the depth of removal shall involve a minimum thickness of removal of 1.0 m. (3.0) ft., measured from the existing surface. Adjacent to Borings 410-1 and 410-2, the removal operations shall extend to depth varying from 1.0 mts. (3.0 ft.) to 2.45 mts. (8.0 ft.), measured from the existing ground surface prevailing during the period of the field work.

Benches, after surface loose soil (slope-washed) removal, 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 dense silty clayey soil at each bench.

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-722. Thus, the exposed upper slope surface using surface

MacMat R, BioMAc, MacGrid Tor similar shall be provided.

Also, drainage facilities of enough capacity shall be provided, to carry all surface water away from the embankment slope mass. As a minimum French Drain, along same elevation benches shall be provided to drain subsurface runoff away from the soil embankment mass. Neglecting to provide these drainage facilities it is possible additional slides will continue to be experienced due to the oversaturation and surface erosion.

5.1.1 Summary of General Construction Guidelines for the Slope Improvements

Some of the engineering guideless for the project, which shall be considered during the re-construction of the roadway soil embankment mass, are the following:

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1. The initial stage is to remove the unstable surface loose material from scarp surfaces and from the toe of the slope, in addition to any loose slope washed material in benches, so as to create a level area on which to rest the new improved backfill material up to the desired grade, until meeting the required crest of slope, edge of PR-722. Therefore, the complete removal and replacement of the upper 3.0 to 8.0 ft. shall be allowed.

2. In some areas an over-excavation may be to assure that a uniform fill section is provided.

3. After surface loose soil (slope-washed) removal, benches shall be provided with a surface stabilization fabric. The minimum width of the benches shall be 1.0 meter.

4. 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 dense silty clayey soil at each bench.

5. Once the benches are constructed, the backfilling operation can commence. 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.

6. After the final grading elevations shall consider surface slope ratios not greater than

2.25H:1V.

7. 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. Thus, the exposed upper slope surface shall be provided with erosion countermeasures, such as MacMat R, BioMAc, MacGrid T or similar.

The construction and earthwork process shall be monitored under the direct supervision of projects geotechnical engineer or approved representative.

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5.2 Foundation Recommendations and Design Parameters for Retaining Wall Units

For this improvement approach, a retaining structure to retain the northern soil embankment mass and any existing structures (i.e. State Road PR-722 pavement structure) shall be considered.

The retaining wall shall be provided all-throughout the affected area parallel to the northern edge of State Road PR-722. Evaluation dictate this retaining structure shall be some 65 meters long, approximately. The minimum depth of foundation (Df) shall vary between 5.0 ft. and 8.0 ft., (Borings 410-1 & 410-2, respectively).

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 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 5.0 ft., well beneath of below any loose fill material.

2. The Retaining Wall solution entails the removal of the upper loose fill section 3.0 to 8.0

ft. [Borings 410-1 & 410-2, respectively] or 5.0 ft [Boring 410-3], during the leveling process.

3. The base backfill material shall be placed above the level of the pre-worked foundation pad in the firm in-situ stiff 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 ( ) 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.

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FIGURE A: Footing in Sloping Grounds

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

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

5.2.1 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 loose unsuitable 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.

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. Once the initial demucking operation is performed and the over excavation to prepare the foundation base at the toe of the northern slope. 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 20.0 ft. wide.

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The soil parameters to be used in the design of the retaining walls are shown in Tables 1 & 1A.

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 410-1 & 410-2

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 Silty Clay, trace sand

(0’-8’) 105 21 600 3.0 Ksf. @ 8.0 ft.*

Silty Clay and Clayey Sandy Silt

(8' -18') 123 24 1,300 .

Residual Material (18' -28') 125 28 - .

Weathered rock (>28’) 130 33 -

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

Recommended Range of values in layers for Borings 410-3

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 Silty Clay, trace sand

(0’-5’) 111 22 500 2.0 Ksf. @ 5.0 ft.*

Silty Clay (5' -14') 120 23 1,200 .

Residual Material (14' -30') 125 28 - .

* 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.

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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 during construction 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 grounds). 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.

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.

The required earthwork for the construction of a new wall would entail the removal of any unsuitable material along the proposed structure alignment. Therefore, it is of upmost importance to take all precautions during the excavation procedures to assure slope stability during construction.

5.3 Combined Alternative recommendations

A combination of a retaining structure (Gabion or Cantilever type) with a new improved slope section (2.25 H: 1V) on top can also be considered by design. Therefore, a shorted retaining can

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be provided at a lower elevation parallel to State Road PR-722 and provided with a new slope section until meeting the desired road side elevation with slope ratio 2.25H:1V, and protected with

MacMat R, BioMAc, MacGrid T or similar. (or similar), as an Erosion Protection to the exposed upper slope surface.

The retaining wall shall also be provided all-throughout the affected area parallel to the northern edge of State Road PR-722, but at a lower elevation (i.e. 469 mts.) resulting in a shorter retaining wall. The length of the wall shall be approximately 65.0 meters, and the minimum depth of foundation (Df) shall be 5.0 ft. (Borings 410-3). Therefore, this alternative entails the removal of the upper 5.0 ft. to allow the base of the wall. Refer to the previous section of this report specific design recommendations.

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 Aibonito. 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

410-1 0’ to 3’ SE 3’ to 25’ SD Deeper than 25’ SC

410-2 0’ to 8’ SE 8’ to 28’ SD Deeper than 28’ SC

410-3 0’ to 5’ SE 5’ to 10’ SD Deeper than 10’ SC

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5.5 Excavations

For most parts of the project, shallow excavations for the foundation excavations can be performed using backhoe equipped with a short tip radius and narrow bucket. 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 fill and upper modified soil section 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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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 structures, 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.