Technical Report - AC-830579_HWY-106.pdf

DEPARTMENT OF TRANSPORTATION

AND PUBLIC WORKS

COMMONWEALTH OF PUERTO RICO

TECHNICAL REPORT

LANDSLIDE AND ROAD DAMAGE EVALUATION

AND REPAIR RECOMMENDATIONS FOR

AÑASCO, LARES, LAS MARIAS, MOCA,

SAN JUAN MUNICIPALITIES

AC-809544 / ER-9999 (318)

FEBRUARY 1, 2019

GROUP - B

PROJECT ID# HIGHWAY KILOMETER MUNICIPALITY

ER-HWY-106 PR-124 21.90 Lares

TABLE OF CONTENTS

INTRODUCTION I

DAMAGE ASSESSMENT II

WORK EXECUTED III

• FIELD SURVEY AND TOPOGRAPHY

• GEOTHECNICAL REPORT

TECHNICAL SOLUTION ALTERNATIVES IV

• ALTERNATIVE I

• ALTERNATIVE II

• ALTERNATIVE III

ALTERNATIVE EVALUATION V

ENVIRONMENTAL CONSIDERATIONS VI

CONSTRUCTABILITY VII

CONSTRUCTION COST VIII

• ALTERNATIVE I

• ALTERNATIVE II

• ALTERNATIVE III

CONSTRUCTION TIME IX

SOLUTION COMPLEXITY X

IMPACT ON RIGHT OF WAY ACQUISITION XI

RECOMMENDATIONS XII

TECHNICAL REPORT

INTRODUCTION I

LANDSLIDE AND ROAD DAMAGE EVALUATION GROUP B

AND REPAIR RECOMMENDATIONS FOR AÑASCO, LARES, Project ID#: ER-HWY-106

LAS MARIA, MOCA, SAN JUAN MINICIPALIES (AC-809544) PR-124, km. 21.90 Lares

I. INTRODUCTION

The Puerto Rico Highway and Transportation Authority (PRHTA) contracted José A.

Batlle & Asociados, C.S.P. (JABA), to provide support in their Emergency Relief Program through the Puerto Rico’s Federal Aid Highway System, and other highways and roads under the Department of Transportation and Public Works jurisdiction. This Technical

Report is part of a multiple site assessment project for similar landslide rehabilitation cases related to damages by Hurricane María on September 20, 2017. The project consists of the evaluation and reconstruction of: Landslide, Slope Instability, Washout, Rock fall and Drainage Considerations.

JABA have executed a Site Reconnaissance, Validate Damage, Investigations, Studies, Develop Technical Report and will Prepare Plans, Specifications and Estimate (PS&E).

The proposed design shall facilitate construction, reduce construction cost, avoid problems during construction the stages and have the least interruption to traffic.

The proposed design shall comply with FHWA’s Emergency Relief Program, defined under 23 CFR 668, Parts A and B. Procedures shall meet FHWA’s Emergency Relief

Manual (Federal-Aid Highways) 2009, PRHTA’s Highway Design Manual, the most recent

AASHTO’s manuals including the Roadside Design Guide, and the PRHTA’s Standard

Specifications for Road and Bridge Construction 2005.

DAMAGE

ASSESSMENT II

II. DAMAGE ASSESSMENT

On April 26, 2018 a Site Reconnaissance was performed on Project ID#: ER-HWY-106 located on road PR-124, Km. 21.90, Municipality of Lares, P.R. There is a landslide on the west side of the road, surrounded by temporary concrete barriers.

It is our opinion that the apparent cause of failure is related to the storm sewer pipe that crosses underground perpendicular to the road and discharge water over the ground at the side of the road. The relatively high flow during storm event eroded the existing fill and native clayey silt soils.

There are no anticipated challenges in this project, other than:

• Excavation for Removal of loose soil and foundation leveling.

• Embankment restoration and slope stabilization (Earth retention system and backfill).

• Erosion Control Blanket and slope stabilization on the Cut Side of the Landslide to avoid further washout and promote vegetation growth.

• Runoff management and drainage by the construction of curb and gutter at the side of the road where landslide occurred and construction of drainage system.

• Erosion control measures to avoid further washout, promote vegetation growth and install rip-rap at runoff water discharge points.

• Pavement Reestablishment by the subgrade preparation, aggregate base course, bituminous base course and bituminous surface course.

• Roadside and Safety by the reestablishment of safety barriers, pavement markings, retro-reflective markers and signage.

José A. Batlle & Asociados, CSP

PROJECT ID # ER-HWY-106

PR-124, KM-21.90 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Topographic map

Project Location Maps

Island map

PR-124, KM-21.90 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Aerial Photo showing Project Scope of Work Limits

PR-124, KM-21.90 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Photo no.2

Project Damage Inspection Photos

Photo no.1

PR-124, KM-21.90 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Photo no.4

Project Damage Inspection Photos

Photo no.3

WORK

EXECUTED III

• FIELD SURVEY AND TOPOGRAPHY

• GEOTHECNICAL REPORT

III. WORK EXECUTED

1. Site Reconnaissance – For a summary of the findings and recommendations (See

Section II)

2. Field Survey and Topography - (See Section III)

3. Geotechnical Report – For a summary of the findings and recommendations (See

Section III)

4. Technical Report which include:

• Schematic Geometric Alignment - (See Section IV)

• Plan and Profile - (See Section IV)

• Plan and Profile Principal Structures - (See Section IV)

• Typical Sections - (See Section IV)

• Cross Sections - (See Section IV)

FIELD SURVEY AND

TOPOGRAPHY

GEOTHECNICAL

REPORT

Geotechnical Report: Site ER HWY 106

Landslide and Road Evaluation and Repair Recommendations PR 124 KM 21.9, Lares, PR

J a c a & S i e r r a E n g i n e e r i n g , P S C

P O B o x 3 6 3 1 1 6 , S a n J u a n , P R 0 0 9 3 6 - 3 1 1 6

R o a d 8 5 0 K m 0 . 2 L a s C u e v a s W a r d , T r u j i l l o A l t o , P R 0 0 9 7 6

T . ( 7 8 7 ) 7 6 1 - 2 5 7 0 w w w . j a c a s i e r r a . c o m

1. Introduction:

The present geotechnical report addresses the geotechnical conditions and recommendations for the road damages at the reference site location. This investigation is prepared based on approved scope of work and economical proposal by

José A. Battle y Asociados, CSP. This report is part of a multiple site assessment project for similar landslide rehabilitation cases related to damages by Hurricane Maria on

September 20, 2017. This report is prepared exclusively for design purposes.

2. Scope of Work:

The scope of work consisted of one (1) test boring to 6.3 mts (20.5 ft) depth. Boring was completed with CME-45 drill rig at accessible locations along the side of the road. Test borings and soil sampling were performed by casing installation in accordance to ASTM

D1452 and soil sampling per Standard Penetration Test (SPT) method per ASTM D1586.

Refer to enclosed boring location plan for reference on boring location in Appendix A

Figure A2.

3. Site Geology

Based on the USGS Geology Map (refer to Appendix A Figure A1) Tmb – Milagros

Formation: Breccia member, predominantly brown to gray tuff-breccia with lesser amounts of lapilli tuff.

Site ER HWY 106

PR 124 KM 21.9, Lares, PR

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t. (787) 761-2570 e. contact@jacasierra.com / www.jacasierra.com

4. Site Stratigraphy

Stratum no. 1: Fill: The upper fill stratum has a thickness of 0.6 mts (2 ft) and consists of sandy silt with traces of gravel. The SPT-N value recorded was 10 blows/ft and the moisture content measured was 25 %.

Stratum no. 2: Soft to Stiff Clayey Silt: The above described fill layer overlays clayey silt with some sand extending to the end of boreholes at 6.3 mts (20.5 ft). SPT-N values registered are ranging from 4 to 17 blows/ft for a soft to stiff consistency. Moisture contents obtained are from 35 to 44 %.

4.1. Groundwater

Groundwater level was not detected within the depth range of the test borings.

Temporary localized perched water may occur after prolonged rain events.

5. Geotechnical Recommendations

5.1. Opinion on Probable Causes for Road Damage

It is our opinion that the apparent cause of failure is related to the storm sewer pipe that crosses underground perpendicular to the road and discharge water over the ground at the side of the road. The relatively high flow during storm event eroded the existing fill and native clayey silt soils.

5.2. Slope Rehabilitation Alternatives

All alternatives shall consider the design of an inlet apron to protect the inlet area of the storm sewer pipe as well as riprap or Reno mattress armoring along the outlet area to control soil erosion from discharge. The remaining slope downhill shall be leveled to uniform inclination and armoring with turf reinforcement the deep-rooted vegetation such as vetiver.

mailto:contact@jacasierra.com

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5.2.1. Concrete Cantilever Retaining Wall:

This option has the advantage that it can be built right on the edge of the road as a

Jersey barrier extension (typical PRHTA section). The closer the retaining wall is to the roadway edge the less the retaining wall height required. The wall shall be embedded at least 1.2 mts (4 ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will be in the order of 1.82 mts

(6.0 ft) at the highest location.

5.2.2. Concrete Gravity Wall:

This option has the advantage of minimizing excavation width at the edge of the road.

The gravity wall can be designed per PRHTA’s standard design section to be verified and adjusted by designer based on the herein provided bearing capacity and earth pressure parameters. Similar to the cantilever wall, it shall be embedded at least 1.2 mts (4 ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will likewise be in the order of 1.82 mts (6.0 ft) at the highest location.

5.2.3. Gabion Wall:

This option will need a retaining wall to be offset from the edge of the road to allow placement of a guard rail or Jersey barrier. The gabions at the proposed locations shall be embedded at least 1.2 mts (4 ft) below ground surface. It is estimated that the gabion wall height will be in the order of 3.62 mts (11.9 ft) at the highest location. This will result in a higher wall if compared with the concrete cantilever and gravity walls above because of offset distance off the edge of the road and steep gradient of the slope. The advantage of this option is that it can be installed with less excavations and disturbance to the existing road.

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5.3. Earth Pressure Parameters for Retaining Wall Design

Strength or Earth Pressure Parameters

Engineered

Fill/Retaining Wall

Backfill

In-Situ Soils -

Drained

Parameters

Cohesion, c kN/sq.mt. (psf) 0 0

Angle of internal friction, φ ˚ 32 25

Moist unit weight, γ kN/cu.mt. (pcf) 20.4 (130) 19.6 (125)

Horizontal seismic coefficient, kh - 0.2

Base shear coefficient, * - 0.3

Net allowable bearing capacity for retaining wall over native soil, qa kN/sq.mt. (psf)

- 96 (2,000)

Table 1: Earth pressure parameters for retained soils

*For passive resistance neglect upper 3 ft. Passive side unit weight of backfill shall be assumed as 15.7 kN/cu.mt. (100 pcf).

It is our opinion that the above recommendations will stabilize the slope against global stability concerns. Other options such as soil nailing with shotcrete were discarded due to cost concerns and the fact that the edge of road was lost and a retaining wall is required to allow re-building the road to its original alignment. MSE walls or slopes will not work on this site due to limitations of space and steepness of the slope which will not allow for creating of suitable base and placement of soil reinforcement into the cut without having to excavate almost the entire road width. If any other option is wished to be considered, we should be provided with the information on the alternative to provide specific recommendations for that option.

6. Generalized Recommendations

6.1. Recommended Backfill Material: All engineered fill shall consist of A-2-4 or A-1

AASHTO Classification fill placed and compacted to 95 % of the modified Proctor density. Engineered fill shall be handled and placed per latest applicable PR Highway

Authority Specifications. Engineered fill shall be monitored by soil technician with guidance from a geotechnical engineer.

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6.2. Fill Recommendations: Any fill shall be constructed upslope in horizontal layers and benched terraces shall be cut at the interface of fill and natural soils. The benches shall have a minimum width of 0.9 mts (3.0 ft) and shall be made at a maximum vertical distance of 0.9 mts (3.0 ft) as fill progresses upward. Unreinforced engineered fill slopes shall not exceed 2:1 (H:V) inclination.

6.3. Drainage: Road drainage shall be controlled by Jersey barriers, curbs and gutters or storm runoff management devices designed in such way that it prevents any overland water discharge over the project areas. Erosion control measures at discharge locations shall be in accordance to the hydraulic specialist design.

6.4. Slope Erosion Control: Protect all slopes with sodding or turf reinforcement. Deep rooted vegetation such as vetiver and fern (“helecho”) is recommended within any area impacted by the project and particularly the slope extending downslope from the toe of the retaining wall. Bare soils exposed upslope should also be protected with deep rooted vegetation.

6.5. Differing Site Conditions: These recommendations are based on test borings performed on locations, which are considered as representative of the subsoil conditions within the site, but not all areas of the site could be explored due to limitations of access. Therefore, differing site conditions could occur. In such instances, we shall be notified to proceed with a field visual inspection directed to formulate the corresponding solution.

6.6. Excavation Safety: Contractor is responsible to adjust excavation inclination and provide shoring, where necessary, to ensure safety of working personnel per latest applicable OSHA excavation safety standards. The contractor shall consult with geotechnical engineer or geologist on excavation inclination and shoring requirements.

6.7. Geotechnical Engineer Confirmation: The excavations shall be coordinated with the undersigned to conduct a site visit by a representative from Jaca & Sierra

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Engineering, PSC to verify conditions and confirm foundation depth among other geotechnical considerations.

Thanks for the opportunity of providing our field investigation, testing and engineering consulting services. Feel free to contact us for any questions on our report.

Respectfully submitted, JACA & SIERRA ENGINEERING, PSC

Carlos R. Sierra Del Llano, MSCE, PE

Geotechnical Engineer

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Appendix A: Geology Map and Boring Location Plan

Figure A1: Site Geology Map – Tobisch, O.T., and Turner, M.D., 1971. Geologic Map of the San Sebastián

Quadrangle, Puerto Rico, Map I-661, Miscellaneous Geologic Investigations, U.S. Geological Survey, Department of the Interior, Washington D.C.

SITE

https://ngmdb.usgs.gov/Prodesc/proddesc_1369.htm https://ngmdb.usgs.gov/Prodesc/proddesc_1369.htm

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Figure A2: Boring Location Plan – Site plan provided by Javier E. Bidot & Associates, PSC

A

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Appendix B: Site Conditions Photographic Images

Figure B1: Existing road conditions

Figure B2: Damaged outlet area

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Figure B3: Downslope at outlet area

Figure B4: Inlet area at side of the road

350.00

349.39

348.17

FILL: sandy silt trace gravel, brown, strong brown

CLAYEY SILT some sand, soft, brown, yellowish red, light gray

CLAYEY SILT some sand, stiff, brown, yellowish red, light gray

Do... relic joints

S-1

S-2

S-3

S-4

S-5

S-6

S-7

SUBSURFACE EXPLORATION LOG

BORING N0.: A

PROJECT

Landslide and Road Evaluation and Repairs (ER-HWY-106)

JOB

OF

SHEET 1

LOCATION PR-124 Km. 21.9, Lares, PR DRILLER/DRILL RIG: Carlos I. Diaz / CME-45

COORDINATES 248152 N 150379 E DATE HOLE STARTED 1-9-19 COMPLETED 1-9-19

DESCRIPTION BY Rommel Cintron ELEVATION TOP OF HOLE (mts): 350 GROUNDWATER (FT) Initial: Not Found Final: ENGINEER Rommel Cintron DRILLING METHOD: Hollow-Stem Auger 2.25" ID TOTAL DEPTH OF HOLE (ft): 20.5

N W Qu PL+LL

"N" - Number of blows required to drive the sampling spoon a distance of 12 in. with a 140 lbs hammer falling 30 in.

"W" - Natural Moisture Content in percentage of dry weight. Initial G.W. Depth "Qu" - Unconfined Compressive Strength in tons per square foot. Final G.W. Depth "Rc" - Core recovery in percent for each successive run. "Rqd" - Rock quality designation.

"WH" - Sample was recovered by advancing the sampler with the weight of the hammer.

"P" - A "P" in the Unconfined Compressive Strength test indicates the use of the pocket Penetrometer.

Elev.

(mts)

0.00

DEPTH

(feet) DESCRIPTION

L E

G E

N D

S a m p le

N o

T Y

P E

B L

O W

S

SPT

N W Qu RC RQD%

20 40 60 80

1 2 3 4

Qu

N-W

(X=NO)PERCENTFINERSIZE

PASS?SPEC.*PERCENTSIEVE

Project No:

Project:

Client:

Elev./Depth:Location:

Date:Source of Sample:Sample No.:

Remarks

Classification

Coefficients

Atterberg Limits

Material Description

AASHTO=USCS=

Cc=Cu=

D10=D15=D30=

D50=D60=D85=

PI=LL=PL=

Particle Size Distribution Report

P E R C E N T F

IN

E R

100 10 1 0.1 0.01 0.001500

GRAIN SIZE - mm

% +75 MM % GRAVEL % SAND % SILT % CLAY

i n i n i n

-1 /2 i n i n

/4 i n

/2 i n

/8 i n

0.0 0.1 22.8 77.1

Figure7943

Landslide and Road Evaluation and Repairs, Lares, PR (ER-HWY-

106)

Jose A. Batlle y Asociados

2-7.5'Lares, PR

1/23/19Project SiteA

Tested by: J. Ortiz

Checked by: Rommel Cintron Aponte, MSCE, PE

A-7-5(15)MH

0.196

175235

Elastic silt with sand

(no specification provided)

JACA & SIERRA

TESTING LABORATORIES

San Juan, Puerto Rico

100.0 99.9 99.4 91.9 82.6 77.1

.375 in.

#4 #10 #40 #100 #200

TECHNICAL

SOLUTION

ALTERNATIVES IV

• ALTERNATIVE I

IV. TECHNICAL SOLUTION ALTERNATIVES

The Project ID#: ER-HWY-106 is located on road PR-124, Km. 22.60, Municipality of

Lares, P.R. The construction works on road PR-124 begins on Km. 22.00 and ends on

Km. 23.00. The total length of construction works is 0.10 Km. For the landslide rehabilitation located on the west side of the road, three (3) Slope Rehabilitation

Alternatives where evaluated. All alternatives considered the design of an inlet apron to protect the inlet area of the storm sewer pipe as well as riprap or Reno mattress armoring along the outlet area to control soil erosion from discharge. The remaining slope downhill shall be leveled to uniform inclination and armoring with turf reinforcement the deep-rooted vegetation such as vetiver.

ALTERNATIVE NO. I – GABION RETAINING WALL

For the landslide rehabilitation a Gabion Retaining Wall is proposed from Km. 22.12 to

Km. 22.88. The total length of the Gabion Retaining Wall is 71.99 Meters and the wall height varies from 0.91 Meters Min. to 3.65 Meters Max. The construction works includes:

• Gabion Retaining Wall

• Excavation for Structures

• Borrow Class B

• Construction of Concrete Barrier Type C

• Construction of Paved Gutter

• Construction of Concrete Slab

• Construction of Half Pavement Section of Sub-Base Course, Aggregate Base

Course, Bituminous Base Course and Bituminous Surface Course

• Cold Milling

• Removal of Guardrail

• Erosion Control Blanket 24 Months of Longevity with Vetiver Grass at front of the

Proposed Retaining Wall measures to avoid further washout, promote vegetation growth and install rip-rap at runoff water discharge points.

• Single Face Guardrail

• Pavement markings

• Drainage Considerations:

o Replace existing crossing (not defined at the proposed concrete barrier location) with a 30 to 36 inches RCP to intercept incoming runoff from east.

An estimated peak flow of 30 cfs considering the 100-year rainfall event is expected from incoming drainage area.

o No major drainage recommendations are considered except for the cleaning and maintenance of existing drainage features.

For Typical Section, Plan, Profile and Cross Sections of this Alternative (See Section IV) and for a Detail Estimate of the Items included in this Alternative (See Section VIII).

ALTERNATIVE NO. II – REINFORCED CONCRETE RETAINING WALL

For the landslide rehabilitation a Reinforced Concrete Retaining Wall is proposed from

Km. 22.12 to Km. 22.88. The total length of the Reinforced Concrete Retaining Wall is

71.99 Meters and the wall height varies from 1.20 Meters Min. to 1.82 Meters Max. The construction works includes:

• Reinforced Concrete Retaining Wall

• Excavation for Structures

• Borrow Class B

• Construction of Concrete Barrier Type C

• Construction of Paved Gutter

• Construction of Half Pavement Section of Sub-Base Course, Aggregate Base

Course, Bituminous Base Course and Bituminous Surface Course

• Cold Milling

• Removal of Guardrail

• Erosion Control Blanket 24 Months of Longevity with Vetiver Grass at front of the

Proposed Retaining Wall measures to avoid further washout, promote vegetation growth and install rip-rap at runoff water discharge points.

• Singla Face Guardrail

• Pavement markings

• Drainage Considerations:

location) with a 30 to 36 inches RCP to intercept incoming runoff from east.

An estimated peak flow of 30 cfs considering the 100-year rainfall event is expected from incoming drainage area.

o No major drainage recommendations are considered except for the cleaning and maintenance of existing drainage features.

For Typical Section, Plan, Profile and Cross Sections of this Alternative (See Section IV) and for a Detail Estimate of the Items included in this Alternative (See Section VIII).

ALTERNATIVE NO. III – REINFORCED SOIL SLOPE

For the landslide rehabilitation a Reinforced Soil Slope is proposed from Km. 22.12 to

Km. 22.88. The total length of the Reinforced Soil Slope is 71.99 Meters and the Slope height varies from 0.57 Meters Min. to 4.21 Meters Max. The construction works includes:

• Reinforced Soil Slope

• Excavation for Structures

• Borrow Class B

• Construction of Single Face Guardrail

• Construction of Curb and Gutter Type F and Concrete Paved Waterway Type II

• Construction of Full Pavement Section of Sub-Base Course, Aggregate Base

Course, Bituminous Base Course and Bituminous Surface Course

• Cold Milling

• Removal of Guardrail

• Removal of Existing Structure abandoned.

• Erosion Control Blanket Equal or Similar to ECP-2

• Pavement markings

• Drainage Considerations:

location) with a 30 to 36 inches RCP to intercept incoming runoff from east.

An estimated peak flow of 30 cfs considering the 100-year rainfall event is expected from incoming drainage area.

o No major drainage recommendations are considered except for the cleaning and maintenance of existing drainage features.

For Typical Section, Plan, Profile and Cross Sections of this Alternative (See Section IV) and for a Detail Estimate of the Items included in this Alternative (See Section VIII).

ALTERNATIVE I

ALTERNATIVE II

ALTERNATIVE III

ALTERNATIVE

EVALUATION V

V. ALTERNATIVE EVALUATION

ALTERNATIVE NO. I – GABION RETAINING WALL

PROS:

• Their strong base prevents them from being dragged away during heavy downpours.

• They help to reduce the velocity of running water, as the rocks dissipate its energy, which helps reduce erosion processes caused by water or excessive seepage on steep or mild slopes.

• As time passes, gaps between the rocks will be filled by vegetation and silt, which will further reinforce the wall.

• Handling and transportation the materials are quite simple, which helps to reduce the time taken to build the Gabions.

• Gaps between the rocks allow water to flow through the structure, helping to maintain a low groundwater level.

• Gabion walls resists breakage and separation, due to the flexibility of the wire mesh construction.

• The gravel and rocks used in gabion construction are natural to the environment and can endure years of wear through water erosion.

• No need for Road Closure during construction. Works can be done in half section of the road.

• Less Impact in Right of Way Area.

CONS:

• This option will need a retaining wall to be offset from the edge of the road to allow placement of jersey barrier, as a result the more retaining wall height is required.

• Estimated Construction Cost is the highest in comparison with the other two

Alternatives.

• More Impact on Earthwork Cut.

ALTERNATIVE NO. II – REINFORCED CONCRETE RETAINING WALL

PROS:

• Can be built on the edge of the road as a jersey barrier.

• The closer the retaining wall is to the roadway edge; the less retaining wall height is required.

• Less Impact in Right of Way Area.

• Estimated Construction Cost is the lowest in comparison with the other two

Alternatives.

CONS:

• The required Excavation for Structure will be to an extent requiring closing the road.

ALTERNATIVE NO. III – REINFORCED SOIL SLOPE

PROS:

• There is no Pros when compare with the other two (2) Alternatives.

CONS:

• Reinforced Soil Slope will not work on this site due to limitations of space and steepness of the slope which will not allow for creating of suitable base and placement of soil reinforcement into the cut without having to excavate almost the entire road width.

• Benching will be required at the contact between fill and in situ soils.

• This alternative is vulnerable to erosion processes caused by water or excessive seepage on steep or mild slopes.

• Estimated Construction Cost is the second highest in comparison with the other two Alternatives

• More impact in Right of Way Area.

• More impact on Earthwork Fill.

A Comparative Table of Alternatives I, II and III, with the more relevant data is included in this Section.

ENVIRONMENTAL

CONSIDERATIONS VI

VI. ENVIRONMENTAL CONSIDERATIONS

This project qualifies for Categorical Exclusion (CE) which meet the definition contained in 40 CFR 1508.4, and, based on experience with similar actions, do not involve significant environmental impacts. They are actions which: do not induce significant impacts to planned growth or land use for the area; do not require the relocation of significant numbers of people; do not have a significant impact on any natural, cultural, recreational, historic or other resource; do not involve significant air, noise, or water quality impacts; do not have significant impacts on travel patterns; or do not otherwise, either individually or cumulatively, have any significant environmental impacts.

The project does not individually or cumulatively have a significant impact on the environment as defined by NEPA, or involve unusual circumstances as defined in 23 CFR

771.117 (d)(13) and is therefore excluded from the requirements to prepare an

Environmental Assessment or Environmental Impact Statement. Based on consideration of prior planning studies, appropriate agency solicitation and thorough environmental review, we have determined that this action results in no significant impacts to the human and natural environment, involves no public controversy on environmental grounds, and no inconsistency with any federal, state or local laws, regulations, and administrative determinations relating to the environment.

CONSTRUCTABILITY VII

VII. CONSTRUCTABILITY

ALTERNATIVE NO. I – GABION RETAINING WALL

• Handling and transportation the materials to sites are quite simple, easy to unload and place, which helps to reduce the time taken to build the Gabions.

• The construction will depend on the availability of materials, equipment and manpower.

• If the supplier has baskets and rock in stock, the contractor will be able to erect the gabions as they get everything at the site. If the supplier has to order materials in, the contractor will have to wait until they’ re delivered.

• Filling the baskets with rock is something that is done by hand. If the contractor has the required manpower, the Gabion Retaining Wall can be done faster.

• This alternative is very amenable to non-skilled manpower with the required supervision.

ALTERNATIVE NO. II – REINFORCED CONCRETE RETAINING WALL

• Handling and transportation the materials to sites with heavy equipment has to be considered in areas of difficult access.

• The construction of the Reinforced Concrete Retaining Wall requires a high-skill manpower.

ALTERNATIVE NO. III – REINFORCED SOIL SLOPE

• Handling and transportation the materials to sites with heavy equipment has to be considered in areas of difficult access.

• Most of the construction is done by heavy equipment and skilled manpower.

CONSTRUCTION

COST VIII

• ALTERNATIVE I

VIII. CONSTRUCTION COST

An Estimated Construction Cost including the Item Number, Specification, Class of Work, Quantity, Unit Price and Total Cost for the three (3) Alternatives evaluated is included in this Section.

CONSTRUCTION

TIME IX

IX. CONSTRUCTION TIME

For the Proposed Construction Works alone, we estimated one (1) month to be completed; but due to the following reasons that has to be considered, such as:

• Construction Permits

• Submittals approvals

• Material available by the supplier or it has to be ordered for fabrication

• Weather delays

We recommend two (2) months for the construction of the Proposed Works.

SOLUTION

COMPLEXITY X

X. SOLUTION COMPLEXITY

There is no complexity in the construction of the three (3) alternatives evaluated. These solutions are conventional for a general contractor, since most of these solutions have been implemented by the PRHTA in the rehabilitation of Landslides in Puerto Rico.

IMPACT ON

RIGHT OF WAY

ACQUISITION XI

XI. IMPACT ON RIGHT OF WAY ACQUISITION

A Land Acquisition Plan and Table with the information of Lot Owner, Lot Number, Area for the three (3) Alternatives evaluated is included in this Section.

RECOMMENDATIONS XII

XII. RECOMMENDATIONS

After the evaluation of the three (3) Alternatives presented, we recommend the Alternative

I – Gabion Retaining Wall for the rehabilitation of the Landslide, based on the following reasons:

• Their strong base prevents them from being dragged away during heavy downpours.

• They help to reduce the velocity of running water, as the rocks dissipate its energy, which helps reduce erosion processes caused by water or excessive seepage on steep or mild slopes.

• As time passes, gaps between the rocks will be filled by vegetation and silt, which will further reinforce the wall.

• Handling and transportation the materials are quite simple, which helps to reduce the time taken to build the Gabions.

• Gaps between the rocks allow water to flow through the structure, helping to maintain a low groundwater level.

• Gabion walls resists breakage and separation, due to the flexibility of the wire mesh construction.

• The gravel and rocks used in gabion construction are natural to the environment and can endure years of wear through water erosion.

• Less Impact in Right of Way Area.

• No need for Road Closure during construction. Works can be done in half section of the road.