Technical Report - AC-831579_HWY-140.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)

GROUP - C

PROJECT ID# HIGHWAY KILOMETER MUNICIPALITY

ER-HWY-140 PR-128 54.77 Lares

FEBRUARY 28, 2019

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 C

AND REPAIR RECOMMENDATIONS FOR AÑASCO, LARES, Project ID#: ER-HWY-140

LAS MARIA, MOCA, SAN JUAN MINICIPALIES (AC-809544) PR-128, km. 54.77 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-140 located on road PR-128, Km. 54.77, Municipality of Lares, P.R. The landslide is located on the North side of the road.

It is our opinion that the apparent cause of failure is related to a shallow landslide of fill material and native saprolitic soils occurring by erosion from overland runoff during storm event. The slide can be described as a soil washout.

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 possible 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-140

PR-128, KM-54.77 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Topographic map

Project Location Maps

Island map

José A. Batlle & Asociados, CSP

PROJECT ID # ER-HWY-140

PR-128, KM-54.77 - LARES, PR

RFP: LANDSLIDE AND ROAD DAMAGE

EVALUATION AND REPAIR RECOMMENDATIONS

DATE: Abril 26, 2018

Aerial Photo showing Project Scope of Work Limits

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 140

Landslide and Road Evaluation and Repair Recommendations PR 128 KM 54.77, 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. Batlle 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 two (2) test borings to 6.3 mts (20.5 ft) depth. Borings were completed with CME-45 drill rig at accessible locations on 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. The area of the landslide was not accessible for performing test borings with portable equipment due to existing debris and safety hazards on the slope surface.

3. Site Geology:

Based on the USGS Geology Map (refer to Appendix A Figure A1) the site’s predominant geologic formation is Tmi – Milagros Formation. Tmi is described as medium-gray feldspathic lapilli tuff and dark-brownish-gray volcanic breccia with interbedded bluish-gray fine-grained andesite lava, and brownish-gray, bedded vitric and crystal tuff, volcanic sandstone and siltstone.

Site ER HWY 140

PR 128 KM 54.77, Lares, PR

P A G E | 2

0 3 / 0 4 / 1 9 Jaca & Sierra Engineering, PSC

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

4. Site Stratigraphy:

Stratum no. 1: Fill: The upper fill stratum has thicknesses of 1.2 to 2.7 mts (4 to 9 ft). The fill material consists of sandy gravel with asphalt debris within the upper 2 feet and sandy clay with some gravel below 2 feet. SPT-N values recorded are varying from 5 to 38 blows/ft. Moisture contents measured are from 8 to 46 %.

Stratum no. 2: Saprolite: The above described fill layer overlays saprolitic soils composed of clayey silt with some sand and traces of weathered rock fragments in the lower horizon from the above-mentioned Milagros Formation extending to the end of boreholes at 6.3 mts (20.5 ft) depth. SPT-N values registered are ranging from 13 to 53 blows/ft. Moisture contents obtained are from 23 to 33 %.

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 a shallow landslide of fill material and native saprolitic soils occurring by erosion from overland runoff during storm event. The slide can be described as a soil washout. At the time of our site visit on

January 15, 2019, the landslide was covered with vegetation and dumped soils.

5.2. Slope Rehabilitation Alternatives:

5.2.1. Gabion Wall:

A gabion wall is favorable for this site due to its inherent ability to drain any water or moisture trapped in the backfill. The base width will be wider if compared to a concrete mailto:contact@jacasierra.com

P A G E | 3

0 3 / 0 4 / 1 9 cantilever or gravity wall. Also, this type of wall will require an offset from the guard rails or concrete barrier at the edge of road. Therefore, it will project further in to the slope and thus result in more height required if compared to the concrete wall options.

This option shall be evaluated by design verification of different section profiles to be made along the extent of the project to evaluate the wall height variations. The wall shall be embedded at least 1.8 mts (6 ft) below slope surface as measured from the lower side.

This will result in a wall height of 6.3 mts (21 ft) at the highest location. When designing this option, it will be important to have measures to prevent water from infiltrating into the wall from the road side. A perforated pipe drain shall be included in the backfill to allow drainage of any water that accumulates on the backside of the wall or that infiltrates thru the wall. These details are well covered in PRHTA standard drawings.

5.2.2. Concrete Cantilever Retaining Wall:

This option has the advantage that it can be built right on the edge of the road as a concrete barrier extension (typical PRHTA section). The closer the retaining wall is to the roadway edge the less the retaining wall height required. This option shall include leveling the remaining slope to uniform inclination and armoring with turf reinforcement the deep-rooted vegetation such as vetiver. The wall shall be embedded at least 1.8 mts

(6 ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will be 4.6 mts (15 ft) at the highest location.

5.2.3. Concrete Gravity Wall:

The concrete gravity wall 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. The wall shall be embedded at least 1.8 mts (6

P A G E | 4

0 3 / 0 4 / 1 9

ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will be 4.6 mts (15 ft) at the highest location.

5.2.4. Anchored Gabion Wall:

Anchored gabion walls are an alternative to reduce the wall width requirements in conventional gabion walls. The anchor can be designed assuming allowable bond strength of 25 psi for non-shrink grout with over 5,000 psi strength. A minimum free length of 10 ft shall be considered. We recommend a minimum of 2 verification tests and proof tests on 5 % of the installed soil nails or anchors. Anchor testing shall be per Soil

Nail Walls Reference Manual FHWA NHI-14-007 February 2015. Similar to the previous explained alternatives, the slopes shall be excavated and leveled to improve their stability to the extent that the toe of the wall remains embedded 1.8 mts (6 ft).

Figure 1: Anchored gabion schematic concept (not to scale)

P A G E | 5

0 3 / 0 4 / 1 9

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 (neglect passive resistance)

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 reinforcements 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. Also note that the recommended wall heights are based on interpretation of landslide plane depths that need to be confirmed during excavation process. Adjustments to these wall heights may be required.

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.

P A G E | 6

0 3 / 0 4 / 1 9

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 ft) and shall be made at a maximum vertical distance of 0.9 mts (3 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.

6.4. Slope Erosion Control: Protect all slopes disturbed by excavations process 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.

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

P A G E | 7

0 3 / 0 4 / 1 9

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

Rommel Cintrón Aponte, MSCE, PE

Geotechnical Engineer

P A G E | 8

0 3 / 0 4 / 1 9

Appendix A: Geology Map and Boring Location Plan

Figure A1: Site Geology Map – Nelson, A.E., and Tobisch, O.T., 1968, Geologic map of the Bayaney quadrangle, Puerto Rico: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-525

SITE

P A G E | 9

0 3 / 0 4 / 1 9

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

A B

P A G E | 1 0

0 3 / 0 4 / 1 9

Appendix B: Site Conditions Photographic Images

Figure B1: Existing road conditions and damaged area

Figure B2: Damaged road area

P A G E | 1 1

0 3 / 0 4 / 1 9

Figure B3: Existing road conditions and damaged area

Figure B4: Downslope at damaged road area

483.00

482.39

481.78

FILL: sandy gravel with asphalt debris, gray, black

FILL: sandy clay some gravel, red, gray

CLAYEY SILT some sand, stiff, red, reddish yellow

Do... very stiff, brownish yellow, gray, relic joints

Do... trace weathered rock fragments, hard

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-140)

JOB

OF

SHEET 1

LOCATION PR-128 Km. 54.77, Lares, PR DRILLER/DRILL RIG: Carlos I. Diaz / CME-45

COORDINATES 247920 N 154743 E DATE HOLE STARTED 1-17-19 COMPLETED 1-17-19

DESCRIPTION BY Rommel Cintron ELEVATION TOP OF HOLE (mts): 483 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

482.00

481.39

479.26

FILL: sandy gravel with asphalt debris, gray, black

FILL: sandy clay some gravel, brownish yellow, red, gray

CLAYEY SILT some sand, stiff, red, brownish yellow

Do... trace weathered rock fragments, hard, relic joints

S-1

S-2

S-3

S-4

S-5

S-6

S-7

SUBSURFACE EXPLORATION LOG

BORING N0.: B

PROJECT

Landslide and Road Evaluation and Repairs (ER-HWY-140)

JOB

OF

SHEET 1

LOCATION PR-128 Km. 54.77, Lares, PR DRILLER/DRILL RIG: Carlos I. Diaz / CME-45

COORDINATES 247917 N 154746 E DATE HOLE STARTED 1-17-19 COMPLETED 1-17-19

DESCRIPTION BY Rommel Cintron ELEVATION TOP OF HOLE (mts): 482 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 3.1 54.7 42.2

Figure7962

Landslide and Road Evaluation and Repairs (ER-HWY-140)

Jose A. Batlle y Associados

4-7.5'Lares, PR

2/13/19Project SiteER-140A

Tested by: J. Cordova

Checked by: Rommel Cintron Aponte, MSCE, PE

A-7-5(2)SM

0.1370.2531.25

114130

Silty sand

(no specification provided)

JACA & SIERRA

TESTING LABORATORIES

San Juan, Puerto Rico

100.0 99.6 96.9 90.2 69.1 51.3 42.2

.5 in.

.375 in.

#4 #10 #40 #100 #200

(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 7.7 27.3 65.0

Figure7962

Landslide and Road Evaluation and Repairs (ER-HWY-140)

Jose A. Batlle y Associados

2-5.5'Lares, PR

2/14/19Project SiteER-140B

Tested by: J. Cordova

Checked by: Rommel Cintron Aponte, MSCE, PE

A-7-5(14)MH

0.744

225331

Sandy elastic silt

(no specification provided)

JACA & SIERRA

TESTING LABORATORIES

San Juan, Puerto Rico

100.0 96.2 93.3 93.0 92.3 89.2 81.3 71.1 65.0

1 in.

.75 in.

.5 in.

.375 in.

#4

#10 #40

#100 #200

TECHNICAL

SOLUTION

ALTERNATIVES IV

• ALTERNATIVE I

IV. TECHNICAL SOLUTION ALTERNATIVES

The Project ID#: ER-HWY-140 is located on road PR-128, Km. 54.77, Municipality of

Lares, P.R. The construction works on road PR-128 begins on Km. 54.82 and ends on

Km. 54.89. The total length of construction works is 0.07 Km. For the landslide rehabilitation located on the south side of the road, three (3) Slope Rehabilitation

Alternatives where evaluated.

ALTERNATIVE NO. I – GABION RETAINING WALL

For the landslide rehabilitation a Gabion Retaining Wall is proposed from Km. 54.82 to

Km. 54.88. The total length of the Gabion Retaining Wall is 46.81 Meters and the wall height varies from 0.91 Meters Min. to 6.34 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 and Concrete Paved Waterway Type I

• 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

• 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.

• Pavement markings

• Drainage Considerations:

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. 54.82 to Km. 54.88. The total length of the Reinforced Concrete Retaining Wall is

46.81 Meters and the wall height varies from 1.20 Meters Min. to 4.57 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

• 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.

• Pavement markings

• Drainage Considerations:

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 – ANCHORED GABION WALL

For the landslide rehabilitation an Anchored Gabion Wall is proposed from Km. 54.82 to

Km. 54.88. The total length of the Anchored Gabion Wall is 46.81 Meters and the Wall height varies from 0.91 Meters Min. to 5.48 Meters Max. The construction works includes:

• Anchored Gabion Wall

• Soil Anchors

• Anchored Gabion Reinforced Concrete Beam

• Excavation for Structures

• Borrow Class B

• Construction of Concrete Barrier Type C

• Construction of Concrete Paved Waterway Type I

• 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 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.

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 second highest in comparison with the other two Alternatives.

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.

CONS:

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

• More impact on Earthwork Cut.

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

ALTERNATIVE NO. III – ANCHORED GABION WALL

PROS:

• Less Impact in Earthwork Cut and Fill.

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.

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 – ANCHORED GABION WALL

• Installation is likely to be more complex than that for Gabion Walls, due to Soil

Anchors, which are driven into the ground behind the wall and the Construction of the Soil Anchors Reinforced Concrete Beam.

• 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.

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.

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