Technical Report - AC-908579_HWY-257.pdf

COMMONWEALTH OF PUERTO RICO

DEPARTMENT OF TRANSPORTATION AND PUBLIC WORKS

HIGHWAY AND TRANSPORTATION AUTHORITY

PRHTA – DESIGN AREA

Site Location Map

NAD83 Coordinate X=204396.296 Y=249102.056

LANDSLIDE AND ROAD DAMAGE EVALUATION

& REPAIR RECOMMENDATIONS

TECHNICAL REPORT FOR

ER-HWY-257, PR-155, KM 36.15

MOROVIS MUNICIPALITY / AC-807544

SUBMITTED BY

IGLESIAS-VAZQUEZ AND ASSOCIATES

ENGINEERS-ARCHITECTS-PLANNERS

REVISED AUGUST 2019

Iglesias Vazquez & Associates Landslide & Road Damage Evaluation & Repair Recommendations

ER-HWY-257, PR-155, KM 36.15, Morovis June 2019

TABLE OF CONTENTS

I. INTRODUCTION …………………………………………………………………...2

II. DAMAGE ASSESSMENT………………………………………………………….2

III. WORK EXCUTED…………………………………………………………………..3

A. SITE RECONNAISSANCE

B. HIGHWAY DESIGN CRITERIA

C. HIGHWAY DESIGN CRITERIA

IV. TECHNICAL SOLUTIONS…………………………………………………………4

V. ALTERNATIVE EVALUATION…………………………………………………….4

ALTERNATIVE A: GABION GRAVITY RETAINING WALL……………...…4

ALTERNATIVE B: REINFORCED CONCRETE RETAINING WALL...……7

ALTERNATIVE C: MECHANICALLY STABILIZED RETAINING WALL/

SLOPE……………………………………………………..9

VI. RECOMMENDATIONS…………………………………………...………………12

APPENDIX A: GEOTECHNICAL STUDY………………………………...…13

APPENDIX B: DRAWINGS………………………………………………...…41

APPENDIX C: PHOTOS………………………………………………………53

APPENDIX D: WEIGHTED VALUES EVALUATION………………………60

APPENDIX E: CONSTRUCTION COST ESTIMATE………………………62

APPENDIX F: FEMA FLOOD MAP…………………………………………..64

Monin Text Box August

ER-HWY-257, PR-155, KM 36.15, Morovis August 2019

I. INTRODUCTION

The project site number ER-HWY-257 is located in State Road PR-155 at Km. 36.15 in the municipality of Morovis, Puerto Rico. The approximate location of the site can be found at 18.276964 N, -66.391756 W. Standard Geographic Coordinate System 204396.296mE 249102.056mN.

State Road PR-155 is located in the municipality of Morovis and moves south towards the municipality of Orocovis.

The road section located within the Morovis municipality discurs from Km. 3.10 to Km.

46.0 with “Catastral” Number 720-101-001-55.

The road classification based on the Puerto Rico State Highway Map and Municipal Boundaries, dated July 1, 2018 is a secondary route.

Puerto Rico State Road PR-155 suffered damages during the event of Hurricane Maria in September 20, 2017. Most of the damages consisted of traffic signs and barriers being torn or impacted by debris and landslides generated by the intense storm downpour and tree uprooting creating a loss of earth cohesion and generating localized flooding which in turn washed away parts of the existing roads.

II. DAMAGE ASSESSMENT

Damage at Km 36.15 of State Road PR-155 was caused by a small landslide along the southern lane of PR-155.

The impact of this landslide is of approximately 20 meters in length. The condition occurred at 50 meters south of km 36.20 marker.

A guardrail on the western lane was affected by the landslide and parts of it are either hanging in the air or badly eroded in its bases.

In addition a cross road storm sewer drainage discharges in to an area not affected by the landslide. The storm sewer discharge pipe will possibly be impacted.

Possible causes for the landslide at the project site are discussed in the Geotechnical Report, Appendix A, by the qualified geotechnical engineer.

We must consider the drainage basin, its flow pattern and the existing infrastructure in order to determine the need for new infrastructure during the design phase of the selected alternative at PR-155 Km 36.15 The impact of this landslide is of approximately 20 meters in length and its drainage basin area is around 3.5 acres. In our opinion, there is no additional runoff discharging heading to the landslide area. The storm infrastructure at the impacted area includes an earth drainage open ditch at the east side of the road.

ER-HWY-257, PR-155, KM 36.15, Morovis

Since the occurrence of this event on this section of the State Road has continued to deteriorate as recurring rain events have occurred, increasing the magnitude of the impact on the infrastructure.

This specific location requires a thorough storm sewer drainage system and specific erosion control countermeasures that will prevent future damage from occurring.

III. WORK EXECUTED

A. SITE RECONNAISSANCE

Initially multiple visits where performed to the impacted site by a multidisciplinary team of professionals that includes surveyors, road engineers, geotechnical engineers and electric engineers. Also other visits where done by individual professionals for acquisitions and environmental disciplines. All of the data collected for these studies where prepared by professionals of various fields. . A soil study was performed for the site, please refer to Appendix A.

B. HIGHWAY DESIGN CRITERIA

The design criteria for the impacted road section is defined as an R-6 based on the Puerto Rico Department of Transportation and Public Works Highway Authority Highway Design Manual.

Design Class Code R-6 has an approximated ADT Range that varies between 2000 to 6000 vehicles. Its minimum service level will be a C and a maximum speed limit of 40 miles per hour for mountainous terrain.

This road section has one lane in each direction of 3.65 meter lane width, without no minimum median present.

The nature of the terrain will allow minimum shoulder widths to vary between 1.2 mt to 2.4 mt. The minimum Right of Way Width for an R-6 roadway is 30 mt. and maximum super elevation is not to exceed 8% at curves, the minimum radius for said curves is 140 mt.

Due to the nature of the existing terrain and roads some variations to the minimum radius for the R-6 designation might be found.

A maximum grade of 8% shall be observed and a minimum grade of 5% will be retained, due to the nature of the existing roadway and the terrain some variations might be found along the project alignment.

C. SURVEY AND TOPOGRAPHIC

The land survey and topographic data was gathered using a combination of both total station survey equipment and RTK GPS based equipment.

ER-HWY-257, PR-155, KM 36.15, Morovis

The coordinate system is Conformal Conic Lambert projection, horizontal datum NAD-83 and the vertical datum uses is Puerto Rico Vertical datum of 2002 otherwise NAVD-27, horizontal exactitude has a minimum accuracy of 1:15,000.

For Survey and Topographic drawings please refer to Appendix B.

IV. TECHNICAL SOLUTIONS

Alternatives for the landslide of this project where provided by the Geotechnical Professional based on the field studies and soil studies performed by the Geotechnical firm.

The alternatives are discussed on the “Analysis, Conclusion and Recommendation” section of the soil study included in Appendix A part of this report.

Amongst the alternatives we find Gabions Gravity Retaining Walls, Reinforced Concrete Wall and Mechanically Stabilized Earth Wall, in some instances a combination of earth works slope stabilization and one of the previous three alternatives may be found.

V. ALTERNATIVE EVALUATION

The Geotechnical Study provides three alternatives for the landslide condition at Km

36.15 of the State Road PR-155. These alternatives include a Gabion Gravity Retaining Wall, a Reinforce Concrete Retaining Wall and a Mechanically Stabilized Retaining Wall.

Any of these alternatives will need to consider a storm sewer management and collection system in order to prevent future hydraulic damage to occur in the areas to be impacted by the recovery works.

These alternatives also must consider the recovery and restitution of any infrastructure located within the affected area, infrastructure may include power, sanitary sewer, water and communications infrastructure. For Weighted Values Evaluation please refer to Appendix D and for more details on Construction Cost Estimate please refer to Appendix E.

A. Alternative A: Gabion Gravity Retaining Wall

1. Environmental Considerations Gabion Walls are environmentally acceptable solutions since their construction is based on mostly nature occurring elements, in addition they are an excellent filter media, allowing water to flow thru them while managing erosion and earth debris. Finally gabions allow for vegetative growth which in turn benefits its characteristics.

Gabion Walls tend to have a bigger footprint than other alternatives, the cut and excavation necessary for their construction in general is larger.

ER-HWY-257, PR-155, KM 36.15, Morovis

Gabions depend on their steel wire boxes in order to retain their structural integrity, if the materials used for the wire boxes is of low quality or no protected adequately their lifespan can be greatly reduced.

2. Constructability

The most complex part of Gabion Retaining Walls construction is the earth movement required to erect the structure, construction of the wall itself is relatively simple, mesh wire boxes are lightweight and simple to transport, and place while rock or fill element placement is straight forward and fast.

Depending on the height of the Gabion Wall, special care must be placed on the security of the personnel working on its construction.

3. Construction Cost The cost estimate for this alternative was performed using current cost database, construction cost in Puerto Rico have been increasing lately, partially due to the lack of construction personnel and rapid increase in construction projects.

Although material are not foreseen to increase dramatically in the short term, construction personnel might escalate in cost from month to month altering projected construction cost estimates.

The construction cost estimate for this alternative Gabion Gravity Retaining Wall is approximately $430,000.00.

4. Construction Time Construction time estimates are based on a contractor capable of certifying approximately $60,000.00 dollars’ worth of monthly work, this is considered an average in the industry for construction of this type of works.

Large contractors will be able to perform the required construction in less time while smaller local contractors might take longer.

Rainfall considerations have not been taken into account since this depends on the time of the year the works are awarded, and considering small periods of time most construction time estimates predict.

Another factor that might influence this estimate will be the amount of construction work being awarded and the availability of qualified contractors at the time of procuring the construction of the selected solution.

Construction time estimate for this alternative Gabion Gravity Retaining Wall is expected to be approximately 7 months.

5. Solution Complexity

From a complexity stand point the Gabion Wall Solution is a relatively simple implementation and is a type of project that can be developed with easily accessible materials. From a labor and expertise of construction standpoint it does not require specialized equipment and a simple training

ER-HWY-257, PR-155, KM 36.15, Morovis would permit most labor personnel understand and undertake its construction.

We must conclude that a Gabion Gravity Wall does not represent a complex solution to the condition thus its implementation would be a simple and effective one.

6. Impact on Right of Way PR-155 is an old state road and this it’s existing right of way is located adjacent to the roads edge.

The implementation of any of the suggested solutions will require an acquisition or construction easement of 14 to 18 meters in order to implement the recommended solution.

This acquisition or construction easement will be determined once talks are established with the land owners and what alternatives might be negotiated with them.

7. Other considerations If a Gabion Gravity Retaining Wall Solution is selected during the construction process the contractor will require a relatively large staging area close or very close to the actual construction site, the management and placement of rocks within the gabion mesh requires its prime material to be readily available.

This method of retaining wall construction is a simple and not very complex endeavor since apart from the footing preparation and earth compaction gabion boxes or cages can be prefabricated elsewhere and brought to the construction site.

The final process of the Gabion Gravity Retaining Wall construction only involves the placement of the rock media inside the cage and the fill, compaction and regrading of the landslide cut slope.

Construction security concerns for the Gabion Gravity Retaining Walls is usually limited to the exposure of workers to the cut slope side required during the installation process, during which phase other landslides might occur if caution and care are not taken.

Regarding the elevation of the Gabion Gravity Retaining Walls, these tend to be large and wide blocks which provide ample footing and working spaces, reducing the possibility of accidents.

Gabion Gravity Retaining Wall drainage system will consist of a storm collecting pipe located at the foot of the temporary slope, and at the base of the Gabion Structure, this pipe will run along the length of the Gabion Structure and will discharge at both ends, the pipe will be covered in a geotextile filter material to prevent clogging as per geotechnical recommendations.

Amongst the infrastructure found at Km 36.15 of PR-155 is one PRASA water main of 4 inch diameter.

ER-HWY-257, PR-155, KM 36.15, Morovis

This line will not require temporary supports during construction since the required cut for any solution will not impact the roadway of PR-155, exposing both lines during construction.

No other infrastructure or pipes where visible of found in the area of interest.

On the east side of the PR-155 a storm sewer collection system exists, which flows forwards a catch basin that discharges thru the pipe seen on the west side.

The catch basin seems to have been either over flowed or clogged with vegetable media during the storm event and was unable to manage the storm flow, additionally the catch basin seems to be somewhat far from the lowest point of the storm sewer collection system.

B. Alternative B: Reinforced Concrete Retaining Wall

Reinforced Concrete Retaining Walls footprint is the smallest of all the proposed alternatives by the Geotechnical Study. The required excavation and cut are relatively small thus impacting much less area than other alternatives.

Reinforced Concrete Retaining Walls are an environmentally sound and effective solution providing a small footprint, thus limiting the impacted area of construction.

This type of solution, on the other hand, provides little integration into its environmental, although it benefits from a long life expectancy it tends to be somewhat limited in the environmental benefits it provides during its lifespan.

Reinforced Concrete Retaining Walls require specialized equipment and personnel for their erection.

The earthwork area required for the construction of the Reinforced Concrete Retaining Wall is basically the same, although smaller area the other solutions require, this would be an expertise required of the contractor on all solutions provided thus it does not represent an advantage or disadvantage to other solutions.

The pre-pouring of concrete phase is the one required specialized personnel. Steel reinforcing rebar and its placement require specialized personnel and equipment in order to obtain a high-quality product.

Placement of the cast in place forms is also a specialty in construction that requires equipment and personnel trained in their use and placement.

Finally concrete pouring is a science on its own and the wrong management of its delivery and pouring process can generate a poor quality structure.

This type of construction solution requires specialized personnel and equipment in order to produce a quality product.

ER-HWY-257, PR-155, KM 36.15, Morovis database, construction cost in Puerto Rico have been increasing lately, partially due to the lack of construction personnel and rapid increase in construction projects.

Although material are not foreseen to increase dramatically in the short term, construction personnel might escalate in cost from month to month altering projected construction cost estimates.

The construction cost estimate for this alternative Reinforced Concrete Retaining Wall is approximately $890,000.00.

approximately $60,000.00 dollars’ worth of monthly work, this is considered an average in the industry for construction of this type of works.

Large contractors will be able to perform the required construction in less time while smaller local contractors might take longer.

Rainfall considerations have not been taken into account since this depends on the time of the year the works are awarded, and considering small periods of time most construction time estimates predict.

Another factor that might influence this estimate will be the amount of construction work being awarded and the availability of qualified contractors at the time of procuring the construction of the selected solution.

Construction time estimate for this alternative Reinforced Concrete Retaining Wall is expected to be approximately 14 months.

A Reinforced Concrete Wall is a complex solution to the landslide condition at the site, although its earthwork is somewhat smaller the required specialized personnel and equipment make its coordination and management of construction more complex and demanding than other solutions.

Specific technical skills along with dedicated equipment and complex coordination make the use of Reinforced Concrete Walls a relatively complex solution.

6. Impacts on Right of Way adjacent to the roads edge.

The implementation of any of the suggested solutions will require an acquisition or construction easement of 14 to 18 meters in order to implement the recommended solution.

This acquisition or construction easement will be determined once talks are

ER-HWY-257, PR-155, KM 36.15, Morovis

Upon considering a reinforced concrete wall solution some other aspects of the works required for the construction must be evaluated.

One of the aspects that must be considered is the contractors’ staging area.

Reinforced concrete wall construction does not require a large staging area adjacent to the construction site.

Most of the works required for this type of solution are specialized and usually pre done elsewhere (steel rebar and forms) and the concrete pour is an activity that takes a small amount of time to perform.

Regarding security for the workers and OSHA compliance, Reinforced Concrete Walls present a challenging risk management solution. Special care must be taken with personnel working on form installation when on the inside of steep slopes and when working on high elevation forms and steel placement.

Reinforced Concrete Retaining Wall drainage will consist of a geogrid drainage collection system adhered to the earth side face of the retaining wall storm waters will be collected at the earth side bottom of the retaining wall through a collecting pipe covered with a geogrid filtering material, discharge will occur at the ends of the retaining walls.

Amongst the infrastructure found at Km 36.15 of PR-155 is one PRASA water main of 4 inch diameter.

This line will not require temporary supports during construction since the required cut for any solution will not impact the roadway of PR-155, exposing both lines during construction.

No other infrastructure or pipes where visible of found in the area of interest.

On the east side of the PR-155 a storm sewer collection system exists, which flows forwards a catch basin that discharges thru the pipe seen on the west side.

The catch basin seems to have been either over flowed or clogged with vegetable media during the storm event and was unable to manage the

C. Alternative C: Mechanically Stabilized Retaining Wall / Slope

Gabion Reinforced Earth Walls or Mechanically Stabilized Retaining Walls are also based mostly on nature occurring elements but allow for higher elevation walls than simply Gabion Gravity Retaining Walls.

They combine being an excellent filter media with the benefits of a mechanically stabilized earth wall providing both a natural water filtration method with good erosion and scour management solution, mechanically stabilized retaining walls also allow for vegetative growth which further enhances their environmental characteristics.

ER-HWY-257, PR-155, KM 36.15, Morovis

The erection of the gabion wall part that conforms a mechanically stabilized retention wall has been discussed elsewhere in this study and is considered to be a simple operation that does not require specialized personnel or equipment.

On the other hand the mechanically stabilized earth wall component of this solution does indeed require both specialized personnel and equipment in order to be performed in a satisfactory means.

This secondary component requires mechanical earth compaction to be performed which also requires a Geotechnical supervision, specialized personnel and compaction equipment, thus making this method only appropriate when large elevations are required for slope stabilization.

database, construction cost in Puerto Rico have been increasing lately, partially due to the lack of construction personnel and rapid increase in construction projects.

Although material are not foreseen to increase dramatically in the short term, construction personnel might escalate in cost from month to month altering projected construction cost estimates.

The construction cost estimate for this alternative Mechanically Stabilized Retaining Wall is approximately $580,000.00.

approximately $60,000.00 dollars’ worth of monthly work, this is considered an average in the industry for construction of this type of works.

Large contractors will be able to perform the required construction in less time while smaller local contractors might take longer.

Rainfall considerations have not been taken into account since this depends on the time of the year the works are awarded, and considering small periods of time most construction time estimates predict.

Another factor that might influence this estimate will be the amount of construction work being awarded and the availability of qualified contractors at the time of procuring the construction of the selected solution.

Construction time estimate for this alternative Mechanically Stabilized Retaining Wall is expected to be approximately 9 months.

A Mechanically Stabilized Retaining Wall is a more complex solution to a localized landslide than the Gabion Gravity Retaining Wall but at the same time might be a better solution where a very high wall is required but the use of a Reinforced Concrete Retaining Wall might be considered impractical due to costs or accessibility of materials to the construction site, ER-HWY-257, PR-155, KM 36.15, Morovis since most of the materials required for its construction are natural occurring elements.

From a labor personnel standpoint it requires more specialized people for its correct and adequate construction but might prove easier to execute than a Reinforced Concrete Retaining Wall.

We might consider in terms of complexity a Mechanically Stabilized Retaining Wall an intermediate effort to construct, less than a Reinforced Concrete Retaining Wall but more than a Gabion Gravity Retaining Wall.

6. Impact on Right of Way adjacent to the roads edge.

The implementation of any of the suggested solutions will require an acquisition or construction easement of 14 to 18 meters in order to implement the recommended solution.

This acquisition or construction easement will be determined once talks are

Mechanically Stabilized Retaining Walls as well as Gabion Gravity Retaining Walls require a large staging area for the contractor in order to place and manage the materials required for the construction, in addition this staging area must be locate nearby or as close as possible to the actual construction site.

The undercut required for this type of construction is also much larger than that required for other alternatives, this requirement usually complicates the MOT of the project since possibly one lane or even the entire roadway may need to be temporary closed.

Large undercuts also present a high safety concern for the personnel involved in the construction, since the possibility of additional landslide is increased.

Finally large earth cuts represent large environmental impacts, especially in the form of erosion, runoff and the amount of large vegetation or trees that may be required to be removed as part of the construction process.

Mechanically Stabilized Retaining Wall drainage system will consist of a storm collecting pipe located at the foot of the temporary slope, and at the base of the Reinforced Earth Blocks, this pipe will run along the length of the Reinforced Earth Blocks and will discharge at both ends, the pipe will be covered in a geotextile filter material to prevent clogging as per geotechnical recommendations.

Amongst the infrastructure found at Km 36.15 of PR-155 is one PRASA water main of 4 inch diameter.

ER-HWY-257, PR-155, KM 36.15, Morovis

This line will not require temporary supports during construction since the required cut for any solution will not impact the roadway of PR-155, exposing both lines during construction.

No other infrastructure or pipes where visible of found in the area of interest.

On the east side of the PR-155 a storm sewer collection system exists, which flows forwards a catch basin that discharges thru the pipe seen on the west side.

The catch basin seems to have been either over flowed or clogged with vegetable media during the storm event and was unable to manage the

VI. RECOMMENDATIONS

Based on the Geotechnical Recommendations for this site the required excavation for the structure foundation is 15 feet (4.57 meters). The implementation of the recommended solution will impact a complete lane of the existing road.

In order to comply with the Geotechnical Recommendations regarding provisional cut excavation slope (1.5 vertical, 1.0 horizontal) and the recommended distance between the new structure and the existing slope the actual depth of the excavation to be performed will be 16.5 feet or 5.0 meters.

The structure will consist of a five level gabion gravity retaining wall combined at the top with a fill sloped at two horizontal to one vertical with an approximate height of 3 meters.

For more details see cross section 2 and 3 of the drawings.

As part of the recommended solution special attention must be paid to the restoration of the existing infrastructure to be impacted during construction including the water line, and the existing storm sewer collection discharge line.

Since the problems seem to originate from the inability of the storm sewer collection system on the east side of the road, a new catch basin will be necessary, located at the lowest elevation of the storm sewer collection system and connected to the existing storm sewer pipe.

All infrastructure impacted by this project will be replaced with new one during the construction process.

Based on the information gathered and analyzed for this particular solution alternative the approximate construction cost will be $430.000.00 and the approximate construction time estimate will be 7 months.

APPENDIX A

GEOTECHNICAL STUDY

LUIS O. GARCIA & ASSOCIATES

GEOTECHNICAL ENGINEERING CONSULTANTS

Partners Luis Oscar García, MSCE, CE Carlos García Echevarría, MSCE

Associate Alejandro E. Soto, MS, PG

AMELIA DISTRIBUTION CENTER, EMMA STREET NO. 26A, GUAYNABO, PR 00968-8007

TEL. (787) 792-2626 FAX (787) 782-5990

Email: cgarcia@geocim.com

GEOTECHNICAL MEMORANDUM

TO : Dr. Eusebio Iglesias, P.E., PhD

Iglesias Vázquez & Associates iva@ivapr.com

FROM : Eng. Carlos García Echevarría, P.E.

Geol. Alejandro Soto, P.G.

RE : Landslide Evaluation PR-155, Km. 36.15, Morovis, PR

ER-HWY-257

JOB NO. : 5160

DATE : February 20, 2019

This memorandum presents the results of a geotechnical investigation of a landslide that impacted State Road PR-155 at Kilometer 36.15 in the Perchas Ward of the municipality of

Morovis. The approximate location of the project site is shown in Figure 1 – Site Location Map.

The objective of the investigation was to evaluate subsoil conditions at the site in order to provide geotechnical recommendations for the design and construction of landslide stabilization alternatives that would enable the full reopening of PR-155. The Puerto Rico Highway and

Transportation Authority (PRHTA) are the project sponsors and Iglesias Vázquez & Associates

(IVA) are the Project Designers. The work was performed in general accordance with our proposal dated May 3, 2018. This report provides a summary of the activities performed during

Landslide at PR-155, Km. 36.15, Morovis, PR February 20, 2019.

the course of the investigation, a description of subsurface conditions encountered at the site, and geotechnical recommendations for the design and construction of landslide stabilization alternatives for the project.

The project site contains one (1) landslide on the outside edge of the roadway approximately 50 feet wide with a steep high slope where the roadway shoulder was undermined and the edge of the roadway pavement was damaged. Concrete barriers were installed at the edge of the roadway for security measures.

The geotechnical investigation performed consisted of the drilling one (1) boring (B-1) to

26.5 feet depth for a total of 26.5 lineal feet of drilling exploration; very hard drilling conditions were encountered at the bottom of the boring providing refusal to the penetration of the augers.

The location of the boring at the site was established in the field by GeoCim by visual observation from existing local references; the presence of underground and aerial utilities in the area and vehicle traffic requirements on the roadway were also taken into consideration in the selection of the location of the boring. The approximate boring location is shown on Figure 2 –

Boring Location Plan; the boring was drilled adjacent and at one end of the existing landslide area.

Geo Cim, Inc., our affiliate geotechnical testing services firm, performed the field and laboratory work. The borings were drilled with a CME-45 drill rig using the "Hollow Stem

Auger-Dry Sample" method of drilling and an Automatic SPT hammer. Soil samples were collected beginning at the ground surface, at 2.5-foot depth intervals to a depth of 10 feet, and at

5-foot depth intervals from a depth of 10 feet to the bottom of the borings. The samples were collected with a split-spoon sampler driven into the ground. The number of blows required to drive the split-spoon sampler into the soil was recorded in the field; the N-value of the SPT represents the number of blows required for the penetration of the last 12 inches of the sampler.

The samples were placed in tightly closed plastic bottles and transported to the GeoCim

Geotechnical Testing Laboratory in Guaynabo for unconfined compression testing (in cohesive samples using a spring tester and/or pocket penetrometer), natural moisture content determinations, and visual/manual soil descriptions following standard laboratory procedures.

One (1) Classification Test, including Sieve Analysis and Atterberg Limits, was performed on a selected sample from the boring. The results of the field operations, laboratory testing, and detailed descriptions of the soils encountered are documented in the boring log included in

Appendix A. Appendix B contains a description of the GeoCim, Inc. drilling, sampling, and testing procedures. Results of the Classification test is provided in Appendix C.

GEOLOGY AND SUBSOIL CONDITIONS

According to the Geologic Map of the Ciales Quadrangle, Puerto Rico published by the

US Geological Survey (USGS) in 1964, the project site lies within the Perchas Lava Member

Formation (Kop) which is described in the geologic map as “Amygdaloidal-basaltic pillow lavas containing a few thin lenses of reworked tuff”. The subsurface conditions encountered at the site is in general agreement with those described in the geologic map.

The subsoil profile seen in boring B-1 consist of an upper Fill layer underlain by a

Thoroughly Weathered Rock Formation to the bottom of the boring. The Fill layer extends from the existing ground surface to about 13 feet depth and is variably described as a Gravel with little sand and trace silt to a depth of 2 feet (this is probably the pavement base course placed during construction of the roadway) and then to 13 feet depth as a Clay with little to some silt to a Silt with little clay in a medium stiff to stiff consistency as indicated by N-values of 5 to 10 blows per foot (bpf). Results of Unconfined Compression Tests performed on SPT samples from the

Fill layer and using a pocket penetrometer indicate medium stiff consistency. Results of a

Classification Tests performed on a sample from the Fill layer at 7.5 feet depth indicate that it classifies as a high plasticity Clay (CH) in accordance with the Unified Soil Classification

System with 89.1% of fines (passing the #200 sieve), and Liquid Limit of 54% and Plasticity

Index of 28%.

Underlying the Fill layer and extending to the bottom of the boring is the Thoroughly

Weathered Rock Formation which is described as breaking down when sampled (at 15 feet depth) as a sandy Silt to silty Sand in a medium dense condition as indicated by N-values of 22 bpf; below about 17.5 feet is described as a moderately weathered, weak to moderately strong volcanic Sandstone in a very dense condition as indicated by N-values of over 100 bpf (with only

3 to 5 inches of sample penetration) indicating virtual refusal to the penetration of the sampler and finally obtaining refusal to the penetration of the augers at the bottom of the boring at 26.5 feet depth. The terminology used to describe the physical character of rock materials in the boring log is explained in Table 1. In general, the N-values and consistency of this formation increase with increasing depth as would be expected in a residual profile where the soils develop by the in-situ weathering and decomposition of the parent rock over geologic time. Groundwater was not observed in the boring.

A detailed description of the soils encountered is provided in the boring log in Appendix

A. Groundwater observations were made during drilling operations or within the open borehole immediately after drilling operations were completed and the augers were removed from the ground. For more accurate determination of groundwater levels or to determine groundwater level variations under different conditions (at times of heavy rain, etc.) and on a long term basis, then installation of piezometers and observation wells and their monitoring during extended periods of time would be required.

ANALYSIS, CONCLUSIONS AND RECOMMENDATIONS

This section of the report presents our analysis, conclusions and recommendations based on the results of the geotechnical investigation and site reconnaissance performed for the landslide area within the site. It is important to note that the main objective of these recommendations is to provide stability to the reconstructed roadway in the landslide areas identified.

Based on the results of the borings drilled and the site reconnaissance performed we understand that the landslide on the outside edge of the roadway is occurring within the upper

Fill layer (visual observations of the landslide area are limited due to heavily vegetated and steep slope conditions) due to erosion caused by uncontrolled surface water runoff over the outside edge of the roadway during the heavy rainfall associated with Hurricane María; additionally, the saturation of the surface soils on the slope may have also contributed to the instability of the slope by increasing their weight while reducing their strength. Several photos of the site obtained during our visit to the site in April 2018 are contained in Appendix D. Any stabilization alternative in this area will have to extend below the upper Fill layer and into the underlying

Thoroughly Weathered Rock Formation. The stabilization alternatives may include the following:

1. Gravity retaining wall such as a Gabion or Concrete wall – this will require an excavation of a minimum of about say 15 feet in order for the wall to bear on the underlying

Thoroughly Weathered Rock Formation. The location of the wall shall be established such that the top of the proposed wall extends to the edge of the reconstructed roadway;

the final depth of the wall shall also provide for the outside bottom edge of the wall to be located a minimum of 3 to 5 feet from the outside edge of the Thoroughly Weathered

Rock Formation on the existing slope which may be approximately established by the

Designer using the topographic survey information. At the required excavation level an

Allowable Soil Bearing Pressure (Qall) of 4,000 pounds per square foot (psf) may be utilized for wall design; PRHTA standard drawings for these walls may be utilized.

For a detailed design, the lateral pressures acting on the retaining wall shall be determined using a triangular earth pressure diagram acting on a vertical plane passing through the heel of the wall and extending from the bottom of the wall to the proposed ground surface. This triangular earth pressure diagram shall be calculated using an

“active” lateral earth pressure coefficient, Ka, and an angle of internal friction (Ø) of 32 degrees for the backfill material to be utilized; a unit weight (γ) of 130 pounds per cubic foot (pcf) may also be used for the backfill material behind the walls. Any other surcharge loads acting on the ground surface at or near the walls must be added to the previously mentioned earth pressures to determine the final design lateral loads acting on the walls.

The above lateral earth pressure recommendations assume that the backfill material behind the wall will consist of an engineered compacted fill constructed as described under the Earthwork Recommendations section of this report. The backfill material within 10 feet from the wall shall be placed in 4 to 6 inch thick layers and compacted with light, hand operated compaction equipment to 90% of the maximum dry density as obtained in the Modified Proctor Test (ASTM D 1557). The backfill material beyond 10 feet from the wall shall be placed in 8 to 12 inches thick layers and each layer compacted to 95% of the maximum dry density as obtained in the Modified Proctor Test

(ASTM D 1557) using conventional compaction equipment.

We have also assumed that the design of the retaining wall will include a drainage system that will provide a fast and efficient way to collect and dispose of any water that may infiltrate behind the wall in order to prevent the development of unbalanced water forces behind the wall; a typical drainage system would include a free draining crushed stone layer behind the retaining wall separated from the backfill material by a geotextile filter fabric (such as Mirafi 140N or equivalent), and a perforated drainage pipe placed at the bottom of the wall and connected to a proper outlet.

Alternatively, other types of drainage composites specifically manufactured for drainage behind retaining walls may be used.

Prior to beginning construction of the retaining wall, the foundation bearing surface for the wall shall be cleaned and any soil disturbed during the excavation operations (or any time thereafter) shall be compacted or removed to provide an undisturbed soil bearing surface. We recommend that a Geotechnical Engineer and/or

Engineering Geologist be present at the site when the landslide area is excavated in order to observe and confirm that the proposed excavation depths extend below the landslide sliding surface and that a firm bearing surface is reached; therefore, the final bearing surface for the retaining wall shall be determined in the field based on observations of the materials exposed by the excavation.

2. Reinforced concrete retaining wall – in this alternative a reinforced concrete retaining wall may be designed following the same recommendations provided above for the

Gravity Retaining Wall, including bearing on the Thoroughly Weathered Rock Formation and the inclusion of adequate drainage measures behind the wall.

3. Mechanically Stabilized Earth Wall – in this alternative this retaining wall may be designed following the same recommendations provided above for the Gravity Retaining

Wall, including bearing on the Thoroughly Weathered Rock Formation and the inclusion of adequate drainage measures behind the wall.

Earthwork Recommendations

The following general earthwork recommendations are provided for construction of any fill or backfill that may be required within the project in the landslide areas.

1. Prior to commencing construction the site shall be cleared and grubbed of vegetation cover and topsoil that may exist at the ground surface and any existing asphalt/concrete pavement from the existing roadway shall be demolished and removed from the site. After the clearing, grubbing, and demolition operations of the existing facilities are completed, and after any cut excavations are performed, the exposed surfaces shall then be proof-rolled with several passes of a heavy vibratory roller to detect any soft soil spot that may have to be removed and to densify any surface soil that may have been disturbed during the clearing and grubbing, and/or cut excavation operations.

2- Excavations into the fill and existing soils near the ground surface may be performed with conventional excavating equipment, including heavy duty bulldozers and/or excavators, as indicated by the results of the borings. In the very dense Thoroughly Weathered Rock

Formation below say about 20 feet depth where virtual refusal to the penetration of the sampler and later refusal to penetration of the augers was attained, excavations may require the use of rock excavating equipment.

3- Materials from required cuts at the site shall not be used as Fill at the site. Fill and/or backfill material to be used at the site shall consist of a non-expansive A-2-4 soil or better in accordance with the AASHTO (American Association of State Highway and Transportation

Officials) Soil Classification system. All fill within the site shall be placed as engineered compacted fill in 8 to 10 inch thick layers and each layer compacted to a minimum of 95% of the Maximum Dry Density as obtained in the Modified Proctor Test (ASTM D-1557); in excavations of limited extent the thickness of the fill layers placed shall be reduced to about 4 to 6 inches in order to attain the above compaction level. Fill required on sloped surfaces shall be placed in horizontal layers starting from the lower elevations and each horizontal layer shall be keyed into the in-situ soils so as to prevent the development of a preferred surface of sliding along the contact of the natural soils and the engineered compacted fill.

4- Temporary cut excavations deeper 4 feet shall be performed with cut slopes not steeper than say about 1(H):1(V); alternatively, the cut shall be properly braced and supported. Since bracing and support of cut excavations is a temporary construction feature, the Contractor shall design and select the most suitable support system for the excavation equipment and technique that he will use in the project.

5- We recommend that final cut and fill slopes (if any) be constructed at inclinations not to exceed 1.5(H):1(V) and 2(H):1(V), respectively. All cut and fill slopes shall be properly and promptly vegetated in order to prevent excessive erosion of the soils that may cause instability of the slopes.

6- The project should be provided with adequate surface drainage measures to collect and conduct runoff to the project storm water system. Under no circumstance should water be allowed to accumulate anywhere within the project or to spill over the recommended retaining walls and/or slope embankments.

We request to be consulted should there be any questions on the intent and general scope of our recommendations. Likewise, we request to be informed of any changes in the scope of this project that may require our revision of these recommendations or if additional recommendations are needed.

N:\0000-project files\5160 Lanslide Evaluations IVA\PR-155 Km 36.15 Morovis\PR-155 Km 36.15 Landslide Report.doc

Table 1: Descriptive Terminology Used to Describe the Physical Properties of Rock for Engineering Purposes

WEATHERING CLASSIFICATION

Fresh No visible sign of weathering

Faintly Weathered Weathering limited to surface of major discontinuities

Slightly Weathered Penetrative weathering developed on open discontinuity surfaces, but only slight

Moderately Weathering extends through the rock mass, but rock is not friable

Highly Weathered Weathering extends through the rock mass and rock is partly friable

Thoroughly Rock is wholly decomposed and friable, retains rock structure and texture

Saprolite Soil that retains the original rock texture and structure

Residual Soil Soil with the original rock texture, structure and composition completely destroyed

FRACTURE SPACING

Fracturing Size Range of Rock Fragments

Crushed Less than 1.5 cm Intensely fractured 1.5 - 3.0 cm Closely fractured 3.0 – 15 cm

Moderately fractured 15 – 30 cm Little fractured 30 cm – 1 m

Massive Greater than 1 m

HARDNESS

Soft Plastic material

Friable Easily crumbled or powdered by fingers Low hardness Can be gouged deeply or carved with a knife

Moderately hard Can be readily scratched by a knife blade; scratch leave heavy trace of dust Hard Can be scratched with difficulty; scratch produces little powder and is faintly visible

Very hard Cannot be scratched with a knife blade

STRENGTH

Plastic Easily deformable with finger pressure Friable Crumbles by rubbing with fingers Weak Unfractured outcrop crumbles under light hammer blows

Moderately strong Outcrop withstands a few strong blows before breaking Strong Outcrop would withstand a few heavy ringing hammer blows, but will yield large fragments

Very strong Outcrop would resist heavy ringing hammer blows and yield dust and small fragments with difficulty

APPENDIX A

BORING LOGS

APPENDIX B

FIELD AND LABORATORY TEST PROCEDURES

GEO CIM, INC.

Appendix B

Field and Laboratory Test Procedures

I. DRILLING METHODS

A. Hollow Stem Auger Boring - Dry Sample method (ASTM-D-1452)

In the auger method, borings are advanced by turning a hydraulic powered auger into the ground in 5 feet increments or less. As the auger penetrates the cuttings rise to the surface on the spirals. The depth from which the material comes, however, cannot be accurately determined. Therefore, soil samples are not taken from the spiral augers. With the use of a hollow stem auger, a sampling apparatus may be inserted in the hollow stem to the bottom of the auger, eliminating the need for casings. The sampling procedures are described in the following paragraphs. Geo Cim, Inc. normally uses CME (Central Mining Equipment) drilling rigs which are trailer mounted and pulled with a 4 x 4 wheel drive F-350 or equivalent truck. The drilling rigs are either CME-45 or CME-55 models.

B. Wash Boring - Dry Sample Method

For inaccessible locations a portable drilling unit is used which consists of a tripod mounted motorized cathead which is used to drive casings and sampling rods to conduct this method of drilling. Borings are advanced into the ground by the wash-boring-dry sample method. The borings are normally cased through most of this length by the drop of either a 350 or 140 lbs. hammer from a height of 30 inches. The casing diameter is 2-1/2 inches. The number of blows for every foot of penetration the casing advanced is recorded and is reported in the boring logs. When driving of the casing becomes too difficult due to the hardness of the soils encountered, and the hole does not cave-in, the boring may be advances without casing by continuous washing out of the soils with the drill rods. The color and nature of the soils washed out (gravel, sand, silts or clay) is examined and recorded in order to determine the extent of each soil strata this is complemented with the sampling operations which are regularly made every five feet.

C. Core Borings (ASTM-D-2113)

Core Borings are used when necessary to penetrate into rock and obtain a continuous rock sample. The sample is obtained by means of a core barrel which is attached to the drill rods. At the end of the core barrel is a special bit studded with industrial diamonds which cuts into the rock. The drill rod, and hence the core barrel and diamond bit are rotated as downward pressure is applied. As the bit cuts into the rock, the rock core is free to move into the inner core barrel head, which is suspended on a swivel and therefore does not follow the motion of the outer core barrel with its bit. Cooling water or bentonite slurry is circulated through the drill rod and the core barrel. Penetration depends on the length of the core barrel and the quality of the rock (amount of joints or fractures). Rock discontinuities such as joints and fractures affect the length of penetration in a given core run. The runs are longer as the rock quality increases. As the core barrel is withdrawn, the core lifter, located inside the diamond bit, wedges itself around the bottom of the rock core and thus permits it to be pulled free from the underlying rock. The two most common core sizes are NWM which produces a core of 2.15 inches diameter and HWM which produces a core 3.00 inches in diameter.

II. SAMPLING IN SOILS

A. Standard Penetration Test (ASTM-D-1586)

The standard penetration tests are made with a split-spoon sampler 2.0 inches/O.D.

diameter, 1,375 inches I.D. diameter, 18 inches long. The sampler is driven into the ground by the drop of a 140 pounds hammer from a height of 30 inches. The number of blows from the three consecutive six inches of penetration of the sampler is recorded and the number of blows for the last foot of penetration is reported as the N-value. The samples are stored and sealed in glass jars for future classification tests in the laboratory.

The standard penetration test has been correlated with the consistency of fine grained soils and with the angle of internal friction or the relative density of sands.