Report_Geotechnical_ER_HWY_112.pdf

ADVANCED SOIL ENGINEERING

GEOTECHNICAL CONSULTING ENGINEERS

P.O. BOX 1286, ISABELA, PUERTO RICO 00662

GEOTECHNICAL CONSULTING ENGINEERING

CONCRETE AND MATERIAL TESTING LABORATORIES

ON THE GEOTECHNICAL EXPLORATION

PERFORMED AT THE SITE OF THE PROPOSED

LANDSLIDE AND ROAD DAMAGE EVALUATION AND REPAIR

RECOMMENDATIONS AT STATE ROAD PR 128,

VEGAS WARD, YAUCO, PUERTO RICO

SUBMITTED TO:

GERMÁN TORRES BERRÍOS & ASSOCIATES – PROJECT DESIGNER

C/O: JOSUÉ TORRES ORTIZ, P.E.

BY:

NELSON MUÑOZ, P.E.

JUNE 17, 2019

FILE NO. 1823-3C FINAL REPORT

PROJECT: ER-HWY-112

P.O. BOX 1286, ISABELA, PUERTO RICO 00662

ON THE GEOTECHNICAL EXPLORATION

PERFORMED AT THE SITE OF THE PROPOSED

LANDSLIDE AND ROAD DAMAGE EVALUATION AND REPAIR

RECOMMENDATIONS AT STATE ROAD PR 128,

VEGAS WARD, YAUCO, PUERTO RICO

1.0 INTRODUCTION:

This report covers the results of a geotechnical exploration conducted at the site of the existing road slope failure at State Road PR 128 km 17.3 and Km. 17.35

(ER-HWY-112), Vegas Ward, Yauco, Puerto Rico.

The investigation was made following instructions from Josué Torres Ortiz, P.E. from German Torres Berríos & Associates – Project Designer. The study was performed in general accordance with the scope of work included in our Proposal

No.19 (Revised), dated June 12, 2018.

This report has been prepared to summarize the data obtained during this study and to present our conclusions and recommendations based on the proposed construction and the subsurface conditions encountered. Design parameters and a discussion of geotechnical engineering considerations related to construction of the proposed structure are included in the report.

This report has been prepared for the exclusive use of the owner, their designers and others involved in the construction and preparation of the plans and specifications of the project.

File No. 1823-3C Page 3

2.0 SITE LOCATION AND PROJECT DESCRIPTION:

The site of the proposed project is located at State Road PR 128 km 17.30 and km 17.35 (ER-HWY-112), Vegas, Yauco, Puerto Rico. State road segments are part of our scope of work. Segments of the road were damaged as a result of intense run-off water, erosion, shallow slumping and earth flows triggered by a significant precipitation by the events of Huracan María in September 20, 2018. The roadways generally consist of two-lane roads located on steep slopes with one side of the road cut into the hillside and the other side of the road constructed on embankment fill. Typical distress caused by the flooding and significant rainfall event generally consisted of erosion, slumping or movement of the roadway embankment along the downslope side of the roadways. Some minor undermining of the roadway pavement or cracking of the pavement near the edge of the roadway occurred along each roadway. Drainage, roadway and embankment improvements including the construction of retaining structures are planned at the subject roadways to stabilize the roadways and repair the damage.

Physical evidence gathered at the site during our field visual inspections make us to believe the slope failure could have been triggered by waters from faulty pipe/swale line connections and damaged catch basin leaking into the fill slope provoking the fill mass saturation with subsequent loss in strength and increase on the corresponding unit weight of the soil. Both eventualities significantly contribute to the weakening of the soil/fill strength properties, thus provoking an instability problem.

File No. 1823-3C Page 4

The following Figure 1 shows portion of US Geological Survey Service

Topographic Map of the Yauco and Punta Verraco Quadrangles with the site location enclosed.

Figure 1: Site Location Map

SITE

File No. 1823-3C Page 5

3.0 SCOPE OF INVESTIGATION:

Field Exploration:

A joint visit was conducted with the project designer to confirm boring locations. All boring locations were adjusted based on utilities interference and client’s requests. The field exploration consisted of drilling two (2) test boring along the proposed construction area of site ER-HWY-112. The location of the borings was as close as possible to the staked locations, subject to utilities interference and drilling convenience. Test borings were drilled to depths varying from 25.0 to 30.0 ft.

with a total footage of 55.0 lin. ft.

The borings were performed using the rotary hollow-stem auger technique in accordance with ASTM D 1452. Samples were obtained using the "Standard

Penetration Test (SPT)", as specified in ASTM D 1586. Please refer to Appendix

No. 1 (Boring Location Map), for boring location.

Maintenance of Traffic (MOT) Safety Controls:

Set up basic MOT safety controls prior to and during the performance of the field drilling and testing operations. Please refer to Appendix No. 8 (Maintenance of Traffic Sheet “MOT”).

4.0 SUBSOIL CONDITIONS & GROUNDWATER:

The general subsoil conditions as disclosed from the test borings drilled at the subject sites are described in each case recommendation separately.

File No. 1823-3C Page 6

The ground water level of the explored site was not encountered within the depths drilled during the time of our field exploratory work, thus indicating that it must be present at a greater depth. However, temporary bodies of water or perched water might be or be found entrapped within the fill deposit or between the zone of transition of fill deposit and virgin soil.

Subsurface water observations were limited to the depths explored using dry auger drilling techniques and within these depths, groundwater was not observed.

The borehole was backfilled upon completion of the water level measurements.

The absence of free water at these boring locations should not necessarily be construed that subsurface water is not present at the site or is deeper than the boring depth. The short-term field observations generally do not permit an accurate evaluation of the subsurface water levels at this location and should not be interpreted as a groundwater study. It is not unusual to encounter groundwater in the granular silty and clayey sands during and after periods of rainfall. It should be noted that the observations made during this investigation may not represent conditions at the time of construction and the presence of groundwater may affect certain construction activities and long-term performance of the foundations. The quantity of transient water is variable and is highly dependent on climatic conditions before and during construction. The foundation contractor should check the subsurface water conditions just prior to foundation excavation activities.

The above information corresponds to a general description of the subsoil conditions of the area, however, for detailed description regarding the soil profile, field and laboratory test results, please refer to Appendix No. 2 (Boring Logs). For detailed description of the procedures followed for the drilling of the test borings and laboratory testing, please refer to Appendix No. 3 (Field and Laboratory Testing

File No. 1823-3C Page 7

Procedures), and Appendix No.5 (Laboratory Test Results).

5.0 U.S. GEOLOGICAL SURVEY MAPS:

The Department of the Interior through its U.S. Geological Survey offices published a Geologic Map No. I-1147The Yauco and Punta Verraco Quadrangles.

This was surveyed by Richard D. Krushensky and Watson H. Monroe and published on 1979. The proposed project lies in a formation described as:

Kat – AUGITE TRACHYBASALT (UPPER MAESTRICHTIAN THROUGH

CAMPANIAN): Dark green or dark-bluish-green, light-brown weathering, abundantly porphyritic augite trachybasalt. Characteristically contains abundant and conspicuous large (1-3 cm long) deep-green augite and rare to sparse small (<.5

cm) tabular and generally dark inconspicuous appearing plagioclase (labradorite-andesine) phenocrysts held in a felted trachytic groundmass composed of abundant microphenocrysts and microlites of plagioclase and some augite in a sparse to common chloritized glass. Granular magnetite in the ground mass in an abundant accessory. Intrusive contacts are chilled and show fewer plagioclase phenocrysts than rock away from contacts. Chilled contacts, smaller stocks, and some widespread areas of the intrusive rocks are widely brecciated. Three generations of brecciation are locally evident in the field. Clasts are mineralogically and texturally alike; they differ only in the degree of crystallization, crystal size, amount of magnetite, and, consequently, color. Locally, contact zones are vesicular and amygdaloidal (calcite and chlorite) and adjacent country rock (chiefly the calcareous siltstone-claystone of the Yauco Formation) is depleted in calcite. Augite is generally fresh, but groundmass glass is invariably chloritized. Areas of alteration

File No. 1823-3C Page 8 show a progressive replacement of groundmass, plagioclase phenocrysts, and augite by chlorite, calcite, and rarely by pistacite. Plagioclase phenocrysts are commonly party saussaritized. Typically, only stubby pseudomorphs of limonite after augite and clay-calcite after plagioclase remain visible in saprolitized augite trachybasalt

Km – MARICAO BASALT (UPPER MAESTRICHTIAN THROUGH

CAMPANIAN): Chiefly thick-bedded (I m+ ) to massive volcaniclastic breccia composed or dark-green, and subordinate dark – to light -gray and dark-red angular to well rounded clasts (predominantly 3-15 cm on a side, rarely to 3m on a side) of generally dense porphyritic augite trachybasalt held in a clay-sandstone or in a coarse sandstone-conglomerate or lithic-crystal tuff matrix. Breccia clasts are composed of conspicuous, abundant, and large (1-3 cm long) augite and smaller.

(.2-5 cm long) plagioclase (labradorite-andesine) phenocrysts in a trachytic groundmass composed of abundant microphenocrysts and microlites of plagioclase and augite in a sparse chloritized glass. Typically, the groundmass is dark colored because of abundant granules of magnetite. Breccia ranges from fresh to deeply weathered and mostly replaced by clay, calcite, and chlorite. Outcrops in the central and dark-brownish-green sandstone and subordinate siltstone. These are composed of rounded to angular lithic and mineral (chiefly augite and plagioclase) clasts and generally unweathered clasts. These rocks are tuffaceous sandstone-siltstone or more probably tuffs. Weathered surfaces of the breccia clasts are studded with conspicuous limonite coated augite phenocrysts weathered into positive relief. Widespread areas of the Maricao are deeply saprolitized; these show little or no breccia texture, but large limonite pseudomorphs after augite are commonly present and diagnostic. Laterally restricted lenses of pale-pink or light-brownish-gray biosparite are composed of angular to rounded fragments of rudists, other pelecypods, plates of calcareous algae, and large foraminifers in a generally

File No. 1823-3C Page 9 sparry matrix. A thick sequence of such calcarenite and interbedded volcaniclastic breccia comprises the summit of Cerro Rodadero. The Maricao locally includes 7-10 m thick fine crystalline sparsely vesicular nonpillowed basalt flows. These lack the coarse augite phenocrysts characteristic of the Maricao Basalt. Volcaniclastic breccia in the sratigraphically upper part of the Maricao includes sparse clasts of angular to subrounded homblende dacite.

Figure 2: U.S. Geological Survey Map

SITE

File No. 1823-3C Page 10

6.0 FOUNDATION RECOMMENDATIONS:

Recommendations for the geotechnical aspects of the project are based on the subsoil study presented in this report. This office warranties that our recommendations are in the line with the generally accepted practice in the field of

Soil Mechanics and Foundation Engineering. This is our only warranty, either expressed or implied.

The use of the subsoil information and recommendations herein detailed for other structures or areas, except when done by specialist, may lead to serious design errors and should not be attempted.

The deposits encountered as disclosed by these test borings, not necessarily represent the most critical conditions of the site and might vary from one boring to another. These recommendations are based on the subsoil conditions as encountered on the test borings rather than the worst conditions of the site.

6.1 Project ER-HWY-112 (Km. 17.30):

Subsurface Conditions:

subject site consist of a man-made fill deposit composed brown silty sand with rock fragments, extending to a depth of 4.0 ft. on boring No.3B-1, below existing ground elevation.

The above described layer is resting over yellowish brown sand with clay some rock fragments, extending to a depth of 8.0 ft.

File No. 1823-3C Page 11

Following the layer described above the exploratory work shows grayish brown sand with rock fragments some clay, extending to a depth of 13.0 ft.

Underlying the aforementioned stratum and extending to the end of the test holes, the exploratory work shows gray rock formation decomposed into rock fragments trace silty sand. Test boring refusal, presumably bedrock, was met at a depth of 25.0 ft.

must be present at a greater depth. However, temporary bodies of water or perched

Three alternatives are considered as a solution to the soil stability problem.

After having evaluated the results of the test borings, we strongly recommend the construction of Gabion Wall, and the construction of a concrete retaining wall system

(Mass Gravity Wall “Ciclópeo” and/or Cantilever). Gabion wall retaining structures is being considered in the project as alternative. Since this wall is proprietary system, the supplier shall design and warrant them to satisfy their internal and external stability. This design will be done in collaboration with German Torres Berríos &

Associates (project designer representing PRHTA). The specific alignment of the wall shall be defined by the project designer. This design will be done by an experienced and qualified structural engineer. The options listed below area based on site limitations and soil conditions.

File No. 1823-3C Page 12

6.1.1 Gabion Wall Recommendations:

We understand that the intended project shall require the design and construction of a retaining wall structure – Gabion Wall, necessary for the stabilization existing slope. Please refer to Figure 5 at Appendix No.6.

The results of our investigation show favorable subsoil conditions to erect the proposed retaining wall structure over continuous wall footing foundation.

The footing of the proposed retaining wall structure shall be designed for an allowable soil bearing pressure of 3,000 lbs. per sq. ft. The base of the footings shall be located at a minimum depth of 12.0 ft. below the existing pavement elevation near Boring 3B-1, (elevation of 348.06 meters).

Since the ground water level of the site was not encountered within the depth drilled at each test hole, no dewatering problems are anticipated during the phase of over excavation and footing excavation. However, any water entering the excavation can be pumped directly from the bottom of them.

The foundation wall system at rest is to be acted by lateral pressure and the lateral earth pressure to act in the walls depends primarily in the type of earth material to be used as backfill. Accordingly, we wish to furnish the soil parameter for computing the lateral pressure.

File No. 1823-3C Page 13

Material Unit Weight

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Compacted Borrow Fill (A-2-4) 125 32 Neglect

Foundation Soil 120 36 Neglect

Table 1: Material Unit Weights and Soil Strength Design Parameters

The material to be used as backfill has to be laboratory tested to verify soil parameters.

According to the pressures and resisting shearing forces, the external stability of retaining walls must be checked by the structural designer, i.e., sliding, and overturning.

Our experience shows that during local rainy periods a temporary perched water level develops within the backfill of the wall surface which in some instances may rise close to the ground surface. This temporary perched water level introduces a lateral pressure to the wall.

A filter fabric should be placed between the gabion baskets and the native soil to prevent the migration of the fine-grained soils into the gabion basket zone.

Placement of the fabric should begin at the top of the slope and extend down the full slope face.

Rock material placed in gabion baskets should consist of hard, angular to sub-rounded, durable stone that is of such quality that it will not disintegrate on exposure to water or weathering during life of the structure. Gabion stone should be

File No. 1823-3C Page 14 between 4 inches and 8 inches in nominal diameter. The range in size should allow for a variation of 5 percent oversize and/or 5 percent undersized rock. The size should be such that a minimum of three layers of rock be achieved when filling the gabion baskets. Gabion baskets should be constructed and placed in accordance with manufacturer guidelines and specifications.

6.1.2 Concrete Retaining Wall Recommendations:

6.1.2.1 Cantilever Retaining Wall:

construction of a concrete retaining wall structure.

shall be located at a minimum depth of 10.0 ft. below the existing pavement elevation near Boring 3B-1, (elevation of 348.70 meters).

The foundations of a retaining wall systems are placed a specified distance below finished grade to provide adequate erosion protection, foundation bearing capacity, and overall global stability when slopes are involved. Please refer to

Figure 3: Typical Wall Embedment Section for specific embedment depth and setback distance.

File No. 1823-3C Page 15

Figure 3: Typical Wall Embedment Section

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Table 2: Material Unit Weights and Soil Strength Design Parameters

File No. 1823-3C Page 16

The material to be used as backfill must be laboratory tested to verify soil

To control the excessive lateral pressure, the wall shall be provided with a foundation wall drain system located over the interior and exterior top surface of foundation wall footings.

The foundation drain system shall be topped with a crushed stone backfill with a grain size of 1/4 to 3/4 in. of at least 1.5 ft. in thickness and 1.0 ft. wide above the wall footings to serve as the vertical drainage media toward the foundation drain.

Also, place a 1.0 ft. thick of crushed stone between the wall and the backfill material to be placed against the wall. The wall shall be provided with a series of properly designed weep holes to avoid the accumulation of water behind the concrete wall during heavy rainy period. The last 2.0 ft. of the backfill material at the top of the wall shall consist of clayey material to reduce the superficial water infiltration.

A geotextile liner should be placed between the crushed stoned and the backfill to prevent mixing of the surrounding soil into the gravel. This will keep the porous spaces in the gravel open for the water to flow through.

File No. 1823-3C Page 17

The crushed stone layer shall be continuous since the top of the wall to the foundation wall footing and drained to the sides of the proposed wall by means of a minimum 2.0 in. perforated PVC pipe.

The retaining wall interior surface in contact with the backfill must be placed with a plastic membrane with an asphaltic coating or similar substitute material to prevent water migration toward the lower level area, that is shall be design water tight.

Similarly, the construction joints of the walls are also properly sealed to prevent migration to any infiltrated water lower level.

An alternative to the standard gravel column used to provide vertical drainage path behind the wall is by substituting the classic column gravel by Geocomposites, such as Terra Drain or equivalent. Due to the high flow transmissibility characteristic found in the Geocomposites, they can be used behind the wall instead of the column of granular material. In addition, we recommend that an appropriate waterproofing sealant, be applied at the interior surface in contact with the Geocomposite to reduce the likelihood of seepage and vapor transmission through the wall.

It should be brought to the consideration of all parties involved, the fact that no matter how well-designed the project is, it shall be necessary to provide full time supervision for the foundation works with special interest in the construction of embankments, cuts, and retaining structures.

It is in the execution of these aspects of the suggested work that most of the problems of development construction can be minimized.

File No. 1823-3C Page 18

6.1.2.2 Mass Gravity Wall “Ciclopeo”:

We understand that the intended project could require the design and construction of a concrete mass gravity wall “Ciclopeo” structure.

shall be located at a minimum depth of 10.0 ft. below the existing pavement elevation near Boring 3B-1, (elevation of 348.70 meters). Once the footing excavation was made the contractor shall notified the soils engineer to make a visual inspection of the excavation for further evaluation and to make the pertinent recommendations if deemed necessary.

The existing talus is a natural one with some minor intervention by man.

Several stability analyses were ran with the assistance of a computer program

(MACSTARS W, Maccaferri Stability Analysis of Soils). We have performed stability analyses to address the factor of safety of global stability. Ground water was not incorporated on the analysis since none was found at the test borings drilled at the area. As presented in Appendix 7 “Wall Stability Analysis Results”, the analyses show a factor of safety equal to 2.09 for static conditions. The analyses show a factor of safety of 1.53 for pseudostatic condition with ground acceleration equal to

0.15g (as per PRHTA Design Guideline 1002). These safety factors comply with those required by the client in a written statement: FS≥1.5, for static condition, and

FS≥1.1, for pseudostatic condition. Residual strength parameters were assigned accordingly to both the fill material and natural material (please verify Appendix

File No. 1823-3C Page 19

No.7 Wall Stability Analysis Results).

Our results indicate that the actual condition of the talus is stable if the construction of the retaining wall is made.

• The design of the mass gravity wall assumes the footing base are founded on dense sand with rock fragments or highly weathered rock fragments.

Foundation improvements below the footing may be required if poor quality or downslope sloping discontinuities at the rock face are encountered. The geotechnical engineer should observe the excavations as dense hard material is encountered to determine the design assumptions remain applicable or if modifications to the designs or foundation improvements are required.

• Our observations and measurements of the joints and fractures in the dense sand or highly weathered rock fragments exposed in the adjacent road cuts suggest that occasional portions of the temporary excavation within bedrock may require support to maintain stability during construction.

File No. 1823-3C Page 20

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Table 3: Material Unit Weights and Soil Strength Design Parameters the wall footings to serve as the vertical drainage media toward the foundation drain.

Also, place a 1.0 ft. thick of crushed stone between the wall and the backfill material

File No. 1823-3C Page 21 to be placed against the wall. The wall shall be provided with a series of properly designed weep holes to avoid the accumulation of water behind the concrete wall such as Terra Drain or equivalent. Due to the high flow transmissibility characteristic found in the Geocomposites, they can be used behind the wall instead of the column of granular material. In addition, we recommend that an appropriate waterproofing

File No. 1823-3C Page 22

6.2 Project ER-HWY-112 (Km. 17.35):

Subsurface Conditions:

subject site consist of a man-made fill deposit composed gray rock fragments some silty sand, extending to a depth of 2.0 ft. on boring No.3B-2, below existing ground elevation.

The above described layer is resting over brown rock fragments some silty sand, extending to a depth of 8.0 ft.

Following the layer described above the exploratory work shows grayish brown sand with rock fragments some clay, extending to a depth of 18.0 ft.

Underlying the aforementioned stratum and extending to the end of the test holes, the exploratory work shows gray rock formation decomposed into rock fragments trace silty sand. Test boring refusal, presumably bedrock, was met at a depth of 30.0 ft.

File No. 1823-3C Page 23 must be present at a greater depth. However, temporary bodies of water or perched

Three alternatives are considered as a solution to the soil stability problem.

After having evaluated the results of the test borings, we strongly recommend the construction of Gabion Wall, and the construction of a concrete retaining wall system

(Mass Gravity Wall “Ciclópeo” and/or Cantilever). Gabion wall retaining structures is being considered in the project as alternative. Since this wall is proprietary system, the supplier shall design and warrant them to satisfy their internal and external stability. This design will be done in collaboration with German Torres Berríos &

Associates (project designer representing PRHTA). The specific alignment of the wall shall be defined by the project designer. This design will be done by an experienced and qualified structural engineer. The options listed below area based on site limitations and soil conditions.

6.2.1 Gabion Wall Recommendations:

construction of a retaining wall structure – Gabion Wall, necessary for the stabilization existing slope. Please refer to Figure 5 at Appendix No.6.

File No. 1823-3C Page 24 allowable soil bearing pressure of 4,000 lbs. per sq. ft. The base of the footings shall be located at a minimum depth of 15.0 ft. below the existing pavement elevation near Boring 3B-2, (elevation of 350.16 meters). After having evaluated the results of the test boring, we strongly recommend to cast the footings over the very dense natural material composed of grayish brown sand with rock fragments. Under no circumstances the footings should be casted on medium brown rock fragments some silty sand. Once the footing excavation was made the contractor shall notified the soils engineer to make a visual inspection of the excavation for further evaluation and to make the pertinent recommendations if deemed necessary.

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Foundation Soil 135 40 Neglect

Table 4: Material Unit Weights and Soil Strength Design Parameters

File No. 1823-3C Page 25

The material to be used as backfill has to be laboratory tested to verify soil

A filter fabric should be placed between the gabion baskets and the native soil to prevent the migration of the fine-grained soils into the gabion basket zone.

Placement of the fabric should begin at the top of the slope and extend down the full slope face.

Rock material placed in gabion baskets should consist of hard, angular to sub-rounded, durable stone that is of such quality that it will not disintegrate on exposure to water or weathering during life of the structure. Gabion stone should be between 4 inches and 8 inches in nominal diameter. The range in size should allow for a variation of 5 percent oversize and/or 5 percent undersized rock. The size should be such that a minimum of three layers of rock be achieved when filling the gabion baskets. Gabion baskets should be constructed and placed in accordance with manufacturer guidelines and specifications.

File No. 1823-3C Page 26

6.2.2 Concrete Retaining Wall Recommendations:

6.2.2.1 Cantilever Retaining Wall:

construction of a concrete retaining wall structure.

shall be located at a minimum depth of 15.0 ft. below the existing pavement elevation near Boring 3B-2, (elevation of 350.23 meters). After having evaluated the results of the test boring, we strongly recommend to cast the footings over the very dense natural material composed of grayish brown sand with rock fragments. Under no circumstances the footings should be casted on medium brown rock fragments some silty sand. Once the footing excavation was made the contractor shall notified

The foundations of a retaining wall systems are placed a specified distance below finished grade to provide adequate erosion protection, foundation bearing capacity, and overall global stability when slopes are involved. Please refer to

Figure 4: Typical Wall Embedment Section for specific embedment depth and setback distance.

File No. 1823-3C Page 27

Figure 4: Typical Wall Embedment Section

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Table 5: Material Unit Weights and Soil Strength Design Parameters

File No. 1823-3C Page 28 the wall footings to serve as the vertical drainage media toward the foundation drain.

Also, place a 1.0 ft. thick of crushed stone between the wall and the backfill material to be placed against the wall. The wall shall be provided with a series of properly designed weep holes to avoid the accumulation of water behind the concrete wall

File No. 1823-3C Page 29 such as Terra Drain or equivalent. Due to the high flow transmissibility characteristic found in the Geocomposites, they can be used behind the wall instead of the column of granular material. In addition, we recommend that an appropriate waterproofing

File No. 1823-3C Page 30

6.2.2.2 Mass Gravity Wall “Ciclopeo”:

We understand that the intended project could require the design and construction of a concrete mass gravity wall “Ciclopeo” structure.

shall be located at a minimum depth of 15.0 ft. below the existing pavement elevation near Boring 3B-2, (elevation of 350.23 meters). After having evaluated the results of the test boring, we strongly recommend to cast the footings over the very dense natural material composed of grayish brown sand with rock fragments. Under no circumstances the footings should be casted on medium brown rock fragments some silty sand. Once the footing excavation was made the contractor shall notified

The existing talus is a natural one with some minor intervention by man.

Several stability analyses were ran with the assistance of a computer program

(MACSTARS W, Maccaferri Stability Analysis of Soils). We have performed stability analyses to address the factor of safety of global stability. Ground water was not incorporated on the analysis since none was found at the test borings drilled at the area. As presented in Appendix “Global Stability Analysis”, the analyses show a factor of safety equal to 1.57 for static conditions. The analyses show a factor of safety of 1.16 for pseudostatic conditions with ground acceleration equal to 0.2g.

Residual strength parameters were assigned accordingly to both the fill material and

File No. 1823-3C Page 31 natural material (please verify Appendix No.7 Wall Stability Analysis Results).

Our results indicate that the actual condition of the talus is stable if the construction of the retaining wall is made.

• The design of the mass gravity wall assumes the footing base are founded on very dense sand with rock fragments or highly weathered rock fragments.

Foundation improvements below the footing may be required if poor quality or downslope sloping discontinuities at the rock face are encountered. The geotechnical engineer should observe the excavations as dense hard material is encountered to determine the design assumptions remain applicable or if modifications to the designs or foundation improvements are required.

• Our observations and measurements of the joints and fractures in the very dense sand or highly weathered rock fragments exposed in the adjacent road cuts suggest that occasional portions of the temporary excavation within bedrock may require support to maintain stability during construction.

File No. 1823-3C Page 32

(pcf)

Angle of Internal

Friction, ɸ (Degree)

Cohesion

(psf)

In situ soil 115 30 Neglect

Table 6: Material Unit Weights and Soil Strength Design Parameters the wall footings to serve as the vertical drainage media toward the foundation drain.

Also, place a 1.0 ft. thick of crushed stone between the wall and the backfill material

File No. 1823-3C Page 33 to be placed against the wall. The wall shall be provided with a series of properly designed weep holes to avoid the accumulation of water behind the concrete wall such as Terra Drain or equivalent. Due to the high flow transmissibility characteristic found in the Geocomposites, they can be used behind the wall instead of the column of granular material. In addition, we recommend that an appropriate waterproofing

File No. 1823-3C Page 34

7.0 EARTHQUAKE CONSIDERATIONS:

Analysis of the relative density and consistency of the ground based on the

SPT N values; it is our opinion that for seismic design this site corresponds to a soil profile type SC according to the American Association of State Highway and

Transportation Officials (AASHTO) LRFD Design Specifications. Shear wave testing of the soils can be used to provide a more thorough evaluation of the seismic classification of site. A 100-foot deep boring was not required by the structural engineer due to size and height of the proposed structure.

8.0 SITE DRAINAGE AND MOISTURE PROTECTION:

Adequate site drainage is critical to reduce the potential for differential soil movement, erosion and subsurface seepage. Under no circumstances should water be allowed to pond adjacent to footings. The site should be graded and maintained such that surface drainage is directed away from structures. In additions, surface drainage should be directed away from the top of slopes into swales or other controlled drainage devices. Roof and pavement drainage should be directed into

File No. 1823-3C Page 35 conduits that carry runoff away from the proposed structure.

In case of basement walls or building walls retaining landscaping areas, a water proofing system should be used on the wall and joints, and a Miradrain drainage panel (or similar) should be placed over the waterproofing. The project architect or civil engineer should provide detailed specifications on the plans for all waterproofing and drainage.

Underground utilities should be leak free. Utility and irrigation lines should be checked periodically for leaks, and detected leaks should be repaired promptly.

Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.

9.0 ROAD PAVEMENT SECTION RECOMMENDATIONS:

All areas to be used as street shall be constructed over 1.5 ft. thick of selected fill material classified as A-2-4 or better material. Please note that whenever the fill thickness is greater than 1.5 ft. thick, the over excavation of the existing material is not required (except any existing vegetation, shrubs, grasses, and unstable material. One (1) feet depth of topsoil removal can be considered, excepted where any other foreign matter exists that could require deeper removal. Once the over excavation is made recompact the exposed grade to detect any surficial weak spots and place at least 1.5 ft. of a fill material classified as A-2-4 or better material properly placed and compacted until final sub base elevation is reached. A minimum 1.5 ft. thick of selected fill material is necessary at all areas below final sub-base elevation. Following the procedures of FILLING OPERATIONS

AND COMPACTION SECTION. If modification to grading is incorporated, we shall

File No. 1823-3C Page 36 be consulted to re-evaluate the submitted recommendations.

The use of an A-2-4 type of material properly placed and compacted at the road area of this project sub-base construction would permits the design of a flexible type of pavement based on a subgrade CBR value of about 25 to 30. This CBR values are based on experience with this type of material. However, the material to be used at the project must be tested to obtain its parameters by means of laboratory tests.

A pavement section is a layered system designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and traffic loadings. Soils are represented for pavement design purposes by means of a soil support value for flexible pavements and a modulus of subgrade reaction for rigid pavements. Both are empirical related to strength. The pavement design thickness shall be properly calculated by the project designer.

The purpose of using the A-2-4 material as sub-base is to increase the overall stiffness of the structure of asphalt pavements. The increase in the overall stiffness of the asphalt pavement reduce deflections thereof, thereby reducing efforts and unit deformations which increases the fatigue life of the asphalt layers. Being the sub-base, a friction material is less susceptible to moisture and significant deformation when cracks in the pavement eventually occur. Once established the sub-base, it is practically permanent and will not only be beneficial to the performance of the initial pavement layers but also for future paving asphalt layers when are eventually rehabilitated. Once established in the initial construction, it is practically impossible, if not difficult, replacing it.

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The proposed road area shall be design with its appropriate drainage and slopes to avoid accumulation of runoff water at the surface. A well-designed drainage system shall constitute an important part of the pavement design itself. A drainage system should be developed to control storm water run-off that may enter from outside or fall within the road curses. Concrete ditches along the roadways may prove to be efficient for collecting storm water run-off that develops on slopes.

However, the hydraulic capacity of these will govern their shape and size; therefore, hydrologic and hydraulic analyses shall be performed by the designer before sizing the necessary drainage structures.

10.0 PROTECTION OF EXCAVATIONS:

All Excavations at the site should be performed in accordance with 29 CFR

Part 1926, “Occupational Safety and Health Standards – Excavations; Final

Rule,” published by the U.S. Department of Labor, Occupational Safety and Health

Administration. Based on the information obtained from the soil borings drilled at the site, we classify the surficial soils as Type B soils. The contemplated excavation can be carried open by sloping the sides cuts a slope ratio 1:1 (H:V). Nevertheless, the excavation progress should be observed and evaluated to detect on time any local concealed underground condition to undertake any corrective measures if so found necessary to improve the cut slope stability. Stockpiles of excavated material should be setback from the edge of the excavation by distance at least equal to the excavation depth.

THE CONTRACTOR SHALL BE RESPONSIBLE FOR ALL TEMPORARY

EXCAVATIONS AT THE SITE. This includes the design of any required temporary slopes, dewatering, and shoring and bracing, as necessary.

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Positive surface gradients should be provided to divert surface runoff water away from excavations for foundations and constructions areas. Ponding of water should be avoided to reduce damage of properly graded areas.

11.0 CONSTRUCTION CONSIDERATIONS:

The following considerations shall be taken into account in the construction of this project.

1. The earthwork shall be conducted under the observation and inspection of a

Geotechnical Engineer or his representative working for the project owner.

2. All relocation of existing underground utilities should be completed before grading begins. The ends of abandoned underground utilities should be permanently sealed to prevent the inadvertent introduction of fluids into the construction area. Any underground utility not removed will be subjected to new pressures that can damage it and affect the new structure. Any septic tanks and drain fields within proposed construction areas and 20 feet outside the construction limits should be excavated and removed.

We recommend any / all utility lines be located outside of planned construction areas, the trenches cleaned of backfill soils, and, after utility emplacement, the trench backfilled with compacted fill. Past experience indicates utility trench backfill is often poorly compacted. Also, cracked or deteriorated pipes can collapse, leak or serve as conduits for subsurface erosion. Any of these conditions can result in excessive settlement of foundations and pavements.

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3. A Geotechnical Engineer from this office (Advanced Soil Engineering) shall observe the bottom of any excavation to verify its conditions with respect to those obtained with borings. Proof-rolling of the excavation bottom may be required, depending on the exposed ground conditions. Any old deleterious fill, organic matter, or soft spot of soil detected at the bottom of any excavation shall be removed and backfilled as specified in Appendix 3.

4. The project excavations shall proceed in an expedite manner to prevent such disturbance of the foundation soil, and they shall be performed under dry conditions. The contractor shall take the required provisions to prevent the seepage and accumulation of water (runoff or temporary groundwater) into the excavations.

5. This report is submitted for the planning and design of the project and it provides some construction considerations that shall be reviewed by the contractor. However, the contractor shall not use this report as the only information to base his bid for the project. This office shall not be held responsible if the contractor uses this information without limitations. The contractor bidding for this project should conduct a careful review of the geotechnical data and documents given in this report. However, we will not be responsible for his interpretation and conclusions made from these data.

The contractor shall visit the project area prior to bidding to become acquainted with the actual conditions of the site.

6. The contractor shall take care to prevent damage onto surrounding structures and utilities due to the construction operations.

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7. The contractor will be solely and completely responsible for his construction method, his method of excavation and support system, the working conditions at the job site, and the project safety measures. This requirement applies continuously, and it is not limited to normal working hours.

12.0 EXCAVATION PROCEDURES:

On the basis of the drilling effort rendered in advancing the test holes and the

“N” values recorded whenever sampling was attempted, all excavations should be performed by excavators, ripper and bulldozer to down grade the area to the required footing foundation base elevation. However, and given that the probability of uncovering isolated boulders or rock formations exists, the use of additional equipment like backhoes, heavy excavators, and / or hydraulic powered tools is likely to be required.

The geotechnical engineer for the project must be fully aware of the following utmost facts during the whole excavation process: first, though no ground water level has been recorded at any of the test borings along the site higher grounds nor any seepage or spring were noticed during our field inspections along said area, sometimes the like could show-up during the excavation process and/or at the long run. If this condition arises, further evaluation of the site development shall be considered at once to revise or modify the recommendations given. Some migrating bodies of infiltrated water may be encountered on excavations after prolonged rain events.

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13.0 SLOPE CONSTRUCTION:

All cut or fill slopes shall be constructed for a geometry not steeper than 2:1

(H:V) regardless of its height and shall be also protected against gully and laminar erosion by providing proper drainage facilities. Fill slope shall be design with a positive drainage to avoid water running over sloping ground. Immediately upon construction of the slopes (either on fill or cut), these shall be protected from the effects of erosion by adequate seeding and planting (erosion control blanket and vetiver grass). Initial maintenance of the fill and cut slopes and their protection shall be continued until stabilization has been assured. It is possible that shallow slope failures or channels caused by erosion may develop in the slopes (either on fill or cut). These shall be promptly fixed to prevent progressive worsening that may lead to large slope failures.

Always start filling from lower ground elevations and continue up the slope.

No down slope filling shall be allowed. As filling up the slope progresses, benches or terraces are to be cut into the receiving soil every meter difference in elevation.

Minimum width of terraces shall be 6.0 ft.

Adequate benching (6.0 feet wide at 15.0 feet maximum vertical spacing) shall be provided in all slopes. A concrete gutter (swale) shall be installed at these terraces along the toe of the resulting slopes to intercept their runoff. This gutter shall be connected to the storm drainage system of the project. There exists the possibility that moisture or temporary groundwater due to runoff percolating at upper grounds may daylight at fill and/or cut slopes or at the ground surface close to the slope toe. If this condition develops, an intercepting deep drain will be required to collect this water before reaching any nearby structure.

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The Contractor shall be responsible for providing with enough and capable equipment for achieving these activities in a timely and effective manner. The geotechnical site technician shall not and will not be in charge of surveying work.

Therefore, project owner surveyor shall impart instructions to contractor and project inspector so that our recommendations can be implemented where necessary.

Any relatively flat surface behind a slope shall be graded in such way as to collect the runoff and conduct in to the storm drainage system of the project. No runoff from these areas shall be discharge onto any slope, or water shall be allowed to pond on these surfaces or on any fill area.

Wherever horizontal space requirement for high earth fill embankments and natural cut slopes cannot be met (as per above slope ratio requirements), special engineered structures shall be provided in order to maximize its stability.

14.0 SITE IMPROVEMENTS:

The site preparation prior to any filling or construction operation is to consist of stripping the topsoil supporting any existing vegetation, shrubs, grasses, and unstable material. Depth of topsoil removal should average one (1) feet, excepted where any other foreign matter exists that could require deeper removal.

Any weak spot uncovered shall be fully excavated and its space replaced in uncompacted layers not exceeding eight (8) inches and each lift be imparted with a minimum percent of compaction of 95% of the fill material maximum dry density as obtained from laboratory compaction test conducted according to ASTM Standard

D-1157.

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The removal of the topsoil shall be performed under the direct supervision of a geotechnical engineer from this office (Advanced Soil Engineering Corp.) or his representative. The aerial extent and depth of removal shall be established by the soil inspector at the field.

All cut or fill slopes shall be constructed for a geometry not steeper than 2:1

(H:V). Steeper fill slopes are not recommended. Wherever horizontal space requirement for high earth fill embankments and natural cut slopes cannot be met

(as per above slope ratio requirements), special engineered structures shall be provided in order to maximize its stability.

15.0 FILLING OPERATIONS AND COMPACTION:

The fill layers required to reach final grading shall be placed and compacted following the recommendations below:

1) Remove any construction debris existing on the area prior to start any filling operation.

2) Place the fill material in layers not exceeding eight (8) inches and each layer shall be imparted with a degree of compaction of 95 percent of the maximum dry density as obtained from the Modified

Compaction Curve Test made according to ASTM D 1557.

3) The fill material shall consist of a non-expansive and inorganic soil material similar to a classification A-2-4 or better material approved by the consultant engineer.

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4) The placement and compaction of the fill layers shall be made under the direct supervision of a soils laboratory.

16.0 ADDITIONAL COMMENTS:

At the time of this report our project general analysis, evaluations and earthwork construction recommendations, have been formulated using preliminary drawings. We strongly recommend that the recommendations covered on this soil report be revised after grading, type of structure, loading condition, flexibility and final floor elevations have been established, so that revised final recommendations can be submitted for design and construction.

All recommendations herein given are based on the spot checks which constitute the test borings made within the investigated area of the parcel and were considered as representative subsoil conditions which are/or might be present along the project.

However, the fact does not exclude the disclosures of a different one that those found, once the construction phase alerts.

Any abnormal condition encountered between borings during the over excavation and construction phase, shall be notified to the soils engineer for further evaluation and to make the pertinent recommendations.

Advanced Soil Engineering (ASE) should be retained to review the project plans and specifications for conformance with the recommendations provided in our report. We are also available to assist the design team in preparing specifications

File No. 1823-3C Page 45 for geotechnical aspects of the project, and performing additional studies if necessary, to accommodate…