Bridge_No_7E_Geotechnical_Report_Final.pdf

Final Geotechnical Report (revised)

Bridge No. 7E Kaumualii Highway, Route 50

Kauai, Hawaii State of Hawaii

Prepared for Federal Highway Administration

Central Federal Lands Highway Division 12300 West Dakota Avenue

Lakewood, CO 80228

December 16, 2015

Hirata & Associates, Inc.

99-1433 Koaha Place

Aiea, HI 96701

9191 South Jamaica Street

Englewood, CO 80112-5946

W.O. 15-5684.1 Page ii

Contents Section Page

1.0 Introduction

1.1 Background and Location

1.2 Purpose and Scope

2.0 Geology and Seismicity

2.1 Regional Geology

2.2 Seismic Design Parameters

3.0 General Subsurface Characterization

4.0 Analysis and Recommendations

4.1 Bridge Foundation

4.1.1 Concrete Pile Axial Resistance

4.1.2 Pile Lateral Load Analysis

4.1.3 Predrilling

4.1.4 Pile Driving

4.1.5 Test Piles

4.2 Wing Walls

4.3 End Posts

4.3.1 Spread Footing Bearing Resistance

4.3.2 Footing Lateral Resistance

4.4 Lateral Design

4.4.1 Passive Earth Pressures

4.4.2 Active and At-rest Earth Pressures

4.4.3 Dynamic Lateral Earth Forces

4.4.4 Drainage

4.5 Bridge Approach Slab

4.6 Pavement Section

4.7 Corrosivity Test Results

4.8 Site Grading

4.8.1 Site Preparation

4.8.2 Structural Excavations

4.8.3 Slope Gradients

4.8.4 Onsite Fill Material

4.8.5 Imported Fill Material

4.8.6 Backfill for Bridge Abutment / Box Culvert and Wing Walls

4.8.7 Compaction

5.0 Special Contract Requirements

6.0 Additional Services

7.0 Limitations

W.O. 15-5684.1 Page iii

Appendixes

A Field Exploration Program & Boring Logs

B Laboratory Testing

C Analytical Report for Corrosivity Testing

HIRATA & ASSOCIATES, INC.

W.O. 15-5684.1 Page 1

1.0 Introduction

1.1 Background and Location

This report provides geotechnical recommendations for the Bridge No. 7E replacement located along Kaumualii Highway, Route 50, in the District of Koloa, Kauai, Hawaii. Bridge No. 7E is located at MP 6.95, approximately 0.3 miles southwest of the Maluhia Road and Kaumualii Highway intersection. Project vicinity and bridge photos are presented on Figures 1 and 2.

FIGURE 1

Project Vicinity Map

The Central Federal Lands Highway Division (CFLHD) of the Federal Highway Administration (FHWA), in cooperation with the Hawaii Department of Transportation is proposing to replace the existing approximately 23-feet long, 28-feet wide, two cell box culvert bridge over a (unnamed) channel to meet current design standards for roadway width, load capacity, pedestrian traffic, bridge railing and transitions, and bridge approaches.

The existing Bridge 7E was constructed in 1933. As-built plans indicate that the box culvert bridge is supported on 16-inch square concrete piles. We understand that Option 1 presented in the Structure Selection Memo, dated February 2015, will be selected for replacement of the existing two cell box culvert.

The replacement bridge will consist of a longer and wider single cell box culvert structure with plan dimensions of approximately 26 feet long by 44 feet wide. Wing walls of the new box culvert will extend out from the edge of the culvert structure about 20 to 25 feet. The new culvert is expected to have similar depth as the existing culvert. Final site grading was not available at the time of this report. The finish grades are expected to generally match existing grades. Besides fills for widening of the bridge approach, we assume that only minor site grading will be required for the project.

W.O. 15-5684.1 Page 2

FIGURE 2

Existing Bridge

1.2 Purpose and Scope

This report provides geotechnical recommendations based on engineering analyses of our subsurface investigation, including the general subsurface characterization, seismicity, boring logs, and laboratory test results. Geotechnical recommendations for the design of bridge abutments, wing walls, end posts, and site grading are presented in this report.

W.O. 15-5684.1 Page 3

2.0 Geology and Seismicity

2.1 Regional Geology

The Island of Kauai is composed of a single deeply eroded shield-shaped volcano with its associated intrusives, breccias, and tuff beds. These rocks and their remnants comprise the Waimea Canyon Volcanic Series, and were erupted during the late Tertiary Period. After the completion of the Kauai shield cone, there was a long period of erosion during which no volcanic activity occurred. The return of volcanic activity resulted in new volcanic rocks spread over large areas of the eroded surface. The products of this period and renewed volcanic activity, along with closely associated sedimentary rocks, are known as the Koloa Volcanic Series.

The Waimea Canyon Series forms the main bulk of the Island of Kauai. The product of this series is divided into four distinct formations: Napali, Olokele, Haupu, and Makaweli. The formations consist of thin-bedded primitive-type olivine basalts (a`a), and massive olivine basalts (pahoehoe) that ponded in calderas and graben.

The eastern half of the Island of Kauai is overlain with lava flows of the Koloa Volcanic Series. The lava flows consist of both pahoehoe and a`a formations extruded from groups of vents aligned in the north-south trends in various locales. The Koloa lava formation is underlain and interbedded with the Palikea formation, which consists of sedimentary breccias that grade laterally into stream-laid conglomerates resulting from the Waimea Canyon Series.

Changes in sea level during the Pleistocene Epoch caused the accumulation of deltas and fans of terrigenious sediments in the heads of Kauai's old bays, accumulation of reef deposits at correspondingly higher elevations, and lagoonal/marine sediments in the quiet waters protected by fringing reefs.

The project site is located in southern portion of the Island of Kauai. The site lies within lavas of the Koloa Volcanic Series. The project site generally consists of recent alluvium resulting from material being transported to sea. Underlying the alluvial soils at deeper depths is basaltic rock built by the extrusion of lavas of the Koloa Volcanic Series. These formations are generally characterized by flows of jointed vesicular basalt interbedded with seams of clinker.

2.2 Seismic Design Parameters

Based on the AASHTO site classification criteria, the predominant soils at the bridge site located at 21.9484o

N latitude and -159.4695o W longitude can be classified as a soft soil profile corresponding to a Seismic Site Class E.

Recommended seismic response parameters for use in design based on 7th Edition of the AASHTO LRFD Bridge Design Specifications represents ground motion corresponding to an exceedance probability of approximately 7 percent in 75 years for an earthquake with an approximate 1000-year return period. The 1000-year return period data for the soil at the bridge site was obtained in accordance with the AASHTO ground motion maps for the probabilistic horizontal acceleration values corresponding to specific peak ground acceleration (PGA) and the spectral coefficients, namely the short and long-period ground acceleration (SS and S1 respectively), and are summarized in Table 1.

W.O. 15-5684.1 Page 4

TABLE 1

Summary of Seismic Parameters for Earthquake with 1000-Year Return Period

Horizontal Peak Ground Acceleration, (PGA) 0.063g Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SS) 0.138g Horizontal Response Spectral Acceleration at Period of 1.0 sec, (S1) 0.040g

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 2.5 Site Factor at Short-Period Range of Acceleration Spectrum, (Fa) 2.5 Site Factor at Long-Period Range of Acceleration Spectrum, (FV) 3.5

Factored Horizontal Peak Ground Acceleration, (AS) 0.157g Factored Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDS) 0.344g Factored Horizontal Response Spectral Acceleration at Period of 1.0 sec, (SD1) 0.140g

Seismic Zone Zone 1

W.O. 15-5684.1 Page 5

3.0 General Subsurface Characterization

Table 2 presents a summary of the subsurface characterization. Boring logs and laboratory test results are presented in the Appendixes A and B.

TABLE 2

Summary of Subsurface Materials for Foundation Design Purposes

Subsurface Depth

(ft) Material Description USCS

Classification Apparent Density

Ground Water Depth

(ft)

BORING 7E1 (ELEVATION +641) – WEST ABUTMENT, BRIDGE 7E

0.0 to 14.0 Clayey SILT MH Medium stiff to soft

13.5

14.0 to 18.0 Clayey SILT MH Medium stiff

18.0 to 22.0 CEMENTED SILT with boulders -- Dense to medium hard

22.0 to 63.0 Clayey SILT with sand and weathered rock fragments MH Medium stiff to soft

63.0 to 77.5 BASALT WS-WM Dense to medium hard

77.5 to 89.0 BASALT WM Hard

BORING 7E2 (ELEVATION +640) – EAST ABUTMENT, BRIDGE 7E

0.0 to 17.0 Clayey SILT MH Medium stiff to soft

14.8

17.0 to 25.0 Cemented SILT with cobbles and boulders -- Dense to medium hard

25.0 to 47.5 Clayey SILT with sand and weathered rock fragments MH Medium stiff to soft

47.5 to 53.0 BASALT WM Hard

W.O. 15-5684.1 Page 6

TABLE 2 (continued) Summary of Subsurface Materials for Foundation Design Purposes

Subsurface Depth

(ft) Material Description USCS

Classification Apparent Density

Ground Water Depth

(ft)

BORING 7E3 (ELEVATION +639) – WEST ABUTMENT, BRIDGE 7E

0.0 to 5.0 Clayey SILT MH Medium stiff

10.1

5.0 to 17.0 Clayey SILT MH Soft to medium stiff

17.0 to 21.0 Cemented SILT with cobbles and boulders -- Medium hard

21.0 to 66.0 Clayey SILT with sand and weathered rock fragments MH Soft to stiff

66.0 to 73.5 BASALT WM Medium hard

BORING 7E4 (ELEVATION +639) – WEST ABUTMENT, BRIDGE 7E

0.0 to 5.0 Clayey SILT MH Medium stiff

9.9 5.0 to 67.0 Clayey SILT with sand and weathered rock fragments MH Soft to stiff

67.0 to 78.0 BASALT WM Hard

W.O. 15-5684.1 Page 7

4.0 Analysis and Recommendations

This section provides a general interpretation of the site investigation and provides recommendations for design parameters at the proposed structure. Generalized subsurface profiles were developed based on data collected during the investigation. The primary structure considered for this project is replacing the existing two cell box culvert bridge structure with a longer and wider single cell box culvert bridge structure.

Our test borings indicate that the bridge site is underlain by soft and moderately compressible clayey silt soils at depths around the invert elevation of the box culvert. The soft soil extended down to depths ranging from about 40 to 67 feet below existing roadway elevation, underlain by stiffer soil and basalt at deeper depths. This finding is consistent with the fact that the existing box culvert is supported on pile foundations.

A thin layer of cemented silt with boulders was encountered in some of our test borings at depths of about 17 to 18 feet below the existing roadway. Some of the old boring logs described it just as a boulder layer.

Alternatives to support the new culvert bridge structure on shallow foundations founded either directly on that cemented silt layer or on structural fill placed on top of the cemented layer were considered. However, this will require relocation of the existing underground fiber optic communication line located adjacent to the existing box culvert on the north. In addition, based on our borings and review of old boring logs by others, the cemented silt with boulders layer was in a variable condition. The thickness of the cemented silt layer was as thin as only 2 feet in many of the old boring logs, and was absent in our boring 7E4. Removing the in-situ soft soil down to 18 feet below the roadway will also require shoring and dewatering as ground water was encountered in our test borings at depths of about 9 to 14 feet. Furthermore, settlement can be expected if the culvert bridge is supported on shallow foundations over the soft soils. Preliminary analysis resulted in estimated settlements as much as 5 to 6 inches. As a result, it is our opinion that it may be prudent to support the new culvert bridge on deep foundations.

4.1 Bridge Foundation

Based on as-built drawings dated 1933, the existing culvert bridge structure is supported on 16-inch square concrete piles, with wings walls cantilevered out from the culvert structure. Due to the underlying soft soils, deep foundations are recommended for support of the proposed Bridge No. 7E replacement.

Recommendations are presented based on the use of 16.5-inch octagonal precast, prestressed concrete piles.

4.1.1 Concrete Pile Axial Resistance

The 16.5-inch octagonal precast, prestressed concrete piles will derive their axial load bearing resistance primarily from end-bearing on the basalt layer underlying the soft and compressible clayey silt. Based on local practice, the following pile axial bearing resistances are recommended for design. Bearing resistance factors are based on Table 10.5.5.2.3-1 in the 7th Edition of the AASHTO LRFD Bridge Design Specifications, and the applied strength limit state resistance factor is 0.65, assuming that pile load testing will be performed. Resistance factors for extreme event limit state and service limit state will be 1.0. Piles should be spaced a minimum 3 pile diameters apart, measured from center to center. Settlement of concrete piles end-bearing on medium hard to hard basalt is expected to be negligible.

TABLE 3

Pile Axial Bearing Value

Extreme Event Limit State 400 kips Strength Limit State 260 kips

W.O. 15-5684.1 Page 8

The depth to the basalt layer varies, ranging from approximately +572 to +592.5 at our boring locations. For cost estimating purposes, a conservative pile tip elevation of +570 is recommended. Based on a bottom of pile cap elevation of 626.93±, a pile length of 60 feet is recommended for preliminary cost estimating purposes. A better estimate of pile lengths required for production driving can be provided after the indicator test pile driving program. The piles should be driven to refusal (20 blows per inch) or until the minimum blow counts determined by Wave Equation Analysis is achieved.

4.1.2 Pile Lateral Load Analysis

The following presents the computed lateral load resistance and maximum induced bending moments in the concrete piles for various pile head conditions and lateral deflections at the pile top. Analyses were performed using the computer program LPILE (Ensoft, Inc.). For our analyses, the piles were assumed to be embedded in a soft clayey silt soil layer having an average undrained shear strength of 500 psf. The piles were assumed to be spaced a minimum 3 pile diameters apart. Final layout of the pile foundations was not available at the time of this report. Preliminary plans in the Structure Selection Memo indicated that the new box culvert will be supported on a single row of 6 piles at each end. As a result, a pile group reduction factor of 0.8 was assumed for the longitudinal direction of the bridge, and an average reduction factor of 0.4 was assumed for the transverse direction. An axial load of 200 kips was assumed in the analyses. Based on Table 10.5.5.2.3-1 in the 7th Edition of the AASHTO LRFD Bridge Design Specifications, the applied strength limit state resistance factor is 1.0.

Table 4 Pile Head Deflection, Lateral Load, and Maximum Induced Moment

Deflection at Pile Top (in.)

Shear (kips)

Computed Max.

Moments (ft-kip)

Depth to Max.

Moments (ft)

Longitudinal Direction, Free Head, Vertical Load = 200 kips

0.25 5.6 26.5 8

0.5 8.1 43.5 9

1.0 11.5 71.4 10

Longitudinal Direction, Fixed Head, Vertical Load = 200 kips

0.25 12 68.4 0

0.5 17.1 107.1 0

1.0 23.1 149.6 0

W.O. 15-5684.1 Page 9

Table 4 (continued) Pile Head Deflection, Lateral Load, and Maximum Induced Moment

Deflection at Pile Top (in.)

Shear (kips)

Computed Max.

Moments (ft-kip)

Depth to Max.

Moments (ft)

Transverse Direction, Free Head, Vertical Load = 200 kips

0.25 3.4 19.6 9.5

0.5 4.9 32.2 10.5

1.0 6.9 52.9 11.5

Transverse Direction, Fixed Head, Vertical Load = 200 kips

0.25 7.4 49.9 0

0.5 10.7 80.7 0

1.0 15.0 122 0

4.1.3 Predrilling

Predrilling is recommended to facilitate driving pile through the cemented silt with boulder layer encountered in our borings at elevations ranging from about +623 to +615. For preliminary cost estimating purposes, predrilling to elevation +610 at all pile location may be assumed. The diameter of the predrilled holes should be only slightly larger than the maximum pile diameter, but large enough to facilitate backfill of the annular space between the pile and predrilled hole. Rock drilling and coring equipment, as well as tools necessary for removal of the cored material, may be required to predrill through boulders, especially for large boulders such as those encountered in boring 7E2. The annular space between the pile and sidewalls of the predrilled hole should be backfilled with clean sand, compacted by water jetting or with sand-cement grout.

4.1.4 Pile Driving

The piles should be driven with a hammer capable of delivering energies in the range of approximately 20,000 to 53,000 foot-pounds of energy per blow. To prevent development of excessive stresses in the piles during the driving operations, the hammer energy (or stroke) should be carefully controlled during the initial stages of pile driving where the pile tip is within the soft soil layer. The minimum driving resistance required will depend on the type of hammer and pile driving equipment used. The contractor should conduct drivability studies to select hammers that will not cause the driving stresses (compression and tension) in the pile to exceed acceptable levels.

4.1.5 Test Piles

Indicator test piles should be driven to help determine production pile lengths and pile driving criteria. In general, approximately 10 percent of the total number of piles for the project should be driven during the indicator test pile driving operations. However, the number of test piles at each end of the bridge should be at least 3. The locations of the indicator test piles should be spread out to provide good coverage of all pile locations.

Indicator test piles should be at least 10 feet longer than that estimated for production piles and should be driven with the same hammer which will be used for production pile driving. The test driving should be

W.O. 15-5684.1 Page 10 monitored by an engineer from our staff. Our office should be notified of any unexpected conditions encountered during the test driving operations, so any necessary changes can be reviewed by us.

Load testing is recommended to confirm the ability of the subsurface soils to support the design pile axial resistance and the pile driving criteria. Load testing can be either a static load test, or a dynamic pile test consisting of monitoring the indicator pile driving with a pile driving analyzer (PDA) and Signal Matching program analyses. The dynamic testing should be performed on all indicator test piles. The tests should be performed in general accordance with ASTM D 4945. Signal Matching program analyses should be performed to confirm the load resistance of the piles at the end of the test driving program.

Since PDA and Signal Matching program analyses are not readily available in Hawaii, a static load test may also be considered. The static load test should be performed on one of the indicator test piles. The load test pile should be subjected to at least 100 percent of the design pile bearing resistance at extreme event limit state. The location of the load test pile should be determined by the construction officer after the indicator test pile program during construction.

4.2 Wing Walls

Based on the invert elevation of the proposed bridge culvert, the maximum wall height is estimated to be about 14 feet. Due to the underlying soft soil, we recommend that the wing walls also be supported on pile foundations. Recommendations presented in the Bridge Foundation section of this report may be used for design. The wing walls should be designed to resist the lateral earth pressures presented in the Lateral Design section of this report.

4.3 End Posts

If needed, spread footings may be used to support the end posts/concrete barriers. Foundations for the end post/concrete barrier are expected to be founded on either new fill or the onsite surface clayey silt. To provide more uniform support, we recommend that all footings be underlain by a minimum 12 inches of aggregate base course. The base course should be compacted to a minimum 95 percent compaction as determined by AASHTO T-180 (ASTM D 1557). The subgrade soil should be compacted to a minimum 90 percent compaction. Soft or loose soils, indicated by pumping conditions, should be removed and replaced with aggregate base course or imported granular structural fill.

4.3.1 Spread Footing Bearing Resistance

Based on our borings, the near surface clayey silt is in a medium stiff condition. The following bearing values are recommended for design of the footings. The bearing resistance factors are based on Table 10.5.5.2.2-1 in the 7th Edition of the AASHTO LRFD Bridge Design Specifications, and the applied strength limit state resistance factor for bearing resistance is 0.45. An allowable bearing resistance of 2,500 psf is recommended for service limit state in order to limit the potential settlement to less than 1-inch.

TABLE 6

Bearing Value for End Post Foundations

Extreme Event Limit State 7,500 psf

Strength Limit State 3,375 psf

Service Limit State 2,500 psf

W.O. 15-5684.1 Page 11

Spread footings should be a minimum of 24 inches in width and embedded at least 24 inches below finish adjacent grade. Footings located on or near the top of slopes should be embedded such that a minimum horizontal distance of 6 feet is maintained between the bottom edge of footing and slope face. The bottom of footing excavations should be thoroughly cleaned of loose material prior to placement of reinforcing steel and concrete.

4.3.2 Footing Lateral Resistance

Resistance to lateral loading may be provided by friction acting at the base of foundations and by passive earth pressure acting on the buried portions of foundations. The following coefficients of friction are recommended. Resistance factors are based on Table 10.5.5.2.2-1 in the 7th Edition of the AASHTO LRFD Bridge Design Specifications. The applied strength limit state resistance factor for coefficient of friction is

0.80. Passive earth pressures are presented in the Lateral Design section of this report.

TABLE 7

Coefficient of Friction

Coefficient of Friction for Extreme Limit State 0.53

Coefficient of Friction for Strength Limit State 0.43

4.4 Lateral Design

In addition to the lateral resistance of vertical concrete piles, resistance to lateral loading may also be provided by passive earth pressure acting on the buried portions of the box culvert and pile caps. The following soil parameters were used to determine the earth pressures for design.

TABLE 8

Summary of Material Property for Design

Material Description Unit Weight (pcf)

Cohesion (psf)

Friction Angle (deg)

Structural Fill 130 0 34

Onsite Clayey Silt 105 200 28

4.4.1 Passive Earth Pressures

Passive earth pressures were computed using the Log-Spiral Method. A wall friction angle value equal to 1/2 times the soil’s friction angle was used. Based on the computed values and local practice, the following passive earth pressures are recommended. Resistance factors are based on Table 10.5.5.2.2-1 in the 7th Edition of the AASHTO LRFD Bridge Design Specifications. The applied strength limit state resistance factor for passive pressure resistance is 0.5. Unless covered by pavement or concrete slabs, the upper 12 inches of soil should not be considered in computing lateral resistance.

TABLE 9

Passive Pressure

Soil Type Extreme Event Limit State (pcf)

Strength Limit State (pcf)

Onsite Clayey Silt 440 220

W.O. 15-5684.1 Page 12

4.4.2 Active and At-rest Earth Pressures

Active earth pressures were computed using the Coulomb Criteria. Based on the computed values and local practice, the following active earth pressures are recommended. In general, a movement of as much as 0.5 percent of the wall height at the top of wall by rotation or lateral translation may be required to reach the active pressure condition. Walls that are not free to deflect sufficiently to permit development of active earth pressure should be designed using the at-rest condition.

TABLE 10

Active / At-rest Pressures

Material Description

Level Backfill

Condition (pcf)

Maximum 2H:1V Sloping Backfill

Condition (pcf)

Restrained / At-Rest

Level Condition (pcf)

Structural Fill 33 52 57

Onsite Clayey Silt 35 65 56

4.4.3 Dynamic Lateral Earth Forces

For dynamic lateral earth pressure considerations, the following dynamic lateral forces may be assumed for seismic loading with maximum peak ground acceleration (amax) of 0.157g. The recommended dynamic lateral force for unrestrained condition assumes that the wall is free to move laterally up to 1 to 2 inches or rotate in the event of an earthquake. The dynamic lateral force may be assumed to act through the mid-height of the wall.

TABLE 11

Dynamic Lateral Earth Forces (Level Backfill Condition)

Wall Height, H (ft)

Backfill Material

Un-Restrained Condition

Restrained Condition

6 Structural Fill 11.4H2 14.7H2

10 Structural Fill 14.8H2 18.1H2

14 Structural Fill 16.2H2 19.7H2 Note: The dynamic lateral earth force has a unit of pounds per lineal foot of wall length.

TABLE 12

Dynamic Lateral Earth Forces (2H:1V Sloping Backfill Condition)

Wall Height, H (ft)

Backfill Material

Un-Restrained Condition

Restrained Condition

6 Structural Fill 17.7H2 25.8H2

10 Structural Fill 23.8H2 35.1H2

14 Structural Fill 26.8H2 40.9H2 Note: The dynamic lateral earth force has a unit of pounds per lineal foot of wall length.

W.O. 15-5684.1 Page 13

The above dynamic lateral earth forces included the static earth pressures and were based on procedures in Section A11.3.2 of the 7th Edition of the AASHTO LRFD Bridge Design Specifications. For un-restrained condition, kh equals to 1/2 times the maximum peak ground acceleration was used. For restrained condition, kh equals to maximum peak ground acceleration.

4.4.4 Drainage

To prevent buildup of hydrostatic pressures, retaining walls should be well-drained. The standard of practice consists of placing a minimum 12-inch thick layer of free-draining gravel at the back of the wall. The gravel should extend from the base of the wall, around subdrains and/or weepholes, and up to within 12 inches of finish grade.

Alternatively, prefabricated drainage geocomposites, such as Miradrain or J-drain, may be used in lieu of the free-draining gravel. As with the free-draining gravel, the drainage geocomposites should be placed at the back of the wall, be connected with the weepholes and/or subdrains (in accordance with manufacturers specifications), and extend to within 12 inches of finish grade. For freestanding walls, the drainage system should be covered by at least 12 inches of low permeability soil, such as silty clay or clayey silt with low expansion potential.

4.5 Bridge Approach Slab

We understand that approach slabs will be constructed behind the bridge abutments. The slabs should be underlain by at least 8 inches of aggregate base course. The base course and subgrade should be compacted to a minimum 95 percent compaction as determined by AASHTO T-180 (ASTM D 1557). The subgrade soil should be compacted to a minimum 90 percent compaction.

4.6 Pavement Section

The AC concrete pavement encountered in borings 7E1 and 7E2 consisted of approximately 8 and 9 inches of asphaltic concrete over approximately 13 and 12 inches of base material, respectively.

Due to the relatively short length of pavement for bridge approaches, based on discussions with Central Federal Lands Highway Division, we understand that new pavement will generally match the existing pavement sections identified in the borings.

4.7 Corrosivity Test Results

Soil samples from boring 7E1 obtained at depths of 3, 9, 14, and 19 feet were tested for alkalinity, chlorides, pH, sodium, sulfates, and sulfides to determine the corrosion potential of the subsurface soils. The tests were performed by TestAmerica in Honolulu, Hawaii, and are presented in Appendix C. The following is a summary of the test results.

W.O. 15-5684.1 Page 14

TABLE 13

Summary of Corrosivity Test Results

Depth (ft)

Alkalinity (mg/Kg)

Bicarbonate Alkalinity (mg/Kg)

Chloride (mg/Kg)

PH

(SU)

Sulfate (mg/Kg)

Sulfide (mg/Kg)

Sodium (mg/Kg)

3 1,500 1,500 7.9 6.22 -- 110 --

9 2,400 2,400 5.6 6.75 -- -- --

14 -- -- 5.3 6.20 19 -- --

19 1,900 1,900 6.3 6.21 140 -- 1700

4.8 Site Grading

4.8.1 Site Preparation

The project site should be cleared of all vegetation, AC pavements, and other deleterious material. Prior to fill placement, the existing ground should first be scarified to a depth of six inches, moisture conditioned to about 2 percent above optimum moisture content, and compacted to a minimum 90 percent compaction as determined by AASHTO T-180 (ASTM D 1557). Soft or loose soils, indicated by pumping conditions, should be removed and replaced with imported granular structural fill.

It is anticipated that the subgrade soil at the invert elevation of the box culvert will be relatively soft and wet. To provide a working based under the box culvert, 12 to 18 inches of clean gravel underlain by a geotextile filter fabric is recommended.

4.8.2 Structural Excavations

Based on our exploratory test borings, we believe that excavations into the surface clayey silt can be accomplished with conventional excavating equipment. Temporary cuts should be stable at slope gradients of 1H:1V (horizontal to vertical) or flatter for temporary conditions. Shoring may be required for excavations extending into the soft/loose deposits below groundwater. It should be the Contractor’s responsibility to conform to all OSHA safety standards for excavations.

4.8.3 Slope Gradients

All cut and fill slopes should be stable at gradients of 2H:1V or flatter. All slopes should be planted as soon as practical to reduce the effects of erosion and weathering.

Fill slopes should be constructed from the bottom up. Fill placed on slopes should be keyed and benched into the existing slope to provide stability for the new fill against sliding. Filling the slope with sliver fills should be avoided. Fill placed in areas which slope steeper than 5H:1V should be continually benched as the fill is brought up in lifts. Fill slopes should be constructed by overfilling and cutting back to the design slope gradient to obtain a well-compacted slope face.

4.8.4 Onsite Fill Material

The onsite clayey silt above groundwater table may be reused in compacted fills and backfills, provided all rock fragments larger than 3 inches in maximum dimension are removed. In addition, the moisture content of the clayey silt should be maintained at about 2 percent above the optimum moisture content during

W.O. 15-5684.1 Page 15 recompaction. The insitu moisture of the surface clayey silt was relatively high, and as a result, air-drying of the soil may be required prior to recompaction.

4.8.5 Imported Fill Material

Imported structural fill should be well-graded, non-expansive granular material and conform to FP-14 704.04 with modifications presented in 5.0 Special Contract Requirements section of this report.

4.8.6 Backfill for Bridge Abutment / Box Culvert and Wing Walls Backfill for the bridge culvert structure should consist of granular structural fill such as the imported structural fill.

4.8.7 Compaction

Structural fill, granular backfill, and granular embankment fill should be placed in horizontal lifts restricted to 8 inches in loose thickness and compacted to a minimum 95 percent compaction as determined by AASHTO T-180 (ASTM D 1557). Fill consisting of cohesive soils such as the onsite clayey silt should be placed in horizontal lifts restricted to 8 inches in loose thickness and compacted to a minimum 90 percent compaction.

Fill placed in areas which slope steeper than 5H:1V should be continually benched as the fill is brought up in lifts. Fill placed on slopes should be keyed and benched into the existing slope to provide stability for the new fill against sliding.

W.O. 15-5684.1 Page 16

5.0 Special Contract Requirements

Section 551. — DRIVEN PILES

551.03 Qualifications.

(a) Professional engineer. Delete the text and substitute the following:

Name of Hawaii licensed civil engineer specializing in geotechnical engineering and a resume describing at least 3 years’ experience in wave equation analyses to perform the wave equation analysis.

551.06 Pile Lengths. Delete the Subsection and substitute the following:

551.06. Pile Lengths. Furnish piles with sufficient length to obtain the required resistance and to extend into the pile cap or footing as indicated in the plans. Furnish test piles at least 10 feet longer than the estimated length of production piles. In addition, increase the length to provide fresh heading and to provide for the Contractor’s method of operation. When test piles are required, furnish piles in the lengths determined by the test piles.

551.07 Test Piles. Delete the first paragraph and substitute the following:

Excavate the ground at the site of each test pile or production pile to the elevation of the bottom of the footing before the pile is driven, unless otherwise accepted by the CO. Furnish test pile at least 10 feet longer than the estimated length of production piles. Drive test piles with the same equipment as the production piles.

551.09 Preboring. Delete the Subsection and substitute the following:

551.09 Preboring. Use augering, wet rotary drilling, coring, or other approved methods of predrilling. Expect boulders to be encountered in predrilling.

Prebore all pile locations to the depths specified in the plans, or to elevation +610, or as directed by CO.

Prebore holes to the least dimension adequate for pile installation. Fill remaining void space around the pile with sand, grout, or other approved material after driving is complete. Do not use a punch or a spud instead of preboring.

Do not impair the capacity of existing piles or the safety or condition of adjacent structures. If preboring disturbs the capacity of previously installed piles or structures, restore the required nominal capacity of piles and structures by approved methods.

551.13 Pile Load Tests. Delete the first paragraph and substitute the following:

Either perform dynamic load tests on all test piles or conduct static load test on a test pile selected by CO.

(b) Static load tests.

(1) Delete the text and substitute the following:

Have a Hawaii licensed structural engineer prepare the drawings;

W.O. 15-5684.1 Page 17

Section 704.04 Structural Backfill. Furnish a suitable, well-graded, non-expansive granular material conforming to the following:

(a) Maximum particle size 3 in (75 mm)

(b) Material passing No. 200 (75-µm) between 8 and 20 percent sieve, AASHTO T 27 and AASHTO T 11

(c) Plasticity index, AASHTO T 90 10 max.

(d) California Bearing Ratio, AASHTO T 193 CBR value, 15 min.

(ASTM D 1883) CBR expansion value, 1.0 percent max.

W.O. 15-5684.1 Page 18

6.0 Additional Services

We recommend that we perform a general review of the final design plans and specifications. This will allow us to verify that the foundation design and earthwork recommendations have been properly interpreted and implemented in the design plans and construction specifications.

For continuity, we recommend that we be retained during construction to (1) observe all pile driving work, including predrilling, indicator test pile driving, and load testing, (2) observe footing excavations prior to placement of aggregate base course layer, reinforcing steel and concrete, (3) review and/or perform laboratory testing on import borrow to determine its acceptability for use in compacted fills, (4) observe structural fill placement and perform compaction testing, and (5) provide geotechnical consultation as required.

Our services during construction will allow us to verify that our recommendations are properly interpreted and included in construction, and if necessary, to make modifications to those recommendations, thereby reducing construction delays in the event subsurface conditions differ from those anticipated.

Appendix A Field Exploration Program & Boring Logs

Plate A1.1

Appendix A: Field Exploration Program & Boring Logs

A1.0 Introduction Hirata & Associates, Inc. completed a field exploration program for Bridge No. 7E, Kaumualii Highway, Route 50, District of Koloa, Island of Kauai, State of Hawaii, Task Number 499069.10.SU.HI, from September 9 through 12, and October 29 through November 7, 2014, for the new bridge. The scope of work for the field exploration program for the new bridge included drilling two borings. The scope of work also included two borings for the proposed detour bridge, which were performed from November 18 through 26, 2014. Each component of the field exploration program was coordinated and observed by a Geotechnical Engineer from Hirata & Associates, Inc. Boring location plans, as well as individual boring logs are attached. These logs represent a compilation of field data and description of the soil samples by Hirata & Associates, Inc.

personnel. The methods used to conduct the field exploration program are described below.

Representative soil and rock samples collected during the field exploration program were transported to Hirata & Associates, Inc. in Aiea, Oahu, Hawaii for testing. A summary of the laboratory testing program is provided in Appendix B.

A2.0 Explorations Hirata & Associates, Inc. of Aiea, Oahu, Hawaii provided the drilling services for the soil borings. Borings were completed using Mobile B80 and B40-L12 truck-mounted drill rigs, and skid-mounted drilling equipment.

The borings for the new bridge were drilled from September 9 through 12, 2014, and from October 29 through November 7, 2014. Two borings at the rear of existing bridge abutments, 7E1 and 7E2, were completed to depths of about 53 and 89 feet below ground surface to explore subgrade conditions. The borings for the proposed detour bridge were drilled from November 18 through 26, 2014. Two borings at the proposed detour bridge abutments, 7E3 and 7E4, were completed to depths of about 73.5 and 78 feet below ground surface to explore subgrade conditions. Borings were drilled and sampled using continuous flight solid stem augers and continuous sample rock coring techniques.

The locations of individual borings were located in the field by measuring/taping offsets from existing features shown on the plans. Boring locations are shown on the Boring Location Plan, Plate A2.2, and are shown below in Table A-1. Surface elevations at boring locations were estimated based on the Topographic Survey provided by CH2M Hill received on December 4, 2014. Following drilling activities, the borings were backfilled with cuttings generated during the drilling operations and borings 7E1 and 7E2 were capped with “Instant Road Repair” by International Roadway Research.

Plate A1.2

TABLE A-1

Field Exploration Locations

Foundation Designation

Boring Number Station Offset

Ground Elevation

Termination Elevation

Basalt Elevation

West Abutment 7E1 106+54.2 6.55 LT 641 ft 552 ft 578 ft

East Abutment 7E2 106+95.1 7.01 RT 640 ft 587 ft 592.5 ft

Detour Bridge W Abutment 7E3 106+35.5 39 LT 639 ft 565.5 ft 573 ft

Detour Bridge E Abutment 7E4 107+14 54 LT 639 ft 561 ft 572 ft

A3.0 Soil and Rock Sampling Representative samples were obtained using a modified California (MC) barrel sampler in general accordance with ASTM D 3550. The MC test procedure involves driving a 3-inch outside diameter sampler lined with 2.42-inch-diameter brass sleeves to a depth of 18 inches with a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampler through each of the 6-inch increments was recorded. The MC resistance, or 3-inch N-value, is defined as the number of blows required to drive the sampler over the second and third 6-inch increments. The N-value provides a means for evaluating the relatively density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine-grained) soils. Because high penetration resistance prevented driving the total length of the sampler at times, the penetration resistance for the partial penetration was recorded where applicable.

As a result of the larger diameter barrel sampler compared to the Standard Penetration Test (SPT) sampler, the MC sampler yields slightly higher raw blow counts when compared to SPT N-values for similar soils. The raw MC blow counts over the second and third 6-inch increments were used to define the relative density and consistency of the subsurface materials. MC samples were sealed with plastic end caps and transported to Hirata & Associates, Inc. for testing.

A bulk soil sample was recovered from boring 7E3 at a depth of about 1 foot below ground surface. The bulk soil sample was placed in a plastic bag and transported to Hirata & Associates, Inc. for testing.

Rock samples were collected from borings using a NX core barrel having an inside diameter of 2.1 inches.

During coring, cuttings were removed from the borehole by circulating water down the drill rods and back up the annulus of the boring. Core runs ranged between approximately 2 and 5 feet in length. Percent recovery and rock quality designation (RQD) values are shown on the boring logs. Percent recovery is the ratio of the length of recovered core to the total length of the core run. RQD is the ratio of the sum of the length of intact core pieces greater than 4 inches long in a run to the total length of the core run. Following drilling, the cores were logged by Hirata & Associates, Inc. personnel, then stored in cardboard core boxes and transported to the Hirata & Associates, Inc. laboratory.

A4.0 Soil and Rock Classification System During the completion of borings, Hirata & Associates, Inc. personnel collected soil/rock samples and prepared field logs of the borings. Soil identification and descriptions, as shown on the field logs, are based on ASTM D2488, a systematic process for identifying and describing individual soil samples by visual and manual means. When sufficient laboratory testing was completed, select samples from borings were classified using the Unified Soil Classification System (USCS). Both the visual soil identification system and

Plate A1.3 the referenced soil classification systems are summarized in the attached Boring Log Legend and USCS plates. Rock samples were classified based on the stratigraphic structure, rock strength, degree of weathering, and other properties. The rock classification system is summarized in the attached Rock Weathering Classification System.

Plate A6.1

Appendix B Laboratory Test Results

Plate B1.1

Appendix B: Laboratory Test Results

B1.0 Introduction Laboratory tests were completed on select soil and rock samples recovered from the field exploration program in general accordance with ASTM testing methods. The laboratory testing program was completed to provide data for engineering studies and to classify the materials into similar geologic groups. The testing program included index tests and geotechnical engineering property tests. The following sections describe the laboratory testing procedures and test results are presented in the attached laboratory reports.

B2.0 Index Tests Classification and index laboratory testing included identification by visual and manual means, and tests to determine natural water content, unit weight, and Atterberg limits. When sufficient laboratory testing was completed, select samples from borings were classified using the Unified Soil Classification System (USCS). Both the visual soil identification system and the referenced soil classification system are summarized in the Boring Log Legend and USCS plates in Appendix A. The final classifications are shown at the appropriate locations on the Boring Logs, Plates A4.1 through A4.11. Index tests are generally conducted on disturbed soil samples. The following sections describe individual index test procedures.

B2.1 Moisture Content Water content was determined for samples retrieved from the exploration in general accordance with ASTM D 2937. To perform this test method, the sample was weighed before and after oven drying, and the water content was calculated. The moisture content of soils, when combined with data obtained from other tests, provides information about the characteristics of the soil, including general correlations with strength, settlement, and workability.

B2.3 Atterberg Limits Liquid and plastic limit tests were performed on selected fine-grained samples. The tests were completed in general accordance with ASTM D 4318. The Atterberg limits include liquid limit (LL), plastic limit (PL), and plasticity index (PI), which is the plastic limit subtracted from the liquid limit. The results of these tests are presented on the USCS plate in Appendix A, and in the following table. These limits are generally used to assist in classification of soils, to indicate soil consistency, and to provide correlation to engineering properties.

TABLE B-1

Atterberg Limit Test Results

Sample Liquid Limit (LL) Plastic Limit (PL) Plasticity Index (PI) 7E2 at 34 feet 75 48 27 7E4 at 3 feet 51 41 10 7E4 at 9 feet 53 46 7

Plate B1.2

B3.0 Geotechnical Engineering Property Tests For Soil Geotechnical engineering property testing for soil included Moisture-Density, Modified Proctor, and Direct Shear tests. Geotechnical engineering property test results are presented in the attached laboratory reports. The following sections describe these test procedures for soil.

B3.1 Moisture-Density In the construction of highway embankments, retaining walls, structure foundations, and many other facilities, loose soils may be compacted to increase their density, strength, and stiffness characteristics.

The results of the moisture-density test provide the maximum dry density attainable under a specified compaction energy for a given soil and the moisture content corresponding to this density. These results of this test aid in the construction quality assurance of compacted soils.

The moisture-density (compaction) relationship of near surface soils along the alignment was performed in general accordance with ASTM D 1557 using a 10-pound rammer and an 18-inch drop height. The results of these tests are presented on Plate B4.1 as graphs of water content versus dry unit weight.

B3.2 In-place Density In-place density tests of select, undisturbed samples were performed in general accordance with ASTM D 2937. This test is performed on relatively undisturbed samples recovered from drive cylinders. The results of this test are shown at the appropriate depths on the Boring Logs, Plates A4.1 through A4.11, and are used to determine the in-place density of soils.

B3.3 Direct Shear Direct shear tests were performed on undisturbed samples in general accordance with ASTM D 3080 to determine the shear strength characteristics of selected materials along a predetermined horizontal plane. The results of these tests are presented on Plates B3.1 through B3.4 as graphs showing shear stress versus normal stress and are used in a variety of geotechnical engineering analyses, including slope stability, foundation design, and earth retention design.

B3.4 Consolidation Consolidation tests were performed on selected relatively undisturbed samples in general accordance with ASTM D 2435 to determine the compression characteristics, creep, stiffness, and flow properties of soils under loading. The samples were inundated during testing to represent adverse field conditions.

The percent of consolidation for each load cycle was recorded as a ratio of the amount of vertical compression to the original height of the sample. The results of the tests are presented on Plates B2.1 through B2.5 as a graph showing effective vertical stress versus percent change in height and are critical in completing settlement analyses.

B3.5 Triaxial Strength Unconsolidated, undrained triaxial strength tests were completed on a selected, undisturbed sample in general accordance with ASTM D 2850 to determine the strength characteristics of soils, including detailed information on the effects of lateral confinement, porewater pressure, drainage, and consolidation. The specimen is initially consolidated to the effective vertical overburden stress prior to shear (one-point test). The results of this test are presented in the following table and on Plates B5.1

Plate B1.3 through B5.5. The results are used in a variety of geotechnical engineering analyses, including slope stability, foundation design, and earth retention design.

TABLE B-2

Unconsolidated-Undrained Triaxial Strength Test Results

Sample Maximum Deviator

Stress Shear Strain at Max.

Deviator Stress Total Confining

Stress 7E1 at 34 feet 725 psf 9.4% 2,000 psf 7E1 at 44 feet 860 psf 14.6% 2,000 psf 7E2 at 5 feet 3,975 psf 13.7% 1,000 psf

7E3 at 28 feet 1,985 psf 14.5% 2,000 psf 7E4 at 19 feet 1,850 psf 15% 2,000 psf

B3.6 Corrosivity of Soils Samples from boring 7E1 obtained at depths of 3, 9, 14, and 19 feet were tested for alkalinity, chlorides, pH, sodium, sulfates, and chlorides. The tests were performed by TestAmerica in Honolulu, Hawaii.

Results are presented in Appendix C.

B4.0 Geotechnical Engineering Property Tests For Basalt Geotechnical engineering property testing for basalt included Uniaxial Compression Tests. The geotechnical engineering property test results and test procedures for basalt are presented in the following section.

B4.1 Uniaxial Compression Test The uniaxial compression test of select basalt core samples was performed in general accordance with ASTM D 7012. In this test, cylindrical basalt specimens are tested in compression without lateral confinement. Basalt core samples were obtained from borings using an NX core barrel having an inside diameter of 2.1 inches. The tests were performed by Construction Engineering Labs in Pearl City, Hawaii. The results of these tests are presented below and are used in a variety of geotechnical engineering analyses, including slope stability, foundation design, and earth retention design.

Table B-3 Uniaxial Compression Test Results

Basalt Core Sample Location Core Sample Type

Moist Unit Weight (pcf)

Compressive Strength (psi)

7E1 from 19 to 22 feet NX Core 184.4 6,618 7E1 from 64 to 66 feet NX Core 190.3 9,095 7E1 from 74 to 76 feet NX…