Attach_8_Supplemental_Info-ScorpionPier_Geotechnical_Report_092418.pdf

September 2018 Scorpion Pier Replacement, Channel Islands National Park, Ventura, California

Geotechnical Report Scorpion Pier Replacement

Prepared for the National Park Service

Project Number: 181422-01.01

Scorpion Pier Replacement, Channel Islands National Park, Ventura, California

Geotechnical Report Scorpion Pier Replacement

Prepared for National Park Service Channel Islands National Park 1901 Spinnaker Drive Ventura, California 93001

Prepared by Anchor QEA, LLC 7755 Center Avenue, Suite 1060 Huntington Beach, California 92647

Geotechnical Report i September 2018

TABLE OF CONTENTS

1 Introduction and Project Understanding

1.1 Geotechnical Scope of Services

2 Site and Subsurface Conditions

2.1 Review of Previous Geotechnical Studies

2.2 Geotechnical Explorations

2.3 Geotechnical Laboratory Testing

2.4 Generalized Subsurface Conditions

2.4.1 Upland Subsurface Conditions

2.4.2 Offshore Subsurface Conditions

3 Geotechnical Engineering Design Recommendations

3.1 Generalized Geotechnical Engineering Properties

3.2 Pile Foundations

3.2.1 Estimated Vertical and Lateral Capacity of Piles

3.2.2 Pile Settlements

3.2.3 Lateral Resistance and Deflection for Fender and Berthing Piles

3.2.4 Pile Spacing

3.3 Pier Approach Ramp

3.3.1 Settlement Over Time

3.3.2 Bearing Capacity

3.3.3 Sheetpile Wall

3.4 Seismic Design Considerations

3.4.1 Liquefaction

4 Construction Considerations

4.1 Pile Installation

4.1.1 Varying Subsurface Conditions

4.1.2 Closed-Ended or Plugged Pile

4.1.3 Pile Load Test

4.2 Pier Approach Ramp

Geotechnical Report ii September 2018

5 Recommendations for Additional Geotechnical Engineering Services

6 Limitations

7 References

TABLES

Table 1 Exploration Summary Table 2 Soil Model Assumptions for Pile Evaluations

Table 3 Pile Types, Anticipated Loads, and Embedment Recommendations

Table 4 Seismic Design Parameters

FIGURES

Figure 1 Site Vicinity Map

Figure 2 Exploratory Boring Locations

Figure 3 Geologic Profile A-A' Figure 4 Geologic Profile B-B'

Figure 5 Replacement Pier and Pile Types Planned for Use

Figure 6 Time Rate of Differential Settlement

APPENDICES

Appendix A Exploration Methods and Boring Logs

Appendix B Laboratory Test Results

Appendix C Results of Analyses of Lateral and Vertical Pile Capacity Appendix D Important Information About Your Geotechnical Report

Geotechnical Report iii September 2018

ABBREVIATIONS

ASCE American Society of Civil Engineers bgs below ground surface CBC California Building Code DE design-level earthquake EPS expanded polystyrene LF linear foot MLLW mean lower low water N/A not applicable NE not encountered NPS National Park Service pcf per cubic foot psf per square foot psi per square inch RQD rock-quality designation SPT standard penetration test USGS U.S. Geological Survey

Geotechnical Report 1 September 2018

1 Introduction and Project Understanding The National Park Service (NPS) is planning to replace the existing pier located at Scorpion Anchorage on Santa Cruz Island. Santa Cruz Island is the largest of the five islands in the Channel Island National Park in Santa Barbara County, California (Figure 1). Santa Cruz Island is one of the most visited destinations in the Channel Islands, and Scorpion Pier is one of the main entry points to the island. The proposed layout of the new pier is shown in Figure 2.

This report presents the results of Anchor QEA, LLC’s geotechnical investigation and provides geotechnical engineering design recommendations for the replacement of Scorpion Pier. The information has been prepared to support the structural engineering design being conducted by Ashton Engineering, Inc., and for preparation of the design plans and specifications for the project.

1.1 Geotechnical Scope of Services

Geotechnical engineering services were completed in general accordance with NPS Task Order No. 140P2018F0056, dated December 2017.

The specific scope of services included in the Task Order and updated based on the results of the geotechnical explorations included the following:

• Conduct a field boring and analysis program to identify the thickness of cobble layers, top of dense rock strata, and the location of the seismic fault line (if possible).

• Provide drilled steel pipe pile design recommendations for static and seismic capacity (axial and lateral), estimated static settlement, and installation considerations.

• Provide recommendations for design and construction of the pier approach ramp.

• Prepare this report to summarize the results of the geotechnical explorations and present conclusions and recommendations.

Figure 1 Vicinity Map

Geotechnical Report Scorpion Pier Replacement, Channel Islands National Park

Source: National Park Service 2017

Existing Pier

Proposed Pier

A

A

B

B

B-7

L-3

L-2

L-1

B-1

B-4

B-3

L-1

0 60

Feet

LEGEND:

Onshore Exploratory Boring

Offshore Exploratory Boring

Cross Section Location and Designation

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Figure 2

Exploratory Boring Locations

Geotechnical Report

Scorpion Pier Replacement, Channel Islands National Park

SOURCE: Topographic survey from B Carr Surveys, dated 10-13-2016.

Bathymetric survey from Ashton, dated 12-21-2010.

HORIZONTAL DATUM: NAD83, California State Plane, Zone V, U.S. Feet

VERTICAL DATUM: Mean Lower Low Water (MLLW)

A

Geotechnical Report 4 September 2018

2 Site and Subsurface Conditions

2.1 Review of Previous Geotechnical Studies

In 2011, TerraCosta Consulting Group, Inc., performed a limited geotechnical assessment of the site for the purpose of selecting a location for and designing the new pier (TerraCosta 2011). The investigation focused on the offshore portion of the project and consisted of in-water jet probes and diver observations in an attempt to identify the approximate thickness of seafloor sediments in which the pier foundation was to be embedded. The report indicated that this effort was a “limited field investigation,” as opposed to a comprehensive investigation involving more traditional borings.

Fifteen jet probes were advanced along three different potential alignments to a depth of penetration at which they could not be advanced further. The probes indicated 0 to more than 10 feet of interbedded sands before encountering refusal on a harder material surface, initially interpreted as potential bedrock (TerraCosta 2011).

To continue this evaluation, NPS contracted geophysical surveys to further evaluate the presence and depth of bedrock in the site areas of interest. Two surveys were performed: one along the planned orientation of the new pier (Legg Geophysical 2017); and the other along the on-land beachfront and pier approach (Southwest Geophysics 2017). Both geophysical reports concluded that thick layers of cobbles, rather than bedrock, appeared to be present below the looser sand sediment, with denser bedrock indicated at greater depths below. A small subsurface fault was indicated at depth in the offshore survey, appearing to offset the bedrock surface by approximately 10 to 15 vertical feet (Legg Geophysical 2017).

As a continuation of the previous geotechnical and geophysical efforts, the investigation and evaluation presented in this report was performed to further the understanding of subsurface conditions, and to allow for direct observation, sampling, and testing of encountered material types.

2.2 Geotechnical Explorations

Borings L-1 through L-3 were advanced at on-land locations on May 2, 2018, and May 3,2018, using a track-mounted drilling rig. Offshore borings B-1 through B-7 commenced on May 3, 2018, and were completed on May 7, 2018, using the drillship R/V Quin Delta. Field procedures used for this investigation, along with boring logs, are included in Appendix A.

Boring locations B-1, B-3, and B-4 were advanced along the alignment of the proposed pier location.

Based on the geophysical data, it was anticipated that bedrock would be encountered in the offshore explorations within 10 to 25 feet of the mudline, with bedrock being deeper further offshore. Borings B-1, B-3, and B-7 were terminated at depths of 24 to 61 feet below existing mudline and did not encounter competent bedrock. Boring location B-7 was advanced along the alignment of the existing pier location to evaluate the subsurface conditions for the possible extension of the structure.

Geotechnical Report 5 September 2018

Due to difficult drilling weather and sea conditions, the work encountered several weather-related delays. Proposed boring locations B-2, B-5, and B-6 were abandoned due to schedule limitations of the investigation, while boring location B-4 was only able to reach a depth of 7.3 feet before being terminated due to conditions.

Figure 2 depicts the locations of each exploration as recorded in the field. Table 1 summarizes the actual as-drilled exploration coordinates along with surface elevations and total boring depths.

Table 1 Exploration Summary

Boring Location1 Latitude Longitude

Total Boring Depth below

Ground or Mudline Surface (feet)

Depth to Bedrock below

Ground or Mudline Surface (feet)

Ground or Mudline Surface

Elevation (feet)

Observed Top of

Bedrock Elevation

(feet)

L-1 34° 02' 56.825" -119°33' 23.850" 31 11.5 8.9 -2.6

L-2 34° 02' 56.700" -119° 33' 23.700" 31 17.0 7.7 -9.3

L-3 34° 02' 56.520" -119° 33' 23.956" 41 30.5 7.6 -22.9

B-1 34° 02' 57.7722" -119° 33' 21.4102" 24 NE -8.3 NE

B-3 34° 02' 58.4450" -119° 33' 20.2425" 44 NE -14.5 NE

B-4 34° 02' 58.1401" -119° 33' 20.6662" 7.3 NE -11.5 NE

B-7 34° 03' 00.3864" -119° 33' 20.7660" 61 NE -13.8 NE

Notes:

1. ”L”-series boring locations were conducted on land. “B”-series locations were conducted offshore.

2. Elevations presented are approximate and based on the topographic or bathymetric survey data at the time of the investigation relative to the boring location.

NE: not encountered

2.3 Geotechnical Laboratory Testing

A total of 19 soil samples collected from the seven soil borings using a split spoon or thin-walled Shelby tube sampler were selected for geotechnical analysis and submitted to an independent geotechnical laboratory, Material Testing and Consultants, Inc., of Burlington, Washington. The soil samples were analyzed for the following parameters:

• Moisture content (ASTM D2216): 18 tests

• Specific gravity (ASTM D854): 10 tests

• Atterberg limits (ASTM D4318): four tests

• Particle size with hydrometer (ASTM D422): four tests

Geotechnical Report 6 September 2018

• Particle size No. 200 wash (ASTM C136): four tests

• Particle size (ASTM C136 and C117): eight tests

• Loss on ignition (ASTM D2974): four tests

• Unit Weight (ASTM D2938): two tests

• One-dimensional consolidation (ASTM D2435): two tests

To expedite the testing schedule, some of the soil samples were sent to HWA GeoSciences, Inc., in Bothell, Washington, which performed testing under subcontract to Materials Testing Consultants, Inc., to support this project. Four selected portions of the recovered rock cores were submitted to Materials Testing Consultants, Inc., for compression testing (ASTM D7012).

The results of this testing are included in Appendix B and summarized in Tables B-1 through B-3.

2.4 Generalized Subsurface Conditions

The site is located on the northeast corner of Santa Cruz Island. Santa Cruz island is the largest, longest, highest, and most rugged of the Channel Islands (Dibblee 1982). Scorpion Pier is located at the terminus of Scorpion Valley. Steep cliffs are present along the seaward side of the valley.

Geologic maps of the region identify the Monterey shale formation and the Miocene era andesitic and basaltic volcanic rock formation often referred to as Santa Cruz Volcanics (Weaver 1969) or Conejo Volcanic Formation (Dibblee 1982). Both formations can be observed in the seaside cliffs north and south of Scorpion Valley. Large boulders, cobbles, sands, and gravels are found along the beach. At the time of the investigation no surface water was observed in Scorpion Creek; however, the area has been historically subject to flooding and erosion. Scorpion Valley is believed to be comprised of predominately alluvium deposits. The three upland borings encountered organic silts and clays near the surface. The interpreted geologic profiles based on soil boring observations are depicted in Figures 3 and 4. Detailed descriptions of soil boring observations are presented in the boring logs (Appendix A). A generalized description of the soil and rock observed in the upland and offshore explorations is presented in the following subsections.

2.4.1 Upland Subsurface Conditions

Sand with gravel was visually observed as the ground surface at the three upland boring locations.

Observations of the ground surface consisted of dry, brown, fine-to-medium sand, with varying amounts of silt and gravel. The thickness of the sand layer at upland locations varied from 2.5 to

6.5 feet. At boring location L-2, the layer graded to sandy gravel to a depth of 8.5 feet.

Organic Silt and Clay were encountered in all three upland boring locations (L-1, L-2, and L-3). The observed consistency was soft to very soft and identified as dark brown to black with occasional sand seams, gravel, and shell hash with an organic odor. The organic deposit varied in thickness from 5 feet to 27.5 feet. It may be the result of earlier blockage of Scorpion Creek from wave action, which

Geotechnical Report 7 September 2018 may have allowed suspended organic and fine materials to settle out over time and accumulate in localized areas before entering the sea. The moisture content of this material ranged from approximately 43% to 90% with an organic content between 2.4% and 8.3%. The liquid limit varied from 45% to 71.5%. Organic silt and clay were not observed in the offshore explorations.

Bedrock was encountered beneath the organic silt and clay deposit at the upland explorations. The rock encountered consisted of predominately medium-hard basalt that was moderately to highly vesicular. The encountered bedrock is believed to be part of the Santa Cruz Volcanic formation. This same formation outcrops along the sloping hillside surface adjacent to boring location L-1. Bedrock was encountered at elevation -2.6, -9.3, and -22.9 feet for boring locations L-1, L-2, and L-3, respectively. This is consistent with the observed upland topography and the valley of Scorpion Creek. The rock-quality designation (RQD) values were less than 50% in most instances, except for L-3, where the RQD was slightly better, at 58%. Unconfined compressive strength testing performed on recovered portions of core resulted in compressive strengths between 323 pounds per square inch (psi) and 7536 psi (see Table B-3 Appendix B).

2.4.2 Offshore Subsurface Conditions

Sand was observed at the mudline in the offshore explorations, consisting of very loose to medium dense, wet, dark brown sand with varying amounts of silt. Broken shells and shell hash were also observed within the sand layer. The thickness of the surficial sand layer varied from 1.5 to 7 feet, increasing in thickness further away from shore.

Gravel and Cobbles were observed at all the offshore explorations underlying the surficial sand layer. Boring locations B-1, B-3, and B-4 terminated in this layer, but advancing the drill tooling through these materials proved to be challenging, with slow progress and poor sample recovery, so a bottom depth of the gravel and cobbles was not identified in these borings. At boring location B-7, gravel was observed to a depth of 24 feet below the mudline.

The gravel and cobbles observed consisted predominately of fine to coarse sub-rounded to well-rounded gravel with varying amounts of sand. Pieces of coarse gravel, cobble, and possible boulder were collected during rock coring attempts at boring locations B-1 and B-3. Attempts at using rock coring methods to further penetrate the gravel and cobble layer provided only marginal sample recoveries. Samples of cobble recovered during rock coring were of mixed composition (volcanic and sedimentary). Split spoon sample recoveries were less than 100% in most instances, often including pieces of crushed or broken rock. Density varied from medium dense to very dense.

Silty Sand and Gravel was observed at boring location B-7 below the gravel and cobbles layer, starting at an approximate depth of 24.5 feet below the mudline. This material may represent highly weathered bedrock material, given its depth, composition, and oxidized (reddish-brown) color. It was

Geotechnical Report 8 September 2018 comprised of dense to very dense silty sandy gravel and transitioned to silty sand with gravel at an approximate depth of 38 feet below the mudline. Rock coring attempts within this layer were unsuccessful.

Bedrock Not Encountered Offshore. Due to difficulties of penetrating through the gravel and cobbles, the offshore borings did not encounter a clear contact with competent bedrock. As noted above, the deepest material layer encountered at boring location B-7 may have been a highly weathered form of the expected volcanic bedrock at depth, but this is not certain.

E l e v a t i o n i n

F e e t

M

L L W

Horizontal Distance in Feet

No Vertical Exaggeration

-80

-60

-40

-20

-80

-60

-40

-20

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400400

A A'

PACIFIC OCEAN

MLLW (0.0')

41' BGS

L

L

L

31' BGS

31' BGS

B

B

B

19' BM

7' BM

44' BM

Conceptual Pier Layout

(not for construction)

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B

7' BM

0 30

Feet

LEGEND:

Sand

Organic Silt and Clay

Gravel and Cobbles

Weathered Bedrock

Bedrock

Figure 3

Geologic Profile A-A'

Geotechnical Report

Scorpion Pier Replacement, Channel Islands National Park

HORIZONTAL DATUM: NAD83, California State Plane, Zone V, U.S. Feet

VERTICAL DATUM: Mean Lower Low Water (MLLW)

NOTES:

Pier shown for illustrative purposes only. Not for construction. Pile depths are not to scale.

BGS = below ground surface

BM = below mudline

Geologic Contact (Inferred)

Geologic Contact (Known)

Boring Identification

Boring Location

Bottom of Boring (in Feet) l e v a t i o n i n

F e e t

M

L L W

Horizontal Distance in Feet

No Vertical Exaggeration

-30

-20

-30

-20

0 20 40

B B'

Riprap

Steel Sheetpile

CAB

Geotextile

10 30

Fill

Existing Ground Surface

31' BGS

31' BGS

L

L

-10 -10

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0 10

Feet

Figure 4

Geologic Profile B-B'

Geotechnical Report

Scorpion Pier Replacement, Channel Islands National Park

HORIZONTAL DATUM: NAD83, California State Plane, Zone V, U.S. Feet

VERTICAL DATUM: Mean Lower Low Water (MLLW)

NOTES:

Pier approach show for illustrative purposes only. Not for construction.

BGS = below ground surface

L

31' BGS

LEGEND:

Sand

Gravel and Cobbles

Organic Silt and Clay

Bedrock

Geologic Contact (Inferred)

Geologic Contact (Known)

Boring Identification

Boring Location

Bottom of Boring (in Feet)

Geotechnical Report 11 September 2018

3 Geotechnical Engineering Design Recommendations The following subsections provide a summary of Anchor QEA’s geotechnical engineering evaluations and recommendations. Further recommendations regarding construction methods are provided in Section 4.

3.1 Generalized Geotechnical Engineering Properties

Based on Anchor QEA’s review of geotechnical laboratory results (Appendix B), published correlations, and experience in similar soil conditions, the parameters in Table 2 were used for the geotechnical analyses.

Table 2 Soil Model Assumptions for Pile Evaluations

Soil Type

Total Unit Weight

(pcf)

Effective Friction Angle (φ), degrees

Cohesion/Undrained Shear Strength (psf)

Sand 110 28 0

Gravel and Cobbles 130 38 0

Notes:

pcf: pound per cubic foot psf: pound per square foot

3.2 Pile Foundations

Figure 5 depicts the proposed layout of the new pier, and the different pile types that are planned for its construction. All piles are anticipated to be steel pipe piles with 0.75-inch wall thickness. The design of the proposed pier consists of the following:

• 18-inch-diameter piles supporting the pier deck and structure

• 16-inch-diameter fender piles (adjoining the pier dock edges)

• 16-inch-diameter berthing piles (for support of berthed vessels)

• 16-inch-diameter piles supporting the gangway platform

It is our understanding that the pier, fender, and gangway piles will be fixed against movement at their tops, while the berthing piles will be free (not fixed) at the head. Because the mudline elevation slopes down to greater depths offshore, the unsupported pile lengths (above mudline) will vary accordingly, ranging from approximately 5 feet above mudline near shore to 40 feet above mudline at the pier’s farthest offshore end.

Geotechnical Report 12 September 2018

Figure 5 Replacement Pier and Pile Types Planned for Use

Anticipated pile loads have been developed by Ashton Engineering for each pile type, as summarized in Table 3. Vertical loads include not only the imposed dead and live loads from pier construction and operation, but also the weights of the steel pipe pile weight and added grout. The lateral loads were determined by an analysis of wave size and energy anticipated at the site, as documented in the separate Wave Load Memorandum (Anchor QEA 2018).

The pier support piles will carry larger loads during the pier construction process than they will during the pier’s operational lifetime. Therefore, Table 3 includes both the anticipated construction loads on the pier piles and their expected long-term operational loads. The pier will be constructed starting at the landside end and will be build bent-by-bent progressively outward (in the offshore direction). Piles will be installed with a large construction crane which will be positioned on the previously installed piles, along with a series of temporary piles needed to help support the crane.

Pier Support Piles Fender Piles Berthing Piles Gangway Platform Piles

Bents 14-16

Bents 8-9

Geotechnical Report 13 September 2018

We understand that the steel pipe piles will installed as drilled shafts, rather than driven into the subsurface. The installation sequence will be as follows:

• An oversized hole will be drilled to the required embedment depth, with a casing following the drill bit to keep the borehole open

• The steel pile will be lowered into the casing to its full depth

• The annular space between the pile and the casing will be filled with grout

• If possible, the casing will be removed, otherwise, it will be left in place

We understand that the piles are not expected to be subjected to any uplift loads.

3.2.1 Estimated Vertical and Lateral Capacity of Piles

Pile load-bearing capacities relative to different embedment depths were estimated using the ALLPILE numerical model, developed by CivilTech Software, which can analyze pile load capacity for various types of piles and loading conditions. The model incorporates the known layer positions, thicknesses, and engineering characteristics for the surficial sand layer, gravel and cobble layer, and bedrock layer into which the piles are expected to be embedded. End-bearing and lateral load-bearing capacity values were applied by ALLPILE for the various soil units expected (as discussed in Section 2.4).

Some of the vertical load-carrying capacity is provided by side (“skin”) friction between the outer surface of the pile and the surrounding soil. Because it is uncertain whether the pile casing will be fully removed, and therefore whether the casing or the steel pile itself will be in contact with the soil, our analysis conservatively applied a skin friction value that represents the contact between the outer casing material and the soil (a lower value than would be provided by the steel pile surface). The portion of pile capacity due to skin friction was calculated using a horizontal to vertical stress ratio of

0.7 and an interface friction angle between the soil/grout and steel piles of 20 degrees.

Table 3 presents a summary of key representative results of the pile analyses. The subsurface conditions, as well as the ground and mudline surface, vary along the length of the pier, so values are presented for three portions of the pier length: its on-land/nearshore portion (Bents 1 through 4);

the approximate midportion of the pier (Bents 8 and 9); and its offshore end (Bents 14 through 16).

The embedment depths for vertical and lateral forces are based on a short-term factor of safety of

2.0 for the construction loading scenario (scenarios 2 and 4), and a long-term factor of safety of 3.0 for permanent operational loading scenarios.

The selected results depicted in Table 3 were derived from the ALLPILE calculation results, which are included in more detail in Appendix C. This appendix includes the subsurface profiles used in the ALLPILE model, factored (“allowable”) pile capacities as a function of embedment depths, soil reaction curves, and predicted lateral deflections for the piles under the anticipated loads.

Geotechnical Report 14 September 2018

For the upland piles near the pier approach, at Bents 1 through 4, the pier support piles are expected to encounter bedrock during installation, although this is less likely for bents farther offshore, because the top of bedrock slopes downward in that direction. (The subsurface profiles shown on Figures 2 and 3 summarize the observed depth to bedrock at boring locations L-1 through L-3.)

Ideally, the piles will be embedded a minimum of 8 feet into the bedrock layer to achieve the necessary vertical capacity. As the depth to bedrock below the ground surface is likely variable, the total length of each pile will vary accordingly. It appears that installing piles to an embedment depth of 30 feet is likely to achieve a sufficient degree of embedment into competent bedrock, even if the organic silt and clay deposit is present at shallow depths below these bents. Farther offshore, the 27-foot embedment depth recommended for Bents 8 and 9 will be sufficient for achieving vertical load capacity if the piles are embedded entirely within the gravel and cobbles layer.

Because the surficial loose sand is likely susceptible to scour from wave action and/or propeller wash from berthing vessels, the pile analyses disregard the upper 4 feet of surficial sand at the end of the pier and the upper 2 feet of surficial sand around the inland and middle piles.

The results of Table 3 are only for 18-inch and 16-inch piles with 0.75-inch wall thickness. If the wall thickness for either pile is increased to a value closer to 1 inch, then the depth to fixity and depth of embedment for lateral load resistance would increase by approximately 1 foot.

3.2.2 Pile Settlements

Due to the type and density of material the piles will be founded on, we estimate that the 18-inch pier piles may settle 0.5 to 1 inch under the temporary weight of the construction crane load, and that their long-term settlement under operational pier loads would be up to 1 inch. Settlement for the fender and berthing piles will be negligible because they experience no vertical loading aside from their own weight.

Geotechnical Report 15 September 2018

Table 3 Pile Types, Anticipated Loads, and Embedment Recommendations

Notes:

1. Lateral loads are considered negligible for the pier-supported piles located at Bents 1 through 4.

2. See discussion in Section 3.2.1 for piles in this area of the pier.

LF: linear foot MLLW: mean lower low water N/A: not applicable

Pile Diameter (inches) Pile Type

Pile Top Elevation

(feet MLLW)

Ground or Mudline Surface

Elevation (feet MLLW) Load Type

Vertical Loads (kip)

Lateral Loads Embedment Analysis Results

Recommended Pile Embedment (feet)

Lateral Load Elevation (feet MLLW)

Lateral Load (kip)

Depth to Fixity (feet)

Depth of Embedment for Lateral Load (feet)

Depth of Embedment for Vertical Load (feet)

Pier Support Piles, landward end (Bents 1–4)1

19.8 8 Construction Load 77.04

N/A N/A Bedrock Elevation

N/A 8 feet into bedrock 302 Operational Load 37.8

Pier Support Piles, midpoint of length

(Bents 8–9)

19.8 -2

Construction Load 77.04 8 2.1 11 15

Operational Load 37.8 21

Pier Support Piles, offshore end (Bents 14–16)

20.6 -10 Construction Load 77.04

9.7 9.75 16 21

Operational Load 37.8 23.5

16 Pier Berthing Piles 19.5 -10 Operational Load none 9.7 9.75 16 22 N/A 22

Gangway Platform

Piles

30.2 -10 Operational Load 8.54 30.2 2.24 14 19 9 19

12 Pier Fender Piles 19.5 -10 Operational Load none 9.7 9.75 13 18 N/A 18

Geotechnical Report 16 September 2018

3.2.3 Lateral Resistance and Deflection for Fender and Berthing Piles Lateral forces from wave loading will be resisted by the passive resistance of the soils surrounding the piles in combination with the structural rigidity of the steel pile piles themselves. Based on wave load analyses described under separate cover by Anchor QEA (2018), the fender and berthing piles will be subjected to an estimated maximum lateral load of 6.5 kips from wave loads. If vessel loading forces are less than maximum lateral wave load (6.5 kips), then they will not be expected to contribute significantly to the analysis.

To achieve sufficient resistance against the estimated wave loads of 6.5 kips, we recommend installing the 16-inch fender and berthing piles to a minimum embedment depth of 21 feet. This is 5 feet below the estimated depth of fixity for these piles (see Table 3). Note that the lateral pile deflections for the berthing piles provided in Appendix C apply to the applied lateral load elevation of 9.7 feet: the wave breaking elevation (Anchor QEA 2018). Deflections at the top of the pile will be somewhat greater, as these piles extend higher. Deflections for the pier piles and gangway support piles presented in Appendix C are relative to an applied lateral load at the top of the pile, approximately elevations 20 and 30 feet, respectively.

3.2.4 Pile Spacing

To minimize reduction in pile capacity due to group effects, and potential for interference between closely-spaced piles during installation, we recommend a minimum spacing of three pile diameters center-to-center between piles, or two pile diameters of clear space between them.

3.3 Pier Approach Ramp

Due to the documented potential for cultural resources at the site, the project will avoid or minimize excavation below the existing ground surface. Therefore, structures and roadways at the site will be built above the existing grade. Fill material will be used to create an approach ramp to connect the existing upland area with the deck elevation of the pile-supported pier. The proposed approach ramp is planned to consist of imported fill, riprap, and steel sheetpiling. The steel sheetpiling will be flanked by supporting riprap and used to retain and protect the imported fill approach ramp from wave action and storm water.

3.3.1 Settlement Over Time

It is proposed that up to approximately 7 feet of fill will be needed for the approach ramp, with the greatest fill thickness being needed at the connection point to the pier. The fill weight will impose vertical stresses on the underlying ground and subsurface, which will result in consolidation of the compressible organic silts and clays observed at boring locations L-1, L-2, and L-3, with thicknesses ranging from 3.5 to 27.5 feet.

Geotechnical Report 17 September 2018

To assess settlement caused by the approach ramp fill, consolidation analysis was performed for each of the three upland boring locations to account for the varying thickness of the organic silt and clay deposits. A geologic profile near the end of the approach where fill thickness is expected to be the greatest (i.e., 5 feet) is shown on Figures 3 and 4, as is the anticipated fill thickness. In general, the thickness of the organic silt and clay is expected to be the thinnest along the northern edge of the approach road closest to the bluff and becoming thicker away from the bluff.

Immediately upon installation of the fill, primary settlement is expected to begin as the underlying deposits consolidate under the load. Total primary settlement is expected to range from 5 to 27 inches for up to 7 feet of fill and is largely dependent on the thickness of the underlying compressible deposits. Because the three upland borings encountered significantly different thicknesses of the compressible organic silt and clay, the amount of settlement that occurs is expected to vary over relatively short distances.

Differential primary settlement could be on the order of 23 inches over a horizontal distance of 33 feet between boring locations L-1 and L-3 for up to 7 feet of fill. The differential settlement is expected to occur over the course of several months, with the majority of settlement occurring over a year’s time. Figure 5 depicts the estimated development of differential settlement over a period of 4 years, as predicted to occur between boring locations L-1 and L-3.

Over the longer term, another type of settlement can be expected: the gradual process of secondary consolidation, which results from slow deformation of the soil fabric under constant loading.

Although this would be expected to develop over many years, it is estimated that another 3 to 8 inches of settlement may occur over a 50-year time frame for 7 feet of fill. Similar to primary settlement, the extent of secondary settlement is influenced by the thickness of the compressible layer and typically more pronounced in organic soils. The rate of plastic deformation occurs at a much slower rate and will need to be taken into consideration throughout the lifespan of the approach ramp. Periodic backfilling and maintenance of the roadway are likely to be required to maintain grades in the future, accounting for the effects of secondary settlement. This evaluation is specific to the soil characteristics observed at the three boring locations. Settlement in other areas along the alignment of the approach may be more or less depending on the subsurface conditions and the thickness of compressible soil deposits.

To lessen or avoid the impacts of settlement on the pier approach ramp after it is constructed, fill pre-loading or the use of lightweight fill could be employed. These potential alternatives are discussed and compared below.

Geotechnical Report 18 September 2018

Figure 6 Time Rate of Differential Settlement

3.3.1.1 Use of Fill Pre-loading

Pre-loading of the pier approach footprint can be a beneficial approach to minimize post-construction primary settlement. This would require surcharging the compressible subgrade with a temporary excess thickness of imported fill material and allowing time for the underlying soils to consolidate a sufficient amount before removing the extra fill. We recommend that an additional 3 feet of fill be placed over the footprint of the pier approach (a total fill thickness of up to 10 feet) and allowed to settle for a period of 60 days or more. Following the pre-loading, the excess fill could be removed to the design grade. We estimate that between 5 to 23 inches of primary settlement would occur within 60 days from the surcharge load, reducing the post-construction primary settlement to 4 inches or less. It is estimated that 1 to 2 inches of settlement may occur per year, so that the remaining amount of primary settlement would be relatively small 4 years after construction.

However, as discussed previously, continued secondary settlement is expected over the lifetime of the approach road.

The time rate of consolidation is affected by a number of different factors, including non-uniformities in the subsurface conditions, which makes predictions only possible for estimated ranges rather than

0.0

5.0

10.0

15.0

20.0

25.0

0 6 12 18 24 30 36 42 48

Se tt le m en t ( in ch es

Time (months)

Time Rate of Settlement

Differential Settlement

Geotechnical Report 19 September 2018 precisely accurate timelines. We recommend monitoring be performed throughout the surcharge period to assess the rate and extent of settlement through the use of periodic elevation surveys.

Groundwater piezometers could also be installed to further monitor the degree of consolidation occurring during the surcharge period. These regular measurements may result in shortening or extending the preloading period to achieve the desired amount of settlement before finishing the approach ramp.

After pre-loading, the excess fill could be stockpiled on site and used as needed for routine maintenance of the roadway to address expected ongoing settlement.

3.3.1.2 Use of Lightweight Fill

Lightweight fill is frequently used as a means of reducing settlement, and can be useful here, although there are practical limits on how much of a difference it will make. Expanded polystyrene (EPS) geofoam is an example of an alternative to traditional aggregate fill used in typical geotechnical applications and has a density of 0.7 to 2.85 pounds per cubic foot (ASTM D6817).

Replacing some of the fill materials with EPS geofoam would reduce the vertical stress imposed on the compressible soils below.

The approach ramp geometry limits how much lightweight fill could be used, and some traditional aggregate fill material would still be required for cover and to provide a leveling pad for the EPS foam. As an example, for a 7-foot thick fill section comprised of 1.5 feet of aggregate fill and 5.5 feet of geofoam, the estimated total primary settlement would be on the order of 1 to 8 inches, leaving a remaining differential settlement of 7 inches. Settlement of this magnitude would need to be managed with routine backfilling and grading of the approach.

Buoyancy and durability should also be taken into consideration when evaluating geofoam.

Polystyrene would be subject to degradation from fuel oil spills. With a density less than water, EPS geofoam fill is buoyant and would need to be anchored or held in place with aggregate fill material.

The thickness of aggregate cover material will also help distribute loads and will determine the required compressive strength of the selected geofoam product.

3.3.2 Bearing Capacity

Due to the soft compressible nature of the existing soil conditions observed below much of the approach road, it is anticipated that the subgrade soils in their currently existing state may not support the full weight of the proposed fill and heavy construction equipment. Therefore, it will be beneficial to construct the fill in a gradual, controlled manner, with the fill materials placed slowly in thin lifts using lightweight equipment. As each lift of fill is placed, the shear strength of the underlying clay and silt will increase as the soils consolidate over time. This increase in shear strength during the construction period, coupled with the lateral resistance provided by the sheetpile wall, Geotechnical Report 20 September 2018 should be sufficient to provide the bearing capacity needed to support the weight of fill.

Nevertheless, if the approach road is needed to support heavy equipment loads, such as a crane, during the construction of the pier, then the contractor should be prepared to use load-lessening procedures, such as crane mats, during the crane’s use. Further evaluation can be performed during the construction preparation process based on the anticipated crane size, load, sequence of use, and configuration.

3.3.3 Sheetpile Wall

It is our understanding that the primary intent of the sheetpile wall is to retain fill materials, support the approach road, and protect both from the potential erosive forces of waves and stormwater. The exterior face of the sheetpile will be supported with riprap. In general, an embedment depth of three times the exposed height is sufficient to resist the anticipated lateral loads during normal use of the approach road. However, the variably shallow depth to bedrock (as shown on Figures 3 and 4) will impede sheetpile penetration to this depth in most locations along the approach road. Depending upon the application of heavier loads during construction, additional reinforcement and or embedment of the sheet piling may be beneficial. We recommend requiring the contractor to manage load application during crane use by applying crane mats (or similar means of distributing loads at the surface) and by keeping the crane positioned toward the northern (hillside) edge of the road rather than directly along the sheetpile wall. Further evaluation can be performed during the construction preparation process based on the anticipated crane size, load, sequence of use, and configuration.

3.4 Seismic Design Considerations

The project site is in a seismically active region located near several earthquake sources, including the Channel Islands Thrust Fault, Santa Cruz Island Fault, Anacapa-Dume Fault, and the Oak Ridge Fault, all located less than 7 miles from the site. Based on the U.S. Geological Survey’s (USGS’s) 2009 Probable Seismic Hazard Analysis Program, there is a 90 to 100% change that a 5.0 magnitude or greater earthquake will occur within 31 miles of the site within the next 50 years, and a 20% probability of a 7.0 magnitude or greater earthquake occurring within that time span (NPS 2015).

Parameters for the design-level earthquake (DE), in accordance with ASCE/COPRI 61-14, were also developed using USGS and ASCE guidance hazard tools and ASCE/SEI 7-05 Standard for Site Class D.

Per the ASCE/COPRI 61-14 guidance, Anchor QEA recommends that the pier structure be designed to comply with protection of life safety under the DE event. Based on ASCE/COPRI 61-14 and the project location, the parameters noted in Table 4 are appropriate for a maximum considered earthquake (MCE) and DE event at the site.

Geotechnical Report 21 September 2018

Design of the pier approach road and its supporting sheetpile should also take into account the potential for seismic loading (and liquefaction, discussed below), although the cost of incorporating full seismic resistance into the design can be weighed against the operability needs for the approach ramp in and following a seismic event. Because it is an infrequently used project element, it may be less costly to repair or rebuild the pier approach road following a seismic event that it is to design it for full resistance.

Table 4 Seismic Design Parameters

Site Class D Risk Category I

Seismic Design Category D Value

Fa 1.0

Fv -

FPGA 1.1

PGA 0.668 g

PGAM 0.735 g

S1 0.541 g

SD1 -

SDS 1.011 g

SM1 -

SMS 1.516 g

SS 1.516 g

TL 8

Notes:

Fa and Fv: site coefficients (unitless) to adjust for Site Class effects FPGA: site coefficient (unitless) to adjust PGA for Site Class effect g: gravity PGA: peak ground acceleration for the DE adjusted for Site Class effect PGAM: peak ground acceleration for the MCE adjusted for Site Class effect S1: mapped spectral acceleration for a 1-second period SD1 and SDS: 5% damped design spectral response accelerations for 1-second period and short period, respectively SM1 and SMS: maximum considered earthquake spectral response accelerations for 1-second period and short period, respectively Ss: mapped spectral acceleration for short period TL: long period transition period

Geotechnical Report 22 September 2018

3.4.1 Liquefaction

Liquefaction can occur when saturated loose soils undergo rapid strength loss due to seismic ground motion. This can result in settlement (at the ground surface and/or at depth), lateral spreading, sand boils, and other disruptions. Ground settlement may then induce downdrag loads onto installed piles as the liquefied soil densifies and settles around the pile.

At this site, there are two soil types that appear to be susceptible to liquefaction: the surficial loose sand encountered offshore (along the offshore pier alignment); and the organic silt and clay deposit encountered at the upland area of the site (along the pier approach ramp). Both material types are predicted to have factors of safety against liquefaction well below 1 in a design-level seismic event, using analytical methods developed by Youd et al. (2001).

For the offshore pier piles, the liquefaction of surficial sand can be expected to apply additional lateral loading to the piles as the sand spreads in its temporarily liquefied state. The temporary lateral loading would be greatest toward the end of the pier, where the sand thickness is 7 feet.

Analytical methods presented by Yokoyama (1997) indicate that lateral stress of 1.2 kips would be applied to the piles during a liquefaction event, with the force applied at roughly the midpoint of the liquefied deposit below the mudline. As the predicted liquefaction lateral stress is smaller than the design wave lateral load, the deflection due to liquefaction will be within the capacity of the pile.

Below the pier approach ramp, the soft, compressible organic silt deposits (as discussed earlier) are susceptible not only to liquefaction-induced settlement, but also potentially to lateral spreading. The magnitude of both effects is related to the thickness of the organic silt deposit (known to be highly variable in the area of our borings). The estimated settlement due to liquefaction is estimated to be between 0.25 and 1.5 feet, depending on the thickness of the liquefiable deposit (Tokimatsu and Seed 1987). Lateral spreading is a related risk; according to the California Geological Survey (2008), similar materials are known to undergo lateral spreading in lightly sloping coastal flood plains, alluvial fans, and beach areas.

While there are available methods to alleviate the combined effects of liquefaction along the pier approach ramp, including installation of vertical “wick” drains, installation of rigid structural elements below the surface, and densification or solidification of the soft soils, each of these methods would add significant costs to the project. The need for such measures should be weighed against the operability needs for the approach ramp in and following a seismic event; it would likely be less costly to repair or rebuild the pier approach road following such an event.

Geotechnical Report 23 September 2018

4 Construction Considerations This section lists various considerations the contractor and design team should review and be prepared for during construction. The list is not intended to be all-inclusive but summarizes some of the conditions that should be anticipated based on Anchor QEA’s experience and evaluation of the subsurface soils. These recommendations should be incorporated into the project plans and specifications.

4.1 Pile Installation

Successful installation of piles is best achieved when the contractor, in conjunction with the geotechnical field representative, is attentive to certain details of the installation. From that standpoint, properly developed specifications and field observations can play an important role in the success of the work, and close monitoring and documentation of the work will help to identify and readily respond to any unusual subsurface or installation conditions that are encountered.

Anchor QEA recommends closely monitoring the following activities when installing the piles:

• Verify drilling equipment and methods prior to beginning operations to confirm that the equipment and methods provided will be sufficient for the differing site conditions anticipated (Section 4.1.2).

• Observe pile handling prior to installation to make sure that handling methods avoid overstressing the piles.

• Observe and document drilling operations, penetration rates, and evidence of relatively hard or soft drilling conditions.

• Observe, document, and obtain representative samples of any soil and rock cuttings (recognizing that the cuttings typically represent materials that were encountered earlier, previous to their appearance at the top of the drill casing).

• When drilling in sandy or silty deposits, contractors often need to maintain water or slurry levels inside casing during drilling to minimize the potential for bottom heave. During penetrations into gravel and cobbles here, bottom heave may be less of an issue, but the contractor should still be prepared for it.

• Verify drilled hole depth, plumbness, depth of casing advancement, and depth of installation of the steel pipe pile into the casing. If the steel pile does not reach the bottom of the hole, that may be evidence that bottom heave occurred.

• Observe and document any obstructions, difficulties, or unusual occurrences during removal procedures.

• If casing is removed, make sure that there is sufficient grout head above the bottom of the casing to provide full application of grout (without voids or gaps) between the steel pile and the surrounding soil.

• Verify pile size and length during installation.

Geotechnical Report 24 September 2018

• Verify installation of pile shoe or grout plug.

• The contractor should maintain a means of continuously monitoring the volume of grout placed within the hole. Verify minimum required grout volume used relative to hole diameter and/or pile size and watch for evidence of excessive amounts of grout going into the hole (evidence of voids or loss of grout into the surrounding subsurface).

• If the grout is placed under pressure, continuously monitor the pressure applied. Drops in pressure may suggest the presence of voids or grout loss.

• Verify grout properties (compressive strength and flowability)

• Monitor for any movement of adjacent piles during drilling operations

Successful pile installation will also be largely dependent upon the selected contractor. It is recommended that only an experienced qualified contractor perform the work. The contractor should have a minimum of 5 years of experience installing piles in a marine environment and should submit proof of at least three prior projects where they have successfully installed piles through gravel, cobbles, and boulders.

4.1.1 Varying Subsurface Conditions

Due to the inherent spatial variability and natural variations in soil and rock, as well as based on the variations encountered during the geotechnical explorations, subsurface conditions encountered in the field cannot be reliably predicted at all locations during drilling operations.