B08_Attach_5_Geotechnical_Report.pdf

www.haleyaldrich.com

REPORT ON

GEOTECHNICAL RECOMMENDATIONS

HALE 259822

INSTALL BURIED FILTERED WATER TANK AND APPURTENANCES

TITLE II – DESIGN DEVELOPMENT SERVICES

HALEAKALĀ, HAWAIʻI

by Haley & Aldrich, Inc.

Honolulu, Hawai’i for

KAULA AE, LLC

Honolulu, Hawai’i

H&A File No. 0208679-000 15 March 2024

0208679-000

HALEY & ALDRICH, INC.

6 Waterfront Plaza 500 Ala Moana Boulevard, Suite 6-250 Honolulu, HI 96813 808.587.7747 www.haleyaldrich.com

SIGNATURE PAGE FOR

REPORT ON

GEOTECHNICAL RECOMMENDATIONS

HALE 259822, INSTALL BURIED FILTERED WATER TANK AND APPURTENANCES

TITLE II – DESIGN DEVELOPMENT SERVICES

HALEAKALĀ, HAWAIʻI

PREPARED FOR

KAULA AE, LLC

HONOLULU, HAWAIʻI

PREPARED BY:

Daniel Shinsato, P.E. (HI) Senior Project Manager Haley & Aldrich, Inc.

REVIEWED AND APPROVED BY:

Mark Zablocki, P.E. (HI) Senior Technical Specialist Haley & Aldrich, Inc.

Daniel Trisler, P.E. (HI) Principal Haley & Aldrich, Inc.

Table of Contents Page

0208679-000 i

List of Figures iii List of Appendices iii

1. Introduction 1

2. Scope of Services and Use of this Report 2

2.1 SCOPE OF SERVICES 2

2.2 USE OF THIS STUDY 2

3. Site and Project Description 3

3.1 GENERAL SITE CONDITIONS 3

3.2 PROPOSED DEVELOPMENT 3

3.3 GEOLOGIC CONDITIONS 3

3.4 SUBSURFACE CONDITIONS 4

3.4.1 General 4

4. Seismic Design Considerations 5

4.1 REGIONAL SEISMICITY 5

4.2 SEISMIC BASIS OF DESIGN 5

4.2.1 Seismic Site Class 6

4.2.2 Seismic Design Parameters 6

4.3 SEISMIC HAZARDS 6

5. Geotechnical Engineering Design Recommendations 8

5.1 SHALLOW FOUNDATIONS 8

5.1.1 Dimensions and Bearing Parameters 8

5.1.2 Lateral Load Resistance 9

5.1.3 Shallow Foundation Subgrade Preparation 9

5.1.4 Settlement of Foundations 10

5.1.5 Special Consideration to Rock Supported Foundations 10

5.2 SLABS-ON-GRADE 10

5.3 PERMANENT RETAINING WALLS 10

5.3.1 Earth Pressures 11

5.3.2 Wall Foundations 11

5.3.3 Wall Drainage and Backfill 11

5.4 EARTHWORK 12

5.4.1 Site Preparation and Grading 12

5.4.2 Temporary Open Cuts 13

5.4.3 Permanent Slopes 14

5.4.4 Structural Fill 14

5.4.5 Placement and Compaction of Structural Fill 16

Table of Contents Page

0208679-000 ii

5.5 PAVEMENT DESIGN 16

6. Recommendations for Continuing Geotechnical Services 17

References 1

0208679-000 iii

List of Figures

Figure No. Title

1 Vicinity Map

2 Site Plan

3 Cross Section A-A’

List of Appendices

Appendix Title

A Exploration Logs

B Geotechnical Laboratory Test Results

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1. Introduction

This report summarizes the subsurface investigations undertaken at the site, provides our interpretation of the subsurface data, and provides geotechnical design recommendations for the proposed 50,000-gallon water tank and appurtenances at the Haleakalā National Park, Hawaiʻi. This work was performed in accordance with our agreement with Kaula AE, LLC (Kaula AE) dated 10 July 2023.

The project includes construction of a new concrete water tank with inside dimensions of approximately 62 feet wide by 24 feet long by 5.8 feet tall. The tank will be partially supported by excavations into an existing slope and new structural fills. Tank walls will be constructed to retain the cut and fill .

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2. Scope of Services and Use of this Report

2.1 SCOPE OF SERVICES

Our geotechnical scope of services included the following tasks:

Compile and review existing subsurface information at and around the project site;

Observe excavation of three test pit explorations to depths ranging between 2 to 3.5 feet, collecting representative geotechnical samples;

Perform limited geotechnical laboratory tests on select samples of soil collected from test pits;

Assess subsurface information including laboratory test results to develop geotechnical parameters for design of the proposed improvements; and

Prepare this report summarizing the results of our investigation and our recommendations for design and construction of the proposed improvements.

2.2 USE OF THIS STUDY

This report is for the exclusive use of Kaula AE for specific application to this project and site. We conducted our services in accordance with generally accepted geotechnical engineering practices for the nature and conditions of services conducted in the same or similar localities, at the time the services were performed, within the constraints of scope, schedule, and budget. We make no other warranty, express or implied.

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3. Site and Project Description

3.1 GENERAL SITE CONDITIONS

The site is within Haleakalā National Park on the island of Maui, Hawai‘i (Figure 1). The proposed site is about 2 miles up Crater Road from the National Park entrance and sits at an elevation of about 7,340 feet. The site sits at the edge of one of the first switchback turn of Crater Road heading up towards Haleakalā summit. According to National Park Service (NPS) personnel, there is a historic supply trail running north to south about 100 feet to the west from the site location and it is important this trail remains undamaged as it is culturally significant.

The site is bounded by open space to the north, east, and west, and existing water tanks to the south.

The ground surface gently slopes downward north between approximate elevation 7,348 to 7,338 feet (elevations are reported in feet in the North American Vertical Datum of 1988) from the access road to the lower portion of the tank. The new tank will use the same access road from Crater Road which was constructed for the current water tanks. There is also a set of concrete stairs with metal hand railings that lead from the turnout road at two water tanks down to two smaller non-potable water tanks.

Known utilities at the site include a metal water pipe that generally runs east to west through the site from the two small non-potable water tanks back towards Crater Road. The surrounding open space is covered with low lying shrubs and grasses.

3.2 PROPOSED DEVELOPMENT

Our understanding of the proposed development is based on conversations with Kaula AE. The development will consist of:

Installation of one 50,000-gallon, partially buried, cast-in-place (CIP) concrete water tank for filtered water;

An option for a new vehicle turnout / parking for 1 to 2 maintenance vehicles, with a two foot tall CRM wall;

A metal railing system between the edge of the vehicle turnout / parking (on the makai side) and the tank site for safety; and

Installation of new water distribution piping, fittings, and appurtenances on both the inlet and outlet sides of the new tank, connecting the tank to the existing water distribution system.

3.3 GEOLOGIC CONDITIONS

Regional site geology is provided in Geologic Map of the State of Hawai‘i—Island of Maui, Sheet 4 (Sherrod et al., 2021). The island of Maui is formed by two shield volcanoes, Haleakalā (east Maui) and the West Maui Volcano, creating what is known as a "volcanic doublet." The process of their formation began approximately 2 million years ago during the Pleistocene Epoch. Lava from Haleakalā volcano flowed and accumulated against the older West Maui mountains, forming an isthmus. The mountain of Haleakalā was formed by three groups of lava flows: Honomanū, Kula, and Hāna. Haleakalā is considered a potentially active volcano (Sherrod et al., 2021). The site has been described as Kula Volcanics lava

0208679-000 4 flows (Qkul) of alkalic basanite and minor picrobasalt. ‘A‘ā is determined to be the dominant type of lava flow in this area. These lava flows are estimated to be 140,000 to 930,000 years old.

Surficial soils in the site area are described in the Natural Resources Conservation Service (NRCS) Web-based soil survey as Kaipoioi loam, 7 to 40 percent slopes (KDIE). This series consists of deep, well drained soils that formed in material weathered from volcanic ash and cinders. These soils are mapped as having a high corrosion risk for steel and a low corrosion risk for concrete. They also are mapped as having slow runoff and moderately rapid permeability.

3.4 SUBSURFACE CONDITIONS

3.4.1 General

We observed the excavation of three test pits by NPS personnel using a Volvo ECR88D excavator. Our interpretation of the subsurface conditions for this study is based on these test pits and our review of geologic mapping from readily available public sources. Test pits TP-1 and TP-2 were excavated north of the proposed water tank location and downslope from the road. TP-3 was excavated south of the proposed water tank near the road. The approximate locations of the test pits are shown on Figure 2.

The field exploration methods and subsurface conditions encountered in our explorations are presented on soil test logs in Appendix A. Laboratory test results for selected samples are presented in Appendix B.

The explorations referenced in this study reveal subsurface conditions only at three locations at the project site; conditions in other areas may be different than those indicated by our test pits.

Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities are underway. If significant variations are later observed, we may need to modify our conclusions and recommendations to reflect additional knowledge.

Soil and Rock Conditions. The three test pits encountered similar subsurface conditions, consisting of

1.5 to 3.5 feet of volcanic ash overlying hard basalt bedrock. The ash gradation was in the silty sand range and the material was judged to be in a medium dense condition. Laboratory testing indicated the ash was non-plastic with moisture contents ranging from 42 to 136 percent (average = 97 percent). Test pit TP-2 penetrated 1 foot of weathered basalt which presented as fractured poorly graded gravel with silt. All three test pits terminated on hard basalt bedrock due to refusal at depths of 1.5 to 3.5 feet below grade.

Groundwater was not encountered, and the site was observed to be dry during excavation of the test pits.

0208679-000 5

4. Seismic Design Considerations

4.1 REGIONAL SEISMICITY

The Hawaiian Islands are formed through complex volcanic and tectonic processes that cause high rates of earthquake activity under the southern portion of the Island of Hawai’i and moderate or low seismicity across the rest of the island chain (Klein et al., 2001). The Hawaiian Islands are formed as the Pacific tectonic plate shifts to the Northwest across the stationary Hawaiian hot spot, creating long lived magma chambers, which feed complex venting systems, resulting in the world’s largest shield volcanoes (Peterson and Moore, 1987). There are three main sources of seismicity in the Hawaiian Islands:

volcanic, tectonic, and mantle (U.S. Geological Survey [USGS], 2023).

Volcanic earthquakes are attributed to the underground movement of magma around and eruptions of active volcanoes. Volcanic earthquakes are most prevalent on the Island of Hawaiʻi which overlies the Hawaiian hot spot, and the risk of seismic activity and degree of ground shaking diminishes with increased distance from Hawai’i Island (DLNR, 2004). There are hundreds to thousands of small earthquakes attributed to volcanic activity in the Hawaiian Islands each year. Volcanic earthquakes are typically less than moment magnitude (M) 4.

Tectonic earthquakes are attributed to slippage along tectonic faults. Minor tectonic earthquakes up to M5 occur on upper crustal faults beneath and within the volcanoes. Tectonic earthquakes from crustal faults are the most numerous types of earthquakes in Hawai’i. Large flank (up to M8) earthquakes occur along the décollement fault, which separates the ancient oceanic crust and the overlying volcanoes at a roughly 5 to 6 miles depth. These are the most dangerous types of earthquakes in Hawai’i since both large earthquakes and local tsunamis originate from the décollement fault (USGS, 2023).

Mantle earthquakes are caused by flexural stresses (bending) of the Earth’s crust and upper mantle, known as the lithosphere, due to the weight of the overlying islands. Mantle earthquakes are usually generated at great depths, more than 12 miles below sea level, and are the most common source of damaging earthquakes north of the Island of Hawaiʻi. These deep offshore earthquakes have been recorded to range between M4.8 and 7.5 (Peterson et. al., 2021)

The project site is located near the top of the active volcano, Haleakalā, which has the potential to generate an earthquake up to and potentially exceeding M8 (Klein et al., 2001). A 2,475-year (2 percent probability of exceedance in 50 years) disaggregation for the project site using 2021 National Seismic Hazard Map (Petersen et al., 2021) for the State of Hawaiʻi indicates that the mean expected moment magnitude earthquake over all potential sources at the site is M6.6.

4.2 SEISMIC BASIS OF DESIGN

Seismic design is assumed to be governed by the Hawaiʻi State Building Code (adopted April 2021), which amends the 2018 International Building Code (IBC). Accordingly, we have provided seismic design recommendations considering the 2018 IBC and American Society of Civil Engineers (ASCE) 7-16, which the 2018 IBC references.

0208679-000 6

4.2.1 Seismic Site Class

We determined the seismic site class using information about the supporting foundation soils in general accordance with the 2018 IBC. The seismic site class is typically determined by measuring shear wave velocities to a depth of 100 feet below ground surface (bgs). However, because of the shallow depth to bedrock at the site, the direct measurement of shear wave velocity was not deemed necessary. Based on the presence of shallow rock and our understanding of the regional geology, we determined the site should be designated as seismic Site Class C.

4.2.2 Seismic Design Parameters

The basis of seismic design outlined in the 2018 IBC is nominally a 2,475-year (2 percent probability of exceedance in 50 years) return period hazard, referred to as the maximum credible earthquake (MCE).

This spectrum is then adjusted for risk and peak direction hazard to form the risk-adjusted maximum considered earthquake (MCER). We obtained the seismic hazard from the ASCE 7-16 Hazard Tool web application (https://asce7hazardtool.online/). The ASCE 7-16 hazard tool is based on a probabilistic seismic hazard analysis that the USGS performed across the United States.

We provide parameters for seismic design in accordance with IBC 2018 in Table 1.

Table 1. 2018 IBC Seismic Design Parameters Parameter Value Latitude 20.760154 Longitude –156.230426 Site Class C Spectral Response Acceleration, Ss 1.054 g Spectral Response Acceleration, S1 0.274 g Site Coefficient, Fa 1.2 Site Coefficient, Fv 1.5 MCEG Peak Ground Acceleration, PGA 0.377 PGA Adjusted for Site Class Effects, PGAM 0.452 Site Coefficient for PGA, FPGA 1.2 Note:

g = acceleration of gravity MCEG = Maximum Considered Earthquake Geometric mean

4.3 SEISMIC HAZARDS

Based on the project location, subsurface conditions, and topography, the risks at the site for fault rupture, lateral spread, and flow failure are generally low.

Tsunami. The site is subject to mapping in the Tsunami Evacuation Zone of the County of Hawaiʻi. Based on maps published by the Hawaiʻi Emergency Management Agency, the site is located outside the area predicted to be affected by tsunamis; as such, the risk at the site for tsunamis is low.

https://asce7hazardtool.online/

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Liquefaction and Subsidence. When cyclic loading occurs during a seismic event, the shaking can increase the pore pressure in loose to medium dense saturated sands and cause liquefaction, or temporary loss of soil strength. This can lead to surface settlement. Based on the presence of shallow bedrock, the risk of liquefaction, seismically induced settlement, or significant ground deformation as a result of liquefaction from the design-level earthquake hazard is low.

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5. Geotechnical Engineering Design Recommendations

This section of the report presents our geotechnical engineering design recommendations and construction guidelines for the proposed water tank. Our recommendations are based on our understanding of the proposed project, results of our subsurface explorations and testing, review of existing information, assessments, analyses, interpretations, and our understanding of the regional geology. If the nature or locations of the proposed facilities are different than we have understood and presented herein, we should be notified so that we can confirm or modify our recommendations as appropriate.

Based on discussions with the design team, the primary geotechnical considerations of this project are:

Surficial Soil/Ash:

– The site is blanketed by 1.5 to 3.5 feet of volcanic ash. The ash has very high in-situ moisture content (>100 percent) and will be difficult to re-use as structural fill. Careful moisture conditioning (e.g., aeration/drying) of the material will be required to obtain proper compaction.

– The in-situ ash is not suitable for direct support of tank or retaining wall foundations.

However, the tank floor slab may be supported by the ash if a minimum of 12 inches of crushed rock is placed below the slab, and that top of the ash is compacted to an unyielding condition.

Bedrock: The surficial ash is underlain by hard basalt. The basalt will be difficult to excavate and will likely require heavy equipment, hoe-ramming, or blasting for removal.

Shallow Foundations. The tank may be supported by shallow foundations that bear directly on basalt rock or on new structural fill. Where in-situ ash is present, the footings shall be deepened or the ash should be overexcavated and replaced with new structural fill.

Retaining Walls. New CIP concrete retaining walls will be incorporated into the water tank to support excavations into the existing slope. The wall will be subjected to earth pressures from retained soil and surcharges from the parking area.

5.1 SHALLOW FOUNDATIONS

The tank and associated retaining walls may be supported by shallow foundations consisting of spread footings and/or mat foundations. The footings must bear on bedrock or new structural fill that bears on bedrock.

5.1.1 Dimensions and Bearing Parameters

We recommend the following for all shallow foundations bearing on the basalt rock:

Foundations should be founded outside of an imaginary one horizontal to one vertical (1H:1V) plane projected upward from the bottom edge of adjacent footings or utility trenches.

Design foundations to bear on the basalt rock or new structural fill using an average net allowable bearing pressure of 10 kips per square foot.

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Use an increase in the allowable soil bearing pressure of up to one-third for loads of short duration, such as those caused by wind or seismic forces.

Isolated column footings should have a minimum dimension of 24 inches.

Continuous strip footings should have a minimum width of 18 inches.

Place the base of all footings at least 18 inches below the lowest adjacent finished grade.

However, footings should also be setback at least 10 feet from slopes steeper than 5H:1V. The horizontal setback is measured from the face of the footing at the toe elevation. Footings should be deepened to achieve this setback if needed.

If foundations are designed as a mat, the mat may be analyzed using a preliminary vertical subgrade modulus (Ks) of 200 pounds per cubic inch for foundations bearing on bedrock or compacted structural fill. We consider this value to be a reasonable starting point for an iterative design process, as the vertical subgrade modulus will vary with foundation size and bearing pressure.

5.1.2 Lateral Load Resistance

Lateral loads on footings can be resisted by passive earth pressures on the sides of footings and by friction on the bearing surface. Allowable coefficient of friction values of 0.55 for footings poured neat on basalt rock or 0.45 for footings poured neat on granular structural fill can be used to calculate resistance to sliding on the base of foundations. An allowable passive resistance of 350 pounds per cubic foot (pcf) may be assumed to act against the sides of the embedded portions of footings, ignoring the upper 1 foot of embedment where the footing is exposed to exterior grades (e.g., not covered by a slab).

The passive earth pressure and friction components may be combined, provided the passive component does not exceed two-thirds of the total.

The lateral resistance values provided above include a safety factor of 1.5.

5.1.3 Shallow Foundation Subgrade Preparation

The following guidelines for foundation subgrade preparation are recommended:

Subgrades below footings should penetrate through the near-surface volcanic ash and expose competent bedrock. The bases of footings should bear on the exposed bedrock surface or may bear on structural fill that bears on bedrock.

– If overexcavation of ash is required to reach the bedrock surface, and structural fill is to be placed, then the width of the overexcavation shall extend 6 inches beyond all sides of the footing for every 1 foot of overexcavation required.

– A representative from Haley & Aldrich, Inc. (Haley & Aldrich) should observe exposed bedrock subgrades to verify suitable bearing surfaces before rebar, formwork, or structural fill is placed.

Footing subgrades on bedrock should be prepared as flat as practical, with the plane of the subgrade nominally 10H:1V or flatter.

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Irregularities in foundation bearing surfaces on bedrock should be leveled with lean concrete or minimum 3-inch thick layer of compacted crushed rock.

Individual footings should not bear partially on on-site soil and partially on bedrock. Should rock be exposed in a portion of a continuous footing or mat foundation bearing area, the excavation should be carried down so that the foundation can bear entirely on rock. Alternatively, the overexcavation of the on-site soil can be backfilled with controlled low strength material (CLSM), lean concrete, or crushed rock that is compacted to at least 95 percent of its maximum dry density as determined by ASTM D 1557.

In general, disturbed or loose bedrock fragments should be removed down to intact bedrock.

Fractured rock may remain at subgrade elevations beneath structures provided the subgrade is compacted with heavy vibratory equipment. Rock that is judged by the Geotechnical Engineer to be significantly disturbed must be removed.

5.1.4 Settlement of Foundations

Under the fully applied recommended bearing pressures, it is estimated that the total settlement of column footings up to 8 feet square or continuous footings up to 4.5 feet wide will be less than 1/2 inch.

5.1.5 Special Consideration to Rock Supported Foundations

The basalt rock layer at depths ranging from 1.5 to 3 feet below existing ground surface is the recommended bearing layer for shallow foundations. Based on proposed water tank and footing elevations, the excavations will encounter hard basalt. The basalt will be difficult to excavate and will likely require heavy equipment, hoe-ramming, and/or blasting for removal.

5.2 SLABS-ON-GRADE

Satisfactory subgrade support for the tank’s concrete slab can be obtained from compacted structural fill or basalt prepared in accordance with Section 5.4 Earthwork. The in-situ ash is not suitable for direct support of the tank floor slab. However, the tank floor slab may be supported by the ash if a minimum of 12 inches of structural backfill is placed below the slab, and that top of the ash is compacted to an unyielding condition.

Additionally, a minimum 6-inch-thick layer of crushed rock should be placed over the prepared subgrade to provide a uniform bearing surface. Crushed rock material placed directly below the slab should be 3/4- to 1-inch maximum size and have less than 5 percent fines.

The floor slab should be reinforced according to the structural engineer’s recommendations. Load-bearing concrete slabs may be designed assuming a modulus of subgrade reaction as described in Section 5.1 Shallow Foundations.

5.3 PERMANENT RETAINING WALLS

Permanent retaining walls will be required to retain the excavations on the southern side of the tank property. We anticipate the retaining walls will have a maximum height of approximately 7 feet. The retaining walls will consist of CIP concrete. The walls should be designed and constructed in accordance with the following recommendations.

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5.3.1 Earth Pressures

Permanent walls that are backfilled with granular backfill should be designed using an equivalent fluid unit weight of 35 pcf for active conditions and 55 pcf for at-rest conditions applied in a triangular distribution. For walls that can move at least 0.1 percent of its height (e.g., yielding wall), the design should use active pressures. Where walls are restrained from moving this distance, then they are considered “non-yielding” and should be designed with at-rest pressures.

Note that the equivalent fluid density does not include any surface loading conditions or loading from groundwater hydrostatic pressure; also, the ground surface behind the wall is assumed to be sloped under a 10-degree angle from the horizontal to accommodate roadway grading. Walls without drainage must be designed for full hydrostatic pressure. Traffic loading can be modelled as a uniform surcharge of 250 pounds per square foot acting on the ground above the retaining wall.

Surcharge forces on the wall can be calculated as the vertical pressure multiplied by a coefficient of active earth pressures (Ka) of 0.27 for active conditions and a coefficient of at rest earth pressures (k0) of

0.41 for at-rest conditions. The lateral surcharge pressures should be applied as a rectangular distribution from the ground surface to the bottom of the tank. The surcharge loads are in addition to the lateral earth pressures, and hydrostatic pressure if the wall is not drained.

Seismic induced lateral pressures may be determined using an equivalent fluid unit weight of 35 pcf. The seismic loads are in addition to the lateral earth pressures and surcharge pressures.

5.3.2 Wall Foundations

The foundations for retaining walls should be designed in accordance with Section 5.1 Shallow Foundations.

5.3.3 Wall Drainage and Backfill

The above design parameters have been provided assuming that back-of-wall drains will be installed to prevent hydrostatic pressures. A minimum 12-inch-wide zone of drain rock, extending from the base of the wall to within 6 inches of finished grade, should be placed against the back of all retaining walls.

(Alternatively, prefabricated drainage panels can be installed on the backs of the retaining walls.)

Perforated collector pipes should be embedded at the base of the drain rock. The drain rock should meet the requirements provided in Section 5.4 Earthwork. The perforated collector pipes should discharge at an appropriate location away from the base of the wall and tank.

The wall backfill should be compacted to a minimum of 95 percent of the maximum dry density, as determined by ASTM International (ASTM) D 1557. However, backfill located within a horizontal distance of 3 feet from retaining walls should only be compacted to approximately 90 percent of the maximum dry density, as determined by ASTM D 1557. Backfill placed within 3 feet of the wall should be compacted in lifts less than 6 inches thick using hand-operated tamping equipment (e.g., jumping jack or vibratory plate compactors). Where pavement will be placed atop the wall backfill, the upper 2 feet of material should be compacted to at least 95 percent of the maximum dry density, as determined by

ASTM D 1557.

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5.4 EARTHWORK

Based on our understanding of the project, we anticipate mass grading will consist of excavations up to 7 feet tall and fills up to 4 feet thick to level the tank subgrade. Additional shallow excavations will be required for installation of utilities and structure foundations. Furthermore, additional excavation and fill placement will be required for removal and replacement of ash materials from beneath footings.

Lastly, we note that even shallow excavations are likely to require removal of hard basalt bedrock.

We recommend that earthwork activities be conducted in accordance with Hawai‘i Department of Transportation Highways 2005 standard specifications. The following sections include our recommendations for structural fill selection, placement, and compaction.

5.4.1 Site Preparation and Grading

5.4.1.1 Stripping and Clearing

Initial site preparation and earthwork operations will include clearing and stripping of surficial organic materials. Based on our explorations, the anticipated depth of stripping will likely average approximately 6 inches. However, actual stripping depths should be evaluated based on observations during the stripping operation. The prepared subgrade should be observed and approved by a representative of Haley & Alrich. Generally, visible organic material (sod, humus, roots larger than ¼-inch diameter, and/or other decaying plant material), debris, and other unsuitable materials should be removed from the subgrade areas. Large bushes, and their root balls should be grubbed out to the depth of the roots, which could exceed 3 feet bgs.

5.4.1.2 Subgrade Preparation and Evaluation

Following completion of site stripping, clearing, and any mass excavation, and prior to the placement of any structural fill, the suitability of the subgrade should be evaluated by proof rolling with a fully loaded dump truck or similar heavy rubber-tired construction equipment to identify any remaining soft, loose, or unsuitable areas. The proof roll should be conducted prior to placing any fill. The proof rolling should be observed by Haley & Aldrich who will evaluate the suitability of the subgrade and identify areas of yielding that are indicative of soft or loose soil. If soft or loose zones are identified during evaluation, these areas should be excavated to the extent indicated by the engineer and replaced with compacted engineered fill.

Where existing ash materials are to remain in place below the tank slab, then the upper 12 inches of the ash should be compacted with a sheepsfoot roller to a firm and unyielding condition, as verified by proof rolling and/or nuclear density testing.

5.4.1.3 Bench Preparation for Fill on Slopes

Fill placed on slopes steeper than 5H:1V (20 percent gradient) will need to be constructed on a series of benches cut into the native slope. The benches should be level or have an outward gradient of

0.5 percent or less. The steps between benches can be up to 4 feet tall, and to allow for transition in the fill thickness and ability to compact that fill at the face of the step, it is recommended they have an inclination of 0.5H:1V or flatter. Bench width can vary depending on feasibility. The keyway is the lowest

0208679-000 13 bench and it must be at least 10 feet wide or one and a half times the width of the compaction equipment, whichever is larger, and have a minimum depth of 2 feet at the downhill toe.

5.4.1.4 Wet Soil Considerations

The site is mantled by 1.5 to 3.5 feet of volcanic ash that will be susceptible to moisture-related disturbance. Disturbance to subgrades containing these soils should be expected during site preparation and earthwork, particularly if these activities are conducted during or after periods of wet weather. Due to the naturally high moisture content of these materials, wet soil construction practices may be necessary during most of the year. Wet soil construction practices include using equipment, such as smooth excavator buckets and tracked equipment, to limit subgrade disturbance.

During wet weather or when adequate moisture control is not possible, it may be necessary to install a granular working blanket to support construction equipment and to provide a firm base on which to place subsequent fill and pavement. Commonly, the working blanket consists of bank run gravel or pit run quarry rock (6-inch maximum size with no more than 5 percent by weight passing a U. S. Standard No. 200 sieve).

Based on our experience, between 12 and 18 inches of imported granular material is generally required to provide stable staging and haul road areas on similar soil subgrades. However, the actual thickness will depend on the contractor’s means and methods and the exposed subgrade conditions, and accordingly, should be the contractor’s responsibility. Additionally, a geotextile fabric should generally be placed as a barrier between the soil subgrade and imported granular material in areas of repeated construction traffic. The imported granular material and the geotextile fabric should meet the specifications in Section 5.4.4 Structural Fill of this report.

5.4.1.5 Excavation

Explorations completed at the site identified relatively shallow bedrock. Earthwork construction will require equipment capable of excavation in this hard material. In our experience, rippers equipped to a large bulldozer can be effective in breaking up hard bedrock to a few or several feet deep to facilitate excavation. However, it is likely that ripping the bedrock may not be completely effective, particularly with increasing depths, and rock hammers or blasting may be necessary to completely remove bedrock encountered within cut areas.

The earthwork contractor should be responsible for providing equipment and following procedures as needed to safely excavate the site soils as described in this report.

5.4.2 Temporary Open Cuts

Excavations should be made in accordance with all local, state, and federal safety requirements. For planning purposes, the surficial soils across the site are likely classified per Occupational Safety and Health Administration standards (OSHA, 2001) as Type C. Additionally, intact bedrock below the surficial materials can be classified as “Stable Rock;” however, the material classification must be reevaluated at the time of construction.

The stability and safety of open trenches and cut slopes depend on several factors, including:

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Type and density of the soil;

Presence and amount of seepage;

Depth of cut;

Proximity of the cut to any surcharge loads near the top of the cut, such as stockpiled material, traffic loads, structures, etc.;

Duration of the open excavation; and

Care and methods used by the contractor.

We recommend:

Protecting slopes from erosion; and

Limiting the duration of open excavations as much as possible.

5.4.3 Permanent Slopes

Permanent slopes up to approximately 8 feet tall are anticipated to be required for the project.

Permanent slopes should not exceed a gradient of 2H:1V, unless they expose competent bedrock.

Steeper slopes that exposed bedrock may be allowed, though they should be evaluated in the field at the time of construction.

Slopes should be planted with appropriate vegetation to provide protection against erosion as soon as possible after grading. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face of the slope.

5.4.4 Structural Fill

Backfill placed below the new tank structure or below new pavement, should be considered structural fill. Fill should only be placed over a subgrade that has been prepared in conformance with the prior sections of this report. A variety of material may be used as structural fill at the site. However, all material used as structural fill should be free of organic matter or other unsuitable materials and should meet specifications provided in the Hawai’i Department of Transportation Highways (HDOT-Highways) 2005 Standard Specification Section 703.06 “Aggregate for Untreated Base.” A brief characterization of some of the acceptable materials and our recommendations for their use as structural fill are provided below.

5.4.4.1 Reuse of Site Soil and Bedrock as Structural Fill

The existing ash has grain size similar to silty sand, though has very high moisture contents (>100 percent). These materials are difficult to compact as an engineered fill and may require significant moisture conditioning for use. We recommend against the use of existing ash as structural fill beneath the tank or as backfill behind retaining walls. We consider its use as general fill outside of the envelope of the tank to be acceptable, although soil moisture content, weather conditions, and placement procedures will be very important to the successful re-use of the ash. Careful control of moisture content will be required to achieve the necessary compaction for the ash. During periods of wet weather, it will likely be infeasible to re-use the ash as general fill. The earthwork contractor should plan

0208679-000 15 accordingly. Even light rainfall can readily saturate stockpiled fill. Providing drainage from or covering a stockpile can help limit this potential problem. Such soils may require considerable drying if left in an unprotected stockpile for an extended period.

Bedrock spoils from mass excavations may be suitable for use as general fill depending upon how it is processed. In general, we recommend bedrock materials be processed to a well-graded crushed material with nominal sizes between 1 and 6 inches.

If either on-site material is used as general site fill, the material should meet the requirements set forth in the HDOT-Highways 2005 Standard Specification Section 703.24 “Granular Material for Embankment.”

5.4.4.2 Imported Granular Fill

Imported structural fill should meet the requirements set in the HDOT-Highways 2005 Standard Specification Section 703.06 for “Aggregate for Untreated Base.”

Where imported granular fill is used as stabilization material atop ash materials for haul roads, staging areas, etc., we recommend the material consist of pit or quarry run rock, or crushed rock. The material should generally be sized between 2 and 6 inches, have less than 5 percent by dry weight passing the U.S. Standard No. 4 sieve, and have at least two mechanically fractured faces. The material should be free of organic matter and other deleterious material. Material meeting the gradations of the HDOT- Highways Division October 2021 “SC-11 Stabilized Construction Entrance/Exit” are generally acceptable for use. Stabilization material should be separated from the base of ash subgrades with a layer of subgrade geotextile that meets the specifications provided in the HDOT-Highways Division October 2021 “SC-11 Stabilized Construction Entrance/Exit.”

5.4.4.3 Drain Rock

Drain rock used for back-of-wall drains shall consist of the HDOT-Highways 2005 Standard Specification Section 703.20 “Structure Backfill Material B.”

5.4.4.4 Crushed Rock

Crushed rock used as aggregate base beneath pavements or atop slab subgrade shall consist of the HDOT-Highways 2005 Standard Specification Section 703.06 “Aggregate for Untreated Base.”

5.4.4.5 Controlled Low Strength Material

If controlled low strength material is used beneath tank footings, it should be in general conformance with the HDOT-Highways 2005 Standard Specification Section 314 “Controlled Low Strength Material (CLSM) For Utilities and Structures.” With an exception to the minimum compressive strength specified within HDOT-Highways Section 314. For strength compatibility with the recommended net allowable bearing pressure for the tank foundations, we recommend a minimum 28-day compressive strength of 200 pounds per square inch for CLSM.

0208679-000 16

5.4.5 Placement and Compaction of Structural Fill

We make the following recommendations for the proposed construction:

Before fill placement can begin, the compaction characteristics of proposed fill material must be determined from representative samples of the structural and drainage fill. Samples should be obtained as soon as possible, but at least one week prior to use on site. A study of compaction characteristics should include determination of optimum and natural moisture contents and maximum dry density of these soils. Additionally, the grain size distribution of the fill should be determined.

Structural fill should consist of imported soil or reused well-graded gravel fill conditioned to meet gradation requirements.

Compact imported structural fill or on-site bedrock spoils to a minimum of 95 percent of the maximum dry density as determined by the modified Proctor (ASTM D 1557) test method, except within 2 feet horizontally of structural walls where the compaction requirement should be 92 percent. Maintain moisture content within 2 percent of the optimum moisture content

(ASTM D 1557).

Compact on-site ash materials used as general fill outside of the tank footprint or in-situ ash subgrade below the tank slab to a minimum of 92 percent of the maximum dry density as determined by the standard Proctor (ASTM D698) test method. Maintain moisture content within 4 percent of the optimum moisture content (ASTM D 1557).

Place structural fill only on dense, non-yielding subgrade soils.

Place and compact all structural fill in even lifts with a loose thickness no greater than 10 inches.

If small, hand-operated compaction equipment is used to compact structural fill, fill lifts should not exceed 6 to 8 inches in loose thickness.

In wet subgrade areas, clean material with a gravel content (material coarser than a U.S.

Standard No. 4 sieve) of at least 30 to 35 percent may be necessary.

The compacted densities of all lifts should be verified by testing. Any material to be used as structural fill should be sampled and tested prior to use on site, to determine its maximum dry density and gradation.

5.5 PAVEMENT DESIGN

Pavement will be required for the parking/turnout adjacent to the tank if this bid option is executed, primarily to be used by passenger vehicles and lightweight trucks. Flexible (asphaltic concrete) pavement may be designed using 2.5 inches of asphaltic concrete on 6 inches of compacted base course gravel. Rigid (concrete) pavement may be designed using 5 inches of concrete on 4 inches of compacted base course gravel. Expansion/contraction joints shall be provided in concrete pavement.

Prior to constructing pavement, the upper 12 inches of subgrade soil shall be moisture conditioned and compacted per Section 5.4 Earthwork.

All material quality and compaction requirements for the pavement section shall be in accordance with HDOT-Highways 2005 Standard Specifications.

0208679-000 17

6. Recommendations for Continuing Geotechnical Services

Recommendations discussed in this report should be reviewed and refined as project elements progress through final design and as more subsurface information is collected. Before construction begins, we recommend that Haley & Aldrich:

Meets with the design team to address geotechnical questions that may arise as the design progresses.

Reviews structural engineer’s foundation plans and calculations.

Reviews geotechnical aspects of the final design plans and earthwork specifications to see that our recommendations were properly interpreted and implemented in the design documents.

Provides review and consultation services during construction to evaluate that the contractor meets the intent of the design and to address differing site conditions or geotechnical issues that may arise.

References

1. ASTM International, 2021. ASTM D1557-21, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)).

2. Hawai’i Department of Transportation, Highways Division (HDOT-Highways), 2005a. Standard Specifications for Road and Bridge Construction.

3. HDOT-Highways, 2005b. Special Provisions for 2005 Standard Specifications for the County of Maui.

4. Klein FW, Frankel AD, Mueller CS, Wesson RL and Okubo PG, 2001. Seismic hazard in Hawaii:High rate of large earthquakes and probabilistics ground-motion maps. Bulletin of the Seismological Society of America 91(3):479–498.

5. Occupational Safety and Health Administration (OSHA), 2001. 29 CFR 1926 Subpart P.

Occupational Safety and Health Administration. March 14, 2001.

6. Petersen MD, Shumway AM, Powers PM, et al., 2021. US National Seismic Hazard Model for the State of Hawaii. Earthquake Spectra. 2022;38(2):865-916. doi:10.1177/87552930211052061.

7. Peterson DW and Moore RB, 1987. Chapter 7: Geologic history and evolution of geologic concepts, Island of Hawaii. In: Decker RW, Wright TL and Stauffer PH (eds) Volcanism in Hawaii, vol. 1350, no.1 (Professional paper). Reston, VA: US Geological Survey, pp.149–189.

8. Sherrod, D.R., Sinton, J.M., Watkins, S.E., and Brunt, K.M., 2021. Geologic map of the State of Hawaiʻi: U.S. Geological Survey Scientific Investigations Map 3143, pamphlet 72 p., 5 sheets, scales 1:100,000 and 1:250,000, https://doi.org/10.3133/sim3143.

9. United States Department of Agriculture, 2006. Natural Resources Conservation Service (NRCS).

Web Soil Survey. https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm.

10. U.S. Geological Survey, 2023. About Earthquakes in Hawaii, (https://www.usgs.gov/observatories/hawaiian-volcano-observatory/about-earthquakes-hawaii)

11. Department of Land and Natural Resources (DLNR). 2004. “Hawaii Dam Safety Guidelines:

Seismic Analysis & Post-Earthquake Inspections.” Circular C131.

https://haleyaldrich.sharepoint.com/sites/KaulaAELLC/Shared Documents/0208679.Kaula AE Haleakala Design Dev Title II/Deliverables/Report/Final/2024_0315_HAI_Kaula_AE_Haleakala_F.docx https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm https://www.usgs.gov/observatories/hawaiian-volcano-observatory/about-earthquakes-hawaii https://www.usgs.gov/observatories/hawaiian-volcano-observatory/about-earthquakes-hawaii

FIGURES

HI

SITE

20°46'30"N

20°45'20"N

156°13'10"W156°14'20"W

BASE MAP SERVICES

Ideal scales for site vincity figures

1 : 108,000 Scale bar = 4 miles

1 : 54,000 Scale bar = 2 miles

1 : 24,000 (default)

1 : 13,500 Scale bar = 0.5 mile

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MAP SOURCE: ESRI

SITE COORDINATES: 20°45'36"N, 156°13'48"W

HALEAKALA WATER TANK

HALEAKALA NATIONAL PARK

KULA, HAWAII

VICINITY MAP

FIGURE 1

APPROXIMATE SCALE: 1 IN = 2000 FT

OCTOBER 2023

CRATER R

D

PROPOSED WATER TANK

EXISTING WATER TANKS

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735 6

7 282

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TEST PIT 2

TEST PIT 3

LEGEND

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TOPOGRAPHIC ELEVATION CONTOUR, 2-FT INTERVAL

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STRUCTURE

0 80 160

SCALE IN FEET

NOTES

1. ALL LOCATIONS AND DIMENSIONS ARE APPROXIMATE.

2. AERIAL IMAGERY SOURCE: HEXAGON IMAGERY PROGRAM,

5 APRIL 2016

HALEAKALA WATER TANK

HALEAKALA NATIONAL PARK

KULA, HAWAII

SITE PLAN

FIGURE 2OCTOBER 2023

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HALEAKALA WATER TANK

HALEAKALA NATIONAL PARK

KULA, HAWAII

CROSS SECTION A-A'

SCALE: AS SHOWN

OCTOBER 2023

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SCALE IN FEET

HORIZ.

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SCALE IN FEET

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10 20

LEGEND

TEST PIT DESIGNATION;

OFFSET BETWEEN TEST PIT AND LINE OF

SUBSURFACE PROFILE

TEST PIT SAMPLE

INTERPRETED GEOLOGIC STRATUM

INTERFACE, DASHED WHERE INFERRED

TOTAL DEPTH

APPENDIX A

Exploration Logs

A-1

APPENDIX A

Field Explorations

We evaluated subsurface conditions at the site by monitoring the excavation of three test pits designated TP-1 through TP-3 on 8 September 2023. The test pit explorations were completed by a Volvo ECR88D Excavator operated by a National Park Service employee. The field explorations were observed by geotechnical staff from Haley & Aldrich, Inc. who classified the various soil units encountered, obtained representative soil and rock samples for geotechnical testing, recorded groundwater conditions (if present), and maintained a detailed log of each exploration. Logs of the test pits are included in this appendix. Results of the laboratory testing are indicated on the exploration logs and are included in Appendix B.

Materials encountered in the explorations were classified in the field in general accordance with ASTM International Standard Practice D 2488 “Standard Practice for the Classification of Soils (Visual-Manual Procedure).” Disturbed (“grab”) samples were collected from sidewalls or excavation spoils during test pit explorations. Sampling intervals are shown on the exploration logs included in this appendix.

The exploration logs in this appendix show our interpretation of the exploration, sampling, and testing data. The logs indicate the depth where the soils change. Note that the change may be gradual. In the field, we classified the samples taken from the explorations according to the methods presented on the Figure A-1 Key to Exploration Logs. This figure also provides a legend explaining the symbols and abbreviations used in the logs.

The approximate locations of the explorations are shown on Figure 2 of the report. Explorations were located in the field using a GPS unit.

Project:

Location:

Project No.:

Haleakala Water Tank, Haleakala National Park Kula, Hawaii 0208-679-000

Figure A-1Key to Exploration Logs Sheet 1 of 2

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Organic Soil; Organic Soil with Sand or Gravel; Sandy or Gravelly Organic SoilOL/OH

CH Fat Clay; Fat Clay with Sand or Gravel; Sandy or Gravelly Fat Clay

Lean Clay; Lean Clay with Sand or Gravel; Sandy or Gravelly Lean ClayCL

Clays

Organics

Highly Organic (>50% organic material)

(based on Atterberg Limits) Silty Clay Silty Clay; Silty Clay with Sand or Gravel;

Gravelly or Sandy Silty Clay

Sand, Gravel Trace Few Cobbles, Boulders Trace Few Little Some

Minor Constituents

<5 5 - 15

<5 5 - 10 15 - 25 30 - 45

Moisture Dry Moist Wet

Absence of moisture, dusty, dry to the touch Damp but no visible water Visible free water, usually soil is below water table

Cuttings

Very loose Loose

Medium dense Dense

Very dense to to to to to

>30 to to to to

>50

Very soft Soft

Medium stiff Stiff

Very stiff Hard

Well Symbols

Sample Description

Relative Density/Consistency Soil…