B08_Att_(4)_2025_01_02_-_Geotechnical_Report_HAVO_Rehabilitate_Water_Treatment_System.pdf

Geotechnical Engineering Report

Task Order 140P2024F0173 Rehabilitate Water Treatment System

Hawaii Volcanoes National Park, Hawaii Island, HI

Prepared for:

Otak, Inc.

11241 Willows Rd NE, Suite 200

Redmond, WA 98052

Prepared by:

Masa Fujioka & Associates

98-021 Kamehameha Highway, Suite 337

Aiea, HI 96701

Version: FINAL

January 2, 2025

MFA Project No. 23732-003

Geotechnical Engineering Report January 2, 2025

MFA Project No. 23732-003 Page i

TABLE OF CONTENTS

1.0 Introduction

2.0 Scope of Work

2.1 Data Review and Project Planning

2.2 Site Reconnaissance and Shear Wave Velocity Survey

2.3 Site Investigation and Laboratory Testing

2.4 Engineering Analysis and Geotechnical Report

3.0 Site Conditions

3.1 Project Location

3.2 Geologic Setting

3.2.1 Regional Geology

3.2.2 General Geology of Hawaii Island

3.3 Mapped Geology

3.4 Geologic Hazards

3.5 Mapped Soils

3.5.1 Manu Silt Loam (rMUB), 0% to 10% slopes

3.5.2 Lava Flows (rLW)

3.5.3 Puaulu Silt Loam (PPC), 0% to 10% slopes

3.5.4 Kilauea Extremely Gravelly Sand (rKUC), 6% to 12% slopes

3.5.5 Heake Very Rocky Sandy Loam (HHC), 6% to 12% slopes

3.6 Site Geomorphology

4.0 Site Reconnaissance

5.0 Field Investigation and Laboratory Testing

5.1 Field Boring Investigation and Sampling

5.2 Findings

5.2.1 Geotechnical Borings

5.2.2 Shear Wave Velocity Testing

5.3 Laboratory Testing

6.0 Discussion and Recommendations

6.1 Structure Foundation Support

6.2 Settlement

6.3 Soil Berms

6.4 Soil Liquefaction

6.5 Seismic Site Classification

6.6 Retaining Walls

MFA Project No. 23732-003 Page ii

6.7 Slabs on Grade

6.8 Stormwater Drainage

7.0 Earthwork

7.1 Subgrade Preparation

7.2 Fill Materials, Placement, And Compaction

7.2.1 Structural Fill

7.2.2 Structural Rock Fill

7.2.3 General Fill

7.2.4 Fill Placement and Compaction

7.3 Utility Excavations

8.0 Pavement

9.0 Plan Review and Services During Construction

10.0Limitations

MFA Project No. 23732-003 Page 1

1.0 Introduction

Masa Fujioka & Associates (MFA) was retained to conduct a geotechnical site investigation and provide geotechnical engineering services for subject project. We understand that the project generally consists of structural repairs and upgrades to the historic rain shed buildings, including demolition and replacement of building 43, rehabilitation of building 241, new CMU structures, removal and replacement of asphalt pavements, replacement of water lines and fencing, and the replacement of existing water treatment systems.

Based on the above, MFA proposed and performed the scope of work detailed herein. This report includes our findings and engineering recommendations as they pertain to the subject project.

2.0 Scope of Work

2.1 Data Review and Project Planning

MFA reviewed readily available soils and geologic information—primarily publicly available Geographic Information System (GIS) data, (United States Department of Agriculture (USDA) soils data, United States Geological Survey (USGS) geological data—and previous geotechnical reports by MFA and others, and plan drawings or record drawings for the site that are furnished to us.

In addition to a review of existing information, MFA performed the following project planning tasks:

MFA prepared and obtained approval of an investigation specific Accident Prevention Plan (APP).

MFA prepared and obtained approval from the client of the proposed boring location plan.

2.2 Site Reconnaissance and Shear Wave Velocity Survey

On August 5, 2024, MFA engineers conducted a site visit to perform geotechnical site reconnaissance. With the aid of national park service (NPS) on-site staff, the proposed boring locations were assessed and then marked at the project site. The marked boring locations were provided to Otak, Inc. for final approval before conducting our field investigation.

During the same site visit, MFA’s engineers conducted a shear wave velocity survey at the project site for the purpose of collecting information for seismic site classification, and to supplement information collected from our geotechnical field investigation. A geotechnical data report summarizing the results and findings from our shear wave velocity survey is presented as Appendix 1, Geotechnical Data Report – ReMi Shear Wave Velocity Testing.

2.3 Site Investigation and Laboratory Testing

Based on a review of available information and an evaluation of mapped soil and geologic conditions for the project site, we proposed to perform up to a total of four (4) geotechnical borings, advanced to a maximum depth of 15 feet below ground surface (bgs).

Shallow bulk samples, which consisted of soil cuttings collected beneath the surficial asphalt concrete (AC) and basecourse fill material, were recovered from each boring location. Soil samples which did not exhibit visible signs of hazardous material contamination were transported to our soils laboratory on Oahu for testing. Select samples were examined, packaged, and submitted to Geotesting Express (Geotesting) in Acton, MA for additional testing.

MFA Project No. 23732-003 Page 2

2.4 Engineering Analysis and Geotechnical Report

Based on the data review, geotechnical field investigation, and soils laboratory analyses, we prepared this geotechnical engineering report containing our findings, geotechnical engineering recommendations, and soils recommendations.

3.0 Site Conditions

3.1 Project Location

The project is located in Hawaii Volcanoes (HAVO) National Park, on the Island of Hawaii. The National Park boundary includes portions of the Mauna Loa volcano, as well as the active Kilauea volcano. The project area is located at the northeast rim of the Kilauea crater. A map of the project is presented in Figure 1, Project Location Map.

3.2 Geologic Setting

3.2.1 Regional Geology

The Hawaiian Archipelago is a 1,600-miles long group of islands, reefs, and shoals, running northwest–southeast, in the Pacific Ocean. The major islands, in the southeast portion of the archipelago, “are basaltic volcanic domes in various stages of dissection.”1 The islands have complex geologic histories that generally include four (4) stages of volcanism, water and wind erosion, sea level change, catastrophic landslides and accompanying tsunami, and subsidence of the crust due to the loads of the volcanoes. The older volcanoes are experiencing rebound of the crust as they erode, and the load gets lighter.

The four (4) stages of eruption of an idealized Hawaiian volcano are: pre-shield, shield, post-shield, and rejuvenated. They are distinguished by lava composition, eruptive rate and style, and stage of development. The rejuvenated stage occurs after up to a few million years of volcanic quiescence.

3.2.2 General Geology of Hawaii Island

The Island of Hawaiʻi—the youngest island in the Hawaiian archipelago, consists of five (5) shield volcanoes, listed in order of most recent volcanic activity: Kilauea in the southeast, Mauna Loa in the south, Hualalai in the west, Mauna Kea in the north-central region, and Kohala in the southwest.2 A sixth volcano, Māhukona, is submerged to the northwest of the island. The chain’s newest volcano, Loʻihi, has not yet broken the ocean surface, and lies southeast of the Island of Hawaii.3

1 Stearns, Harold T. 1966. Geology of the State of Hawaii. Palo Alto: Pacific Books.

2 Peterson, D.W. and Moore, R.B. 1987. Geologic history and evolution of geologic concepts, Island of Hawaii. U.S. Geological Survey Professional Paper 1350, pp. 149-189.

3 Sherrod, D.R., Sinton, J.M., Watkins, S.E., and Brunt, K.M. 2007. Geologic Map of the State of Hawaii [with accompanying text]. Open-File Report 2007-1089. United States Geological Survey.

MFA Project No. 23732-003 Page 3

The four (4) stages of eruption of an idealized Hawaiian volcano are: preshield, shield, postshield, and rejuvenated. They are distinguished by lava composition, eruptive rate and style, and stage of development. The rejuvenated stage occurs after a few million years of volcanic quiescence. There are no preshield lavas exposed on the Island of Hawaii. Kilauea and Mauna Loa are considered by this definition to be shield-stage volcanoes, while Hualalai, Mauna Kea, and Kohala are postshield.

None have reached the rejuvenated stage.4

The oldest parts of Kohala are estimated to be about 1 million years old (Ma), with the exposed flows all younger than 0.78 Ma. The youngest flows are probably at least as young as about 0.12 Ma and possibly younger. The youngest flows of Mauna Kea are estimated to be less than 10,000 years old.

Mauna Kea is the highest summit in the state and the state’s only volcano to have been glaciated during the most recent ice age.5 Hualalai, Mauna Loa, and Kilauea have all erupted since A.D. 1790.6

3.3 Mapped Geology

The area where the project site lies is mapped in the Geologic Map of the State of Hawaii7. The geologic features underlying the project site are mapped as lava flows belonging to Puna Basalt series from the Kilauea volcano (geologic symbol Qp4o) and Caldera Wall Rocks (Qcw). Lava Flows (Qp5) also belonging to the Puna Basalt series from the Kilauea Volcano comprises the caldera floor in the northeastern portion of nearby Kilauea caldera. A mapping of the geologic features is presented in Figure 2, Project Geologic Map. Standard error of the mapping is 100 m (±50 m ).

3.4 Geologic Hazards

The United States Geological Survey (USGS) categorized and mapped lava-flow hazard boundaries for the Island of Hawai’i. Note, that the project site is located within an area classified as Zone 1—the most severe hazard zone—which includes summits and rift zones of Kilauea […] where vents have been repeatedly active in historical time.8

3.5 Mapped Soils

A soils map of the project area is provided by the USDA Natural Resources Conservation Service (NRCS), based on mapping in 1972 by the USDA Soil Conservation Service (SCS), predecessor to the NRCS, in cooperation with the University of Hawaii (UH) Agricultural Experiment Station.

The soils within the project site boundary are mapped as Manu silt loam (map symbol rMUB). Within 1 mile of the project boundary, the mapped site soils come in contact with mapped areas containing Lava flows (rLW) to the south, Kilauea extremely gravelly sand (rKUC) and Heake very rocky sandy loam (HHC) to the west, and Puaulu silt loam (PPC) to the north of the project area. A soils map is presented in Figure 3, Project Soils Map. The Soil Survey for this area was mapped at a 1:12,000 scale.

4 Wolfe, E.W. and Jean Morris. 1996. Geologic Map of the Island of Hawaii. [with accompanying text, I-2524-A]. United States Geological Survey.

5 Sherrod, et al. Op cit.

6 Wolfe and Morris, Op cit.

7 Sherrod, et al. Op cit.

8 Wright, T.L., Chun, J.Y.F. ,Esposo, Joan, Heliker, Christina, Hodge, Jon, Lockwood, J.P., and Vogt, S.M., 1992, Map showing lava-flow hazard zones, Island of Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-2193, scale 1:250,000.

MFA Project No. 23732-003 Page 4

3.5.1 Manu Silt Loam (rMUB), 0% to 10% slopes

Manu silt loams (rMUB) consist of well-drained silt loams that formed in volcanic ash, cinders, and pumice. Manu series soils exist at elevations from 3,000 to 4,000 feet and are found on the windward side of Mauna Loa. In a representative profile, the surface layer is a very dark brown silt loam about 3 inches thick over approximately 5 inches of very dark grayish-brown fine sandy loam, underlain by stratified layers of coarse sand, fine sandy loam or loamy sand, and dark yellowish-brown pumice.

Manu silt loams generally exist to a depth of 36 inches, below which hard Pahoehoe lava bedrock is found. This soil exhibits rapid permeability, slow runoff, and slight erosion hazard.9

3.5.2 Lava Flows (rLW)

Lava Flows (rLW) are a miscellaneous land type, consisting of either a’a or Pahoehoe lava flows.

Lava has practically no soil covering and is bare of vegetation, except for mosses, lichens, ferns, and ohia trees. A’a lava flow is rough and broken, while Pahoehoe lava has a billowy, glassy surface that is relatively smooth.10

3.5.3 Puaulu Silt Loam (PPC), 0% to 10% slopes

The Puaulu silt loam (PPC) consists of well-drained silt loams that formed in volcanic ash, found on uplands, at elevations ranging from 3,800 to 4,500 feet. The soils exist in a surface layer that is dark reddish-brown, generally 7 inches thick, underlain by alternating layers of volcanic ash, pumice, and cinders.11

3.5.4 Kilauea Extremely Gravelly Sand (rKUC), 6% to 12% slopes Kilauea extremely gravelly sands (rKUC) formed in volcanic ash, pumice, and cinders at elevations ranging from 200 to 4,000 feet. In a representative profile, dark-brown extremely gravelly sand is underlain by stratified layers of volcanic sand, gravel, cinders, and pumice. These soils exhibit rapid permeability and slow runoff.12

3.5.5 Heake Very Rocky Sandy Loam (HHC), 6% to 12% slopes

Heake series soils consist of well-drained sandy loams that formed in recent volcanic ash and pumice. Heake very rocky sandy loam soils are located on the south side of Mauna Loa volcano, near the Kilauea crater. Up to roughly one-third of the surface consists of pahoehoe lava rock outcrop. In a representative profile, the surface soil layer consists of very dark brown or dark grayish-brown sandy loam and fine sand, underlain by similarly colored fine sand and pumice. Pahoehoe lava bedrock may be expected at a depth of about 17 inches below the surface. This soil exhibits rapid permeability and medium runoff, with moderate erodibility.13

9 Sato, Harry H., et al. and United States Department of Agriculture, Soil Conservation Service, in cooperation with the University of Hawaii Agricultural Experiment Station. “Soil Survey of Island of Hawaii, State of Hawaii.” Washington, D.C.: U.S. Government Printing Office, December 1973. pp.38 10 Ibid. pp.34 11 Ibid. pp,47 12 Ibid. pp.30 13 Ibid. pp.16

MFA Project No. 23732-003 Page 5

3.6 Site Geomorphology

The HAVO rainshed facility consists of a rainwater treatment facility and maintenance yard which serves the national park, and is located at the northeast rim of the Kilauea caldera, nearby to the existing Kilauea Visitor Center (KVC). The project area is situated at an approximate elevation of 4,000 feet above mean sea level (MSL). The general topography of the project site slopes downward to the east and southeast, with elevations ranging from approximately 3,970 feet MSL at the northwest corner of the project area to 3,940 feet MSL at the park entrance to the east, and approximately 3,930 feet MSL at the southern boundary of the project area. Slopes range from 0% to 6%. A topographic map with contours is presented in Figure 4, Project Contour Map.

4.0 Site Reconnaissance

On August 5, 2024, an MFA project engineer conducted a geotechnical reconnaissance to observe site conditions for issues that could potentially impact the field investigation, such as equipment access, overhead utilities, and possible obstructions. HAVO staff were present to assist MFA in identifying the locations of buried utilities. Following the reconnaissance, the proposed boring locations were marked in the field by MFA.

5.0 Field Investigation and Laboratory Testing

5.1 Field Boring Investigation and Sampling

MFA’s geotechnical investigation was conducted from August 28 – August 29, 2024 and consisted of four (4) total geotechnical borings. Prior to drilling, Geotek performed a geophysical survey and toned the site, and final boring locations in the field. Drilling was conducted using a Geoprobe 7822DT track-mounted drill rig, equipped with 8-inch outer diameter hollow auger. For the purpose of collecting rock core samples, rotary wash drilling was utilized with a PQ-core sampler.

General descriptions of the subsurface conditions encountered in the borings are presented in Section 5.2.1 Geotechnical Borings, and the approximate boring locations are presented in Figure 5, Boring Location Map.

In general, geotechnical drilling was conducted from existing ground surface to maximum depths of 15 feet bgs. Soil samples were visually classified in the field, in general accordance with ASTM D2488.

Soil samples were taken using a 1½-inch inner diameter split-spoon sampler, advanced using Standard Penetration Test (SPT) methods, in general accordance with ASTM D1586. Samples of relatively undisturbed soil were also collected for pertinent laboratory tests using a modified California (Mod-Cal) barrel sampler at various depths. Shallow bulk soil samples were collected from the drill cuttings from depths between 1 foot to 6 feet bgs.

The SPT tests were used to determine the relative density or stiffness of cohesionless and cohesive soils, respectively. SPT tests were also used to make determination of refusal when encountering hard materials. In general accordance with ASTM standard ASTM D1586, SPT refusal is determined when 50 or more, hammer blows are required to advance the SPT sampler 6 inches.

MFA Project No. 23732-003 Page 6

When rock coring was conducted, percent recovery and Rock Quality Designation (RQD) were determined for each core run as applicable. Percent recovery is the percentage of rock core recovered over the length of the total core run (distance that the core barrel was advanced). RQD is the cumulative length of core pieces measuring 4.0 inches or more (measuring from center of core) over the length of the core run, expressed as a percentage. Classification of rock quality based on RQD is presented in Table 1 below.

Table 1. Classification of Rock based on RQD RQD (Rock Quality Designation)

Classification of Rock Quality

0-25% Very Poor

25-50% Poor

50-75% Fair

75-90% Good

90-100% Excellent

Upon completion of each boring, the boreholes were backfilled with hydrated bentonite and drill cuttings, with the exception of boring B4, which was backfilled by the National Park Service due to a large void encountered during drilling.

A log of the subsurface conditions encountered is presented in Figure 6, Logs of Borings. Soils were classified in general accordance with the Unified Soil Classification System (USCS), Exhibit 1. A boring log legend is presented as Exhibit 2. A Rock Classification System is presented as Exhibit 3.

Select recovered soil samples were subjected to testing in MFA’s soils laboratory for laboratory identification, compaction, and CBR analyses. The results of our laboratory testing are presented in Appendix 2, MFA Laboratory Test Data, and select test results are included in Figure 6, Logs of Borings.

One soil sample and two rock core samples were transported to Geotesting Express (Geotesting) in Acton, MA for analyses of soil shear strength, rock shear strength, compressive strength, and measurement of unit weight.. The results of Geotesting’s laboratory testing are presented in Appendix 3, Geotesting Express Laboratory Test Data.

5.2 Findings

5.2.1 Geotechnical Borings

In general, subsurface conditions encountered from our geotechnical borings consisted of granular soils derived from basalt rock underlain by thin layers of pumice and tephra deposits. Basalt bedrock was encountered at depths between 5 and 6.5 feet bgs. In borings B1 and B2, the drilling method was switched from hollow auger drilling to PQ diamond bit coring upon encountering SPT refusal.

The subsurface conditions encountered in each geotechnical boring are detailed below. The logs of borings are presented as Figure 6, Logs of Borings. Photos of the rock core samples are shown in Appendix 4, Photos of Rock Core Samples.

MFA Project No. 23732-003 Page 7

Boring B1 Boring B1 was conducted in a grassy landscaped area near the entrance to the rainshed facility. The boring encountered materials consisting of loose to very loose granular materials derived from basic igneous rock, from the surface to approximately 5 feet bgs, where groundwater was encountered— likely perched water located above basalt bedrock. Olive colored pumice (reticulite) and tephra materials were encountered in the soils below 5 feet bgs until transitioning to a thin layer of very loose poorly graded basalt gravel. Basalt bedrock was encountered at 6.5 feet bgs, at which point the drilling method switched over to PQ coring. Core samples from 6.5 feet to 11 feet bgs consisted of slightly weathered basalt rock, with occasional to moderate fracturing. Core recovery of this run was 40% and RQD was poor, with a measured value of 37%. A core sample from 11 feet to 15 feet bgs was not recovered, despite drilling feedback indicating coring through rock or hard material. The sample likely remained attached to the bedrock layer. The boring was terminated at 15 feet bgs.

Boring B2 Boring B2 was conducted in a gravel parking area. The boring encountered conditions similar to those in Boring B1, consisting of loose to very loose granular materials derived from basic igneous rock from the surface to approximately 4 feet bgs. The material graded with olive colored pumice and tephra materials until the boring encountered basalt bedrock at 5 feet bgs, at which point the drilling method switched over to PQ coring. Core samples collected from 5 feet to 16 feet bgs consisted of slightly weathered grey basalt rock, with occasional to moderate degrees of fracturing with the exception of a high degree of fracturing in core materials collected from 11 to 12.5 feet bgs. Core recovery from 5 feet to 13 feet bgs was 75% and RQD was poor, with a measured value of 39%. Voids or pockets of soft material were encountered from 7 to 7.5 feet bgs. Core recovery from 13 feet to 16 feet bgs was 75% and RQD was good, with a measured value of 75%. A void was encountered from 14 to approximately 14.8 feet bgs. The boring was terminated at 15 feet bgs.

Boring B3 Boring B3 was conducted in a gravel parking area at the north end of the project site. The boring encountered medium dense granular materials derived from basic igneous rock from the ground surface, which transitioned to very loose granular materials from approximately 4 feet bgs until 7 feet bgs. The boring was terminated at 7 feet bgs upon encountering auger and SPT refusal.

Boring B4 Boring B4 was conducted in a paved area located adjacent to the rain catchment basin. Surface asphalt concrete pavement measured 3 inches thick and was underlain by approximately 9 inches of basecourse material. The boring encountered medium dense granular materials derived from basic igneous rock, from 1 feet to 2.5 feet bgs, and transitioned to very loose granular materials which graded with olive reticulate pumice and tephra materials. A void was encountered from 4 feet to 5.5 feet bgs before the boring encountered very dense basaltic granular materials. Groundwater and SPT refusal were encountered at approximately 6.5 feet bgs.

MFA confirmed with the Client that no structures were planned in proximity to this boring. Auger drilling continued through basalt bedrock from 6.5 to 11 feet bgs, where a void was encountered from 11 feet to 13 feet bgs. We understand from discussions with NPS staff that the void encountered is likely a known lava tube that aligns approximately eastward from the project site. Auger drilling advanced through basalt bedrock from 13 feet to 14.5 feet bgs, where soft material was encountered.

The boring was terminated at 15 feet bgs.

MFA Project No. 23732-003 Page 8

5.2.2 Shear Wave Velocity Testing

As summarized in Appendix 1, MFA performed shear wave velocity testing at the project site, using refraction microtremor (ReMi) methods, in order to supplement our geotechnical investigation, and in order to determine the seismic site classification.

We conducted ReMi surveys at five (5) locations. Two (2) ReMi survey lines were performed for the purpose of generating 1-dimensional shear wave velocity profiles and to assist in determining seismic site classification, as discussed in Section 6.4 Seismic Site Classification. Three (3) ReMi survey lines were performed to collect data for the purpose of generating 2-dimensional shear wave velocity profiles and to aid in identifying potential voids in the site subsurface in limited portions of the site.

The 2-dimensional profiles were conducted in the northeast portion of the project site. The 2-dimensional data indicated lower density near-surface layer approximately 5 feet in thickness, with an indicated shear wave velocity of approximately 650 feet per second (ft/s). The velocity gradually increased to 960 ft/s at a depth of 12 feet bgs. A more dense high velocity 1200 ft/s layer was indicated, followed by a reduction in shear wave velocity to between 800 and 960 ft/s at approximately 20 feet bgs. This reduction likely indicates the presence of softer material at this depth.

5.3 Laboratory Testing

Laboratory testing performed by MFA consisted of Atterberg limits (ASTM D4318), gradation tests (ASTM D6913/D1140), modified compaction tests (ASTM D1557), moisture-density test, and CBR (ASTM D1883). The results of laboratory testing performed by MFA are presented in Appendix 2.

One soil sample and two rock core samples were transported to Geotesting for analyses of soil shear strength (ASTM D3080), rock shear strength (ASTM D5607), uniaxial compressive strength (ASTM D7012D) and unit weight of rock (ASTM D4543). The results of Geotesting’s laboratory testing are presented in Appendix 3.

6.0 Discussion and Recommendations

6.1 Structure Foundation Support

Our field investigation generally encountered loose granular materials derived from basic igneous rock, underlain by relatively thin pumice and tephra deposits, directly overlying basalt bedrock. Our drilling investigation indicated differing degrees of fracturing in the rock, as well as the presence of voids within the bedrock of up to 2 feet in depth.

Laboratory testing indicated that the near surface soils were non-expansive and indicated high strength, with CBR values generally ranging from 35% to 72% when compacted to 95 percent of their maximum dry density, as determined from laboratory compaction testing.

Based on the above, we recommend supporting new structures at the project site on shallow foundations, with footings constructed on subgrades consisting entirely of competent basalt bedrock, or on compacted structural fill or compacted structural rock fill—in accordance with Section 7.2 Fill Materials, Placement, and Compaction, placed directly on top of competent basalt bedrock. Due to the presence of tephra and soft pumice deposits encountered directly above bedrock, we recommend that these materials be excavated and wasted during construction.

MFA Project No. 23732-003 Page 9

During foundation excavations, if competent bedrock is encountered at the floor and sidewalls of the excavations, the foundations can be constructed directly on the bedrock and designed with the following parameters:

Allowable Vertical Bearing Pressure: 5,000 PSF with 1/3 increase for wind and seismic loads Allowable Lateral Bearing Pressure: 500 PSF per foot below grade Friction Coefficient: 0.5

MFA should be consulted if a bearing capacity greater than 5,000 PSF is required.

If the foundation excavations do not encounter bedrock, or straddle between areas of competent bedrock, granular soils, or cobbles and boulders, the foundations should be constructed entirely on compacted structural fill or compacted structural rock fill—in accordance with Section 7.2, and placed over prepared subgrade per Section 7.1 Subgrade Preparation. Foundations based on the above can be designed with the following parameters:

Allowable Vertical Bearing Pressure: 3,000 PSF with 1/3 increase for wind and seismic loads Allowable Lateral Bearing Pressure: 200 PSF per foot below grade Friction Coefficient: 0.35 Subgrade Reaction Modulus: 250 psi/inch

We recommend that footings should be embedded a minimum of 12 inches below the lowest adjacent exterior grades. For heavier structures, with an allowable bearing pressure of 5,000 PSF, footings should be embedded a minimum of 24 inches below lowest adjacent exterior grade.

During construction, we recommend checking for the presence of voids and lava tubes within basaltic rock. Checking for, and remediation of voids is normally performed by proof-rolling with a heavy vibratory compactor or by probe and grout operations, under the observation of a geotechnical engineer, in accordance with Section 7.1.

6.2 Settlement

We estimate that structures supported by shallow foundations constructed to our recommendations above may experience immediate settlement on the order of up to 0.5 inches, with up to half as differential settlement.

Based on mapped soils and geologic data, and the findings of our investigation, we do not anticipate long-term consolidation settlement to be a concern.

6.3 Soil Berms

We understand that berms up to 8 inches in height and 2.5 feet in width are planned around the perimeter of the water catchment basin. We recommend constructing the berms on subgrades prepared per Section 7.1. The berms may consist of structural fill materials, placed and compacted in general accordance with recommendations in Section 7.2, and be fully confined within a non-woven geotextile fabric. Due to the anticipated high strength of structural fill, the geotextile should be overlapped a minimum of 12 inches and thermally bonded, or as recommended by the manufacturer.

For berms constructed to the above, a maximum slope steepness of 1:1.5 vertical to horizontal feet may be allowed. MFA should be consulted if the design will differ from the above.

MFA Project No. 23732-003 Page 10

6.4 Soil Liquefaction

Soil liquefaction is a loss of soil structure and occurs when a material loses strength in response to dynamic loading, such as vibration or shaking, during a seismic event or sudden large change in stress conditions. Typically, liquefaction potential is high in saturated or partially saturated, poorly-graded (uniform particle size), sandy soils, that are loose or low in density, such as in loose sand, located below sea level. Soft cohesive soils with high clay or silt content typically do not experience liquefaction, however softening can occur with dynamic loading, potentially resulting in loss of strength.

Based on the findings of our geotechnical field investigation, we do not anticipate soil liquefaction to be a concern for this site.

6.5 Seismic Site Classification

MFA conducted two (2) Refraction Microtremor (ReMi) surveys for the purpose of determining the seismic site classification. The surveys indicated average shear wave velocities of 1,317 feet/second and 1,214 feet/second for the top 100 feet of the site subsurface. These values are consistent with the characteristic values of Seismic Site Class CD, as defined by the American Society of Civil Engineers (ASCE) 7 and the International Building Code (IBC). Our geotechnical data report summarizing ReMi testing and our findings is presented as Appendix 1.

The probabilistic ground motion values for the project site are presented in Table 2 below, as obtained from the ASCE Hazard Tool for a Risk Category II site. MFA defers to others for assignment of Seismic Design Category.

Table 2. Probabilistic Ground Motion Values

Peak Ground Acceleration

(g)

SS

(g)

S1 (g)

1.42 3.06 1.37

6.6 Retaining Walls

We understand that areal fills are planned, to be retained by cantilevered concrete cast-in-place retaining walls up to 10 feet in height. We understand that concrete slabs-on-grade will be supported on the retained soils. In order to support the concrete slabs, we recommend that backfill materials consist entirely of imported structural fill, compacted to 95 percent relative compaction.

In order to minimize the increase of soil pressures resultant from a buildup of pore water pressure, we recommend that structural fill backfill behind retaining walls extend a minimum lateral distance of ½ the wall height. Perforated subdrains be installed along the base of the retaining walls. Free-draining gravel should be placed a minimum lateral and vertical distance of 1 foot around the perforated drains, and be wrapped in a non-woven geotextile fabric.

In addition to the recommended design parameters for foundations as described in Section 6.1, retaining walls constructed to the recommendations above may be designed for the following:

Active pressure: 37 PCF equivalent fluid Passive pressure: 390 PCF equivalent fluid, ignore the top foot unless paved

MFA Project No. 23732-003 Page 11

At-rest pressure: 56 PCF equivalent fluid Active seismic earth pressure coefficient: 1.3 Passive seismic earth pressure coefficient: 2.1

The above design values are for vertical retaining walls with relatively level sloped soils placed at the front of the retaining wall, and level backfills sloped 0 degrees from horizontal. Backfill materials have an assumed unit weight of 120 PCF and internal friction angle equal to 32°. The backfill materials used for construction and associated laboratory data should be reviewed by MFA prior to their import to the project site.

6.7 Slabs on Grade

We understand that reinforced concrete slabs-on-grade are planned. The slabs-on-grade should be supported on a vapor barrier, over minimum 4 inches of compacted capillary water barrier material consisting of clean poorly graded gravel, over subgrade materials prepared in accordance with Section 7.1.

6.8 Stormwater Drainage

We recommend the use of positive drainage to keep moisture away from slabs and foundations. The finished grade from the edges of buildings to 10 feet away should be sloped up to 5 percent to provide positive drainage away from foundations. If building roof runoff is intercepted with gutters and down spouts, the downspout should be discharged at least 10 feet away from the edges of the buildings or foundations, or diverted away by concrete swales or conduits.

7.0 Earthwork

7.1 Subgrade Preparation

The ground surface in areas of proposed construction should be cleared, stripped, and grubbed to a depth sufficient to remove all pavements, slabs, appurtenances, vegetation, roots, and other debris.

Following stripping, subgrade preparation in areas of proposed structures should consist of the following:

If a footing excavation for a structure consists entirely of competent rock, fully uncover rock and remove rock surface to a depth sufficient to expose hard rock and roughly level rock surface.

Otherwise, near surface volcanic materials (silty sand and silty sand with gravel as well as hard rock) should be over excavated to a depth of 3 feet below bottom of footings to a lateral distance of 3 feet beyond footings. This recommendation also applies to subgrades in slab-on-grade areas.

Subgrade soils should be reviewed by the geotechnical engineer by direct observation. Approved subgrade soils should be proof-rolled with a large compactor such as an 825B sheepsfoot compactor, having a minimum of 30 tons static weight, under direct observation of the geotechnical engineer. In areas where space is limited, we understand it may be difficult to use a large compactor. In these areas, subgrade soils should be proof-rolled, under direct observation of the geotechnical engineer, using means and methods appropriate for the material and area.

MFA Project No. 23732-003 Page 12

Any soft or weak areas indicated by the geotechnical inspection or proof-rolling should be excavated and replaced with compacted structural fill or compacted structural rock fill to the satisfaction of the geotechnical engineer.

Subgrade surfaces to receive structural fill or structural rock fill should be properly scarified, moisture conditioned to within ±3% of optimum moisture, and compacted to 95% of the maximum dry density, for granular soils and 90% for cohesive soils as determined by ASTM D1557, or to the satisfaction of the geotechnical engineers for areas that consist of oversized materials or in-situ hard cork, which are not generally suitable for compaction testing.

Structural fill or structural rock fill can then be placed in a controlled manner in general accordance with Section 7.2.

For pavement areas, subgrade prepared should consist of the following:

Subgrade soils should be reviewed by the geotechnical engineer by direct observation. Approved subgrade soils should be proof-rolled with a large vibratory roller, having a minimum of 20 tons static weight, under direct observation of the geotechnical engineer.

Any soft or weak areas indicated by the geotechnical inspection or proof-rolling should be excavated and replaced with compacted structural fill, CLSM, grout or lean concrete to the satisfaction of the geotechnical engineer.

If utilized, structural fill should be placed in a controlled manner in general accordance with Section 7.2 under the direct observation of the geotechnical engineer.

Subgrade surfaces should be properly scarified, moisture conditioned to within ±3% of optimum moisture, and compacted to 95% of the maximum dry density, for granular soils and 90% for cohesive soils as determined by ASTM D1557, or to the satisfaction of the geotechnical engineers for areas that consist of oversized materials or in-situ hard cork, which are not generally suitable for compaction testing.

Footings at locations requiring a bearing capacity of 5,000 PSF should be probed to check for cavities and voids. The probes should be drilled to a depth of at least 10 feet below the bottom of the foundation, using either pneumatic or rotary drilling equipment. A minimum of one (1) probe should be drilled for every 50 square feet of footing area, and every 10 feet along continuous wall footings. Any voids encountered during probing activities should be backfilled with CLSM, grout or lean concrete. Alternatively, the voids can be backfilled with compacted structural fill or structural rock fill. If large deep cavities are detected, additional probing should be performed to determine the extent and depth of cavities. The probe drilling and grouting should be performed under the observation of the geotechnical engineer.

7.2 Fill Materials, Placement, And Compaction

All proposed fill materials should be inspected and tested. Test results should be submitted to the geotechnical engineer for review and approval prior to import to the site.

Note that soil characteristics may be variable and should be further reviewed and possibly tested by a geotechnical engineer prior to reuse on site.

MFA Project No. 23732-003 Page 13

7.2.1 Structural Fill

Structural fill should consist of on-site or imported materials classified by ASTM D2487 as GW, GM, GP-GM, GW-GM, SW, SW-SM, or SP-SM, that are free of organic matter, debris, and particles larger than 3 inches in maximum dimension, with a maximum CBR expansion of 1%. Structural fill used in areas beneath building slabs and pavements should have a minimum CBR value of 30% when tested in accordance with ASTM D1883.

7.2.2 Structural Rock Fill

On-site volcanic materials including rock fragments, cobbles, and boulders that are free of organic matter, debris, and particles larger than 6 inches in maximum dimension are anticipated to be suitable for structural rock fill.

7.2.3 General Fill

General fill may be placed in non-structural areas. Materials used for general fill should consist of suitable on-site materials or imported materials classified by ASTM D2487 as GW, GP, GM, GP-GM, GW-GM, GC, GP-GC, GM-GC, SW, SP, SM, SC, SW-SM, SW-SC, SP-SM, SP-SC that are free of organic matter, debris, and particles larger than 3 inches in their maximum dimension.

7.2.4 Fill Placement and Compaction

Structural Fill: All structural fill placed under building slabs or pavements should be moisture conditioned to within plus or minus 3% of optimum moisture and compacted to a minimum 95% of maximum density as determined by ASTM D1557. Structural fill materials placed in non-structural areas may be compacted to the same requirements as general fill materials.

Structural Rock Fill: Structural rock fill should be placed in 12-inch-thick loose lifts, moisture conditioned, and compacted with a large 30-ton minimum static weight compactor such as an 825B. Structural rock fill would not be suitable for compaction testing, and placement and compaction should be closely monitored by the geotechnical engineer. Compaction testing of the structural rock fill is not practical due to the maximum dimension of the particles in this material.

The adequacy of compaction should be determined by on-site evaluation of the material placement and compaction procedures. Appropriate compaction procedures should be developed during the initial stages of earthwork, including correlating the required number of passes of the compaction equipment with the relative density of the fill. The fill placement and compaction operation should be observed by the geotechnical engineer on a full-time basis to determine when sufficient passes have been made, and additional passes do not produce an increase in relative density.

General Fill: General fill materials may be placed in non-structural areas and should be moisture conditioned to within plus or minus 3% of the optimum moisture content and compacted to 90% of the maximum dry density as determined by ASTM D1557.

Structural and general fill materials should be placed in 8-inch maximum loose lifts and compacted utilizing compaction equipment. The loose lift thickness should be reduced to 6 inches when placed and compacted in confined areas, such as beneath or adjacent to foundations. Where power driven, hand-tampers (i.e. “jumping jacks”) are used, the maximum loose lift thickness should

MFA Project No. 23732-003 Page 14 also be reduced to 6 inches. In areas where footings are formed, the remaining annulus between the footing edge and the excavation face should have a minimum width to allow hand-held equipment to compact the backfill material.

7.3 Utility Excavations

We anticipate that on-site utility excavations may be performed with standard excavation equipment.

For utility excavations reaching depths greater than 5 feet bgs, equipment capable of excavating basaltic bedrock may be required.

Depending on utility type, bedding may consist of a minimum of 6 inches of either sand or gravel (S4C or 3B Fine, for example) below the bottoms of pipes or conduits, and a minimum thickness of 12 inches above the top of the conduits. Light vibratory compaction should be employed on the bedding before placement of conduits and atop the upper bedding material before placement of overlying fills or slabs.

For utility trenches in paved areas, select borrow materials should be used when backfilling over pipe bedding up to the bottom of the basecourse elevation. Each backfill lift shall be placed and compacted in general accordance with Section 7.2.4 Fill Placement and Compaction. Select borrow materials shall comply with the State of Hawaii Department of Transportation (DOT) Standard Specifications Section 305 – Aggregate Subbase Course.

In lieu of backfilling with select borrow, controlled low-strength materials (CLSM) or flowable fill— designed by others, may be used. Materials used shall comply with State of Hawaii DOT Standard Specifications Section 314 – CLSM for Utilities and Structures.

Utility trenches performed in un-paved areas may be backfilled with general fills and compacted in accordance with the requirements of Section 7.2.4.

All trenches or excavations deep enough to fall under Occupational Safety and Health Administration (OSHA) regulations should be shored or sloped back in accordance with said OSHA regulations prior to entry. Shoring systems, if required, should be designed, or reviewed by a licensed professional engineer.

8.0 Pavement

CBR testing on bulk soils collected at the site generally correlated to high strength subgrade soils present at the site (a CBR values ranging from 35% to 72%).14

Paved surfaces at the project site are assumed to be subjected to light vehicle traffic consisting of up to 50 daily passes of large pickup truck traffic, small pickup truck traffic, and passenger car traffic over a design life of 25 years.

Based on the above, we recommend the following flexible pavement section:

3 inches of asphalt concrete or match existing, whichever is greater; over

14 Asphalt Institute MS-1 Thickness Design – Highway & Streets, 9th edition

MFA Project No. 23732-003 Page 15

6 inches of basecourse (CBR ≥80%, compaction ≥100% of maximum dry density per ASTM D1557); over subgrade prepared per Section 7.1 Subgrade Preparation

9.0 Plan Review and Services During Construction

We recommend that foundation, pavement, and grading plans, and project specifications be reviewed by the geotechnical designer of record—MFA, to check for general conformance with our recommendations. We recommend that MFA be retained to observe site excavation and subgrade preparation, monitor subgrade and fill compaction, and review suitability for on-site soils for re-use as fill materials.

10.0 Limitations

We have prepared this geotechnical engineering report for the use of the designated project architects and engineers, in accordance with generally accepted soils and foundation engineering practices. No other warranty, expressed or implied, is made as to the professional advice included in this report.

The subsurface conditions assumed in preparing this report require confirmation by close monitoring during construction. The nature and extent of variations in subsurface conditions may not become evident until construction.

The geotechnical recommendations and conclusions presented in this report are based on the following assumptions:

1. The scope of the construction project, as described, does not change appreciably.

2. Significant variations in soil properties from those encountered during our reconnaissance do not occur.

3. The geotechnical engineer will be retained to observe actual field conditions encountered during construction to check the applicability of the recommendations presented in this report and to recommend appropriate changes in construction procedures, if differing conditions occur.

This report may not contain sufficient information for the purposes of other parties or for other uses.

MFA Project No. 23732-003

LIST OF ATTACHMENTS

FIGURES

Figure 1. Project Location Map

Figure 2. Project Geologic Map

Figure 3. Project Soils Map

Figure 4. Project Contour Map

Figure 5. Boring Location Map

Figure 6. Logs of Borings by MFA

EXHIBITS

Exhibit 1. Unified Soil Classification System

Exhibit 2. Boring Log Legend

Exhibit 3. Rock Description System

APPENDIX

Appendix 1. Geotechnical Data Report – ReMi Shear Wave Velocity Testing

Appendix 2. MFA Laboratory Test Data

Appendix 3. Geotesting Express Laboratory Test Data

Appendix 4. Photos of Rock Core Samples

MFA Project No. 23732-003

FIGURES

Figure 1. Project Location Map

Figure 2. Project Geologic Map

Figure 3. Project Soils Map

Figure 4. Project Contour Map

Figure 5. Boring Location Map

Figure 6. Logs of Borings

Rehabilitate Water Treatment System

Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community 0 0.5 1

Miles

Hawaii Volcanoes National Park Volcano, Hawaii Island

Figure 1 Project Location Map

Legend Project Boundary $

Notes:

1. Site boundary modified by MFA and is considered approximate.

Project Location

MFA Project No:

Approved By:

Drawn By:

Drawn Date:

732-003

RTI

EN

09/2024

0 0.5 1

Miles

Hawaii Volcanoes National Park Volcano, Hawaii Island

Figure 2 Project Geology Map

Legend Project Boundary $

Project Location

MFA Project No:

Approved By:

Drawn By:

Drawn Date:

732-003

RTI

EN

09/2024

Symbol: Qp4o Name: Puna Basalt Type: Lava flow Lithology: Pahoehoe & A'a

Symbol: Qp5 Name: Puna Basalt Type: Lava flows

Symbol: Qcw Name: Caldera Wall Rocks Type: Lava flow, thin tephra deposits

Symbol: Qk1o Name: Ka'u Basalt Type: Lava flow Lithology: Pahoehoe & A'a

Symbol: Qp4 Name: Puna Basalt Type: Lava flow Lithology: Pahoehoe & A'a

Symbol: Qk4 Name: Ka'u Basalt Type: Lava flow Lithology: Pahoehoe & A'a

Notes:

1. Project area boundary is approximate and referenced from existing plans.

2. Geology data source: Sherrod, David R., J.M. Sinton, S.E. Watkins, and K.M. Brunt. 2007. Geologic map of the State of Hawai`i: U.S. Geological Survey Open- File Report 2007-1089 [http://pubs.usgs.gov/of/2007 /1089/]. Map unit boundaries are only as accurate as the source data; contacts should be considered approximate. Standard error is 330 ft (±165 ft).

0 0.5 1

Miles

Hawaii Volcanoes National Park Volcano, Hawaii Island

Figure 3 Project Soils Map

Legend Project Boundary $

Project Location

MFA Project No:

Approved By:

Drawn By:

Drawn Date:

732-003

RTI

EN

09/2024

Symbol: rMUB Name: Manu Silt Loam Slope: 2 to 6 percent Erodibility: Slight

Symbol: rLW Name:Lava Flows Slope: 40 to 99 percent

Symbol: rKUC Name:Kilauea Extremely Gravelly Sand Slope: 6 to12 percent

Symbol: PPC Name:Puaulu Silt Loam Slope: 0 to 10 percent Erodibility: Slight

Symbol: HHC Name: Heake Very Rocky Sandy Loam Slope: 6 to 12 percent Erodibility: Moderate

Symbol: rPHB Name: Puhimau Silt Loam Slope: 2 to 6 percent Erodibility: Moderate

Symbol: rKGD Name: Ke'ei Extremely Rocky Muck Slope: 6 to 20 percent Erodibility: Slight

Notes:

1. Project area boundary is approximate and referenced from existing plans.

2. Soils data source: USDA Natural Resources Conservation Service (NRCS). 1972. Soils [Statewide GIS layer], with associated Soil Survey Geographic (SSURGO) data. Retrieved May 2009 from Hawaii Statewide GIS Program website, http://hawaii.gov/dbedt/gis/download.htm.

Map unit boundaries are only as accurate as the source data; contacts should be considered approximate.

3980 ft

3960 ft

4000 ft

3940 ft

Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community 0 100 200 300 400 500

Feet

Hawaii Volcanoes National Park Volcano, Hawaii Island

Figure 4 Project Contour Map

Legend Project Boundary 20 ft Elevation Contours $

Project Location

MFA Project No:

Approved By:

Drawn By:

Drawn Date:

732-003

RTI

EN

09/2024

Notes:

1. Project area boundary is approximate and referenced from existing plans.

2. Contour data source: State of Hawaii Office of Planning. Retrieved October 14, 2020 from http://planning.hawaii.gov/gis/download-gis-data -expanded/

B4

B3

B2

B1

Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community 0 100 200 300 400 500

Feet

Hawaii Volcanoes National Park Volcano, Hawaii Island

Figure 5 Boring Location Map

Legend Project Boundary

Geotec…