ATTACHMENT 4 - GEOTECHNICAL RECONNAISSANCE REPORT.pdf

Geotechnical Reconnaissance Report

Proposed 4-Acre Site for Development of Future Scientific Facilities

Pacific International Space Center for Exploration Systems (PISCES)

Free-Space Laser Communications Ground Terminal

Near the Summit of Mauna Loa, Island of Hawai’i

TMK: Portion of (3) 4-4-016: 001

Project No. 0006772 for

The Research Corporation of the University of Hawai’i c/o Pacific International Space Center for Exploration Systems (PISCES)

99 Aupuni Street, Suite 212-213 Hilo, Hawai’I, 96720

Attention: Mr. Robert M. Kelso Executive Director, PISCES by

Stewart Engineering, Inc.

131 Hekili Street Suite 113

Kailua, Oahu, Hawaii 96734

April 22, 2016

Project No. 731

Table of Contents

Page

Introduction Brief Summary of Findings Site Description Future Project Facilities Site Reconnaisance General Surface Ground Conditions USDA Soil Survey General Site Geology USGS Lava Flow Hazards Zone Map Future Lava Inundation Probability Preliminary Geotechnical Considerations General Site Preparation Excavations Use of Onsite Materials for Engineered Fill and Backfill Foundations Estimated Foundation Settlements Concrete Slabs-on-Grade...................……………….……… Retaining Walls Seismic Design Parameters Lava Tubes and Other Voids Probing for Tubes and Other Voids Pavements………………………………………………………….. 27 Site Drainage Limitations

Appendix

Figure No.

General Project Location Map Reconnaissance Photo Locations Geologic Map With Lava Flow Lava Flow Hazard Map Lava Inundation Study Site Reconnaissance Photos....................................................... 6 to 14 References…………………………………………………………… 15

Geotechnical Reconnaissance Report Proposed 4-Acre Site for Development of Future Scientific Facilities Pacific International Space Center for Exploration Systems (PISCES)

Free-Space Laser Communications Ground Terminal Near the Summit of Mauna Loa, Island of Hawaii

TMK: Portion of (3) 4-4-016: 001

Project No. 0006772

Introduction

We have performed a geotechnical reconnaissance of a 4-acre site near the existing Mauna Loa Observatory (MLO) complex on the island of Hawaii. The geotechnical reconnaissance was contracted by the Research Corporation of the University of Hawaii for the benefit of the Pacific International Space Center for Exploration Systems (PISCES). The resulting preliminary report is to be used only as a reference by organizations considering development of future research facilities on the site. The report may not be relied upon for any design and construction of facilities. Any organization considering development of the site needs to commission a complete geotechnical and environmental investigation.

The purpose of our work was to observe and evaluate the surface ground conditions on the site and provide general preliminary geotechnical information that would be useful for organizations considering the feasibility of future scientific research facilities on the site.

Our scope of work consisted of the following:

1. Provide a licensed geotechnical engineer and certified geologist to perform a geotechnical reconnaissance of the site, and generally map and photograph the site using a GPS unit that is accurate to around 20 feet.

2. Look for surface anomalies such as ground cracks, tubes, loose materials, bubbles, blisters, and other void-prone formations.

3. Review the 1973 U.S.D.A. Soil Survey for the Island of Hawaii for the site.

4. Evaluate the field reconnaissance, soil survey, and other geologic hazards information.

5. Provide a preliminary draft report for review by PISCES.

Project No. 731 Stewart Engineering, Inc.

6. Prepare this geotechnical reconnaissance report that summarizes our findings, and presents geotechnical considerations that are geared to addressing potential site development including site preparation, excavation difficulties, use of onsite materials for engineered fill and backfill, foundation types, slabs-on-grade, settlements, pavements, retaining walls, seismic and future lava flow considerations, lava tube potential, general site drainage considerations, and probing and grouting during construction.

Our field work was limited to a visual reconnaissance of the ground surface of the site. No test pits, test borings, sampling, or any other invasive or destructive methods were included in our scope of work.

Stewart Engineering, Inc., PISCES and RCUH emphasize that this report is preliminary in nature and is only intended for a general, preliminary feasibility evaluation of the subject 4-acre parcel for potential future development. We also emphasize that the geotechnical considerations and guidelines for development that are presented in this report are preliminary and not intended to be interpreted as geotechnical recommendations for final design and construction of any specific facility or structures on the site.

Any future project to be considered within the 4-acre site will need a separate detailed geotechnical report that is supported by a comprehensive site investigation including test borings and/or test pits that provide adequate subsurface ground information for final design and construction. The future detailed geotechnical investigations should be performed at the specific location of the facilities planned, and the geotechnical report recommendations should be directed toward the specific project designs, scope, foundation loads, and structural tolerances.

This geotechnical reconnaissance report has been prepared in general accordance with the scope of services outlined in our contract with RCUH, P.O. # Z10121512, dated March 3, 2016.

Brief Summary of Findings

In our opinion, the two overriding geotechnical considerations for development of the subject 4-acre site are the relatively high risks posed by future earthquakes and future lava flows. Both of these natural events are unpredictable in timing and strength, but both are certain to occur on or near this site in the future.

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The site is located below the active northeast rift zone near the summit of Mauna Loa, one of the most active volcanos in the world. It has averaged an eruption approximately every 6 years over the past 3,000 years, and has experienced 33 lava flows since 1843. A 1975 lava flow threatened the nearby Mauna Loa Observatory (MLO) facility, and a 1984 flow disrupted power to the MLO.

A 2012 study by the USGS entitled “Lava Inundation Probability for the North Flank of Mauna Loa”, concluded that the subject site has an approximate 1 to 8 percent risk of inundation by a lava flow within the next 50 years, and an 8 to 33 percent risk of inundation indicated for some nearby areas within the next 50 years.

A lava flow diversion barrier should be considered for protection of any facilities that are built on the site, similar to a barrier that was built in 1986 for the nearby MLO facility. A diversion barrier essentially consists of a triangular-shaped berm constructed of compacted on-site rocky materials, that is located in the most probable path of future flows to divert them away from the site.

Mauna Loa experiences many earthquakes, some of which can be very strong. When making the decision to build sensitive structures like an astronomical telescope on this earthquake prone site, one must take into consideration the frequent occurrence of mild to moderate earthquakes and the occasional occurrence of strong earthquakes in the general area.

Aside from significant earthquake and lava flow considerations, the site generally appears to be well suited for development of both light to heavy structures using typical construction methods that are commonly required on lava rock sites on the island of Hawaii.

The terrain on the 4-acre site is generally mildly sloping, without significant irregular contours that would tend to unreasonably hinder design and construction. No obvious signs of lava tubes or other significant voids, which are very common on the island, were apparent on the surface of the site.

The ground conditions on the site are predominated by loose, ragged, a’a lava that is primarily less than 12 inches in size, with a flow of relatively hard, intact pahoehoe lava roughly through the center of the site. The depths and lateral extent of these two major surface ground types is not known since test pits and borings were not included in our scope of work.

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The loose a’a lava should be easy to excavate and readily crushed into excellent engineered fill and backfill, since it is relatively brittle and naturally sized to be handled by even a small onsite crusher. The intact pahoehoe lava is harder and much more difficult to excavate, but could probably be ripped and processed onsite into suitable engineered fill.

The intact pahoehoe rock has excellent foundation bearing strength and other engineering properties, provided there are no voids below the surface. The loose a’a is generally not considered suitable to support structures, but if it is removed and adequately crushed and processed, it should make excellent fill and backfill material that is also expected to have very good bearing capacity and other engineering properties if it is adequately compacted

Site Description

The 4-acre undeveloped rectangular site is located near the end of the Mauna Loa Access Road, a paved public road that ends at the existing Mauna Loa Observatory (MLO) at an elevation of approximately 11,000 feet near the summit of Mauna Loa.

Google Earth software shows the center of the 4-acre site to be approximately 1,100 feet west of the existing MLO facility. Based on the GPS coordinates provided for the site boundaries, the dimensions of the 4-acre site are roughly 300 feet wide by 600 feet long, with the length of the site bearing in a north-south direction.

A rough, unpaved 4-wheel drive road connects the site with the end of paved Mauna Loa Access Road, and crosses the site near the middle. The surface of the site is predominately broken a’a lava and loose clinker that is typically less than 12 inches in size, with a flow of pahoehoe lava traversing the length of the parcel near the center. The pahoehoe flow is estimated to cover roughly 1/3 of the 4-acre site.

At the time of our field reconnaissance, there was no vegetation and no significant soil deposits seen on the site, which generally slopes mildly down from south to north. No site-specific topographic map was available at the time of this report, so precise elevations are not known.

Google Earth shows a maximum elevation of approximately 11,180 feet on the south end of the site, with a minimum elevation of approximately 11,070 feet on the north end.

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The general location of the site is shown on the General Project Location Map, Figure 1 of the Appendix. An overview of the 4-acre site and MLO that includes the locations of geotagged photos obtained during the reconnaissance is shown on Appendix Figure 2.

A geologic map showing the general site location in relation to historic lava flows is shown on Figure 3. Photos obtained during our site reconnaissance and referenced on Figure 2 are shown on Figures 6 through 14.

Future Project Facilities

Potential future projects identified by RCUH include Laser Communication Ground Stations for orbital and deep space assets, microwave receivers, and solar and geophysics observatories. In addition, future scientific facilities could include Large (10-meter class), Medium (4-meter class) and Small (1-meter class) astronomical telescope projects and related facilities.

No structural loads, grading information, or any other project information is known at this time. It is our understanding that future facilities that are small to large in scope could be considered for the four-acre property, and we have considered this information in preparing the preliminary geotechnical considerations and general information contained in this report.

Site Reconnaissance

Reconnaissance of the 4-acre site was accomplished on March 9 and March 23, by a licensed geotechnical engineer and a certified professional geologist from Stewart Engineering, Inc. Our reconnaissance was limited to visual observations and taking photographs of areas of interest on the property. No test pits, test borings, sampling, or any other invasive or destructive methods were included in our scope of work.

The site was located in this remote area using approximately 126 perimeter GPS coordinates provided in the form of a .KMZ file by John Hamilton of PISCES. The .KMZ file was utilized with several GIS applications for assistance with locating the site. A handheld GPS-enabled device running a professional mobile GIS application was used to locate the site boundaries during the site reconnaissance. The accuracy of the GPS device is estimated at roughly 15 to 20 feet.

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Although there were no excavations conducted on the subject site, we observed some existing exposed cut slopes at the nearby MLO facility, and along the paved Mauna Loa Access Road.

General Surface Ground Conditions

Most of the surface of the 4-acre parcel consists predominantly of loose, ragged a’a lava rock or clinker that is predominantly less than 12 inches in size, with some isolated individual fragments up to roughly 2 to 3 feet in maximum size.

Most of the individual fragments appeared to be brittle and easily broken down by impact forces.

No fine-grained soil was observed within the clinker deposits. These loose deposits appeared to cover roughly 70 percent of the site.

An irregular but generally continuous flow of pahoehoe lava traverses the length of the parcel from south to north, roughly near the center of the 4-acre site. Most of the pahoehoe flow was rounded and billowy, with some ropy formations and some isolated small rounded domes that can indicate the presence of voids beneath the surface.

A few relatively small, isolated, ragged conical lava features extended vertically several feet above the predominant smoother pahoehoe flow. Some broken or cracked zones were observed in portions of the pahoehoe lava, but no lava tubes or other large voids open to the ground surface were observed in our reconnaissance.

No significant soil deposits were seen in either the a’a or pahoehoe formations throughout the site. However, isolated pockets of very thin tan silty to sandy ash soil were observed in depressions in some of the pahoehoe lava.

The isolated silty tan soil is not considered significant from an engineering or development standpoint except for dust control considerations during site work. However, larger pockets of concentrated ash soils could exist beneath the surface of the site.

The pahoehoe flow generally appeared to be older than the surrounding a’a flows that covered the perimeter edges of the pahoehoe. The depths of the a’a and pahoehoe flows on the site are not known.

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Cuts that we observed in the nearby MLO facility exposed relatively thin pahoehoe flows that were roughly 1 foot to 2 feet thick, overlain and underlain by relatively loose a’a clinker flows.

USDA Soil Survey

The U.S.D.A Soil Conservation Service Soil Survey for the Island of Hawaii classifies the predominant natural surface materials in the general area as Lava Flows, A’a and Pahoehoe (rLV and rLW).

A’a lava (rLV) is described as rough and broken lava with clinker, hard, sharp pieces piled in tumbled heaps, with practically no soil cover and little or no vegetation. The Pahoehoe (rLW) ground type is described as having a predominantly smooth or billowy surface, with some rough or broken surface features and hummocks and pressure domes.

The descriptions given by the Soil Survey for a’a (rLV) and pahoehoe flows (rLW) are generally consistent with the two predominant lava formations observed on the surface of the subject 4-acre site.

General Site Geology

The subject 4-acre site is situated on the northern flank and near the summit of Mauna Loa, one of the most active volcanos in the world. Mauna Loa has averaged an eruption approximately every 6 years for the last 3,000 years.

The USGS Map of Historical Lava Flows indicates that Mauna Loa has experienced 33 lava flows since 1843 and last erupted in 1984. Many of these flows (31 percent) occurred along the northeast rift zone that is immediately south and east of the subject site.

The summit region of Mauna Loa has been the site of 38 percent of the eruptions. Many of the summit eruptions remained in the summit caldera, but others have spilled out of the caldera into the northwest and northeast quadrants of the volcano.

Some of Mauna Loa’s larger eruptions occurred at the summit, along the northeast rift zone, or on the north flank in 1843, 1852, 1855-56, 1859, 1873, 1880-81, 1933, 1935, 1940, 1942, 1949, 1975, and 1984.

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The eruption in 1975 threatened the MLO facility. The 1984 eruption at the summit and along the northeast rift zone (at elevations varying from 12,400 feet to 9,350 feet), cut off power to the nearby MLO facility and threatened the town of Hilo to the east. Future lava flows in the area around the proposed site are a near certainty, but the type of flow, extent, location, and timing are unpredictable.

The lava flows upon which the MLO facility was built are thought by some researchers to have been deposited in the mid-1800’s. The subject 4-acre site is situated upon two of the many lava flows that comprise the ongoing shield-building phase of the volcano’s growth. These two flows consist of the upper, younger a’a basalt that predominates the site, and an underlying older pahoehoe basalt flow that generally trends downward in a south to north direction through roughly the center of the site.

It was noted during our reconnaissance that the pahoehoe flow is exposed in outcrops on both the east and west sides of the site, which tends to indicate it might continuously underlie the younger a’a flow.

Although not confirmed by test pits, the clinkery, rubbly a’a lava that characterizes most of the ground surface probably grades into a more massive, or solid, basalt with depth that would tend to contact the underlying older pahoehoe flow.

The surface of the pahoehoe flow is generally characterized by lobes and ropey flow segments that overtop other pahoehoe flow segments, resulting in thickening of the flow. Pahoehoe flows are often characterized by flow tubes, a principal method of advancing the flow front.

However, no large tubes or voids extending below the ground surface were observed within the pahoehoe flow on the site. Only small air pockets less than one inch in diameter were observed in some of the ropey formations.

USGS Lava Flow Hazards Zone Map

A map showing general volcanic hazard zones on the island of Hawaii has been prepared by the U.S. Geological Survey (USGS) and last was last revised in 1987. The current volcanic hazard map divides the island into zones that are ranked from 1 through 9 based on the

!8 probability of future coverage by lava flows, with Zone 1 being the most severe ranking and Zone 9 the least severe. (See Figure 4 of the Appendix).

Lava flow hazard zones are based mainly on the location and frequency of both historic and prehistoric eruptions. Historic eruptions include the first documented flows, beginning in the early 1800's, and those eruptions that are known from Hawaiian oral traditions. The volcanic hazard zones also take into account topographic features of the volcanoes that affect the distribution of lava flows. The hazard map is general in nature and is based on the assumption that future eruptions will be similar to those in the past.

The Lava Flow Hazard Zone Map was not intended to be used at a scale necessary to identify individual parcels on the map, but is intended to identify general areas. The hazard zone boundaries are approximate.

Areas within Hazard Zone 1 are estimated to have been at at least 25 percent covered by lava since 1800. Zone 1 areas include the summit and rift zones of Mauna Loa where vents have been repeatedly active in historic time. Zone 2 includes areas adjacent to and downslope from active rift zones, where the percentage of area covered by lava since 1800 is estimated between 15 and 25 percent.

The subject 4-acre site appears to be within Volcanic Hazard Zone 2, but is also near and immediately down slope of the Zone 1 Mauna Loa northeast rift zone. The proposed site is located in an area that poses a definite but unpredictable risk from volcanic activity in the future.

The change in the degree of hazard from one zone to the next is generally gradual rather than abrupt, and the change can occur over the distance of a mile or more. Within a single hazard zone, the severity of hazard may vary on a scale too fine to map. These variations may be the result of gradual changes that extend across the entire zone. For example, the hazard posed by lava flows decreases gradually as the distance from vents increases.

Other direct hazards from eruptions, such as fragment fallout from volcanic eruptions and ground cracking and shifting, are not specifically considered on the USGS map. These hazards tend to be greatest in the most severe lava flow hazard zones and are considered a definite risk for the subject 4-acre site.

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Future Lava Inundation Probability

In 2012, the USGS investigated an area of 2.5 km by 5.5 km surrounding the NOAA Mauna Loa Observatory (MLO), which includes the subject 4-acre property, to assess the probability of lava inundation of the MLO and the surrounding area. USGS prepared an informative single sheet summary report entitled “Lava Inundation Probability for the North Flank of Mauna Loa”, which is included as Figure 5 of the Appendix.

A reduced scale color-coded map included with the USGS summary report indicates that most of the proposed site is in an area that is estimated to have a probability of lava inundation in the range of approximately one to three percent over the next 50 years, with some smaller areas in the range of three to eight percent.

However, the nearby access road and MLO facility is estimated to have a much higher 8 to 33 percent probability of lava inundation over the next 50 years. It should also be noted that the MLO facility was threatened by a 1975 summit eruption, and lost power as a result of lava flows from a 1984 eruption.

A lava inundation barrier consisting of a triangular shaped filled berm was constructed upslope of the MLO in 1986 to divert or deflect future lava flows away from the facility. The berm is triangular in section and appears to consist of compacted a’a clinker taken from the surrounding area. It was apparently constructed in an upslope area that is most likely to intercept and divert future lava flows that could impact the MLO facility.

In addition to the threat of inundation from flows from the summit and northeast rift zone, the subject site is also at risk from molten lava and ash spattered or ejected from volcanic fountains from both new and re-activated vents that are outside of the summit and the northeast rift zone, and from noxious eruption gases. The site will also be subjected to earthquakes related to these unpredictable volcanic events.

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Preliminary Geotechnical Considerations and Guidelines for Site Development

General

The geotechnical considerations and guidelines for site development presented below are preliminary and general in nature. They are not intended to be used for a specific project or structure. They are intended to provide general but practical geotechnical input for preliminary designs in order to assist those considering a future project on the site to better evaluate the feasibility of the site for their particular development.

The considerations and guidelines presented below cover most ground related issues that affect design and construction on most projects on the island of Hawaii. Topics include excavations, the use of onsite materials for engineered fill and backfill, foundation types, slabs-on-grade, settlements, pavements, retaining walls, seismic and future lava flow considerations, probing and grouting for voids during construction, and general site drainage considerations.

An obvious important construction consideration for this site is its remote location, which is a factor for any project being considered on the site by a prospective developer. While the remoteness of the site is generally discussed in these considerations and guidelines, any prospective developer should evaluate the site’s remote location and its impact on logistics along with the related cost impacts on construction.

Site Preparation

Site work including equipment mobilization, excavations, fill placement, probing for voids, truck and equipment traffic, crushing, and other activities, will create dust. Site work could require significant dust control restrictions due to the desire of the nearby NOAA facility to maintain the surrounding air as clear as possible.

Although the site surface is predominated by rocky materials with very little ash soils or other fines, experience on similar rocky sites in the Kona area has shown that significant dust can be generated from typical grading operations, especially during dry weather periods, even though very little soil might exist on the site.

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Restrictions and requirements for air quality for this site should be investigated and clarified with the governing agencies and other affected parties as part of due diligence to assess the site for dust control during all site work from the start of clearing and grubbing through final grading.

More than a typical number of water trucks might be necessary to adequately control dust during site clearing and grubbing, grading, excavations, void probing, and processing fill materials. Water sources should be investigated since it is our understanding there is no construction water source available at the NOAA facility.

Site preparation should be relatively straight forward since the site had no vegetation or debris to remove at the time of our reconnaissance, and is generally expected to consist mainly of preparing ground surfaces in areas that are going to be filled.

Such preparation would include over-excavating loose areas to an adequate depth, or until suitable dense material is encountered, and proof-rolling the surface as a check for near surface tubes, voids, or loose pockets. Proof-rolling is typically done with heavy equipment such as a large dozer or heavy compactor.

For heavy structures or structures that are sensitive to settlements, the in-situ loose a’a and clinker may require removal to a depth of 5 feet or more, or until hard, intact lava rock is encountered. The depth and lateral extent of removal of in-situ loose rock will depend upon the bearing loads and settlement tolerances of the structures to be supported.

In general, such over-excavated areas are typically backfilled with well-graded crushed rock no greater than approximately 3 inches in maximum size, compacted in thin uniform lifts to at least 95 percent of ASTM D 1557 maximum dry density. Specific backfill materials and compaction procedures would depend on the backfill materials available, and the type and sensitivity of the structure that will be supported by the backfilled area.

For example, if a heavily loaded foundation or a structure that is very sensitive to small settlements is located over a backfilled area, lean concrete or flowable fill (controlled low strength material, or CLSM) might be necessary instead of compacted backfill materials.

CLSM is generally a lean mixture of sand and cement that has excellent bearing properties, with a compressive strength typically between 100 to 1,000 pounds per square inch (psi), but it can

!12 be excavated by a backhoe without blasting or hoe-ramming. It is capable of supporting relatively high foundation loads without significant settlement.

A sufficient number of operational water trucks should be maintained on the site at all times from the start of site clearing to provide adequate dust control, which is expected to be a continuing consideration in this dust-sensitive area.

If voids or lava tubes are encountered during site preparation and excavation work, these undesirable conditions should be fully exposed and cleaned out until suitable dense material or intact lava rock is encountered, with the resulting depression backfilled with suitable backfill materials, lean concrete, or Controlled Low Strength Material (CLSM).

Excavations

Excavation of the relatively loose a’a and clinker materials that predominate the 4-acre site should be easily accomplished by standard backhoes and excavators. Dozers and excavators can usually mass excavate these types of loose lava formations effectively without extraordinary effort.

Since no test pits were performed, the depth of the loose a’a clinker is not known, but it should be expected to vary significantly throughout the site. Loose clinker and a’a lava can sometimes extend deep below the ground surface, but they tend to be more fused, harder, and more difficult to excavate with depth. Dozers with single rippers are often necessary to effectively mass excavate in fused a’a or clinker.

Trench excavations in the loose a’a and clinker can usually be accomplished relatively easily by an excavator. However extensive caving and sloughing of excavation sides in these loose materials should be anticipated, requiring shoring or sloping to safely work on underground utilities or structures.

Excavations into the solid pahoehoe lava flow that roughly bisects the 4-acre site lengthwise are generally expected to encounter difficult resistance to penetration due to the hardness of this relatively intact lava formation. Large dozers (D-10 or larger) equipped with a single ripper are usually required to mass excavate this type of intact lava rock effectively.

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Hoe-rams and large excavators are usually required to excavate trenches into intact pahoehoe lava formations, or into fused a’a and clinker. Jackhammers are sometimes needed for isolated hard rock that is not accessible to an excavator or a hoe-ram. Blasting is sometimes used in areas that are particularly hard and difficult to remove, but blasting might not be permitted on this sensitive site.

Ragged, caving conditions should be expected for all trenches and other excavations dug into intact rock because most lava rock on the island of Hawaii is fractured and broken to some degree. This common rock condition typically results in the unavoidable removal of irregular blocks or chunks of rock from excavation walls, rather than uniform removal of material limited by the width of the excavator bucket.

Lava rock formations can vary significantly over short vertical and lateral distances. Highly variable subsurface lava rock formations should be expected randomly throughout the 4-acre site. Large voids, lava tubes, and loose ash soil pockets were not seen on the surface during our site reconnaissance, but these unpredictable subsurface conditions are common on the island of Hawaii and could exist on this site at random locations and depths.

Excavations should generate predominantly broken a’a lava rock and clinker, which we believe could be used as engineered fill if they are processed, sized, and compacted in accordance with the preliminary recommendations of this report, below.

Most of the loose a’a and clinker observed on the surface of the site appeared to be relatively brittle and should tend to break down readily into smaller sizes under the action of heavy equipment, or a rock crusher. The a’a and clinker are considered to be usable as a suitable source of engineered fill and backfill without extraordinary crushing effort.

Excavations into the intact pahoehoe flow in the center of the 4-acre site are expected to generate predominantly angular boulders between roughly 1 foot to several feet in dimension, with some smaller rock sizes. Larger blocks of hard, intact lava up to 8 feet or more in dimension can often be generated on intact lava rock sites.

The excavated pahoehoe will need more crushing and processing than the smaller loose a’a and clinker, and is generally not expected to be a consistent economical source of engineered

!14 fill unless it is run through a crusher. The larger chunks and blocks usually need breaking up by a hoe-ram into sizes that are small enough to be accepted by an on-site crusher.

Permanent slopes that are cut into the loose a’a and clinker should generally be constructed no steeper than a 2 Horizontal: 1 Vertical (2H:1V) grade.

Permanent slopes that are cut into dense, fused a’a and clinker, or highly broken rock can usually be cut as steep as 1.5H:1V.

Steeper slopes can be allowed in massive, slightly broken intact lava rock, but the steeper slopes generally would need a field evaluation made by the project geotechnical engineer during grading to verify the rock condition and acceptable slope inclination.

Use of Onsite Materials for Engineered Fill and Backfill

If adequately crushed and processed, the onsite rocky materials should make excellent engineered fill, backfill, and select borrow. Adequate crushing and screening should result in relatively well-graded granular materials that are non-expansive, not sensitive to moisture, relatively readily compactable, with very good bearing and pavement support properties.

In our opinion, it is important to produce as much fill and backfill as possible on this remote site with a crusher, rather than importing them from an off-site borrow source. The use of an onsite crusher is generally a more important consideration if a relatively large amount of embankment is planned, as opposed to a smaller project for which importing a small amount of fill and backfill might be more economical.

Using onsite crushers is a common construction practice on the island of Hawaii since most construction sites have rocky ground conditions and the costs of importing suitable fill and backfill materials usually exceed the cost of maintaining a crusher to process the available onsite excavated rock.

Crushers create dust, and the use of an onsite crusher on this site during grading and site work could have significant restrictions due to the desire of the nearby NOAA MLO facility to maintain the surrounding air as clear as possible. Experience has shown that even very small amounts of fine ash soil can result in dusty conditions from crushing and grading activities.

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Restrictions and requirements for air quality for this site should be investigated and clarified with the governing agencies as part of a due diligence effort to assess the site for the feasibility of an onsite crusher, and for grading work in general.

Onsite rocky materials will require a crusher to adequately break them down into suitable sizes for fill and backfill. Most of the loose a’a and clinker that predominate the surface of the site is less than about 12 inches in size and appear to be relatively brittle, which makes it well suited for processing with even a relatively small crusher.

In addition, most of the relatively brittle loose onsite a’a and clinker seen on the surface should break down readily if spread in loose lifts of less than about 12 inches and rolled with heavy equipment such as a Caterpillar 825B sheepsfoot compactor, a 15-ton vibratory drum compactor, or large dozers (D-9 or larger).

The onsite loose a’a clinker that predominates the surface of the 4-acre site is not considered to be suitable material from which base course could be produced. The brittleness of most of the clinker will tend to make it break up readily if subjected to a Los Angeles Abrasion Test (AASHTO T 96), with excessive loss that, in our opinion, would probably exceed the 50 percent loss requirements for base course required by the Standard Specifications for Public Works Construction for the County of Hawaii (1986).

We believe the clinker should be suitable for the onsite production of select borrow, which is generally considered to be a superior fill and backfill material that is typically recommended for use in critical fills and backfills, such as within the upper 2 to 3 feet of building subgrades.

Select borrow is defined by the Standard Specifications to be a granular material, such as crushed rock, that is less than 3 inches in maximum dimension, with no more than 15 percent passing a No. 200 sieve, and a minimum California Bearing Ratio of at least 25.

The massive, intact pahoehoe lava near the center of the site is expected to break up into larger chunks and blocks that will need more processing than the a’a clinker. The larger blocks will probably need breaking up by a hoe-ram into sizes that are small enough to be accepted by a portable onsite crusher. Most of the intact pahoehoe is not considered to be amenable to effective crushing by heavy equipment.

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Crushed rock from the denser, harder pahoehoe flow is considered to be more suited for onsite base course production, but will generally require more work to excavate, break into suitable sizes for a mobile crusher, and crush, compared to the lighter, more brittle clinker. Although various base course sizes and gradation variations are allowed on the island of Hawaii, the most common base course is 1.5-inches in maximum size.

Base course should conform to the requirements of the Standard Specifications of the Department of Public Works for the County of Hawaii (1986), including a maximum plasticity index (PI) of 6, a minimum sand equivalent of 35 percent, a maximum LA Abrasion loss of 50 percent, and a minimum CBR value of at least 85 when compacted to 95 percent of ASTM D 1557 maximum dry density.

In our opinion, engineered fill within the upper 3 feet of graded pads that support buildings or other structures should generally consist of well-graded crushed rock that is no greater than 3 inches in maximum dimension. The 3-inch minus crushed rock is also generally recommended for the upper 2 feet of fill placed in pavement subgrades.

In portions of engineered fills greater than 3 feet below finished grade, the maximum rock size in the well-graded crushed rock mixture can be increased to 6 inches.

For engineered fills, both the 3-inch minus and 6-inch minus materials should generally be placed in lifts not exceeding 12 inches in loose thickness and compacted to at least 95 percent of ASTM D 1557 maximum dry density. Heavy dozers are recommended to spread and track successive lifts of these materials, supplemented by heavy sheepsfoot or vibratory compactors.

Sufficient water should be used so that no dust is created during grading operations. Water sources should be identified prior to grading to ensure that adequate construction water is available during all site work on this dust sensitive site.

Boulders up to 12 inches to 18 inches in maximum dimension are frequently used in deeper engineered fills on the island of Hawaii, and can be considered for use in deep fills at the subject 4-acre site. Their use would depend on the extent and depth of fills, the fill materials available, the grading contractor’s equipment and capabilities, and the types of structures to be supported by the boulder fills.

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The use of such larger boulder fills should be limited and strictly controlled during grading by the project geotechnical engineer. Typically, boulder fills are placed in lifts that do not exceed the thickness of the maximum boulder size. Thus, the loose lift thickness for 18-inch minus rocky fill material should not exceed 18 inches.

The initial lift of boulder fills should generally be spread and tracked into place using a D-9 dozer, or larger. Multiple passes of a heavy sheepsfoot compactor (825B or equivalent) or a heavy vibratory steel drum roller, should be accomplished after tracking by the dozer. Sufficient passes by the compactor should be made until there are no signs of significant movement in the lift prior to placing the next lift of rocky fill. Rocky fills should be built up in successive uniform lifts by repeating these procedures.

Fill slopes constructed with on-site crushed rock materials should generally be built no steeper than 2Horizontal:1Vertical (2H:1V).

Trench backfill and retaining wall backfill should consist of well-graded onsite crushed rock with no rocks greater than 3 inches in dimension. Backfill should generally be placed in lifts not exceeding 8 inches in loose thickness and compacted to at least 95 percent ASTM D 1557 maximum dry density using hand-operated mechanical compaction equipment.

Bedding materials around underground utilities and structures should conform to the Standard Specifications for Public Works Construction for the County of Hawaii. Generally, crushed rock that is less than 1 inch in maximum size conforms to bedding requirements of Hawaii County Standard Specifications.

Due to their coarse consistency, rocky fills that consist of rocks greater than about 3 inches in maximum size often cannot be accurately tested using conventional field density testing methods. Such rocky fills should be periodically observed by the project geotechnical engineer to verify that approved materials and effective compaction procedures and equipment are used by the grading contractor.

Periodic field density tests should be performed in rocky materials that are less than 3 inches in size to evaluate the degree of compaction being attained.

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Foundations

In our opinion, the site is suitable for the use of conventional spread and strip foundations and reinforced slab-on-grade foundations to support most structures without extraordinary or unusual designs, provided the general preliminary guidelines in this report are followed.

Foundations can bear upon intact natural lava rock, dense welded a’a formations, or rocky engineered fill that is adequately compacted in accordance with the general grading recommendations of this report.

In order to minimize the risk of differential settlements, especially from earthquakes, foundations that support an individual settlement sensitive structure should generally bear upon uniform materials.

Individual foundations should not bear partially on cut natural ground and partially on fill. Some variation to this general guideline can be made depending on the subsurface ground conditions exposed, the structural loads, and the sensitivity of the structure to settlements.

Foundations should not bear on loose clinker, loose a’a, or ash soil pockets. Individual foundations should not bear partly on intact rock and partly on fill. Support of foundations on unsuitable or variable materials can result in local stress and differential settlements, with resulting cracking and distress to the foundations and other building elements.

Uniform bearing conditions are an especially important consideration for structures that are very sensitive to settlement and other ground movements, which are complicated by the seismic risks on this site.

Preliminary designs for spread, strip, and reinforced slab foundations can be made using the following preliminary geotechnical parameters:

max. allowable bearing capacity in compacted fill: 2,500 pounds per square foot (psf) max. allowable bearing capacity in intact rock: 4,000 psf friction factor (concrete on engineered fill): 0.40 friction factor (concrete on intact rock): 0.50 passive lateral pressure (engineered fill): 200 pounds per cubic foot (pcf);

equivalent fluid passive lateral pressure (intact rock): 400 pounds per cubic foot (pcf);

equivalent fluid subgrade modulus (engineered fill): 100 pounds per cubic inch

!19 subgrade modulus (intact rock): 200 pounds per cubic inch concrete/intact rock bond strength for piers: 30 pounds per square inch (psi) unit weight of intact lava rock: 140 pounds per cubic foot unit weight of compacted engineered fill: 130 pounds per cubic foot

Except for the maximum allowable bearing capacities, no safety factors have been applied to the above values. These values are not for final design, but only presented to provide preliminary design parameters to assist with preliminary feasibility evaluation of construction on the site.

Deep foundations such as drilled, cast-in-place reinforced concrete piers or grouted micropiles could be required for structures with large lateral and uplift forces such as towers, telescopes, or communications discs.

Preliminary designs for reinforced concrete piers or grouted micropiles can be made using the above parameters and a concrete/intact rock bond stress of 50 pounds per square inch (psi), assuming the rock is clean and free of loose material.

Estimated Foundation Settlements

Settlement estimates for future structures whose foundation loads, size, and designs are not known is very speculative and should be looked at as approximate guidelines rather than accurate predictions to be relied upon for future designs. We do not attempt in this reconnaissance report to predict what structural settlements resulting from earthquakes, volcanic events, or the presence of lava tubes and voids, might be, and consider such an exercise as too speculative.

Foundation settlement estimates due to static loads and relatively transitory live loads, like from wind forces, are more feasible to make than estimates for settlements caused by earthquakes, or ground movements resulting from volcanic activity.

These natural events are unpredictable, and could range from mild to severe, or even catastrophic, in this area of frequent earthquakes and relatively frequent volcanic eruptions.

Building over lava rock always entails some risk that unidentified lava tubes and other voids exist beneath foundations and structures, despite reasonable efforts by consultants, designers, !20 and contractors. Many years of experience has shown that voids can exist at random locations and it is difficult to completely eliminate the risk of their presence economically.

However, it should be noted that we generally do not consider the ground conditions we observed on the subject 4-acre site to be highly susceptible to future settlements under static and transitory wind loading conditions, provided appropriate guidelines for foundations, engineered fills, and retaining walls are followed.

The intact pahoehoe rock consistency is variable, but generally appears to be hard. It should be capable of supporting high bearing loads without significant settlements, provided the thickness of the intact rock is verified, probe and grout operations confirm there are no significant underlying tubes or voids in the affected bearing zone, and all the recommendations herein and in the final geotechnical report are followed.

Usually the bearing capacity in intact pahoehoe rock is limited by what anomalies or irregularities might be present rather than simply the compressive strength of the intact rock.

The loose clinker that predominates the 4-acre site is unsuitable as foundation bearing material in its natural loose condition. However, if it is removed down to dense to intact rock, crushed and processed into recommended sizes, and replaced and compacted in thin lifts as engineered fill, it should make an excellent dense bearing material that would be expected to be non-expansive, non-plastic, not sensitive to moisture, and generally capable of supporting moderate to relatively high bearing loads without excessive settlements.

There were no soft or highly compressible soils seen on the site that would be expected to settle significantly, only very isolated deposits of tan ash soil that are considered insignificant from a bearing or foundation settlement perspective.

Pockets of loose, powdery ash soils can sometimes be randomly found in intact lava rock and clinker or a’a deposits, but no definitive signs of their presence were observed during our site reconnaissance. If found during construction, they would have to be removed and replaced with approved fill materials.

Provided the preliminary guidelines presented in this report for grading and foundation design are followed and a maximum allowable bearing capacity of 2,500 psf is used, we would not

!21 expect individual spread foundations that bear upon engineered fill and support small, relatively lightly loaded structures to settle more than roughly 3/4-inch total and 1/2-inch differential from static loads and short term transitory live loads, not including earthquake loads.

Provided the preliminary guidelines presented in this report for grading and foundation design are followed and a maximum allowable bearing capacity of 4,000 psf is used, we would not expect individual spread foundations that bear upon intact pahoehoe rock that is free of voids to settle more than roughly 1/2-inch (total and differential) from static loads and short term transitory live loads, not including earthquake loads.

Preliminary settlement estimates for large reinforced concrete slab-on-grade or mat foundation systems that support broad, relatively heavy area loads for large structures can be estimated using the modulus of subgrade reaction provided in the Foundations section, above.

The above preliminary settlement values are only approximate. More accurate settlement estimates and estimates of seismic-related settlements should be accomplished by the project geotechnical engineer for specific structures after subsurface information has been generated by test borings or test pits, and after specific building loads and settlement tolerances of the planned structures are known.

Concrete Slabs-on-Grade

Concrete slabs-on-grade can be supported on intact lava rock or approved rocky engineered fill that conforms to the preliminary guidelines of this report. A 4-inch thick layer of clean, crushed drain rock (100% passing 1-inch, 0% passing 3/8-inch) is generally recommended below all building slabs to provide a capillary moisture barrier and relatively uniform bearing material throughout the slab-on-grade.

An impermeable membrane should be placed between the gravel layer and the bottom of the slab concrete as a moisture barrier for interior slabs. The membrane can be deleted if slab moisture is not important for elements such as lanais, sidewalks, or other exterior slabs.

It is essential that moisture-sensitive slabs-on-grade are thoroughly waterproofed with fail-safe…