kaneohe/kailua sewer tunnel project

Kaneohe/Kailua Sewer Tunnel Project

Geotechnical Baseline Report

February 2013

Prepared by:

Jacobs Associates 465 California Street, Suite 1000

San Francisco, CA 94104

Kaneohe/Kailua Sewer Tunnel Project Geotechnical Baseline Report

Jacobs Associates -ii- Rev. 0 / February 2013

Distribution To: Richard Harada Wilson Okamoto Corporation From: Steve Klein, PE, GE Jacobs Associates Prepared By: Tom Pennington, PE Jacobs Associates Phaidra Campbell

Jacobs Associates John Waggoner, RG, CEG Jacobs Associates

Reviewed By: Steve Klein, PE, GE Jacobs Associates

John Stolz, PE Jacobs Associates


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Table of Contents

1 Introduction ...................................................................................................................................... 1

1.1 Purpose and Scope............................................................................................................. 1

1.2 Report Organization ............................................................................................................ 2

1.3 Geologic and Geotechnical Investigations .......................................................................... 2

2 Project Description ........................................................................................................................... 3

2.1 Kaneohe/Kailua Sewer Tunnel ........................................................................................... 3

2.2 Kaneohe Shaft .................................................................................................................... 4

2.3 Kailua Tunnel Influent Pump Station (TIPS) Shaft .............................................................. 4

2.4 Tunnel Access Shaft ........................................................................................................... 5

2.5 Kailua Drop Shaft and Tunnel Adit ...................................................................................... 5

3 Site Conditions ................................................................................................................................. 7

3.1 Geologic Setting .................................................................................................................. 7

3.2 Previous Tunnel Construction Experience .......................................................................... 8

3.3 Geologic Units ..................................................................................................................... 8

3.3.1 Soil Deposits .......................................................................................................... 8

3.3.2 Rock Units ............................................................................................................ 11

3.4 Rock Properties ................................................................................................................. 12

3.4.1 Weathering and Alteration ................................................................................... 12

3.4.2 Intact Rock Strength ............................................................................................ 13

3.4.3 Rock Density ........................................................................................................ 13

3.4.4 TBM Boreability Testing ....................................................................................... 13

3.4.5 Rock Mass Discontinuities ................................................................................... 14

3.4.6 Rock Mass Quality ............................................................................................... 15

3.4.7 Rock Mass Types................................................................................................. 15

3.4.8 Hydraulic Conductivity ......................................................................................... 16

3.5 Groundwater Conditions ................................................................................................... 16

3.6 Hazardous Gas ................................................................................................................. 17

3.7 Seismicity .......................................................................................................................... 17

3.8 Contaminated Soil and Groundwater ................................................................................ 18

4 Anticipated Ground Conditions ...................................................................................................... 19

4.1 Reach 1 (Station 0+15 to 5+00) ........................................................................................ 19

4.1.1 Grain Size Distribution and Plasticity ................................................................... 20

4.1.2 Strength and Consistency .................................................................................... 20

4.1.3 Groundwater and Hydraulic Conductivity ............................................................ 21

4.1.4 Potential Ground Behavior ................................................................................... 21


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4.2 Reach 2 (Station 5+00 to 10+00) ...................................................................................... 21





4.3 Reach 3 (Station 10+00 to 162+00) .................................................................................. 23

4.3.1 Mineralogy ............................................................................................................ 24

4.3.2 Strength ................................................................................................................ 24

4.3.3 Discontinuities ...................................................................................................... 24




4.4 Reach 4 (Station 162+00 to 163+50) ................................................................................ 26



4.4.3 Discontinuities ...................................................................................................... 27




5 Tunnel Construction Considerations .............................................................................................. 29

5.1 Tunnel Initial Support Requirements ................................................................................. 29

5.2 Conventionally Mined Tunnel at the KWPTF .................................................................... 30

5.2.1 Ground Stabilization ............................................................................................. 30

5.2.2 Excavation Methods ............................................................................................. 31

5.2.3 Initial Support Requirements ................................................................................ 31

5.3 Starter Tunnel and Tunnel Adit at the KRWWTP ............................................................. 31

5.3.1 Ground Improvement ........................................................................................... 31



5.4 TBM Tunnel ....................................................................................................................... 33


5.4.2 Open Main-Beam TBMs ...................................................................................... 33

5.4.3 TBM Performance Estimates ............................................................................... 34


5.5 Design Ground Loads ....................................................................................................... 35

5.6 Pre-excavation Probing, Grouting, and Drainage ............................................................. 35

5.7 Groundwater Inflows ......................................................................................................... 35


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5.8 Water Treatment and Disposal ......................................................................................... 36

5.9 Tunnel Final Lining ............................................................................................................ 36

5.10 Muck Disposal ................................................................................................................... 36

6 Shaft Construction Considerations ................................................................................................ 39

6.1 Kaneohe Shaft .................................................................................................................. 39

6.1.1 Anticipated Subsurface Conditions ...................................................................... 39

6.1.2 Excavation Support Requirements and Excavation Methods .............................. 39

6.1.3 Excavation Support System Design and Lateral Earth Pressures ...................... 40

6.1.4 Groundwater Control ............................................................................................ 40

6.2 Kailua TIPS Shaft .............................................................................................................. 41





6.3 Tunnel Access Shaft ......................................................................................................... 43

6.3.1 Anticipated Ground Conditions ............................................................................ 43




6.4 Kailua Drop Shaft .............................................................................................................. 45





6.5 Water Treatment and Disposal ......................................................................................... 47

6.6 Muck Disposal ................................................................................................................... 47

7 Geotechnical Instrumentation and Monitoring ............................................................................... 49

7.1 Surface Instrumentation .................................................................................................... 49

7.2 Tunnel Instrumentation ..................................................................................................... 49

8 References ..................................................................................................................................... 51

9 Glossary ......................................................................................................................................... 55

10 Revision Log .................................................................................................................................. 59


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List of Tables

Table 1. Summary of Field and Laboratory Test Data for Soil Deposits .................................................... 63

Table 2. Descriptive Terms for Intact Rock Strength .................................................................................. 64

Table 3. Basalt Density According to Weathering Category ....................................................................... 65

Table 4. BTS, CAI, and Punch Penetration Test Results ........................................................................... 65

Table 5. Petrographic Analysis Summary ................................................................................................... 66

Table 6. Rock Mass Types .......................................................................................................................... 67

Table 7. Groundwater Level Measurements ............................................................................................... 68

Table 8. Tunnelman’s Ground Classification .............................................................................................. 69

Table 9. Definitions of Ground Behavior Terms .......................................................................................... 70

Table 10. Discontinuity Orientations ........................................................................................................... 71

Table 11. Rock Mass Type Distribution for Reach 3 .................................................................................. 71

Table 12. Minimum Design Ground Loads for Tunnel Initial Supports ....................................................... 71

List of Figures

Figure 1. Project Location Map

Figure 2-1. Geologic Profile, Plan and Legend

Figure 2-2. Geologic Profile, Station 0+15 to 38+00




Figure 2-6. Detailed Geologic Profile, Reaches 1 and 2

Figure 2-7. Geologic Profile, Kailua TIPS Shaft and Starter Tunnel

Figure 3. Rock Contour Map, Kailua TIPS Shaft and Starter Tunnel

Figure 4. Inferred Extent of Ko’olau Caldera

Figure 5. Intact Rock Strength Summary

Figure 6. RQD Distribution

Figure 7. RMR Distribution

Figure 8. Q Index Distribution

Figure 9. Core Recovery and RQD at Tunnel Depth

Figure 10. Hydraulic Conductivity Distribution

Figure 11. Gradation Summary – Lagoonal & Estuarine Deposits

Figure 12. Gradation Summary – Older Alluvium

Figure 13. Gradation Summary – Weathered Basalt


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Figure 14. Discontinuity Orientations

Figure 15. Discontinuity Spacing Distribution

Figure 16. Tunnel Loading Diagram

Figure 17. Potential Key Blocks

Figure 18. Lateral Earth Pressure Diagrams – Kaneohe Shaft and Kailua TIPS Shaft

Figure 19. Lateral Earth Pressure Diagrams – Kailua Drop Shaft and Tunnel Access Shaft

Appendices

Appendix A. Previous Tunnel Construction Experience


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Addendum No. 3, Revised: 4/22/13

1 Introduction The Kaneohe/Kailua Sewer Tunnel Project involves construction of a sewer tunnel between the Kaneohe Wastewater Pretreatment Facility (KWPTF) and the Kailua Regional Wastewater Treatment Plant (KRWWTP) on the island of Oahu in Hawaii. In addition, other facilities will be constructed as part of this Contract, as discussed below. The tunnel is intended to convey wastewater flows from the KWPTF to the KRWWTP and to provide storage for peak wet-weather flows, thereby reducing overflows that occur when wastewater flows exceed the capacity of the existing KRWWTP. The project location is shown in Figure 1. The primary component of this project is an approximately 16,340-foot-long, 120-inch minimum inside-diameter (ID) tunnel. The other facilities include near-surface diversion pipelines, a tunnel junction structure, and a vortex drop structure at the upstream end at the KWPTF; an intermediate tunnel access shaft located off the access road to the Kapaa Water Tank Site along Mokapu Saddle Road; and near-surface diversion pipelines, a drop structure, and a large shaft for the future pump station and two small shafts at the KRWWTP. The City and County of Honolulu, Hawaii, retained Wilson Okamoto Corporation (WOC) as the prime consultant and Jacobs Associates (JA) as a specialty subconsultant to design the tunnel and related elements of the project. Brown and Caldwell and Yogi Kwong Engineers (YKE) are designing the facilities at the KWPTF and KRWWTP, which are also included in this Contract. 1.1 Purpose and Scope This Geotechnical Baseline Report (GBR) was prepared for the City and County of Honolulu, Hawaii, for use in advertising for construction bids and administering the construction contract. This GBR was prepared based on an evaluation and interpretation of the data presented in the Geotechnical Data Report (GDR) (YKE, 2013a), inspection of soil/rock samples, review of regional and local geology, and tunneling experience in Hawaii. The objectives of this GBR are to:

• Provide a summary of the anticipated ground conditions, ground behavior, and groundwater conditions in order to facilitate the Owner’s and the Contractor’s understanding of the geotechnical conditions and ground behavior to be addressed for bidding and construction of the main tunnel and four of the shaft excavations.

• Establish baselines for the anticipated geotechnical conditions for certain elements of the

project (as described herein) to be relied upon in the preparation of the bid.

• Assist in administering differing site conditions clause contained in the Contract Documents, for the elements discussed herein, by providing a basis for their evaluation.

Ground behavior described herein is based on the stated assumptions regarding construction means and methods. If different methods or sequences are employed, ground behavior may will likely vary from




that described. The Contractor must review and evaluate the Contract Documents, together with the GBR, GDR, and other geotechnical information, and consider how its selected means and methods will affect ground behavior and the construction of the tunnel/shaft facilities. This will require the assistance of a qualified geotechnical engineer/engineering geologist. The GBR is contractually binding and although not the exclusive source of geotechnical information, the General Conditions of the Contract provide that the GBR takes precedence over the GDR and any other geotechnical information, references, or interpretations. This report does not address geotechnical conditions for the near-surface pipelines, diversion structures, or Tunnel Junction Structure at the KWPTF or the near-surface pipelines and related diversion structures and shafts at the KRWWTP. The geotechnical conditions for these project elements have been evaluated by others (YKE, 2013b; YKE, 2013c). 1.2 Report Organization Section 2 provides additional description of the project elements. Section 3 provides a discussion of the primary sources of geologic/geotechnical information and the regional and site geology. Section 4 describes the provides the baseline ground conditions and ground behavior that are to be assumed for construction and bidding. Sections 5 discusses and 6 provide discussions of construction considerations for the tunnel regarding issues that, in the designer’s opinion, stand out as having particular importance for construction contractors to consider when developing their construction approaches and bids. Section 6 discusses ground conditions and construction considerations for shaft construction. Section 7 summarizes the rationale for the instrumentation and monitoring requirements contained in the project Specifications. A glossary of terms used in this report is included in Section 9. 1.3 Geologic and Geotechnical Investigations Geologic and geotechnical information is available from published reports and from two subsurface investigations that were completed for the project. The most recent investigation was performed by YKE. It focused on the current tunnel alignment, and the findings are contained in the GDR. A prior investigation was performed by GeoLabs, focusing on several potential tunnel alignments. Those findings are contained in the Preliminary Geotechnical Exploration Report (PGER) (GeoLabs, 2011). Relevant information from other geologic investigations, including for other nearby projects, was reviewed and is incorporated in the GDR and was considered in preparing this GBR. References are provided in the GDR and herein. Terms used to describe geologic conditions are defined in the GDR and only defined in this report if they are not used in the GDR. Figure 2-1 provides a map of the project alignment, showing the locations of borings that are relevant to the current tunnel alignment.




2 Project Description The Kaneohe/Kailua Sewer Tunnel is a minimum 120-inch ID conveyance and storage tunnel that will convey wastewater flows from the KWPTF to the KRWWTP. The purpose of the tunnel and associated improvements at the KWPTF and KRWWTP is to bring the City and County of Honolulu into compliance with the 2010 judicial Consent Decree by providing additional means of wastewater conveyance and storage capacity, which will reduce future overflows when capacity of the existing KRWWTP is exceeded. In addition, the tunnel will replace the existing 42-inch-diameter force main that conveys pretreated wastewater from the KWPTF to the KRWWTP. The Kaneohe/Kailua Sewer Tunnel Project includes the construction of a tunnel approximately 16,340 feet long (see Figure 1); near-surface diversion pipelines, a tunnel junction structure, and a vortex drop structure at the Kaneohe Shaft; an intermediate tunnel access shaft located at the Bureau of Water Supply (BWS) Kapaa Water Tank Site along Mokapu Saddle Road; and near-surface diversion pipelines, two shafts, a drop shaft, and a large shaft for the future pump station at the KRWWTP (Kailua Tunnel Influent Pump Station (TIPS)). More detailed descriptions of the project facilities relevant to this report are presented in the following sections. 2.1 Kaneohe/Kailua Sewer Tunnel From west to east, the tunnel alignment begins at the KWPTF in Kaneohe and crosses beneath the Kawa Stream and the adjacent Bay View Golf Park. After crossing the golf park, the tunnel crosses Kaneohe Bay Drive and continues along Moakaka Place before passing beneath two privately owned properties at the end of Moakaka Place. The tunnel follows a southeasterly course for approximately 1,000 feet along state-owned conservation land (Oneawa Hills) and then turns to the northeast, crossing Mokapu Saddle Road and passing below the access shaft site located at the BWS Kapaa Water Tank Site to the north of Mokapu Saddle Road. The tunnel continues in a northeasterly direction for approximately 1,800 feet and obliquely passes below the Interstate H-3 right-of-way. After passing underneath the H-3, the tunnel continues along conservation land for approximately 6,000 feet and then passes below the Aikahi Gardens townhome complex and parallels Halia Street for a distance of about 300 feet. The tunnel then crosses Kaneohe Bay Drive and enters the KRWWTP site. From KWPTF to KRWWTP the tunnel maintains a constant slope of about 0.167 percent. Tunnel invert elevations are approximately El. -34.7 feet at the KWPTF and El. -62 feet at the KRWWTP; ground cover above the tunnel ranges from approximately 20 feet to over 600 feet. The tunnel is designed to convey wastewater under gravity flow and is therefore not anticipated to be exposed to significant internal pressure during operation. The tunnel is required to have a watertight final lining to control leakage and is to be lined with glass fiber-reinforced thermosetting resin pipe (GFRP), except for the downstream end of the tunnel, which will be lined with concrete to accommodate the connection to the TIPS. The annulus outside the GFRP will be backfilled with low density cellular concrete with the exception of pipe connections, at the ends of the tunnel, and at the access shaft, which will be backfilled with structural concrete.




The tunnel geologic profile is shown in Figures 2-2 to 2-7. The tunnel is expected to encounter primarily basaltic rock with sections of soft ground, residual soils/weathered rock, and mixed face conditions at the KWPTF and along a portion of the alignment beneath the Bay View Golf Park. The tunnel is also expected to encounter weathered rock at the KRWWTP, adjacent to the Kailua TIPS Shaft. 2.2 Kaneohe Shaft Flows will only enter the tunnel at the existing KWPTF by means of the Kaneohe Shaft. This shaft is approximately 54 feet deep and about 30 feet in diameter. Connection to the existing flow regime at the KWPTF will be by means of two new diversion structures and two diversion pipelines, which will consolidate and divert flows from the existing pretreatment facilities into the tunnel. The flows will be consolidated at the Tunnel Junction Structure located adjacent to the Kaneohe Shaft and then directed to the tunnel through two vortex drop shafts constructed within the Kaneohe Shaft. In addition to conveying flows to the tunnel, the Kaneohe Shaft will serve as the construction shaft for the conventionally mined tunnel. This section of tunnel is anticipated to extend from the shaft (Station 0+15) to about Station 11+00. Following completion of mining from the KRWWTP, the KWPTF site and shaft will be used as staging for installation and backfill of the GFRP within the tunnel. Construction sequencing is indicated on the Contract Drawings and in the Specifications. 2.3 Kailua Tunnel Influent Pump Station (TIPS) Shaft The downstream end of the tunnel terminates at the Kailua TIPS Shaft at the KRWWTP, where flows will be pumped from the tunnel for treatment and disposal. Connection of the Kailua TIPS Shaft to the KRWWTP will be by means of new diversion structures and diversion pipelines, which will consolidate and divert flows from the existing treatment facilities into the tunnel via the Kailua Drop Shaft and the Tunnel Adit. The 87-foot ID Kailua TIPS Shaft will provide the primary access to the tunnel and serve as the launch shaft for the tunnel boring machine (TBM). The size of this shaft is controlled by pump station requirements, not by tunnel construction requirements. Construction work will be staged primarily from a 2.3-acre site within the KRWWTP. Since extended work hours are allowed at this site as part of the project Noise Variance, the staging area will require construction of a temporary sound wall to mitigate noise and light impacts on the adjacent residential community. Details of the sound wall are provided on the Contract Drawings, and noise and vibration requirements are provided in the Specifications. The Kailua TIPS Shaft will be excavated to a depth of approximately 95 feet, which is about 21 feet below the invert of the tunnel. This depth is required for construction of the TIPS structure, which is not part of this Contract. After excavation to the TIPS structure foundation level, the shaft can be backfilled to provide a temporary working pad for tunnel construction. This backfill is to be removed following completion of the Contract and prior to handover of the shaft to the follow-on construction contractor for the TIPS. With the exception of the GFRP tunnel lining between Station 162+15 and the Transition Tunnel Structure at about Station 162+90, and the Tunnel Adit, installation and backfill of the GFRP tunnel




lining within the tunnel are required to be staged from the KWPTF. Details of construction sequencing requirements are indicated on the Contract Drawings and in the Specifications. The pump station will be constructed within the Kailua TIPS Shaft under a separate, follow-on contract. 2.4 Tunnel Access Shaft The Tunnel Access Shaft is located in the central portion of the tunnel alignment at Station 78+86. This shaft is approximately 275 feet deep and will be lined with a 96-inch ID GFRP riser. The shaft is to be excavated by raise bore methods to a diameter of about 11 to 12 feet. Connection of the Tunnel Access Shaft to the tunnel will be accomplished with a GFRP Tee section. The Tee section and the surrounding tunnel GFRP lining will be backfilled with structural concrete. The remaining riser pipe will be backfilled with cellular concrete up to the ground surface. Just below the ground surface the riser pipe will be fitted with a fiber-reinforced polymer frame and air-tight lid. A precast concrete manhole cover will be constructed over the lid, as indicated in the Contract Drawings. Other surface improvements at the Tunnel Access Shaft site include site grading and construction of a gravel pad to stage future personnel and equipment for entry into the shaft and tunnel during tunnel operation. 2.5 Kailua Drop Shaft and Tunnel Adit Flows from the existing Kailua Influent Pump Station (KIPS) at the KRWWTP will be conveyed to the tunnel just upstream of the Kailua TIPS Shaft through a near-surface 48-inch diameter pipeline and drop structure that will drop flows to the tunnel. The drop structure will be located west of the Kailua TIPS Shaft and will connect to the tunnel through a 33-inch diameter drop shaft, known as the Kailua Drop Shaft, and a 96-inch diameter tunnel adit, known as the Tunnel Adit. Both the Kailua Drop Shaft and Tunnel Adit will be constructed with GFRP. The Tunnel Adit is located about 110 feet upstream of the Kailua TIPS Shaft (at approximate Station 162+40) and it extends for a horizontal distance of approximately 20 feet. The Kailua Drop Shaft will connect to the crown of the Tunnel Adit at a depth of approximately 67 feet below the ground surface, at about El. -50 feet. A plunge pit will also be constructed within the Tunnel Adit pipe to collect flows entering from the Kailua Drop Shaft. Excavation, installation, and backfill of the Kailua Drop Shaft and Tunnel Adit pipes will require coordination with tunnel excavation, construction of the drop structure and near-surface pipelines, and the installation of the GFRP lining in the tunnel.




3 Site Conditions 3.1 Geologic Setting The island of Oahu was formed by two volcanoes: the older Waianae Volcano of the Waianae Volcanic Series in the west, and the younger Ko’olau Volcano of the Ko’olau Volcanic Series in the east (closest to the project site). Following an eruptive stage during which the island was formed, a period of quiescence began. During this volcanic quiescence, the island’s form was modified by erosional forces and the occurrence of the massive Nuuanu Landslide, which removed much of the eastern flank of the Ko’olau Volcano. The remaining western portion of the Ko’olau Volcano and remnants of the caldera wall now form the summit of the Ko’olau Range. Although much of the Ko’olau Caldera has been removed by landsliding and erosion, its remnants have been interpreted to extend approximately from Kaneohe to Waimanalo and from the Ko’olau summit to seaward of Lanikai, with its center located near Kawainui Swamp. Examination of the dip of lava flows, frequency of dikes, and cross-cutting dike relationships has led to the interpretation that there may be an inner and outer caldera that formed at different times. Figure 4 shows the inferred extent of the inner and outer caldera, and the location of the Kaneohe/Kailua Tunnel. As a result of being within the collapsed caldera, the project is within a quite different and more geologically complex area than that of the existing H-3 and Wilson highway tunnels, which are outside the caldera, within the volcanic shield. It is believed that during the eruptive stage, and also after caldera collapse, rising magma was partly confined by the walls of the caldera structure, and thus magma in the project area formed thick, near-horizontal, dense, lava flows. During caldera collapses, the ponded lavas, as well as volcanic breccias, were locally subjected to hydrothermal alteration as well as chemical alteration from rising gases within the caldera, forming local weakened zones. The caldera area also contains a variable (and typically high) concentration of volcanic dikes. Geologic mapping suggests as many as 1,000 dikes per mile of horizontal distance in some areas, and averaging more than 100 dikes per mile (Macdonald, 1956). Sediment, transported from the mountains to the valleys as colluvium, was eventually carried away by streams and deposited along the base of the mountain, gradually forming broad alluvial fans. Pleistocene climatic oscillations resulted in sea level changes, which created paleo-shorelines around the island. High stands of the sea, in combination with subsidence of the island, deposited marine and lagoonal sediments upon terrestrial alluvial fans, forming a coastal plain. Conversely, low sea level stands caused consolidation of the soft lagoonal deposits and broadening of the coastal plain. Following the period of quiescence and erosion that lasted roughly 1 million years, another stage of volcanism occurred, albeit on a smaller scale. This rejuvenation is referred to as the Honolulu Volcanic Series, and was markedly different than the main shield building stage of the islands. Volcanoes near the study area belonging to the Honolulu Volcanic Series include the Castle vent and the Ulumewao vent, which erupted tuffaceaus cinder as well as lava. Mokapu Peninsula, on which Kaneohe Marine Corps Base is situated, is largely composed of cinder and tuff deposits as well as basalt flows from the Honolulu Volcanic Series, such as Hawaiiloa, Pali Kilo, Pyramid Rock, and Moku Manu (Winchell, 1947). Many of the Honolulu Volcanic Series eruptions are difficult to date, but the earliest eruptions took place




roughly 800,000 years ago along the windward coast and ended approximately 30,000 years ago with several eruptions along the Koko Rift Zone in the southeast portion of Oahu (Gramlich et al., 1971). 3.2 Previous Tunnel Construction Experience Notable tunnels that have been constructed on Oahu include the Tetsuo Harano Tunnels along Interstate H-3; the Wilson Tunnels along State Route 63; and the (Likelike Highway); and the Pali Tunnels along State Route 61 (the Pali Highway). As shown in Figure 4, these existing tunnels were constructed through a prominent northwest trending ridgeline west of the Kaneohe/Kailua project. As such, the geologic setting for those existing tunnels is different than that which will be encountered in the Kaneohe/Kailua Sewer Tunnel Project. A summary of the geology and available construction records for these tunnels is provided in Appendix A. 3.3 Geologic Units Based on the GDR, the following geologic units have been identified along the tunnel alignment:

• Artificial Fill (Qaf) • Lagoonal and Estuarine Deposits (Qa) • Recent Alluvium (Qa)Coralline Detritus (Qcrs) • Older Alluvium (QTao) • Colluvium • Alluvium/Colluvium • Weathered Basalt • Basalt Lava Flows (QTkkl) • Dike Complex (QTkkdc) • Basalt Breccia (QTkkbr)

The general characteristics of these units are described below. 3.3.1 Soil Deposits For soil and soil-like materials (i.e. e.g., residual soil and basalt rock that is extremely weathered), the relevant field and laboratory test results are presented in the PGER and GDR. Table 1 summarizes these data. General characteristics and properties of the primary soil units are described below. Artificial Fill (Qaf) Artificial Fill is present along portions of the project and is generally associated with commercial and residential developments, roadways, and underground utilities. The fill materials were generally derived from nearby sources and typically consist of poorly to well-compacted soils with particle sizes ranging from fines (grains not visible) to boulder sizes (greater than 12 inches in diameter). Locally, the fill may contain organic material. In Boring B-35, located along the Interstate H-3 shoulder, fill consisted primarily of silty basalt gravel with basalt cobbles and boulders. It is believed that this material was placed to fill in a gulch during construction of Interstate H-3. At the KRWWTP, fill within the limits of




the former primary and final clarifiers, trickling filter, and related structures and utilities will consist of backfill placed following demolition of these structures, which are scheduled to be demolished in 2013 under a separate contract (refer to the Contract Drawings for the extent of demolition activities). The backfill generally consists of silty sand with gravel, with a maximum particle size of 1-1/2 inches. Lagoonal and Estuarine Deposits (Qa) Back-reef lagoonal deposits were likely formed from past depositions of soft clays, silts, and sands in low-energy environments within lagoons, swamps, and estuaries behind the near shore fringing coral reefs. As coral reefs grow, these deposits can also accumulate coral and limestone fragments, fine sand, coral limestone gravel, cobbles, boulders, shells, organics, and decomposed vegetation. The Lagoonal Deposits encountered in the borings consist mainly of gray to brown, saturated, very soft to medium stiff silts and clays, and very loose to medium dense, clayey and/or silty coralline sands and gravels. These soils are also considered highly compressible if subjected to increased stress levels. Organic materials, shells, and coral fragments are common in these deposits. Estuarine deposits generally result from past depositions of soft mud, silts, and sands in low energy environments of lower courses of rivers open to the sea. In contrast to lagoons, estuaries are commonly oriented approximately perpendicular to the coast. Characteristics of estuarine deposits are usually affected by river runoff, tidal forces, and/or waves. This soil unit was found to underlie the fill materials in Borings B-30 and B- 31. In Borings B-30 and B-31, estuarine deposits were approximately 53 and 35 feet thick, respectively. The estuarine deposits encountered in the exploratory borings consist mainly of saturated and highly compressible, dark gray, very soft to soft organic clays. Shells and wood fragments are common in these deposits. Based on laboratory testing performed on samples of Estuarine Deposits obtained from investigations for the tunnel (YKE, 2013a) and KWPTF pipeline facilities (YKE, 2013c), moisture contents of up to 150 percent % and organic contents of up to 30 percent 50% are expected. Recent Alluvium (Qa) Recent Alluvium consists primarily of terrestrial sediments from streams and is typically the result of sedimentation occurring in ancient buried stream channels or accumulations in sedimentation basins or estuaries. Recent Alluvium was encountered at approximately 60 feet below ground surface at Boring B-30 at the KWPTF. The Recent Alluvium is approximately 16 to 18 feet thick at this location, and generally consists of dark gray, medium dense, highly weathered basalt gravel and cobbles with some silt and sand. Coralline Detritus (Qcrs) Coralline Detritus form primarily as a result of wave actions on the coralline reefs during different stands of the sea level. Coralline detritus was encountered at the KRWWTP in Borings B-40, B-41, and B-42. The coralline detritus encountered are generally gray, off-white to brown, very loose to medium dense, clayey coralline sands or gravel with and gravels. In these borings, the coralline detritus is intercalated with the Older Alluvium, probably because of past influx of sediments during storm events and related paleo sea-level changes, which formed the interface between the two geologic settings and resulted in complex and highly variable geologic contacts in this area.




Older Alluvium (QTao)

Older Alluvium consists primarily of terrestrial sediments from streams and is typically the result of sedimentation occurring in ancient buried stream channels or accumulations in basins or estuaries. The Older Alluvium encountered generally consists of brown, reddish brown, dark gray, medium stiff to hard fat clay, and elastic silt with sand and basalt gravel, and cobbles, and boulders, and black and brown, loose to very dense, silty or clayey sand or gravel and cobbles and boulders.

The presence of basalt gravel in alluvial deposits is indicative of the presence of exposed basaltic lava flows in the vicinity or upstream of the project area. Coralline sands and gravel may be found in the alluvium and may be indicative of a paleo-shoreline or may suggest deposition from a storm event. Thick layers of coralline detritus intercalated with the Older Alluvium were encountered Borings B-40, B-41, and B-42 and are most likely related to past influx of sediments during storm events and paleo sea-level changes..

Colluvium

Colluvium includes deposits that accumulate on slopes. These deposits were encountered locally in the borings and include soil and rock debris, which is sometimes not differentiated from man-made fill, and is included therein on the boring logs. Colluvium was encountered at Borings B-33B, B-35A, and B-38.They generally consist of brown and dark gray basalt or basalt breccia gravel, cobbles, and boulderswith varying amounts of sand.

Alluvium/Colluvium

In Borings B-40, B-41, and B-42, Alluvium/Colluvium was encountered at shallow depths, below the Artificial Fill, from approximately 1 to 11.5 feet below the existing ground surface. Difference between the alluvium and colluvium were are not significant enough to be differentiated. This soil unit consists mostly of medium stiff to stiff brown to dark gray high plasticity clay with trace sand, gravel, and organics. It is probable that the clayey soil is derived from stream deposits during low stands of the sea from nearby streams such as Kawainui Stream or from eroded material from Ko`olau basalt located immediately upslope and southwest of the KRWWTP site.

Weathered Basalt

Weathered Basalt primarily consists of a heterogeneous mixture of weathered rock and soil-like materials (residual soils and saprolite) formed by in situ weathering and decomposition of the basalt bedrock. Weathered Basalt retains the original rock fabric and relict structure (i.e., discontinuities) of the parent rock, and also contains intact rock components (layers, rock fragments, boulders, and corestones) ranging from gravel-size to boulder-size, embedded in a soil-like matrix. The rock components are not an intact rock mass and as such are surrounded by a soil matrix. Soils encountered in the Weathered Basalt typically consist of mottled reddish to orange brown elastic silt, sandy silt, silty to clayey sand, and/or silty to clayey gravel with basaltic cobbles. The strength characteristics of these soils vary from stiff to hard for the fine-grained soils, and from medium dense to very dense for the coarse-grained soils. Rock components blocks of the Weathered Basalt have strengths that range from extremely weak to medium very strong, and




exhibit weathering that ranges from extremely weathered to unweathered. Generally the rock components of the Weathered Basalt become more frequent and extensive with depth as the effects of weathering diminish. Core recoveries in Weathered Basalt range from 0 to 100 percent, averaging about 70 percent, and RQD values typically range from 0 to 50 percent, averaging about 10 percent. Locally higher RQD values are encountered where less weathered basalt rock is present. 3.3.2 Rock Units Bedrock in the project area consists of basalt rocks, which are mapped as three subunits: Basalt Lava Flows, Basalt Breccia, and Dike Complex (Sherrod et al., 2007). These three subunits were typically not identified on the boring logs. Rather, nearly all the rock was logged as basalt, with limited intervals identified as Basalt Breccia and Dike Complex. Based on laboratory test results in the GDR, it appears that the three varieties of basalt have similar strength ranges; therefore, for the purposes of this GBR they are considered as one geologic unit, Basalt. However, the differences between the subunits are described below. Basalt Lava Flows (QTkkl) The Basalt Lava Flows are composed chiefly of thickly bedded lavas that ponded within the caldera. The unweathered to slightly weathered basalt lavas are typically gray, hard to very hard, medium strong to very extremely strong, nonvesicular to slightly vesicular, closely to moderately fractured with local widely to very widely spaced fractures. Where highly weathered to moderately weathered, the basalt consists of gray, brown, olive, and reddish brown and is commonly closely to intensely fractured. These flows contain frequent dikes. Hydrothermal alteration is locally present and is typically recognized by greenish gray and/or reddish colors, and secondary minerals. The secondary minerals fill or partially fill rock fractures, sometimes forming green veins and healed fractures. The Basalt Lava Flows are documented as being relatively uniform molten basalt deposits with few clinker zones along the margin lava flows. The Basalt Lava Flows unit also exhibits little systematic petrographic variation across the deposit, with only random variations in plagioclase and olivine content (Garcia, 1979). Basalt Breccia (QTkkbr) Basalt Breccia originated either from the collapse of the Ko’olau caldera or as the result of explosive eruptions. It is believed that the breccia found in this region is throat breccia that built up chiefly as talus within a crater or caldera (Stearns and Vaksvik, 1935). In some borings, local zones of fused Basalt Breccia, probably from fusion of sheared basalt, were observed. The Basalt Breccia generally consists of angular to subangular brownish gray to reddish to gray basalt clasts in a strongly cemented fine-grained matrix. The Basalt Breccia encountered in the borings ranges from slightly to highly weathered, moderately hard to moderately soft, medium strong to very strong, and is commonly moderately to intensely fractured. Dike Complex (QTkkdc) Dikes Complex rocks are formed from magma intruding into existing rock. Because this magma is insulated by the country rock, it cools more slowly than surface lava flows. As a result, the dikes tend to be denser than surface lavas. Typically the dikes are sheet-like structures, with steep dip angles and




northwest trends (Walker, 1987). However, orientations vary and dikes often intersect one another. Dike intersections can form essentially impermeable walls that can trap groundwater, creating perched water tables. When a dike intrudes another body of rock, it can alter the host rock, either in the form of hydrothermal alteration or low-grade contact metamorphism. This can be seen as green to greenish gray or reddish colors near the zone of intrusion.

Dike Complex rocks encountered in borings range from slightly to highly weathered, moderately hard to very hard, and medium strong to strong. Walker (1987) reports that dike thickness varies widely, ranging from a few inches to tens of feet thick with an average thickness of 2.5 feet. The percentage of rock within the Dike Complex that is comprised of dikes ranges from 30 to 70 percent %. The degree of fracturing in the dikes varies widely, ranging from very widely fractured to crushed. Dike Complex rocks can be seen on exposed quarry walls, a couple of thousand feet south of the tunnel alignment. The dikes also form two complementary sets. The primary set is orientated northwest-southeast and roughly parallels the northeast-southwest trending rift zone that is interpreted to extend along the northeastern flank of the Oahu Island. The secondary, complimentary set is orientated northeast-southwest.

The presence of basalt dikes is not limited to the “dike complex” as presented in the USGS map of Hawaii (Sherrod et al., 2007). Dikes are present in all basalt subunits described herein. Because most of the borings had a vertical orientation, the frequency of the steeply dipping dikes cannot be accurately determined by the borings. Their frequency is better evaluated from outcrops, such as the cut slopes along Interstate H-3.

3.4 Rock Properties

The geotechnical investigation program completed comprehensive field and laboratory tests on rock samples of the in situ rock mass. Some of the rock properties for tunnel and shaft construction are summarized below.

3.4.1 Weathering and Alteration

The basalt rock has been subjected to varying degrees of chemical weathering and hydrothermal alteration (both referred to herein as weathering). As a result, in most locations a variable and irregular weathering profile is present. The degree of weathering typically decreases with depth below the ground surface. However, weathering also occurs at depth in the rock mass, commonly within and/or along faults, shears, or intensely fractured zones. The extent of weathering was recorded on the boring logs using the descriptive weathering terms defined in the GDR.

Hydrothermal alteration within the rock mass is extensive throughout the Ko’olau Caldera and surrounding caldera boundary rocks, primarily as a result of circulating gas and heated water. Effects of alteration—as evidenced by mineral-filled vesicles, presence of secondary minerals, including clay minerals; and localized discoloration—are noted in basalt samples.

MacDonald (1983) observed that the basalt rocks of the Ko’olau Caldera are altered, with pyroxene commonly changed to chlorite and clay minerals. Vesicles within the rock mass were also noted to be in-




filled with secondary minerals, such as quartz, zeolites, and epidotes. Garcia (1979) reports the presence of secondary minerals, including opal and chalcedony, and also notes petrographic variation within basalt rocks, including random variations in plagioclase and olivine content. 3.4.2 Intact Rock Strength As reported in the GDR, rock strength was investigated by performing Unconfined Compressive Strength (UCS) tests, Point Load Index (PLI) strength tests, and Indirect (Brazilian) Tensile Strength (BTS) tests. As is commonly observed, rock strength was found to decrease with an increase in the extent of weathering/alteration. A total of 65 70 UCS and 226 269 PLI tests were performed on select samples of rock obtained from borings along the project alignment. These include 46 51 UCS tests and 171 239 PLI tests performed during the latest geotechnical investigations, as conducted by YKE, and 19 UCS tests and 30 PLI tests performed during the previous investigation phase, as conducted by GeoLabs. Twenty (20) Thirty-nine (39) of the 226 269 PLI tests were disregarded from the strength evaluation due to structural failures, samples that were obtained from Weathered Basaltmoderately to highly weathered, or sample sizes that did not meet ASTM requirements. One UCS test from Boring B-41 was performed on a basalt cobble and was therefore not considered in the evaluation of rock strength. The distribution of the UCS and PLI test results is summarized in Figure 5. As shown, the UCS of unweathered to moderately weathered rock ranges from less than 2,000 psi to nearly 30,000 36,000 psi, indicating a strength range from weak to very extremely strong rock, per the International Society for Rock Mechanics (ISRM) intact rock strength categories (ISRM, 1978). ISRM intact rock strength categories are summarized in Table 2. Generally, samples tested for UCS were described as being either unweathered or slightly weathered, and failing across the rock fabric. However, some samples were observed to fail along a pre-existing plane of weakness within the sample. The results from these tests were reported as structural failures. The location of these samples and photographs of the failed samples are provided in the GDR. 3.4.3 Rock Density Rock density data are available for 64 66 samples and it can be seen that density increases with decreasing degree of weathering. For summary purposes, density is summarized into two weathering categories: (1) unweathered to slightly weathered, and (2) moderately weathered to extremely weathered. The results are summarized in Table 3.




3.4.4 TBM Boreability Testing TBM boreability testing was performed by the Colorado School of Mines, Earth Mechanics Institute (EMI), to aid in the evaluation of TBM performance. Tests performed include Indirect (Brazilian) Tensile Strength (BTS), Cerchar Abrasivity Index (CAI), Punch Penetration, and Petrographic Analyses. The results are presented in the GDR and are summarized in Table 4 and Table 5. UCS and BTS results from 24 samples tested at similar depths indicate that the ratio of UCS to BTS ranges from 3 to 37 with an average value of 17. Disregarding one BTS and two UCS tests that were determined to be structural failures rather than failures through intact rock, the average ratio of UCS to BTS is 19. CAI test results range from 1.3 to 3, indicating that the basalt is an abrasive to very abrasive rock (Plinninger, et al., 2003). 3.4.5 Rock Mass Discontinuities Discontinuities in the basalt include fractures (joints), veins and healed fractures, shears, sheared and altered zones, and lithologic lithology contacts, veins and healed fractures, and fractures that formed as a result of building and subsequent collapse of the Ko’olau Caldera. These discontinuities have been considered in the rock mass types defined in Section 3.4.7 and also the reach descriptions provided in Section 4.3. Orientation and condition of discontinuities will influence ground behavior, ground support requirements, and TBM performance. These considerations are discussed in Sections 5 and 6. Dikes There are dike features located throughout the alignment. The primary dike features generally have a dip direction ranging between about 10° and 60° and 90° with a predominant dip direction of 35°. This orientation corresponds to Joint Set 3. Other secondary dike features are present and have dip directions ranging from about 70° to 350° 115° to 310° and dip angles ranging from about 5° to 90° 25° to 88°. These secondary dikes generally correspond to Joint Sets 1, 2, and 4, but are less frequent. Based on rock outcrop mapping in the vicinity of the project site, Walker (1987) reports that the dike features tend to be sub-vertical to vertical with an average thickness of approximately 2 to 3 feet. Thirty (30) to 70 percent % of rock, as measured linearly along the tunnel alignment, is estimated to consist of dikes. Fractures Fracturing and joint sets within the basalt are present at various orientations throughout the tunnel alignment but generally consist of two systematic vertical to subvertical joint sets with varying frequencies. One joint set approximately parallels the axis of the Ko’olau Volcano and rift zone and follows a general northwest-southeast trend. This set is parallel with regional strike of dikes in this area (Walker, 1987). The second, complementary joint set generally follows a northeast-southwest trend. These two joint sets tend to be closer to vertical towards the eastern end of the alignment, with a predominant dip decreasing to about 20 to 60 degrees towards the western end of the alignment. These




joint sets are generally anticipated to parallel the orientations of dikes. In addition, randomly orientated fractures were noted in most of the borings along the alignment. Increased fracturing was also observed at some dike margins, as noted in Boring B-34A at various depths. These fractures may represent cooling joints that developed at dike boundaries following formation of the dike structure. Where present, these fractures are likely to occur at orientations normal to the dike margins. Sheared and Altered Zones Discrete sheared and altered zones are present in the basalt rock mass, as evidenced by reduced core recoveries and rock quality designation (RQD), presence of crushed rock and clay- and silt- filled fractures, and loss of water circulation during drilling of boreholes performed for the project. Examples of sheared and altered zones encountered in some of the borings include Boring B-22 from 195 to 287 feet below ground surface (multiple zones); Boring B-35 from 220 to 242 feet below ground surface; Boring B-36 from 147 to 152 feet below ground surface; and Boring B-37 from 270 to 295 feet below ground surface. These zones generally parallel the dominant fracture and joint orientations, and are present at tunnel depth. Sheared and altered zones are typically undulating to planar features ranging from 10 to 30 feet in thickness. The frequency of occurrence of these zones is difficult to estimate given the widely spaced borings and the predominant vertical to subvertical discontinuity orientations; however, several of these zones are likely to be encountered in the tunnel. Also, some of these zones may trend parallel with the tunnel alignment, intersecting the tunnel over several hundred feet. The sheared and altered zones will generally consist of closely to intensely fractured rock, and intact rock fragments, gravel size or smaller, with clay, silt, and sand joint infillings. Zones of closely spaced joints may be encountered on both sides of crushed zones, and heavier water inflows are anticipated in localized areas. 3.4.6 Rock Mass Quality Rock mass quality was evaluated using two widely used indices: Rock Mass Rating (RMR; as defined by Bieniawski, 1988); and Rock Quality Tunneling Index (Q; as defined by Barton, 1988). These indices were estimated for 15- to 20-foot intervals of rock core, which corresponds approximately to the excavated size of the tunnel. Figures 6, 7, and 8 show the results of distribution of the RQD, RMR, and Q-values based on the available boring data. Figure 9 shows the distribution of core recovery and RQD at tunnel depth along the tunnel alignment. 3.4.7 Rock Mass Types For the purposes of describing rock mass conditions in the tunnel, three rock mass types (RMTs) have been defined. RMTs are defined based on the physical characteristics of the rock and its the rock’s anticipated behavior in the tunnel. The rock assigned to a particular class is expected to perform similarly in the tunnel excavation, although the various RMTs represent a range of behaviors and not a single unique behavior. Based on boring information, the three RMTs are:




B1: “Good rock,” primarily characterized by massive, moderately jointed rock. B2: “Fair rock,” primarily characterized by moderately blocky and seamy rock. B3: “Very poor to poor rock,” primarily characterized by very blocky and seamy rock and

crushed zones. Summary descriptions of the three RMTs are provided in Table 6 and include anticipated ranges of RQD, RMR, and Q values, and a description of anticipated ground behavior, degree of fracturing, and weathering characteristics for each RMT. 3.4.8 Hydraulic Conductivity Stearns and Vaksvik (1935) report that hydrothermally altered Kailua basalts are “nearly impermeable because secondary minerals have virtually filled all interstices through which ground water usually moves.” The recovered rock core samples provide abundant examples of fractures and vesicles that are filled with white mineralization, presumed to be calcium carbonate. The Basalt Breccia of the Oneawa Hills is believed to be clastic (but not flow breccia) and possibly “throat breccia” that has been “built up chiefly as talus within the caldera. It appears to mark the site of the main vent of the Ko’olau Volcano.” It is reported that cementation has rendered these breccias nearly impermeable, and as a result they have not undergone weathering as quickly as adjacent rocks (because of lack of structure). As noted above, it is reported that dikes commonly form barriers to lateral groundwater flow, and as a result they can locally trap groundwater at relatively high elevations. For these reasons, the basalt in the Dike Complex is generally regarded to be a poor-yielding source of water (for domestic water supply) (Takasaki and Mink, 1982). Estimates of hydraulic conductivity were developed based on the results of in situ packer pressure tests and falling head tests performed in borings along the tunnel alignment, and on results of a pump test performed at the KRWWTP. Results from the final design investigations (YKE, 2013a) and preliminary investigations (GeoLabs, 2011) were considered. In total, 126 152 tests were performed along the tunnel alignment; this total includes 35 41 tests from investigations performed at the KRWWTP (in Borings B-2, P-11, B-39, B-40, and B-41, and B-42). The maximum measured hydraulic conductivity was 8.76 x 10-3 centimeters per second (cm/sec) from Boring P-11 at a depth of about 38.5 to 40 feet below ground surface. Ground conditions within this test interval consisted of moderately to closely fractured, moderately weathered to slightly weathered basalt. Tests in other locations exhibited lower hydraulic conductivities, typically less than 3 x 10-5 cm/sec. Figure 10 summarizes the distribution of the available hydraulic conductivity data. 3.5 Groundwater Conditions Groundwater along the project alignment occurs in two zones: a shallow perched aquifer in surficial soil deposits, and at depth in the bedrock. The primary sources of groundwater are from rainfall infiltration and from hydraulic connection with the adjacent Kaneohe Bay and Kailua Bay. At the KWPTF and KRWWTP sites, groundwater is brackish and groundwater levels are subject to seasonal and tidal fluctuations. Maximum changes in groundwater level at these sites typically occur during the rainy




season, which is from November to March. Groundwater along the tunnel alignment is not brackish, and groundwater levels are influenced by precipitation. Groundwater flow in the shallow aquifer generally occurs within higher permeability soils, such as Coralline Detritus, Recent Alluvium, Older Alluvium, and Weathered Basalt, while the lower permeability Lagoonal and Estuarine Deposits and Basalt both serve as an aquitard, resulting in perched groundwater. Groundwater flow within the bedrock is controlled by secondary porosity—or flow through open joints, fractures, sheared zones, and altered zones—of the rock mass rather than the porosity of the crystalline rock. Groundwater is conveyed along these secondary features and is influenced by the effects of weathering and alteration of the rock mass. Based on in situ hydraulic conductivity testing, weathering of the contact between rock and overlying soils has resulted in increased hydraulic conductivities and is likely a primary source of groundwater movement within the regional groundwater regime. Perched groundwater is also present in the Basalt along the tunnel alignment. As discussed in Section 3.4.8, groundwater flow within the Oneawa Hills is influenced by the presence of dikes and the degree of alteration and weathering within the rock mass. Cemented breccias, hydrothermally altered basalt, and basalt dikes often serve as barriers to groundwater flow since they exhibit reduced porosity due to presence of secondary minerals filling voids, fissures, and vesicles. Based on readings from monitoring wells installed along the project alignment, groundwater levels at the KWPTF and KRWWTP sites range from about 11 to 12 7 to 21 feet below ground surface. Average gGroundwater levels along the tunnel range from about 35 to 400 feet below ground surface. This corresponds to groundwater levels ranging from about 50 to 180 feet above the tunnel. Table 7 presents the anticipated groundwater levels along the tunnel alignment based on monitoring well readings. Groundwater levels are also presented in Figures 2-1 through 2-7. Detailed water level measurements are provided in the GDR. Because of the lack of a significant soil overburden over the tunnel along the Oneawa Hills, and given the relatively low hydraulic conductivities measured within rock mass, the storage capacity of the rock mass overlying the tunnel is judged to be low, however the steeply dipping joints and dikes along the alignment could provide avenues for water infiltration into the tunnel in response to heavy rainfall events. 3.6 Hazardous Gas Neither the GDR nor the PGER mentions encountering methane or hydrogen sulfide gas. However, both reports indicate that organic materials are present in the Lagoonal and Estuarine Deposits, and Older Alluvium. Further details regarding water chemistry testing results are provided in the GDR. The basalt rock is not known to contain hazardous gas, and based on the available data it seems unlikely gas will be encountered in this unit. However, because some of the soil units contain organic materials, the tunnel may encounter methane gas, including dissolved methane gas in the groundwater. Therefore the tunnel should be considered “potentially gassy.” All work should be carried out in accordance with OSHA’s requirements for this classification.




3.7 Seismicity The Kaneohe/Kailua Sewer Tunnel Project is located in a seismically active region, dominated by active and ongoing volcanism. The seismic hazard is considered high, largely because of the potential for earthquakes beneath several active volcanoes on the Island of Hawaii. These earthquakes can be directly attributed to active volcanic processes within the Earth’s lithosphere due to the underground movement of magma. However, some earthquakes in volcanic areas do exhibit traits of tectonic earthquakes, such as movement along pre-existing faults within the volcano caused by the movement of magma. The earthquake hazard is highest on the Island of Hawaii. However, the potential for seismically induced ground movements is also present on the other islands, albeit generally in reduced intensity from southeast to northwest. The project has been designed in accordance with the seismic design requirements of the International Building Code (ICC, 2012) and ASCE Standard 7-10 (ASCE, 2010). The design earthquake for the project has a 2 percent probability of exceedance in 50 years (2,500-year approximate return period). Based on the design 2,500-year return period, the estimated short period peak ground acceleration (PGA) is 0.64 g. 3.8 Contaminated Soil and Groundwater The geotechnical investigations performed at the KWPTF and KRWWTP did not encounter contaminated soil or groundwater at these locations. Additionally, contamination was not encountered in explorations completed along the tunnel alignment. Therefore, soil and groundwater contamination is not expected to be encountered in the excavation of the shafts or tunnel.




4 Anticipated Ground Conditions For the purpose of describing anticipated ground conditions and providing baselines, the tunnel is divided into four reaches. The geologic profile shown in Figures 2-2 through 2-7 provides a summary of selected information from the geotechnical investigations and shows the identified reaches. The reaches contain three general types of ground:

1. Soil deposits ranging from soft compressible silts and clays to medium stiff to hard fat clays and elastic silts.

2. Weathered rock consisting of slightly weathered to extremely weathered basalt and residual soil deposits (saprolite), including mixed face conditions of soil and weathered rock in the heading at the same.

3. Slightly weathered to unweathered, variably fractured rock with localized zones of moderately to extremely weathered rock.

The reach boundaries correspond to transition zones for the geologic units anticipated to be encountered in the tunnel. The designated reach boundary generally corresponds to where contacts between adjacent geologic units cross the tunnel crown. The location of the boundary between each tunnel reach is approximate and is to be expected to vary in either direction. Reach boundaries between Reaches 1 and 2, and between Reaches 2 and 3, each are expected to vary by up to 100 feet. The reach boundary between Reaches 3 and 4 is expected to vary by up to 50 feet. Baseline ground conditions and ground behavior are provided for each of the identified tunnel reaches. For the purpose of this GBR, ground conditions in rock tunnel sections have been classified using the terminology presented by Terzaghi (Proctor and White, 1968) and are summarized in Table 8. Ground behavior has been classified using the terminology presented by Heuer (1974) and summarized in Table 9. Conditions associated with the three RMTs identified for the project are described in Table 6. In describing the anticipated ground conditions, several terms are used to describe rock strength, discontinuities, and weathering. Definitions of these terms are summarized in the following:

• Descriptive terms for intact rock strength are summarized in Table 2. • Descriptive terms for discontinuity condition and fracture spacing are described in the GDR. • Descriptive terms for rock weathering are described in the GDR.

Where tunnel depths are discussed in the following sections, the depths referenced are measured to the tunnel invert (of the final lining). Where SPT N-values are discussed in the following sections, it shall be assumed these values represent NFIELD values that have been corrected for sampler type. 4.1 Reach 1 (Station 0+15 to 5+00) Reach 1 extends from the Kaneohe Shaft at the KWPTF to Station 5+00 at the Bay View Golf Park. The depth to the tunnel invert within this reach ranges from about 40 to 43 feet. As the tunnel passes beneath




Kawa Stream at Station 4+00, the cover between the stream bottom and the crown of the tunnel is about 21 feet. Beginning at the shaft, the tunnel will encounter Estuarine Deposits to approximately Station 5+00. At approximately Station 4+30, Older Alluvium will be encountered in the invert and gradually slope upwards until it encompasses the full height of the tunnel face at approximate Station 5+00. Descriptions of the Older Alluvium soils are provided under Reach 2 (Section 4.2). The geologic profile for Reach 1 is provided in Figures 2-2 and 2-6. Subsurface conditions in Reach 1 consist primarily of very soft to soft elastic organic silts and fat clays, with varying amounts of sand and gravel, and organic materials. Occasional layers of sands, gravels, and shell fragments are also expected to be interbedded with fine-grained soils, and the thickness of these layers is expected to be less than 5 feet. 4.1.1 Grain Size Distribution and Plasticity Figure 11 is a summary plot of grain size data for the Estuarine Deposits that are expected to be encountered. It is anticipated that over 80 percent of soils encountered in this reach will be organic silts and clays with varying amounts of sand, gravel, and organic material. The fines fraction (percent of silt- and clay-sized particles; grain size <0.074 mm) of these soils is anticipated to range from 50 to 99 percent, and clay content (grain size <0.002 mm) is anticipated to range from 20 to 45 percent. The remaining 20 percent of soils encountered in this reach are anticipated to include clean poorly graded sands, well-graded sand and gravel mixtures, and silty and clayey sands. The organic silts and clays typically have high to very high plasticity, with liquid limits ranging from 74 to 109 and averaging 92. The plasticity index ranges from 34 to 58 and averages 48. Moisture contents of the silts and clays range from 44 to 151 percent and average 78 percent. Moisture contents of the organic silts and clays are typically within 15 percent of the liquid limit, indicating the deposits are normally consolidated. Organic contents of the soils in this reach range from 9 to 30 percent and average 14 percent. 4.1.2 Strength and Consistency Standard Penetration Test (SPT) blow counts for the Estuarine Deposits are summarized in Table 1. Consistency of the fine-grained soils ranges from very soft to very stiff, with 85 percent of the blow counts being 4 blows per foot or less (indicating very soft to soft soils). Undrained shear strengths for the silts and clays in the Estuarine Deposits were estimated using field testing techniques (pocket penetrometer, pocket torvane) and laboratory testing (triaxial compression). It is anticipated that undrained shear strengths will range from 0 to 3,000 pounds per square foot (psf) and average approximately 450 psf. The results of undrained shear strength testing are provided in the GDR.




4.1.3 Groundwater and Hydraulic Conductivity Groundwater levels within this reach are expected to be about 35 feet above the tunnel invert. Seven falling head tests were performed in Estuarine Deposits within this reach. Based on these tests, hydraulic conductivities within the Estuarine Deposits in Reach 1 range from 4.3 x 10-6 to 3.8 x 10-3 cm/sec. No baseline is provided for groundwater inflows into the tunnel as jet grouting is required to stabilize the soils in this reach in advance of tunnel excavation. 4.1.4 Potential Ground Behavior Because tunneling within Reach 1 is below the groundwater table, the untreated Estuarine Deposits are expected to be squeezing or fast raveling ground. Where sand and/or gravel layers are encountered, the Estuarine Deposits will exhibit flowing behavior. As indicated on the Contract Drawings, tunnel excavation through Reach 1 will be by conventional tunneling methods and will require ground stabilization by jet grouting methods prior to excavation. The above descriptions of potential ground behavior are for untreated ground; however, these behaviors can also be expected if windows of untreated soil are encountered. After proper treatment and curing, the jet grout stabilized soils should exhibit the characteristics of firm ground. 4.2 Reach 2 (Station 5+00 to 10+00) Reach 2 extends from Station 5+00 to Station 10+00. The depth to the tunnel invert within this reach ranges from about 43 to 120 feet and extends below the Bay View Golf Park. As the tunnel progresses beyond Station 5+00, it will encounter Older Alluvium for a distance of approximately 350 feet to about Station 8+50. Weathered Basalt is expected to be encountered beginning at about Station 7+75 and the amount of weathered rock will gradually increase at approximate Station 8+50 where the face will be entirely in Weathered Basalt. As the tunnel advances further, the Weathered Basalt will become less weathered until Station 10+00, where it is expected to be slightly weathered to unweathered Basalt at the (start of Reach 3). The geologic profile for Reach 2 is provided in Figures 2-2 and 2-6. The Older Alluvium in Reach 2 generally consists of medium stiff to hard elastic silts and fat clays, with varying amounts of sand, gravel, cobbles, and boulders. Layers of clayey sand and clayey gravel with cobbles are present and anticipated to have a maximum thickness of 10 feet. Abundant gravel and cobbles are expected throughout this unit. , and the The maximum cobble size will not exceed 12 inches and total volume of cobbles encountered will be less than 20 percent of the excavated volume of the Older Alluvium in the tunnel. Larger corestones and fragments of rock (cobble- and boulder-sized material) embedded in a soil-like matrix of gravel, sand, silt, and clay are expected to be encountered as the tunnel transitions from Older Alluvium to Weathered Basalt. The Weathered Basalt consists of slightly weathered to extremely weathered basalt in a soil matrix that ranges from very dense clayey to silty sand to stiff to hard fat clay and elastic silt. Gravel, cobble and boulder-sized basalt fragments and corestones are expected throughout




the unit, and the maximum boulder or corestone size will be 48 inches. The percentage of cobble and boulder-sized fragments and corestones are anticipated to be less than 35 percent of the excavated volume of Weathered Basalt in the tunnel. As the tunnel transitions into the Basalt, the rock will become gradually less weathered to the end of this reach, where the rock will be slightly to moderately weathered. 4.2.1 Grain Size Distribution and Plasticity Figures 12 and 13 present summary plots of grain size data for the Older Alluvium and Weathered Basalt soils, respectively, that are expected to be encountered. The grain size data indicates the soils are primarily fine grained silts and clays, with lesser amounts of sand. The fines fraction (percent of silt- and clay-sized particles) of Older Alluvium is expected to range from 10 to 85 percent, with over 70 percent of soils encountered, by volume, having a fines content of between 40 and 85 percent. It should be noted the grain size data presented in Figures 12 and 13 represent the grain size distribution of gravel-sized particles and smaller, and the amount of cobble and boulder-sized materials is not included in these gradations due to sampling limitations. The fine-grained silts and clays of the Older Alluvium typically have high to very high plasticity, with liquid limits ranging from 50 to 125 and averaging 70. The plasticity index ranges from 22 to 96 and averages 38. Moisture contents of the silts and clays range from 6 to 86 percent and average 41 percent. Only one grain size test was performed on a sample of the soil matrix of the Weathered Basalt in this reach; however the fines fraction is anticipated to be similar to that of Weathered Basalt encountered in other reaches and is therefore assumed to range from 20 to 60 percent. The fine-grained silts and clays of the Weathered Basalt matrix typically have high to very high plasticity. Only one Atterberg limits test was performed on a sample of the soil matrix of the Weathered Basalt in this reach; however Atterberg limits and moisture contents are anticipated to be similar to that of Weathered Basalt encountered in other reaches. Liquid limits are anticipated to range from 40 to 75 and average 55. The plasticity index is anticipated to range from 25 to 45 and average 35. Moisture contents of the silts and clays are anticipated to range from 20 to 75 percent and average 40 percent. 4.2.2 Strength and Consistency Consistency of the Older Alluvium ranges from stiff to hard for fined-grained soils and from medium dense to very dense for coarse-grained soils. Consistency of soil components of the Weathered Basalt ranges from very stiff to hard. Undrained shear strengths for fine-grained soils within the Older Alluvium were estimated using field testing techniques (pocket penetrometer, pocket torvane) and laboratory testing (triaxial compression). It is anticipated that undrained shear strengths will range from 400 to 7,250 psf and average 2,350 psf. Undrained shear strengths for fine-grained soils (or matrix) within the Weathered Basalt will range from 1,150 to 8,150 psf and average 5,250 psf. The results of undrained shear strength testing are provided in the GDR.




UCS data for cobbles and boulders within the Older Alluvium and rock fragments and corestones within the Weathered Basalt in Reach 2 are limited; however, UCS and PLI strength testing from borings at other locations along the project alignment indicates that the unconfined compressive strength of these materials Weathered Basalt rock fragments ranges from 400 to 10,000 psi, with an average of about 2,600 psi. 4.2.3 Groundwater and Hydraulic Conductivity Groundwater levels within this reach are expected to range from about 25 to 80 feet above the tunnel crown. No packer tests were performed within the tunnel zone within this reach; however, one packer test was performed in Weathered Basalt in Boring B-32 and three packer tests were performed in Basalt in Boring B-32 and B-32A. Additionally, nine falling head tests were performed in Older Alluvium in Borings B-31, B-32 and B-32A. Based on these tests, hydraulic conductivities within Reach 2 range from 1 x 10-5 to 4 x 10-3 cm/sec. For baseline purposes, instantaneous heading inflows in this reach will not exceed 200 gpm and maximum sustained inflows for the entire reach will not exceed 100 gpm. These baselines exclude the jet-grouted portion of Reach 2 described in Section 4.2.4. 4.2.4 Potential Ground Behavior Considering that Reach 2 is below the groundwater table, the Older Alluvium is expected to be firm to raveling ground. Where sand and/or gravel lenses with little binder, such as clay or silt, are present, these zones will exhibit slow to fast raveling and flowing behavior. In the zone of mixed-face and weathered rock conditions between Stations 8+50 and 10+00, the Weathered Basalt is expected to be firm to raveling ground. Because of high groundwater levels present along the adjacent Oneawa Hills, increased groundwater inflows may be encountered within the Older Alluvium and the Weathered Basalt, and at the contacts between the Older Alluvium and Weathered Basalt, and Weathered Basalt and Basalt. These inflows will contribute to instability of the tunnel excavation. Control of groundwater inflows into the tunnel by predrainage (using drain holes) and/or pre-excavation grouting, in addition to presupport measures, will be necessary to prevent unstable ground conditions from developing. The jet grout stabilization has been extended into this reach to treat the initial 150 feet of the Older Alluvium to Station 6+50 to ensure that all of the Estuarine Deposits are treated, including the weaker soils present at the contact between the Estuarine Deposits and Older Alluvium. 4.3 Reach 3 (Station 10+00 to 162+00) Reach 3 extends beneath the Oneawa Hills from Station 10+00 to the KRWWTP at about Station 162+00. The depth of the tunnel invert ranges from about 80 feet at the KRWWTP to 670 feet at Station 35+50. The tunnel passes beneath Kaneohe Bay Drive (in Kaneohe), beneath Moakaka Place, and under an existing residence at the end of Moakaka Place before heading under primarily undeveloped land along the Oneawa Hills. After passing beneath Mokapu Saddle Road and H-3, the tunnel follows the Oneawa Hills ridge before passing beneath Halia Street and Kaneohe Bay Drive (in Kailua). At about Station 160+50, the tunnel enters the KRWWTP.




The rock in Reach 3 is Basalt, which has been mapped at the ground surface as Basalt Lava Flows, Basalt Breccia, and Dike Complex Basalt, which are all variably intruded by basalt dikes. The rock mass in this reach ranges from unweathered to slightly weathered, except along some dike boundaries and within shear zones, in which the degree of weathering ranges from highly weathered to slightly weathered. In general, the rock is medium strong to very extremely strong and moderately fractured to massive, except at some dike boundaries and at shear zones, where the rock mass is weakened and more fractured. The geologic profile for Reach 3 is provided in Figures 2-2 through 2-5. 4.3.1 Mineralogy Several basalt samples were subjected to thin section petrographic analysis. The results of these analyses indicate that the primary mineral constituent of the basalt is plagioclase and pyroxene with frequent vesicles that have been infilled with quartz and other secondary minerals. The petrographic composition of the basalt rocks, including the dikes, is to be expected to be within the percentages listed in Table 5. 4.3.2 Strength UCS data for the basalt rocks in this reach indicate that the strength for intact rock in the slightly weathered to unweathered basalt ranges from 3,000 to 30,000 psi, with an average of 11,500 psi, which corresponds to weak to very strong rock. Point load index strength (Is50) within this rock ranges from 0 to 1,500 psi, and averages 425 about 400 psi. This corresponds to an equivalent UCS range of 0 to about 36,000 psi, and an average of 9,750 psi (assuming a conversion factor of 24.4). Intact rock strength within shear zones will be significantly lower because of weathering/fracturing effects, and will range in strength from soil-like to 10,000 psi, or extremely weak to strong rock. For baseline purposes, it is anticipated that the UCS of intact, slightly weathered to unweathered rock in this reach will range from 3,000 to 3036,000, psi with an average of 15,000 psi. The more weathered rock associated with dikes, alteration zones, and shear zones, will exhibit strength characteristics similar to those discussed in Section 4.2.2 for Weathered Basalt. 4.3.3 Discontinuities Discontinuities observed in the basalt rock core and from road cuts near the tunnel alignment consist primarily of joints that are smooth to slightly rough with tight to narrow apertures. The joints are variable but form the joint sets provided in Table 10. Joint Set 3 represents the discontinuities associated with dominant northwest-southeast striking dike structures. In addition to the predominant joint sets, joints will also occur at random orientations. The distribution joints that form the above sets and the random orientations are shown in Figure 14. Rock fracturing in the basalt rock ranges from crushed to very widely fractured, with the majority of the rock ranging from closely fractured to very widely fractured. The distribution of fracture spacing for each RMT is provided in Figure 15. Dike thickness in this reach ranges from several inches to tens of feet thick. The dikes predominantly trend northwest and are typically steeply inclined at greater than 60 degrees from horizontal. The




percentage of dikes expected to be encountered, as measured linearly along the tunnel alignment, is 30 to 70 percent of the rock mass on a volumetric basis. Shear zones are anticipated in Reach 3 and will predominantly trend northwest or northeast, be inclined greater than 60 degrees from horizontal, and will range in width from a few inches to 10 feet (as measured along the tunnel). Shear zones less than 2 feet wide are present randomly throughout the rock mass and will occur at an overall average spacing along the tunnel of one per 100 feet of tunnel. In addition, it is to be expected that a total of 10 shear zones that range in width from 2 feet to 10 feet wide will be encountered. Eight of these features will cross at a high angle to the tunnel alignment and will each measure up to 20 feet in length along the tunnel. The other two of these features will be subparallel to the tunnel and will each be present for over 100 feet of tunnel. 4.3.4 Rock Mass Quality The rock mass in Reach 3 is variably fractured, ranging from massive to crushed rock. In general the rock mass is massive, moderately jointed, and blocky and seamy. Within shear zones and at some dike boundaries the rock mass is very blocky and seamy and crushed. Histograms of RQD, RMR, and Q values for the Basalt in this reach are presented in Figures 6, 7, and 8, respectively. The overall average RQD is 68 the average RMR is 57, and the median Q value is 5.6. About 28 percent of the Basalt has an RQD of 90 or greater; five percent of the Basalt has an RMR of 80 or greater; and five percent of Basalt has a Q value of 100 or greater. As described above, RMTs have been established to characterize ground conditions and potential ground behavior. For baseline purposes within Reach 3, the distribution of RMTs provided in Table 11 shall be assumed. Detailed descriptions of the RMTs, including anticipated ranges of RQD, RMR, and Q, and ground behavior, are provided in Table 6. Shear zones are anticipated in Reach 3 and will predominantly trend northwest or northeast, be inclined greater than 60 degrees from horizontal, and will range in width from a few inches to 10 feet (as measured along the tunnel). Shear zones less than 2 feet wide are present randomly throughout the rock mass and will occur at an overall average spacing along the tunnel of one per 100 feet of tunnel. In addition, it is to be expected that a total of 10 shear zones that range in width from 2 feet to 10 feet wide will be encountered. Eight of these features will cross at a high angle to the tunnel alignment and will measure 20 feet in length along the tunnel. The other two of these features will cross the tunnel subparallel and will affect 100 feet of the tunnel. These features Shear zones will contain very blocky and seamy rock to crushed rock with clay and silt seams up to 1-foot in width, and may contain several shears that could be separated by relatively intact rock (massive to moderately blocky and seamy rock). 4.3.5 Groundwater and Hydraulic Conductivity Groundwater levels within this reach are expected to range from about 80 to 190 feet above the tunnel invert. Based on packer tests performed in borings within this reach, hydraulic conductivities are expected to range from 1 x 10-8 to 9 x 10-3 cm/sec.




The dikes are anticipated to act as partial barriers to groundwater flow, and inflows will increase and decrease as the tunnel progresses through the rock mass between the dikes. In intensely fractured ground within shear zones, higher groundwater inflows are to be expected. If flows from these zones are not mitigated by predrainage or grouting, instantaneous heading inflows of 450 gpm are to be expected at each zone. Total steady state inflows into this reach the tunnel that are not mitigated by grouting are expected to be 500 gpm, or an average of about 3.3 gpm per 100 feet of tunnel length. Pre-excavation grouting measures within this reach are to be developed by the Contractor in accordance Specification requirements. An estimate of the amount of pre-excavation grouting anticipated has been made and the quantities are provided in the Specifications. For baseline purposes, the Contractor shall assume that the inflow criteria provided in the Specifications will be exceeded, and pre-excavating grouting will be required in accordance with the Specifications, along a total length of 2,000 feet of tunnel in Reach 3, or about 13 percent % of the total length of this reach. The specific locations of pre-excavation grouting cannot be identified in advance of tunnel excavation; however the Contractor shall assume that pre-excavation grouting may be required at any point along the tunnel alignment. Probe holes in advance of tunnel excavation are required to determine the need for grouting. 4.3.6 Potential Ground Behavior Ground behavior of RMTs B1 and B2 is expected to be controlled by the rock mass structure with respect to the orientation of the tunnel excavation. In general, rock encountered in RMT B1 is expected to be moderately jointed and stable; however, localized unstable rock blocks or wedges will be daylighted by the tunnel excavation. In areas where the joints confining the blocks are infilled with clay, or where joint orientations are unfavorable, the blocks will be unstable and will fall out of the roof and sidewalls. Potential unstable rock blocks, or wedges, formed by the anticipated joint sets in Reach 3 are presented in Figure 17. Fracture orientations within this reach are expected to be variable; however the likelihood of unstable blocks developing along shallow dipping joints (Joint Sets 1 and 4) will be higher at the western end of the alignment. Rock encountered in RMT B2 is expected to be moderately blocky and seamy, exhibit slow raveling conditions, and fast raveling conditions where flowing groundwater is encountered. RMT B3 is expected to exhibit slow to fast raveling/caving conditions. The altered nature of the rock mass in RMT B3, including the presence of weak rocks, shear zones, crushed to closely fractured rock, silt and clay infilling materials, and presence of groundwater all will contribute to the instability of the rock mass. Control of groundwater inflows into the tunnel by predrainage (using drain holes) and/or pre-excavation grouting will assist in preventing unstable ground conditions from developing. Summary descriptions of the three RMTs are provided in Table 6. Definitions of ground behavior are provided in Table 8 and Table 9. 4.4 Reach 4 (Station 162+00 to 163+50) Reach 4 extends from the end of Reach 3 to the Kailua TIPS Shaft, a distance of about 150 feet. The depth of the tunnel invert within this reach ranges from about 65 to 70 feet. The tunnel is beneath the




KRWWTP property in this entire reach. Reach 4 also includes the Tunnel Adit that connects the Kailua Drop Shaft with the tunnel. From the TIPS Shaft at Station 163+50 to the end of Reach 4 at Station 162+00, a full face of Weathered Basalt will be encountered for a distance of about 15 feet, followed by mixed face of Weathered Basalt and Basalt will be encountered for a distance of about 35 feet, and then followed by a full face of Basalt to the end of this reach. As the tunnel transitions into the Basalt, the rock encountered will become less weathered to the end of this reach where it will be moderately to slightly weathered. The geologic profile for Reach 4 is provided in Figure 2-7. 4.4.1 Grain Size Distribution and Plasticity Refer to Section 4.2.1 for descriptions of grain size distribution of the Weathered Basalt soils expected to be encountered in Reach 4. The fine-grained silts and clays of the Weathered Basalt matrix typically have high to very high plasticity. Only four Atterberg limits test were performed on samples of the soil matrix of the Weathered Basalt in this reach. Liquid limits are anticipated to range from 40 to 75 and average 55. The plasticity index is anticipated to range from 25 to 45 and average 35. Moisture contents of the silts and clays are anticipated to range from 20 to 75 percent and average 40 percent. 4.4.2 Strength and Consistency The consistency of the soil matrix of the Weathered Basalt is expected to range from medium dense to very dense for coarse-grained soils and from very stiff to hard for fine-grained soils. Undrained shear strengths for fine-grained soils within the Weathered Basalt will range from 4,000 to 8,150 psf and average 5,850 psf. The results of undrained shear strength testing are provided in the GDR. Because of the greater degree of weathering in this reach, rock strength will increase as the reach transitions from Weathered Basalt to Basalt. UCS of intact basalt and rock fragments and corestones within the Weathered Basalt are anticipated to range from 400 to 15,000 psi, with an average of 5,000 psi. The strength of the Basalt rock will be similar to that discussed in Section 4.3.2 for Reach 3. 4.4.3 Discontinuities Discontinuities consist primarily of joints that are smooth to slightly rough with tight to narrow apertures. The joints are variable but generally form Joint Sets 2 and 3, provided in Table 10. In addition to the predominant joint sets, joints will also occur at random orientations. The distribution joints that form the above sets and the random orientations are shown in Figure 13. Rock fracturing in the Basalt basalt rock ranges from crushed to moderately fractured, with a majority of the rock ranging from crushed to closely fractured to moderately fractured. 4.4.4 Rock Mass Quality




The Basalt in Reach 4 will range from moderately blocky and seamy to very blocky and seamy with some crushed rock. As described above, RMTs have been established to characterize ground conditions. For baseline purposes within Reach 4, 25 percent of the Basalt will be RMT B2 and 75 percent will be RMT B3. This corresponds to lengths of about 25 and 100 feet, respectively, for RMTs B2 and B3. 4.4.5 Groundwater and Hydraulic Conductivity Groundwater levels within this reach are expected to range from about 60 feet above the tunnel invert. Based on packer and falling head tests performed in Borings B-39, B-2, and P-11 within this reach, hydraulic conductivities are expected to range from 2 x 10-6 to 8.8 x 10-3 cm/sec. For baseline purposes, instantaneous heading inflows in this reach, assuming an ungrouted tunnel, will not exceed 300 gpm and maximum sustained inflows for the entire reach will not exceed 100 gpm. 4.4.6 Potential Ground Behavior Considering that Reach 4 is below the groundwater table, the Weathered Basalt is expected to be firm to fast raveling ground. Where sand and/or gravel lenses with little binder, such as clay or silt, are present, these zones will exhibit fast raveling to flowing behavior. Ground behavior in Basalt is expected to be slow to fast raveling depending on the degree of weathering, strength, and fracture characteristics. Potentially unstable rock blocks and wedges will develop around the tunnel excavation where adverse discontinuity orientations are encountered. Potential unstable rock blocks, or wedges, formed by the anticipated joint sets in Reach 4 are presented in Figure 17, although the fracture orientations in this reach are expected to be more random than Reach 3 and consequently block sizes and shapes will be highly variable. Because of high groundwater levels present along the adjacent Oneawa Hills, increased groundwater inflows may be encountered within the Weathered Basalt, and at the contact between the Weathered Basalt and Basalt. These inflows will contribute to instability of the tunnel excavation. Control of groundwater inflows into the tunnel by pre-excavation grouting is required between Stations 162+00 and 163+50 to prevent unstable ground conditions from developing.




5 Tunnel Construction Considerations The Kaneohe/Kailua Sewer Tunnel will be excavated through a several geologic formations, including Estuarine Deposits, Older Alluvium, Weathered Basalt, and weak to very strong Basalt rock. As discussed in Section 4, ground conditions and ground behavior are expected to vary considerably, depending on the type of ground encountered and its physical properties (i.e., grain size distribution, consistency, strength, weathering, and discontinuities). The range of anticipated ground conditions and ground behavior should be considered carefully in the selection of tunneling methods and equipment, and also in the initial ground support types and methods of installation. Several previous local tunneling projects have been completed through similar igneous rock formations on the island of Oahu. Appendix A provides a brief summary of these projects, including the Tetsuo HaranoH-3 Tunnel, Wilson Tunnels, and the Pali Tunnels. The tunnel excavations will need to be sized to accommodate the Contractor’s proposed initial support system, the required final lining, the minimum backfill thickness around the final lining, and the line and grade tolerances provided in the Specifications. It is anticipated that the tunnel will be excavated to a size of about 13 to 15 feet in diameter for the TBM mined tunnel, and 16 to 18 feet for the conventionally mined tunnel sections. To minimize the potential for disturbance to nearby residences, blasting is not permitted outside the limits of the KRWWTP (west of tunnel Station 161+00). Blasting is not permitted for conventionally mined excavations within the KWPTF and the Bay View Golf Park because of the proximity of nearby residences and presence of sensitive soils. Where blasting is allowed, controlled blasting techniques, including strict vibration control, are required. 5.1 Tunnel Initial Support Requirements The Kaneohe/Kailua Sewer Tunnel will have a two-pass support system consisting of an initial support system installed immediately with the following excavation and a final lining system installed after tunneling tunnel excavation has operations have been completed. Initial support systems for the tunnel will consist of support elements installed for ground support, excavation stability, and safety during the work. Initial support requirements vary along the tunnel because of the range of ground conditions discussed in Section 4. Initial support systems for the tunnel will be selected, designed, installed, and maintained by the Contractor in accordance with the minimum design criteria in the Specifications, as discussed below. In selecting and designing the initial support systems, the Contractor will need to evaluate a range of interrelated factors, including but not limited to:

• Size and shape of the tunnel excavation • Strength, behavior, and other physical characteristics of the ground • Variability of the ground conditions along the alignment • Groundwater conditions • Orientation, spacing, and characteristics of discontinuities in the rock mass




Construction factors such as the selected tunneling equipment, excavation methods, and other construction access or staging requirements

Design ground loads for the initial support systems are discussed below in Section 5.5.

5.2 Conventionally Mined Tunnel at the KWPTF At the west end of the tunnel alignment between Station 0+15 and about Station 11+00, tunnel excavation from the Kaneohe Shaft at the KWPTF will be through Estuarine Deposits and Older Alluvium, mixed-face conditions of overburden soils overlying Weathered Basalt, Weathered Basalt, and Basalt. The intent is to advance this section of tunnel through the soil deposits and weathered rock to rock suitable for excavation with a hard rock TBM. Conventional tunnel excavation techniques are to be used for this tunnel section; however blasting methods are prohibited. From Station 0+15 to 6+50, jet grouting is required prior to performing excavation to stabilize unstable soil deposits. Requirements for ground stabilization, excavation, and initial support within these zones are discussed below. 5.2.1 Ground Stabilization Tunnel excavation from Station 0+15 to 6+50 will require ground stabilization by jet grouting methods to avoid ground instability, excessive ground movements and loss of ground, surface settlement, and groundwater inflows during tunnel excavation. Ground stabilization is intended to strengthen the existing soils and reduce their permeability such that the tunnel can be advanced safely using conventional excavation methods. Without adequate stabilization, ground encountered in the starter tunnel excavation will ravel, flow, run, and migrate into the excavation. Low ground cover above the tunnel crown is expected to increase the potential for and magnitude of surface settlements, piping, and sinkholes if ground movements within the tunnel are not sufficiently controlled. Jet grouting in this area is anticipated to be difficult due to the presence of Estuarine Deposits which consist of saturated very soft to soft organic silts and clays with organics. Jet grouting in these soils, while feasible, is likely to experience reduced column diameters, blockages around the drill string due to squeezing and flowing ground, ground heave, and retarded strength gain of the soil-cement mass. Due to the low strength of these soils, the amount of air used during the jetting process will need to be carefully considered as its use will increase the risk of hydrofracturing in the ground, resulting in ground heave and possibly grout leakage at the ground surface. Recent Alluvium and Older Alluvium underlying the Estuarine Deposits generally consist of stiff to very stiff clays and silts, and medium dense to very dense silty to clayey gravels and poorly graded gravels, with cobbles and boulders. Jet grouting in these soils is expected to be difficult due to the presence of cobbles and boulders, which may deflect the drill string during drilling causing deviation of the jet grout column. Also these materials can cause a shadowing effect where the grout mix is unable to penetrate behind the cobbles and boulders. In light of the potential difficulties discussed above, the Contractor must consider selection of its jetting parameters and column layout carefully so that the jet grout stabilization meets the requirements of the Specifications. The Contractor must also consider these difficulties when planning and sequencing its




work such that impacts to the construction schedule are minimized, and the work restrictions contained in the Specifications are met. The Contractor is required to perform comprehensive test programs and additional site investigations to confirm subsurface conditions along the zone of ground stabilization and to develop the jetting parameters to be used during production jet grouting. The Contractor shall verify by means of in situ and laboratory testing, for test programs and production grouting, that the stabilized soil columns meet the requirements of strength and permeability. The Specifications indicate the minimum column overlap; however it is the Contractor's responsibility to ensure complete stabilization of the ground for tunnel construction even if the amount of overlap must be increased. The Contractor's specific means and methods will be an important factor in this determination. 5.2.2 Ground Improvement The Contractor will be responsible for selection and implementation of the ground improvement measures required prior to excavating the conventionally mined tunnel in accordance with the Specifications. Possible ground improvement measures include (1) predrainage; (2) pre-excavation grouting; and (3) a combination of both of these measures. Considering the variability of the ground conditions along the conventionally mined tunnel alignment, these measures, in addition to presupport and face support measures (see Section 5.2.4), may be required. Without adequate stabilization, the ground encountered in the conventionally mined tunnel excavation will tend to ravel, flow, and migrate into the excavation. Because of the relatively low hydraulic conductivity, pre-excavation grouting is not expected to be effective in improving ground behavior or providing groundwater cutoff in ground where soils have high silt and clay contents, where rock fractures have clay infilling and in areas of intact basalt. Where Weathered Basalt is encountered, higher hydraulic conductivities are likely, and the Contractor’s ground improvement design must account for open zones, including the need for cased holes during installation to avoid caving conditions, and the need for additives in the grout mix to fill voids. Pre-excavation grouting, if used in these areas, may require multiple stages to effectively stabilize the ground and provide a sufficient groundwater cutoff. Effectiveness of pre-excavation grouting for ground improvement should be evaluated based on criteria such as grout take rather than the inflow criteria as used for groundwater inflow control. To be effective, the improved ground must have sufficient strength such that raveling of the excavation is prevented, sufficient stand-up time is provided to allow installation of the initial support, and groundwater flows are adequately cut off so that inflows are minimized. For baseline purposes, it is assumed that 75 percent of the conventionally mined tunnel excavation between Station 6+50 and 11+00 will require ground improvement, presupport, and/or face support measures. Feasible face support, presupport, and initial support methods are described in Section 5.2.4.




5.2.3 5.2.2 Excavation Methods Excavation through the jet grout stabilized soils, Older Alluvium, Weathered Basalt, and Basalt is to be performed by conventional methods using equipment such as roadheaders, hydraulic excavators, and/or hoe rams (impact hammers) selected by the Contractor. Blasting methods are not allowed. 5.2.4 5.2.3 Initial Support Requirements Initial support through the jet grout stabilization and conventionally mined section of tunnel is anticipated to consist of steel ribs or lattice girders with shotcrete. Timber lagging or shotcrete will be required to support the ground between steel rib sets. Because of the potential for ungrouted zones within the jet grout stabilization that may not have received sufficient jet grouting treatment, and due to the potential for unstable ground conditions to develop within the Older Alluvium and Weathered Basalt, the Contractor should prepare for shortened advance round lengths, expeditious installation of ground support, presupport measures such as grouted spiling, crown bars, channel forepoling, and face support measures such as breastboarding and partial face advance, and other methods, as determined by the Contractor. The need for presupport and face support will be related to the ground conditions and the effectiveness of methods implemented for ground improvement and groundwater control. 5.3 Starter Tunnel and Tunnel Adit at the KRWWTP Excavation of the a starter tunnel from the Kailua TIPS Shaft at the KRWWTP site is anticipated to be required in order to launch the TBM and to facilitate construction of the Tunnel Adit, Kailua Drop Shaft, and the Transition Tunnel structure. It is the Contractor’s responsibility to determine the extent and dimensions of the starter tunnel and Tunnel Adit as needed for construction operations and construction of the structures indicated on the Contract Drawings. The starter tunnel shall be designed to extend sufficiently far into suitable rock appropriate for TBM assembly and the initiation of TBM mining operations. Excavation of the starter tunnel and Tunnel Adit will be by conventional excavation methods, including drill-and-blast methods, where this is allowed. The length of the starter tunnel will be determined by the Contractor based on the length of the TBM, construction access requirements, the results of pre-excavation probing and grouting efforts, and the effectiveness of the Contractor’s selected ground improvement and groundwater control measures. Blasting methods shall not extend beyond the KRWWTP site at approximate Station 160+50. 5.3.1 Ground Improvement The Contractor will be responsible for selection and implementation of the mandatory ground improvement measures required prior to excavating the starter tunnel in accordance with the Specifications. Possible ground improvement measures include (1) predrainage; (2) presupport and face support of the tunnel; (3) (2) pre-excavation grouting; and (3) a combination of both of these measures (4) combinations of any of the three measures. Considering the variability of the ground conditions along the starter tunnel alignment, several of these measures, in addition to presupport and face support measures (see Section 5.3.3), may be required. Without adequate stabilization, the ground encountered in the starter tunnel excavation will tend to ravel, flow, and migrate into the excavation.




Because of the relatively low rock mass hydraulic conductivity, pre-excavation grouting is not expected to be effective in ground where the fractures have clay infilling and in areas of intact basalt. Where Weathered Basalt is encountered, higher hydraulic conductivities are likely, and the Contractor’s grouting design must account for open zones in the rock mass, including the need for cased holes during installation to avoid caving conditions, and the need for additives in the grout mix to fill voids. Pre-excavation grouting, if used in these areas, may require multiple stages to effectively stabilize the ground and provide a sufficient groundwater cutoff. Effectiveness of pre-excavation grouting for ground improvement should be evaluated based on criteria such as grout take rather, than the inflow criteria as used for groundwater inflow control. To be effective, the improved ground must have sufficient strength such that raveling of the excavation is prevented, sufficient stand-up time is provided to allow installation of the initial support, and groundwater flows are adequately cut off so that inflows are minimized. 5.3.2 Excavation Methods Excavation of the starter tunnel, and the Tunnel Adit will encounter variable weathered and fractured rock, including saprolite and residual soil. Excavation of these materials can be achieved by conventional methods using a roadheader, hydraulic excavator, or drill-and-blast methods. Drill-and-blast methods are to utilize controlled blasting techniques with strict control of blasting vibrations in accordance with the Specifications. The Specifications also address preconstruction survey and vibration monitoring requirements. Special attention should be paid to protecting the existing 42-inch force main that crosses over the tunnel in this area. For baseline purposes, it is assumed that 75 percent of Reach 2 will require presupport of the tunnel, and application of face support. Feasible tunnel presupport, face support, and initial support methods are described further in Section 5. 5.3.3 Initial Support Requirements Initial support through this tunnel section will consist of steel ribs or lattice girders with shotcrete. Shotcrete lagging will be required to support the ground between steel rib sets. Because of the potential for unstable ground conditions anticipated along the starter tunnel, the Contractor should prepare for shortened advance round lengths, expeditious installation of ground support, face support measures, and presupport measures such as grouted spiling, crown bars, and other methods, as determined by the Contractor. The most effective method(s) will depend on the ground conditions encountered and the means and methods selected for advancing the tunnel. The need for presupport and face support will be related to the ground conditions and the effectiveness of the methods implemented for ground improvement and groundwater control. 5.4 TBM Tunnel Because of the length of the tunnel alignment, anticipated ground conditions, and the concerns of the local community, nonexplosive excavation methods are to be used for a majority of the tunnel. Use of a hard rock TBM is required from the end of the starter tunnel at the Kailua TIPS Shaft at approximate Station 162+00 to the end of the conventionally mined tunnel near Station 11+00. Note that the start and end




stations of the bored tunnel are to be determined by the Contractor to suit the selected means and methods. 5.4.1 Excavation Methods Based on the results of the geotechnical investigations and assessment of anticipated ground conditions, a TBM is suitable for excavating the tunnel through the basalt rock that will be encountered in this project. The Specifications include specific requirements for the TBM to be used on this project. Key considerations for selection and design of the TBM, and for the Contractor’s means and methods for bored tunnel construction, are:

Strong to very strong rock with wide joint spacing Zones of weaker, highly to moderately weathered rocks Face instability in blocky rock that will tend to block the buckets and jam the cutterhead Occasional (no more than one percent of the tunnel drive length) side gripper bearing problems

where closely jointed, very blocky and seamy rock, and/or crushed rock is encountered in the tunnel sidewalls

5.4.2 Open Main-Beam TBMs

The basalt rock in Reach 3 is expected to be strong enough to provide adequate thrust reaction for the side grippers of an open main-beam TBM, except in areas indicated in Section 5.4.1. In the massive, very strong rock, it will be important to provide sufficient power delivered to the cutterhead such that the TBM is not torque limited at the desired penetration rate. Low profile muck buckets and bucket lips should be considered to efficiently remove cuttings from the face to reduce the potential for regrinding of the muck and to limit plucking of rock from the face. Sufficient space should be provided behind the cutterhead to install initial support systems, including rock dowels reinforcement and steel ribs. As a minimum, a finger shield should be provided for safety in blocky ground. It will also be necessary to install rock bolts in between the fingers to stabilize potentially unstable rock blocks. The TBM should have the ability to drill probe holes and drain holes ahead of the tunnel face in the positions shown in the Contract Drawings. Excavation of the bored tunnel will also need to consider the presence of blocky ground at the face of the TBM as this will impact rotation of the cutterhead and will cause rock to break out of the face. Loosened blocks and slabs in advance of or above the heading may shift toward the cutterhead, creating obstructions and resulting in voids around the perimeter of the excavation. These blocks and slabs could also jam the cutterhead where they are too large to pass through the cutterhead openings, and cause disc cutter, muck bucket, and conveyor damage, reducing available torque and reducing TBM production. Blocks formed by the intersection of joints or fractures will be prone to fallout in the crown and haunch where joints are oriented adversely with respect to the excavation orientation. The potential for block fallout will be highest where joints are persistent and closely to moderately spaced. In shear zones, areas of more intense jointing and/or fracturing, and where joints and fractures contain infill material, overbreak and potential wedge failures above the crown and in the tunnel haunch are




expected. Where soft infill material and highly altered, highly fractured, and/or disintegrated rock are encountered, TBM cutters could potentially remove more material than can be accounted for by the theoretical volume of the tunnel, leading to overexcavation, chimneying, and possible collapse of the roof, particularly when water is present. Inappropriate cutterhead speed also may cause higher machine vibration, promoting more loosening of material and chimneying, jamming and reducing TBM production rates. These areas will also require increased ground support. Fallout of material from the sidewall also will result in reduced or minimal sidewall gripper thrust action and limit the ability of the TBM to advance without remedial measures such as sidewall cribbing or backfilling. 5.4.3 TBM Performance Estimates Several rock samples were sent to the Earth Mechanics Institute at the Colorado School of Mines in Golden, Colorado, for testing to evaluate TBM boreability. Some of the tests performed include punch penetration response, unconfined compressive strength, Brazilian tensile strength, petrographic analyses, and Cerchar Abrasivity Index. The results of the TBM boreability tests and other rock property tests are provided in the GDR. A summary of the test results are also included in Table 4 and Table 5. Instantaneous penetration rate estimates are not included in this GBR and are the responsibility of the Contractor. The average values indicated in Table 4 should be assumed to be baseline average values for TBM performance and cutter wear estimates. Other factors that should be considered include:

The maximum and average unconfined compressive strength baseline values for the basalt rock. Mineralogy of the various rock types, as discussed in Section 3 and the GDR. Range of other test results that will influence TBM boreability and cutter wear, including punch

penetration response, Cerchar Abrasivity, quartz content, point load, and Brazilian tests. Fracture frequency and RQD values for the basalt rocks, indicated in Figures 6 and 15.

In addition to the above factors, actual penetration rates and cutter wear will be influenced by the compatibility of the TBM with the ground conditions encountered, cutter and cutterhead maintenance schedules, and machine factors, such as net thrust delivered to the cutters, torque, horsepower, number of cutters, type, size, and spatial array of cutters, and cutterhead rotational speed. Cutter wear estimates should be developed based on the rock type, strength, abrasive mineral content, and the Cerchar Abrasivity test results, and individual TBM geometry and design of rolling cutter assemblies. 5.4.4 Initial Support Requirements Rock block loosening is anticipated to be the primary source of rock loading on the initial support system. Feasible initial support systems capable of providing the required ground support include spot bolting localized rock reinforcement, pattern bolting rock reinforcement, and steel ribs. Additional supplemental measures include wire mesh, welded wire fabric, mine straps, shotcrete, and timber lagging. Water pressure, water flow along joint surfaces, and the presence of joint infill material will reduce the stand-up time of blocks ground at the face, in the crown, and/or sidewalls, and will contribute to block ground movement and fallout. The timely support of the ground, including the installation of presupport measures, will be required to limit ground movements and loosening loads on the support system.




5.5 Design Ground Loads Estimates of ground loads were made for the design of the initial support system. Ground loads were estimated for the anticipated ground conditions described in Section 4 based on the rock load concept first developed by Terzaghi, and modified by Deere (Proctor and White, 1968; Deere et al., 1969). Initial support requirements and design ground loads should be determined from the baseline ground conditions indicated for each tunnel reach, not on the basis of baseline rock strength values or rock mass quality evaluations. Design ground loads for initial supports developed for the range of anticipated ground conditions are summarized in Table 12. The Contractor will be required to design the tunnel initial supports to withstand the vertical and horizontal pressures indicated in the tunnel loading diagrams shown in Figure 16. 5.6 Pre-excavation Probing, Grouting, and Drainage Probing, grouting, and drainage ahead of the tunnel excavation must be implemented as specified and shown on the Contract Drawings for all tunnel excavations, to achieve the following objectives:

Reduce groundwater inflows into the tunnel to facilitate tunnel construction Improve ground behavior to facilitate excavation and installation of support measures Minimize groundwater impacts that could affect local hydrostatic conditions

Pre-excavation grouting requires the injection of grout to fill openings in the rock mass. Typical pre-excavation grouting will not penetrate intact rock or joint infillings with low porosity. In zones of weathered/altered rock, clay-filled shears and clay fault gouge, or intensely fractured rock, grout penetration is expected to be limited because of low hydraulic conductivity, so the effectiveness of pre-excavation grouting for groundwater control will also be limited. In areas where the rock exhibits high hydraulic conductivity, treatment of the fractured rock mass through drainage and grouting is expected to be more effective. 5.7 Groundwater Inflows Estimated groundwater inflows into the tunnel are discussed in Section 4, including baseline instantaneous heading inflows and maximum inflows for each tunnel reach. The Contractor should develop work plans, including water handling and treatment provisions to cope with the anticipated groundwater inflow quantities. Measures must be implemented to prevent groundwater from accumulating in the tunnel and to maintain safe working conditions. Pumping facilities will be required in the tunnel for downgrade drives, such as the conventionally mined tunnel in Reach 2. 5.8 Water Treatment and Disposal Temporary water treatment plants will be required at each of the shaft sites (Kaneohe Shaft and Kailua TIPS Shaft) to treat all water used and encountered during tunnel excavation. Treatment levels and discharge criteria must be in compliance with the Specifications and the applicable National Pollutant Discharge Elimination System (NPDES) Permit for the project. The required water treatment plants must be sized and designed by the Contractor to ensure adequate capacity to handle the maximum potential




flows into the shafts, along with other construction water and storm water run-off from each construction site, as applicable. Design flows, determined by the Contractor, should be consistent with the proposed groundwater control measures implemented in the tunnel. 5.9 Tunnel Final Lining A final lining consisting of GFRP will is to be installed in the tunnel to provide a durable and hydraulically efficient system for conveying wastewater flows, and to minimize infiltration of water and exfiltration of wastewater into the ground. The final lining is designed to withstand long-term ground loads and external groundwater pressures, provide erosion and corrosion protection, and facilitate inspection of the tunnel. Low density cellular concrete backfill is specified as the backfill material, with sections of structural concrete required at Tee sections and at shaft connections. The Contractor is responsible for determining clearances necessary to account for the specific construction means and methods and required tolerances to ensure that the final lining can be installed properly. The Specifications also provide temperature limits for heat of hydration of the cellular concrete backfill and include requirements for monitoring backfill temperature during placement. Installation of the GFRP final lining will need to consider the need for blocking and bracing to counteract buoyant pressures during backfill placement, with special consideration needed at shear zones where the presence of soft infilling material may require the Contractor to install additional blocking, or revise the blocking arrangement, to account for the lower bearing capacity of the ground in these localized areas. The Contractor’s initial support systems installed during tunnel excavation must be compatible with the requirements for groundwater control and for placement of backfill concrete around the final lining, if applicable. The initial support systems must not encroach on the clearance envelope required for installation of the final lining. The Contract Drawings and Specifications provide requirements for control of the groundwater inflows for proper construction of the final lining and for proper placement of concrete backfill around the lining. Panning, drain pipes, and other drainage provisions are specified to divert groundwater inflows to an invert drain pipe to allow groundwater to be drained from the tunnel without adversely impacting the backfill concreting operations. 5.10 Muck Disposal Tunnel construction will generate approximately 165,000 cubic yards of earth and rock spoils materials (muck), assuming a swell factor of about 1.8 for an excavated tunnel diameter of 13.5 feet for the TBM tunnel, and a swell factor of 1.6 for an excavated tunnel diameter of 17 feet (horse-shoe shaped) for conventionally mined tunnels. This volume of muck will need to be permanently disposed of at acceptable disposal sites. Disposal of tunnel muck at acceptable disposal sites is the Contractor’s responsibility for muck generated at the KRWWTP, KWPTF, and Tunnel Access Shaft sites. The Contractor is to submit proposed disposal sites for review, in accordance with the requirements of the Specifications.




6 Shaft Construction Considerations The Project involves construction of four permanent shafts, as discussed in Section 2. These shafts are:

• Kaneohe Shaft • Kailua TIPS Shaft • Tunnel Access Shaft • Kailua Drop Shaft

Development of the shaft excavation will require installation of shoring/excavation support systems and implementation of groundwater control measures. Shaft excavation support systems are to be constructed as indicated on the Contract Drawings. The following sections discuss anticipated subsurface conditions and shaft construction considerations. Site development issues, including access, roads, and erosion and sediment control are addressed on the Contract Drawings and in the Specifications. 6.1 Kaneohe Shaft The Kaneohe Shaft will be used to facilitate the excavation of over 1,000 feet of conventionally mined tunnel and will serve as the retrieval shaft for the TBM. In addition, the shaft site will be used as staging for installation of the final tunnel lining. Jet grout stabilization in advance of excavation is required from Station 0+15 to 6+50, as indicated on the Contract Drawings. Following tunnel construction and completion of the final shaft lining, a vortex drop structure will be constructed within the shaft that, after completion, will divert flows collected at the KWPTF into the tunnel. The Kaneohe Shaft is centered at Station 0+00. The shaft has a finished diameter of 26.5 feet (36-foot-diameter to outside of slurry wall). The invert of excavation (to bottom of tremie slab) is located at about El. -38 feet (about 43 feet below ground surface). 6.1.1 Anticipated Subsurface Conditions Subsurface conditions (based on Boring B-30) consist of Artificial Fill between the existing ground surface (approximate El. +4.5 feet) and El. -2 feet. Estuarine Deposits are present between approximately El. -2 feet and El. -54 feet, with Recent Alluvium present below El. -54 feet. Older Alluvium is expected to be present below about El. -74 feet. The invert of the shaft excavation is located in the Estuarine Deposits, whereas the bases of the slurry wall panels are located in the Recent Alluvium. For Estuarine Deposits, refer to Sections 4.1.1 and 4.1.2 for descriptions of grain size distribution and plasticity, and strength and consistency, respectively. Based on groundwater monitoring in the vicinity of the shaft, groundwater levels vary with the tide and groundwater is to be anticipated to be brackish. The static groundwater table is to be expected to vary between El. 0 feet and El. +2 feet. The final lining for the shaft and tremie slab has been designed for a maximum flood elevation of +9 feet.




6.1.2 Excavation Support Requirements and Excavation Methods Because of the presence of the weak, compressible soil deposits and a high groundwater table, a rigid, watertight excavation support system is required to maintain excavation stability and to avoid surface subsidence due to lateral displacement of the support system and groundwater drawdowns. Therefore, slurry diaphragm walls extending to the full depth of the shaft excavation, as well as a watertight concrete tremie slab, are required for the excavation support system and to control stability of this shaft excavation. Minimum wall depths below the base of the shaft excavations are shown on the Contract Drawings, and are governed by shaft bottom stability, groundwater control, and uplift considerations. Slurry wall panel excavation can be accomplished using clamshell bucket or hydromill excavation methods. To reduce the impacts of possible obstructions in the Fill materials, the alignment of the slurry wall panels shall be pre-excavated to a depth of 15 feet to remove obstructions and backfilled with lean concrete mix prior to construction of the guide walls. Verification of panel vertical alignment is required to ensure that the panels do not become misaligned to such an extent that the finished slurry wall will not work as a compression ring. The Contractor shall assume that panels will require backfilling and re-excavation periodically in order to maintain verticality. Refer to the Specifications for pre-excavation requirements and verticality tolerances. Careful control of slurry density and levels will be required to maintain sidewall stability during panel excavation, and to minimize ground losses. Open-graded gravel soils are anticipated within the Recent Alluvium. In addition, the presence of dense gravel with cobbles and boulders will reduce excavation rates and require special tooling and excavation techniques, including frequent mucking of panel bottoms. Overexcavation and increased concrete overpours during panel placement are expected in this zone. Excavation of upper soils within the shaft interior can be carried out using conventional excavating equipment such as mechanical excavators. When groundwater is reached, excavation must be “in the wet,” and can be carried out using dredging or clamshell excavation methods. 6.1.3 Excavation Support System Design and Lateral Earth Pressures Lateral earth and hydrostatic pressures assumed for the design of shaft excavation support systems are shown in Figure 18. and assume the existing surface elevation at the Kaneohe Shaft site will be graded to El. +4.7 feet. Surcharge pressures due to construction equipment and traffic live loads are included in the design for pressures up to the limit indicated. If actual surcharge pressures are higher, the Contractor should increase the design surcharge pressures as necessary to be consistent with planned construction operations. 6.1.4 Groundwater Control Key construction considerations for installation of slurry walls at the Kaneohe Shaft include installation of an impervious excavation support system and installation of a tremie invert slab to provide full groundwater cutoff and to prevent bottom instabilities during excavation. Water levels must remain at an equivalent level to the surrounding groundwater level so that drawdown or underseepage does not occur, which may result in consolidation settlements of the surrounding soft clays and silts. Refer to the




Specifications for the minimum required water level within the shaft during excavation. Once the excavation reaches below the planned level of the bottom seal and the shaft is flooded, a concrete tremie slab shall be placed and keyed into the slurry wall such that the excavation support system is engaged in resisting uplift forces on the tremie slab. 6.2 Kailua TIPS Shaft The Kailua TIPS Shaft will be used to launch the TBM and to stage the tunnel excavation work. The future influent pump station will also be constructed inside the Kailua TIPS Shaft excavation after tunnel construction is complete. The Kailua TIPS Shaft is centered at approximate Station 163+94. The shaft has an ID of 87 feet (95-foot-diameter to outside of slurry wall). The invert of the excavation is located at El. -83.5 feet (about 96 feet below ground surface). Cutoff grouting below the base of the slurry panels is required prior to excavation to provide a groundwater cutoff. 6.2.1 Anticipated Subsurface Conditions The existing surface elevation at the Kailua TIPS shaft site ranges from approximately El. +12.5 feet to +9.5 feet. Subsurface conditions (based on Borings P-1, P-2, P-3, P-8, P-9, P-10, B-39, B-40, B-41, and B-42) generally consist of 5 feet of Artificial Fill located below the existing ground surface. Below the Artificial Fill is Alluvium/Colluvium Deposits, which vary in thickness across the site from about 5 to 15 feet. At the center of the shaft, below the Alluvium/Colluvium, is a layer of Lagoonal Deposits which has a maximum thickness of about 7 feet. Underlying the Lagoonal Deposits and Alluvium/Colluvium is the Older Alluvium which generally extends from about El. +3 feet to El. -50 feet. The Older Alluvium is intercalated with Coralline Detritus and contains layers of coralline gravels and sand. Weathered Basalt underlies the Older Alluvium and generally slopes downward from the south to the north across the shaft site. The Weathered Basalt will be a transition zone from the saprolite, residual soil and weathered rock horizon to unweathered to slightly weathered rock. This zone has a variable thickness across the shaft and will range from El. -16 feet to El. -67 feet at the southern portion of the shaft and from El. -50 feet to El. -93 feet at the northern portion of the shaft. Basalt extends below the Weathered Basalt, or from El. -67 feet to El. -93 feet. See Figure 3 for anticipated Basalt and Weathered Basalt contours within the Kailua TIPS Shaft. The Basalt located in the vicinity of the shaft is predominantly characterized as RMT B3 material. For the Older Alluvium and Weathered Basalt only, refer to Section 4.4.1 for baselines of grain size distribution and plasticity, and to Section 4.4.2 for baselines of strength and consistency. The boundary between Weathered Basalt and the Basalt rock unit is not uniform and is expected to vary in depth and consistency across the shaft excavation. The general trend of the Weathered Basalt/Basalt contact, as indicated in Figure 2-7, is downward sloping from south to north across the shaft site. However, interbedded (up to 10 feet in vertical profile) moderately to slightly weathered rock is anticipated to be present within the Weathered Basalt unit, likely a result of preferential weathering that has occurred along discontinuities and at dike margins. In addition, localized deeply weathered zones are anticipated to extend below the contact between Weathered Basalt and Basalt indicated in the geologic profile in Figure 2-7. Weathering will be to a greater extent adjacent to fractures that transmit water and




in rocks that are more susceptible to decomposition. The Contractor is to anticipate encountering intact and relatively unweathered rock immediately adjacent to more weathered, soil-like materials. Intact rock strength of the Basalt basalt rock is expected to increase with depth and range from extremely weak to very strong. Thirty-six (36) Forty-nine (49) PLI strength tests completed on rock samples obtained from Borings P-2, P-3, P-8, P-9, P-10, B-39, B-40, B-41, and B-42 have varying point load strengths (Is50) between 1 psi and 1,291 psi, and an average value of 130 152 psi. This corresponds to UCS values of 29 psi to 31,500 psi and an average UCS value of about 3,200 3,710 psi, based on a conversion factor of 24.4. Five UCS tests were completed in Borings P-3, P-8, B-39 and B-41 and indicate weak to strong rock with strengths ranging from about 1,700 to 9,100 psi and an average strength of about 4,350 psi. For baseline purposes, the average strength of Basalt within the TIPS Shaft should be assumed to be 5,000 psi. Based on groundwater monitoring in the vicinity of the shaft, the groundwater level varies with the tide and is anticipated to be brackish. The static groundwater table varies between El. 0 feet and El. +5 feet. 6.2.2 Excavation Support Requirements and Excavation Methods Because of the presence of the weak, compressible soil deposits and a high groundwater table, a rigid, watertight excavation support system is required to maintain excavation stability and to avoid surface subsidence due to lateral displacement of the support system and groundwater drawdowns. Therefore, slurry walls extending to the full depth of the shaft excavation are required as part of the excavation support system. Slurry walls will need to penetrate into rock and must be designed to be watertight through panels and panel joints. Slurry wall panel excavation through Lagoonal Deposits and Alluvium/Colluvium can be accomplished using a clamshell or hydromill. Excavation through the Older Alluvium, Weathered Basalt, and Basalt will require use of a hydromill, reamers, coring, or other mechanical means to break up soil and rock prior to removal. The required panel excavation through these zones will result in difficult excavation conditions where the relatively high strength and abrasiveness of the units will impact the capability of the equipment to operate effectively. Pick Cutter wear and frequent cutter breakage should be anticipated. To reduce the impacts of obstructions in Fill materials, the alignment of the slurry wall panels shall be pre-excavated to remove obstructions and backfilled with lean concrete mix prior to construction of the guide walls. Verification of vertical panel alignment is required to ensure that the panels do not become misaligned to such an extent that the finished slurry wall will not work as a compression ring. The Contractor shall assume that due to geologic conditions the panels will require backfilling and re-excavation periodically in order to maintain verticality. Refer to the Specifications for pre-excavation requirements and verticality tolerances. Careful control of slurry density and levels will be required to maintain sidewall stability during panel excavation, and to minimize ground losses. Open-graded gravel soils are anticipated within the Older Alluvium and Weathered Basalt units. Also open zones are anticipated in the Weathered Basalt and Basalt, as evidenced by fluid loss during drilling of exploratory borings. The Contractor shall assume that slurry loss will occur within each panel during excavation and be prepared to implement measures to




minimize slurry losses by backfilling panel excavations with lean mix or by pre-treating these zones by grouting. In addition, the presence of cobbles and boulders within the Older Alluvium, basalt fragments and corestones within the Weathered Basalt, and less weathered rock within the Basalt, will reduce excavation rates and require special tooling and excavation techniques, including shaving of sidewalls to maintain verticality, and frequent mucking of panel bottoms. Excavation of the shaft interior through the Lagoonal Deposits, Alluvium/Colluvium, and Older Alluvium, and soil-like material encountered in the Weathered Basalt unit, can be carried out using conventional excavating equipment such as mechanical excavators. For intact rock blocks within the Weathered Basalt and for excavation through the Basalt rock unit, hydraulic splitters or drill-and-blast techniques will be required. 6.2.3 Excavation Support System Design and Lateral Earth Pressures Lateral earth and hydrostatic pressures assumed for the design of shaft excavation support systems are shown in Figure 18. and assume the existing surface elevation at the Kailua TIPS Shaft site will be graded to El. +11.25 feet. Surcharge pressures due to construction equipment and traffic live loads are included in the design for pressures up to the limit indicated. If actual surcharge pressures are higher, the Contractor should increase the design surcharge pressures as necessary to be consistent with planned construction operations. 6.2.4 Groundwater Control Cutoff grouting below the base of the slurry wall panels will be required to provide a groundwater cutoff around the perimeter of the shaft. Groundwater control through the shaft invert is expected to be by drainage provisions, such as dewatering sumps. For baseline purposes, it is anticipated that a sustained groundwater inflow through the shaft invert will be less than 100 gpm (not including infiltration into the shaft from the ground surface, rainwater, and inflows from leaks in slurry walls). 6.3 Tunnel Access Shaft The Tunnel Access Shaft will be used for future inspection and maintenance activities for the tunnel. The shaft will have a GFRP riser and a sealed corrosion-resistant lid to prevent gases from exiting the tunnel The Tunnel Access Shaft is centered at approximate Station 78+86 along the tunnel alignment and is located at the BWS Kapaa Water Tank Site at the surface. The GFRP riser pipe has a finished ID of 96 inches and extends from approximately El. +238 feet to approximately El. -38 feet at the crown of the tunnel. The total length of the shaft is about 276 feet. 6.3.1 Anticipated Ground Conditions The surface elevation at the Tunnel Access Shaft is approximately El. +240 feet. Subsurface conditions (based on Boring B-34A) consist of approximately 2.5 feet of Artificial Fill overlying approximately 5 feet of Weathered Basalt, overlying Basalt Breccia. Between El. +237.5 feet and El. +232.5 feet, the Weathered Basalt consists of highly to extremely weathered basalt and gravels and cobbles with silt and




sand. Below El. +232.5 feet the Basalt Breccia consists of massive to moderately jointed and moderately blocky and seamy rock (classified as RMT B1 and B2). The Basalt Breccia is slightly weathered, hard, and medium strong to very strong. The Basalt Breccia is intersected by basalt dikes (Dike Complex), which are also generally slightly weathered, hard to very hard, and medium strong to strong. The degree of fracturing within the Basalt Breccia generally ranges from very widely to closely fractured. Localized zones of intensely fractured and crushed rock are present at various depths and are typically located along dike margins. Very blocky and seamy rock with crushed and disintegrated zones (classified as RMT B3) is expected between the following elevations: El. +232 feet to El. +217 feet, El. +205 feet to El. +192 feet, El. +178 feet to +172 feet, El. +127 feet to +121 feet, El. +44 feet to +37 feet, and El. -30 feet to -45 feet. In total these zones correspond to about 25 percent 30 % of the shaft length. The remainder of the shaft length consists of rock that is classified as RMT B1and RMT B2. The intact strength of the rock is expected to range from weak to very strong. Fifty (50) Twenty (20)PLI strength tests were completed in Borings B-34A and B-22 and ranged from 50 psi to 920 1,420 psi, which corresponds to UCS values of about 1,100 psi to 22,500 34,300 psi and an average UCS of about 13,900 psi based on a conversion factor of 24.4. Four UCS tests were completed in Boring B-34A and six UCS tests were completed in Boring B-22. These test and indicate medium strong to very strong rock with strengths ranging from 6,100 5,250 psi to 21,800 psi, and an average UCS of about 12,100 psi. For baseline purposes, the average strength of Basalt within the Access Shaft should be assumed to be 15,000 psi. Based on groundwater monitoring in the vicinity of the shaft, the static groundwater table is expected to be at El. +35.5 feet. Perched groundwater is anticipated to be within the Weathered Basalt zone and possibly within the upper 50 feet of the shaft. 6.3.2 Excavation Support Requirements and Excavation Methods Construction of the Tunnel Access Shaft will is to be by raise bore methods. The excavated diameter of the shaft will be determined by the Contractor, and shall be sufficiently large to accommodate installation of the 8-foot ID GFRP riser while meeting the specified tolerances provided in the Specifications. The shaft bore is anticipated to be about 11 to 12 feet in excavated diameter. Excavation of the shaft will be influenced by several factors, including machine characteristics, operator experience, intact rock strength, rock mass discontinuities, groundwater, and in situ stress. The upper 10 feet of the Tunnel Access Shaft excavation will encounter Artificial Fill, Weathered Basalt, and more highly fractured and slightly weathered Basalt Breccia. In this zone the Contractor should expect to encounter a heterogeneous mixture of soil-like materials with intensely fractured to crushed rock. Unless supported prior to excavation, these materials will be susceptible to localized raveling and sloughing, particularly where groundwater or surface runoff enters the shaft. It will be necessary for the Contractor to support this portion of the shaft prior to raise bore excavation. Excavation support elements will need to be installed to a depth where the rock is suitable for raise bore methods. Selection of raise bore equipment and operational parameters will need to consider the presence of steeply dipping joints, dike features, and the intersection of both with the lower angle joints present in the Basalt.




The Contractor should anticipate overbreak in the shaft due to block or wedge fallout and raveling in the crushed zones described above and should plan for placing concrete backfill in excess of the theoretical volume. In addition, design of foundations for the raise bore headworks must consider the potential presence of weak surficial soils. 6.3.3 Excavation Support System Design and Lateral Earth Pressures Excavation support systems for the Tunnel Access Shaft will be designed, furnished, installed, and maintained by the Contractor. Support requirements for the shaft can be expected to change with depth because of the ground conditions and groundwater levels that will be encountered during construction. Support systems are to be selected and designed in accordance with the design criteria in the Specifications and as discussed herein. The overburden materials, including the Weathered Basalt, will require continuous support in the shaft excavation. Appropriate support systems for circular excavations in overburden deposits and Weathered Basalt include liner plates, a steel casing, or circular steel ribs with liner plates, timber lagging, and/or shotcrete. Other feasible approaches include soldier piles with lagging (timber, steel plates, or shotcrete) and internal bracing systems. These support systems should extend at least 5 feet into the underlying moderately to slightly weathered rock. Below the overburden soils and Weathered Basalt, the Tunnel Access Shaft is expected to be in massive, moderately jointed rock to moderately blocky and seamy rock. Pattern rock reinforcement and/or shotcrete is considered to be an appropriate support system for these conditions. The rock reinforcement should be designed to stabilize rock wedges and blocks that will form around these shaft excavations resulting from the joint sets indicated in Table 10. Typical rock reinforcement should consist of tensioned or untensioned rock bolts/dowels encapsulated with cement grout. In some areas, however, the pattern of rock reinforcement will need to be supplemented with additional rock reinforcement members and the use of localized surface treatment measures such as steel straps, wire mat lagging, and/or shotcrete as necessary to stabilize the shaft walls and to contain small rock blocks/pieces that could drop from between the rock reinforcement. Minimum lateral earth pressures for the design of shaft excavation support systems are shown in Figure 19. Surcharge pressures due to construction equipment and traffic live loads should be added to the lateral pressures shown to account for loads other than those exerted by the ground and groundwater. If no specific surcharge loading is included in design of the excavation support system, then at a minimum the surcharge pressure shown in Figure 19 should be added to the design lateral earth pressure. Groundwater pressures should be accounted for in the design lateral pressures unless effective positive drainage measures are provided to relieve hydrostatic pressures. 6.3.4 Groundwater Control For baseline purposes, the Contractor shall assume that 100 gpm of groundwater inflow will be encountered during raise bore excavation. The Contractor shall account for this groundwater inflow in addition to the groundwater inflow anticipated for the TBM mined tunnel (Section 4).




6.4 Kailua Drop Shaft The Kailua Drop Shaft will be used to direct flows from the existing Kailua Influent Pump Station to the tunnel. The design of the Kailua Drop Shaft includes a fully lined shaft with a 33-inch ID GFRP riser and connection to the Tunnel Adit pipe. The Kailua Drop Shaft is offset from the sewer tunnel by approximately 20 feet to the northeast and extends below the Kailua Drop Structure from approximately El. -24 to the crown of the Tunnel Adit at about El. -50. Construction considerations for the Kailua Drop Structure are outside the scope of this report. Refer to YKE Geotechnical Investigation Report (YKE, 2013b) for additional details regarding this structure. 6.4.1 Anticipated Subsurface Conditions Subsurface conditions (based on Boring P-11) consist of approximately 2 feet of Artificial Fill overlying Weathered Basalt and Basalt. Weathered Basalt extends to about 31 feet below the existing ground surface (about El. -15) and consists of silty gravel with moderately to highly weathered basalt gravel and cobbles, and seams of clay and silt. Basalt extends below the Weathered Basalt to below the bottom of the Kailua Drop Shaft and Tunnel Adit (below about El. -64 feet). Within the Kailua Drop Shaft and Tunnel Adit, the Basalt is generally slightly weathered to moderately weathered and moderately to intensely fractured (classified as RMT B3 material). Intact rock strength of the Basalt ranges from extremely weak to moderately strong and is expected to increase with depth. Eleven (11) PLI strength tests were completed on rock samples encountered at Boring P-11 and ranged from about 10 psi to 700 psi, which corresponds to UCS values of about 200 psi to 17,000 psi based on a conversion factor of 24.4. One UCS test was completed in Boring P-11 and indicated strong rock with a strength of about 9,000 psi. For baseline purposes, the average strength of Basalt within the Kailua Drop Shaft should be assumed to be 10,000 psi. Based on groundwater monitoring in the vicinity of the shaft, the groundwater level varies with the tide and is anticipated to be brackish. The static groundwater table is anticipated to be at El. +1 feet. 6.4.2 Excavation Support Requirements and Excavation Methods Construction of the Kailua Drop Shaft will be by “top-down” drilling techniques using a core barrel or down-the-hole hammer to drill the shaft from either the ground surface or from within the Kailua Drop Structure and Microtunnel Retrieval Shaft invert. Selection of the excavated dimension of the Drop Shaft is the responsibility of the Contractor and shall be sufficiently large to accommodate installation of a steel casing to support the shaft opening. A 33-inch ID GFRP riser will then be placed within the steel casing and backfilled and will serve as the Kailua Drop shaft into the Tunnel Adit. The shaft bore is anticipated to be approximately 5 feet in excavated diameter. The Kailua Drop Shaft excavation will encounter Artificial Fill, Weathered Basalt, and moderately to highly weathered Basalt that is moderately to intensely fractured. Excavation through these materials will be susceptible to localized raveling and sloughing, particularly where groundwater or surface runoff enters the shaft. For top-down shaft excavation, these conditions may require the Contractor to continuously case the drilled hole to minimize overexcavation and to maintain shaft sidewall stability.




6.4.3 Excavation Support System Design and Lateral Earth Pressures Support systems for the Kailua Drop Shaft will consist of a steel casing grouted into place. The casing shall be designed, furnished, and installed by the Contractor. Minimum lateral earth pressures for the design of Kailua Drop Shaft steel casing are shown in Figure 19. Surcharge pressures due to construction equipment and traffic live loads should be added to the lateral pressures shown to account for loads other than those exerted by the ground and groundwater. If no specific surcharge loading is included in design of the excavation support system, then at a minimum the surcharge pressure shown in Figure 19 should be added to the design lateral earth pressure. Groundwater pressures should be accounted for in the design lateral pressures. 6.4.4 Groundwater Control The Contractor shall assume that groundwater inflow will be encountered during shaft excavation. The Contractor shall account for this groundwater inflow in addition to the groundwater inflow anticipated for the TBM-bored tunnel (see Section 4). For baseline purposes, the Contractor shall assume that 50 gpm of groundwater inflow will be encountered during shaft excavation. 6.5 Water Treatment and Disposal Based on information available from the GDR, and in recognition of the construction processes, it is anticipated that all water collected from the tunnel and shafts will require treatment prior to discharge in order to meet the requirements of the discharge permit. The Kailua TIPS shaft will be the main area for treating and discharging groundwater and construction water during construction. Given the potential for temporary groundwater inflows during tunnel and shaft construction, the installed shaft pump capacity and treatment plant must be sized and designed by the Contractor to ensure adequate capacity to handle the maximum potential shaft and tunnel inflows, along with other construction water and storm water run-off from each construction site, as applicable. for For baseline purposes, the Contractor shall provide treatment plant with a minimum capacity of 1,200 gpm to handle all flows, leakage, and construction water. Water treatment, handling, and disposal must be in accordance with the discharge permit requirements in the Specifications and Special Provisions. 6.6 Muck Disposal Muck is to be disposed of in accordance with the requirements of Section 5.10.




7 Geotechnical Instrumentation and Monitoring Geotechnical instrumentation and monitoring of the tunnel and shaft construction are required as detailed in the Specifications and as shown in the Contract Drawings. Key objectives of the instrumentation include to the following:

• Monitor the performance of the shaft and tunnel excavations by measuring the ground movements caused by their excavations.

• Monitor ground deformations around the tunnel to verify the initial support performance and requirements.

• Measure groundwater inflows to compare with baseline values and to verify the performance and need for control measures.

The geotechnical instrumentation will include surface instruments and survey monitoring points as well as underground instruments inside the tunnel. The details of the required instrumentation and monitoring are presented in the Contract Drawings and Specifications and summarized below. 7.1 Surface Instrumentation Required surface instrumentation for monitoring the tunnel excavations will consist of optical survey control points, inclinometers, piezometers, and multipoint borehole extensometers. The objectives will be to monitor ground movements in the vicinity of nearby surface and subsurface structures during tunnel excavation. In addition, buried utilities must also be monitored with utility monitoring points to verify that the utilities are not disturbed by adjacent excavations. Required surface instrumentation for monitoring the performance of shaft excavations will consist of optical survey control points, utility monitoring points, inclinometers with settlement casings, and piezometers. Vibration monitoring is required at locations identified on the Contract Drawings where blasting- or TBM-generated vibrations are likely to impact nearby structures. In addition, vibration monitoring is required at the Tunnel Access Shaft and at 500-foot intervals along the tunnel alignment. Vibration/Noise Control Monitoring Zones are also indicated on the Contract Drawings and where overlying residential structures are sensitive to construction vibrations from tunnel excavation activities are indicated on the Contract Drawings. These zones correspond to areas along the tunnel alignment where the Contractor is required to implement specific measures to reduce vibrations arising from locomotive operation in the tunnel. Detailed requirements are provided in the Specifications. 7.2 Tunnel Instrumentation Required tunnel instrumentation will consist of convergence monitoring points and support system deformation monitoring points. A typical instrumented tunnel section will consist of an array of convergence reference points. The performance of the tunnel excavation will be monitored at locations where the tunnel is excavated in stabilized (i.e., jet grouted) ground and where the tunnel intersects major




features such as shear zones. At these locations, ground movements will be monitored to evaluate the tunnel stability and initial support performance. Groundwater inflow measurements are required at the tunnel headings and at portal locations. Acceptable measurement methods include flowmeters (for pumped flows) and weirs (for flows draining by gravity).




8 References Abrahamson, L., and W.H. Hansmire. 1989. Geotechnical exploration for the H-3 Highway Trans-Koolau Tunnel. In Proceedings of the Rapid Excavation and Tunneling Conference, Englewood, CO: Society for Mining, Metallurgy, and Exploration. American Society of Civil Engineers (ASCE). 2010. Minimum Design Loads for Buildings and Other Structures. ASCE Standard ASCE/SEI 7-10, Reston, VA. Barton, N. 1988. Rock mass classification and tunnel reinforcement selection using the Q-System, In Rock Mass Classification Systems for Engineering Purposes, L. Kirkaldie, Ed., ASTM Special Technical Publication 984, Philadelphia. Bieniawski, Z.T. 1988. The Rock Mass Rating (RMR) system (Geomechanics classification) in engineering practice. In Rock Mass Classification Systems for Engineering Purposes, L. Kirkaldie, Ed., ASTM Special Technical Publication 984, Philadelphia. Deere, D.U., A.H. Merritt, and R.F. Coon. 1969. Engineering Classification of In Situ Rock: Technical Report No. AFWL-TR-67-144, Kirtland Air Force Base, NM, 280 pp. (Available from the U.S. Department of Commerce, NTIS, Springfield, VA, Pub. No. AD848798.) Garcia, M. 1979. Field Trip Guide to the Hawaiian Islands [Oahu and Hawaii], Special Publication—Hawaii Institute of Geophysics. GeoLabs. 2011. Preliminary Geotechnical Exploration Report, Kaneohe to Kailua Wastewater Facilities Plan. Gramlich, J.W., V.A. Lewis, and J.J. Naughton. 1971. Potassium-argon dating of Holocene Basalts of the Honolulu Volcanic Series, Geological Society of America Bulletin, 82 (5). Hansmire, W.H., J.W. Critchfield, M.H. Nicholls, and C.R. Kolell. 1993. Construction of the Trans-Koolau Tunnel. RETC 1993 Proceedings, Boston, MA, 1081–1099. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc. Hatanaka, M., and A. Uchida. 1996. Empirical correlation between penetration resistance and of sandy soils, Soils and Foundations, Vol. 36, No. 436 (4). Heuer, R.E. 1974. Important ground parameters in soft ground tunneling. In Proceedings of the Subsurface Exploration for Underground Excavation and Heavy Construction Conference, New England College, Henniker, New Hampshire, American Society of Civil Engineers, New York. International Code Council (ICC). 2012. International Building Code. Washington, D.C.




International Society for Rock Mechanics (ISRM). 1978. Suggested methods for the quantitative description of discontinuities in rock masses. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 15 (6). Jacobs, J.D., 1975. Some tunnel failures and what they have taught. In Hazards in tunneling and on falsework. Institution of Civil Engineers. Macdonald, G.A. 1956. The structure of Hawaiian volcanoes, Koninklijk Nederlandsch Geologisch-Mijnbouwkundig Genootschap. Verhandelingen, 16. MacDonald, G.A. 1983. Volcanoes in the Sea: The Geology of Hawaii, 2nd Edition. Honolulu HI: University of Hawaii Press. Peck, R. B. 1981. Weathered-rock portion of the Wilson Tunnel, Honolulu. In Proceedings of Soft-Ground Tunneling, Failures and Displacements, Conference, D. Reséndiz and M. Romo, Eds., Instituto de Ingeniería, National University of Mexico. London: A.A. Balkema. Plinninger, R., H. Kasling, K. Thuro, and G. Spaun. 2003. Testing conditions and geomechanical properties influencing the CERCHAR abrasiveness index (CAI) value. In International Journal of Rock Mechanics and Mining Sciences, 40 (2). Proctor, R.V., and T.L. White. 1968. Rock Tunneling with Steel Supports, with an Introduction to Tunnel Geology by Karl Terzaghi. Youngstown, OH: Commercial Shearing. Richardson, T.L., and J.L. Reighelderfer. 2001. Completion of the H-3 Highway Tunnel, In Proceedings of the Rapid Excavation and Tunneling Conference. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc. Romero, V.S., and C. Mimura. 2006. The role of engineering geology on rehabilitation of the Likelike Highway Wilson Tunnel, Oahu, Hawaii. In Proceedings of the 57th Annual Highway Geology Symposium. Denver, CO: Colorado Geological Society. Sherrod, D.R., J.M. Sinton, S.E. Watkins, and K.M. Brunt. 2007. Geologic Map of the State of Hawai’i, US Geological Open-File Report, 2007–1089. Stearns, H.T., and K.N. Vaksvik. 1935. Geology and Ground-water Resources of the Island of Oahu, Hawaii, Bulletin 1, United States Geological Survey, printed by Wakaui Publishing Company, Wailuku, HI. Takasaki, K.J., and J.F. Mink. 1982. Water Resources of Southeastern Oahu, Hawaii, US Geological Survey Water-Resources Investigations 82-628, 97. Walker, G.P.L. 1987. The dike complex of Koolau Volcano, Oahu: Internal structure of a Hawaiian rift zone. Volcanism in Hawaii: Vol. 2, R.W. Decker, T.L. Wright, and P.H. Stauffer, Eds., US Geological Survey Professional Paper 1350, Washington, DC.




Winchell, H. 1947. Honolulu series, Oahu, Hawaii, Geological Society of America Bulletin, 58 (1). Yogi Kwong Engineers (YKE). 2013a. Geotechnical Data Report, Kaneohe to Kailua Conveyance Gravity Sewer Tunnel, Kaneohe to Kailua, Hawaii. Yogi Kwong Engineers (YKE). 2013b. Geotechnical Investigation Report, In Support of the Kailua RWWTP Diversion Pipelines, Kaneohe/Kailua Sewer Tunnel, Kailua RWWTP, Oahu, Hawaii. Yogi Kwong Engineers (YKE). 2013c. Geotechnical Investigation Report, In Support of the Kaneohe WPTF Diversion Pipelines, Kaneohe/Kailua Sewer Tunnel, Kaneohe WPTF, Oahu, Hawaii.




9 Glossary Advance Rate: The distance of tunnel excavated per unit of time, often expressed as feet per day or feet per week. Alluvium: Clay, silt, sand, or gravel deposited during a comparatively recent geologic time by a stream or other body of running water. Aquitard: A confining bed or layer that retards but does not prevent the flow of water to or from an adjacent aquifer. Breccia/Brecciated: A coarse-grained clastic rock, composed of angular or subangular rock fragments of varied or uniform composition, produced by the crushing and fracturing of preexisting rocks as a result of tectonic forces. Clinker: Fragments of basalt that form as a result of cooling at the margins of an active lava flow. Colluvium: Any heterogeneous mass of soil material or rock fragments deposited chiefly by mass-wasting, usually at the base of a steep slope or cliff. Conventional Tunneling Method: The construction of underground openings of any shape with a cyclic construction process of: (1) excavation by using drill-and-blast methods or mechanical excavators (except full-face tunnel boring machines); (2) mucking; and (3) installation of ground support elements such as steel ribs or lattice girders, rock reinforcement bolts, and/or shotcrete. Corestone: An intact rock block that is formed as a result of weathering of a jointed rock mass. Dike: A body of igneous rock that cuts across the structure of adjacent rocks. Discontinuity: The general term for any mechanical break or fracture in a rock mass having zero or low tensile strength. It is the collective term for most types of joints, dike contacts weak bedding planes, weak schistocity or foliation planes, weakness zones, shears, and faults. Fault: A break in rock in which displacement of the neighboring rock mass is apparent. The evidence for such displacements can be juxtaposed rock types, brecciation and/or gouge, and slickensides. A shear with significant continuity, which can be correlated between observation locations, can be termed a fault. Fault Zone: A break in rock composed of a number of subparallel faults separating lens-shaped blocks of undeformed rock, or a tabular band of finite width containing brittle shattered, pulverized rock or gouge. Gouge: A predominantly clay material, but can include silt-, sand-, and/or gravel-sized material that occurs along the wall of a shear or fault formed through the shearing and crushing of country rock. Joint: A natural parting or mechanical break in rock exhibiting no evidence of displacement. Joint Sets: Groups of joints having similar strike and dip within a region or area.




Interbedded: Soil or rock beds of different character that are arranged or deposited in layers. Muck: Broken rock that results from tunnel excavation. Normally Consolidated: Soil defined as having an in situ state of effective stress equal to the maximum effective stress that it has experienced. Overbreak: The amount of rock excavated outside the contractor’s selected excavation dimension because of geological factors and the contractor’s means, methods, and workmanship. Geological factors influencing overbreak include adverse orientation and spacing of bedding, foliation and/or discontinuities relative to the tunnel surface, low in situ stress, and the presence of fault gouge/breccia. Residual Soil: Soil that is derived from saprolite but that has undergone additional weathering such that the intergranular bonds between soil grains are broken and relict structures are no longer present. Rock Quality Designation (RQD): A modified core recovery percentage in which all pieces of sound core over 4 inches long are counted as recovery. RQD denotes the percentage of intact and sound rock retrieved from rock core that is equal to or greater than 4 inches in length. Rock Reinforcement: A general term describing initial support systems that act in such a manner as to reinforce the rock mass, increasing its capacity to participate in the support of the tunnel or shaft opening. This could include rock dowels, rock bolts, friction dowels, steel straps, welded wire fabric, drainage, and pre-excavation grouting used for ground improvement, and other appurtenances, but does not include steel sets and shotcrete. Saprolite: Soil that is a product of in situ weathering of rock. Saprolite has engineering characteristics similar to that of soil; however it retains the relict structure of the bedrock and derives its cohesion from intergranular bonds between soil particles. Shear: A structural break or discontinuity usually less than 2 inches wide where differential movement has occurred along a surface or zone of failure. This movement is indicated by the presence of slickensides or striations on one or both joint surfaces and/or the presence of clay or brecciated gouge infilling material. Usually reserved for breaks where the direction and amounts of displacement cannot be determined. Shear Zone: A general term for a zone usually greater than 2 inches wide with subparallel boundaries in which shear strain is localized; shear zones may be ductile (no discontinuities across the zone where the rock is plastically deformed), brittle (i.e., fault zone), or brittle-ductile. Strata: Layers of soil or rock that are visually separable from other layers above or below. Tunnel Boring Machine (TBM): A machine that excavates a circular tunnel with a circular cross section by means of a rotating cutterhead to full size in one continuous operation. Tectonic: Of or relating to forces in the Earth’s crust.




Vein: A discontinuity that has been infilled or mineralized with a material different from the surrounding rock. Weathering/Alteration: Weathering is the destructive process or group of processes whereby soil and rock materials, exposed to atmospheric agents at or near the Earth’s surface, are changed in character (color, texture, composition, firmness, or form), with little or no transport of the loosened or altered material. Specifically, weathering involves the in situ disintegration and chemical decomposition of rock. Most weathering occurs at the surface, and weathering effects generally decrease with depth. Weathering may also take place at considerable depths, such as in jointed rocks that permit easy penetration of atmospheric oxygen and circulating water. Alteration is a change in the mineralogic composition of a rock brought about by physical or chemical means (examples of physical means include shearing and faulting). Alteration may occur at any depth, and oxides may or may not be present. The degree of discoloration and oxidation in the body of the rock and on fracture surfaces could be very different from those produced by weathering. However, weathering and alteration are sometimes not distinguishable.



10 Revision Log Revision No. Date Revision Description

0 February 2013 Issued for Bid Advertisement



Tables




Table 1. Summary of Field and Laboratory Test Data for Soil Deposits

blows/ ft

0 - Refusal 9 63 "WOH" - 24 0D 240 0 - 25 8 11 0 - Refusal 9D 280 1 - Refusal 32D 202

lb / ft3 61 - 108 81 21 30 - 106 57 84 65 - 93 --C 4 55 - 136 78 74 54 - 138 87 44

percent 12 - 58 32 28 17 - 151 75 145 15 - 72 41 8 8 - 80 42 144 15 - 73 36 66

-- 48 - 63 64 - 109 89 43 - 152 84 50 - 74 64

-- 30 - 33 28 - 60 47 12 - 123 56 25 - 42 36

percent 21 - 95 47 15 6 - 85 41 28 19 - 67 47 11

Strength Parameters

degrees 17 - 73 35 47 17 - 44 20 221 21 - 43 29 9 20 - 65 32 170 22 - 80 43 160

Deformation Parameters

lb / ft2 8.5E+03 - 1.6E+06 1.4E+05 62 4.2E+03 - 3.8E+05 4.7E+04 110 7.1E+03 - 4.0E+05 1.3E+05 11 7.1E+03 - 1.9E+06 2.2E+05 279 1.4E+04 - 1.9E+06 7.2E+05 202

-- 0.15 - 0.42 0.32 63 0.15 - 0.50 0.42 240 0.15 - 0.42 0.30 11 0.15 - 0.45 0.32 280 0.15 - 0.45 0.32 202

Earth Pressure Coefficients

-- 0.04 - 0.71 0.43 47 0.31 - 0.71 0.66 221 0.32 - 0.64 0.51 9 0.10 - 0.65 0.47 170 0.02 - 0.63 0.32 160

-- 0.02 - 0.55 0.28 47 0.18 - 0.55 0.49 221 0.19 - 0.47 0.35 9 0.05 - 0.49 0.31 170 0.01 - 0.46 0.20 160

SPT = Standard Penetration TestA Properties represent soil-like components of the Weathered Basalt. Refer to Section 3.5 for descriptions and properties of rock fragments within this unit.B

C Not provided due to limited data set.D Value represents median of data set. Average not provided due to non-numerical SPT N-values, e.g., "weight of hammer" (WOH) and "refusal". E Applies to cohesive soils only. Data set includes SPT N-value correlations with su, and results of undrained triaxial (TXUU), pocket penetrometer, and torvane shear strength test results.

Active - KA

At Rest - Ko

--C --C33

Young's Modulus -

Es

Drained Friction Angle - φ'

140

Units Range Average

SPT - NFIELD

ValuesB

0- 4,500 34 0 -1,425 139

3

Applicable Unified Soil Classification System Units

Range Average

Artificial Fill (Qaf)

AverageNo. of Tests

No. of Tests

Lagoonal/Estuarine Deposits (Qa)

GC, SM, CL, MH, CH, OH

AverageNo. of Tests

Weathered Basalt

(QTkkb)A

GP, GM, GC, SM, SC, ML, MH, CH

SPT N-values obtained using the Dames & Moore Type "U" Sampler were converted to equivalent SPT blowcounts. No other corrections (i.e., overburden, hammer type, etc.) were performed for the N-values reported herein.

1014,37596 -7,150Undrained Shear

StrengthE - sulb / ft2 -1,600 200 0 1,725 16,125239

Poisson's Ratio - ν

Recent/Older Alluvium (Qa, QTao)

GP, GM, GC, SM, SC, MH, MH/SM, CH

GP-GM, SM, CL, MH

Corraline Detritus (Qcrs)

Range

13

Fines Content --C --C

GW, GM, SM, SC, ML, CL, MH, CH

Range Range No. of Tests

Liquid Limit - LL

Plasticity Index - PI

No. of Tests

Average

Moisture Content -

w c

In Situ Dry Density -

γd

Description

33



Table 2. Descriptive Terms for Intact Rock Strength

ISRM Strength Category

Unconfined Compressive Strength (psi)

Characteristics

Extremely Weak 35–150 Specimen can be indented by

thumbnail.

Very Weak 150–700 Specimen crumbles under firm blows

with point of geological hammer and can be peeled with a pocket knife.

Weak

700–3,500 Specimen can be scraped and peeled with difficulty using a pocket knife. Shallow indentations made by firm blow with point of geological hammer.

Medium Strong 3,500–7,000 Specimen can be fractured with a

single firm blow with geological hammer.

Strong 7,000–14,500

Specimen can be indented up to 5 mm with the sharp end of a geologic hammer. Cannot be scraped or peeled with a knife.

Very Strong 14,500–35,000 Hand-held specimen can be broken with geologic hammer when subjected to multiple blows.

Extremely Strong >35,000 Many blows with geologic hammer required to break or chip specimen.

Modified after ISRM (1978).




Table 3. Basalt Density According to Weathering Category

Weathering Category Number of Tests

Minimum (lb/ft3)

Maximum (lb/ft3)

Average (lb/ft3)

Standard Deviation

(lb/ft3)

Unweathered to Slightly Weathered Basalt

55 57 149 178 167 7

Moderately Weathered to Extremely Weathered Basalt

9 130 166 153 12

Table 4. BTS, CAI, and Punch Penetration Test Results

Rock Type

Brazilian Tensile Strength (psi)

Cerchar Abrasivity Index (CAI)

Punch Penetration Test (Peak Slope in kips/in.)

No. Range Average No. Range Average No. Range Average

Basalt 12 401–1,595 925 12 1.3–3 2.2 11 124–317 197



Table 5. Petrographic Analysis Summary

Rock Type Bor

ings

% P

lagi

ocla

se

% C

lay1

% O

paq

ues

2

% C

lin

opyr

oxen

e

% A

ugi

te

% K

-Fel

dsp

ar

% C

hlo

rite

% C

hal

ced

ony

% M

agn

etit

e

% C

hlo

rop

hae

ite

% Q

uar

tz

% C

alci

te

% B

asal

t G

lass

% V

esic

les3

Altered Basalt (from Dike Complex)

B-17 20–25

20–48

20 10 - 8 5 - - - 2 - 10 -

Basalt Breccia

B-33A B-34

40-68

- - - 5-15 - - - 10-12

- 7-35 - -- -

Vesicular Basalt

B-33A B-33B B-35A B-36 B-37 B-38

33–77

- - 0–35 5–30 - - 0–6 0–7 0–12 0–48 0–3 - 0-12

Porphyritic Basalt

B-35 56 - - 30 - - - - 4 10 - - - -

1 Denotes fine grained phyllosilicates in general. 2 Refers to all materials that are opaque (and sometimes semiopaque) to transmitted light. 3 Refers only to vesicles that are open and without mineral in-filling.




Table 6. Rock Mass Types

Rock Mass

Type

Ground

Condition1

Fracture

Spacing2

Discontinuity

Conditions

Weathering or

Alteration2

Intact Rock

Strength3

Rock Mass

Rating

(RMR)

Tunneling

Quality

Index (Q)

Ground Behavior4

B1

“Good Rock”

Massive,

moderately

jointed rock

Moderate

to Very

Wide

Smooth to rough,

no infilling, surface

staining only;

lesser amounts of

slightly altered

joint walls

Unweathered to

slightly

weathered

Medium

Strong to

Very

Extremely Strong

>60

(Good to

Very Good

Rock)

>40

(Very Good

to Extremely

Good Rock)

Excavation stability controlled

by rock structure (block and

wedge failure with localized

spalling and stress slabbing).

Stand-up time ranges from hours

to days. Joints between rock

blocks are generally in intimate

contact, and excavation does not

require immediate support.

B2

“Fair Rock”

Moderately

blocky and

seamy rock

Moderate

to Close

Smooth to rough,

no infilling, surface

staining only;

lesser amounts of

slightly altered

joint walls

Unweathered to

moderately

weathered

Medium

Strong to

Strong

40 to 60

(Fair Rock)

4 to 40

(Fair to

Good Rock)

Excavation stability controlled

by rock structure (block and

wedge failure with localized

shallow shear failure); slow

raveling; fast raveling where

flowing groundwater is

encountered. Stand-up time

ranges from minutes to hours.

B3

“Very Poor to

Poor Rock”

Very blocky

and seamy

rock with

crushed

zones

Crushed to

Close

Zones/bands

containing clay

minerals or silty,

sandy, gravelly, or

crushed zones thick

enough to prevent

rock wall contact

Unweathered to

Highly

Weathered

Very Weak

to Medium

Strong

<20 to 40

(Poor to Very

Poor Rock)

<0.1 to 4

(Poor to

Extremely

Poor Rock)

Slow to fast raveling/caving.

Stand-up time ranges from

minutes to one hour. Pre-support

and face stabilization are

required.

1 Refer to Table 8 for a description of ground conditions. 2 Refer to the GDR for definitions of fracture spacing and weathering. 3 Refer to Table 2 for descriptive terms for intact rock strength. 4 Refer to Table 9 for a description of ground behaviors.




Table 7. Groundwater Level Measurements

Monitoring Well (Boring)

Station Surface

Elevation (ft)

Average Maximum Groundwater

Elevation (ft)

Approximate Groundwater Height Above Tunnel Crown

(ft)2

B-30 -0+20 4 5 1 3 25 27

B-32A 11+00 104 55 82

B-17 15+80 102 67 94

B-33A (Well #1)

30+02 245 118 126 148 156

B-33A (Well #2)

30+02 245 150 173 180 203

B-33B 60+30 165 118 125 153 160

B-34 77+23 131 50 83 88 121

B-22 79+10 242 33 71

B-34A 78+85 240 35 73

B-35 102+26 150 20 32 72 84

B-37 140+27 460 53 62 101 110

B-2 160+99 23 -1 4 49 52

B-39 163+15 11 -1 4 51 54

B-40 164+91 13 1 2 53 55

B-41 163+77 13 1 3 53 55

1 Groundwater measurements obtained from GeoLabs B-2, B-17, and B-22 were obtained between

January 2010 and August 2010. Groundwater levels monitored by YKE in borings B-30 through B-41

were obtained between December 2011 and January 2013. 2 1 Crown of tunnel final lining. 3 Only one reading performed



Table 8. Tunnelman’s Ground Classification

Classification Behavior

Intact Consists of material that will stand unsupported for several days or longer. On account of the injury to the rock due to blasting, spalls may drop off the roof several hours or days after blasting. This is known as a spalling condition.

Hard, Stratified Consists of individual strata with little or no resistance against separation along the boundaries between strata. The strata may or may not be weakened by transverse joints. In such rock, slabbing and spalling conditions are common.

Massive/ Moderately Jointed

Contains joints and cracks, but the blocks between joints are in contact and are intimately interlocked such that excavated walls do not require immediate support. In rocks of this type, spalling conditions may be encountered.

Blocky and Seamy

Consists of chemically intact or nearly intact rock fragments, separated from each other by joints or other discontinuities that are imperfectly interlocked. In such rock, vertical surfaces may require support. When individual blocks are larger than 2 feet, the rock is called moderately blocky and seamy; when blocks are smaller than two feet, the rock is called very blocky and seamy.

Crushed Crushed but chemically intact rock that has the character of crusher run. If most or all of the fragments are as small as fine sand grains and no recementation has taken place, crushed rock below the water table exhibits the properties of water-bearing sand.

Modified from Terzaghi (Proctor and White, 1968) and Deere et al. (1969).



Table 9. Definitions of Ground Behavior Terms

Classification Behavior

Firm Rock or soil material that will stand unsupported in a tunnel for several days or longer. The term includes a great variety of materials: sands and sand-gravels with clay binder, stiff unfissured clays at moderate depths, and massive rock.

Squeezing

Squeezing ground slowly advances into the tunnel without perceptible volume increase. Squeezing conditions are associated with a high percentage of microscopic and submicroscopic particles of micaceous minerals or of clay minerals with a low swelling capacity. A prerequisite for squeeze is an overstress of the material close to the tunnel opening; hence, for a given material the overburden stress is an important parameter.

Swelling Ground Swelling ground advances into the tunnel chiefly because of expansion. The capacity to swell seems to be limited to those rocks that contain clay minerals, such as montmorillonite, with a high swelling capacity.

Raveling/Caving Ground

Raveling and caving ground is used to describe a material that gradually breaks up into chunks, flakes, or angular fragments after the ground has been exposed in the tunnel. The process is time-dependent, and materials may be classified by the rate of disintegration as fast or slow raveling. If the raveling process starts within a few minutes, the ground is fast raveling. Otherwise, it is referred to as slow raveling. Examples are fine moist sand, gravels with some clay binder, stiff fissured clays, jointed rocks, and weak rocks.

Running Ground Running ground indicates a material that will invade the tunnel until a stable slope is formed at the face. Stand-up time is zero or nearly zero. Examples are clean medium to coarse sands and gravels above the groundwater level. If running ground has a trace of cohesion, then the run is preceded by a brief period of progressive raveling. Materials intermediate between running and raveling are described as cohesive-running.

Flowing Ground Flowing ground acts as a thick liquid and differs from running ground in that it invades the tunnel not only from above and from the sides, but also through the bottom. If the flow is not arrested, it continues until the tunnel is completely filled.




Table 10. Discontinuity Orientations

Joint Set Average Dip/Dip Azimuth (degrees)

Range in Dip (degrees)

Range in Azimuth (degrees)

1 22/270 + 15 + 40 2 77/309 + 25 + 25 3 82/035 + 20 + 25 4 22/122 + 15 + 50

Table 11. Rock Mass Type Distribution for Reach 3

Rock Mass Type Percent of Reach Estimated Based on

Boring Data

Percent of Reach To Be Assumed in Bid

B1 47 46 40 – 50 B2 32 30 – 35 B3 22 15 – 25

Table 12. Minimum Design Ground Loads for Tunnel Initial Supports

Reach Ground Condition / Rock Mass Type

Recommended Design Ground

Load (Hv), Circular Tunnel 1,2 (feet)

Recommended Design Ground Load (Hv),

Conventional Tunnel 1,2,3 (feet)

Ratio of Horizontal to

Vertical Ground Rock Load (Kh)

1 Jet-grout stabilized

soils – Z4 0.5 (Z)4

2, 4 Soils, mixed face

conditions, Weathered Basalt

– 1.1 (B+H) 0.5

3 RMT B1 0 to 0.25B – 0

3 RMT B2 0.25B to 0.35 (B+H) – 0

3 RMT B3 0.7 (B+H) – 0 1 B is the excavated tunnel span (diameter or width) and H is the excavated height. 2 Does not account for additional load due to intersections with shafts and tunnel adit.

Contractor to estimate ground load based on actual configuration of shaft and tunnel adit

intersections. 3 See Figure 15 for the loading diagrams for tunnel support system design. 4 Z is depth from ground surface to tunnel springline. Contractor to assume buoyant

unit weight of ground (i.e., undrained conditions). Does not account for load sharing

with jet grout stabilized block. Contractor to estimate ground load based on actual

excavation configuration, size, and selection of tunnel initial support type and spacing.



Figures

KANEOHE KAILUA

FIGURE 1 PROJECT LOCATION MAP

KANEOHE/KAILUA SEWER TUNNEL FEB. 2013

Kaneohe/Kailua Sewer Tunnel

Map data ©2012 Google, INEGI

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FIGURE NO.

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REVISION

KANEOHE / KAILUA

SEWER TUNNEL

GEOLOGIC PROFILE

STATION 15+00 TO 38+00

0

FEBRUARY 2013

2 - 2

0100 100 200

FEET

050 50 100

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HORIZONTAL

VERTICAL

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SEWER TUNNEL

GEOLOGIC PROFILE

STATION 38+00 TO 82+50

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FEBRUARY 2013

2 - 3

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FIGURE NO.

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KANEOHE / KAILUA

SEWER TUNNEL

GEOLOGIC PROFILE

STATION 82+50 TO 124+00

0

FEBRUARY 2013

2 - 4

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KANEOHE / KAILUA

SEWER TUNNEL

GEOLOGIC PROFILE

STATION 124+00 TO 163+50

0

FEBRUARY 2013

2 - 5

0100 100 200

FEET

050 50 100

FEET

HORIZONTAL

VERTICAL

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040 40 80

FEET

FIGURE NO.

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REVISION

020 20 40

FEET

KANEOHE / KAILUA

SEWER TUNNEL

DETAILED GEOLOGIC PROFILE

REACHES 1 AND 2

0

FEBRUARY 2013

2 - 6

HORIZONTAL

VERTICAL

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020 20 40

FEET

FIGURE NO.

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REVISION

010 10 20

FEET

KANEOHE / KAILUA

SEWER TUNNEL

GEOLOGICAL PROFILE

KAILUA TIPS SHAFT AND STARTER TUNNEL

0

FEBRUARY 2013

2 - 7

HORIZONTAL VERTICAL

020 20 40

FEET

A

-

B

-

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FIGURE NO.

DATE

REVISION

KANEOHE / KAILUA

SEWER TUNNEL

ROCK CONTOUR MAP - KAILUA

TIPS SHAFT AND STARTER TUNNEL

FEBRUARY 2013

3

040 40 80

FEET

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FIGURE 4INFERRED EXTENT OF KO’OLAU CALDERA


Kaneohe/Kailua Sewer Tunnel

Approximate Boundary of Outer Caldera

Inferred Caldera Rim

Tetsuo Harano (H‐3) Tunnels

Wilson Tunnels

Map data ©2012 Google, INEGI

Pali Tunnels

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FIGURE 5INTACT ROCK STRENGTH SUMMARY


*Data reflects both UCS and PLI test results. PLI data converted to equivalent UCS using a conversion factor of 24.4 in accordance with ASTM D5731.

(ISRM, 1978 Terms)

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130

2

4

6

8

10

12

14

16

18

20

10,000 20,000 30,000

Percen

tage

of T

ests

Unconfined Compressive Strength (psi)

Very Strong

Extremely Strong

StrongMedium StrongWeak

Extrem

ely to

Very W

eak

FIGURE 6 RQD DISTRIBUTION


0

5

10

15

20

25

30

35

40

Very Poor0-25

Poor25-50

Fair50-75

Good75-90

Excellent90-100

Perc

enta

ge o

f Cor

e

Rock Quality Designation (RQD)

RQD Distribution (Average RQD = 67)

FIGURE 7RMR DISTRIBUTION


0

5

10

15

20

25

30

35

40

45

50

Very Poor<20

Poor21‐40

Fair41‐60

Good61‐80

Very Good81‐100

Percen

tage

of C

ore

Rock Mass Rating (RMR)

RMR Distribution (Average = 57)

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FIGURE 8 Q INDEX DISTRIBUTION


0

5

10

15

20

25

30

ExceptionallyPoor

0.001-0.01

Extremely Poor0.01-0.1

Very Poor0.1-1

Poor1-4

Fair4-10

Good10-40

Very Good40-100

Extremely Good100-400

ExceptionallyGood

400-1000

Perc

enta

ge o

f Cor

e

Tunnelling Quality Index (Q)

Q Distribution (Median = 5.6)

FIGURE 9 CORE RECOVERY AND RQD AT TUNNEL DEPTH


Invert

Crown

B-33A585' NW

B-33B1178' NW

B-34721' NW

B-35203' NW

B-361,115' NW B-37

394' NWB-38

25' NW

B-22210' NW

B-32A90' SW

B-2135' SE

B-17100' NE

B-35A509' NW

13.5' Dia.Tunnel Excavation

Notes:1. See Section 4 for descriptions of ground conditions within each reach.2. Direction indicates general direction relative to the tunnel alignment. Distances are measured perpendicular to the tunnel.3. (*) indicates RQD not estimated due to mechanical fracturing required to extract core from core barrel.

Station (ft)

-80

-60

-40

-20

0

Ele

vatio

n (f

t)

P-1122' E

100/53

100/58

100/73

100/77

100/33

100/40

100/77

100/80

93/78

100/100

100/87

100/85

100/90

100/45

100/89

100/90

100/90

100/100

100/100

100/90

98/88

100/68

100/100

100/100

100/38

100/63

100/56

100/58

100/35

100/87

100/88

100/100

73/50

100/100

100/100

100/67

100/62

96/47

100/87

96/53

100/75

100/83

100/67

100/77

100/70

100/82

100/40

100/92

100/33

90/30

100/30

100/45

100/30

100/45

100/58

60/47

100/30

100/40

100/0

100/100

100/100

100/67

100/100

100/50

100/60

100/95

100/63

100/100

100/85

100/87

100/100

100/100

100/100

100/100

100/100

100/100

100/85

100/*

100/93

100/43

100/23

100/27

100/70

100/92

100/100

100/100

100/97

100/100

100/100

100/97

100/62

100/33

100/58

100/87

100/53

100/20

100/45

Reach 2

Reach 3 Reach 3 Reach 4

78/11

80/15

100/100

21/0

33/0

22/0

69/37

B-3940' W

100/82

Recovery (%)

Rock Quality Designation (RQD) (%)

Approx. BasaltContact

B-32a30' NE

Boring Number

Projected Distance and Direction from Tunnel Alignment

10+00 20+00 30+00 40+00 50+00 60+00 70+00 80+00 90+00 100+00 110+00 120+00 130+00 140+00 156+00 160+00 164+00

B-34A8' NW

Approx. BasaltContact

158+00 162+00

FIGURE 10HYDRAULIC CONDUCTIVITY DISTRIBUTION


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0

2

4

6

8

10

12

14

1 2 3 4 5 6 7 8 9

Percen

tage of Tests

RMT B1 (64 Tests)

RMT B2 (46 Tests)

RMT B3 (29 Tests)

Weathered Basalt and Older Alluvium (13 Tests)

<10‐6 3x10‐6 10‐4 10‐3 10‐2

k (cm/sec)10‐5 3x10‐5 3x10‐4 3x10‐3

Total Number of Tests = 152

<3x10‐7

FIGURE 11 GRADATION SUMMARY – LAGOONAL & ESTUARINE DEPOSITS


From boring performed in Kaneohe From boring performed in Kailua

Test Location Key

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

Per

cen

tag

e F

iner

by

Wei

gh

t (%

)

Partical Size "D" (mm)

B-18 (26') B-18 (61') B-19 (10')

B-30 (15') B-31 (23.5') B-40 (15')

B-41 (15.5') P-4 (18.5') P-5 (14')

P-5 (35') P-6 (21') P-6 (21')

Silt or Clay Fine Medium Coarse Fine Coarse

Gravel Sand Silt or Clay

Fine Medium Coarse Fine Coarse

Gravel Sand

FIGURE 12 GRADATION SUMMARY – OLDER ALLUVIUM



Test Location Key

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

Per

cen

tag

e F

iner

by

Wei

gh

t (%

)


B-17 (30') B-18 (66') B-19 (61') B-32 (77') B-32a (7')B-32a (42.5') B-32a (63.5') B-40 (49') B-42 (22') B-42 (33.5')P-1 (11') P-1 (16.5') P-1 (30') P-3 (19') P-3 (22.5')P-3 (46') P-3 (56') P-8 (32') P-8 (50.5') P-10 (20')




Gravel Sand

FIGURE 13 GRADATION SUMMARY – WEATHERED BASALT


0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

Per

cen

tag

e F

iner

by

Wei

gh

t (%

)


B-32a (87')

B-39 (25')

B-39 (40.5')

B-41 (80')

B-42 (72.9')

P-2 (60')

P-2 (75')

P-3 (71')

P-3 (96.8')

P-10 (26')




Gravel Sand


Test Location Key

FIGURE 14 DISCONTINUITY ORIENTATIONS


*Refer to GDR for discontinuity orientations at boring locations along tunnel alignment.

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FIGURE 15DISCONTINUITY SPACING DISTRIBUTION


0

10

20

30

40

50

60

70

80

90

100

<0.2 0.2 0.2‐0.7 0.7 0.7‐2 2 2‐6.5 >6.5

Percen

tage

of C

ore

Approximate Fracture Spacing (ft)

B1 (1,794 LF of core)

B2 (1,244 LF of core)

B3 (807 LF of core)

FIGURE 16TUNNEL LOADING DIAGRAM


Pv

Conventional TunnelCircular Tunnel

Kh PvKh Pv

Notes:1. Pv = Ground Load, Hv x Total Unit Weight of Rock. See Table 3 for total unit weight of rock.

2. See Table 12 for design ground loads Hv and Kh.

FIGURE 17POTENTIAL KEY BLOCKS


Note:1. See Table 10 for joint orientations.

AD

DE

ND

UM

NO

. 3, R

EV

ISE

D: 4

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FIGURE 18LATERAL EARTH PRESSURES – KANEOHE SHAFT AND KAILUA TIPS SHAFT


AD

DE

ND

UM

NO

. 3, R

EV

ISE

D: 4

/22/

13

FIGURE 19LATERAL EARTH PRESSURES – KAILUA DROP SHAFT AND TUNNEL ACCESS SHAFT


AD

DE

ND

UM

NO

. 3, R

EV

ISE

D: 4

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13


Jacobs Associates App A -1- Rev. 0 / February 2013


Appendix A. Previous Tunnel Construction Experience There are many existing tunnels on the island of Oahu, including those constructed for highways, water conveyance, and military purposes. This appendix provides a summary of the geology and construction of selected non-military tunnels, with the intention of providing background information on conditions present in the vicinity of the proposed Kaneohe/Kailua Sewer Tunnel. Tetsuo Harano (H-3) Tunnels The following information on the geology and construction of the Tetsuo Harano (H-3) Tunnels is summarized from Abrahamson and Hansmire (1989); Hansmire et al. (1993); and Richardson and Reighelderfer (2001)1. The H-3 Tunnels are located along Interstate H-3 where it crosses the Koolau Mountain Range. Their location is shown in Figure 4 and in Figure A-1 below.

Figure A-1. Oblique view of H-3 Tunnels (looking southwest)

From portal cut to portal cut, the tunnels are 4,890 and 5,165 feet in length. They were excavated at approximately 50 feet wide and 39 feet high to provide for two lanes of traffic in each direction. Ten (10) 8-feet ID (finished) cross passages were also constructed.

1 Full references for the cites in Appendix A are provided in Section 8 (References) in the main body of this GBR.

H-3

Tunnels




Photo A-1. Completed Portal Structures for H-3 Tunnels

Geology The tunnels were constructed entirely through Ko’olau Basalts that were deposited during the shield-building stage of the development of Oahu. Today, the original volcano is highly eroded and in some locations intensely weathered. Because exploration drilling was only done at the portals, a full-length exploratory tunnel was driven to determine geologic conditions. Lava beds in the vicinity of the tunnel dip at about 5 degrees to the west along the general tunnel alignment. The basalt flows characteristically consist of a series of dense rock and clinker that are formed by a’a and pahoehoe lava flows. The core of the a’a flows is typically strong rock with an unconfined compressive strength of 14,000 to 36,000 psi, requiring blasting. The clinker portion is much less dense and is rough and jagged, composed of brecciated lava, but has commonly been compressed in varying degrees to a coherent unit. The strength of the clinker is low, and although it could be excavated by backhoe, it was typically blasted along with the stronger rock. The pahoehoe rocks typically contain substantial vesicles and have unconfined compressive strengths of 7,000 to 14,000 psi, and thus also required blasting. There are also thin weathered tuff layers (volcanic ash) that are interlayered with the lava flows, and intrusive dikes consisting of strong basalt. Rock jointing was characteristically discontinuous, tight, and slightly rough to rough. Lava bed thicknesses generally ranged from 1 to 10 feet. Joints in one bed would typically not be seen in units above and below. The lava beds could generally be mapped as fairly continuous when considering the mountain as a whole. However, on a closer scale, the relative composition of dense basalt and clinker in the tunnel face would change substantially over a few tunnel blast round lengths.




At the Halawa portal, the original volcanic rock is weathered to saprolite, which has a strength comparable to hard clay. When disturbed and wet in surface excavations, saprolite readily deteriorated to a silt material. In the tunnel, it would stand for hours without significant raveling and was excavated with backhoes or light-duty roadheader-type mechanical excavators. Groundwater was a concern during design. High pressure water was thought to be present where trapped between impervious basalt dikes. Such conditions, however, were not encountered. The exploratory tunnel encountered no substantial water. In the main tunnel construction, relatively minor water dripping in many sections prompted installation of a waterproof membrane in the wettest areas to ensure a dry tunnel. Construction Tunneling started from portal excavations into the steep slopes of the Koolau Range. At the Haiku Portals, excavations were in rock. No special difficulties were encountered in making vertical cuts of over 100 feet high in order to start tunneling. At the Halawa Tunnels, ground conditions were substantially different, with portal excavations in saprolite. Extensive studies had been made of the ground support required, and a full design was prescribed in the contract. The highest cuts at the portal faces had shotcrete and 20-foot-long dowels. Other areas had shotcrete and 10-foot-long dowels. Early stages of Halawa Portal excavation and outbound tunneling exhibited some movement and cracking of shotcrete. One excavation face next to the inbound tunnel portal failed without warning. This prompted an immediate reconsideration of the design. Tunneling was halted in the outbound tunnel where some movements and cracking of unknown significance had been observed. Portal cuts were cut down further and additional support measures and shotcrete were provided. Over the outbound tunnel portal, 80-foot-long tiebacks were installed to ensure portal stability and permit tunneling to resume. Within two weeks of the failure, tunneling operations started again at the inbound portal. Remedial work for the portal cuts required several months to accomplish. Nine tunnel excavation stages were specified where the tunnel was in rock. A top heading was to be driven by advancing a center drift and then slashing each side. A middle and lower bench were then to be excavated, each with a center cut and two side slashes. Tunneling on the Haiku side began in rock using the specified stages and conventional drilling and blasting. As experience and confidence about ground behavior developed, the excavation sequence was gradually simplified. The top heading height was increased from 18 feet to 20 feet to facilitate mucking operations. Experimental ripping of the benches was done at Haiku. A Cat D9L with a single ripping tooth equipped with an impact hammer was effectively able to excavate the rock, except in very strong, massive rock situations. However, it was difficult to provide adequate ventilation and lighting. Most of the Haiku Tunnel was therefore excavated with a top heading and a single bench, all by drilling and blasting. In the top heading, the center drift and two slashes were offset longitudinally, but were usually fired at once. The bench was excavated with horizontal blast holes. Typical round lengths were 10 to 12 feet. The rock portion of the Halawa Tunnel was excavated similar to Haiku, except the top heading was further simplified to two drifts, rather than three.




At Halawa, tunneling began in saprolite using mechanical equipment. The saprolite was easily excavated with a large backhoe. The contractor also made use of a roadheader-type cutterhead attachment, mounted on a Komatsu 400 tracked excavator. This machine was effective in trimming saprolite to the desired excavation line. Excavation stages in saprolite were made smaller and shorter than specified near the portals to control ground movements. Excavation increments were limited in some cases to 2 feet but generally to 4 feet, with the heading excavated in several increments. Saprolite was present only for about the first 100 to 200 feet of tunneling. Thus, once satisfactory procedures were established, the saprolite tunnel work was rapidly completed and did not affect overall project progress in a major way. Performance of the tunnels in saprolite was monitored by instrumentation, which verified that convergence was within acceptable limits. The average calendar day advance rate for the top heading was 8 feet/day at Haiku and 11 feet/day at Halawa. The average equivalent full-size tunnel advance rate was 8 feet/day at Haiku and effectively 7 feet/day at Halawa. The Haiku crew worked three shifts, six days per week. The Halawa crew worked two 10-hour shifts, six days per week Atlas Copco 245 Rocket Boomers were used for drilling blast holes. Muck was removed using CAT 966 rubber-tired loaders. Trucks often could be loaded directly from the muck pile without extra handling. At Haiku, the muck was placed and compacted to form part of a future H-3 interchange embankment. At Halawa, the saprolite was wasted at a designated dump site. Rock muck was stockpiled for reuse as select fill at the tunnel approach area and on other H-3 projects. Pattern rock reinforcement bolts, combined with shotcrete, was used in the top heading throughout the main tunnels in rock. The sidewalls were virtually unsupported. Swellex rock dowels were the principal type of rock reinforcement used in the main tunnels by both contractors. Resin-encapsulated rebar dowels were used in the cross passages and portal rock cuts. In saprolite, cement-grouted dowels appeared more effective than resin-encapsulated dowels. Some hollow-core dowels were used, but most cement-grouted dowels were made in the field by taping plastic tubing to rebar. Workers quickly learned to install a suitable cement-grouted dowel in this manner. A full-perimeter pattern of dowels was used. In the sidewalls, the dowels were lengthened to 20 feet. Sidewall dowels were installed sub-horizontally; installation was made more constructible by use of an air track for drilling. Heavier reinforcement was needed for shotcrete at the Halawa Portals to help control ground movements. As an expedient measure, light reinforcing bar grids, already being used on site for precast retaining wall panels, were used instead of the specified wire mesh. The 6-foot by 12-foot grids were cut into 2-foot strips, rolled with a smooth drum roller to make them fit the tunnel sidewall, and then encased in shotcrete. After placement of a waterproof membrane, the tunnel lining construction sequence began by placing the arch footings and starter wall, followed by placing the arch, erecting precast flues, casting the ceiling, and finally casting the divider wall. Arch concrete was placed using a 50-foot-long section of collapsible steel forms. Concrete was pumped through guillotine-type valve connections in the crown to completely fill the forms to a vertical bulkhead. Concrete mix for tunnel construction has a minimum 28-day compressive strength of 3,000 psi. The specified water-cement ratio resulted in considerably higher actual strength, averaging around 6,000 psi. Super-plasticizer was used to yield a very fluid, 8-inch slump mix. The




concrete pumped easily and filled the crown area very well. Contact grout volumes were generally low. Core samples confirmed that there was no significant segregation of the mix during placement. The amount of overbreak was governed by excavation methods and survey control, not by geological factors. The Haiku contractor was somewhat unconcerned about overbreak at first because of the relatively more economical concrete available to the contractor. Later improvements in survey control reduced the Haiku overbreak considerably. Average Haiku overbreak was about 14 inches. The Halawa contractor had consistently lower overbreak, averaging about 9 inches. This is attributable to close survey control, refinements in blast round design, trimming tights with the roadheader attachment on the tracked excavator, and learning from the earlier experience at the Haiku Tunnel.




Wilson Tunnels (State Route 63: Likelike Highway) The Wilson Tunnels are located along the Likelike Highway (State Route 63) in the Districts of Honolulu and Koolaupoko. Their location is shown in Figure 4 and in Figure A-2 below.

Figure A-2. Oblique View of Wilson Tunnels (looking southwest)

Bore 1, previously named the Kalihi Tunnel, carries two lanes of traffic up an approximately 6 percent grade in the direction of Honolulu. Bore 2 is parallel and to the south of Bore 1, with a center-to-center distance of 119 feet, and carries two lanes of traffic down an approximately 6 percent grade in the opposite direction towards Kaneohe. Bore 1 is 2,780 feet long and Bore 2 is 2,813 feet long. The western and eastern portals are identified as the Kalihi and Kaneohe Portals, respectively.

Wilson

Tunnels




Photo A-2. Portals of Wilson Tunnels

Maximum ground cover above the tunnels is approximately 870 feet, located about 2,100 feet east of the Kalihi Portals. A common ventilation shaft serves both tunnels and is located approximately 935 feet east of the Kalihi Portals. There is approximately 180 feet of ground cover above the tunnel at the shaft. Water leakage near the Kalihi Portal and extending approximately 1,200 feet east into the tunnels has posed maintenance and aesthetic problems for a number of years. Geology Information on the geology and construction of the Wilson Tunnels is summarized from Romero and Mimura (2006). The Wilson Tunnels are located at the upper head of Kalihi Valley along the Koolau Pali. In general, the Ko’olau Mountain Range and the Ko’olau Pali are composed of layered volcanic rocks that consist of alternating sequences of thin flows of basaltic a’a and pahoehoe lavas that were erupted from rift zone vents of the Koolau Volcano. Regionally, the bedding inclination of the lava flows dip gently seaward toward the south and southwest from the summit region of the Ko’olau Pali. The individual lava flows range in thickness from less than about 5 feet to about 30 feet. Typically, the basalt rock grades with depth from extremely weathered and weak rock (saprolitic) near the surface to progressively less weathered and harder rock materials. The weathering gradation may occur over intervals of tens of feet to hundreds of feet in depth depending on the degree of chemical and physical decomposition the rock has experienced. The lavas of the summit of the Ko’olau Volcano are typically deeply weathered due to the high rainfall and extensive groundwater aquifers encompassed by the volcano. The layered basaltic rock is considered to be very porous because of the presence of closely spaced rock joints, rubbly clinker seams, lava tubes and voids, and other irregular contacts that occur




between the individual lava flow layers. Rainfall that does not run off as stream flow percolates downward through the porous volcanic layers. Intrusive seams of fine-grained, dense basaltic rock, referred to as volcanic dikes, transect the layered and porous basaltic rock, which compose the mass of the Ko’olau Volcano. The fine-grained, dense rock character of the volcanic dikes emplaced within the surrounding porous, layered volcanic rock acts to retard the free percolation of groundwater in localized zones. Kalihi Valley is a large erosional U-shaped valley formed by the incision of flowing streams and mass wasting (landslide collapse) of the adjacent valley walls. As a result, the valley floor has been partially filled with thick accumulations of alluvial and colluvial materials that represent the eroded and transported products of the volcanic mountain range. Since the valley filling processes occurred over very long periods of time, the deeper alluvial and colluvial materials are more weathered and are typically semi-consolidated because of burial beneath thick overburden layers of more recent alluvial and colluvial deposits. The older alluvial/colluvial materials are referred to as Quaternary Age Older Alluvium. The Older Alluvium deposits generally consist of decomposed basaltic cobbles and boulders in a tight matrix of clayey and fine sandy soil. The ground surfaces of the Kalihi Valley floor, especially along the existing stream drainages and other topographic depressions, may be mantled with some Recent Alluvium. These deposits are generally unconsolidated and consist of various eroded and transported earth materials consisting of soft/loose sediments (clays, silts, sands, and gravels) with some cobbles and boulders. The materials encountered during Bore 1 excavation are older alluvial/colluvial deposits and some saprolitic/residual soils at the Kalihi end of the tunnels. Less weathered basalt rock associated with the Ko’olau Volcanic Series was encountered approximately midway and through the Kaneohe end of the tunnels. The saprolitic/residual soils encountered by the tunnels represent a gradational zone of extremely to completely weathered basalt rock located at the margin of the less weathered basalt rock penetrated by the bores. The saprolitic and residual soils deposits represent the in situ, deeply weathered product of the basaltic rock. Therefore, the deposits resemble soil that includes silt, sand, and decomposed rock. Severe problems were encountered with the construction of Bore 1 within the Older Alluvium and saprolitic/residual soil deposits, as described below. Construction Construction bids for Bore 1 were received October 20, 1953, and the contract was awarded to a Joint Venture of Gibbons & Read from Salt Lake City and E.E. Black Ltd. from Honolulu. Tunnel excavation commenced on January 8, 1954, from the Kaneohe Portal at the eastern end in rock and was driven full face with little support. Near the end of May 1954 tunnel excavation transitioned from rock to “earth,” which ranged from highly weathered rock, to extremely weathered rock (saprolite), to residual soil, to transported soil deposits. Full face excavation was employed with horseshoe-shaped steel sets (structural steel) on approximately 3-foot centers until difficulties were encountered in the earth (soft-ground) section. Excavation was by drill-and-blast in rock and hand-mining in the soil deposits. As the tunnel was advanced from sound rock into weathered “soil-like” conditions, progressive sloughing and spalling were experienced in the upper part of the tunnel face.




In the summer of 1954, several tunnel collapses and subsequent surface sinkholes were experienced on July 10, 27, and 28, ultimately leading to a large collapse on August 14, which killed five construction workers (Jacobs, 1975). The largest sinkhole was recorded at the ground surface, at about 75 feet in diameter and 30 feet deep. Initial ground cover at that location was approximately 100 feet. “A continuous zone of disturbed material extended from the bottom of the tunnel to the ground surface” was noted by Peck (1981). Following the collapse on August 14, construction ceased while consideration was given to alternative methods of completion. Tunnel excavation restarted in February 1956 using a different approach for the excavation sequence. In principle, soft-ground tunneling techniques were implemented. This approach was distinctly different from that of classic hard-rock tunneling. Small-sized tunnels (drifts) were used to excavate the overall tunnel in stable increments, in a method that is known as the “stacked drift.” Details of execution varied, but generally proceeded as follows: First, a small exploration drift in the top heading was mined from both ends of the tunnel (collapsed section and undisturbed ground from Kalihi Portal) to facilitate drainage and to explore the geology. Two footing drifts were then excavated and filled with concrete to form footings and part of the sidewalls. Excavation of arch drifts then proceeded in top-down sequence to the footing drifts. The drifts were excavated in short longitudinal sections and supported by steel sets. Tunnel concreting varied, and appears to have ranged from initially only concreting between steel sets, to casting the full thickness of concrete lining as the tunnel heading advanced. Detailed records are not available. New tunnel lining sections were designed with substantially thicker walls and very wide footings, which in the extreme were a full-width flat structural invert and in some cases a curved structural invert. The concrete lining was completed in June 1957, and the tunnel was opened to two-way traffic in October 1958. Initially the design included three separate lining sections, which ranged in thickness from 1 to 1.5 feet. Various invert slabs and footing widths were indicated for ground conditions ranging from “soft-ground” to rock. However, because of the extraordinary difficulties encountered during tunneling, five additional variations of the tunnel lining for soft-ground conditions were developed, with selection based on the conditions encountered in an 8-foot by 9-foot top drift, which was the first exploratory drift. These variations consisted of lining thicknesses ranging from 32 inches to 5 feet, as well as various curved invert slab and footing geometries. The construction for Bore 2 began in 1957. In November 1960 both tunnels were opened to traffic in the present configuration. Based upon experience with Bore 1, four separate lining sections were designed for Bore 2. These lining sections range in thickness from 14 inches to 3 feet, with curved invert slab and footing geometries similar to those of Bore 1.




Pali Tunnels (State Route 61: Pali Highway) The Pali Tunnels were the first of the three sets of highway tunnels that have been constructed through the Pali Ridge. The length of the Pali Tunnels is approximately 1,080 feet (eastbound) and 497 feet (westbound). Judging from construction photographs, the tunnels were excavated to about 25 feet wide by 20 feet high. The Pali Tunnels are located along State Route 61, as shown in Figure 4 and in Figure A-3 below.

Figure A-3. Oblique View of Pali Tunnels (looking southeast)

Published information was not located on geology; however, the tunnels were likely constructed through similar rock conditions as those described above for the Wilson and H-3 tunnels. An internet search provided limited information on the Pali Tunnels, but one description suggested that the flow from existing waterfalls in the area was notably less following tunnel construction. An historic construction photograph indicates the tunnel was advanced by drill-and-blast techniques, and also shows ponded water at the tunnel heading.

Pali

Tunnels




Photo A-3. Pali Tunnel Heading

Work on the Pali Highway, which was a territorial project, began on August 1, 1955. Although the improved highway opened on May 11, 1957, the Pali opening was limited to Honolulu-bound traffic, and it required four more years, until August 1, 1961, before the remaining tunnels in the $6 million project were finished and the highway opened in the configuration that exists today.




Photo A-4. Construction at the Honolulu end of one of the Pali Tunnels in 1956

Photo A-5. Portal Structures for the Pali Tunnels