Appendix B Hurricane Cliffs Hydropower Pump Storage Project Preliminary Geotechnical Report Forebay and Afterbay Reservoir Sites

TABLE OF CONTENTS

HURRICANE CLIFFS HYDROPOWER PUMP STORAGE PROJECT Forebay & Afterbay Reservoir Sites Washington County, Utah

PRELIMINARY GEOTECHNICAL REPORT

I. INTRODUCTION ...... 1 1. PROJECT DESCRIPTION ...... 1 2. PURPOSE AND SCOPE ...... 1 3. PREVIOUS STUDIES ...... 2 II. GEOLOGIC INVESTIGATION ...... 3 1. REGIONAL GEOLOGY ...... 3 2. SITE GEOLOGY ...... 4 A. FOREBAY ...... 5 B. AFTERBAY...... 7 3. GEOLOGIC HAZARDS ...... 11 Gypsum and Collapsible Soils ...... 11 Fissures ...... 11 Rock Fall ...... 12 Open Joints and Fractures in Basalt ...... 12 4. SEISMOTECTONIC SETTING AND EARTHQUAKE HAZARDS ...... 12 Afterbay Faults ...... 12 Hurricane Fault Zone ...... 13 Warner Valley Fault ...... 13 Graben Fault ...... 13 Forebay Faults ...... 14 5. SEISMIC CONSIDERATIONS ...... 14 6. GROUNDWATER ...... 14 III. SUBSURFACE INVESTIGATIONS ...... 15 1. GENERAL DESCRIPTION ...... 15 2. FOREBAY ...... 16 Alluvium & Highly Weathered Mudstone ...... 16 Atterberg Limits ...... 17 Mechanical Analyses ...... 17 Dry Unit Weight and Moisture Content ...... 17 Proctor Tests ...... 17 Direct Shear and Triaxial Shear Tests...... 18 Soluble Salt ...... 18 Dispersive Clay...... 18 Lower Red Member of the Moenkopi Formation ...... 18 Atterberg Limits ...... 19 Dry Unit Weight and Moisture Content ...... 19 Unconfined Compressive Strength ...... 19 Point Load Tests...... 19 Timpoweap Member of the Moenkopi Formation ...... 19 Atterberg Limits ...... 19 Dry Unit Weight and Moisture Content ...... 20 Unconfined Compressive Strength ...... 20 Point Load Tests...... 20 Slake Durability...... 20 Rock Canyon Conglomerate Member of the Moenkopi Formation ...... 20 Dry Unit Weight and Moisture Content ...... 20 Unconfined Compressive Strength ...... 20 Point Load Tests...... 20 Harrisburg Member of the Kiabab Formation ...... 21 Atterberg Limits ...... 21 Dry Unit Weight and Moisture Content ...... 21 Unconfined Compressive Strength ...... 21

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page i Point Load Tests...... 21 3. AFTERBAY ...... 21 Younger Alluvium ...... 22 Atterberg Limits ...... 23 Mechanical Analyses ...... 23 Dry Unit Weight and Moisture Content ...... 24 Consolidation Tests ...... 24 Proctor Tests ...... 24 Soluble Salt ...... 24 Older Alluvium ...... 25 Atterberg Limits ...... 26 Mechanical Analyses ...... 26 Dry Unit Weight and Moisture Content ...... 26 Soluble Salt ...... 27 Unconfined Compressive Strength and Unconsolidated Undrained Strength ...... 27 Point Load Tests...... 27 Scoria/Vuggy, Gravelly Basalt Layer ...... 27 Grass Valley Basalt Flow ...... 27 The Divide Basalt Flow ...... 28 Navajo Sandstone ...... 28 Mechanical Analyses ...... 29 Dry Unit Weight and Moisture Content ...... 29 Unconfined Compressive Strength ...... 29 Point Load Tests...... 29 Lab Permeability Tests ...... 29 4. BENCH LAKE CLAY BORROW SOURCE ...... 29 Atterberg Limits ...... 30 Mechanical Analyses ...... 30 Dry Unit Weight and Moisture Content ...... 30 Soluble Salt ...... 30 Dispersive Clay...... 30 IV. ENGINEERING design considerations and recommendations ...... 31 1. FOREBAY ...... 31 Foundation Treatment ...... 32 Embankments ...... 32 Option 1 North and South Dams ...... 32 Zone I and IA ...... 32 Zone II and III ...... 33 Zone IV, IVA, and IVB ...... 33 Option 2 North and South Dams ...... 33 Zone I ...... 33 Zone II and III ...... 34 Zone IV ...... 34 Riprap and Bedding ...... 34 Option 3 South Dam ...... 34 Waterway Channel ...... 34 Outlet Works ...... 34 Spillway ...... 35 Instrumentation ...... 35 2. AFTERBAY ...... 35 Option 1 and 2 ...... 35 Foundation Treatment ...... 35 Embankment ...... 36 Zone I ...... 36 Zone II and III ...... 37 Zone IV ...... 37 Riprap ...... 37 Option 3 ...... 37 Option 4 ...... 37 3. ESTIMATED QUANTITIES ...... 38 References ...... 50

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page ii FIGURES & TABLES Vicinity Map ...... Figure 1 Geologic Map ...... Figure 2 Geologic Map Descriptions ...... Figure 2a Forebay Option 1 – Boring and Test Pit Locations ...... Figure 3 Forebay Option 2 – Boring and Test Pit Locations ...... Figure 4 Afterbay Options 1 and 2 – Boring and Test Pit Locations ...... Figure 5 Afterbay Option 3 – Boring and Test Pit Locations ...... Figure 6 Afterbay Option 4 – Boring Locations ...... Figure 7 Bench Lake Borrow Area – Site Plan & Test Hole Locations ...... Figure 8 Forebay – Generalized Geologic Cross Section, North Dam, Options 1 and 2 ...... Figure 9 Forebay – Generalized Geologic Cross Section, South Dam, Option 2 ...... Figure 10 Forebay – Extended Generalized Geologic Cross Section ...... Figure 10a Afterbay – Generalized Geologic Cross Section, South Dam, Options 1 and 2 ...... Figure 11 Afterbay – Generalized Geologic Cross Section, Center of Basin ...... Figure 12 Afterbay – Generalized Geologic Cross Section, North Dam ...... Figure 13 Afterbay – Generalized Geologic Cross Section, Option 4, Section A from Fig. 7 ...... Figure 13A Afterbay – Generalized Geologic Cross Section, Section B from Figure 7 ...... Figure 13B Forebay – Rockfill Embankment Section, South Dam, Option 1 ...... Figure 14 Forebay – Rockfill Embankment Section, North Dam, Option 1 ...... Figure 15 Forebay – Earthfill Embankment Section, South Dam, Option 2 ...... Figure 16 Forebay – Earthfill Embankment Section, North Dam, Option 2 ...... Figure 17 Forebay – Channel Profile & Sections, Option 2 ...... Figure 18 Afterbay – Embankment Section, South Dam, Option 2 ...... Figure 19 Afterbay – Embankment Section, North Dam, Option 2 ...... Figure 20 Afterbay – Embankment Section, Option 3 ...... Figure 21 Afterbay – Embankment Section, Option 4 ...... Figure 22 Forebay – Area & Capacity Curves, Option 1 ...... Table 1 Forebay – Area & Capacity Curves, Option 2 ...... Table 2 Afterbay – Area & Capacity Curves, Option 1 ...... Table 3 Afterbay – Area & Capacity Curves, Option 2 ...... Table 4 Afterbay – Area & Capacity Curves, Option 3 ...... Table 5 Afterbay – Area & Capacity Curves, Option 4 ...... Table 6 APPENDIX A – FOREBAY, Field and Laboratory Testing Borings Logs Core Photo Logs Laboratory Testing Test Pits Logs Laboratory Testing APPENDIX B – AFTERBAY, Field and Laboratory Testing Borings Logs Core Photo Logs Laboratory Testing Test Pits Logs Photographs Laboratory Testing Back-up Data APPENDIX C – BENCH LAKE, Field and Laboratory Testing Boring Logs Laboratory Testing APPENDIX D – WLA Report

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page iii

3. PREVIOUS STUDIES

No previous subsurface investigation studies were identified at any of the proposed reservoir sites. Geologic mapping of the areas has been performed by the Utah Geologic Survey (UGS) and these maps have served as geologic base maps for the study.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 2 II. GEOLOGIC INVESTIGATION

1. REGIONAL GEOLOGY

The proposed Hurricane Cliffs Hydropower Pumped Storage Project site is located within the immediate area of the St. George basin. The St. George basin is located within the Transition Zone between the Colorado Plateau to the east and the Basin and Range Province to the west (Stokes, 1987).

The Colorado Plateau Province is approximately centered near the Four Corners area of Utah, Arizona, Colorado, and New Mexico and covers about 130,000 square miles. The province is typified by relatively flat-lying sedimentary rock units which make up numerous plateaus and mesas. The rocks within this region typically show little evidence of deformation caused by large scale faulting and folding. This province is bound by a transition zone and the Basin and Range Province on the west and south, and by the Rocky Mountain Province to the north and east. In contrast, the surrounding provinces are highly faulted and folded due to extensive compressional and extensional forces over millions of years. While the Colorado Plateau Province is typified as relatively stable and flat-lying, there are some normal faults and localized areas of deformation, such as the San Rafael Swell.

The topography of the Basin and Range Province to the west is the result of structural extensional forces within the North American Plate. These extensional forces have generated a series of generally north-south trending normal faults. These faults have created a series of horsts and grabens or uplifted mountains and down-dropped valleys. This repeated series creates the distinctive linear topography of alternating mountain ranges and valleys of the Basin and Range province to the west (Stokes, 1977).

The St. George basin is bounded on the east by the Hurricane fault and on the west by Gunlock fault in Utah (Grand Wash fault in Arizona). The basin is bounded to the north by the Pine Valley Mountains. The core of the mountains consists of a very large quartz monzonnite laccolith, which may be one of the largest laccoliths in the world (Cook, 1957, 1960b, Biek and others, 2007). The basin opens up toward the south into the Shivwitts Plateau, in Arizona.

Displacement has been greatest on the Hurricane fault, with the basin having been down- dropped to the west. The Hurricane fault is a long northerly trending fault which extends from within northern Arizona up toward Cedar City in Utah. Recent studies have divided the fault into several segments. The structure and stratigraphy of the St. George basin more

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 3 closely resemble that of the Colorado Plateau than the Basin and Range Province (Lund and others, 2008).

Bedrock and unconsolidated deposits in the region range in age from the Paleozoic to the Holocene. Exposed bedrock consists predominately of Permian, Jurassic and Triassic age (140-290 million years ago) sedimentary deposits with some younger Tertiary igneous intrusions with rhyolite, dacite and andesitic flows and Quaternary Basalt flows, fissures and cinder deposits. Basalt flows followed old topographic lows. Since deposition of the basalt, the less resistant surrounding sedimentary rocks have eroded away leaving the basalt covered channels now standing as ridges, resulting in an inverted topography. Sedimentary deposits in the area generally dip gently toward the east. Compressional forces associated with eastward thrusting during the Cretaceous age Sevier Orogney have created several anticlines in the region such as the Harrisburg and Virgin Anticlines and the Washington Dome.

2. SITE GEOLOGY

The study area is located within The Divide Quadrangle in Washington County. A geologic map of the quadrangle was completed in 2004 by the Utah Geologic Survey (Map 197 Hayden, 2004). A portion of this geologic map showing the general study area is shown in Figure 2. Detailed descriptions of the geologic units on the map are shown on Figure 2a.

The Afterbay reservoir sites are located on alluvial fan deposits which radiate from the base of the Hurricane Cliffs east of the sites. The cliff rises about 1,200 feet above the valley floor and exposes about 1,000 feet of Permian Age deposits. The Hurricane Cliffs are the result of faulting along the Hurricane Fault Zone, which is classified as a normal fault with down to the west displacement. This places the Afterbay sites on the hanging wall side of the fault. The Forebay reservoir sites are located to the east above the Hurricane Cliffs on the footwall side of the fault. The Hurricane Fault Zone is considered the dividing line between the Colorado Plateau Province to the east, and the transition zone to the Basin and Range Province to the west. Preliminary design includes a vertical shaft to carry water from the Forebay down through the bedrock within the Hurricane Cliffs. A tunnel and penstock will then bring the water from the shaft out from within the cliff to the powerhouse and Afterbay reservoir in the valley away from the toe of the cliff. The tunnel and penstock will cross the Hurricane Fault Zone. The geology of this report is related to the dam sites for the Forebay and Afterbay and does not discusses details related to the shaft, tunnels, penstock, etc.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 4 A. FOREBAY

The Forebay site consists of a broad north-south trending strike valley bounded on the west by gently westward rising bedrock which is dipping down to the east. The east side is bounded by a ridge of Triassic sedimentary rock capped with limestone. A northern and southern dam are planned to contain water in the reservoir.

The North Dam trends in a north easterly direction as shown on Figure 2. The southwestern side (left) of the northern dam will be located on bedrock of the Timpoweap and the Rock Canyon Conglomerate members of the Moenkopi Formation (Triassic), which unconformably overlay the Harrisburg Member of the Kaibab Formation (Permian). A geologic cross-section showing our interpretation the subsurface bedrock is shown in Figure 9. Bedrock in the area appears to be dipping gently down toward the east at about 3 to 5 degrees. Figure 9 shows the locations of Test Holes and a summary of the percent of rock recovered, RQD and the relative permeability of the zones tested. There is generally little to no alluvial cover over bedrock in this area. It should be noted that the Harrisburg Member is known for having significant gypsum deposits. The Harrisburg Member exposed in the large wash downstream of the north dam site shows large distorted and wavy to rolling bedding. This is due to the dissolution of gypsum within the member. It should also be noted that the overlying Timpoweap member is not distorted but has a natural dip to the east. This would suggest that the dissolution of gypsum and distortion of the bedding took place prior to the deposition of the Timpoweap member.

At the maximum section of the North Dam is a wash which drains the northern end of the basin out to the west and over the Hurricane Cliff. In general, the alluvial cover over the bedrock along the alignment of the North Dam is relatively thin to non- existent, with the exception of the wash at the maximum section. Test Pit FB-15 along the side of the wash encountered about 15 feet of alluvium. The northeast (right) abutment of the dam extends over shallow Timpoweap and onto Quaternary basalt from the Divide Lava Flow. The elevation of the fractured basalt and its scoriaceous zones with high permeabilities may control the height of the dam in this area.

The South Dam (Option 2) trends in a relatively east-west direction. Bedrock in the area appears to be dipping down toward the east at about 4 to 6 degrees. The west side of the dam overlies bedrock of the Timpoweap Member of the Moenkopi Formation (Triassic) which overlies the Rock Canyon Conglomerate Member of the Moenkopi. The Rock Canyon Conglomerate unconformably overlies the Harrisburg

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 5 Member of the Kaibab Formation of the Permian age as shown on Figures 10 and 10a. Figure 10 shows a generalized cross section through the Southern Dam alignment (Option 2) with the locations of Test Holes. It should be noted from Figure 10 that the thickness of the Rock Canyon Conglomerate varies greatly and may not be deposited in some areas. Figure 10a shows a Generalized Geologic Cross Section starting from the Virgin Limestone above the left abutment and extending toward the west, past the right abutment and down the Hurricane Cliff face. The thickness of the rock units, fault dips and amount of displacements are generalized. The Rock Canyon Conglomerate is not a continuous unit over the region. This member is found within paleo-channels which have been eroded into the Harrisburg Member.

Much of the eastern side of the basin lies relatively flat (gentle slope) where the Lower Red Member of the Moenkopi Formation overlies the Timpoweap. The Lower Red Member is much less resistant to weathering than the Timpoweap and has formed the lowest portion of the valley. Further up the slope to the west, the Lower Red Member has been eroded away. Just above the basin floor there are a few localized mounds which contain layers of red-brown mudstone and shale which are interbedded with yellowish-brown siltstone, sandstone, limestone and some mudstone. The contact between the Lower Red and the Timpoweap members is gradational and likely has some interbedded facies changes. The contact between the two members has been defined by J. Hayden (2004) as corresponding “to the top of the highest yellowish-brown siltstone, sandstone, and limestone interval, above which lies reddish-brown siltstone and mudstone of the lower red member”. It is our opinion that these mounds of interbedded red and yellow material are part of the upper transitional zone of the Timpoweap and not mapped as part of the Lower Red Member. We have outlined the approximate boundaries of the gradational transition zone on Figure 2. This area is significant in that it contains layers of potentially less permeable mudstone overlying the more pervious fractured limestone. The material may act as a blanket over the limestone and reduce seepage. Additional study is needed in order to clarify the extent and the properties of the material in this area.

In the central portion of the valley, there generally appears to be about 3 to 15 feet of alluvium (average of about 10 feet) overlying highly weathered mudstone of the Lower Red Member of the Moenkopi, which becomes less weathered with depth. The test pits in the basin area could generally be dug down, on average, about 5 feet into the weathered mudstone before refusal with the trackhoe. It should be noted that some gypsum is common in the Lower Red Member. The east (left) abutment of the dam will rest against the Lower Red Member which rises about 150 feet and is capped by about 50 feet of more resistant limestone of the Virgin Limestone member

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 6 of the Moenkopi. The red-brown mudstone with some siltstone of the Lower Red Member exposed in this cliff shows a significant amount of gypsum in the form of stringers, nodules and a few thin layers. Some layers appear to be up to ½ inch thick. Nodules appear to be up to 1 inch in diameter, with stingers from 1/32 to ¼ inch. The percentage of soluble salts documented in the alluvium will be discussed later in this report.

The lower part of the basin between the two dams generally consists of about 10 feet of alluvial material overlying the Lower Red Member along the eastern side of the basin. The western side of the basin begins where the alluvial cover meets the easterly dipping more resistant Timpoweap Member. The Timpoweap creates a dip slope with a relatively thin alluvial cover. The central, eastern and southern end of the basin drains toward the south while a high region causes runoff in the far northern end of the basin to drain to the north. This high area may result in a relatively large dead pool forming in the southern end of the basin unless a significant trench is cut to bring water through the high area.

No faults have been mapped or were observed within the Forebay reservoir site. The nearest mapped fault is the Anderson Junction Segment of the Hurricane Fault Zone located about 1,600 to 2,900 feet (.049-0.88 km) west of the North Dam location and 1,400 to 3,500 feet (0.43-1.07 km) west of the South Dam location. The distance from the fault varies due to the main trace of the fault being located at the base of the cliff with several broken fault strands mapped just along the top of the cliff to the east. It should be noted that most of the strands along the top of the cliff appear to be related to extensional slumping and toppling features, and not deep seated tectonic features.

Jointing patterns have been noted in the exposed bedrock of the Harrisburg, Timpoweap and Virgin Limestone members. The primary joint set trends about North 15 to 25 degrees West and North 60 to 70 degrees East. Secondary cross cutting joints trend about North 20 to 40 degrees East.

B. AFTERBAY

The Afterbay reservoir will be located west of the Forebay below the Hurricane Cliff and Hurricane Fault and about 1,200 feet lower in elevation. During this study, four locations have been considered as potential reservoir sites for the proposed Afterbay. These locations are shown on Figure 2.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 7 Options 1 and 2 are located on westward sloping alluvial fan deposits which begin at the toe of the Hurricane Cliffs. These deposits extend to the west where they transition onto easterly dipping basalt and terminate against the basalt ridge to the west. This ridge is capped by the Quaternary age Grass Valley Lava Flow and cinder cone which have been dated at about 1.4 to 0.96 ± Ma (Hayden, 2004; Biek and others, 2007). Sandstone bedrock is exposed at the south end of the ridge, showing the bedrock core of the ridge to be Jurassic age Navajo Sandstone. Due to back tilting associated with the Hurricane Fault, the Grass Valley Lava Flow dips down to the east and extends under the alluvial fan deposits to the east.

As shown on Figure 11 and based on Test Hole borings 09-AB-1 to 09-AB-4, the basalt increases with depth to the east below the southern dam alignment for Options 1and 2. Figure 12 shows a generalized geologic cross section extending north-south through the maximum section of the basin and extends below all three dams of Options 1 and 2. The cross section passes through Borings 09-AB-3, 09-AB-5 and 09-AB-6. As shown on Figure 12, Boring 09-AB-5 (North Dam Option 1 site) is located near the high point (Elevation ~3,600 feet) between the north dam and south dams for Option 2. This figure shows significant changes in the subsurface paleo- topography between Borings 09-AB-3 and 09-AB-6. Boring 09-AB-5 shows deeper Navajo Sandstone overlain by the Grass Valley Basalt and scoria and later covered by older alluvium. This area was still lower in elevation when the Divide Basalt flowed off of the cliff from the east. The Divide Basalt flowed into this area of lower topography, filling in the older channel. This younger and more resistant basalt flow has likely contributed to the higher elevation of the surficial deposits in this area today. Figure 13 shows a generalized geologic cross section extending from west to east along the North Dam alignment of Option 2. The section is based primarily on Boring 09-AB-6 drilled near the maximum section. This boring appears to have encountered basalt from the Grass Valley Basalt flow from the west, with some interbedded scoria layers. Grass Valley Basalt is exposed at the surface toward the left abutment as shown in Test Pit AB-TP-17. Boring 09-AB-10 encountered alluvial deposits which, while having a few interbedded layers with some of the characteristics of older alluvium, more likely resemble younger alluvium. It should be noted that the assumed dip angle of the bedding shown on Figure 13 is interpolated from the dip angles observed from the boring shown on Figure 11. Additional deeper borings are needed to better define the subsurface geology in this area.

Alluvial deposits have been classified into two major groups, younger and older deposits. The younger deposits generally are yellowish to light-brown in color and

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 8 appear to be derived from the types of the material exposed in the cliffs to the east. Older deposits are typically denser, red-brown silty to clayey deposits with varying amounts of sand and gravel. Some of the older deposits are indurated and contain angular mudstone fragments and appear as relatively young weakly cemented, clayey conglomerate to conglomeratic mudstone. Due to the typically higher fines content and the denser and indurated characteristics, the older alluvium may have relatively lower permeability rates than the younger deposits. This older alluvium appears to have been derived predominately from red-brown mudstone and siltstone deposits such as the Lower Red Member of the Moenkopi. In this area, the Lower Red Member, which would have been exposed at the top of the Hurricane Cliffs, has been eroded away and is now only found on the eastern side of the Forebay area. The erosion of the Lower Red Member may be the source material for this older alluvium in the Afterbay. While we have divided the alluvium into major groups of younger and older, there are areas of transition and areas where all the characteristics from one area do not apply to the next area.

East of the proposed Power House location for Option 1 and 2 is a lava flow which cascades part way over the Hurricane Cliff and ends at the top of the Brady Canyon Member of the Toroweap Formation(as shown on the geologic map in Figure 2) (Hayden, 2004). This flow comes from the Divide Basalt flow to the east. The Divide Basalt is younger than the Grass Valley flow, having been dated at about 0.41± Ma (Biek and others, 2007). This flow is not exposed at the surface within the basin area of the Afterbay. Seismic and magnetic surveys completed by WLA for this project have documented the presence of basalt beneath the alluvial deposits. Survey maps completed by WLA are included in Appendix D of this report. Based on the positioning of basalt, the Divide Basalt flow was encountered in Test Boring 09-AB- 7 at the Power House location as shown in Figure 11. The Divide flow was also encountered in Test Boring 09-AB-5 which is located near the maximum section of the North Dam alignment of Option 1 as shown in Figure 12. Test Boring 09-AB-5 included basalt from both the older Grass Valley flow and the younger Divide flow separated by about 20 feet of older alluvium. Beneath the Grass Valley Basalt, at a depth of 245 feet, is the Navajo Sandstone. Test Boring 09-AB-06 was drilled near the maximum section of the North Dam alignment of Option 2 as shown in Figure 13. This hole encountered only one basalt flow which overlays Navajo Sandstone. We have assumed this flow is part of the Grass Valley Basalt.

Options 3 and 4 are located south of the basalt ridge as shown on Figure 2. No basalt is projected within the area of either of these options. Option 3 is locate on young alluvial deposits with a mound of older alluvium mapped to the west as shown on

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 9 Figure 2. Test Boring 09-AB-09 was drilled near the northwest end of the proposed dam. This hole penetrated about 50 feet of alluvium before encountering Navajo Sandstone. It is anticipated that the alluvial cover for Option 3 will become thicker going to the east.

Option 4 is located just west of Option 3. Option 4 extends through an area with many undulating ridges of Navajo Sandstone outcrops near the right (west) abutment. The right leg of the dam trends across an area that has been mapped as the northern end of a fault. As shown on the Geologic Map in Figure 2, the fault extends from a faulted graben located to the south. It should be noted that the fault appears to be dying out in this area, and is not mapped much further to the north. The surficial deposits at the central portion of the dam are mapped as eolian wind blown sand deposits. The left (east) abutment is located on material which is mapped as older alluvium. Based on test borings and site observations, the alluvial cover along the alignment is relatively thin with Navajo Sandstone below.

Figure 7 shows a plan view of Option 4 with the locations of the test borings. As shown on Figure 7, Test Boring 09-AB-11 was drilled on the center line of the dam, near the left (east) abutment. Test Boring 09-AB-12 was drilled near the middle of the dam and just east of the maximum section. Test Boring 09-AB-13 was drilled toward the right abutment and near the fault zone associated with the graben feature. This boring was drilled at an angle in a westerly direction so that it would cut across the projected fault trace.

Figure 13A shows a generalized geologic cross-section through the dam alignment. As shown on this figure and on the boring logs, sandstone bedrock was encountered at a depth of about 7 feet in Test Boring 09-AB-11 and was very highly weathered down to about 15 feet. Test Boring 09-AB-12 encountered highly weathered sandstone at about 9 feet, with a little more competent rock at about 15 feet. Test Boring 09-AB-13 was drilled on the sandstone outcrop with relatively competent rock at the surface. It should be noted that at an angled drilling depth of about 19 to 24 feet the rock was highly fractured. This fractured zone may correspond with the eastern side of the projected fault. In this area there is no evidence of surficial displacement. The projection of the fault is noted only as a zone about 4 feet wide where the sandstone cannot be traced as solid rock. While some of the core was not recovered in this area, core which was recovered did not show any evidence of offset. At a depth of about 78 feet, sandstone bedrock appeared to become more transitional with siltstone to sandy siltstone layers with non-eolian bedding structures. This

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 10 material may be the basal transition zone between the Navajo Sandstone and the underlying Kayenta Formation.

3. GEOLOGIC HAZARDS

A preliminary evaluation of geologic hazards has been completed for this site. This evaluation included a review of geologic maps, aerial photos, test pits and borings. Hazards related to faulting will be discussed in a separate section of this report.

Gypsum and Collapsible Soils Bedrock in the area is noted for having significant gypsum deposits. Alluvial fan deposits are typically noted for the potential for collapse and settlement when they become wet. The results of our testing for soluble salts and collapsible soils are discussed in detail later in this report. Test pits and borings in the Afterbay have confirmed the presence of both collapsible soils and significant amounts of gypsum and soluble salt. Gypsum was noted in both the alluvial fan sediments and in the wind blown alluvium mixed with the basalt scoria near the surface on the west side of the Option 1 and Option 2 reservoir sites.

A significant source of gypsum in the Afterbay comes from the Paleozoic rocks exposed in the Hurricane Cliffs. Reconnaissance of the cliff face found massive deposits of gypsum tens of feet thick exposed in the Woods Ranch Member of the Toroweap Formation (Early Permian). Significant gypsum layers were also noted in the Seligman Member just below the Brady Canyon Member. Gypsum is also common in the Harrisburg Member of the Kiabab Formation (Permian) (Hayden, 2004), however significant outcrop exposures of gypsum were not observed (see Figure 2a for detailed descriptions of units).

In the Forebay, significant amounts of gypsum were noted in the mudstone of the Lower Red Member and within the basin fill alluvial material derived from the Lower Red Member.

Fissures Along the top of the Hurricane Cliffs there are also some open and covered fissures which parallel the jointing at about North 20 degrees West. Most fissures are within about 20 feet of the cliff face, however a few fissures or collapse like structures have been noted about 200 feet east of the cliff. Fissures were also noted in the Virgin Limestone ledge which stands above the left abutment of the South Dam in the Forebay. Most of these fissures were partially covered by alluvium. Some fissures are open up to 6

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 11 inches and can be found about 25 feet east of the edge of the cliff. Some of these fissures are noted on the Geologic Map in Figure 2.

Rock Fall There is a significant rock fall hazard along the Hurricane Cliff face. There are many places where very large blocks of rock have and could fall into the Afterbay sites for Options 1, 2 and 3. Some of the rock fall hazard is associated with the large toppling and slumping features which have been observed along the top of the cliff. Above the north side of Option 4 the sandstone is capped with basalt. Boulders of basalt from this area are significantly smaller and less hazardous than the large limestone blocks east of Options 1, 2 and 3.

Open Joints and Fractures in Basalt In some of the Afterbay Option 1 and Option 2 borings, air was noted sucking down the hole when basalt and scoria layers were encountered. This indicates an open connection between basalt exposed at the surface and subsurface.

4. SEISMOTECTONIC SETTING AND EARTHQUAKE HAZARDS

The St. George region is located within the Intermountain Seismic Belt. The Intermountain Seismic Belt (ISB) is a seismically active zone, which extends for more than 800 miles. The zone extends from northern Montana down through northern Arizona and ranges in width from about 62 to 124 miles. Faults within this zone show evidence of large magnitude earthquakes of greater than ML = 7.0. This zone corresponds roughly with the eastern edge of the Basin and Range Province (Arabasz and Smith, 1981).

Afterbay Faults No faults have been identified as passing through the Afterbay Reservoir sites for Options 1, 2 and 3. (ref. WLA’s report in Appendix D). The nearest mapped potential active Quaternary fault in the Afterbay area is the Anderson Junction segment of the Hurricane Fault Zone located about 900 feet (0.27km) east of the Option 1 and 2 sites. For Option 3 site the fault is located about 900 feet (0.27km) east of the north and south arms and about 2,000 feet (0.61km) east of the main portion of the dam. The fault is about 2,600 feet east of the Option 4 site. Option 4 is located in the vicinity of a mapped faulted graben which has not been identified as active.

Based on the data from the four test holes drilled along the southern alignment of Options 1 and 2 and as shown on Figure 11, the orientation of the bedding shows relative good continuity between test holes. This continuity suggests that there is no evidence of major

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 12 fault displacement passing through this dam site. The faults surrounding the Afterbay sites are discussed below.

Hurricane Fault Zone The Hurricane Fault Zone is a normal fault and has been divided into six sections based on independent movement during seismic events. The Anderson Junction section is located within this study area. This fault section covers a length of about 38 miles (61 km) and is capable of generating a magnitude 7.2 earthquake. The fault is steep dipping at about 70 to 83 degrees (Biek 2003). The fault shows evidence of at least 20 m of Late Quaternary displacement with the most recent rupture probably during the early Holocene. Displacement measurements at various locations and on deposits of different ages range from 0.6 m, 5-7 m, and 18-20 m. The fault has a recurrence interval about 5- 50 k.y with a sliprate of about 0.2-1.0 mm/yr. (USGS Quaternary fault and fold database)

Mapping of the Hurricane Fault Zone in The Divide Quadrangle shows the fault to be highly bifurcated along the cliff face. Due to the complexity of the fractures along the cliff face and after conversations with the UGS, it is our opinion that some of the traces mapped as faults may be landslide or toppling features rather than deep seated faulting features (Hayden, 2004).

Warner Valley Fault As shown on the geologic map in Figure 2, the Warner Valley Fault is located south of the site and is mapped as possibly trending north toward Options 1, 2 and 3. The fault has not been studied in detail, but is well defined in the south by an eroded scarp with several feet of normal down to the west displacement. As the fault trends north, it tapers out or is masked by younger alluvium. It is unknown if the fault continues to the north or trends to the northeast and merges into the Hurricane Fault. No evidence of faulting was noted, based on the test borings drilled in the Afterbay area. Additional studies are needed to better classify the potential activity of the fault and its’ location.

Graben Fault The graben fault is an unnamed feature located along the west side of the valley south and west of Option 4 as shown on Figure 2. Just south of the alignment, the graben appears to become a single strand with down to the west displacement. No surficial displacement is noted on this strand, however, it shows as a lineament of vegetation change on aerial photos. This lineament may pass under the right abutment of Option 4, but it becomes unclear on aerial photos at this point and may have pinched out. Further to the north is the Navajo Sandstone ridge capped by the Grass Valley Basalt. There is no

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 13 evidence of the fault continuing to the north and rupturing the overlying Quaternary basalt.

This graben has not been studied in detail but appears as a significant topographic feature with more than 15 feet of displacement. Due to poor Quaternary exposures, it is not known if the fault has had Quaternary movement or if it should be considered potentially active. Additional studies are needed to better classify the fault.

Forebay Faults No faults have been mapped or were observed within the Forebay reservoir site. The nearest mapped fault is the Anderson Junction Section of the Hurricane Fault Zone located about 1,600 to 2,900 feet (.049-0.88 km) west of the north dam site and 1,400 to 3,500 feet (0.43-1.07 km) west of the south dam site. The distance from the fault varies due to the main trace of the fault being located at the base of the cliff and several broken fault strands mapped just along the top of the cliff to the east. It should be noted that most of the strands along the top of the cliff appear to be related to extensional slumping and toppling features, and not deep seated tectonic features. Details of the Hurricane Fault are discussed in the Afterbay section of the report.

5. SEISMIC CONSIDERATIONS The Hurricane Fault Zone is the closest, longest and most active fault zone in the study area. The fault has been divided into six sections with the Anderson Junction section located within this study area. It is likely that the Maximum Credible Earthquake (MCE) at this site will be governed by this segment. This section covers a length of about 38 miles (61 km). Based on fault geometry the section is capable of generating an earthquake with a magnitude of about 7.2. Due to the close proximity of the site on both the foot and hanging wall sides of the fault, we anticipate relatively large Peak Ground Accelerations (PGA). Based on rough calculations, we have estimated possible PGA values ranging from about 0.6 to 0.75g or greater. A detailed deterministic seismic evaluation of the site is needed to better define the seismic conditions.

6. GROUNDWATER No springs were noted within the study area. At this time no ground water has been documented in any of the test borings. Some of the test borings in the Afterbay still have slotted PVC installed so that additional readings can be taken. It is not anticipated, however, that groundwater will influence design and construction of the reservoirs.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 14 III. SUBSURFACE INVESTIGATIONS

1. GENERAL DESCRIPTION

Subsurface investigations performed to date include the following:

NO. OF NO. OF LOCATION BORINGS TEST PITS FOREBAY 10 26 AFTERBAY 14 18 BENCH LAKE CLAY BORROW 3

Drilling was performed using a CME-55 rotary rig. In general, borings were advanced through the overburden using NW size casing with a rock bit and water as the drilling fluid. For deep borings in alluvial deposits where the NW casing could not be advanced, drilling mud was used to maintain an open hole. Sampling was performed in the alluvial deposits at about five-foot intervals.

Disturbed samples were obtained by driving a split-spoon sampler through a distance of 18 inches, using a 140 lb. hammer dropped from a distance of 30 inches. The number of blows taken to drive the sampler through each 6 inches of penetration is recorded on the drill logs. The sum of the last 2 blow counts (12 inches), corrected for hammer energy and overburden, represents the standard penetration value. Undisturbed samples were obtained by pushing a thin-walled Shelby tube into the soil using the hydraulic pressure of the drill rig.

Continuous coring was performed in bedrock using HQ and NQ wireline systems. The quality of the bedrock is characterized by the percent of core recovered, along with the rock quality designation (RQD). The RQD is the percent of material within a cored interval that is twice as long as the cored diameter (segment at least 4 to 5 inches long).

Permeability tests were performed at select intervals in the alluvial deposits and the bedrock. The permeability tests were performed in accordance with procedures outlined in the U.S. Bureau of Reclamation Earth Manual for Packer-type tests, measuring horizontal permeability.

Test pits were excavated using a CAT 345 Trackhoe. Both disturbed and undisturbed samples were obtained from the test pits at select intervals. In-place density tests were also performed at select locations in the younger alluvium.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 15 Each sample obtained in the field was classified in the laboratory according to the Modified Unified Soil Classification System. The symbol designating the soil type according to this system, is presented on the boring logs. A description of the Modified Unified Soil Classification System is presented in Appendix A, and the meaning of the various symbols, shown on the logs, can be obtained from this figure.

The results of most of the field and laboratory tests are included on the boring and test pit logs, with a summary of tests and test results provided in the Appendix A.

2. FOREBAY

The location of exploratory borings and test pits in the proposed Forebay area is shown on Figures 3 and 4. The drill logs, core photos and laboratory testing results are included in Appendix A. Summary tables of the borings are located at the front of Appendix A. It will be observed from Figure 4 that 4 borings were drilled along the alignment for South Dam Option 2 (FB DH-09 through FB DH-12). The borings ranged in depth from 117 to 238 feet. FB TP-17 and FB TP-27 were excavated along the alignment to depths of 17 and 6.5 feet, respectively. The geologic profile presented in Figure 10 was developed based upon the information obtained from the borings and test pits.

It will also be noted from Figure 4 that 4 borings were drilled on the alignment of the North Dam and abutments (FB DH-15 through FB DH-18), and that 2 test pits were excavated along the alignment (FB TP-15 and FB TP-16). The borings ranged in depth from 78 to 102 feet, and the test pits extended to a depth of 15 and 2 feet, respectively. The geologic profile presented in Figure 9 was developed based upon the information obtained from the borings and test pits.

Borings FB DH-13 & FB DH-14 were drilled within the basin to help define the characteristics of the alluvium and determine the depth to bedrock. These borings extended to a depth of about 30 feet. It will be noted from Figure 3 that FB DH-13 is near the alignment of South Dam Option 1. Test Pits FB TP-18 through FB TP-26 and FB TP-28 through FB TP-40 were excavated within and adjacent to the reservoir basin, as shown on Figure 4.

Alluvium & Highly Weathered Mudstone The alluvial deposits in the reservoir basin area consist predominately of silty clay with clayey sand and silty sand layers. The alluvial deposits vary in thickness from 1 to 18 feet and are typically underlain by highly weathered mudstone (east of the green-hatched area in Figure 4), which becomes more competent depth. The results of field and laboratory

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 16 testing of the alluvial and highly weathered mudstone material are included on the Test Pit Logs and summarized in Table 1, Summary of Test Data in the Test Pit section of Appendix A.

Laboratory tests performed to define the characteristics of the this material included (1) Atterberg Limits, (2) mechanical analysis, (2) dry unit weight, (3) moisture content, (4) soil moisture density relationship (proctor), (5) direct shear and triaxial shear, (6) soluble salt, (7) dispersive clay, (8) point load tests, and (9) slake durability. The results of all but the shear tests are summarized in Table 1. The results are discussed below as follows:

Atterberg Limits Atterberg limit tests were performed on 25 samples retrieved from the test pits. This test determines the liquid limit, plastic limit, and the plasticity index of soils and distinguishes the boundaries of the several consistency states of plastic soil to assist in classifying the soil. It will be observed from Table 1 that the plastic soils classify as ML, CL-ML, CL-1 and SC-SM.

The Liquid Limit ranges from 19 to 32 with an average of 24, and the Plasticity Index from 3 to 10, with an average of 6.

Mechanical Analyses Mechanical analyses were completed on 25 samples of the soil overburden and weathered bedrock. Of the 25 samples, 10 were granular classifying predominantly as SC-SM. It will be noted from Table 1 that these samples had 3 to 36% (ave. 19%) gravel size particles, 31 to 58% (ave. 41%) sand size, and 34 to 49% (ave. 40%) silt size material. The 15 cohesive samples had 0 to 23% gravel (ave. 6%), 9 to 42% sand (ave. 25%), and 50 to 91% (ave. 69%) silt and clay size material.

Dry Unit Weight and Moisture Content The in-place moisture content ranged from 3 to 12% (ave. 7%). The in-place dry unit weight varied from 76 to 127 pcf (ave. 92 pcf).

Proctor Tests Soil moisture density (proctor) tests were performed in accordance with ASTM D 698 procedures. The maximum dry density ranged from 105 to 127 pcf (ave. 114 pcf). The optimum moisture content varied from 10.5 to 18.5% (ave. 16.1%).

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 17 Direct Shear and Triaxial Shear Tests A multi-stage consolidated undrained triaxial shear test with pore pressure measurements and a consolidated drained direct shear test was performed on remolded samples of Sandy Lean Clay from Test Pit FB TP-26. The test results of the shear tests are included in the test pit section of Appendix A. It will be observed that an effective friction angle of 38.9 degrees with 156 psf cohesion was obtained from the triaxial test, and 36.4 degrees with 144 psf cohesion from the direct shear test.

Soluble Salt Twenty-three soluble salt tests were run on samples obtained from the test pits. The tests were completed in accordance with the Bureau of Reclamation Earth Manual, Test Designation E-8. The results of the soluble salt tests are presented in Table 1. The soluble salt content ranged from 1.5 to 14.3% with an average of 7.8%.

Dispersive Clay Dispersive clay tests were performed on 14 samples from the test pits in accordance with ASTM D 4647, Method A, and the results are included in Table 1. The following table is a summary of the classification categories:

DISPERSIVE CLAY CHARACTERISTICS BY PIN HOLE TEST METHOD CATEGORY DESCRIPTION D1, D2 DISPERSIVE ND 4, ND 3 SLIGHTLY TO MODERATELY DISPERSIVE ND 2, ND 1 NON-DISPERSIVE

Five of the samples classified as Non-Dispersive (ND-2), with the remaining 9 samples classifying as slightly to moderately dispersive (ND-3).

Lower Red Member of the Moenkopi Formation The approximate contact between the Lower Red Member and the Timpoweap Member of the Moenkopi Formation is shown on Figure 4, with the Lower Red Member on the east side of the green-hatched area.

It will be observed from the geologic cross section for South Dam Option 2 in Figure 10 that the east side of the reservoir basin is underlain by the Lower Red Member. Drill Hole FB-12, located on the left (east) abutment extended through approximately 135 feet of this formation. It will be noted that the bedrock exhibited excellent core recovery and high RQD’s with low (<30 ft/yr) permeability rates. This member consists of red-brown

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 18 silty mudstone with some siltstone layers. Core photos included in Appendix A show the mudstone to have many gypsum stringers and nodules with very few fractures.

Atterberg Limits Six Atterberg limit tests were performed on pulverized samples of the mudstone from Boring FB-12. The liquid limit ranged from 25 to 27, with the plastic index varying from 6 to 10.

Dry Unit Weight and Moisture Content The in-place dry unit weight of 10 samples of the mudstone in Boring FB-12 ranged from 130 to 161 pcf (ave. 145 pcf). The in-place moisture content ranged from 1.4 to 12.8% (ave. 6.2%).

Unconfined Compressive Strength Eight unconfined compressive strength tests were performed on samples of the mudstone obtained from Boring FB-12. The unconfined compressive strength ranged from 1344 to 3258 psi (ave. 2251 psi).

Point Load Tests Point load tests were performed on 15 samples of the mudstone, with the point load

index Is(50) ranging from 6 to 152 (ave. 62).

Timpoweap Member of the Moenkopi Formation The westerly side of the reservoir basin is underlain by the Timpoweap Member of the Moenkopi Formation. Drill Holes FB-9, 10 and 11 (South Dam Option 2, Figure 10) and FB-16 and 17 (North Dam, Figure 9) extended through this formation. These borings were cored at an angle to optimize intersection of joints. This member includes layers of mudstone, limestone, siltstone and conglomerate. It will be observed from Figure 10 that drilling resulted in excellent core recovery with low to moderate RQD. Permeability tests conducted in this member ranged from 9 to 7800 ft/yr, with several zones greater than 1000 ft/yr. Gypsum was not observed in this member.

Atterberg Limits Four Atterberg limit tests were performed on pulverized samples of the Timpoweap mudstone layers from Borings FB-10, 11, and 17. The liquid limit ranged from 28 to 36, with the plastic index varying from 9 to 16.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 19 Dry Unit Weight and Moisture Content The in-place dry unit weight of 14 samples of the bedrock ranged from 132 to 169 pcf (ave. 158 pcf). The in-place moisture content ranged from 0 to 10.5% (ave. 1.7%).

Unconfined Compressive Strength Fourteen unconfined compressive strength tests were performed on samples of the bedrock. The unconfined compressive strength ranged from 200 to 15,595 psi (ave. 7085 psi).

Point Load Tests Point load tests were performed on 19 samples of the bedrock, with the point load

index Is(50) ranging from 6 to 2164 (ave. 736).

Slake Durability Slake durability tests were performed on four samples of the Timpoweap Formation, with the slake durability index (2nd cycle) of the mudstone ranging from 33.6 to 46.7%, and the limestone/siltstone from 96.4 to 98.9%.

Rock Canyon Conglomerate Member of the Moenkopi Formation This member underlies the Timpoweap Member and consists predominately of conglomerate and limestone. It will be observed from Figure 10 that the member was about 120 feet thick in Boring FB-9, and only about 10 feet thick in Boring FB-11. Core recovery was excellent, with the RQD frequently above 70%. Permeability tests in this member ranged from no measurable loss to greater than 7000 ft/yr with several zones greater than 1000 ft/yr.

Dry Unit Weight and Moisture Content The in-place dry unit weight of 12 samples of the bedrock ranged from 142 to 167 pcf (ave. 160 pcf). The in-place moisture content ranged from 0 to 0.4% (ave. 0.2%).

Unconfined Compressive Strength Fourteen unconfined compressive strength tests were performed on samples of the bedrock. The unconfined compressive strength ranged from 4724 to 15,454 psi (ave. 8701 psi).

Point Load Tests Point load tests were performed on 24 samples of the bedrock, with the point load

index Is(50) ranging from 436 to 1898 (ave. 1115).

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 20 Harrisburg Member of the Kiabab Formation The Moenkopi Formation is underlain by the Harrisburg Member of the Kiabab Formation.

Atterberg Limits Six Atterberg limit tests were performed on pulverized samples of the Harrisbury mudstone layers from Borings FB-9, 11, and 16. The liquid limit ranged from 21 to 41, with the plastic index varying from 8 to 23.

Dry Unit Weight and Moisture Content The in-place dry unit weight of 22 samples of the bedrock ranged from 108 to 170 pcf (ave. 156 pcf). The in-place moisture content ranged from 0 to 24.4% (ave. 1.8%).

Unconfined Compressive Strength Twenty-one unconfined compressive strength tests were performed on samples of the bedrock. The unconfined compressive strength ranged from 3201 to 14,330 psi (ave. 7642 psi).

Point Load Tests Point load tests were performed on 37 samples of the bedrock, with the point load

index Is(50) ranging from 28 to 2088 (ave. 649).

3. AFTERBAY

The location of exploratory borings and test pits in the proposed Afterbay area is shown on Figures 5, 6 and 7. The drill logs, core photos and laboratory testing results are included in Appendix B. Summary tables of the borings are located at the front of Appendix B. It will be observed from Figure 5 that 4 borings were drilled along the alignment for South Dam Options 1 and 2 (AB DH-1 through AB DH-4). The borings ranged in depth from 134 to 210 feet. Test Pits AB TP-01 through AB TP-04 were excavated along the alignment to depths ranging from 14 to 26.5 feet. The geologic profile presented in Figure 11 was developed based upon the information obtained from the borings and test pits. Boring AB DH-7, drilled to a depth of 271 feet at the proposed location of the Power House Station about 800 feet upstream of the alignment, was projected onto the alignment to assist in evaluating the profile.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 21 It will also be noted from Figure 5 that Boring AB DH-5 was drilled near the maximum section of Option 1 North Dam and Boring AB DH-6 was drilled near the maximum section of Option 2 North Dam. These borings extended to depths of 248 and 174 feet, respectively. Boring AB DH-10 was located on the right abutment of Option 2 North Dam, extending to a depth of 50 feet. Test Pits AB TP-08 through AB TP-10 were excavated along the alignment of Option 1 North Dam and Test Pits AB TP 16 though AB TP 19 were excavated along the alignment of Option 2 North Dam. Nine additional test pits (AB TP 01, 05, 06, 07, 11, 12, 13, 14 and 15) were excavated in the reservoir basin. The tests pits extended to depths of between 12 and 22 feet. Data obtained from these borings and test pits was used to develop the profiles shown in Figures 12 and 13.

Boring AB DH-8 and AB DH-9 were drilled in the vicinity of Afterbay Options 3 and 4 at locations shown in Figures 6 and 7. These borings were drilled to depths of 64 and 60 feet, respectively. Borings AB-11, 12, and 13 were drilled along the proposed alignment of Option 4 and Boring AB-14 was drilled in the vicinity of the proposed Power House Station for Option 4, at locations as shown in Figure 7. Borings along the Option 4 dam alignment extended to depths of between 100 and 107 feet. Boring AB-14 was drilled to a depth of 249 feet, encountering Navajo Sandstone at a depth of 211 feet. The geologic profiles shown in Figures 13A and 13B was developed using the boring data.

Younger Alluvium It will be noted from Figures 11 through 13 that a near surface zone of younger alluvium exists throughout the Option 1 and 2 areas. The younger alluvial deposits on the west side of the valley (west of the roadway) appear to be less than 10 feet thick and are underlain by a zone of scoria/vuggy basalt cobble and boulder size fragments with abundant gypsum deposits which extend to a depth of up to 30 feet below the ground surface.

The younger alluvium is 20 to 30 feet thick across the valley floor, and increases to as deep as 80 feet at the proposed high water level on the east side of the basin. These deposits consist predominately of silty/clayey gravel with sand and cobbles. A surface layer of low density (75 to 95 pcf) silty sand and sandy clay with gravel was encountered in a number of the test pits, extending 3 to 9 feet below the surface. These deposits exhibited a pinhole type structure indicative of moisture sensitive, collapsible soils. Below this surface layer, no pinhole-type structure was observed, and the in-place density of the deposits was significantly greater.

The thickness of younger alluvium encountered in Borings AB DH-8 and DH-9 in the Option 3 area was 15 and 5 feet, respectively, deepening to about 48 feet in Boring AB- DH 14.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 22 Constant head field permeability tests were performed in the younger alluvium by drilling 5 feet ahead of the casing and monitoring the amount of water required to maintain a constant head at the top of the casing. The results of these tests are shown on the boring logs. Tests were performed at 36 locations in the younger alluvium, with the permeability rate varying from 30 to 4959 ft/yr (ave. 761 ft/yr). It will be noted that 4 of the 36 tests exceeded 2000 ft/yr.

Laboratory tests performed to define the characteristics of the this material included (1) Atterberg Limits, (2) mechanical analysis, (2) dry unit weight, (3) moisture content, (4) consolidation, (5) soil moisture density relationship (proctor), (6) triaxial shear, and (7) soluble salt tests. The results of all but the consolidation and shear tests are included on the Boring and Test Pit Logs and summarized in Table 1, Summary of Test Data, in the Boring and Test Pit sections of Appendix B.

The results are discussed below as follows:

Atterberg Limits Atterberg limit tests were performed on 37 samples retrieved from the test pits. This test determines the liquid limit, plastic limit, and the plasticity index of soils and distinguishes the boundaries of the several consistency states of plastic soil to assist in classifying the soil. It will be observed from Table 1 that 13 of the 34 granular samples tested were non-plastic. The Liquid Limit of the Minus No. 10 material ranges from 17 to 45 with an average of 23 and the Plastic Index ranges from 1 to 23, with an average of 5.

Atterberg limit tests were performed on 30 samples of the Younger Alluvium obtained from the borings. It will be noted from Table 1 that 15 of the 30 samples were non-plastic. The Liquid Limit of the minus no. 10 material of the other 15 samples ranges from 18 to 40 with an average of 30. The Plastic Index ranges from 6 to 32 with an average 20.

Mechanical Analyses Mechanical analyses were completed on 37 samples from the test pits. Of the 37 samples, 34 were granular classifying predominantly as GM, SM, GC-GM and SC- SM. It will be noted from Table 1 that these samples had 3 to 74% (ave. 44%) gravel size particles, 15 to 60% (ave. 34%) sand size, and 5 to 46% (ave. 21%) silt and clay size material. Hydrometer analyses were also performed on these samples.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 23 Gradation curves for the samples tested are included in the Test Pit section of Appendix B.

Dry Unit Weight and Moisture Content The in-place dry unit weight was determined at 36 locations in the upper 15 feet of the test pits, with the value ranging from 79 to 125 pcf (ave. 109 pcf). Six of the test locations in the upper 6 feet had dry unit weights less than 95 pcf and appeared collapsible.

The in-place moisture content was determined at 60 locations within the upper 20 feet of the test pits, and the value ranged from 1.5 to 10% (ave. 4.1%).

Consolidation Tests The compressibility characteristics of the near surface low density cohesive and sandy younger alluvium deposits were evaluated by performing six consolidation tests, and the results of these tests are also presented in Appendix B.

During performance of the consolidation tests, each sample was loaded at the natural moisture content until a load intensity of 0.58 tsf had been reached. At this point in the loading cycle, each sample was permitted to absorb water without any increase in the load intensity. Soils having collapsible characteristics always settle without any increase in the load when they become wet or saturated. It will be noted that the percent collapse ranged from 2.1 to 9.2% (ave. 4.5%).

Proctor Tests Soil moisture density (proctor) tests were performed on 5 samples in accordance with ASTM D 698 procedures. The maximum dry density ranged from 122 to 139 pcf (ave. 129 pcf). The optimum moisture content varied from 6.8 to 11.1% (ave. 9.7%).

Soluble Salt Thirty four soluble salt tests were run on samples obtained from the test pits. The tests were completed in accordance with the Bureau of Reclamation Earth Manual, Test Designation E-8. The results of the soluble salt tests are presented in Table 1. The soluble salt content ranged from 0.5 to 19.4% with an average of 10.2%.

Eight soluble salt tests were run on samples of the Younger Alluvium obtained from the borings. The results of the soluble salt tests are presented in Table 1 of the Boring Section of Appendix B. The soluble salt content ranged from 3.3 to 15.1% with an average of 9.5%.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 24 Older Alluvium It will be noted from Figures 11 through 13 and 13B that a zone of older alluvium exists beneath the valley floor and the east side of the Option 1, 2 and 3 areas. The older alluvium is darker in color, significantly denser and typically has a larger quantity of clay fines than the younger alluvium. It will be noted that excellent recovery was obtained while coring in the older alluvium in Boring AB-04 and AB-14 and photos of the core recovery are included in the Boring section of Appendix B.

The older alluvium at the South Dam location of Options 1 and 2 ranges from about 5 feet thick at the maximum section to an estimated thickness of about 150 feet at the proposed high water level on the east side of the basin. The Basalt Divide Flow interrupts the older alluvium on the east side.

Constant head field permeability tests were performed in the older alluvium by drilling 5 feet ahead of the casing and monitoring the amount of water required to maintain a constant head at the top of the casing. The results of these tests are shown on the boring logs. Tests were performed at 11 locations in the older alluvium in Borings AB DH-1, 3, 4, 5 and 6 with the permeability rate varying from 7 to 73 ft/yr (ave. 31 ft/yr). In Boring AB DH-10, east of the right abutment of Option 2 North Dam, the material between 15 and 50 feet has been described as possible older alluvium. Permeability tests were performed at seven 5-foot intervals through this zone. The permeability was significantly higher, ranging from 55 to 8700 ft/yr, with an average of 2278 ft/yr.

Permeability tests were also performed in the material identified as older alluvium in Borings AB DH-8 and DH-9 in the Option 3 area. Thirteen intervals were tested, with the permeability ranging from 266 to 6551 ft/yr (ave. 1639 ft/yr).

Permeability tests were performed in the alluvium in Borings AB DH 11 and 12 along the Option 4 alignment. The permeability ranged from 483 to 1530 ft/yr.

Laboratory tests performed to define the characteristics of this material included (1) Atterberg Limits, (2) mechanical analysis, (2) dry unit weight, (3) moisture content, (4) soluble salt tests, and (5) unconfined compressive strength, unconsolidated undrained shear strength and point load tests. The results of all tests are included on the Boring Logs and summarized in Table 1, Summary of Test Data, in the Boring section of Appendix B. The results are discussed below as follows:

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 25 Atterberg Limits Atterberg limit tests were performed on 16 samples retrieved from Borings AB DH-1, 3, 4, 5, 6 and 7. Five of the samples classified as Non-plastic. The liquid limit of the other 11 samples ranged from 20 to 40 (ave. 28), and the plastic index ranged from 3 to 20 (ave. 9).

Three tests were performed on samples of the possible older alluvium (?) from Boring AB DH-10. These samples all classified as Non-plastic.

Atterberg limit tests were performed on 10 of the samples identified as older alluvium from Borings AB DH-8 and DH-9 in the Option 3 area. Eight of the samples classified as Non-plastic. The liquid limit of the other 2 samples was 37 and 23, with a plastic index of 17 and 6, respectively.

Thirteen tests were performed on samples from Boring AB-14, located near the proposed power house for Option 4. The liquid limit ranged from 24 to 53 (ave. 39) and the plastic index ranged from 5 to 28 (ave. 15).

Mechanical Analyses Mechanical analyses were performed on 16 samples retrieved from Borings AB DH- 1, 3, 4, 5, 6 and 7. The gravel ranged from 0 to 69% (ave. 23%), sand 23 to 84% (ave. 41%), and silt/clay 8 to 54% (ave. 36%).

Three tests were performed on samples of the possible older alluvium (?) from Boring AB DH-10. The gravel ranged from 28 to 36% (ave. 33%), sand 38 to 45% (ave. 42%), and silt/clay 23 to 27% (ave. 26%).

Mechanical analyses were performed on 24 of the samples identified as older alluvium from Borings AB DH-8 through 14 in the Option 3 and 4 areas. The gravel ranged from 0 to 45% (ave. 33%), sand 28 to 87% (ave. 46%), and silt/clay 11 to 71% (ave. 39%).

Hydrometer analyses were also performed on some of these samples. Gradation curves for the samples tested are included in the Boring section of Appendix B.

Dry Unit Weight and Moisture Content Dry unit weight tests were performed on 6 samples retrieved from Borings AB DH-4 and 6. The dry density ranged from 103 to 118 pcf (ave. 111 pcf). Dry unit weight

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 26 tests were also performed on 14 samples from Boring AB DH-14, with the dry density ranging from 105.3 to 126.5 pcf (ave. 116 pcf).

The in-place moisture content was determined at 30 locations from the Afterbay borings in the Option 1 and 2 area with the moisture ranging from 0.1 to 23.5% (ave. 10.3%). The in-place moisture content was determined on 16 samples from the Option 3 and 4 area, with the moisture ranging from 5.4 to 19.8% (ave. 14%).

Soluble Salt Twenty-seven soluble salt tests were run on samples obtained from the borings. The results of the soluble salt tests are included on the boring logs and summarized in Table 1 of Appendix B. The soluble salt content ranged from 0.5 to 15.3% with an average of 9.1%.

Unconfined Compressive Strength and Unconsolidated Undrained Strength Eight UC and UU tests were performed on samples of the old alluvial clay/mudstone from Boring AB-14. The strength ranged from 120 to 380 psi (ave. 258 psi).

Point Load Tests Point load tests were performed on 6 samples of the clay/mudstone from Boring AB-

14, with the point load index Is(50) ranging from 2 to 23 (ave. 7.5).

Scoria/Vuggy, Gravelly Basalt Layer It will be noted from Figures 11 through 13 that a layer of scoria/vuggy gravelly basalt exists between the older alluvium and the Grass Valley Basalt Flow, on top of the Divide Flow Basalt and between the Grass Valley Basalt Flow and Navajo Sandstone. This layer exhibited very high permeability and, as stated previously, air was reported sucking down the hole at some locations when the layer was encountered. At the boring locations, the thickness of this layer ranged from 5 to 20 feet.

The results of permeability tests are shown on the boring logs. Sixteen tests were performed in this layer with the results ranging from 137 to 10,875 ft/yr (ave. 3883 ft/yr).

Grass Valley Basalt Flow The Grass Valley Basalt Flow dips from west to east toward the Hurricane Fault. As shown in Figure 11, the flow is about 60 to 90 feet thick at the alignment for the South Dam of Options 1 and 2. On the west side of the basin, the top of the flow was encountered at a depth of between 20 and 30 feet below the existing ground surface dipping to the east at a rate of about 8.5 degrees. Boring AB DH-04 encountered the

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 27 Basalt Flow at a depth of about 185 feet below the surface. Continuous coring was performed through the bedrock, and the percent recovery and rock quality designation (RQD) are shown on the boring logs and on Figures 11, 12 and 13. It will be observed that near 100% recovery was obtained during coring and that the RQD was typically greater than 70%, with occasional low RQD intervals. Photos of the core recovery are included in the Boring section of Appendix B.

Field permeability tests were performed at 10 foot intervals using wireline packer techniques as the borings were advanced. The horizontal permeability was measured typically varying the pressure from low to high to low. The results of the tests are included in Appendix B and summarized on the boring logs and Figures 11 through 13. The results of 24 tests ranged from 3 to 3746 ft/yr (ave. 1031 ft/yr). Water loss in the basalt flow is associated with joints and fractures. It will be noted that the borings were drilled vertically and may not have optimized intersection of joints.

The Divide Basalt Flow The Divide Basalt Flow was encountered in Boring AB DH-5 near the maximum section of Option 1 North Dam, as shown in Figure 12. This flow originates from the east and is located in only a portion of the study area. In the test boring, the flow was about 45 feet thick. The recovery varied from 48 to 100%, and the RQD ranged from 8 to 100% in the 5 foot intervals. The permeability ranged from 204 to 4621 ft/yr in the 5 intervals tested. Photos of the core recovery are included in the Boring section of Appendix B.

Navajo Sandstone Borings AB DH-1, 2, 3, 5, and 6 in the Option 1 and 2 area extended 3 to 24 feet into the Navajo Sandstone as shown on the boring logs and in Figures 11 through 13. The depth to Navajo Sandstone at these boring locations varied from 110 feet below the surface in Boring AB DH-2 to 245 feet below the surface in Boring AB DH-5.

Navajo Sandstone was encountered at a depth of 30 feet in Boring AB DH-8 and 58 feet in Boring AB DH-9 in the Option 3 area. The Navajo Sandstone was cored in AB DH-8 from 40 to 64 feet. The recovery ranged from 16 to 90%, with 0% RQD. The permeability ranged from 536 to 2323 ft/yr with an average of 1467 ft/yr.

Along the dam alignment for Option 4, Navajo Sandstone was encountered at a depth of about 8 feet in Boring AB DH-11, 9 feet in AB DH-12, and at the surface in AB DH-13. The recovery ranged from 0 to 100% (ave. 78%), with the RQD also varying from 0 to 100% (ave. 33%). The permeability ranged from 14 to 5665 ft/yr, with an average of 1840 ft/yr.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 28 Mechanical Analyses Mechanical analyses were completed on 25 samples of the sandstone from the borings in Option 4. It will be noted from Table 1 that these samples had 0 to 2% (ave. 0.1%) gravel size particles, 46 to 92% (ave. 76%) sand size, and 8 to 54% (ave. 24%) silt and clay size material. Gradation curves are included in Appendix B.

Dry Unit Weight and Moisture Content The in-place dry unit weight of 25 samples of the bedrock ranged from 111 to 135 pcf (ave. 126 pcf). The in-place moisture content ranged from 3.3 to 20.5% (ave. 8.3%).

Unconfined Compressive Strength Thirteen unconfined compressive strength tests were performed on samples of the sandstone obtained from Borings AB-11, 12, and 13. The unconfined compressive strength ranged from 670 to 3600 psi (ave. 1767 psi).

Point Load Tests Point load tests were performed on 19 samples of the sandstone, with the point load

index Is(50) ranging from 3 to 39 (ave. 12.4).

Lab Permeability Tests Constant head permeability tests were performed on 7 samples of the sandstone obtained from Borings AB-11, 12 and 13. The primary permeability ranged from 4.7 x 10-6 to 1.5 x 10-4 cm/sec. (ave. 4.6 x 10-5 cm/sec).

4. BENCH LAKE CLAY BORROW SOURCE

The Bench Lake clay borrow was used as the source for the impervious clay core during construction of the Sand Hollow Reservoir. Approximately 520,000 cu yd was obtained from this site, and testing during construction resulted in the following average parameters:

NO. OF TEST TESTS RANGE AVERAGE PERFORMED Liquid Limit 159 28 to 42 33 Plastic Index 159 11 to 25 15 Soluble Salts 121 0.3 to 8.8% 3.6% Dispersive Clay 118 ND1-83, ND2-28, ND3-7 Max. Dry Density 31 102 to 114.5 pcf 111.8 pcf Optimum Moisture 31 16 to 21.5% 18.2%

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 29 Strength tests performed on this material resulted in an effective friction angle of 30 degrees with 200 psf cohesion used in design.

During this study, three additional borings were drilled in the borrow source to evaluate the quantity and quality of the remaining material. The location of the borrow source is shown on the vicinity map in Figure 1, and the boring locations are shown on the site plan in Fig. 8.

The boring logs and summary for tests performed during this study are included in Appendix C. It will be noted that lean clay extended to a depth of 50 feet in Boring 1, 30 feet in Boring 2, and 108 feet in Boring 3. Laboratory tests performed to define the characteristics of this material included (1) Atterberg Limits, (2) mechanical analysis, (2) dry unit weight, (3) moisture content, and (4) soluble salt tests. The results are discussed below as follows:

Atterberg Limits Atterberg limit tests were performed on 17 samples retrieved from the borings. The liquid limit ranged from 26 to 43 (ave. 35), and the plastic index ranged from 9 to 24 (ave. 19).

Mechanical Analyses Mechanical analyses were performed on the 17 samples. The sand ranged from 1 to 35% (ave. 12.4%), and silt/clay 65 to 99% (ave. 88%).

Dry Unit Weight and Moisture Content Dry unit weight and moisture content tests were performed on 16 samples retrieved from the borings. The dry density ranged from 94 to 119 pcf (ave. 108 pcf), and the in-place moisture content ranged from 11 to 24% (ave. 16%).

Soluble Salt Eighteen soluble salt tests were run on samples obtained from the borings. The soluble salt content ranged from 1.2 to 9.1% with an average of 3.4%.

Dispersive Clay Dispersive clay tests were performed on 18 samples from the borings Four of the samples classified as Non-Dispersive (ND-1), one as Non-Dispersie (ND-2), and thirteen as slightly to moderately dispersive (ND-3).

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 30 IV. ENGINEERING DESIGN CONSIDERATIONS AND RECOMMENDATIONS

1. FOREBAY

Based upon results of the field investigations, it is recommended that the maximum high water level in the Forebay not exceed elevation 4713 feet. This is the approximate elevation of the bottom of the basalt flow at the north end of the proposed reservoir basin. Two options have been considered for the South Dam location. Area and capacity curves/tables are shown in Tables 1 and 2.

Option 1 is located 1500 feet north of Option 2 as shown in Figures 3 and 4. A reservoir with the South Dam placed at this location would result in about 4,068 acre feet of storage, which provides about 3500 acre feet of storage and 500 acre feet of dead pool for the proposed pump storage project, assuming an inlet at about elevation 3687 feet. The South Dam would have a maximum height of 65 feet and the North Dam about 35 feet. A small channel would be required, about 13 feet deep, through the high area of the basin to achieve the 3687 ft. elevation.

A reservoir with the South Dam placed at Option 2 would result in 11,760 acre feet of storage. To maintain access to all but about 500 acre feet of the storage requires a deep channel excavated to about elevation 3640 feet as shown in Figure 9. It will be noted that a storage capacity of about 7600 acre feet can be achieved without constructing the North Dam.

The Hurricane Cliffs are located about 2500 feet west of the reservoir basin. The easterly edge of the green hatched area in Figure 4 represents the approximate contact of the Lower Red Member of the Moenkopi Formation with the Timpoweap Member of the Moenkopi Formation. The bedding dips down in an easterly direction, away from the Hurricane Cliffs, at about 5 degrees. The channel has been positioned with the objective of maintaining the cut in the low permeability Lower Red Member. The Timpoweap Member has layers of mudstone, limestone, siltstone and conglomerate with varying permeability. Several zones were encountered with rates greater than 1,000 ft/yr. Some transitional (Lower Red and Timpoweap) areas of mudstone exist within the green-hatched area (see Figure 2), which will reduce seepage from the basin. The Rock Canyon Conglomerate Member of the Moenkopi Formation underlies the Timpoweap Member. Borings extending into this member also had several intervals with permeability rates in excess of 1,000 ft/yr. As shown on Figure 10a, this member exits at the face of the Hurricane Cliffs. It will be noted that at least 3 faults have been mapped between the proposed reservoir and the cliff face. These faults will likely interrupt seepage flow from the basin.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 31 Additional studies will be required during final design to better address the potential of water seeping from the reservoir and exiting at the face of the Hurricane Cliffs. For this study, it has been assumed that a connection will exist and it is recommended, therefore, that the westerly side of the reservoir be lined with an impervious membrane.

Foundation Treatment

The following foundation treatment has been considered:

x Excavate the entire dam embankment footprints to weathered mudstone or limestone bedrock. x Extend the cutoff trench about 5 feet into competent bedrock. It is expected that the depth of the cutoff trench will vary from about 5 to 25 feet. x Install a grout curtain to an estimated depth of about 75 feet for the Option 1 South Dam, 100 feet for the Option 2 South Dam and 50 feet for the North Dam. The grout curtain for the South Dam will extend east of the maximum section until the thickness of the Lower Red Member is at least 50 feet. x Install a 30 inch continuous slot cutoff extending about 20 feet into the bedrock at the base of the cutoff trench. The purpose of the continuous slot is to provide a positive cutoff through the near surface zone which may have gypsum stringers and lenses susceptible to erosion. x Install a downstream blanket filter and drain at the foundation contact, with a drain at the downstream toe.

Embankments

Option 1 North and South Dams The proposed embankment sections for the Option 1 North and South Dams are shown in Figures 14 and 15. The recommended section includes a clay core with upstream and downstream rockfill sections. The zones are discussed below:

Zone I and IA Limited testing of the alluvium and weathered mudstone in the reservoir basin show the material to classify predominately as CL-ML type soil with an average Plasticity Index of 6. The samples tested had an average of 7.8% soluble salts. For the preliminary design, we have considered using a 10 ft. wide Zone I membrane constructed of lean clay obtained from the Bench Lake Borrow Source, with an upstream core of Zone IA constructed of silty clay obtained from the reservoir

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 32 basin. The Bench Lake Borrow Source is about 17 miles from the site. It is recommended that additional borrow studies be performed to determine if closer sources of acceptable material exist. The Frog Hollow basin is a potential source.

Zone II and III A 5 foot wide sand filter and 4 foot wide gravel drain have been placed behind the Zone I clay. These zones will have similar gradation and quality requirements of concrete sand and aggregate. For this study, it has been assumed that the processed filter and drain material will come from a local commercial aggregate source.

Zone IV, IVA, and IVB The upstream and downstream basalt rockfill zones include a 6 inch minus processed transition zone (Zone IVA) adjacent to the upstream clay core and downstream drain, followed by 24 inch minus rockfill (Zone IV), with an outer zone of 36 inch minus rockfill (Zone IVB). It is anticipated that the rockfill will be quarried from the surface basalt rock that bounds the north and northeast side of the reservoir basin.

Embankment side slopes of 2 horizontal to 1 vertical have been used for preliminary design. These slopes are considered conservative and may be steepened during final design.

Option 2 North and South Dams The proposed embankment sections for the Option 2 North and South Dams are shown in Figures 16 and 17. The recommended section includes a clay core with upstream and downstream earthfill sections. A deep channel excavation will be required for the pump storage project if the South Dam alignment is used to maximize storage in the Forebay. This excavation will result in over 2 million cubic yards of alluvium, weathered mudstone and mudstone. For this option, it has been assumed that the excavated material will be processed and used to construct the embankments. The zones are discussed below:

Zone I For the preliminary design, we have considered using a Zone I central core constructed of lean clay obtained from the Bench Lake Borrow Source. The Bench Lake Borrow Source is about 17 miles from the site. It is recommended that additional borrow studies be performed to determine if closer sources of acceptable material exist. The Frog Hollow basin is a potential source.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 33 Zone II and III A 5 foot wide sand filter and 4 foot wide gravel drain have been placed behind the Zone I clay. These zones will have similar gradation and quality requirements of concrete sand and aggregate. For this study, it has been assumed that the processed filter and drain material will come from a local commercial aggregate source.

Zone IV Zone IV will consist of earthfill from the required channel excavation and reservoir basin. It is anticipated that the Lower Red Member mudstone will require processing, including pulverizing, for use in the embankment.

Riprap and Bedding Protection of the upstream slope against wave action and erosion will be required. It is anticipated that a 2 foot thick layer of rock riprap (perpendicular to the slope), underlain by 1 foot of sandy gravel bedding will be required to protect the slope. Rock for use as riprap can be quarried from the Basalt Borrow Source.

Option 3 South Dam This option considers constructing the South Dam to an initial elevation of about 4690 feet, sufficient to provide about 4000 acre feet of storage for the pump storage project, with the option of raising the dam in the future. We have considered a central core rockfill section similar to Option 1 for this option.

Waterway Channel We have assumed a channel with side slopes of 3 horizontal to 1 vertical and a 50 foot bottom width. To protect the slopes from erosion, we have assumed that the channel will be lined with 1 foot of sandy gravel and 2 feet of riprap size rock. A profile and section views of the channel are shown in Figure 18.

Outlet Works We have assumed that an outlet works will be required for emergency draining of the reservoir. This outlet may be incorporated into the pump storage waterway or include a low level outlet near the maximum section of the South Dam.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 34 Spillway Since the proposed reservoir is an off stream site, spillway requirements to pass the PMF are not anticipated to be large. It is anticipated that a spillway can be efficiently constructed around the west abutment of the South Dam.

Instrumentation The final design should include survey monuments at about 200 foot centers along the embankment crest of each dam and piezometer banks at select locations.

2. AFTERBAY

Four reservoir site options have been considered for the Afterbay of the Pump Storage Project. Area and capacity curves/tables are shown in Tables 3 through 6 for the options.

Options 1 and 2 appear to provide the most efficient waterway alignment from the Forebay to Sandhollow Reservoir. These sites, however, have the most complex geology and are considered by us to be the least desirable locations for the Afterbay reservoir, with the greatest risk of poor performance. Outlet works, spillway and instrumentation recommendations for the Afterbay sites are similar to the Forebay sites. Each of the Afterbay sites is discussed below as follows:

Option 1 and 2 The South Dam location is the same for both Option 1 and 2. To achieve the assumed active storage capacity of 3,500 acre feet requires the South Dam and Option 1 North Dam to be about 100 feet high and the South Dam and Option 2 North Dam to be about 75 and 65 feet high, respectively. The same foundation treatment and embankment sections have been assumed for the North and South Dams for both options. Due to the permeability of the Younger Alluvium, it is recommended that the reservoir basin be lined to reduce seepage from the basin. Lining the reservoir will also reduce the risk of differential settlement of the embankments due to the relatively high soluble salt content (~10%) in the alluvial materials.

Foundation Treatment

The following foundation treatment has been considered:

x Referencing the generalized geologic section in Figure 11, we recommend that the entire embankment footprint to stripped to the Grass Valley Basalt bedrock on the west side of the valley, extending east until the depth to

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 35 bedrock exceeds about 30 feet. This action will remove the abundant gypsum observed in the alluvial/basalt surface layer as well as the highly pervious scoria and vuggy basalt layer. x The basalt foundation upstream of centerline should be dental grouted to fill all joints and fractures. x A grout curtain is recommended, extending about 60 feet into the basalt bedrock. x It is recommended that the upper 10 feet of Younger Alluvium be stripped from beneath the entire embankment footprint across the valley floor and east side to remove the low density collapsible deposits observed in the test pits. x Following removal of the surface 10 feet, we recommend excavating a partial cutoff trench an additional 20 feet as shown in Figures 19 and 20. x It is recommended that a cement-bentonite slurry wall extend 60 feet below the excavated cutoff, into the alluvial deposits to force water away from the embankment foundation and reduce seepage. x We recommend that a 10-foot thick layer of lean clay be placed on the foundation upstream of the clay core to reduce the seepage entering the alluvial deposits. x Install a downstream blanket filter and drain at the foundation contact, with a drain at the downstream toe.

Embankment

The proposed embankment sections for Option 2 South and North Dams are shown in Figures 19 and 20. The recommended section includes a clay core with upstream and downstream earthfill sections. Preliminary stability analyses indicate that an upstream slope of 3.25 horizontal to 1 vertical will be required to accommodate the sudden drawdown condition. The downstream slope has been flattened to 3 horizontal to 1 vertical to increase the length of the drainage layer beneath the dam. The zones are discussed below:

Zone I The central core consists of lean clay obtained from the Bench Lake Borrow Source. Zone I will also line the upstream embankment foundation.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 36 Zone II and III A 5 foot wide sand filter and 5 foot wide gravel drain have been placed behind the Zone I clay. These zones will have similar gradation and quality requirements of concrete sand and aggregate. For this study, it has been assumed that the processed filter and drain material will come from a local commercial aggregate source. It will be noted on Figures 19 and 20 that 3 feet thick layers of filter and drain blanket the downstream embankment footprint. During final design, consideration should be given to widening the filter and drain zones where the embankment foundation transitions from a bedrock foundation to an alluvial foundation.

Zone IV Zone IV will consist of earthfill from the reservoir basin.

Riprap Protection of the upstream slope against wave action and erosion will be required. It is anticipated that a 2 foot thick layer of rock riprap (perpendicular to the slope), will be required to protect the slope. Rock for use as riprap can be quarried from the Basalt on the west side of the basin.

Option 3 This option requires a long embankment about 90 feet high to obtain an active storage of about 3,500 acre feet. The alignment was positioned to maintain the same floor elevations as Options 1 and 2. The alluvial deposits are shallower and located directly on Navajo Sandstone, without basalt flow interruptions. The foundation treatment and embankment section used for Options 1 and 2 have been used for Option 3. Although this site requires significantly more embankment material and hence, greater initial cost, it is considered, at this time, a better reservoir site than Options 1 and 2. Factors discouraging the use of this site include (1) its close proximity to the Hurricane Fault, (2) the possibility that the Warner Valley Fault crosses the proposed alignment, and (3) the rockfall hazard.

Like Options 1 and 2, it has been assumed that the reservoir basin would require lining for this option.

Option 4 It is our opinion that Option 4 represents the best reservoir site for the Afterbay. Navajo Sandstone bedrock is exposed across about 50% of the embankment footprint. The older alluvial deposits on the other half are less than 20 feet thick. To achieve 3,500 acre feet of active storage requires an embankment with a maximum height of about 100 feet. A

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 37 cutoff trench can be excavated into the Navajo Sandstone along the entire alignment. Blanketing of the reservoir basin is not required. Both earthfill and rockfill embankment sections are feasible for the site. Figure 22 represents an earthfill section.

It will be noted that we have assumed a grout curtain extending about 60 feet below the base of the cutoff trench and a continuous concrete filled slot extending about 10 feet below the cutoff trench. The embankment would include a central clay core (Zone I), constructed using clay from the Bench Lake Borrow Source. Filter and Drain material (Zones II and III) have been assumed to come from a commercial aggregate source. Zone IV for the earthfill dam would be excavated from the reservoir basin and area to the east, if needed.

While this site, in our opinion, is the best reservoir site, the feasibility of efficiently getting water from the Forebay to Sand Hollow requires further evaluation.

3. ESTIMATED QUANTITIES

The estimated quantities for all options are shown in the tables on the following pages:

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 38 FOREBAY, OPTION 1-SOUTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 30 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 36,400 Lin. Ft 4c Pressure Testing 1100 Hr. 4d Grout Hole Connections 550 Each 4e Placing Grout 72,800 Cu. Ft. 4f Cement 36,400 Bags 5 Excavation, Cutoff Trench, Rock 30,000 Cu. Yds. 6 Excavation Foundation, Common 92,500 Cu. Yds. 7 Rock Foundation Preparation 16,500 Sq. Yds. 8 Cutoff Slot Trench 2,600 Lin. Ft 9 Channel Excavation, Unclassified 77,000 Cu. Yds. 10 Earthfill, Zone I 49,200 Cu. Yds. 11 Earthfill, Zone IA 97,700 Cu. Yds. 12 Rockfill, Zone IV, IVA and Zone IVB 440,100 Cu. Yds. 13 Sand Filter, Zone II 28,500 Cu. Yds. 14 Sand and Gravel Drain, Zone III 12,800 Cu. Yds. 15 Reservoir Lining 62 Acres 16 Spillway 1 Lump Sum 17 Outlet Works 1 Lump Sum 18 Instrumentation 1 Lump Sum

Assumptions 1 Storage -4068 ac. Ft. 2 Earth-Rockfill Structure 3 West side of reservoir will be lined 4 Channel Excavation will be earthfill

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 39 FOREBAY, OPTION 1-NORTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 5 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 8,000 Lin. Ft 4c Pressure Testing 400 Hr. 4d Grout Hole Connections 200 Each 4e Placing Grout 16,000 Cu. Ft. 4f Cement 8,000 Bags 5 Excavation, Cutoff Trench, Rock 10,000 Cu. Yds. 6 Excavation Foundation, Common 5,800 Cu. Yds. 7 Rock Foundation Preparation 2,500 Sq. Yds. 8 Cutoff Slot Trench 800 Lin. Ft 9 Earthfill, Zone I 7,800 Cu. Yds. 10 Earthfill, Zone IA 4,600 Cu. Yds. 11 Rockfill, Zone IV, IVA and Zone IVB 29,000 Cu. Yds. 12 Sand Filter, Zone II 3,300 Cu. Yds. 13 Sand and Gravel Drain, Zone III 1,400 Cu. Yds. 16 Instrumentation 1 Lump Sum

Assumptions 1 Storage -4068 ac. Ft. 2 Earth-Rockfill Structure 3 West side of reservoir will be lined

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 40 FOREBAY OPTION 2-SOUTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 25 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 45,000 Lin. Ft 4c Pressure Testing 1600 Hr. 4d Grout Hole Connections 800 Each 4e Placing Grout 90,000 Cu. Ft. 4f Cement 45,000 Bags 5 Excavation, Cutoff Trench, Rock 30,000 Cu. Yds. 6 Excavation Foundation, Common 180,700 Cu. Yds. 7 Rock Foundation Preparation 22,300 Sq. Yds. 8 Cutoff Slot Trench 2,400 Lin. Ft 9 Channel Excavation, Unclassified 2,309,000 Cu. Yds. 10 Earthfill, Zone I 200,800 Cu. Yds. 11 Earthfill, Zone IV 1,507,000 Cu. Yds. 12 Sand Filter, Zone II 46,000 Cu. Yds. 13 Sand and Gravel Drain, Zone III 43,500 Cu. Yds. 14 Riprap and Bedding 53,000 Cu. Yds. 15 Reservoir Lining 114 Acres 16 Channel Lining 190,000 Cu. Yds. 17 Spillway 1 Lump Sum 18 Outlet Works 1 Lump Sum 19 Instrumentation 1 Lump Sum

Assumptions 1 Storage -11,760 ac. Ft. 2 Earth-Rockfill Structure 3 West side of reservoir will be lined 4 Deep Channel Excavation

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 41 FOREBAY OPTION 2-NORTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 25 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 8,000 Lin. Ft 4c Pressure Testing 400 Hr. 4d Grout Hole Connections 200 Each 4e Placing Grout 16,000 Cu. Ft. 4f Cement 8,000 Bags 5 Excavation, Cutoff Trench, Rock 10,000 Cu. Yds. 6 Excavation Foundation, Common 8,000 Cu. Yds. 7 Rock Foundation Preparation 22,300 Sq. Yds. 8 Cutoff Slot Trench 800 Lin. Ft 9 Earthfill, Zone I 9,800 Cu. Yds. 11 Earthfill, Zone IV 35,200 Cu. Yds. 12 Sand Filter, Zone II 3,300 Cu. Yds. 13 Sand and Gravel Drain, Zone III 2,800 Cu. Yds. 14 Riprap and Bedding 3,700 Cu. Yds. 15 Instrumentation 1 Lump Sum

Assumptions 1 Storage -11,760 ac. Ft. 2 Earth-Rockfill Structure 3 West side of reservoir will be lined 4 Deep Channel Excavation

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 42 FOREBAY, OPTION 3-SOUTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 30 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 45,000 Lin. Ft 4c Pressure Testing 1600 Hr. 4d Grout Hole Connections 800 Each 4e Placing Grout 90,000 Cu. Ft. 4f Cement 45,000 Bags 5 Excavation, Cutoff Trench, Rock 30,000 Cu. Yds. 6 Excavation Foundation, Common 180,700 Cu. Yds. 7 Rock Foundation Preparation 22,300 Sq. Yds. 8 Cutoff Slot Trench 2,400 Lin. Ft 9 Earthfill, Zone I 97,300 Cu. Yds. 10 Earthfill, Zone IA 198,700 Cu. Yds. 11 Rockfill, Zone IV, IVA and Zone IVB 1,020,200 Cu. Yds. 12 Sand Filter, Zone II 36,500 Cu. Yds. 13 Sand and Gravel Drain, Zone III 15,400 Cu. Yds. 14 Reservoir Lining 62 Acres 14 Spillway 1 Lump Sum 15 Outlet Works 1 Lump Sum 16 Instrumentation 1 Lump Sum

This option uses earth-rockfill, building the dam to elev. 4690 ft. with footprint such that it can be raised to 4720 ft. later.

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 43 AFTERBAY, OPTION 1 SOUTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 42 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 12,250 Lin. Ft 4c Pressure Testing 500 Hr. 4d Grout Hole Connections 250 Each 4e Placing Grout 24,500 Cu. Ft. 4f Cement 12,250 Bags 5 Excavation, Foundation, Common 1,008,100 Cu. Yds. 6 Cement-Bentonite Cutoff Wall 1,200 Lin. Ft 7 Rock Foundation Preparation 35,700 Sq. Yds. 8 Earthfill, Zone I 511,100 Cu. Yds. 9 Earthfill, Zone IV 1,432,500 Cu. Yds. 10 Sand Filter, Zone II 95,600 Cu. Yds. 11 Sand and Gravel Drain, Zone III 91,700 Cu. Yds. 12 Riprap 43,500 Cu. Yds. 13 Reservoir Liner 32 Acres 14 Spillway 1 Lump Sum 15 Outlet Works 1 Lump Sum 16 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 44 AFTERBAY, OPTION 1 NORTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 42 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 15,000 Lin. Ft 4c Pressure Testing 500 Hr. 4d Grout Hole Connections 250 Each 4e Placing Grout 30,000 Cu. Ft. 4f Cement 15,000 Bags 5 Excavation, Foundation, Common 975,600 Cu. Yds. 6 Cement-Bentonite Cutoff Wall 940 Lin. Ft 7 Rock Foundation Preparation 34,900 Sq. Yds. 8 Earthfill, Zone I 347,600 Cu. Yds. 9 Earthfill, Zone IV 971,800 Cu. Yds. 10 Sand Filter, Zone II 77,700 Cu. Yds. 11 Sand and Gravel Drain, Zone III 74,000 Cu. Yds. 12 Riprap 36,900 Cu. Yds. 13 Reservioir Liner 32 Acres 14 Outlet Works 1 Lump Sum 15 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 45 AFTERBAY, OPTION 2 SOUTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 70 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 9,600 Lin. Ft 4c Pressure Testing 320 Hr. 4d Grout Hole Connections 200 Each 4e Placing Grout 19,200 Cu. Ft. 4f Cement 9,600 Bags 5 Excavation, Foundation, Common 662,000 Cu. Yds. 6 Cement-Bentonite Cutoff Wall 962 Lin. Ft 7 Rock Foundation Preparation 22,000 Sq. Yds. 8 Earthfill, Zone I 255,200 Cu. Yds. 9 Earthfill, Zone IV 686,000 Cu. Yds. 10 Sand Filter, Zone II 59,000 Cu. Yds. 11 Sand and Gravel Drain, Zone III 56,400 Cu. Yds. 12 Riprap 26,600 Cu. Yds. 13 Reservoir Liner 59 Acres 14 Spillway 1 Lump Sum 15 Outlet Works 1 Lump Sum 16 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 46 AFTERBAY, OPTION 2 NORTH DAM ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 70 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 13,300 Lin. Ft 4c Pressure Testing 500 Hr. 4d Grout Hole Connections 250 Each 4e Placing Grout 26,600 Cu. Ft. 4f Cement 13,300 Bags 5 Excavation, Foundation, Common 900,500 Cu. Yds. 6 Cement-Bentonite Cutoff Wall 960 Lin. Ft 7 Rock Foundation Preparation 29,800 Sq. Yds. 8 Earthfill, Zone I 284,000 Cu. Yds. 9 Earthfill, Zone IV 688,000 Cu. Yds. 10 Sand Filter, Zone II 60,500 Cu. Yds. 11 Sand and Gravel Drain, Zone III 57,700 Cu. Yds. 12 Riprap 30,900 Cu. Yds. 13 Reservioir Liner 59 Acres 14 Outlet Works 1 Lump Sum 15 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 47 AFTERBAY, OPTION 3 ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 66 Acres 5 Excavation, Foundation, Common 1,300,000 Cu. Yds. 6 Cement-Bentonite Cutoff Wall 4,800 Lin. Ft 9 Earthfill, Zone I 934,400 Cu. Yds. 11 Earthfill, Zone IV 4,050,500 Cu. Yds. 12 Sand Filter, Zone II 73,700 Cu. Yds. 13 Sand and Gravel Drain, Zone III 69,800 Cu. Yds. 14 Riprap 71,800 Cu. Yds. 14 Reservoir Liner 57 Acres 15 Outlet Works 1 Lump Sum 16 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 48 AFTERBAY, OPTION 4 ESTIMATED QUANTITIES Bid Item No. Item Quantity Unit 1 Mobilization and Demobilization 1 Lump Sum 2 Clearing and Grubbing and Stripping 25 Acres 4a Grout Mobilization and Demobilization 1 Lump Sum 4b Drilling Rock 45,000 Lin. Ft 4c Pressure Testing 1600 Hr. 4d Grout Hole Connections 800 Each 4e Placing Grout 90,000 Cu. Ft. 4f Cement 45,000 Bags 5 Excavation, Cutoff Trench, Rock 18,500 Cu. Yds. 6 Excavation Foundation, Common 36,400 Cu. Yds. 7 Rock Foundation Preparation 22,300 Sq. Yds. 8 Cutoff Slot Trench 3,700 Lin. Ft 9 Earthfill, Zone I 304,700 Cu. Yds. 11 Earthfill, Zone IV 969,400 Cu. Yds. 12 Sand Filter, Zone II 56,400 Cu. Yds. 13 Sand and Gravel Drain, Zone III 59,900 Cu. Yds. 14 Riprap 43,000 Cu. Yds. 15 Spillway 1 Lump Sum 16 Outlet Works 1 Lump Sum 17 Instrumentation 1 Lump Sum

RB&G ENGINEERING, INC. H:\DAMS\HurricaneCliffsReservoirSites\REPORTS\report.03-10.doc Provo, Utah Page 49 REFERENCES

Arabasz, W.J., and Smith, R.B., 1981, Earthquake prediction in the Intermountain seismic belt - An intraplate extensional regime, in Earthquake prediction - an international review: American Geophysical Union, Maurice Ewing Series, v. 4, p. 248-258.

Biek, R.F-2003, Geologic map of the Hurricane quadrangle, Washington County, Utah: Utah Geological Survey Map 187, 61 p., scale 1:24,000.

Biek, R.F., Rowley,P.D., Hacker, D.B., Hayden, J.M., Willis,G.C., Hintze, L.F., Anderson, R.E., and Brown, K.D., 2007, Interim geologic map of the St. George 30’ x 60’ quadrangle and the east part of the Clover Mountains 30’ x 60’ quadrangle, Washington and Iron Counties, Utah: Utah Geologic Survey map OFR-478, 70 p., 2 plates, 1:100,000.

Cook, E.F., 1957, Geology of the Pine Valley Mountains, Utah: Utah Geological and Mineral Survey Bulletin 58, 111 p.

Cook, E.F., 1960, Geologic atlas of Utah - Washington County, Utah: Utah Geological and Mineralogical Survey Bulletin 70, 119 p, scale l:125,000.

Hayden, J.M., 2004, Geologic map of The Divide quadrangle, Washington County, Utah: Utah Geological Survey Map 197, 32 p., 2 plates, scale 1:24,000.

Lund, R.W., Knudsen, T.R., Vice, G.S., Shaw, L.M., 2008, Geologic hazards and adverse construction conditions St. George – Hurricane metropolitan area, Washington County, Utah: Utah Geologic Survey, Special Study 127, 105 p.

Stokes, W.L., 1988, Geology of Utah, Utah Museum of Natural History, University of Utah.

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