W912QR25R0016_CERT_Final_Vol5_TunnelGBR_MainReport-0000.pdf

Solicitation For Rough River Dam Safety Modification Project Phase II - New Outlet Works and Cutoff Wall, Rough River Reservoir, Falls of Rough, KY

P2: 145870

Design-Bid-Build

Tunnel Geotechnical Baseline Report (GBR) Main Report

Certified Final

20 December 2024

W912QR25R0016

ARIMS: 1200

Disposition: Permanent

W912QR25R0016_CERT_Final_Vol5_TunnelGBR_MainReport-0000

Rough River Dam

Geotechnical Baseline Report for Tunnel Construction

CUI

Rough River Dam (KY03012)

Geotechnical Baseline Report for Tunnel Construction

ROUGH RIVER, FALLS OF ROUGH, KY

LOUISVILLE DISTRICT, LRD DIVISION

Report Status: Certified Final, February 2022

Controlled by: U.S. Army Corps of Engineers Controlled by: CELRL-EDT-D Limited Dissemination Control: FEDCON POC: John Baird, LRL, 502-315-6483 i ii

TABLE OF CONTENTS

1 Introduction ...................................................................................................................................... 1-1

1.1 Description and Purpose of GBR ........................................................................................... 1-1

1.2 Relation to Contract Documents ............................................................................................ 1-1

1.3 Organization of Report ........................................................................................................... 1-2

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

2.1 Project Location ...................................................................................................................... 2-3

2.2 Existing Project Layout ........................................................................................................... 2-3

2.3 New Tunnel Summary ............................................................................................................ 2-3

3 Geologic Setting .............................................................................................................................. 3-5

3.1 Regional Geology ................................................................................................................... 3-5

3.2 Subsurface Investigations ...................................................................................................... 3-5

3.3 Site Geology ........................................................................................................................... 3-5

4 Characterization and behavior of Engineering Geologic Units ..................................................... 4-12

4.1 Rock Characterization .......................................................................................................... 4-12

4.2 Ground Behavior .................................................................................................................. 4-20

5 Construction Considerations ......................................................................................................... 5-23

5.1 Anticipated Obstructions....................................................................................................... 5-23

5.2 Downstream Portal ............................................................................................................... 5-24

5.3 Upstream Portal .................................................................................................................... 5-25

5.4 Tunnel Conduit ..................................................................................................................... 5-25

5.5 Muck Handling and Disposal ................................................................................................ 5-26

5.6 Instrumentation Monitoring ................................................................................................... 5-26

6 References .................................................................................................................................... 6-27

APPENDIX

Appendix A ........................................................................................................................................ A-1

LIST OF FIGURES

Figure 4-1: Frequency distribution of unit weight in the Big Clifty sandstone unit. .......................... 4-12

Figure 4-2: Frequency distribution of compressive tests in the Big Clifty sandstone unit. ............... 4-13

Figure 4-3: Frequency distribution of Young’s Moduli in the Big Clifty sandstone unit. ................... 4-14

Figure 4-4: Frequency distribution of Poisson’s Ratio in the Big Clifty sandstone unit. ................... 4-15

Figure 4-5: Frequency distribution of splitting tensile tests in the Big Clifty sandstone unit. ........... 4-16

Figure 4-6: Frequency distribution of CAI in the Big Clifty sandstone unit. ...................................... 4-17 iii

Figure 4-7: Direct shear test results from the Big Clifty sandstone unit. .......................................... 4-18

Figure 4-8: Frequency distribution of anchor bond strength in the Big Clifty sandstone unit. ......... 4-19

Figure 4-9: Frequency distribution of RQD in the Big Clifty Sandstone unit. ................................... 4-20

LIST OF TABLES

Table 2-1: Key Existing Project Elevations ......................................................................................... 2-3

Table 2-2: Key Tunnel/Portal Elevations ............................................................................................ 2-4

Table 3-1: Typical Rock Joint Orientations ......................................................................................... 3-9

Table 4-1: Numerical distribution of representative unit weight data in the Big Clifty sandstone unit

(outliers removed). ............................................................................................................................ 4-12

Table 4-2: Numerical distribution of representative compression data in the Big Clifty sandstone unit

(outlier removed). .............................................................................................................................. 4-13

Table 4-3: Numerical distribution of representative Young’s Moduli data in the Big Clifty sandstone unit (outliers removed). ..................................................................................................................... 4-14

Table 4-4: Numerical distribution of representative Poisson’s Ratio data in the Big Clifty sandstone unit (outlier removed). ....................................................................................................................... 4-15

Table 4-5: Numerical distribution of representative tensile strength data in the Big Clifty sandstone unit. .................................................................................................................................................... 4-16

Table 4-6: Numerical distribution of representative CAI data in the Big Clifty sandstone unit (outlier removed). .......................................................................................................................................... 4-17

Table 4-7: Numerical distribution of representative friction angle (ɸ) in the Big Clifty sandstone unit.4-

Table 4-8: Numerical distribution of representative anchor bond strength data in the Big Clifty sandstone unit (outlier removed). ..................................................................................................... 4-19

Table 4-9: Numerical distribution of RQD data in the Big Clifty sandstone unit. .............................. 4-20

Table 4-10: Groundwater Inflow along Tunnel Length ..................................................................... 4-22

Table 4-11: Site Class C Peak Horizontal Ground Acceleration Summary (New Outlet Works) (USGS

2014) ................................................................................................................................................. 4-22

Table 5-1: Boreholes Encountered Along Tunnel Alignment ........................................................... 5-24

Table 5-2: 28-Day Grout Mix Strengths ............................................................................................ 5-24

LIST OF ACRONYMS AND INITIALISMS

ASCE .............................................................................................. American Society of Civil Engineers

ASTM ................................................................................. American Society for Testing and Meterials

CAI ................................................................................................................... Cerchar Abrasivity Index

COE ............................................................................................................................ Core of Engineers

GBR .......................................................................................................... Geotechnical Baseline Report

GDR ............................................................................................................... Geotechnical Data Report

GIR ...................................................................................................... Goetechnical Interpretive Report

NAVD ..................................................................................................... North American Vertical Datum iv

NGVD .................................................................................................... Nation Geodetic Vertical Datum

RMR ........................................................................................................................... Rock Mass Rating

RQD ................................................................................................................ Rock Quality Designation

RSR ...................................................................................................................... Rock Structure Rating

Mh ........................................................................................................................ Hardinsburg Sanstone

Mgh ............................................................................................................................. Haney Limestone

Mgb ........................................................................................................... Big Clifty Sandstone Member

Mgb (sh-u) ..................................................................................................... Upper Big Clifty Shale Bed

Mgb (ss) ...........................................................................................................Big Clifty Sandstone Bed

Mgb (int) ........................................................................................................ Big Clifty Interbedded Bed

Mgb (sh-l) ...................................................................................................... Lower Big Clifty Shale bed

Mgc .................................................................................................................... Beech Creek Limestone

El ........................................................................................................................................ Elwren Shale

Mr ........................................................................................................................... Reelsville Limestone

Ms .............................................................................................................................. Sample Sandstone

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1 INTRODUCTION

1.1 Description and Purpose of GBR

This Geotechnical Baseline Report (GBR) summarizes the geotechnical basis for construction of the Rough River Dam New Left Abutment Tunnel. The GBR was developed using tunnel specific investigations, data, and the supporting documentation contained within the Tunnel Geotechnical Data Report (GDR).

This Tunnel GBR provides information relevant to subsurface conditions, referred to as the baseline conditions. The purpose of the Tunnel GBR is to:

• Set baselines for geotechnical conditions and material behavior expected to be encountered during construction associated with the conduit tunnel excavation.

• Identify important construction considerations, key project constraints, and selected requirements to be addressed by the Contractors during bid preparations and construction after award.

• Establish the basis for the evaluation of claims and resolution of differing site conditions.

The contractual baselines do not represent warranties by the Government of the actual subsurface conditions that will be encountered by the Contractor. Rather, the purpose of the baseline is to translate the results of past geotechnical investigations and analysis, laboratory testing, various construction activities, project performance, and technical interpretation of subsurface data into clear descriptions of subsurface conditions to provide a basis for bidding purposes.

The Tunnel GBR is based upon several assumptions regarding the sequence of construction, the means and methods, and workmanship to be employed by the Contractor. The anticipated behavior of subsurface materials as described herein will be influenced by the means and methods proposed by the Contractor and accepted by the Government during construction; and therefore, behavior may vary from that described in this report. The Contractor must evaluate the soil, rock, and groundwater conditions described herein as they relate to, and interact with, the means and methods selected by the Contractor for construction. The contractor will employ construction methods consistent with and conforming to the specifications, contract drawings, and this document.

Any means and methods proposed by the Contractor where the Contractor believes the baseline becomes invalid or requires modification must be raised and discussed during the bid phase prior to the bid opening. The Contractor has the duty to inform the Government of the baselines the Contractor believes are invalid or require modification during the bid phase.

1.2 Relation to Contract Documents

The Tunnel GBR is provided as a Contract Document in Volume 5 of the technical package. This Tunnel GBR references the Tunnel GDR, representing information obtained through multiple rounds of field investigations, instrumentation installations, and investigative grouting activities conducted on the Rough River Dam left abutment. Also, included as part of the Tunnel GDR are the results of laboratory testing performed on soil and rock samples collected during various rounds of investigation, including the detailed descriptions of field and laboratory testing data and methods.

Boring logs, and summary tables of laboratory test results and histograms depicting the distribution of various laboratory testing data are presented in the Tunnel GDR. The Tunnel GDR is a contractual document included in Volume 5 of the technical package. Additional project history and investigation for the entire Rough River Dam Project are included in the Geotechnical Interpretive

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Report (GIR) provided FOR INFORMATION ONLY in Volume 6 of the technical package. The Project Scope of Work is included in SPECIFICATION 01 11 00 SUMMARY OF WORK. Refer to the Contract Drawings for specific alignment, location, and details associated with the project. If there are any inconsistencies between the Tunnel GBR and the Tunnel GDR, the Tunnel GBR shall take precedence.

The Tunnel GBR is not intended to present the minimum required design and standards of construction contained in the Plans and Specifications. Nothing in the GBR should be construed as amending or altering the Plans and Specifications or applicable FAR clauses or relaxing the standards of construction. Plans and specifications shall take precedent over the Tunnel GBR and Tunnel GDR.

The technical concepts, terms, and descriptions in this report follow standards commonly used in geotechnical engineering/engineering geology which have specific meaning pertaining to the work.

Bidders should have a qualified geotechnical engineer or qualified engineering geologist carefully review this Tunnel GBR so that a complete understanding of the information presented in this report is developed prior to submitting a bid.

1.3 Organization of Report

This document broadly follows the principles contained in the ASCE document entitled “Geotechnical Baseline Reports for Construction – Suggested Guidelines”, dated 2007 and is comprised of an Introduction (Section 1.0) and the following five sections, as detailed below:

• Section 2.0 (Project Description) presents descriptions about the project locations, purpose, and components.

• Section 3.0 (Geologic Setting) summarizes the field investigations and geologic units in the area of the tunnel.

• Section 4.0 (Characterization and Behavior of the Engineering Geologic Units) presents the characterization and behavior of the material types present along the project alignment, including the behavior of the different engineering units classified on the project.

• Section 5.0 (Construction Considerations) presents the Tunnel and Portals construction considerations.

• Section 6.0 (References).

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2 PROJECT DESCRIPTION

2.1 Project Location

Rough River Dam is located in Kentucky on the Rough River, 89.3 miles above its confluence with the Green River. The project is in south-central Kentucky, approximately 60 miles southwest of Louisville, approximately 30 miles west of Elizabethtown, Kentucky and approximately 20 miles northwest of Leitchfield, Kentucky. A location map is provided in the appendix (Figure A-1).

2.2 Existing Project Layout

Currently, the Rough River Dam is comprised of an earthen dam, right abutment outlet works, and left abutment unlined open cut spillway (Figure A-2). The dam consists of homogeneous impervious earth fill with a downstream rock toe, dumped riprap stone protection on the upstream face, and a crest elevation (top of parapet wall) of elevation 559 ft-NGVD29 and a crest road elevation of 555.5 ft-NGVD29. The outlet works consists of a control tower discharging to a 12- by 12-foot, semi-elliptical concrete conduit that leads to the stilling basin. The outlet works has a service gate discharge capacity of 5,580 cubic feet per second (cfs) at a flood pool elevation of 524 ft-NGVD29.

The open cut spillway located in the left abutment is founded in rock and has a design capacity of 22,000 cfs. The maximum cut depth is about 45 feet with an excavation width of 65 feet. The length of the spillway is about 1,800 feet with a 6-foot-wide concrete sill for grade protection of the spillway crest at elevation 524 ft-NGVD29. Key existing project elevations are included in Table 2-1. Vertical datum in this report is COE Dam Datum (NGVD29). The conversion factor to NAVD88 is -0.43 ft.

Reservoir Summer and Winter pool elevations are standard elevations set forth by the Water Control Manual and will not deviate due to construction activities. For additional details on the construction and operational history of the existing project, refer to the GIR.

Table 2-1: Key Existing Project Elevations

Elevation

(NGVD29)

Winter Pool 470

Restricted Summer Pool 490

Spillway Crest 524

Dam Elevation 559

Pool of Record 527.4

2.3 New Tunnel Summary

A new tunnel conduit on the left abutment is one of the features within the Dam Safety Modification Phase 2: New Outlet Works and Cutoff Wall contract (Figure A-2). The major features of work in the Phase 2 contract consists of construction of a seepage cutoff wall, new intake tower, new conduit, and new stilling basin. The new outlet works will be constructed in the left dam abutment to the right of the emergency spillway to replace the existing conduit on the right abutment. This GBR applies solely to the tunnel feature of work between the upstream and downstream portals below the ground surface. Vertical excavation of the upstream portal face is associated with the tower excavation and detailed in Specification 31 23 05.00 06 MASS EXCAVATION and Specification 31 60 00.00 06 FOUNDATION PREPARATION. Vertical excavation of the downstream portal face is associated with the stilling basin excavation in Specification 31 23 05.00 06 MASS EXCAVATION and

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Specification 31 60 00.00 06 FOUNDATION PREPARATION. All horizontal excavation within the portals must be accomplished with mechanical methods. It describes the baseline geotechnical conditions and specified ground behavior to be expected during tunnel excavation and construction.

This work will include but not be limited to tunnel and portal (upstream and downstream) rock excavation, disposal, initial support, and final lining.

The upstream portal connects the intake tower to the transition and tunnel conduit (Figure A-3). The upstream portal is located at Sta. 9+96.9. Stabilization of the rock slope above the portal face is associated with the intake tower feature of work and specified in 31 60 00.00 06 Foundation Preparation. The transition section is the portion of the tunnel that narrows from a 19-ft by 25.5-ft rectangular excavation at the tower/portal face to the 16-ft diameter tunnel excavation at Sta.

10+56.9. The rock tunnel will be approximately 1,000 feet long and lined with a 12-inch abrasion resistant reinforced concrete with an inside diameter of 14 feet (lined). The downstream portal connects the tunnel with the stilling basin. The downstream portal is located at Sta. 19+92.75.

Stabilization of the rock face above and surrounding the downstream portal face is associated with the stilling basin feature of work and specified in Section 31 68 13 Rock Slope Reinforcement and Section 31 71 16.00 06 Rock Tunneling Key elevations are provided in Table 2-2. Details of the tunnel and portal dimensions can be found in the contract plans.

The downstream portal will be the primary heading for the tunnel excavation. The tunnel and portals shall be excavated by mechanical methods only. Rock excavation using drill-and-blast techniques is prohibited. Excavations will require initial support. Minimum initial support requirements are described in Section 31 68 13 Rock Slope Reinforcement and Section 31 71 16.00 06 Rock Tunneling. Both portals will be stabilized by horizontal rock dowels and rock fence. The downstream portal will be constructed with permanent steel sets for rock support and will be integrally cast into the concrete liner and headwall upon tunnel completion.

Table 2-2: Key Tunnel/Portal Elevations

Feature Elevation

(NGVD29)

Upstream Cofferdam Protection 524

Downstream Sheet Pile Protection (Top) 453.5

US Portal Invert (Excavated) 437.5

US Portal Crown (Excavated) 456.5

DS Portal Invert (Excavated) 436.19

DS Portal Crown (Excavated) 453.19

The location and radius of the tunnel has been chosen to avoid areas of high grout takes experienced during installation of the grout curtain and to maximize the amount of cap rock above the Haney Limestone, avoid karstic limestone and to maximize the amount of cover above the tunnel crown (Figures, A-6 & A-7). Details of the tunnel alignment and dimensions can be found in the Volume 1 Plans. By placing the tunnel into the left abutment, it minimizes the amount of exposed limestone above it while maintaining a separation between the limestone and the tunnel crown of at least 1.5 times the width of the tunnel. The invert elevation of the tunnel was chosen to maximize the distance between it and the limestone unit below.

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3 GEOLOGIC SETTING

3.1 Regional Geology

Rough River Dam is located in the northwestern portion of the Mississippian Plateau in Kentucky.

The Rough River valley is a relatively narrow entrenchment cut into middle Mississippian age rocks that dip down to the southwest at a rate of about 85 feet per mile. The rocks of middle Mississippian age were deposited on a shallow-marine shelf across western and west-central Kentucky. The normal shelf deposition of skeletal carbonates was periodically interrupted by deposition of deltaic and littoral sandstones and shales which pro-graded from the north and northeast. The Rough Creek Graben and Rough Creek Fault, major regional tectonic features, are found approximately seven miles south of the dam. The Locust Hill Fault is located 1.5 miles southeast of the dam.

Neither of those distant faults are active and there are no documented faults at the dam site.

Additional description of the regional geology is provided in the GIR.

3.2 Subsurface Investigations

Several subsurface investigations have been performed at the dam site between 1941 to present day. All historical investigations, details, and testing across the entire dam site are included in the GIR FOR INFORMATION ONLY. Specific data and testing associated with the left abutment investigations are contained in the Tunnel GDR. This data was used to analyze the baseline conditions of the rock to be encountered during tunnel construction and includes the following investigations:

2019 Phase II Outlet Works Investigation – 1900 series borings

2018 Phase I Outlet Works Investigation – 1800 series borings

2016/2017 Phase 1B Drilling and Grouting

2012 Geotechnical Exploration, Geophysics, and Piezometer Installations – 1200 series borings

The Contractor’s Completion Report for the Phase 1B slurry control grouting conducted between 2015 and 2017 is available in Volume 6 of the Contract Package FOR INFORMATION ONLY. The Contractor’s Completion Report contains drilling production rates for soil, rock coring, percussion rock drilling, grout results, pressure tests, and difficulties encountered during construction. The USACE Foundation Completion Report for the 2016/2017 slurry control grouting is attached as an appendix to the GIR and is also included FOR INFORMATION ONLY. Boring Logs may be referenced in Volume 6: Phase 1B Boring Logs.

3.3 Site Geology

Materials at the site include dam embankment fill overlying residual soils, fluvial deposits, and sedimentary rock. Tunnel and portal excavation and construction will be performed entirely within one bedrock unit, the Big Clifty Sandstone (Mgb ss). Geologic units were described following EM 1110-1-2908 Rock Foundations.

3.3.1 Soil

In general, the soil stratigraphy on the left abutment consists of fill and residual soils. Overburden was left in place on the left abutment consisting of clay near the dam centerline and along the abutments and transitioning to clayey sand and sandy clay at the base of the abutments across the valley. The left upstream abutment was previously developed as a golf course and has random fill

3-6 composed of lean and plastic clay overlying native residual silty clays and lean clays. Overburden thickness encountered in borings ranges from 2.5 to 30 feet on the left abutment. Thicker soil deposits are also associated with infilling of karst solution features. Classification and properties of the left abutment soils are provided in the GIR.

3.3.2 Rock Units

The project is founded on the Chester Series which includes the Hardinsburg Sandstone, Golconda Formation (Haney Limestone, Big Clifty Sandstone, and Beech Creek Limestone), Elwren Shale, Reelsville Limestone and Sample Sandstone. The descriptions below focus on the rock unit to be encountered during tunnel excavation (Big Clifty Sandstone) and summarize karst susceptible units above (Haney Limestone) and below (Beech Creek Limestone) the tunnel. These two karst units are not expected to impact the tunnel construction. The Haney Limestone is approximately 30 feet (1.5 tunnel diameters) above the tunnel crown, and Beech Creek Limestone is approximately 25 feet below the tunnel invert. Both limestone units are hydraulically separated from the tunnel by at least 6 feet of shale and the Beech Creek is not expected to have developed mature karst below the tunnel due its significant distance below the rock surface. The full stratigraphic column is included in the appendix (Figure A-4 and Figure A-5) and a description of each rock unit at the site is provided in the GIR. For specific depths of geologic units in relation the excavation, refer the Volume 1 Plans.

Descriptions of the geologic units are as specified in EM 1110-1-2908 Rock Foundations.

Haney Limestone (Mgh)

The Haney Limestone is the unit directly above the Big Clifty Sandstone. The Haney Limestone Member is a hard, light gray cherty limestone with a fine to coarse crystalline texture. The member contains broken fossil particles, oölitic beds, and several stylolites. The bedding is very thin to thick bedded with some laminated beds. In many cases, the fossils fragments have been replaced by silica mineralization, so that when the limestone has been chemically weathered away, the fossil fragments stick out away from the remaining matrix. The member is also marked locally by horizons of ovoid chert nodules up to 0.4-foot-long. There are also very continuous chert beds which are approximately 0.1to 0.3 feet in thickness and found in the lower portion of the unit. The chert weathers to a whitish, pinkish, and light-gray color and creates angular fragments that are abundant in the red residuum. The basal part contains small pyrite nodules and abundant silicified fossils. The member is a ledge former in outcrops and ranges from 50 to 60 feet thick at the site.

Locally, this unit is highly karstic when it is exposed or near the surface. In areas that the unit is capped by the Hardinsburg Sandstone, karstic conditions are greatly reduced. Tunnel location and alignment was chosen specifically to maximize the amount of length that it is under both the Haney and the Hardinsburg formations. Solution features on the site have been discovered within this member and have been observed to be as large as 40 feet deep and 40 feet wide. (Figure A-6 and Figure A-7). These features were located during the installation of the grout curtain through the advancement of grout holes on 5 foot centers. The largest solution feature discovered to date is in an exposed section of the formation that is at the surface and not covered by the overlying unit.

More information regarding the Phase 1B grouting program can be found in the Volume 3 REF drawings for Phase 1B As-Builts. The tunnel alignment was chosen to maximize the distance from these features and is approximately 75 ft to the left and approximately 24 ft below them. The Haney Limestone is hydraulically separated from the unit below by the upper Big Clifty shale. As such it contains a perched water table that acts independently from surrounding units and only interacts with the reservoir during very high pools.

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Big Clifty Sandstone (Mgb)

The tunnel will be constructed entirely through the Big Clifty Sandstone member. The stratigraphy of the Big Clifty Sandstone member (Mgb) has been broken into four units, including the Upper Shale, Sandstone, Interbedded Sandstone and Shale, and the Lower Shale. Each of these units are described below. None of these units are karstic.

Upper Big Clifty Shale (Mgb sh-u)

The upper Big Clifty shale is dark gray to dark olive in color, is very fine to fine grained with a clayey to silty texture and is moderately hard to soft. This unit is slightly to moderately weathered in the left abutment, and once exposed this unit desiccates quickly making it slake readily. The Upper Shale ranges from 3-6 feet thick (Figure A-8). The fine grain and clayey fabric of this unit makes it an aquiclude to the limestone above, hydraulically separating the units.

Big Clifty Sandstone (Mgb ss)

The Big Clifty sandstone is light grey to light brown or orange in color. It is fine to coarse grained, thin to thick bedded, and moderately hard. The sandstone often contains cross-bed and ripple-mark structures (Figure A-9). There are occasional clayey shale beddings up to 1 foot thick that are similar in composition to the Upper Shale (Mgb sh-u). The shale bedding layers are discontinuous laterally, their depth varies vertically, and their frequency varies across the unit. The exact location and frequency of the seams are unknown. Refer to Specification 31 71 16.00 06 Rock Tunneling regarding the protection of shale seams from slaking and desiccation. The sandstone is a quartz arenite marked by carbonaceous material and iron staining due to a high iron content. Open fracture planes with manganese have been observed. The member is about 40 feet thick. The Big Clifty sandstone is not karstic. Within the bounds of the tunnel and portal excavation, the sandstone is un-weathered. When exposed to the elements this unit is susceptible to become “drummy”, oxidize and become darker orange or red in color, and weaken the matrix of the unit allowing pieces to break off.

The contact for the Big Clifty sandstone (Mgb ss) with the Big Clifty Interbedded (Mgb int) is transitional from sandstone to shale. The sandstone in the lower part of the Big Clifty sandstone (Mgb ss) can be either orange or white to light gray. Because of this, the contact is easily mistaken in the field when based in color. Differentiation with the interbedded unit should be based upon an increase in the number of shale beds as opposed to color.

Big Clifty Interbedded Sandstone and Shale (Mgb int)

The Big Clifty Interbedded Sandstone and Shale is a combination of black shale and white to light gray sandstone/siltstone and appears to be a transitional unit from both the overlying sandstone unit and underlying Lower Shale, making it more difficult to determine an upper/lower contact. The contact with the overlying sandstone unit is easily mistaken in the field when based on color.

Differentiation with the interbedded unit should be based upon an increase in the number of shale beds as opposed to color (Figure A-10). The unit is not always vertically continuous as it has been found to interfinger with the overlying sandstone unit. It is fine grained and thinly bedded, with soft sediment deformation and some siltstone. The siltstone is light yellowish-brown to light olive-gray and occurs as nodules and thin lenses in shale and sandstone. The shale lenses, when exposed, cause partings in the sandstone portions. The soft sediment deformation at the base of this unit affects the shale underlying unit and is responsible for slicken-sided surfaces. These slicken-sides appear to be localized to the soft sediment deformation effects and do not appear to be laterally continuous for large distances. The thickness of the interbedded unit ranges from 1 to 15 feet thick.

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The shale layers in this section are susceptible to desiccation and slaking when allowed to dry or allowed to go through cyclic wetting/drying.

Big Clifty Lower Shale (Mgb sh-l)

The Lower Big Clifty Shale is dark gray to dark olive in color and very fine to fine grained with a clayey texture (Figure A-11). Lenses of anhydrite up to ¼ inch in thickness and pyrite veins approximately ¼ inch in diameter have been observed in this unit. The upper 2 feet may be difficult to differentiate in the field as it does not have a conformable transition from the interbedded unit above due to soft sediment deformation. The shale contains limestone beds up to 8 inches thick towards the base. It was observed during drilling that the limestone beds contained pyrite nodules up to ¼ inch in diameter. This unit is also very susceptible to desiccation and slaking when allowed to dry or allowed to go through cyclic wetting/drying.

Beech Creek Limestone (Mgc)

The Beech Creek Limestone unit is directly below the Big Clifty Sandstone. The Beech Creek Limestone Member is a fine- to medium-grained hard limestone with a light to dark gray color. It has platy to thin beds and contains several stylolite seams throughout. A fossiliferous zone of brachiopod Inflatia is present in the upper 2 feet and is a stratigraphic marker. The member is a ledge former in outcrops and ranges from 10 to 12 feet thick beneath the dam.

Locally, this unit is highly karstic when it is exposed or near the surface. Conduits, ≥2.5in-3ft in diameter and >100ft long, are common and have been encountered on the right abutment where this unit is at the surface. When this unit is covered by the Big Clifty Lower Shale, karstic conditions are greatly reduced. The tunnel invert elevation was chosen to ensure cover over the Beech Creek Limestone. This unit will not be encountered during tunnel construction.

3.3.3 Rock Structure

Rock structure of the project is dictated by a regional dip direction of all formations, depositional bedding and formation contacts, joint orientations (where present), valley stress relief fractures, karstic solution features, and fracturing of overlying rocks due to dissolution of underlying rocks (destabilized fractures). The reader should refer to the GIR for more detailed descriptions of the aforementioned features.

The regional dip is approximately 2-3° towards the downstream left abutment (west). While there are known fault zones near the project, there are no known faults or shear zones within the localized footprint of the project area.

Some formations have consistent thicknesses and contacts across the project site. In general, the limestone and shale formations fall into such a category. However, there are some formations (as well as units within formations), due to their depositional environments, which can thicken and thin locally. These types of units usually have a reciprocal relationship with an adjacent unit, such that one will thicken as the adjacent unit thins. In general, the sandstone, shale, and interbedded units within the Big Clifty fall into this category.

Jointing occurs readily in the relatively “brittle” limestone formations, and manifest in predictable joint sets which are observable and measurable around the site. The Haney Limestone exhibits two vertical orthogonal sets (major and minor) and one horizontal set (bedding planes). The major vertical and near vertical joint sets are oriented at approximately 320° (N40°W) and 50° (N50°E).

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Typical bedding planes measured in both the Haney and Big Clifty Sandstone (Mgb) dip 10° (true) with a dip direction of 250°. Regular joint sets have not been observed or measured in the relatively more “ductile” sandstone and shale deposits; however, near vertical random joints are found in the Big Clifty Sandstone. Joints observed within the sandstone and shale formations appear to terminate within the units at bedding planes. The frequency and length of vertical joints within the sandstone and shale beds are unknown. Joints within the sandstone will be encountered but will not transverse into multiple units and are localized in the sandstone. Valley stress relief fractures/structures are more likely to be discovered on the downstream end, within the vicinity of the downstream portal. These fractures have been accounted for in the design of the downstream portal.

When observable, these sandstone and shale formations and units also show some inherent lithological fabric that was retained from deposition. Data and exploratory methods specific to the Big Clifty Sandstone can be found in the GDR section 2.1.4. The same random joint pattern was observed in the Big Clifty sandstone and shale units encountered during the construction of Patoka Dam, IN approximately 60 miles from Rough River Dam.

For baseline purposes, the Big Clifty Sandstone (Mgb ss) jointing consists of horizontal bedding joints with randomly spaced vertical joints. The horizontal bedding joints are spaced from <2 inches to up to 3 feet apart. The ranges of the rock jointing orientations are summarized in Table 3-1.

Table 3-1: Typical Rock Joint Orientations

Joint

Dip Angle Range

Dip Direction

Range

Units

Bedding 1-14 250 All

J1 70-90 240 Haney Limestone

J2 70-90 135 Haney Limestone

Random 71-80 random Big Clifty Sandstone

Valley stress fractures have been readily observed along both the upstream and downstream right abutment formations, in particular the Big Clifty Sandstone. These fractures are continuous for several hundred feet and can penetrate thick and massive beds as well as thinner bedded rippled beds of the sandstone lithologies. Valley stress fractures have not been observed in the left abutment. This was a factor in the decision to place the tunnel in the left abutment. Due to the shallower slope of the left abutment in relation to the right, the mechanisms needed to create these fractures, while still present, are reduced in intensity thus reducing the likelihood of the fractures being present. This reduction does not eliminate the possibility of valley stress relief fractures. They are more likely to occur in areas of the excavation with reduced overburden cover such as the downstream portal. This is a major consideration for the downstream portal design discussed in section 5.2.

3.3.4 Rock Weathering

The limestone formations are highly karstic and contain solution voids, solution widened joints and bedding planes, and cavernous openings near the ground surface. These features have been formed throughout the geologic history of the project site. These features occur along the joint structure orientation of the carbonate formations and also along horizons which are dictated by paleo-groundwater movement and paleo-phreatic surfaces. All of these varying sized features can

3-10 be soil-filled, water-filled, and/or air-filled features. If the overlying rock has been destabilized, it is possible for large rock blocks to have fallen into the karstic void space, as well.

Drill cores from the 1800-series and 1900-series borings in the left abutment indicate the Upper Big Clifty shale (Mgb sh-u) is moderately to highly weathered across the entire left abutment. Once exposed, this unit desiccates quickly causing the material to slake readily. In areas of high relief, such as the right abutment, exposures of the Upper Big Clifty Shale undermine the overlying Haney Limestone resulting in cantilevered layers of limestone and occasional displaced blocks of Haney.

Cores from the Big Clifty Sandstone (Mgb ss), interbedded sandstone and shale (Mgb int) and Lower Shale (Mgb sh-l) have moderate weathering near the valley but become less weathered with depth into the left abutment. The Lower Big Clifty Shale, like the Upper Shale, is also very susceptible to desiccation and slaking when allowed to dry or allowed to go through cyclic wetting/drying.

3.3.5 Groundwater

The major source of groundwater in the Big Clifty Sandstone is from the reservoir, however reactions to pool are slow and attenuated. Restricted summer pool is EL 490 and winter pool is at EL 470.

When the general term "Summer Pool" is used in this Contract, the Restricted Summer Pool of 490 NGVD29 is inferred. The influence of the reservoir is greatest on the upstream side and diminishes downstream with distance from the source. Piezometers upstream of the dam centerline typically fluctuate between EL 477 and EL 485 (PZ-48 and PZ-65B). Piezometers downstream of the dam centerline typically fluctuate between EL 469 and EL 478 (PZ-49 and PZ-64B). Influence from rainwater is minimal due the upper Big Clifty shale at the top of the unit and the lower Big Clifty shale at the bottom. Both beds act as aquitards that separates the unit from the highly karstic limestone units above and below. This results in a perched aquifer in the Haney Limestone. There are also shale layers within the sandstone bed that vary in thickness and frequency and likely act to reduce connectivity. The bedding planes are not laterally continuous across a large area due to the cross-bedded and random nature of deposition. This truncation of bedding planes would reduce the overall connectivity of the unit. It has been shown that it can take between 7-11 days for a change in pool elevations to be reflected in the Big Clifty Sandstone. The cumulative effect of all of these features and measured reactions to the primary water source result in a unit with very low recharge and discharge rates. Seepage through the sandstone, both steady state and instantaneous, is expected to be low. The lugeon values from pressure testing in the Big Clifty Sandstone ranged from zero to

11.5. Of the 113 water test performed in the unit, only 26 produced a recordable flow indicating the majority of water inflow will be from secondary porosity through isolated fractures. It is expected that the majority of these features will exist at or near the shale seams within the sandstone. Piezometer plots and pressure test data can be found in the GDR Appendix D and E.

3.3.6 Air Quality

Natural gas was encountered while drilling multiple boreholes between Stations 20+00 and 21+50 along the dam centerline in the valley section of the dam. The gas, possibly methane, was typically encountered 30-40 feet above the top of rock in sandy overburden soils with heavy organics.

Several borings during the Phase 1B drilling and grouting also encountered oil within the Sample Sandstone unit within the valley center. There was little to no oil found outside of the valley Stations (19+82 to 21+22). The tunnel construction will be performed within the Big Clifty Sandstone which is approximately 100 feet below the overburden on the left abutment and 80 feet above the Sample Sandstone with multiple rock units between them. Tunnel construction will not encounter the known gas or oil producing units and therefore, for baseline purposes, tunneling efforts will not encounter natural gas or oil. Details of the borings that encountered oil or natural gas are

3-11 included in the GIR. The Big Clifty sandstone (Mgb ss) and the Big Clifty Interbedded (Mgb int) contains a high silica content. For baseline purposes, the contractor will assume that the risk of silicosis exists within the tunnel and portal excavations. Refer to Specification 31 71 16.00 06 Rock Tunneling Section 3.5.1 Air Quality regarding air quality within the tunnel excavation.

4-12

4 CHARACTERIZATION AND BEHAVIOR OF ENGINEERING

GEOLOGIC UNITS

The tunnel and portals will be constructed entirely within the Big Clifty Sandstone (Mgb ss) unit.

Physical, mechanical, and behavioral engineering properties were characterized for the Big Clifty Sandstone unit and are presented below. Field logs and laboratory testing on rock samples for this and all other units are included in the GDR and GIR. Figure A-12 shows the location of all exploratory boreholes and Figure A-13 shows the location of Phase 1B grout holes in the left abutment.

4.1 Rock Characterization

4.1.1 Unit Weight

The wet unit weight was determined on 33 rock core samples extracted from PZ-53, the 1200 series, and the 1800 series boreholes. Unit Weight is affected by iron content and degree of cementation. The wet unit weight data is summarized in Figure 4-1 and Table 4-1 with the raw data located in the GDR Appendices. For baseline purposes, the range of wet unit weight of the Big Clifty Sandstone is presented in Figure 4-1 and Table 4-1.

Figure 4-1: Frequency distribution of unit weight in the Big Clifty Sandstone unit.

Table 4-1: Numerical distribution of representative unit weight data in the Big Clifty Sandstone unit (outliers removed).

Unit Weight, Mgb (ss)

(pcf)

High 148.3

Median 143.7

Low 131.8

Average 142.5

4-13

Standard Deviation 3.7

4.1.2 Unconfined Compressive Strength

The rock strength of the Big Clifty Sandstone unit is based upon uniaxial compressive strength tests using ASTM D 7012, Method D. The tests were performed on 22 rock core samples extracted from PZ-53, the 1200 series, and the 1800 series boreholes. The data for this parameter is summarized in Figure 4-2 and Table 4-2 with the raw data located in the GDR Appendices. One outlier (980 psi) was removed from the data set, as it failed prematurely on an iron-rich zone in the sidewall of the sample and is not considered to represent the overall compressive strength of the unit. Mechanical excavation methods, machinery, or other equipment must be suited for all compressive strength values listed in the base line statement. For baseline purposes, the range of compressive strength of the Big Clifty sandstone is presented in Figure 4-2 and Table 4-2.

Figure 4-2: Frequency distribution of compressive tests in the Big Clifty sandstone unit.

Table 4-2: Numerical distribution of representative compression data in the Big Clifty sandstone unit (outlier removed).

Uniaxial Compression Values, Mgb (ss)

UCS (psi)

High 9,942

Median 7,630

Low 4,050

Average 7,349

Standard Deviation 1,734

4.1.3 Elastic Modulus

The Young’s Modulus (E) of the Big Clifty Sandstone unit is based upon uniaxial compressive strength testing using ASTM D 7012, Method D. The Young’s Modulus was determined on 14 rock core samples extracted from PZ-53 and the 1800 series boreholes. The data for this parameter is summarized in Figure 4-3 and Table 4-3 with the raw data located in the GDR Appendices. One outlier (0.39x106 psi, same sample that produced the 980 psi result) was removed from the data set, 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 More

Fr e q u e n cy

UCS, psi

Compressive Strength, Mgb (ss)

4-14 as it was not considered to represent the overall elastic modulus of the sandstone. For baseline purposes, the range of Young’s Modulus for the Big Clifty Sandstone is presented in Figure 4-3 and Table 4-3.

Figure 4-3: Frequency distribution of Young’s Moduli in the Big Clifty sandstone unit.

Table 4-3: Numerical distribution of representative Young’s Moduli data in the Big Clifty sandstone unit (outliers removed).

Young’s Modulus, Mgb (ss) x106 psi

High 3.7

Median 2.8

Low 1.3

Average 2.7

Standard Deviation 0.7

4.1.4 Poisson’s Ratio

The Poisson’s Ratio (ν) for the Big Clifty Sandstone unit is based upon uniaxial compressive strength testing using ASTM D 7012, Method D. Poisson’s Ratio was determined on 13 rock core samples extracted from PZ-53 and the 1800 series boreholes. The data for this parameter is summarized in Figure 4-4 and Table 4-4 with the raw data located in the GDR Appendices. One outlier (0.07, same sample that produced the 980 psi result) was removed from the data set as it is not considered to represent the overall condition of the sandstone.