W912QR25R0016_CERT_Final_Vol6_ ProjGIR_1of16-0000.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

Geotechnical Information Report (GIR) Vol. 6 (1 of 16)

Certified Final

20 December 2024

W912QR25R0016

ARIMS: 1200

Disposition: Permanent

W912QR25R0016_CERT_Final_Vol6_ ProjGIR_1of16-0000

Controlled by: U.S. Army Corps of Engineers Controlled by: CELRL-ED Limited Dissemination Control: FEDCON POC: Troy O’Neal (DSPM), 513-684-3804

Rough River Dam (KY03012) Geotechnical Interpretive Report New Outlet Works and Cutoff Wall

ROUGH RIVER, FALLS OF ROUGH, KY

LRL DISTRICT, LRD DIVISION

Report Status: Draft, June 2024 ii

Introduction Purpose and Limitations of Geotechnical Interpretive Report (GIR) Relation to Contract Documents Organization of Report Project Authorization Project Location and Population at Risk Risk Driving Failure Modes Rough River Dam Safety Modification and DSAC History

Project Overview Existing Conditions

Project Features Dam Embankment Outlet Works Emergency Spillway Original Construction Overview Groundwater

Dam Safety Modification (DSM) Project DSM Phase 1A (Road Relocation) DSM Phase 1 Intermediate (Automated Instrumentation Installation) DSM Phase 1B (Exploratory Drilling and Grouting)

Geologic Profile Updates and Overburden Soils Project Operations

Flood Pool Event Frequency 2011 Record Pool

Overview of Planned Rehabilitation Site Specific Soils and Rock

Summary of Geologic Data 2018 Phase 1 Outlet Works Investigation 2019 Phase 2 Outlet Works Investigation

On-Site Soils Dam Embankment Foundation Soils Borrow Areas

Left Upstream Abutment Area Left Downstream Abutment Area Upland Disposal and Staging Areas

Old Campground Area Geology

Regional Geology Stratigraphy and Profiles for Cutoff Wall and New outlet Works Karst Potential Abrasivity

On-Site Bedrock Hardinsburg Formation Haney Limestone Big Clifty Sandstone iii

Beech Creek Limestone Elwren Shale Reelsville Limestone Sample Sandstone Rock Structure

Groundwater Haney Limestone Big Clifty

Seismicity Induced Seismicity Previous Seismic Evaluation Site Classification Seismic Hazard Curve Disaggregation

Work Area Descriptions and Construction Considerations Overview Site Preparation for the New Control Tower

Work Area Description Construction Considerations

Excavation of Approach Channel Work Area Description Construction Considerations

Site Preparation for the New Stilling Basin and Apron Work Area Description Construction Considerations

Excavation and Construction of the Retreat Channel Work Area Description Construction Considerations

Modification of Old Campground Work Area Description Construction Considerations

Construction of Cutoff Wall Working Platform Work Area Description Construction Considerations

Installation of the Cutoff Wall Work Area Description Construction Considerations

Critical Areas B1 & B4 (Overburden in Contact with Haney LS) Critical Areas B2 & B3 (Overburden in Contact with Beech Creek LS) Valley Restriction (Foundation Soil in Contact with the Reelsville Limestone) 115 Critical Area A (Conduit)

Spoil Placement, Site Restoration, and Road Relocation Excavation of Outlet Tunnel Construction of the Control Tower Service Bridge Abutment

Work Area Description Construction Considerations iv

Acronyms AEP Annual Exceedance Probabilities ASCE American Society of Civil Engineers ASTM American Society for Testing and Materials BCLS Beech Creek Limestone CEUS Central and Eastern United Sates DSAC Dam Safety Action Classification DSM Dam Safety Modification DSMR Dam Safety Modification Report DSOG Dam Safety Senior Oversight Group ERDC Engineering and Research Design center FAR Federal Acquisition Regulation FIO For Information Only GBR Geotechnical Baseline Report GDR Geotechnical Data Report GIR Geotechnical Interpretive Report GIS Geographic Information System ICOLD International Commission of Large Dams MCE Maximum Credible Earthquake MDE Maximum Design Earthquake MSL Mean Sea Level NAVD North American Vertical Datum NGVD Nation Geodetic Vertical Datum OATV Optical and Verification Hole Drilling OBE Operating Basis Earthquake OW Observation Well PE Probability of Exceedance PFM Potential Failure Mode PFMA Potential Failure Mode Analysis PGA Peak Horizontal Ground Acceleration PMF Probable Maximum Flood PSHA Probabilistic Seismic Hazard Analysis PZ Piezometer RMR Rock Mass Rating RQD Rock Quality Designation RW Relief well SEI Structural Engineering Institute SOG Senior Oversight Group SQRA Semi-Qualitative Analysis UCS Unconfined Compressive Strength USACE US Army Corps of Engineers USBR US Bureau of Reclamation USGS United States Geologic Survey

Rock Formation Abbreviations Mh Hardinsburg Sandstone Mgh Haney Limestone Mgb Big Clifty Sandstone Mgb (sh-u) Big Clifty-Upper Shale Mgb (ss) Big Clifty-Sandstone Mgb (int) Big Clifty-Interbedded Mgb (sh-l) Big Clifty-Lower Shale Mgc Beech Creek Limestone El Elwren Shale Mr Reelsville Limestone Ms Sample Sandstone

INTRODUCTION

Purpose and Limitations of Geotechnical Interpretive Report (GIR) This report includes subsurface information from field investigations and associated laboratory test results along with USACE’s interpretation of the subsurface conditions to support design efforts for the new outlet works and cutoff wall project and is considered essential information for the establishment of technical requirements and limitations applicable to construction. The design and construction considerations provided herein are for information only (FIO). The GIR is not intended to provide contractual baseline conditions for the entire project as these baseline conditions have been incorporated into the plans and specifications. The appendices contain geotechnical and geological data associated with multiple historic designs, investigations, and rehabilitations to support design assumptions and provide the available historic information for the dam.

Relation to Contract Documents The New Outlet Works and Cutoff Wall GIR is provided FIO in Volume 6 of the technical package. The GIR includes project history, soil and bedrock conditions based on previous investigation for the entire Rough River Dam Project, and applications of this information to design elements essential to the New Outlet Works and Cutoff Wall Design. Nothing in the GIR should be construed as amending or altering the Plans and Specifications, applicable FAR clauses, or other contract requirements or standards for construction. This GIR references the Phase 1 Construction Materials and Foundation Completion Report contained in Volume 6 of the technical package as FIO. References to the new tunnel (conduit) are used in this manual only in general terms; details of the tunneling and portals required for this project are covered under a separate Tunneling Geotechnical Baseline Report (GBR) and Tunneling Geotechnical Data report (GDR).

Organization of Report This document has been formatted to include the New Outlet Works information and the cutoff wall information and follows the following outline:

Chapter 1: Introduction (Purpose of Report, Project Location and Assessed Risks) Chapter 2: Project Overview (Project Features, Construction History Summary) Chapter 3: Site Specific Soils and Rock (Properties of Project Soils and Rocks) Chapter 4: Work Area Descriptions and Construction Considerations

Appendix A: Synopsis of Construction History and Performance Appendix B: Boring Location Plans and Boring Logs Appendix C: Soil and Rock Testing and Analyses by Investigation Appendix D: Not Used – Instrumentation and Monitoring included in Volume 5

Joint Instrumentation and Monitoring Plan (JIMP) Appendix E: Analysis of Upstream Filter and Dewatering Appendix F: Analysis of Downstream Cofferdam and Dewatering Appendix G: Analysis of Downstream Filter for Stilling Basin Abandonment Appendix H: Analysis of Cutoff Wall Work Platform Appendix I: Analysis of Upland Disposal Area and Archery Berm

Project Authorization The flood protection plan for the Ohio River Basin, which included the construction of the Rough River Dam, was authorized by the Flood Control Act approved 28 June 1938 (Public Law 761, 75th Congress, 3rd Session), revised under a report titled “Rough River and Tributaries, Kentucky” and published as House Document No. 535, 78th Congress, 2nd Session, 1944. Water supply was authorized per the Water Supply Act of 1958 (43 U.S. Code § 390b). Water supply agreements are in place with Leitchfield, KY (120 acre-feet) and Grayson County, KY (260 acre-feet). During the fall and winter months, the lake is kept at a relatively low level (winter pool) to store the runoff from large rainfall events common to that time of year for later release after the swollen streams and rivers below the dam have receded and can receive the release of the stored water without consequences. The pool extends upstream approximately 45 miles when the reservoir is at the spillway crest elevation.

Project Location and Population at Risk Rough River Dam is located on the boundary between Breckinridge and Grayson counties in Kentucky. It reduces flood impacts to several small, rural towns in Kentucky. The city of Falls of Rough, KY (2020 population of about 2,800) is located 6 miles downstream of the dam and would be the area most adversely impacted by both non-breach and breach events. Life loss in Falls of Rough is driven by the amount of warning time, flood depths, and sampled mobilization rates. Within the entire impact area, mean depth on structures for the top of active storage (TAS) breach is 6 ft. For Falls of Rough, the mean depth on structures is 21 ft. As breach flows continue downstream, the depth dissipates, which reduces the likelihood of life loss occurring in most areas. Although, consequences are generally concentrated in Falls of Rough, life loss occurs in other rural areas located adjacent to the river (Figure 1).

Figure 1: Flood Inundation Extent.

Risk Driving Failure Modes A Potential Failure Mode Analysis (PFMA) was completed in 2008 followed by an Expert Opinion Elicitation (EOE) in 2011 which indicated the foundation for Rough River Dam posed unacceptable risks from internal erosion related failure modes. At the time of Phase 1B construction, the dam was assigned a Dam Safety Action Classification (DSAC) Classification 2 (High Urgency) ranking based on the following Potential Failure Modes (PFM):

14 - Concentrated leak erosion along the conduit 21A - Concentrated leak erosion into and along the Haney Limestone on the right abutment 22 - Concentrated leak erosion into and along the Haney Limestone on the left abutment 23A - Concentrated leak erosion of the valley soil along the BCLS 23C - Erosion into the untreated valley center and lower left abutment BCLS

Additional risk assessments were completed in 2016 and 2017 as grouting was nearing completion. These risk assessments indicated that the two primary risk driving failure modes were PFM 22 Internal Migration (stoping) into and along the left abutment Haney Limestone, and PFM 23A scour (concentrated leak erosion (CLE)) into the right abutment BCLS. These karstic formations are present on both sides of the incised valley.

A Semi-Quantitative Risk Assessment (SQRA) was performed between 2022 and 2023 to re-evaluate the existing condition of the dam. The draft Rough River Dam Construction Materials and Foundation Completion Report was utilized as a resource during the SQRA. The SQRA indicated the foundation for Rough River Dam posed unacceptable risks from internal erosion related failure modes. The dam was assigned a DSAC 2 (High Urgency) ranking based on the following PFM’s:

PFM 1: Overtopping PFM 4: CLE along the right side of the conduit PFM 5: CLE into/along defects in the foundation rock (right side BCLS) PFM 17: Internal migration (stoping) into defects in untreated Haney Limestone at left abutment PFM 22: Backwards Erosion and Piping (BEP) through foundation soils in the original river channel

Rough River Dam Safety Modification and DSAC History The purpose of the Dam Safety Modification Project is to reduce risks associated with potential dam failure and the associated loss of life below tolerable risk guidelines. In 2005 Rough River Dam was evaluated through a Screening Portfolio Risk Assessment and was assigned a DSAC Classification 2 (High Urgency) ranking by the Dam Safety Senior Oversight Group (DSOG).

The key risk contributors involve erosion into or along the karstic rock foundation. A PFMA was performed in 2008 which ultimately lead to approval for the 2012 DSMR which recommended completion of an exploratory grouting program and a seepage barrier across the dam foundation and to be saddled around the conduit.

The project was broken into phases with Phase 1A relocating the existing state highway to the upstream slope of the dam between 2014 and 2015. The Phase 1B Exploratory Drilling and Grouting Program began in the fall of 2015 and was completed in 2017. Because grout was observed exiting downstream of the stilling basin end sill into the apron area in 2016, a Semi- Qualitative Risk Analysis (SQRA) was performed which concluded there was direct evidence of adverse conditions at the project which had the potential to result in unacceptable performance and the possible uncontrolled release of the reservoir. A post-grouting risk assessment was conducted upon the conclusion of the Phase 1B grouting to evaluate the effectiveness of the cutoff wall to reduce the project risk below the tolerable risk guidelines. The risk assessment concluded that grouting had some success to temporarily reduce risks to the dam.

The Phase 2 concrete cutoff wall was fully designed in 2017. The design included a plan to place the cutoff wall around the existing conduit; however, during a Safety Assurance Review, it was determined the conduit did not have the structural capacity to handle the anticipated increase in loading from the cutoff wall. These concerns ultimately rendered the 2012 DSMR incomplete and resulted in cancellation of the Phase 2 Solicitation. In 2018, a Constructability Evaluation and an SQRA were conducted to complete the 2012 DSMR. The 2020 DSMR Supplement, prepared in accordance with ER 1110-2-1156 to analyze the effectiveness of the design options, concluded that the most effective approach for installing the cutoff wall required the installation of a new outlet works within the left abutment followed by total abandonment of the original outlet works. During the design of this option, the DSOG discussed the results of the 2017 Post- Grouting Risk Assessment and changed the project classification from a DSAC 2 to a DSAC 3.

The existing condition of the dam and associated risks were re-evaluated during an SQRA conducted between 2022 and 2023. The updated risk assessment flagged continued concerns with internal erosion failure modes that resulted in the dam being reclassified back to a DSAC 2 rating.

PROJECT OVERVIEW

Existing Conditions Project Features

The major features of the existing Rough River Dam project include an earthen dam, an outlet works positioned at the base of the right abutment, and an emergency spillway near the left abutment (Figure 2). The project was designed and referenced to the COE Datum which is equivalent to the National Geodetic Vertical Datum of 1929 (NGVD29) and MSL. All elevations in this report are in NGVD29 unless otherwise referenced. To obtain NAVD88, 0.43 ft should be subtracted from any elevation provided in NGVD29 (NGVD29-0.43 ft = NAVD88).

Figure 2: Plan view of existing Rough River Dam project.

Table 1: Pertinent Existing Project-Related Data

Physical Data Dam Type Earth Core with Rock Fill Maximum Height 130 feet Length 1,590 feet Existing Crest Elevation** 555.1 NAVD88; 555.53 NGVD29 (+5’ parapet wall placed in 2006 = 559.53) Spillway Crest Elevation 523.57 NAVD88; 524 NGVD29 Spillway Type Open Cut Spillway Dimensions 65 feet wide; Design Q=22k cfs Control Works 12’ X 12’ semi-elliptical concrete culvert Conduit Invert Elevation 430 ft NGVD29 (at inlet)

Hydrology Drainage Area 454 mi2 Total Rainfall from PMP (HMR 51/52) 27.8 inches Probable Maximum Flood (PMF) Peak Inflow 344,700 cfs Maximum PMF Pool Elevation 556.26 NAVD88; 556.69 NGVD29 Maximum Recorded Pool Elevation 526.88 NAVD88; 527.35 NGVD29 Maximum Recorded Outflow 6,400 cfs (peak; includes spillway) Maximum Recorded Inflow 36,500 cfs (24-hr average) Average Flow at Dam Site 660 cfs Maximum Conduit Discharge Capacity at Spillway Crest 5,580 cfs

Operating Levels

Pool Elevation (ft, NGVD29*)

Elevation (ft, NAVD88)

Storage (acre-ft)

Winter 470 469.57 29,800 Normal Summer 495 494.57 120,010

Restricted Summer 490 489.57 95,940 Flood Control 470 to 524 469.57 to 523.57 334,380 Top of Dam 554 553.57 775,000

* The project was designed and referenced to the COE Datum, which equals NGVD29 and MSL. Subtract 0.43 feet from NGVD29 datum to obtain NAVD88.

**Crest was raised in 1959 before impoundment and again in 2007. Up to 0.3 feet of settlement observed between 2007 and 2022.

Dam Embankment The dam consists of a 1,590-foot long, earth-filled embankment having a maximum height of 130 feet above the streambed with an originally constructed crest width of 40 feet. The existing condition crest width is 30 feet wide. The maximum width at the base of the dam is 819 feet. The dam embankment consists of low permeability lean and fat clay fill. The structure is founded on residual soils along the left abutment and alluvial soils within the valley center and at the base of the abutments. The right abutment was founded on rock and had limited stripping and slush grouting. Internal drainage for the embankment is provided by a 10-foot thick, 1.0H:2.0V inclined drain starting at elevation 495 and connected to a 2-foot thick, basal filter blanket on the downstream ground surface starting 50 feet downstream of the dam centerline and extending to the downstream toe. Between the existing river channel and the right abutment outlet conduit, a 2-foot-thick basal filter blanket was also installed from 50 feet upstream of the dam centerline to the upstream toe. A total of 368 12-inch diameter sand drains were advanced in the upstream and downstream blankets (227 upstream and 141 downstream) between the historic channel and outlet conduit. The sand drains had rows split spaced on 13-foot centers with the bottom of the well terminated at the top of the underlying bedrock (Figure 5). Three relief wells were installed at the downstream toe in the left riverbank foundation to reduce uplift pressures and to control the water movement through the alluvial soils left in place.

The original upstream dam face has 4 feet of dumped riprap stone protection underlain by 12 inches of spalls and choker material. The downstream rock toe consists of 15,000 cubic yards of material and has a top elevation of 460 feet with an upstream slope of 1.0H:1.0V. A volume of 1,141,400 cubic yards of earth and rock material was required for the original construction. In 1959, the top of dam was raised from elevation 551 feet to 554. In 2007, the top-of-dam elevation was raised again from elevation 554 to 555.5. Additionally, a concrete parapet I-wall was constructed to extend the level of protection for wave-wash up to 559.53 feet. A downstream slurry wall was installed in 2007 to prevent the continued migration of embankment into the rock toe. An upstream work platform was constructed to relocate the existing state highway (aka Falls of Rough Road) in 2014 where the roadway is currently trafficked.

Figure 3: Dam Cross Section with Drainage Blanket and Drainage Wells (Sta.21+50)

Figure 4: Typical Dam Cross Section without Drainage Blanket and Drainage Wells (Sta.

20+90)

Figure 5: Drainage Blankets and Drainage Well Configuration Profile.

Outlet Works The outlet works provides a discharge capacity of 3,000 cubic feet per second (cfs) with normal summer pool (elevation 495), and 5,580 cfs at spillway crest level (elevation 524). The outlet works is located at the base of the right abutment and founded predominately on the karstic Beech Creek Limestone. The dry-type control tower has three hydraulically-operated 4.75-foot by 9.5-foot vertical lift slide gates (invert elevation of 430) and two 24-inch low-flow bypass pipes (invert elevation of 450), discharging to a 12-foot by 12-foot, semi-elliptical concrete conduit that leads to a stilling basin. The semi-elliptical section of the conduit is 548 feet long, varies from 12 -18 inches thick, and has a drainage gradient of 0.2 percent. There are five seepage collars along the outlet conduit spaced every 60 ft. The conduit drains into an energy dissipating stilling basin and concrete apron that directs the flow through a riprap-lined retreat channel. The stilling basin was originally a 52-ft-long dispersal bucket and has had several remedial repairs. In 2007, the end sill and apron were removed and extended increasing the stilling basin length to 139 feet with the addition of five baffle blocks. A 144-foot, simple-span, steel truss service bridge extends from the control tower to a roadway on the right abutment.

Figure 6: Conduit Profile

Emergency Spillway A 65-ft wide, 1,800-ft long uncontrolled, unlined, open rock cut emergency spillway was excavated on a 1H:4V slope roughly 33 ft deep into rock. Water enters the spillway through a natural drainage valley in the left abutment and flows over a 6-ft-wide concrete sill with a crest elevation of 524 ft, installed for grade protection, after which the spillway slopes downstream at

1.5 percent and spills approximately 400 ft beyond the left abutment. The Contractor overshot the rock leaving the ragged appearance in the walls and floor (Figure 7). Overburden was excavated with 2H:1V side slopes. The spillway is crossed by Kentucky Highway 79 using a single span, simply supported, steel multi-girder bridge with a cast-in-place concrete deck extending approximately 36 ft above the spillway floor. The spillway side slopes are lined only at the bridge location to support the bridge structure. The floor of the spillway is the Haney Limestone and is described in Chapter 3. Performance of the spillway during the 2011 record pool event is discussed in Paragraph 2.3.1.1.

Figure 7: Current Spillway Condition.

Original Construction Overview Two contracts were awarded to construct the Rough River Dam project. A contract for the tower and outlet works was awarded in 1955. A contract for construction of the dam and spillway was awarded in May 1957 and proceeded concurrently with construction of the outlet works to expedite completion of the project. The embankment was completed in November 1958, and the project was placed in limited operation in October 1959 after the dam was raised. The dam was placed into full operation in December 1960 after foundation grouting in the abutments was completed. Design of the project features was aided by pre-construction and construction explorations. Key construction items pertinent to the Phase 1 Project include the original outlet works construction, right abutment dental treatment (Special Treatment Zone), natural alluvium and overburden left and place, and abutment grouting. A summary of key construction information is contained in Figure 8. A detailed synopsis of the original dam construction is included in Appendix A.

Figure 8: Key Construction Summary.

Groundwater There are multiple sinkholes and springs identified across the project site. Sinkholes have been observed within the spillway floor, behind the project office, along a hiking trail downstream of the project office, and along the campground access road. Springs have been observed upstream of the left abutment, in the tree line downstream from the left embankment toe, and beneath the downstream footprint of the dam on the left abutment.

The groundwater conditions at the site are complex and groundwater encountered across the project site is not consistent. This is attributed to perched groundwater within Haney Limestone overlying restrictive shales (i.e., upper Big Clifty shale) on the left abutment. Instrumentation on the upper left abutment indicates groundwater as high as elevation 545 and as low as elevation 495 in the left dam abutment and is typically well above summer pool levels. This condition is attributed to the void structure within the Haney Limestone, the large upland drainage area to the south of the drainage basin, and the presence of a draped basal filter (inclined chimney and horizontal blanket drains) present along the downstream dam foundation. Groundwater conditions for earthwork on the upper left abutment encountered groundwater a few feet above the top of rock in most locations.

Groundwater in the lower left abutment generally exists at the ground surface during wet periods mostly influenced by rainwater, dam seepage and abutment groundwater influence seeking the valley center. This is evident in a series of test pits advanced along the downstream left abutment in late fall of 2019 which indicated groundwater to exist just below the ground surface in the campground area and recreational area. A seepage area at the base of the left abutment (~Station 18+00 to 18+30) is attributed to a combination of dam seepage, the filter blanket and surface water runoff. A spring present in the left abutment (~200 feet downstream from the dam toe) regularly saturates the area between the existing tailwater recreation area. Relief wells located closer to the valley on the left indicate artesian pressure from Relief Well #1 at the toe of the dam which flows regularly slightly above the riser height at elevation ~446.75. Relief wells #2 and #3 have historically not had any flow.

Groundwater from the right abutment is mainly from surface water runoff. The perched water groundwater found in the Haney Limestone within the left abutment is not found in the right abutment to the same extent. The right abutment Haney groundwater levels are typically found just a few feet above the base of the formation (elevation ~495-437). PZ59, installed in late 2011, has read dry since installation. The absence of a perched water table in the right abutment can be attributed to the topography of the catchment basin to the north of the dam. There is a prominent ridge just upstream of the dam that runs roughly parallel to the dam centerline. This ridge is thought to direct the ground water to the north and south parallel to the strike of the abutment that drain away from the area.

During Construction, groundwater was encountered above the base of several of the conduit monoliths. The groundwater was channeled to sumps and removed, diverted, or drained. Water seepage was also observed at the ground surface of the former river channel, downstream of the centerline of the dam, subsequent to the dewatering and stripping operations. Construction photographs indicate that efforts were made to pump and divert the water from the site; however, water remained present prior to fill placement. During stilling basin dewatering in 2012 and 2016 artesian conditions were noticed in the stilling basin indicative of high levels of seepage exiting into the stilling basin. After completion of the 2017 grouting this condition was not observed during dewatering in 2020.

Across the dam foundation the phreatic surface in the dam embankment ranges from approximately elevation 480 on the upstream slope to approximately elevation 445 on the downstream slope controlled by the inclined chimney and horizontal blanket drains. Relief wells and instrumentation indicate seasonal artesian groundwater conditions at the toe of the dam.

Dam Safety Modification (DSM) Project The Dam has a long history of previous maintenance and rehabilitation in addition to the previous phases of the Dam Safety Modification Project. A detailed narrative on the previous phases of the Dam Safety Modification Project are included in Appendix A and the Phase 1 Construction Materials and Foundation Completion Report contained in Volume 6. Previous design and construction activities which directly pertain to the Phase 2 project are as follows:

Phase 1A – Relocation of SR 79 (2014-2015) Phase 1 Intermediate - Install additional “real-time” instrumentation (2014-2015) Phase 1B – Exploratory Drilling and Grouting (2015-2017) Phase 2 Cutoff Wall Design (2017)

- Solicitation Canceled (critical design flaw discovered)

- New Outlet Works and Cutoff Wall Design (2020-2022)

DSM Phase 1A (Road Relocation) In spring of 2014, KY Highway 79 was relocated to the upstream face of the dam to serve as a traffic platform for the Phase 1B and Phase 2 Projects. The road relocation required altering the upstream slope of the dam between elevations 495 to 550 to a 2H: 1V (Table 2). The slope modification was achieved by constructing a rock trench toe at elevation 495 ft. The modified slope provides a 30 ft wide roadway surface at elevation 550. Benches 8 to 10 feet wide and not exceeding 4 feet in height were excavated across the dam. Rock fill was placed and compacted in 2-ft-thick lifts. The Contractor advanced both rock fill and riprap simultaneously up to elevation 550 (Figure 9). Special considerations for raising piezometer standpipes and placing rock fill around existing instruments were required. Traffic was rerouted onto the new road in the Spring of 2015. Figure 9 and Figure 10 depicts a typical road embankment section with benching details and construction photos. The overall project placed 36,414 cubic yards (65.5 tons) of rock fill covered by approximately 14,758 cubic yards (22 tons) of Kentucky Transportation Cabinet (KYTC) Class III riprap on the dam face. All utilities previously located on the crest of the dam were moved to the new road location.

Table 2: Modified Slope Geometry Upstream Downstream

Slope Elevation (feet MSL) Slope Elevation

(feet MSL) 2.0H:1.0V 554-550 2.0H:1.0V 554-539 2.0H:1.0V 550-495 2.5H:1.0V 539-531 3.0H:1.0V 495-471 3.0H:1.0V 531-base4.0H:1.0V 471-base

Figure 9: As-Built Geometry for the Upstream Slope and Toe Trench at Elevation 495 ft.

Figure 10: Construction Sequence for Phase 1A.

DSM Phase 1 Intermediate (Automated Instrumentation Installation) A total of 58 fully grouted vibrating wire transducers were installed in 20 boreholes along the upstream and downstream crest of the dam. The system included an Automated Data Acquisition System (ADAS) to monitor effects of the future grout curtain installation on the dam foundation during planned grouting activities. For additional information on the instrument installation see the Phase 1 Construction Materials and Foundation Completion Report contained in Volume 6. Additional details on the ADAS system are in the Joint Instrumentation and Monitoring Plan (JIMP) in Volume 5.

DSM Phase 1B (Exploratory Drilling and Grouting) Detailed information for Phase 1B Project can be found in the Phase 1 Construction Materials and Foundation Completion Report and boring logs contained in Volume 6. The Phase 1B project consisted of a base contract for exploratory purposes and a modification contract for production drilling and grouting. A brief summary of the Phase 1B Project is provided below.

2015-2016 Phase 1B Base Contract:

Rough River Dam Safety Modification Phase 1B – Exploratory Drilling and Grouting was awarded in April 2015. The stated goal of the project was to install two partial grout lines to explore and evaluate subsurface conditions, to determine the extent of the pre-treatment required, and to establish remediation methods in preparation for a future cutoff wall. The base contract included 154 boreholes to be advanced from the dam crest to further define the foundation conditions through soil and rock sampling, water pressure tests, grout takes, instrumentation responses, etc. Two partial grout lines totaling 1,670 ft in length were placed parallel and offset from the dam centerline by 7.5 ft upstream (U-Line) and 10 ft downstream (D-Line). The grout lines were installed straddling the alignment of the proposed cutoff wall. Holes drilled on the U- Line were battered at 20 degrees from vertical towards the left abutment between Station 9+16 and 21+16. Holes drilled on the D-Line between Station were battered at 20 degrees from vertical towards the right abutment between Station 19+82 and 25+82. The base contract boreholes were drilled through the embankment/overburden soils into rock, and to a bottom elevation of 354, or approximately 10 feet into the Sample Sandstone. The holes were divided into 6 zones (from left to right) depending primarily on the formations that were in direct contact with the embankment/overburden material and other defined project features (Figure 11). Each zone required the first 15 ft of bedrock to be downstage grouted at gravity pressure (gravity grout zone) for the entire length of the formation before deeper grouting was allowed to commence.

Critical areas where the embankment was in contact with the karstic limestone were split-spaced down to tertiary holes (5 ft on center). Boreholes of opposite batter orientation crossed in the area of the historic river valley to ensure full coverage. There were 3 vertical holes on each side of the existing conduit. There is a zone of untreated rock below and extending 5 ft on either side of the conduit.

Figure 11: Phase 1B Base Contract Boreholes.

The dam embankment and underlying overburden was drilled with resonant sonic drills as described in ER 1110-1-1807 (dated 31 July 2014). Grout hole drilling in rock was performed with water-actuated, down-the-hole hammers and standard rotary diamond coring drills. As part of the base contract the Contractor was required to perform optical and acoustic televiewer (OATV) surveying for primary holes and 20 verification holes. Borehole stages and water pressure testing were assigned by the Government. Water pressure testing and grouting occurred in prescribed stages in bedrock ranging from 15 to 30 ft with the intent to isolate specific formations to the greatest extent possible. Grout stages were grouted using balanced and stable grout mixes approved by USACE. The grout mixes were thickened as required and was directed by the Government. The grouting program did not grout holes to closure as the program was exploratory in nature and intended for slurry control in advance of a future cutoff wall.

All grouting operations were conducted in accordance with EM 1110-2-3506 (dated 28 February 2013). The grout program was designed to effectively treat the weathered rock interface by isolating the embankment and soil foundation from high pressures, reducing the risk for hydrofracture. The project specifications particularly required that instrumented packers be used for all water pressure testing and grout injection. The Contractor was further required to provide and operate an Automated Grouting Monitoring and Data Collection System to provide daily updated data collection and reporting of volume, pressure, rate of flow during grouting and Lugeon values during pressure testing. All data obtained through the drilling and testing program was made available through a real time geographic information system interface.

Notable Events:

1. Borehole DXS2192: Grout emerged in the tailwater area near the stilling basin within 30 minutes of initiating grouting (approximately 500 feet downstream from the injection point) (Figure 12).

Figure 12: Grout injected from borehole DXS2192 exiting at the stilling basin end sill.

2. Borehole DXP2232: PZ35 received enough grout to expel water up through its standpipe onto the ground surface. Dye which had been injected into PZ40 in 2010 was observed exiting the top of PZ35. The instrument was grouted up and taken out of service.

3. Boreholes DXP242-A and UXP2242-2: A large void was encountered across these two boreholes in the vicinity of conduit monolith 12. This is the same location where a large karst feature was observed to have exited the original conduit foundation mapping area (Appendix A). The feature was noted by rod drops in the tooling encountered at a depth of 133 feet vertically below the dam. The void and infilling varied from 4 to 6 feet across the boreholes.

4. Borehole DXP2582: Large grout outbreak in the upper right abutment with grout exiting into the ravine downstream of the abutment at approximately elevation 535.

A smaller grout outbreak was noted while grouting Borehole DXP2462.

Figure 13: Grout exiting the left abutment advanced from borehole DXP2582.

5. Embankment Cracks: Seventeen borings encountered vertical cracks while drilling through the embankment. Cracks were identified in extruded soil samples that were observed to be naturally fractured longitudinally in the direction of drilling.

Generally, the cracks were observed along the periphery of the valley abutments located above the Beech Creek Limestone outcrops. The cracks were noted to be parallel to the core axis and are summarized in Table 3. Three samples were discolored with what appeared to be mineral staining. Numerous samples were noted to have irregular recoveries consisting of highly broken soil plugs and reduced sample diameters. These recovered samples are indications the embankment and foundation soil was less dense in these areas.

Table 3: Embankment cracks encountered during Phase 1B grouting

Hole Depth of Fracture Elevation

Length of (ft.) Material From To From To

UXT1871 60 65 498.9 494.2 5 CL

UVP1860 91 93 469 467 2 CL

UXS1886 68 75 491.4 484.8 7 CL-ML

UXS1886 67 73 492.3 486.7 6 CL

UXT1891 45 48 513 510.2 3 CLg

UXT1891 70 74 489.5 485.8 4 CL

UXS1906 55 65 503.6 494.2 10 CLg

UXS1926 55 60 503.6 498.9 5 CL

DXT1931 124 135 438 427 11 CL-ML

DVP1935 98 112 457 443 14 CL

UXP1936 55 56 503.6 502.7 1 CL

UXT1941 56.5 62 502.2 497 5.5 CL

UXT1951 64 67 495.2 492.3 3 CL

DXP1966 105 115 455 445 10 CL

UXS2172 65 67 494.2 492.3 2 CL

DXT2177 67 74 492.3 485.8 7 CL/CH

DVP2187 105 110 456 451 5 CL/CH

2016-2017 Phase 1B Contract Modification:

On the basis of conditions encountered during the initial phase it was determined that a cutoff wall was necessary, and the original contract was modified to consist of a complete two-line grout curtain with an additional 154 boreholes. Beginning in June 2016, the Government issued a series of Contract Modifications requiring that additional production drilling and grouting work be performed. The modification work extended the curtain fully from Station 9+16 to 25+82 along the upstream and downstream portions of the crest. The modification work continued with the upstream and downstream offsets for the production grout lines. Holes drilled on the D-Line between Station 9+26 and Station 21+06 were inclined 20 degrees from vertical towards the left abutment. Holes drilled on the U-Line between Station 19+82 and 25+82 were inclined 20 degrees from vertical towards the right abutment. The work shifted from an exploratory focus to a production emphasis with less rock core obtained, less OATV, and prescribed downstage grouting in the left abutment Haney Limestone.

Figure 14: Phase 1B Modified Contract Boreholes.

Phase 1B Completion Summary:

Ultimately, the project successfully installed a total of 308 production grout holes and 20 verification holes. These holes required 32,422 linear ft of overburden and embankment drilling, 7,477 linear feet rock coring, 26,058 linear feet percussion rock drilling, and a total of 212,763 gallons (1,053 cubic yards) of grout injected into the foundation. There was a limited amount of additional drilling and grouting associated with abandoned boreholes. The Phase 1B work was completed in April 2017.

Geologic Profile Updates and Overburden Soils After Phase 1B was completed the upstream and downstream grout line was studied fully to evaluate soil and bedrock stratigraphy across the two grout lines. The geologic profile that is contained in the Phase 1B As-Builts has since been adjusted and the content of the left in place alluvial deposits across the valley have been better defined. The upstream and downstream geologic profiles shown in the Geology Section and in the Volume 3 plans are the most up to date stratigraphy and supersedes any previous interpretations or theories documented within the historical record. Overburden stick logs from Phase 1B (Figure 15) are included in the project plans for both the upstream and downstream grout line on sheets CTW-REF124 and CTW- REF125 of the Contract Drawings. Phase 1B confirmed fluvial deposits across the valley center consist of a broad range and combinations of silts, clay, sands, gravels, and organic material.

These deposits begin at ~Station 17+30 to 22+50 ending on the left side of the conduit. The fluvial deposits taper off to the left of Station 17+30 as the valley rises out of the river channel.

Overburden soils on the left abutment generally consists of lean clays with some gravel and silt.

Across the historic valley, large sand deposits were encountered (SP, SP-SC, and SP-SM) in historic flood plain areas left of the historic channel between Station 20+00 and the conduit.

Some deposits near Station 21+00 were as deep as 40 feet. To the left of the channel, these deposits are typically under a layer of clay (CL, CL-ML) that separated them from the embankment above. Organic and woody matter were encountered in several holes.

Figure 15: Extents of Typical Overburden Soils.

Project Operations The project was designed and is operated as a flood control structure; between the months of November and March the project targets a flood control pool of 470, known as Winter Pool, so the reservoir can accept large inflows. A pool restriction has been incorporated into the Water Control Manual which delays the spring fill start date from March 15 to April 1, and lowers the target Summer Pool elevation from 495 (normal) to 490 (restricted). The project has a spillway with a control sill at elevation 524 and all releases below this elevation are considered controlled while releases above it are considered uncontrolled. Seasonal lake levels will pursue the Restricted Summer Pool operating guide curve (Figure 16) throughout construction. The Normal Summer Pool may be re-instated after acceptance of the outlet works AND cutoff wall (Figure 16). Historical documentation for reservoir levels, project rainfall, and other climatic information are included in the Contract in the SPECIFICATON 00 31 19.23 06 WEATHER AND WATER

STAGE DATA AND RESTRICTIONS. Hydrographs are included in the plans. The stage frequency curves for the reservoir and the tailwater are shown in Figure 17 and Figure 18. The stage frequency curve will be the same for both the existing and new outlet works.

Figure 16: Rough River Normal and Restricted Summer Pool Operation Guide Curves.

Figure 17: Stage Frequency Curve for the Reservoir.

Figure 18: Stage Frequency Curve for the Tailwater Area.

Flood Pool Event Frequency The dam has experienced several high pool events since its construction. The dam is inspected daily when the pool is between elevation 490 and 520, and twice a day when above 520 per the Surveillance and Monitoring Plan. During spillway flow the Emergency Operations Center would be open at the District office for external coordination, and access to the tailwater may be disrupted.

Table 4: Previous High Pools Pool Elevation Date

527.40 (Pool of Record) 04 May 2011

521.61 24 Feb 1989

521.19 22 May 1983

520.90 28 Sep 1979

517.94 22 Mar 1997

517.12 28 Dec 2007

517.10 22 May 1984

2011 Record Pool Rough River Lake experienced the pool of record of elevation 527.4 on 4 May 2011. During this event, the pool was above the spillway elevation for the only time since construction (elevation

524) from 28 April through 8 May 2011. The uncontrolled open cut spillway beyond the left abutment activated for 10 days and at its peak had approximately 3.3 feet of water flowing over the unlined control sill. The topsoil and grass covering the spillway floor was mostly removed but no damage to the rock floor of the spillway was noted (Figure 19). Head cutting was noted at the terminal end of the spillway where it discharges into the ravine. However, the head cutting was limited to a zone of excavated material that was wasted in this area after excavation of the spillway cut and a zone of residual clay. The ravine also sustained significant scour at the upper end. Materials eroded from the end of the spillway were deposited in the ravine and campground at the lower end of the ravine.

Figure 19: Spillway terminus during (5 May 2011) and after (15 May 2011) record pool.

Overview of Planned Rehabilitation A Dam Safety Modification Report (2012) was produced in response to a DSAC Classification 2 (High Urgency) ranking. The essence of the report identified that the project failed to meet tolerable risk guidelines due to the potential for piping through untreated, solutioned and excavation-damaged bedrock. It was determined that a concrete cutoff wall installed through the crest of the dam and founded below the karstic bedrock would be necessary to prevent the piping. In preparation for installation of the cutoff wall, two grout curtains were installed, one upstream and one downstream of the anticipated cutoff wall alignment. It was discovered during a review of the cutoff wall design that the outlet conduit was structurally inadequate to withstand the installation of the cutoff wall. Since no alternatives were found to install the wall without closing the conduit for an unacceptable duration, it was determined necessary to construct a new outlet works within the left abutment (Figure 20). Figure 21 shows a more detailed breakdown of the major areas of work to achieve this goal. Other required ancillary work, such as establishing haul roads and site grading, are included in this contract but not shown here for clarity. Several of the major construction features penetrate differing soil horizons and cut through multiple rock units.

Major features of geotechnical work include:

• A reinforced concrete control tower 177 feet tall, 56 feet wide, and 60 feet long with two

6.25-feet x 14-feet hydraulically operated service and emergency gates.

- The control tower excavation requires an approximate 650 feet long earth cofferdam founded on dentally treated bedrock protecting the excavation up to elevation 525.

- A double-line grout curtain is required around the perimeter of the control tower pit excavation reduce the amount of dewatering required.

- Construction of a 150-foot-long bridge on a processed rock fill abutment.

• An approximate 970 feet long, 14 feet inside diameter tunnel with a 12-inch thick, 6,000 psi abrasion resistant reinforced concrete liner (tunnel excavation and construction requirements are in the Tunneling GBR and GDR).

• Stilling Basin: The stilling basin is a USBR Type 3 basin that will be 115 feet long and 40 feet wide with a dentated end-sill.

- The stilling basin excavation requires an approximate 760 feet long sheet-pile seepage cutoff and cofferdam up to elevation 453.5.

• The stilling basin rock excavation will extend approximately 300 feet downstream from the stilling basin and require a concrete apron and trapezoidal channel to protect exposed shale in the excavation.

• The retreat channel will be a 600+ feet long earth excavation requiring 36 inches of 18-inch maximum sized limestone and stone bedding along both sides of the retreat channel.

• An approximate 945 feet long trapezoidal approach channel, 50 feet wide channel with 6H:1V side slopes excavated into bedrock. Portions of the excavation require underwater blasting and mechanical excavation.

• Abandonment of the existing outlet works.

• Construction of a construction work platform.

• The cutoff wall must be a 1,640 feet + long, 2 feet minimum thick, concrete cutoff wall fully extending through the embankment, existing outlet conduit, and into the foundation bedrock.

• Relocations: Highway 79 will be located back to the crest of the dam.

• Abandonment of the existing retreat channel and stilling basin.

Figure 20: Overview of rehabilitation components.

Figure 21: Areas of notable soil- and rock-related rehabilitation activities.

SITE SPECIFIC SOILS AND ROCK

Summary of Geologic Data Several subsurface investigations have been performed at the site between 1941 to present day.

Specific details, testing, and analyses associated with these investigations are contained in the Appendix B and C. Previous investigations at the dam site have shaped the geologic characterizations over time. Historic subsurface information for the dam and the resulting interpretations have evolved over time. In general, information obtained for the dam over the past 20 years and resulting interpretations based on that information takes precedence over observations recorded during original feasibility and construction of the dam. Interpreted soil and rock assumptions utilized for design of the Phase 2 DSM are described in the sections that follow:

The Contractor’s Completion Report for the Phase 1 slurry control grouting conducted between 2015 and 2017 is available in Volume 6 of the Contract Package FOR INFORMATION ONLY.

This document 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 2015-2017 slurry control grouting is also included Volume 6 FIO. During 2018 and 2019 a Geotechnical Exploration was conducted to determine subsurface information to support the new outlet works.

2018 Phase 1 Outlet Works Investigation The 2018 Outlet Works investigation was based on a preliminary left abutment alignment and consisted of ten borings. Preliminary drilling locations included one hole in the upstream approach channel, two holes in opposing corners of the tower footprint, four holes along the length of the tunnel, two holes in opposing corners of the stilling basin footprint, and one hole in the downstream retreat channel.