W912QR25R0016_CERT_Final_Vol6_ ProjGIR_2of16_A-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 (2 of 16) Appendix A

Certified Final

20 December 2024

W912QR25R0016

ARIMS: 1200

Disposition: Permanent

W912QR25R0016_CERT_Final_Vol6_ ProjGIR_2of16_A-0000

Rough River Dam Geotechnical Data Report for Tunnel Construction

Volume 6: Project GIR

Appendix A - Synopsis of Construction History (2 of 16)

ROUGH RIVER, FALLS OF ROUGH, KY

LOUISVILLE DISTRICT, LRD DIVISION

ROUGH RIVER, FALLS OF ROUGH, KY

LOUISVILLE DISTRICT, LRD DIVISION

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

INSTRUMENTATION AND MONITORING

Appendix E

ANALYSES OF THE UPSTREAM FILTER AND DEWATERING

Appendix F

ANALYSES OF THE DOWNSTREAM COFFERDAM AND DEWATERING

Appendix G

ANALYSES OF DOWNSTREAM FILTER FOR STILLING BASIN ABANDONMENT

Appendix H

ANALYSES OF CUTOFF WALL WORK PLATFORM

Appendix I

ANALYSES OF UPLAND DISPOSAL AREA AND ARCHERY BERM

A-1

SYNOPSIS OF CONSTRUCTION HISTORY AND PERFORMANCE

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 and into full operation in December 1960. Design of the project features was aided by pre-construction and construction explorations. The dam was originally constructed as a homogeneous, impervious earth fill dam with a gate-controlled outlet works on the right abutment and an uncontrolled open cut spillway approximately 400 feet beyond the left abutment of the dam. The design and construction of each project feature is discussed in detail below.

1. EARLY INVESTIGATIONS

Prior to proposing a flood control structure on Rough River, a preliminary examination and survey of the river was made in 1884-85, primarily in the interest of navigation. During the initial proposal of the project in the early 1930s, maps from the US Geological Survey (USGS) were available for most of the Rough River drainage area. A survey from the mouth of the river to Hardin Springs, KY was made with transit and stadia cross sections across the entire flood plain at approximate mile intervals. In addition, cross sections of the bed of the river were developed at one third mile intervals. Two thirds of the length of the river were not considered topographically conducive to a flood control dam. The most favorable topography was above the Falls of Rough, but could not be too far upriver as to leave a large portion of the drainage area unprotected.

Therefore, the most feasible location of the dam was restricted to 11 miles between Falls of Rough and the mouth of North Fork. A site 6.25 miles upstream of Falls of Rough was selected for investigation. No borings were drilled but rock outcroppings and general topography were inspected and used to select the site and make the proposal.

Once the project was authorized by the Flood Control Act of 1938, two potential sites for the dam were identified from available maps and filed reconnaissance. Site B at River Mile 89.3 (about 500 feet upstream of the early 1930s proposed site) and Site C at Mile 88.8. Geologic and topographic features were considered in the selection and layout of the final selected site. Core borings were drilled at Sites B and C to determine the subsurface condition and select the dam site.

Site C was eliminated due to the highly weathered rock in the foundation of the spillway and highly soluble Glen Dean Limestone that would cause a seepage concern at the abutment and reservoir rim. Borings and investigations at Site B revealed that the conditions were favorable for the construction of the dam. The foundation rock was an adequate strength to support the conduit, spillway and maximum height of the embankment dam. As a result, Site B was selected for the final project location. Once the site was selected, the foundation was further explored with core borings, auger borings, and test pits. The borings and test pits characterized the overburden soils that were used in the foundation designs and borrow materials. Chapter 3 provides additional details of the pre-construction explorations.

2. EMBANKMENT

The dam consists of a 1,590-foot long, earth-filled embankment having a maximum height of 130 feet above the streambed with a 40 feet wide crest width as shown in Figure 1. The maximum width at the dam base of 819 feet. The original upstream face has 4 feet of dumped riprap stone protection underlain by 12 inches of spalls and choker material. The rock at the downstream toe

A-2 is limestone that has a top elevation of 460 and 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 2007, the top-of-dam elevation was raised to 555 and a 4 feet parapet wall was added for wave wash protection up to elevation 559 to meet current hydrologic requirements. The embankment side slopes are summarized in Table 1. KY Highway 79 was moved to the upstream crest in 2014 where the roadway is currently trafficked (Figure 2). Details of these two modifications to the embankment are discussed in the 0 Major Modifications/Repairs section.

The dam embankment consists of low permeability lean and fat clay fill. Internal drainage of the embankment is provided by a 10-foot thick, 1.0H:2.0V inclined drain starting at elevation 495, as well as a 2-foot thick, basal filter blanket on the stripped downstream ground surface extending to the toe of the dam. The structure is founded on residual soils along the left abutment and alluvial soils within the valley center. Three relief wells were installed at the downstream toe in the left bank foundation in an attempt to reduce uplift pressures and to control the water movement through the soil.

There is no core trench, rock treatment, or grouting between the conduit and the left upper left abutment. Along the right abutment the structure is founded on limestone, in which a special treatment zone was slush grouted and treated with dental concrete and concrete bulkheads at several overhangs and ledges. A comprehensive review of the construction photographs indicated that numerous rock overhangs remained in place as embankment material was placed along the right abutment.

Figure 1: 1958-2006 Typical Cross-Section of Rough River Dam.

Figure 2: 2020 Typical Crest Cross Section

A-3

Table 1: Exterior Embankment Slopes Downstream Upstream

Slope (Horizontal on Vertical)

Elevation (feet, MSL)

Slope (Horizontal on Vertical)

Elevation (feet, MSL)

2.0H:1.0V 554 to 539 2.0H:1.0V 554 to 550 2.5H:1.0V 539 to 531 2.0H:1.0V 550 to 495

3.0H:1.0V 531 to base 3.0H:1.0V 495 to 471 4.0H:1.0V 471 to base

*Upstream embankment slope includes KY79 embankment.

Two cofferdams were constructed prior to placing the embankment fill. An upstream cofferdam (Figure 3) protected the work area and was eventually incorporated into the final dam embankment while a diversion dam (Figure 4) directed river flow to the outlet works. A downstream cofferdam constructed in the original river channel (Figure 5) prevented the tailwater from backing up onto the downstream embankment. No information is available describing the materials or methods used to construct the cofferdams. Construction photos and as-built drawings provide a few details about the structures. As-built drawings show that the upstream cofferdam was constructed to EL 465 out of impervious materials and partially incorporated into the upstream embankment toe as shown on the previous cross sections. Once the main embankment dam reached EL 471, the crest and upstream slope of the cofferdam was removed and replaced with a rock face.

A-4

Figure 3: Upstream Cofferdam (Plan View and Construction Photo)

Figure 4: Upstream Diversion Dam

A-5

Figure 5: Downstream Cofferdam (Plan View and Construction Photo)

A-6

Construction of the dam began in May 1957. The footprint of the dam was cleared and stripped of unsuitable material and wasted in the disposal areas. The source of the majority of unsuitable material was the river channel and adjacent banks. Several springs were uncovered in the river channel during material removal. The water from the springs was removed and the area stabilized with crushed rock. The Foundation Report (Volume 6) stated rock ledges and deteriorated rock exposed on the right abutment were removed by blasting, mechanical, and hand methods to provide a satisfactory slope for embankment backfill. Solution channels, vertical and horizontal seams, cracks, crevices and loose areas were repaired by slush grouting. Additional surface treatment was required within a “Special Treatment” zone on the right abutment that consisted of placing bulkheads and slush grouting of deep solution features to provide a suitable slope surface.

Both abutments were also treated with a single grout line prior to and after embankment fill was placed. Details of the grouting and Special Treatment zone are discussed in section 3 Dam Foundation Treatment. Prior to the placement of embankment fill, the stripped surface was scarified, disced and aerated where required and then rolled with a 60-in diameter double sheeps-foot rollers until satisfactory compaction was obtained.

The dam embankment borrow was primarily from the current airport area in the State Park on the left abutment (Figure 6). Rock excavated from the outlet works area was stockpiled and placed in the embankment rock toe. Suitable excavated earth was stockpiled and used for compacted backfill (of the conduit) or in the embankment. A 6-foot deep inspection trench was constructed along the centerline of the dam from Sta. 17+00 to Sta. 21+50. The trench was 10 ft wide at the top and tapered to 8 feet at the bottom. A 1-foot deep inspection trench was excavated to rock from Sta. 13+20 to Sta. 17+00.

A filter blanket with an inclined drain was constructed on the downstream portion of the dam between Sta. ~12+50 and ~23+75. A filter blanket and drain were also installed between Sta.

~22+50 and ~20+50 on the upstream side. The upstream filter and a portion of the downstream filter contained drainage wells which are described in the Valley Foundation Treatment section below (Figure 7). The inclined drain is 10-foot thick, sloping 1.0H:2.0V starting at elevation 495 and connects to the 2-foot thick, basal filter blanket constructed on the stripped foundation soils.

Three relief wells were installed at the downstream toe in the left bank foundation in an attempt to reduce uplift pressures and to control the water movement through the soil.

A-7

Figure 6: Borrow (yellow) and Disposal (orange) Areas

A-8

Figure 7: Location of Filter Blanket

Dozers and motor graders were used to spread the embankment fill in uniform depth lifts prior to compaction with 60-in diameter double drum sheep foot rollers. Compaction tests were well distributed over the length and height of the fill with particular attention given to areas immediately adjacent to the right abutment. Where compaction tests showed a density below 95%, the deficient areas were recompacted and retested. As a result, the embankment was considered to be well constructed.

The thickness of the upstream rock blanket varied during construction. The rock slope was originally designed for a total thickness of 5-foot consisting of a 4-foot thick layer of protection stone over a 1-foot thick blanket of spalls and choker material. As construction progressed, a shortage of heavy protection stone form commercial sources caused the thickness of the upstream slope protection to be reduced. The upstream rock blanket is 5-foot thick from the base of the dam to EL 492 and 3-foot thick from EL 492-524. Above EL 524, the blanket is also 3-foot thick but the top 2 feet are unprocessed sandstone stockpiled from the spillway excavation which is smaller than the 50-100 lbs size range required for coarse protection stone.

The construction photographs indicate that the embankment construction was suspended for the winter just below the top of the foundation filter to the minimum required winter elevation of 490 in November of 1957 (Figure 8). Prior to the shutdown, an inspection report stated the embankment was constructed to EL 490 on the right abutment and sloped up to EL 500 on the left abutment. There is no discussion of staged construction in the construction documents; therefore, it is not known if the erosion fissures were completely remediated when construction picked up

A-9 again the following Spring of 1958. However, the foundation report generally states that proper earthwork techniques were used during embankment placement through the use of scarification, discing and aeration or adding water where needed, and compaction was achieved using 60-inch diameter sheeps-foot rollers.

Figure 8: 1957-1958 Winter Shutdown

3. DAM FOUNDATION TREATMENT

Treatment of the dam foundation was determined from the type and condition of the materials encountered during exploration investigations and construction excavation. Overburden soils left in place within the valley required treatment to improve drainage. Several rock units were targeted for foundation treatment, particularly where karstic conditions were encountered within the limestone units. The following sections describe the foundation conditions and treatment along the dam right abutment, valley, and left abutment. The geologic profile drawing of the dam 7.5 feet upstream of the dam centerline is shown in Figure 9.

A-10

Figure 9: Rock Stratigraphy at Dam 7.5 ft Upstream of Centerline

A-11

4. RIGHT ABUTMENT FOUNDATION TREATMENT

The right abutment extends from Station 22+45 to 25+40. A large portion of the abutment is founded on the Haney Limestone and Big Clifty Sandstone Member. The Haney Limestone was observed to have karst features on the abutment. The Big Clifty Sandstone Member contained mostly massive, cross-bedded, poorly cemented sandstone with intermittent thinly bedded shale seams. The shale seams present within the mass, especially nearer the weathered top of rock portion in contact with the Haney Limestone, were highly weathered and have altered to either clay-filled or open zones within the sandstone mass. These shale/clay seams appeared to be non-continuous across the entire Member, but can be locally significant defects in the sandstone. In general, the upper and/or lower contacts of this sandstone member were either open or clay-filled.

As a result, the units were treated with a single grout line and a “Special Treatment” area was identified where several pockets or cavities were too deep to be satisfactorily corrected by grouting.

The “Special Treatment” zone was cleaned and treated with either slush grouting or concrete bulkheads, depending on how deep the rock features were. This effort was conducted in order to provide a suitable slope against which to place compacted backfill. Internal erosion was not a consideration, so the integrity of the treatment is not clear. The actual area and location of the special treatment area is not known, but appears to extend from elevation 450 (approximate top of fill at conduit) up to elevation 524. Based on the detail provided in the original construction drawings and the foundation report, the width of the treatment area at elevation 450 was approximately 70 feet, tapering up to 5 feet at the top of the treatment zone (Figure 10). Three concrete bulkheads were placed between elevation 490 and 515 to correct deep features. It is assumed that these were associated with shale seams within the Big Clifty Sandstone and solution features contained within the Haney Limestone.

A-12

Figure 10: Right Abutment Special Treatment Zone

A-13

There is not extensive documentation regarding the foundation treatment beyond the Special Treatment area for the right abutment. However, it was indicated in the Foundation Report that the right abutment was stripped of overburden down to the top of rock and the overhanging and deteriorated rock was removed (Figure 11).

Figure 11: Removal of Deteriorated Rock at the Right Abutment

The Foundation Report specifically notes the following in regard to the right abutment:

“After the overburden had been removed from the right abutment area, overhanging rock ledges of limestone, sandstone, and shale showing considerable evidence of deterioration were exposed.

The overhanging and deteriorated rock was removed by blasting, mechanical and hand methods and the face of the bluff was dressed to provide a satisfactory slope and surface against which to place compacted backfill. Solution channels, vertical and horizontal seams, cracks, crevices and soft shaly surfaces were repaired by slush grouting.”

However, a comprehensive review of the construction photographs indicated that numerous rock overhangs may have remained in place, especially upstream and downstream of the special treatment zone. As illustrated in Figure 12, embankment material was placed directly against areas of the abutment where overhangs were present.

A-14

Figure 12: Construction Photograph of Overhanging Rock Left in Place

During dam construction in 1958 foundation grouting initially consisted of a single-line grout curtain in the abutments. A total of 15 grout holes were advanced on the right abutment from Station 22+73 to Station 24+14. The holes were advanced at the bedrock contact with soil stripped and removed. Grouting holes were drilled 20 degrees maximum into the abutment, at a 20-foot maximum center-to-center spacing, to a bottom elevation of 435 in the Big Clifty Lower Shale. A total of 695 bags of grout were used in 14 of the holes. An additional 135 bags were injected into hole R-1 (nearest the conduit); however, it openly communicated with the adjacent conduit excavation, so it is not certain how much was actually taken by the formation and how much simply flowed into the excavation from As-Built and notes in DM No. 3. From the limited information available about the grouting, it appears that most of the grout takes were associated with vertical stress relief fractures and bedrock that was blast damaged which was encountered at or below elevation 450. While no rock core was obtained during the grout hole drilling, it would appear the grout takes are primarily associated with the Big Clifty interbedded sandstone and shale and the lower shale formation. Grouting on the left abutment was from Station 13+90 to 11+80 in the Big Clifty Sandstone and Lower Haney Limestone. The grouting holes were drilled vertically, at a 20-foot center-to-center spacing, to a bottom elevation of 475 into the Big Clifty Sandstone.

In 1960 additional grouting was performed on the abutments following the discovery of additional bedrock solutioning during excavation for a downstream recreation site access road. The subsequent foundation grouting on the left abutment was from Station 13+16 (on the downstream edge of the crest) to 6+06 (at the Highway 79 bridge abutment), 16-foot center-to-center spacing, 20 degrees into the abutment, to a bottom elevation of 475 into the Big Clifty Sandstone. During Phase IB grouting grout on the left abutment was extensively encountered exceeding five feet thick. The grout can be distinguished from latter grouting endeavors by identification of fine black aggregates and in some instances pea-gravel-sized coarse aggregate.

Another grout line was advanced from Station 23+90 to 27+46 along the dam centerline, mostly on 20-foot center-to-center spacing, 20 degrees into the right abutment, to a bottom elevation of 485 to the base of the Haney Limestone. Prior grout treatment at Rough River Dam is shown

A-15 below. Any hole to take over 10 bags of cement was to be split spaced. No documentation has been found which discusses the conditions encountered during this grouting effort.

Figure 13: Geologic Profile along Dam Centerline, with Grout Treatment

5. LEFT ABUTMENT FOUNDATION TREATMENT

The left abutment extends from Station 9+50 to 18+50. The overburden was left in place on this abutment. The left abutment contains an incised drainage channel which is roughly parallel to the dam as shown in Figure 14Error! Reference source not found.. On either side of this drainage channel the topography protrudes farther towards the valley. Between Stations 13+20 and 17+00, an inspection trench approximately 1-foot deep to the top of rock was excavated. From Stations 17+00 to 21+50 a 6-foot deep inspection trench was installed, but no mention of rock was noted.

Apparently, after observations of the soil conditions were made, the trench was backfilled with compacted soils. Soil properties of the foundation and embankment materials are described in Chapter 4.

A-16

A single-line grout curtain was also installed along the centerline of the left abutment in two phases. Prior to construction of the dam, the first phase of the grout curtain was installed along the inspection trench alignment. The grout holes were vertical and extended to elevation 475 on 20-foot centers between Stations 11+80 and 13+90. It appears that this curtain was intended to penetrate through the Haney Limestone and the upper contact of the Big Clifty Sandstone. This resulted in the majority of the Big Clifty Sandstone and the entirety of the underlying Beech Creek Limestone remaining untreated.

Solutioning associated with the Haney Limestone was encountered during the construction of an access road for a recreation site downstream of the left abutment. As a result, a second phase of grouting was initiated to include a grout line at the left abutment from Station 6+06 to 13+16 (Figure 13). These holes were placed on 16-foot centers angled 20° into the left abutment. The grout holes penetrated through the embankment, into rock, down to an elevation of 475, which corresponds to the bottom of the Haney Limestone. Any hole to take over 10 bags of cement was to be split spaced. No documentation has been found which discusses the conditions encountered during this grouting effort.

Figure 14: Conceptual Drawing of Formation Contact Geometries associated with Ravine in Left Abutment

6. VALLEY CENTER FOUNDATION TREATMENT

The valley extends approximately from Station 18+50 to 22+45. The fine silt deposits in the pre-construction streambed were removed prior to placing the dam embankment. The remainder of the valley center soils were left in place and bedrock was not observed, treated, or documented.

Until Phase IB Exploratory Grouting was completed it is not certain as to the complex nature of the rock condition associated with the top of rock drop-off along the nested valley. The foundation soils along the right bank (Sta. 21+00-22+45) of the original river channel have a maximum depth

A-17 of about 30 feet with no natural drainage stratum so a system of vertical sand drains upstream and downstream of the centerline of the dam was installed to facilitate consolidation of the foundation clays beneath the embankment (Figure 15 and Figure 16). No drains were placed within 50 feet of the dam axis. The 12-inch-diameter, sand drains were excavated drilled to bedrock on a 13-foot center-to-center spacing, and filter-graded sands were placed with a tremie. A total of 368 sand drains were installed (141 downstream and 227 upstream of the centerline of the dam). The downstream and upstream vertical sand drains are connected to a 2-foot thick, basal filter blanket.

Figure 15: Vertical Sand Drain As-Built Details

A-18

Figure 16: Construction of Vertical Sand Drain System (3D view and photo)

The left bank soil foundation consists of about 40 to 50 feet of interbedded sands and clays. Along the left abutment above elevation 450, the abutment generally has 5-15 feet of overburden overlying bedrock. Below elevation 450 there are randomly interfingered clays, silts, and silty sand along the left flood plain of the historic valley. As a result of the natural drainage strata encountered in the original geotechnical investigation of the left bank foundation, three relief wells were installed at the downstream toe during the original construction in an attempt to control the seepage and reduce uplift pressures. RW-1 reflects artesian pressures at seasonal pool and above, and the flow is generally less than 1 gallon per minute. WP-1, located directly adjacent to RW-1, exhibits

A-19 artesian flow from a hole drilled through the top of the cap. This artesian condition is experienced year-round with slight increases in flows at increased pool and/or tailwater.

7. OUTLET WORKS

The outlet works provides a discharge capacity of 3,000 cubic feet per second (cfs) with conservation 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 outlet works consists of a control tower (dry type), with 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 and has a drainage gradient of 0.2 percent. There are five seepage collars on 60-foot spacings at the center of the dam. The conduit leads to a and energy dissipating stilling basin and directs the flow through a riprap-lined retreat channel to the river’s original course. The stilling basin was originally a 52-foot long dispersal bucket. An emergency impoundment during embankment construction resulted in high stilling basin discharges and erosion of the end sill. The end sill was repaired and a concrete apron over derrick stone was added downstream of the outlet bucket. In 2007, the end sill and apron were removed and extended the stilling basin to 139-foot long with five baffle blocks. A 144-foot, simple-span, steel truss service bridge extends from the control tower to a roadway on the right abutment.

A-20

Figure 17: Profile of Original Outlet Works

A-21

Construction of the outlet works began in November 1955 and was completed in January 1958.

The original construction, the outlet works consisted of a tower monolith, two transition monoliths, 27 conduit monoliths, and the outlet bucket structure. The left side of the conduit trench was excavated at a 2H:1V slope into native overburden; whereas, 20 to 30 feet of rock excavation was required along the right side of the conduit trench to achieve the 1H:4V slope. Most of the rock excavation was conducted by drilling and blasting complimented by mechanical excavation. The tower and approximately two-thirds of the U/S portion of the conduit was founded on the Beech Creek Limestone. The remaining D/S portion of the conduit and stilling basin was founded on the Big Clifty Lower Shale underlain by the Beech Creek Limestone.

During the conduit trench excavation, the limestone was documented to contain a significant amount of karstic features (Figure 18 through Figure 21). The excavation from the tower to Monolith 8 contained varying degrees and frequency of karstic limestone, solution channels, mud seams and open joints. Karstic features were not observed in Monoliths 9 through 13, which were founded on shale. A large karstic feature re-entered the excavation on the riverward side wall of Monolith 15, along with smaller vertical joints which extended in the foundation excavation of Monoliths 14 to 18. It was suggested by the geologist who mapped the excavation as part of the Foundation Report that the reason why there were no solution features observed from Monoliths 9 to 13, was because the features exiting out of the riverward side wall in Monolith 8 ran adjacent to the conduit excavation and re-entered at Monolith 15. These features were cave sized and ran sub-parallel to the conduit exiting the excavation toward the left (valley side). Where excavated in the limestone, karst features were dentally treated with concrete.

The features which were encountered in the base of the tower and conduit excavations were cleaned with an air-water jet to remove clay infilling and dentally treated with concrete. Where the natural dip of the ground caused the excavation to run deeper than designed the limestone foundation received a lean concrete mud mat between 0.5 and 2 feet thick. The shale foundation was covered with a 3-inch thick concrete seal coat prior to placing concrete. The concrete was then placed in approximately 18-in layers and consolidated with internal vibrators.

The left side of the conduit trench was excavated at a 2H:1V slope into native overburden; whereas, 20 to 30 feet of rock excavation was required along the right side of the conduit trench to achieve the 1H:4V slope, as indicated in the design drawings. The construction photographs indicate that blasting efforts were applied during the conduit excavation; however, the design memorandums, foundation reports and original construction drawings do not discuss the specific blasting methods that were used. For that time period, a pre-split method was often used, with blast hole spacings of 12 to 30 inches. Based on construction photographs, the rock exposed along the right side of the conduit trench may not have been treated upon completion of the blasting and excavation efforts. The conduit itself was not cast against the right abutment, however the seep rings were per notes in the As-Built Drawings. Seepage water encountered above the founding elevations of the monoliths was channeled to sumps and removed by pumping.

Features which extended outside the excavation limits did not receive treatment. In fact, the top of rock adjacent to the outlet works did not have the soils stripped from it. Those solution features which exited the conduit excavation side walls or those present outside the excavation lines were not observed, characterized, treated, or documented.

There was no foundation grouting associated with the outlet works foundation.

A-22

Figure 18: Karstic Features encountered during Outlet Works Excavation (Control Tower, Outlet Barrel, Conduit Monoliths 1-3)

A-23

Figure 19: Karstic Features encountered during Outlet Works Excavation (Conduit Monoliths 4-11)

A-24

Figure 20: Karstic Features encountered during Outlet Works Excavation (Conduit Monoliths 12-19)

A-25

Figure 21: Karstic Features encountered during Outlet Works Excavation (Conduit Monoliths 20-27, Outlet Bucket)

A-26

8. SPILLWAY

A 65-foot wide, 1,800-foot long uncontrolled, unlined, open rock cut emergency spillway was excavated roughly 45 feet deep into rock approximately 400 feet beyond the left abutment. A 6-foot-wide concrete sill for grade protection at the crest at elevation 524 at +0.5 percent, and then slopes down away from the crest at 1.5 percent through the spillway. Water enters the spillway through a natural drainage valley in the left abutment. Overburden was excavated back to 2H:1V side slopes, and rock cuts through the spillway were 1H:4V for all strata of rock. Spillway construction was accomplished by blasting. The Contractor reportedly used an unproved ammonia explosive material which resulted in overshooting of the rock resulting in a ragged appearance in the slopes and floor. The spillway is traversed by Kentucky Highway 79 using a single span, simply supported, steel multi-girder bridge with a cast-in-place concrete deck extending approximately 36 feet above the spillway floor. The spillway side slopes are lined at the bridge location to support the bridge structure. The plan view of the spillway is shown below in Figure 22Error! Reference source not found.. The floor of the spillway is the Haney Limestone and is described in the GIR body. Performance of the spillway is discussed below in regard to the recent spillway flow event and resulting erosion.

Figure 22: Spillway Plan

9. PROJECT PERFORMANCE

Project performance is monitored in accordance with the Operations and Maintenance Manual and the Surveillance and Monitoring Plan. Project staff are on site daily to inspect the dam and instrumentation for changes in performance. More detailed inspections are performed and documented on a regularly scheduled basis and in response to unusual events.

A-27

10. INSPECTIONS

The dam and appurtenant structures are inspected on an annual, routine, and intermediate basis.

Annual and routine inspections occur after specified time intervals (i.e. Annual and Periodic Inspections). Intermediate inspections are unscheduled and typically occur after unusual loading events or as the result of unusual behavior.

10.1 ANNUAL INSPECTIONS

Several types of inspections are performed once a year. These include Annual Instrumentation Reviews and Intermediate Inspections. Annual Instrumentation Reviews have been performed annually since 1998 to review all instrumentation readings from the past year and compare them with all previous readings to determine if there are changes in trends. A summary of the instrumentation is included in Appendix D. Intermediate Inspections have been performed since 2001 to monitor the condition of the project for unusual or unexpected behavior in between Periodic Inspections. All major inspection findings are also summarized in the following scheduled Periodic Inspection Report.

10.2 PERIODIC INSPECTIONS

Periodic Inspections are conducted on a 5-year cycle to inspect the present physical condition of the dam and appurtenant structures, evaluate instrumentation readings, and provide maintenance, dam safety, and life safety recommendations. The first Periodic Inspection at Rough River was performed in 1969. Since then, Periodic Inspections have been performed every five years with the most recent 11th PI completed in 2018. Generally, the embankment, spillway, and outlet works structures have been reported to be in good condition and operational with the exception of the following observations: Erosion of the retreat channel, sinkhole development on the downstream slope, and undersized spillway and stilling basin. These major inspection findings are further described in the following paragraphs. Any remediation associated with these conditions are described in 0 Major Modification/Repairs.

10.3 HIGH POOLS

The dam has experienced several high pool events since its construction. During high pool events (pools above summer pool EL 495) the dam is inspected daily. When the pool exceeds EL 520, the dam in inspected twice a day. When the pool reaches the pool of record, the IRRM Plan calls for a determination if 24-hour surveillance is required. The table below lists the progression of the pool of record.

Table 10-1: History of Pool of Record 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

514.07 22 May 1967

A-28

10.4 2011 POR PERFORMANCE

During April-May 2011 historic rainfall resulted in a record pool, spillway flow, and high tail water levels at Rough River Dam. The project was under 24-hour surveillance for 15 days (27 April – 11 May) during the event. Performance observations from the event are recorded in the 2011 Record Pool Inspection, Stilling Basin De-Water Inspection memo and summarized below.

Spillway:

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

Overall, the spillway performed very well. The control sill performed well and no damage was observed (Figure 23). The floor of the spillway consists of in place bedrock with a thin topsoil cover which supported some grass growth. The topsoil was mostly removed along with the grass cover but no damage to the floor of the spillway was noted (Figure 24). Head cutting was noted at the terminal end of the spillway before the water enters the ravine to which the spillway discharges. 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 (Figure 25). The wasted material consists of stone ranging from 1 to 10+ foot boulders, measured on long axis. Some intact bedrock, Haney Member of the Golconda Formation (limestone), was exposed during the event but remained in place (Figure 25). The highly weathered epikarstic features exposed in this scoured area of the spillway ranged from clay-filled features to completely open with no infilling at all. If spillway flow had continued for a longer duration, it is likely that erosion would have continued until intact bedrock was exposed at which point the erosion would likely have arrested, as evidenced by the durability of the in place limestone that was exposed.

The ravine that the spillway discharges into (Figure 26) had some significant scour at the upper end along with deposition of boulders which grade to gravel and silt at the lower end. The campground at the lower end of the ravine and its confluence with Rough River received damage from inundation and deposition of silt load.

There is currently a vertical ledge at the terminal end of the spillway. The project has suggested to grade this slope to an approximate 1:1 slope by pushing the shot rock up against the vertical slope. This will armor the cut somewhat and remove the vertical slope that could be a public safety issue due to the close proximity of a nature trail. This is a low priority as this will have no effect on the spillway performance. Additional photos and daily inspection reports during the event are found in the 2011 Record Pool Inspection, Stilling Basin De-Water Inspection memo.

A-29

Figure 23: Spillway Control Sill (left photo 5 May 2010; right photo 15 May 2011)

Figure 24: Spillway cut (left photo 5 May 2010; right photo 15 May 2011)

Figure 25: Terminal end of spillway cut (left photo 5 May 2011; right photo 15 May 2011).

A-30

Figure 26: Spillway discharge flow through ravine downstream of spillway through the campground area.

Stilling Basin:

During the 2011 pool of record, once the lake level reached the spillway crest the main service gates of the outlet works were opened to 100-percent in accordance with the Reservoir Regulation Manual. Conduit outflows exceeded 5,000 cfs from 8 May 2011 through 18 May, 2011. These releases and downstream uncontrolled runoff resulted in extreme high tail water levels (peak EL 455.8) that were sustained for the majority of the event (Figure 27). The record tailwater conditions resulted in damage to the left stilling basin training wall, the gutter along the right stilling basin training wall, and erosion of the right descending retreat channel bank.

On April 28, a lateral deflection on the second (downstream-most) section of the left stilling basin wall was observed. Compared to the dynamic movements observed during a previous high discharge event, this deflection appeared to be permanent. It was further noted that the lateral offset between the first and second sections of the wall had not been present the day before. In addition to the wall offset, increased vibration of the wall was also observed. The chaotic flow in the stilling basin was producing large undulations in the water surface that resulted in pounding type impact forces against the walls. Gate changes had been made that morning and all three gates were fully open (at 30/10ths), releasing a maximum of 5,600 cfs through the conduit. Dam safety determined that a detailed structural inspection of the wall needed to be undertaken as soon as possible.

An inspection team monitored the movement of the wall the following day during the maximum release and during gate operations. Only visual monitoring could be performed at this time because of the amount of water on the elevated walkway. No cracking of the concrete elevated walkway was found. Outflow through the conduit was then reduced to 4,800 cfs to allow the inspection team to measure the offsets (13/8 inches) and make a saw cut to monitor continued permanent deflections (Figure 28). Inspection team members walking on the elevated walkway felt that pounding of the wall was less frequent and of lower magnitude than during the fully open flows. The maximum deflections due to pounding were reduced to ¼- to ½-inch.

A-31

Figure 27: 5 May high tail water and high discharge.

Figure 28: Permanent left wall deflection

Once the pool and tail water receded and the conduit releases could be reduced, a detailed structural inspection of the dewatered stilling basin took place on June 7, 2011. New cracks on the left stilling basin wall were observed parallel to contraction joints and at the base of the wall. The wall displacement was also measured at this time without the water load on the inside of the basin. The permanent deflection was measured to be 5/8 inches. This is a reduction of ¾ inches from the displacements measured on April 29, 2011, which were recorded when the saw cut was made.

Surveyed deflections at the saw cut indicate that the wall moved away from the stilling basin by hinging at the bottom of the wall. Based on the performance of the wall during the high pool event

A-32 and subsequent inspections, it was determined that the left stilling basin wall was permanently damaged and in the very early stages of structural failure. Remediation of the wall by repairing the cracks and adding a land side buttress wall was recommended and is described in section 11.10.

No signs of distress were observed in the right wall of the stilling basin. This wall is 2’-6” thick as opposed to the 1’-6” of the left wall. Additionally, the right wall is anchored into rock. There was extensive damage to the concrete paved ditch behind the right wall. The concrete that formed the ditch collapsed due to loss of the granular backfill underneath (Figure 29). The concrete was undermined on the rock side because the concrete had not been placed all the way to the rock face, leaving an exposed section of granular fill. The fill was removed by the continuous waves spraying up into the wall during the high release period resulting in progressive undermining and collapse.

Damage to the concrete ditch did not pose a threat to the stability of the north wall. Remedial work consisted of the removal and replacement of the gutter section along the right training wall and grading and rip rap placement along a section of the right descending retreat channel bank.

Figure 29: Right stilling basin wall gutter.

Embankment/Abutments:

Overall the embankment dam performed satisfactorily during the pool of record event with no indications of structural distress evident. Wave action from high tail water caused erosion rills to deepen where grass cover was missing above the rock toe (Figure 30). The area was repaired by placing rip rap along the dam toe up to EL 460. Instrumentation readings were taken at an accelerated schedule in accordance with the IRRMP. Several instruments (PZ-13A, -42, -35, -36, -40, and -41) had trends that were of concern during the event and indicated possible interconnected open or episodic opening of solution features. The pool of record had little to no effect on the historical seeps on the right and left abutments. Flow from the left abutment seeps were minor and always observed to be clear. The right abutment seep is controlled by rainfall and does not appear to be connected to the pool.

A-33

Figure 30: Embankment toe erosion.

11. SPECIAL EVENTS

11.1 DOWNSTREAM SINKHOLE

On 26-27 September 2002, the remnants of Hurricane Isidore generated up to 6.5 inches of rainfall in a 24-hour period over portions of Kentucky. On 27 September 2002, project personnel discovered a sinkhole on the downstream slope of the dam at about 464 feet from the crest, measuring 3 feet by 6 feet at the ground surface and 3 feet deep (Figure 31). Inspections of the sinkhole were conducted hourly during the first two days and reduced over the following days as there were no changes observed to the sinkhole. Eleven borings were drilled in and around the sinkhole and the rock toe to characterize the embankment soil and foundation. After review of the as-built drawings and drilling results, it was determined that the mechanism that caused the sinkhole development was likely related to the lack of a filter material between the rock toe and the earth fill, allowing the earth embankment to ravel into the large voids of the rock toe. A slope stability analysis indicated that an immediate embankment failure was not likely however, corrective action should be taken to prevent further soil migration into the rock toe. The sinkhole was then backfilled and re-seeded.

A-34

Figure 31: Observed sinkhole (September 2002)

In June 2003, the sinkhole showed renewed activity and several shallow depressions developed on the downstream slope just upstream of the rock toe. The sinkhole measured 3 feet by 2.5 feet at the surface and 1.5 feet deep (Figure 32). A roughly 6-inch diameter throat extended downstream about 3 feet. Seventeen borings were drilled in accordance with the Dam Safety Assurance Program (DSAP) to further evaluate conditions surrounding the rock toe. Details of the drilling exploration are included in Chapter 3. Nearby instruments showed no significant change from the previous readings. Based on an evaluation of the construction records, geotechnical investigations, and other observations, it was confirmed that the embankment soil was raveling into the porous rock toe due to a lack of filter material. During intense hydrologic events where the embankment was exposed to significant surface water, the severity of the conditions associated with the rock toe generally increased and migration of soil into the rock toe accelerated. The concern was that further migration of soil particles into the rock toe would propagate instability of the downstream slope. The original 2002 sinkhole backfill was excavated and replaced with clean sands in order to easily identify further progression until the area could be remediated. A combination barrier wall and filter blanket method was selected to remediate the soil migration into the rock toe. A description of the resulting rock toe remedial measures is provided in section 11.7 Rock Toe Repair.

A-35

Figure 32: 2003 Sinkhole

11.2 UPSTREAM DEPRESSIONS

In 2003, three potential sinkholes were identified on the upstream slope of the dam (Figure 33) near the outlet works between the old river channel and the conduit at an elevation just below summer pool Elevation 495. The first depression was approximately 4 feet in diameter and 3.5 feet deep. A throat could not be observed. There was a pressure gage from an abandoned instrument near the depression No evidence of water flow or sediment transport was observed. A second potential sinkhole was observed left of the first in line with PZ-13A which has since been removed.

This depression was approximately 3 feet in diameter and 3 feet deep. A third potential sinkhole approximately 2 feet deep and 2 feet wide was also identified in line with the KYTC fasten Seatbelt Sign. Instruments did not indicate any changes with the exception of Seismic Instrument C which had been triggered that week. The Center for Earthquake Research and Information indicated several seismic events with magnitudes less than 2.0 had occurred but this would not have triggered Seismic Instrument C. These depressions were likely a result of manmade alterations of the rip rap or settlement around old instruments and not considered a dam safety concern.

A-36

Figure 33: Potential sinkholes on upstream slope

11.3 STILLING BASIN DEWATERING

The stilling basin has been dewatered multiple times for routine inspections and for construction activities. A 1979 inspection dewatering identified undermining of the paved retreat channel and a hole within the paved section 10 feet from the downstream end and 2 feet from the right abutment retaining wall (Figure 34). The scour and hole was repaired the following year. In June 1984, a section of the concrete apron immediately downstream of the flip bucket was found to be damaged.

Upon dewatering, an 18-foot by 15-foot section of concrete was missing and the soil and rock below had been eroded to a depth of approximately 8 feet and extending up to 10 feet laterally beneath the adjacent slabs (Figure 35). The downstream end of the apron was covered with rock assumed to be from the scour hole and displaced grouted rip rap from the left bank. The rock pile was approximately 18 feet wide by 40 feet in length and ranging up to about 3.5 feet in height.

Additionally, the downstream end of the apron adjacent to the right concrete wall was again undermined a depth of 2 to 4 inches extending 42 inches upstream. Repair of the stilling basin is described in section 11.5.

A-37

Figure 34: 1979 Apron Erosion

Figure 35: July 1984 Rip Rap (left) and Apron (right) Scour

In 2007, the stilling basin was dewatered to facilitate construction of the 90 ft stilling basin extension (see section 11.8 for construction details). During construction, multiple boils were observed near the left stilling basin wall and seepage was noted emerging from the exposed shale downstream of the original stilling basin structure. This was located in the new stilling basin floor excavation.