design, construction, operation, and maintenance of the BAP is consistent with recognized and generally accepted good engineering standards.

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2 design, construction, operation, and maintenance of the BAP is consistent with recognized and generally accepted good engineering standards. In addition to the field inspection, Associated Engineers, Inc. reviewed existing engineering data and past inspection reports for the impoundment. Engineering data included geotechnical engineering reports, design reports, construction reports, design drawings, as-built drawings and instrumentation reports. The overall inspection consisted of a visual inspection of the BAP embankments (upstream slope, crest, and downstream slope), appurtenant structures, and visual inspection using a remotely operated camera of applicable hydraulic structures underlying or passing through the impoundment/embankment. The BAP embankment visual inspection was conducted on September 21 and 22, 2017 by Associated Engineers, Inc. Project Manager Justin Lamb P.E. and Senior Environmental Specialist Scott McGarvie. The visual inspection of hydraulic structures underlying or passing through the impoundment/embankment was performed by Glenn Underwater Services, Inc. and based on their findings, found to be in acceptable operating condition. The visual inspections were completed with the goal of identifying signs of distress or malfunction of the CCR unit. Any indications of distress, unusual or adverse behavior, or malfunction of the CCR unit and structures were noted. This inspection may be compared to the previous inspection results for changes evident since Note that all instrumentation data and CCR material survey volume and elevation information were provided by LG&E and KU to Associated Engineers, Inc. (i) CCR Surface Impoundment Geometry The BAP is enclosed by a continuous embankment with pond elevation higher than the natural ground surface beyond the embankment toe. The embankment configuration is generally rectangular and can be described as having four sides (north, east, south and west). The north embankment is longer than the south and the west embankment includes a bend in plan geometry to accommodate this difference in length. An access road is located along the entire crest length. An access ramp to the embankment crest is located along the south exterior slope and additional ramps are located on the west and north slopes. The north, west and south embankments include a Mechanically Stabilized Earth (MSE) wall constructed on the top of an earthen embankment base while the east embankment is constructed wholly of earthen fill. The typical downstream slope for the north embankment varies between 1.7H:1V and 1.5H:1V. The east, south and west downstream slopes vary between approximately 2H:1V and 2.3H:1V. The BAP upstream slopes are approximately 2H:1V. The BAP does not have a principal spillway. The emergency spillway is a reinforced concrete box culvert six feet wide by four feet deep with concrete aprons flanking the box culvert at the intake and discharge sides. The emergency spillway discharges to the Gypsum Storage Pond (GSP) on the north embankment with the spillway outlet located at the downstream embankment toe. There have been no significant changes to the geometry of the impounding structure since the previous 2016 annual inspection. CCR Rule Annual Inspection Report (cont.) 2

3 (ii) CCR Surface Impoundment Instrumentation The BAP instrumentation includes piezometers, survey monuments, inclinometers, weirs, and a pond level gage. Piezometers are open standpipe-type installations that are manually read using a water level indicator. Inclinometer casings are installed at the embankment crest and are manually read using a digital inclinometer system. Survey consists of signs fastened to the MSE wall, prisms placed on the MSE wall, and concrete monuments placed on the embankment below the MSE wall. Pond water level elevation is measured using a non-contact radar water level sensor. (ii) a - Piezometers Maximum Recorded Reading (ft.) ((3) PZ PZ-4C( PZ-4C( PZ-4T (3) PZ-5 (3) PZ-5C PZ-5T PZ PZ-6T PZ PZ-7T PZ PZ PZ PZ-11 (3) PZ-11C( PZ-11C( PZ-11T PZ-12 (3) PZ-26C Maximum recorded reading since July 26, 2016 and ending September 18, 2017 (unless noted with (3) next to station name). 3) Maximum recorded reading since July 26, 2016 and ending December 13, (ii) b - Inclinometers Maximum Cumulative Displacement ( Elevation (ft.) Upslope-Downslope (in.) Cross-slope (in.) IN CCR Rule Annual Inspection Report (cont.) 3

4 Maximum Cumulative Displacement ( Elevation (ft.) Upslope-Downslope (in.) Cross-slope (in.) IN IN IN IN Maximum cumulative displacement in inches since December 13, (ii) c - Pond Level Gage Maximum Recorded Reading (ft.) ( BAP Maximum recorded reading since July 26, (ii) d - Survey Monuments POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION ( (+0.04) (+0.04) (+0.06) / / (-0.02/ (0.00) Elevation (ft.) ( CCR Rule Annual Inspection Report (cont.) 4

5 POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION POSITION Northing ( Easting / (-0.06) / / (-0.06) (0.00) Elevation (ft.) ( CCR Rule Annual Inspection Report (cont.) 5

6 POSITION POSITION (3) POSITION POSITION (3) POSITION POSITION POSITION POSITION POSITION (3) POSITION POSITION (3) POSITION POSITION POSITION POSITION POSITION (3) POSITION SIGN SIGN Northing (+0.07) / (-0.02/ ( / / / (-0.01/ ( Easting ( (- 0.04) / / Elevation (ft.) ( (- 0.03) (-0.09) (0.00) (0.00) CCR Rule Annual Inspection Report (cont.) 6

7 SIGN SIGN SIGN SIGN SIGN SIGN SIGN SIGN SIGN SIGN Northing (+0.04) ( Easting (+0.04) Elevation (ft.) ( Readings associated with the maximum recorded change in Northing, Easting, and Elevation since July 28, 2016 and ending November 15, 2016 (unless noted with (3) next to station name). The maximum change in readings when compared to the July 28, 2016 readings are shown in parentheses. Maximum readings in one direction are either positive or negative. 3) Readings associated with the maximum recorded change in Northing, Easting, and Elevation since July 28, 2016 and ending September 19, The maximum change in readings when compared to the July 28, 2016 readings are shown in parentheses. Maximum readings in one direction are either positive or negative. (ii) e - Weirs Maximum Recorded Reading (ft.) ( SW Weir SE Weir Maximum recorded reading since July 26, CCR Rule Annual Inspection Report (cont.) 7

8 (iii) CCR Surface Impoundment Contents Elevations The BAP water level was Elevation ft. on August 9, CCR elevations range from Elevation 457 ft. to 520 ft. The water depth within the pond varied from 0 to approximately 55 ft. Elevations and depths are based on August 9, 2017 survey information. (iv) CCR Surface Impoundment Storage Capacity The total storage capacity of the BAP is million cubic yards at Elevation 518 ft. The remaining BAP storage capacity at Elevation 518 ft. is million cubic yards. Volumes are based on August 9, 2017 survey information. (v) CCR Surface Impoundment Contents Volumes The total volume of stored CCR is estimated to be million cubic yards. The volume of impounded water is estimated to be million cubic yards. Volumes are based on the August 9, 2017 survey information. (vi) CCR Surface Impoundment Structural, Operational, and Safety Items The preamble to the CCR final rule identifies appearances of structural weaknesses that may include, but are not limited to, nine general item categories. These signs of structural weaknesses may range from minor items that will be added to the routine maintenance plan to deficiencies that could have the potential to disrupt the operation and safety of the structure. The inspection findings consisted of maintenance items and items that were not observed to be signs or potential signs of significant structural weakness. No deficiencies or disrupting conditions that would require immediate measures to remedy were identified in the inspection. The operation and maintenance of the BAP is in accordance with generally accepted good engineering standards. Inspection findings are grouped by category and described below. Visual Inspection Category Observed? Comment No. 1. Excessive, turbid, or sediment-laden seepage No 2. Signs of piping and other internal erosion No 3. Transverse, longitudinal, and desiccation cracking No 4. Slides, bulges, boils, sloughs, scarps, sinkholes, or depressions 5. Abnormally high or low pool levels No 6. Animal burrows Yes 6 7. Excessive or lacking vegetative cover Yes 3, 4, 5, 7 No CCR Rule Annual Inspection Report (cont.) 8

9 Visual Inspection Category Observed? Comment No. 8. Slope erosion Yes 1, 2 9. Debris No Comment No Comment Minor erosion on downstream slopes of the BAP west and south embankments. Minor to moderate erosion; minor slumping on upstream slopes of the BAP west and east embankments. Sparse vegetation on downstream slopes of the BAP west, south and east embankments. Sparse vegetation on upstream slopes of the BAP west, north and east embankments. Disturbance on the BAP south embankment (east end) and east embankment (south end) downstream slopes for construction of future bridge/landfill. Minor to extensive animal burrows and disturbed ground on the downstream slopes of the BAP west and east embankments. Excessive vegetation on the west embankment downstream slope; trees/shrubs on the downstream slope at the intersection of the BAP and the GSP east embankments. The inspection findings consisted of maintenance items and items that were not observed to be signs or potential signs of significant structural weakness. No deficiencies or disrupting conditions that would require immediate measures to remedy were identified in the inspection. The operation and maintenance of the BAP is in accordance with generally accepted good engineering standards. (vii) CCR Surface Impoundment Changes There have been no significant changes to the impounding structure since the previous 2016 CCR annual inspection. Placement of additional CCR material in the impoundment is ongoing. No changes that will negatively affect the stability or operation of the Bottom Ash Pond have occurred since the 2016 CCR Rule Annual Surface Impoundment Report. CCR Rule Annual Inspection Report (cont.) 9