Mid-West Electric Consumers Association Overview Briefing August 2017 Gary Hinkle, P.E. Operations Division Omaha District

U.S. Army Corps of Engineer FY17 Customer Funded Hydropower Program Tracking 46 projects 17 in design, 8 in acquisition, 21 awarded and in construction Awarded 21 contract actions including: Installing digital governors at Big Bend Replacing bulkheads at Fort Peck Replacing powerhouse potential and current transformers at 5 plants Refurbishing intake gate hoist gear boxes at Big Bend Installing programmable logic controllers at Big Bend and Garrison Replacing 480V transformers at Gavins Point Replacing intake motor controls at Oahe Replacing generator exciters at Gavins Paint and Oahe Making site improvements in the generator yard at Garrison 9 cost shares will be closed out with FY18 contract $122.5M customer and revolving funds in FY17/18 (74% toward Randall Rehab) Completed Hydropower Program Management Plan to implement 2016 HMP Utilizing new project support docs and schedule templates to streamline execution

August 2017 Reservoir General COnDitions Past Runoff Last month’s runoff was 101% of normal. July system inflows were 3.3 MAF. Total system storage on July 31 – 61.4 MAF (Down from 61.8 MAF on June 30) Forecasted Annual Runoff – CY 2017 A discussion on the forecast can be found on the Missouri River Water Management website. http://www.nwd-mr.usace.army.mil/rcc/reports/forecast.html Basic – 27.9 MAF (110% of Normal) UB – 29.2 MAF LB – 26.7 MAF Gavins Releases July – 31,700 cfs average release. Releases are currently near 31,000 cfs and will be adjusted as needed based on bird habitat and river conditions downstream.

August 2017 Reservoir Monthly Study Current Water-Year Balancing : balanced for all 3 conditions Basic – Be at the base of flood control. System storage at 56.1 MAF Lower Basic – Below the base of flood control. System storage at 54.1 MAF Upper Basic - At the base of flood control. System storage at 56.1 MAF. Navigation Service Levels The July 1st System storage check was 61.8 MAF. Full-service navigation support Navigation Season Support Length (Jul 1 System Storage Check) Full navigation season; If Upper Basic – 10-day extension. Gavins Winter Release (December thru February) - Sept 1 system storage of 58.0 MAF or more results in a Gavins Point winter release would be at least 17,000 cfs for all 3 conditions. Energy Generation Last month – 1.12BKWhrs actual – long-term average for July, 0.94 BKWhrs. Forecast – Basic Simulation – 9.6 BKWhrs. Long-term average approx 9.3 BKWhrs

CY 2017 Missouri River Runoff Above Sioux City, Iowa Million Acre-Feet Aug 1, 2017 Forecast – 27.9 MAF – 110% Average: 25.3 MAF

Gavins Point Annual Release Million Acre-Feet Aug 1, 2017 Forecast Upper Basic: 21.7 MAF Lower Basic: 19.7 MAF

Missouri River Mainstem System Forecasted Energy Generation Energy in GWh Upper Basic: 10,400 GWh Basic: 9,600 GWh Lower Basic: 9,600 GWh

Mainstem System Generation Million Megawatt Hours Forecast Aug 1, 2017 Forecast Upper Basic: 10.4 Lower Basic: 9.6

System Storage August 1st Forecast Storage in Million Acre-Feet Top Exclusive Flood Control – 72.4 maf Base Exclusive Flood Control – 67.7 maf upper basic Actual basic Base Flood Control – 56.1 maf lower basic Navigation Preclude – 31 maf 2016 2017 2018

OAHE Peaking Concerns Flood stage at the Pierre gage is 13 feet The top of the sheet pile wall at Marion Gardens in Fort Pierre corresponds to a stage of approximately 11 feet.  

OAHE Peaking Concerns Since construction of Oahe Dam, historic elevations for typical operations at the Pierre gauge varied from a low of elevation 1419.00 feet msl to a high of elevation 1427.50 feet msl. It is not uncommon to have daily fluctuations of 5 to 7 feet in the Missouri River and in the development canals. 1427.50 feet msl corresponds to 13.2 ft at the Pierre gauge. Dept of Army Permit; Special Permit Conditions That all structures shall be constructed to a minimum elevation of 1430.00 feet msl or otherwise be flood proofed. That the permittee will advise all lot owners within the Marians Gardens development area of the Corps of Engineers‘ concern regarding flood levels and water level fluctuations In years with high runoff including 1995, 1996, 1997, 2010 and 2011, releases required to evacuate water from the reservoir system result in generally high river stages (above 1425.3 ft elev). Additionally, higher daily average releases in combination with hydropower peaking can result in elevated stages for short periods during the day. Hydropower peaking has occurred both before and after the construction of the Marion Gardens development. There have been a number of occasions since construction with river stages above the approximate top of the sheetpile wall.

Reference Stage (corresponds to elevation 1427.5) Stage used as target level during winter Stage used as notification level during winter Recent Peak Stage (July 2017) Approximate stage near top of sheetpile wall This slide shows the stages at Pierre as well as the approximate top of the sheetpile wall at Marion Gardens. There are a couple of things to note on the graphic: in 2011, the stage went above 19 feet and in the early years (1978 to late 1986) we only got a few readings per day, so that's why it looks like dots.

The second slide in the attached file shows hourly stages at Pierre for the past 15 days. We lowered the daily average release this week in order to get a couple feet of water out of Fort Randall reservoir, so stages are peaking around 10 to 10.5 feet instead of 11 to 11.5 ft as they have the past couple weeks. This is only a temporary change since once we get Fort Randall back down, releases will return to previous levels in order to evacuate flood water stored in the reservoir system and prepare for next year.

Or Google “Corps Missouri River” Thank You! http://www.nwd-mr.usace.army.mil/rcc/ Or Google “Corps Missouri River”