US Army Corps of Engineers BUILDING STRONG ® Mark Twain Lake Water Control Manual Update Joan Stemler St. Louis District Water Control

BUILDING STRONG ® 2008 Event Overview  Record flood event in July/August ► Pool = NGVD ► Outflow = 54,000 cfs  Funding was provided to update the Water Control Manual (WCM) ► WCM was over due to be updated  Additional items funded ► Updated Tailwater Rating Curve ► Inundation Mapping for various flow scenarios ► Updated Hydrology

BUILDING STRONG ® The Goal  Reduce pool elevations without increasing downstream flooding while enhancing other project purposes ► Flood Control ► Hydropower ► Recreation ► Fish and Wildlife ► Water Supply

BUILDING STRONG ® Process  Solicit input from the stakeholders, emergency responders, and the public (6 meetings)  Present alternatives to be analyzed (5 meetings)  Analyze the alternatives (>150 alternatives)  Present findings and propose a preferred operating plan and take comments (9 meetings)  Respond to comments and concerns (7 meetings)  “Official” 30 day comment period  Send draft WCM for Division approval

BUILDING STRONG ® Alternatives

BUILDING STRONG ® Crop Season Release Alternatives  Change Crop Release Restriction to (Max releases are based on downstream conditions): ► 8,000 ► 10,000 ► 12,000  Graduated Scales ► Max release: 8,000 at elevation and is increased as elevation increases to max 14,000 at elevation (No Miss River restriction) ► When Miss River in flood, max 2,000 at <609.0 increasing to equivalent 24-hr generation at (approximately 8,000). Max releases are based on downstream conditions ► When Miss River is not in flood and in crop season, sliding scale for max discharge 6,000 at <606.0 and 12,000 at Max releases are based on downstream conditions

BUILDING STRONG ® Mississippi River Release Alternatives  Release ahead of the Mississippi River crest and cut 24 hours prior to the crest  Remove the Mississippi River restrictions  Change the pool elevation where the Mississippi River is no longer operated for from to: ► ► ►  Change the Mississippi River release restriction from 2,000 to 6,000  Raise the Mississippi River stage restriction: ► Plus 5 feet ► Plus 3 feet

BUILDING STRONG ® Maximum Release Alternatives  For pool elevations above release: ► 14,000 ► 24,000  For pool elevations above release 75% of inflow

BUILDING STRONG ® Surcharge Regulation  If pool elevation is forecasted to reach surcharge (water on the ground), the max discharge may be preempted increased to discharge called for on the surcharge curve for that given elevation and inflow.  Recession side of Surcharge - Target 1 to 2 foot fall per day not to exceed previous max event release until pool elevation: ► ► ► 615.0

BUILDING STRONG ® Winter Drawdown and/or Guide Curve Change  Season Guide Curve Nov thru March ►  Other Alternatives Analyzed ► Season Guide Curve Nov thru March (Bottom of Reservoir) ► Year Round Guide Curve (Bottom of Hydropower Pool is 592.0)

BUILDING STRONG ® Fish Spawn Alternatives  Fish Spawn Pool Elevations: ► 606 thru 620

BUILDING STRONG ® Summary of Proposed Changes  Crop Release Restriction ► Increased from 6,000 to 10,000 Releases are based upon downstream conditions  Mississippi River Release Restrictions: ► Max Release – when Louisiana or St. Louis is at or forecasted to be at or above flood stage and not on the recession side of the hydrograph : Pool Elevation lowered from to Increased from 2,000 to 6,000 Cut to 2,000 24hr prior to crest Releases are based upon downstream conditions

BUILDING STRONG ® Summary of Proposed Changes  Surcharge ► Max Release: If pool elevation is forecasted to reach surcharge (water on the ground), the max discharge may be preempted increased to discharge called for on the surcharge curve for that given elevation and inflow. Recession side of Surcharge - Target 1 to 2 foot fall per day not to exceed previous max event release until pool elevation  Fish Spawn ► Start date changed from May 1 st to April 23 rd ► Pool Elevation at or below 610.0

BUILDING STRONG ® Proposed Plan vs Current Plan

BUILDING STRONG ® 1993 Actual Proposed ElevDiff (ft) Actual Proposed

BUILDING STRONG ® 2008 Actual Proposed ElevDiff (ft)FlowDiff (cfs) Actual ,000- Proposed ,910-28,090

BUILDING STRONG ® Deviation 2010 Actual WCM ElevDiff (ft) WCM Actual

BUILDING STRONG ® NEPA National Environmental Policy Act

BUILDING STRONG ® 30 Day NEPA Review Period  The EA will be distributed to all interested parties ► Includes all attendees of public meetings that provided an address  All interested parties are given 30 days to review the environmental assessment and provide comments

BUILDING STRONG ® 30 Day Review Period Continued  All comments received will be addressed on an individual basis, including any new or ongoing concerns  Such comments will be incorporated into the Environmental Assessment  A “Finding of No Significant Impact”, signed by the St. Louis District’s Commander, concludes the NEPA process assuming the public review results in a determination of no significant impact to the human environment

BUILDING STRONG ® Questions or Comments about NEPA?  NEPA Contact Brandon M. Schneider Environmental Compliance Section Planning and Environmental Branch (CEMVS-PD-E) St. Louis District, U.S. Army Corps of Engineers 1222 Spruce Street St. Louis, Mo PH:  EA will be posted at

BUILDING STRONG ® Approval Process for Revision of Water Control Plan  “Finding of No Significant Impact” from NEPA process is required  Review and approval of plan from Mississippi Valley Division (Vicksburg, MS) is required.

BUILDING STRONG ® ? ? ? Questions ? ? ?