USEPA / AmerenUEMeramec Power PlantIntake Structure Site VisitMarch 4, 2009 USEPA IntakeStructure Site Visit2Meramec Power Plant General Notes4 steam-generatingunits: ~835MW totalBegan Operation:1953Capacity Factor:76.3% (2008)March 4, 2009 USEPA IntakeStructure Site Visit3Meramec Power PlantMississippi River Overview2ndlongest river in North AmericaLength: 2,320 milesDrainage area: ~41% of North America(combined Mississippi and Missouri River)Channelized from Alton IL to Gulf of MexicoHigh silt content288 mg/L TSS (average 2007-2008)1,140 mg/L TSS (max, May 2007)Inlet condenser erosion led to SS tube retrofitHistoric high flow events:1993: 1,070,000 cfs(USGS St. Louis gauge)2008: 716,000 cfs(USGS St. Louis gauge)Average flow: 171,400 cfsUSGS St. Louis, 2000-2007March 4, 2009 USEPA IntakeStructure Site Visit4Meramec Power PlantIntake Structure DesignShoreline intakeAverage 2007-2008 Mississippi waterwithdrawal ~382,000gpm (851cfs)Design flow = 468,400gpm (1,044cfs)Eight intake bays/pumpsMarch 4, 2009 USEPA IntakeStructure Site Visit5Meramec Power PlantIntake Structure DrawingMarch 4, 2009 USEPA IntakeStructure Site Visit6Meramec Power PlantTraveling Screen & Bar Rack DesignBar rack on 3” center (2008-2009)Original 8 X13 ft, 3inch spacingTraveling screen replacement (1999-2004)Original screens: 1950’s drives/technology/frame integrityDual-flow design, decreased debris carryover to condenser3/8” mesh screensScreen approach velocity1.2 fps (Units 1/2)1.3 fps (Units 3/4)Screen wash discharge to flumeScreen rotationDetermined by∆P“Normal” (15”)“Fast” (3ft)Screens designed for 5ft max DPMarch 4, 2009 USEPA IntakeStructure Site Visit7Meramec Power PlantIntake Bay DrawingMarch 4, 2009 USEPA IntakeStructure Site Visit8Meramec Power PlantIntake Structure MaintenanceScheduled routine visual inspectionReplace repair damaged screensContinuous operation and monitoringduring severe debris loadingBackwash baysMarch 4, 2009 USEPA IntakeStructure Site Visit9Meramec Power PlantIntake Structure Debris ImpactsHistoric debris issuesScreensLeaves during Spring and FallTraveling screen damage4-5 baskets damaged with each major debris eventBar rackLogs and other DebrisBackwash baysEvents cause load reductions or outagesMarch 4, 2009 USEPA IntakeStructure Site Visit10Production losses due to ScreensECR MR 2006-01 High screen differential causes highbackpressure and load drop. Screen damageECR MR 2003-0098 All units experiencing high backpressure due to leaves at the caisson. Unit 3 tripped onhigh backpressure.ECR MR-2002-0094 Unit 4 tripped due to highcondenser pressure. Failed screens caused debris tobe carried into condensersECR MR-2002-0099 High differential across racks andscreens caused cavitation of circulating water pumps.Unit trip.ECR MR 2000-46 Screen failed allowing trash to becarried into plant. Unit 4 taken offMarch 4, 2009 USEPA IntakeStructure Site Visit11Meramec Power PlantTraveling Screen Matted DebrisMarch 4, 2009 USEPA IntakeStructure Site Visit12Meramec Power PlantIntake Structure Upgrade ProjectBar rack replacement (2009)Rake to remove debrisTraveling screen replacement (1999-2004)Dual-flow designDecreased debris carryoverMarch 4, 2009 USEPA IntakeStructure Site Visit13Meramec Power PlantIntake Structure Bar Rack UpgradeMarch 4, 2009 USEPA IntakeStructure Site Visit14Meramec Power PlantIntake Impingement Mortality StudiesConducted in 2005-2006No T&E species~95.8% shad & drum (2005-2006)~95.9% shad/drum/carp (2005-2006)March 4, 2009 USEPA IntakeStructure Site Visit15Meramec Power PlantIntake Draft Technology AssessmentConducted prior to remand of Phase II RuleFine mesh screens not evaluatedDual-flow Ristroph screens with expanded intake1.0fps screen velocity, 3/8” screen meshFour new bays with pumpsNew fish return system$84M (2002 estimated)Ristroph screens with reduced intake flow1.0fps screen velocity, 3/8” screen mesh20% flow reductionNew fish return system73.3M (2002 estimated)March 4, 2009 USEPA IntakeStructure Site Visit16Meramec Power PlantIntake Draft Technology Assessment (Part 2)Bar rack barrier1” spacing located on intake structure face0.5fps approach velocityTrash rake system$7.6M (2002 estimated)Wide-slot Cylindrical Wedgewire screensBulkhead mounting (19’ fromintake structure face)0.5fps approach velocity20 screens (each 4.5’Dx15’L)Air backwash system (no provisions for biofouling)$76.5M (2002 estimated)Fixed screen with bar rack1⁄2” mesh on bar rack barrier0.5fps approach velocityTrash rake system$9.2M (2002 estimated)March 4, 2009 USEPA IntakeStructure Site Visit17Meramec Power PlantFine Mesh Screen ConcernsDebris loading with fine mesh screensLarge freshwater inland riverNon-point source runoffEntrainment survivability with high debrisIcing and fine mesh screensIntake expansion potentialPotential reinforcement of structure and screensUnknown impacts on plant reliabilityDebrisLow river elevation operationViability of national standard – additional researchneededSite-specificity: large freshwater river & lakeMarch 4, 2009 USEPA IntakeStructure Site Visit18Meramec Power PlantComments and questions