1. ch205i1-6766.ppt / 1

2. ch205i1-6766.ppt / 2 What the WPCP Expansion Project Is Increase treatment capacity to 12 million gallons per day (mgd) ADWFIncrease treatment capacity to 12 million gallons per day (mgd) ADWF Replace and increase capacity of WPCP Outfall Diffuser in Sacramento RiverReplace and increase capacity of WPCP Outfall Diffuser in Sacramento River

3. ch205i1-6766.ppt / 3 Existing Outfall Installed in 1970s, repaired/modified in 1992Installed in 1970s, repaired/modified in 1992 Existing outfall capacity is limited to 11 mgd ADWF or 27.5 mgd PWWFExisting outfall capacity is limited to 11 mgd ADWF or 27.5 mgd PWWF Existing outfall diffuser design will not provide optimized dilution in the futureExisting outfall diffuser design will not provide optimized dilution in the future

4. ch205i1-6766.ppt / 4 New Outfall Design Criteria Able to convey 15 mgd ADWF or 37.5 mgd PWWF by gravityAble to convey 15 mgd ADWF or 37.5 mgd PWWF by gravity Sized for buildout flows to minimize number of times work must be done in riverSized for buildout flows to minimize number of times work must be done in river Outfall design incorporates features to maximize dilutionOutfall design incorporates features to maximize dilution

5. ch205i1-6766.ppt / 5 History of Gravel Bar Encroachment

6. ch205i1-6766.ppt / 6 Alternatives Considered by City’s Geomorphologist Continued dredgingContinued dredging Spur dikesSpur dikes Relocate gravel barRelocate gravel bar Pilot channel to Big Chico CreekPilot channel to Big Chico Creek Moveable diffuserMoveable diffuser Relocate outfall downstreamRelocate outfall downstream

7. ch205i1-6766.ppt / 7 Continued Dredging Not a permanent solutionNot a permanent solution Dynamics of river unpredictableDynamics of river unpredictable High costHigh cost Extensive permitting requirementsExtensive permitting requirements

8. ch205i1-6766.ppt / 8 Spur Dikes Could limit growth of gravel barCould limit growth of gravel bar City would still need to replace outfall diffuser in current location to achieve 12 mgd capacityCity would still need to replace outfall diffuser in current location to achieve 12 mgd capacity City would still need to increase capacity of existing outfall pipeline to achieve 15 mgd capacityCity would still need to increase capacity of existing outfall pipeline to achieve 15 mgd capacity

9. ch205i1-6766.ppt / 9 Relocate Gravel Bar Existing bar excavated and moved to opposite bankExisting bar excavated and moved to opposite bank Remaining east bank reshapedRemaining east bank reshaped West bank riprappedWest bank riprapped Two to three spur dikes to maintain flow alignmentTwo to three spur dikes to maintain flow alignment

10. ch205i1-6766.ppt / 10 Channel to Big Chico Creek Channel excavated through park to Big Chico CreekChannel excavated through park to Big Chico Creek Provides constant flow through creek to prevent sediment from filling in east bankProvides constant flow through creek to prevent sediment from filling in east bank

11. ch205i1-6766.ppt / 11 Moveable Diffuser Drive piles in toe of leveeDrive piles in toe of levee Extend pipeline downstream as neededExtend pipeline downstream as needed Work in the river multiple timesWork in the river multiple times

12. ch205i1-6766.ppt / 12 Relocate Outfall Downstream Move outfall diffuser 1200’ downstreamMove outfall diffuser 1200’ downstream Route new outfall pipe to new locationRoute new outfall pipe to new location Expected life of 15-20 yearsExpected life of 15-20 years May have to move outfall again in futureMay have to move outfall again in future

13. ch205i1-6766.ppt / 13 Alternative Evaluation (1) Based on CALTRANS Butte City Project and MWH report prepared for steering committee. ++o Relocate Diffuser o-o Moveable Diffuser --? Pilot Channel --? Relocate Bar o (1) o (1)-+ Spur Dikes ---Dredging Cost Regulatory Issues Lifetime Evaluation Criteria Alternatives

14. ch205i1-6766.ppt / 14 Recommended Alternative Needed for City to move forward with EIR process for projectNeeded for City to move forward with EIR process for project EIR mentions M&T project and potential for joint projectEIR mentions M&T project and potential for joint project Not all M&T project alternatives present a joint benefitNot all M&T project alternatives present a joint benefit City’s EIR proceeding with relocation of outfall diffuser 1200’ downstreamCity’s EIR proceeding with relocation of outfall diffuser 1200’ downstream

15. ch205i1-6766.ppt / 15 Expected Outfall Project Timetable EIR public review period ends 3/21/05EIR public review period ends 3/21/05 Design complete late spring 2006Design complete late spring 2006 Construction start late summer 2006Construction start late summer 2006 Outfall work most likely summer 2007Outfall work most likely summer 2007