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What the WPCP Expansion What the WPCP Expansion Project IsProject Is

• Increase treatment capacity to 12 Increase treatment capacity to 12 million gallons per day (mgd) ADWFmillion gallons per day (mgd) ADWF

• Replace and increase capacity of Replace and increase capacity of WPCP Outfall Diffuser in Sacramento WPCP Outfall Diffuser in Sacramento RiverRiver

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Existing OutfallExisting Outfall

• Installed in 1970s, repaired/modified in Installed in 1970s, repaired/modified in 19921992

• Existing outfall capacity is limited to 11 Existing outfall capacity is limited to 11 mgd ADWF or 27.5 mgd PWWFmgd ADWF or 27.5 mgd PWWF

• Existing outfall diffuser design will not Existing outfall diffuser design will not provide optimized dilution in the futureprovide optimized dilution in the future

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New Outfall Design CriteriaNew Outfall Design Criteria

• Able to convey 15 mgd ADWF or 37.5 Able to convey 15 mgd ADWF or 37.5 mgd PWWF by gravitymgd PWWF by gravity

• Sized for buildout flows to minimize Sized for buildout flows to minimize number of times work must be done in number of times work must be done in riverriver

• Outfall design incorporates features to Outfall design incorporates features to maximize dilutionmaximize dilution

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History of History of Gravel Bar Gravel Bar EncroachmentEncroachment

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Alternatives Considered by Alternatives Considered by City’s GeomorphologistCity’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

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Continued DredgingContinued Dredging

• Not a permanent solutionNot a permanent solution

• Dynamics of river unpredictableDynamics of river unpredictable

• High costHigh cost

• Extensive permitting requirementsExtensive permitting requirements

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Spur DikesSpur Dikes

• Could limit growth of gravel barCould limit growth of gravel bar

• City would still need to replace outfall City would still need to replace outfall diffuser in current location to achieve diffuser in current location to achieve 12 mgd capacity12 mgd capacity

• City would still need to increase City would still need to increase capacity of existing outfall pipeline to capacity of existing outfall pipeline to achieve 15 mgd capacityachieve 15 mgd capacity

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Relocate Relocate Gravel BarGravel Bar

• Existing bar excavated Existing bar excavated and moved to opposite and moved to opposite bankbank

• Remaining east bank Remaining east bank reshapedreshaped

• West bank riprappedWest bank riprapped• Two to three spur Two to three spur

dikes to maintain flow dikes to maintain flow alignmentalignment

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Channel to Big Chico CreekChannel to Big Chico Creek

• Channel excavated Channel excavated through park to Big through park to Big Chico CreekChico Creek

• Provides constant Provides constant flow through creek flow through creek to prevent sediment to prevent sediment from filling in east from filling in east bankbank

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Moveable DiffuserMoveable Diffuser

• Drive piles in toe of Drive piles in toe of leveelevee

• Extend pipeline Extend pipeline downstream as downstream as neededneeded

• Work in the river Work in the river multiple timesmultiple times

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Relocate Outfall Relocate Outfall DownstreamDownstream

• Move outfall Move outfall diffuser 1200’ diffuser 1200’ downstreamdownstream

• Route new outfall Route new outfall pipe to new pipe to new locationlocation

• Expected life of Expected life of 15-20 years15-20 years

• May have to move May have to move outfall again in outfall again in futurefuture

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Alternative Evaluation Alternative Evaluation

(1) Based on CALTRANS Butte City Project and MWH report prepared for steering committee.(1) Based on CALTRANS Butte City Project and MWH report prepared for steering committee.

++++ooRelocate DiffuserRelocate Diffuser

oo--ooMoveable DiffuserMoveable Diffuser

----??Pilot ChannelPilot Channel

----??Relocate BarRelocate Bar

oo(1)(1) --++Spur DikesSpur Dikes

------DredgingDredging

CostCostRegulatory IssuesRegulatory IssuesLifetimeLifetime

Evaluation CriteriaEvaluation Criteria

AlternativesAlternatives

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Recommended AlternativeRecommended Alternative

• Needed for City to move forward with Needed for City to move forward with EIR process for projectEIR process for project

• EIR mentions M&T project and potential EIR mentions M&T project and potential for joint project for joint project

• Not all M&T project alternatives present Not all M&T project alternatives present a joint benefita joint benefit

• City’s EIR proceeding with relocation of City’s EIR proceeding with relocation of outfall diffuser 1200’ downstreamoutfall diffuser 1200’ downstream

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Expected Outfall Project Expected Outfall Project TimetableTimetable

• 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