BCRUA Deep Water Intake Alternative Site Study

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BCRUA Deep Water Intake Alternative Site Study

• November 15, 2007

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Project timeline

• Phase 1 30 mgd (summer 2010)
• Floating intake
• 78-inch raw water pipeline
• Regional water treatment plant
• Treated water pipelines to Leander, Cedar Park,
  Round Rock
• Phase 2 70 mgd (2016)
• Deep water intake (may be accelerated depending
  on lake levels)
• 84-inch raw water pipeline from intake to Phase 1
  pipeline
• Water treatment plant expansion

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Phase 1 Intake

• Floating intake will utilize existing Twin
  Creeks barge
• Barge will be expanded with eight new pumps
• Expected to operate until deep water intake is
  constructed

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Phase 1 Intake (contd)
Cedar Park Intake
Twin Creeks Intake
View looking west from shoreline
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Need for Deep Water Intake

• LCRA manages Lake Travis
• LCRAs management plan predicts Travis may drop
  below elevation 576 in a severe drought
• An intake below 576 is required to ensure water
  is available in such a drought

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Need for Deep Water Intake (contd)

• Deep water is only accessible near the original
  river channel
• The Volente area offers access to deep water and
  is in closest proximity to the BCRUA, Cedar Park,
  Leander/LCRA plant site

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Site Alternatives Study

• To determine which site is the most suitable for
  an intake structure
• Seven sites in the Volente area under study
• Four types of intakes under study

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Site Alternatives Study (contd)

• Selection will be based on multiple criteria
• Minimizing cost
• Compliance with regulatory requirements
• Minimizing social impacts
• Minimizing environmental impacts
• Elimination of all impacts is an unattainable
  goal

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Site Alternatives Study (contd)

• Social impacts include
• Construction impacts (noise, dust, traffic
  disruption, etc.)
• Aesthetics (visibility, architecture, lighting,
  noise, traffic, etc.)
• Recreation impacts (restricted area, navigation
  hazards, etc.)

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Site Alternatives Study (contd)

• Environmental impacts include
• Construction impacts (noise, dust, etc.)
• Geologic impacts (groundwater, karst)
• Habitat impacts (endangered species, particularly
  birds and karst invertebrates)
• Water quality

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Alternative Sites
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Alternative Intakes

• Four types of intakes to be evaluated at each
  site
• Microtunnelled lake tap
• Microtunnelled lake tap with remote pump station
• Tower
• Inclined pump

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Microtunnelled Lake Tap
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Microtunnelled Lake Tap (contd)

• Advantages
• No structure in lake
• Maximum opportunity for aesthetic/architectural
  compatability with surroundings
• Disadvantages
• Second most expensive to construct
• Cannot be located in flood plain
• Must be within 1,200 feet of deep water

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Microtunnelled Lake Tap withRemote Pump Station

• Similar to Microtunnelled Lake Tap, but a smaller
  gate shaft near the lake feeds water through a
  deep tunnel to a pump station further away from
  the lake
• A smaller building is located at the lake
• The larger pump station is located elsewhere

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Microtunnelled Lake Tap withRemote Pump Station
(contd)

• Advantages
• No structure in lake
• Maximum opportunity for aesthetic/architectural
  compatability with surroundings
• Gate shaft might be in flood plain with suitable
  design
• Disadvantages
• Most expensive to construct
• Gate shaft must be within 1,200 feet of deep water

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Tower Intake
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Tower Intake (contd)

• Advantages
• Moderate construction cost
• Can be constructed in flood plain
• Disadvantages
• Large structure in lake
• Increased visibility

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Inclined Pump Intake
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Inclined Pump Intake (contd)

• Advantages
• Lowest construction cost
• Pump station can be constructed in flood plain
• Disadvantages
• Inclined pumps have increased maintenance
  problems, and 2,000 HP installations are unproven
• Pump barrels are exposed on lake shore

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Site Selection Process

• Study Initiation
• Public meeting to solicit comments and future
  participation
• Technical/Feasibility Review - Evaluate 28
  alternatives for feasibility, cost, pipeline
  routing (approx 2 months)
• Working meeting to discuss findings and review
  selection criteria and weighting factors
• Environmental/Social Impacts Review - Evaluate
  selection criteria (approx 2 months)
• Working meeting to present preliminary selection
  and solicit input
• Finalize Selection - Evaluate comments and update
  selection matrix (approx 1 month)
• Working meeting to present final selection

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Questions Comments

• Please
• Provide comments regarding
• Selection criteria
• Alternative sites, any other potential sites
  within the study area
• Intake alternatives
• Hold all questions relating to water rights,
  alternative sources, and participation in the
  City of Austins project