BCRUA Deep Water Intake Alternative Site Study November 15, 2007.
-
Upload
anthony-york -
Category
Documents
-
view
213 -
download
0
Transcript of BCRUA Deep Water Intake Alternative Site Study November 15, 2007.
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
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
Need for Deep Water Intake
• LCRA manages Lake Travis
• LCRA’s 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
Need for Deep Water Intake (cont’d)
• 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
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
Site Alternatives Study (cont’d)
• 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
Site Alternatives Study (cont’d)
• Social impacts include:–Construction impacts (noise, dust,
traffic disruption, etc.)–Aesthetics (visibility, architecture,
lighting, noise, traffic, etc.)–Recreation impacts (restricted
area, navigation hazards, etc.)
Site Alternatives Study (cont’d)
• Environmental impacts include:– Construction impacts (noise, dust,
etc.)– Geologic impacts (groundwater,
karst)– Habitat impacts (endangered species,
particularly birds and karst invertebrates)
– Water quality
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
Microtunnelled Lake Tap (cont’d)
• 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
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
Microtunnelled Lake Tap withRemote Pump Station (cont’d)
• 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
Tower Intake (cont’d)
• Advantages:– Moderate construction cost– Can be constructed in flood plain
• Disadvantages:– Large structure in lake– Increased visibility
Inclined Pump Intake (cont’d)
• 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
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