BARRABA WATER SUPPLY Construction of Split Rock Dam Pipeline and Ancillary Works
Long history of unreliable water supply Water restrictions in place 50% of time over 10 years to 2012 Various studies looked at options incl. Pipeline Groundwater Off stream storage Augmenting Connors Crk Dam
Option Pros Cons Pipeline Very secure/reliable Cater for increased demand Public support High Cost Groundwater Low Cost Questionable reliability Hard Water Increased demand? No public support Off stream storage Medium cost no obvious site for large off stream storage Duplicating Split Rock Dam Questionable reliability Connors Crk Dam Low Cost Blue Green Algae Problems Yield too low Siltation
Council confirmed its support of the pipeline option in 2008 NSW Govt provided 1/3 funding based on estimated cost of $19.66 Million election 2011 Australian Govt provided 1/3 funding as part of Member for New England s agreement to form government Sept 2011 Council to provide remaining 1/3
Capacity Current Demand Average Peak Day 0.3ML/day 1.1ML Concept design recommended 200 mm diameter pipeline Route 7 Routes investigated Oakhampton Road preferred
Elevation (RL in m AHD) Pressures 700 Split Rock Dam - Barraba Pipeline Long Section 650 600 High Point 550 500 Barraba WTP 450 Pump Station 400 0 5000 10000 15000 20000 25000 30000 Chainage (m)
Water quality Lower hardness than water in Manilla River upstream of dam Blue Green Algae may be a problem Treatment Plant Upgrading Need to treat for Iron and Manganese Continuous dosing of PAC for Algae Automatic operation Intermediate connections Allowed if so, how and what conditions
Concept Design Hunter Water Australia Detailed Design - NSW Public Works after a tender process Construction awarded to Leed Construction Pty Ltd after tender process
28km, 225 mm diameter Ductile Iron Pipeline (Diameter amended during detailed design) Current Demand Stage 1 35L/sec Stage 2 47L/sec Stage 3 71L/sec Average 0.3ML/day 1.0ML/day 1.4ML/day 2.0ML/day Peak Day 1.1ML 3.0ML/day 4.1ML/day 6.1ML/day 32KW (180HP) multi-stage, split case, horizontally mounted, centrifugal pumps (duty/standby) 1.5 ML Break Pressure Tank (BPT) approximately centrally located
Under pressure between Dam and BPT, gravity BPT to WTP Barraba Water Treatment Plant Powder Activated Carbon Dosing (Taste and Odour) Potassium Permanganate Dosing (Iron and Manganese) Automation (Telemetry/SCADA)
TWL 594.0m BPT MoL 592.0m LEGEND BPT - Break Pressure Tank BT - Balance Tank DAF - Dissolved Air Floatation FFL - Finished Floor Level FSL - Full Supply Level MoL - Minimum Operating Level TWL - Top Water Level WTP - Water Treatment Plant FFL ~587.0m Rising Main Gravity Main 35 L/s Split Rock Dam Barraba Pipeline System TWL ~516.0m FFL ~510.0m BT WTP DAF DAM FSL 446.0m SPLIT ROCK DAM 35 L/s DAM MoL 408.0m PUMP STATION FFL 406.0m
Timeframe Construction commenced March 2013 Commissioning December 2013 Completed January 2014 Cost of construction $14.3 Million
Trenching 28 Kilometres Challenges 225mm Diameter DICL 5.5 m lengths wrapped Once underway a length of pipe installed every 10 minutes
Pipework Challenges Across bridge over spillway at Split Rock Dam Up the side of the excavation at Pump Station
Challenges Split Rock Dam Pump Station Connection to existing discharge from Dam High pressures up to 250 m head Water hammer
Challenges Plant Keeping the old plant operating whilst new works completed
Challenges Telemetry/Communication Looked at mobile, radio and fibre Chose radio 4 repeater stations required with poles 18-20 meters in height
Road alignment Challenges Majority of pipeline to be located beside existing road in road reserve Survey found existing roads were not in the reserves Negotiation with landowners to shift reserves onto existing roads
Variation 2yrs of testing water quality in Split Rock dam before final design completed November 2013 State water commenced a bulk water transfer out of Split Rock Dam Transfer concluded February 2014 Dam level fell from 80% to 20% Raw water quality plummeted New process could not treat raw water at the design flow rate
Variation Raw water quality improved over the next 2-3 months Concerns Future bulk transfers Turn over of the Dam Consultants engaged to look at design modifications to treat poor raw water Need to move quickly because Money still available under original work Funding from Aust Govt ended in June 2014 Possibility of using original contractor to do any additional work as a variation
Variation Raw water quality issues Manganese up to 2.3 mg/l Iron up to 0.6 mg/l Total Organic Carbon up to 10mg/l Raw water ph of >9.5 Dosing of KMnO 4 was removing Mn but soluble Mn was passing through process before being oxidised by Chlorine in clear water tank - turbidity Low DO conditions reduced effectiveness of KMnO 4 Significant day to day shifts in Mn Jar testing indicated dosing PAC and KMnO 4 simultaneously reduces effectiveness of KMnO 4
Solution Variation Additional on line monitoring for Mn concentration Coated media process to remove residual soluble Mn not removed by KMnO 4 Additional monitoring equipment to monitor ph, Oxidation Redox Potential (ORP) and Chlorine residual Modifications to gas chlorine dosing to maintain coated media process in operation Improve contact time of KMnO 4 Acid dosing system for ph correction and further online ph monitoring Modification of DAF bullhorns to reduce bubble size
Work completed Variation Additional monitoring including online Mn New dosing point for Chlorine upstream of DAF coated media process Baffle installed in Balance Tank to improve contact time Aerator installed in Balance tank Acid dosing system installed Modification of DAF bullhorns
Variation Work commenced September 2014 Completed January 2015 Australian Government made a one off payment based on estimated cost Final cost of variation - $1.7 Million Plant has operated well since all work completed
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