3 Getting to the work site DiabloBoathouseDiablo damHighway 20To Ross damDiablo Dam and boat house
4 Project Location: Ross Hollow Jet Valve House DamValve houseHollow JetValvesOpening toTunnelDiablo Lake /Skagit River
5 ProblemPast O&M work (sandblasting) left lead in the sediment in the tunnel.Can’t pump tunnel dry without discharging lead into Diablo LakeGoalRemove lead to allow future O&M work to pump tunnel dry when needed for inspections and repairs
6 Plan view By-pass intake structure Ross Lake Diablo Lake Tunnel and twoBy-pass penstocksHollow Jet Valves &Valve House
10 Scope of work Install temporary weir (vendor) or permanent weir (SCL) Install rock fall fence (vendor)Remove and treat 1,000,000 gallons of water from tunnel to remove suspended lead (vendor)Remove 10 – 30 cy sediment (vendor)Verify & Dispose sediment – could be dangerous waste (SCL)
11 1. Opening to tunnel Lake level can fluctuate 4-5 feet daily. ~8-ftHigher lake level (elev 1205)~5-ftLower lake level (elev 1199)Lake level can fluctuate 4-5 feet daily.The lake may have waves.
12 1. Install weir Weir Isolate tunnel from fluctuating lake levels Protect workersKeep debris out of tunnelContractor can use SCL weir or build their own temporary weirProposed SCL metal weir (install in June or October depending on Contractor’s preference)
13 2. Rock fall Protection (vendor) Temporary fence
14 3A. Mobilize Valve House Spill way Temp rock fence SCL Barge Ross Dam
15 Vendor Submittals (pre-mobilization) Health & Safety PlanHazardous waste handling planWork planContact infoWater Tectonics Electro-coagulation operation manualScheduleSpill control planBarge loading & operation plan *Temporary weir *Rock fall fenceEquipment and materials* Need engineer stamp
16 Vendor Mobilization Load water treatment equipment on barge Provide generator, pumps, worker shack, sani-can, ladders, lights, etc.* Some size restrictions: tunnels, barge load, barge access, etc.
17 3B. De-water Tunnel Pump out clean water & direct discharge to lake Pump out dirty* water and treat prior to discharge Approximately 750,000 – 1,000,000 gallonsWater is ~12 – 16-ft deep*Dirty = > 5 NTU turbidity
18 3C. Water Treatment on Barge Discharge to Diablo LakepumpTunnelshackSand filterBack flush tankSettling tank #2Settling tank #1Source tankElectro coagulationSani cangenerator80T BargeNot to scaleWater Tectonics is the MANDATORY SUB-CONTRACTORMust use Electro-Coagulation Treatment System
19 4. Remove Sediment Workers enter all ten chambers Remove sediment (dredge? Pressure wash? Sweep?)Dirty water and sediment pass through treatmentSediment collects in tanks
20 5A. Verification Clean water is discharged Batch testing 1 – 3 timesWeekly water discharge samplesSub-contractor operationsChambers are clean and lead freeVisual inspectionWater samples
21 5B. Waste disposal Vendor will: SCL will: Unload tanks from barge Transfer sediment to waste containersDispose of other debris (trash, sani-can, misc. debris)SCL will:Test for dangerous wasteHaul lead-contaminated sediment and sand filter media to proper disposal site
22 Misc. Vendor tasks Collect samples & deliver to lab Provide crew boat to shuttle staffProvide lodging for crewsReporting to SCL and EcologySite cleanup (non-hazardous materials)Demobilization
24 Mandatory Pre-bid meeting At SKAGIT – meet at Newhalem General StoreRSVPBring Hard Hat & Lock Out Tag Out locksRead and be ready to sign SCL LOTO policyIf you don’t bring LOTO locks, you will be left behind at the General Store.
25 Vendor selection Requirements Pre-qualifications Worked off barge Attend mandatory pre-bid Skagit site visit- Will use Water Tectonics as sub- Can obtain insurance in a timely mannerPre-qualificationsWorked off bargeRemoved underwater sedimentHandled contaminated material