strontia springs reservoir sediment removal 4/17/14 … springs sediment... · sediment traps...
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Strontia Springs Reservoir Sediment Removal
4/17/14 Update
Denver Water ExperienceSouth Platte Collection System
• 1996 Buffalo Creek Fire• 2000 High Meadow• 2001 Polhemus• 2002 Snaking• 2002 Schoonover• 2002 Hayman• 2012 Lower North Fork• 2012 Lake George• 2012 Springer• 2012 Trout Creek
1996 Buffalo Creek FireFloating Timber at Strontia Springs
Ash Plume at Strontia Springs
Sediment Traps
Sediment Removal at Cheesman ReservoirTributary Sediment Traps
Sediment Removal at Cheesman Reservoir
Year
Turkey Creek SedimentRemoved
Goose CreekSedimentRemoved
TotalSedimentRemoved Annual Cost
UnitCost
CY CY CY $ $/CY2003 0 0 0 $ 871,562 2004 0 0 0 $ 16,819 2005 25,100 8,020 33,120 $ 334,028 $ 10.09 2006 15,420 14,160 29,580 $ 262,395 $ 8.87 2007 63,620 0 63,620 $ 288,129 $ 4.53 2008 34,250 18,875 53,125 $ 197,412 $ 3.72 2009 15,720 0 15,720 $ 277,931 $ 17.68 2010 0 0 0 $ 9,798 Total 154,110 41,055 195,165 $ 2,258,074 $ 11.57
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
Sedi
men
t Inf
low
s -C
Y
Year
Strontia Springs ReservoirSediment Management Options
Original Plan
No Action
Dredge and Monitor
Dredge and Maintain Inflows
28,000 cy/yearInflow Expected
Strontia Springs Reservoir Sediment Deposit
Original River Grade
Reservoir Spillway El. 6002
Dredging Limit El. 5940
Geotechnical Investigation
Geotechnical Investigation
Geotechnical Investigation
Geotechnical Data
Strontia Dredging Cost Status April 2014
Contractor’s Original Bid (Feb. 2010) $31,150,000
Contract Status
Original Contract Value (Apr. 2010) $30,046,500Contract Quantity of Sediment 625,000 CY
Final Contract Value* $17,082,176Final Quantity of Sediment Removal 228,353 CY
$74.80/CY
* Post Settlement
Dredging System Layout
Strontia Springs Reservoir Sediment Removal Plan
• 14” Hydraulic Cutterhead Dredge• Dredge Supply 7650D Diesel Marlin -
104 feet long• 800 HP Prime Mover, 350 HP Cutter
and Auxiliary • 40-inch Impeller• 300 cy per hour
• Booster Pumps• 3 Floating Diesel Pumps• 6 Land Electric Pumps• 800 HP Each
18” HDPE SDR 11 Slurry Pipeline
Dredge Mobilization – Fall 2010
Marlin Dredge Assembly – April 2011
Marlin Dredge Assembly – April 2011
Backup and Main Dredge
On Water Booster Pumps
Dredging Operations
Water to Land Transition
Dredging Operations
Dredging Operations
Primary Slurry Scalping Plant
Upper Canyon Screening Plant for +1/4” Material
Land Side Booster Pumps
Dredging Slurry Dewatering
Kassler Filter Bed Dewatering Plant for Desanding of Slurry
Kassler Filter Bed Stockpile
Screening Plant Operations
Upper Canyon Scalping PlantScreens ¼” + Materials
Kassler Filter Bed Screening Plant
Screens ¼” - Materials
Hydrographic Survey
Hydrographic Survey
Slurry Pumping Technical InformationSlurry Properties
Water Density 62.42 pcf AVolume Conversion 7.48 gal/cf
Assumed Slurry Density 14.0% By Volume B
Sediment Specific Gravity 2.65 (Incl. Organics) CWtd. Avg. SG 1.231 D=(1-B)*1.0+B*C
Calc'd Slurry Density 76.8 pcf E=D*ACalc'd Slurry Density 30.1% By Weight
Vol Wt. (lbs) Wt. %Solids 14.0% 23.2 30.1%
Water 86.0% 53.7 69.9%
Total 76.8
Hourly Production Requirements (24 Work Hours/Work Day)
Dredging Quantity 625,000 CYWork Days
Work Day Schedule/WeekContractor Original Plan 117.0
Operating Uptime/Day 83.3% Operate 20 hrs of each dayRequired Solids Rate 120 cf solids/min
Required Pumping Rate 6,422 gpm
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
Jan‐11 Feb‐11 Mar‐11 Apr‐11 May‐11 Jun‐11 Jul‐11 Aug‐11 Sep‐11 Oct‐11
Cumulative Prod
uctio
n CY
Mon
thly Produ
ction CY
Month
Strontia Reservoir DredgingBaseline, April, & May Forecast Production
Orig. Baseline Monthly Plan Forecast May Monthly Production Baseline Plan Cumulative
Forecast April Cumulative Forecast May Cumulative
Slurry Pumping Production
Sediment Profile – Proposed and Final Dredging Limits
Sediment Investigation
Slurry Pumping Technical Information• ANSI Slurry Classification• The American National
Standards Institute ("ANSI") and the Hydraulic Institute ("HI") have developed standards for design and operation of slurry pumps.
• ANSI/HI Standard 12.1-12.6 classifies slurries in different categories based on particle sizes and volumetric concentration, as shown in Figure 10, below.
• The higher the slurry class, the more wear the slurry will cause.
Slurry Pumping Technical Information
• ANSI Slurry Classification
• Therefore, for each increase in slurry class, the standards recommend a reduction in maximum head per pumping stage and maximum peripheral speed of pump impellers to reduce wear and increase system reliability.
• Table 7 documents the maximum recommended operating conditions for the various slurry classes.
Slurry Pumping Technical Information
• SS – Silty Sand• MS – Medium Sand• CS – Coarse Sand
Transporting coarse slurries at high concentrations results in high wear and lower system reliability
Slurry Pumping Technical Information
• Pumping Slurry is Less Efficient than Pumping Water
Dredging Project Status
• 228,000 cy Removed by Nov. 2011• Contractor Demobilized by June 2012• 10 to 20 Years of Reservoir Service
Restored• Manganese Levels Reduced in Raw
Water
No Action is Not an Option