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Strontia Springs Reservoir Sediment Removal 4/17/14 Update

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Page 1: Strontia Springs Reservoir Sediment Removal 4/17/14 … Springs Sediment... · Sediment Traps Sediment Removal at Cheesman Reservoir Tributary Sediment Traps. Sediment Removal at

Strontia Springs Reservoir Sediment Removal

4/17/14 Update

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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

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1996 Buffalo Creek FireFloating Timber at Strontia Springs

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Ash Plume at Strontia Springs

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Sediment Traps

Sediment Removal at Cheesman ReservoirTributary Sediment Traps

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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

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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

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Strontia Springs Reservoir Sediment Deposit

Original River Grade

Reservoir Spillway El. 6002

Dredging Limit El. 5940

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Geotechnical Investigation

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Geotechnical Investigation

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Geotechnical Investigation

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Geotechnical Data

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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

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Dredging System Layout

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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

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18” HDPE SDR 11 Slurry Pipeline

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Dredge Mobilization – Fall 2010

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Marlin Dredge Assembly – April 2011

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Marlin Dredge Assembly – April 2011

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Backup and Main Dredge

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On Water Booster Pumps

Dredging Operations

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Water to Land Transition

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Dredging Operations

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Dredging Operations

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Primary Slurry Scalping Plant

Upper Canyon Screening Plant for +1/4” Material

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Land Side Booster Pumps

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Dredging Slurry Dewatering

Kassler Filter Bed Dewatering Plant for Desanding of Slurry

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Kassler Filter Bed Stockpile

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Screening Plant Operations

Upper Canyon Scalping PlantScreens ¼” + Materials

Kassler Filter Bed Screening Plant

Screens ¼” - Materials

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Hydrographic Survey

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Hydrographic Survey

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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

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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

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Sediment Profile – Proposed and Final Dredging Limits

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Sediment Investigation

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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.

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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.

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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

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Slurry Pumping Technical Information

• Pumping Slurry is Less Efficient than Pumping Water

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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

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No Action is Not an Option