strontia springs reservoir sediment removal 4/17/14 … springs sediment... · sediment traps...

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