napa plant site desalting modeling summary november 10, 2009
DESCRIPTION
DFG Agreement included Cargill removal of residual salt in the plant to the extent possible to facilitate restoration Cargill successfully harvested and removed approximately 350,000 tons (since 2003) Estimated 300,000 to 350,000 tons remain in the plant –Pickle Ponds (Unit 3, B1, B2, B3) salt removed –Residual salt remains in crystallizer beds with 2 to 6-inch salt crust Continued harvesting not physically possible Cargill explored other ways to meet desalination obligation BackgroundTRANSCRIPT
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Napa Plant Site Desalting Modeling Summary
November 10, 2009
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Overview
1. Background2. Approach to Salt Removal3. Breach Concept4. Field Experiments (Salt Dissolution)5. 2-D Modeling
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• DFG Agreement included Cargill removal of residual salt in the plant to the extent possible to facilitate restoration
• Cargill successfully harvested and removed approximately 350,000 tons (since 2003)
• Estimated 300,000 to 350,000 tons remain in the plant– Pickle Ponds (Unit 3, B1, B2, B3) salt removed– Residual salt remains in crystallizer beds with 2 to 6-inch salt crust
• Continued harvesting not physically possible
• Cargill explored other ways to meet desalination obligation
Background
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BackgroundApproach to Salt Removal
• Other salt pond breach successes– NSM Pond 4 - temporary, localized effects (within natural variability at 5
days; ambient at 26 days)– NPS Ponds 9 and 10 - met RWQCB requirements within 24 hrs
• Develop breach concept to minimize impacts
• Field experiments to understand salt crust dissolution– Redwood City– Napa Plant Site
• Modeling to size breach for minimal impact– 2-D Model– Validation
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Breach Concept
Napa River
Crystallizer Bed Salt Crust
Less Saline LayerMudflat Weir
High Saline Layer
Dissolutiontons/day
Tidal Exchange Two layers exist within Site
MudflatBreach
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• Goal: better understand expected salt dissolution mechanism and rates
• Redwood City crystallizer dissolution tests showed dissolution rate over first 12 days <0.05 in/day
• Napa dissolution tests showed: – More dissolution in higher velocity areas – Clear stratification within the test area – Middle and top salinity levels 30 to 44 ppt
Field Experiments
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2-D Modeling • Advection/Dispersion Model• Objective: Evaluate breach concept for
desalting the South Unit given restoration breach location
• 2-Dimensional for internal Plant Site and Napa River
• 1-Dimensional for sloughs and external ponds
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• Dissolution is the primary mechanism for salt loss • Salt dissolves at a constant rate (0.05 in/day)• Stratified high salinity layer within internal Plant
Site remains throughout simulation• Low velocities exist within internal Plant Site• External breach occurs at Mudflat elevation• Internal breaches per proposed Restoration Plan
2-D Modeling Assumptions
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• Modeling Period (August-October 2000)– Flow (USGS Gauging Stations at Oak Knoll
Avenue and Agua Caliente)– Tides (NOAA Tide Stations at Mare Island and
mouth of Sonoma Creek)– Ambient salinity (USGS Mare Island Causeway
Station)• Seasonally variability > 20 ppt• Daily variability on the order of 5 ppt
– Salt dissolution (Schaaf & Wheeler)
2-D Modeling Input Data
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Salt Mass Estimate
Beds Salt Mass (tons)
B1+B2 16,000
B3 32,000
Unit 3 32,000
Crystallizers 240,000
Total 320,000 Unit 3
B-2
B-3
B-1
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-
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
8/16/2000 8/26/2000 9/5/2000 9/15/2000 9/25/2000 10/5/2000 10/15/2000
Date
Dis
solu
tion
Rat
e (to
n/da
y)
Rate of Salt DissolutionB-1 & B-2 Salt Mass Dissolved
Unit 3 Salt Mass Dissolved
B-3 Salt Mass Dissolved Crystallizer Beds Salt Mass Dissolved
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Input Data -Salinity
Salinity Data Typical (1999-2005)
Seasonal Variability of 20 ppt
Average Salinity Readings at Mare Island Causeway Station
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Input Data - Salinity
Daily Variability of 5 ppt
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Model Results
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Location B: Napa River Outside Mudflat
Location A: Napa River Upstream
Location C: Outside Primary Breach
Notch
CCBB22 CCBB11
CCBB77
CCBB44
CCBB33
CCBB66 CCBB55
CCBB88 CCBB99 UUnniitt 33
BB--33
BB--22
Modeling ResultsEvaluation Points
Internal
External (Breach & River)
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Modeling Results - Salinity
Location B: Napa River Outside Mudflat
Location A: Napa River Upstream
Location C: Outside Primary Breach
Notch
CCBB22 CCBB11
CCBB77
CCBB44
CCBB33
CCBB66 CCBB55
CCBB88 CCBB99 UUnniitt 33
BB--33
BB--22
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PaletteAbove 30
29 - 3028 - 2927 - 2826 - 2725 - 2624 - 2523 - 2422 - 2321 - 2220 - 2119 - 2018 - 1917 - 1816 - 17
Below 16Undefined Value
8/22/2000 2:00:00 AM, Time step: 146, Layer: 0
20 40 60 80 100 120 140 160 180(Grid spacing 20 meter)
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
(Grid
spa
cing
20
met
er)
Salt
70-foot Breach
Modeling Results - SalinityMaximum Salinity – after 6 days
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PaletteAbove 30
29 - 3028 - 2927 - 2826 - 2725 - 2624 - 2523 - 2422 - 2321 - 2220 - 2119 - 2018 - 1917 - 1816 - 17
Below 16Undefined Value
8/22/2000 2:00:00 AM, Time step: 146, Layer: 0
20 40 60 80 100 120 140 160 180(Grid spacing 20 meter)
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
(Grid
spa
cing
20
met
er)
Salt
70-foot Breach
Modeling Results - Salinityafter 8 days
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PaletteAbove 30
29 - 3028 - 2927 - 2826 - 2725 - 2624 - 2523 - 2422 - 2321 - 2220 - 2119 - 2018 - 1917 - 1816 - 17
Below 16Undefined Value
8/22/2000 2:00:00 AM, Time step: 146, Layer: 0
20 40 60 80 100 120 140 160 180(Grid spacing 20 meter)
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
(Grid
spa
cing
20
met
er)
Salt
70-foot Breach
Modeling Results - Salinityafter 28 days
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PaletteAbove 30
29 - 3028 - 2927 - 2826 - 2725 - 2624 - 2523 - 2422 - 2321 - 2220 - 2119 - 2018 - 1917 - 1816 - 17
Below 16Undefined Value
8/22/2000 2:00:00 AM, Time step: 146, Layer: 0
20 40 60 80 100 120 140 160 180(Grid spacing 20 meter)
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
(Grid
spa
cing
20
met
er)
Salt
70-foot Breach
Modeling Results - Salinity after 42 days
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Location B: Napa River Outside Mudflat
Location A: Napa River Upstream
Location C: Outside Primary Breach
Notch
CCBB22 CCBB11
CCBB77
CCBB44
CCBB33
CCBB66 CCBB55
CCBB88 CCBB99 UUnniitt 33
BB--33
BB--22
Loc. A
Loc. C
Loc. B
Modeling Results – Location C
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Location B: Napa River Outside Mudflat
Location A: Napa River Upstream
Location C: Outside Primary Breach
Notch
CCBB22 CCBB11
CCBB77
CCBB44
CCBB33
CCBB66 CCBB55
CCBB88 CCBB99 UUnniitt 33
BB--33
BB--22
Loc. A
Loc. C
Loc. B
Modeling Results – Location B
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Location B: Napa River Outside Mudflat
Location A: Napa River Upstream
Location C: Outside Primary Breach
Notch
CCBB22 CCBB11
CCBB77
CCBB44
CCBB33
CCBB66 CCBB55
CCBB88 CCBB99 UUnniitt 33
BB--33
BB--22
Loc. A
Loc. C
Loc. B
Modeling Results – Location A
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2-D Modeling
70’ Breach
Maximum Salinity
Difference (ppt)
Max. Salinity Duration
Location C: Outside Breach
Max. Hourly 10 Once a day for three days
Max. Tidally Averaged 4 6 days
Location B: Outside Mudflat
Max. Hourly 2 Once a day for two days
Max. Tidally Averaged <2 -
Location A: Napa River
Max. Hourly <2 -
Max. Tidally Averaged <2 -
• Experience demonstrates saline brines can be released in an environmentally acceptable manner
• Field experiments clarified dissolution mechanism and rates
• Modeling results showed that Salinity within Napa River remains within natural variability
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Questions?
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Input Data - Flow
Flow Data Typical (1999-2005)
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Input Data - Tidal
Tidal Data Typical per Historical Means