dona bay watershed management program florida stormwater …€¦ · venice area in the 1950’s to...
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Dona Bay Watershed Management Program Florida Stormwater Association
December 9, 2015
Sarasota County Watersheds
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Average annual rainfall per each watershed based on Sarasota County ARMs Program data from 2003 through 2010.
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2003 2004 2005 2006 2007 2008 2009 2010
Rai
nfa
ll (i
nch
es)
Annual Average Rainfall by Basin (SCG ARMS Data Avg)
Sarasota Bay Roberts Bay North Little Sarasota Bay
Dona Bay Lemon Bay Myakka
Integrated Watershed-Based Approach
Flood Protection
Water Supply
Natural Systems
Water Quality
Dona Bay Watershed Management Plan
Objectives
Provide a more natural
freshwater/saltwater regime in the tidal
portions of Dona Bay
Provide a more natural freshwater flow
regime pattern for the overall Dona Bay
watershed
Protect existing and future property
owners from flood damage
Protect or improve existing water quality
and avoid or mitigate water quality
impairment
Develop potential alternative water
supply options that are consistent with,
and support other plan objectives
Dona Bay Watershed Management Plan Biological Indicators
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Sarasota Bay Seagrass Coverage 1988 to 2012 Darker Green -
continuous grass beds
Lighter Green - sparse grass beds
Dona Bay Watershed Management Plan Biological Indicators
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Dona Bay Watershed Management Plan Biological Indicators
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Dona Bay Watershed History
Cow Pen Slough drained and diverted water from the Myakka River to Dona Bay in the late 1960’s for agriculture.
Blackburn Canal cut across the Venice area in the 1950’s to drain a portion of the Myakka River to Roberts Bay.
These drainage activities increased the amount of surface water draining to Dona and Roberts Bay five fold.
Impacts of Increased Flow
• Excess freshwater has substantially altered the balance of salt and freshwater
• Destabilized estuarine ecology (i.e. oysters)
• Increased sediment and nutrient loading
Dona Bay Water Quality
Dona Bay Watershed Management Plan Recommendations
WATERSHED ENHANCEMENT PROJECTS
A. Weir reconstruction
B. Albritton watercourse excavation
C. Pinelands borrow pit connections
D. West Pinelands Restoration
E. Pipeline from Pinelands to Venice Minerals
F. Venice Minerals reservoir construction
345 ac. 1.8 bg
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Any reductions in the amount of “excess” freshwater would not only be expected to help
restore a more natural salinity range, but pollutant loads to Dona Bay would be reduced as
well.
Pollutant reductions can be achieved by volume reductions and by increased treatment.
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Dona Bay Conveyance System Project Success and Targets
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Dona Bay Conveyance System Project
North Pinelands Diversion Weir
North Pinelands Intake - conveyance and treatment area
North Pinelands Reservoir - conveyance and treatment area
Phase 2 and Existing Excavated Cells – additional storage and future excavation areas for the Landfill
Conveyance to North Lake (existing north borrow pit) – conveyance and treatment area
Dona Bay Conveyance System Project
Connection to South Lake (existing south borrow pit) – conveyance and treatment area
Pipeline to Pinelands Rehydration Area – wetland rehydration
Flood-stage relief to canal
Overflow to South Pinelands Storage System
Phase 2 Diversion to Venice Minerals Storage Facility - future reuse water supply and potable water supply
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Dona Bay Conveyance System Project Benefits
Benefits:
Diverts fresh water flow for treatment.
Reduce nitrogen loads to Dona Bay by over 15%.
Rehydrate Wetlands
Compatible with alternative water supply.
Increased storage for flood events.
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Dona Bay Conveyance Project Construction
Dona Bay Water Treatability Study
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Constituents of Concern
- Organic Matter
- Color
- Turbidity
- Dissolved solids (TDS)
- Taste & Odor
- Microbes
- Hardness
- Iron
Dona Bay Water Treatability Study Pilot Process Selection
20 Process Alternatives
Pilot Treatment Plant
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Potable Water Treatment Alternatives
Conventional Pretreatment
Dual Media Filter (w/ GAC)
1C
Conventional Pretreatment
Dual Media Filter
Biological Roughing Filter
1E
Biological Roughing Filter
Fixed Bed IX (FBIX) MF/UF 4A
Conventional Pretreatment Biological Filter 2A
RESERVOIR
Biological Roughing Filter MF/UF 3E
Conventional Pretreatment
Desalting
Desalting
Desalting
Desalting
Desalting
Alternative Water Uses - Value Add-on
Dona Bay Watershed area is within the Southern Water Use Caution Area (SWUCA)
SWFWMD adopted SWUCA Recovery Plan to reduce groundwater withdrawals
SWFWMD promotes use of surface water an alternative to groundwater in SWUCA
Currently over 12 million gallons a day of permitted groundwater withdrawals for agriculture in the Dona Bay Watershed area
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Questions
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Molly C Williams, PE Sarasota County Stormwater Utility Manager [email protected] 941-525-2487