Tampa Bay East Port Expansion Hydrographic Study William Miller, - - PowerPoint PPT Presentation

Tampa Bay East Port Expansion Hydrographic Study

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William Miller, Ph.D., P.E. December 6, 2018

• Project Description
• FDEP requirements
• Satisfaction of FDEP requirements
• Effects on McKay Bay

Overview

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Project Description

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Expansion of East Port with fill in East Bay and dredging portion of bay

Section 10.2.4.3(b) of the statewide Environmental Resource Permit Applicant’s Handbook (FDEP, 2018)

• Requires a hydrographic study to document the “flushing

time” of the water at the docking facility

• Flushing Time: “the time required to reduce the

concentration of a conservative pollutant to ten percent of its original concentration”

• “flushing time of less than or equal to four days … for

docking facilities”

• pollutants “leaving the site of the docking facility will be

adequately dispersed in the receiving water body so as to not cause violations of water quality standards based on circulation patterns and flushing characteristics of the receiving water body”

FDEP Flushing Requirements

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• Reduce concentration of “conservative pollutant”

to less than 10% of original concentration in less than 4 days

• Not adversely affect adjacent waters (receiving

body)

• conservative pollutant:
• ne that does not decay or settle out

Key FDEP Requirements

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• How is pollutant concentration reduced?
• Advection/Dilution:
• tide and currents dilute pollutant over time by a

physical exchange of water

• Diffusion:
• pollutant molecules disperse to areas of lower

concentration

• Both mechanisms modeled

Physical Mechanism

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• US Army Corps of Engineers RMA2/RMA4 suite
• RMA2 models hydraulics (advection by tide and

currents)

• RMA4 models pollutant transport (dilution and

diffusion)

• RMA4 model uses the hydraulics from the RMA2

model

Numerical Model

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• Hillsborough Bay, East

Bay, and McKay Bay

• Inputs from Hillsborough,

Palm, and Alafia Rivers

• Calibrated for water

surface elevation (WSE) and current speed

RMA2 Model

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Bathymetry (ft NAVD) Palm River Hillsborough River Alafia River Tampa Bay

• Good WSE and current

calibrations

RMA2 Calibration of Existing Conditions

Taylor Engineering | 9 Velocity Calibration Points Water Surface Elevation Calibration Points Bathymetry (ft NAVD)

Water Surface Elevation

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

current speed (ft/s)

Current Speed Calibration, Station V3

Model Results Measured Data

Current Speed

• Modified

Model to Include Fill and Dredging

Modified Model

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Proposed Fill Area for Berths

Bathymetry (ft NAVD)

Dredged area Dredged area Dredged area

• Simulate pollutant

transport during neap and spring tides

• Average diffusion

coefficient of 12 m2/s

• Observed values in

estuaries:

• Avg. Range: 100 – 300

m2/s

• Low values: 10 – 50

m2/s

• Fischer et al. Mixing in

Inland and Coastal Waters

Pollutant Simulation

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Tidal Flushing of Facility

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84 hrs

Neap Tide Minimal river discharges (65 cfs) D = 12 m2/s Flushing Time = 84 hrs Satisfies FDEP requirement

• Second requirement

not to aversely affect adjacent waters

• Multiple sample

points outside of facility

Adjacent Waters

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M1 M2 M3 M4 M5 M6 M7 E1 E2 E3 T1

• Small increases in

pollutant concentrations

• Increases temporary as

pollutant flushes from adjacent waters

• Satisfies Second

Requirement

Concentrations in Adjacent Waters

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McKay Bay East Bay and Hillsborough Bay

• Hydraulic Effects
• Effects on Ability to Remove Pollutants from McKay

Bay

Effects of Project on McKay Bay

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Hydraulic Effects on McKay Bay

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• Water Surface Elevation

Hydraulic Effects on McKay Bay

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• Discharge through causeway bridge

• Simulate transport of

substance beginning at various locations in McKay Bay

• Simulate with and

without project

• Compare

residence/flushing time

• f the substance

Effects on Ability to Remove Pollutants

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Concentration (ppt)

2 1 3 4 5 8 6 7

Test Area 2 McKay Bay NNE Test Area 1 McKay Bay NE Test Area 3 McKay Bay SW

• Minimal change in residence time
• < 3% change in mean of maximum concentrations at all

sample points

• Maximum 0.2 – 0.4 ppt maximum difference over entire

model run period

Modeled Effects on McKay Bay

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Test Area Change in TRES (hrs) Mean Diff. (ppt) RSMD (ppt) Normalized MD Normalized RSMD Concentration (ppt) Mean of Maximum Existing Mean of Maximum Project Maximum Change

• 1. McKay Bay NE

0.10 0.12 1.9% 2.3% 6.61 6.63 0.40

• 2. McKay Bay NNE

0.08 0.09 2.8% 3.2% 2.57 2.63 0.20

• 3. McKay Bay SW

0.09 0.10 2.1% 2.5% 5.04 5.04 0.30

• Proposed project flushes within four-day FDEP

requirement

• Minimal effects on adjacent waters
• Minimal effects on McKay Bay hydraulics
• Minimal effects on McKay Bay flushing

Summary

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• Questions?

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