Saving Texas Largest Freshwater Marshes: McFaddin NWR Presented By: - - PowerPoint PPT Presentation

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Saving Texas Largest Freshwater Marshes: McFaddin NWR Presented By: - - PowerPoint PPT Presentation

Jul 22, 2023 276 likes •477 views

Saving Texas Largest Freshwater Marshes: McFaddin NWR Presented By: Stephanie L. Gonzales, PE LJA Engineering, Inc. Overview ! ! Project Area and Background ! ! Marsh Impacts ! ! Protection Berm ! ! Design ! ! Construction ! ! Beach and Dune

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Presented By: Stephanie L. Gonzales, PE

LJA Engineering, Inc.

Saving Texas’ Largest Freshwater Marshes: McFaddin NWR

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Overview

!! Project Area and Background !! Marsh Impacts !! Protection Berm !! Design !! Construction !! Beach and Dune Nourishment !! Sand Source Investigation !! Preliminary Design !! Dredging Method !! Sediment Delivery

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Project Area and Background

!! McFaddin Beach and National Wildlife Refuge

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Project Area and Background

Need !! Salt Bayou Watershed – 100,000 ac.

  • f Fresh and Brackish Marsh

!! Feeding and resting habitat for waterfowl !! Protective buffer between the Gulf

  • f Mexico and the GIWW

Purpose

  • ! Reduce frequency of saltwater

inundation into the interior marshes

  • ! Protect the marshes from high tide

and low energy storm events.

  • ! Reduce Erosion to that of typical

sandy beaches

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Marsh Impacts: Storm Events

September 9, 2008 September 15, 2008 October 2, 2008

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Marsh Impacts: Annual Erosion Rates

Erosion Rates Entire Shoreline: Aug ‘05 to Feb ‘09 = -21.4 ft/yr Feb ‘09 to Apr ‘10 = -34.0 ft/yr White’s to Perkins: Aug ‘05 to Feb ‘09 = -25.6 ft/yr Feb ‘09 to Apr ’10 = -33.4 ft/yr

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Design of Protection Berm

!! 5 yr. Storm Approximation with +5ft NAVD88 Protection Berm

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!"#$%&'#()*%"+,

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Beach and Dune Nourishment

Alternatives Analysis !! Key Points !! Borrow Source Identification !! Sediment Configuration !! Dredge Type !! Sediment Delivery !! Screening Factors !! Costs !! Construction Time !! Impacts to the Environment !! Navigation

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Sand Source Investigation

Investigation Area

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Sand Source Investigation

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Preliminary Design

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Trailing Suction Hopper Dredge

  • ! Low Mobilization & Operating Costs
  • ! Utilizes Short Pipelines
  • ! Can “Bottom Dump” Overburden
  • ! Can work in Adverse Conditions
  • ! Higher Risk to Endangered

Species

  • ! Lower Production Rates
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Sediment Delivery – Hopper Dredge

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Cutter Suction Dredge

!! !! !!

  • ! High Mobilization & Operating Costs
  • ! Operates in Fair Weather
  • ! High Production
  • ! Low Risk to Endanger Species
  • ! Works Well in Various Sediments
  • ! Continuous Pumping
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Sediment Delivery - CSD

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Beach and Dune Nourishment

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Interagency Efforts

Beach and Dune Nourishment (Phase III):

  • ! CIAP providing initial funding for construction
  • ! Texas General Land Office providing management and oversight
  • ! GLO providing funding for engineering (CEPRA)

Protection Berm (Phase I & II):

  • ! US Fish and Wildlife Services (USFWS) and Jefferson County providing

funding for construction (CIAP)

  • ! Texas General Land Office (GLO) providing management and
  • versight
  • ! Jefferson County and GLO Disaster Recovery (DR) providing funding

for engineering & environmental management (CIAP)

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Questions / Comments?

Contact Information: Stephanie Gonzales slgonzales@ljaengineering.com