lake osborne muck dredging by D3a5QFT7

VIEWS: 6 PAGES: 50

									    LAKE OSBORNE
MUCK DREDGING PROJECT
Presentation Overview
•   What are the Chain of Lakes?
     – How have the lakes become degraded?
     – Palm Beach County’s Involvement
        - State of the Lakes Plan

•   What is Muck?
•   - How does muck develop?
     – How much muck is in the lake and how do we know?
        - Surveys
     - What is the County’s plan?
        - Lake Osborne Muck Dredging Project

•   Lake Osborne Muck Dredging Project
     – Brennan Marine Professionals
     – Dredging Equipment
     – Dewatering Plant
     – Drying Methods
     – Disposal of Muck

•   Future of the Project
    CHAIN OF
     LAKES
•   Part of a natural lake system
    that, at one time, extended
    from West Palm Beach to
    Delray Beach

•   The E4 canal connects Pine
    Lake, Lake Clark, Lake
    Osborne, Lake Eden, Lake
    Ida

•   Freshwater lakes:
     – provide habitat for native
       flora & fauna
     – replenish drinking water
       supplies
     – store and filter storm
       water
     – provide recreational
       opportunities
     – aesthetically appealing
Degradation of
a System



                 Historical dredge &
                 fill activities, urban
                 encroachment &
                 discharge from
                 canals.....
...lead to the lakes’ waters becoming
   overloaded with nutrient-rich organics




                                South Lobe of Lake Osborne (1986)
As a result, excessive plant life (algal blooms) develops
throughout the Chain of Lakes causing a decrease in water
quality & reduction in oxygen levels




HYDRILLA
            STATE OF THE LAKES PLAN
   The lakes’ decreasing quality prompts Palm Beach County’s Department of
    Environmental Resources Management to commission a report in 1997 to
address how to enhance and improve the freshwater system and its management

                  The plan focuses on the following goals:
         • Restore and Protect Wetland Habitats
            • Protect & Improve Water Quality
               • Control Exotic Vegetation
             • Maintain & Enhance Fisheries
 • Enhance Public Participation & Environmental Awareness
MUCK
What is MUCK?
  Muck is organic and inorganic
  sediments, sands, silt, debris and
  other materials

How does MUCK form?
  Muck is a result of the excess
  nutrients in the water. Excess
  nutrients are attributed to:
  -Lakes’ extensive development
  -Herbiciding of non-native
   vegetation
  -Discharge of several canals

How long has MUCK been
accumulating throughout the lakes?
    -50 plus years
 Photo Credit: SFWMD
(Know the Flow Poster)
   In 2002, the County contracts with the survey company, Morgan & Eklund,
         INC., to measure the amount of muck throughout Lake Osborne



• Method of Measurement:
  dual frequency transducer

• Transducer captures the top
   of the muck layer and natural
   sandy lake bottom to determine
   muck’s thickness
         LAKE OSBORNE
     MUCK DREDGING PROJECT

•   Surveys reveal 700,000 CY of muck
    cover the sandy lake bottom

•   In response, Palm Beach County develops
    the Lake Osborne Muck Dredging Project

       County divides the dredging of
       the southern lobe into phases:

    Phase I: removal of approximately 20,000
    cubic yards of muck, in situ, from a
    199,241 square foot section

    Phase II: removal of approximately 85,000
    cubic yards of muck, in situ from a
    1,015,010 square foot section
    LAKE OSBORNE
MUCK DREDGING PROJECT

•   County decides to pay selected
    contractor by the square footage
    vs. cubic yard because of the
    consistency of the material

•   Muck is difficult to measure
    volumetrically because there is no
    defined top layer

•   1.2 million square feet
    (approximately 28 acres)
    throughout the project site

•   $1.12 per square foot

•   Total project cost for Phase I & II:
    1.4 million dollars
•   County awards Brennan Marine Professionals Phase I of the contract in March
    2004
•   Brennan receives Phase II of the project if they are able to meet project
    deliverables & complete work within allotted time frame for Phase I
•   Project Time Frames:
         Phase I - 45 days from Notice to Proceed to mobilize all equipment (no
                    payment for mobilization)
                    70 calendar days after mobilization to complete dredging and
                    dewatering of material from Phase I
         Phase II – 300 calendar days from issuance of the second Notice To
                     Proceed to complete Phase II
Spring 2004: Brennan receives Notice to Proceed
in March and begins to mobilize equipment in April




             Mobilization at Melear Park: April 22, 2004
  Fusing & placement of polyethylene plastic pipe




Mobilization:
April 22, 2004
Eight (8) inch intake pipeline transports
muck (slurry) to the dewatering plant
Buoys & signage along the pipelines warn
recreational users of the pipes’ presence
Dredging Equipment
8” Swinging Ladder Rotating Cutter Head Suction Dredge
 - 3 Spud System
 - Hydraulically Actuated Spud Frame enables dredge to
   walk along the lake bed
CUTTER HEAD
                        Interface between the dredge
                        operator & field conditions




Dredge Operator Booth
                      High Tech Instrumentation on
                          the Dredge Includes:

RTK Global Positioning System         DREDGEPACK Software
RTK Positioning System            •   Uses county surveys that
provides sub-centimeter               designate dredge depths
accuracy for position of dredge
and cutter head
                                  •   Screen displays operator
                                      position & amount of material
                                      being removed

                                  •   Tracks & recalculates the
                                      amount of material to be
                                      excavated

                                  •   Displays new calculations on
                                      the screen until achieving
                                      designated dredge depth
Pay Survey
Deliverable
Dredge Track Lines:
demonstrate where the
dredge’s cutter head is
working throughout the
day
Dewatering Plant
Underflow (slurry) entering dewatering plant
SAND WHEEL (used initially)
Wheel removes sand from slurry




                       Contains 200-mesh
                       (.074 mm) screens
SCALPER
Removes debris & organics by
gravity feeding slurry through a
belt screen

                        FRAC TANK
                        Slurry homogenizes in frac tank
                         (Only minus 200-mesh /.074 mm
                        solids remain)
VIBRATORY
  SCREEN

            •   Material travels over a 5’ x 7’
                vibrating screen (35-mesh/0.5
                mm)

            •   Vibration causes the sands &
                larger material to move toward
                the discharge end of the screen
                where it is placed on the radial
                stacker

            •   Material finer than 35-mesh/0.5
                mm drops through the screen
                into a sump
    HYDROCYCLONES
      (now in use)
•    Slurry collecting in sump is
     pumped and delivered to two
     cyclonic separators

•    The cyclonic separators
     perform like a centrifuge, using
     320-mesh screens to further
     separate the slurry



    - Finer material spins out the
      top of the separators &
      moves toward the frac tank

    - Larger material falls to the
      bottom of the separators &
      passes over the dewatering
      screen for a second time
Dewatering
  Screen
Radial Stacker




 Material passing over the dewatering
 screen falls onto the radial stacker
 Fine material leaves
 via top of cyclone
                        FRACTANK
                            •   Slurry now contains only 320-
                                mesh solids

                            •   First injection of chemical:
Slurry flows into
                                Aluminum-Chloride-Hydroxide
frac tank
                                (a coagulant)

                            •   Slurry homogenizes in the tank




                                Flow regulator (injects chemical into
                                tank at a controlled rate)
THICKENER




               Twin Clarifier Tanks




      Inflow
       Flocculent
        Mixture
•   Second chemical injected:
      FLOC NALCO 83906                               Control Panel
         Optimer Plus

•   Chemical mixes with water
    pumped from an underground
    well

•   Solution added to the slurry
    contains 1-3% of chemical

•   Injection of chemical into the
    slurry is computer controlled and
    based upon the consistency of
    the material

•   Opitmer Plus (flocculent) helps
    the organics organize into a
    semi-solid mass


                                        Well Water
Chemical & slurry mix together in
the flocculent injection tank



                                                           Slurry separates into the
                                                                      twin clarifiers


                                                                Return water flows to
                                                               the top & exits via the
                                                                       overflow pipe


                       Overflow Pipe


                                                         Makeup Well
Generator
                                                           Water

                                                                           Well
                                       Fuel
                                                       Auxiliary Pump




                    Slurry sinks to the bottom of the clarifiers and
                    exits via the underflow pipe
    End Results:
       Overflow
•   Return water is diverted back
    to Lake Osborne via the
    11.5” overflow pipe

•   Return water can not exceed
    29 NTUs (Nephelometric
    Turbidity Units) above lake’s
    background level

•   Overflow is monitored for
    high turbidity levels twice a
    day at the overflow tank
    using a nephelometer
Overflow Tank
    End Results:
       Underflow

• Underflow exits the dewatering
  plant and is pumped into a drying
  bed

• The processed muck remains
  within the bed for a week for
  further dewatering
MANIFOLD
    GEO BAGS

• First dewatering method

• Allows for further
  concentration of slurry for
  hauling

• Contractor assembled five
  bags in total (500 CY per
  bag)
Drying Beds   (now in use)
                    MUCK REMOVAL




•   Muck remixes with
    sand from the radial
    stacker
                                Processed Material
•   Parks Department
    uses mixture as a soil    Output = 600 CY per day
    amendment throughout
    various County parks
    and at the site of a
    future County golf
    course
   Anticipated Benefits
    • Improved water quality & environment
         • Enhanced boating & fishing
• Re-establishment of native benthic vegetation
          • Increased property value
   • Enriched top soil for use in public parks
             The Project’s Future
• South Florida Water Management District (SFWMD) dedicates
  $200,000 in matching grant funding for the continued excavation of
  muck from Lake Osborne
  Proposed
Dredge Areas
for Phase III

								
To top