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Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007

REMOVAL OF ORGANIC BOTTOM SEDIMENTS FROM LAKE MAGGIORE UTILIZING AN INTEGRATED HIGH CAPACITY HYDRAULIC DREDGING AND RAPID MECHANICAL DEWATERING SYSTEM

Gary Drake Phoenix Process Equipment Company Louisville, KY Kirk Davis, P.G. Jahna Dredging, Inc. Lake Wales, FL

Introduction

Lake Maggiore is a 380-acre freshwater lake in St. Petersburg, Florida. The lake was formerly connected to Tampa Bay via Salt Creek. In the 1940’s a water control structure was built on the northwestern corner of the lake to control storm water and eliminate tidal influences. Like many Florida lakes, a thick accumulation of organic muck deposits had resulted in shallow lake conditions, declining water quality, poor water clarity, persistent algae blooms, and a reduction in recreational use of Lake Maggiore. In order to reverse these negative highly eutrophic conditions caused in part by the nutrient rich muck deposits, the City of St. Petersburg contracted for the removal of approximately 1.5 million in-situ cubic yards of lake bottom sediments.

Project feasibility studies evaluating numerous lake restoration options concluded that hydraulic dredging in conjunction with mechanical dewatering was the most economical approach based on available sediment disposal options. Jahna Dredging Inc. was awarded a contract for the sediment removal and dewatering which included modifying existing state and federal environmental permits to construct a commercial scale dewatering plant and to return clear plant effluent back into Lake Maggiore.

Purpose

The purpose of the presentation is to share specific project design information and valuable execution experience to assist lake managers plan restoration projects including:

  • 1.

    Extensive pre-dredging sediment sampling and material characterization to determine mass balance, material throughput, and system flow diagrams.

  • 2.

    Fine sediment dewaterability studies leading to equipment sizing and polymer selection.

  • 3.

    Design, erection, and operation of a high capacity hydraulic cutterhead dredge integrated for continuous operation with a temporary mechanical dewatering facility.

  • 4.

    Overview of production rates, dewatered material types, and haul volumes.

  • 5.

    Water quality and environmental monitoring.

  • 6.

    Sediment hauling and disposal limitations and considerations.

  • 7.

    Estimated ranges in cost for sediment dredging, dewatering, and disposal.

Session 8A – Page 4

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