Launch Slideshow

Image

Floating dredging equipment minimizes traffic congestion

Floating dredging equipment minimizes traffic congestion

  • Image

    http://www.pwmag.com/Images/tmp121B%2Etmp_tcm111-1353040.jpg?width=300

    true

    Image

    300

    As the sediment was removed, it was dewatered, and the resulting cake was trucked to the Eagle Point Landfill, Ball Ground, Ga., approximately 45 miles from the reservoir. Photos: Cobb County-Marietta Water Authority

  • Image

    http://www.pwmag.com/Images/tmp121C%2Etmp_tcm111-1353041.jpg?width=300

    true

    Image

    300

    The reservoir was restored to its original 14-foot depth within six months.

  • Image

    http://www.pwmag.com/Images/tmp121D%2Etmp_tcm111-1353042.jpg?width=150

    true

    Image

    150

    Usually, a single contractor dredges and dewaters. But this project's deadline required using two specialists — one to supply mobile belt presses and another for recessed chamber presses — working simultaneously.

By Steve Gibbs

DETAILS:

Owner: Cobb County-Marietta (Ga.) Water Authority
No. customers: 750,000 residential accounts
Two treatment plants: 72-mgd potable water treatment facility — coagulation, sedimentation, filtration, and disinfection
86-mgd potable water facility (coagulation, sedimentation, filtration, and disinfection) with 25-million-gallon storage reservoir
Design engineering: Civil Engineering Consultants, Marietta, Ga.
General contractor: Heavy Constructors Inc., Marietta, Ga.
Timeline: May through November 2010
Cost: $4 million

In November 2010, the Cobb County-Marietta Water Authority (CCMWA) in suburban Atlanta completed the largest dredging and dewatering project in its 53-year history.

The project was completed in half the normal time so managers could proceed with $100 million in planned upgrades to CCMWA's Wyckoff Water Treatment Plant, one of two treatment plants that serve the area. The facility upgrades were designed to meet EPA's Stage 2 Disinfectant and Disinfection Byproduct Rule (Stage 2 DBP Rule) of 2006, implemented to help reduce potential cancer and reproductive and developmental health risks from disinfection byproducts, such as trihalomethanes (TTHM) and haloacetic acids (HAA5), that are formed in water through disinfectants used to control microbial pathogens. The standards go into effect April 2012.

In addition to building a $30 million granular activated carbon filtration system at the Wyckoff plant, projects include adding new conventional treatment process trains (flocculation, sedimentation, and granular media filtration), replacing flocculation and sedimentation basins, and adding a chemical feed building. All are being funded through the authority's capital improvements budget.