Mattawoman Water Reclamation Facility – Primary Clarifier No. 1 Improvements

Key Accomplishments

Johnston Construction Company

• Coordinated the complete rehabilitation and modernization of the primary clarification process while maintaining operation of the surrounding wastewater-treatment facility.
• Furnished and installed new process mechanical piping, pumping equipment and valves associated with Primary Clarifier No. 1.
• Furnished and installed a new primary clarifier mechanism within the existing concrete clarifier basin.
• Installed a center-column-supported, center-feed clarifier mechanism designed to continuously remove settled sludge while uniformly collecting clarified effluent through the peripheral launder.
• Installed the clarifier's new center drive assembly, center support column, center cage, sludge-collection rake arms, feedwell, surface scum-skimming system, effluent weirs, scum baffle and associated structural components.
• Installed a clarifier mechanism designed for treatment flows of approximately 10 MGD average and 20 MGD peak within the 130-foot-diameter basin.
• Installed new sludge-removal rake assemblies designed to sweep settled solids from the clarifier floor toward the sludge-withdrawal sump.
• Installed new surface-scum collection equipment, including skimming assemblies and the associated scum collection box and piping.
• Installed the clarifier access bridge, center-drive operating platform, handrails and associated structural components required for equipment operation and maintenance.
• Constructed a new concrete effluent launder as part of the clarifier rehabilitation.
• Installed new clarifier floor grout to establish the required floor configuration and support efficient solids collection.
• Coordinated concrete work, structural modifications and equipment anchorages required for installation of the new clarifier mechanism.

Concrete Services Division

• Served as the concrete subcontractor to Johnston Construction Company for the Primary Clarifier No. 1 Improvements at the Mattawoman Water Reclamation Facility.
• Performed specialized structural concrete work supporting rehabilitation of the facility's existing 130-foot-diameter primary clarifier.
• Furnished the labor, formwork-related materials, tools and equipment necessary to perform CSD's contracted concrete forming, placement, finishing and curing work.
• Constructed the new concrete components associated with the 130-foot-diameter clarifier, including:
• Associated clarifier concrete improvements
• Performed extensive curved-wall formwork required for the circular clarifier configuration.
• Furnished and installed formwork for the new clarifier launder wall.
• Furnished and installed formwork for the new supported launder slab.
• Performed concrete placement for the clarifier's structural walls.
• Performed concrete placement for supported structural slabs.
• Completed concrete float and screed finishing operations.
• Performed pointing and patching of completed concrete surfaces to provide a finished structural installation.
• Furnished labor and supplies required for proper concrete curing.
• Performed concrete-accessory labor associated with items such as waterstop and embedded concrete accessories.

B & R Electrical Contractors

• Served as the electrical subcontractor to Johnston Construction Company for rehabilitation of Primary Clarifier No. 1 at the Mattawoman Water Reclamation Facility.
• Furnished the labor, materials, tools and supervision required to complete BRE's electrical scope.
• Performed the work in accordance with the project's applicable Division 16 Electrical and Division 17 Instrumentation and Control requirements.
• Executed electrical work based on project Drawings T-1, E-1, I-1 and I-2, together with Addenda 1, 2 and 3 and the applicable project specifications.
• Performed electrical demolition associated with the clarifier pumping systems.
• Disconnected and modified existing electrical systems as necessary to accommodate replacement and rehabilitated process equipment.
• Furnished and installed Toshiba variable frequency drives (VFDs) included in BRE's electrical package.
• Integrated the new VFDs with the associated pump motors and control systems.
• Installed VFD power and control wiring and coordinated the required field interfaces.
• Supported variable-speed operation of the associated process equipment through the new VFD systems.
• Coordinated VFD control circuitry, field terminals and required input/output interfaces with the project's instrumentation and control systems.
• Installed and coordinated grounding of VFD enclosures and associated electrical equipment.
• Supported manufacturer-required VFD startup, operational testing and final adjustment in accordance with the project specifications.
• Coordinated testing of VFD remote-control and indication features.