Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement

Key Accomplishments

Johnston Construction Company

• JCC constructed a new deeper reinforced-concrete clarifier tank supported by an auger cast-in-place pile foundation designed to resist settlement and hydrostatic uplift caused by the site’s high-groundwater conditions.
• The new clarifier included an integral return activated sludge pumping station, integral scum well, new piping, valves, access structures, stairways, grating, railings, electrical systems, lighting, instrumentation, and process controls.
• JCC removed, stored, rehabilitated, modified, and reinstalled the existing clarifier mechanism, including the rake assembly, influent center column, bridge, drive unit, center cage, scum equipment, effluent weirs, density-current baffle, algae-cleaning system, and associated components.
• The existing clarifier mechanism was modified from an 8-foot sidewater-depth configuration to operate within the new 10-foot-sidewater-depth clarifier tank.
• JCC coordinated off-site rehabilitation of the existing clarifier drive by the original equipment manufacturer and reinstalled the refurbished equipment following completion of the new tank.
• The project included reinstallation of the existing return activated sludge pumps, new RAS discharge valves and valve vault, new interconnecting process piping, electrical upgrades, process-control improvements, testing, startup, and operator training.
• Construction was completed within an active wastewater treatment facility, requiring careful shutdown planning, groundwater control, excavation support, equipment protection, testing, and coordination with plant operations.
• Johnston Construction Company completed the Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement project in Lexington Park, Maryland. The project was performed for the St. Mary’s County Metropolitan Commission and designed by RK&K, LLP.
• The St. Mary’s County Metropolitan Commission awarded Johnston Construction Company Contract No. 22-04-C, Project No. 8191SR. The contract required JCC to provide all labor, materials, tools, equipment, transportation, supervision, and incidental services necessary to complete the clarifier replacement. The contractual completion period was 456 calendar days.
• The existing Secondary Clarifier No. 1 had been damaged by hydrostatic uplift during high-groundwater conditions after the failure of groundwater-relief components. The existing tank had lifted unevenly, making replacement of the concrete tankage necessary while allowing much of the existing clarifier mechanism and mechanical equipment to be rehabilitated and reused.
• JCC coordinated the overall construction effort, including mobilization, scheduling, submittals, erosion and sediment controls, demolition, excavation support, groundwater control, pile installation, reinforced-concrete construction, process-mechanical work, structural metals, clarifier-equipment rehabilitation, piping, electrical systems, controls, testing, startup, training, restoration, and project closeout.
• The work began with demolition of the existing Secondary Clarifier No. 1 concrete tankage.

Concrete Services Division

• Concrete Services Division, LLC completed the concrete work associated with the Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement.
• CSD furnished the labor, form materials, tools, equipment, finishing supplies, curing materials, and concrete accessories required for the project.
• The work included forming and concrete placement for the new clarifier foundation, base slab, circular walls, effluent trough, return activated sludge pump well, sludge well, grade beams, equipment-support features, stairs, and related structural components.
• CSD completed footing, slab-on-grade, curved-wall, straight-wall, column, special, bulkhead, and box-out formwork.
• The project included concrete encasement around the influent and return activated sludge piping and construction of associated pipe-support and grade-beam systems.
• CSD completed concrete placement, floating, screeding, pointing, patching, curing, joint work, waterstop installation, vapor-barrier installation, and related concrete-accessory work.
• The concrete construction was coordinated with Johnston Construction Company’s excavation, reinforcing-steel installation, concrete purchasing, pumping, testing, piping, clarifier-equipment installation, and overall project schedule.
• The work was performed within an active wastewater treatment facility and required close coordination with the ongoing clarifier replacement and plant operations.
• Concrete Services Division, LLC completed the concrete portion of the Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement in Lexington Park, Maryland.
• CSD’s work supported the construction of the replacement Secondary Clarifier No. 1 and its associated return activated sludge pumping and process structures.
• The concrete scope included the labor, formwork, tools, equipment, finishing materials, curing supplies, waterstop, vapor barrier, joint materials, and other accessories necessary to construct the project’s reinforced-concrete structures.
• The principal concrete feature was the new circular clarifier tank.
• CSD installed the formwork and completed concrete placement for the clarifier foundation, base slab, exterior circular walls, effluent trough slab, effluent trough wall, and associated structural features.
• The new clarifier tank required accurately formed circular construction to establish the required diameter, wall alignment, floor elevations, process geometry, and equipment-support conditions.

B & R Electrical Contractors

• B & R Electrical Contractors, Inc. completed the electrical work associated with the Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement.
• BRE furnished the labor, materials, tools, equipment, and supervision required for the electrical work.
• The project included demolition of the existing wiring serving Secondary Clarifier No. 1 and the return activated sludge pumps.
• BRE removed and reinstalled existing electrical disconnects, the seal-leak relay panel, and the clarifier control panel for reuse with the replacement clarifier system.
• BRE installed conduit, power and control wiring, boxes, devices, supports, grounding components, and final equipment connections.
• The work included electrical connections and startup support for the clarifier mechanism and return activated sludge pumps.
• BRE furnished and installed two new floats for the return activated sludge pump pit.
• The electrical work was coordinated with Johnston Construction Company’s clarifier demolition, tank reconstruction, process piping, mechanical-equipment installation, and startup activities.
• B & R Electrical Contractors, Inc. completed the electrical portion of the Marlay Taylor Water Reclamation Facility Secondary Clarifier No. 1 Replacement in Lexington Park, Maryland.
• BRE’s work supported the replacement of Secondary Clarifier No. 1 and the associated return activated sludge pumping facilities.
• The electrical scope began with demolition and disconnection of the existing wiring serving the clarifier and RAS pumps. BRE identified and protected the existing electrical equipment designated for reuse.
• The work included removal and reinstallation of the existing electrical disconnects, seal-leak relay panel, and clarifier control panel. These components were coordinated with the removal, rehabilitation, modification, and reinstallation of the existing clarifier equipment.
• BRE installed the conduit, conductors, boxes, devices, fittings, supports, flexible connections, grounding components, and equipment terminations required for the completed electrical system.
• The raceways and wiring were coordinated with the replacement clarifier tank, RAS pump well, structural components, process piping, equipment locations, and maintenance-access requirements.