Mattawoman Wastewater Treatment Plant Energy-Saving Improvements – UV System Upgrade

Key Accomplishments

Johnston Construction Company

• JCC constructed the new UV System No. 3 channel first, followed by phased demolition and replacement of existing UV System Nos. 2 and 1.
• The project included temporary bulkheads, channel draining, pumping, dewatering, cleaning, shutdown coordination, concrete demolition, reinforced-concrete construction, equipment installation, and restoration.
• JCC installed new influent slide gates, stop-log frames, utility-water channel interconnections, effluent-control components, structural grating, stairs, handrails, and aluminum diamond-plate channel covers.
• JCC coordinated electrical modifications, new circuit breakers, temporary electrical distribution, UV-equipment wiring, instrumentation, control panels, SCADA integration, system commissioning, testing, and operator training.
• The subcontract identified the project as the Charles County WWTP UV Replacement, NORESCO Project No. 192107.CN.001, and established a required substantial-completion date of July 15, 2025. The contract identified NORESCO as the contractor and Johnston Construction Company as the subcontractor.
• The project upgraded the existing UV disinfection process at the Mattawoman Wastewater Treatment Plant. The improvements included construction of three new UV-treatment channels and replacement of the existing UV disinfection systems with new energy-efficient treatment equipment.
• JCC coordinated the overall construction effort, including design assistance, project management, scheduling, submittals, demolition, temporary facilities, shutdown planning, dewatering, structural concrete, process-mechanical work, metal fabrication, electrical work, instrumentation, controls, equipment installation, testing, commissioning, training, and closeout.
• The work was performed within an active wastewater treatment plant. Existing facilities were required to remain in continuous operation, and construction activities had to create the least possible interference with treatment operations.
• A major project requirement was maintaining at least two operational UV disinfection systems throughout construction. The operating systems could consist of a combination of existing and newly installed units.
• The construction was organized into multiple coordinated phases.
• Phase 0 included installation of a new 30-inch crossover spool piece and gate valve between the influent piping serving UV System No. 1 and UV System Nos. 2 and 3.
• This new crossover arrangement supported the temporary and permanent flow-control requirements necessary for the phased UV-system replacements.

Concrete Services Division

• CSD constructed the reinforced-concrete channels, walls, slabs, footings, supported slabs, equipment-support areas, and structural modifications required for three new ultraviolet disinfection systems.
• The work included approximately 213 cubic yards of concrete associated with the phased UV-channel improvements.
• CSD installed footing forms, slab-on-grade forms, straight-wall forms, supported-slab forms, reinforcing dowels, vapor barrier, waterstop, and related concrete accessories.
• The project included approximately 416.88 square feet of footing forms, 730.33 square feet of slab-on-grade forms, 1,197.49 square feet of straight-wall forms, and 73.50 square feet of supported-slab forms.
• CSD placed approximately 158.35 cubic yards of slab-on-grade concrete, 109.96 cubic yards of wall concrete, and 1.44 cubic yards of supported-slab concrete under the subcontract’s detailed billing quantities.
• The concrete work included approximately 2,585 square feet of floating and screeding, 1,271 square feet of pointing and patching, and more than 5,000 square feet of concrete curing.
• CSD installed approximately 1,423 reinforcing dowels to connect new concrete construction to existing UV-treatment structures.
• The overall project replaced and expanded the ultraviolet disinfection process at the Mattawoman Wastewater Treatment Plant. Three new UV disinfection systems were installed together with new concrete channels, influent and effluent structures, slide gates, weir gates, stop-log frames, structural access systems, electrical distribution, instrumentation, controls, and SCADA connections.
• CSD’s work provided the principal structural concrete improvements necessary to create and modify the treatment channels supporting the new UV equipment.
• The concrete subcontract referenced Structural Drawings S-1 through S-6 and the project requirements for earthwork, concrete reinforcement, cast-in-place concrete, Portland cement concrete, non-shrink grouts and mortars, and construction sequencing.
• CSD coordinated its work with Johnston Construction Company’s phased construction schedule, UV-equipment layouts, demolition limits, existing structures, reinforcing steel, embedded items, electrical conduits, gate frames, equipment supports, access grating, and process piping.
• The project required the wastewater treatment plant to remain in continuous operation. At least two UV disinfection systems had to remain operational throughout construction.
• The first major phase included construction of the new UV System No. 3 channel adjacent to the existing UV facilities.
• Before concrete construction began, Johnston Construction Company coordinated temporary channel isolation, bulkheads, draining, pumping, dewatering, structural demolition, and removal of the existing chlorine-contact-tank slab and gravel fill.

Electrical Services Division

• ESD furnished and installed the conduit, conductors, connections, boxes, devices, electrical gear, lighting, instrumentation raceways, underground ductbank, and related electrical components required for three new ultraviolet disinfection systems.
• The electrical distribution work included ten 30-amp disconnect switches, three 100-amp disconnect switches, three 100-amp circuit breakers, three 30-amp circuit breakers, one 20-amp circuit breaker, and three power-meter totalizers.
• ESD installed power and control conduit and wiring for three UV-transmittance transmitters, with one transmitter serving each new UV disinfection system.
• The project included control conduit for high- and low-level floats serving the three UV channels and additional floats incorporated into ESD’s revised scope.
• ESD installed power and control wiring for the motor-operated weir gates and utility-water slide gate associated with the UV-treatment channels.
• New UV-area site lighting included fixtures, poles, conduit, conductors, controls, grounding, concrete foundations, and final electrical connections.
• The work was carefully phased so that two UV disinfection systems remained operational throughout construction using a combination of existing and newly commissioned equipment.
• ESD coordinated electrical demolition, circuit-breaker replacement, energization, testing, and startup with Johnston Construction Company, NORESCO, the UV-equipment supplier, control-system personnel, and Charles County plant operations.
• The overall project replaced and expanded the existing ultraviolet disinfection process at the Mattawoman Wastewater Treatment Plant. Three new UV disinfection systems were installed together with new concrete treatment channels, slide gates, weir gates, stop-log frames, structural access systems, electrical distribution, instrumentation, controls, and SCADA connections.
• ESD’s work provided the electrical infrastructure necessary to power, control, monitor, and operate the three new UV systems and their associated gates, instruments, lighting, and auxiliary equipment.
• The work began with electrical demolition and make-safe activities associated with the existing UV disinfection equipment.
• ESD identified, isolated, disconnected, and removed designated electrical circuits, conductors, conduits, circuit breakers, boxes, devices, and equipment connections serving systems scheduled for demolition.
• Electrical demolition was coordinated with JCC’s removal of existing UV equipment, concrete channels, structural components, gates, piping, and related treatment-process facilities.
• Existing electrical systems that remained in operation were protected throughout construction. Lockout and tagout procedures were coordinated with Johnston Construction Company, NORESCO, and Charles County plant personnel before affected equipment was disconnected.