Clarksburg 1.0 MG Composite Elevated Water Storage Facility

Key Accomplishments

Johnston Construction Company

• Constructed the site drainage and tank-overflow infrastructure, including drainage piping, precast structures and the tank overflow drain system. JCC's scope also included continuation of the tank's 4-inch floor-drain piping outside the foundation and construction of the associated French-drain system.
• Installed the new 16-inch water-main system and associated appurtenances connecting the elevated storage tank to WSSC's distribution system. The overall facility design connected the new 16-inch main to an existing 24-inch water main, with the tank operating in WSSC's 760A/B pressure zone.
• Completed the tank-site water-main connections and associated valve work, including the connection to the existing system, blow-off assembly, ductile-iron tank stub-out connection and flexible joint coupling required to integrate the new elevated tank with the distribution network.
• Installed a sacrificial cathodic-protection system for the new water main and appurtenances, providing corrosion protection for buried metallic piping incorporated into the permanent water-distribution improvements.
• Constructed and equipped the below-grade altitude valve vault and bypass system, including piping, valves, pipe supports, link seals, straps, polyethylene encasement, heating and ventilation components, sump pump, splash block, access hatches, miscellaneous metals, insulated flanged joints and associated conduit. The altitude valve system was designed to control filling and draining of the new elevated tank.
• Installed Trenwa trench boxes and electrical trenches required for the completed tank facility, coordinating the work with Landmark and the electrical subcontractor so civil and electrical installations could proceed without interfering with subsequent tank and electrical construction.
• Completed final site grading and restoration to establish positive drainage away from the elevated tank structure. JCC's work included finish grading, curb and paving-edge backfill, placement of topsoil, final seeding, removal of temporary erosion-control structures when approved and restoration of disturbed construction areas.
• Coordinated testing, adjustment, startup and training associated with the utility systems installed under JCC's subcontract, together with required inspection, survey and record-documentation activities necessary for final turnover of the civil work.
• Executed the civil work on a site requiring substantial coordination of earthwork, utilities and the tank-construction sequence. The approximately 1.6-acre site was located near I-270 and MD Route 121 and incorporated the elevated tank, below-grade altitude valve vault and stormwater-management facilities within an area of varying existing grades.
• The new elevated tank was designed for WSSC's 760A/B pressure zone. A new 16-inch water main connected the tank to an existing 24-inch distribution main, while a below-grade altitude valve vault controlled filling and draining of the storage tank. The project also incorporated associated piping, valves, drainage, site development, grading, access improvements and stormwater-management facilities.
• JCC's direct subcontract encompassed the civil infrastructure surrounding and serving the new elevated tank. Early work included installation and maintenance of erosion and sediment controls, stabilized construction access, clearing and grubbing and preparation of the site for subsequent tank and utility construction. JCC was also responsible for coordination with sediment and erosion-control inspectors and for maintaining its portion of the work in accordance with project environmental requirements.
• The drainage portion of JCC's work included the complete site-drainage system and tank-overflow infrastructure. This incorporated drainage piping, precast drainage structures, the tank overflow drain system and continuation of the 4-inch tank floor drain beyond the foundation to the associated French drain. These systems were integrated with the surrounding finished grades to direct water away from the elevated tank structure and maintain proper drainage across the completed site.

Concrete Services Division

• Performed the specialized cast-in-place concrete package for the altitude valve vault serving WSSC's new 1-million-gallon Clarksburg Elevated Water Storage Facility. The completed vault formed a key component of the new water-storage system because the altitude-valve arrangement controls filling and draining of the elevated tank within WSSC's 760A/B pressure zone.
• Completed concrete forming and placement for the principal components of the altitude valve vault, including the sump slab, bottom slab, structural walls, top slab, concrete topping and concrete pipe supports. CSD's subcontract also included the concrete pipe support associated with the project blow-off piping.
• Executed approximately 81 cubic yards of concrete placement across the contracted vault components, including approximately 38 CY of slab-on-grade concrete, 26 CY of wall concrete, 14 CY of supported-slab concrete and 3 CY of miscellaneous fill concrete.
• Constructed approximately 2,088 square feet of concrete formwork, consisting of approximately 211 SF of slab-on-grade forms, 1,395 SF of straight-wall forms, 466 SF of supported-slab forms and 16 SF of special forming. The work required the forms to be fabricated, erected, stripped and maintained in accordance with the project's concrete and formwork requirements.
• Performed the complete concrete-finishing sequence across approximately 3,449 square feet of finished surfaces. The documented work included approximately 1,260 SF of float-and-screed finishing, 312 SF of floor-hardener work and 1,877 SF of pointing and patching, providing the finished concrete surfaces required for the vault structure.
• Provided curing operations for approximately 3,348 square feet of concrete surfaces, coordinating curing procedures with concrete placement and environmental conditions to protect the completed concrete while strength developed. Project specifications required cast-in-place concrete work to comply with ACI requirements for placement, finishing, curing and quality control.
• Installed approximately 150 linear feet of special waterstop at concrete joints within the vault construction. The project specifications required waterstop systems to be properly supported and positioned within the forms during concrete placement so joint integrity and watertight performance could be maintained.
• Constructed 13 concrete pipe pads / supports associated with the vault and process piping system. These concrete supports formed part of the infrastructure required to properly support piping within the completed altitude-valve system.
• Performed forming, concrete-placement labor, finishing, curing, concrete-accessory installation, winter-protection labor and dowel-placement labor while coordinating closely with Johnston Construction Company for supporting resources. JCC provided or paid for concrete material, pumping services, concrete testing, winter-protection blankets and heaters, and material-handling equipment, while CSD coordinated those services with its concrete operations.
• Completed the vault concrete as part of the larger 1-million-gallon composite elevated water-storage facility, which also incorporated a new 16-inch water main connected to an existing 24-inch main, site drainage, stormwater-management improvements and the altitude-valve system.
• Concrete Services Division, LLC completed the concrete construction package associated with the Clarksburg Elevated Water Storage Facility in Montgomery County, Maryland. The project was constructed for the Washington Suburban Sanitary Commission, with Landmark Structures I, L.P. serving as the Prime Contractor and Johnston Construction Company performing the major civil and utility subcontract work.
• The overall project provided a new 1-million-gallon composite-style elevated water storage tank within WSSC's 760A/B pressure zone. The facility incorporated a new 16-inch water main connecting the tank to an existing 24-inch distribution main, together with an altitude valve vault designed to control filling and draining of the tank.
• CSD's direct work concentrated on the cast-in-place concrete components of the altitude valve vault and associated pipe supports. The subcontract specifically included forming and concrete-placement work for the sump slab, bottom slab, walls, top slab, concrete topping and pipe supports, along with the concrete pipe support serving the blow-off piping.
• The concrete package incorporated approximately 81 cubic yards of concrete placement. This included slab-on-grade, wall, supported-slab and miscellaneous concrete work. To form these structural components, CSD constructed approximately 2,088 square feet of formwork, including straight-wall forms, supported-slab forms, slab-on-grade forms and special forming.