Second Street Sewage Pumping Station Emergency Wet Well Repairs

Key Accomplishments

• Constructed one new reinforced-concrete beam and two reinforced-concrete struts on top of the existing wet-well ceiling/floor slab to provide permanent structural support associated with replacement of the deteriorated slab. The existing slab was specifically designated to serve as the bottom form for this new concrete construction.
• Performed demolition of the existing deteriorated wet-well ceiling slab and removal of demolition debris from the wet well, coordinating demolition with the subsequent reinforced-concrete reconstruction.
• Worked within the confined environment of an existing reinforced-concrete sewage wet well. The City's qualification requirements specifically required successful prior experience with concrete demolition and construction in confined spaces, reflecting the specialized nature of the work.
• Provided engineered shoring for the wet-well structural work, with the shoring design required to be signed and sealed by a Professional Engineer registered in the State of Maryland.
• Designed, erected, braced and removed the formwork required for the new cast-in-place concrete construction. The specifications placed complete responsibility for form design, engineering, erection, bracing, shoring, stripping and reshoring on the contractor and required compliance with ACI 301, ACI 318 and ACI 347.
• Constructed rigid formwork capable of resisting construction loads and maintaining the required structural alignment, including properly braced panels, shores, supports, form ties and openings necessary to produce concrete true to the dimensions, elevations and shapes shown on the contract drawings.
• Furnished and installed reinforcing steel for the structural concrete work in accordance with ACI, ASTM and CRSI requirements. The project specified ASTM A615 Grade 60 deformed reinforcing steel, with reinforcement fabricated from approved shop drawings and securely placed to maintain the required position and concrete cover.
• Coordinated reinforcing-steel fabrication around restricted site access. The specifications expressly recognized that access limitations could prevent full-length reinforcing bars from being brought into the work area and required the site to be evaluated before fabrication to determine whether reinforcing splices would be necessary.
• Placed high-strength structural concrete designed specifically for wastewater infrastructure. The specifications required 4,500 psi minimum 28-day compressive strength, a maximum 0.45 water-cement ratio, and a 2- to 4-inch slump for all concrete.
• Concrete construction was required to comply with ACI 301, ACI 304R, ACI 309R, ACI 318 and ACI 350, including the environmental-engineering concrete requirements appropriate for wastewater structures.
• Prepared the existing structure for new concrete placement, including installation of reinforcing steel and dowels prior to concrete placement, cleaning of the forms and reinforcement, removal of excess water and use of bond-inhibiting material where new concrete was placed directly against existing concrete scheduled for demolition.
• Consolidated cast-in-place concrete using internal vibration to achieve dense, uniform structural concrete without segregation, voids or honeycombing. Specifications required experienced vibrator operators and sufficient equipment to consolidate newly deposited concrete promptly, with standby vibration equipment maintained at the site.