Servicing does not dictate community design –unparalleled system flexibility and scalability

In historic gravity sewers, straight alignment in both horizontal and vertical planes are an essential part of the functionality of the sewer system, with maintenance holes required for every change in grading or horizontal directional change and at regular 100 metre intervals along the piping system; these linear requirements are driven by the need to carry solids in the piping system. The Clearford clarifier tank removes solids from the waste stream; the piping system carries only the liquid portion of sewage. The SBS™ main piping system can be installed with curvilinear alignment, as well as with variable grading within the overall main and lateral systems. The design and installation of the main pipe can tolerate siphons and sections of negative gradients, provided that clarifier tank outlets are kept above the high points in the piping system. The key parameter of the design is the hydraulic grade line that will meet the overall negative gradients as the system flows from the higher elevations to the lower elevations.

Impact on Community Planning

Historic gravity sewers are associated with grid system community planning elements and are cost sensitive relative to high sewer lengths and larger lot frontages. Small Bore Sewers™ can be utilized for communities that prefer more natural planning with curves and community contours that are not restricted by the rigid nature of historic sewer design; the SBS™ is more suitable to applications where spatial separation is a key component of community design. SBS™ main costs are normally half of the cost of historic mains and can be more economically applied to existing rural communities requiring re-servicing, or new rural communities that prefer larger lots in rural settings. Variable alignment allows community planners to create plans that are not based upon grid system geometrics, right angled bends, and tee intersections.

Construction Variables

During construction of historic gravity sewers, if unknown subsurface obstacles are found, the re-design and realignment process can be very complex – driven by the need to provide for continuous negative gradients and linearity in the piping system, as well as the need for the addition of maintenance holes for every change and vertical direction of the piping system. With the SBS™ system, in combination with either open trench installation or trenchless technology methodology, if surface or subsurface obstructions are encountered, the design engineer can quickly react to incremental changes in both vertical and horizontal alignment to avoid costly removals or costly reinstatement of existing infrastructure. The asset of variable grading in the piping system allows any required modifications during construction to be efficiently addressed by the design engineer; changes can be made in a timely fashion with the least amount of associated cost.