The Brudenell Fairway Chalets are located just outside of the community of Georgetown, and around 35 minutes from Charlottetown. Designing a sewage system in a rural development, which still sees high tourist traffic in the summer months, called for a practical, low-maintenance and cost-effective sewer servicing solution.
Not only does the site provide some of the most beautiful lodgings on Prince Edward Island, it also gives an example of the environmental benefits of an alternative sewer servicing system - specifically, a septic tank effluent gravity (STEG) sewer designed by ETC engineers.
The Fairway Chalets wastewater collection and treatment system is composed of three segments: the STEG sewer, a pressure sewer force main and a pressurized leaching chamber disposal field. The system is designed so that at full build-out, septic tank effluent from 22 chalets and a laundry facility discharges to a four-inch (100 mm) effluent sewer located along the front of the buildings.
The collection sewer drains into a wet-well effluent pumping station. The combined flow is pumped through a force main to a central, pressurized Infiltrator™ Leaching Chamber Disposal Field.
The most significant feature of effluent sewers is that primary pretreatment is provided in septic tanks upstream of each connection. With the settleable solids removed, it is not necessary to design the collector mains to maintain minimum self-cleansing velocities. Without the requirement for minimum velocities, the pipe gradients may be reduced and, as a result, the depths of excavation. The need for manholes at all junctions, changes in grade and alignment, and at regular intervals is eliminated.
The system in inherently watertight by design, as infiltration and grit, which commonly enter through manholes, are eliminated. Except for the need to evacuate the accumulated solids in the septic tanks periodically (usually once every seven to 12 years) STEG sewers operate similarly to conventional sewers.
Pipes used are plastic and smaller than conventional sewer pipes. They are less expensive, easier to install and less likely to have wastewater seep out, or to have other water to infiltrate the system.
The pipes do not have to continuously slope downward, like conventional sewers. Instead, they can be buried at shallower depths (just below frost line) and can follow the natural contours of the land. This saves significantly on excavation costs.
The plastic pipes can also be routed around ponds, lakes, trees, houses and other obstacles. This minimizes disruption to the environment and again saves money for developers and communities.
Any site that can be sewered with conventional gravity sewers can usually be sewered with STEG.
Advantages include smaller pipe size, shallower depth of burial, reduced overall gradient, ability to reverse (inflective) gradient for selected portions of the system, reduced infiltration/inflow, and no manholes.
STEG systems are well suited to previously developed or underdeveloped areas with low to moderate relief. Site constraints such as shallow soil, rolling (undulating) terrain and shallow groundwater can be overcome with STEG system.