Comprehensive Guide to Type B Dispersal Beds: OBC Section 8.7.8 Septic Requirements
Sarah's Expert Insight
OBC Compliance Specialist
"In regions like Muskoka with high bedrock or London with varying soil permeability, Type B Dispersal Beds are a critical solution for sites that cannot support traditional gravity systems. As a senior consultant at empcontracting.ca Inc. your construction contractor in London, Ontario, I find that the mandatory Level IV treatment and pressurized dosing are the best defenses against environmental contamination in high-water-table areas."
Navigating the 2024 Ontario Building Code (OBC) for advanced sewage systems requires technical precision. As specialists at empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every installation meets the rigorous standards of Section 8.7.8 to protect local groundwater and property value.
General Requirements for Type B Dispersal Beds
According to OBC 8.7.8.1, Type B dispersal beds must adhere to the general requirements of standard leaching beds while following strict site limitations. Specifically, these beds cannot be located in areas where the average slope exceeds a ratio of one unit vertically to seven units horizontally (1:7), ensuring stability and preventing runoff issues.
Construction and Technical Standards
Effluent Quality and Level IV Treatment
A Type B dispersal bed must be used in conjunction with a treatment unit that produces high-quality effluent. The system must meet Level IV treatment unit standards as defined in Table 8.6.2.2. This higher level of pre-treatment is essential for the pressurized distribution that follows.
Physical Dimensions and Bed Configuration
- Shape: Must be rectangular with the long dimension oriented parallel to the site’s contours.
- Depth: The total depth from the bottom of the stone layer to the finished grade must not exceed 1,000 mm in soils with a percolation time (T-time) greater than 15 minutes.
- Vertical Separation: The stone layer's bottom must remain at least 600 mm above the high groundwater table, bedrock, or soil with a percolation time exceeding 50 minutes.
Pressurized Distribution and Dosing
Unlike gravity-fed systems, Type B beds require a pressurized distribution system. This system must maintain a pressure head of at least 600 mm at the furthest point. At empcontracting.ca Inc. your construction contractor in London, Ontario, we prioritize the requirement that pipes be self-draining to prevent freezing during Ontario winters, featuring orifices at least 3 mm in diameter for uniform dosing.
Stone Layer and Pipe Specifications
The stone layer must consist of washed septic stone, free of fine material, extending 250 mm below the pipe and 50 mm above it. Pipe spacing is restricted to a maximum of 1.2 meters apart, with the outermost pipes located no more than 600 mm from the edge of the bed. If a site requires multiple beds, a minimum separation of 5 meters between stone layers must be maintained.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.