OBC On-site Sewage Systems flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Building Code Act purpose

Ontario statute that authorizes the building code, establishes the chief building official and inspectors, and provides enforcement powers including orders to comply and stop-work orders.

Part 8 scope

Division B Part 8 governs sewage systems serving one lot with design capacity of 10,000 litres per day or less, covering treatment, distribution, and dispersal requirements.

Sewage system definition

A system for the treatment and disposal of sewage serving a single lot, including treatment units, distribution piping, and dispersal components such as leaching beds.

Permit before construction

A building permit must be obtained from the principal authority before constructing, extending, altering, or repairing a sewage system, and work must follow approved plans.

Site evaluation purpose

An assessment of soil texture, permeability, depth to bedrock and water table, slope, and lot size that determines the feasible system type and size.

Percolation rate (T-time)

The time in minutes for water in a test hole to drop 25 millimetres, used to classify soil permeability and size the dispersal area.

Seasonal high water table

The highest expected groundwater elevation, determined from soil mottling, monitoring wells, or local records, which sets the minimum trench bottom elevation.

Reserve area requirement

An identified and protected area of comparable size to the primary dispersal area, kept available for a replacement system if the original fails.

Design daily flow

The estimated volume of sewage produced per day, based on bedrooms, fixtures, or occupancy, used to size the tank and dispersal area.

Hydraulic loading rate

The volume of effluent applied per unit area of soil per day, selected from soil texture and treatment level to size the dispersal area.

Typical residential sewage strength

Residential sewage commonly contains about 200 to 300 mg/L BOD5 and 200 to 300 mg/L suspended solids, with grease and settleable solids removed in the tank.

Clear water prohibition

Footing drains, roof leaders, and other clear-water sources shall not be connected to the sewage system because they overload the tank and dispersal area.

Septic tank retention time

A tank provides at least about 24 hours of liquid retention at design flow, allowing solids to settle and scum to float before effluent exits.

Minimum tank capacity

Part 8 sets a minimum tank volume, typically 3,600 litres for a single-family dwelling, with additional capacity for extra bedrooms or fixtures.

Tank pumping trigger

The tank should be pumped when combined sludge and scum depth reaches about one-third of the tank depth, to protect the dispersal field.

Effluent filter function

A device at the tank outlet that captures fine solids, reducing loading to the dispersal field, and requires regular cleaning to prevent backup.

Leaching bed definition

A dispersal system of distribution pipe in gravel-filled trenches, sized by daily flow and soil loading rate, with level or uniformly sloped perforated pipe.

Filter bed purpose

A dispersal system using sand or other filter medium to provide additional treatment where native soil is marginal, improving effluent quality before it reaches groundwater.

Mound system definition

A raised dispersal system built with sand fill above natural grade, used where bedrock or the water table is too close to the surface for a conventional bed.

Distribution box function

A level, accessible box that divides effluent equally among distribution pipes or trenches, preventing one trench from receiving disproportionate flow.

Dose volume basis

The batch volume delivered per pump cycle, typically the distribution pipe volume plus a fraction of daily flow, sized to rest the soil between doses.

Total dynamic head

The sum of static lift and friction losses in the discharge line, used with the required dose rate to select a pump.

Pump chamber alarm

A high-level float and alarm that warns of pump failure or high water in the chamber, set below the inlet invert to prevent backup into the building.

Check valve requirement

A valve on the pump discharge that prevents effluent from flowing back into the chamber, paired with an isolation valve for maintenance.

Well setback purpose

A required horizontal distance between a sewage system and a drinking-water well, larger than most other setbacks, to protect water quality from contamination.

Surface water setback

A specified minimum horizontal distance from a leaching bed to a watercourse, lake, or pond, intended to protect surface water from nutrient and pathogen loading.

System location restrictions

Sewage systems shall not be placed under driveways, parking areas, or buildings, and must remain accessible for maintenance and inspection.

Setback measurement basis

Setbacks are measured horizontally from the system component, such as the trench edge or tank wall, to the feature, and must be shown on the site plan.

Required inspection stages

Inspections are required before covering the tank, before covering distribution piping, and at final completion; work must not be covered before authorization.

Failure indicators

Surfacing effluent, odour, slow drains, and soggy ground over the dispersal area indicate system failure and require prompt investigation and repair.

Site plan contents

A drawing showing lot boundaries, buildings, wells, watercourses, setbacks, system layout, and reserve area, submitted with the permit application.

Permit amendment

A required approval for changes to approved plans; work must not proceed on the changed portion until the amendment is issued.