Div. B › Part 8 › 8.7 › 8.7.2 — Design and Construction Requirements

8.7.2.1 — General Requirements

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(1) A leaching bed shall not be located,

(a) in an area that has an average slope that exceeds one unit vertically to four units horizontally,

(b) in soil or leaching bed fill having a percolation time of,

(i) less than one minute, or greater than 125 minutes if constructed as a shallow buried trench, or

(ii) less than one minute, or greater than 50 minutes for all other leaching beds, or

(c) in or on an area that is subject to flooding that may be expected to cause damage to the leaching bed or impair the operation of the leaching bed.

(2) A leaching bed shall not be covered with any material having a hydraulic conductivity less than 0.01 m/day.

(3) The surface of the leaching bed shall be shaped to shed water and together with the side slopes of any raised portion, shall be protected against erosion in such a manner as to not inhibit the evaporation and transpiration of waters from the soil or leaching bed fill, and to not cause plugging of the distribution pipe.

(4) No part of a leaching bed shall be sloped steeper than 1 unit vertically to 4 units horizontally.

(5) A leaching bed shall be designed to be protected from compaction or any stress or pressure that may result in,

(a) the impairment or destruction of any pipe in the leaching bed, or

(b) the smearing of the soil or leaching bed fill.

OBC Definitions

Defined terms on this page

distribution pipe

means a line or lines of perforated or open jointed pipe or tile installed in a leaching bed for the purpose of distributing effluent from a treatment unit to the soil, as defined in Part 8 of Division B, or leaching bed fill in the leaching bed.

fill

means soil, rock, rubble, industrial waste such as slag, organic material or a combination of these that is transported and placed on the natural surface of a soil or rock or organic terrain; it may or may not be compacted.

leaching

means dispersal of liquid by downward or lateral drainage or both into permeable soil, as defined in Part 8 of Division B, or leaching bed fill.

leaching bed

means an absorption system constructed as absorption trenches or as a filter bed, located wholly in ground or raised or partly raised above ground, as required by local conditions, to which effluent from a treatment unit is applied for treatment and disposal and that is composed of, (a)the soil, as defined in Part 8 of Division B, leaching bed fill or other filter media that is contained between the surface on which the sanitary sewage is applied and the bottom of the bed, (b)the leaching chamber or the distribution pipe and the stone or gravel layer in which the distribution pipe is located, and (c)the backfill above the distribution pipe or the leaching chamber, including the topsoil and sodding or other anti-erosion measure, and the side slopes of any portion elevated above the natural ground elevation.

leaching bed fill

means unconsolidated material suitable for the construction of a leaching bed, placed in the area of the leaching bed in order to obtain the required unsaturated zone below the distribution pipes or leaching chambers and the required lateral extent such that the effluent is absorbed.

percolation time

means the average time in minutes that is required for water to drop one centimetre during a percolation test or as determined by a soil evaluation or analysis.

shallow buried trench

means an absorption trench that contains a chamber or leaching chamber.

soil

means , except for the purposes of Part 8 of Division B, a portion of the earth’s crust that is fragmentary or such that individual particles of a dried sample may be readily separated by agitation in water, and includes boulders, cobbles, gravel, sand, silt, clay and organic matter.

construct

to do anything in the erection, installation, extension or material alteration or repair of a building and includes the installation of a building unit fabricated or moved from elsewhere; Act

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