8.33. An underground tank must be installed on a backfill foundation at least 300 mm thick, that exceeds the tank’s perimeter by at least 300 mm and is composed of one of the following materials:(1) in the case of a fibreglass tank, pea gravel, rounded pea gravel between 3 and 20 mm or crushed stone at least 3 mm and not more than 13 mm; in addition, each material used must be clean and without dust, sand, debris, organic material, ice or snow so that not more than 3% of its weight passes through a 2.5 mm sieve;
(2) in the case of a steel tank, clean or natural sand free of stones compacted to at least 90% of the optimal density of the modified proctor determined according to CAN/BNQ Standard 2501-255, Soils - Determination of the Water Content-Dry Density Relation - Modified Effort Compaction Test (2,700 kN.m/m3), published by the Bureau de normalisation du Québec, and be without stone, debris, organic material, ice or snow; or
(3) in the case of a jacketed steel underground tank, clean or natural sand free of stones compacted to at least 90% of the optimal density of the modified proctor determined according to CAN/BNQ Standard 2501-255, Soils - Determination of the Water Content-Dry Density Relation - Modified Effort Compaction Test (2,700 kN.m/m3), published by the Bureau de normalisation du Québec, and be without stone, debris, organic material, ice or snow, or pea gravel or rounded pea gravel between 3 and 20 mm.