Backfill and granular sub-base compaction

S6.7.13: Backfill must be selected and placed in accordance with S5.
S6.7.14: Granular sub-base material must be placed in accordance with S6.2. If the sub-base is bound it will be extracted as part of the core and reinstated in accordance with S6.7.17.
S6.7.15: A layer of pea gravel may be used to aid levelling of the core. The layer must not exceed 50 mm in thickness at any point.