A comparison of secondary drainage systems: Shelton Gravel Band Slit trench drainage Shelton Shelton System 25™ Drainage sand slitting Lightening-drain™ Two or three pass One pass operation One pass operation One pass operation operation Trench width 25mm Trench width 25mm Trench width 50mm Trench width 35mm Trench 300mm Trench depth 350mm Trench depth 250mm Trench depth 450mm Spacings usually 400mm Spacings usually 400mm Spacings usually Spacings usually 500mm to 1,000mm to 1,000mm 1,000mm to 2,000mm to 1,000mm Aggregate brought up to Aggregate brought Aggregate brought Aggregate brought 2” of surface, topped off close to surface close to surface close to surface with free draining sand Cost per linear unit = Cost per linear unit = Cost per linear unit = x Cost per linear unit = 3x 2x 4-5x Negligible chance of Little chance of trench Moderate risk of trench Little chance of trench trench opening-up in opening-up in dry opening-up in dry opening-up in dry dry weather weather weather weather Safety: Excellent Safety: Good Safety: Some risks Safety: Good Must be undertaken Best undertaken when Best undertaken when Best undertaken in dry when soils are moist to soils are on the dry soils are on the dry side conditions very moist side Minimum labour Minimum labour Minimum labour Minimum labour requirement: two requirement: one requirement: two requirement: three persons, preferably person persons, preferably three persons three Output per day: circa Output per day: circa Output per day: circa Output per day: circa 6000 metres 3000 metres 3000 metres 1500-2000 metres
A comparison of secondary drainage systems: Shelton Gravel Band Drainage Shelton System 25™ Slit trench drainage sand slitting Shelton Lightening-drain™ One pass operation One pass operation Two or three pass operation One pass operation Trench width 25mm Trench width 25mm Trench width 50mm Trench width 35mm Trench 300mm Trench depth 350mm Trench depth 250mm Trench depth 450mm Spacings usually 400mm to 1,000mm Spacings usually 400mm to 1,000mm Spacings usually 1,000mm to 2,000mm Spacings usually 500mm to 1,000mm Aggregate brought close to surface Aggregate brought close to surface Aggregate brought up to 2” of surface, topped off with free draining sand Aggregate brought close to surface Cost per linear unit = x Cost per linear unit = 2x Cost per linear unit = 3x Cost per linear unit = 4-5x Negligible chance of trench opening-up in dry weather Little chance of trench opening-up in dry weather Moderate risk of trench opening-up in dry weather Little chance of trench opening-up in dry weather Safety: Excellent Safety: Good Safety: Some risks Safety: Good Must be undertaken when soils are moist to very moist Best undertaken when soils are on the dry side Best undertaken in dry conditions Best undertaken when soils are on the dry side Minimum labour requirement: one person Minimum labour requirement: two persons, preferably three Minimum labour requirement: two persons, preferably three Minimum labour requirement: three persons Output per day: circa 6000 metres Output per day: circa 3000 metres Output per day: circa 3000 metres Output per day: circa 1500-2000 metres
A_comparison_of_secondary_drainage_systems.docx