!|5:1 to 15:1||Underdrain Required <br> if < 15 mm/hr||1 to 3||5 to 10||0.5 to 6||No||4m (3m if impermeable liner<br>is used)Building foundation,<br> Underground utilities, drinking<br>water wellhead protection areas||1 m||2 Yr | !|5:1 to 15:1||Underdrain Required <br> if < 15 mm/hr||1 to 3||5 to 10||0.5 to 6||No||4m (3m if impermeable liner<br>is used)Building foundation,<br> Underground utilities, drinking<br>water wellhead protection areas||1 m||2 Yr |