The amount of soluble salt solids remaining in the heel are likely to be small because so much of 
(soluble salt solids; remaining; L:in the heel) (The amount of soluble salt solids; are; likely to be small) (The amount of soluble salt solids; to be; small)
soluble salt solids The amount of soluble salt solids The amount of soluble salt solids
remaining are to be
L:in the heel
likely to be small
small