The spreadsheet also provides an opportunity to calculate the migration of substance by means of pore water transportation through the unsaturated zone

Can you repeat this sentence, but add in punctuation?
The spreadsheet also provides an opportunity to calculate the migration of substance by means of pore water transportation through the unsaturated zone.
San Sebastian is situated on the coast in the very north of Spain 20 km west of the French border

Can you repeat this sentence, but add in punctuation?
San Sebastian is situated on the coast in the very north of Spain, 20 km west of the French border.
The lowland areas are also planted with cut flowers and a variety of fruits and vegetables many are grown all year round under glass

Can you repeat this sentence, but add in punctuation?
The lowland areas are also planted with cut flowers and a variety of fruits and vegetables, many are grown all year round under glass.