I feel not fair with these answers so I am just checking.
1. Caesar pitched camp two miles from the river.
Caesar castra dua milia passuum a flumine posuit.
2. He fortified the camp with a ditch fifteen feet wide and nine feet high.
(Is) castra fossá quindecim latós pedés atque válló novem altós (pedés).
I'm not sure, whether latus, altus should be accusative. Can some one explain as I am doubtful!
3. The camp ...