Fig. 3. Pile height (thick solid line) and chamber [a (black squares), b (empty squares), and c (gray squares)] elevation at Day 1 (a), Day 4 (b), Day 8 (c), Day 12 (d), Day 16 (e), and Day 20 (f) before each day's sampling. The four horizontal lines in each day's graph represent the elevation of the thermocouples situated at the bottom (line with cross), bottom middle (dash line), top middle (line with X), and top (solid line).