The path forms a rectangle with dimensions $2,000$ ft by $3,500$ ft.

Perimeter of the path:

$P = 2(2,000 + 3,500) = 2(5,500) = 11,000 \text{ ft}$

Total distance for 15 trips:

$15 \times 11,000 = 165,000 \text{ ft}$

Convert to miles ($1$ mile $= 5,280$ ft):

$\frac{165,000}{5,280} \approx 31.25 \approx 31 \text{ miles}$