A manufacturing plant discharges clean water into a lake. Due to natural processes, the concentration of a chemical in the water decreases exponentially with distance $x$ (in miles) from the discharge pipe: $C(x) = C_0 e^{-0.5x}$. At what distance (to the nearest tenth of a mile) is the concentration reduced to $10\%$ of its initial value $C_0$? (Use $\ln(10) \approx 2.3026$)