  We study $B^{+}\to \pi^{+}\pi^{0}\pi^{0}$ using 711 $\rm{fb}^{-1}$ of data
collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB
asymmetric-energy $e^{+}e^{-}$ collider. We measure an inclusive branching
fraction of $(19.0\pm 1.5\pm 1.4)\times 10^{-6}$ and an inclusive \textit{CP}
asymmetry of $(9.2 \pm 6.8 \pm 0.7)\%$, where the first uncertainties are
statistical and the second are systematic; and a $B^{+}\to
\rho(770)^{+}\pi^{0}$ branching fraction of $(11.2\pm 1.1\pm 0.9
^{+0.8}_{-1.6})\times 10^{-6}$, where the third uncertainty is due to possible
interference with $B^{+}\to \rho(1450)^{+}\pi^{0}$. We present the first
observation of a structure around 1 GeV/$c^{2}$ in the $\pi^{0}\pi^{0}$ mass
spectrum, with a significance of 6.4$\sigma$, and measure a branching fraction
to be $(6.9\pm 0.9\pm 0.6)\times 10^{-6}$. We also report a measurement of
local \textit{CP} asymmetry in this structure.
