  We present observations and analysis of the massive molecular outflow
G331.512-0.103, obtained with ALMA band 7, continuing the work from Merello et
al. (2013). Several lines were identified in the observed bandwidth, consisting
of two groups: lines with narrow profiles, tracing the emission from the core
ambient medium; and lines with broad velocity wings, tracing the outflow and
shocked gas emission. The physical and chemical conditions, such as density,
temperature, and fractional abundances are calculated. The ambient medium, or
core, has a mean density of $\sim 5\times 10^6$ cm$^{-3}$ and a temperature of
$\sim 70$ K. The SiO and SO$_2$ emission trace the very dense and hot part of
the shocked outflow, with values of $n_{\rm H_2}\sim10^9$ cm$^{-3}$ and $T \sim
160-200$ K. The interpretation of the molecular emission suggests an expanding
cavity geometry powered by stellar winds from a new-born UCHII region,
alongside a massive and high-velocity molecular outflow. This scenario, along
with the estimated physical conditions, is modeled using the 3D geometry
radiative transfer code MOLLIE for the SiO(J$=8-7$) molecular line. The main
features of the outflow and the expanding shell are reproduced by the model.
