  We present $^{12}$CO, $^{13}$CO, and C$^{18}$O data as the next major release
for the CHaMP project, an unbiased sample of Galactic molecular clouds in $l$ =
280$^{\circ}$-300$^{\circ}$. From a radiative transfer analysis, we
self-consistently compute 3D cubes of optical depth, excitation temperature,
and column density for $\sim$300 massive clumps, and update the $I_{\rm
CO}$-dependent CO$\rightarrow$H$_2$ conversion law of Barnes et al (2015). For
$N$ $\propto$ $I^p$, we find $p$ = 1.92$\pm$0.05 for the velocity-resolved
conversion law aggregated over all clumps. A practical, integrated conversion
law is $N_{\rm CO}$ = (4.0$\pm$0.3)$\times$10$^{19}$m$^{-2}$ $I_{\rm
CO}^{1.27\pm0.02}$, confirming an overall 2$\times$ higher total molecular mass
for Milky Way clouds, compared to the standard $X$ factor.
  We use these laws to compare the kinematics of clump interiors with their
foreground $^{12}$CO envelopes, and find evidence that most clumps are not
dynamically uniform: irregular portions seem to be either slowly accreting onto
the interiors, or dispersing from them. We compute the spatially-resolved mass
accretion/dispersal rate across all clumps, and map the local flow timescale.
While these flows are not clearly correlated with clump structures, the
inferred accretion rate is a statistically strong function of the local mass
surface density $\Sigma$, suggesting near-exponential growth or loss of mass
over effective timescales $\sim$30-50 Myr. At high enough $\Sigma$, accretion
dominates, suggesting gravity plays an important role in both processes. If
confirmed by numerical simulations, this sedimentation picture would support
arguments for long clump lifetimes mediated by pressure confinement, with a
terminal crescendo of star formation, suggesting a resolution to the 40-yr-old
puzzle of the dynamical state of molecular clouds and their low star formation
efficiency.

Astrophysics of Galaxies