  We combine datasets from the CGM$^{2}$ and CASBaH surveys to model a
transition point, $R_{\rm cross}$, between circumgalactic and intergalactic
media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies
at z < 0.5 with precisely measured spectroscopic redshifts, all having impact
parameters of 0.01 - 20 comoving Mpc from 28 QSO sightlines with
high-resolution UV spectra that cover H I Ly$\alpha$. Our best-fitting model is
an exclusionary two-component model that combines a 3D absorber-galaxy cross
correlation function with a simple Gaussian profile at inner radii to represent
the CGM. By design, this model gives rise to a determination of $R_{\rm cross}$
as a function of galaxy stellar mass, which can be interpreted as the boundary
between the CGM and IGM. For galaxies with $10^8 \leq M_{\star}/M_{\odot} \leq
10^{10.5}$, we find that $R_{\rm cross}(M_{\star}) \approx 2 \pm 0.6 R_{\rm
vir}$. Additionally, we find excellent agreement between $R_{\rm
cross}(M_{\star})$ and the theoretically-determined splashback radius for
galaxies in this mass range. Overall, our results favor models of galaxy
evolution at z < 0.5 that distribute $T \approx 10^{4}$K gas to distances
beyond the virial radius.
