diff --git a/CHANGELOG.md b/CHANGELOG.md
index f934664..3eee6de 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 ### Added
 
+## [4.20.0] - 2023-10-14
+
+### Added
+
+- Added support for Milan at NCCS
+  - Uses Open MPI 4.1.5 on SCU17 rather than Intel MPI due to issues with Intel MPI
+
 ## [4.19.0] - 2023-07-27
 
 ### Changed
diff --git a/build.csh b/build.csh
index 2e63f5b..68545ea 100755
--- a/build.csh
+++ b/build.csh
@@ -128,6 +128,7 @@ while ($#argv)
 
    # specify node type
    #------------------
+   if ("$1" == "-mil")  set nodeTYPE = "Milan"
    if ("$1" == "-rom")  set nodeTYPE = "Rome"
    if ("$1" == "-cas")  set nodeTYPE = "CascadeLake"
    if ("$1" == "-sky")  set nodeTYPE = "Skylake"
@@ -297,10 +298,12 @@ if ($SITE == NCCS) then
    if ($nT == any) @ NCPUS_DFLT = 40
    if ($nT == sky) @ NCPUS_DFLT = 40
    if ($nT == cas) @ NCPUS_DFLT = 48
+   if ($nT == mil) @ NCPUS_DFLT = 128
 
    if ($nT == any) set proc = 'any'
    if ($nT == sky) set proc = 'sky'
    if ($nT == cas) set proc = 'cas'
+   if ($nT == mil) set proc = 'mil'
 
    # If we are using GNU at NCCS, we can*only* use the cas queue
    # as OpenMPI is only built for Infiniband
@@ -891,6 +894,7 @@ flagged options
    -account account     send batch job to account
    -walltime hh:mm:ss   time to use as batch walltime at job submittal
 
+   -mil                 compile on Milan nodes (only at NCCS)
    -rom                 compile on Rome nodes (only at NAS)
    -cas                 compile on Cascade Lake nodes
    -sky                 compile on Skylake nodes (default at NAS)
diff --git a/g5_modules b/g5_modules
index 4be7bd2..b529ab7 100755
--- a/g5_modules
+++ b/g5_modules
@@ -74,6 +74,9 @@ if (($node =~ discover*) || ($node =~ borg*)  || \
 
    set site = "NCCS"
 
+   # NCCS now has both SLES15 and SLES12 machines
+   set OS_VERSION=`grep VERSION_ID /etc/os-release | cut -d= -f2 | cut -d. -f1 | sed 's/"//g'`
+
 else if (($node =~ pfe*) || ($node =~ tfe*) || \
          ($node =~ r[0-9]*i[0-9]*n[0-9]*) || \
          ($node =~ r[0-9]*c[0-9]*t[0-9]*n[0-9]*)) then
@@ -123,20 +126,30 @@ if ( $site == NCCS ) then
 
    set mod1 = GEOSenv
 
-   set mod2 = comp/gcc/11.2.0
-   set mod3 = comp/intel/2021.6.0
+   if ( $OS_VERSION == 12 ) then
 
-   set mod4 = mpi/impi/2021.6.0
+      set mod2 = comp/gcc/11.2.0
+      set mod3 = comp/intel/2021.6.0
+      set mod4 = mpi/impi/2021.6.0
+      set mod5 = python/GEOSpyD/Min4.11.0_py3.9_AND_Min4.8.3_py2.7
+      set basedir = /discover/swdev/gmao_SIteam/Baselibs/ESMA-Baselibs-7.14.0/x86_64-pc-linux-gnu/ifort_2021.6.0-intelmpi_2021.6.0
+      set usemod1 = /discover/swdev/gmao_SIteam/modulefiles-SLES12
 
-   set mod5 = python/GEOSpyD/Min4.11.0_py3.9_AND_Min4.8.3_py2.7
+   else
+
+      set mod2 = comp/gcc/12.3.0
+      set mod3 = comp/intel/2021.6.0
+      set mod4 = mpi/openmpi/4.1.5/intel-2021.6.0
+      set mod5 = python/GEOSpyD/Min23.5.2-0_py3.11
+      set basedir = /discover/swdev/gmao_SIteam/Baselibs/ESMA-Baselibs-7.14.0/x86_64-pc-linux-gnu/ifort_2021.6.0-openmpi_4.1.5-SLES15
+      set usemod1 = /discover/swdev/gmao_SIteam/modulefiles-SLES15
 
-   set basedir = /discover/swdev/gmao_SIteam/Baselibs/ESMA-Baselibs-7.14.0/x86_64-pc-linux-gnu/ifort_2021.6.0-intelmpi_2021.6.0
+   endif
 
    set mods = ( $mod1 $mod2 $mod3 $mod4 $mod5 )
    set modinit = /usr/share/modules/init/csh
    set loadmodules = 0
 
-   set usemod1 = /discover/swdev/gmao_SIteam/modulefiles-SLES12
    set usemods = ( $usemod1 )
    set usemodules = 1