diff --git a/src/main/python/gov/usgs/earthquake/nshmp/netcdf/converters/convert_2018a.py b/src/main/python/gov/usgs/earthquake/nshmp/netcdf/converters/convert_2018a.py
index f5e0ffd66ca357098addf4e3fcdb1b1005252cb9..34aa3fe051127b8f9649d74dfc93fcda019dd431 100644
--- a/src/main/python/gov/usgs/earthquake/nshmp/netcdf/converters/convert_2018a.py
+++ b/src/main/python/gov/usgs/earthquake/nshmp/netcdf/converters/convert_2018a.py
@@ -72,7 +72,7 @@ class Convert2018A:
         self._site_class_mask_array = np.zeros(
             [self._dimensions.lat.size, self._dimensions.lon.size], int
         )
-        self._imt_mask_array = np.zeros([self._dimensions.lat.size, self._dimensions.lon.size], int)
+        # self._imt_mask_array = np.zeros([self._dimensions.lat.size, self._dimensions.lon.size], int)
 
         self._data_array = np.full(
             [
@@ -176,6 +176,7 @@ class Convert2018A:
 
         with ThreadPoolExecutor() as executor:
             for index, _info in enumerate(netcdf_info):
+
                 info: NetcdfInfo = _info
                 futures.append(
                     executor.submit(
@@ -242,10 +243,12 @@ class Convert2018A:
         if not curves_file.exists:
             raise Exception(f"File ({curves_file}) not found")
 
+        imls = self.metadata.imls.get(netcdf_info.imt)
         imt_dir = curves_file.parent
         imt_index = self._get_imt_index(imt=netcdf_info.imt)
+        imt_mask_array = np.zeros([self._dimensions.lat.size, self._dimensions.lon.size], int)
         site_class_index = self._get_site_class_index(site_class=netcdf_info.site_class)
-        imls = self.metadata.imls.get(netcdf_info.imt)
+
         print(f"\t Converting [{imt_dir.parent.name}/{imt_dir.name}/{curves_file.name}]")
 
         with open(curves_file, "r") as curves_reader:
@@ -278,8 +281,8 @@ class Convert2018A:
                 self._data_array[
                     site_class_index, imt_index, latitude_index, longitude_index, :
                 ] = values
-                self._imt_mask_array[latitude_index, longitude_index] = 1
-            self._site_class_mask_array += self._imt_mask_array
+                imt_mask_array[latitude_index, longitude_index] = 1
+            self._site_class_mask_array += imt_mask_array
 
     def _set_imt_indices(self) -> dict[Imt, int]:
         imt_indices: dict[Imt, int] = dict()