diff --git a/src/erad/gdm_mapping.py b/src/erad/gdm_mapping.py
index d2a1f5dc..1f4a3647 100644
--- a/src/erad/gdm_mapping.py
+++ b/src/erad/gdm_mapping.py
@@ -1,10 +1,28 @@
+from contextlib import contextmanager

+

 import gdm.distribution.components as gdc
 import gdm.distribution.equipment as gde
+from gdm.distribution.enums import LineType
 
 from erad.enums import AssetTypes
 from erad.models.asset_mapping import ComponentFilterModel
 
+# Feature flag: when True, classify distribution MatrixImpedanceBranch components using

+# equipment.construction (LineType) instead of the c_matrix threshold heuristic.

+USE_CONSTRUCTION_ATTRIBUTE: bool = False

 
+

+@contextmanager

+def construction_attribute_enabled(enabled: bool = True):

+    """Temporarily set USE_CONSTRUCTION_ATTRIBUTE within a `with` block."""

+    global USE_CONSTRUCTION_ATTRIBUTE

+    old = USE_CONSTRUCTION_ATTRIBUTE

+    USE_CONSTRUCTION_ATTRIBUTE = enabled

+    try:

+        yield

+    finally:

+        USE_CONSTRUCTION_ATTRIBUTE = old

+

 asset_to_gdm_mapping = {
     AssetTypes.switch: [
         ComponentFilterModel(
@@ -40,10 +58,11 @@
         ),
         ComponentFilterModel(
             component_type=gdc.MatrixImpedanceBranch,
-            component_filter=lambda x: x.equipment.c_matrix[0, 0]
-            .to("microfarad/kilometer")
-            .magnitude
-            > 0.05
+            component_filter=lambda x: (
+                x.equipment.construction == LineType.UNDERGROUND
+                if USE_CONSTRUCTION_ATTRIBUTE
+                else x.equipment.c_matrix[0, 0].to("microfarad/kilometer").magnitude > 0.05
+            )
             and x.buses[0].rated_voltage.to("kilovolt").magnitude < 35.0,
         ),
     ],
@@ -57,10 +76,11 @@
         ),
         ComponentFilterModel(
             component_type=gdc.MatrixImpedanceBranch,
-            component_filter=lambda x: x.equipment.c_matrix[0, 0]
-            .to("microfarad/kilometer")
-            .magnitude
-            < 0.05
+            component_filter=lambda x: (
+                x.equipment.construction == LineType.OVERHEAD
+                if USE_CONSTRUCTION_ATTRIBUTE
+                else x.equipment.c_matrix[0, 0].to("microfarad/kilometer").magnitude < 0.05
+            )
             and x.buses[0].rated_voltage.to("kilovolt").magnitude < 35.0,
         ),
     ],