Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/PlLinesCreator/PlLinesCreator.cs
===================================================================
diff -u -r6866 -r6867
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/PlLinesCreator/PlLinesCreator.cs	(.../PlLinesCreator.cs)	(revision 6866)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/PlLinesCreator/PlLinesCreator.cs	(.../PlLinesCreator.cs)	(revision 6867)
@@ -438,13 +438,20 @@
     private bool IsPenetrationZoneCompletelyWithinInfiltrationZoneFor1DGeometry(double penetrationLength)
     {
         SoilProfile1D relevantSoilProfile = GetRelevantSoilProfileForAquiferLayersSearch();
-        double bottomLevelLowestInBetweenAquiferCluster = relevantSoilProfile.GetInBetweenAquiferClusters.Last().Item2.TopLevel;
+        // Determine the top level of the infiltration layers:
+        // - if no in-between aquifer is present, it is the surface line
+        // - if at least one in-between aquifer is present, it is the bottom level of the lowest in-between aquifer
+        double bottomLevelLowestInBetweenAquiferCluster = relevantSoilProfile.TopLevel;
+        if (relevantSoilProfile.GetInBetweenAquiferClusters.Count > 0)
+        {
+            bottomLevelLowestInBetweenAquiferCluster = relevantSoilProfile.GetInBetweenAquiferClusters.Last().Item2.BottomLevel;
+        }
+        
         double topLevelBottomAquifer = relevantSoilProfile.BottomAquiferLayer.TopLevel;
-        // The infiltration layers are the aquitards situated between the bottom aquifer (topLevelBottomAquifer) and:
-        // - the surface line if no in-between aquifer is present
-        // - the lowest in-between aquifer (bottomLevelLowestInBetweenAquiferCluster) if at least one in-between aquifer is present
+        // The infiltration layers are the layers situated between the bottom aquifer (topLevelBottomAquifer) and the top level
+        // of the infiltration layers (bottomLevelLowestInBetweenAquiferCluster)
         IList<SoilLayer1D> infiltrationLayers = (from SoilLayer1D layer in relevantSoilProfile.Layers
-                                                 where (relevantSoilProfile.InBetweenAquiferLayer == null || layer.TopLevel < bottomLevelLowestInBetweenAquiferCluster) &&
+                                                 where layer.TopLevel <= bottomLevelLowestInBetweenAquiferCluster &&
                                                        layer.TopLevel > topLevelBottomAquifer select layer).ToList();
 
         if (infiltrationLayers.Count > 0)