Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingSoilProfile.cs
===================================================================
diff -u -r96a31b6c1e568fbbe87fb72f13f0a76b065bdf77 -rdc324dd8b87bdcef3d6ed1c0a8f7ee721ffadfbd
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingSoilProfile.cs	(.../PipingSoilProfile.cs)	(revision 96a31b6c1e568fbbe87fb72f13f0a76b065bdf77)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingSoilProfile.cs	(.../PipingSoilProfile.cs)	(revision dc324dd8b87bdcef3d6ed1c0a8f7ee721ffadfbd)
@@ -152,7 +152,7 @@
                 {
                     currentTopAquiferLayer = null;
                 }
-                if (currentTopAquiferLayer != null && pipingSoilLayer.Top <= level)
+                if (currentTopAquiferLayer != null && pipingSoilLayer.Top < level)
                 {
                     break;
                 }
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs
===================================================================
diff -u -r96a31b6c1e568fbbe87fb72f13f0a76b065bdf77 -rdc324dd8b87bdcef3d6ed1c0a8f7ee721ffadfbd
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs	(.../PipingSoilProfileTest.cs)	(revision 96a31b6c1e568fbbe87fb72f13f0a76b065bdf77)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs	(.../PipingSoilProfileTest.cs)	(revision dc324dd8b87bdcef3d6ed1c0a8f7ee721ffadfbd)
@@ -335,7 +335,6 @@
             Assert.AreEqual(0.4, result, 1e-8);
         }
 
-
         [Test]
         public void GetTopAquiferLayerThicknessBelowLevel_AllAquiferLayersAboveLevel_NaN()
         {
@@ -365,6 +364,30 @@
         }
 
         [Test]
+        public void GetTopAquiferLayerThicknessBelowLevel_BottomAquiferLayerTopEqualToLevel_BottomAquiferLayerThickness()
+        {
+            // Setup
+            var pipingSoilLayers = new[]
+            {
+                new PipingSoilLayer(2.1)
+                {
+                    IsAquifer = true
+                },
+                new PipingSoilLayer(1.1)
+                {
+                    IsAquifer = true
+                },
+            };
+            var profile = new PipingSoilProfile(string.Empty, 0.0, pipingSoilLayers);
+
+            // Call
+            var result = profile.GetTopAquiferLayerThicknessBelowLevel(1.1);
+
+            // Assert
+            Assert.AreEqual(1.1, result);
+        }
+
+        [Test]
         public void GetTopAquiferLayerThicknessBelowLevel_LevelBelowProfile_ArgumentException()
         {
             // Setup