Index: Ringtoets/Common/src/Ringtoets.Common.Service/DesignWaterLevelCalculationActivity.cs
===================================================================
diff -u -r2ebc37cd8cfea18e73b2db4975be5a48272ba9ba -r7e5847c20d3ca698e55690d8abb6d3f9aaffd313
--- Ringtoets/Common/src/Ringtoets.Common.Service/DesignWaterLevelCalculationActivity.cs	(.../DesignWaterLevelCalculationActivity.cs)	(revision 2ebc37cd8cfea18e73b2db4975be5a48272ba9ba)
+++ Ringtoets/Common/src/Ringtoets.Common.Service/DesignWaterLevelCalculationActivity.cs	(.../DesignWaterLevelCalculationActivity.cs)	(revision 7e5847c20d3ca698e55690d8abb6d3f9aaffd313)
@@ -78,6 +78,12 @@
 
         protected override bool Validate()
         {
+            if (AlreadyCalculated)
+            {
+                State = ActivityState.Skipped;
+                return true;
+            }
+
             return DesignWaterLevelCalculationService.Validate(
                 hydraulicBoundaryLocation.Name,
                 hydraulicBoundaryDatabaseFilePath,
@@ -86,12 +92,8 @@
 
         protected override void PerformCalculation()
         {
-            if (!double.IsNaN(hydraulicBoundaryLocation.DesignWaterLevel))
+            if (State != ActivityState.Skipped)
             {
-                State = ActivityState.Skipped;
-            }
-            else
-            {
                 RingtoetsCommonDataSynchronizationService.ClearDesignWaterLevel(hydraulicBoundaryLocation);
 
                 calculationService.Calculate(
@@ -110,7 +112,15 @@
 
         protected override void OnFinish()
         {
-            // hydraulicBoundaryLocation.NotifyObservers();
+            // hydraulicBoundaryLocation.NotinfyObservers();
         }
+
+        private bool AlreadyCalculated
+        {
+            get
+            {
+                return !double.IsNaN(hydraulicBoundaryLocation.DesignWaterLevel);
+            }
+        }
     }
 }
\ No newline at end of file
Index: Ringtoets/Common/src/Ringtoets.Common.Service/WaveHeightCalculationActivity.cs
===================================================================
diff -u -r2ebc37cd8cfea18e73b2db4975be5a48272ba9ba -r7e5847c20d3ca698e55690d8abb6d3f9aaffd313
--- Ringtoets/Common/src/Ringtoets.Common.Service/WaveHeightCalculationActivity.cs	(.../WaveHeightCalculationActivity.cs)	(revision 2ebc37cd8cfea18e73b2db4975be5a48272ba9ba)
+++ Ringtoets/Common/src/Ringtoets.Common.Service/WaveHeightCalculationActivity.cs	(.../WaveHeightCalculationActivity.cs)	(revision 7e5847c20d3ca698e55690d8abb6d3f9aaffd313)
@@ -78,6 +78,12 @@
 
         protected override bool Validate()
         {
+            if (AlreadyCalculated)
+            {
+                State = ActivityState.Skipped;
+                return true;
+            }
+
             return WaveHeightCalculationService.Validate(
                 hydraulicBoundaryLocation.Name,
                 hydraulicBoundaryDatabaseFilePath,
@@ -86,12 +92,8 @@
 
         protected override void PerformCalculation()
         {
-            if (!double.IsNaN(hydraulicBoundaryLocation.WaveHeight))
+            if (State != ActivityState.Skipped)
             {
-                State = ActivityState.Skipped;
-            }
-            else
-            {
                 RingtoetsCommonDataSynchronizationService.ClearWaveHeight(hydraulicBoundaryLocation);
 
                 calculationService.Calculate(
@@ -112,5 +114,13 @@
         {
             // hydraulicBoundaryLocation.NotifyObservers();
         }
+
+        private bool AlreadyCalculated
+        {
+            get
+            {
+                return !double.IsNaN(hydraulicBoundaryLocation.WaveHeight);
+            }
+        }
     }
 }
\ No newline at end of file
Index: Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs
===================================================================
diff -u -rcc39748cdc122bfcc9bfb27e6e1ac9b7c558b5bf -r7e5847c20d3ca698e55690d8abb6d3f9aaffd313
--- Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs	(.../DesignWaterLevelCalculationActivityTest.cs)	(revision cc39748cdc122bfcc9bfb27e6e1ac9b7c558b5bf)
+++ Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs	(.../DesignWaterLevelCalculationActivityTest.cs)	(revision 7e5847c20d3ca698e55690d8abb6d3f9aaffd313)
@@ -222,14 +222,13 @@
         }
 
         [Test]
-        public void Run_HydraulicLocationNonNaNDesignWaterLevel_ValidationAndCalculationNotPerformedAndStateSkipped()
+        public void Run_HydraulicLocationDesignWaterLevelSet_ValidationAndCalculationNotPerformedAndStateSkipped()
         {
             // Setup
             string validFilePath = Path.Combine(testDataPath, validFile);
             const string locationName = "locationName";
             const string activityName = "GetActivityName";
 
-
             var calculationMessageProviderMock = mockRepository.Stub<ICalculationMessageProvider>();
             calculationMessageProviderMock.Stub(calc => calc.GetActivityName(locationName)).Return(activityName);
             calculationMessageProviderMock.Stub(calc => calc.GetCalculationName(locationName)).Return(activityName);
@@ -250,7 +249,7 @@
             Action call = () => activity.Run();
 
             // Assert
-            TestHelper.AssertLogMessagesCount(call, 2);
+            TestHelper.AssertLogMessagesCount(call, 0);
             Assert.AreEqual(ActivityState.Skipped, activity.State);
             mockRepository.VerifyAll();
         }
Index: Ringtoets/Common/test/Ringtoets.Common.Service.Test/WaveHeightCalculationActivityTest.cs
===================================================================
diff -u -rcc39748cdc122bfcc9bfb27e6e1ac9b7c558b5bf -r7e5847c20d3ca698e55690d8abb6d3f9aaffd313
--- Ringtoets/Common/test/Ringtoets.Common.Service.Test/WaveHeightCalculationActivityTest.cs	(.../WaveHeightCalculationActivityTest.cs)	(revision cc39748cdc122bfcc9bfb27e6e1ac9b7c558b5bf)
+++ Ringtoets/Common/test/Ringtoets.Common.Service.Test/WaveHeightCalculationActivityTest.cs	(.../WaveHeightCalculationActivityTest.cs)	(revision 7e5847c20d3ca698e55690d8abb6d3f9aaffd313)
@@ -203,7 +203,7 @@
         }
 
         [Test]
-        public void Run_HydraulicLocationNonNaNWaveHeight_ValidationAndCalculationNotPerformedAndStateSkipped()
+        public void Run_HydraulicLocationWaveHeightSet_ValidationAndCalculationNotPerformedAndStateSkipped()
         {
             // Setup
             string validFilePath = Path.Combine(testDataPath, validFile);
@@ -230,7 +230,7 @@
             Action call = () => activity.Run();
 
             // Assert
-            TestHelper.AssertLogMessagesCount(call, 2);
+            TestHelper.AssertLogMessagesCount(call, 0);
             Assert.AreEqual(ActivityState.Skipped, activity.State);
             mockRepository.VerifyAll();
         }
Index: Ringtoets/HydraRing/src/Ringtoets.HydraRing.Calculation/Parsers/ReliabilityIndexCalculationParser.cs
===================================================================
diff -u -re69acb9595f7bf1d202ddd1fb51934b66768b75d -r7e5847c20d3ca698e55690d8abb6d3f9aaffd313
--- Ringtoets/HydraRing/src/Ringtoets.HydraRing.Calculation/Parsers/ReliabilityIndexCalculationParser.cs	(.../ReliabilityIndexCalculationParser.cs)	(revision e69acb9595f7bf1d202ddd1fb51934b66768b75d)
+++ Ringtoets/HydraRing/src/Ringtoets.HydraRing.Calculation/Parsers/ReliabilityIndexCalculationParser.cs	(.../ReliabilityIndexCalculationParser.cs)	(revision 7e5847c20d3ca698e55690d8abb6d3f9aaffd313)
@@ -60,9 +60,9 @@
                     }
                 }
             }
-            catch
+            catch(Exception e)
             {
-                throw new HydraRingFileParserException();
+                throw new HydraRingFileParserException("", e);
             }
         }