Index: Ringtoets/GrassCoverErosionOutwards/src/Ringtoets.GrassCoverErosionOutwards.Forms/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRow.cs
===================================================================
diff -u -r85c24f25efa5c7d92df2c952bcf1de53dc15276f -r4bcead3f76f6dce4ac4d13ce5dda2f1f6d1d0b2c
--- Ringtoets/GrassCoverErosionOutwards/src/Ringtoets.GrassCoverErosionOutwards.Forms/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRow.cs	(.../GrassCoverErosionOutwardsFailureMechanismSectionResultRow.cs)	(revision 85c24f25efa5c7d92df2c952bcf1de53dc15276f)
+++ Ringtoets/GrassCoverErosionOutwards/src/Ringtoets.GrassCoverErosionOutwards.Forms/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRow.cs	(.../GrassCoverErosionOutwardsFailureMechanismSectionResultRow.cs)	(revision 4bcead3f76f6dce4ac4d13ce5dda2f1f6d1d0b2c)
@@ -225,6 +225,42 @@
             }
         }
 
+        /// <summary>
+        /// Gets or sets the indicator whether the combined assembly should be overwritten by <see cref="ManualAssemblyCategoryGroup"/>.
+        /// </summary>
+        /// <exception cref="NotSupportedException">Thrown when <see cref="FailureMechanismSectionAssemblyCategoryGroup"/>
+        /// is a valid value, but unsupported.</exception>
+        public bool UseManualAssemblyCategoryGroup
+        {
+            get
+            {
+                return SectionResult.UseManualAssemblyCategoryGroup;
+            }
+            set
+            {
+                SectionResult.UseManualAssemblyCategoryGroup = value;
+                UpdateInternalData();
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the manually selected assembly category group.
+        /// </summary>
+        /// <exception cref="NotSupportedException">Thrown when <see cref="FailureMechanismSectionAssemblyCategoryGroup"/>
+        /// is a valid value, but unsupported.</exception>
+        public SelectableFailureMechanismSectionAssemblyCategoryGroup ManualAssemblyCategoryGroup
+        {
+            get
+            {
+                return SelectableFailureMechanismSectionAssemblyCategoryGroupConverter.ConvertTo(SectionResult.ManualAssemblyCategoryGroup);
+            }
+            set
+            {
+                SectionResult.ManualAssemblyCategoryGroup = SelectableFailureMechanismSectionAssemblyCategoryGroupConverter.ConvertFrom(value);
+                UpdateInternalData();
+            }
+        }
+
         public override void Update()
         {
             UpdateDerivedData();
Index: Ringtoets/GrassCoverErosionOutwards/test/Ringtoets.GrassCoverErosionOutwards.Forms.Test/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRowTest.cs
===================================================================
diff -u -r85c24f25efa5c7d92df2c952bcf1de53dc15276f -r4bcead3f76f6dce4ac4d13ce5dda2f1f6d1d0b2c
--- Ringtoets/GrassCoverErosionOutwards/test/Ringtoets.GrassCoverErosionOutwards.Forms.Test/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRowTest.cs	(.../GrassCoverErosionOutwardsFailureMechanismSectionResultRowTest.cs)	(revision 85c24f25efa5c7d92df2c952bcf1de53dc15276f)
+++ Ringtoets/GrassCoverErosionOutwards/test/Ringtoets.GrassCoverErosionOutwards.Forms.Test/Views/GrassCoverErosionOutwardsFailureMechanismSectionResultRowTest.cs	(.../GrassCoverErosionOutwardsFailureMechanismSectionResultRowTest.cs)	(revision 4bcead3f76f6dce4ac4d13ce5dda2f1f6d1d0b2c)
@@ -64,6 +64,9 @@
                 Assert.AreEqual(result.DetailedAssessmentResultForFactorizedLowerLimitNorm, row.DetailedAssessmentResultForFactorizedLowerLimitNorm);
                 Assert.AreEqual(SelectableFailureMechanismSectionAssemblyCategoryGroupConverter.ConvertTo(result.TailorMadeAssessmentResult),
                                 row.TailorMadeAssessmentResult);
+                Assert.AreEqual(result.UseManualAssemblyCategoryGroup, row.UseManualAssemblyCategoryGroup);
+                Assert.AreEqual(SelectableFailureMechanismSectionAssemblyCategoryGroupConverter.ConvertTo(result.ManualAssemblyCategoryGroup),
+                                row.ManualAssemblyCategoryGroup);
             }
         }
 
@@ -101,6 +104,67 @@
             }
         }
 
+        [Test]
+        public void UseManualAssemblyCategoryGroup_SetNewValue_NotifyObserversAndPropertyChanged()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var observer = mocks.StrictMock<IObserver>();
+            observer.Expect(o => o.UpdateObserver());
+            mocks.ReplayAll();
+
+            FailureMechanismSection section = FailureMechanismSectionTestFactory.CreateFailureMechanismSection();
+            var result = new GrassCoverErosionOutwardsFailureMechanismSectionResult(section);
+            result.Attach(observer);
+
+            bool newValue = !result.UseManualAssemblyCategoryGroup;
+
+            using (new AssemblyToolCalculatorFactoryConfig())
+            {
+                var row = new GrassCoverErosionOutwardsFailureMechanismSectionResultRow(result);
+
+                // Precondition
+                Assert.IsFalse(result.UseManualAssemblyCategoryGroup);
+
+                // Call
+                row.UseManualAssemblyCategoryGroup = newValue;
+
+                // Assert
+                Assert.AreEqual(newValue, result.UseManualAssemblyCategoryGroup);
+                mocks.VerifyAll();
+            }
+        }
+
+        [Test]
+        public void ManualAssemblyCategoryGroup_SetNewValue_NotifyObserversAndPropertyChanged()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var observer = mocks.StrictMock<IObserver>();
+            observer.Expect(o => o.UpdateObserver());
+            mocks.ReplayAll();
+
+            var random = new Random(39);
+            var newValue = random.NextEnumValue<SelectableFailureMechanismSectionAssemblyCategoryGroup>();
+
+            FailureMechanismSection section = FailureMechanismSectionTestFactory.CreateFailureMechanismSection();
+            var result = new GrassCoverErosionOutwardsFailureMechanismSectionResult(section);
+            result.Attach(observer);
+
+            using (new AssemblyToolCalculatorFactoryConfig())
+            {
+                var row = new GrassCoverErosionOutwardsFailureMechanismSectionResultRow(result);
+
+                // Call
+                row.ManualAssemblyCategoryGroup = newValue;
+
+                // Assert
+                FailureMechanismSectionAssemblyCategoryGroup expectedCategoryGroup = SelectableFailureMechanismSectionAssemblyCategoryGroupConverter.ConvertFrom(newValue);
+                Assert.AreEqual(expectedCategoryGroup, result.ManualAssemblyCategoryGroup);
+                mocks.VerifyAll();
+            }
+        }
+
         #region Registration
 
         [Test]