diff --git a/main/src/com/google/gridworks/GridworksServlet.java b/main/src/com/google/gridworks/GridworksServlet.java
index a4ce74207..864dba6e4 100644
--- a/main/src/com/google/gridworks/GridworksServlet.java
+++ b/main/src/com/google/gridworks/GridworksServlet.java
@@ -182,7 +182,7 @@ public class GridworksServlet extends Butterfly {
             _timer = null;
         }
         if (ProjectManager.singleton != null) {
-            ProjectManager.singleton.save(true); // complete save
+            ProjectManager.singleton.dispose();
             ProjectManager.singleton = null;
         }
 
diff --git a/main/src/com/google/gridworks/ProjectManager.java b/main/src/com/google/gridworks/ProjectManager.java
index dda313e92..cf8dcb708 100644
--- a/main/src/com/google/gridworks/ProjectManager.java
+++ b/main/src/com/google/gridworks/ProjectManager.java
@@ -61,6 +61,17 @@ public abstract class ProjectManager {
 
         preparePreferenceStore(_preferenceStore);
     }
+    
+    public void dispose() {
+        save(true); // complete save
+
+        for (Project project : _projects.values()) {
+            project.dispose();
+        }
+        
+        _projects.clear();
+        _projectsMetadata.clear();
+    }
 
     /**
      * Registers the project in the memory of the current session
@@ -211,7 +222,7 @@ public abstract class ProjectManager {
                          *  It's been a while since the project was last saved and it hasn't been
                          *  modified. We can safely remove it from the cache to save some memory.
                          */
-                        _projects.remove(id);
+                        _projects.remove(id).dispose();
                     }
                 }
             }
@@ -374,12 +385,12 @@ public abstract class ProjectManager {
      * @param projectID
      */
     protected void removeProject(long projectID){
+        if (_projects.containsKey(projectID)) {
+            _projects.remove(projectID).dispose();
+        }
         if (_projectsMetadata.containsKey(projectID)) {
             _projectsMetadata.remove(projectID);
         }
-        if (_projects.containsKey(projectID)) {
-            _projects.remove(projectID);
-        }
     }
 
     //--------------Miscellaneous-----------
diff --git a/main/src/com/google/gridworks/model/OverlayModel.java b/main/src/com/google/gridworks/model/OverlayModel.java
index 50476660b..d933a750b 100644
--- a/main/src/com/google/gridworks/model/OverlayModel.java
+++ b/main/src/com/google/gridworks/model/OverlayModel.java
@@ -3,5 +3,9 @@ package com.google.gridworks.model;
 import com.google.gridworks.Jsonizable;
 
 public interface OverlayModel extends Jsonizable {
-
+    public void onBeforeSave();
+    
+    public void onAfterSave();
+    
+    public void dispose();
 }
diff --git a/main/src/com/google/gridworks/model/Project.java b/main/src/com/google/gridworks/model/Project.java
index d5d262903..d3070e38e 100644
--- a/main/src/com/google/gridworks/model/Project.java
+++ b/main/src/com/google/gridworks/model/Project.java
@@ -67,6 +67,16 @@ public class Project {
         this.id = id;
         this.history = new History(this);
     }
+    
+    public void dispose() {
+        for (OverlayModel overlayModel : overlayModels.values()) {
+            try {
+                overlayModel.dispose();
+            } catch (Exception e) {
+                logger.warn("Error signaling overlay model before disposing", e);
+            }
+        }
+    }
 
     public Date getLastSave(){
         return this._lastSave;
@@ -83,6 +93,14 @@ public class Project {
     }
 
     public void saveToOutputStream(OutputStream out, Pool pool) throws IOException {
+        for (OverlayModel overlayModel : overlayModels.values()) {
+            try {
+                overlayModel.onBeforeSave();
+            } catch (Exception e) {
+                logger.warn("Error signaling overlay model before saving", e);
+            }
+        }
+        
         Writer writer = new OutputStreamWriter(out);
         try {
             Properties options = new Properties();
@@ -93,6 +111,14 @@ public class Project {
         } finally {
             writer.flush();
         }
+        
+        for (OverlayModel overlayModel : overlayModels.values()) {
+            try {
+                overlayModel.onAfterSave();
+            } catch (Exception e) {
+                logger.warn("Error signaling overlay model after saving", e);
+            }
+        }
     }
 
     protected void saveToWriter(Writer writer, Properties options) throws IOException {
diff --git a/main/src/com/google/gridworks/protograph/Protograph.java b/main/src/com/google/gridworks/protograph/Protograph.java
index 527d71a7e..eb8de5540 100644
--- a/main/src/com/google/gridworks/protograph/Protograph.java
+++ b/main/src/com/google/gridworks/protograph/Protograph.java
@@ -23,6 +23,19 @@ public class Protograph implements OverlayModel {
         return _rootNodes.get(index);
     }
     
+    @Override
+    public void onBeforeSave() {
+    }
+    
+    @Override
+    public void onAfterSave() {
+    }
+    
+    
+    @Override
+    public void dispose() {
+    }
+    
     static public Protograph reconstruct(JSONObject o) throws JSONException {
         Protograph g = new Protograph();