diff --git a/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayAction.java b/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayAction.java
index b48dcf231b..46f785216e 100644
--- a/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayAction.java
+++ b/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayAction.java
@@ -39,6 +39,7 @@ import org.eclipse.ui.PlatformUI;
  * Date       	Ticket#		Engineer	Description
  * ------------	----------	-----------	--------------------------
  * 6/27/06                  randerso    Initial Creation.
+ * 12/10/2013   1353        rferrel     Changes for non-blocking DamDisplayControlDlg.
  * 
  * </pre>
  * 
@@ -46,15 +47,25 @@ import org.eclipse.ui.PlatformUI;
  * 
  */
 public class DamDisplayAction extends AbstractHandler {
+    private DamDisplayControlDlg damDisplayDlg;
 
-	@Override
-	public Object execute(ExecutionEvent arg0) throws ExecutionException {
-	    Shell shell = PlatformUI.getWorkbench().getActiveWorkbenchWindow()
-        .getShell();
-	    DamDisplayControlDlg damDisplayDlg = new DamDisplayControlDlg(shell);
-	    damDisplayDlg.open();
+    /*
+     * (non-Javadoc)
+     * 
+     * @see
+     * org.eclipse.core.commands.AbstractHandler#execute(org.eclipse.core.commands
+     * .ExecutionEvent)
+     */
+    @Override
+    public Object execute(ExecutionEvent arg0) throws ExecutionException {
+        if (damDisplayDlg == null) {
+            Shell shell = PlatformUI.getWorkbench().getActiveWorkbenchWindow()
+                    .getShell();
+            damDisplayDlg = new DamDisplayControlDlg(shell);
+        }
+        damDisplayDlg.open();
 
-		return null;
-	}
+        return null;
+    }
 
 }
diff --git a/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayControlDlg.java b/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayControlDlg.java
index 29c95eb47d..e48c0ed7f3 100644
--- a/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayControlDlg.java
+++ b/cave/com.raytheon.viz.hydro/src/com/raytheon/viz/hydro/damdisplay/DamDisplayControlDlg.java
@@ -65,17 +65,17 @@ import com.raytheon.viz.ui.dialogs.CaveSWTDialog;
  * 
  */
 public class DamDisplayControlDlg extends CaveSWTDialog {
-    private static final String GREATER_THAN = "greater than";
+    private final String GREATER_THAN = "greater than";
 
-    private static final String EQUAL_TO = "equal to";
+    private final String EQUAL_TO = "equal to";
 
-    private static final String LESS_THAN = "less than";
+    private final String LESS_THAN = "less than";
 
-    private static final String ALL = "All";
+    private final String ALL = "All";
 
-    private static final String CENTER_LAT_TOKEN = "hv_center_lat";
+    private final String CENTER_LAT_TOKEN = "hv_center_lat";
 
-    private static final String CENTER_LON_TOKEN = "hv_center_lon";
+    private final String CENTER_LON_TOKEN = "hv_center_lon";
 
     /**
      * Dam volume combo box.
@@ -161,13 +161,18 @@ public class DamDisplayControlDlg extends CaveSWTDialog {
      *            Parent shell.
      */
     public DamDisplayControlDlg(Shell parent) {
-        super(parent);
+        super(parent, SWT.DIALOG_TRIM, CAVE.DO_NOT_BLOCK);
         setText("Dam Display Control");
 
         waitCursor = new Cursor(parent.getDisplay(), SWT.CURSOR_WAIT);
         arrowCursor = new Cursor(parent.getDisplay(), SWT.CURSOR_ARROW);
     }
 
+    /*
+     * (non-Javadoc)
+     * 
+     * @see com.raytheon.viz.ui.dialogs.CaveSWTDialogBase#constructShellLayout()
+     */
     @Override
     protected Layout constructShellLayout() {
         GridLayout mainLayout = new GridLayout(1, true);
@@ -176,6 +181,13 @@ public class DamDisplayControlDlg extends CaveSWTDialog {
         return mainLayout;
     }
 
+    /*
+     * (non-Javadoc)
+     * 
+     * @see
+     * com.raytheon.viz.ui.dialogs.CaveSWTDialogBase#initializeComponents(org
+     * .eclipse.swt.widgets.Shell)
+     */
     @Override
     protected void initializeComponents(Shell shell) {
         setReturnValue(false);
@@ -384,9 +396,10 @@ public class DamDisplayControlDlg extends CaveSWTDialog {
                 PointDataControlManager pdcManager = PointDataControlManager
                         .getInstance();
                 DamLocationResource dlr = pdcManager.getDamLocationResource();
-                dlr.unload();
-                pdcManager.setRedraw(true);
-
+                if (dlr != null) {
+                    dlr.unload();
+                    pdcManager.setRedraw(true);
+                }
             }
 
         });