diff --git a/java/src/org/broadinstitute/sting/gatk/datasources/simpleDataSources/ResourcePool.java b/java/src/org/broadinstitute/sting/gatk/datasources/simpleDataSources/ResourcePool.java
index 82f949441..5a9e61068 100755
--- a/java/src/org/broadinstitute/sting/gatk/datasources/simpleDataSources/ResourcePool.java
+++ b/java/src/org/broadinstitute/sting/gatk/datasources/simpleDataSources/ResourcePool.java
@@ -79,8 +79,11 @@ abstract class ResourcePool <T,I extends Iterator> {
         synchronized(this) {
             // Find and remove the resource from the list of allocated resources.
             T resource = resourceAssignments.get( iterator );
-            resourceAssignments.remove(resource);
+            Object obj = resourceAssignments.remove(iterator);
 
+            // make sure we actually removed the assignment
+            if (obj == null)
+                    throw new StingException("Failed to remove resource assignment; target key had no associated value in the resource assignment map");
             // Return the resource to the pool.
             if( !allResources.contains(resource) )
                 throw new StingException("Iterator does not belong to the given pool.");
diff --git a/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReads.java b/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReads.java
index 71ecf8a3f..370536ae9 100755
--- a/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReads.java
+++ b/java/src/org/broadinstitute/sting/gatk/traversals/TraverseReads.java
@@ -2,8 +2,8 @@ package org.broadinstitute.sting.gatk.traversals;
 
 import net.sf.samtools.SAMRecord;
 import org.apache.log4j.Logger;
-import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
 import org.broadinstitute.sting.gatk.WalkerManager;
+import org.broadinstitute.sting.gatk.contexts.AlignmentContext;
 import org.broadinstitute.sting.gatk.datasources.providers.ReadReferenceView;
 import org.broadinstitute.sting.gatk.datasources.providers.ReadView;
 import org.broadinstitute.sting.gatk.datasources.providers.ShardDataProvider;
@@ -16,7 +16,6 @@ import org.broadinstitute.sting.gatk.walkers.Walker;
 import org.broadinstitute.sting.utils.GenomeLoc;
 import org.broadinstitute.sting.utils.GenomeLocParser;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 
 /*
@@ -53,9 +52,7 @@ import java.util.Arrays;
  * <p/>
  * This class handles traversing by reads in the new shardable style
  */
-public class TraverseReads extends TraversalEngine {
-    final ArrayList<String> x = new ArrayList<String>();
-
+public class TraverseReads extends TraversalEngine {    
     /** our log, which we want to capture anything from this class */
     protected static Logger logger = Logger.getLogger(TraverseReads.class);