$new_array = array();
foreach ($array as $row)
{
  $key = substr($row['WBS Element'],0,10);

  $new_array[$key]['WBS Element'] = $key; // optional
  $new_array[$key]['Proj System Status'] += $row['Proj System Status'];
  $new_array[$key]['CY Actuals'] += $row['CY Actuals'];
  $new_array[$key]['ITD Actuals'] += $row['ITD Actuals'];
  // same for Overall Commitment, etc...
}