Unable to find writable var_dir

#0 /www/sites/stg.bunzlpd.com/files/html/app/code/core/Mage/Core/Model/Config/Options.php(66): Mage_Core_Model_Config_Options->getVarDir()
#1 /www/sites/stg.bunzlpd.com/files/html/lib/Varien/Object.php(112): Mage_Core_Model_Config_Options->_construct()
#2 /www/sites/stg.bunzlpd.com/files/html/app/code/core/Mage/Core/Model/Config.php(200): Varien_Object->__construct(Array)
#3 /www/sites/stg.bunzlpd.com/files/html/app/Mage.php(740): Mage_Core_Model_Config->__construct(Array)
#4 /www/sites/stg.bunzlpd.com/files/html/app/Mage.php(679): Mage::_setConfigModel(Array)
#5 /www/sites/stg.bunzlpd.com/files/html/index.php(89): Mage::run('', 'store')
#6 {main}