Royal Dutch Shell PLC oil spills that haven’t been cleaned up for over eight years have contributed to “astonishingly high” levels of pollution in a Nigerian community, according to a consultant who helped produce a confidential damage assessment for Shell and its partners in the cleanup. Shell admitted liability for two large oil spills from a broken pipeline in 2008 in Bodo, a Niger Delta fishing community that, according to U.K. court claims, was inundated with over 500,000 barrels of oil—roughly twice the amount when…