Complex sentence: In 2000, Clear Path International (CPI) was still working to remove unexploded ordnance left by the United States in QQuảng Trị province, which was at the time the largest unexploded ordnance removal effort by an NGO in Vietnam's history.
Split into simpler sentences: In 2000, Clear Path International (CPI) was still working to remove unexploded ordnance left by the United States in Quang Tri Province. This was at the time the largest unexploded ordnance removal effort by an NGO in Vietnam's history.