Complex sentence: There is a memorial on the old airfield at the bombbay loading pits, which had been filled in for safety reasons but were both recently excavated in conjunction with the 60th Anniversary Commemoration of the Battles of Saipan and Tinian.
Split into simpler sentences: There is a memorial on the old airfield at the loading pits, which had been filled in for safety. Both pits were recently reopened in conjunction with the 60th Anniversary Commemoration of the Battles of Saipan and Tinian.