Complex sentence: Calnev is an interstate pipeline crossing California and Nevada therefore it's managed by PMHSA and inspected by federal agents, however for portions of pipeline exclusively within California or Nevada are able to be inspected by respective State agencies.
Split into simpler sentences: Calnev is an interstate pipeline crossing California and Nevada therefore it's managed by PMHSA and inspected by federal agents. However, portions of pipeline exclusively within California or Nevada could be inspected by respective State agencies.