Start-up of the massive synthetic natural gas plant in Coal Country will be delayed another week because of problems in a critical process area.

Dakota Gasification Co., shut down the plant at the end of June for a $25 million, front-to-back tune up and hoped to be back in gas production Friday.

However, workers found substantial corrosion in a phenosolven vessel and it will be July 10 at the soonest before repairs are complete and gas is back in the pipeline.

Company spokesman Floyd Robb said the weeklong delay doesn't affect the plant's 700 workers, who will be starting up other parts of the process in the meantime.

Each day's production costs the company about $700,000, making the delay an expensive and unwelcome turn of events.

Robb said other phenol vessels required welding repairs, but the corrosion on one of the largest vessels was substantial and involved replacing steel that had to be specially ordered from Houston.

The plant makes synthetic natural gas from lignite coal off two trains, A and B, but the phenol process is common to both trains.

Gas can't be produced until it's back on line.

DGC has never gone to "black plant" status in its 20 years of operation. Plant officials said DGC has the distinction of running longer without a total shutdown than any process plant in the country.

The time had come for maintenance on parts common to both gas production trains.

Plant officials spent 18 months planning 5,600 specific work orders completed during the back plant outage.

(Reach reporter Lauren Donovan at 888-303-5511, or lauren@westriv.com.)