Keystone Sub Work???

Saw a long string of cars in the siding at Rockwood loaded with new rails. A little after that I saw a CSX work train reversing it’s direction on the S&C Branch and then heading west on the Keystone Sub. Being of sound but simple mind I put 2 & 2 together and figured there was some line work going to happen. [:D] Anyone know where the work is and how much it will impact traffic on the line?

Thanks,
Brian