First off, you're looking at the New Castle Secondary Track, not the Delmarva Secondary Track at Route 7/Bear-Corbitt Road. The "double track" your referring to is actually NS extending Tasker Siding (from where it begins/ends at MP WO 7.5). First phase of the construction will run from Rt. 7 to MP WO 7.0. Second phase will be next year to run it from MP WO 7.0 to the TASKER station sign at Washington Street/Rt. 141 in the town of New Castle. It's not double tracking - it's just extending Tasker Siding. The siding extension is actually occupying the site of the other main track that the PRR pulled-up in the late 1960s (after passenger service ended in 1965).
Talk to you later,