After exiting the Algoa helix, the train will travel a stretch and reach Virginia point, which is directly below the intersection of the UP Glidden and BSNF Galvesto tracks at upper deck. The Galveston causeway stretches from that point west to where the word "Alvin" is.
The peninsular will host an industry and the Galveston Bay. The space between Alvin up to Rosenberg on lower deck will be Galveston terminal which will have UP and BNSF yards, intermodal terminal and petrochemical industry.
Lower deck track plan is still in my head but I am seeing a clearer vision now :)