The embankment in the Lowell yards was part of the line that orginally connected the (orginal) Boston & Maine Lowell branch to the Old Colony/New Haven Lowell Branch.
Before the B&M absorbed the B&L (Boston & Lowell) there were 2 competing lines between Lowell and Lawrence. Utimately, they kept the B&M line which ran (for the most part) north of the B&L. This is still in use as part of the Gulford Frieght main.
However, in the Lowell Yard, the B&M orginally crossed over the B&L yard via the embamkments you see. The line crossed Gorham street to the right side of the Dunkin Donuts, ran along side Manchester Street (where they have recently built some condos) and connected with the OC/New Haven around the area of the Plain Street bridge (which was laid out differently in that era.)
When the B&M absorbed the B&L, they built a connector from the B&M Lowell Branch to the B&L main line. This is why there is an embankment at Meadowcroft Street and the main line makes a funny curve. You can also find the orginal B&L Lawrence branch, still buried in the parking lot of the industries back there. It looks like an industrial spur, but it is a straight shot towards the Concord river, and the long-gone B&L Concord River bridge.
Meanwhile, on the other side of the tracks, the B&M constructed a very steep incline and curve so they could serve the few customers that they had along the stretch between the yard and the OC connection. This included a short siding at what is now the Party store, some industries along Manchester Street (now the Dunkin Donuts/Condos), and the Oil/Coal dealer that is still there. I have no idea when service ultimately ended on that line, but it was gone before I moved to the neigborhood in 1995. By then, the rail was still in place at the crossings but paved over. Everything is gone now, and you wouldn't know that a railroad once was there.
Even I moved out in 2000, but still have family who live nearby.
Map of the area in 1893 that shows the original configuration:
http://historical.maptech.com/getImage. ... g&state=MA
-Ed Lecuyer