Hello, again! The second treasure map of the Toxic Valley is one of the easiest to find. Just fast-travel to Clarksburg, which is south of Wavy Willard's Water Park and north of the Smith Farm and the Eastern Regional Penitentiary near the dried lakebed. If you're the Wastelander I think you are, you'll be familiar with the town from when you rescued Freddy Wood or solved the Picnic Panic mystery. Oh yeah, there will be a number of Feral Ghouls about. I suggest sorting them before attempting the treasure hunt.
Once that task is complete, head directly south-southwest uphill bearing just to the left of the visible trees. Keep the high-voltage tower in the distance on your left. Utter accuracy of position isn't as important as heading up hill toward the power pylon. Look for a spot where you can put a stand of trees in front of you on your right, the power pylon straight in front of you, and the Clarksburg water tower almost 90 degrees to your left. Search the ground there for a tell-tale gray dirt mound with black rocks littered through it. I know you don't have a cap to your name to pay for my fine directions, but somewhere in my journal I wrote down where you can buy me a cup of coffee, if you're of a mind to.