There is parking in the lot off Superior Avenue. There are closer roads but there is no good access to the cache. From I-95 take 216 east, turn right (south) on All Saints, then right when that ends at Old Scaggsville Rd, then an immediate left onto Superior Ave which ends at the park. I'm laying this all out so you don't end up in someone's yard.
It is a decent hike to get to the cache. If you head south to gazebo, then LEFT to the trail down to river it's well over a mile one way. If you stay near the Patuxent river it's a long and perilous but beautiful journey. If you switch to the pipeline easement trail that heads uphill by one of the feeder streams it's easier going, but not as scenic. This is located at the "short cut" waypoint. You might want to go in along the river and take the short cut back. You would do this by heading east from the cache instead of heading back down the hill. Another way in is to head west from the parking lot and follow the stream south towards the river. In this case you are starting at the "frog pond" waypoint. The faint trail along the stream joins the one along the river just past the "short cut" waypoint. This will save you maybe three tenths of a mile but requires a little bushwacking initially (there will be more later anyway).
The bridge in question is the I-95 bridge over the Patuxent river. Be sure to head down from the cache site to check out the dramatic view. Some people don't like this sort of thing encroaching on their green spaces but I find the combination of nature and technology fascinating.
Happy Caching!