South Central Pond?
I think I just found a watermark in Google Maps: South Central Pond, across the Duwamish from S Boeing Access Road. On the satellite view it shows up as a building and parking lot.
Then there's the non-existent roundabout on this map. I think this one's a simple error, since there is a roundabout at Cordata and Kellog (and now one at Westerly as well).