I just found the duck at the far NE corner of E Vadnais Lake.  I parked on Centerville across from Garceau's Hardware and walked down to the lake.  The long-tailed was swimming and (mostly) diving with 30 commom goldeneyes near hundreds of ring-necked ducks.  Also, yesterday I stopped at Brownsville in far SE MN to watch the hundreds of noisy tundra swans.