With the Encore tower behind them, Jeff Caldwell and Jillian Kramer, both of Encore Boston Harbor,were part of a crew that volunteered with the Mystic River Watershed Association (MyRWA) last Thursday, Aug. 2, to remove invasive water chestnuts from the Mystic River in Everett. MyRWA has led such volunteer efforts for several years to try to clear the watershed of a pesky plant species.