Lake levels will fluctuate during the draw down, but boaters should be aware that Seattle City Light may rapidly vary the lake level without notice. It is therefore recommended that boaters refrain from using their vessels on Diablo Lake from May 12 through June 15 and again from September 15 through October 31 so as not to be stranded. While lake levels are low, National Park Service staff will clean sediment off the public boat ramp at Colonial Creek Campground. Normal lake levels will resume June 16 through September 14, and again on approximately November 1, 2015.
Seattle City Light will also complete work on the docks located on the east side of Diablo Lake near the Ross Haul Road. These facilities will be open to visitors on June 12, 2015. The Ross Haul Road between Ross Powerhouse and the tunnel, as well as the Diablo Lake Trail Bridge, will be closed through June 20 and again September 7 through November 4, 2015.