The 520 sunken vessels:
In October 2003, SCRET was contacted by representatives of CH2M Hill, consultants to the Washington Department of Transportation (DOT), and asked to provide information on three sunken vessels in Lake Washington that were located by DOT in connection with its 520 bridge replacement project.
In July 2003, DOT retained Golder Associates to conduct a side scan survey of a small area on either side of the existing 520 bridge. The purpose of the side scan sonar survey was to locate any submerged cultural resources that might be affected by the 520 bridge replacement project. The three sunken vessels were located during this survey. DOT retained CH2M Hill to evaluate the historical significance of the three sunken vessels.
In October 2003, DOT engaged commercial divers to inspect and video the three sunken vessels. The commercial divers used surface supplied diving gear, with a video camera mounted on the helmet of one of the divers. The commercial divers used trimix as the breathing gas for the dives on Sunken Vessel #1 (190 feet) and Sunken Vessel #2 (200 feet) and air for the dive on Sunken Vessel #3 (170 feet). The commercial divers reported their findings to DOT and CH2M Hill.
From November 2003 to January 2004, SCRET conducted an independent investigation and evaluation of the three sunken vessels. SCRET divers explored each of the sunken vessels and obtained video documentation of the sites. The SCRET divers used standard DIR diving practices, including the use of trimix as the breathing gas on all dives.
Set forth below is a map showing the location of the current 520 bridge and the area on either side of the exiting bridge that was surveyed with side scan sonar by Golder Associates.
Side scan sonar survey area.
The map below shows the existing 520 bridge and the locations of the three sunken vessels, which we have labeled Sunken Vessel #1, Sunken Vessel #2 and Sunken Vessel #3.
Location of three sunken vessels.
The drawing below shows the existing 520 bridge, the proposed 520 replacement bridge (north of the existing bridge) and the location of the three sunken vessels (the three triangles). While not directly in the path of the proposed replacement bridge, the three sunken vessels are close enough to be affected (potentially) by the anchors for the proposed replacement bridge.
Proposed 520 replacement bridge.