Pretoria Boiler Relocation Project 2016
Jack Decker | Published on 8/15/2016
Pretoria Boiler Relocation Project
By Jack Decker
As members of the GLSPS, we love to dive, we love to dive shipwrecks and we love to dive shipwrecks in Lake Superior. We dive shipwrecks to discover their secrets. But above all, we love to preserve the shipwrecks for others to experience.
While taking an underwater archeological class through the Wisconsin Underwater Archeological Association in July, 2015, Tim Pranke and I talked with Tamara Thomsen and Caitlin Zant about how the boiler of the ship wreck Pretoria has been moved away from the wreck site by wave action. This is a travesty because as the boiler is pushed around by waves, it is getting further damaged. Plus, since it is further away from the wreck, divers probably won’t see this important piece of the wreck.
This sounded like a GLSPS project to the four of us. The schooner-barge Pretoria, at 338 feet long, was one of the largest wooden ships to sail the Great Lakes. The barge was built by James Davidson in West Bay City, Michigan, and launched on July 26, 1900. It sank in a storm in 1905, about a mile and a half off the north side of Outer Island in the Apostle Islands.
It lies at a depth of about 55 to 60 feet. Incidentally, the same storm also claimed the Sevona. The boiler was salvaged off the Pretoria wreck in the late 1950’s, then returned to the wreck in 2001, with help from the GLSPS. This was actually one of the first projects the GLSPS undertook. For more detailed information, please follow this link to the GLSPS website: Pretoria Boiler PIB Project. After returning home from the underwater archeological class, Tim dived into his personal library trove of shipbuilding books and the internet looking for information on boilers of the Pretoria’s time period.
Tim and I had a running bet between each other as to the actual overall dimensions of the boiler. From his research, we believed the boiler could weigh from 6000 pounds to 8000 pounds. But, this was a guess. If we were to move the boiler, we needed a more accurate weight and that meant measuring the boiler. We started talking with other GLSPS members, GLSPS Board members, and others with knowledge of moving large, heavy objects underwater. Approval by the GLSPS Board of Directors was obtained to proceed with this project. Project members, Tim Pranke, Jack Decker, Phil Kerber, Jim Christenson, Corey Daniel and Ken Knutson.
At this point, planning got serious. Since the Preservation is docked at Silver Bay Marina, distances to the Pretoria were calculated to determine amount of fuel required. Emergency and foul weather docking/anchorages had to be figured in, as well. The Captains’ Log came in handy for determining fuel usage. Picking weekends that promised good weather and participation was critical. Due to its location and not having data on the boiler, the project was split into two projects: Assessment and Securement. The Assessment project would allow us to measure and document the boiler, and scout for a permanent location. The Securement project would be the actual lifting and moving of the boiler to a permanent location, then securing it to the bottom. Because of the diving level required to participate, (level 6 & TT) the participants were selected by experience and research knowledge of the Pretoria shipwreck.
The Assessment Project occurred June 17 - 19, 2016. Members that attended were Jim Christenson, Ken Knutson, Tim Pranke, and Jack Decker. The four of us left early Friday morning, June 17. 2016, from Silver Bay Marina, heading East across the Big Lake to Outer Island. Searching at the coordinates with a drop camera, the boiler came into view on the third pass. We made several more passes and headed to the main wreck for drop camera views looking for a place to secure the boiler. Back at the boiler coordinates, we dropped anchor, dove down the anchor line and proceeded to document the boiler, taking pictures and video, and gathering other pertinent dimensions.
All the flue tubes had fallen out of place and were piled up on the bottom side of the boiler. Calling it a day, we headed to the dock at the Outer Island Light House for the night. Found fresh bear footprints in the sand on the beach. On Saturday, we did 2 dives on the main wreck, scouting for locations to secure the boiler. A storm front was coming in, so we left the wreck site for Silver Bay Marina late Saturday afternoon, not having seen any bears.
The relocation Project occurred August 12 - 14, 2016, with the following members on board: Jim Christenson, Corey Daniel, Phil Kerber, Ken Knutson, Tim Pranke, and Jack Decker. Ken, again, captained the R/V Preservation. Using the info obtained during the Assessment Project,
Tim figured the boiler weighed at least 9000 pounds, submerged. Given we were dealing with Lake Superior and wanting more lift than needed, we packed enough lift bags for almost twice that amount. We loaded an extra compressor, 400+ feet of air hose, and more than enough, hopefully, lift bags. An underwater drill, securement plates, and rock bolts were also brought along on this project. We were not sure we would have time to secure the boiler this time but brought the hardware (3 plates and several lengths of chain) were loaded on board just in case we did.
Jim Christenson and Tim Pranke were first scouting for a possible boiler relocation area. Jim Christenson looking for possible sites as well. Jack Decker and Tim Pranke documenting the Pretoria boiler and its measurements. Jim Christenson and Tim Pranke examining bottom of the boiler. Plenty of chains and lifting straps rounded out our equipment. The six of us left Silver Bay Marina at 1:30 AM, Friday, August 12. Our plan was to be at Outer Island for an early breakfast and prep the Prez to be at the wreck site by mid-morning. Though no wind was blowing, the waves mid lake were 6 – 8 feet. Docking at Outer Island Lighthouse proved too difficult, so we went to South Twin Island to wait for calmer seas.
Calmer seas didn’t arrive until Saturday afternoon. We motored over to Outer Island Lighthouse and prepped the boat and lifting hardware. Two 2000 lb. lift bags were deployed on the boiler, one on each side. A 6000 lb. lift bag was deployed from the fire box opening to approximately 15 ft. below the surface. This was not enough. Another bag with 4000 pounds of lift was added, for a total of 14,000 pounds of lift. The rigging of the lift bags were cleared by our resident Commercial diver Phil Kerber and started the lifting procedure. We finally lifted the boiler off the bottom and then used the Preservation to tow it to our selected site ground zero.
When lowered into it's designated spot, the boiler ended up on its side, just off the port stern of the wreck. It’s on the leeward side of a rock ledge, sheltered from the waves. Just about three feet where we intended it to land. Great job guys!! Time on site ran out before we could drill into the bedrock (sandstone here) to secure chains around the boiler. Even though the boiler is now sitting next to the wreck, we still have the future project of securing the boiler to the bottom of the lake.
An additional project on this wreck site will be to locate the fire door of the boiler. We believe it was attached to the boiler when the boiler was put back into the water. The R/V Preservation was docked at Outer Island lighthouse dock. with diver Tim Pranke. Sunset, Outer Island.
The GLSPS would like to thank everyone that participated in the Pretoria Boiler Relocation Project. A special thank you to Tim Pranke for researching the boiler project for the last year (or more). His hard work and dedication in preparing for this project paid off and allowed this project to be a success. Thank you to the topside crew, Ken Knutson and Phil Kerber. Thank you to Phil Kerber, Jay Hanson, and Bob Olson for expert advice and the use of their commercial dive equipment. Thank you also to Tamara Thomsen and WUAA for help in first implementing the idea of the boiler being moved and securing applicable permits to perform this type of work on a historical shipwreck.
FYI: No damage to the shipwreck was encountered after the final dive of the project.
Pretoria Boiler Relocation Project Leader
Co Project Leader - Diver
Co - Captain RV Preservation
Commercial Diving Consultant
Dive Safety Officer
Lead Captain - RV Preservation