Minnesota Suburban Lakes Underwater Archaeology Project: Anomaly Assessment

MHM's primary goal for the MSLNA-AA Project, a Phase 1 archaeological reconnaissance survey, was to determine the nature of specific anomalies?possible shipwrecks & other submerged sites - after conducting targeted sonar scanning of possible anomalies using new and improved sonar equipment - exceeded expectations and produced several positive outcomes. In Prior Lake, MHM identified 5 new wrecks (A57, A59, A66, A67, A74), 3 new submerged maritime sites (A30, A8.2, A72), 2 ?other? objects (A25, A60), a tree (A68), and 1 anomaly requires re-evaluation (A41). Also during this project, MHM?s targeted side and down imaging sonar re-scanning of Prior Lake using updated sonar equipment allowed for the identification of 13 anomalies as false targets comprised of bottom contours or vegetation (A23, A33, A37, A39, A40, A45), rocks (A11, A34, A35, A38, A58, A70) and a tree (A65) - without dive reconnaissance. In Medicine Lake, MHM identified 2 new wrecks (A18, A74), 2 vehicles, (A46, A59), a small cluster of barrels (A73.1-A73.2), and a canoe-shaped weed cluster (A75). Also during this project, MHM?s targeted side and down imaging sonar re-scanning of Medicine Lake using updated sonar equipment allowed for the identification of 2 anomalies as false targets comprised of bottom contours (A70, A72) - without dive reconnaissance. In Lake Johanna, MHM identified 1 new wreck, 2 new submerged maritime sites, 1 'other object, and 1 false target. Also during this project, MHM's targeted side and down imaging sonar re-scanning of Lake Johanna allowed for the identification of 2 anomalies as false targets comprised of bottom contours/vegetation - without dive reconnaissance. Where appropriate, Minnesota Archaeological Site Forms were submitted to the Office of the State Archaeologist and the identified wrecks were placed into their historical contexts after conducting maritime historical research. More specifically, of particular significance to the maritime history of the Prior Lake area in terms of watercraft design and construction. the Wooden Flat Bottomed Row Boat Wreck (21-SC-116) is unique in Minnesota's archaeological record because of her construction attributes. MHM contends, at least currently, that 21-SC-116 is the oldest wreck on the bottom of the lake, likely sinking before 1910. Twelve Minnesota Archaeological Sites and 2 museum collection watercraft identified by MHM have many shared attributes with 21-SC-116, and she joins a list of significant small craft sites. The frames are attached to the transom with large bolts with roves. Rarely are Minnesota small craft identified with bolt and rove construction. Further, the structural components that comprise the wreck's quarters are upright frames that are formed from rough tree branches. The boatwright did not fashion rectangular beams for these quarter supports; instead, strong branches were cut, they were stripped of bark and smaller branches, and used in the vessel's construction in that state. The only Minnesota watercraft MHM has identified with an attribute remotely similar to the rough-hewn frames of 21-SC-116 is The Constitution/Old Ironsides - the oldest known wooden planked boat in Minnesota - 3D scanned and documented by MHM in 2019 during a Legacy Amendment-funded Minnesota Small Craft Study. The Constitution/Old Ironsides has floors on her flat bottom that are comprised of stripped and twisted tree branches. The Wooden Flat Bottomed Row Boat Wreck and The Constitution/Old Ironsides are preserved cultural resources - made in Minnesota - that contain construction elements previously unknown in the archaeological and maritime historical records. Also, the Flat-Bottomed Row Boat Wreck (21-RA-85) identified during this project in Lake Johanna, is 1 of the 12 wrecks that is comparable with 21-SC-116, at least in general type and construction. The 2 newly identified steel wrecks in Prior Lake - the Steel Outboard Wreck (21-SC-113) and the Steel Outboard Motor Boat Wreck (21-SC-114) - join the 8 other small (under 30.00 feet long) steel wreck sites identified to date in Minnesota. These 8 wrecks each provide MHM with a wide range of construction attributes that can provide details of the changes to small steel watercraft from the late 18th into the 19th centuries. The documentation of future sites, along with these known wrecks, will provide historians and scholars with opportunities to further study these protected submerged cultural resources. The preservation and conservation in situ of these types of wrecks are particularly significant due to the lack of specimens that survive above water. Scrapping and recycling of steel boats has placed the 10 small steel wrecks on the bottom of Minnesota's lakes that MHM has identified - from Prior Lake, Lake Johanna, Medicine Lake, Lake Pulaski, Lake Minnetonka, and White Bear Lake - some of the last surviving watercraft of their type and design in the state. In Medicine Lake, the Fiberglass Outboard Motor Boat Wreck (Anomaly 18) is similar to the Shell Lake Portager Wreck (21-HE-508) in Lake Minnetonka; MHM determined this wreck is an early 1950s fiberglass prototype Portager model constructed in Shell Lake WI. Anomaly 18, like the Portager Wreck, has upright sides and a flat tub-like bottom. Anomaly 18's Minnesota watercraft registration information does not coincide with the archaeological data recorded by MHM, a situation that has been found concerning many wrecks in Minnesota. The preliminary documentation of this wreck has brought up more archaeological questions than answers, in itself a measurable outcome. In consideration of non-wreck maritime sites identified during the MSLNA-AA Project, the Big Dock (Anomaly 22) in Lake Johanna is a physical representation of environmental conditions during the 1930s; MHM contends this purpose-built dock was created for use during the big drought and was laid directly on the lakebed. It is the largest dock - by far - of any similar structure documented to date by MHM - in the smallest Lake MHM has so far surveyed using remote-sensing side and down-imaging sonar and SCUBA reconnaissance. These wrecks and sites join dozens of other submerged cultural resources already identified in other suburban lakes including White Bear Lake, Lake Waconia, Lake Pulaski, and Lake Minnetonka. Comparing and associating these new sites with known sites increases our understanding of the historical contexts within which these cultural resources operated or were exploited by Minnesotans. As more Minnesota wrecks are documented, the changes in watercraft design and construction will more completely fill-out the maritime historical record. Many of the smaller craft on the bottom of Minnesota's suburban lakes represent nearly 140 years of our relationship with historical personal watercraft. When the internal combustion engine began to replace steam-powered boats in the late 19th and early 20th Century, watercraft operation became possible for 1 person to do since a boiler operator was not longer necessary. The rapid development of the outboard motor set up the proliferation of personal watercraft, made of wood, steel, aluminum, and fiberglass. The higher speeds attained by internal combustion engines also led to changes in hull design. The diversity of nautical, maritime, and underwater sites so far identified in Minnesota's suburban lakes are tangible examples of the rich maritime history of central Minnesota. Through research, diving on wrecks and anomalies to collect pertinent data, and ensuring that the collected information is accessible by the public, MHM will continue to investigate the submerged cultural resources of Twin Cities area lakes into the future. Comparison of sonar data from the 3 lakes in this study, recorded from different directions and during times of the year, have revealed new sites as well as false targets that do not require reconnaissance using SCUBA. This new data allows MHM to produce smart and efficient dive plans; this will continue into the future. The results of the MSLNA-AA Project summarized above is connected to all the work that came before and that will come after its completion. It is clear that the types of sites that exist in our suburban lakes are diverse, archaeologically and historically significant, and worthy of great attention; the historic period wrecks represented in these lakes span over 130 years of local maritime culture. Lastly, the large and significant data produced during the suburban lakes projects has and will be used for comparison, identification, and analysis purposes as MHM identifies wrecks and maritime resources on the bottom of other Minnesota lakes. Additionally, MHM's vetting of volunteer divers ? choosing only ethical, responsible people who understand our Mission to locate, document, preserve, and conserve Minnesota's finite submerged cultural resources within a not-for-profit paradigm ? led to a productive and honest working environment in the field. Fundamentally, MHM conducted sound nautical and maritime archaeology, strong maritime historical research that produced trustworthy data for analysis and future use, and we chose a group of trustworthy volunteers to assist us with the fulfillment of this project's goals.