MN Suburban Lakes Nautical Archaeology Project: Targeted Sonar Survey & Anomaly Assessment

MHM's primary goal for the MSLNA-TSS-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. As a whole, the MSLNA-TSS-AA Project produced interesting and significant results investigating 14 anomalies in 4 lakes in 4 counties using SCUBA. MHM dove upon and identified 7 wrecks, recognized an additional 2 wrecks in sonar data that will be targeted during future research, 14 possible wrecks, 11 maritime sites or objects, and 8 ?other? objects in Prior Lake, Lake Pulaski, Medicine Lake, and Lake Johanna. Of the 7 wrecks, MHM acquired Minnesota Archaeological Site Numbers for 5 of them from the OSA: 1 in Lake Pulaski, 3 in Medicine Lake, 1 in Lake Johanna. The wrecks in Medicine Lake and Lake Johanna are the first underwater archaeological sites identified in these lakes. In time, the 2 unidentified wrecks in Prior Lake and Medicine Lake, along with the possible wrecks, will be investigated using SCUBA. Recognized sites will get site numbers once they qualify for that status under OSA guidelines. Specifically in Prior Lake, MHM recognized the 4th wreck in that lake (Anomaly 57) and 4 possible wrecks (Anomalies 58, 59, 63, 64). It is archaeologically necessary to investigate these anomalies using SCUBA to determine their nature and rudimentarily document them if warranted. Anomaly 1 is a maritime site comprised of 2 pontoons; dive reconnaissance on this site is essential to determine whether it is a capsized raft or boat. Two other potential maritime sites - the possible Fish House/Dock Box (Anomalies 8.2) and Fish House (Anomaly 30) will also require SCUBA reconnaissance to determine their natures. If one or both of these anomalies is a Fish House, it is a piece of material culture that represents a significant activity for a large number of Minnesotans. Another maritime site that also represents Minnesota transportation is the possible Snowmobile site; diving is required on Anomaly 65 to determine its nature. Some maritime sites identified in 2016 and through new sonar footage in Prior Lake during the MSLNA-2 Project have sufficient detail that diving on them will not be necessary in the future. Those anomalies include the Large Dock (Anomaly 54), Dock Section (Anomaly 63), and the different combinations of boat lifts, canopies, and frames (Anomalies 41, 4, 6, 8.1, 28.1, 28.2). These maritime resources are expected to be found on the bottom of Minnesota?s lakes because of their use as shoreline infrastructure that are often susceptible to high winds. Also, MHM does not plan on conducting dive reconnaissance on the Power Pole (Anomaly 5), Barrels (Anomaly 56.1-56.5), or the V-Shaped Object (Anomaly 56); if a day?s dive plan and tank air could accommodate a quick drop onto these objects, MHM would consider some data collection. Therefore, one more season of fieldwork will allow MHM to determine the nature of the new wreck (Anomaly 57), possible wrecks (Anomalies 1, 58, 59, 63, 64), and the other possible maritime/transportation sites (Anomalies 8.2 30, 65) in 2-3 days of fieldwork. Specifically in Lake Pulaski, MHM recognized the 8th and 9th wrecks in that lake (21-WR-206, Anomaly 51) and the future investigation by SCUBA of Anomalies 58 and 59 will take 1 day of fieldwork to complete. Specifically in Medicine Lake, additional fieldwork will be required to determine the nature of 3 possible wrecks (Anomalies 10, 36, 70) and a large object with an interesting acoustical signature that may be a wreck, vehicle, or another type of site (Anomaly 46); this anomaly is intriguing. MHM has no plans to dive on the series of barrels (Anomalies 34.1-34.7) and poles/tree remains (Anomalies 60a-A60i) unless research questions arise that can only be answered with additional fieldwork. The other unknown anomalies will require additional sonar survey to produce additional detailed images or SCUBA reconnaissance to confirm their nature (Anomalies 52, 59, 67, 69, 71, 72, 73.1-73.2). Further SCUBA reconnaissance fieldwork in Medicine Lake would require between 1 and 5 days to complete. Specifically in Lake Johanna, additional fieldwork will be required to determine the nature of 6 possible wrecks (Anomalies 20, 24, 25, 27, 30, 31), and further historical research into the probable identification the Possible Round Wreck or Recreational Float (Anomaly 21) and the Metal Buoy (Anomaly 26). While the identification of the Big Dock (Anomaly 22) is not in question, MHM may conduct dive reconnaissance on the site if future historical research suggests additional information can be attained through fieldwork. MHM has not located photographs of a large dock on Lake Johanna, either through historical imagery nor through aerial photography. The Ice Rink and Goal (Anomaly 19.1-19.2) appear to be exactly what MHM has determined they are, but the substance that comprises the ice rink is unknown. MHM suggests it is a large plastic tarp or tarps, information discernible only with SCUBA reconnaissance. Beyond any archaeological implications of the presence of a large tarp on the bottom of a somewhat small lake - it could be covering archaeological resources that cannot be identified while it lies on the bottom - ecological concerns may be of interest to the Minnesota DNR. The investigation of the 6 possible wrecks and information gathering on identified anomalies will be part of a research plan during future archaeological fieldwork. These wrecks and sites join dozens of other submerged cultural resources already identified other suburban lakes including White Bear Lake, Lake Waconia, 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. Other maritime sites identified during the MSLNA-TSS-AA Project 2 large docks in Prior Lake (Anomaly 54) and Lake Johanna (Anomaly 22), as well as small dock sections in Prior Lake. As with Lake Minnetonka and White Bear Lake, among dozens of objects blown into the lake by strong storms or deposited there by the habit of disposing of unwanted objects (sometimes by accident) on the ice or dumped from boats. These include Anomalies 26, and 19.1-19.2 in Lake Johanna and Anomalies 7 and 56 in Lake Pulaski. 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 4 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-TSS-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 120 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.