2020 Lake George Limnology Report
Total Page：16
File Type：pdf, Size：1020Kb
2020 Limnology Report Lake George (73-0611-00) St. Cloud, Minnesota STCLO 155152 | March 2021 2020 Limnology Report Lake George (73-0611-00) St. Cloud, Minnesota SEH No. 155152 Prepared for: City of St. Cloud – Public Utilities Division Prepared by: Short Elliott Hendrickson Inc. 1200 25th Avenue South P.O. Box 1717 St. Cloud, MN 56302-1717 320.229.4300 Prepared by: March 22, 2021 Ericka Massa, Graduate Scientist Date March 22, 2021 Prepared by: Erik Bye, Graduate Scientist Date Reviewed by: March 22, 2021 Joel Asp, Sr. Scientist Date Contents Certification Page Contents 1 Introduction ................................................................. 1 1.1 History .................................................................................................... 1 1.2 Background ............................................................................................ 2 2 Terms and Definitions ................................................. 6 3 Water Quality Assessment ......................................... 8 3.1 Data Collection Methods ........................................................................ 8 3.2 Results ................................................................................................... 8 4 Aquatic Plant Assessment ........................................ 22 4.1 Methods ................................................................................................ 22 4.2 Results ................................................................................................. 23 4.3 Action/Improvement Considerations ..................................................... 24 5 Fisheries Assessment ............................................... 24 5.1 Methods ................................................................................................ 24 5.2 Results ................................................................................................. 24 5.3 Action/Improvement Considerations ..................................................... 26 6 Summary ................................................................... 26 6.1 Scheduled 2021 Activities .................................................................... 27 7 Bibliography .............................................................. 28 SEH is a registered trademark of Short Elliott Hendrickson Inc. 2020 LIMNOLOGY REPORT STCLO 155152 i Contents (continued) List of Tables Table 1 – Lake George Morphometric ........................................................................ 2 Table 2 – TSI calculations from 2018-2020 .............................................................. 22 Table 3 – 2020 Vegetation Survey Results .............................................................. 23 Table 4 – Length of Select Species Sampled - All Gear Combined ......................... 25 Table 5 – Catch Per Unit Effort (CPUE) of Select Species Sampled........................ 25 List of Figures Figure 1 – Site Location Figure 2 – 2018 Aerial Photograph Figure 3 – Watershed Area Figure 4 – Water Quality Sample Points Figure 5 – Aquatic Vegetation Sample Points List of Graphs Graph 1 – 2018 Dissolved Oxygen Profile Graph 2 – 2019 Dissolved Oxygen Profile Graph 3 – 2020 Dissolved Oxygen Profile Graph 4 – 2018 Lake Temperature Profile Graph 5 – 2019 Lake Temperature Profile Graph 6 – 2020 Lake Temperature Profile Graph 7 – Total Nitrogen Average Values (2018-2020) Graph 8 – N:P Ratio and Rainfall 2020 Graph 9 – Total Phosphorus Average Values (2018-2020) Graph 10 – Chlorophyll-a Average Values (2018-2020) Graph 11 – Secchi Depth Average Values (2018-2020) Graph 12 – Secchi Depth vs. Alum Doses 2020 2020 LIMNOLOGY REPORT STCLO 155152 ii Contents (continued) List of Appendices Appendix A Water Quality Raw Data Site Appendix B Photographs Appendix C 2020 Pond 52 Memo Appendix D NW Storm water treatment system \\sehinc.com\panzura\pzprojects\pt\s\stclo\155152\4-prelim-dsgn-rpts\2020 final limnology report 03222021.docx 2020 LIMNOLOGY REPORT STCLO 155152 iii 2020 Limnology Report Lake George (73-0611-00) Prepared for City of St. Cloud Public Utilities Division 1 Introduction Lake George (Lake) is a eutrophic, manmade lake that was placed on Minnesota’s Impaired Waters 303(d) List in 2012 because it was considered non-supporting of aquatic recreational use due to low water clarity, elevated phosphorus, and excessive algae blooms. The water quality affects aquatic recreation such as swimming, wading, and fishing. Additionally, aesthetic issues are related to algae growth including odor, low water clarity and surface growth, as well as potential for future toxic algae blooms, which can harm local wildlife and humans (Graham et al., 2016). The Lake George area includes the Lake George Municipal Complex and Eastman Park (Park); the most utilized Park in the City. Weekly summer music events are held in the Park with an estimated attendance of 125,000 people annually; Lake George is a centerpiece of these events and many other community events. The Park has activities associated with the Lake including walking trails, paddle boat rentals, fishing opportunities, and wintertime skating. Lake health is important for Park users and the City of St. Cloud. The 2017 Park & Recreation Master Plan, through community outreach, noted Lake George as one of the City of St. Cloud’s greatest assets. Figure 1 and Figure 2 show the site location and current aerial image (2017) for the Lake George area. The management objective for Lake George is to reduce the phosphorus concentration allowing the Lake to be removed from the State’s impaired waters 303(d) List and create a healthier condition for the ecosystem and Lake users. 1.1 History The following information is from a St. Cloud Times article called “St. Cloud Area Then and Now: Lake George”: Lake George was first surveyed in 1855 by R.B. Blake. The Lake (and surrounding wetland) covered 50 acres and was vegetated with wild rice and reeds. Lake George was a shallow, spring-fed lake with a small creek that meandered into it from the west, and the outlet drained through a ravine to the Mississippi River. In the 1870s, the Lake was drying up and reeds, muck, and scum were increasing. In the 1880s, people petitioned the City to buy the land around the Lake and dam the outlet to increase the water levels. In the 1890s, a corduroy road was built across the southern portion of the wetland and eventually became 7th Street South. STCLO 155152082 Page 1 In the 1910s, St. Cloud Ice Company harvested ice from Lake George to sell to residences when the Mississippi River ice was deemed too dirty for public use by state authorities. In 1921, water level in Lake George became dangerously low with the Pantown development. Water that once flowed to the Lake was diverted to the Sauk River. The 50- acre wetland shrunk to about half that size and was shallower. In 1927 – 1928, St. Cloud began dredging the Lake out. The fill was placed on the north and south end; additional fill from the St. Cloud Hospital was also used. By the end of the dredging and fill, Lake George was approximately 8 acres with a maximum depth of 35 feet. In 2002, the City completed a Lake George Shoreline Restoration Project. The project restored a portion of the Lake George shoreline and established a buffer zone by planting over 110 trees and 17,000 native plants and grasses. In 2009 & 2010, water quality studies were completed. In 2012, Lake George was listed as an impaired water under the 303(d) Impaired Waters List. In 2012, the MPCA conducted a study on the water quality of lakes in the Mississippi River Watershed, including Lake George. In 2017, the Lake George Sub-Watershed Assessment and Water Quality Improvement Implementation Plan was completed. In 2018, City of St. Cloud began in-lake aluminum sulfate (alum) treatments. 1.2 Background Lake Morphometric and Watershed Characteristics Lake George is a small, deep lake located near downtown St. Cloud, Minnesota. Lake George is thermally stratified in the summer and is characterized by steep banks with 46% littoral area. The approximate size and depth shown below is from the MNDNR Lakefinder website. Table 1 – Lake George Morphometric Shore Maximum Watershed Area Littoral Area Length Mean Depth Depth Area 8.55 acres 4 acres 0.43 miles 16.1 feet 32 feet 135 acres Lake George is a eutrophic lake that has been heavily manipulated over the decades. One of the largest physical changes occurred in 1927 – 1928 when the Lake was excavated from approximately 10-feet deep to its current 32-feet and the wetland perimeter was filled. 2020 LIMNOLOGY REPORT STCLO 155152082 Page 2 The sub-watershed includes two primary storm drain inlets into Lake George (north and south). The north inlet includes runoff from 76.5 acres of residential, institutional, commercial and Highway 23 corridor land uses. Runoff from 59.5 acres of runoff is treated in the underground StormTrap detention system and underground Contech filtration system. The treatment systems were installed in the 2020. The remaining 17 acres of runoff from the north inlet area enters directly into Lake George with little to no stormwater treatment. The south inlet includes 58.5 acres of runoff primarily from residential land use. Small rain events are treated in an existing stormwater sedimentation pond located on the south side of Eastman Park (known as Little George). There are no known inputs from streams into Lake George. A detailed watershed map is provided in Figure 3. The watershed of Lake George consists of mostly