2002 Draft Natural Resources Management

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Langton Lake has benefited tremendously from concerted efforts by local residents and the City for its protection. Two efforts that stand out are the successful intervention to prevent filling of the southerri part af the Lake in the 1970's, and the construction of a detention basin to treat runoff from rnuch of the new industrial and commercial developments to the sot�th of the lake. The c�esire to protect Langton Lake was also in large part responsible for passagc of a shoreland zoning ordinance by the City in 1974, making Roseville the first city in the state to take such action. Technical Findings Due to a lack of available data for water quality in Langton, the City ini�iated a limited sampling effort for selected water quality parameters. The samplin� was undertaken during the 2001 growing season on June 7th, July 17th and August 23rd Water Quality Water clarity, measured by secchi depth, often indicates a lake's overall water quality, especially the amount of algae present. Growing season secchi depth for Langton averaged aronnd 2.5 feet in 2001(Appendix A, Table 1}. Generally, sun�ight of adequate intensity to support rooted plant growth can penetrate a lake water calu�mn to 1.5-2 times lake secchi depth. This explains to a lar�e extent why almost all of Langton Lake supports lush submergent veQetation since the maxinnum depth of the Lake, at 5 feet, is only about twice the water clarity reading. The seasonal mean concentration for total phosphorus in Langton is 80 u� (ppb) (Appendix A, Table 1). This puts Langton Lake in category D, described in the Metro Lake water quality repor� card as "poor quality with recreational use severely impaired." It is encouraging however, to note that it is close enou�h to the uppez' limit of 69 ug/1 in category C(averaac quality; moderate impairment for recreational use, often in the later half of summer) to make it an achievable goa� for the future. There is little historical water quality data for Langton Lake available in the state's water quality database. The Minnesota Pollutian Contro� Aaency's {MPCA} lake �vater quality database indicates that the summer mean water quality readin� for the south bay was l.b feet in 1984 and Crty of Roseville `�� Pnrks Natru-ctl Resouree Mcniagement