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TWIN LAKE HYDROLOGIC ANALYSIS 1.0 INTRODUCTION This report summazizes the findings of a hydrologic study of Twin Lake. The study sought to establish the maximum allowable normal-water level for the lake, to investigate flooding potential, and to identify strategies that would diminish the likelihood of flooding and degradation of Twin Lake's water quality. The work described in this report was begun in April, 1993. The Ramsey-Washington Metro Watershed District (RWMWD) commissioned the study as a part of continuing evaluations of sub- watersheds within the District. Barr Engineering Co. (Barr) conducted the study and prepared this report. 2.0 BACKGROUND 2.1 Location Twin Lake is located in Ramsey County, in the Saint Paul suburb of Little Canada (USGS White Bear Lake West, Minnesota Quadrangle; Range 22, Township 30, Sections 31 and 32). The lake is situated just north of the junction of Interstate Highways 694 and 35E, and just south of Vadnais Lake. (See location map, Figure 1.) At the water surface elevation of 869 feet MSL, as shown on the USGS Quadrangle, the lake has an area of approximately 37 acres. 2.2 Relationship to.Lazaer Watersheds Twin. Lake and its direct watershed comprise part of the County Ditch 16 watershed, which is in turn part of the lazger Phalen chain of Iakes watershed. This Phalen chain of lakes watershed is located an the northern half of the RWMWD. Vadnais Lake and its watershed is not included in the RWMWD, even though it naturally overflows to Twin Lake, the subject of this report. Overflows are possible, but rare because the City of St. Paul water utility draws its water from Vadnais Lake, thus controlling water levels. 231621264\TWINLAKE.RPTV~I 2