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4.0 INDIVIDUAL WATER MANAGEMENT PLANS 4.1 Water Bodies Chosen for Inclusion in Section 4.2 of the Plan VBWD chose 33 water bodies for inclusion in Section 4.2 of the plan based on VBWD's knowledge of the following; ■ Past or possible future flooding problems ■ Intercommunity drainage problems ■ Water quality issues and data ■ Revisions to previously -published flood elevations ■ Existing or possible future impacts to VBWD's Project 1007 drainage system ■ Outstanding water resources 4.2 Organization of Individual Water Management Plans The individual water management plans are organized into three general groups: water bodies which are part of VBWD's Project 1007 drainage system; water bodies tributary to Valley Branch Creek; and landlocked water bodies. Within the Project 1007 system, the individual water management plans begin at the upstream end (Silver Lake) and proceed downstream, to Rest Area Pond. For the landlocked water bodies, the individual water management plans begin generally in the north and proceed to the south and east. 4.2.1 Silver Lake Water Management Plan 4.2.1.1 Location and General Description Silver Lake is a DNR-protected water (#62-1P) located in Subwatershed LL29 (or SL1 in North St. Paul's Surface Water Management Plan), directly west of T.H. 120 in the Cities of North St. Paul and Maplewood. The lake has a surface area of about 70 acres and a maximum depth of approximately 20 feet. The watershed area in comparison to the lake area is relatively small. The Silver Lake tributary area is 466 acres and is comprised of Subwatersheds SVR1, LL28 and LL29. Development in the tributary watershed is almost complete, including the City of White Bear Lake portion of the watershed. Figure 2-3 shows the tributary watershed. 4.2.1.2 Drainage Patterns and Stormwater Issues The outlet from Silver Lake is a V-notch weir located at Century Avenue (T.H. 120) on the east side of the lake. The overflow point of the weir is at Elevation 988.5. Water from the lake flows under Century Avenue (T.H. 120) to a large DNR-protected wetland (#82-375W) in the Greens of Silver Lake development, located in the City of Oakdale. Some homes adjacent to the lake experienced basement flooding in 1984 and 1985 when the lake rose above Elevation 989.5. Whether this was entirely due to the lake elevation is not clear. The DNB's ordinary high water elevation (OHW) is 989.7. According to the North St. Paul Flood Insurance Study, the 100-year flood elevation of Silver Lake is 991.0. More recent hydrologic model results (by ( Oakdale and VBWD) show the 100-year flood elevation of the lake to be approximately 0.5 foot lower. The City of North St. Paul and VBWD will enforce the 991.0 flood elevation until the C city revises the Flood Insurance Study. The results of a 1976 VBWD survey found one home 23\82\045\SEC4.RPT\KMH 1 DRAFT: June 23, 1994