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Comprehensive Stormwater Management Plan Northeast Lino Lakes Drainage Improvement Project WSB Project No. 2929-79 Page 15 5 PROPOSED CONDITIONS MODELS After establishing the revised existing conditions models to use as a baseline for comparison in Section 3, we developed the proposed conditions modeling in cooperation with RCWD to ensure compatibility with the District modeling procedures. The proposed conditions reflect future land uses in the study area, assumed site grading to drain the study area to the central storm drainage system, assumed private disconnection of agricultural drain tile within the study area, and conceptual regional stormwater storage BMPs connected by a new open conveyance system and revised outlet to Peltier Lake (Figure 13, Appendix A and Appendix C). 5.1 Hydrology Updates Curve numbers were estimated using the MLCSS, City of Lino Lakes, and City of Hugo 2030 projected land uses, NRCS soil data, recent wetland delineations, and the National Wetland Inventory. The following assumptions were made: 1. Hugo and Lino Lakes will be fully built out per their 2030 approved land use plans 2. Future development will be graded to drain to a regional BMP; this may include the use of drain tile or imported fill to improve drainage in clay soils. A hydrologic soil group type B was assumed for new development. 3. Existing wetlands within the RCWD Wetland Management Corridor (WMC) will be preserved or restored per RCWD Rules within the WMC in Lino Lakes. Many of the existing wetlands have been drained and are currently farmed. By protecting and improving the quality of the existing wetlands, the proposed curve number is reduced in several subcatchments. Tables 5-1 and 5-2 provide a summary of the land uses and curve numbers used in the modeling: Table 5-1. Proposed Land Uses, Impervious Percentages, and Curve Numbers LAND USE DESCRIPTION 1 MAX. IMPERVIOUS PERCENTAGE 1 A 2 B 2 C 2 D 2 TP 3 [MG/L] Large lot residential 10% 59 74 82 86 0.46 Low density residential 40% 47 65 76 82 0.50 Medium density residential 50% 54 70 79 84 0.30 High density residential 65% 70 81 87 90 0.40 Commercial 75% 86 91 93 94 0.22 Industrial 75% 81 88 91 93 0.25 Public semi-public 65% 39 61 74 80 0.18 Vehicular right-of-way 75% 83 89 92 93 0.25 Mixed use 75% 77 85 90 92 0.22 Wetland management corridor 0% 30 58 71 78 0.03 1 Lino Lakes 2030 Comprehensive Plan 2 NRCS National Engineering Handbook 3 MPCA Minnesota Stormwater Manual