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Comprehensive Stormwater Management Plan Northeast Lino Lakes Drainage Improvement Project WSB Project No. 2929-79 Page 6 2 EXISTING CONDITIONS The CSMP area is almost entirely within the City of Lino Lakes, however the CSMP does include upstream contributing land from the City of Hugo. This section provides a brief overview of the existing conditions used in the conceptual design of this CSMP. 2.1 City of Hugo The City of Hugo contributes 215 acres of the nearly 1,350-acre area and has an existing flow rate of 50.3 cfs into the City of Lino Lakes and ACD 55 drain tile system. Hugo has existing stormwater infrastructure and storage related to commercial and residential development east of Elmcrest Avenue. These sites were permitted under the City of Hugo’s permit program, followed RCWD rules, and instituted a more stringent rate control standard of 0.1 cubic feet per second (cfs) per acre limit on the 100-year event (Hugo 2002). 2.2 City of Lino Lakes The majority of the CSMP area is located within the City of Lino Lakes and serviced by the agricultural drain tile systems, ACD 55 and ACD72. ACD 55 and ACD 72 drain tiles were designed to provide drainage for agricultural lands and are already at capacity, limited by the existing crossings under I-35E. The City of Lino Lakes has also identified this area as being a Runoff Sensitive Area for stormwater rate and volume control given the limitations of the existing ditch system (Lino Lakes 2005). Low points in the area can remain inundated for weeks following the 100-year event due to the limited pipe capacity in the County Ditch systems. Because the low-lying areas take so long to drain back to their normal water levels, the next rain event may compound flooding beyond the 100-year flood level. Constraints of the drain tile system have limited landowners’ ability to develop their land consistent with the City of Lino Lakes’ Comprehensive Plan. Development must meet RCWD Rule C for Stormwater Management Plans, which includes water quality and rate control. However, since the existing drainage system is at capacity under existing conditions, RCWD has established reduced peak rates for the maximum discharge rate under development on all sites draining to ACD 55 and ACD 72 (Houston Engineering, Inc. 2013). Unfortunately, the soils underlying most the area are poorly suited for infiltration, have a high groundwater table, or are wetlands, all of which limit stormwater management opportunities and the volume reduction requirement of Rule C. As discussed in Section 1.3.5.1 there is a small commercial development in Lino Lakes at Main Street and Otter Lake Road. Due to the limited capacity of the existing ACD 55 Branch 8 drain tile system, the McDonald’s development was required to install a water reuse and spray irrigation system in addition to meeting the standard RCWD rules to reduce the stormwater runoff volume for the 2-year event from their site (RCWD Permits #13-029 and #13-040) and alleviate some of the burden on ACD 55 Branch 8. 2.3 Existing Land Uses Most the land in the CSMP area is agricultural or undeveloped (Table 2-1 and Figure 2, Appendix A) (Metropolitan Council 2017) and drains to one of the county ditch systems via unbuffered surface inlets. Table 2-1. Metropolitan Council Generalized Existing Land Use within the CSMP Land Use Hugo East Central West Lino Total CSMP Total Agricultural 59.2 385.8 400.6 98.4 884.8 944.1 Farmstead 4.7 7.5 0.0 0.0 7.5 12.2 Institutional 0.5 0.0 0.4 0.0 0.4 0.9