#04 - RFP for Land - Laserfiche WebLink

Home Browse Search

Cyphers Logistic Park AUAR 37 March 2022 The following stormwater management requirements will be adhered to: • City of Lake Elmo Code of Ordinances; 105.04-XIV Stormwater and Erosion and Sediment Control • City of Lake Elmo Comprehensive Surface Water Management Plan • Valley Branch Watershed District Standards • National Pollution Discharge Elimination System permit requirements will be determined for each new development within the AUAR Study Area . This permit requires 80 percent TSS removal and meeting existing run-off rates for the 2, 10, and 100-year storm events. Stormwater will be managed on site and will maintain the current drainage patterns to the discharge points . The proposed development within the AUAR s tudy area will require compliance with the standards of the VBWD and the City of Lake Elmo for water quality, volume control, rate control, and erosion control. For new, nonlinear developments that create 6,000 square feet or more of new impervious surface on sites without restrictions, stormwater runoff volumes will be controlled, and the post-construction runoff volume shall be retained onsite for 1.1 inches of runoff from impervious surfaces. In addition to the water quality retention requirements , the City and VBWD r equires the peak rate of stormwater runoff from the developed site shall not exceed the existing peak rate of runoff for all critical duration events, up to and including the 100-year return frequency storm event for all points where discharges leave a site during all phases of development. Design criteria shall be the 2-, 10-, and 100-year 24-hour storms with respective 2.8, 4.2, and 7.3-inch rainfall depths with VBWD-approved time distribution and the 7.2-inch 100- year 10-day snowmelt event. The soil profile is anticipated to be clayey having a poor permeability rate. Per VBWD regulations, developments must exhaust options to infiltrate the 1.1-inch water quality volume before alternate means of treatment can be considered. Alternate options to infiltratio n may include but are not limited to underground detention, underground infiltration, stormwater reuse, surface biofiltration, and green roofs. In addition to potential soil permeability issues, karst geology may be present in the area. If karst formations are found onsite, the stormwater mitigation measures must follow both M PCA and VBWD requirements. Stormwater modeling of runoff and temperature controls will be completed as part of the final design of each project phase to provide volume and temperature control for the proposed improvements. The modeling will be performed to ensure conformance to all City of Lake Elmo and VBWD standards. Outfalls will be defined as part of the final design of each project phase. The following design/construction standar ds are to be adhered to during construction: • Grading of the infiltration basins shall be accomplished using low-impact, earthmoving equipment to prevent compaction of the underlying soils. • Infiltration basin excavation shall be held 1 foot above the botto m of the excavation until the contributing drainage areas with exposed soils have been fully stabilized. • Divert upland drainage areas to prevent runoff from entering the excavated basins or into the work areas.