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The underground filtration system consists of chambers, angular stone, 18 inches of clean <br />washed concrete sand, 6 inches of stone, and an under drain (see Appendix A). The concrete <br />sand filtration layer design is consistent with the Minnesota Stormwater Manual. The Central <br />Pond (Figure 2) consists of approx. 2 feet of media (3" mulch, 4" planting soil, 12" sand /steel, <br />and 8" draintile) and provides stormwater treatment for 1.6 acres of parking lot runoff. <br />Figure 2 — Filtration Basin <br />Tree trenches (Figure 3) are proposed the length of the parking lot islands eliminate the need <br />for irrigation, promote healthy tree growth, and address the Watershed District's requirements. <br />Figure 3 — Tree Trench <br />Additional BMPs above and beyond the RWMWD permit program requirements are a <br />consideration that Metro Transit would like to pursue under the RWMWD Cost Share Program. <br />This includes porous concrete sidewalk at the bus stop area. <br />Hwy 36 and Rice Street Park and Ride <br />Storm Water Narrative — 90% Review Set <br />8/5/2011 <br />33 <br />Page 1 5 <br />