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X City of Arden Hills Page 10 of 63 October 7, 2022 Also, the portion of the proposed trail remaining to be constructed is located within three hundred feet of a waterbody and its construction would disturb more than an acre of land, both of which trigger the need for an RCWD Erosion and Sediment Control permit for this project. Based on the anticipated area of additional impervious surfacing and disturbed area during construction, construction of the remaining portion of the proposed trail will require the project to meet MPCA permitting requirements. RCWD requirements are separate from MPCA requirements and applicable requirements for both agencies will need to be met, however there are some design elements and construction practices that will meet some of the requirements for both agencies. Vegetated buffer strips will be needed for a majority of the project where the construction of infiltration basins or wet ponds is not feasible. The costs for constructing infiltration basins or wet ponds are not included in this report since the areas that are feasible for their construction will not be identified until the field survey information is available during the final design phase of the project. Any wetland in the proximity of the trail area will need to be delineated, and any impacts will need to be mitigated in accordance with the Wetland Conservation Act. Based on the National Wetland Inventory layer at the RCWD MapViewer online, it was determined that there are some wetlands in the project vicinity. These are shown in Figure 3 in Appendix A at their approximate locations. If any portion of a delineated wetland will be disturbed or filled in, an RCWD Wetland Permit would be needed. The costs for wetland mitigation are not included in this report. It not anticipated that any construction will occur outside of the current street right-of-way. A brief mention of the Interstate 694 crossing is warranted here. Old Snelling Ave. / Old Highway 10 passes beneath the eastbound and westbound bridges for Interstate 694 for a length of about 150 feet. Over this length, it is an urban section with concrete curb and asphalt paving between the back of curb and the toe of concrete slope protection beneath and between the bridges, on both sides of the roadway. This asphalt paving appears to be wide and flat enough to serve as the surfacing for the proposed trail over this length. However, the dimensions and conditions should be checked during the final design phase of the project to confirm its suitability for reuse as part of the proposed trail, and the quantitative information in this updated report does not include an exception for this portion of the proposed trail. A point regarding impacts to the roadway culverts and entrance culverts along the proposed trail is warranted here. It appears that about half of the entrances along the proposed trail corridor (along the west side of Old Snelling Ave. / Old Highway 10) have drainage culverts beneath them, at various offsets from the edge of the roadway. The transverse location of the proposed trail within the right-of-way at these locations will determine the extent of the impacts to these culverts and whether they need to be extended or relocated. For the purposes of this study, it was assumed that an entrance culvert located where the proposed trail transverse location recommendation is “Constrained” will not be impacted, and an entrance culvert located where the proposed trail transverse location recommendation is “Preferred” will be impacted and need to be relocated. These are noted with callouts in Figure 3 in Appendix A. The original report also noted the presence of a 4’x5’ box culvert across Old Snelling Ave. / Old Highway 10 just south of Valentine Ave. and stated that it will need to be extended. The presence and condition of this box culvert was unable to be verified with this updated study, therefore the assumption is being made that the extension of box culvert is still required. The locations and conditions of all drainage features along the proposed trail corridor should be determined early in the final design phase of the project to properly evaluate impacts and account for them with the final design.