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Feasibility Report Page 9 Snelling Avenue North and County Road E - Street and Utility Improvements City Project Number PW 20-0100 DRAFT The segment of Snelling Avenue located north of Arden Place drains to a storm sewer system within the intersection at County Road E. From this intersection, runoff is conveyed north through 18-inch and 21-inch diameter storm sewer pipes that discharges into a wetland located in the southwest quadrant of Snelling Avenue North and the railroad crossing (Public Waters #194W), within the Valentine subwatershed area. Ramsey County has conducted a CCTV inspection of this 18-inch and 21-inch storm sewer and documented that a majority of pipe segments are in poor to failing condition with cracks, voids and multiple joint failures. The existing storm sewer system is shown in Appendix D. The two project areas are not identified within the Flood Hazard Areas Map contained within the City’s Surface Water Plan, with the exception of the Lake Josephine outlet channel crossing at the new Snelling Avenue bridge structure near the south end of the project corridor. A wetland delineation review was conducted with Rice Creek Watershed District during preparation of this feasibility report. A copy of the wetland boundary determination and Wetland Conservation Act decision for the project corridor is provided in Appendix E. Minor additional wetland delineation work may be required during the design process based on the extent of storm sewer replacement north of the Snelling Avenue and County Road E intersection for Public Waters #194W noted above. 2.7 Environmental Conditions During the geotechnical investigation process for this feasibility study, the geotechnical firm reported “Apparent Hydrocarbon Odors” at 11 of the 15 soil boring locations. In response to this information, the City hired a consultant to conduct an environmental investigation to assist with identification of potential contaminants within the project area. The scope of work for the environmental investigation included a Phase I Environmental Site Assessment (ESA) and a field investigation to evaluate the current subsurface soil, groundwater and soil vapor conditions along the project corridor. The investigation identified elevated contamination levels at two locations along the corridor designated as environmental borings EB-3 and EB-8. Polycyclic aromatic hydrocarbons (PAH) and diesel range organics (DRO) impacted soil above the MPCA reuse criteria was identified at these two locations. Benzo(a)pyrene was detected in soil samples at EB-3 and EB-8 above the Tier II Industrial and Tier 1 Residential soil reference values criteria. DRO also exceeded the MPCA criteria for unregulated full, which will require disposal of excavated regulated fill at an MPCA-permitted landfill during construction. Following completion of the field investigation, the City authorized the environmental consultant to prepare a Response Action Plan, a Construction Contingency Plan and a MPCA Brownfields enrollment application for the project. A copy of the Phase I ESA, Field Investigation Report and Response Action Plan are provided in Appendix F.