07-20-2020-WS - Laserfiche WebLink

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Phase I Environmental Site Assessment Old Snelling Avenue & County Road E Improvements WSB Project No. 015447-000 Page 5 MPCA’s Screening Soil Leaching Value (SLV) of 1.4 mg/kg. Concentrations of PAHs and the corresponding BaP Equivalent were identified above the laboratory reporting limits in sample SP-3 but below MPCA regulatory criteria. · DRO was detected at a concentration of 103 mg/kg in stockpile sample SP-1, exceeding the MPCA unregulated fill criteria for DRO of 100 mg/kg. DRO was identified at concentrations of 66 mg/kg and 9.4 mg/kg in samples SP-2 and SP-3, respectively, below the regulatory standard. Landfill disposal of the soil from Stockpiles A and B was required based on BaP Equivalent and/or DRO concentrations detected above the MPCA’s criteria for unregulated fill. A total of 486 cubic yards of contaminated soil was removed offsite during the bridge replacement project. Soil from the third stockpile (Stockpile C) met the MPCA’s criteria of unregulated fill and as a result, did not require disposal at a landfill. 2019 Geotechnical Borings In preparation for the roadway improvements project, 15 geotechnical soil borings (B-1 through B- 15) were completed throughout the Project Corridor in October 2019. The borings were advanced to 14.5 feet below grade and were advanced approximately every 400 linear feet. While completing the borings, an “apparent hydrocarbon odor” was noted at varying depths in 11 of the 15 boring locations. The hydrocarbon odor was reported at locations throughout the Project Corridor at various depths ranging from 0.3 to 14.5 feet below grade. No analytical soil samples were collected during the geotechnical investigation. Groundwater was encountered at 14 feet below grade at boring B-1, located at the south end of the Project Corridor near Bridge 62J17, and at boring B-12, located at the north end of the Project Corridor at County Road E. Groundwater was not encountered in the other borings. 2020 Memo Todd Blomstrom, the City of Arden Hills Public Works Director and City Engineer, prepared a memo in response to WSB’s request for historical material spills, tanks, response calls, or hazardous material releases at the Project Corridor or adjacent sites. City staff had no recollection of any spills or releases at the Project Corridor. The following additional information was provided in the 2020 Memo: · According to water main record plans dated 1968 and 1969, an 8-inch high pressure natural gas pipeline historically extended along the east side of Old Snelling Avenue from TH-51 to County Road E. This pipeline was believed to have been replaced in 2018. · An abandoned petroleum pipeline was discovered along Round Lake Road south of Ramsey County Road 96 several years ago. Based on the information provided, the pipeline was located approximately two miles northwest of the Project Corridor and is not assumed to be located at or adjacent to the Project Corridor.