XCG was contracted to complete a Phase I ESA for a downtown Edmonton office tower that shares a three storey underground parking garage with the adjacent property. The client had the intention of purchasing the adjacent property, but the owner would not allow any due diligence investigations (i.e. Phase I ESA, Phase II ESA) to be conducted on it. Therefore, all investigations were required to be completed on the subject property or the adjacent City of Edmonton property in order to characterize the site.
The Phase I ESA conducted by XCG revealed the historical presence of a retail fuel outlet (RFO) adjacent to the property, within the footprint of the existing parking garage. XCG was then contracted to complete a Phase II ESA on the client’s property, to further investigate the historical presence of the RFO on the adjacent property. Since the footprint of the underground parking garage includes a portion of the adjacent property, a boundary survey was conducted to determine the location of the property line within the parking garage to ensure all investigative activities were conducted on the client’s property only.
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The Phase II ESA investigation was proposed to include the advancement of three boreholes with the installation of monitoring wells within the underground parking garage area adjacent to the property line, to facilitate the collection of soil and groundwater samples for chemical analysis for PHCs, BTEX, and lead. Due to competent hard till encountered in the subsurface, the drill rig was unable to achieve the proposed depths necessary to facilitate monitoring well installation and groundwater sampling. However, from the soil samples that were collected from these shallow boreholes, the concentrations of BTEX exceeded the Alberta Tier 1 Soil Remediation Guidelines and strong olfactory odours resembling weathered gasoline as well as elevated soil vapour concentrations were detected in the boreholes.
Due to low overhead clearance in the parkade and the competence of the till layer beneath the slab of the parkade, an alternative drill rig that would be both capable of accessing the parkade and providing enough power and torque to reach the desired depth to facilitate groundwater monitoring well installation was not available. It was then recommended to conduct a Supplemental Phase II ESA with a drilling program at street level.
Due to the presence of the underground parking garage and buried underground utilities at the site, the street level drilling program was required to be conducted on the City of Edmonton property adjacent to the subject site and adjacent property along the sidewalks located to the west and south. This required procuring all necessary permits required to drill and install monitoring wells on the City of Edmonton property, including a Utility Line Assignment (ULA) permit and an On-Street Construction and Maintenance (OSCAM) permit. All permits required safety and/or traffic control requirements and reporting requirements.
Based on the results of the Supplemental Phase II ESA, as well as the Phase I ESA and Phase II ESA, all completed by XCG, it was concluded that the likely source of PHC impacts found in both soil and groundwater from the investigations is the former RFO historically located adjacent to the subject property boundary.
This information obtained will be used in the negotiation of the purchase and sale agreement between both parties.