Targus was retained to perform an environmental site assessment (Phase I ESA and additional non-ASTM services) of three commercial buildings located in the West End historic district in downtown Dallas. Two of the buildings were constructed in the early 1900s. The third building was a parking garage with a retail ground floor occupied by a charter school.
No recognized environmental conditions associated with the historic buildings were identified. However, prior uses of the parking garage parcel had included a dry cleaner, filling/ service station, manufacturing facilities, automotive repairs, and printing operations. To evaluate potential impacts to the ground floor retail (school) beneath the parking garage, Targus conducted soil and groundwater sampling and analysis. Soil borings converted to groundwater monitoring wells were installed at exterior perimeter locations based on accessibility. The drilling was performed after hours in walkways due to tenant and traffic considerations. Trichloroethylene (TCE) was detected in one of the soil samples and in three of four groundwater samples at concentrations below the Texas Commission on Environmental Quality (TCEQ) Texas Risk Reduction Program (TRRP) Tier 1 Protective Concentration Levels (PCLs).
A passive sub-slab ventilation system had been installed by others beneath the retail space (school) to mitigate volatile organic compounds (VOCs), including TCE, detected in soil vapor during previous testing. To assess potential vapor intrusion and indoor occupant exposures, Targus conducted an after-hours indoor air sampling event. Several VOCs were detected, but concentrations were generally consistent with VOC concentrations in sampled ambient air and were below Texas Risk Based Exposure Limits (RBELs). Targus concluded that the collective vapor mitigation measures appeared to remain effective in keeping chemical concentrations below risk-based comparison values. The VOCs were considered to be a controlled recognized environmental condition. The groundwater monitoring wells and investigation-derived waste were removed in accordance with applicable regulations and the client closed this transaction.