Client: Northwest New Mexico Council of Governments (NWNMCOG)
Location: Gallup, New Mexico, USA
Challenge. Investigate and mitigate recognized environmental conditions (RECs) to allow reuse of property as a mixed-use residential and retail development
Solution. INTERA conducted a Phase II ESA and provided remedial planning under the NWNMCOG Coalition Brownfields Assessment Grant at a lot located near the intersection of Coal Avenue and Puerco Drive (Coal & Puerco Site). Community Area Resource Enterprise 66 proposed to redevelop the site by constructing a mixed-use residential/retail development. While the property is primarily a vacant and undeveloped plot of land, it also includes a two-story building—the former Liberty Hotel. The property was also formerly used by a number of radio, refrigeration, and auto body service and supply companies. To address the RECs identified during a Phase I ESA, we performed a Phase II assessment that included preparing a Quality Assurance Project Plan (QAPP) Addendum (since the project was federally-funded) that integrated the conceptual site model and sampling and analysis plan (SAP). Potential contaminants of concern at the Coal & Puerco Site included volatile organic compounds, petroleum hydrocarbons, and heavy metals. INTERA’s Phase II ESA field activities included a geophysical survey, soil boring and sampling, and installing and sampling four monitoring wells. Our Phase II ESA activities identified perchloroethylene (PCE) in groundwater and soil vapor beneath the site. A passive soil gas survey was performed to determine if the source of the PERC was on- or off-site. As part of the Phase II ESA, INTERA also worked with the NWNMCOG and the New Mexico Environment Department to develop a plan for protecting the proposed development and to investigate impacts to groundwater in the immediate area. The distribution of the PCE in groundwater and the results of the passive soil gas survey were used to conclude that a dry-cleaning facility, located immediately to the north of the property, was the source of PCE. To address this issue, INTERA developed a conceptual plan for preventing soil vapor from negatively impacting the indoor air quality of the new building being planned as part of the site redevelopment. Based on the results of the Phase II ESA, we recommended that a subsurface vapor ventilation system be installed around the Liberty Hotel to mitigate the accumulation of harmful vapors within the building, a synthetic barrier and soil venting system be installed for any future structures on the property to protect against soil vapor intrusion, and further investigation activities be performed to delineate PERC in groundwater in the area northwest of the Coal & Puerco Site. INTERA subsequently worked with NMED and the responsible party (a dry-cleaner owner/operator) to determine the vertical and lateral extent of the PCE groundwater plume and evaluate long-term remedial options.