Laserfiche WebLink
Phase II Subsurface Investigation <br /> Tracy Comers Shopping Center <br /> 3225 North Tracy Boulevard <br /> Tracy,California 95376 <br /> Partner Project Number P14-129814.2 <br /> December 19,2014 <br /> Page 16 <br /> samples SG1 through SG4 due to high concentrations of analytes. As a result, reporting limits were <br /> elevated for cis-1,2-DCE,trans-1,2 DCE,and vinyl chloride above the applicable indoor air screening levels. <br /> Discussion <br /> Partner conducted a Phase II Investigation at the Quality Cleaners unit in the Tracy Corners Shopping <br /> Center to investigate the potential impact of PCE and related CVOCs in sub-slab soil gas as a consequence <br /> a potential release or releases from the dry cleaning facility. The scope of the Phase II Investigation <br /> included the installation of four sub-slab soil gas probe samples and analysis of four samples and one <br /> duplicate sample for PCE,TCE,cis-1,2-DCE,trans-1,2-DCE,and vinyl chloride. <br /> PCE was detected in all four soil gas sample and one duplicate sample. Soil gas concentrations were <br /> converted into theoretical indoor air concentrations using the DTSC recommended attenuation factor. <br /> Applying the applicable DTSC foundation attenuation factor of 0.05 results in a calculated theoretical <br /> indoor air concentration of 165 pg/m3 of PCE and 17.5 pg/m3 of TCE. The conversion resulted in indoor <br /> air concentrations above the DTSC recommended value for PCE of 2.08 pg/m3 at four locations and above <br /> the EPA RSL for TCE of 3.0 pg/main one location (SG3). <br /> The comparatively low PCE concentrations in soil gas and the presence of TCE suggest that the solvent <br /> release is relatively old and that natural attenuation is occurring. <br /> Due to the presence of PCE and TCE in sub slab soil gas samples, Partner recommends soil and <br /> groundwater sampling to delineate the PCE and TCE impacted media at the subject property. <br /> Summary and Conclusions <br /> Partner conducted a Phase II Subsurface Investigation at the subject property to investigate the potential <br /> impact of CVOCs in soil gas as a consequence of a potential release or releases from dry cleaning <br /> operations. The scope of the Phase II Subsurface Investigation included the installation of four sub-slab <br /> soil gas probes. Four soil gas samples and one duplicate sample were analyzed for PCE,TCE, cis-1,2 DCE, <br /> trans-1,2 DCE,and vinyl chloride. <br /> Material encountered below the concrete floor of the dry cleaning unit consisted of silty sand. <br /> Based on the field observations and analysis of soil gas samples there is evidence (detection of PCE and <br /> TCE)that constituents have migrated below the concrete slab of the dry cleaning facility. <br /> Conversion of PCE and TCE concentrations into theoretical indoor air concentrations indicated that <br /> regulatory criteria are exceeded. Based on these findings, there appears to be a discernible vapor <br /> intrusion condition. <br /> Based on the subsurface investigation, there is evidence of a release of hazardous materials from the <br /> subject property and Partner recommends further investigation with respect to the dry cleaning facility at <br /> this time. <br /> PARTNER <br />