WORK PLANS - Laserfiche WebLink

Home Browse Search

PCE was detected in sub-slab soil gas at concentrations exceeding the applicable regulatory screening criteria. The source of the impacts is likely related to the former on-site dry cleaning facility. The regulatory exceedances indicate evidence of a release and represent a potential concern to human health and/or the environment. As such, Partner recommended additional investigation to further evaluate the identified subsurface impacts and potential vapor intrusion concern. 2.3 Geology and Hydrogeology Review of the United States Geological Survey (USGS) Lodi North, California Quadrangle topographic map indicates the subject property is situated approximately 50 feet above mean sea level, and the local topography is sloping gently to the southwest. Refer to Figure 2 for a topographic map of the site vicinity. The subject property is situated within the Great Valley Geomorphic Province of California.The Great Valley is comprised of pre-Tertiary igneous and metamorphic rocks. The Coastal Ranges, to the west, are comprised of pre-Tertiary and Tertiary semi-consolidated to consolidated marine sedimentary rocks. The geologic formations within San Joaquin County vary in origination in geologic times ranging from Recent to Pre-Cretaceous. Six to ten miles of sediment have been deposited within the Central Valley and include both marine and continental gravels, sands, silts and clays. During the middle Cretaceous (-100 million years ago), parts of the Great Valley were inundated by the Pacific Ocean resulting in deposition of marine deposits. Marine conditions persisted through the middle Tertiary period after which time sedimentation changed from marine to continental. The material source for the continental deposits is the Coastal Ranges and Sierra Nevada which are composed primarily of granite, related plutonic rocks, and metasedimentary and metavolcanic rocks from Late Jurassic to Ordovician age. Based on borings advanced during this investigation, the underlying subsurface consisted of a varying combination of sandy silt and silt from the ground surface to approximately 30 feet below ground surface (bgs). From 31 to 40 feet bgs, the subsurface consisted predominantly of medium- to coarse-grained sand. Groundwater was encountered during this investigation between 36.1 and 36.7 feet bgs. Refer to Appendix A for boring logs from this investigation. Additional Subsurface Investigation Report PARTNER Project No.23-400162.14 July 31,2023 Page 3