ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Dune Sand Much of the area surrounding the city of Manteca is covered by Holocene-age(10,000 years old or younger) Dune Sand deposits (Wagner,Bortugno, and McJunkin 1991). Inland dunes usually exist in the form of ridges, small hills, and knolls found on ancestral lake beds and outwash plains. Modesto Formation Piper et al. (1939)were the first to publish detailed geologic maps in the southern Sacramento/northern San Joaquin Valley areas, and they designated the older alluvial Pleistocene deposits as the Victor Formation. However, in 1959,Davis and Hall proposed a subdivision of the Victor Formation into the Turlock Lake(oldest), Riverbank(middle), and Modesto(youngest)Formations. The type section of Modesto was designated along the south bluff of the Tuolumne River south of Modesto.Marchand and Allwardt(198 1)proposed that the name Victor Formation be abandoned and that the Turlock Lake,Riverbank, and Modesto Formations be adopted as formal nomenclature for Quaternary deposits in the Sacramento and San Joaquin Valleys. Most later researchers have followed this recommendation. In the San Joaquin Valley and in the project area in particular,the Modesto Formation forms alluvial fans of the Stanislaus River and can be divided into upper and lower members.Researchers differ as to the age of this formation: Marchand and Allwardt(198 1)place the age between approximately 12,000 and 42,000 years B.P.; Atwater(1982)places the age from 9,000 to 73,000 years B.P.,while Helley and Harwood(1985)follow Marchand and Allwardt's dating scheme. The upper member is composed primarily of unconsolidated,unweathered,coarse sand and sandy silt.The lower member of the Modesto Formation is composed of consolidated, slightly weathered, well-sorted silt and fine sand, silty sand, and sandy silt. The Modesto Formation is underlain by various rock units reflecting the changing nature of depositional sediments, from alluvial fan to lacustrine to marine,including the Riverbank Formation(mid-Pleistocene),the Turlock Lake Formation(early Pleistocene),the Corcoran Clay(early Pleistocene),the Tulare Formation(Plio- Pleistocene), and the San Joaquin Formation(late Pliocene). PALEONTOLOGICAL RESOURCE INVENTORY METHODS A stratigraphic inventory and paleontological resource inventory were completed to develop a baseline paleontological resource inventory of the project area by rock unit,and to assess the potential paleontological productivity of each rock unit. Research methods included a review of published and unpublished literature, and complied with Society of Vertebrate Paleontology(1995)guidelines. Stratigraphic Inventory Geologic maps and reports covering the geology of the surrounding study area were reviewed to determine the exposed rock units and to delineate their respective distributions in the project study area. Paleontological Resource Inventory Published and unpublished geological and paleontological literature was reviewed to document the number and locations of previously recorded fossil sites from rock units exposed in and near the proposed project area and the surrounding region,as well as the types of fossil remains each rock unit has produced. The literature review was supplemented by an archival search conducted at the University of California Museum of Paleontology(UCMP) in Berkeley, California, on March 8, 2007. EDAW Manteca WQCF and Collection System Master Plans EIR Paleontological Resources 4.8-2 City of Manteca