Planning Commission Supplemental Materials 11-12-25 (2)

CULTURAL RESOURCES SURVEY REPORT 4400 Black Ave 14 ARCHAEOLOGICAL SENSITIVITY ASSESSMENT NATIVE AMERICAN ARCHAEOLOGICAL SENSITIVITY Based on an evaluation of the environmental setting and features associated with known sites, Native American resources in this part of Alameda County have been found on the banks and mid-slope terraces above seasonal and perennial waterways within the Amador Valley and within Holocene-age landforms. The soil in the project area consists of Holocene alluvial fan deposits, classified by the USDA as Sycamore silt loam with slopes of 0 to 2 percent. It is a silty alluvium derived from sedimentary rock found on fans and flood-plain steps (Witter et al. 2006; USDA 2023). The project area is on gently sloped, Holocene-era soils near a major freshwater source, the Arroyo del Valle. These factors usually indicate an area sensitive to buried Native American resources. However, the project area was at the edge of the Pleasanton marsh complex rather than on banks or mid-slope terraces, suggesting it was potentially covered with swamp or standing water during part of the year or that these ecological zones were close by, which would make it a less attractive place to live. This historical ecology data suggesting the area was not desirable for habitation is supported by the lack of known prehistoric Native American sites within ¼ mile of the project area. Therefore, the project area has a low sensitivity for buried Native American archaeological resources. HISTORIC-PERIOD ARCHAEOLOGICAL SENSITIVITY Several factors can be used to infer an area’s sensitivity for buried historic-era archaeological resources (Caltrans 2007). These include surface scatters of artifacts, documentary sources (historical maps, deeds, or photographs), standing buildings or structures that suggest patterns of land use (homes, barns, ponds, fences, industrial facilities), and ecological or landscape features (steep hills, bodies of water, wetlands). During the Mission and Rancho periods, the Amador-Livermore Valley was mainly used to raise cattle (Hoover et al. 1966). During the Rancho period, one of the rancho owners, Juan Pablo Bernal, built an adobe house near the project area in the 1850s. Examination of the 1862 and 1983 survey plats and the records of the land grant cases suggest the house was likely located approximately 350-400 feet southwest of the project area under the current Amador Valley High School sports fields. Unfortunately, there is no surviving record of the size of the adobe nor descriptions of outbuildings that might have been present (Dyer 1862; Healy 1863; Hendry and Bowman 1940:633-634). By 1878, the project area was part of 1167 acres owned by Joseph F. Black. The 1878 map by Thompson and West shows a structure and garden near the project area, but it appears to have been located to the south on the property of Amador Valley High School and south of the Bernal Adobe. After, Black’s death, the project area was used by E.R. Lilienthal for hop cultivation until 1912 (MacLennan 2014:46- 47). Aerial photographs and topographic maps from the 20th century show the project area remained undeveloped through the mid-1960s (USGS 1906; Fairchild Aerial Surveys 1939; USGS 1941; USGS 1953; Cartwright Aerial Survey 1965). The project area, therefore, is moderately sensitive for historic era resources, as auxiliary structures associated with the Bernal Adobe may have been located in the project area, but we lack the historical records to make a definitive determination.