_DEIR - Laserfiche WebLink

City of Pleasanton—Hidden Canyon Residences and Preserve Biological Resources Draft EIR 3.3-2 FirstCarbon Solutions https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480016/EIR/3 - Draft EIR/21480016 Sec03-03 Bio Resources.docx Oak woodland habitat characterizes the area with coast live oak trees predominating. Other tree species include California bay, big-leaf maple, valley oak, and elderberry, in addition to ornamental and fruit trees in residential areas. A total of 208 individual trees over 6 inches in diameter were observed on the project site during the 2020 Tree Report. The report documented 23 distinct tree species and identified 95 Heritage Trees. While all trees exceeding 6 inches in diameter were surveyed, only those meeting the criteria for Heritage Trees are protected under the City’s Tree Protection Ordinance. Given that tree growth rates typically slow with age, it is unlikely that additional trees have reached Heritage Tree status since the 2020 report. Soils, Topography, and Hydrology Seven soil types from five soil series—Clear Lake, Diablo, Los Gatos, Los Osos, and Millsholm—were identified on the project site. Of the five soil series, Clear Lake and Diablo soils are considered hydric. Hydric soils are soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part. Under sufficiently wet conditions, they support the growth and regeneration of hydrophytic vegetation, and seasonal wetlands do occur on Diablo soils in the northern portion of the project site. Clear Lake and Diablo soils make up a large portion of the site. The other soil types are not considered hydric, although hydric inclusions may occur. Diablo soils are mildly alkaline, and populations of Congdon’s tarplant occur predominantly on this soil type on the project site; however, other soils of the site are not known to support edaphic conditions for special-status plant species (i.e., the soils of the remainder of the site are neither serpentine nor alkaline). The project site ranges in elevation from approximately 440 feet National Geodetic Vertical Datum (NGVD) at the east end of the site to approximately 730 feet NGVD in the west end of the site. The project site consists of rangelands with Devaney Creek and its tributary running through it and a small, developed area. Seasonal wetlands occur in the northeastern portion of the property. Average annual rainfall is approximately 16 inches, most of which falls between October and April. Stormwater runoff readily infiltrates the site’s soils; when field capacity has been reached, gravitational water drains into the seasonal drainages and the creek on-site as shallow groundwater or as surface sheet flow, which then flows into Devaney Creek on the opposite side of Dublin Canyon Road. Vegetation Five biotic habitats were identified on the 128.5-acre development site and open space, including California annual grassland, mixed riparian woodland, oak woodland, chaparral, and seasonal wetland (Exhibit 3.3-1). Each of these habitats are described below. In addition to biotic habitats, the eastern corner of the project site is developed with homes and outbuildings. A comprehensive list of plant species observed can be found within the Biological Evaluation in Appendix C.