Affected Environment
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CHAPTER 3: AFFECTED ENVIRONMENT INTRODUCTION This chapter describes the project area’s natural, social, and economic environments, with particular emphasis on those elements that could be affected by the project under consideration. Such descriptions not only provide greater insight into the issue areas of concern, they also establish a baseline against which potential impacts of the alternatives can be compared. The following sections focus on the current status of each element and any trends that may be evident. The environmental resources and topics discussed in this chapter are the same and presented in the same order as in Chapter 4—Environmental Consequences. AC34 America’s Cup / Environmental Assessment 3-1 AFFECTED ENVIRONMENT This page intentionally left blank 3-2 AC34 America’s Cup / Environmental Assessment Geology, Soils and Seismicity 3.1 GEOLOGY, SOILS AND SEISMICITY This section provides a summary of geologic resources that are known or might be present in the vicinity of the proposed 34th America's Cup (AC34) project and could be affected by (or have an effect on) the various events or structural components associated with the project. As used by the National Park Service (NPS), the term “geologic resources” refers to both geologic features and geologic processes. Geologic features include unique, exemplary, or outstanding rock outcrops, erosional formations, or landscapes that represent a significant public recreational or aesthetic attraction or that offer significant scientific or educational value. Geologic processes are the natural, physical, and chemical forces that act within natural systems and on human developments across a broad spectrum of space and time. Such processes include, but are not limited to, weathering, erosion and sediment transport, glaciation, karst processes, shoreline processes, and seismic and volcanic activity. As defined here, fossils and fossil-containing formations would also be considered a geologic feature; however, paleontological resources are dismissed from further consideration in Chapter 1. Sediment transport is also a geologic process; however, impacts of sedimentation and dredging are discussed in Section 4.2, Hydrology and Water Quality. The affected environment relevant to the proposed AC34 project is described in terms of the general geologic setting, specific geologic and soil resources, and natural hazards that might affect or be affected by the AC34 events. Where necessary, the affected environment is described individually for each of the AC34 sites within federally managed lands, or for AC34 activities or actions requiring federal approvals. The study area associated with geology and soils impacts would be all landside federal lands upon which AC34 venues have been proposed or that would likely serve as secondary race viewing locations. This section focuses on locations in the study area where facilities would be built, and that are likely to receive a large amount of foot traffic, either at established AC34 spectator venues or at secondary viewing locations. 3.1.1 Regional Geologic Setting San Francisco is located in the northern portion of the San Francisco peninsula, which is part of the geologically complex California Coast Ranges geomorphic province (Norris and Webb 1990). The Coast Ranges province is characterized by a series of northwest-trending ridges and valleys that run roughly parallel to the San Andreas fault zone and can be further divided into the northern and southern ranges that are separated by San Francisco Bay. San Francisco Bay lies within a broad depression created from an east-west expansion between the San Andreas and the Hayward fault systems. The San Andreas fault, the Hayward fault, and associated subsidiary faults are indicators of the tectonic forces that that characterize the margin between the Pacific Plate and the North American Plate, where the Pacific Plate slowly creeps northward past the North American Plate. The Bay and northern portion of the San Francisco peninsula are within a structural down-dropped block between the northern Santa Cruz Mountains to the west and Diablo Mountain Range to the east. Much of the Coast Range province is composed of sedimentary deposits and volcanic rocks, including dune sands at Crissy Field, artificial fill at SAFR, and older, stiffer Franciscan bedrock made up of sandstones, chert, greenstone, greywake and shale that underlie hillsides likely to be used as secondary viewing areas. AC34 America’s Cup / Environmental Assessment 3.1-1 AFFECTED ENVIRONMENT 3.1.2 Geologic Features and Soil Resources The following description of geologic and soil resources is derived from the NPS Geologic Resources Inventory (GRI) program and the NPS Soil Resources Inventory (SRI), which seek to evaluate the geologic resources of all national park units designated as having significant natural resources (NPS 2009, NPS 2011). Geographic information systems (GIS) data related to the Golden Gate National Recreation Area (GGNRA), as well as Point Reyes National Seashore and Fort Point National Historic Site, were reviewed to describe the geologic and soil setting of the AC34 project. The following geologic and soil units are considered a geologic resource as defined above, based on their relative rarity, sensitivity to disturbance, and ability to support rare and endangered plant species (NPS 2009; NPS 2011; Elder 2001; Presidio Trust 2002): Serpentinite rock and serpentine soil Colma Formation and other coastal sand dunes Wetland soils (hydric soils) None of the soil units in the study area, as mapped by the Natural Resources Conservation Service (NRCS), are characterized as hydric soils (soils formed under conditions of saturation, flooding, or ponding), which are important in supporting unique wetland vegetation (NPS 2011). However, some constructed wetlands do exist in the study area, as further described below. Each of the AC34 locations analyzed in this EA, and the sensitive geologic and soil resources they contain, are further described below. 3.1.2.1 Crissy Field Crissy Field is a former military airfield that was part of the United States Army base at the Presidio (described below) and became part of the GGNRA in the 1990s. Crissy Field has undergone a major habitat restoration that included the conversion of approximately 22 acres of former airstrips into a tidal marsh with interpretive paths. Geologic mapping of the region identifies the flat portions of Crissy Field as being underlain by a mixture of artificial fills and beach sand (NPS 2009). Further, the Natural Resources Conservation Service has mapped Crissy Field as being primarily underlain by “urban land” and “orthents” soil units (NPS 2011). Orthents are soils that lack horizon development due to either steep slopes or parent materials that contain no permanent weatherable minerals. Typically, Orthents are exceedingly shallow soils. These soils are generalized map units representing disturbed areas or soil units that for other reasons have not developed natural soil horizons or distinct organic topsoil. Neither of these soil units is defined as hydric soils, although recent restoration of the tidal marsh has supported and continues to support the development of wetland vegetation communities. The heavily vegetated bluffs located between Crissy Field and Doyle Drive are underlain by the Colma Formation and Younger Dune Sands to the east and serpentine rocks of the Franciscan Complex to the west (NPS 2009). 3.1-2 AC34 America’s Cup / Environmental Assessment Geology, Soils and Seismicity 3.1.2.2 The Presidio The Presidio is situated at the southern base of the Golden Gate Bridge, along San Francisco’s northern shoreline. The Presidio is a former United States Army post and was one of the oldest continuously operating military posts in the nation until it was transferred to civilian use in 1994. The Presidio’s coastal bluffs are arguably one of the last undeveloped areas left in San Francisco. The Presidio Trust Management Plan (PTMP) states that “the Presidio contains some fragile geologic resources, including the Colma Formation dunes, and the serpentine outcrops and bluffs at Inspiration Point and south of Crissy Field” (Presidio Trust 2002). Eight of the 12 rare plants found at the Presidio—including the federally endangered Presidio clarkia and Raven’s manzanita, the latter of which is represented by a single plant—grow on serpentinite. Some species are confined to just one or a few outcrop areas. The northern edge of the Presidio, from the Golden Gate Bridge and Fort Point east to Battery East and in the vicinity of Lincoln Boulevard, contains bluff-top locations that offer several prime locations for elevated, panoramic views of Central San Francisco Bay. These locations include the Crissy Field overlook on Lincoln Boulevard, Inspiration Point, the Bay Trail, and Battery East (see Section 3.9, Visual Resources). These areas are mapped as containing a combination of artificial fills, slope and ravine debris, undifferentiated surficial deposits, and serpentine rocks (NPS 2009). Soils in the area mapped as “rock outcrop-orthents” reflect the underlying slope-forming serpentine rock of the northern Presidio (NPS 2011). The serpenitine rock is mapped between Lincoln Boulevard and Mason Street, and also along sloped areas paralleling the northwestern end of Crissy Field Avenue, all of Long Avenue, and the southern half of Marine Drive. Serpentine rock also underlies the sloped areas south of Fort Point and North of the Golden Gate Bridge