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Chapter 3
Affected Environment
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Introduction

This chapter presents a description of resource topics analyzed in this environmental assessment and baseline (or existing) conditions under each resource topic. Topics were selected for environmental analysis based on federal law, regulations, and executive orders; National Park Service management policies; and concerns expressed by the public, park staff, or other agencies during the public scoping process. A short rationale for the inclusion of each topic is discussed below in the Topics Considered in this Environmental Assessment section. Topics that were dismissed from further analysis in this environmental assessment are discussed at the end of this chapter.

Resource topics are described in relation to two geographical areas that could be affected by the alternatives: regional setting and local setting. The regional setting in this environmental assessment is Yosemite Valley, which is the geographic basis for the cumulative impacts analyses in Chapter 4, Environmental Consequences. An analysis of the Lower Yosemite Fall Project in a larger regional context is found in the Yosemite Valley Plan. The local setting encompasses 56 acres (referred to as the Lower Yosemite Fall area in this environmental assessment). The actual construction work for trails, bridges, and other facilities would be performed within the local setting.

Regional Setting – Yosemite Valley

Yosemite National Park lies on the western slope of the Sierra Nevada range in central California between the San Joaquin Valley to the west and the Great Basin to the east. Yosemite Valley was cut and sculpted by the downslope movement of glaciers, forming the Valley about 1 million years ago. After the last glacier left the Valley about 15,000 years ago, a lake referred to as Lake Yosemite was formed behind the materials deposited by the glaciers at about 4,000 feet in elevation. Glacial and stream sediment underlies the floor of Yosemite Valley to a depth of over 1,000 feet (Huber 1989).

Local Setting – Lower Yosemite Fall Area

The Lower Yosemite Fall area is situated in Yosemite National Park at the north side of the Yosemite Valley at the base of Lower Yosemite Fall (see figure 1-1). The area is bounded on the southwest by Yosemite Lodge, on the east by Yosemite Village, on the south by Northside Drive, on the north side by the Valley wall, and to the west by talus (an accumulated mass of rock fragments lying at the base of a steep slope). (For some resource topics discussed in this environmental assessment [such as noise, air quality, scenic, and wildlife], the local setting may extend beyond the boundaries shown on figures 2-1 through 2-3.) The Lower Yosemite Fall area, which extends up Yosemite Creek from Northside Drive to a point just beyond Yosemite Falls bridge (see figure 2-1), consists of approximately 56 acres of primarily braided stream channels and mixed conifer forest with pockets of riparian and oak woodland plant communities. The alluvial fan (sediment fanning out at the base of Lower Yosemite Fall) of Yosemite Creek dominates the upstream local setting, while the lower portion consists of meandering seasonal stream channels dominated by a dense forest canopy. Currently, the Lower Yosemite Fall area includes a parking area (for private vehicles and tour buses), a shuttle bus stop, a restroom, and a series of trails and bridges that provide access close to the base of Lower Yosemite Fall and views of both the Upper and Lower Yosemite Falls.

Throughout this environmental assessment, the environmental analysis will focus on the impacts of actions within the Lower Yosemite Fall area for the resource topics presented in this chapter.

Topics Considered in this Environmental Assessment

The federal and state Endangered Species Acts (and associated legislation), Clean Water Act, Clean Air Act, and National Environmental Policy Act (NEPA) require that the effects of any federal undertaking on natural resources be examined. In addition, the National Park Service management policies and natural resource management guidelines call for the consideration of natural resources in planning proposals. Significant natural resources, such as special-status species, exist within the park and could be affected to varying degrees by implementation of the alternatives.

The Lower Yosemite Fall area is located at the north edge of Yosemite Valley, at the base of Yosemite Falls within Yosemite National Park—an area of abundant natural resources. It is therefore necessary to characterize these natural resources and the environmental consequences to these resources that would result from implementation of Lower Yosemite Fall Project alternatives.

Analysis was performed for the following natural resource topics:

• Wetlands
  
• Geology, Geologic Hazards, and Soils
  
• Hydrology and Water Quality
  
• Floodplains
  
• Vegetation
  
• Wildlife
  
• Special-Status Species
  
• Air Quality
  
• Noise

The National Historic Preservation Act, the Archeological Resources Protection Act, the Native American Graves Protection and Repatriation Act, and NEPA require that the effects of any federal undertaking on cultural resources be examined. In addition, National Park Service management policies and cultural resource management guidelines call for the consideration of cultural resources and Native American consultation in planning proposals. The Lower Yosemite Fall area contains cultural resources and is a contributing element within the Yosemite Valley Cultural Landscape.

Analysis was performed for the following cultural resource topics:

• Archeological Resources
  
• Ethnographic Resources
  
• Cultural Landscape Resources, including Historic Sites and Structures

Analysis of social resources examines the effects of the Lower Yosemite Fall Project on the social environment in Yosemite Valley. The park’s scenic resources are a major component of the park visitor’s experience. Conserving the scenery is a crucial component of the National Park Service 1916 Organic Act and the park’s enabling legislation. Stewardship of Yosemite National Park requires consideration of two integrated purposes: to preserve Yosemite’s unique natural and cultural resources and scenic beauty, and to make these resources available to visitors for study, enjoyment, and recreation.

Analysis was performed for the following social resource topics:

• Scenic Resources
  
• Visitor Experience
  
• Park Operations and Facilities
  
• Recreation
  
• Transportation
  
• Energy Consumption

Wetlands are transitional areas between terrestrial and aquatic ecosystems, where water is usually at or near the surface or the land is covered by shallow water. Wetlands have many distinguishing features, the most notable of which are unique soils, saturated for at least part of the year, and vegetation adapted to or tolerant of saturated soils. Wetlands are considered highly valued resources because they perform a variety of hydrological and ecological functions vital to ecosystem integrity.

In August 2001, a wetland survey of the Lower Yosemite Fall area was performed to delineate and identify wetlands that could be affected by proposed improvements to bridges and trails in the Lower Yosemite Fall area. The survey classified and delineated two types of wetlands: Cowardin wetlands and "jurisdictional" wetlands (Jones & Stokes 2001).

The Cowardin system is used as the basis for wetland classification and protection by the National Park Service. The Cowardin system classifies wetlands based on the type of vegetative cover and lifeform, flooding regime, and substrate material. Jurisdictional wetlands are delineated and classified to meet regulations of Section 404 of the Clean Water Act (U.S. Army Corps of Engineers 1987). Cowardin wetlands include jurisdictional wetlands, but may also include certain non-vegetated sites and sites lacking soil, if they meet specific criteria.

One small area of approximately 126 square meters (0.03 acre) was identified as a jurisdictional wetland at Bridge #5. This wetland is on a gravel bar within the ordinary high water mark of the stream channel and is classified as a palustrine emergent wetland. Vegetation is sparse in this wetland, and it is flooded during high water periods. The upland boundary of the wetland was clearly evident to the wetland surveyors by the change in vegetation.

In addition to a small jurisdictional wetland delineated near Bridge #5, all drainages within the Lower Yosemite Fall area are classified as Cowardin wetlands (U.S. Fish and Wildlife Service 1979). These drainages, within the beds of the braided creek channels, have a nonsoil substrate that is saturated and/or covered by shallow water at some time during the growing season. These wetlands are typically narrow, encompassing the bottom portion of the creek beds. Very little wetland vegetation is found in these areas because of the intermittent nature of the flows within the creek channels.

The distinguishing geologic feature of the Lower Yosemite Fall area is a gently sloping (4% grade), active alluvial fan (sediment deposited at the base of the Lower Yosemite Fall) that extends from the base of Lower Yosemite Fall to the Valley floor. Sheer granite cliffs and associated talus slopes and boulders bound the fan to the north and east. Covering approximately 74 acres, the talus-alluvial slope ranges in elevation from approximately 4,000 feet above mean sea level at the north end to 3,950 feet msl near Northside Drive. Rock materials comprising the alluvium (heaped rock fragments and sediment) are composed almost entirely of granite ranging in size from fine sand to boulders, deposited through ancient glacial activity, rockfall events, and hydrologic processes. The flow of water through Yosemite Creek is responsible for transporting, depositing, and shaping the rock materials into the complex alluvial fan visible today.

Weathering processes break down talus to smaller particles that are transported by water and eventually become deposited in alluvial fans or in stream channels. The surface soil in Yosemite Valley consists primarily of granitic soils in various stages of decomposition. Generally, the rock material varies in size depending on its location on the alluvial fan. Materials closer to the sheer cliffs that have not undergone mechanical weathering processes or transportation by water are large boulders that range from a few feet to several feet across. This material makes up the narrow channel at the base of Lower Yosemite Fall and the upper portion of the alluvial fan. Sizes of the rock material decrease down-fan to the south and east. The southern and eastern margins of the alluvial fan consist of finer-grained material and support a larger variety of vegetation. These areas have an established soil horizon composed of fine-grained sand and silts. (A soil horizon is a layer of soil, approximately parallel to the soil surface, with characteristics produced by soil-forming processes.) Finer-grained soil erodes more readily than soil containing quantities of cobbles and boulders. Erosion of the finer-grained sandy soils occurs along unpaved trails with heavy foot traffic and along unprotected stream banks.

Subsurface materials are consistent with those expected in an alluvial fan produced by weathering and transport of rockfall talus. Previous geophysical subsurface exploration using ground-penetrating radar and seismic refraction determined that four definable layers occur within the first 50 feet of the subsurface (Treadwell and Rollo 1998). The uppermost layer is described as loose, unconsolidated soil and boulders. A denser layer of cobbles, boulders, and soil underlies the surface layer. The third layer consists of decomposed or weathered granite. The fourth and deepest layer consists of less weathered, more intact granite. The depths and thickness of these layers vary depending on the location of the alluvial fan.

Geologic hazards associated with forces such as earthquakes and rockfalls present potentially harmful conditions to visitors, personnel, and facilities in Yosemite National Park, although the Sierra Nevada range in Yosemite National Park is not considered an area of particularly high seismic activity. No active or potentially active earthquake faults have been identified in the mountain region of Yosemite National Park (Hart 1990). The park can undergo seismic shaking associated with earthquakes on fault zones to the east and west margins of the Sierra Nevada range, as has occurred in the past. These fault zones include the Foothills fault zone, the volcanically active area in the Mono Craters – Long Valley Caldera area, and along the various faults within the Owens Valley fault zone (California Division of Mines and Geology 1996).

Although earthquakes felt by people in Yosemite National Park are relatively infrequent, they have occurred in the past and are likely to occur in the future. The potential estimated peak horizontal accelerations produced by the various regional faults in the central California and Sierra Nevada region are relatively low (Petersen et al. 1999). Most people would likely feel ground shaking, but structural damage would be negligible to slight in buildings constructed according to modern building standards.

Rockfall is used as a generic term to refer to all slope movement processes, including rockfall, rockslide, debris slide, debris flow, debris slump, and earth slump. Rocks have become dislodged and fallen off the sheer granite cliffs throughout the geologic history of Yosemite. Rockfalls can displace large volumes of rock and occur because of such processes as the climate-related expansion and contraction of rock, seismic shaking, or exfoliation, which is the peeling away of layers of rock.

Most rockfalls are associated with triggering events such as earthquakes, rainstorms, or periods of warming that produce rapid melting of snow. The magnitude and proximity of the earthquake, intensity and duration of the rainfall, the thickness of the snowpack, and the pattern of warming all influence the triggering of rockfalls. However, some rockfalls occur without a direct correlation to an obvious event and are probably associated with gradual stress release and exfoliation of the granite rocks (U.S. Geological Survey [USGS] 1998).

More than 400 rockfalls have been recorded within Yosemite National Park; some have resulted in injury and, on occasion, death. Rockfalls can also damage or destroy roads, trails, and buildings.

Two types of areas of potential rockfall impacts have been identified in Yosemite Valley. The first is the area closest to the Valley or canyon walls, which is called the talus slope zone. The majority of previous rockfalls have occurred in this zone. The second area, referred to as the rockfall shadow zone, extends out from the talus slope zone and is the area in which rocks may travel out from the talus. Most of the local setting and area for the Lower Yosemite Fall Project is located within the rockfall shadow zone but is outside of the talus slope zone (USGS 1999). The frequency and magnitude of rockfall events vary considerably. Many small rockfalls may occur every year and go unnoticed, while larger rockfalls occur much less frequently (USGS 1998). The Yosemite Falls Bridge, viewing area, and portions of trail segments are located on the border of the talus slope zone.

The National Park Service, in cooperation with the U.S. Geological Survey, is currently identifying potential geologic hazards in developed areas, including areas most susceptible to rockfalls (USGS 1998). The National Park Service is revising its management policies regarding geologic hazards, with the intent to better protect park visitors and staff by avoiding placement of structures in areas with high potential for rockfall impact.

Contaminated soils have been confirmed in an area within the Lower Yosemite Fall area, east of the eastern trail. This area was used as a warehouse and maintenance facility from approximately 1919 to 1957. Substances associated with the warehouse and maintenance facilities include lead, volatile organic compounds, polychlorinated biphenyls, and diesel. Lead was reported at concentrations above the regulatory threshold (the concentration threshold set by regulatory agencies) established by the California Environmental Protection Agency at one location. Volatile organic compounds were reported at concentrations well below any regulatory thresholds that would require cleanup action. A polychlorinated biphenyl result was reported at an area directly north of the former warehouse and maintenance facility at concentrations well below the regulatory thresholds.

While the sampling that was conducted was intended to focus on the specific areas with the greatest potential of being contaminated, the extent of compounds associated with the former warehouse and maintenance facility has not been fully determined. Additional sampling may be required to develop a deeper understanding of the impacts of the former warehouse and maintenance facility. The National Park Service shall comply with all appropriate requirements for addressing potential remediation and/or cleanup.

Water entering the Valley from Yosemite Creek falls from a height of 2,425 feet in two separate vertical falls joined together by a 675-foot chain of cascades. The water travels a distance of 1,430 vertical feet from Upper Yosemite Fall and 320 feet over Lower Yosemite Fall. Upon reaching the Valley floor, water is channeled through a narrow, boulder-laden gorge and into a main flow channel east of the Yosemite Falls Bridge. The main channel carries the flow across the top of the alluvial fan until the braided stream channels divert the flows down-fan to the south (see figure 2-1). The braided stream channels vary in size and capacity. In the center portion of the alluvial fan, water can be diverted through several channels. These channels converge towards the lower portions into four streams that eventually join into one main stream course that carries flow under Northside Drive and into the Merced River.

During the late winter and early spring, frazil ice forms at the base of both Upper and Lower Yosemite Fall. (Frazil ice is slush formed from small ice crystals that develop when the air temperature drops below freezing.) Although frazil ice lacks the erosional force of regular stream ice, it can cause streams to overflow their banks and change course.

Water flow over the alluvial fan is dependent on the season and amount of surface water runoff. During periods of heavy spring runoff, water can cover the unchannelized portions of the alluvial fan and occupy nearly all the channels within the braided stream system. In seasons of low flow, such as late summer or mid-winter, water may occupy one or two of the prominent channels, leaving the other channels with no flow or containing pooled water. During periods of high flows, most areas on the alluvial fan are inundated with flood flow (Weaver 1992). During periods of low flows, the area may be entirely devoid of surface flows.

The flow patterns in the braided stream system are variable and continue to change. High flows can redistribute cobbles and boulders, forming new channels or restricting others. A channel that carried large flows in the past may currently receive flows only in periods of flood stage. Flood flows can also dislodge boulders from the sheer cliffs, adding material to the alluvial fans. Stream channels on an alluvial fan can either down-cut or migrate laterally. Channel down-cutting appears to occur at a slower rate than lateral channel migration. The layer of compacted granite boulders that underlies the alluvial fan reduces the rate of channel down-cutting.

Previous human-made modifications within the Lower Yosemite Fall area include the construction of boulder dams and levees at the head of the alluvial fan, bridge construction, and filling and placement of protective bank armor at various bridge abutments. These modifications have altered the natural stream hydrology of the alluvial fan (Weaver 1992).

Significant lateral stream channel migration can occur down-fan, where the granitic alluvium is overlain by a well-established soil horizon. As the streams migrate laterally, the water flows undercut the banks and periodically lead to bank collapse. When a bank collapses, the additional sediment is discharged into the river and trees dislodge from the bank and fall into the river. Eventually, the fallen trees can restrict water flow in the river and alter the flow pattern, thus leading to additional bank undercutting. The National Park Service does not usually remove fallen trees from the streams (NPS 1998b).

Groundwater is the only source of potable water in Yosemite Valley and is considered to be of good quality. Water systems providing potable water comply with federal regulations that require regular monitoring and inspection. Recreational use can cause trail and streambank erosion that may increase turbidity and the levels of suspended solids in the river or stream. Surface runoff in Yosemite Creek can contain a variety of contaminants, including detergents and other wastes from day visitors and petroleum hydrocarbons from vehicles (NPS 2000b). The parking area is potentially a non-point source of pollution that could affect water quality. (Non-point source pollution occurs when water runs over land or through the ground, picks up pollutants, and deposits them in surface waters or introduces them into groundwater.) The restroom in the Lower Yosemite Fall area is connected to a sewage system and wastewater is pumped to the El Portal Wastewater Treatment Plant.

Periodic flooding of the Merced River and its tributaries is a key component to the hydrologic system of Yosemite Valley. Since the early 1900s, 11 major flood events have been recorded in the Valley. The largest floods occurred in 1937, 1950, 1955, and 1997. These floods were considered to be 50- to 100-year storm events, with flows on the Merced River that are estimated to have exceeded 22,000 cubic feet per second (NPS 1997a). A 100-year storm event represents the annual peak flow that has a 1% chance of being equaled or exceeded in any given year. The January 1997 flood is regarded as the largest on record and is used to predict the 100-year floodplain of the central Yosemite Valley area. Based on the observation of maps of the Merced River and Yosemite Valley, most of the Lower Yosemite Fall area was inundated by the flood of 1997 and is thus within the 100-year floodplain.

The flow of water through the Merced River and its tributaries is affected by snowmelt in the high country, rainfall events in early fall and late spring, and thunderstorms that may cause flash flooding in the summer. Water flow through the rivers and streams of Yosemite Valley is greatest during the spring periods of peak snowmelt. Notable flood events occur when unseasonably warm, winter tropical rainstorms melt the high country snowpack, as occurred during the record flood event in January 1997 (NPS 1997a). Average annual precipitation in Yosemite Valley is 36.5 inches (Williamson et al. 1996); snow comprises approximately 95% of the total annual precipitation.

The Lower Yosemite Fall area is dominated by incense-cedar (Calocedrus decurrens) intermixed with subdominants of California black oak (Quercus kelloggii), Pacific ponderosa pine (Pinus ponderosa), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii). Occasional canyon live oak (Quercus chrysolepis), white alder (Alnus rhombifolia), and big-leaf maple (Acer macrophyllum) are interspersed. Several large and moderate size snags (standing dead trees) occur throughout the area. Vegetation currently occurring within the Lower Yosemite Fall area can be described as intermediary between Mixed Conifer Series and Incense-Cedar Series (Sawyer and Keeler-Wolf 1995).

The understory is sparse and dominated by western azalea (Rhododendron occidentale); bracken fern (Pteridium aquilinum); incense-cedar; California black oak; pine seedlings, saplings, and immature incense-cedar; and downed logs. Virtually all of the saplings or immature tree species recorded in this area are incense-cedar.

White alder and big-leaf maple are isolated in small pockets along the lower reaches of the braided stream fan, while canyon live oak occurs most frequently in the uplands adjacent to the upper reach of Yosemite Creek, just below the base of Lower Yosemite Fall. With the exception of the active stream channels themselves, the tree canopy (overstory) cover is dense and little light penetrates the lower layers of the canopy to the forest floor.

Incense-cedar is the dominant overstory and understory conifer, comprising almost half of all mature tree species recorded in the area. The upper portion of the Lower Yosemite Fall area, just below the base of Lower Yosemite Fall, contains California black oak that best represents the described historic vegetation mosaic for the area.

Two native fungal pathogens have important impacts on the tree resources in Yosemite Valley: Heterobasidion annosum (Ha) and Armillaria ssp. (Arm) (Rizzo and Slaughter 1997). The Ha fungus causes a root and butt decay in conifers, leading to tree mortality or predisposing the tree to bark beetle attack, colonization, and subsequent death. The Arm fungus causes root and butt decay in oaks, conifers, and hardwoods; it does not generally cause tree mortality unless the tree becomes stressed. The Ha fungus has been identified within the Lower Yosemite Fall parking area. Both fungi may exist throughout the local setting.

Non-native plant species are also found within the Lower Yosemite Fall area. Himalayan blackberries are present along braided stream channels, at the very eastern edge of the Lower Yosemite Fall area. Mat-forming species such as puncture vine, spurge, and purslane, are present along the bicycle trail parallel to Northside Drive, east of Yosemite Creek.

The Lower Yosemite Fall area provides movement corridors, forage, nesting, and resting and perching areas for wildlife. However, the high level of ongoing human disturbance, such as human presence and high noise levels from cars and buses, greatly reduces the value of the Lower Yosemite Fall area for local wildlife. Species identified as using the area include the common flicker (Colaptes auratus), scrub jay (Aphelocoma coerulescens), raven (Corvus corax), Anna’s hummingbird (Calypte anna), Bewick’s wren (Thryomanes bewickii), chestnut-backed chickadee (Parus rufescens), brown towhee (Pipilo fuscus), American crow (Corvus brachyrhyncos), raccoon (Procyon lotor), black-tailed deer (Odoicoileus hemiounus californicus), coyote (Canis latrans), and striped skunk (Mephitis mephitis) (NPS 1998c). All are species considered highly tolerant of human disturbance.

Black bear (Ursus americanus) travel through the Lower Yosemite Fall area and may occasionally forage on oaks and acorns within the area. Snags are important for hairy woodpecker (Picoides villosus) and provide excellent nesting substrate for owls and other raptors. Bats, including the fringed myotis bat (Myotis thysanodes) and the long-eared myotis bat (Myotis evotis) are found within the Lower Yosemite Fall area. The seasonal water provided by drainages provides a source of fresh drinking water for species and likely provides breeding opportunities for amphibian and aquatic-dependent species. Peregrine falcons (Falco peregrinus) fly over or make occasional use of the area.

Fisheries resources within Yosemite Valley have historically been low in species diversity. All fish species were eliminated from the area during the last period of glaciation, and the numerous waterfalls of the Sierra Nevada prevented subsequent repopulation of the rivers by upstream migration. By the time the first Euro-American settlers arrived, only the lower reaches of the Tuolumne and Merced Rivers contained significant fish populations, including native rainbow trout (Oncorhynchus mykiss), Sacramento sucker (Catostomus occidentalis), Sacramento squawfish (Ptychocheilus grandis), hardhead (Mylopharodon conocephalus), California roach (Hesperoleuscus symmetricus), and riffle sculpin (Cottus gulosus). Stocking of rainbow trout and brown trout (Salmo trutta) began during the late 1800s and was continued until 1978 (NPS 2000b).

Several factors combine to create suboptimal habitat quality for fisheries resources in Yosemite Creek, especially within the local setting. These include the following: (1) severe climate conditions (i.e., floods, frazil ice, low summer flows), (2) low nutrient availability due to a general lack of typical riparian vegetation, (3) shallow channels, and (4) unstable stream banks with limited vegetative cover. Therefore, fish are unlikely to use the Lower Yosemite Fall area to a significant extent, although the presence of a few riffles with appropriate gravel sizes may sometimes enable trout to spawn in Yosemite Creek during spring. Smaller species such as riffle sculpin may occupy the braided channels late into the summer.

Special-status species considered in this analysis are listed in Appendix B. Based on absence of preferred habitat and/or park records/observations within the Lower Yosemite Fall area, most of these special-status species are not further analyzed in this environmental assessment. The special-status species that have potential habitat within the Lower Yosemite Fall area include bald eagle (federal threatened, California endangered), Wawona riffle beetle (federal species of concern), harlequin duck (federal species of concern, state species of special concern), American peregrine falcon (California endangered), and 10 species of bats (seven federal species of concern; four state species of special concern).

The Lower Yosemite Fall area is not a primary habitat for bald eagles, and eagles have not been observed nesting in the area or the Valley. Birds may fly through the area on occasion; however, bald eagles do not depend on the habitat located in and around Yosemite Falls and Creek.

Habitat for the Wawona riffle beetle may be present within the Lower Yosemite Fall area within creek channels that have consistent year-round flows on rocks and mossy areas. This tiny beetle is an aquatic species. Because most channels in the Lower Yosemite Fall area are dry during some portion of the year, potential habitat for the Wawona riffle beetle is very limited.

No observations of the harlequin duck were recorded in Yosemite Valley between 1980 and 1999; however, a pair was observed on the Merced River in 2000. Even though this species may have once nested in the Valley, it is expected that with the amount of human disturbance/presence in the Lower Yosemite Fall area, this species would not likely be found there. Also supporting this conclusion is the intermittent nature of and the sparse ground cover around the creek channels.

The American peregrine falcon forages over a variety of habitats, including wooded areas, meadows, and rivers. The primary prey of the peregrine falcon is a variety of bird species, but its prey also includes mammals, insects, and fish. The peregrine falcon has relatively strict nesting requirements: vertical cliff habitat with large potholes or ledges that are inaccessible to land predators. The peregrine falcon may forage over the Lower Yosemite Fall area. The closest known nest site is on the north cliff face of Yosemite Valley near The Ahwahnee, outside of the Lower Yosemite Fall area.

Of the 10 special-status bat species known to inhabit the Valley, four have been recorded in recent surveys within the Lower Yosemite Fall area (long-eared myotis, fringed myotis, Yuma myotis, and pallid bat). Though the other six special-status bat species have not been confirmed in the Lower Yosemite Fall area (spotted, small-footed myotis, pale big-eared, greater western mastiff, long-legged myotis, and Townsend’s big-eared bat), suitable habitat is present and the bats are expected to be in the area. Roosting locations for these bat species in the Lower Yosemite Fall area would likely include hollow snags, crevices in bark of mature trees, and rock crevices.

Yosemite National Park is classified as a mandatory Class I area under the federal Clean Air Act (42 USC 7401 et seq.). This air quality classification is aimed at protecting parks and wilderness areas from air quality degradation. The act gives federal land managers the responsibility for protecting air quality and related values from adverse air pollution impacts, including visibility, plants, animals, soils, water quality, cultural and historic structures and objects, and visitor health. The Yosemite Valley is in Mariposa County, which is regulated by Mariposa County Air Pollution Control District.

The Federal Clean Air Act, as amended in 1990, requires the U.S. Environmental Protection Agency to identify national ambient air quality standards to protect public health and welfare. Standards have been set for six criteria pollutants: particulate matter less than 10 microns in diameter (PM₁₀), carbon monoxide (CO), nitrogen oxides (NO_x), sulfur dioxide (SO₂), ozone (O₃), and lead (Pb). An area where a standard is exceeded more than three times in three years can be considered a nonattainment area subject to planning and pollution control requirements that are more stringent than for areas which meet standards.

The California Air Resources Board has set ambient air quality standards to protect public health and welfare that are more strict than the national standards. Under the 1988 California Clean Air Act, air basins were designated as attainment, nonattainment, or unclassified for the state standards. Mariposa County exceeds two California ambient standards: ozone throughout the county and PM₁₀ in Yosemite Valley.

Mariposa County Air Pollution Control District is responsible for developing a state implementation plan for federal and state nonattainment pollutants in its jurisdiction. State implementation plans define control measures that are designed to bring areas into attainment. Mariposa County is currently in attainment or is unclassified for all national ambient air quality standards. As discussed above, Mariposa exceeds two California ambient standards. Basic components of a state implementation plan include legal authority, an emissions inventory, an air quality monitoring network, control strategy demonstration modeling, rules and emission limiting regulations, new source review provisions, enforcement and surveillance, and other programs as necessary to attain standards.

Schools, child care centers, hospitals, and convalescent homes are considered to be more sensitive than the general public to poor air quality because the population groups associated with these land uses have an increased susceptibility to respiratory distress. Persons engaged in strenuous work or exercise also have increased sensitivity to poor air quality. Residential areas are considered more sensitive to air quality conditions than commercial and industrial areas because people generally spend longer periods of time at their residences. Recreational areas are also considered sensitive compared to commercial and industrial areas due to the greater exposure to ambient air associated with outdoor activities. Trail and recreational users at the Lower Yosemite Fall area would be the closest sensitive receptors to activities from the Lower Yosemite Fall Project.

Natural sources of noise in Yosemite Valley include waterfalls, rushing water, wind, and wildlife. There is also noise from human activities and mechanical devices such as automobiles, trucks, and transit buses. Environmental noise usually is measured in A-weighted decibels (dBA)¹. Environmental noise typically fluctuates over time, and different types of noise descriptors are used to account for this variability. Typical noise descriptors include the energy-equivalent noise level (L_eq) and the day-night average noise level (L_dn)². Generally, a 3-dBA increase in ambient noise levels represents the threshold at which most people can detect a change in the noise environment; an increase of 10 dBA is perceived as a doubling of loudness. Ambient (background) noise levels in Yosemite Valley typically range from the 60 to 65 dBA L_dn. As a point of reference, a conversation between two people would typically measure about 60 dBA. A noise level above 80 dBA can cause hearing loss if prolonged.

The main source of noise in the northern part of the Lower Yosemite Fall area is predominately the sound of Lower Yosemite Fall, which could range up to 80 dBA. In the southern portion of the Lower Yosemite Fall area, traffic on Northside Drive and in the parking area is the predominate source of noise. In the eastern section of the Lower Yosemite Fall area, which is located more than 300 feet from both the waterfall and the road, the predominate source of noise may be people talking and/or from the adjacent playground.

During a statistical motor vehicle noise survey (24-hour, A-weighted) performed during the winter of 1999, the daytime and nighttime ambient noise level average was 60 dBA at the Lower Yosemite Fall area, 275 feet from the main roadway centerline. For Yosemite Valley, A-weighted noise emission levels for diesel and electric buses, based on distances ranging from 100 to 400 feet from the source, averaged between 52 and 64 dB and between 45 and 57 dBA, respectively (NPS 2000b). Sound levels monitored for noise other than natural sounds, motor vehicles, buses, and aircraft along the Lower Yosemite Fall trail ranged from 44 to 47 dBA, with maximum observed levels of 66 dBA when people passed the sound monitor on the trail. Notably, there was no water in Yosemite Creek when the monitoring was performed (NPS 2000b). Noise from construction activities generally decreases at 6 to 7 dBA for every doubling of distance, so as the distance increases from any noise source, the contribution of noise associated with that source decreases.

Some land uses are considered more sensitive to ambient noise levels than others because of the amount of noise exposure (in terms of both exposure duration and insulation from noise) and the types of activities typically involved. Residences, motels and hotels, schools, libraries, churches, hospitals, and parks and other outdoor recreation areas are generally more sensitive to noise than commercial and industrial land uses. Trail and recreational users in the Lower Yosemite Fall area would be the sensitive receptors closest to activities from the Lower Yosemite Fall Project.

The National Historic Preservation Act, the Archeological Resources Protection Act, the Native American Graves Protection and Repatriation Act, and NEPA require that the effects of any federal undertaking on cultural resources be examined. In addition, National Park Service management policies and cultural resource management guidelines call for the consideration of cultural resources in planning proposals.

Seven designated archeological sites lie within the Lower Yosemite Fall area. These include sites associated with the American Indian habitation of the Valley, early Euro-American homesteads, a concessioner warehouse complex, a sawmill operated by John Muir, and an early concessioner tourist camp (Camp Lost Arrow). Each of these seven recorded sites is described in the following sections.

Site CA-Mrp-58. Site CA-Mrp-58 is the Yosemite Falls Indian Caves, which consist of a series of meandering fissures (cracks) between boulders. A single boulder with three mortar cups (a depression in the rock formed from pounding acorn) situated beneath the overhang of a larger boulder occurs at the site. Because no subsurface investigation has been conducted at this site, it is unknown whether cultural deposits occur within the Lower Yosemite Fall area. Lacking such data, it is assumed herein that the site, located immediately adjacent to the western trail to the base of Lower Yosemite Fall, is within the Lower Yosemite Fall area boundary.

Site CA-Mrp-240/303/H. Site CA-Mrp-240/303/H is located directly west of Yosemite Creek and north of Yosemite Lodge in the Lower Yosemite Fall area. Seven stationary milling features (large stones or bedrock used for the processing or milling of foods) with a total of 63 mortar cups and three milling slicks (smooth parts of a stone where grains were milled) have been recorded at Site CA-Mrp-240/303/H, while sparsely scattered obsidian tools and debris are apparent on the surface and below the surface (Hull et al. 1998).

Ethnographic studies have suggested that Site CA-Mrp-240/303/H represents at least a portion of the former American Indian village of Koom-I-ne (Bibby 1994). Furthermore, this site has been the location of historic Euro-American activities, in particular the establishment of Camp Yosemite by the U.S. Cavalry in this area in 1906. Early topographic maps indicate the location of six buildings along the old road to the main bridge (Yosemite Falls Bridge), and these dwellings were apparently known as "Soapsuds Row." Old Yosemite Lodge was constructed near the Site CA-Mrp-240/303/H area in 1915 (Hull et al. 1998).

Development within this site includes Yosemite Lodge, the Lower Yosemite Fall parking area, Northside Drive, multi-use paved trails, subsurface utility lines, and the existing restroom.

Site CA-Mrp-749. Site CA-Mrp-749 is located north of the Merced River within the Lower Yosemite Fall area. The site consists of scattered prehistoric flaked and ground-stone artifacts; a small quantity of historic artifacts are also present (Hull and Kelly 1995).

Archeological trenches dug at the site revealed that the deposit extends to a depth of approximately 3 feet. Recently, a team of archeologists investigating the Hutchings-Sovulweski Homesites recovered artifacts of American Indian origin near the bank of Yosemite Creek that may be associated with Site CA-Mrp-749. As such, the boundaries of Site CA-Mrp-749 may be expanded or combined with those of the above-mentioned homesites.

Hutchings–Sovulewski Homesites (Site YC-12). The fruit orchard planted by James Mason Hutchings after 1864, in what is now the Lower Yosemite Fall area, comprises the surface evidence of Site YC-12. This site area also formerly contained the Hutchings cabin, barn, sheds, and other outbuildings that were once part of his homestead.

The cabin was built of hewn logs joined with a V-notch and rested on a stone foundation. It had a covered open porch on one side and a later frame, board, and batten addition on the opposite end. Shakes clad the roof and chinked the cracks between the logs. The home was heated by a large stone fireplace and chimney (NPS 1987; Olmsted 1880).

The Hutchings family resided in the cabin at least on a part-time basis until 1902. After James Mason Hutchings’ death, the structure was used to store hay for several years, until it was cleaned out in 1906 and assigned to Park Superintendent Gabriel Sovulewski (Pavlik 1988).

In 1909, the former Hutchings cabin was demolished (NPS 1987). A year later a new, two-story, wood-frame home was built for Gabriel Sovulewski in the same vicinity. The Sovulweski home was the first residence built in Yosemite Valley by the Department of the Interior. In the late 1920s, the Yosemite Advisory Board deemed the Sovulewski home an obstruction on the landscape and recommended its removal. After failed requests by Sovulewski to relocate the structure, the home was removed in the fall of 1936 (Pavlik 1988).

Recent excavations at this site identified structural remains likely associated with the Sovulewski home and refuse associated with both Hutchings and Sovulewski and Camp Lost Arrow.

Hutchings Sawmill and Camp Lost Arrow (Site YC-5). Site YC-5 consists of the reported remains of the James Hutchings sawmill (in the northeast portion of the Lower Yosemite Fall area) built by John Muir in 1869 and operated by Muir until the summer of 1871. The sawmill was constructed to process fallen timber to be used in the making of cottages for Hutchings Upper Hotel and Black’s Hotel. As depicted in a painting dated approximately 1871, two post-1882 photographs by George Fiske, and a line drawing by Muir, the mill building was a 1½-story structure with a front gable roof and rough-hewn vertical board siding. The structure was situated on the east branch of Yosemite Creek and powered by water obtained from a ditch that took water from farther up Yosemite Creek (Johnston 1995).

Today, the physical remains present at the Hutchings sawmill site include what are generally believed to be the millrace ditch (an open channel that provides water to a sawmill) and spillgate. National Park Service photographs taken in the 1940s identify the Muir’s millrace.

Recent archeological investigations reveal that in addition to the millrace, remnants of Camp Lost Arrow also occur within Site YC-5. Camp Lost Arrow was a camp established for tourist use in 1901. Originally named Camp Yosemite but renamed Camp Lost Arrow to avoid confusion with the Army’s Camp Yosemite, the establishment was situated near the site of Hutchings’ former sawmill (Johnston 1995). Originally consisting of a series of tents, the camp ultimately contained "… electric lights, wood-frame office buildings, bathhouse with four bathrooms, warehouse, and a dining hall seating more than two hundred" (Johnston 1995). The season of operation was evidently restricted to the period when Yosemite Creek flowed, as the creek served as the camp’s sewer outlet (Johnston 1995). Camp Lost Arrow was closed after the 1915 season, corresponding to the opening of Yosemite Lodge.

No physical remains of the sawmill were identified. Information recently uncovered by National Park Service staff suggest that the mill itself was located in the vicinity of the backyard of a residence adjacent to the Lower Yosemite Fall area. Consultation with a State Historic Preservation Officer may be needed to concur the site’s historical significance.

Curry Company Warehouse Complex (Site YC-11). The current Site YC-11 includes a 130-meter stretch of the east bank of Yosemite Creek with three warehouse footings, a concentration of granite and other riprap materials (broken stones loosely assembled) for bank stabilization, decomposing concrete block perhaps associated with a shop building, a creekside dumping of asphalt or oil, lumber riprap or refuse, and a sparse historic refuse deposit.

The complex was constructed just prior to 1919 and razed in approximately 1957. The complex included four warehouses; paint, electric, furniture repair, and plumbing shops; a storage facility; a cottage; and a garage. Both electric and sewer systems were part of the original construction.

Rock Ring. Recently a ring of stacked rock was identified in the Lower Yosemite Fall area by National Park Service staff. When National Park Service archeologists subsequently visited the rock ring, the feature could not be assigned either temporal or ethnic affiliation. It is unknown whether a cultural deposit occurs within the vicinity of the rock ring.

Ethnographic resources consist of features of the landscape that are linked by members of a contemporary community to their traditional ways of life. As more specifically defined in the NPS-28 Cultural Resources Management Guidelines (NPS 1991), ethnographic resources are any "site, structure, object, landscape, or natural resource feature assigned traditional, legendary, religious, subsistence, or other significance in the cultural system of a group traditionally associated with it." A traditional cultural property is an ethnographic resource that is eligible for listing on the National Register of Historic Places. An Ethnographic Evaluation of Yosemite Valley: The American Indian Cultural Landscape (Bibby 1994) identified and documented cultural and natural resources associated with American Indian occupation and use of the Valley. American Indians still living in the region provided oral history and assisted in the location of ethnographic resources. The area evaluated extended from Pohono Bridge to Mirror Lake and Happy Isles, and included all historic areas of human habitation, sites of traditional and contemporary spiritual value, marked and unmarked graves, and areas of past and present resource gathering and food processing. Most sites and features are historic, and tradition holds that many have long histories of use. The ethnographic evaluation recommended that Yosemite Valley be designated a Traditional Cultural Property and listed on the National Register of Historic Places as a district. As of this date, none of the ethnographic resources located in Yosemite Valley have been formally designated as Traditional Cultural Property.

Based upon research completed by the National Park Service (Bibby 1994), five ethnographic resources are located within the Lower Yosemite Fall area. These ethnographic resources include the ethnographic village of Koom-I-ne, a bedrock milling feature with historic use citation, an area used for the gathering of helli (large white mushrooms, possibly Lentinus lepideus), a large grove of California black oaks where acorns were and continue to be gathered, and a location where bracken fern was and continues to be procured. These resources have been designated as numbers 50, 51, 52, 55, and 67, respectively, in the Bibby (1994) study.

Koom-I-ne. Among the several ethnographic villages within the Valley was Koom-I-ne, which was located at least partially within the Lower Yosemite Fall area. According to one report, this was the most important village in the Valley (Merriam 1976). Koom-I-ne is at least partially represented in the archeological record by site CA-Mrp-240/303/H.

Helli. The National Park Service’s American Indian consultants identified an area within the Lower Yosemite Fall area where helli mushrooms are gathered (Bibby 1994). This particular mushroom "has continued to be one of the most important, regularly gathered resources in Yosemite Valley" (Bibby 1994). Helli first appears in May and is evidently present for harvest through the summer.

California Black Oaks. The National Park Service identified a large grove of California black oaks within the Lower Yosemite Fall area (Bibby 1994). Within this grove are individual trees that have been associated with particular individuals. Acorns were the most important plant food to American Indians in California, including the Southern Sierra Miwok.

Bedrock Milling Feature. Within the confines of archeological site CA-Mrp-240/303, and thus also associated with the ethnographic village of Koom-I-ne, is a large boulder containing 38 mortar cups. This particular feature appears to be the same as that referred to by early Yosemite Valley resident Laurence Degnan. In a letter written in September 1954, Degnan, in reflecting on his earlier observations, mentioned that he had seen the grinding of acorns atop the large boulder along the road to Lower Yosemite Fall (Bibby 1994).

Bracken Fern. Bracken fern, an important component of traditional basket making to the Southern Sierra Miwok and Mono Lake Paiute, is prevalent throughout Yosemite Valley. Not all bracken fern, however, exhibits the required physical characteristics needed for basket weaving (e.g., length, straightness, and ease of extraction). A number of local weavers identified the eastern channel of Yosemite Creek as one location where the bracken fern was traditionally gathered for use in basket making (Bibby 1994).

A nomination for listing the Yosemite Valley cultural landscape as a historic district in the National Register is being formalized. According to the NPS-28 Cultural Resources Management Guidelines (NPS 1991), a cultural landscape is a reflection of human adaptation and use of natural resources. It is often expressed in the way land is organized and divided, patterns of settlement, land use, systems of circulation, and the types of structures that are built. The boundaries of the Yosemite Valley cultural landscape extend from Valley rim to rim and from Pohono Bridge to Mirror Lake and Happy Isles, including the Valley walls themselves and several historic trails. Historic view corridors to Yosemite Falls also contribute to the significance of the Yosemite Valley cultural landscape (see the Scenic Resources section of this chapter).

The Lower Yosemite Fall area contributes to the significance of the Yosemite Valley cultural landscape. Among its contributions are its natural systems and features and pedestrian circulation patterns, including the trail to the base of Lower Yosemite Fall. A number of contributing elements to the Yosemite Valley cultural landscape occur within the Lower Yosemite Fall area, including the Hutchings Orchard, millrace of the Hutchings sawmill site, Muir plaque, Clark bench, Valley Loop Trail, Lost Arrow Trail, and Auto Road.

Hutchings Orchard. The Hutchings homesite has been described previously in the Archeological Resources section of this chapter. By 1868 the Hutchings homestead included a fruit orchard and vegetable garden of several acres. The orchard, the third in the Valley, was planted soon after the house was built—certainly by 1868 when John Olmsted visited Hutchings and reported on the presence of the orchard (Johnston 1995).

When the orchard was surveyed in 1991, 53 trees (primarily apple trees, but including two cherry trees and one pear tree) were identified (Kennedy 1991). The orchard formerly extended farther north into the playing fields, and it is depicted on several historic maps of the area as being of much greater extent than currently remains.

Hutchings Sawmill Site. The physical remains present at the Hutchings sawmill site include the millrace ditch and spillgate. The sawmill and the millrace were constructed and operated by John Muir. National Park Service photographs taken in the 1940s identify the millrace.

Muir Plaque. The Muir plaque is a bronze rectangle placed in commemoration of John Muir’s 96th birthday, 10 years after his death. The plaque is fixed to a fairly round granitic boulder. Although the plaque was installed in 1924 by the California Conference of Social Work, it was formally dedicated in 1934. Anecdotal reports indicate that the plaque is placed at the location of Muir’s cabin, which is unlikely, because the area is often under water during parts of the year. The plaque site is located near Clark bench (discussed below), and Yosemite Falls is visible from the plaque site.

Clark Bench. Clark bench is a stone bench constructed of shaped granitic slabs and is rounded by wear. The bench structure rests on a concrete foundation that is undercut by periodic flooding of Yosemite Creek. The granite seat was created and placed in memory of Galen Clark (1814-1910), the guardian of the Yosemite Grant for 21 years. Clark bench was originally built in the meadow south and opposite of Hutchings Orchard and Gabriel Sovulewski’s house in 1911 and moved to its current location when the present road was realigned.

Lost Arrow Trail. Lost Arrow Trail was constructed in 1907 in conjunction with Camp Yosemite, later called Camp Lost Arrow. The trail provided access to the camp from what is today Northside Drive (the segment in this area was named Lost Arrow Drive). Portions of the trail were evidently reconstructed in 1928 and 1929, when 3 or 4 miles of dust-proof trails were built to points of interest along the Valley walls. One such segment extended through the Lost Arrow section to the foot of Yosemite Falls, connecting with the Lost Arrow Nature Trail, laid out in 1927 by Clifford Presnell as the first nature trail in the Valley. It was succeeded by a permanent nature trail, part of the eastern trail completed between 1929 and 1933. The trail crosses a number of footbridges and passes the Muir plaque and Clark bench on its current route. The majority of the trail is sand, duff, or what is considered a natural surface. The trail surfaces at the bridge approaches are generally asphalt or cement. This resource includes five bridges on the Lost Arrow Trail and one bridge on a trail branch leading east.

Valley Loop Trail. The Valley Loop Trail through Yosemite Valley currently follows the configuration of the Yosemite Valley Bridle and Footpath Improvements Map, as approved by Superintendent C. G. Thomson. There were, however, numerous other incarnations of these trails throughout the Valley from the earliest years, developed informally along existing commercial and private trails. By 1892 there were 24 miles of bridle trails, and by 1916 several additional trails had been constructed. By 1916, when the Yosemite National Park Supervisor published a list of existing roads and trails within the park, no formal Valley Loop Trail existed, but the Yosemite Falls Trail was noted as one of the original components (NPS 1998b).

The Valley Loop Trail, designed in the late 1920s, necessitated the construction of 14 bridges within Yosemite Valley. Of those 14 bridges, eight (including the Yosemite Falls Bridge) are to be reconstructed or rehabilitated. "Sections of the bridle path completed in 1928 ran from Happy Isles to Mirror Lake, . . . , from North Road to Ahwahnee Kite . . . , from Old Village to Four mile Trail, along Yosemite Creek, along Tenaya Creek, and behind the Indian village" (NPS 1998b; Land and Community Associates 1994). The trail, in basically the same location, is also depicted on early 1900s historic maps of the Valley.

Auto Road. This road appears to overlie what was one of numerous trails to the base of Lower Yosemite Fall in use from the earliest years to the present. In 1873 Jon Conway constructed a horse toll road to Lower Yosemite Fall, but it was taken over and declared a free road shortly thereafter. Another trail to Lower Yosemite Fall, in approximately the location of the Auto Road, was depicted on a map of Yosemite Valley completed in the late 1870s but was undoubtedly in use long before that time. In 1888, it was noted that the commissioners who administered Yosemite Valley for the state had completed the Yosemite Falls Trail. The trail is depicted in approximately the same location as the Auto Road on other historic maps of Yosemite Valley. By 1907, the year that private automobiles were banned from the Valley, this trail was depicted as a road with a turnaround. The automobile ban was rescinded in 1913, on the north side of the Merced River only, and the Auto Road was used by motor vehicles for many years. It was finally closed to motor vehicles in the 1950s.

Hutchings View Corridor and Western Trail View Corridor. The Lower Yosemite Fall area is designated the highest scenic category (A Scenic) in the Yosemite Valley Plan (NPS 2000b). The A Scenic category is one of three criteria-based categories (A through C) for classifying views from existing viewpoints within the park’s significant scenic features. The Lower Yosemite Fall area meets the following A Scenic criteria: (1) the area was most commonly chosen by eminent early photographers and painters; and (2) it contains what are currently considered some of the most significant scenic views within Yosemite National Park. Inherent in the beauty of the Yosemite Falls area are its various natural landmarks and view corridors. Lower Yosemite Fall is the predominant landmark at the main viewing terrace and Yosemite Falls Bridge; at this location, Sentinel Dome and Half Dome are also visible to the south and east, respectively. Countless artists have captured the inspiring views of the landscape via the Western Trail and Hutchings view corridors (see figure 2-2). The Western Trail view corridor provides the most spectacular view of Yosemite Falls. This view corridor extends from the Lower Yosemite Fall parking area to Sentinel Rock on the south side of the Valley. Views of the Upper Yosemite Fall cliffs, Lost Arrow Spire, Yosemite Point Buttress, and Castle Cliffs are also available from various locations within the Lower Yosemite Fall area.

Yosemite National Park’s scenic resources are a major component of the visitor’s experience, and conserving the scenery is a crucial component of the National Park Service 1916 Organic Act and the park’s enabling legislation. Yosemite National Park was established primarily for its natural and scenic features. These features include high peaks, sheer cliffs, massive granite domes, waterfalls, expansive wilderness, and giant sequoias. The Merced River, El Capitan, Half Dome, Mt. Watkins, and the Valley’s magnificent waterfalls are some of the resources that contribute to the highly valued visual quality of the park. The 1980 General Management Plan identifies 11 significant scenic features: Half Dome, Yosemite Falls, El Capitan, Bridalveil Fall, Three Brothers, Cathedral Rocks and Spires, Sentinel Rock, Glacier Point, North Dome, Washington Column, and Royal Arches.

The Lower Yosemite Fall area is one of the major visitor destination areas in the park. Approximately 750,000 of Yosemite National Park’s nearly 4 million annual visitors begin their visit to Yosemite Falls in the existing Lower Yosemite Fall parking area, arriving by foot, bicycle, commercial bus, park shuttle bus, or cars. Some tour buses unload passengers at the Lower Yosemite Fall parking area. From the parking area, a majority of visitors walk to and from the base of Lower Yosemite Fall using the western trail. The principal use of this area is viewing Yosemite Falls; however, other recreational and educational opportunities are available. Visitors also use the area for nature study, photography, hiking, exploration of the talus caves or "spider caves," and rock scrambling. In addition, visitors may participate in interpretative walks and other educational activities such as learning games or cave exploration conducted by the Yosemite Institute and the National Park Service.

A Phase I study of the Lower Yosemite Fall area trails and viewing areas was conducted in August and September 1998 (Manning 1999). A separate Visitor Use Study of the area was conducted from August 6 through 9, 1999, which is only a week removed from the fourth busiest day of the previous year (Shacklett 2000). The numbers from the Visitor Use Study are probably lower than they would be for the actual fourth busiest peak day because of the difference of one week and the lower than average park visitation numbers during 1999. According to the Phase I study, an estimated 5,500 visitors per day spend an average of 9 minutes walking the western trail to the falls and 21 minutes viewing the falls (Manning 1999). During the peak visiting season, visitors may crowd at the base of Lower Yosemite Fall on the viewing platform and Yosemite Falls Bridge. Respondents in the Visitor Use Study indicated that they were less tolerant of the number of people they encountered at the viewing area than they were of the number of people on the trail.

It has been projected that in the future, 50% of visitors will use the restroom during a 1-hour visit to the Lower Yosemite Fall area. The 50% factor is derived from a restroom fixture count study for the new visitor facilities at Grand Canyon National Park (Shacklett 1996). According to the 1999 Visitor Use Study of the Lower Yosemite Fall area, the average current restroom use per hour on a mid-summer day was 119 for the women’s side and 109 for the men’s side (Shacklett 2000).

The existing restroom occupies a highly prominent location within the Western Trail view corridor near the western trail. It is over 40 years old and is showing signs of deterioration. As a result, the view of Lower Yosemite Fall along the Western Trail view corridor is somewhat diminished by the restroom. In addition, the restroom contains an inadequate number of toilet fixtures (seven) and does not meet federal accessibility standards. During peak visitation, the restroom in the Lower Yosemite Fall area receives heavy use from park visitors. As a result, visitors often wait in line to use the facility, and restroom services may not be readily accessible to visitors in wheelchairs.

Two trails lead from the Lower Yosemite Fall parking area to the base of Lower Yosemite Fall. The most direct route, the western trail along Yosemite Creek, varies between approximately 8 to 12 feet wide, and is generally straight, but narrows, curves, and becomes steeper as it nears the north viewing platform. Pedestrians commonly walk on the unpaved soils adjacent to this trail, thus causing soil compaction and loss of vegetation. Educational exhibits along the western trail discuss Yosemite Falls and American Indian history associated with the area. The other route, which crosses several channels of Yosemite Creek and then starts to follow the eastern channel, is less traveled and not clearly delineated. Composed partially of pavement and partially of dirt, the eastern trail winds through the wooded area between the western trail and National Park Service housing area to the east. The eastern trail crosses the braided creek via several bridges and joins the Valley Loop Trail just before it reaches the Yosemite Falls Bridge at the base of Lower Yosemite Fall.

An additional trail segment—part of the Valley Loop Trail—veers west from the western trail and leads to the Upper Yosemite Fall Trail trailhead. The western trail leads directly from the parking area to the base of Lower Yosemite Fall along a deteriorated roadbed. This is a wide, clearly impacted corridor that leads from the primary arrival point to the base of Lower Yosemite Fall. The western trail is the most heavily traveled route to and from the base of Lower Yosemite Fall. The eastern trail is less obvious and not well signed and, as a result, less traveled. In addition, accessibility to the base of Lower Yosemite Fall for visitors in wheelchairs does not meet federal accessibility standards because the gradient of the western and eastern trails is too steep approaching the viewing platform.

The primary bridge used by visitors at the Lower Yosemite Fall area is the Yosemite Falls Bridge, which crosses Yosemite Creek at the base of Lower Yosemite Fall. The bridge is approximately 15 feet wide and is composed of steel, wood, stone, concrete, and asphalt. The railings along the bridge indicate signs of wear as the result of weather erosion as well as visitor use. In addition to the Yosemite Falls Bridge, visitors may use a series of bridges (Bridges #1 through #6) to cross braided streams and complete a loop trip using both the western and eastern trails. However, the deteriorated state of some bridges may hinder the accessibility of completing the loop trip or accessing Lower Yosemite Fall via the eastern trail. For example, one portion of Bridge #6 has collapsed.

Yosemite Lodge is situated just southwest of the Lower Yosemite Fall area, and foot traffic between Yosemite Lodge and the fall area can be heavy. The southern edge of the Lower Yosemite Fall area is bounded by Northside Drive, which is a main intra-Valley travel corridor for vehicles, pedestrians, and bicycles, as well as the Valley exit road. Adjacent to the northeastern edge of the Lower Yosemite Fall area is a residential area for National Park Service staff. The eastern trail runs adjacent to the backyards of two residences. Yosemite Lodge serves as an access point to several popular climbing areas including Swan Slab, Three Open Brooks, and Sunnyside Bench.

Various divisions of the National Park Service manage the public utilities within the Yosemite Valley. The National Park Service’s Division of Facility Management manages electricity. The Division of Facility Management is responsible for the maintenance and repair of all National Park Service-owned facilities. Specific maintenance services are provided by Facility Management branches composed of a Buildings and Grounds branch, a Roads and Trails branch, a Utilities (water/sewer/power) branch, and a Design and Engineering Professional Services branch. The Buildings and Grounds branch is responsible for cleaning and maintaining restrooms, and solid waste collection and water and wastewater system maintenance is performed by the Utilities branch.

Power is provided by Pacific Gas and Electric Company via an electric substation below Yosemite Valley. The high voltage is stepped down at the substation and transported via the El Portal Road and Northside Drive in the Valley.

Water is produced and chlorinated at the three wells located near Yosemite Lodge, and pumped to the 2.5-million-gallon storage tank at Happy Isles. Drinking water is then distributed to local users. Wastewater is collected at the Yosemite Creek Lift Station, located near Yosemite Lodge and the production wells. From the lift station, wastewater is pumped to the El Portal Wastewater Treatment Plant outside the park.

Northside Drive is a major utility corridor for Yosemite Valley. Underground pipelines along Northside Drive include sewage, water, power, and telephone lines. Water, sewer, and power lines are located beneath the Lower Yosemite Fall parking area in the Lower Yosemite Fall area, at a depth of approximately 5 feet (NPS 1998c). Other abandoned lines may exist in the vicinity of Northside Drive.

An array of passive, social, and active recreational opportunities exist in the Lower Yosemite Fall area, including rock climbing, walking and hiking, bicycling, bird watching, informal picnicking, photography, and artistic pursuits such as painting.

The principal use at the Lower Yosemite Fall area is viewing of Yosemite Falls, mainly from the vantage points at the viewing platform near Yosemite Falls Bridge and along the western trail. Most visitors do not venture beyond the western trail, and therefore do not explore other recreational opportunities available in the area.

Rock climbing is a popular sport in Yosemite Valley. Climbing occurs along the rock walls to the west and north of the Yosemite Falls area. Access points to staging areas are via the western trail and the eastern trail.

Various trails are within and connect to the Lower Yosemite Fall area for day hikers and backpackers en route to more distant destinations. The western trail and the eastern trail form a circuit along the braided stream network of Yosemite Creek and provide a dynamic setting for day hikers because of the rushing water coursing through the tranquil environment. Two connecting paths, the Yosemite Falls Trail and the Valley Loop Trail, lead to other destinations of the park.

Bicycling is a popular way of enjoying and exploring Yosemite Valley. Bicycles are required to use paved trails and roads and are not allowed on the pedestrian trails. However, there is a bicycle trail alongside Northside Drive that provides access to the Lower Yosemite Fall area from other parts of the Valley. Horseback riding (referred to as stock use in the Yosemite Valley Plan) on the eastern trail by private users or an occasional park ranger occurs during the day.

Informal picnicking, sunbathing, and exploration of the streams and caves are a part of the visitor experience at the Lower Yosemite Fall area. Frequently, picnic sites become a base for exploring the park.

The ability to sit or stand quietly, absorbed in thought or in awe of one of Yosemite’s majestic views, is basic to the park experience. Artistic pursuits are also fundamental to the enjoyment of Yosemite Valley, which provides inspiration for artistic expression. Bird and animal observation and nature study are also popular and occur in the Lower Yosemite Fall area.

Access roads into Yosemite Valley enter near the west end of the Valley and merge into Southside Drive, a two-lane, one-way eastbound road that parallels the south side of the Merced River. Northside Drive, a westbound road that is parallel to and north of the Merced River, is two-way in the segments adjacent to Yosemite Village, the Lower Yosemite Fall area, and Yosemite Lodge. It converts to one-way travel from just west of Yosemite Lodge to Pohono Bridge.

Northside Drive, Southside Drive, and Sentinel Bridge Road (the road connecting Northside Drive and Southside Drive located south of Yosemite Village) are the major thoroughfares traversing Yosemite Valley. Northside Drive, located south of the Lower Yosemite Fall area, is well traveled by vehicles and bicycles, both for accessing points within the Valley and as an exit from the Valley.

Most visitors to Yosemite travel by private vehicle, but tour buses accommodate a significant percentage of visitors. In August, an average of 63 daily commercial tour bus trips enter the park. It is assumed that all tour buses visit the Valley during their stay in the park. Tour buses carry an average of 1,673 visitors per day into the Valley. This represents about 12% of the 13,742 visitors that are estimated to enter the Valley on an average day in August. In addition, a small number of visitors use regional transit buses operated by VIA Adventures, Inc./Grayline of Yosemite (VIA) and the Yosemite Area Regional Transportation System (YARTS). An average of 73 visitors per day rode to Yosemite Valley on the 15 to 17 daily round-trips operated by VIA and YARTS in June and July 2000.

Traffic counts taken at the El Capitan crossover indicate that about 10% of the traffic that enters the east end of the Valley near the Yosemite Chapel is recirculating from Northside Drive via the El Capitan Bridge (NPS 2001c).

The parking area at the southwest corner of the Lower Yosemite Fall area is used by visitors. Fifty-two parking spaces are available at the parking lot, 22 of which are for buses and the other 30 for cars. Shuttle buses transport visitors from other parts of the Valley to the Lower Yosemite Fall parking area.

Visitors also use the pedestrian and bicycle trails to enter the Lower Yosemite Fall area. The Valley Loop Trail, the Yosemite Falls Trail, and two pedestrian trails connect to the Lower Yosemite Fall area. A multi-use paved trail is located north of and parallel to Northside Drive.

In April 1999, the U.S. Department of Interior entered into a formal Memorandum of Understanding with the Department of Energy to promote the use of energy-efficient and renewable energy technologies and practices in the national parks. This partnership officially inaugurated the program titled "Green Energy Parks: Making the National Parks a Showcase for a Sustainable Energy Future." The California Energy Plan is the state’s principal energy planning and policy document (California Energy Planning 1992). According to the plan, which recognizes the connection between energy use and air pollution, approximately 80% of the state’s air pollution is caused by burning fossil fuels. The plan finds that increasing energy efficiency is the lowest cost alternative for improving air quality.

Gasoline and diesel are the primary fuels consumed by automobiles, trucks, and buses used in the area. A California Air Resources Board model (called BURDEN) has been used to estimate motor fuel consumption associated with proposed plans, employee commuting patterns, and utilization of National Park Service and concessioner vehicles that operate in the Valley. Annual fuel consumption for heavy trucks, urban buses, and shuttle buses was derived from estimates of vehicle miles traveled and typical fuel economy values for these vehicle types. The results of this analysis indicate that approximately 2,905,800 gallons of gasoline and approximately 230,200 gallons of diesel would be necessary to power automobiles, trucks, and buses (NPS 2000b).

High voltage electricity, provided by Pacific Gas and Electric Company, is transformed to a lower voltage at a substation in Yosemite Valley and distributed within the Valley by the National Park Service Division of Maintenance. Results of an energy analysis show that approximately 5,585,092 kilowatt hours are necessary to power National Park Service facilities and operations (NPS 2000b). A small amount of energy is required for the operations of the Lower Yosemite Fall visitor area. Currently, electricity powers lighting in the parking area, the restroom, and along Northside Drive.

Topics Dismissed from Further Analysis

There will be no direct, indirect, or cumulative impact on the following resources as a result of the implementation of any alternatives proposed in this environmental assessment.

Implementation of the Lower Yosemite Fall Project would have no impact on the designated night sky or wilderness experience in Yosemite Valley. The Lower Yosemite Fall area is not located within the designated Wilderness of Yosemite National Park. In addition, this project was not considered in the night sky or wilderness analyses in the Yosemite Valley Plan (see Vol. IB, Chapter 4, pages 4.2-207) and, consequently, this topic is not considered in this environmental assessment.

Land uses within Yosemite National Park are classified as "Parklands," regardless of the individual types of land uses that occur within the park. The proposed actions in the Lower Yosemite Fall area would not affect the Parklands land use within Yosemite Valley; therefore, land use is not discussed further in this environmental assessment.

The Lower Yosemite Fall Project is a relatively small (56-acre), localized project. No aspect of any alternative of this project would result in effects to the regional economy, local economy, or the park concessioner; socioeconomics, therefore, are dismissed from further analysis in this environmental assessment.

Environmental justice analyses determine whether a proposed action would have "disproportionately high and adverse human health or environmental effects . . . on minority populations and low-income populations." The National Park Service and other federal agencies have determined that a disproportionately high and adverse effect on minority and low-income populations means an adverse effect that would result in either of the following two scenarios:

• The effect is predominately borne by a minority population and/or a low-income population.
  
• The effect will be suffered by the minority population and/or low-income population and is appreciably more severe or greater in magnitude than the adverse effect that will be suffered by the non-minority population and/or non–low-income population.

No aspect of any alternative of the Lower Yosemite Fall Project would result in disproportionately high and adverse human health or environmental effects on minority or low-income populations; therefore, environmental justice is not considered in this environmental assessment.

There are no agricultural lands in the Lower Yosemite Fall area, nor would the proposed actions under Alternatives 2 and 3 have indirect effects on downstream agricultural lands. Thus, no further discussion of this topic is necessary.

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¹ A decibel (dB) is a unit of sound energy intensity. Sound waves, traveling outward from a source, exert a sound pressure level (commonly called "sound level") measured in dB. An A-weighted decibel (dBA) is a decibel corrected for the variation in frequency response of the typical human ear at commonly encountered noise levels.

² L_eq, the energy-equivalent noise level (or "average" noise level), is the equivalent steady-state continuous noise level which, in a stated period of time, contains the same acoustic energy as the time-varying sound level that actually occurs during the same period. L_dn, the day-night average noise level, is a weighted 24-hour noise level. With the L_dn descriptor, noise levels between 10:00 p.m. and 7:00 a.m. are adjusted upward by 10 dBA to take into account the greater annoyance of nighttime noise as compared to daytime noise.

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