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ALTERNATIVE
5 The analysis of potential impacts from actions implemented under Alternative 5, Yosemite Village and out-of-Valley parking (El Portal, Henness Ridge, and Foresta), are presented in this section. Water
Resources
This section analyzes impacts on water resources: hydrology, including floodplain values, and water quality. Impacts to water resources are described by area (i.e., Yosemite Valley, El Portal, Wawona, and out-of-Valley parking locations) and are characterized as long-term alterations or restoration of hydrologic processes (e.g., water flow and flood regime) or water quality (e.g., turbidity, and non-point source pollution from vehicles or recreational use). YOSEMITE VALLEY HYDROLOGY Actions to implement the River Protection Overlay include the removal of development within 150 feet of the river. These actions would restore the river to more natural geomorphologic conditions through restoration of stream banks (i.e., stream bank stability) and the 100-year floodplain. The River Protection Overlay would allow natural processes to prevail in the river and floodplain and minimize the alterations of the floodplain due to existing and future facilities. Further, removal of development from the River Protection Overlay would potentially reduce visitor degradation of stream banks and the river channel by concentrating visitor use away from the river. Examples of these areas include Housekeeping Camp, certain meadow roads and turnouts, and campsites immediately adjacent to the river. Removal of facilities from the River Protection Overlay would allow natural floodplain alterations and lateral movement of the river channel (i.e., meandering), and increase opportunities for restoration of riparian vegetation, which would reduce unnatural erosion and deposition. Ultimately, the implementation of the River Protection Overlay would result in a regional, long-term, major, beneficial impact on hydrology and floodplain values. At Camp 6, the River Protection Overlay would be restored, including oxbows and cut-off channels that once existed in the area. Changes to the existing river dynamics through restoration of oxbows and braided streams could, over time, become more locally pronounced and eventually contribute to restoration of natural stream flow conditions downstream of the Camp 6 area. Restoration actions at Camp 6 would result in localized, long-term, moderate, beneficial impacts on hydrology and the floodplain values. The Camp 6 parking facility would be situated within a portion of the floodplain that could experience floodwater velocities up to 3 feet per second and floodwater depths exceeding 5 feet in places, as was observed during the January 1997 flood. These facilities, although in an area of low relief and not likely to divert flood flow due to obstructions, could impede the rivers ability to naturally migrate and change course during the extreme flood events. For example, an asphalt pavement surface could hinder the formation of natural flow channels or accelerate surface soil erosion once the asphalt surface and underlying base material is scoured and removed by high-velocity flood waters. A flat-surface parking facility could also reduce the area available to the river for sediment deposition and new bank slope formation. In addition, riverbank stability (soils compaction and vegetation loss) could be reduced due to the radiating impacts associated with the increased concentration of visitors. Overall, development of a parking facility and picnic area in the Camp 6 area could result in localized, long-term, moderate, adverse impacts on hydrology and floodplain values. The construction of a picnic area at the location of the former Lower River Campground would have a long-term, minor, adverse impact on hydrology due to radiating impacts of increased visitor use to a sensitive stretch of riverbank. The transit center at Yosemite Village would be constructed outside of the 100-year floodplain, but the concentration of visitors would have radiating impacts to the river and its hydrologic processes. This would be a long-term, minor, adverse impact. At Yosemite Lodge, Northside Drive would be rerouted to the edge of the 100-year floodplain, and parking would be reconfigured, but would remain in the 100-year floodplain. This would result in a long-term, minor, adverse impact on hydrology because flood flow would be altered. The removal of three structures at Ahwahnee Row that are located in the 100-year floodplain would have a long-term, localized, minor, beneficial impact on floodplain values by removing impediments on flood flow (particularly pooling in this area). Restoration areas include the portions of Yosemite Lodge (including motel units that impede flood flow and the former cabins area), Upper and Lower River Campgrounds, and roads from Stoneman and Ahwahnee Meadows that are in the 100-year floodplains. Removal of these facilities and restoration would restore the hydrologic process of flooding, and would be a long-term, moderate, beneficial impact on hydrology. The presence of a bridge as a fixed structure within a river course can cause alterations in river flow and result in localized morphologic changes to the beds and banks of the river. Morphologic changes attributable to bridge placement, and that are most readily observable, would include scour holes on the downstream side of the abutment, formation of deposition bars downstream of the scour holes, bank instability, unnatural erosion and deposition, changes in flow velocity, and localized channel widening. Removal of these fixed structures would provide for restoration of natural erosion and deposition processes; allow the river to meander and naturally alter course; and reduce flooding potential by removing flow impediments. The impacts of bridge removal would be noticeable as scour holes and downstream deposition bars caused by their in-river abutments diminish and the riverbank is reestablished by natural flow patterns. Bridge removal would continue to improve natural river flow dynamics along extended reaches of the river, and the impacts would be observable for years to come. Sugar Pine Bridge constricts the river severely, largely because this bend of the river immediately downstream of the Tenaya Creek confluence has always been dynamic. The approach road that connects Ahwahnee Bridge to Sugar Pine Bridge eliminated the numerous small cutoff channels that existed prior to construction in 1929. The loss of the numerous small cutoff channels, combined with the constriction of the river by Sugar Pine Bridge, has forced the creation of a single large cutoff channel immediately adjacent and parallel to the approach road. Removal of Sugar Pine Bridge and the approach road and restoration of the riverbank (vegetation, bank slope, channel width) would be a localized, long-term, major, beneficial impact on the Merced Rivers hydrology, by reducing unnatural erosion and scouring, reducing unnatural deposition downstream of the bridge, and allowing the river to meander. Ahwahnee Bridge moderately constricts flood flow, and has two center piers in the river channel that trap logs at high flows. The trapped logs threaten the structure, but are also important components of the hydrologic and biologic processes of the Merced River. Removal of Ahwahnee Bridge and restoration of the riverbank (vegetation, bank slope, and channel width) would be a localized, long-term, moderate, beneficial impact on the Merced Rivers hydrology by reducing scouring and unnatural erosion, and by allowing large, woody debris to remain in the river. Removal of these two bridges would also be a localized, long-term, major, beneficial impact on floodplain values by removing impediments to flood flow, particularly large flood events such as the January 1997 flood event. Local, short-term, minor, adverse impacts to hydrology may occur during bridge removal due to construction activities in the main river channel. The possible reconstruction of Swinging Bridge would have long-term, localized, minor, beneficial impacts to the Merced Rivers hydrology, because the bridge abutments would be removed from the river channel (although some piers would remain in the river). Local, short-term, minor, adverse impacts to hydrology may occur during reconstruction due to construction activities in the main channel. At Yosemite Creek, the human built rock rubble pile blocking the western channel would be removed, as would the pedestrian bridge and its abutments immediately upstream of the Yosemite Creek Bridge (vehicle). Removal of these impediments would restore hydrologic processes such as annual spring runoff, particularly restoration of flow to the western channel of the braided stream network, and would be a long-term, minor, beneficial impact on hydrology. Local, short-term, negligible, adverse impacts to hydrology may occur during removal due to construction activities in the western channel during low water. A new vehicle bridge would be constructed downstream of the existing Yosemite Creek Bridge. The abutments of the new bridge would be outside of normal high water and would minimally impact hydrologic processes. This would result in a long-term, minor, adverse impact on hydrology. Local, short-term, minor, adverse impacts to hydrology may occur during bridge construction due to construction activities in the main channel. Cascades Diversion Dam was constructed in 1917 to impound water for the intake structure that diverted river flows to a downstream powerhouse. Use of the powerhouse to generate hydroelectric power was discontinued in 1985, as was the diversion of river flows. The dam is located at a natural breakpoint in the channel gradients: upstream of the dam the gradient is .01 feet/feet; downstream of the dam the gradient is .06 feet/feet. The pool and backwater created by the dam extend upstream from the dam about 550 feet. The dam is in danger of failure: outside of spring snowmelt runoff and rain-on-snow winter floods, water flows under the dam instead of through the spillway or over the dam. Failure of the dam would result in unmitigated release of the sediment trapped behind the dam, and materials that comprise the dam. Removal of the dam would have a localized, long-term, major, beneficial impact on the Merced Rivers hydrology by preventing the adverse impacts of dam failure and by restoring the free-flowing condition of the river: sediment transport would be unimpeded; natural low-water and flood flow would be restored; and riparian vegetation currently displaced by the pool and backwater would be restored on the riverbanks. Removal of Cascades Diversion Dam would also be a localized, long-term, major, beneficial impact on floodplain values by removing a substantial impediment to flood flow: both annual spring runoff, and large flood events such as the January 1997 flood event. Reconstruction of the El Portal Road between the Cascades Diversion Dam and Pohono Bridge could have a beneficial impact on hydrology if the footprint of the existing bank stabilization in the river is reduced, or could have an adverse impact on hydrology if the footprint of the existing bank stabilization in the river is increased. Additional environmental compliance, including a Wild and Scenic River Act Section 7 determination, would be necessary before this segment of road can be reconstructed. YOSEMITE VALLEY WATER QUALITY Actions to implement the River Protection Overlay would remove sources of pollutants and reduce erosion and sedimentation by removing facilities and limiting activities associated with facility use and maintenance. These activities include construction and maintenance of visitor use facilities. Additionally, the possible realignment or relocation of roads, trails, and visitor facilities could reduce the introduction of refuse and bacteria by visitors. The removal of the concessioner stable and Swinging Bridge Picnic Area and restoration to natural conditions would reduce a source of nutrients, coliform, turbidity, and other water pollutants to the Merced River. Overall, actions to implement the River Protection Overlay would result in a regional, long-term, moderate, beneficial impact on water quality by removing development immediately adjacent to the Merced River. The removal of parking spaces from Curry Orchard, Yosemite Falls, the concessioner stable, Stoneman Meadow, and roadside areas throughout the Yosemite Valley would substantially reduce the potential sources of non-point source pollution that are inherent in areas with heavy, concentrated vehicular use. Vehicles can release pollutants onto pavement, including asbestos, heavy metals, petroleum-based products, and other chemicals such as ethylene glycol. Some fraction of these chemicals can be carried by surface-water runoff to streams, and eventually the Merced River. A formalized parking facility would be established at Camp 6, and a transit facility at Yosemite Village; stormwater pollution controls would be incorporated into the facilities design (possible treatment methods include sand filters, underground water collection and treatment tanks, or oil/water separators). Replacing the existing parking areas listed above with a formalized parking facility at the Camp 6 area would reduce non-point source pollution from stormwater runoff from large paved surfaces, resulting in a regional, long-term, moderate, beneficial impact on water quality. The construction of a gas station in Yosemite Village would be a new source of non-point source pollution. Impacts on water quality would be mitigated through stormwater pollution controls at the facility, and have a localized, long-term, minor, adverse impact on water quality. The increased use of shuttle buses would reduce the number of vehicle miles traveled in the Valley, and allow the removal of some roads (e.g., roads through Stoneman and Ahwahnee Meadows). This would have a long-term, minor, beneficial impact on water quality by reducing non-point source pollution. EL PORTAL HYDROLOGY As a result of a U.S. Army Corps of Engineers study (1998), the flood protection levee (hereafter, "levee") in the Hennesseys Ranch area would need to be raised and extended in order to protect employee housing, the impacts of which would be two-fold. First, the levee would limit and possibly redirect natural river flow through a localized reach of the river during a 100-year flood event, reducing channel width and increasing flows or eddies depending on floodwater velocity and height. The levee is above the normal high water line and would not affect the river flow during normal spring runoff periods. Increasing the length and height of the levee would be a localized, long-term, minor, adverse impact on the rivers hydrology because this reach of river has low susceptibility to bank scour, erosion, and slope instability. Secondly, any structure intended to prevent flooding has the potential to limit the natural formation and function of that rivers floodplain. Most of the Merced River in El Portal confined within a bedrock gorge channel, and the floodplain is narrow due to the river gradient and resistant bedrock. Consequently, the majority of the floodplain is more resilient and less susceptible to adverse impacts of altered river flow. The area at Hennesseys Ranch is one of the few flat, alluvial floodplain sections adjacent to the Merced River at El Portal. The alluviated area was formed through years of river sediment deposition. After construction of the existing flood protection levee, this area was isolated from further sediment deposition because the levee height prevented inundation by large flood flow such as the January 1997 flood event, which was the largest flood event in the 80+ years of stream gauge data at the Pohono gauging station. When compared to the impact of the existing flood protection levee in the No Action Alternative, increasing the length and height of the levee would be a localized, long-term, minor, adverse impact on floodplain values because only flood flow greater than the January 1997 flood event would be affected. Removal of housing from the River Protection Overlay at Hennesseys Ranch and restoration of the area would have long-term, minor, beneficial impacts on hydrology by restoring river-related communities and hydrologic processes. Construction of new housing in the 100-year floodplain but outside of the River Protection Overlay would require the modification of the levee (discussed above), and would result in radiating impacts to the riverbank due to increased employees living in the area. These radiating impacts would have a long-term, minor, adverse impact. Two pedestrian bridges would be constructed in the vicinity of Hennesseys Ranch. The bridges and their abutments would be designed to not interfere with the free-flowing condition of the river, and the banks of this river reach are relatively stable and resilient. The two pedestrian bridges would have localized, long-term, minor, adverse impacts on the rivers hydrology and floodplain values. Local, short-term, minor, adverse impacts on hydrology may occur during construction due to construction activities in the main channel. EL PORTAL WATER QUALITY Actions to implement the River Protection Overlay would reduce discharge of non-point source pollutants into the river by providing a buffer area where development is removed (e.g., at Hennesseys Ranch) and future development is constrained (e.g., at Village Center and Railroad Flat). Water quality could be adversely impacted by runoff associated with increased parking spaces for both visitors and employees, although this impact would be mitigated by non-point source pollution controls at large paved areas. The increase in employees living in El Portal would likely result in increased recreational use of the river and subsequent increase in fecal coliform and bacteria levels, resulting in a regional, long-term, minor, adverse impact on water quality. Wastewater from all new buildings (e.g., housing, park headquarters, etc.) would be connected to the existing sanitary sewage system and would meet all applicable water treatment requirements. The impacts of Alternative 5 on water quality in El Portal would be localized, long-term, minor, and adverse, due to increased non-point source pollution resulting from increased development. WAWONA HYDROLOGY Construction of employee housing in Wawona would be outside of the 100-year floodplain, approximately 1,000 feet away from the South Fork Merced River. Radiating impacts to the river due to increased numbers of employees accessing the river would reduce bank stability and result in localized, long-term, negligible, adverse impacts on hydrology and floodplain values. WAWONA WATER QUALITY Actions to implement the River Protection Overlay would reduce discharge of non-point source pollutants into the river by providing a buffer area where future development is constrained. Water quality could be adversely impacted at the new employee housing by runoff associated with increased parking spaces, although this impact would be mitigated by non-point source pollution controls at large paved areas. Wastewater from all new buildings would be connected to the existing sanitary sewage system and would meet all applicable water treatment requirements. The impacts of Alternative 5 on water quality in Wawona would be localized, long-term, minor, and adverse. FORESTA HYDROLOGY AND WATER QUALITY The project site at Foresta is approximately three-quarters of a mile from Crane Creek, but has no rivers, streams, or other hydrologic features, and surface runoff is the only pertinent hydrologic process. A parking facility, Volunteers-in-Parks campground, 14 houses, and a new National Park Service stable at McCauley Ranch (depending on the outcome of the Wilderness Feasibility Study) would be constructed in the Foresta area. These actions would have a localized, long-term, negligible, adverse impact on hydrology resulting from reduced ground cover and potentially increased runoff. These actions would result in increased non-point source pollution, which would be mitigated through stormwater pollution controls at the parking facility, and have a localized, long-term, minor, adverse impact on water quality. HENNESS RIDGE HYDROLOGY AND WATER QUALITY Henness Ridge has no significant hydrologic features, and surface-water runoff is the only pertinent hydrologic process. The construction of a parking facility would have localized, long-term, minor, adverse impacts on hydrology resulting from reduced ground cover and potentially increased runoff. Construction of a parking facility would increase non-point source pollution, which would be mitigated through stormwater pollution controls, and would have a localized, long-term, minor, and adverse impact on water quality. BIG
OAK FLAT, TIOGA PASS, AND SOUTH ENTRANCE The locations of these entrance stations have no major rivers, streams, or other hydrologic features. Surface-water runoff is the only pertinent hydrologic process. A visitor center and associated visitor service facilities would be constructed, resulting in reduced ground cover and potentially increased runoff. These actions would have a localized, long-term, negligible, adverse impact on surface water hydrology. These actions would have a localized, long-term, negligible, adverse impact on water quality resulting from increased non-point source pollution associated with development. CONCLUSION The collective actions of this alternative have regional, long-term, moderate, beneficial impacts on hydrology and water quality, largely due to the removal of facilities in Yosemite Valley from the River Protection Overlay and the 100-year floodplain and removal of the bulk fuel storage facility in El Portal. The beneficial impacts of removing two bridges, Cascades Diversion Dam, campsites, Housekeeping Camp units, etc., have been weighed against the adverse impacts on hydrology and water quality in El Portal due to increased development near the river. CUMULATIVE IMPACTS This section assesses the impacts of past, present, and reasonably foreseeable future actions to water resources. The actions identified below have generally occurred within the watershed of the Merced Riverboth main stem and South Fork. Past Actions The water resources of the Merced River have been historically affected by a variety of actions within the floodplain since Euro-American settlement. In Yosemite Valley, the transportation network interferes with flooding and surface-water flow, and lodging, campgrounds, and other structures have been constructed in and immediately adjacent to the river channel. In El Portal, a large portion of the riverbank has been artificially stabilized to protect primary roads and buildings immediately adjacent to the river. Because artificial stabilization of the riverbank began in the 1800s, the Merced River has been separated for decades from substantial portions of its floodplain. During spring runoff floods, this riprap serves to keep the channel from moving, and quickly conveys the water downstream. During winter floods, artificial bank stabilization prevents damage to dwellings and roads in the best-protected sections, but increases bank destruction where there is little or no artificial bank stabilization. Present Actions The El Portal Road Improvement Project (NPS) is currently under way from the park boundary to the Cascades Diversion Dam, and affects river-related communities of the Merced River immediately adjacent to the roadway. Natural resources are protected during construction by implementation of a compliance-monitoring program, erosion and sediment controls, hazardous materials controls, revegetation and reclamation, and excluding construction from sensitive habitats. Between El Portal and Yosemite Valley, riprap has been placed in some locations along the north bank of the Merced River to protect the reconstructed El Portal Road, altering the overall flow regime of the river. Reasonably Foreseeable Future Actions Reasonably foreseeable future actions proposed in the region are separated below into four general categories: (1) projects expected to have a net beneficial impact; (2) projects expected to have both beneficial and adverse impacts; (3) projects expected to have a net adverse impact; and (4) projects that have no impact relative to the actions of this alternative. Reasonably foreseeable future projects that could have a net beneficial impact on water resources of the Merced River include:
These projects would have net beneficial impacts on water resources through improved coordination of resource management activities and restoration, although there might be site-specific or short-term, adverse impacts. Reasonably foreseeable future projects that could have both beneficial and adverse impacts on water resources include:
These projects would have beneficial impacts on water resources by removal of facilities, restoration, and slope stabilization, and adverse impacts on water resources through increased non point source water pollution. Reasonably foreseeable projects that could have a net adverse impact on water resources include:
These projects would have adverse impacts on water resources through increased use and facility development, which could result in stream bank instability and increased non-point source water pollution. Beneficial impacts on water resources of past, present, and reasonably foreseeable future projects on the Merced River watershed would be related to removal of facilities from the riverbanks and floodplain, restoration of previously developed areas and areas significantly impacted or altered by visitor use, removal of channel obstructions, and reduced human-related impacts. Adverse impacts of these projects on the Merced River watershed would be related to increased use and facility development, which could result in stream bank erosion, soil compaction, loss of vegetation, refuse accumulation, non-point source pollution generation, and degradation of stream characteristics and water quality in the Merced River. Overall, the past, present, and reasonably foreseeable future projects would have a long-term, minor, beneficial impact on water resources. The actions of this alternative would have a long-term, moderate, beneficial impact on water resources. The actions of this alternative, in combination with past, current, and reasonably foreseeable future projects would have a long-term, moderate, beneficial impact on water resources. Floodplains
This evaluation identifies non-exempted actions within the floodplain that could increase or decrease risk to human life and property by adding or removing housing and facilities from floodplains. The proposed removal and addition of non-exempted facilities from the floodplain are listed below by area and summarized in table 4-117; all impacts would be long-term unless otherwise noted (see plate E for Yosemite Valley flood extent). For related effects on floodplain values and hydrology, see the Water Resources section in this chapter.
YOSEMITE VALLEY Cascades Diversion Dam Dam safety engineers have classified the Cascades Diversion Dam as a "high hazard potential structure" and assigned a Safety of Dams condition of "unsatisfactory." This classification requires immediate corrective action. The removal of the dam would be a long-term, localized, major, and beneficial impact to human health and safety. Concessioner Stable Area A moderate, beneficial impact would result from the removal of houses and tent cabins (49 employee beds) and the concessioner stable from the floodplain. This beneficial impact would be related to reduced risk to both human life and property during a flood event. Although the area would be redeveloped as campgrounds, this type of facility is exempt from National Park Service Floodplain Management Guideline. Campgrounds would be located outside the River Protection Overlay and designed to minimize flood flow. Housekeeping Camp The removal of 164 housekeeping units and retention of 84 units in the 100-year floodplain would result in a moderate, beneficial impact because overnight lodging within the 100-year floodplain would be reduced, decreasing flood-related risk to both human life and property. Compared to the No Action Alternative, the beneficial effect related to human life is limited, however, because the units are not in use during the winter flood season. Yosemite Village Removal of the Concession Headquarters, Indian Creek employee housing (14 employee beds), and removal of three Ahwahnee Row houses (three employee beds) from the floodplain would result in an overall moderate, beneficial impact because fewer people would be living and working within the floodplain and flood hazard related to human safety would be reduced. Redevelopment of this area would minimize placement of structures in the floodplain and include mitigation measures to protect people during flood events. With mitigation, in accordance with National Park Service Floodplain Management Guideline, risk to both human safety and property would be a minor, adverse impact.
Yosemite Lodge Area Removal of the Superintendents House (Residence 1) and five motel units from the floodplain would result in a moderate, beneficial impact because overnight lodging within the floodplain and the associated risk to human safety and property would be reduced. Relocation of the Wellness Center and nearby custodial cabins outside the floodplain would also result in a minor, beneficial impact because the number of facilities and people working within the floodplain would be reduced, resulting in a reduction in the flood hazard related to human safety and property. New overnight parking would be developed that incorporates design standards to minimize the effect on flood flow and allow for runoff, resulting in a negligible, adverse impact. Adverse effects in the Yosemite Lodge area would be further reduced by designs that minimize impacts on natural flood processes and flood damage to structures, and by preparation of evacuation plans and routes (evacuation routes would be located outside the floodplain). EL PORTAL Village Center Moderate, beneficial impacts at the Village Center would result from the adaptive reuse of El Portal Hotel (removal of 12 employee beds and relocation of Yosemite Institute Office), and the removal of the Motor Inn cabins (24 employee beds) because overnight occupation of the floodplain would be reduced. Removal of the bulk fuel storage facility would result in a moderate, beneficial impact on human safety because the number of people working within the floodplain would be reduced. Adaptive reuse of these facilities would include mitigation consistent with National Park Service Floodplain Management Guideline to reduce the risk of property damage due to flooding. Parts of the Village Center area that would be redesigned to support commercial services and parking would be placed out of the floodplain where possible. For new structures constructed in the floodplain an evacuation and safety plan would be developed. With these mitigation measures in place, there would be a minor adverse impact. Hennesseys Ranch The construction of 656 new employee beds at Hennesseys Ranch would be a major, adverse impact on human safety because employee beds would be constructed within the 100-year floodplain. However, because mitigation would be incorporated into the design to protect employees and structures during flood events (e.g., raising and extending the levee, evacuation planning), the overall impact would be reduced to moderate and adverse. WAWONA There would be no impact to the South Fork Merced River floodplain because the employee housing considered for Wawona would be outside the floodplain. CONCLUSION Beneficial impacts in Yosemite Valley would include removal from the floodplain of 164 housekeeping lodge units, the kennel, concessioner stables and associated housing (49 employee beds), the Superintendents House (Residence 1), five Yosemite Lodge motel units, the Wellness Center and nearby custodial cabins, and 14 employee beds at Indian Creek. The Concession Headquarters and Indian Creek employee housing would be redeveloped as parking/visitor services, and new overnight parking would be developed at Yosemite Lodge which would have a minor, adverse impact on the floodplain. Overall, the aggregate impact of these actions in combination with mitigation in Yosemite Valley would be moderate and beneficial, because the flood-related risk to human safety and property would be reduced. Actions in El Portal would include removal from the floodplain of 36 employee beds (moderate, beneficial) and the bulk fuel facility (moderate, beneficial), removal or adaptive reuse of El Portal Hotel (employee housing and Yosemite Institute Office; moderate, beneficial), 656 employee beds at Hennessey Ranch (moderate, adverse) and redevelopment of Village Center (minor, adverse). Beneficial impacts would be related to reduction in the flood-related hazard to human safety. Adverse effects to both human safety and property associated with new development or redevelopment/adaptive reuse within the floodplain would be minimized by mitigation (e.g., design and siting specifications, extending and raising existing levees, and a mandatory evacuation plan) resulting in a net minor, adverse impact. The total net effect of Alternative 5 would be moderate and beneficial, because the number of people working and overnight lodging/housing within the floodplain would be reduced (reducing flood-related risks to human safety), and mitigation would be implemented to reduce adverse effects on human safety and property associated with development/redevelopment within the floodplain. CUMULATIVE IMPACTS The impacts of past, present, and reasonably foreseeable future actions to floodplain values discussed herein are based on analysis of past, present, and reasonably foreseeable future actions in the Merced River watershed from its source near the crest of the Sierra Nevada to Briceburg Bridge. The actions identified below include those projects that have the potential to affect the floodplain of the Merced River. Past Actions The Merced River has been historically affected by a variety of actions within the floodplain since Euro-American settlement. In El Portal, from the park boundary to Briceburg Bridge, a large portion of the riverbank has been artificially manipulated. Much of this manipulation is riprap used to stabilize the riverbanks by the California Department of Transportation to protect Highway 140. The National Park Service and Yosemite Motels also placed riprap in the Merced River channel to rebuild roads (e.g., Foresta Road) and protect buildings immediately adjacent to the river. Because stabilization of the riverbank began in the 1800s, the Merced River has been separated for decades from substantial portions of the floodplain in the Merced River Canyon. During spring runoff floods, this riprap serves to keep the channel from moving, and quickly conveys the water down to Lake McClure. During winter floods, bank stabilization prevents damage to dwellings and roads in the best-protected sections, but increases bank destruction where there is little or no bank stabilization. Present Actions No current actions are increasing or decreasing flood-related risk to human life. Between El Portal and Yosemite Valley, riprap has been placed in some locations along the north bank of the Merced River to protect the reconstructed El Portal Road. This riprap would have essentially no flood-related risk to life or property. Reasonably Foreseeable Future Actions Reasonably foreseeable future actions that could have a potential cumulative beneficial or adverse effect on risk to human life and property during flood events are:
Cumulative effects of past, present, and reasonably foreseeable future actions would have both beneficial (e.g., implementation of the Trailer Village Closure Plan) and adverse (i.e., increased development of overnight lodging units and offices within the floodplain at El Portal) impacts on human life and property during flood events. In El Portal, approximately 59 employee trailers with 68 employee beds at Hennesseys Ranch (currently Trailer Village) would continue to be scheduled for removal from the 100-year floodplain. This action which occurs outside the scope of actions considered in the Final Yosemite Valley Plan/SEIS, is in accordance with the current provisions of the Trailer Village Closure Plan (NPS 1993b). Cumulative adverse impacts of these potential future projects on the floodplain hazard of the Merced River would be related to increased overnight use and facility development. In El Portal, potential overnight residents and hotel visitors would slowly increase from approximately 1,300 to about 1,600 beds because of the Yosemite Motels expansion and the Yosemite View parcel land exchange. This represents an increase of approximately 25% in the number of people potentially affected during a flood. Overall, the past, present, and reasonably foreseeable future actions listed above would have a long-term, moderate, and adverse effect on risk to human life and property due to the amount and type of new development planned within the floodplain. The total net effect of Alternative 5 would be moderate and beneficial, because overnight lodging/housing within the floodplain would be reduced (reducing flood-related risk to human safety), and mitigation would be implemented to reduce adverse effects on human safety and property associated with development/redevelopment within the floodplain. Effects associated with this alternative, in conjunction with other past, present, and reasonably foreseeable future cumulative actions, would be long-term, minor, and adverse, because potential flood-related impacts to human safety and property from cumulative actions outside the scope of the Final Yosemite Valley Plan/SEIS (e.g., increased overnight lodging within the floodplain in El Portal would increase flood-related risk to human safety and property) would outweigh the beneficial impacts of this alternative. Wetlands
In this section, wetlands were evaluated in the following locations: Yosemite Valley, El Portal, Tioga Pass Entrance, South Entrance, and Foresta. The Henness Ridge, Wawona, and Big Oak Flat Entrance locations have no wetlands and are not discussed below. There are no actions proposed at Badger Pass, South Landing, or Hazel Green in this alternative. SIZE Yosemite Valley Wetland impacts would take place in the wetland types in Yosemite Valley shown in table 4-118. Acres of impacts are estimated based on geographic information system analysis of meadow and riparian vegetation types from the Yosemite Valley vegetation map (NPS 1994e). There would be a net gain of 104 acres of wetlands in the Valley. In Yosemite Valley, about 131 acres of wetlands would be restored, 12 acres of new development in wetlands would take place, and 15 acres of redevelopment in potential wetlands would take place under Alternative 5. Overall, this would be a moderate, long-term, beneficial impact on the size of wetlands in Yosemite Valley.
Restoration would take place primarily at the cabin area at Yosemite Lodge, parts of Upper and Lower River Campgrounds, North Pines Campground, Lower Pines Campground, Backpackers and Group Campgrounds, the River Protection Overlay portion of Housekeeping Camp, Camp 6, and Swinging Bridge Picnic Area. New development in wetlands could take place on 12 acres. Wetland delineation would be completed prior to the planning and design phase for Curry Village, where potential wetlands have been identified, to maximize the opportunity for wetland avoidance and minimization of adverse impacts. If wetlands are present in the area, adverse impacts would be avoided during site design and minimized through design modifications to the greatest extent practicable. If potential adverse impacts on wetlands are disclosed in subsequent planning efforts, additional compliance documentation would be completed as appropriate. Potential impacts to wetlands would require a Wetland Statement of Findings to be prepared in accordance with Directors Order #77-1. Wetlands proposed for restoration by this Final Yosemite Valley Plan/SEIS would be counted toward the compensation of wetlands if needed for future compliance. A wetland delineation and a functional analyses would be included in each Statement of Findings. A U.S. Army Corps of Engineers 404 permit would be prepared as required. Redevelopment in potential wetlands under Alternative 5 would occur on about 15 acres (see table 4-118). The larger areas of redeveloped wetland would occur at Sentinel Beach Picnic Area and Upper Pines Campground. Wetland delineation would be completed prior to the design phase for the proposed Sentinel Beach Picnic Area. Wetland delineation has been completed for Upper Pines Campground (Kleinfelder 1998). Redevelopment within wetland boundaries would be avoided in the Upper Pines Campground area. Redevelopment in areas adjacent to wetlands would occur primarily at Yosemite Lodge, Yosemite Village, and Ahwahnee parking. Redevelopment could have a minor, beneficial effect on neighboring wetlands if water flows that sustain wetlands are improved in the site design. Redeveloped wetlands may be considered an adverse impact if the sites still qualify as wetlands. Procedural Manual #77-1, Section 5.4 states that "development activities proposed for wetland sites that have been modified or degraded as a result of human activities" (but still meet the wetland definition) are considered "new actions" subject to Directors Order #77-1 and other statutes. Consequently, degraded wetlands should not be treated as preferred development sites simply because they are already in an impacted condition. Out-of-Valley Areas No impacts on the size of wetlands would occur at Henness Ridge, El Portal, South Entrance,Tioga Pass Entrance, or Foresta. INTEGRITY Yosemite Valley The integrity of wetlands would be improved by actions proposed in Alternative 5 in terms of the benefits of the River Protection Overlay such as the re-establishment of riverine and palustrine forest wetlands along the Merced River. The restoration of campgrounds to natural conditions would also decrease foot traffic along the Merced River and allow these wetlands to become reestablished. Under Alternative 5, no transportation-related activities would directly benefit wetlands. Transportation-related activities that could have indirect adverse impacts on wetlands include the realignment of Northside Drive south of Yosemite Lodge and construction of a new bridge across Yosemite Creek. These indirect impacts would include increased runoff and potential changes to wetland hydrology. These impacts would be mitigated through treatment ponds and road design. Direct impacts to riverine and palustrine forest would occur with the new bridge construction across Yosemite Creek; however, this would be a minor, adverse impact because of the existing level of impact that has occurred to these wetlands. Out-of-Valley Areas In El Portal, implementation of the River Protection Overlay and protection of existing wetlands at Hennesseys Ranch would minimize wetland impacts. Rebuilding the levee could adversely affect wetlands within the levee alignment. These impacts would be minimized by restoration of the riverine and palustrine forest wetlands between the levee and the rivers edge. Should parking be constructed near the El Portal Community Hall, site designs would protect the historic river channel. Impacts on wetlands in El Portal are expected to be long term and minor and would not affect the overall viability of wetlands in the area. In Foresta, a one and one-half acre artificial palustrine scrub shrub wetland (in an old borrow pit) is directly adjacent to the proposed parking site and is expected to be impacted by heavy foot traffic. This would be a long-term, minor, adverse impact on wetlands in Foresta, with implementation of appropriate mitigation measures (see Vol. IA, Chapter 3). Wetlands adjacent to McCauley Ranch would be avoided through site design with relocation of stable operations to Foresta. Radiating impacts from increased nutrients and potential non-native plant species introductions from the stables would be minimized by aggressive management of stock waste and feed. CONNECTIVITY Yosemite Valley The entire riparian corridor in Yosemite Valley along the Merced River would be restored, reconnected, and protected from future degradation by implementation of the River Protection Overlay and removal of campgrounds at Upper and Lower Rivers Campground and other areas. This would be a long-term, major, beneficial impact on palustrine forest wetland connectivity in Yosemite Valley, though benefits to palustrine emergent wetlands would be minor. Out-of-Valley Areas No additional adverse impacts on wetland connectivity would take place in El Portal, Foresta, Henness Ridge, or Tioga Pass Entrance beyond those presented in Alternative 1. CONCLUSION Under Alternative 5 there would be a 104-acre net gain in the size of wetlands. The implementation of the River Protection Overlay would enhance the integrity of existing wetlands along the Merced River. Wetlands would remain fragmented by campgrounds and roads in Stoneman and Ahwahnee Meadow, parking at Camp 6, and other infrastructure. The actions that are proposed in Alternative 5 would have a long-term, moderate, beneficial impact on the size, integrity, and connectivity of wetlands in Yosemite Valley. Under Alternative 5 there would be a long-term, minor, adverse impact on wetland integrity in Foresta and El Portal. Henness Ridge would have no wetland impacts. Heavy foot traffic would have minor impacts to wetland integrity at the Tioga Pass Entrance. CUMULATIVE IMPACTS Past, present, and reasonably foreseeable future actions that could have a cumulative impact on wetlands are all considered to be long term. Regional and parkwide planning efforts such as the Sierra Nevada Framework for Conservation and Collaboration (USFS); U.S. Forest Service management plans for adjacent wilderness; the Wilderness Management Plan Update (NPS); and the Fire Management Plan Update (NPS) could provide benefits to the size, integrity, and connectivity of wetlands. Cooperation among land management agencies would increase the opportunity to share common objectives and improve resource protection. These plans could also increase knowledge of resources and recreational use; they have the potential to have long-term, moderate, beneficial impacts on wetlands, though the proposed management direction has not been finalized. The Merced Wild and Scenic River Comprehensive Management Plan would affect wetlands through zoning and management designed to protect the river system and adjacent wetlands with long-term, major, and beneficial impacts. The Tuolumne Meadows Water and Wastewater Improvements (NPS) project and the Mariposa Creek Pedestrian/Bike Path (Mariposa Co.) project are in the early stages of planning. Until the scope and design of these projects is determined, it is not possible to determine the extent of impacts on wetlands in these areas. Other projects approved or planned for construction that could have beneficial effects on wetlands include erosion mitigation projects in Tamarack, Yosemite Creek, Bridalveil, and Hodgdon Meadows, and the Merced River at Eagle Creek Ecological Restoration Project (Yosemite Valley). Erosion control could enhance and strengthen palustrine forest and palustrine scrub shrub wetlands. The Eagle Creek project would revegetate riverbanks of palustrine forest and palustrine scrub shrub wetland. The erosion control and restoration projects would have long-term, localized, and therefore minor, beneficial impacts on wetlands. Projects approved or planned for construction that could have adverse effects on wetlands include the Yosemite View Parcel Land Exchange (NPS), University of California, Merced campus (Merced Co.), and the Hazel Green Ranch (Mariposa Co.) project. The Yosemite View Parcel Land Exchange could directly affect existing palustrine forest and palustrine emergent wetlands. A wetland traverses the Hazel Green Ranch site, though proposed new development would not take place within the wetland corridor. The long-term direct impacts on wetlands would be moderate and adverse due to the relative rarity of undeveloped wetlands between the elevations of 1,000 and 3,000 feet and the relative importance of remaining habitat in the Sierra Nevada. Foothill areas below about 3,300 feet appear to have the greatest loss of wetlands of any region in the Sierra Nevada (UC Davis 1996a) and are particularly important in terms of their productivity and diversity. Large-scale benefits to wetlands could take place as a result of regional and parkwide planning efforts such as the Sierra Nevada Framework for Conservation and Collaboration (USFS) and the Merced River Plan. Should substantial or full implementation of the actions included in these plans occur over time, long-term cumulative impacts on wetlands may, on balance, be moderate and beneficial. These regional plans are tempered by adverse impacts that include existing infrastructure to divert water away from wetlands in Yosemite Valley, and projects impacting wetlands outside the park with the potential direct loss of wetland habitat, including at the Yosemite View Parcel Land Exchange (NPS), and University of California Merced campus (Merced Co.) projects. When the impact of the past, present, and future actions are combined with the actions proposed in Alternative 5, there would be a minor, beneficial impact on wetland size. Soils
The following discussion identifies and characterizes the soils impacts expected from implementation of Alternative 5. Impact intensities are based on the size, type, and disturbance history of the soil resources impacted. Soil resources are identified as highly valued resources (HVR), resilient (R) or other (O). The primary activities that would affect soil resources are discussed for each of the project areas. Generally, adverse impacts to soils would include a combination of soil removal, profile mixing, compaction, erosion, and contamination. Beneficial impacts would occur as a result of soil restoration. Construction-related impacts (such as compaction from equipment and erosion) would be expected to be short term and temporary, because they would be minimized through the use of Best Management Practices and would occur for a limited time. All other impacts are expected to be long term unless otherwise noted. YOSEMITE VALLEY Approximately 228 acres would be affected by actions proposed under Alternative 5 (table 4-119). Highly valued resource soils comprise 122 acres, resilient soil resources comprise 83 acres, and other soils comprise 23 acres. Of the total area affected, 161 acres would be restored, while 67 acres would be associated with new development. Construction-related impacts (short-term) would be negligible to minor because Best Management Practices would be used to minimize erosion and to contain construction activities to the immediate area. Some minor discrepancies between acreages in the text and tables may occur due to rounding, differences in mapping sources, and because impacts less than 1 acre were not mentioned in the text. A summary of affected Valley soils is found in table 4-119.
Curry Village Approximately 22 acres would be affected by actions proposed under Alternative 5: 15 of these acres would be restored (HVR=9, R=3, O=3); and 7 acres would be developed (R=5, O=2). The proposed development activities would have a negligible, adverse effect on soil resources because of their small size (7 acres) and focus on resilient soil resources. Overall, Alternative 5 would have a minor, beneficial effect on the soil resources in Curry Village. Yosemite Lodge Approximately 49 acres would be affected by actions proposed under Alternative 5: 42 of these acres would be restored (HVR=18, R=23, O=1); and 7 acres would be developed (R=6, O=1). Restoration of the floodplain area between Yosemite Lodge and the Merced River would result in major, beneficial impacts to soil resources. Construction activities, such as those required for additional housing units and the new bridge south of the Yosemite Creek Bridge, would have negligible, adverse impacts since these activities are concentrated on resilient soils and the size of the impact would be relatively small. The overall impact to soil resources at Yosemite Lodge would be major and beneficial. Yosemite Village Approximately 20 acres would be affected by actions proposed under Alternative 5: 6 of these acres would be restored (HVR=5, O=1), and 14 acres would be developed (R=6, HVR=8). The adverse impacts would be due to construction activities related to the visitor center, and day-visitor parking. The net effect of the actions proposed at Yosemite Village would be a negligible, adverse effect on soil resources. West Valley Approximately 11 acres would be developed by actions proposed under Alternative 5 (R=7, O=4). Adverse effects are related primarily to the construction of the North American Wall Picnic Area and the El Capitan crossover. Both activities would occur on previously undisturbed resilient or other soil resources. The overall impact of activities planned for the west Valley would be minor and adverse because of the relatively small impact area and resource type. Campgrounds A total of 126 acres would be affected by actions proposed under Alternative 5: 97 of these acres would be restored (HVR=86, R=11); and 29 acres would be developed (R=27, O=2). Fewer campground areas would be restored under Alternative 5, with a resulting lesser beneficial impact. Campground restoration activities would result in moderate, beneficial effects. Adverse effects would be related to the development of new campground areas. Nearly all of the proposed area for new campgrounds would affect resilient soil resources. Generally, the impacts of campground development would be less disturbing to soil resources than other construction activities. Thus, although the area of impact would be relatively large (29 acres), the actual area of soil disturbance would be much less extensive. Adverse effects due to campground development are expected to be moderate. The overall impact within the campground area would be moderate and beneficial due to the amount of restoration proposed. Roads and Trails Transportation corridors such as multi-use paved trails and roadways have the potential to affect several soil resource types. Generally, trail construction would occur adjacent to existing linear corridors such as roads or utilities, or would be upgrades of existing informal trails. The impact of new trail construction would be adverse; however, the impact would be minor since the impacts would primarily be in linear segments of previously disturbed soils. New trails would be constructed to accommodate surface and subsurface water flow. Additionally, upgrades to existing trails would decrease erosion in high-use areas. Overall, the construction of new roads and trails would have minor, adverse effects. OUT-OF-VALLEY Soils information is limited for many of the out-of-Valley locations. The following discussion is based on the available general soils information or extrapolated from other local soil surveys. It is assumed that out-of-Valley impacts would likely occur on resilient soil resources, because the geographic features outside of the Valley tend to be less constricting than those in the Valley. Disturbance to highly valued resource soils would be avoided as practicable, to reduce the likelihood of impacts on highly valued resource soils. General Best Management Practices and design requirements would reduce potential impacts to other soils. Thus, the following discussion is based on the premise that the majority of adverse impacts would occur on resilient soil resources, where feasible. El Portal All of the impacts at El Portal would be long-term and adverse. Impacts are related to the construction of parking facilities and employee housing. Soils within the El Portal area tend to be susceptible to mass movement and erosion and have substantial development limitations. Therefore, Best Management Practices and other mitigation measures described in Vol. IA, Chapter 2, Soil Mitigation would be implemented to minimize erosion and soil movement. Due to the size of the proposed activities and the limited space available for construction, this alternative would have a moderate, adverse impact on soil resources in the El Portal area. Henness Ridge Under Alternative 5, construction of a parking facility at Henness Ridge would require a relatively small area of development. Generally, the soils at Henness Ridge are suitable for the proposed activity. Impacts are expected to be moderate and adverse. Foresta Impacts to soils in Foresta would occur if the National Park Service and concessioner stables are relocated to McCauley Ranch, and as a result of the reconstruction of employee beds destroyed in the 1990 A-Rock fire. However, impacts would be minor and adverse, because soils in these areas tend to be resilient and the area of impact would be relatively small. A day-visitor parking facility would also be constructed in Foresta, and would result in moderate, adverse impacts to soils. Wawona The soils within the Wawona area have mostly minor limitations for structures. Construction of housing facilities would occur on mostly resilient soils that are suitable for this use and would be expected to cause minor and adverse soil impacts. Entrance Stations Development or redevelopment of visitor centers near the existing entrance stations would result in adverse impacts to soil resources. The centers would be developed adjacent to existing stations, and generally would be located in areas suitable to the proposed use. The size of impact for each facility would be relatively small in relation to the surrounding soil resources. The impact due to construction of visitor centers would be negligible and adverse. CONCLUSION Four out of the five Valley locations would have overall beneficial impacts under this alternative, which proposes restoration of 161 acres and new development of 67 acres. West Valley would have the largest adverse impact. This adverse impact would be offset to a large extent by the restoration of 114 acres of highly valued resource soils, 33 acres of resilient soils, and 14 acres of other soil resources. The proposed developments would be focused on resilient soils (51 acres). Thus, the overall impact of Alternative 5 in the Valley would be minor and beneficial. The actions under Alternative 5 would affect approximately 80 acres outside of the Valley. Most of this impact would be focused on resilient soil resources. Proper use of engineering controls and mitigation measures would result in an overall moderate, adverse impact on out-of-Valley soils. Overall, Alternative 5 would have beneficial impacts on 161 acres and adverse impacts on approximately 67 acres. Out-of-Valley development would affect approximately 80 acres of non-highly valued resource soils. Generally, the facilities that would be relocated outside of the park would affect less sensitive resources than are currently being affected in the Valley. Furthermore, facility design and construction would use current technologies and Best Management Practices to minimize impacts. Out-of-Valley impacts would be locally moderate and adverse, but would occur on resilient soil resources at all locations except for El Portal. The overall impact for Alternative 5 would be negligible and beneficial because of the smaller scale restoration and adverse impacts at El Portal, Henness Ridge, and Foresta. CUMULATIVE IMPACTS The impacts of past, present, and reasonably foreseeable future areawide projects would be the same as described under Alternative 2, minor and adverse. In relation to the expected impacts resulting from areawide projects, the beneficial impacts related to restoration under this alternative would be substantial because they would be the primary beneficial impacts on soil resources that would occur | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||