4.3.2

near vertical as the rock structure will allow. The diversion of drainage reduces the amount of percolation
into and through the rock, thus reducing the transport of acidiry and potentially toxic metals. Steepening of
slope angles reduces the surface area exposed to precipitation. Furtber measures include using a source of
alkalinity in the drainage system.
Strategies used on the Cherohala Skyway to minimize acid drainage from cut slopes and additional measures
that could be applied to cut slopes to minimize acid production include: excavating slopes as steep as the
structural conditions would allow to reduce the exposed area and the amount of runoff; diverting runoff
around the cut face using limestone rip rap or concrete-lined ditches to retard acid production within the
rocic; and seeding flatter slopes with native grasses as soon after exposure as possible. An additional
measure for consideration in mitigating acid drainage from cut slopes in AP rocks is diversion of runoff from
the cut face area into open limestone channels (Ziemkiewicz et a1.1977). The alkalinity of the limestone
reduces acidity-causing precipitation of inetals, but the turbulence of the flow prevents the reactive surface of
the limestone rip rap from being coated with secondary iron materials. Another treatment that could be
effective, but is costly, is the formation of a grout curtain above the cut slope to prevent groundwater from
percolating through the bedrock and flushing acid and metals into the slope drainage.
4.3.1.5 Impairment Evaluation
Impairment (as defined by NPS policy) to the topography, geology, and soils of GSMNP and the AT would
not occur under the No-Action Alternative, Monetary Settlement Alternative, Laurel Branch Picnic Area,
and the Partial-Build Altemative to Bushnell. The Northem Shore Corridor is not likely to impair the
topography, geology, and soils of GSMNP or the AT based on the information obtained to date. Due to the
magnitude of this alternative, it is likely that additional NEPA documentation would be required to address
sit�specific impacts not currently known, to determine detailed avoidance, minimization, and mitigation
measures as they relate to final design, and to re-evaluate the impairment determination related to
topography, geology, and soils.
4.3.2 Floodplains and Floodways
While the No-Action and Monetary Settlement alternatives would not impact floodplains within GSMNP,
Laurel Branch Picnic Area, the Partial-Build Alternative to Bushnell, and tbe Northern Shore Corridor would
encroach on the 100-year floodplain at locations of major stream crossings (Figure 3-3). If an alternative
involving construction is implemented, encroachments could be minimized during mare detailed design.
In compliance with Executive Order 1] 988 and Director's Order #77-2, a Statement of Findings for
floodplains would be developed and released for public review if a partial-build or build alternative was
selected for implementation. A Statement of Findings explains why an alternative with floodplain impacts
was identified as the preferred alternative, and details such information as a description of the flood hazard
assumed by implementation of the proposed action, an analysis of the comparative flood risk among
alternatives, a summary of the effects on floodplain values associated with the proposed action, and an
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-107
North Shore Road Final Environmental Impact Statement

evaluation of the proposed mitigation measures. For any study alternative tbat impacts floodplains, more
detailed design and additional field surveys may be required before a Statement of Findings is developed.
4.3.2.1 Methodology for Assessing Floodplain Impacts
Existing conditions were assessed based on available topographic data of GSMNP. A Flood Insurance Study
(FIS) for Swain Count}�, North Carolina was prepared by the FEMA in 1983. However, the FIS did not
include base flood elevations within GSMNP. The locations of 100-year floodplains for drainage areas of 1
mi2 (260 ha) or greater at proposed roadway crossings were identified on the topographic maps from
approximate flood heights computed using a technique developed by the United States Geological Survey
(Coble 1979), which is based on statistical data obtained from stream gages located in the North Carolina
mountains.
The streams in the project area are steep with narrow, confined valleys and floodplains. Drainage areas,
associated with alternatives that include roadways that traverse streams, ranged in size from 1 to 45 mi� (260
to 11,655 ha). Flood heights for the 100-year flood event ranged from 4 to 9 ft(1.2 to 2.7 m) above the
channel bottom, with the resulting width of the floodplain varying from 30 to 350 ft(9 to 107 m).
This section refers to the associated roadway, as applicable, for the Laurel Branch Picnic Area, Partial-Build
Alternative to Bushnell, and the Northern Shore Corridor. It does not discuss any related overlooks, parking
lots, picnic shelters, restroom facilities, or buildings because these other site-specific facilities likely would
be located above the 100-year floodplain, based on the topographic conditions of the area.
Under the guidelines of NPS DO 77-2 the Laurel Branch Picnic Area entrance/exit road, as well as the
Principal Park Road and Primitive Park Road, were determined to be Class I Actions, because they are man-
made features that are prone to flood damage, result in impacts to natural floodplain values, and are occupied
by individuals. Class I Actions are subject to the FPS floodplain policies and procedures if they lie within the
100-year floodplain.
Proposed conditions were assessed based on harizontal and vertical alignments (functional level of design)
of an alternative's roadway overlaid on topographic data of GSMNP. Preliminary bridge ar culvert sizes
were determined at each of the major stream crossings based on a headwater-to-depth ratio of about 1.2 for
an assumed 25-year design storm, following general highway hydraulic design guidelines. Hydrologic
computations for these determinations were prepared using regional regression equations (Pope et al. 2001)
and hydraulic structure sizing was accomplished in accordance with NCDOT guidelines (Hankins 1999).
The severity and extent of impacts were generally evaluated in terms of the change in flooding depths
upstream of a proposed bridge or culvert. Flood hazard was assessed in terms of overtopping of an
alternative's roadway. Encroachment of construction activities, such as placement of roadway embankment,
can change the hydraulic characteristics of a floodplain, directly affecting its function as a resource and
causing impacts to surrounding areas due to changes in the extent of inundation. Tl�e affected flood levels
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-108
North Shore Road Final Environmental Impact Statement

occur infrequently during the life of a constructed facility after discrete storm events, with inundation lasting
from hours to several days, depending on the size of the watershed. The 100-year flood event has a
probability of occurrence of 1 percent during any given year. Floodplain impacts are addressed with respect
to their potential effects on existing natural resources, such as terrestrial communities and wildlife, and on
existing and proposed man-made facilities located within and adjacent to the floodplains. Impacts to streams
channels and riparian areas are addressed in Section 4.4.2 of this document, and additional detail is provided
in Appendix M.
Type
Impact rypes are either beneficial (having a positive effect on floodplains) or adverse (having a negative
effect on floodplains).
Context
Context categorizes the extent of the impact as local or regionaL Local impacts extend upstream a distance
equal to the width of the floodplain or downstreain four times the width of the floodplain, measured from the
limits of the encroachment. Regional impacts extend upstream or downstream within the subject watershed
and beyond the local limits.
Duration
Short-term impacts are those that occur only during construction of a partial-build ar build alternative.
Long-term impacts remain after construction is complete.
Intensity
Intensiry defines the severiry of the impact and ranges from no/negligible to major.
No/Negligible
Effects cause no measurable or perceptible changes in floodplain size, integrity, continuity, or function.
Minor
Effects are measurable or perceptible and localized within a relatively small area. Floodplain storage
capaciry would not be affected. Impacts result in 100-year flood elevations up to 1 foot (0.3 m) higher than
the existing flood elevations and would not be expected to affect the function of the alternative or
surrounding resources.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-109
North Shore Road Final Environmental Impact Statement

Moderate
Effects would cause a long-term change in the floodplain in terms of primary functions and values. Impacts
result in 100-year flood elevations more than 1 foot (0.3 m) higher than the existing flood elevations and
would not be expected to affect the function of the alternative or surrounding resources, but may require
special mitigation design.
Major
Effects on the floodplains would be substantial and permanent; floodplain storage capacity would be
changed; floodplain function would be permanently altered. Impacts result in 100-year flood elevations
more than 1 foot (0.3 m) higher than the existing flood elevations, have the potential to affect the function of
the altemative or surrounding resources, and require special mitigation design.
4.3.2.2 Summary of Impacts
The proposed actions were found to encroach on the 100-year floodplain at the locations of major stream
crossings, which are shown in Figure 3-5. The encroachments consist of fill in the existing floodplains due
to roadway embanlanents. The intensities of the impacts result from the increase in 100-year flood
elevations due to the size of tbe proposed drainage structures and the site topography. The amount of
encroachment could be reduced by moving the roadways farther from existing floodplains. The intensities of
impacts could be reduced by the use of larger drainage structures or longer bridges. There is no significant
difference in impacts among the various alternatives with the exception of the Southern Option at Hazel and
Eagle Creek Embayments. This option has substantially fewer impacts than the Northern Shore Corridor
baseline because it avoids the parallel encroachment of Shehan Branch.
All impacts noted in this section for the Laurel Branch Picnic Area, as well as all options and road types
associated with the Partial-Build Alternative to Bushnell and the Northern Shore Corridor, would be adverse
and long-term. However, the intensity of the impacts would vary with the amount of fill and length of bridge
encroachment within the floodplain. While the area of impact for the Laurel Branch Picnic Area would be
smaller than that of the Northern Shore Corridor, the impact intensity would be major due to anticipated
inundation of the roadway.
4.3.2.2.1 No-Action
The No-Action Alternative would have no impact on floodplains.
4.32.22 Monetary Settlement
The Monetary Settlement Altemative would not directly impact floodplains in the project study corridors.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-110
North Shore Road Final Environmental Impact Statement

4.3.2.2.3 Laurel Branch Picnic Area
Local impacts for Laurel Branch Picnic Area may include approximately 0.4 ac (0.16 ha) of fill within the
floodplain, while regional impacts may include roughly 0.1 ac (0.04 ha) of fill within the floodplain. While
these areas of impact would be smaller than those for the Northern Shore Corridor, both would result in
impacts that would be major due to anticipated inundation of the roadway.
4.3.2.2.4 Partial-Build Alternative to Bushnell (Primitive and Principal Park Roads)
The Partial-Build Alternative to Bushnell (Primitive Park Road) would not be expected to result in local
impacts. Regional impacts for the Partial-Build Alternative to Bushnell (Priinitive Park Road) would include
approximately 0.3 ac (0.12 ha) of fill within the floodplain, resulting in impacts that would be moderate.
Local impacts for the Partial-Build Alternative to Bushnell (Principal Park Road) would include
approximately 390 linear ft(119 m) of bridge encroachment, resulting in impacts that would be minor. The
Partial-Build Alternative to Bushnell (Principal Park Road) would not be expected to result in regional
impacts.
Southern Option at Forney Creek Embayment (Primitive and Principal Park Roads)
The Southern Option at Forney Creelc Embayment for the Primitive Park Road would a�oid fill within the
floodplain, avoiding the moderate, regional impact described for tbe baseline route. However, unlike the
northern route at Forney Creek, wbich would avoid bridge encroachment, the southern option for the
Primitive Park Road would have roughly 420 ft(128 m) of impacts related to bridge encroachment within
the floodplain. This impact would be local and minor.
The Southern Option at Forney Creek Embayment for the Principal Park Road would include an additional
100 linear ft (30 m) of bridge encroachment that would be local. Even with the additional length, it would
not be expected to alter the local, minor impact far the Partial-Build Alternative to Bushnell (Principal Park
Road).
4.3.2.2.5 Northern Shore Corridor (Primitive and Principal Park Roads)
Local impacts for the Northern Shore Corridor (Primitive Park Road) would include approximately 3.7 ac
(] .5 ha) of minor impacts and 0.2 ac (0.08 ha) of moderate impacts caused by fill and roughly 155 linear ft
(47 m) of negligible impacts and 1801inear ft (55 m) of minor impacts caused by bridge encroachment
within the floodplain. Regional impacts for the Northern Shore Corridor (Primitive Park Road) would
include approximately 2.l ac (0.8 ha) of moderate impacts and 1.7 ac (0.7 ha) of majar impacts caused by fill
within the floodplain.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-111
North Shore Road Final Environmental Impact Statement

Local impacts far the Northern Shore Corridor (Principal Park Road) would include approximately 1.7 ac
(0.7 ha) of minor impacts and 0.4 ac (0.2 ha) of moderate impacts caused by fill, as wel] as 2401inear ft(73
m) of negligible impacts and 570 linear ft(174 m) of minor impacts caused by bridge encroachment within
the floodplain. Regional impacts for the Northern Shore Corridor (Principal Park Road) would include
approximately 3.1 ac (1.3 ha) of minar impacts, 1.2 ac (0.5 ha) of moderate impacts, and 1.6 ac (0.6 ha) of
major impacts caused by fill within the floodplain.
Southern Option at Forney Creek Embayment (Primitive and Principal Park Roads)
As compared with the baseline, the Southern Option at Forney Creek Embayment (Primitive Park Road)
would have approximately 0.3 fewer ac (0.12 ha) of fill related to impacts that would be regional and
moderate. However, it also would have roughly 420 additional ft(128 m) of bridge encroachment related to
impacts that are local and minar.
As compared to the baseline, the Southern Option at Forney Creek Embayment (Principal Park Road) would
have has approximately ] 00 additional ft(30 m) of bridge encroachment related to impacts that are local and
minor.
Southern Option at Hazel and Eagle Creek Embayments (Primitive and Principal Park Roads)
As compared with the baseline, the Southern Option at Hazel and Eagle Creek Embayments (Primitive Park
Road) would have 3.7 fewer ac (1.5 ha) of fill and 180 fewer linear ft(55 m) of bridge encroachment related
to impacts that are local and minor. However, it also would have 2,445 additional linear ft(745 m) of bridge
encroachment that are local and negligible. This southern option also would have less regional impacts with
roughly 1.3 fewer ac (0.5 ha) of fill related to moderate impacts, and 1.6 fewer ac (0.6 ha) of fill related to
major impacts.
As compared to the baseline, the Southern Option at Hazel and Eagle Creek Embayments (Principal Park
Road) would have approximately 1.7 fewer ac (0.7 ha) of fill and 180 fewer linear ft(55 m) of bridge
encroachment related to impacts that are local and minor. However, it also would have 2,445 additional
linear ft(745 m) of bridge encroachment that are local and negligible. This southern option would have less
regional impacts with roughly 3.1 fewer ac (13 ha) of fill related to minor impacts, 1.2 fewer ac (0.5 ha) of
fill related to moderate impacts, and 1.6 fewer acres (0.6 ha) of fill related to major impacts.
Southern Option Crossing Fontana Dam (Primitive and Principal Park Roads)
The Southern Option Crossing Fontana Dam (Primitive Park and Principal Park Roads), as compared to the
baseline, would have approximately 0.2 fewer ac (0.08 ha) of fill related to impacts that are local and
moderate.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-112
North Shore Road Final Environmental Impact Statement

4.3.2.2.6 Cumulative Impacts
Other actions in the study area were reviewed to determine potential cumulative impacts to floodplains and
floodways. The Fontana Dam, as an impoundment of the Little Tennessee River, flooded large portions of
its floodplain. According to tbe project's DEIS, the Ravensford Land Exchange would include transfer of
approximately 4 percent (80 ac [32.37 ha]) of the floodplains within GSMNP (NPS 2003d). Wl�ile this
impact would constitute a minor to moderate impact overall on this resource, the impacts due to proposed
development on this site were determined to be negligible. While private development outside the Park
could impact floodplains and floodways in the study area, overall development is limited due to the large
percentage of land under public ownership. As a result, these impacts are eXpected to be negligible.
4.3.2.3 Options to Address Potential Impacts
If the Laurel Branch Picnic Area, Partial-Build Alternative at Bushnell, ar the Northern Shore Corridor is
implemented, more detailed designs would be developed that provide additional information and
opportunities for avoidance, minimization, and mitigation of floodplain impacts. Design strategies that could
be employed are listed below.
Avoidance Techniques
In some areas where embankment (fill) would be placed in the floodplain and parallel to the stream, it may
be desirable to shift the roadway alignment further away from the stream to avoid the encroachment.
Shifting the alignment may result in changes to slope stabiliry, earthwork quantities, and impacts on other
adjacent resources. In some cases of perpendicular crossings of flood prone areas, it may be possible to
avoid impacts by completely spanning the floodplain. Some design modifications that include longer
bridges or roadway length increase may also raise the construction costs.
Minimization Technigues
Methods for minimization of floodplain impacts include the avoidance techniques described above.
Additionally, consideration can be given to increasing the hydraulic capacity of crossing structures by
increasing the height and width of culverts, or by providing longer bridge spans and/or a bigher bridge deck
with more room for the water to flow under the bridge. The addition of supplementary structures, such as
additional culverts ar bridges adjacent to the primary stream crossing, can serve to lessen flood impacts
while relieving erosive stresses on the stream channel during flooding events.
Mitigation Techniques
Embankment slopes subject to overtopping or otherwise exposed to swiftly moving flood waters may be
protected by armoring or vegetative plantings. Higher embankments may be considered to preclude
overtopping of roadways. However, any roadways subject to inundation would require warning signs.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-113
North Shore Road Final Environmental Impact Statement

4.3.2.4 Impairment Evaluation
Impairment (as defined by NPS policy) to the floodplains and floodways of GSMNP and the AT would not
occur under the No-Action Alternative, Monetary Settlement Alternative, Laurel Branch Picnic Area, and the
Partial-Build Alternative to Bushnell. The Northern Shore Corridor is not likely to impair the floodplains
and floodways of GSMNP or the AT based on the information obtained to date. Due to the magnitude of
this alternative, it is likely that additional NEPA documentation would be required to address sit�specific
impacts not currently known, to determine detailed avoidance, minimization, and mitigation measures as
they relate to final design, and to re-evaluate the impairment determination related to floodplains and
floodways.
4.3.3 Hazardous Materials and Underground Storage Tanks
The No-Action Alternative is not expected to have an impact on the hazardous material and waste sites
identified and discussed in Section 3.3.3.
The Monetary Settlement Alternative is not anticipated to impact hazardous material and waste sites.
The Laurel Branch Picnic Area, Partial-Build Alternative to Bushnell, and the Northern Shore Corridor could
impact these sites because the alternatives would require construction activities. However, because these
three alternatives are entirely within GSMNP and none of the known hazardous material or waste sites are
within GSMNP, impacts are unlikely.
Illegal drug activity, especially the manufacturing and dumping of inethamphetamine, is a concern.
Although made mostly by mixing common household ingredients, a potentially harmful chemical is
produced in the process. Therefore, a drug production and dump site would be a potential hazardous waste
site. Increased access to GSMNP with the Partial-Build Altemative to Bushnell or the Northern Share
Corridor would increase the potential for manufacturing methamphetamine within the Park.
These assessments are preliminary and are not intended to stand in place of more detailed studies of
subsurface soils and groundwater, if warranted, at a later date. Furthermore, if a partial-build or build
alternative were chosen, site conditions would be thoroughly assessed prior to construction to ensure that no
hazardous materials or waste sites are encountered.
Due to the low potential for impacts to underground storage tanks and most hazardous materials, few
cumulative effects were identified. The Partia]-Build Alternative to Bushnell and Northern Share Corridor
would provide new access into the Park and add to the total number of potential locations for illegal drug
activity, including the manufacturing and dumping of inethamphetamines. However, since these alternatives
would extend existing Lake View Road and would not connect to other roadways in the Park network they
would not increase the occurrence of those illegal activities on other Park roads.
Clarification of the term "baseline" for this project:
The Partial-Build Alternative to Bushnell and the Northern Shore Corridor include a baseline route, as well as options to that route.
Baseline routes and options are detailed in Section 2.5 and shown on Figure 2-8. Baseline routes have been compared to existing
conditions. Impact analyses for the options are shown as a difference from the associated baseline route.
Environmental Consequences — 4-114
North Shore Road Final Environmental Impact Statement