BIOLOGICAL RESOURCES EVALUATION TECHNICAL MEMORANDUM - SOUTHEAST EXTENSION PROJECT LINCOLN STATION TO RIDGEGATE PARKWAY - RTD FASTRACKS
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Biological Resources Evaluation
Technical Memorandum
Southeast Extension Project
Lincoln Station to RidgeGate Parkway
Prepared for:
Federal Transit Administration
Prepared by:
Denver Regional Transportation District
May 2014
Southeast Extension
Biological Resources Technical Memorandum
Table of Contents
Page No.
Chapter 1.0 Introduction .........................................................................................................1-1
1.1 Background .............................................................................................................. 1-1
1.2 Regulatory Environment ........................................................................................... 1-1
Chapter 2.0 Alternatives Evaluated ........................................................................................2-1
Chapter 3.0 Affected Environment .........................................................................................3-1
3.1 Vegetation ................................................................................................................ 3-1
3.2 Wildlife ......................................................................................................................3-2
3.2.1 Threatened, Endangered, and Sensitive Species ........................................ 3-3
Chapter 4.0 Impact Evaluation and Mitigation ......................................................................4-1
4.1 Vegetation ................................................................................................................ 4-1
4.1.1 No Action Alternative .................................................................................... 4-1
4.1.2 Preferred Alternative..................................................................................... 4-1
4.1.3 Vegetation Mitigation .................................................................................... 4-2
4.2 Wildlife ......................................................................................................................4-2
4.2.1 No Action Alternative .................................................................................... 4-2
4.2.2 Preferred Alternative..................................................................................... 4-3
4.2.3 Wildlife Mitigation.......................................................................................... 4-4
4.3 Threatened, Endangered, and Sensitive Species .................................................... 4-4
4.3.1 No Action Alternative .................................................................................... 4-5
4.3.2 Preferred Alternative..................................................................................... 4-5
4.3.3 Threatened, Endangered, and Sensitive Species Mitigation ........................ 4-9
Chapter 5.0 References ...........................................................................................................5-1
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List of Figures
Figure 1-1 FasTracks Plan .................................................................................................... 1-2
Figure 1-2 Study Area ........................................................................................................... 1-3
Figure 2-1 No Action Alternative ........................................................................................... 2-1
Figure 2-2 Preferred Alternative ............................................................................................ 2-3
Figure 3-1 Prairie Dog Colonies ............................................................................................ 3-6
Figure 4-1 Preferred Alternative Prairie Dog Impacts (Parking Option 1, 2019) ................... 4-6
Figure 4-2 Preferred Alternative Prairie Dog Impacts (Parking Option 2, 2019) ................... 4-7
Figure 4-3 Preferred Alternative Prairie Dog Impacts (Parking Options 1 and 2, 2035) ....... 4-8
List of Tables
Table 3-1 Threatened and Endangered Species, and/or Species of Special Concern
Potentially Found in the Study Area ................................................................... 3-4
Table 4-1 Preferred Alternative Prairie Dog Impacts ............................................................. 4-5
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Biological Resources Technical Memorandum
Chapter 1.0 Introduction
This Technical Memorandum was prepared in support of the Southeast Extension
Environmental Assessment initiated by the Regional Transportation District (RTD) in 2012.This
Technical Memorandum focuses on biological resources in or adjacent to the Southeast
Extension study area. The purpose of this analysis is to evaluate the potential impacts of the
project to biological resources. This report documents the study methodology, results, and
impacts to conformity and mitigation measures for biological resource impacts.
1.1 Background
In November 2004, RTD voters approved the FasTracks initiative to expand and improve public
transit service within the Denver Metropolitan Region (Metro Region). The comprehensive
FasTracks Plan, which formed the basis of the FasTracks ballot initiative, includes the
construction and operation of new fixed-guideway transit lines, improved bus service, and park-
n-rides throughout the Metro Region. The Southeast Extension was included in the RTD
FasTracks program and is in the currently adopted Regional Transportation Plan (RTP). The
fixed-guideway transit elements (rail and bus rapid transit) of the FasTracks Plan are shown in
Figure 1-1.
The proposed action is to extend transit service south into the City of Lone Tree to serve the
increased population and employment generated by planned development in the City of Lone
Tree. The Southeast Extension study area is located in northern Douglas County, and includes
the City of Lone Tree and portions of Highlands Ranch and the Town of Parker. It begins at the
existing end-of-line Lincoln Avenue LRT station and extends south along I-25 to the I-
25/RidgeGate Parkway interchange. It includes areas of planned development south of Lincoln
Avenue on the east and west side of I-25 (see Figure 1-2).
1.2 Regulatory Environment
Biological resources include wildlife; vegetation; and threatened, endangered, and sensitive
species. Federal, state, and local regulations protect wildlife and vegetation in the study area.
Additional protection often applies to public (local, regional, or federal) preserves, management
areas, parks, or other legally protected areas. The Colorado Wildlife Commission and Colorado
Parks and Wildlife (CPW) regulate non-endangered wildlife at the state level. Federal protection
also occurs for non-endangered wildlife under the Fish and Wildlife Coordination Act of 1934
and the Migratory Bird Treaty Act of 1918.
The Fish and Wildlife Coordination Act requires consultation with the U.S. Fish and Wildlife
Service (USFWS) and the state wildlife agency to prevent loss of and damage to wildlife
resources from projects that may impound, divert, control, or otherwise modify the waters of any
stream or water body. The Migratory Bird Treaty Act (MBTA) provides for protection of all native
migratory game and nongame birds with exceptions for the control of species that cause
damage to agricultural or other interests. Similar protections and prohibited activities are
included in the Bald and Golden Eagle Protection Act.
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Figure 1-1
FasTracks Plan
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Figure 1-2
Study Area
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Executive Order 13112 directs federal agencies whose activities may affect the status of
invasive species to control populations of such species in a cost-effective and environmentally
sound manner, monitor invasive species populations, and provide for restoration of native
species and habitat conditions in ecosystems that have been invaded.
At the state level, the Colorado Noxious Weed Act was enacted to control and eradicate noxious
weeds on public and private lands (35-5.5-101, et seq., CRS). The Act contains a state list of
noxious weed species. Executive Order D 006 99 (1999) by the Governor of Colorado directed
state departments to reduce the spread of noxious weeds resulting from their activities, to
develop integrated weed management plans, and to cooperate with the state weed coordinator
and the weed control efforts of local governments. Douglas County maintains an Undesirable
Plant Management Plan (Douglas County, 1991) in accordance with the requirements of this
Act. The Plan includes a complete listing of identified noxious weeds.
Plant and animal species whose populations have declined to a point where extinction is
imminent are afforded legal protection under federal and state laws. Federally-listed threatened
and endangered species and designated critical habitat are regulated by the Endangered
Species Act (ESA) of 1973. The USFWS is authorized to identify species in danger of extinction
and provide for their management and protection. The USFWS also maintains a list of species
of special concern.
Colorado has enacted laws and adopted regulations to protect state-designated threatened,
endangered, and sensitive species, in addition to the federally-listed species. Under Colorado’s
Nongame, Endangered, or Threatened Species Conservation Act, state-designated threatened
or endangered species are protected.
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Chapter 2.0 Alternatives Evaluated
This technical memorandum evaluates the effects of two alternatives – a No Action Alternative
and the Preferred Alternative. These alternatives are described below.
The No Action Alternative assumes no new improvements would be constructed other than
currently committed projects identified in the 2035 RTP. This alternative includes the existing
bus routes in the area and a new bus route (Route 411) connecting Parker and the Lincoln
Station along RidgeGate Parkway. The CDOT project that includes I-25 widening from
RidgeGate Parkway to C-470 is also included as part of this alternative. Figure 2-1 shows the
No Action Alternative.
Figure 2-1
No Action Alternative
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The Preferred Alternative includes a 2.3-mile, double-track light rail extension that runs south
from the existing Lincoln Station along the west side of I-25, crosses to the east side of I-25 just
north of the Sky Ridge Medical Center, and continues south to the RidgeGate Parkway
interchange. This alternative provides three new stations. The Sky Ridge Avenue Station across
from the Sky Ridge Medical Center and the Lone Tree City Center Station situated in the core of
the RidgeGate planned development are both planned as kiss-n-ride stations without parking. A
new end-of-line station at RidgeGate Parkway would provide a park-n-ride. Access to the
RidgeGate Station would be provided from Havana Street via two access roads. All three
stations would accommodate feeder bus service. The light rail tracks would be grade separated
via an overpass where they cross Lincoln Avenue, I-25, and RidgeGate Parkway. One at-grade
crossing is proposed on a minor roadway near the Sky Ridge Station.
Two parking design options are being considered at the RidgeGate Station, as described below:
Option 1: This option would provide a 1,300-space surface parking lot on opening
day (2019). In 2035, the surface parking lot would be replaced with two parking
structures that would accommodate a total of 2,100 parking spaces. The southern
parking structure would consist of four levels and the northern parking structure
would consist of three levels.
Option 2: This option would provide one 4-level, 1,300-space parking structure on
opening day (2019). In 2035, an additional 3-level parking structure would be built
north of the first structure that would provide 800 parking spaces, for a total of 2,100
spaces.
The two parking structures in 2035 would be the same design and configuration under both
parking options.
The Preferred Alternative is shown on Figure 2-2.
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Figure 2-2
Preferred Alternative
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Chapter 3.0 Affected Environment
Habitats intersecting the Southeast Corridor Light Rail Extension project and within 300 feet of
the proposed alignment and stations were identified by conducting field reconnaissance in 2008,
2009, 2012 and 2013. Based on the habitat types identified and the results of the field
investigations, the wildlife, vegetative communities, and vegetation types in the study area were
identified.
The Southeast Corridor Light Rail Extension project is located in the western edge of the Great
Plains region that extends east from the foothills of the Rocky Mountains. Elevations range from
5,400 to 6,000 feet and topography is flat to gently rolling. Annual precipitation is low (12 to 18
inches), with six to seven arid months per year. Most of the precipitation falls as snow in the
winter and during spring thunderstorms. Precipitation is often less than rates of evaporation and
plant transpiration, resulting in moisture deficits and a semi-arid climate (Natural Resource
Conservation Service [NRCS], 2006; Bailey, 1995). Average annual temperature ranges from
45 to 55 degrees Fahrenheit with an average frost-free period of about 160 days (NRCS, 2006).
The study area is designated as Land Resource Region G, Western Great Plains Range (67B)
by the NRCS (2006), and as the Palouse Dry Steppe Province (M330) by Bailey (1995). The
natural community in the vicinity of the study area is commonly referred to as shortgrass prairie,
with components of wetland and riparian habitats along natural streams.
The Southeast Corridor Light Rail Extension project is located in rapidly developing areas on the
edge of the Denver metropolitan area. The portion of the alignment to the north of Lincoln
Avenue is fully developed with office complexes, roads, parking lots, and landscaping. South of
Lincoln Avenue, some areas have been recently developed and others are being readied for
development with preliminary grading, roads, and underground utilities in place. To the east of I-
25, the land has not yet been developed, but has been moderately impacted by prior and
current agricultural activities such as cattle grazing.
3.1 Vegetation
In its natural state, shortgrass prairie vegetation is dominated by bunch grasses that are
sparsely distributed, including grama (Bouteloua spp.), wheatgrass (such as Agropyron spp.),
needlegrass (Stipa spp.), and dropseed (Sporobolus spp.). Flowering plants include daisies
(Erigeron spp.), sunflower (Helianthus sp.), and locoweed (Oxytropis spp.). Common shrubs
include sagebrush (Artemisia spp.) and rabbitbrush (Chrysothamnus spp.).
Because the study area is in a rapidly developing area, several areas are fully developed and
landscaped, while others show signs of recent activity (such as revegetated utility corridors).
The southern portion of the study area has been less directly affected by development and
contains remnants of native shortgrass prairie variously impacted by prior and current
agricultural activity. In addition to the vegetation noted above, these areas include milkvetch
(Astragalus sp.), cactus (Opuntia sp.), Yucca species, fringed sage (Artemisia frigida), and wild
rose (Rosa sp.). There are also a variety of introduced species (such as Bromopsis sp.); weedy
species such as knapweed (Acosta spp.), cheatgrass (Bromus [Anisantha] tectorum), and thistle
(Carduus sp., Breea sp.); and others associated with disturbed areas such as clover (Melilotus
spp.), prickly lettuce (Lactuca spp.), ironweed (Bassia sp.), goosefoot (Chenopodium sp.), field
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bindweed (Convolvulus arvensis), and rough cocklebur (Xanthium strumarium). During field
evaluations of vegetative communities, the following sources were consulted: PLANTS
database (NRCS, 2008), Weber and Wittmann (1996), Carter (2006), and Wingate (1994).
Wetlands are associated with landscape depressions and natural drainages where groundwater
is close to the surface, surface water is common, or precipitation collects. Wetland habitat is
often dominated by herbaceous plants, including cattails (Typha spp.), bulrush (Scirpus spp.),
sedges (Carex spp.), and willows (Salix spp.). Riparian habitat is common along perennial and
ephemeral streams. These habitats support woody communities dominated by shrubs such as
willows, plum (Prunus sp.), and snowberry (Symphoricarpos sp.), and trees such as
cottonwoods (Populus deltoides), box elder (Acer negundo), and Russian olive (Elaeagnus
angustifolia) (Mutel and Emerick, 1992; Benedict, 1991).
A variety of terms are used in federal and state laws for undesirable plants and animals,
including weeds, noxious weeds, alien species, non-native species, exotic species, and invasive
species. In the Southeast Corridor Light Rail Extension project, the following state-listed weeds
were identified: knapweed (Centaurea spp.), cheatgrass, Canada thistle (Cirsium arvense),
musk thistle (Carduus nutans), and bindweed (Convolvulus sp.). The Douglas County
Undesirable Plant Management Plans (Douglas County, 2012) places knapweed on List A,
which indicates it is required to be eradicated. Canada thistle and musk thistle appear on List B,
which indicates that they are to be contained and suppressed. However, List B notes that
tamarisk species also must be eradicated. Cheatgrass and bindweed appear on List C, which
indicates that its removal and control is at the landowner’s discretion.
3.2 Wildlife
Overall, the study area contains remnants of native shortgrass prairie; however, the landscape
is dominated by vegetation indicative of current and past disturbance. Two perennial streams
are located in the southeastern portion of the study area (Cottonwood Creek and Happy Canyon
Creek). Although lowland riparian habitat represents about three percent of the State’s area,
from a wildlife standpoint, such habitat is considered some of the most productive in the State
and has the highest species diversity, including special status species (Brinson, et al. 1981;
Knopf, et al. 1988; Jones, et al. 2003).
The highest quality habitat in terms of size, contiguity, and diversity is that associated with
Happy Canyon Creek. It is a fairly intact example of a plains cottonwood system, with an
extensive overstory and wetland areas. However, both upstream and downstream
developments currently limit access and its usefulness for wildlife. Cottonwood Creek has been
substantially degraded by grazing livestock.
As a result of past and present human activity, the developed northern portion of the study area
includes a limited number and diversity of species. This is primarily a result of the following
conditions related to urban areas:
Habitat fragments are too small to be used permanently by wildlife and are often used by
wildlife only at night or early morning.
Habitat is low quality because of low plant and habitat diversity. Further, the small size and
lack of habitat diversity tend to increase predation.
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Other necessary habitats, such as those for water, feeding, and nesting, are too far away or
are blocked by barriers such as roads, traffic, or other human activity.
Exotic plant species and domestic pets further limit the usefulness of these areas for wildlife
(Hartley and Hunter, 1998; Villard, et al. 1999; Marzluff, et al. 1998; McKinney, 2002; Jones,
et al. 2003; and Crooks, et al. 1999).
Water quality is often poor (Schoonover, et al. 2005).
Wildlife access to the project corridor is generally from the undeveloped areas to the south and
east. The Chatfield Basin Habitat Conservation Area is about three miles southwest of the study
area. Several bird species are migrants, such as flycatchers, thrushes, and warblers (Andrew
and Righter, 1992), and raptors are often seen, such as red-tailed hawk (Buteo jamaicensis),
Swainson’s hawk (Buteo swainsonii), and turkey vulture (Cathartes aura). An active red-tailed
hawk nest has been observed in a large cottonwood tree in Cottonwood Creek. The most
common wildlife species are generalists that depend on, adapt easily to, or are associated with
human development. These are listed below.
Birds: robin (Turdus migratorius), grackle (Quiscalus quiscula), mourning dove (Zenaida
macroura), magpie (Pica hudsonia), northern flicker (Colaptes auratus), starling (Sturnus
vulgaris), house sparrow (Passer domesticus), pigeon (Columba livia).
Waterfowl: Canada goose (Branta canadensis) and mallards (Anas platyrhynchos).
Mammals: coyote (Canis latrans), red fox (Vulpes vulpes), mule deer (Odocoileus
hemionus), raccoon (Procyon lotor), muskrat (Ondatra zibethicus), cottontail rabbit
(Sylvilagus sp.), striped skunk (Mephitis mephitis), fox squirrel (Sciurus niger), and rodents
such as deer mice (Peromyscus maniculatus).
Reptiles: garter snakes (Thamnophis spp.) and bull snakes (Pituophis melanoleucus)
(Mutel and Emerick 1992, Benedict 1991).
Amphibians/Aquatic life: bullfrogs, (Rana catesbeiana), Western chorus frog (Pseudacris
triseriata), and Crayfish (Orconectes sp.).
3.2.1 Threatened, Endangered, and Sensitive Species
Table 3-1 provides the species listed by USFWS and the State of Colorado that are identified as
threatened, endangered, or special concern (unlisted) species, and have the potential to occur
in the project corridor. This list was developed by reviewing reports, surveys, and other
materials developed by the USFWS and CPW. The Colorado Natural Heritage Program (CNHP)
also reviewed its natural resource elements database of known occurrences in the corridor
extending 150 meters (500 feet) on each side of the corridor centerline. “Natural resource
elements” include significant natural communities and rare, threatened, or endangered plants
and animals. CNHP reported no such occurrences in the project corridor (CNHP, 2008).
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Table 3-1 Threatened and Endangered Species, and/or Species of Special Concern
Potentially Found in the Study Area
Common Name Scientific Name Status1 Potential for Occurrence
Mammals
Preble’s meadow Zapus hudsonius preblei FT, ST Unlikely, suitable habitat limited
jumping mouse (Happy Canyon Creek); prior surveys
negative
Black-tailed prairie dog Cynomys ludovicianus SSC2 Present
Northern pocket gopher Thomomys talpoides macrotis SSC Habitat may be present
Birds
Bald eagle Haliaeetus leucocephalus ST Unlikely; transient
Western burrowing owl Athene cunicularia ssp. ST May be present; shares habitat with
hypugaea prairie dogs
Piping Plover Charadrius melodus FT, ST Unlikely; transient
Least tern Sternula antillarum FE, SE Unlikely; transient
Whooping crane Grus americana FE, SE Unlikely; transient
Mexican Spotted Owl Strix occidentalis lucida FT, ST Unlikely; transient
Ferruginous hawk Buteo regalis SSC May be present
Fish
Iowa darter Etheostoma exile SSC Unlikely: habitat degradation
Common shiner Luxilus cornutus SSC Not likely present due to habitat
degradation
Pallid Sturgeon Scaphirhynchus albus FT Not present ; unsuitable habitat
Greenback cutthroat Oncorhynchus clarki stomias FT Unlikely: habitat degradation
trout
Reptiles
Common garter snake Thamnophis sirtalis SSC Likely present
Amphibians
Northern leopard frog Rana pipens SSC Likely present
Plants
Ute ladies’-tresses orchid Spiranthes diluvialis FT Unlikely: habitat limited and
degradation
Colorado butterfly plant Gaura neomexicana FT Unlikely: habitat limited and
degradation
Western Prairie Fringed Plantanthera praeclara FT Not present ; unsuitable habitat
Orchid
Sources: CNHP, 2008; CDOW, 2009; USFWS, 2009 a,b,c, USFWS 2013
Notes: 1FT = federal threatened; FE = federal endangered; ST = state threatened; SE = state endangered; SSC = state species of special concern (CDOW,
2009; CNHP, 1996). 2 In 2004, the black-tailed prairie dog was removed from the ESA candidate species list. In December 2008, USFWS indicated that the
agency would review the federal status of the species (USFWS, 2009b).
The study area and adjacent areas were then assessed for possible habitat for each listed
species in Table 3-1. Likely areas were surveyed to determine the presence or absence of
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individuals or populations of each species. Threatened, endangered, and sensitive species that
could potentially occur within the study area are discussed below:
Preble’s Meadow Jumping Mouse: In 2000, USFWS issued a block clearance zone for the
Denver metropolitan area for the Preble’s meadow jumping mouse (USFWS, 2009a). This
means that ESA provisions related to the mouse do not apply within the zone. The
Southeast Corridor Light Rail Extension project, south of Lincoln Avenue, is outside this
exclusion zone, so suitable habitat was evaluated.
There are two perennial streams in the project corridor, Cottonwood Creek and Happy
Canyon Creek. Both areas have historically been subjected to grazing. Cottonwood Creek
does not have the quantity and quality of herbaceous and shrub components characteristic
of suitable Preble’s habitat. Happy Canyon Creek has a better-developed riparian plant
community, especially tree and shrub components. The understory is less well developed,
but could plausibly support the mouse. Information included in the Douglas County Habitat
Conservation Plan indicated that prior evaluations of this area did not find suitable habitat or,
if suitable habitat was found, trapping was conducted, and no Preble’s were collected
(Douglas County, 2005). Last, the alignment for the Southeast Corridor Light Rail Extension
project is situated between the interstate and an existing frontage road, eliminating any
potential project impacts to Happy Canyon Creek.
Black-Tailed Prairie Dog: The initial field surveys conducted in the fall of 2008 and spring
2009 for the Environmental Evaluation identified four prairie dog colonies within the project
corridor. One colony west of I-25 and immediately south of Lincoln Avenue; two colonies
east of I-25 between Lincoln and RidgeGate Parkway, and one colony east of I-25 and
south of RidgeGate Parkway. During field surveys in the late summer 2012, it was found
that the colony west of I-25 and immediately south of Lincoln Avenue was removed due to
construction, the two colonies east of I-25 between Lincoln and RidgeGate Parkway
combined into one colony (Colony A), and the colony east of I-25 and south of RidgeGate
Parkway is now bisected into two colonies (Colonies B and C) by Havana Street (see Figure
3-1). Colony A east of I-25 between Lincoln and RidgeGate Parkway is approximately 275
acres; however between 2009 and 2012 it appears that the sylvatic plague impacted both
this colony and Colony B to the southeast of Havana Street (approximately 25 acres). Only
approximately 2 percent of Colonies A and B remain active. Colony C south of RidgeGate
Parkway and west of Havana has decreased in size as a result of soil stockpiling for nearby
construction activities that occurred in late 2012 associated with development within the City
of Lone Tree. Colony C is currently an active colony that is approximately 13 acres in size,
and appears unaffected by the plague. Colony B continues to change in size as a result of
soil stockpiling and borrowing for nearby construction activities associated with development
within the City of Lone Tree.
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Figure 3-1
Prairie Dog Colonies
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Northern Pocket Gopher: In 2003, a petition was submitted to USFWS to list the Douglas
County pocket gopher as a threatened or endangered species. The Douglas County pocket
gopher is 1 of 58 subspecies of the northern pocket gopher, 9 of which are located within
Colorado (Hall, 1981). The northern pocket gopher is a state species of concern, but is
considered a non-regulatory species. The USFWS denied the petition to list the Douglas
County pocket gopher because the species was more widespread in Douglas County than
reported in the petition and there are questions of the species’ current subspecific taxonomy
(Federal Register, 2006). The northern pocket gopher inhabits a variety of habitats including
deep soils, heavily compacted soils, and shallow gravel. Because of their use of fragmented
habitats, the population size of each colony is small. Much of the study area has been
heavily disturbed due to development and grazing, but numerous rodent holes and habitat
for the northern pocket gopher occur in the study area.
Western Burrowing Owl: Western burrowing owls are dependent on burrowing mammals
such as prairie dogs whose burrows they use for nesting and roosting. Surveys to locate
burrowing owls in the three colonies in the study corridor were conducted for several weeks
in the latter half of April 2009 and September 2012. No owls were observed.
Common Garter Snake: The common garter snake occurs along the South Platte and its
tributaries below 6,000 feet, especially near marshes, ponds, and stream edges
(Hammerson, 1999). Two streams (Happy Canyon Creek and Cottonwood Creek) provide
suitable conditions for the snake.
Ferruginous Hawk: Although a common resident in Colorado (Andrews and Righter, 1992),
no ferruginous hawks or their nests were observed during several site visits to the corridor
during 2008, 2009, and 2012.
Greenback Cutthroat Trout: The Greenback cutthroat trout inhabits cold swift-flowing
streams with adequate spawning habitat (such as cover and overhanging banks, vegetation,
and riffles) during spring. The two streams within the study area do not provide the
necessary habitat for the Greenback cutthroat trout (USFWS, 2013).
Pallid Sturgeon: The Pallid sturgeons are bottom-oriented, large river fish that are found
along the Missouri and Mississippi rivers and some tributaries from Montana to Louisiana,
such as the Platte River (USFWS, 2013). The two streams within the study area do not
provide the necessary habitat for the Pallid Sturgeon.
Northern Leopard Frog: The northern leopard frogs occur along the banks and shallow
areas of marshes, ponds, streams, and other bodies of permanent water (Hammerson,
1999). Two streams (Happy Canyon Creek and Cottonwood Creek) provide suitable
conditions for the frog.
Ute Ladies’-Tresses Orchid: Potential Ute ladies’-tresses orchid habitat in the Southeast
Corridor Light Rail Extension study area includes Cottonwood Creek and Happy Canyon
Creek. However, the degraded and disturbed nature of Cottonwood Creek, plus inadequate
hydrology and heavy clay soils, eliminated further consideration. At Happy Canyon Creek,
the alignment for the study is situated between the interstate and an existing frontage road,
and does not come in contact with the creek. USFWS has designating a block clearance
zone for the Cherry Creek drainage, to which Cottonwood Creek and Happy Canyon Creek
are tributaries.
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Colorado Butterfly Plant: The Colorado butterfly plant is found in moist areas of
floodplains. Current range of the plant is restricted to Platte and Laramie Counties in
southeastern Wyoming and Weld County, Colorado. Historically, native populations were
also known from Boulder, Douglas, and Larimer counties in Colorado, but these populations
are believed to be extirpated (CPC, 2009). Both Cottonwood Creek and Happy Canyon
Creek are degraded and disturbed, which would limit the species habitat.
Western Prairie Fringed Orchid: The western prairie fringed orchid is associated with the
central and lower reaches of the Platte River in Nebraska and does not occur within the
study area.
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Chapter 4.0 Impact Evaluation and Mitigation
The sections below discuss potential impacts to biological resources from the Southeast
Corridor Light Rail Extension project. These impacts should be viewed in the larger context of
proposed development south of Lincoln Avenue. This area is recognized as an “urban center”
by the City of Lone Tree, Douglas County, and DRCOG. Further, the Preferred Alternative
footprint is fully contained within the 3,500-acre RidgeGate Planned Development, which
includes a city center, commercial mixed-use development, residential mixed-use development,
rural residential development, and open space. In this context, potential impacts to vegetation;
wildlife; and threatened, endangered, and sensitive species are described below.
Avoidance and minimization of impacts are most effectively achieved during planning and
project design. Toward these ends, the light rail footprint has been narrowed with the use of
retaining walls in many areas. Additional minimization occurs during construction through the
use of best management practices (BMPs), such as effective erosion control, proper material
handling and storage, and fencing to keep personnel and equipment out of sensitive areas.
These types of operating requirements would be specified in construction plans.
4.1 Vegetation
Potential effects to vegetation from the No Action Alternative and Preferred Alternative are
described below.
4.1.1 No Action Alternative
The No Action Alternative would not result in any direct, indirect, construction-related, or
cumulative impacts to vegetation beyond those that would occur under currently programmed or
planned projects.
4.1.2 Preferred Alternative
The direct, indirect, construction-related, and cumulative impacts of the Preferred Alternative are
described below.
Direct Impacts
There would be approximately 60 acres of impacts to vegetation from the Preferred Alternative,
assuming a 60-foot-wide work area, staging areas, and RidgeGate station and park-n-ride lot.
About 83 percent of those impacts (approximately 50 acres) would occur in areas that have
been recently graded, previously disturbed and revegetated (such as the highway right-of-way),
or used for grazing. The most common species in such areas is smooth brome (Bromus
inermis), a perennial Eurasian grass widely used along roadsides for soil stabilization (Weber
and Wittman, 1996).
Of the 60-foot-wide work area, assuming a final rail corridor width of 40 feet, the area of
vegetation that would be permanently lost north of RidgeGate Parkway would be approximately
7.4 acres. The remaining 20-foot-wide area would be temporarily impacted and would be
revegetated. Several ornamental trees and shrubs would be lost from existing landscaped areas
north of Lincoln Avenue. South of RidgeGate Parkway, the RidgeGate Station and park-n-ride
would impact vegetation in varying degrees, depending on the parking option selected. In 2019,
Parking Option 1 would impact approximately 22.7 acres of vegetation, and Parking Option 2
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would impact approximately 14.6 acres. In 2035, both parking options would impact
approximately 18.4 acres of vegetation.
Indirect Impacts
The most likely indirect impact to vegetation would occur from the spread of non-native, weedy
species. Based on the final construction footprint, approximately 20 acres of unpaved, disturbed
ground would be susceptible to weedy plant species, especially along the drainage ditches on
both sides of the track.
Construction Impacts
The total construction area (including track embankment, staging areas, and parking lot) is
estimated to be 60 acres in size for the Preferred Alternative. Approximately 20 acres of
temporary impacts to vegetation would result from the Preferred Alternative. This is an estimate
of the area along the rail corridor that would be revegetated after construction.
Cumulative Impacts
Cumulative impacts are not anticipated for this resource.
4.1.3 Vegetation Mitigation
Mitigation measures for potential impacts to vegetation resources include the following:
Direct Impacts
Replace any upland trees impacted on CDOT right-of-way at a 1:1 ratio.
When possible, use native species for landscape plantings at Park-n-Ride and stations.
If impacts occur to riparian areas within CDOT right-of-way, Senate Bill 40 Certification
will be necessary and obtained.
Indirect Impacts
Develop noxious weed management plan.
Perform continuous weed control within CDOT and RTD rights-of-way, and replant
native species throughout the project until construction completion.
Temporary Construction Impacts
Reseed with native species, control invasive species, and use weed-free hay/mulch
within the right-of-way.
Revegetate disturbed areas that would not be paved or part of the new track
embankment
4.2 Wildlife
Potential effects to wildlife from the No Action Alternative and Preferred Alternative are
described below.
4.2.1 No Action Alternative
The No Action Alternative would not result in any direct, indirect, construction-related, or
cumulative impacts to wildlife beyond those that would occur under currently programmed or
planned projects.
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4.2.2 Preferred Alternative
The direct, indirect, construction-related, and cumulative impacts of the Preferred Alternative are
described below.
Direct Impacts
The Preferred Alternative would result in direct impacts to wildlife. The Preferred Alternative
corridor is either located within developed areas or parallels I-25 and a frontage road. In the
context of the RidgeGate Planned Development, it is unlikely that the Preferred Alternative
would act as a barrier to wildlife movement; however fencing along the rail corridor could
impede wildlife movement. The total area of potential wildlife habitat impacted would be
approximately 60 acres; the total permanently lost acreage beneath the Preferred Alternative,
including the RidgeGate station and park-n-ride at RidgeGate Parkway, would be approximately
40 acres. To the extent that these areas represent permanent habitat loss, some wildlife would
be displaced. However, these animals would likely relocate to the open space directly east of
the Preferred Alternative footprint. The existing red-tailed hawk nest adjacent to the light rail
bridge over Cottonwood Creek will likely be abandoned after construction begins, because of
the close proximity to development of both the planned Lone Tree City Center and Southeast
Corridor Light Rail Extension project. The Preferred Alternative would span Cottonwood Creek;
therefore, no direct impacts to wildlife from the crossing would occur.
Indirect Impacts
The Preferred Alternative would result in minimal indirect impacts to wildlife as a result of
disturbance from human activity, potential loss of prey, or loss of habitat. The impact would be
minimal primarily because the study area is composed of developed or developing urban areas
that have already been or will soon be bisected by roadways, including I-25 and RidgeGate
Parkway.
Aquatic life and amphibians may occur in the study area along Cottonwood Creek. Indirect
impacts to these species may occur from erosion along the riverbanks.
Construction Impacts
The Preferred Alternative would result in minimal temporary construction impacts to wildlife.
Wildlife that currently occupies the study area or uses the area for forage or prey is likely
accustomed to noise and movement due to proximity to I-25 and rapidly developing areas.
However, the increase in noise and activity during construction of the Preferred Alternative may
cause wildlife to temporarily leave the area.
Direct wildlife mortality of small terrestrial and burrowing animals could occur during
construction-related ground clearing and earth-movement. Direct wildlife mortality due to
collisions with construction vehicles could also occur during construction activities.
Disturbance of migratory birds, such as the active red-tailed hawk nest observed in the
immediate vicinity of the Preferred Alternative at Cottonwood Creek, are subject to the MBTA.
Although the provisions of the MBTA are applicable year-round, most migratory bird nesting
activity in eastern Colorado occurs during the period of April 1 to August 31. However, some
migratory birds such as the red-tailed hawk are known to nest outside of the aforementioned
primary nesting season period. The USFWS has requested that RTD coordinate with the
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Colorado Parks and Wildlife for implementation of their Raptor Guidelines for anticipated
impacts to nesting raptors.
If the proposed construction project is planned to occur during the primary nesting season for
migratory birds or at any other time that may result in the take of nesting migratory birds,
coordination with the USFWS will be required to determine appropriate mitigation and impact
avoidance options.
Cumulative Impacts
The Preferred Alternative would result in minimal cumulative impacts to wildlife as a result of
disturbance from human activity, potential loss of prey, or loss of habitat.
4.2.3 Wildlife Mitigation
Mitigation measures for potential impacts to wildlife resources include the following:
Direct Impacts
RTD will comply with the requirements of the MBTA (refer to temporary construction
mitigation below).
Indirect Impacts
Use BMPs to avoid water quality impacts to, and tree removal along, Cottonwood Creek.
Temporary Construction Impacts
RTD will comply with the requirements of the MBTA.
Although provisions of the MBTA are applicable year-round, most migratory bird nesting
activity in eastern Colorado occurs during April 1 to August 31. However, some
migratory birds are known to nest outside of primary nesting season (e.g., raptors can
nest in woodland habitats between February 1 and July 15).
If construction is planned to occur during primary nesting season or at any other time
that may result in the take of nesting migratory birds, the USFWS recommends that RTD
have a qualified biologist conduct a field survey of affected habitats and structures to
determine absence or presence of nesting migratory birds.
Conduct nesting bird surveys during the nesting season. In some cases, such as on
bridges or other similar structures, nesting can be prevented until construction is
complete
Contact the USFWS Colorado field office immediately for further guidance if field survey
identifies the existence of one or more active bird nests that cannot be avoided by
planned construction activities. Adherence to these guidelines will help avoid the
unnecessary take of migratory birds and the possible need for law enforcement action.
RTD will coordinate with CPW and implement their Raptor Guidelines, as needed
4.3 Threatened, Endangered, and Sensitive Species
Potential effects to threatened, endangered, and sensitive species from the No Action
Alternative and Preferred Alternative are described below.
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4.3.1 No Action Alternative
The No Action Alternative would not result in any direct, indirect, construction-related, or
cumulative impacts to threatened, endangered, and sensitive species beyond those that would
occur under currently programmed or planned projects.
4.3.2 Preferred Alternative
The direct, indirect, construction-related, and cumulative impacts of the Preferred Alternative are
described below.
Direct Impacts
No federally-listed species, nor their designated habitats, were identified in the project corridor.
Therefore, there would be no impacts to such species.
Within the footprint of the project corridor, assuming a 30-foot-wide buffer and RidgeGate
station and park-n-ride lot, disturbance would occur in two areas of known black-tailed prairie
dog (state species of concern) activity; however, the impacts would vary. North of RidgeGate
Parkway, the Preferred Alternative would impact approximately 4.4 acres of the approximate
275-acre prairie dog Colony A. South of RidgeGate Parkway, the RidgeGate Station and park-
n-ride would impact prairie dog Colony C (which is approximately 13 acres) in varying degrees,
depending on the parking option selected. In 2019, Parking Option 1 would impact
approximately 9.29 acres of Colony C, and Parking Option 2 would impact approximately 7.02
acres of Colony C. In 2035, both parking options would impact approximately 10.29 acres of
Colony C. Construction of Havana Street and RidgeGate Parkway intersection and roadway
improvements in 2035 to mitigate traffic impacts would impact approximately 1.4 acres of
Colony B and would result in no impacts to Colony C. These impacts are summarized in Table
4-1 and shown on Figure 4-1 through Figure 4-3. Because Colony A could conceivably expand
into open areas to the east, impacts would be minimal. These impacts should be viewed in the
context of the intensity of the approved development plans for these areas. Any impacts to
prairie dogs on CDOT right-of-way would follow the January 2009 Black-tailed Prairie Dog
Policy (CDOT, 2009).
Table 4-1 Preferred Alternative Prairie Dog Impacts
Prairie Dog Prairie Dog Colony Track, Station, and Station Impacts from Havana St. & RidgeGate
Colony Size (Acres) Access Roads Impacts (Acres)* Pkwy. Improvements (Acres)*
Preferred Alternative North of RidgeGate Parkway
Colony A 275 4.4 N/A
Preferred Alternative South of RidgeGate Parkway
Parking Option 1 2019
Colony C 13 9.29 None
Colony B 25 None None
Parking Option 2 2019
Colony C 13 7.02 None
Colony B 25 None None
Parking Option 1 & 2 2035
Colony C 13 10.29 None
Colony B 25 None 1.4
*Assumes a 30ft impact buffer
Source: Jacobs, 2014
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Figure 4-1
Preferred Alternative Prairie Dog Impacts (Parking Option 1, 2019)
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Figure 4-2
Preferred Alternative Prairie Dog Impacts (Parking Option 2, 2019)
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Figure 4-3
Preferred Alternative Prairie Dog Impacts (Parking Options 1 and 2, 2035)
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Indirect Impacts
Aquatic life, amphibians, and the common garter snake may occur in the study area along
Cottonwood Creek and Happy Canyon Creek. There would be no impacts from this project to
the common garter snake or its habitat in Happy Canyon Creek. There is suitable habitat for the
Northern Leopard frog along Happy Canyon Creek and Cottonwood Creek. Happy Canyon
Creek is beyond the impact area of the proposed project; therefore, there would be no impacts
to the frog or its habitat from this project. In the southwest portion of Cottonwood Creek, suitable
habitat is limited because the drainage is smaller and heavily impacted by grazing. As the
drainage flows north behind the SkyRidge Medical Center, east of RidgeGate Parkway and west
of I-25, it enters a small detention pond that is suitable to the northern leopard frog. However,
the detention pond is located approximately 620 feet from the preferred alternative and would
not be impacted by the project. Indirect impacts to aquatic life and amphibian species may occur
from erosion within the study area.
Construction Impacts
Because habitats for the common garter snake and northern leopard frog are close to the
project, these species could experience some impacts as a result of potential changes in water
quality during construction. Implementation of BMPs would avoid such impacts. Direct mortality
of black-tailed prairie dogs could occur during construction-related ground clearing, earth-
movement, and vehicle collisions.
Cumulative Impacts
As the southeast metro area continues to develop, wildlife (especially black-tailed prairie dogs)
will be displaced or removed.
4.3.3 Threatened, Endangered, and Sensitive Species Mitigation
Mitigation measures for potential impacts to threatened, endangered, and sensitive species
include the following:
Direct Impacts
RTD/the contractor will adhere to the FasTracks Prairie Dog Mitigation Policy. The
FasTracks program first established its Prairie Dog Mitigation Policy in 2007, as RTD
takes seriously its efforts to avoid, minimize or mitigate for impacts to our environment.
The mitigation policy states (in order of preference) that RTD will:
- First avoid, minimize and/or mitigate for impacts to prairie dogs if feasible;
- Second, relocate prairie dogs if RTD can obtain permission and find property and
the relocation is not cost prohibitive;
- Third, donate prairie dogs to raptor rehabilitation programs or to the USFWS ferret
program;
- Finally, humanely euthanize on site as a last resort.
The policy clearly states, “At no time will RTD authorize earth-moving activities that
result in the burying of live prairie dogs.” In an effort to find suitable land for relocations,
RTD has established a Working Group composed of interested parties to look for ways
to clear the obstacles RTD has encountered in trying to implement live relocations.
Burrowing owl surveys will be conducted within one year prior to construction.
Vegetation and trees removed along Cottonwood Creek will be replaced.
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Indirect Impacts
Permanent BMPs will be implemented to control erosion.
Temporary Construction Impacts
BMPs will be implemented during construction to control erosion.
A construction barrier between construction areas and active prairie dog colonies will be
erected to minimize interaction with adjacent colonies.
Prairie dogs will be removed from the construction side of the barriers prior to the
initiation of ground-disturbing construction activities.
FTA, in cooperation with RTD, has prepared BA for the FasTracks program to address
South Platte depletions. As a result of the Biological Opinion obtained from the USFWS,
water usage during construction will be tracked and gallons used will be provided to the
FasTracks environmental group on an annual basis.
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Chapter 5.0 References
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