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WETLAND MITIGATION PLAN
BEST BUY STORE #225
4030 SOUTH COLLEGE AVENUE
FORT COLLINS, COLORADO
PREPARED BY NOLTE ASSOCIATES, INC.
MARCH 29,2000
CONCEPTUAL WETLANDS MITIGATION PLAN
BEST BUY STORE #225
FORT COLLINS, COLORADO
PREPARED BY NOLTE ASSOCIATES, INC.
Introduction
The Best Buy Company is proposing an expansion of its retail store at 4030 South
College Avenue, Fort Collins, Colorado (see attached Vicinity Map). The proposed
developments include the eastward expansion of the building (increasing the square feet
of gross leasable area from 28,521 to 42,769), a new 50-space (approximate) parking lot
located north of the building, a new loading area on the east side (rear) of the building,
and two access drives from John F. Kennedy Boulevard. These proposed improvements
will occur on undeveloped land abutting the existing building to the north and east and
will result in the disturbance of approximately 20,090 square feet of existing on -site
wetland area. A field survey was conducted on October 21, 1999 by Advanced
Professional Engineering, Inc. to determine the extent of the wetlands. The
determination was based on plant composition, soil types, and hydrologic features.
The wetlands occur along a drainage ditch that bisects the undeveloped land
approximately 660 feet from north to south, with a short westward branch of
approximately 120 feet just north of the building. The dominant vegetation identified in
the wetlands includes:
Cattail (Typha sp.),
Creeping spikerush (Eleocharis palustris),
Hardstem bulrush (Scripus acutus),
Peachleaf willow (Salix amygdaloides),
Big -leaf cottonwood (Populus deltoides),
Siberian elm (Ulmus pumila), and
Smooth brome (Bromus inormus).
To mitigate for the disturbed wetlands, Nolte Associates has prepared a wetland
mitigation plan (see attached plan) to compensate for the loss of habitat value caused by
construction on the undeveloped land. The overall goals of the mitigation plan include
enhance the remaining undeveloped area by:
Maintaining the hydrological process of the drainage ditch.
Increasing the wetland area from the existing 20,090 s.f. to approximately
23,310 s.f. by improving the wetland area of the new drainage ditch and
creating a new storm water detention pond.
• Stockpiling wetland topsoil and saving naturally occurring seeds for
redistribution in the new wetland areas.
• Creating a riparian enhancement area of approximately 26,760 s.f. using the
undeveloped lands adjacent to wetlands to plant native plants.
This document includes the conceptual design for maintaining and enhancing the wetland
hydrology, soils, and vegetation of the mitigation area. The mitigation plan describes the
proposed methods for vegetating the mitigation site. The hydrological functions would be
obtained by excavating to depths enabling surface water inundation and soil saturation to
occur. Once constructed, data would be collected in monitoring reports and submitted to
the City of Fort Collins.
Existing On -Site Description
Location
The wetland mitigation site is located in the City of Fort Collins, Laramie County,
Colorado between the rear of the Best Buy Store at 4030 South College Avenue and John
F. Kennedy Boulevard to the east. The site is located in a part of the west 1/2 of Section
36, Township 7 North, Range 69 West of the Sixth P.M.
Existing Conditions
An oldfield plant community that has developed on apparent fill soils occupies most of
the mitigation site. A drainage ditch bisects the site from north to south with a short
westward extension located approximately in the middle. Hydrophytic vegetation occurs
along the drainage ditch.
Vegetation
The oldfield plant community is almost entirely herbaceous, with the dominant species
being crested wheatgrass (Agropyron cristatum) and summer cypress (Kochia scoparia).
Also occurring are smooth brome (Bromus inormus), meadow fescue (Festuca pratensis),
cheeseweed (Malva neglecta), white prairie aster (Aster falcatus), Canadian thistle
(Cirsium canadensis), sunflower (Helianthus sp.), and annual brome (Bromus
commutatus). There are two species of trees present, Siberian elm (Ulmus pumila) and
big -leaf cottonwood (Populus deltoides).
Hydrophytic vegetation found along the ditches includes cattail (Typha sp.), creeping
spikerush (Eleocharis palustris), and hardstem bulrush (Scirpus acutus). There are three
species of trees found in the existing wetlands, peachleaf willow (Salix amygdaloides),
big -leaf cottonwood, and Siberian elm.
Soils
The oldfield plant community occurs on what appears to be fill soils. Soil test pits dug in
the areas of hydrophytic vegetation revealed that mucks occur in the topsoil horizon.
Yellowish -orange clays that have cemented underlie them. Pits dug in the grassed swales
revealed soils there have a higher sand content, are moist but not saturated, and are a
uniform brown in color. No signs of soil reduction (mottling, gleying, organic streaking)
were observed.
Hydrology
The only visible evidence of hydrologic features noted in the survey were the drainage
patterns. However, standing water was present at the middle culvert outfall.
Wetland Construction
Surveying
No excavation will be started until the mitigation site has been surveyed and staked in
accordance with the Best Buy Store 4225 Mitigation Plan. The final grades will be
verified by the engineer following excavation.
Earthwork
This item covers clearing, excavation and grading, disposal, placement, topsoiling, and
compaction of all materials within the approximately half -acre wetland mitigation area
and the approximately six -tenths acre riparian area.
• Vegetation Clearing
The first task initiating implementation of the mitigation plan is the clearing of existing
vegetation. Woody vegetation cleared from the site will be disposed of at an approved
off -site location. Temporary fencing to protect it during construction will surround the
existing big -leaf cottonwood that is to be protected in place. The fencing will preferably
be placed at the tree's drip line; in any case it will be placed a minimum of five (5) feet
from the trunk.
• Excavation and grading
After the wetland areas have been cleared the topsoil will be salvaged and temporarily
stockpiled (no more than 12-inches deep) in an upland area adjacent to the mitigation
site. Stockpiling will be done as directed on the wetland mitigation plan.
After removal and stockpiling of the topsoil, the subsoil will be excavated to final grade
as shown on the site -grading plan. The excess subsoil will be stockpiled in an upland
area adjacent to the mitigation site.
Topsoiling
Once the mitigation site has been excavated to final grade, topsoil will be reapplied
(within 30 days of being stockpiled) within the new wetland areas. Topsoiling will
consist of the excavated topsoil from the existing wetland areas that has been stockpiled
on adjacent upland areas.
Wetland Site Design
The design plans, shown on the Best Buy Store #225 Wetland Mitigation Plan, include
improvements to the drainage channel that will be widened and the bottom grades
flattened. A new detention pond will be constructed that will create a new wetland area
The total area of the new wetland areas is approximately 23,310 square feet. In addition
to the wetland reconstruction, approximately 26,760 square feet of adjacent upland area is
being improved and replanted with native plants to provide an extended riparian habitat
area.
Establishment of site hydrology that will provide sufficient water, at the frequency and
duration required for wetland vegetation, is essential to the success of wetland recreation
projects. It has been established that soil saturation, not inundation, fulfills the water
requirements of wetland vegetation. The hydrologic conditions at the site are currently
maintained by surface water. The intention of the wetland mitigation plan is to maintain
saturation of the soil within the bottom areas of the drainage ditch and new detention
pond. An irrigation system will be constructed to augment surface runoff as required to
maintain a healthy wetland and riparian ecosystem.
Species for Planting
It is proposed that emergent wetland plants would not be planted within the mitigation
site. The wetland areas would be allowed to revegetate from the seed bank that naturally
occurs in the reapplied wetland topsoil. A grass seed mixture would be used to reseed the
wetland mitigation area for erosion control until wetland plants establish themselves.
The NRCS will be contacted for a recommended seed mix. If an acceptable wetland
growth is not established after two (2) growing seasons (as determined by the City of Fort
Collins Environmental Planner), the wetland areas will be over -seeded with a mixture of
wooly sedge (Carex lanuginosa), hardstem bulrush (Scripus acutus), fowl mannagrass
(Glyceria striata stricta), and big bluegrass (Poa juncifolia).
Trees and shrubs to be planted within the wetland and adjacent riparian area will include
bigleaf cottonwood (Populus deltoides), ponderosa pine (Pinus ponderosa), western
hawthorn (Crataegus succulenta), yellow mountain willow (Salix monticolor), red -twig
dogwood (Cornuus stonifera), western sand cherry (Prunes besseyi), and black common
chokecherry (Prunus virginiana melanocarpa). The large bigleaf cottonwood currently
located in approximate middle of the north -south drainage will be protected and will
remain.
The adjacent riparian area will be seeded with a combination of blue grama (Bouteloua
gracilis), sideoats grama (Bouteloua curtipendula), and buuffalograss (Buchloe
dactyloides).
Soil Erosion and Sediment Control
Soil erosion and pollution control measures will be in place during construction and for
the first two years of the wetland mitigation project. The work will address site specific
grading. Temporary erosion control measures will be used to correct unforeseen
conditions that may develop during construction.
It is recommended that hay bales and/or silt fencing be placed in a continuous line
between the drainage ditch and construction activities, and at least one place across the
downstream end of the ditch. Replacement of these erosion control measures may be
necessary during the construction period. Any slopes greater than 4:1 (horizontal to
vertical) will be protected with erosion control matting (recommend SuperGro Erosion
Control Fabric manufactured by Amoco).
Other soil erosion and pollution control measures will include:
• Construction staging areas will not be located 9in the wetland riparian areas;
• All reasonable measures will be taken to avoid excess application and
introduction of chemicals into the wetland/riparian areas;
• Refueling of construction equipment will occur at a minimum 50-foot distance
from the wetland/riparian areas;
• Construction equipment will be stored at a minimum 50-foot distance from
the wetland/riparian areas.
Monitoring
Following restoration the City of Fort Collins Environmental Planner will assess the
wetland mitigation site plant establishment for a period of two (2) years. The status and
effectiveness of the planting will be evaluated. If, at the end of the two-year period, an
acceptable growth has not been established the areas will be over -seeded as specified on
the wetland mitigation plan.
VICINITY MAP
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