HomeMy WebLinkAboutEAST RIDGE - PDP - 33-98D - SUBMITTAL DOCUMENTS - ROUND 1 - WETLANDS DOCUMENTSWETLAND MITIGATION AREA WITHIN TRACT K
100'UETLAN BUFFER
.PROPOSED WETLAND FORGE
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100' WETLAND BUFFER
LANDSCAPE NOTES
PRAIRIE DEED -' _0 BE APPLIED IN ALL AREAS
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LANDSCAPE PLAN.I
WETLAND TABULATIONS
EXISTING WETLAND AREA PRIOR TO DISTURBANCE • 6.15 AG,
DISTURBED UETLAND • I.SA AC.
PROPOSED MITIGATED AREA (BOUT. OF EXST. ILETLANDI • 1.S4 AC.
MITI AT " A A WITHIN 5E2tIENT PQREMAYS • 1.50 A
TOTAL MRIGATED LETLAND AREA . 344 AC.
CUTTINGS NOTES
Curri
-CUTTINGS TO BE BUNDLEC. SPECIES TO BE RANDOMLY PLACED WITWIN CUTTINGS AREAS
INDICATED ON THE PLANS
-INSERT 3/4' MIN. CIA., 4'-B' LENGTH CUTTINGS INTO SOIL.
-MAINTAIN 3-4 BUDS ABOVE BOIL
.NO LE58 THAN 1/2 TOTAL LENGTH OF CUTTING TO BE INSERTED INTO SOIL.
CUTTINGS TO ORIGINATE FROM LIVE WOOD, I-3 YEARS OLD
-SPACE CUTTINGS :'-6' O.C.. RANDOM SPACING
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APPLICATION
BLUE DRAMA
23a
B.PPALO GRADS
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GREEN NEEDLEGRASS
20%
DRILLED - rL55,PL5/ACRE
BIDEOATS DRAMA
2C%
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e STERN WWEATGRASB
25%
a OP MIX
APPLICATION
NEBRASKA SEDGE
15a
BALTIC R16W
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SWITCWGRASS
15%
AMERICAN THREE-
SCUARE 5ULRJSu
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BROADCAST - 30L5S/PI_S/ACRE
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EXISTINS AV81JR5ED WETLAND
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Attachment A
East Ridge Wetland Mitigation Plan
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weed infestations will be noted and mapped if helpful. Control measures will be planned.
Control measures on the site may include a mix of chemical and mechanical control.
Chemical control includes application of approved herbicides at recommended levels.
Mechanical control includes mowing and localized shovel removal of weeds. Prevention
of weed infestations is accomplished on the site by maintaining desirable vegetation on
the site.
6.0 References
McKee, T. 2003. Army Corps of Engineers, Natural Resources Specialist, Letter
Regarding the Jurisdictional Status of East Ridge Wetlands. Sent to T. Geiselman, Water
Quality Technology, Inc., November 2003.
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Moore, D. 2005. Natural Resources Specialist, City of Fort Collins, Standard
Development Agreement Requirments.
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Natural Resources Conservation Service (formerly Soil Conservation Service) 1981a.
Seeding Rates. Colorado Agronomy Note No. 61.
Natural Resources Conservation Service (formerly Soil Conservation Service) 1981b.
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Standards and Specifications, Critical Area Planting. Technical Guide, Sect. V.
Colorado.
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Natural Resources Conservation Service (formerly Soil Conservation Service) 1991.
Standard and Specifications Range Seeding. Technical Guide, Section IV, Colorado.
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Natural Resources Conservation Service. 1995. Grass Seeding Information for Colorado.
1 Water Quality Technology, Inc. 2003. Wetlands Delineation for the East Ridge
Development.
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of the first growing season and in late summer of the remaining growing seasons. The
status and effectiveness of the vegetation will be evaluated and the results reported to the
City of Fort Collins Natural Resources Department semi-annually for review. This
reporting will be completed by City staff.
The performance criteria for revegetation is as follows (Moore 2005):
• Areas seeded in the Spring shall be inspected for required coverage each
immediately subsequent Autumn not later than October 1st. Areas seeded at any
other time shall be inspected each immediately subsequent Summer not later than
August 1 st. The required coverage for the first inspection shall be ten (10) viable
live seedlings of the specified species per 1000 square centimeters (approximately
one square foot), or fifty percent (501/6) coverage of the specified foliage as
measured from five feet (5') directly overhead, with no bare spots larger than
1000 square centimeters. At the time of the second growing season inspection,
there shall be seventy-five percent (75%) foliage cover of the specified species
planted as measured from five (5') directly overhead. No more than ten percent
(10%) of the species noted on the site may be weedy species as defined by Article
III, Section 2041 of the Code of the City. The Developer shall be responsible for
weed control at all times. Determination of required coverage will be based on
fixed transects each ten meters in length, randomly placed in representative
portions of the seeded areas, with plant species or bare ground/rock/litter being
noted every ten (10) centimeters along each transect. The Developer shall
warrant all seeded areas for three (3)-growing seasons from the date of
completion. The Developer shall rework and reseed per original specifications
any areas that are dead, diseased, contain too many weedy species, or fail to meet
the coverage requirement at no additional cost to the City.
Maintenance -
No mowing of the wetland mitigation site will occur or be permitted unless needed for
control of noxious weeds.
Noxious weeds will be controlled in the mitigation site and adjacent upland areas as
needed. The only Larimer County regulated weed currently known to be present on the
site is the Canada thistle (Larimer County Weed Control District 2002). Other weeds
present on the site include field bindweed (Convolvulus arvensis), kochia (Kochia
scoparia), pigweed (Amaranthus retroflexus), cheatgrass (Bromis tectorum), sunflower
(Helianthus annuus) and other species. The current level of weed infestation on the site
is much lower than surrounding lands. Many of the weed species currently present along
ditch banks and field margins within surrounding agricultural lands provide quality food
and cover to a variety wildlife species.
Weed control on the mitigation site and adjacent upland area will be completed on an
' annual basis. Monitoring for weeds should be completed twice each growing season
(late May and early August) to inventory weed species on the property. The locations of
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1 The sediment forebays will be seeded with the wetland seed mix to help improve
filtration and water quality. The forebays will need to be dredged occasionally to remove
accumulated sediment. Outlets from the forebays will allow overflow into the wetland
1 ea.
1 The entire wetland area is designed to also serve as a stormwater detention site. The area
is designed to attenuate the flows of a 100-year storm event. An outlet in the southern
section of the site will allow stormwater to drain into the Lake Canal. The outlet will be
1 set above the existing elevation of the wetland to allow for drainage of stormwater flows
without impacting wetland hydrology. After a major storm event the water will drain
back to existing wetland elevation.
In addition, anon -potable irrigation pond will be constructed adjacent to the wetland
mitigation site (Attachment A). Water for this pond will come from existing water rights
1 via local irrigation ditches. This pond will be used to support wetland hydrology and
wetland vegetation as needed. The eastern edge of the pond is designed to transition
naturally and gently into the mitigated wetland area. When the pond is filled water will
1 flow naturally into the wetland area. If needed the pond can be used to supplement
wetland hydrology in the mitigation site.
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5.0 Wetland Monitoring and Maintenance
Monitoring-
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etland mitigation success can vary according to many factors. These factors may
include: changes in hydrology associated with climate or offsite development, excavation
of the mitigation site to improper elevations, infestations of noxious weeds, inadequate
monitoring of the excavation contractor during construction, and many other factors.
Because of these uncertainties post -construction monitoring of the mitigation site is
required. If wetland mitigation is not successful additional corrective actions will be
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completed.
1 The wetland mitigation sites will be monitored during and immediately after construction
has been completed to ensure that the wetland mitigation sites have been constructed
correctly. Construction monitoring will be completed by the developer/contractor with
1 input from the City of Fort Collins.
Post construction wetland and upland monitoring will be completed by the City of Fort
1 Collins in cooperation with the developer. If wetland and upland vegetation does not
establish, weeds infestations occur or other issues arise, corrective measures will be
communicated to the land development firm responsible for the management of on -site
1 operations. The City of Fort Collins will require that the mit' ea develo
wetland vegetation equivalent to the existmg mg wetlan The Developer shall
ensure that au weuanas and uplands are propeny mamLained nor a three-year period
' following construction thereof to ensure that the vegetation and hydrologic regime are
fully established. Monitoring of the vegetation shall occur at least in June and September
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If wetland plants do not become established within the mitigation site within the initial
growing season, supplemental planting or seeding may be warranted. Supplemental
planting within the mitigation site may include the planting of plugs (3-inch diameter),
which include soil and a viable plant, or seeding with wetland species. Specifications
If
supplemental plantings or seeding would be developed only if initial seeding is
t successful.
The proposed location and species for shrub and tree plantings in and adjacent to the
mitigation site are shown on the Attachment A, Wetland Mitigation Plan. Adjacent to the
wetland and within areas proposed for natural vegetation, native tree and shrub species
will be planted. Species that are proposed will provide good quality wildlife habitat on
the site. Shrubs will be planted as bare root or container stock. Willows, dogwood and
narrowleaf cottonwoods will be planted as dormant cuttings. Shrub and tree planting
with bare root or cuttings will be completed during the early to mid spring period during
plant dormancy. Container plantings will be completed anytime during the spring to fall
period. Trees will be planted as container stock and cutting depending on species
(Attachment A). Trees will be planted between early spring and fall periods.
Supplemental irrigation may be needed for one or two growing seasons for planted trees
and shrubs.
The upland side slopes located immediately adjacent to the wetland mitigation site will
be reseeded with an upland seed mix. Native plant species will be used in the seed mix
(see Attachment A, Native Prairie Mix). Erosion control structures, including silt fences,
will be installed to reduce soil erosion into the mitigation site during construction.
Seeding rates are based on recommendations from the Natural Resources Conservation
Service (MRCS 1981a,b). Certified weed free seed should be used for seeding. A firm,
relatively weed free seedbed is needed for seeding. After site preparation the
recommended seed mix will be drill seeded at recommended rates (broadcast seeding will
be at twice the drilled rate). Mulch (straw or native hay, or hydromulch) should be
applied at a rate of around 2,000 pounds per acre after seeding. Mulch can be applied by
hand, or by a mechanical blower. Straw mulch should be crimped into the seedbed to
prevent erosion and wind loss. Seeding should be completed generally between
November 1 and May I (Natural Resources Conservation Service 1991, 1995).
It is anticipated that species diversity and plant cover within the constructed wetlands will
' be similar to pre -construction conditions approximately 3-years after wetland
construction has been completed.
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4.1.4 Wetland Mitigation Site Hydrology
Based on current knowledge much of the water that supported wetlands in the area during
the past was provided by agricultural water runoff. As a replacement to agricultural
runoff stormwater flows from the adjacent subdivision will be channeled into the wetland
area. The wetland mitigation site will serve a duel purpose as a stormwater detention
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area. To help prevent siltation into the wetland mitigation site stormwater flows will be
channeled into 2 sediment forebays prior to discharge into the wetland mitigation site.
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Table 1. Species Recommended for Wetland Fringe and Wetland Planting, East Ridge Wetland Mitigation
Wetland Seed Mix
% of Mix Species Common Name
15 Carex nebraskensis Nebraska sedge
5 Juncus balticus Baltic rush
15 Panicum virgatum
10 Scirpus pungens (americanus)
20
Scirpus validus
33 Spartina pectinata
1 Healianthus mdtalhi
1
Verbena hastate
Switchgrass
American three -square
bulrush
Soft stem bulrush
Prairie cordgrass
Marsh Sunflower
Blue Vervain
Drill Seed at 15 pounds per acre, Broadcast seed at 30 pounds per acre
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The mitigation site excavation elevation will be designed to promote the establishment of
wetland vegetation. The mitigation site will be excavated at or slightly below the
existing elevation of the protected wetland area. The goal of mitigation site excavation
is to provide saturated soils at the ground surface after reapplication of wetland topsoil.
This will help ensure proper hydrology for establishment and maintenance of wetland
vegetation. The actual elevation of excavation will be determined at the time of
construction based on existing conditions. The excavation contractor will remove surface
soil in the mitigation site until saturated soil and standing water is present. Soils within
these mitigation sites should be saturated at the soil surface for the majority of the
growing season.
�, ,� J�. � k-gaVtion g(�n11,Pri( o K-S v�0 Acrc� � dI7mme is e y a er site construction the stockpiled wetlanopsoil and plant V
materials from disturbed wetland area will be applied at a depth of at least 6 inches on the
bottom and side slopes of the mitigation site. If the subsoil located immediately below the
surface soil is determined to be highly permeable, an additional soil layer consisting
primarily of clay, may need to be added to decrease water infiltration. This layer may
require compaction with construction equipment prior to inundation or saturation. If
stockpiled wetland soils are not sufficient to cover the entire mitigation areas, additional
topsoil from nearby upland sites will be added.
Immediately, after construction of the mitigation site, the area will be inundated for
several days to allow for the complete saturation of surface soils.
4.1.3 Wetland and Upland Revegetation
As discussed above, stockpiled wetland soils will be spread over the mitigation site after
final contouring. The use of salvaged wetland surface soils and plant materials has
distinct advantages over use of upland or subsurface soils. Using native wetland soils
allows a representation of plants from all successional stages in constructed wetlands.
Higher species richness and increased cover can be expected in wetlands created with
salvaged topsoil instead of subsoil or upland soil.
The recommended species to be used in wetland revegetation are listed in Table 1. These
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species were chosen to fit a variety of hydrologic regimes that should be characteristic of
the wetland mitigation site. For example, Baltic rush (Juncus balticus) and Nebraska
sedge (Carex nebraskensis) are adapted to seasonally saturated soils. American
threesquare (Scirpus americanus) grows best in areas inundated with shallow water.
Switchgrass (Panicum virgatum) establishes rapidly in wet and seasonally wet soils.
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Herbaceous wetland plants (Table 1) will be planted by seeding. Where possible plants
will be seeded by drill seeding. Seeding rates should be doubled for broadcast seeding.
Seeds should be from local sources if possible. Seeding of wetland plants is not as
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successful as using live plants. Seeds may need the freeze thaw cycles of a winter period
to break dormancy. Seeding should occur during the spring (mid April to June 15) or fall
(September 1 to mid October).
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3.0 Wetland Impacts
Wetland fill is proposed along the north edge of the wetland area. The fill is associated
with construction of a proposed park. A total of 1.94 acres of wetland will be filled with
project construction. Attachment A, Wetland Mitigation Plan shows the area to be filled.
The wetland area will be used in the future as a stormwater detention site. As a result,
vegetated areas around the wetland will be graded and disturbed for construction of
sediment forebays and a non -potable irrigation pond. Attachment A shows details of
proposed forebays and the non -potable pond.
4.0 Wetland Mitigation
Because the wetland on the site is non -jurisdictional wetland mitigation is not required by
the COE. However, wetland mitigation is required on the site by the City of Fort Collins.
The following discussion details the design, and the general construction specifications
for the wetland mitigation area.
Based on conversations with the City of Fort Collins wetland mitigation on the site will
be required on a 1 to 1 basis. There are 1.94 acres of wetland being removed by
construction of the proposed park. Wetland mitigation will be planned to create at least
1.94 acres of new wetland to replace filled wetland. In addition, 1.5 acres of wetland will
be created within the sediment forebays. The proposed wetland mitigation area is
detailed in attached Wetland Mitigation Plan Map (Attachment A).
4.1.1 Protection of Wetlands During Construction
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The boundary of existing wetland vegetation will be fenced or staked erior to �
construction to avoid additional wetland impacts. To protect existing wetland vegetation
' no work will be allowed within the fenced/staked area. Construction personnel will be
informed of the limits of wetland disturbance. A construction inspector will be present to
prevent inadvertent additional wetland impacts.
' 4.1.2 Wetland Mitigation Site Excavation
' The first step in the mitigation will be to salvage surface soils and plant materials
(rhizomes, tubers, shoots, seeds) (minimum depth — 1 foot) from the existing wetland to
be disturbed by park construction. This salvaged soil will be stockpiled in an adjacent
' upland area. The stockpile will be watered periodically during the wetland construction
phase, if needed, to prevent the drying of plant materials and to maintain plant viability.
These stockpiled soils will be spread over the proposed mitigation site after construction.
' to 14 f 0 WS lM O-V� 3' i Vu
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1.0 Introduction and Project Description
The East Ridge site is located in the City of Fort Collins, southeast of the intersection of
Timberline Road and East Vine Drive. The legal description is T7N, R68W, S8, NEIA;
Lat. 400 25' 091"N, Long. 104' 47' 139W).
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A wetland delineation for the project area was completed during October of 2003 (Water
Quality Technology, Inc. 2003). One wetland of 6.19 acres was located on the
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development site. The delineation was sent to the Corps of Engineers (COE) to determine
jurisdictional status of the wetlands on the site. The COE determined that the wetland on
the site is isolated (not connected to other wetlands or water) and is not under their
jurisdiction (McKee 2003).
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2.0 Existing Wetland Description
Vegetation:
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One non -jurisdictional palustrine emergent wetland of 6.19 acres is located on the site.
This wetland occurs in a natural depression along the southern site boundary. The
wetland is located in a small enclosed drainage basin with no connection to other
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drainages or wetlands. The dominant plant present in wetland is cattail (Typha latifolia),
with a fringe of bulrush (Scirpus validus), American threesquare (Scirpus americanus),
reed canarygrass (Phalaris arundinaceae), curly dock (Rumex crispus), creeping
spikerush (Eleocharis palustris), Canadian thistle (Cirsium arvense) and a few other
species. The wetland area has decreased greatly in size over the last 3 years. A previous
delineation showed a wetland of 12.57 acres in size in 2002. There are indications that
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the wetland vegetation may continue to decline on the site without the additional of
agricultural or other manmade runoff.
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Soils and Hydrology:
' The soils on the site are mapped as Auepts Loamy, this is a hydric soil type in Larimer
County (Soil Conservation Service 1980). The soils within the wetland area are mainly
sandy clay loam in texture in the A horizon and clay to clay loam in texture in the B
' horizon. A strong clay layer is evident within the wetland on the site. Evidence of
reducing conditions includes mottling, and low chroma colors. During March (2005)
saturated soil conditions were present at a depth of around 16-18 inches.
No flowing or standing water was observed within the wetland. The wetland receives
flows from agricultural runoff and likely groundwater. The heavy clay layer may
' indicate a perched water table in the wetland area. The size of the wetland has decreased
dramatically in the last 6 years. Previous agricultural operators drained excess irrigation
water into the wetland area. Recent agricultural operations have not drained agricultural
runoff into the site. Without additional manmade water input it is possible the wetland
may continue to decrease in size.
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Table of Contents
1.0Introduction.................. ... ............ ... .....I.................. 1
2.0 Existing Wetland Description ................. .......................1 1
3.0 Wetland Impacts............................................................ 2
4.0 Wetland Mitigation............................................................ 2
4.1.1 Protection of Wetlands During Construction .................2
4.1.2 Wetland Mitigation Site Revegetation ....................... 2
4.1.3 Wetland and Upland Revegetation .............................. 3
4.1.4 Wetland Mitigation Site Hydrology ............................. 4
5.0 Wetland Monitoring and Maintenance ......................................... 5
6.0 References ........................................... I ................ 7
Attachment A -Wetland Mitigation Plan
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East Ridge
Wetland Mitigation Plan
Prepared for:
East Ridge of Fort Collins, LLC
4190 North Garfield
Loveland, CO 80538
Completed by:
Wildland Consultants, Inc.
1001 Jefferson Drive
Berthoud, CO 80513
March, 2005
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