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HomeMy WebLinkAboutWATERFIELD FOURTH FILING - FDP190009 - SUBMITTAL DOCUMENTS - ROUND 1 - WETLANDS DOCUMENTSWaterfield Wetland Restoration Plan WATERFIELD DEVELOPMENT April, 2019 Presented to: Thrive Home Builders 1875 Lawrence St., Ste. 900 Denver, CO 80202 Prepared by: Wetland Restoration Plan Waterfield Property i TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................... 1-1 1.1 Site Setting ..........................................................................................1-1 1.2 Canada Thistle Phenology .....................................................................1-2 2.0 WETLAND RESTORATION METHODOLOGY ...................................... 2-1 2.1 Assessment of Baseline Conditions .........................................................2-1 2.2 Canada Thistle Control ..........................................................................2-2 2.3 Interim Monitoring ................................................................................2-3 2.4 Promotion of Desirable Vegetation .........................................................2-3 2.5 Success Monitoring ...............................................................................2-4 2.6 Maintenance Phase ...............................................................................2-4 3.0 REFERENCES .................................................................................... 3-1 Tables Table 2.3-1 Waterfield Wetland Restoration – Recommended Seed Mix 2-4 FIGURES Figure 1.2-1 Canada thistle root system. 1-2 Wetland Restoration Plan Waterfield Property ii ACRONYMS AND ABBREVIATIONS Cedar Creek Cedar Creek Associates, Inc. City City of Fort Collins CDA Colorado Department of Agriculture CNWA Colorado Noxious Weed Act Property Waterfield Property USACE United States Army Corps of Engineers WSS Wetland Soil Survey Wetland Restoration Plan Waterfield Property 1-1 1.0 INTRODUCTION Cedar Creek Associates, Inc. (Cedar Creek) is contracted to provide ecological support by developing an approach for restoration of an existing wetland at the Waterfield Property (Property) infested with Canada thistle (Cirsium arvense), and development of a monitoring plan to evaluate success of restoration efforts. The goals of restoration at the Property in this context are to 1) reduce Canada thistle cover and 2) increase cover of desirable native plant species. In order to achieve these goals, Cedar Creek will work closely with a weed specialist (Paratex of Loveland, CO), landscape architects at Ripley Design, and the City of Fort Collins (City). Cedar Creek will also provide support to create effective yet aesthetically pleasing natural habitat buffer zones and detention basins. 1.1 Site Setting The Property is an approximately 89-acre parcel located north of East Vine Drive and west of North Timberline Drive and Merganser Drive in the southwest ¼ of Section 5 (Township 7 North, Range 68 West) of Fort Collins, CO. The majority of the Property is composed of upland alfalfa hayfield, but the centrally-located and isolated wetland exists in a depression with gentle side slopes that appears to collect runoff irrigation water and may also benefit from a high water table. All wetland areas are located within Aquepts, loamy and Aquepts, ponded soil map units (Phelan 2018). Both Aquept soil types are also described as very poorly drained by the Web Soil Survey with high water tables – zero to 18 inches depth to water table for Aquepts, ponded and 6 to 18 inches for Aquepts, loamy (WSS, 2019). The vegetative cover within the wettest central portion of the wetland primarily consists of common cattail (Typha latifolia) and hardstem bulrush (Schoenoplectus acutus) while the outer perimeter of the wetland is dominated by reed canarygrass (Phalaris arundinacea) or cattail. The wetland boundary is defined either by a shift in vegetative dominance cattail or reed canarygrass to dominance by Canada thistle or smooth brome (Bromus inermis). Small stands of Russian olive (Eleagnus angustifolia) grow along the eastern wetland perimeter. Cedar Creek observed open mud flats during the original delineation in 2012 but historical aerial imagery indicates that wetland vegetation completely invaded the mud flats by 2014. M. Phelan (formerly of Cedar Creek) surveyed the wetland again in 2018, at which time it was observed that wetland had decreased in area from 8.46 acres in 2012 to 5.45 acres in 2018. The 2018 wetland survey revealed that much of the reduction in wetland area occurred in the north, east, and south Wetland Restoration Plan Waterfield Property 1-2 portions wetland, with the reduction stemming from either reduced irrigation runoff and/or changing climatic conditions (Phelan 2018). 1.2 Canada Thistle Phenology Canada thistle is a dominant species within the wetland perimeter, transition, and non-cropped upland areas of the Property. Unfortunately it is also one of the most troublesome noxious weeds in the US, and is designated as a ‘List B’ species in the Colorado Noxious Weed Act (CNWA). The species can infest a diversity of land and soil types – roadsides, ditch banks, riparian zones, meadows, pastures, both irrigated and dry cropland, and mesic (moist) soils. Canada thistle is an aggressive non-native, deep-rooted, perennial plant (CDA 2015). The larger first flush of the troublesome weed occurs when rosettes emerge from April to May. Flowering occurs in late spring and throughout the summer, often followed by a second flush in the fall. However, a flush is possible any time during the growing season if sufficient soil moisture is available. Canada thistle also reproduces by seed or vegetatively; seeds account for long distance dispersal while vegetative reproduction from its root system accounts for local spread. Seed set occurs in mid- to late- summer, with 1,000-1,500 seeds produced per plant that are dispersed by animals, vehicles, and/or wind. Seeds remain viable for up to 20-22 years. Canada thistle has an extensive system of creeping horizontal roots, otherwise known as rhizomes. Vertical roots grow six to 15 feet deep, and rhizomes extend 15 feet or more in any direction (Figure 1). Rhizomes as small as a ¼ inch long have enough stored energy to develop new plants and can survive for 100 days without nutrient replenishment from photosynthesis (CSU 2013). Figure 1.2-1 Canada thistle root system (from Dow AgroScineces Canada) Wetland Restoration Plan Waterfield Property 2-1 2.0 WETLAND RESTORATION METHODOLOGY The wetland restoration plan will focus on the reduction of Canada thistle and promotion of desirable vegetation. An adaptive management approach will be adopted that incorporates baseline assessments, interim monitoring, and success monitoring to inform treatment and seeding efforts. The first three years of restoration efforts will be intensive and incorporate multiple methods for controlling Canada thistle (cultural, chemical, and mechanical). Seeding of desirable vegetation during the initial three years will focus on native grass species that will compete with Canada thistle for resources and still be generally unaffected by herbicide applications. Reduction of Canada thistle will also allow better expression of native species already present but in a suppressed state. Aspects of Canada thistle’s phenology can be exploited to a land manager’s benefit, with the goal being to stress the plant to the point that root stores of nutrients and energy are exhausted. The plants draw on root stores for the first spring flush, and the plants should be allowed to grow to the bud stage but then killed to prevent seed production. Additional treatment of top growth should be implemented mid-summer as the plants recover from the initial spring treatment to further stress the plant and to prevent seed set. The most critical step is the fall treatment with a translocating herbicide, in which the herbicide is applied to top growth but is transported to the root system as the plant stores nutrients and energy in the roots in preparation for the spring. Seeding of native grasses will provide competition for resources while being generally unaffected by herbicide applications, and early establishment of native species that will be desired in the long-term future as well. 2.1 Assessment of Baseline Conditions Vegetative cover will be assessed in the spring of Year 1 at the early bud stage of Canada thistle, and conducted prior to any control treatments. Vegetation will be quantified with a point-intercept methodology utilizing custom-built ‘laser bars’ to expedite the process. Five cover transects will be representatively located in each of the three zones in which Canada thistle is present – the wetland perimeter, wetland/upland transition zone, and the uplands, for a total of 15 transects. The results will form the baseline from which future monitoring can judge the shift in vegetative composition, and ultimately for success determination. Soil samples from each zone (wetland perimeter, wetland/upland transition zone, and upland) will be conducted for standard agronomic testing (e.g., nutrients, organic matter, and salinity). Soil analysis will provide valuable input for fine-tuning the seed mixes of desirable species during the initial phase of Canada thistle treatment and subsequent seed mixes. Wetland Restoration Plan Waterfield Property 2-2 2.2 Canada Thistle Control The approach to Canada thistle control encompasses an initial intensive three-year, multiple treatment per year approach. Years 2 and 3 are repeats of Year 1, but treatment options can be modified given the results of interim monitoring (Section 2.3). The goals of the spring and summer treatments are eliminating top growth and preventing seed set; treatments should be timed so that the top growth is removed during the early bud stage, thereby allowing the thistle to invest substantial resources in to the top growth while still preventing seed production. The method of control can be either mechanical or chemical – mechanical removal would entail mowing, whereas the chemical method entails the use of an herbicide (‘chemical mowing’). The type of herbicide used is not critical in the spring and summer treatments as the goal is the removal of top growth. Considerations to be weighed when choosing between mechanical or chemical methods for the spring and summer treatments would include cost and whether heavy equipment can access the Property due to ground conditions (i.e., too wet). Chemical treatment during the fall season is critical because that is when Canada thistle begins to transfer nutrients to its root system in preparation for its initial spring growth. Using a translocating herbicide, in which the herbicide is applied to top growth but is transferred to the root system, is paramount for this treatment. Tillage of the soil, either intentionally or accidentally by the use of heavy equipment (i.e., mechanical mowing during wet soil conditions), should be avoided at all costs in order to avoid the fracturing of Canada thistle roots and stimulation of vegetative reproduction. The following timeline is recommended for each year of the initial intensive three year period: Spring – Removal of top growth at the early bud stage by either mechanical (mowing) or chemical methods. The goal is to prevent seed set. Method is dependent on cost and ground conditions (i.e., if ground is to wet for tractors and/or mowers, a ‘chemical mowing’ is preferable). Summer – Removal of top growth, again at the early bud stage, to further stress thistles and prevent seed set. Method is dependent on cost and ground conditions (i.e., if ground is to wet for tractors and/or mowers, a ‘chemical mowing’ is preferable). Fall – A critical stage of treatment. Treatment with a translocating herbicide while the plants are transporting nutrients to the root system. Wetland Restoration Plan Waterfield Property 2-3 Late Winter / Early Spring – Seeding with desirable grass species to provide competition for resources in subsequent years (see Section 2.4). 2.3 Interim Monitoring Interim monitoring of vegetative cover will be conducted during the spring of Year 2 to assess the effectiveness of Year 1 treatments and to provide feedback for an adaptive management approach. Vegetative cover monitoring during the spring of Year 3 could serve as the final success monitoring (Section 2.5) or as additional interim monitoring given the effectiveness of treatments up to that point. Methodology of interim monitoring is identical to that used for the assessment of baseline conditions (Section 2.1). 2.4 Promotion of Desirable Vegetation Seeding desirable vegetation provides multiple benefits – providing competition to Canada thistle for resources, shading young Canada thistle out, preventing bare ground as Canada thistle is eliminated, and providing early establishment of native vegetation for a more natural habitat. Species to be seeded should be limited to native perennial grasses, cool or warm season, that are generally facultative of soil moisture conditions (can handle moist and dry soils) (Table 1). Seeding forb species should be avoided in the initial intensive phase of Canada thistle treatment as forbs (broad leaved species) are susceptible to most herbicides. The recommended species and seeding rates suggested in Table 1 can be altered given the results of soil analysis. For example, if saline conditions are present then salt-tolerant species such as alkali sacaton (Sporobolus airoides) or inland saltgrass (Distichlis spicata) can be substituted. Total seeding rate should remain consistent with broadcast applications typical for native seedings (approximately 48 pounds / Pure Live Seed / Acre), which are double the seeding rate than when drill seeded (Table 1). Timing of seeding is recommended in late winter to early spring in order to take advantage of ideal climatic conditions for germination and to achieve sufficient maturity of growth to be unaffected by spring herbicide applications. Seeding should not occur when the ground is frozen, covered by snow, or too wet. Typical seedbed preparation, such as ripping or discing, should be avoided in order to prevent a flush of Canada thistle growth by fracturing the root system. Soil should be exposed by hand raking, followed broadcast seeding, and finally a second light raking to insure soil-seed contact. Wetland Restoration Plan Waterfield Property 2-4 Seeded species can be diversified after successful treatment of Canada thistle during the initial intensive three year treatment period. Obligate species can be introduced to the central wetland area given sufficient hydrology, and broader mix of grasses as well as forbs can begin to be seeded and/or planted in to the wetland perimeter, wetland/upland transition zone, and uplands. 2.5 Success Monitoring Success monitoring methodology conducted in Year 4 (2022) mirrors the assessment of baseline conditions and monitoring. It will be conducted in spring at the bud stage of remaining Canada thistle. A success standard of 1-3% total cover of Canada thistle is proposed. If the success standard is met then treatment will then transition to the maintenance phase, otherwise another year of intensive treatment similar to the initial three years is proposed. 2.6 Maintenance Phase After the success standard of the initial intensive treatment phase is met, Canada thistle control measures will transition to a less-intensive maintenance phase. Total elimination of Canada thistle is extremely difficult; therefore the goal of the maintenance phase is the prompt elimination of new individuals in order to prevent new infestations. Treatments will consist of spot treating during the critical times of year – spring (early bud stage) and fall (root translocation). Five years of maintenance treatment is recommended. Table 2.3-1 Waterfield Wetland Restoration - Recommended Seed Mix Scientific Name Common Name Rate (lbs/PLS/ac) 1 Nw P Andropogon gerardii Big Bluestem 5.0 N P Elymus lanceolatus lanceolatus Streambank/Thickspike Wheatgrass 10.2 N P Elymus trachycaulus Slender Wheatgrass 7.6 N P Nasella viridula Green Needlegrass 6.6 Nw P Panicum virgatum Switchgrass 3.0 N P Pascopyrum smithii Western Wheatgrass 11.0 Nw P Schizachyrium scoparium Little Bluestem 4.6 Total 48.0 N=Native, Nw=Warm Season, I=Introduced, X=Noxious 1 Pounds / Pure Live Seed / Acre Wetland Restoration Plan Waterfield Property 3-1 3.0 REFERENCES Colorado Department of Agriculture (CDA) – Conservation Services. 2015. Canada thistle identification and management. Factsheet. Colorado State University Extension. 2013. Canada thistle. Fact Sheet No. 3.108. Phelan, M. 2018. Technical Memo ‘Wetland and other waters of the US delineation for the Waterfield subdivision property in Fort Collins, CO. Courtesy Ripley Design, Inc. Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at https://websoilsurvey.sc.egov.usda.gov/. Accessed 4/10/2019. Urban Drainage and Flood Control District (Urban Drainage). 2016. Chapter 13 – Revegetation. In Urban Storm Drainage Criteria Manual, Vol. 2. 13-i to 13-72.