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HomeMy WebLinkAboutENCLAVE AT REDWOOD - FDP220014 - SUBMITTAL DOCUMENTS - ROUND 2 - ENVIRONMENTAL REPORT (3) Enclave at Redwood Natural Habitat Buffer Zone Weed Management Plan July, 2021 Revised February, 2023 PO Box 272150 Fort Collins, CO 80527 i Table of Contents 1.0 Introduction ................................................................................................................................1 2.0 Existing Conditions ......................................................................................................................2 3.0 Weed Management......................................................................................................................3 3.1 Best Management Practices ....................................................................................................3 3.2 Weed Treatment Options and Recommendations .....................................................................3 3.2.1 Cheatgrass (C List) ................................................................................................4 3.2.2 Canada Thistle (B List)...........................................................................................5 3.2.3 Field Bindweed (B List) ..........................................................................................7 3.2.4 Leafy Spurge (B List) .............................................................................................8 3.2.5 Common Mullein (C List) ........................................................................................9 3.2.6 Russian Olive (B List)........................................................................................... 11 4.0 Stormwater Detention Pond ....................................................................................................... 13 5.0 Weed Monitoring ....................................................................................................................... 14 6.0 Literature Cited and Data Sources .............................................................................................. 15 Enclave at Redwood Weed Management Plan 1.0 INTRODUCTION The Weed Management Plan is part of the Applicant’s goal to improve the ecological and aesthetic character of the Natural Habitat Buffer Zone (NHBZ ) proposed on the Enclave at Redwood property (Site). Weed management is an integral tool in facilitating res toration success and a significant component of the strategy to improve ecological function and habitat quality in the NHBZ. The goal of th is Natural Habitat Buffer Zone Weed Management Plan is to provide guidance on specific treatments and recommendations best management practices that will help prevent the spread and establishment of noxious weeds on Site and support successful restoration and establishment of native vegetation communities in the NHBZ. The natural features and habitat s encompassed by the proposed NHBZ include s Lake Canal, the wetland contained by the stormwater drainage feature that runs along the northern border of the Site, the proposed stormwater detention pond, and upland and riparian habitat in the southwestern co rner of the Site. Weed management strategies have been designed to complement restoration goals where they apply to the overall NHBZ, as well as where they specifically apply to the proposed stormwater detention pond. On a broad scale, w eed management will strengthen the NHBZ’s ability to minimize or adequately mitigate the foreseeable impacts of development on wildlife usage of habitat on Site, and contribute to efforts to improve the overall ecological value of existing and proposed habitat. In addition, weed management strategies will support the groundwork laid during restoration and landscape design of the proposed stormwater detention feature, which aims to establish an ecologically valuable habitat that meets the City of Fort Collins’ (City) goals outlined in their Design Standards and Guidelines for Stormwater and Detention Facilities (2009). 2.0 EXISTING CONDITIONS A field evaluation of noxious and invasive weeds was implemented in April 2021 to inform this Weed Management Plan. The survey was conducted outside the growing season , after most vegetation had senesced, thereby precluding a definitive identification of all weed species present on Site. Given the pervasive nature of noxious weeds, it is likely that noxious weed species common to the area are present on or at risk of spreading to the Site. As such, weeds Canada thistle (Cirsium arvense) and field bindweed (Convolvulus arvensis ) have been considered in weed management planning efforts for the NHBZ , in addition to noxious weed species observed on Site during the April 2021 survey. Noxious weeds addressed in this Plan include cheatgrass (Bromus tectorum – C List), Canada thistle (Cirsium arvense – B List), field bindweed (Convolvulus arvensis – C List), leafy spurge (Euphorbia esula – B List), and common mullein (Verbascum thapsus – C List). Several Russian olives (Elaeagnus angustifolia – B List) are present on Site, which are considered by the City to provide some degree of value to wildlife in the form of cover and cooling that may outweigh the benefits of their removal to native vegetation, as determined on a site-by -site basis. Russian oliv e treatment has been covered in this Plan for the purpose of informing removal efforts if determined to be appropriate for the proposed development and project goals. Otherwise, this plan is not intended to prescribe or otherwise recommend removal of existing Russian olive trees present on Site. Noxious weeds are classified in the state of Colorado based on the foll owing characteristics: • List A species are not well established in Colorado, are potentially a large problem to this state, and require mandatory eradication by local governing agencies. Prescribed techniques for management of List A species are hand pullin g, digging, or herbicide application. Mowing, grazing, and insect bio-control are not acceptable forms of management for these species. • List B species are common enough in parts of the state that eradication is not feasible, though the species are still recommended for eradication, suppression, or containment depending on distribution and densities around the state. Prevention of seed dispersal may be accomplished by mowing, hand pulling, tillage, grazing, or herbicide application. • List C species are widespread and well established. Control of List Band C species is recommended but not required by the state. However, local governing bodies may still require management. 3.0 WEED MANAGEMENT 3.1 Best Management Practices Noxious weeds are common in urban and developed areas, and construction-related ground disturbance creates ideal conditions for the spread of noxious weeds. Nevertheless, there are some general practices that can be followed to limit the spread and/or establishment of noxious weeds during cons truction activities. Pre-Construction Phase • Treat existing noxious weed populations that could be spread by construction activities, especially individual plants and small infestations. Aggressive treatment of existing weed populations greatly reduces the ability of the weeds to rebound in post -construction conditions. Seeding, Planting, and Post -construction Phases • Require equipment (especially dirt -moving equipment like bulldozers and excavators) to be washed and weed-free before entering the Site. • Use only certified weed-free straw and mulch for erosion control projects, including weed -free fiber roll barriers and/or sediment logs. • Obtain soil components, amendments, seed mixes, and mulches from weed -free sources. • Establish and maintain vigorous, desi rable vegetation to discourage weeds. • Mulch any non -vegetated surfaces to minimize the amount of noxious weed seeds that will reach the soil surface and germinate. • Monitor all seeded areas for any weed infestations post -construction and to inform subsequent weed management activities. 3.2 Weed Treatment Options and Recommendations A Licensed Pesticide Commercial Applicator (LPCA) for Larimer County will be used to apply herbicide to control noxious weeds on this Site . Permits for LCPA may contain additional t erms and conditions that go beyond the scope of this management plan. The LCPA will perform the application in accordance with applicable laws and regulations and permit stipulations. All herbicide applications must follow US Environmental Protection Agenc y label instructions, including taking proper precautions (proper storage, following spill clean -up procedures, and proper disposal of containers ). Application of herbicides will be suspended when any of the following conditions exists: • Wind velocity exceeds 6 miles per hour (mph) during application of liquids or 15 mph during application of granular herbicides. • Snow or ice covers the foliage of noxious weeds. • Precipitation is occurring or is imminent. Vehicle-mounted sprayers (e.g., handgun, boom, and injector) will be used mainly in open areas that are readily accessible by vehicle. Hand application methods (e.g., backpack spraying, hose and wand spraying) that target individual plants will be used to treat small or scattered weed populations in rough terrain. Calibration checks of equipment will be conducted at the beginning of spraying and periodically to ensure that proper application rates are achieved. Specific treatment plans (as well as herbicide recommendations) for the noxious weeds present on Site are described below. All noxious weeds are expected to require multiple years of treatment to effectively control populations. 3.2.1 Cheatgrass (C List) Species Background Cheatgrass is a highly adaptable winter annual grass that thrives in arid, semi -arid, and cold environments. It is one of the most competitive non -natives in the Western US . Cheatgrass derives its competitive advantage by emerging very early in the year, producing easily transportable seeds, and altering fire regimes to create a positive fire feedback loop that favors its growth over other species. Seeds can remain viable for up to three years in the soil. Control Approach The control approach focuses on mechanical and cultural methods to remove existing populations, provide competition for resources, and reduce bare ground cover. Mowing is not recommended as the action leave roots behind, stimulate flower production, and disperse seeds. Hand collecting, bagging, and disposal are recommended. Cheatgrass is often a contaminant of purchased seed mixes, straw, and stormwater control materials; care must be taken to purchase weed -free materials. Currently , there are no biological control agents for cheatgrass authorized in Colorado. Pre-Construction • Removal of existing populations by carefully hand-pulling plants without spreading the seed and bagging all parts of the cut plants. • Ensure all materials (seed mixes, straw, stormwater control materials, etc.) are certified weed free, and ensure dirt-moving equipment is washed prior to mobilizing to Site. • Mechanical spot -treatment of individuals during the construction phase to prevent spread. Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete cheatgrass. • Mulching exposed non -seeded areas to prevent germination of seed or vegetative re -growth. • Mechanical spot -treatment of individuals. 3.2.2 Canada Thistle (B List) Species Background Canada thistle is one of the most troublesome noxious weeds in the US. As such, long -term vigilance will be necessary to prevent re-colonization. Canada thistle is an aggressive non -native, deep-rooted, perennial plant (CDA 2008). The plant first emerges as a rosette, the first flush of which occurs from April to May. Flowering occurs in late spring and throughout the sum mer, 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. 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). Control Approach 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 midsummer 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 app lied 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. Biological control agents exist for Canada thistle but are not recommended for the Enclave project due to timing restrictions and the use of herbicid es. Pre-Construction • Herbicide treatment in the spring and summer to eliminate top growth, followed by a fall application of a translocating herbicide. • If possible, plan grading operations to avoid moving Canada thistle -infested soil/subsoil from one location to another on Site to avoid spread by root fragments. • Spot-treatment of individuals (either mechanically or chemically) during the construction phase to further stress plants and prevent seed set. Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete Canada thistle. • Mulching exposed non -seeded areas to prevent germination of Canada thistle seed or vegetative re-growth. • Spot-treatment of individuals both mechanically or with herbicide during the construction phas e to further stress plants and prevent seed set. Herbicide Recommendations Table 1 below contains the herbicide recommendations provided by the Colorado Department of Agriculture (CDA) (2008) for Canada thistle in range conditions. 3.2.3 Field Bindweed (B List) Species Background Field bindweed is problematic throughout Colorado; the species is one of the most competitive perennial weeds and can infest a diversity of land and soil types – cultivated areas, pastures, lawns, gardens, roadsides, and waste areas. Field bindweed is an aggressive non -native, deep-rooted, perennial plant, whose seeds can remain viable for up to 40 years in the soil (CDA 2015a). It spreads vegetatively by both long, spreading above-ground vines and below -ground rhizomes, and its difficulty in eradication primarily lies with its large taproot that can grow 20 feet deep. Control Approach Control of field bindweed will likely be a long -term process and should focus on continually stressing the plants and preventing seed set to exhaust the seed bank. Treating as much field bindweed as possible prior to construction will decrease the amount of invading individuals post -construction. Spot treatment of bindweed with herbicides during construction is also highly recommend ed to prevent new establishment. Mechanical treatment of field bindweed is largely ineffective but can be useful during a large flower flush to prevent seed set. Species-specific biological control agents exist for field bindweed but are not recommended for the Enclave project due to timing restrictions and the use of herbicides. Pre-Construction • Two herbicide treatments (one just after full -bloom and one in the fall) to eliminate top -growth and prevent seed set. • Spot-treatment of individuals (either mec hanically or chemically) during the construction phas e. Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete field bindweed. • Mulching exposed non -seeded areas to prevent germination of field bindweed seed or vegetative re-growth. Herbicide Recommendations Table 2 below contains the herbicide recommendations provided by the CDA (2015a) for field bindweed in range conditions. 3.2.4 Leafy Spurge (B List) Species Background Leafy spurge has adapted to a wide variety of habitats in Colorado, though it is more commonly associated with mesic conditions, and effectively crowds out other plant species. Once established, its rapid growth rate, extensive root system, and high seed production rate make it difficult to manage. Leafy spurge is one of the earliest species to emerge in the spring; one large flower can produce up to 130,000 seeds. Control Approach Control of leafy spurge will likely be a long -term process and should focus on continually stressing the plan ts in order to exhaust energy stores within the root system and preventing seed set to exhaust the seed bank. Treating as much leafy spurge as possible prior to construction will decrease the amount of invading individuals post -construction. Spot treatment of leafy spurge with herbicides during construction is also highly recommended to prevent new establishment. Mechanical treatment of leafy spurge is largely ineffective for long-term control due to the extensive root system, but can reduce seed production if repeated every two to four weeks during the growing season. Pre-Construction • Herbicide treatment in the spring and summer to eliminate top growth. • If possible, plan grading operations to avoid moving leafy spurge -infested soil/subsoil from one location to another on Site to avoid spread by root fragments. • Spot-treatment of individuals (either mechanically or chemically) during the construction phase to further stress plants and prevent seed set . Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete leafy spurge. • Mowing every two to four weeks during the growing season to reduce seed set. • Mulching exposed non -seeded areas to prevent germination of seed or vegetative re -growth. • Spot-treatment of individuals either mechanically or with herbicide during the construction phase to further stress plants or prevent seed set. Herbicide Recommendations Table 3 below contains the herbicide recommendations provided by the CDA (2015 b) for leafy spurge in range conditions. 3.2.5 Common Mullein (C List) Species Background Common mullein is found throughout Colorado and is most strongly associated with heavily disturbed sites (i.e., roadsides and trails). Common Mullein was not observed in the 2015 evaluation of noxious weeds but was recorded on Site in 2021. Common mullein is an aggressive non -native, biennial species that reproduces by seed. A seed produces a rosette in the fall or spring during the first year of growth; during the second year the stem bolts, flowers, sets seed, and the plant dies. A single robust plant can produce between 100,000 to 250,000 seeds from June through August. Common mullein is difficult to control given the amount of seed produced and seed bank left in the soil. Control Approach Noxious weed monitoring during the growing season will provide more information on the extent of common mullein on Site, so that populations can be targeted with the appropriate measures. In most scenarios, the control approach for managing common mullein focuses on preventing seed set. Chemical control is recommended for common mullein. Biological control agents exist for common mullein but have not been approved in Colorado. Pre-Construction • Removal of existing individuals by hand pulling or digging when the soil is moist, prior to flowering. If flowers are present, pull plants carefully and bag them so as not to distribute the seed. • Herbicide application during the rosette phase in spring and/or fall, as well as the bud/early flower stage in the spring. • Spot-treatment of individuals (either mechanically or chemic ally) during the construction phase to further stress plants and prevent seed set. Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete common mullein. • Mulching exposed, non -seeded areas to prevent germination of seed or vegetative re-growth. Herbicide Recommendations Table 4 below contains the herbicide recommendations provided by the CDA (2009) for common mullein in range conditions. 3.2.6 Russian Olive (B List) Species Background Russian olive is found throughout Col orado but is most strongly associated with open riparian zones. Russian olive is an aggressive non -native, perennial tree that frequently sprouts suckers. It has the capability of fixing nitrogen in its roots and outcompetes native plants by interfering wi th soil nutrient cycling, constraining natural plant succession, and reducing water availability for other plants. Control Approach The control approach for Russian olive focuses on preventing new establishment of trees. Because plants are already presen t on Site, the recommended method for control is cut -stump treatments. This treatment constitutes cutting down the tree with a hatchet or chainsaw and immediately applying an approved herbicide to the surface of the stump. This treatment is the most effect ive if applied in the fall. Pre-Construction • Removal of existing individuals using the cut -stump treatment to prevent suckers and eventual establishment of new trees. Post-Construction • Establishment of healthy stands of desirable vegetation to out -compete Russian olive. • Mulching exposed, non -seeded areas to prevent germination of vegetative re -growth. Table 4 Herbicide Recommendations for Common Mullein (CDA, 2009) Herbicide Rate1 Application Timing and Restrictions Chlorsulfuron (Telar XP)1-3 oz./acre Apply to rosette stages in spring or fall prior to bolting. Add non-ionic surfactant @ 0.32 oz/gallon water or 1 pint/100 gallon water. 2,4-D Picloram (Grazon P+D)2 4 pints/acre Apply to rosette stages in spring or fall prior to bolting. Add non-ionic surfactant @ 0.32 oz/gallon water or 1 pint/100 gallon water. DO NOT apply near trees, shrubs, or high water table. Picloram (Tordon 22K)2 1-2 quarts/acre Apply to rosette stages in spring or fall prior to bolting. Add non-ionic surfactant @ 0.32 oz/gallon water or 1 pint/100 gallon water. DO NOT apply near trees, shrubs, or high water table. Metsulfuron (Cimmaron)1 oz./acre Apply to rosette stages in spring or fall prior to bolting. Add non-ionic surfactant @ 0.32 oz/gallon water or 1 pint/100 gallon water. 1Rates are approximate and based on equipment with an output of 30 gallons per acre. Read label for exact rates 2This is a Restricted Use Pesticide Table 5 below contains the herbicide recommendations provided by the CDA (2 015c) for Russian olive in range conditions. Table 5 Herbicide Recommendations for Russian Olive (CDA, 2015c) Herbicide Rate Application Timing and Restrictions Cut stump treatment: Apply to the cambial layer of the tree immediatley after the cut-stump treatment and to roots above the soil surface. Basal bark treatment: Spray the roots above the soil surface, root collar, and lower trunk to a height of 12-15" above the ground until they are wet but not dripping, Glyphosate (Redeo- approved aquatic label)1 Undiluted (100% solution) or 50% solution in basal bark oil. Cut stump treatment: Apply to the cambial layer of the tree immediatley after the cut-stump treatment and to roots above the soil surface. Diluted solutions require regular agitation. Treat summer to fall, with fall being the most effective. 2These are non-selective products and will kill any vegetation contacted. Triclopyr (Garlon 4, Remedy) 20-30% solution in basal bark oil. The herbicide Pathfinder comes pre-mixed in oil and does not require dilution. 4.0 STORMWATER DETENTION POND Weed management activities occurring within the vicinity of the stormwater detention pond should be implemented in accordance with the City’s Landscape Design Standards and Guidelines fo r Stormwater Detention Facilities (2009). Regular mowing, aimed to prevent seed production and distribution , will be the primary method of weed control in the proposed stormwater detention pond vicinity . If possible, mowing should be timed to occur just before seed head production and/or flowering of noxious weed populations observed on Site. This timing will preclude seed distribution and potential establishment of new populations, while maximizing the amount of energy each plant expends on production of new growth before removal. Annual monitoring results will include any recommendations and/or observations of vegetation progress throughout the growing season (if identified), which may help facilitate the ideal timing for mowing to occur. Careful spot spraying of noxious weeds may be implemented if determined necessary and applied in compliance with the City’s required weed control standards for stormwater detention ponds (2009) and other pertinent regulations. All herbicides considered for use will be carefully vetted prior to their application to avoid damage to seedling grasses and non -target plants, as well as preclude inappropriate or irresponsible use near aquatic habitats . As a precautionary measure, h erbicides approved for aquatic use will be applied when soil conditions are dry and no precipitation is expected for several days , unless determined necessary for restoration success and otherwise unavoidable. This will minimize the potential risk of unintended transport of chemicals into aquatic habitats and/or groundwater via runoff. Upland areas, and riparian/drainage bank slopes starting above the ordinary high water mark , may be sprayed with non - aquatic herbicides so long as they are non -persistent and applied in accordance with the manufacturer’s directions and recommendations. As a general best management practice, herbicides approved for aquatic use will be preferentially selected over those that are not even in upland areas , when reasonably feasible. Cattails are likely to establish in the proposed stormwater detention areas due to their abundance locally and directly adjacent to the Site . Though they are a native species, their ability to compete with seeded species often leads to diminished biodiversity and u nsuccessful establishment of seeded species, if left unmanaged. Cattails should be suppressed for a minimum of three years to allow less aggressive native species to establish , though up to five growing seasons is recommended if seeded species have not achieved strong establishment at that time. Cattails can be successfully controlled through manual removal; hand pulling or cutting stalks below the water line before flowering is the recommended control method for any populations that may establish on Site. 5.0 WEED MONITORING Noxious weed monitoring will occur for three years following restoration of the Site. Monitoring methodologies and NHBZ success criteria are presented in the Natural Habitat Buffer Zone Monitoring Plan (Cedar Creek 2021). 6.0 LITERATURE CITED AND DATA SOURCES Cedar Creek Associates, Inc. 2021. Enclave at Redwood Natural Habitat Buffer Zone Monitoring Plan . May, 2021. City of Fort Collins. 2009. Landscape Design Standards and Guidelines for Stormwater and Detention Facilities. November, 2009. City of Fort Collins. 2021. Land Use Code. March 5, 2021. Colorado Department of Agriculture (CDA) – Conservation Services. 2008. Canada thistle identification and management. Factsheet. Colorado Department of Agriculture (CDA) – Conservation Services. 2009. Common Mullein identification and management. Factshee t. Colorado Department of Agriculture (CDA) – Conservation Services. 2015a. Field bindweed identification and management. Factsheet. Colorado Department of Agriculture (CDA) – Conservation Services. 2015b. Leafy spurge identification and management. Factsheet. Colorado Department of Agriculture (CDA) – Conservation Services. 2015c. Russian Olive identification and management. Factsheet. Colorado Department of Agriculture (CDA) – Conservation Services. 2019. Cheatgrass identification and management. Factsheet. Colorado State University Extension. 2013. Canada thistle. Fact Sheet No. 3.108. Siegel, S. and Donaldson, S. 2003. Measures to prevent the spread of noxious and invasive weeds during construction activities. University of Nevada Cooperative Extension, Fact Sheet FS -0359.