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HomeMy WebLinkAboutHOMESTEAD AT CLARENDON HILLS - FDP200032 - - ENVIRONMENTAL REPORT (2) 937 Mallard Drive, Ft. Collins, CO 80521 * (970) 224 -0851 * www.bluemountainenvironmental.com February 16, 2021 Ken Mitchell 1021 Nightingale Drive Fort Collins, CO. 80525 RE: Homestead at Clarendon Hills Natural Habitat Buffer Zone Ecological Restoration Mr. Mitchell: The City of Ft. Collins requires the Natural Habitat Buffer Zone at the proposed Homestead at Clarendon Hills development be restored to native ecological condition because it adjoins a City designated Natural Area. The Buffer Zone occurs on the south side of the Smith Lateral irrigation ditch encompassing approximately 0.45 acres. The area is presently dominated by exotic perennial grasses including smooth brome (Bromus inermis) and crested wheatgrass (Agropyron cristatum) which occur with a variety of other native and exotic species. Two state listed noxious species including Canada thistle (Cirsium arvense) and houndstongue (Cynoglossum officinale) are also present in small patches. We recommend complete eradication of existing vegetation through herbicide application followed by reseeding as here outlined in Table 1 below to fulfill City requirements. Additional detail provided subsequently. Table 1. Summary of ecological restoration activities for the Natural Habitat Buffer Zone. Year Activity 1 Herbicide treatment to control non-native grasses and noxious weeds 2 Plant cover crop of sterile sorghum in spring. Irrigate if necessary to promote seed germination and plant growth. Allow cover crop to grow through summer. Mow if necessary before planting native seed mix. Plant native seed mix in late fall. 3 Irrigate if necessary to promote seed germination and plant growth. If annual weeds are present mow monthly with mowing heights no less than 4 to 6 inches. Use spot herbicide control in necessary. 4 Irrigate if necessary to promote plant growth. If annual weeds are present mow monthly with mowing heights no less than 12 inches. Use spot herbicide control if necessary. 5 Irrigate if necessary to promote plant growth. If annual weeds are present mow monthly with mowing heights no less than 12 inches. Use spot herbicide control if necessary. Determine if success criteria for vegetative cover has been met. If criteria has not been met maintain growth for additional year. 6 Irrigate if necessary to promote plant growth. If annual weeds are present mow monthly with mowing heights no less than 12 inches. Use spot herbicide control if necessary. Homestead at Clarendon Hills Natural Habitat Buffer Zone Ecological Restoration 937 Mallard Drive, Ft. Collins, CO 80521 * (970) 224 -0851 * www.bluemountainenvironmental.com Determine if success criteria for vegetative cover has been met. Herbicide Treatments Existing vegetation including exotic perennial grasses noxious species must be eradicated before the site can be seeded with native species. The Larimer County Weed District recommends treating exotic perennial grasses with Rodeo near wetlands and Roundup on uplands. It is anticipated that three to four treatments will be necessary within the first year. Herbicide treatments should be applied to portions of the Natural Habitat Buffer Zone that occur south of wetlands as designated on site plans dated February 2021. It is anticipated that Herbicides used to control these species will be used at appropriate rates and timing so as not to interfere with the following years plantings of a cover crop (spring year 2) and a native seed mix (fall year 2). Vehicular traffic will be excluded from the area with fencing to prevent soil compaction and/or rutting. Management of noxious species is as follows: Canada thistle: Chemical control of Canada thistle can be achieved with Aquatic 2,4-D Herbicide per label recommendations. Apply in spring when thistle is 10 to 15 inches tall; prebud to early bud stage. Mowing is also an effective means of decreasing plant vigor and seed set. When seed heads are encountered they should be clipped well below the apex, bagged, and disposed of in a dumpster. Houndstongue: Because houndstongue is a biennial forb the preferred means of control is mechanical. Mowing second year plants during flowering but before seed maturation to reduce seed production and kill the plant. This practice shall be repeated annually to exhaust the soil seed bank. Chemical control of houndstongue can be achieved with Aquatic 2,4-D Herbicide per label recommendations. When seed heads are encountered they should be clipped well below the apex, bagged, and disposed of in a dumpster. Herbicide application is to be conducted by a licensed commercial pesticide applicator. New populations or species of Colorado listed noxious weeds discovered within the Natural Habitat Buffer Zone shall be managed with appropriate integrated techniques. Establish Cover Crop Plant a cover crop of sterile sorghum in spring of year two in so that there is one additional growing season to deplete the seed bank and control undesirable species. The cover crop will also prevent erosion and condition soils for planting of native seeds in the fall. Seed bed preparation such as mowing or tilling is not necessary before seeding the cover crop. A no-till native grass seeder shall be used to plant sterile sorghum at a rate of 5 pounds pure live seed (PLS) per acre after May 15 or after the last frost when soil temperatures are above 65OF. Seeds will be planted ½ to ¾ inch deep in rows 7 to 12 inches apart. The cover crop will be allowed to grow throughout the summer. If dry conditions persist after seeding irrigation may be Homestead at Clarendon Hills Natural Habitat Buffer Zone Ecological Restoration 937 Mallard Drive, Ft. Collins, CO 80521 * (970) 224 -0851 * www.bluemountainenvironmental.com necessary for successful seed germination. If dry conditions exist during the growing season irrigation may be necessary for adequate plant establishment. Allow cover crop to grow through summer. Mow if necessary before planting native seed mix. Plant native seed mix in late fall. Planting Native Grass and Forb Seed Drill seed the restoration seed mix described in Table 2 below in the fall of year two. The mix may be purchased from Pawnee Butts Seed Company, Arkansas Valley Seed or Western Native Seed. Seed bed preparation such as mowing or tilling is not necessary before seeding. A no-till native grass seeder will be used to plant the native seed mix. If growth of the sterile sorghum crop is determined to be to tall or dense for effective use of the no -till seeder, mowing the sterile sorghum will be conducted before seeding. Native grass and forb seed will be planted between November 15 and April 15. Seeds will be planted ¼ to 1/2 inch deep in rows 7 to 12 inches apart. Irrigate if necessary to promote seed germination and plant growth in year 3. The decadent cover crop of sterile sorghum will moderate microclimate conditions of the seed bed. If annual weeds are present mow monthly with mowing heights no less than 4 to 6 inches. Hand pull or use spot application of herbicides to control other undesirable species as necessary. Maintenance of Seeded Area If dry conditions are present in the spring of year 2 and/or year 3, irrigation may be necessary for successful seed germination and early plant establishment. If natural precipitation is determined to be insufficient for plant establishment over the growing season of year 2 or year 3, irrigation may be necessary. The area will be mowed (native seed mix only) every month during the first growing season (year 3) if annual weeds are present. Mower height will be set to 4 -6” high, no lower. If annual weeds are present during year 4 mowing will be continued with mowing heights no lower than 12 inches. Manage undesirable species with hand pulling, or herbicide application as necessary during or after year 2, application will be done by spot control using a hand-held or backpack sprayer or wick applicator. Success Criteria Success criteria for security release is detailed in the Development Agreement (DA) which is specific to each project. The standard success criteria is 70% average cover with less than 10% cover of noxious weeds and no bare ground areas greater than 1 square foot. Cover requirements are expected to be achieved 3 years after seeding the native seed mix under normal growing conditions of temperature and natural moisture. Homestead at Clarendon Hills Natural Habitat Buffer Zone Ecological Restoration 937 Mallard Drive, Ft. Collins, CO 80521 * (970) 224 -0851 * www.bluemountainenvironmental.com Table 2. Native grass and forb mix for Clarendon Natural Habitat Buffer Zone. Common Name Scientific Name Growth Form* PLS/lbs. (x1000) PLS/SF PLS lbs./ac. sideoats grama Bouteloua curtipendula g 190 10 2.29 blue grama Bouteloua gracilis g 825 10 0.53 buffalo grass Buchloe dactyloides (burr) g 56 2 1.56 purple prairie clover Dalea purpurea f 293 3 0.45 Canada Wildrye Elymus canadensis g 115 10 3.79 thickspike wheatgrass Elymus lanceolatus g 154 5 1.41 annual sunflower Helianthus annuus g 115 5.5 2.08 hairy goldenaster Heterotheca villosa hs 330 3 0.40 gayfeather Liatris punctata f 168 3 0.78 blue flax Linum lewisii f 293 3 0.45 western wheatgrass Pascopyrum smithii g 120 10 3.63 mountain goldenbanner Thermposis montana f 30.6 5 7.12 Total 69.5 24.5 * g=grass, f=forb, hs=halfshrub PLS = Pure Live Seed SF = Square Foot Drill seeding of native species would occur at the end of the first year and site management, including irrigation, hand pulling, mowing and herbicide treatment of undesirable species will likely continue for three years thereafter. Feel free to contact me with questions. Sincerely, Matt Tobler Natural Resource Specialist, Certified Ecologist Blue Mountain Environmental Consulting, LLC