Loading...
HomeMy WebLinkAboutTHE GROVE AT FORT COLLINS - PDP - 16-10B - REPORTS - ENVIRONMENTAL REPORT (3)L. Ripley 4/4/11 Page 2 of 2 zone. Aside from the coyote willow, the only other woody species growing along the ditch embankments are 14 large eastern cottonwoods (Populus deltoides) and one green ash (Fraxinus pennsylvanica). The bottom of the ditch and lower 2 to 3 feet of the inner ditch embankments are relatively bare of any vegetation, probably the result of water inundation during the growing season and/or mechanical clearing from ditch maintenance activities. Once irrigation water is removed from the abandoned ditch segment, it is likely that the strips ofreed canarygrass and Emory sedge would slowly be lost and be replaced by stands of smooth brome that would move down the embankment slope as soil conditions dry. It would also be expected that the two pockets of coyote willow would die off as soil moisture levels drop. Smooth brome cover would likely.also spread down to the base of the inner ditch embankments. It is not anticipated that annual weeds would dominate vegetation cover on inner ditch embankments since they are not currently common along the upper portions of the ditch banks, and smooth brome should spread aggressively down the lower slopes once soil moisture levels are reduced. It is somewhat uncertain what vegetation will become established along the bare ditch bottom. Soils along the ditch bottom appear to be a mix of sands and clayey soils. Smooth brome would likely spread into the clay soil areas, but sandy soils are not favorable for smooth brome establishment. Sandy areas have low moisture holding capacity and may remain relatively bare of vegetation except for few annual weeds such as cheatgrass (Anisantha tectorum). Overall however, I would not expect the majority of the currently bare ditch areas to become dominated by weedy species. I discussed the possible fate of the 14 cottonwoods and one green ash along the abandoned portion of the ditch with Tim Buchanon, City Forester. Tim indicated the fate of these trees is somewhat uncertain, but since the trees have become established along the ditch and have adapted to increased soil moisture conditions from ditch seepage, it is likely they will slowly decline and may die off completely in 10 to 20 years. Most of these trees are near the end of their maximum lifetime and loss of a water source to their roots could speed up their expected decline. There is some potential that seepage from the new ditch alignment could be a sufficient water supply replacement to maintain the current vigor of some of the existing trees, but this is uncertain as well. Wildlife use of the abandoned ditch segment as movement corridor is not likely to change and may be improved without water flow. Mitigation plantings proposed by The Grove project for the buffer zone would increase vegetation diversity and cover along the north side of the ditch, and herbaceous vegetation cover would increase within the ditch once water flow is stopped. Lack of water flows in spring and summer would also improve the travel corridor for terrestrial species. As the mature trees age and die off, overall songbird diversity and use of the corridor may decline until trees planted in the buffer zone mature in stature. Linda, this concludes my second update for the ECSR for the Grove Project. Please let me know if you have any questions or require further assistance. Sincerely, CEDAR CREEK ASSOCIATES, INC. C,� T. Michael Phelan Principal and Senior Wildlife Biologist CEEMME C�I3EElE1}S - 4t6 W06hko Am*.. Foo Cam. CO 0=1. OM 4934M April 4, 2011 Linda Ripley VF Ripley Associates 401 W. Mountain Ave., Suite 200 Fort Collins, CO 80521 RE: The Grove ESCR Update #2 Regarding the Re -location of the Larimer No. 2 Canal Linda: This letter report is submitted to address questions the City of Fort Collins has asked relating to habitat changes along the current alignment of the Larimer No. 2 Canal once the ditch owner realigns the canal to the south as planned. Realignment of the ditch to the south of its existing alignment would be the only change in project area baseline conditions since submittal of the December 9, 2010 ECSR update for The Grove project area. Based on a proposal received from the Board of Directors of the Larimer No. 2 Canal, the existing ditch alignment along the southern edge of The Grove project area would be straightened and moved to the south because of concerns regarding ditch slope stability issues with the current alignment and the proposed Grove development. The abandoned ditch segment would remain in place and under ownership of the ditch company but would no longer carry irrigation water along most of its length adjacent to the south boundary of The Grove project area. The following text provides an assessment of how habitat values would change along the abandoned ditch segment. Projected Habitat Conditions for the Abandoned Segment of the Larimer No. 2 Canal The buffer between The Grove development and the abandoned segment of the Larimer No. 2 Canal would remain the same. The south edge of the proposed Grove development would maintain an average buffer width of greater than 50 feet from the Larimer No. 2 Canal, but there would be a buffer width of less than 50 feet along a few segments of the south edge of the development. A constant 50-foot buffer would create a buffer area of 88,849 square feet (2.04 acres). With the current proposal and an average buffer width of greater than 50 feet, a buffer area of 100,068 square feet (2.30 acres) would be created. Proposed buffer areas are depicted on the Site Plan provided in the PDP submittal package. Buffer segments with less than optimal buffer widths will be mitigated and other buffer segments will be enhanced by plantings of native shrubs and trees to create additional habitat and vegetation structural diversity as well as natural visual shielding between the proposed development and the interior portions of the buffers. Native shrub and tree cover is essentially lacking in the proposed buffer areas, and plantings of native woody species would provide considerable habitat enhancement for these areas beyond their existing conditions. In addition, plantings of native woody species to enhance habitat and provide visual shielding is consistent with the performance standards described under Section 3.4.1(E)(1) of the Land Use Code and would maintain the effectiveness of the buffer areas even where the buffer distance would be less than the City buffer zone standards. Details of native species to be planted as well as the locations, configurations, and density of native shrub and tree plantings are shown on the Landscape Plan provided in the PDP submittal package. The existing outer slopes of the ditch embankments and inner slopes down to approximately 3 to 4 feet from the bottom of the ditch are vegetated primarily by relatively dense stands of smooth. brome (Bromopsis inermist ), an upland non-native grass species. Narrow (2 to 3-foot wide), non -continuous strips of reed canarygrass (Phalaroides arundinacea) and Emory sedge (Carex emoryil) are the wetland herbaceous species supported at the average high water line along the lower portion of the inner ditch embankments. Two small pockets of coyote willow (Salix exigua) also grow at one site along this wetland 1 Scientific nomenclature for vegetation follows: Weber, W. A. and R. C. Wittmann. 2001. Colorado Flora: Eastern Slope, third edition. University Press of Colorado, Boulder, Colorado. 488 pp.