Memo. 1.0 Introduction

Transcription

1 Memo Wetland, Wildlife & Vegetation Specialists To: Steve Rogers, Golder Associates From: Andy Herb, AlpineEco CC: Date: August 31, 2015 Re: Boxelder Dam Sites B2 and B3: Results of Vegetation, Wetlands, and TES Habitat Field Survey 1.0 Introduction North Poudre Irrigation Company (NPIC) was an original sponsor of the Boxelder Creek Watershed Project that constructed five flood control dams in the 1970s and early 1980s. Two of these dams, Boxelder Creek Watershed Dams B2 and B3 (ure 1) were originally constructed to protect agricultural land in north central Colorado from flooding. After 35 years of population growth and land development, these rural dams now protect highly developed areas of unincorporated Larimer County, Wellington, Timnath, and parts of eastern Fort Collins. In July 2013, the Colorado Division of Water Resources/Dam Safety Branch raised the hazard classification of both dams from significant to high. The Boxelder B2 and B3 dams are now required to meet higher state and federal dam safety standards (NPIC 2015). In May 2015, a watershed planning study was begun to evaluate alternatives for rehabilitating the dams to serve current needs and meet higher dam safety standards. As part of the study, AlpineEco investigated the sites for the presence of wetlands and other waters features, Colorado-listed noxious weeds, and habitat for plants listed as federally threatened and endangered species (TES). This memo provides a very brief summary of the findings. 2.0 Methods On June 18, 2015, Andy Herb (senior ecologist) walked both sites to identify and map the habitats present, record noxious weeds, and investigate the sites for potential habitat for TES plants. Wetlands were mapped based on the presence of hydrophytic vegetation, which is a conservative approach since both hydric soils and wetland hydrology were assumed to be present. A formal wetland delineation was not conducted. The presence and relative abundance of all Colorado-listed noxious weeds (CDOA 2015) observed was recorded in the field. No detailed mapping of weeds was conducted. For the purposes of this project, TES plants include those listed as threatened or endangered by the US Fish and Wildlife Service. For Larimer County, these include Colorado butterfly plant (Gaura neomexicana ssp. coloradensis) and Ute ladies -tresses (Spiranthes diluvialis), both of which prefer somewhat wet/subirrigated habitats (wetlands) that are not too shaded and/or overgrown. All field mapping was done on 1 inch equals 200-foot scale color aerial photographs and digitized using ArcGIS software. All botanical nomenclature in this memo, unless otherwise noted, follows the PLANTS Database (NRCS 2015). AlpineEco ٠ 1127 Adams Street ٠ Denver, CO ٠

2 3.0 Results The results from the field survey are presented in the following sections. ure 2 shows Dam Site B2 (Boxelder Creek) and ure 3 shows Dam Site B3 (Coal Creek). Photos of Dam Site B2 are in Attachment A and photos of Dam Site B3 are in Attachment B. 3.1 Dam Site B2 (Boxelder Creek) The acre study area for Dam Site B2 is located approximately 8 miles northwest of the town of Wellington, Colorado in Larimer County, just southeast of the intersection of County Road (CR) 15 and Buckeye Road (ure 2). The site is situated immediately downstream of the confluence of Boxelder Creek and Rawhide Creek, and contains a portion of Boxelder Creek (both above and below the dam). The area upstream of the dam is heavily grazed and this reach of Boxelder Creek is very degraded. The channel appears to have been straightened and/or dredged, and is approximately 10 feet below the surrounding grade with nearly vertical banks. The area along the channel is dominated by weedy vegetation and no wetlands are present. Boxelder Creek below the dam appears to have been disturbed and reconstructed as part of the installation of the dam, and is very straight and deep as a result of more recent dredging. Substantial wetlands are present in this area. The site contains four main habitats or land cover types (USGS 2000), including disturbed grasslands, open water, human developments, and wetlands. The overwhelming majority of the site (93.1 percent) is covered by disturbed grasslands, which includes the dam embankment. Most of the remaining area is covered by open water associated with Boxelder Creek (4.4 percent). Table 1 lists the four habitats present, their size, and a general description. Table 1: Habitats Found in the B2 Dam Site Study Area Land Cover Type 1 Area (acres) Percent of Study Area Disturbed Grassland General Description Mainly disturbed short- or mid-grass prairie; dominated by non-natives Open Water Standing or flowing water, including ponds, streams, ditches, and canals Human Developments Mostly unvegetated; dirt roads, pavement, concrete, etc. Wetland Mostly PEM wetlands; some PSS Total Land Cover Types are based on the Colorado Gap Analysis Project (USGS 2000) Disturbed grassland areas dominate the B2 study area (ure 2) and were likely short- or mid-grass prairie that were disturbed by previous activities/land uses. This includes the dam embankment itself as well as most of the surrounding lands that were grazed, farmed, used as borrow sites, or otherwise disturbed. This cover type is dominated by non-native grasses, namely smooth brome (Bromus inermis) and crested wheatgrass (Agropyron cristatum). Other common species include sweetclover (Melilotus officinalis), western wheatgrass (Pascopyrum smithii), cheatgrass (Bromus tectorum), field bindweed (Convolvulus arvensis), curlycup gumweed (Grindelia squarrosa), blue grama (Bouteloua gracilis), buffalograss (Bouteloua dactyloides), and sand dropseed (Sporobolus cryptandrus). Most of this cover type that is not part of the dam embankment is currently grazed by cattle. Some black-tailed prairie dogs are also present. Page 2

3 Wetlands in the B2 study area are confined to the areas below the dam. Most of the wetlands are associated with Boxelder Creek, including the large backwater area below the spillway (ure 2). There are two wetland types in the study area, including palustrine emergent (PEM) and palustrine scrub-shrub (PSS). PEM wetlands are those dominated by herbaceous vegetation (grasses, grass-likes, and forbs) and PSS wetlands are those dominated by shrubs or trees less than 20 feet tall (Cowardin, et al. 1979). PEM wetlands in the study area are mostly dominated by common threesquare (Schoenoplectus pungens), Nebraska sedge (Carex nebrascensis), meadow foxtail (Alopecurus pratensis), common spikerush (Eleocharis palustris), softstem bulrush (Schoenoplectus tabernaemontani), and cattail (Typha spp.). PSS wetlands are mostly dominated by narrowleaf willow (Salix exigua), with some peachleaf willow (Salix amygdaloides). Some habitat for TES plants is present in these wetlands. Many Colorado-listed noxious weeds (CDOA 2015) were observed in the B2 study area during the brief site visit. These are listed in Table 2 along with their status, relative abundance, and general habitat preferences. Table 2: Noxious Weeds Found in the B2 Dam Site Study Area 1 Common Name Scientific Name General Habitat General Distribution in Appropriate Habitats 2 List B Species Hoary cress (whitetop) Cardaria draba Riparian habitats and moist areas Abundant Musk thistle Carduus nutans Open, upland areas Common Diffuse knapweed Centaurea diffusa Open, upland areas Common Canada thistle Cirsium arvense Riparian habitats and moist areas Abundant Russian olive Elaeagnus angustifolia Riparian habitats and moist areas Few Redstem filaree Erodium cicutarium Open, upland areas Abundant Leafy spurge Euphorbia esula Riparian habitats and moist areas Few Dalmatian toadflax Linaria dalmatica Open, upland areas Few List C Species Downy brome (cheatgrass) Bromus tectorum Open, upland areas Abundant Field bindweed Convolvulus arvensis Open, upland areas Abundant Quackgrass Elytrigia repens Riparian habitats and moist areas Abundant Common mullein Verbascum thapsus Open, upland areas Few 1 Nomenclature from CDOA 2015; no List A species observed 2 General distribution guidelines: few = <1 cover; common = 1 to 5 cover; abundant = >5 cover Page 3

4 3.2 Dam Site B3 (Coal Creek) The 59.6-acre study area for Dam Site B3 is located approximately 6 miles north of the town of Wellington, Colorado in Larimer County, just northeast of the intersection of CR 7 and Hackamore Road (ure 3). The study area contains a portion of Coal Creek (below the dam), which is a tributary to Boxelder Creek. The creek in this area is vegetated and contains wetlands, but does not have a defined channel. The site contains three main habitats or land cover types (USGS 2000), including disturbed grasslands, wetlands, and human developments. Nearly the entire site (99.3 percent) is covered by disturbed grasslands, which includes the dam embankment and spillway. Most of the remaining area is wetland associated with Coal Creek (0.5 percent). Table 3 lists the three habitats present, their size, and a general description. Table 3: Habitats Found in the B3 Dam Site Study Area Land Cover Type 1 Area (acres) Percent of Study Area Disturbed Grassland General Description Mainly disturbed short- or mid-grass prairie; dominated by non-natives Wetland PEM wetlands Human Developments Mostly unvegetated; mainly dirt roads Total Land Cover Types are based on the Colorado Gap Analysis Project (USGS 2000) Disturbed grassland areas dominate the B3 study area (ure 3) and are very similar to those found at the B2 site. They were likely short- or mid-grass prairie that were disturbed by previous activities/land uses. This includes the dam embankment and spillway as well as most of the surrounding lands that were grazed, farmed, used as borrow sites, or otherwise disturbed. This cover type is dominated by non-native species, especially crested wheatgrass (Agropyron cristatum) on the north-facing slopes and burningbush (Bassia scoparia) on the south-facing slopes. Other common species include many of those observed at the B2 site as well as sideoats grama (Bouteloua curtipendula) and widely scattered shrubs. Wetlands in the B3 study area are confined to Coal Creek below the dam (ure 3). These are PEM wetlands dominated by broadleaf cattail (Typha latifolia) and common spikerush. Other common wetland plants include foxtail barley (Hordeum jubatum), curly dock (Rumex crispus), and meadow foxtail. Some limited habitat for TES plants is present in these wetlands. Four Colorado-listed noxious weeds (CDOA 2015) were observed in the B3 study area during the brief site visit. These are listed in Table 4 along with their status, relative abundance, and general habitat preferences. Page 4

5 Table 4: Noxious Weeds Found in the B3 Dam Site Study Area 1 Common Name Scientific Name General Habitat General Distribution in Appropriate Habitats 2 List B Species Canada thistle Cirsium arvense Riparian habitats and moist areas Common Dalmatian toadflax Linaria dalmatica Open, upland areas Few List C Species Downy brome (cheatgrass) Bromus tectorum Open, upland areas Common Field bindweed Convolvulus arvensis Open, upland areas Common 1 Nomenclature from CDOA 2015; no List A species observed 2 General distribution guidelines: few = <1 cover; common = 1 to 5 cover; abundant = >5 cover 4.0 Conclusions Dam Site B2 is on Boxelder Creek (just below its confluence with Rawhide Creek) and covers approximately acres. It is over 93 percent disturbed grassland which is dominated by non-native plant species. Approximately 1.4 acres of wetlands are present below the dam. These wetlands contain potential TES plant habitat. Boxelder Creek upstream of the dam is badly degraded and does not contain wetlands. Many noxious weed species are present throughout the study area. Dam Site B3 is on Coal Creek (a tributary to Boxelder Creek) and covers approximately 59.6 acres. Over 99 percent of the site is disturbed grassland and only 0.3 acre of wetlands are present (below the dam only). The wetlands contain some limited potential TES plant habitat. Four noxious weed species are present in the study area. 5.0 Recommendations If ground disturbing activities are planned for either site, a formal wetland delineation will be required by the US Army Corps of Engineers (Corps) as part of the Section 404 of the Clean Water Act permitting process. The delineation should be done during the growing season and securing a permit (depending on the nature of the activity) could take upwards of a year. The permit application must include information on how the project will not adversely affect cultural resources or TES. Any wetlands permanently lost as a result of the project must be replaced (compensatory mitigation). This can be done on- or off-site. Presence/absence surveys for both TES plants (Colorado butterfly plant and Ute ladies -tresses) will be required to ensure compliance with the Endangered Species Act. The survey should take place in late July/early August when the plants are flowering. Results of the survey should be included with the Section 404 permit application. If plants are found in the planned impact area and cannot be avoided, further coordination will be required with the Corps and US Fish and Wildlife Service. A Noxious Weed Management Plan should be prepared for the project in order to ensure proper management of noxious weed before, during, and after construction. Page 5

6 6.0 Literature Cited Colorado Department of Agriculture (CDOA) Noxious weed website: Accessed in August. Cowardin, Lewis M., Virginia Carter, Francis C. Golet, and Edward T. LaRoe Classification of Wetlands and Deepwater Habitats of the United States. U.S. Department of the Interior, Fish and Wildlife Service, FWS/OBS-79/31. Natural Resources Conservation Service (NRCS) PLANTS Database website: Accessed in August. North Poudre Irrigation Company (NPIC) Website: Accessed in August. US Geological Survey (USGS) Colorado Gap Analysis Project: A Geographic Approach to Planning for Biological Diversity. The Mid-Continent Ecological Science Center of the USGS Biological Resources Division. In partnership with Colorado Division of Wildlife and University of Wyoming. Page 6

7 MainMap Extent! Fort Collins! Denver! Grand Junction! Pueblo! Durango B2 Dam Site B3 Dam Site Larimer County Weld County 87 Wellington Miles 08/30/2015 Boxelder Dams ure 1 Location Map

8 Rawhide Creek FLOW 2-3 Boxelder Creek 2-1 FLOW Boxelder Creek Legend Vegetation Disturbed Grassland (123.5 acres) Human Developments (1.8 acres) Water (5.9 acres) Wetland (1.4 acres) Detail Map Extent Study Area ,000 1,500 Feet 08/30/2015 Boxelder Dams ure 2 B2 Dam Site Overview Map

9 Rawhide Creek FLOW Boxelder Creek FLOW Legend Disturbed Grassland (123.5 acres) Human Developments (1.8 acres) Water (5.9 acres) Wetland (1.4 acres) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 2-1 B2 Dam Site Vegetation 08/30/2015

10 Legend Disturbed Grassland (123.5 acres) Human Developments (1.8 acres) Water (5.9 acres) Wetland (1.4 acres) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 2-2 B2 Dam Site Vegetation 08/30/2015

11 Legend Disturbed Grassland (123.5 acres) Human Developments (1.8 acres) Water (5.9 acres) Wetland (1.4 acres) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 2-3 B2 Dam Site Vegetation 08/30/2015

12 Boxelder Creek FLOW Legend Disturbed Grassland (123.5 acres) Human Developments (1.8 acres) Water (5.9 acres) Wetland (1.4 acres) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 2-4 B2 Dam Site Vegetation 08/30/2015

13 FLOW Coal Creek Legend Vegetation Disturbed Grassland (59.2 acres) Human Developments (0.1 acre) Wetland (0.3 acre) Detail Map Extent Study Area ,000 1,500 Feet 08/30/2015 Boxelder Dams ure 3 B3 Dam Site Overview Map

14 Legend Disturbed Grassland (59.2 acres) Human Developments (0.1 acre) Wetland (0.3 acre) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 3-1 B3 Dam Site Vegetation 08/30/2015

15 Coal Creek FLOW Legend Disturbed Grassland (59.2 acres) Human Developments (0.1 acre) Wetland (0.3 acre) Study Area Photo Point Feet 1 in = 200 ft Boxelder Dams ure 3-2 B3 Dam Site Vegetation 08/30/2015

16 Attachment A B2 Dam Site Photographs

17 Attachment A B2 Dam Site Photographs Photo 1: Disturbed grasslands upstream of dam, looking west Photo 2: Disturbed grasslands on dam, looking east C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 1

18 Attachment A B2 Dam Site Photographs Photo 3: Disturbed grasslands downstream of dam, looking southeast Photo 4: Disturbed grasslands downstream of dam, looking east C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 2

19 Attachment A B2 Dam Site Photographs Photo 5: Boxelder Creek upstream of dam, looking southeast (downstream) Photo 6: Boxelder Creek upstream of dam, looking northwest (upstream) C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 3

20 Attachment A B2 Dam Site Photographs Photo 7: Boxelder Creek below dam, looking southeasst (downstream) Photo 8: Boxelder Creek below dam, looking northwest (upstream) C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 4

21 Attachment A B2 Dam Site Photographs Photo 9: Boxelder Creek below dam, looking southeast (downstream) Photo 10: Irrigation ditch below dam, looking south (downstream) C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 5

22 Attachment A B2 Dam Site Photographs Photo 11: Spillway, looking north Photo 12: Spillway, looking northwest C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 6

23 Attachment A B2 Dam Site Photographs Photo 13: Wetlands below spillway, looking west C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B2 Dam Site Photo Log.doc 7

24 Attachment B B3 Dam Site Photographs

25 Attachment B B3 Dam Site Photographs Photo 1: Disturbed grasslands on dam embankment, looking east Photo 2: Disturbed grasslands on dam embankment, looking northeast C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B3 Dam Site Photo Log.doc 1

26 Attachment B B3 Dam Site Photographs Photo 3: Disturbed grasslands on dam embankment, looking west Photo 4: Disturbed grasslands on dam embankment, looking southeast C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B3 Dam Site Photo Log.doc 2

27 Attachment B B3 Dam Site Photographs Photo 5: Wetlands below the dam in Coal Creek, looking south Photo 6: Disturbed grasslands at spillway, looking northwest C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B3 Dam Site Photo Log.doc 3

28 Attachment B B3 Dam Site Photographs Photo 7: Disturbed grasslands at spillway, looking northeast Photo 8: Disturbed grasslands upstream of dam, looking southwest C:\Users\Andy\Desktop\AlpineEco\Projects\ Boxelder Dams\Submittal\ B3 Dam Site Photo Log.doc 4