Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...

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Powerline Flood Retarding Structure Pinal County, AZ Draft Supplemental Watershed Plan and Environmental Assessment mesquite bosques provide valuable food, shelter, and travel corridors for multiple mammal, avian, and reptile species. Additionally, higher plant species diversity was observed within the mesquite bosques. The majority of the mesquites observed within the bosque ranged from 20-30 feet in height. The width of the mesquite bosque ranged from 200 feet to over 650 feet. The most common plants observed in the upland areas were creosote bush (Larrea tridentata) and within and along the washes the velvet mesquite (Prosopis velutina) was the dominant plant species. A non-inclusive listing of plant species observed during the “windshield survey” is included in Table 4-1. Multiple grasses (native and non-native), weedy species, and wildflowers were also observed. The overall vegetation cover within the project area is approximately 10-20 percent. However, along the larger washes and within the mesquite bosques, vegetation cover is much higher approximately 60-80 percent. Table 4-1 Non-Inclusive Listing of Vegetation Common Name Scientific Name Comments velvet mesquite Prosopis velutina Dominant species washes/near cattle ponds blue paloverde Parkinsonia florida Sporadic occurrences catclaw acacia Acacia greggii Sporadic occurrences ironwood Olneya tesota Sporadic occurrences Mexican paloverde Parkinsonia aculeata Isolated occurrence desert hackberry Celtis pallida Sporadic occurrences, near large areas of mesquite fremont cottonwood Populus fremontii Two trees observed in southern portion of project area desert broom Baccharis sarothroides Common throughout creosote Larrea tridentata Dominant species in upland areas desert globe mallow Sphaeralcea ambigua Sporadic occurrences brittle bush Encelia farinosa Common throughout barrel cactus Ferocactus spp. Occasionally observed, more common in southern portion of project area saguaro Carnegiea gigantea Occasionally observed. Arizona grape Vitis arizonica Associated with mesquite bosques, larger washes, and cattle ponds 4.9 WETLANDS /SIGNIFICANT NEXUS ANALYSIS Kimley-Horn prepared a Significant Nexus Analysis (SNA) for the PVR FRSs Rehabilitation or Replacement Project (Kimley-Horn, May 2012) in order to determine if the project area contains areas considered jurisdictional by the U. S. Army Corps of Engineers (Corps) under Section 404 of the Clean Water Act (CWA). The SNA was submitted to the Corps of Engineers in June 2012 and USDA- NRCS Page 4-5 January 2013 Kimley-Horn and Associates, Inc.
Powerline Flood Retarding Structure Pinal County, AZ Draft Supplemental Watershed Plan and Environmental Assessment the Corps has submitted the SNA to the U.S. Environmental Protection Agency (EPA) in January 2013. In October 2008, a 6.9-mile reach of the Lower Gila River from Powers Butte to Gillespie Dam was designated a “traditional navigable water” or TNW by the U.S. Army Corps of Engineers (Corps). Therefore, the nearest TNW to the project area is the Lower Gila River from Powers Butte to Gillespie Dam. The project limits consist of the District’s modified easement area (6,237 acres) with the Arizona State Land Department (ASLD), which includes the FRSs, flood pool areas, Powerline Floodway, and maintenance access roads. This SNA includes the project limits and extends to the TNW via the Powerline Floodway, the East Maricopa Floodway (EMF) and Gila River. The waters analyzed do not significantly affect the chemical, physical, and biological integrity of the downstream TNW, therefore, the waters appear not to be jurisdictional waters of the U.S. Concurrence has not been received by the Corps or EPA as of the date of this report. Further discussion of the SNA is provided in the “Investigation and Analysis Report” in Appendix D. 4.10 FISH AND WILDLIFE Kimley-Horn conducted a Biological Evaluation (BE) study for the PVR FRSs Rehabilitation or Replacement Project and is documented in the report titled “Powerline, Vineyard Road and Rittenhouse Flood Retarding Structures Rehabilitation or Replacement Project - Biological Evaluation” (Kimley-Horn, July 2010). The purpose of the biological evaluation was to document the existing habitat conditions of the project area, and document any species or species specific habitat observed during field biological reconnaissance visits. This assessment focused on gathering general habitat information for the project area and the potential for any threatened, endangered, candidate, or other sensitive species or associated species habitat to occur within the project area. The majority of the project area is flat and sparsely vegetated, with the majority of the vegetation occurring along the ephemeral washes. Very dense mesquite bosques, containing velvet mesquite (Prosopis velutina), blue paloverde (Parkinsonia florida), catclaw acacia (Acacia greggii), and cottonwoods (Populus fremontii) (very rare) are present near and adjacent to the FRSs. The mesquite bosques provide valuable food, shelter, and travel corridors for multiple mammal, avian, and reptile species. Additionally, a higher plant species diversity was observed within the mesquite bosques. The majority of the mesquites observed within the bosque ranged from 20-30 feet in height. The width of the mesquite bosque ranged from 200 feet to over 650 feet. There are no fish in the project area. 4.11 THREATENED AND ENDANGERED SPECIES The U.S. Fish and Wildlife Service (USFWS) threatened, endangered, proposed, and candidate species lists for Pinal (dated March 5, 2012) and Maricopa (dated January 19, 2012) Counties were reviewed by a qualified biologist to determine species potentially occurring in the project vicinity. A qualified biologist reviewed these lists and determined that no threatened, endangered species or critical habitat would be affected by a future proposed project. Suitable habitat is present for the USDA- NRCS Page 4-6 January 2013 Kimley-Horn and Associates, Inc.
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