Abstract
RES North America, LLC is evaluating the feasibility of wind power development in Columbia County, Washington. The proposed Hopkins Ridge Wind Project is located in the rolling hills northeast of the town of Dayton, Washington. The proposed development will be approximately 200 MW, depending on turbine model selected, electricity markets, transmission constraints, and results of site surveys. While there are currently no plans for developing more than 200 MW, the area studied for the project was larger than the current proposed development to insure that possible changes to the proposed development would be covered and to encompass surrounding area for potential future wind plant expansion.
In support of the environmental impact evaluation for the project, a detailed 12-month baseline avian resources study plan was developed and implemented at the site to assist in project design and for use in evaluating potential avian impact s from the project. The study protocol was developed in cooperation with the Washington Department of Fish and Wildlife and the U.S. Fish and Wildlife Service and based on expertise and experience of WEST, Inc. studying wind power effects on birds and wildlife. Information and results from the baseline avian study will be used in the overall environmental impact assessment for the project.
Studies conducted for the project include fixed- point surveys that targeted raptors and large birds, roadside surveys for bald eagles, raptor nest surveys, vegetation/habitat mapping, rare plant surveys, and general wildlife observations. The principal goa ls of the baseline studies were to: (1) quantitatively describe the temporal and spatial use by birds of the study area; and (2) provide baseline information on avian species and their habitat sufficient to use in evaluating the probable impact of the development. Methodology of the surveys for each study component is provided below in the text of the report.
For the avian use surveys (fixed-point surveys), use estimates of the study area by species and groups were calculated as the number of detections per survey (30 minutes) standardize to a fixed plot (800 m radius). Two measures of species diversity in the study area were also calculated. Frequency of occurrence was calculated as the percent of surveys where a particular species was observed. Species composition was represented by the mean use for a species divided by the total use for all species and multiplied by 100 to provide percent composition. An exposure index was calculated by species and group which was a relative measure of the risk of each species coming in contact with a turbine based on use of the study area, the proportion of observations of a species flying, and the proportion of observations of a species flying within the rotor swept area.
A total of 252 30-minute point count surveys were conducted between March 26, 2002 and March 14, 2003. Based on these fixed-point survey s, passerines comprised slightly more than 65% of all birds observed; raptors comprised approximately 12% of all birds observed; corvids (magpies, crows, and ravens) comprised approximately 8% of all birds observed; and all other groups combined (e.g., upland game birds, doves, waterfowl, shorebirds, and others) comprised approximately 15% of all birds observed. Based on the use estimates from the fixed-point surveys, the four most abundant species in the study area were horned lark (2.6 detections/30- minute survey), American robin (0.86 detection/ survey), common raven ( 0.48 detection/survey), and red-tailed hawk (0.38 detection/survey. Together these species comprised more than 52% of the total bird use during the fixed-point surveys. The most abundant raptors observed were red- tailed hawk (102 observations), northern harrier (61 observations), rough-legged hawk (40), and American kestrel (19). On average approximately one red-tailed hawk was observed every 2.6 surveys, one northern harrier every 4.5 surveys, one rough-legged hawk every 7.4 surveys, and one American kestrel every 12.0 surveys. As a group, approximately one raptor was observed per 30-minute survey (0.96).
Ten roadside surveys were conducted for bald eagles from January 29 to March 12, 2002 and from December 28, 2002 to February 11, 2003 along the Tucannon River Road, which parallels the Tucannon River riparian corridor. No bald eagles were observed during the surveys, however, one bald eagle was observed during a fixed-point surveys in the project area on October 5, 2002.
Two aerial surveys for raptor nests were conducted (April 30-May 2 and June 6, 2002) within the raptor nest study area (the study area plus two-mile radius buffer). The total area surveyed was approximately 122 square miles (315 km 2 ). A total of 104 raptor or large stick nests were located, 53 of which were classified as active nests during the first survey. Nest density for buteos (ferruginous hawk, red-tailed hawk, Swainson? hawk) was approximately 0.34 nest/mi2 (0.13 nest/km2). Nest density for all raptors located (buteos, falcons, owls) was approximately 0.43 nest/mi2 (0.16 nest nest/km2). One active ferruginous hawk nest, a state threatened species, was located approximately 2 miles (3.2 km) north of the Project; however, this nest failed to produce chicks in 2002.
Seven basic vegetation types (cropland, grassland, CRP, pine forest , riparian, developed, orchard) occur in the study area. The cropland type (wheat fields) was the most abundant and made up approximately 52% of the study area (approximately 14,485 acres). The grassland type made up approximately 39% of the study area (approximately 10,840 acres). The remaining types were minor components of the study area comprising less than 10% of the area combined. The CRP vegetation type (5%) was found in the northwest portion of the study area and the riparian type (0.9%) was found primarily along Willow Creek within the study area. The proposed development for 200 MW will only affect the cropland vegetation type. The grassland and riparian vegetation types occur in draws and ravines running towards the Tucannon River and Willow Creek, and will not be directly affected by the project. The pine forest stands are located in the southern part of the study area and the CRP land is located in the northwest portion. Neither of these vegetation types will be affected by the proposed project. The Tucannon River riparian corridor was located outside the proposed development area and will not be directly affected by the project.
Four species of mammals (coyote, mule deer, elk, and white-tailed deer) and one species of reptile (gopher snake) were recorded in the study area during the studies. Other than a single bald eagle, no federally listed threatened or endangered species were observed in the study area. State listed species recorded during the studies included golden eagle, ferruginous hawk, peregrine falcon, and merlin.
The estimates of avian use from the study area were similar to other sites studied for wind development in the western U.S. The species diversity was relatively low with several common species comprising the majority of observations. Raptor use and raptor nest density were higher than estimates for other wind sites that have been studied in Washington and Oregon due to the abundance of red-tailed hawk nests in the study area. Estimated impacts from the project are not expected to exceed what has been reported from other newer gene ration wind plants that have been studied. Additional discussion topics and potential mitigation measures to off-set or minimize impacts are addressed in the text below.