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Buffalo Ridge

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Buffalo Ridge is a large expanse of rolling hills in the southeastern part of the larger Coteau des Prairies, and is the second-highest point in Minnesota standing 1,995 feet (608 m) above sea level. Buffalo Ridge is located in the southwest corner of Minnesota and because of its high altitude and high average wind speed, has been transformed into a place for creating alternative energy. Buffalo Ridge is part of Lincoln County near the small towns of Hendricks and Lake Benton. Currently, over 200 wind turbines stand in the Buffalo Ridge and Lake Benton area. Buffalo Ridge is also the first wind farm created in any of the states surrounding Minnesota.

File:Minnesotarelief.png
Buffalo Ridge is located within the Minnesota portion of the Coteau des Prairies, which is the light spot in the lower left hand corner of this relief map.

Geology

Buffalo Ridge is commonly considered the land extending through Lincoln, Lyon, Pipestone, Murray, Rock, and Nobles counties; however, it is actually an elevated drainage divide located between the Mississippi and Missouri watersheds. Buffalo Ridge is a subsection of the Coteau des Prairies and is considered the inner coteau.[1] The inner coteau is the highest point of the Coteau des Prairies[2] This is due to the large amount, up to 800 feet (244 m), of pre-Wisconsin (generally considered Kansas drift) age glacial till that was left after the glaciers receded. Inner coteau is made up of extremely stream-eroded glacial deposits of pre-Wisconsin glacial drift, which is then covered by a 6 to 15 foot (1.8 to 4.6 m) thick deposit of a wind blown silt called loess. This covering results in the creation of an area with long, gently sloping hills. Loess is an easily eroded material and because of this, there are few lakes and wetlands in the inner coteau area, however the result of this highly erosive material promotes well established dentritic drainage networks, which flow heavily into the Missouri River system and slightly into the Minnesota River system. The bedrock geology of inner coteau consists of Sioux quartzite and red Upper Precambrian quartzite that in most areas is covered by glacial till. Cretaceous shale, sandstone and clay make up the layers beneath the quartzite. Loamy, well-drained soils like Mollisols-Aquolls and Udolls containing Borolls and Ustolls dominate the soils of the inner coteau. On the areas of eroded glacial deposits, dry prairie and moist prairie soils like Cummins and Grigal are present. These soil types, along with the temperate climate,[3] combine to make the perfect growing conditions for tall grass prairie, which covers almost the entire inner coteau.

Climate

Buffalo Ridge has a temperate climate with an average twenty-four to twenty-seven inches (0.6 to 0.7 m) of precipitation per year and thirty-six to forty inches (0.9 to 1.0 m) of snowfall per winter. The average ice out date is around April 5 and the spring green-up generally occurs between May 1 and May 10. Peaking fall colors tend to occur around October 20 and there are generally forty to fifty thunderstorm days per year.

Tornado of 1992

Main article: Mid-June 1992 Tornado Outbreak

On the weekend of June 13, 1992 a large storm struck the northwest corner of South Dakota and within a span of three hours, golf ball-sized hail and up to ten and a half inches of rain fell around the area. This was just a precursor to the terrible storm which was about to hit. On June 16, another storm struck eastern South Dakota and southwestern Minnesota destroying over one hundred homes and businesses in South Dakota. These supercells created many large damaging tornadoes, the first one forming in Charles Mix County and moved toward Mitchell, South Dakota. The second formed in Miner County, South Dakota and the third formed south of Pierre, South Dakota both causing considerable property damage. The fourth tornado formed near the town of Leota in southwest Minnesota and spawned a maxi tornado. It was on the ground for almost an hour and a half and completely destroyed the towns of Chandler and Lake Wilson, Minnesota. In Chandler alone, the property damage came to be over fifteen million dollars. This tornado was later classified as an F5 tornado on the Fujita Scale and turned out to be the only F5 tornado to occur in the United States in 1992. Another tornado formed in South Dakota later in the day and made its way to Minnesota where it struck the town of Chandler for the second time along with Colton and Dell Rapids. The storm system that created these tornadoes and severe storms finally moved east on June 18.

Wind farm

In 1994, a Minnesota legislative mandate rose the demand for wind power. Buffalo Ridge's geography is suitable for wind power. Buffalo Ridge’s wind power history has been split into three phases of construction. The first phase took place in 1994. The first wind farm cluster was built on Buffalo Ridge in the town of Lake Benton. This first cluster was built by the Kennetech Corporation (also the owners of Buffalo Ridge) and consisted of seventy-three wind turbines. The second phase occurred in 1998. Zond Energy Systems built the next wind farm cluster in Hendricks, Minnesota. This farm consisted of one hundred and forty-three Z-750 wind turbines with each turbine standing two hundred fifty-seven feet (78 m) high and weighing around one 196,000 pounds (88,904 kg) each. Each turbine can deliver the annual electricity needs of two hundred and fifty homes. The third phase occurred in mid 1999 and added one hundred megawatts of power to the existing output. In 2001, the Minnesota legislature required Northern States Power, now Xcel Energy, to produce or contract up to four hundred and twenty-five megawatts of wind energy by the year 2002. By that time, four hundred and fifty turbines stood on Buffalo Ridge creating three hundred megawatts of energy and delivering that power to up to 110,000 homes. By the end of 2001, Xcel Energy obtained an approval to upgrade its transmission lines on Buffalo Ridge to provide up to eight hundred and twenty-five megawatts of power. Last year PPM Energy and Xcel Energy began construction of a one hundred and fifty megawatt project called the MinnDakota Wind Power Project. This project not only adds sixty-seven more wind turbines to the Buffalo Ridge wind farm, but also adds wind turbines in Brookings County, South Dakota.

Anyone who has the money can own a windmill on Buffalo Ridge. Small projects, projects less than two megawatts in size, are offered subsidies of 1.5 cents per kilowatt-hour for the power sold to utilities. These small projects are also exempt from property taxes, and are permitted net metering providing back up power when the wind is not generating power.

Future plans

As for the future of Buffalo Ridge as a wind farm, Xcel has contracted an additional three hundred megawatts of wind energy by 2010 and must obtain ten percent of its own electricity from renewable sources by 2015. Xcel is expected to lengthen its wind power contracts from three hundred and two megawatts to one thousand one hundred and twenty five megawatts by 2010.

Birds, bats, and windmills

Concerns involved with wind turbines revolve around the affected bird and bat populations that surround the Buffalo Ridge area; however this concern seems to be very minor. A study featured in The American Midland Naturalist found that eighty-four to eighty-five percent on the seventy species of birds that live in the Buffalo Ridge area fly above or below the height of the wind turbine blades. During a study conducted in 1996, by Western EcoSystems Technology, it was concluded that an estimated average of 1.4 birds were killed per wind turbine during the seven-month study. Another eight-month study was done in 1997 and found that 1.1 birds were killed per turbine. Also, available evidence from the “Interim Report: Bat Interactions with Wind Turbines at the Buffalo Ridge, Minnesota Wind Resource Area: 2001 Field Season,” shows that most bat mortalities caused by windmills occur during the fall to migrant and dispersing bats and not to resident breeding populations. It was concluded by this same study that 2.45 to 3.21 bats die per turbine which is very low compared to the number of bat deaths by lighthouses, communication towers, tall buildings, power lines, and fences. In 1996, Western EcoSystems Technolygy was contracted by Northern States Power to create an avian monitoring program for Buffalo Ridge. Its primary goals for Buffalo Ridge were to evaluate the risks to avian species by monitoring the wind power development and its effect on the avian species while at the same time using that information to reduce avian mortalities on Buffalo Ridge. According to the studies, humans are more dangerous to bird populations than windmills.

Footnotes

  1. ^ http://www.dnr.state.mn.us/ecs/251Bc/index.html
  2. ^ DNR, Minnesota DNR, http://www.dnr.state.mn.us/ecs/251Bc/index.html.
  3. ^ USGS, Northern Praire Research Center, http://www.npwrc.usgs.gov/resource/habitat/rlandscp/s2-2-1.htm.

Works cited


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