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Resource Documents: Colorado (4 items)


Documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. These resource documents are provided to assist anyone wishing to research the issue of industrial wind power and the impacts of its development. The information should be evaluated by each reader to come to their own conclusions about the many areas of debate.

Date added:  April 1, 2017
Colorado, Noise, RegulationsPrint storyE-mail story

Independent Infrasonic Investigations: Golden West Wind Facility, El Paso County, CO

Author:  Rand, Robert


Differential acoustic pressure measurements were acquired and logged at three homes in the vicinity of the Golden West Wind Facility in El Paso County, Colorado during December 2015 and January 2016. A week of data was analyzed for each of the three homes and daily spectrograms produced which are attached. Each day’s data consisted of approximately 4.3 million differential pressure samples with a week comprised of some 30.5 million samples.

Preliminary investigation confirmed the presence of recurring acoustic pressure oscillations at 0.2 to 0.85 Hz (the “blade pass frequency” or BPF) which are associated to the Golden West wind turbine rotations. At times multiple oscillation frequencies were observed, consistent with multiple turbines operating at different rotation rates. Oscillations appeared to be more pronounced when the turbines are more upwind rather than downwind. Neighbors reported they are mostly downwind due to turbine location relative to home location and for the prevailing winds in the region.

Typical BPF total acoustic power were computed for example portions of the differential pressure data sets. Crest factors (the ratio of RMS to peak levels) were also computed for segments dominated by wind turbine rotation and uncontaminated by other noise, with typical crest factors of 13-19 dB. Totalized BPF RMS levels ranged from 56 to 70 dB re 20uPA, with peak levels from 71 to 89 dB. The RMS and peak levels are similar to those found at other sites with appeals to stop the noise, legal action, and homes abandoned.

It is understood from neighbors that they have experienced disturbance since the turbines started operating whereas prior to turbine operation there was no similar disturbance. It is understood that neighbors report improvement when turbines are shut down (not rotating) or when they remove themselves physically away from the Facility a distance of several miles.

El Paso County noise regulations define “Sound” as oscillations in pressure (or other physical parameter) at any frequency, and, prohibits noise disturbance due to acoustic oscillations.

The analysis is far from complete in that numerous segments of each day at each monitoring location could be analyzed and associated to journal entries and/or medical data. The reported association of proximity to the operating facility to disturbance in health and quality of life appears supported by the acoustic data acquired for this preliminary investigation. These preliminary investigations suggest that there is a condition of noise disturbance due to very low frequency acoustic pressure oscillations in the vicinity of the Golden West Wind Facility when it is operating, with more severe impacts downwind.

Download original document: “Independent Infrasonic Investigations: Golden West Wind Facility, El Paso County, CO

[NWW thanks Friends Against Wind for providing the video.]

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Date added:  March 30, 2011
Colorado, Impacts, Iowa, Montana, North Dakota, South Dakota, Texas, WyomingPrint storyE-mail story

Wanzek heavy/industrial constructors

Author:  Wanzek Construction

Top of the World Wind Farm, Glenrock, WY, Duke Energy

Top of Iowa Wind, Kensett, IA, Madison Gas & Electric

Three Buttes Wind, Glenrock, WY-

Oliver County Wind, Center, ND, FPL/Next Era Energy Resources

NoTrees Wind, Odessa, TX, Duke-Energy

Langdon Wind, Langdon, ND, FPL/Next Era Energy Resources

Kit Carson Wind Farm, Burlington, CO, Duke Energy

Goat Mountain Wind, Robert Lee, TX, Edison Mission Energy

Endeavor Wind, Harris, IA, FPL/Next Era Energy Resources

Charles City Wind, Charles City, IA, MidAmerican Energy

Cedro Hill Wind Farm, Bruni, TX, Edison Mission Energy

Cedar Hills and Diamond Willow Wind Farms, Rhame, ND and Baker, MT, MDU Resources

Burleigh County Wind, Wilton, ND, FPL/Next Era Energy-Resources

Buffalo Ridge Wind Farm, White, SD, Iberdrola Renewables

Barton Wind, Barton, IA, Iberdrola Renewables

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Date added:  October 11, 2010
Colorado, Noise, RegulationsPrint storyE-mail story

Draft noise regulation, Clear Creek County, Colo.

Author:  Engineering Dynamics

This draft regulation references many ordinances laws and regulations in effect by many cities and counties in the U. S. and other countries. Also, referenced are technical papers, reports and nationally recognized standards relating to wind turbines. …

Wind Farm Noise Emissions
Noise emission from the site shall not be greater than the dB(A) slow and dB(C) slow, one-hour energy equivalent exceedance levels:

Exceedance Value – %

Hourly Exceedance Level Turbine Noise

dB(A) Slow – Leq

dB(C) Slow – Leq



















Pure Tones
Pure tones shall be defined using un-weighted one-third octave level as existing when the one-third octave band levels adjacent to the one-third octave band containing the tone are 5 dB or more less at frequencies greater than 500 Hz. Below 500 Hz, the differences must be 8 dB for center frequencies, 160, 200, 250. For center frequencies of 125 Hz and lower the differences must be 10 dB. If there are pure tones present as described in this section, then the audible noise standard shall be reduced by 5 dB.

Low Frequency Noise or Infrasound Noise
No low frequency noise or infrasound noise from wind turbine operations shall be created which causes the noise level at the project boundary or at a one-mile radius beyond the closest turbine, which ever is greater to exceed the following limits:

1?3 Octave Band Center Frequency (Hz)

Sound Pressure Level (Leq)





























No impulsive noise from wind turbine operations shall be created which causes the noise level at the project boundary or at a one-mile radius beyond the project boundary or noise setback boundary that exceeds the following limits as measured by either of the two following methods.

Clear Creek County Planning Department may require seismic (ground vibration) measurements at selected locations, when the site is in operation.

Download original document: “Draft wind turbine noise regulation

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Date added:  April 20, 2010
Colorado, Emissions, Grid, TechnologyPrint storyE-mail story

How Less Became More: Wind, Power and Unintended Consequences in the Colorado Energy Market

Author:  Bentek Energy

Study Objectives:

Key Findings:


In 2004, Colorado became the 17th state to adopt renewable energy standards when voters passed Amendment 37. Colorado reaffirmed its commitment to wind and solar energy in 2007 when the Legislature passed HB 1281, increasing the requirement for utilities to purchase renewable energy by 100%. Colorado also approved the Climate Action Plan, which relies on renewable energy to play a central role in the state’s strategy of reducing “greenhouse gas emissions by 20% below 2005 levels by 2020″.

Policymakers’ stated hope was that renewable energy would not only be a major tool to reduce carbon emissions, but also, by displacing conventional fuels, would reduce smog and other air pollution, presumably by reducing sulfur dioxide (SO2) and nitrous oxides (NOX), the principal components of ozone and smog.

This report, which examines four years of Public Service Company of Colorado (PSCO) hourly operational history, illustrates how coal cycling, which in part results from wind generation, negates the emission benefits of wind energy. Integrating an intermittent, must take resource, such as wind energy, requires PSCO to cycle its coal and natural gas-fired plants. The incidents of coal cycling have risen markedly with the introduction of 775 MW of wind capacity since 2007.

Coal-fired power plants are designed to run most efficiently at stable rates and are not well-suited to accommodate the load variability imposed by the integration with wind generation. Cycling causes coal-fired power plants to operate less efficiently, and reduces the effectiveness of their environmental control equipment, which together drive up emissions. Paradoxically, using wind energy in such a way that it forces utilities to cycle their coal generation often results in greater SO2, NOX and CO2 emissions than would have occurred if less wind energy were generated and coal generation was not cycled.

An analysis of the Electric Reliability Council of Texas (ERCOT), which also operates under a RPS mandate to utilize wind energy, validates the emissions findings for PSCO. The underlying problem is the same for both PSCO and ERCOT: wind generation frequently cannot be accommodated without forcing coal-fired units to cycle.

Whereas natural gas-fired combustion turbines and combined-cycle facilities are designed to accommodate cycling, coal equipment is not. Coal boilers are designed to be operated as a base load resource – in other words, to operate at a consistent output level all the time. Because gas resources are not fully utilized to offset wind energy produced in PSCO and ERCOT, coal units are being cycled. Emission levels are increasing, not decreasing, at PSCO and ERCOT coal units because the units are being cycled to compensate for wind generation.

The results of this study help explain why PSCO’s coal-fired plants located in the Denver non- attainment area have experienced an increase in SO2, NOX and CO2 over the past few years. Four of the five most frequently cycled coal plants are located in proximity to Denver. The results also suggest that this problem will worsen over time unless more gas generation is utilized to absorb wind generation variability.

There are national implications as well. Congress and the Obama Administration are considering a national RPS. Before such a national standard is implemented, there is a compelling need to better understand how intermittent sources of energy such as wind can be integrated with existing nuclear, coal and natural gas capacity without producing cycling-induced emissions problems.



Effective wind energy requires sufficient flexible natural gas generation in order to avoid cycling coal facilities. Enacting RPS’s that require more than 5-10% of wind energy for electricity generation will significantly add to emissions unless more flexible natural gas generation is utilized. The report recommends:

  1. Short term. (1-2 years)
    Limit the utilization of wind generation to that which can be offset by cycling existing natural gas facilities.
  2. Long term (Beyond 2012)
    Utilities operating under RPS should consider adding significantly more combined cycle and combustion turbine gas plants to their generation mix. Adding more natural gas plants will reduce the need to cycle coal facilities in all but the most extreme situations.

This report was prepared for the Independent Petroleum Association of Mountain States (IPAMS).

Download original document: “How Less Became More

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