Northern Colorado Area Plan – Ault to Cloverly Transmission Project

Transmission lines are a vital link used to deliver electricity over long distances from power sources (generation) to transmission substations closer to homes and businesses. A strong transmission system guarantees reliable electricity. Utilities connect their transmission systems to neighboring systems run by other utilities. These interconnected systems form regional grids that allow power to flow from one area to another, ensuring reliable and efficient electric delivery to customers, even during emergencies.

The flow of electricity cannot easily be controlled, and it cannot discriminate between generation sources. Instead, power follows the path of least resistance and carries power derived from diverse resources, such as wind, solar, natural gas, and coal.

Electricity also cannot be stored; it must be generated, transmitted, and distributed for immediate use. Traveling at almost the speed of light – 186,000 miles a second – electricity arrives where it’s demanded at almost the same time it’s produced.

Regional transmission organizations (RTOs) ensure reliable power supplies, adequate transmission infrastructure, and competitive wholesale electricity prices.

In Colorado, the Colorado Public Utilities Commission (CPUC) regulates utilities to ensure reliable electricity delivery.

Public Service Company of Colorado (PSCo, a subsidiary of Xcel Energy) provides electricity and natural gas to customers in Colorado. The service area of PSCo covers more than 8,200 square miles, with 4,615 miles of transmission.

Electric utilities consider the following factors when deciding whether to construct transmission facilities above ground or bury them.

• Power Restoration. Damage to underground powerlines is difficult to pinpoint and repairs may take a few weeks to several months to complete. Damage to overhead lines is easy to locate and typically takes several hours or days to repair.
• Capacity Requirements. Many cables are often required to match the capacity of the overhead circuit. Additional components increase the underground cost as a duct bank, vaults, splices, and terminations are required that also can reduce overall system reliability.
• Line-length Challenges. High-voltage underground lines may require additional equipment to ensure proper electrical performance along the distance of the transmission line. The additional equipment translates to a higher overall cost, limits the length of the underground line installation, and increases the likelihood of failure because of additional components. A system study would be required to determine if this additional equipment would be required.
• Multiple Cables and Cooling Options. Overhead lines are air cooled and widely spaced for safety. Underground cables are installed in concrete-encased PVC duct banks. Heat generated by the cables is dissipated into the earth.
• Construction Impacts. Burying transmission lines results in more environmental impacts than placing them overhead. A 230 kV overhead line typically requires erecting structures and placing foundations every 800 to 1,000 feet. Typical structures are up to 120 feet tall, while the diameter of the foundation ranges from 5.0 to 8.0 feet. Burying a 230 kV double-circuit transmission line at a minimum would require a continuous trench or duct bank at least 3.5 feet wide at the bottom and 7.0 feet deep. Considerable clearing and grading would be necessary; dust and noise from construction would last three to six times longer than it would for overhead construction. Large concrete splice vaults or access structures are needed at 2,000- to 2,500-foot intervals. Permanent access to the vaults is required to make repairs when needed.
• Easement and Land Purchase Requirement. An overhead line typically has a wider easement footprint than an underground line.
• Life Expectancy. Underground high-voltage transmission lines have a life expectancy of 40+ years, while overhead lines have a life expectancy of more than 80 years.
• Costs. An underground 230 kV line costs 10 to 15 times more than an overhead line due to time, materials, processes, the need to include transition substations, and the use of specialized labor. A proposed overhead double-circuit 230 kV line would cost $1 million per mile. Part of the added cost to bury lines may include routing and boring to avoid other underground installations, such as water, natural gas, and sewer lines. An overhead line often can be routed around or over these difficult areas.
• Electric and Magnetic Fields. Electric and magnetic fields generally are greater directly over an underground installation (the earth does not provide shielding) and directly under an overhead installation. Magnetic fields tend to decrease more rapidly with distance from underground installations compared to overhead lines.
• Noise and Lighting. Overhead high-voltage lines can emit hiss or hum noises. Underground lines are silent except in the immediate area near the transition substations, which are lighted throughout the night for security purposes.
• Transition Stations. High-voltage underground transmission lines require small transition stations wherever the underground cable connects to overhead transmission. Transition stations require grading, access roads, storm water management facilities, and fencing.
• Site Restoration. Site restoration for underground construction is a much larger endeavor than it is for overhead construction because soil is disturbed along the entire route. Top soils have to be restored and returned to vegetated areas, and all hard surface areas must be re-established to meet local codes. Vegetated areas may require up to two years to return to pre-construction conditions. Trees and large shrubs would not be allowed above the underground line due to potential problems with roots. In farmland or natural areas some herbaceous vegetation and agricultural crops may be allowed to return in the right-of-way.

If you are considering operating a vehicle within a height greater than 14 feet, contact your local utility company. Call first, even if it appears the line has clearance exceeding 14 feet. And always remember:

• Physical contact with power lines is extremely hazardous and can cause a lethal shock. Equipment SHOULD NOT be operated under a power line in a manner that causes contact or near-contact with the wires.
• DO NOT lift, elevate, or pass under a power line any object, tool, or vehicle that could make contact or near-contact with the wires.
• To help prevent arc flashing, or an explosion, it is recommended that equipment, antennas, and people stay at least 14 feet away from any energized power line.

Electric fences, being specially insulated from the ground, can pick up a charge from power lines. Usually, the charge will drain off when the charger unit is connected to the fence; however, when the charger is disconnected either for maintenance or when the fence is being built, a small shock may be produced. Call Xcel Energy for assistance. Typically, symptoms such as shock can be prevented by:

• Shorting out one or more of the fence insulators to the ground with a wire when the charger is disconnected, or
• Installing an electric filter that will ground charges induced from a power line while still allowing the charger to be effective. Again, contact Xcel Energy for assistance if you have questions—every situation is unique.

Yes, as long as you take these precautions:

• Prevent a solid stream of water from hitting the wires. Equipment with nozzles that are small in diameter or spray a fine mist typically is not problematic because the solid part of the water stream will not reach the power line wires. Also, an intermittent spray of water will not conduct significant amounts of electricity. Even large-diameter nozzles operating at their normal spray angle typically will not reach the wires with a solid stream. However, at no time should the solid part of a water steam touch power-line wires. Should that happen, turn the water off by switching the pump off before trying to correct the problem.
• Make sure the irrigation system is well grounded. If you have questions as to whether or not your irrigation system is adequately grounded, call your local electric utility.
• Check with utility before installing a new irrigation system. Each system should be reviewed on a case-by-case basis; questions about the installation and operations of an irrigation system adjacent to or under a power line should be directed to your electric utility.
• DO NOT install long lengths of pipe parallel and adjacent to power lines. They should be laid out at right angles to power lines, if possible, to reduce risk of pipes building up an induced charge.
• Be careful when moving the pipelines. When loading irrigation pipelines, stay at least 50 feet from power lines to avoid any chance of raising them too close to the wires.

No. Here are some easy rules to follow:

• Do not fly kites or model airplanes near any power line.
• Always fly kites and model planes so the wind carries then away from power lines, and television or radio antennas.
• Call your electric utility if a kite or plane becomes snagged in a power line. DO NOT pull the string or climb a power-line structure, pole, or ladder to get it down.
• If a model airplane is caught in the power line, let go of the control line immediately and call your electric utility for assistance.
• DO NOT attempt to retrieve it yourself.

No. Fires should not be started under a power line. Smoke and hot gases from fires can create a conductive path for electricity.

• A fire could damage the poles or wires and result in an outage.
• It is possible that the power line could flash to the ground through hot air and smoke, which is a serious safety hazard.

Xcel Energy follows strict power line maintenance standards. Power lines are inspected regularly (usually during fall or winter months) and by air to look for the following:

• Non-compatible vegetation and hazards within the right-of-way.
• Equipment needing repair or replacement.
• Right-of-way encroachments, which can be hazardous to safety and reliable operations.
• Anything that might jeopardize safe, reliable operation of the power line.

Utilities must visit the right-of-way for these inspections, but visits may be minimal, and landowners will be contacted prior to inspections or maintenance. However, in cases of emergency, advance contact may not be possible.

Electrocution of birds typically is not associated with transmission lines greater than 138 kilovolts (kV) because generally the electrical components are separated enough that a bird can avoid contact with two of them, which would fatally complete a circuit. Problems that do arise can be corrected in two primary ways:

• Isolation – moving the components farther apart to get the necessary clearance.
• Insulation – using covers on various electrical components to prevent contact with the component that would cause the electrocution.

There are measures that can be taken before construction and after construction.

Pre-construction efforts

• Use vegetation, topography, or man-made structures to shield lines.
• Cluster lines together.
• Site lines away from obvious flyways if possible.

Post-construction efforts

• Modify habitats.
• Create habitats on the same side of the power line to minimize crossings.
• Minimize human activities/disturbances near the line (educational process).

Marking lines

Marking lines with various types of markers can decrease but not eliminate bird collisions. The different types of markers vary in effectiveness. Devices include bird and swan flight diverters and clamp-on markers. Xcel Energy has used a variety of these markers on its lines. The decision to use them is based on:

• Effectiveness
• Line voltage rating
• Weight of markers
• Wind/ice loading factors
• Durability
• Ease of installation
• Effect on the viewshed
• Susceptibility to vandalism

Electric fields are created by voltage. The voltage on an electric wire is caused by electric charges that can exert force on other nearby charges. Electric fields are found near any electric device that is plugged in, even if it not operating. For instance, plugging an appliance such as a lamp or hair dryer into a wall socket applies the voltage to the cord, which is then surrounded by an electric field. Electric fields are strongest closest to the source, and the higher the voltage the stronger the field.

Magnetic fields are created by current. When charges move they produce an electric current that can exert forces on other electric currents. For instance, turning on an appliance, such as a lamp or hair dryer creates a flow of current, which causes a magnetic field. Magnetic fields are strongest closest to their source and are higher when more current is drawn.

EMF is found everywhere electricity is used. Household appliances such as hair dryers, electric blankets, and blenders produce EMF. Office equipment such as computers and copy machines produce EMF. Even the earth has its own magnetic field. In normal everyday life, it is impossible to avoid electric and magnetic field exposure. EMF is everywhere in our environment and occurs in nature as well. Field levels from household appliances and office equipment are about the same or greater than those fields found near power lines.

Radio waves, microwaves, and X-rays are different and more powerful forms of electric and magnetic energy and should not be confused with the power frequency EMF addressed here.

Anything that generates, distributes, or uses electricity creates EMF. Figure 1 is a list of some appliances and machines commonly found in homes or offices and the magnetic field levels found nearby.

We also encounter a wide variety of EMF in other ways―natural and man-made. The earth’s atmosphere creates slowly varying electric fields, and thunderstorms produce very intense electric fields that are occasionally discharged by a lightning bolt. The earth’s core produces a steady magnetic field, as can easily be demonstrated with a compass needle which points to magnetic north. This magnetic field has a strength of about 550 milligauss (mG).

Magnetic fields from the earth or from small magnets exert forces on electric currents or on other magnetic objects, as when a compass needle points toward a nearby magnet. Magnetic fields are common in our lives. Many children’s toys contain magnets and many of us use refrigerator magnets, generating fields of about 100,000 to 500,000 mG.

An increasingly common diagnostic procedure, magnetic resonance imaging (MRI), uses fields of about 20,000,000 mG. If you were to spin a magnet at a rate of 60 times a second, you would get an alternating magnetic field like the fields produced by power lines.

Figure 1. Typical 60 hertz magnetic field levels from some common home appliances

Source: National Institute of Environmental Health Services/National Institutes of Health: EMF Associated with the Use of Electric Power

Exposure levels vary from individual to individual and from home to home, but a study by the Electric Power Research Institute (EPRI) puts the background levels of power line magnetic fields in the typical United States home at between 0.5 mG and 4 mG with an average of 0.9 mG. Levels rise the closer you get to the source of the field. Most people are exposed to greater magnetic fields at work than in their homes. See Figure 1.

Figure 1. Typical 60 hertz magnetic field levels from some common home appliances

Source: National Institute of Environmental Health Services/National Institutes of Health: EMF Associated with the Use of Electric Power

Because magnetic fields are not shielded by ordinary materials, burying power lines won’t keep the fields from passing through the ground. In fact, underground lines can produce higher levels of magnetic fields directly above the line at ground level because these lines are located closer to you (5 feet below) compared to overhead lines (25 to 30 feet above). However, the strength of the magnetic field from underground lines falls away more quickly to the side with distance than from overhead lines because of the way the lines are built.

Compared to overhead lines, underground lines are significantly more expensive to install (up to 10 to 20 times more expensive), more difficult to repair and can have greater environmental impacts because of the disturbance of the soil to install the underground lines. Since recent research results provide no conclusive connection between EMF exposure and health effects, burying lines isn’t a reasonable alternative.

There are no federal standards limiting residential or occupational EMF exposure. Several states have set standards for the allowed level of magnetic fields from new power lines. The Colorado Public Utilities Commission has determined that magnetic fields for new power lines of 150 mG or less are reasonable at the edge of the right-of-way. Other states have established similar standards of 150 to 200 mG for new transmission power lines.

The EMF levels produced by appliances vary from manufacturer to manufacturer and model to model. The designs of many newer model appliances, in general, often produce lower fields than older models. An example is electric blankets where new blankets produce much lower fields than those produced 20 years ago. There is no federal certification program on EMF levels so beware of advertisements on appliances making claims of federal government certification of low or zero EMF levels.

The issue has been studied for more than 40 years by government and scientific institutions around the world. The balance of scientific evidence indicates exposure to EMF does not cause disease.

EMF Sources and Useful Links

The following are links to more information (and Denver area) studies on electric and magnetic fields:

• The National Institute of Environmental Health Services (NIEHS) offers information on a variety of EMF topics. In June of 2002 they prepared EMF: Electric and Magnetic Fields Associated with the Use of Electric Power, Questions and Answers. This booklet, along with other helpful links, can be found at www.niehs.nih.gov/health/topics/agents/emf/.
• Electric and Magnetic Fields: Facts, Western Area Power Administration www.wapa.gov/newsroom/pdf/emfbook.pdf
• “Electromagnetic fields and public health,” World Health Organization fact sheet, www.who.int/mediacentre/factsheets/fs322/en/index.html. More general information on EMF can be found at www.who.int/peh-emf/en/.
• “Unproven Risks – Non-Ionizing Radiation” (2008), The American Cancer Society. www.cancer.org/docroot/NWS/content/NWS_2_1x_The_Environment_and_Cancer_Risk.
• Wertheimer, N and E Leeper, 1979. Electrical wiring configurations and childhood cancer. American Journal of Epidemiology, Volume 109, pages 273-84.
• Savitz, D, H Wachtel, F Barnes, E John and J Tvrdik, 1988. Case – control study of childhood cancer and exposure to 60 Hz magnetic fields. American Journal of Epidemiology, Volume 128, pages 21-38.
• Pearson, R and L Zaffanella, 2003. Association of residential magnetic fields with contact voltage; measurements in 191 Denver area homes. Electric Power Research Institute, Palo Alto, CA, Technical Report 1005569.

High levels of power line EMF can interfere with a pacemaker’s ability to sense normal electrical activity in the heart. Most often, the electric circuitry in a pacemaker might detect the interference of an external field and direct the pacemaker to fire in a regular, life-preserving mode. This isn’t considered hazardous and actually is a life-preserving default feature. There have been cases with dual-chamber pacemakers triggering inappropriate pacing before the life-preserving mode takes over. Newer pacemakers have been designed to be less susceptible to this type of interference.

The American Conference of Governmental Industrial Hygienists (ACGIH) issued guidelines for EMF exposure for workers with pacemakers or implantable defibrillators. Maximum safe exposure for workers with these medical devices at 60 hertz (the frequency of most transmission lines) is 1.0 G (1,000 mG) for magnetic fields and 1.0 kilovolt per meter for electric fields. Non-electronic metallic implants (artificial limbs, screws, pins, etc.) can be affected by high magnetic fields like those produced by MRI devices but are generally unaffected by the lower magnetic fields produced by most other sources.

If you wish to reduce EMF levels in your vicinity, you can do so by recognizing that your exposure is determined by the strength of the magnetic fields given off by things around you, your distance from the source of the field, and how much time you spend in the field. Creating distance between yourself and the sources of EMF is the easiest way to reduce exposure. Standing back―even an arm’s length away―from appliances that are in use is a simple first step. Remember, EMF decreases dramatically with distance. This is more feasible with some appliances than with others, but the following simple recommendations will help you reduce your EMF exposure at home:

• Move motor-driven electric clocks or other electrical devices away from your bed.
• Be aware that electric motors change electricity into mechanical energy by using magnetic fields, so any motorized appliance (e.g., hairdryers, shavers, fans, vacuum cleaners, air conditioners) will produce magnetic fields.
• Stand away from operating appliances that use a lot of electricity.
• Sit a few feet away from the television and at least an arm’s length from the computer screen. Liquid crystal or plasma displays (LCDs), however, produce very low levels of EMF compared to the older cathode-ray tube (CRT) displays.
• Limit the time you’re exposed to a magnetic field by turning appliances, like computer monitors, off when you’re not using them.

Although conclusive results on the potential for health effects from EMF are not yet known, utilities typically take prudent actions in response to concerns about EMF. For example:

• Xcel Energy continues to financially and technically support and participate in scientific research on EMF and monitor results of research activities by utility, government, and private groups.
• Xcel Energy gathers and shares emerging information on EMF and communicate openly and honestly with the public on EMF matters.
• Xcel Energy investigates alternative design and siting approaches for and upgradeding transmission facilities to reduce public exposure to EMF, particularly when facility siting may occur in populated areas.

EMF Sources and Useful Links

The following are links to more information (and Denver area) studies on electric and magnetic fields:

• The National Institute of Environmental Health Services (NIEHS) offers information on a variety of EMF topics. In June of 2002 they prepared EMF: Electric and Magnetic Fields Associated with the Use of Electric Power, Questions and Answers. This booklet, along with other helpful links, can be found at www.niehs.nih.gov/health/topics/agents/emf/.
• Electric and Magnetic Fields: Facts, Western Area Power Administration www.wapa.gov/newsroom/pdf/emfbook.pdf
• “Electromagnetic fields and public health,” World Health Organization fact sheet, www.who.int/mediacentre/factsheets/fs322/en/index.html. More general information on EMF can be found at www.who.int/peh-emf/en/.
• “Unproven Risks – Non-Ionizing Radiation” (2008), The American Cancer Society. www.cancer.org/docroot/NWS/content/NWS_2_1x_The_Environment_and_Cancer_Risk.
• Wertheimer, N and E Leeper, 1979. Electrical wiring configurations and childhood cancer. American Journal of Epidemiology, Volume 109, pages 273-84.
• Savitz, D, H Wachtel, F Barnes, E John and J Tvrdik, 1988. Case – control study of childhood cancer and exposure to 60 Hz magnetic fields. American Journal of Epidemiology, Volume 128, pages 21-38.
• Pearson, R and L Zaffanella, 2003. Association of residential magnetic fields with contact voltage; measurements in 191 Denver area homes. Electric Power Research Institute, Palo Alto, CA, Technical Report 1005569.