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Path 15 is an portion of the north–south power transmission corridor in
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
, U.S. It forms a part of the Pacific AC Intertie and the California-Oregon Transmission Project. Path 15 is part of The Western Electricity Coordinating Council's links of electrical intertie paths in the western United States. Path 15, along with the Pacific DC Intertie running far to the east, forms an important transmission interconnection with the
hydroelectric plants Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...
to the north and the fossil fuel plants to the south. Most of the three AC 500 kV lines were built by
Pacific Gas and Electric The Pacific Gas and Electric Company (PG&E) is an American investor-owned utility (IOU). The company is headquartered in the Pacific Gas & Electric Building, in San Francisco, California. PG&E provides natural gas and electricity to 5.2 milli ...
(PG&E) south of Tesla substation. Path 15 consists of three lines at 500 kV and four lines at 230 kV. The 500 kV lines connect Los Banos to Gates and Los Banos to Midway. All four 230 kV lines have Gates at one end with the other ends at Panoche, Gregg, and McCall. There are only two connecting PG&E lines north of Tracy substation that connect Path 15 to Path 66 at the Round Mountain substation. The third line between Los Banos and Gates substation, south of Tracy, is operated by the Western Area Power Administration (WAPA), a division of the
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United States ...
. This line was constructed away from the other two lines and is often out of sight. Most of the time the lines are in California's Sierra foothills and the Central Valley, but there are some PG&E lines that come from
power plants A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many pow ...
along the shores of the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
and cross the
California Coast Ranges The Coast Ranges of California span from Del Norte or Humboldt County, California, south to Santa Barbara County. The other three coastal California mountain ranges are the Transverse Ranges, Peninsular Ranges and the Klamath Mountains. ...
and connect with the intertie. The
Diablo Canyon Power Plant The Diablo Canyon Power Plant is a nuclear power plant near Avila Beach in San Luis Obispo County, California. Since the permanent shutdown of the San Onofre Nuclear Generating Station in 2013, Diablo Canyon has been the only operational nucl ...
and the Moss Landing Power Plant are two examples.Route descriptions and tower designs are based on Google Earth images.


The route

The route is generally west of Interstate 5 from the Los Banos substation, west of Los Banos, to the Midway substation, near
Buttonwillow Buttonwillow is an unincorporated community and census-designated place in the San Joaquin Valley, in Kern County, California. Buttonwillow is west of Bakersfield, at an elevation of ). The population was 1,508 at the 2010 census, up from 1,266 ...
.


Connecting lines to Path 15 – Round Mountain to Los Banos substation

The two connecting PG&E
power lines Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is d ...
start at Round Mountain substation at Round Mountain. The parallel
PacifiCorp PacifiCorp is an electric power company in the western United States. PacifiCorp has two business units: # Pacific Power, a regulated electric utility with service territory throughout Oregon, northern California, and southeastern Washington. ...
and PG&E lines north of Round Mountain are considered to be Path 66, not Path 15. These connecting lines to Path 15 will consist of two 500 kV lines until south of Tracy. Heading south, the lines run through the foothills of the northern Sierra Nevada mountains towards the Table Mountain Substation () northwest of Oroville. The lines head southeast from Table Mountain Substation; near the
Sutter Buttes The Sutter Buttes (Maidu: ''Histum Yani'' or ''Esto Yamani'', Wintun: ''Olonai-Tol'', Nisenan: ''Estom Yanim'') are a small circular complex of eroded volcanic lava domes which rise as buttes above the flat plains of the Sacramento Valley in Su ...
the two lines separate. One line heads almost due south, passing to the west of
Sacramento ) , image_map = Sacramento County California Incorporated and Unincorporated areas Sacramento Highlighted.svg , mapsize = 250x200px , map_caption = Location within Sacramento ...
and east of
Davis Davis may refer to: Places Antarctica * Mount Davis (Antarctica) * Davis Island (Palmer Archipelago) * Davis Valley, Queen Elizabeth Land Canada * Davis, Saskatchewan, an unincorporated community * Davis Strait, between Nunavut and Gre ...
. The other line continues southwest for some distance and then turns south and enters the Vaca-Dixon Substation along
Interstate 505 Interstate 505 (I-505) is a north–south auxiliary Interstate Highway in the Sacramento Valley in Northern California. It is a spur auxiliary route of I-5 that runs from near Dunnigan south to I-80 in Vacaville. I-505 is primarily a ru ...
. The Vaca-Dixon substation () was the world's largest substation at the time of its inauguration in 1922. Just north of the
Sacramento River The Sacramento River ( es, Río Sacramento) is the principal river of Northern California in the United States and is the largest river in California. Rising in the Klamath Mountains, the river flows south for before reaching the Sacramento� ...
and the city of
Antioch Antioch on the Orontes (; grc-gre, Ἀντιόχεια ἡ ἐπὶ Ὀρόντου, ''Antiókheia hē epì Oróntou'', Learned ; also Syrian Antioch) grc-koi, Ἀντιόχεια ἡ ἐπὶ Ὀρόντου; or Ἀντιόχεια ἡ ἐπ� ...
the two lines rejoin and head in a south-southeasterly direction. The two PG&E lines span across both the Sacramento and
San Joaquin River The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
s on massive pylons along with the lone 500 kV Western Area Power Administration Path 66 line. Western's Path 66 line then turns east and runs parallel to the two PG&E lines to the west as all three lines head southeast. Both PG&E lines run to the west of the
Clifton Court Forebay Clifton Court Forebay is a reservoir in the San Joaquin River Delta region of eastern Contra Costa County, California, southwest of Stockton. The estuary region the forebay is located in is only 1m to 3m above mean sea level. History The b ...
and cross Interstate 580 before entering the Tesla substation west of Tracy. Leaving the Tesla Substation () one PG&E line heads southwest and two parallel PG&E lines continue in a south-southeasterly direction along the eastern
foothills Foothills or piedmont are geographically defined as gradual increases in elevation at the base of a mountain range, higher hill range or an upland area. They are a transition zone between plains and low relief hills and the adjacent topogr ...
of the
Diablo Range The Diablo Range is a mountain range in the California Coast Ranges subdivision of the Pacific Coast Ranges in northern California, United States. It stretches from the eastern San Francisco Bay area at its northern end to the Salinas Valley ...
and the western edge of the San Joaquin Valley. Only one of the two parallel lines heading southeast connects with Path 15, since one line serves as a connector to WAPA's Tracy Substation. This connector line abruptly turns north when a rare, tall dual-circuit WAPA line meets the two PG&E lines. The same dual-circuit line carries the third 500 kV line that joins the lone southeastward PG&E line. South of this point is where the 500 kV transmission system consists of three lines, not two. Despite being located in the eastern
foothills Foothills or piedmont are geographically defined as gradual increases in elevation at the base of a mountain range, higher hill range or an upland area. They are a transition zone between plains and low relief hills and the adjacent topogr ...
of the Diablo Range, the two eastern lines cross a body of
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
- the O'Neill Forebay of the massive
San Luis Reservoir The San Luis Reservoir is an artificial lake on San Luis Creek in the eastern slopes of the Diablo Range of Merced County, California, approximately west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its nort ...
(just to the east of the San Luis Dam) on several artificial
island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An isla ...
s. The lone southwestward 500 kV PG&E line crosses the Diablo Ridge, rising to 808 m (2,650 feet) near Mount Hamilton.
Google Earth Google Earth is a computer program that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satellite images, aerial photography, and geog ...
elevation for
GNIS The Geographic Names Information System (GNIS) is a database of name and locative information about more than two million physical and cultural features throughout the United States and its territories, Antarctica, and the associated states of ...
coordinates.
The same line then heads into the Metcalf substation near San Jose and the
Metcalf Energy Center The Metcalf Energy Center is a 605 megawatt combined cycle power plant located in Silicon Valley, located in unincorporated Coyote Valley, south of San Jose, California and north of Morgan Hill, California. The power plant is owned by Calpine ...
. Leaving Metcalf substation, the line crosses the southern
Santa Cruz Mountains The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central and Northern California, United States. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from ...
with a 230 kV line and enters the large Moss Landing Power Plant substation in Moss Landing. The same line then heads east to rejoin the parallel PG&E lines at the Los Banos substation, effectively forming a 500 kV loop.


Path 15–Los Banos to Midway substation

South of the Los Banos substation () the three 500kV lines (two PG&E and one WAPA) continue to head southeast, with the lone WAPA line running to the west of the two parallel PG&E lines. The lines regroup as they enter the Gates Substation near
Coalinga Coalinga ( or ) is a city in Fresno County and the western San Joaquin Valley, in central California about 80 miles (128 km) southeast of Salinas. It was formerly known as ''Coaling Station A'', ''Coalingo'', and ''Coalinga Station''. Th ...
. The Los Banos-Gates third 500 kV line is the only WAPA-built section of 500 kV line in Path 15 and the third WAPA 500 kV line is also the only line with triple-
bundle conductor An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
s in Path 15. Exiting the Gates substation (), two parallel PG&E lines continue heading southeastward and one line heads southwest with a 230 kV line. This 500 kV line once again crosses the Diablo Range as it heads towards the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
. The line crosses Highway 101 in Atascadero and
Highway 1 The following highways are numbered 1. For roads numbered A1, see list of A1 roads. For roads numbered B1, see list of B1 roads. For roads numbered M1, see List of M1 roads. For roads numbered N1, see list of N1 roads. For roads numbered S ...
near
Morro Bay Morro Bay (''Morro'', Spanish for "Hill") is a seaside city in San Luis Obispo County, California. Located on the Central Coast of California, the city population was 10,757 as of the 2020 census, up from 10,234 at the 2010 census. The town ...
. After crossing some rugged coastal hills, the line enters the Diablo Canyon Power Plant substation. Due to the massive amount of power generated by the plant, a second 500 kV line was built alongside the first, as the parallel lines head east to form another 500 kV loop. These parallel lines cross Highway 101 north of
Pismo Beach Pismo Beach (Chumash: ''Pismuʔ'') is a city in the southern portion of San Luis Obispo County, in the Central Coast area of California, United States. The estimated population was 8,072 at the 2020 census, up from 7,655 in the 2010 census. It ...
and traverse over some southern coastal mountains. After reaching a height of over 1,200 m or 3,937 feet, the two parallel lines head down the arid foothills of the southern San Joaquin Valley and split up. The two lines rejoin just before entering the Midway Substation () near
Buttonwillow Buttonwillow is an unincorporated community and census-designated place in the San Joaquin Valley, in Kern County, California. Buttonwillow is west of Bakersfield, at an elevation of ). The population was 1,508 at the 2010 census, up from 1,266 ...
. The other two eastern lines also head into the same substation from the north.
Southern California Edison Southern California Edison (or SCE Corp), the largest subsidiary of Edison International, is the primary electricity supply company for much of Southern California. It provides 15 million people with electricity across a service territory of ap ...
's (SCE) two Path 26 lines connect to PG&E's grid at the Midway Substation. A PG&E line heading southeast from Midway substation is the third line of Path 26, not Path 15. Eventually, this line is replaced with SCE towers.


Substations

From north to south:


Connecting power lines

*Round Mountain *Table Mountain *Vaca-Dixon *Tesla *Metcalf *Moss Landing *Diablo Canyon


Path 15

*Los Banos, the substation is approximately west of Los Banos *Gates, located about east of
Coalinga Coalinga ( or ) is a city in Fresno County and the western San Joaquin Valley, in central California about 80 miles (128 km) southeast of Salinas. It was formerly known as ''Coaling Station A'', ''Coalingo'', and ''Coalinga Station''. Th ...
*Midway, one mile (1.6 km) east of
Buttonwillow Buttonwillow is an unincorporated community and census-designated place in the San Joaquin Valley, in Kern County, California. Buttonwillow is west of Bakersfield, at an elevation of ). The population was 1,508 at the 2010 census, up from 1,266 ...


Western Area Power Administration's third line north of Tracy

WAPA's 500 kV line starts at the Captain Jack substation () well to the northeast of Round Mountain. This is the Western Area Power Administration's (WAPA) Path 66 transmission line. It also heads southwest across the Modoc Plateau and crosses
Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...
near Cottonwood (north of
Red Bluff Red Bluff(s) may refer to several places in North America: Places Canada *Red Bluff, British Columbia, a community near Quesnel, British Columbia, Canada ** Red Bluff First Nation, a First Nations band government headquartered near Quesnel, ...
). West of Cottonwood the line turns south and enters an
electrical substation A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and ...
near Olinda. At Olinda, lines carrying power from
Shasta Dam Shasta Dam (called Kennett Dam before its construction) is a concrete arch-gravity dam across the Sacramento River in Northern California in the United States. At high, it is the eighth-tallest dam in the United States. Located at the north ...
and other nearby
United States Bureau of Reclamation The Bureau of Reclamation, and formerly the United States Reclamation Service, is a federal agency under the U.S. Department of the Interior, which oversees water resource management, specifically as it applies to the oversight and opera ...
facilities connect with the line. This is the end of Path 66, but WAPA's 500 kV line continues from Olinda Substation along the western edge of the Sacramento Valley. Near Antioch the line runs parallel with the two PG&E lines. All three lines cross both the Sacramento and San Joaquin Rivers on very large
pylons Pylon may refer to: Structures and boundaries * Pylon (architecture), the gateway to the inner part of an Ancient Egyptian temple or Christian cathedral * Pylon, a support tower structure for suspension bridges or highways * Pylon, an orange mar ...
. The WAPA line turns away from the PG&E lines and heads for another large substation near Tracy. South of Tracy Substation (), it continues as a large, dual-circuit 500 kV line that connects with the PG&E lines as they leave Tesla Substation.


Issues

;Other power lines that follow Path 15 From Tesla substation to Midway substation, a set of 230 kV lines follows the main 500 kV lines. The dual-circuit 230 kV power lines run to the east of the 500 kV lines. Most of these lines were built by PG&E. ;Power transmission capacity Path 15 can transmit 2,000-3,265 MW of
electrical power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billion ...
from north to south. The capacity for south to north power transmission is 4,800-5,400 MW. ;Parallelism of Interstate 5 (south of Tesla substation) In the section south of Tracy, the eastern two lines form an infrastructure corridor along with an aqueduct and
Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...
and provide some artificial scenery to look at, especially when they do not run in the hills west of Interstate 5. The eastern parallel PG&E lines cross Interstate 5 twice. ;Environmental impacts The northern part of this electrical transmission corridor (including Path 66) is visible from space and
Google Earth Google Earth is a computer program that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satellite images, aerial photography, and geog ...
as lines of bare, treeless ground. This is because the power lines here run through
forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
s of
conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ext ...
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s which appear dark-green from space. The utility companies here have logged and sometimes
clear-cut Clearcutting, clearfelling or clearcut logging is a forestry/ logging practice in which most or all trees in an area are uniformly cut down. Along with shelterwood and seed tree harvests, it is used by foresters to create certain types of fo ...
the land to create a
right-of-way Right of way is the legal right, established by grant from a landowner or long usage (i.e. by prescription), to pass along a specific route through property belonging to another. A similar ''right of access'' also exists on land held by a gov ...
for the power lines due to the fact that a
wildfire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identi ...
could start when an
electrical arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma; the plasma may produce visible light. A ...
occurs between the lines and a tree if they come close enough to each other.


Differences in tower design

Like Western Area Power Administration's 500 kV line, the tower design for the entire transmission system is not the same, although the difference is not as dramatic as on the WAPA line. For the PG&E line, the differences are subtle and from a casual, far away view, it looks like the towers are all the same for the entire power line. It seems to be south of the Table Mountain substation, the tower legs spread apart from the tower bridge (upper section of tower) down to the tower base and there are four
guy line A guy-wire, guy-line, guy-rope, or stay, also called simply a guy, is a tensioned cable designed to add stability to a free-standing structure. They are used commonly for ship masts, radio masts, wind turbines, utility poles, and tents. A th ...
s for tower stability. In contrast, the towers to the north of Table Mountain have thinner legs and look like thin sticks from far away. The weaker tower legs have two additional guy lines for stability. As for the tower bridge, the towers south of Table Mountain have five X's in between the tower legs. The towers north of Table Mountain have only four X's. In addition, the tower arms on either side of the towers have smaller steel bars inside for added strength. In the northern towers, they are positioned like
equilateral In geometry, an equilateral triangle is a triangle in which all three sides have the same length. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each oth ...
triangle A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, any three points, when non- colline ...
s, but south of Table Mountain, they are shaped like
right triangle A right triangle (American English) or right-angled triangle ( British), or more formally an orthogonal triangle, formerly called a rectangled triangle ( grc, ὀρθόσγωνία, lit=upright angle), is a triangle in which one angle is a right a ...
s. See below for a visual comparison. ;Visual reference Image:Pacific Gas and Electric 500 kV power lines.JPG, PG&E lines near the I-580 /
I-205 Interstate 205 may refer to either of two unconnected Interstate Highways in the United States, both of which are related to Interstate 5 * Interstate 205 (California), a connector in the San Francisco Bay Area * Interstate 205 (Oregon–Washin ...
interchange; anothe
view
Image:PG&E wires crossing highway 36.JPG, Thinner towers north of Table Mountain crossing SR 36, cutting through the woodlands of the Sierra foothills. They resemble the southern towers to the left, but look closely to see the differences.


History

This entire project was built in the 1970s and 1980s in order to provide California and the
Southwest The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...
with excess hydropower from the
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Thou ...
without actually having to construct any new power plants. During the cold Pacific Northwest winters, power is sent north due to heater use. This transfer reverses in the hot, dry summers, when many people in the South run air conditioners. In order to do this the maximum south-to-north transmission capacity is 5,400 MW for most parts, but between Los Banos substation and Gates substation, there were only two 500 kV lines. The capacity at this electricity bottleneck was only 3,900 MW, and this was identified in the 1990s as a trouble spot, but no one acted upon it. This bottleneck was one of the leading causes of the
California electricity crisis California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
in 2000–2001. To remedy this problem, WAPA along with several utilities built a third 500 kV line between these two substations to eliminate this transmission constraint and raise the maximum south-to-north transmission capacity to 5,400 MW. The project was completed under budget and on time on December 21, 2004. California's
governor A governor is an administrative leader and head of a polity or political region, ranking under the head of state and in some cases, such as governors-general, as the head of state's official representative. Depending on the type of political ...
,
Arnold Schwarzenegger Arnold Alois Schwarzenegger (born July 30, 1947) is an Austrian and American actor, film producer, businessman, retired professional bodybuilder and politician who served as the 38th governor of California between 2003 and 2011. ''Time'' ...
attended the commissioning ceremony at California-ISO's control center in
Folsom Folsom may refer to: People * Folsom (surname) Places in the United States * Folsom, Perry County, Alabama * Folsom, Randolph County, Alabama * Folsom, California * Folsom, Georgia * Folsom, Louisiana * Folsom, Missouri * Folsom, New Jerse ...
.


References


External links


Interstate 5 Pictures of Path 15
* More pictures of Path 15 from West Coast Road
here
an

{{Power Transmission Corridors of the Western United States Western Interconnection Energy infrastructure in California