Riparian habitat threatened by proposed project, San Pedro River advocates say

The San Pedro River basin has been called a biological treasure in the desert. It's a riparian refuge for more than 60 species of mammals, 14 species of fish and 41 species of reptiles and amphibians, and the millions of birds that use the river as a migratory flyway.

But critics of a proposal to build a utility corridor along the west side of the river say it could threaten the health of the habitat and the survival of the wildlife.

Conservation groups and residents along the river are opposing the 45-mile stretch of utility corridors, which would be carved out on public lands to accommodate a more than decade-old power transmission project that would cut through the San Pedro River Valley.

An April 2022 draft environmental impact statement prepared by the Bureau of Land Management concluded that the SunZia Southwest Transmission Project would likely accelerate habitat loss, alter conditions for migratory bird species and remove riparian vegetation that provides habitat and a source of food for wildlife. The loss of riparian vegetation would also result in erosion and sediment buildup, the agency found, which could affect river flow and health, hinder fish species’ ability to find food, and impair their health and ability to reproduce.

Conservation groups are calling on the Arizona Corporation Commission to withdraw the certificate of environmental compatibility for the project, citing recent changes in ownership, among other issues.

“This is our last remaining wild area, this was an area that was labeled by the Nature Conservancy as one of the world’s last greatest places and this is extremely important,” said Peter Else, who has lived along the San Pedro since 2005.

“It’s hemispherically important for the migration of avian species, it’s very very important for connecting the Sky Islands region of southern Arizona to each other and if we go and mess that up like we did with every other river valley in the developed areas of Arizona, we are going to lose that and we are going to lose that permanently.”

The proposed 550-mile-high voltage transmission line is intended to bring renewable energy from the proposed SunZia Wind Farm in New Mexico to its western terminus in Pinal County. The more than $8 billion project has been in the planning and approval stages for nearly 15 years.

Else has opposed the proposed path since the route through the San Pedro River Valley was first introduced in 2015. He said he is not opposed to expanding renewable energy projects in the state but thinks the construction along the proposed route would harm the land and the wildlife that lives there.

For the past nine years, he has led the Lower San Pedro Watershed Alliance, an all-volunteer conservation group of about 100 landowners and an additional 100 supporting members.

In January, Else recruited two attorneys to file a complaint in Arizona Superior Court, calling on the corporation commission to withdraw the project's certificate of environmental compatibility. The complaint outlines the recent acquisition of the line from a California-based power company. Transmission lines and power plants must be approved by the commission and acquire a certificate of environmental compatibility from the line siting committee.

On the San Pedro: A conservationist's dream of restoring habitat has dimmed

About 45 miles of the project would run along the San Pedro River on land overseen by the Bureau of Land Management. It would include the construction of towers, lines, footings, access roads and other infrastructure.

The proposed route would enter the state in Graham County, near its southern border with Cochise County, cross the river just north of Benson, and continue north along the west side of the river valley. It would follow the path of the river north through Pima and Pinal counties, nearing the boundaries of Saguaro National Park East and Coronado National Forest and finally leave the river valley about 45 miles north, near Oracle.

The route would be roughly 25 miles north of the San Pedro Riparian Conservation Area, an Ecologically Rich Area that was established by the BLM in 1998 to protect critical habitat for wildlife, vegetation and water flow.

“This is not a typical NIMBY situation, not in my backyard,” Else said. “This is a regional land use and planning issue. We're talking about 33 miles, that's a substantial portion, of the 199 miles that pass through Arizona’s most remote and ecologically sensitive landscape of the San Pedro River.”

Near Benson, stretches of the San Pedro River sit dry except when rainfall brings runoff.
Near Benson, stretches of the San Pedro River sit dry except when rainfall brings runoff.

Project could further imperil 'important bird area'

The entire San Pedro River is considered an important corridor for birds and other wildlife species. Over 300 bird species have been recorded there, including migrant and permanent breeding species. Conservation groups oppose the proposed transmission route because they believe it would be catastrophic for the thousands of bird species that converge there annually.

In 2020, the BLM adjusted the project's route in an area of New Mexico after consulting with the U.S. Department of Defense and White Sands Missile Range. Southwestern Power Group, which at the time owned the rights to develop the line, asked the BLM to amend the project's right-of-way that allowed builders to cut through the missile range.

At the time the company argued that adjusting the route could help win support from the Defense Department and reduce opposition from New Mexico conservation groups, who feared the line would irreparably harm flocks of migrating birds and other wildlife and damage the area’s pristine landscapes.

Peter Else walks next to a gate post that was buried by over 3 feet of clay sediment in 2017 flooding on his property by the San Pedro River north of Mammoth, Arizona.
Peter Else walks next to a gate post that was buried by over 3 feet of clay sediment in 2017 flooding on his property by the San Pedro River north of Mammoth, Arizona.

Else and other conservationists would like a similar amendment along the San Pedro River.

“Why couldn’t we have that here?” said Sandy Bahr, director of the Sierra Club’s Grand Canyon Chapter. “Why couldn’t we say, 'okay, site it along I-10 and underground it, so you aren’t affecting people in those communities,' and then you're siting it along a major transportation corridor and you’re not impacting one of our state's most important rivers?”

The Lower San Pedro River was designated an "Important Bird Area" by the Audubon Society and consists of 6,938 acres of riparian habitat along nearly 59 miles of the river from the “narrows” north of Cascabel, to the confluence with the Gila River at Hayden. The region supports the largest breeding population of gray hawks in the U.S., about 40% of the species' population, as well as the largest population in the U.S. for the threatened yellow-billed cuckoo.

The riparian areas have already been threatened in recent decades by groundwater pumping, improper livestock grazing, fire, development and drought. A transmission line would likely further threaten the area and the migratory birds that use it, conservationists say, contributing to habitat fragmentation and degradation, especially for the cuckoo.

The assessment acknowledges that construction of the project is expected to cause behavioral changes for the yellow-billed cuckoo, due to a short-term increase in noise and vibration caused by construction equipment, traffic and blasting. This would likely disturb nesting of other wintering birds that converge on the San Pedro and could potentially damage suitable habitat and deter birds from using the nearby area.

The yellow-billed cuckoo was listed as threatened by the Arizona Game and Fish Department in the 1980s. The bird’s population fell from 850 pairs in 1979 to fewer than 170 pairs by the new millennium, which led to its listing in 2014 as threatened under the Endangered Species Act.

“The yellow-billed cuckoo is an imperiled species, it is listed under the federal Endangered Species Act and that means it’s in trouble, like species don’t get listed unless they are in trouble,” Bahr said. “A major factor for species being imperiled is loss of habitat, and now we are going to take out additional habitat for a bird that is struggling for survival.”

Construction and transmission-related infrastructure, along with vegetation removal and other disturbances, would adversely affect riparian areas suitable for foraging, stopover and breeding activities, the BLM found.

“During construction, the project would disturb land and remove vegetation associated with the permanent structures, ancillary facilities, access roads, and footings as well as temporary use areas,” according to the BLM assessment.

The disturbance would likely remove suitable nesting and foraging habitat for bird species that use the area and could result in a direct take of bird nests if done during the nesting season. For species like the yellow-billed cuckoo, nesting has been essential to rebuilding a healthier population. The loss of a nest or nesting areas would likely hinder reproduction rates for the cuckoo and other rare and threatened species, according to experts.

The project would also require overland travel along the project right-of-way, along the access roads and in work areas. That could affect ground-nesting and roosting birds and contribute to vegetation loss in riparian areas.

“When you put in transmission lines, you’re effectively creating roads," Bahr said. "When you do that, that causes habitat fragmentation and is an invitation for additional damage from off-road vehicles.”

Riparian losses: On the San Pedro River, water use is drying up stretches of a biodiverse 'ribbon of green'

Loss of vegetation could increase erosion

The BLM says it anticipates construction to occur in the months outside of nesting season to minimize the short-term effects. Birds typically nest from March through the beginning of August, which would leave roughly six months to complete construction of more than 40 miles of utility corridors.

And the expected disturbances to habitat would likely continue well past the construction phase, as the project would permanently alter the landscape along the river. Only 12 miles of the proposed route currently has utility infrastructure in place, mostly in the form of underground gas lines. SunZia Transmission would require the construction of at least 33 miles of new permanent structures, including towers, lines, ancillary facilities, access roads, substations and footings.

Transmission lines have long been linked to significant bird mortality, according to the National Wildlife Federation, which says as many as 11.6 million birds are killed by electrocution from such lines annually. This could be extremely troubling along key stretches of the river, where bird densities during migration can reach 75 to 100 birds per hectare.

“This is a failure, in my mind both at the federal level and at the state level to find the least impactful route to transport this wind primarily to California,” Else said. “So, I’m going to follow it for as long as I can and so that my conscience will be clear that I did everything possible to keep this travesty from happening.”

The BLM’s assessment says maintenance activities that would occur past construction would also affect species behavior and degrade habitat. Maintenance for the infrastructure would include trimming trees and woody vegetation within the transmission line wire zone in riparian and woodland areas, directly affecting nesting and roosting birds.

Trimming trees would also open the canopy and allow for invasive species, such as salt cedar, to establish in waterways, according to the BLM.

The San Pedro River flows beside reeds in June 2021.
The San Pedro River flows beside reeds in June 2021.

Salt cedar, or tamarisk, grows rapidly from seedlings and is difficult to eradicate. It has been considered un-killable in many areas because of its extensive and deep root system. Research shows that salt cedar can reduce river flow by trapping and stabilizing sediment, increasing over-bank flooding and creating permanent sandbars. Salt cedar can be even more dangerous in the arid Southwest, because the plant uses large amounts of water, which affects aquatic organisms such as frogs, fish, salamanders and other species that rely on the river for water supply.

The BLM assessment also addressed the proposed project's potential for long-term impacts to riparian vegetation and habitat. The vegetation is critical in supporting diverse wildlife habitat, reducing erosion and sedimentation of water ways. In the western United States, riparian areas account for less than 1% of the land area, but are among the most productive and valuable natural resources.

“We’ve lost so much riparian habitat in our state and some of the places we still have it is along the San Pedro,” Bahr said, “This line could have been located away from the river, and to put it there and lose even more of this essential habitat is irresponsible.”

A reduction of habitat means a significant loss of shelter and food supply for the hundreds of species that call the basin home.

“A lot of common and uncommon species rely on riparian habitat,” Bahr said. “It’s important in a lot of different ways.”

With less stream bank vegetation, soil is exposed to runoff and subsequent erosion. The excessive sediment load not only pollutes water but fills stream pools and covers rocky stream bottoms where fish typically feed. Sediment in stream beds disrupts the natural food chain by destroying habitat where the smallest stream organisms live and can cause massive declines in fish populations.

According to the EPA, sediment pollution is the most common pollutant in rivers in the U.S. While natural erosion produces nearly 30% of the total sediment in the United States, accelerated erosion from human use of land accounts for the remaining 70%. The most concentrated sediment releases come from construction activities.

The erosion brings a slew of issues, as sediment deposits can alter the flow of water and reduce water depth. Nutrients transported by sediment have also been linked to activation of blue-green algae that release toxins that can cause illness in both humans and animals. It is more deadly for animals, and if ingested by wildlife, livestock, or pets, can lead to death.

Less stream bank vegetation will also cause water to warm faster as it is exposed to more direct sunlight. This was a contributing factor to the near extinction of the Apache Trout on the western edge of the state. Sediment also can potentially clog fish gills, reducing resistance to disease, lowering growth rates and affecting fish egg and larvae development.

Cottonwood trees are reflected in the San Pedro River in June 2021.
Cottonwood trees are reflected in the San Pedro River in June 2021.

Changes to project plan are significant

Phoenix-based Southwestern Power Group has been working since 2008 to develop SunZia Southwest Transmission Project, which would require the construction of two transmission lines. Last year, the rights to build one of the transmission lines was sold to Pattern Energy, who also owns the rights to develop the wind farm in New Mexico.

In 2015, during the federal permitting process, Southwestern Power Group outlined a series of proposed lines. One of the alternate routes would have cut through metropolitan Tucson but was scrapped over concerns of environmental justice because the proposed line would have required the demolition of low-income homes in the city.

Another route through the Sulphur Springs Valley was rejected after a SunZia witness explained that the “route was primarily problematic to the Arizona Game and Fish Department because it conflicted with their grassland restoration in the area.”

The BLM then settled on the proposed route through the San Pedro River Valley. All routes presented to the BLM intersected with the proposed Willow Substation in Graham County. When Southwestern Power Group applied for the permits, the company owned the rights to build a gas-powered plant and planned to hook up the plant to the SunZia Line. But officials say the projects are not related.

SunZia developers originally opposed the route through the San Pedro River valley because it was “a unique watershed and riparian environment” where damage from the project “will be very difficult to mitigate.”

Peter Else walks through invasive tamarisks, which have flourished on his property by the San Pedro River.
Peter Else walks through invasive tamarisks, which have flourished on his property by the San Pedro River.

But the new developer of one of the transmission lines says it supports the current proposed route and has worked with federal agencies to ensure minimal impacts to the San Pedro.

“After thorough analysis, the BLM selected the current route, which was also reviewed and approved by the Arizona Corporation Commission. Given the extensive environmental review, Pattern supports this final chosen route,” said Adam Cernea Clark, senior environmental and natural resources manager at Pattern Energy. “Pattern will continue to work actively with state and federal natural resource specialists as well as members of the conservation community as the project moves forward.

Representing Else in court is Ilan Wurman, a professor of law at the Sandra Day O'Connor College of Law at Arizona State University. Wurman believes the green light for this proposed route on federal land was, in part, likely a product of a 2011 Obama-era policy that promoted the construction of renewable energy.

The administration’s Rapid Response Team for Transmission, focused on building infrastructure that would support clean energy. The team's initial focus was to expedite the permitting process for seven major transmission lines across the country. One of those lines was SunZia. Construction is slated to begin later this year.

The siting committee is required to give special consideration to the protection of areas that are unique because of biological wealth or because they are habitats for rare and endangered species. Else believes the Arizona Corporation Commission failed to properly assess these risks for this project.

The corporation commission's department of communications did not respond to a request for comment from The Arizona Republic.

Reservoir proposed near Apache Lake: SRP wouldn't use it to boost Arizona's water supply

“From our perspective we don’t think a certificate of environmental compatibility should have been granted in the first place,” said Bahr. “For whatever reason the commission process didn’t seem to understand the value of the San Pedro.”

Else and Wurman say the nature of the project has changed significantly since it was approved in 2015, which is why they believe its certificate should be vacated. The original plan called for the construction of two transmission lines, one alternating current and one direct current. The AC line was marketed as a way for other renewable projects to hook up to the line once developed. A DC line cannot be connected to other projects.

Last year, SunZia filed an amendment request to the commission to split the two lines into separate ownership. The amendment sought to authorize the use of updated structure design changes and additional structure types associated with the direct current line and to divide the original certificate into two, which would allow the projects to be financed separately.

“If they are separately financed, it’s entirely possible that second line may never be built and that’s the whole bait and switch,” Wurman said. “You promised at least one AC line for all these benefits, a reliability loop in Tucson, developing solar power in southeastern Arizona, now there may only be a direct current line.”

Because Pattern Energy only owns the rights to develop the DC line, the future of a separately funded AC line is left in limbo, according to Wurman. And because the DC line cannot facilitate hookups, Wurman argues that the project may never bring renewable energy to Arizona, but state land would be used to get energy from the wind farm in New Mexico to private owners in California, where Pattern Energy is based. He says this is grounds for the certificate to be vacated, as the project would not only harm the ecology of the San Pedro, but a need cannot be identified.

“Their statutory mandate involves bringing delivering economical electricity to Arizona and balancing that need for Arizona with impacts to the environment,” said Else. “If the purpose and need of the project has changed significantly since 2016 and the Arizona Corporation Commission is not recognizing that significant change, you can’t even assess whether the need is going to be met.”

But Cernea Clark disputes the claims that the project would not bring renewable energy to the state.

“Arizona’s electricity demand is growing quickly, and access to diversified high production energy resources is key to ensuring ongoing system reliability," he said. “The SunZia Transmission line connects the high production wind resource in central New Mexico to the Arizona market and broader western markets.”

Wurman believes that renewable energy is important for Arizona, but believes the certificate and proposed route should be reworked in order to protect state lands.

“Once you build these things in the San Pedro River Valley that’s forever, and the damage is done,” Wurman said. “I’ll take a few extra years of them having to permit versus a hundred years of damage to the San Pedro River Valley.”

Else’s passion for the river and the wildlife that relies on it will likely continue to fuel his fight against the project’s proposed route.

“Desert rivers are a very rare thing and when you have one that is still natural and intact you do everything you can to help preserve it,” he said. “And so I’ll do whatever I can to keep this travesty from unfolding.”

Spring came early. Why that's bad for Arizona's water supply

Jake Frederico covers environment issues for The Arizona Republic and azcentral. Send tips or questions to

Environmental coverage on and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at and @azcenvironment on FacebookTwitter and Instagram.

You can support environmental journalism in Arizona by subscribing to azcentral today

This article originally appeared on Arizona Republic: San Pedro River utility corridor project would threaten area, some say