Tackling Nevada's tough soil on a tight timeline

Racking company TerraSmart provided a quick solution for securing racking legs in Nevada's tough caliche soil on a 250-MW solar power project that was on a tight timeline.

By Tony Kryzanowski

Native-owned lands comprise roughly 70,000 acres in Clark County, Nevada, an arid area that includes the city of Las Vegas. The county—in the prime Sunbelt of the American Southwest—has great potential for solar power, but the caliche soil in the area has presented a significant financial and technical hurdle to solar development—until now.

Caliche is described as a layer of soil 12" to 24" deep in which the particles have been cemented together by lime, topped by 8" to 12" of light sand. The challenge is to penetrate the cemented layer and provide stability for the racking legs.

A company called TerraSmart has developed a cost-effective, quick, and nearly simultaneous survey, drilling, and ground screw installation system for the posts or legs that anchor the solar panel racking system in this soil type. TerraSmart says that deploying its technology will have a "transformative" impact on planning and developing future solar power projects in this prime area, estimating that its system provides cost savings of between 50 and 100 percent over the expensive and time-consuming alternative of using concrete to support the legs.

A successful trial of TerraSmart's system was conducted on the recently completed 250-MW Moapa Southern Paiute solar power project located on 2000 acres of the Moapa River Indian Reservation in Nevada.

Ryan Reid, TerraSmart's CEO, says finding a cost-effective and quick method of anchoring a solar installation in this soil type certainly was having an impact on the development of planned solar projects in places like Clark County. Now that a method has been discovered and successfully demonstrated, other solar developers working in the area have taken notice.

"We're already working with several other companies that do work on very similar soils across the desert terrain in the western part of the country because of the exposure that we received on this particular project," says Reid. "It has really opened up the doors to a lot of other companies that have encountered the same issues on sites very similar to this. We're definitely going to see a big surge of business in that market moving into next year. There's nobody else who does this."

The Moapa Southern Paiute Solar project is owned by a subsidiary of First Solar Electric LLC with the subsidiary having the same name as the project. Located 35 miles northeast of Las Vegas, the project is a fixed-tilt solar farm that features more than 3.2 million First Solar advanced photovoltaic thin film solar modules.

First Solar acquired the project, which was in an advanced stage of development with a power purchase agreement (PPA) in place, from K Road Power Holdings LLC in 2013. It then launched project construction. One of the project's greatest challenges was finding a cost-effective solution to anchor the racking system into the caliche soil that could be done quickly.

Reid says that First Solar considered as many as five different solutions to overcome the caliche soil issue, ultimately choosing the TerraSmart option to provide a turnkey system for the project. It was important to find a cost-effective technical solution that could also be installed within First Solar's aggressive timeline.

Not only does the Moapa Southern Paiute Solar project demonstrate an effective technical solution to anchoring legs in the caliche soil, it is also a major milestone for solar power development on American native-owned land as it is the first utility-scale solar project on U.S. tribal lands.

Power produced from the installation will be sold to the Los Angeles Department of Water and Power (LADWP) through a 25-year PPA when it becomes fully operational at the end of this year. LADWP has a goal of achieving 33 percent renewable power generation by 2020, and the Moapa Southern Paiute Solar project will be helping the move toward that goal. The power utility is mandated by California State law to stop all coal-power use by 2020.

"The Moapa Southern Paiute Solar Project is a significant step toward the LADWP's effort to achieve a major transformation of the city's power supply—one that has greater reliance on renewable energy resources and zero coal power," said Marcie Edwards, general manager at LADWP at the time of project launch.

A new on-site substation was built for the project as well as a 5.5 mile, 500 kV transmission line, connecting to the existing Crystal Substation, serving California. The power generated by this project will provide electricity to about 93,000 Los Angeles homes.

The project will do more than provide an opportunity to generate millions of dollars in income for the Moapa Band of Paiutes for lease payments, consulting fees, the purchase of goods and services, and construction and operations jobs, as the tribe pursues its goal of developing 1.5 gigawatts (GWs) of renewable energy. It will also address an ongoing health concern on the Moapa River Indian Reservation. Power utility NV Energy intends to shut down its four coal-fired power generating units at the 50-year-old Reid Gardner Generating Station by 2017. The station is located immediately adjacent to the reservation.

Some of that lost power generation potential at the Reid Gardner Generating Station is being replaced with solar power, as First Solar is also currently working with the Moapa Band of Paiutes on the 100-MW Aiya Solar Project, approximately 40 miles north of Las Vegas. Power generated from this project will connect to the grid at the Reid Gardner Generating Station.

First Solar has yet another solar project in development on native-owned land, working with the LasVegas Paiute Tribe to develop the 100-MW Snow Mountain solar power plant on the Snow Mountain Reservation in the northwestern part of the Las Vegas Valley. As with the Aiya solar power project, this project will also be connected to the NV Power grid.

The Moapa Southern Paiute Solar project will displace 178,000 metric tons of carbon dioxide annually, or the equivalent of taking 34,000 cars off the road. In addition to the 93,000 homes this project will energize, the two additional First Solar projects on native land will provide power for another 50,000 homes.

TerraSmart's scope of construction on the Southern Paiute project began in July 2015. It included implementing its proprietary survey, drilling, and ground screw installation technology. The company completed its work about a year later.

While providing First Solar and the tribe with a workable racking solution, TerraSmart was also under considerable time pressure. Reid says that during the project's first phase, they were required to install between 1250 and 1500 ground screws per day. They were able to accomplish this task using a proprietary GPS software solution developed over six months in partnership with a positioning solutions provider called Trimble. This allowed their custom designed Atlas Copco rock drill and ground screw installation machines to survey locations with a high degree of accuracy then drill the holes for the ground screws, with installation a day later. The ability to perform these functions one after the other accelerated installation of the posts for the racking system and helped make up time on the project's construction schedule.

During the project's first phase, TerraSmart installed between 1250 and 1500 ground screws per day. They were able to accomplish this task using a proprietary GPS software solution, which allowed their custom designed Atlas Copco rock drill and ground screw installation machines to survey locations with a high degree of accuracy, then drill the holes for the ground screws.

The geographical location of this solar project presented a number of other challenges. The temperature on the busy worksite could at times reach 115 to 120 degrees, thus requiring specific protocols for mandatory breaks for workers so that it was a safe working environment. The site was also busy 24 hours a day, with anywhere from 1,000 to 1,500 workers on-site at any given time.

Tribe leaders at the Moapa River Indian Reservation had some specific demands regarding opportunities for construction jobs and also respect for the land. First Solar says that it provided about 400 construction jobs to tribe members on average, in addition to seven ongoing operations and maintenance positions. Furthermore, under the Environmental Impact Statement and Biological Opinion provided in connection with the United States Fish & Wildlife Service, First Solar provided the tribe, together with the U.S. Bureau of Land Management, with more than $1.6 million in mitigation fees for desert tortoise protection.

"First Solar is committed to being a good neighbor through our community involvement and through the environmentally sensitive design of our solar projects," the company says. "We will continue to engage the tribe, as well as neighbors, community groups, environmental groups, and business organizations to ensure that the Moapa Southern Paiute Solar Project remains a valued and respected business in Clark County."

Reid says TerraSmart was held to the same high standard by First Solar and the tribe, enduring close scrutiny and demonstration of its survey, drilling, and ground screw anchoring method to prove that it would work and perform over the long haul, while respecting the impact of their equipment and workers on the landscape. The drill holes are about four-and-a-half-feet deep. Reid adds that TerraSmart's method is a much cleaner solution with a lot less land disturbance compared to the concrete anchor alternative.

"Stewardship of our lands is paramount, and carefully utilizing this precious resource to spur economic development is an ideal solution," says Robert Tom, chairman, Moapa Band of Paiutes. "TerraSmart showed incredible respect for our land and our combined approach of minimizing impact while maximizing resources."