In what will be the official unveiling of the first two completed miles of the San Antonio River restoration and recreation project Saturday, the public will be able to witness how closely engineers can mimic nature.

Though much of the two miles, from Lone Star Boulevard to Mission Road, opened in December, Saturday will be the first time joggers, walkers and cyclists can navigate trails from San Pedro Creek to Mission Road.

Knee-high and sometimes towering native grasses and flowers dominate the first mile. By the second mile, grass is sparse but growing out of the brown dirt.

The restoration of the river's ecosystem, which encompasses a total of eight miles, remains a work in progress. Mark Sorenson, the project's manager, said he expects the final six miles, Phase 3, will open by August 2013, and that dirt excavation on that section is ahead of schedule by several months.

The full restoration, however, won't be finished until several years later, by late 2014 or 2015, when about 17,000 trees and shrubs of 40 varieties are planted along the last six miles. By November, 3,000 trees will be planted along the project's first mile, with 3,000 more planted along the second mile later, said Steven Schauer a spokesman for the San Antonio River Authority.

Saturday also will include the opening of the Mission Concepción portal, a stone masoned archway and trail, the first of four that will link the river to missions Concepción, San José, San Juan Capistrano and Espada. The portals will be opened one by one as Phase 3 progresses.

Unlike the project's first two miles, the remaining six will be much wider and more rural. Both sides of the river bank will resemble parkland and the city's urban influences will have less effect on the river, said Irby Hightower, a co-chair on the River Oversight Committee.

Plans are in the works to reopen channelized and submerged portions of the river near Padre Drive and Acequia Park as well as Loop 410 and Brown Park. This will make the river flow where it used to centuries ago.

There also are plans to build arching pedestrian bridges that eventually will be covered by tree canopies. Within the next 50 years, the planted grasses and trees and revived ecosystem will reach maturity.

Sixty years ago, the river was modified and straightened, becoming a glorified drainage ditch. Now it's beginning to look more like a typical South Texas river, but everything about it is engineered — down to the placement of the 23,000 trees and shrubs and the addition of riffle structures and embayments in the river, Schauer said.

More Information Saturday's events Pre-ceremony: Mariachis will perform on Theo Avenue bridge, 10-10:30 a.m. Opening ceremony: Interior Secretary Ken Salazar will speak, along with County Judge Nelson Wolff and other dignitaries, 10:45-11:45 a.m. Post ceremony: Musical performances along the trail and in Roosevelt Park, 11 a.m.-2 p.m. A guide to events, parking and shuttles is online at sanantonioriver.org Source: San Antonio River Authority Statistics Earth moved: 3.5 million cubic yards Number of plants: 23,000 trees and shrubs Plant diversity: 40 native tree/shrub species, 60 native grasses and flowers Size: 334 acres, more than 15 miles of trails Budget: $245.7 million Start/finish date: June 2008/Aug. 31, 2013 Source: San Antonio River Authority See More Collapse

All of the trees will be planted according to GPS coordinates because the southern portion of the river still needs to help evacuate floodwater from the city. The trees have to be placed far enough away from each other to survive, but not so close to the banks as to be washed away.

But the river will never be a self-sustaining ecosystem and will require regular touchups, said Lee Marlowe, natural resource management specialist with the San Antonio River Authority, which is managing the bulk of the project.

Following Wednesday's rain, litter made its way into the river and crews were needed to clean it.

“There are a lot of ways to do a restoration project, but you are always at the mercy of Mother Nature,” Marlowe said.

The project was severely delayed when native grasses failed to grow in low-nutrient soils. The river's banks were infested with invasive, non-native plants and weeds that had to be removed.

“If you had to call this project anything, you'd call it an excavation project,” Sorenson said.

Grasses along the second mile are starting to grow in much of the original soil without problem, Marlowe said.

The hope is that this project will help revitalize a part of the river that was degraded in the 1950s, when, in an effort to mitigate flooding, the U.S. Army Corps of Engineers channelized the river.

For those who live near the river, or were born and raised in the area, like Bexar County Judge Nelson Wolff, who played an instrumental role in the county's decision to fund most of the Mission Reach, the project is a long time coming and reflects shifts in the city's development and growth.

For much of the later half of the 20th century, the North Side became the focus of a development boom that left southern neighborhoods in the shadows. But that started changing 10 years ago with the establishment of Texas A&M University's San Antonio campus, and later the Toyota truck plant on the South Side, Schauer said.

“Every time we talked about the river, things went north,” Wolff recalls. “It was one of those things where the South Side was going to get screwed again.”

Hightower said a subcommittee is starting to assess the economic impact the project will have on surrounding neighborhoods.

He said he doesn't expect there to be a land grab along the river, but a more grass-roots redevelopment. Within the next 10 years, he foresees the industrial properties that line the banks will be redeveloped for medium-sized residential and mixed-use projects.

“It allows people to slowly change their neighborhoods. That's the type of long-term change in opinion you want to generate,” Hightower said.

Cindy Taylor, president of the South San Antonio Chamber of Commerce, said the project has had an almost immediate effect on area residents, stopping short of calling it a renaissance.

She said residents are starting to repaint their homes and revive their neighborhoods.

“There is so much pride in ownership,” Taylor said. “It's incredible to see it come back to life. We are experiencing what the missionaries and priests were experiencing when they built the missions.”