With the help of Laughlin-Thyssen, the Mission Reach portion of the San Antonio River Improvements project is expected to provide stable, maintainable flood control while increasing recreational and economic development opportunities for the community.

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The San Antonio River has played a central role in the urban fabric of the city of San Antonio, but the river’s full potential as an economic incubator and environmental symbol has yet to be realized. A multi-year transformation project is expected to change all of that by providing stable, maintainable flood control while increasing recreational and economic development opportunities for the community.

The San Antonio River Improvements Project is a $216.6 million ongoing investment by the city of San Antonio, Bexar County, the U.S. Army Corps of Engineers (USACE) and the San Antonio River Foundation to bring flood control, amenities, ecosystem restoration and recreational improvements along 13 miles of the San Antonio River.

The transformation project is divided into three “reaches” – the Museum, Downtown and Mission Reach.

A concerted community effort to revitalize the river began in 1998 when Bexar County, the city of San Antonio and the San Antonio River Authority created the San Antonio River Oversight Committee. The 22 civic and neighborhood leaders appointed to the committee were given the responsibility of overseeing the planning, design, project management, construction and funding necessary to complete the project.

In May, the U.S. Army Corps of Engineers Fort Worth District awarded Houston, Texas-based Laughlin-Thyssen (L-T) the contract for phase one of the Mission Reach portion of the project.

Mission Reach is an eight-mile-long stretch divided into four segments for construction, including from Lone Star Boulevard to Mission Road, Mission Road to SE Military Drive, SE Military Drive to I-410 and I-10 to Mission Espada.

“From a local sponsor’s perspective, we were concerned about getting as much possible competition involved in the process as possible,” San Antonio River Authority General Manager Suzanne Scott recalls.

The River Authority will provide project and technical management, as well as overall project coordination between the project partners. “There is lots of activity in Texas and lots of other projects that the Corps is not even involved in, so we worked with the Corps to get the word out about the project and make sure that local contractors knew about it.”

According to USACE Project Manager Charissa Kelly, Laughlin-Thyssen was awarded the contract based on a best-value process in which several factors were taken into consideration. These included past construction and specialized construction experience, effective management techniques, construction duration and the utilization of small, disadvantaged businesses. Phase one of the four-phase project to restore Mission Reach will focus on river improvements.  

Laughlin-Thyssen Vice President of Construction Ron Grier says as of early August, L-T was performing early site excavation on a mile-and-one-quarter of the river. Grier says roughly 350,000 yards of excavated soil will be hauled off site, and 30 yards of embankment with 10 weir structures will be installed to control the flow rate of the river.

“There is a lot of dirt moving – some 350,000 cubic yards of dirt on this phase alone,” explains Chip Worley, an engineer with the USACE. “There are about 20 to 25 trucks being loaded on a daily basis.”

Advanced Design
Careful consideration and detail were put into the design and construction of the Mission Reach. Several specialists served as consultants to the project, including landscape architects, hydrologists, civil engineers, structural engineers, biologists and cost management professionals.

During the design process, the multidisciplined team, led by architecture firm Carter Burgess, worked in a workshop environment. The team discussed the process and plans in length, and created a concept that was not only unique, but also transparent to the owners, says Jacque Thomas, project manager with Carter Burgess.

The design had to account for the establishment of the vegetation, sub-surface and surface soil preparation, seed handling, seeding operations and controlling the spread of any non-native plants. The overall task project stakeholders were charged with was how to achieve flood control that is sensitive to the environment while putting vegetative features back into the river system. “We started by looking at using fluvial geomorphology technique,” explains Kelly. “We used that to look at how the river could mimic the flow and function of a standard river.”

Fluvial geomorphology is based on the natural river-forming process and therefore can reduce erosion, balance sedimentation and restore the environment to a more natural environment. The technique will help designers re-create the contoured path of the river where possible, restore the gradually de­scending slopes of the riverbanks and re­move the concrete rubble lining the river channel. At several intervals along the Mission Reach, stacked pieces of limestone will be used to create small dams, or weirs, to prevent erosion of the river bottom.

Restoring the Landscape
The landscape of the San Antonio River has provided geological and climatic features that have produced a wide variety of habitats and eco-regions. Yet, over the years, little has been done to improve the aesthetic appeal and further diversify the natural habitat. In total, the project will introduce 24,000 native trees, 56 acres of native grasses, 113 acres of aquatic habitat, 320 acres of riparian habitat, as well as eight miles of bike-and-hike trails along the river.

The master plan identifies more than 100 projects, including footbridges, overlooks, pocket parks, public art, amphitheaters, outdoor classrooms, walking and biking trails, restored wetlands and marshes and other features.

Native trees, grasses and plant life will be introduced along the river’s edge in­cluding pecan, redbud and wild olive trees, buttonbush shrubs, Texas bluebonnets and scarlet sage among others. Seed- and fruit-producing species will also be introduced, and the planting of native understory species will also provide stratification along the river.

Causing a Diversion
Because of the complexity of the project, L-T prefers to self-perform a large portion of the work, Grier says.

“Sequencing is crucial when we are diverting the river,” he explains. “Some of the things that we will subcontract will be items like driving sheet piling and the installation of concrete work for the weirs.”

L-T will handle the excavation, backfill work, toe protection, the gabions and riprap. All scheduling is managed using Primavera Systems, and the schedule is monitored daily. L-T currently staffs the project with about 10 people, but will peak at 50 as work progresses, Grier notes.  He estimates by spring 2009, L-T’s portion of the project will reach the halfway point.

The biggest challenge L-T faces on the project is diverting the river. “There are a variety of channel protection features such as erosion control and slope protection, but in order to do that work, we have to divert the river, which is a major part of our work,” Grier notes.

The risk, he says, is keeping the river flowing without endangering employees or equipment, especially in the event that the area gets hit with heavy rains, causing the river to overflow. “That’s part of the risk of the job, and we anticipate that there will be flood events,” he says.

To divert the river, the company is digging a diversion channel to move the river while the restoration work is being completed on the river bottom. “During the project, we clear only the areas that we are working on at the time,”?Grier says. “We don’t want to have the entire river section opened up, so we will divert the river only around the specific sections that we are working on.”

To reduce risk onsite, the company operates a safety program, which is managed by a full-time safety officer.

If the project progresses as expected, phase one is expected to be completed in November 2009, and the total Mission Reach project is expected to wrap up in 2012.