In 2000 the Corps of Engineers received approval from Congress for the Tres Rios Ecosystem Restoration and Flood Control Project. This project will improve and enhance a 7-mile long, 1500 acre section of the Salt and Gila Rivers in southwestern Phoenix. The project consists of a flood protection levee, effluent pump station, emergent wetlands, and riparian corridors and open water marsh areas to replace existing non-native salt cedar in the river. Construction of the levees and emergent wetlands has been completed, with construction of the pump station and riparian and river areas currently underway. The Tres Rios Full Scale Project is being 65% funded by the Corps, with 35% coming from the local sponsor, SROG. Technical and financial assistance has also been provided by the Flood Control District of Maricopa County. View the construction schedule for more information.
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The water source for the Tres Rios Full Scale Project is highly treated effluent from the 91st Avenue WWTP. This Project has many goals. The primary goals are flood protection for the local residents and habitat restoration for the native animals. However, there are also very important water quality, recreation, and education components of the Project. Project completion is highly dependent on yearly funding from Congress, making public support a vital part of this process.
Flood Control Levee
This 4 ¼ mile long structure was built to protect homeowners and businesses on the north bank of the rivers from the Salt and Gila River flood events from approximately 105th Avenue to the confluence of the Gila and Agua Fria Rivers. The levee is being designed to protect the community from river flows up to the 100-year flood (this is a flood that is expected to occur approximately once every 100 years, or in other words, every year has a 1 in 100 chance of seeing this type of a flood). The Salt River Project manages the dams upstream along the Salt and Verde Rivers, where most flood water releases originate. For more information, Visit the SRP website.
The full scale Tres Rios project consists of the construction of approximately 480 acres of emergent wetlands. These wetlands will help further clean the highly-treated effluent from the 91st Avenue Wastewater Treatment Plant, provide wildlife habitat, and create a public amenity unique to this area which will include multi-use trails, picnic areas, and an environmental education center for visitors to experience the spirit of the historic river. The emergent wetlands phase was completed in May 2010.
The full scale wetlands was built on the bank of the river, protecting it from river flows.
Effluent Pump Station
Creating wetlands in the desert is a challenge mainly because of one thing - water. This vital resource is in high demand to promote growth, sustain industry, and provide life to our yards, parks, and agricultural areas. Tres Rios is taking advantage of an underutilized source of high quality water - treated wastewater. Reusing this water to sustain the environment is a smart thing to do for our community. In order to get this water to the wetlands, a 300 million gallon per day pump station will be constructed within the 91st Avenue Wastewater Treatment Plant. Along with providing water to sustain the wetlands, the pump station will also ensure the Treatment Plant can operate when water is flowing in the river.
Riparian and Open Water features in the river
Most of the rivers in the Southwestern United States have become choked with a non-native plant, the Salt Cedar, or tamarisk. This plant was originally brought into this country in the 1800's as an ornamental, and for stream bank stabilization. However, in the 20th century we started to realize the danger of importing foreign plants into our fragile desert environment. Sonoran desert wildlife has lived with the native plants for millions of years. The plant and animal communities have evolved together, with the animals using the plants for shelter and food, and the plants using the animals for seed dispersal. Native plants are perfectly suited to sustain native animal populations. Now, the salt cedar has displaced many of our native plants. The salt cedar invasions have thrown off the natural balance between plants and animals, making survival much more difficult for our native wildlife.
To reverse this process, Tres Rios will be removing large tracts of salt cedar and replanting native cottonwood/willow riparian corridors. In some areas, where the salt cedar is very thick and will be impossible to replace, the river sediment will be dug down and filled with water. This will prevent regrowth of the salt cedar, provide habitat for waterfowl, and offer a cleared channel for flood flows to utilize.