Dallas Floodway Extension
The Dallas Floodway Extension (DFE) is one of five local projects authorized by Congress in 1965 as part of a basin-wide plan for the Trinity River. The original plan, which included channels and levees along the river and some tributaries, was never built for lack of funding and local support. As a result of flooding in 1989 and 1990, the City of Dallas asked the U. S. Army Corps of Engineers to re-evaluate the recommendations of the plan and to assess structural as well as non-structural alternatives.
The locally preferred plan for the DFE Project, developed jointly by the City and the Corps of Engineers, includes a linear length of 270-acres of swales and wetlands, known as the Chain of Wetlands". Located along the west side of the Trinity River, the Chain of Wetlands will extend from Cedar Creek to Loop 12, which represents a distance of approximately four miles. These wetlands will include water management capabilities to provide additional environmental benefits.
About 3 miles of protective levee will be located along the Union Pacific Railroad that is parallel to Lamar Street. This Lamar Levee will provide the Lamar area with 800-year flood protection, while extending the Dallas Floodway East Levee from the DART Bridge to the Rochester Park Levee. The Cadillac Heights Levee will be about 2.5 miles long and will provide the Cadillac Heights vicinity with 800-year flood protection. The Cadillac Heights Levee is actually a ring levee that starts at high ground (near the junction of 11th Street and J Street) just downstream of Cedar Creek and will extend to the Central Wastewater Treatment Plant, before wrapping back to the west to Kiest Blvd to high ground.
These improvements will lower flood elevations and thereby increase the level of flood protection for the downtown Dallas vicinity, Oak Cliff, and West Dallas from the 300-year event to the 500-year event, which represents a little less than 800-year flood protection that is known as Standard Project Flood (SPF) level. The DFE project will establish SPF protection for downstream areas such as Rochester Park, the Lamar area and Cadillac Heights. The project reduces recurrent flooding for approximately 12,500 structures, and increases flood protection for the Central Wastewater Treatment Plant from 140-year flood levels to 500-year flood levels.
The DFE project will also realign the Trinity channel at Interstate 45 to protect the bridge structure, which is a designated National Defense Highway component. In addition, recreation facilities (trails, access areas, etc) will provide linkages between the Great Trinity Forest, neighborhoods and high employment areas. The environmental mitigation plan will consist of the purchase of about 1,179 acres of land for forest preservation and restoration, which will augment the establishment of the Great Trinity Forest. The DFE project requires an additional 1,200 acres of real estate to facilitate the Chain of Wetlands, levees, and flood conveyance. Of this 1,200 acres, about 800 acres will directly contribute to the establishment of the Great Trinity Forest as well.
On August 28,1996, the Dallas City Council approved the "Chain of Wetlands" concept for the DFE Project. On March 26, 1997, protective levees for the Lamar and Cadillac Heights neighborhoods were approved by the City Council. The voters of Dallas authorized the issuance of General Obligation Bonds on May 2, 1998 for the City's share of the $140 million project, estimated to be about $24.7 million.
The Corps of Engineers produced the General Re-evaluation Report and Integrated Environmental Impact Statement (EIS) in February 1999, which was (Record of Decision) finalized on December 1, 1999.
City and Corps officials signed a Project Cooperation Agreement in December 2001 that outlines the fiscal and project responsibilities for project construction.
In April 2002, the Corps of Engineers was directed by the Federal District Court in Fort Worth to hold on construction until the Corps had augmented its 1999 EIS to include the additive effects of other studies/projects in combination with the DFE Project. The Corps submitted this information (Supplement to the EIS) to the Court in November 2003. Subsequently, the Court lifted its injunction against DFE Project on May 5, 2004, which enabled the Corps to restart project construction.
The Corps completed removal of the Sleepy Hollow Golf Course (at Loop 12 along the west bank of the Trinity) clubhouse and maintenance shed, in addition to, structures on the Cody property (at the south end of Lamar Street) by separate contracts in Summer 2004.
Cell D project construction was awarded in July 2004 for $2.5 million and completed in October 2005. The Corps completed a partial wetland planting test area in October that represents about 4 percent of the total wetland area of the cell that is to be ultimately populated by plants. 15 different species of wetland plants from the Lewisville Aquatic Ecosystem Research Facility (LAERF) at Lewisville Lake was transplanted to Cell D. Depending on how the different plant species survive, the Corps will then fully plant the wetland cell during 2006. Cell D will also represent an ongoing research project with respect to wetland plants. The Corps will seasonally operate Cell D for about two years to see how all the wetland plants respond and how wildlife responds to the wetland cell. Lessons learned with respect to protective cages, which plant species do best, and what optimum approach to adjusting the water elevation in the wetland cell will be applied to the remaining Chain of Wetlands as they are constructed in the future.
In August 2005, the Corps awarded a $26 million construction contract to T.J. Lambrecht for wetland cells E, F, and G, that will extend from SH-310 to Loop-12. The construction contract for these 107 acres of wetlands will also include a river realignment at IH-45 in an effort to address hydraulic problems with the IH-45 bridge. The construction contract is expected to be completed by summer 2007.
Other aspects of the Dallas Floodway Extension Project are under design that includes about 60 acres of additional Chain of Wetlands and about five miles of levees that will be located upstream of IH-45. The recreation facilities and environmental mitigation component will soon be under design as well. The entire project should be completed in 2012, if all goes well with Federal funding.
As the Corps of Engineers continues detailed design for the DFE Project, the City continues property acquisitions to facilitate the footprint for the project. Detailed information on the DFE Project can be found at the Corps' Web site. The City's fact sheet also provides additional detailed information.
