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Title: Final Interim Feasibility Report and Integrated Environmental Assessment : Pecan Bayou Watershed, Brownwood, Texas
Authors: United States. Army. Corps of Engineers. Fort Worth District
Keywords: Brownwood (Tex.)
Environmental management
Environmental protection
Flood control
Publisher: United States. Army. Corps of Engineers. Fort Worth District.
Abstract: This document presents the results of the plan formulation process leading to the identification of a recommended plan for local flood damage reduction in Brownwood, Texas. The investigation into water resource problems and opportunities within the Pecan Bayou watershed, including the city of Brownwood, began with the Pecan Bayou Lake, Colorado River Basin, Texas, Reconnaissance Report, completed in March 1994. The report concluded that Pecan Bayou Lake, an authorized Federal project, was no longer economically feasibility, but there was a Federal interest in conducting additional detailed studies for flood damage reduction along Pecan Bayou and Willis Creek in Brownwood. With the support of the city, a cost-shared feasibility study was initiated in January 1995. Various alternatives, both structural and non-structural, were investigated to reduce flood damages along Pecan Bayou and Willis Creek. The initial conclusion of these investigations indicated that channel improvements provided the most cost-effective means for reducing flood damages. Nonstructural alternatives were investigated but have offered a minimal positive benefit-to-cost ratio (BCR) and/or had extremely minimal net benefits to economically justify through the 1 percent (100-year) flood event. Therefore, non-structural alternatives were eliminated from further study. The analysis of a grass lined channel and swale configurations on Pecan Bayou with 10-, 50-, and 100-foot bottom widths all revealed negative net benefits and benefit-to-cost ratios of 0.36, 0.24, and 0.19 respectively. Therefore, an economically feasible alternative could not be identified along Pecan Bayou and no further detailed investigations were conducted. Channel modification investigations on Willis Creek with 10-, 25-, 45-, and 60-foot bottom widths, however, offered significantly higher net benefit results and positive benefit-to-cost ratios with the 45-foot bottom width being the optimum channel modification alternative. Further refinement of this alternative, to include a diversion channel, optimized the 45-foot bottom width with a diversion channel as the Recommended Plan, as well as the National Economic Development (NED) Plan, with expected net benefits of $313,600 with a positive BCR of 1.55 to 1.0. The National Economic Development (NED) Plan identified in this investigation would consist of 15,680 feet of channelization of Willis Creek within the city of Brownwood. The improvement would consist of modifying the existing channel into a grass-lined trapezoidal channel with side slopes of 1 vertical to 3.5 horizontal with a bottom width of 40 feet with pilot channel. The channel depth would vary between 4 and 11 feet deep with the top varying between 40 to 135 feet wide. A diversion channel will be constructed approximately 1200 feet downstream of 14th Street Bridge to the 4th Street Bridge. The improvement would also require box culvert modifications to the 14th Street Bridge and 4th Street Bridge, side slope modifications at Austin Avenue Bridge, and some storm drain and utility relocations. Riprap will be placed at the bridge approaches for erosion protection. Environmental mitigation measures in the form of avoidance would consist of bypassing several oxbows and allowing them to continue to serve as wildlife habitat and wetlands. Additionally, approximately 102.1 acres of reforestation would be undertaken to replace the habitat removed by the channel excavation. The overall flood damage reduction plan would have estimated first costs of $8,270,190 and annual project costs of $574,000. The resultant BCR is 1.55 to 1.0 with net benefits estimated at $313,600. This plan would reduce expected annual damages by 92 percent; eliminate all damages caused by the 10 percent ACE event and would reduce nearly 90 percent of the damages caused by the 1-percent event. The final array of alternatives formulated by the Fort Worth District has been evaluated in accordance with required Federal evaluation procedures. These include procedures from the "Principles and Guidelines", the National Environmental Policy Act (NEPA), and other Federal environmental review and consultation requirements. Consideration has been given to all significant aspects in the overall public interest including engineering feasibility and economics, social, and environmental effects to provide the best solution for meeting the objectives of the Pecan Bayou watershed area and supported by the city of Brownwood.
Description: Interim Feasibility Report and Integrated Environmental Assessment
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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