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Trinity River COMMON VISION Program

Introduction

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Regional Environmental Impact Statement

This cooperative effort began in the early 1980's with the preparation by the Corps of a Regional Environmental Impact Statement to address the cumulative impacts of its individual permitting decisions. A working group of staff professionals from the affected local governments and NCTCOG provided input. The Draft Regional EIS first compared the cumulative impacts of two opposite philosophical approaches for utilizing the 100-mile river corridor -- maximum environmental quality vs. maximum development -- and found that maximum development would result in flood flows that would overtop existing levees in Dallas and Irving. Given the seriousness of these preliminary findings, a special Strategy Committee of elected officials was formed and each local participant provided funding support on a pro-rata basis to NCTCOG as convenor and facilitator.

As expected, local involvement in the Corps' preparation of the Final Regional EIS was much more intense, with many meetings and several new development scenarios crafted between the two extremes. The Final Regional EIS found that these more moderate development scenarios would not only result in the Dallas Floodway levees still being overtopped with catastrophic results, but that properties in upstream cities would also sustain considerable flood damages. Thus no city could assure adequate flood protection for itself by itself -- only a common approach could be successful.

Mother Nature Makes Her Point

Although no proof was required, Mother Nature stepped in anyway. Major floods occurred in May/June 1989, April/May 1990 and December/January 1992 in the upper Trinity River. Over a dozen lives were lost during the 1989 flood events within the Metroplex, and hundreds of millions of dollars of damages were sustained.

During the 1980's, the Trinity River also experienced several major fish kills associated with depressions in dissolved oxygen during rise events. Extensive followup studies by the state determined that ambient dissolved oxygen concentrations in the river have improved and rise-associated dissolved oxygen effects have waned. Reduced effluent ammonia levels have resulted from implementation of in-plant nitrification requirements. Thus, toxicity became the main factor impacting the system by the late 1980's.

Trinity River Corridor

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