DRAINAGE, EROSION AND OTHER ENVIRONMENTAL IMPACTS OF ELEVATED, DEPRESSED AND AT-GRADE LEVEL FREEWAYS IN TEXAS

To answer questions being raised by abutting residents and businesses about proposed elevated and/or depressed freeway improvements in the urban and suburban areas of Texas, a four-year study has been conducted to estimate the social, economic and environmental effects of such freeway designs. Eight existing, two under construction and one approved for construction freeway sections have been studied on a before-, during-, and after-construction basis. The sections selected for study range from being in predominately residential suburban areas to predominantly commercial-industrial downtown areas. The specific effects of the three types estimated for each study section are as follows: (1) social impacts: population changes, neighborhood accessibility, neighborhood cohesion and community services; (2) economic impacts: relocation and mitigation costs, business sales, property uses and values, tax revenues, employment and income and user costs; and (3) environmental impacts: aesthetics, drainage and erosion, noise and air pollution, vibration and hazardous spills. The literature review and a survey of highway agencies in other states were used to determine the appropriate procedures or models and mitigation measures to implement in estimating the social, economic and environmental impacts of elevated and depressed freeways. The results of the study, presented in six separate reports according to types of effect, can be used by highway planning and designing engineers to prepare environmental statements and documents of the expected social, economic and environmental impacts of proposed elevated and depressed freeway projects. Also, the results can be disseminated at the public hearings for a proposed project. This report presents the findings of the drainage, erosion, hazardous spill, vibration and aesthetic effects of elevated, depressed and at-grade level freeways. The findings indicate that the grade level differences are significant for almost all of the factors studied. Therefore, the maintenance costs varied accordingly. The specific grade level designs of each freeway study section also affected maintenance costs.