7.11.4 Environmental Mitigation Plans

Mitigation for impacts due to highway improvements must be defined in project environmental documents, permit conditions, or agreements with regulatory or resource agencies. Mitigation measures are typically defined, without much detail, during preliminary engineering. Mitigation details to be implemented during construction must be delineated in plans and specifications.
Mitigation of environmental impacts due to the presence of hazardous materials may also be necessary. Mitigation measures typically include soil liners to contain hazardous materials, groundwater removal and treatment, and soil removal and disposal. Often, design modifications can be made to eliminate migration of underground contaminants and thereby eliminate the need for mitigation.
Mitigation details may include design drawing details showing special features such as protection of historic properties or mitigation of environmental concerns. Obtain design input from a landscape architect and biologist with knowledge of biologic processes and skills to meet the mitigation commitment.
Offsite mitigation may justify separate construction contracts and schedules for this work. Developing regional mitigation alternatives may be desirable for TxDOT and regulatory agencies. The TxDOT PM should consult with the Director of Transportation Planning and Development and ENV at the start of detailed design.
Considerations concerning mitigation plans include:
  • Coordinate with District environmental staff, landscape architect and drainage design staff to determine the most cost-effective, sustainable solution to meet the environmental commitment;
  • Mitigation may need to be completed before construction, and if mitigation requires the acquisition of property, acquisition of these parcels must be prioritized;
  • For mitigation requiring post-construction monitoring, have the technical expert develop a reporting process for monitoring. Monitoring may likely be long term, and a defined reporting process will ensure uniformity during this time; and
  • Timing of the completion of mitigation plans is project-specific and must be driven by the terms of agreement and permit requirements with resource agencies.