Project Summary

Summary

The report will be a combined feasibility report and environmental impact statement complying with requirements of the U.S. Army Corps of Engineers and the Council of Environmental Quality, and is intended to reduce duplication and paperwork. The integrated report will be prepared to:

  1. summarize the findings, results, and data collected for historic and existing conditions in the study area, and to forecast the most likely future without-project conditions, pertaining to physical and biological resources, cultural resources, socioeconomics, and recreation
  2. identify problems, opportunities, objectives, and constraints for the study area
  3. and formulate preliminary alternative plans

Without-Project Conditions The lower portions of San Juan, Oso and Trabuco Creeks are currently adversely impacted from a variety of water resource and related land resource problems. Most of the issues stem from widespread changes in the watershed, from the initial conversion of natural habitat for agriculture, followed by urbanization. The results can be seen in the changed hydrologic regime, channel instability, habitat loss, ecosystem degradation, and decline in water quality. Development in the watershed has replaced natural habitat with structures, roads, and other infrastructure; natural channels have been replaced by drains, culverts, and engineered channels; paved surfaces allow less infiltration and create greater runoff within remaining natural channels; Large rainfall events produce larger runoff volumes, delivered with higher velocities, resulting in higher rates of erosion and increased channel instability. These changes have produced widespread negative trends in the immediate area of San Juan, Oso, and Trabuco Creek channels. The trends include channel degradation (incision of the invert or channel bed); decline in floodplain moisture (lowering of the water table) resulting to loss of riparian habitat and associated wildlife; expansion of the extent of invasive species; and damage to nearby infrastructure (utilities, roads, trails). Lower San Juan and Trabuco Creeks contain the most unstable reaches in the watershed drainage system.

Preliminary Measures and Alternatives The integrated report will present preliminary alternative measures that address the problems and opportunities identified through the planning process. Measures will be organized by broad categories such as: flood risk management, channel stabilization, habitat improvement/preservation, and water quality improvement. Measures carried forward will be combined, in various configurations, to form a preliminary set of alternative plans. These preliminary plans will be developed to encompass the broadest range of potential alternatives and will be subjected to a more rigorous evaluation. Preliminary plans include flood risk management features to protect adjacent infrastructure and property; stabilization and protection of existing channel and floodplain; and reconnection of upstream with downstream aquatic habitat. A No Action plan was also assessed.

Feasibility Study Documentation Process Future documents that will be released during the course of the feasibility study will include:

  1. a report summarizing alternatives formulation, evaluation, and identification of a tentatively recommended plan
  2. draft feasibility report for public review
  3. pre-final feasibility report
  4. final feasibility report. Environmental compliance documentation will be integrated into the general investigation feasibility study