Our reputation is based on the extensive knowledge of our staff of environmental planning professionals.

What Can We Provide?

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Denise Duffy & Associates, Inc. provides environmental sciences, planning, and biological consulting services throughout Central and Northern California. Since 1984, we’ve been providing high-level professional services to public and private sector clients.

DD&A is passionate about making a difference – by helping our clients, using sound science and finding creative solutions – we continue to grow in the quality of environmental consulting services provided and in our passion for the environment.


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As a planning and environmental consulting firm with a full range of biological and ecosystem services, DD&A provides

  • Environmental impact assessments
  • Natural resources analysis
  • Resource agency permitting assistance
  • Contract planning
  • Biological assessments in support of CEQA and NEPA documents
  • Natural environment studies
  • Wetland delineations
  • Restoration plans
  • Special-status species surveys and management.
  • County entitlements
  • Expert review of project development
  • Detailed evaluation of environmental resources
  • Identification of innovative solutions for avoiding impacts

DD&A is supported by technical capabilities for graphic materials (GIS, Adobe, and a variety of publishing software), California Natural Diversity Database subscription, and all necessary field and office equipment for the completion of natural resource and environmental evaluations.


DD&A has a well-respected reputation in the preparation of environmental documentation in compliance with the National Environmental Policy Act (NEPA) and the California Environmental Quality Act (CEQA). From focused environmental assessments on smaller projects, to inter-jurisdictional reports on large-scale planning efforts, DD&A has a proven track record for meeting client needs and successfully completing the requirements for state and federal environmental review.

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DD&A is certified by the State of California as a Small Business (#0020855) and a Woman-Owned Business (#13824). DD&A is also certified by the Supplier Clearinghouse for the Utility Supplier Diversity Program of the California Public Utilities Commission as Diversified Supplier #1007A045.