Weed-Free Aggregate Resources

Gravel pile with invasive plants
Using gravel infested with invasive plant material can spread invasive plants, like this Dyer’s Woad.

Quarries and gravel pits are perennially disturbed areas which make them high quality habitat for many invasive plants. Within quarries, invasive plant seeds land on and contaminate recently mined sand and gravel, collectively known as aggregate. When the contaminated aggregate is transferred to a project site, these seeds are distributed and can easily establish.

Working with quarry operators to treat quarries contaminated with invasive plants is the most cost-effective method to preventing weeds from establishing along roadsides and disturbed areas where aggregate will be used. The documents on this page can help land managers and quarry managers set-up programs to prevent the spread of invasive plants.


Weed Free Aggregate Program for Land Managers


This manual, Weed Free Aggregates for Land Managers, will help land managers to start up their own regional weed-free aggregate program. It contains:

  • Where to look for invasive plants in a quarry
  • Contract language
  • Case studies
  • Frequently asked questions
  • Glossary


Weed Free Aggregate Program for Quarries Managers


This manual, Weed Free Aggregates for Quarry Managers, will help quarry managers prepare for weed-free aggregate certification. It contains:

  • An overview of the weed-free aggregate program
  • How invasive plants spread in a quarry
  • Where to look for invasive plants in a quarry
  • Best management practices
  • Case studies
  • Frequently asked questions


Regional Programs for Weed-Free Aggregate:


These documents will help land managers set-up weed-free aggregate programs. Regional program documents differ only by the weed list and resource lists. Regions were defined by the Geographic Subdivisions of California, as listed in The Jepson Manual, Second Edition.

Each regional document contains: Program overview, weed management plan for quarries, inspection protocols, invasive plant list by region, weed control resources, certificate of inspection, quarry information and site history, and definitions.

For more information, contact Cal-IPC.