California Department of Resources Recycling and Recovery (CalRecycle) 

Diversion Study Guide


Note: This page contains historical information from CalRecycle's statewide goal measurement prior to 2007 that estimated a diversion percentage. For 2007 and subsequent years, CalRecycle compares reported disposal tons to population to calculate per capita disposal expressed in pounds/person/day. This new goal measurement system is described in CalRecycle's Goal Measurement: 2007 and Later web page. Since the annual per capita disposal rate is based on disposal tons, any biomass will not be reported as disposal. In other words, there is no cap on the amount of material a jurisdiction can send to biomass. Therefore, sending material to biomass will help to reduce disposal. A Biomass Facility Diversion Claim Sheet is no longer required for submittal with the jurisdictional Annual Report.

The California Integrated Waste Management Act of 1989 (Act, AB 939) required local governments to prepare planning documents for achieving the 25 percent diversion goal for 1995 and the 50 percent diversion goal for 2000. These plans included a solid waste generation study that quantified the amounts and identified the types of solid waste disposed and diverted from each jurisdiction in its base year. Based upon the solid waste generation study results, jurisdictions identified and selected appropriate programs to address the targeted waste stream that would help achieve the diversion mandate.

Originally, the Act required jurisdictions to measure the amount of waste generated (i.e., disposal plus diversion) in 1995 and 2000 to demonstrate compliance. In order for jurisdictions to establish their base-year generation amounts, it was necessary to quantify a base-year diversion amount. For the purpose of the State’s AB 939 diversion calculations, the definition and method for data measurement can be found in Public Resources Code section 41781(a)(2) and related regulations. In 1992, legislation amended the Act, eliminating the need for future generation measurements by establishing a standard methodology for a disposal reduction measurement system.

This guide has been developed to provide jurisdictions with information and tools to help you calculate a new base year in a cost-effective manner. 

Calculating a new base year is necessary if the 1990 base-year diversion tonnage estimates are found to be inadequate. In 1990, when all jurisdictions in the state were required to establish their base-year solid waste generation amounts, jurisdictions had to rely on the best available data at that time, which in many jurisdictions has since been found to be incomplete or erroneous. For example, many jurisdictions have found errors in their original diversion estimates, including misallocation of regional data to the jurisdiction, flawed volume-to-weight conversions, and missing or underestimated tonnage. These errors and omissions in the base-year generation data make it difficult to accurately measure progress toward achieving the diversion requirements.

Many jurisdictions feel that establishing a new base year, as opposed to correcting the flaws in the original base year, is the preferred solution to resolving data problems in terms of accuracy and long-term cost. In addition, at its January 25–26, 2000 meeting, CalRecycle set limitations on base year corrections. It will not accept corrections to any CalRecycle-approved base-year disposal or diversion tonnage amount that is more than three calendar years old.

This guide provides information on how to perform a diversion study to establish a new base year. Topics covered include:

  • Benefits of conducting a diversion study.
  • Determining if a base-year problem exists.
  • Designing a diversion study.
  • Conducting a diversion study.
  • Addressing restricted wastes.
  • Analyzing data and calculating diversion.
  • Submitting a new base year to the California Department of Resources Recycling and Recovery (CalRecycle).

This diversion guide is also a tool to help properly identify changes in the waste stream since 1989 and also to allow jurisdictions to make changes in the implementation of new or expanded programs based on this information.

Results from a diversion study must be properly documented and will require supporting documentation regarding existing programs that substantiate the proposed new base-year diversion rate.

New base-year diversion rates must also be representative of a jurisdiction’s diversion activities. While some activities are easier to quantify, e.g., tonnage records, other activities may require estimation. Thus, these activities will require a higher degree of substantiation and a higher level of scrutiny by CalRecycle.

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Last updated: March 19, 2000
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