Site Investigation Process (SIP)


LEA Advisory No. 3 provided useful guidance to LEAs on the investigation of closed, illegal, and abandoned (CIA) sites in California. The Site Investigation Process (SIP) presented on these web pages is designed to replace the previous guidance provided in LEA Advisory No. 3, which is now rescinded.

This guidance still provides LEAs with documentation tools (site identification form and site assessment form) and procedures for ranking the CIA sites for field investigation, enforcement, and remediation prioritization, as well as for inspection frequency reduction and archiving. Enhancements to office investigation procedures and new Web-based information links have been added to make the SIP guidance a more powerful investigation tool.

CalRecycles Permitting and LEA Division hopes that LEAs find the following web pages useful for administering their responsibilities at CIA sites.


Local enforcement agencies (LEAs) are required to investigate and inspect closed, illegal, and abandoned disposal sites (CIA sites) pursuant to Title 14, California Code of Regulations (14 CCR) sections 18083 and 18303Public Resources Code (PRC) section 45013 requires that CalRecycle, upon request by the LEA, provide assistance in the inspection and investigation of CIA sites.

On February 25, 1993, CalRecycle approved a staff-developed procedure—termed the Site Investigation Process (SIP)—for investigating and evaluating such CIA sites. In addition, CalRecycle Remediation, Closure, and Technical Services Branch has developed a website to provide Web-based technical assistance for investigation, enforcement, and remedial scoping of CIA sites.

If you have questions regarding the SIP, please contact your CalRecycle Closure and Remediation Branch staff liaison.

Site Description

There are approximately 2500 closed, illegal, and abandoned (CIA) disposal sites in California. Of these, 2122 CIA sites are pre-regulation (or legacy) municipal solid waste disposal sites. These sites were privately owned or leased and serviced local communities, townships, cities, and counties. About 506 of these 2122 sites are burn sites. Of the total 2500 sites, 206 are landfills closed with a permit, and 73 sites are illegal disposal sites. The Board maintains a list of priority CIA sites being worked on by LEA and CIWMB staff.

Closed, Illegal and Abandoned Disposal Sites: A pie chart illustrating the distribution of these sites by type.


The following definitions relevant to CIA sites are contained in Title 27, California Code of Regulations.

Closed Site—A disposal site that has ceased accepting waste and was closed in accordance with applicable statutes, regulations, and local ordinances in effect at the time.

Clean Closed Site—A disposal site that has been closed in accordance with applicable statutes, regulations, and local ordinances in effect at the time, with complete removal of its wastes with their transferal to another approved, operating disposal site for final disposal.

Abandoned Site—A disposal site where there is no responsible party.

Illegal site—A disposal site that is not permitted and not exempt from obtaining a permit and is not closed or excluded from the requirement to obtain a solid waste facilities permit. (Active unpermitted sites which an LEA intends to permit are not considered CIA sites.)

Problems and Hazards

CIA sites can present a variety of potential hazards to the health and safety of the public as well as adverse impacts to the environment.  Some specific effects of CIA sites are described below.

Vector and pest breeding

Newer illegal sites may provide attractants, such as food wastes, for pest vectors; breeding areas, such as old tires and other open containers, that can attract mosquito breeding; or shelter for rodents and other pests.

Physical hazard and injury to public and wildlife

Exposed and/or inadequately covered wastes can pose a potential hazard to human health and safety as well as a danger to wildlife or domestic animals. Human visitors to a disposal site may injure themselves by sharp objects in the refuse (for example, fencing, rebar, broken glass). Containers of hazardous materials may be present on-site. Wildlife attempting to graze, forage, scavenge, or browse can injure themselves or ingest potentially hazardous materials or be fouled or entangled in certain waste materials such as wire, cording, or mesh.

Potential hazardous materials

Unregulated sites can serve as attractant sites for illegal disposal of hazardous materials, both contained or non-contained. These can become a danger to future visitors to a site, as well as be damaging to the environment.

  • Lead exposure—Exposed burn ash can contain statistically significant levels of lead which exceed California definitions for hazardous waste (for example, exceed the total threshold limit concentration (TTLC) of 1000 milligrams/kilogram for lead).
  • Dioxins and furans—Exposed burn ash can contain combustion byproducts containing dioxins and furans, which are known carcinogens.
  • Radiological hazards—Disposal sites operating in the 1920s–1940s may contain low-level radiological waste from medical equipment and other equipment using radioactive sources (instrument dials).
  • Military waste—Disposal sites at former Department of Defense installations may contain hazardous wastes, ordnance, and other wastes from military equipment maintenance and operations.

Adverse impacts to the environment

Nonaqueous liquid or water-soluble solid substances may permeate the underlying soil and invade underlying aquifers, or drain into adjacent watersheds and cause surface water, groundwater, and/or soil contamination. Possible airborne impacts include volatilization to the atmosphere and inhalation (fugitive dust and waste particulates). Liquid or soluble materials can be assimilated through vegetation and migrate into the food chain from herbivores to predators or possibly to humans. Landfill gas can adversely impact plant development.

Adverse impact of interference with future land uses (economic feasibility)

As local development continues in more rural locations, some activities may eventually encroach upon existing illegal sites. Cleanup, or its potential costs, may reduce the prospect of considering a CIA site for development. Furthermore, migration of landfill gas can limit potential uses.

Landfill gas. Landfill decomposition gas contains methane, which is explosive in concentrations of 5–15 percent by volume in air, as well as carbon dioxide and trace gases. Due to land-use development encroaching on older disposal sites, residential, commercial, and industrial structures and infrastructure (for example, utility corridors) could create conditions under which migrating landfill gas could pose potential explosion hazards and oxygen-deficient environments.

(Select each image to see a larger version. Use your “back” button to return.)

Drawing of typical landfill gas migration routes


Typical gas migration routes

Photo of settlement of old landfill in parking lot


Impact of differential settlement and gas migration on building structures

Attractants for future illegal disposal activities

When a CIA site is continually used for illegal disposal activities, it attracts future parties and repeat users to continue illegally dumping their waste.

Photo of illegal dump site


Illegal Dump Sites are an “attractive nuisance”

Loss of usable or recyclable materials

Disposal of larger materials or white goods and other recyclables potentially puts these items out of the recycling loop. If a site is too difficult to clean out and recover these materials, they may be left in place and covered.

Adverse visual impact

Illegal sites or abandoned sites can pose a negative visual impact, especially in more remote areas where recreational visitors may come across a site. Sites located along roads present immediate impacts to all who pass by.

Photo of an abandoned disposal site


Legacy municipal site


CIA sites can present a significant financial burden on the unsuspecting party or regulating agency, municipality, or county that discovers a site. Cleanup typically involves field investigation, testing, and evaluation of the waste materials for classification for waste disposal, as well as for determining remedies and risk assessment to determine the institutional controls to be applied (for example, land-use and deed restrictions).

Costs for clean closure or consolidation and capping often can exceed the market value of the property. For most private responsible parties, the economic burdens associated with a CIA site are difficult to offset unless a revenue-producing beneficial use (storage, parking, golf driving range, etc.) for the property can be implemented to offset capital remedial costs, maintenance, and monitoring.

Site Characterization

Site identification

A CIA site may be identified and located by one of several methods:

  • Research and information request through the Freedom of Information Act (FOIA) from counties, cities, and municipal public works agencies for former municipal disposal sites. Public works records may have maps and drawings showing the location of former municipal disposal sites.
  • Research of rescinded Regional Water Quality Control Board (RWQCB) waste discharge requirements (WDR) for disposal sites operated from the 1960s–1980s. Former sites may also be included under the air and water Solid Waste Assessment Testing (SWAT) program.
  • Sites can be identified through complaints or notification from private individuals discovering a site (for example, developers and geotechnical consultants discovering waste during routine construction activities). The reporting party may notify the LEA by anonymous means, whereupon the LEA visits the site and determines if the site is in violation of the minimum requirements for compliance.
  • The LEA may discover new CIA sites while conducting inspections of nearby facilities or known CIA sites.
  • Interviews with local fire department, waste hauler personnel, and local developers or construction contractors may provide information on past disposal practices and the location of former disposal sites (contact information for local fire departments can be found by visiting the “counties” or “cities” links above.)
  • Sites can be identified through historical aerial photos, general plans, and solid waste management plans. City and county historical societies may have information on past municipal disposal practices.
  • U.S. Geological Survey (USGS) maps depicting gravel mining operations should be reviewed to determine if any local mines were reclaimed for landfilling.

Below is a  Historic Aerials photo of 14th Avenue Landfill, Sacramento County


Below is a U.S. Geological Survey topographical map of 14th Avenue Landfill, Sacramento County


  • Transfer stations and legacy illegal disposal sites have been located over old municipal landfills.
  • Burn sites are usually collocated with active permitted landfills.
  • Wastewater treatment plants have been sited over old municipal disposal areas.

When a CIA site is located, it is the responsibility of the enforcement agency to inspect the site pursuant to  Title 14, California Code of Regulations (14 CCR) sections 18083 and 18303.  A procedure was developed for investigating and evaluating such sites.  This procedure—termed the Site Investigation Process (SIP)—provides a method that allows the LEA and CalRecycle staff to evaluate and identify a CIA site and to assess and determine the magnitude of potential hazard a CIA site might have on public health and safety and the environment.

The SIP provides:

  • A standard investigation procedure for a one-time evaluation of CIA sites.
  • Guidance for classification of sites with respect to public health and safety and the environment.
  • A mechanism to ensure rapid response for sites requiring emergency action to protect public health and safety and the environment, or enforcement action to clean up illegal dumping.
  • A mechanism to identify sites that warrant no further LEA action and therefore eliminate their inspection requirement in the LEA’s Enforcement Program Plan (EPP).
  • A mechanism to document the acceptability of reduced inspection frequency at appropriate sites.
  • A technical basis for determination of appropriate closure, remediation, or corrective action and enforcement follow up.

Site access

Should an LEA be denied site access, an inspection warrant may be necessary.  The LEA should contact its legal counsel for the proper procedures for obtaining an inspection warrant. A site access form is available for use. Statutory authority for site access can be found.


Two forms have been developed to assist in providing documentation on the investigation of CIA sites:

Although LEAs are not required to use these SIP forms, LEAs are encouraged to complete the forms to identify a new CIA site or to characterize an existing site pursuant to their EPP. The following discussion of the SIP forms and process is illustrated in the SIP flowchart.

Site Identification Form. This form compiles basic information on land use on and adjacent to the site, waste type, disposal history, and current site conditions. The form is completed using a preliminary review of site information and a field inspection. A limited site investigation may be necessary to complete the form.

Guidance on obtaining property ownership information (for example, titles and deeds, assessor parcel maps, etc.) can be found on the Phase I office investigation page of the CIA Web site. Useful aerial photographic information, which can provide geographical coordinates (latitude and longitude) and provide land-use and adjacent land-use information, is also available.

A goal of the Solid Waste Information System (SWIS) used by CalRecycle to track CIA sites is to use Geographical Information System (GIS) software to organize data by geographical location. In order to use this software, each CIA site must have latitude and longitude coordinates. If the site’s address or general map location is known, internet resources such as Microsoft’s TerraServer Web site, or software such as “USA Street Atlas” can be used to find the latitude and longitude coordinates for a site if you do not have access to a hand-held Global Positioning System (GPS) receiver.

The form provides for an LEA “recommendation” to indicate whether the site warrants emergency response due to immediate threat to public health and safety and the environment, action under local ordinances to clean up illegal dumping, completion of the Site Assessment Form, or no further action. Examples of instances where no further action is warranted include sites:

  • Whose wastes have been removed (clean closure).
  • Where disposal of solid waste cannot be confirmed, small sites which contain inert wastes.
  • That do not fall under LEA jurisdiction (hazardous waste sites).

Site Assessment Form. This form contains questions whose answers determine potential threats to public health and safety and the environment. It tabulates detailed information on disposal site characteristics, landfill gas emissions, leachate seeps, burn ash exposures, and postclosure land use. Once the form is completed, the site classification can be established using the information.

Disposal site classification categories “A,” “B,” and “C” respectively refer to confirmed, suspected, or not confirmed or suspected gas migration or leachate seeps, burn ash, or putrescible material exposures with significant threat of pollution or nuisance or public health threat. Classification categories A and B and emergency conditions, as determined in the Site Identification Form, could lead to corrective action(s). Category “C” sites warrant minimal action(s) to prevent human or animal contact with waste and action(s) to ensure postclosure land use is compatible with protection of public health and safety and the environment.

Although the previous SIP advisory stated that burn dumps would likely be in the “C” category, recent experience indicates that burn dumps should be in category “A” or “B” if public health hazards exist or there is nearby development. However, if burn dumps are adequately closed, they would be in the “C” category.

Category “D” sites should warrant no further action. Inert sites should be in this category if there is no active dumping. Also, sites which were clean-closed would be category “D” sites. Category “U” (unconfirmed) sites are sites where the disposal of solid waste can be neither confirmed nor denied. Category “X” (not a solid waste disposal site) sites are sites where no solid waste disposal has occurred or sites which do not fall under the jurisdiction of the LEA (for example, hazardous waste sites regulated by the Department of Toxic Substances Control).

The number following the “A,” “B,” and “C” category designations indicates the proximity of the site to public and environmental receptors as defined by postclosure land uses. CalRecycle approved the SIP classification categories as part of a Solid Waste Clean-up Program Board item in December 2001.

Follow-up actions

If the applicable closure requirements were not implemented at the time waste acceptance ceased, the site is subject to all of the existing closure requirements contained in Title 27, California Code of Regulations (27 CCR).  In general, sites that accepted waste after October 18, 1984, with wastes left in place, must have a final cover that includes a low-permeability layer.

Regardless of the last date waste was accepted, should the site pose a threat to public health and safety or the environment, or be a significant nuisance, the minimum closure standards should be applied. Pursuant to 27 CCR section 21100 (d), LEAs can implement the closure regulations as necessary or appropriate.  Staff in CalRecycle Closed, Illegal and Abandoned Site Section can provide both office and field investigation assistance to obtain information and data that will quantify site conditions as they relate to State minimum standards for the purpose of enforcement actions and remedial scoping.

Also, new postclosure activities that could jeopardize the integrity of previously closed sites or pose a potential threat to public health and safety or the environment will also invoke the closure requirements. Please see LEA Advisory No. 51 for further guidance on postclosure land use.

LEAs may refer sites that pose a significant threat to public health and safety and the environment, where the responsible parties either cannot be identified, have no financial resources, or are recalcitrant and unresponsive to enforcement action, to CalRecycle Solid Waste Disposal and Codisposal (AB 2136) Program for potential follow-up action.

Inspection Frequency


Sites suitable for elimination from the required quarterly inspection frequency and the workload analysis portion of the LEA’s Enforcement Program Plan (EPP) are sites that:

  • Cannot be located even after a thorough documented search (These sites can either be Category U or X depending upon the documentation.).
  • Have been certified as clean closed by the LEA/RWQCB/CIWMB with supporting documentation (for example, clean-closure plan and certification of closure).
  • Are not solid waste disposal sites (Category X).
  • Are Category “D” (no threat).

To request the elimination of required inspections, the LEA should submit the request along with the supporting documentation to the Board’s Remediation, Closure, and Technical Services Branch (RCTS). Upon concurrence by RCTS staff, no further inspection of the subject sites would be required and RCTS staff would inform LEA Support Services staff that the sites could be eliminated from the EPP workload analysis.

However, sites eliminated from the required inspection schedule will still be listed on the LEA’s EPP. Generally, only Category “X” and clean-closed Category “D” sites will be placed on an archive list maintained by the Board.


Reduction of inspection frequency for category “A,” “B,” or “C” sites may be appropriate when it can be established that the site will not pose a significant threat to the public health and safety and the environment if inspected at less than a quarterly frequency.

LEAs may request a reduction in CIA site inspection frequency by submitting a request to the Board’s Remediation, Closure, and Technical Services staff for concurrence.  The submittal should include the following:

  1. SIP forms (or other appropriate forms) for the site.
  2. Documentation that closure, remediation, or corrective action requirements have been met for the site. Documentation may include final office and field investigation reports, as-built plans and specifications for the remedy, and construction completion or clean-closure reports.
  3. Documentation demonstrating adequacy of the proposed inspection frequency to ensure the protection of public health and safety and the environment.
  4. Tracking system which will ensure notification of the LEA prior to changes in the site’s land use that may jeopardize the integrity of previously closed sites or pose a potential threat to public health and safety and the environment.

A suggested method for tracking CIA site land-use or zoning changes or proposed construction on CIA sites is to establish a memorandum of agreement between the LEA and the local land use planning authority (city or county planning departments), building department (which approves construction and grading permits), and/or public works agency to provide notification of any proposed changes to disposal site conditions. A clearly marked map depicting the location of known CIA site locations (for example, those inspected and listed on the LEA’s EPP) should be provided to the agency with specific affected addresses and parcels. A short list of processes and permits that could flag a postclosure land use of a CIA site would be:

  • Real estate transaction transferring property title or deed (city or county Assessor’s Office).
  • Land-use zoning change in general plan (city or county planning department).
  • Building, construction, or grading permit (city or county building department).
  • CEQA document and public notification for proposed project (city or county planning department).

The inspection frequency for sites other than category “C” should generally not be less than once a year.  However, for category “C” sites, one inspection every two years may be appropriate.

If you have questions regarding EPP amendments for reduction of inspection frequencies, please contact your LEA Branch staff liaison.

Inspection Forms

The Site Investigation Process forms are designed for use in one-time investigations of CIA sites. Ongoing inspection documentation of CIA sites can be done using the following form. Landfills that closed under the current closure standards (i.e., have a final cover) should be inspected using this same form.

Note: This form replaces the following:

  • Closed Facility Inspection Report (CalRecycle Form 56)
  • Closed Site Inspection Report (CalRecycle Form 55)

The Remediation, Closure, and Technical Services Branch is working on a CIA Inspection Guidance Manual.

For more information contact: Solid Waste Facilities,