Protecting Public Health and the Environment.

Sump Waste

A sump is a pit or tank that catches liquid runoff for drainage or disposal. Sump waste is the mixture of dirt, grime, and grit that accumulates in a sump. Sump waste is considered solid waste and may be hazardous, depending on its content. Under the federal Resource Conservation and Recovery Act (RCRA), which Idaho has adopted by reference into state rules, owners and/or operators of facilities where sumps are in operation must demonstrate they have adequately determined if the contents of the sumps are hazardous prior to shipping the sump waste off site for disposal.

Determining if Sump Waste is Hazardous

The content of waste collected in a sump depends upon the type of business that is using the device. For example, car wash residue and material washed in the floors of vehicle maintenance shops differs from waste that is placed in floor sumps in manufacturing plants. Regulations allow the determination whether sump waste is hazardous to be made through knowledge of process, chemical analysis, or a combination of both.

Knowledge of Process

In some cases, generator knowledge of the process or materials that produced the waste may be used to document that hazardous wastes have not entered the pump. With many listed wastes, generator knowledge is appropriate because the physical/chemical makeup of the waste is generally well known and consistent from facility to facility.

For example, facilities that limit the type of use (i.e., washing new or used cars) and access (i.e., company cars only) to the sump may be able to show that no hazardous constituents/wastes are used in the processes that discharge or drain into the sump, thereby establishing that the sump contains no hazardous wastes.

Note: Although knowledge of process is less costly than chemical analysis, facilities must ensure that this information accurately reflects the current processes and materials being used. If generator knowledge is used alone or in conjunction with sampling and analysis, facilities must maintain detailed documentation that clearly demonstrates the information is sufficient.

Chemical Analysis

If the sump is associated with engine washing or degreasing processes, used oil or used antifreeze spills or disposal, or the use or spilling of hazardous chemicals/ materials, or is located in an area where there are no controls on who has access to the sump, the knowledge of process nonhazardous determination is not allowed. In this case, a sample of the sump waste may have to be submitted to a laboratory for chemical analysis.

Chemical analysis is generally used for determining  the following hazardous waste characteristics:

  • Flash point to determine ignitability
  • pH to determine corrosivity
  • Toxicity Characteristic Leaching Procedure (TCLP) to determine toxicity

If pesticides are associated with the sump, a pesticide scan test also is required.

Preliminary screening tests, which tend to be less expensive, may be used as part of the determination. If the results reveal concentrations of total metals in excess of TCLP levels, however, additional samples and analyses for the TCLP level of the specific metals involved may be necessary to determine if the sump waste is hazardous.

Testing Frequency

Facilities that do not change processes and continue to control access may only need to test the sump waste one time.

Facilities that restrict access by design to only private vehicles (as opposed to commercial trucks), for example, may need to test the sump waste periodically, perhaps once a year.

Facilities that do not restrict access, such as public car washes, or are involved with truck washing where cargo holds are washed, need to test the sump waste each time before removal and disposal.

All analytical results must be kept on file at the facility for at least 3 years; it is recommended that records be kept on file indefinitely.

Disposing of Sump Waste


If the sump waste is nonhazardous, it may be disposed of in a municipal solid waste landfill (MSWLF). However, before disposal at a MSWLF, all nonhazardous sump waste must pass the paint filter test (method 9095) to determine whether free liquids exist in the waste.

Some MSWLFs do not allow sludges to be dumped unless the total petroleum hydrocarbon (TPH) level is tested and is found to be below 1,000 parts per million (ppm). This is a local requirement and not part of the state and federal hazardous waste regulations. Check with the specific MSWLF you plan to use. If the test is required, it can be done at the same time as the test for hazardous constituents. Additionally, sump wastes that are not hazardous but contain significant levels of TPH should not be placed on the ground because the waste may cause surface or ground water contamination.


If the sump waste is determined to be a regulated hazardous waste, the facility must count the sump waste toward the facility's generator status. If the sump waste is determined to be hazardous and the generator of the waste is a small quantity generator or a large quantity generator, the waste must be disposed of in a permitted hazardous waste treatment, storage, and disposal (TSD) facility. Contact DEQ for the location of a TSD facility near you.

Staff Contacts

Hazardous Waste Bureau Chief
Natalie Creed
DEQ State Office
Waste Management & Remediation Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0506

DEQ Guidance

The Key to Managing Your Sump Waste: Determining if it's Hazardous

More Information

Test Methods for Evaluating Solid Waste, Physical/Chemical Methods

Related Pages

How to Determine Your Generator Status

Treatment, Storage, and Disposal Facilities in Idaho