California waste code 521 Mud pumped out of a drilled well or bore.

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Based on California Title 22 and DTSC guidance
Nothing is stored

Miscellaneous
Mud from drilling

A drilling operation produced the hazardous mud.

Hazardous mud from a drilling operation. A muddy texture alone does not make it drilling mud.

Is California code 521 hazardous waste?

Not from the code alone. Waste must first be found hazardous. Code 521 isn't a restricted code, but a restricted category that fits takes priority over it. A code that isn't restricted doesn't make waste non-hazardous.

When a shipment needs the Uniform Hazardous Waste Manifest, enter 521 in Item 13 for the waste line. Use one California code, plus the federal RCRA codes when the waste is federally hazardous.

RCRA waste meets a federal listing or characteristic, with no federal exclusion that applies. Non-RCRA waste is hazardous under California rules only. California presumes hazardous waste is RCRA unless the generator shows it isn't, so keep that determination.

What does California code 521 cover?

This code is for hazardous fluid or residue from drilling. Mud-like consistency isn't enough. The federal exclusion covers only specified oil, gas or geothermal exploration or production sources, and California hazards can remain.

Official wording: 22 CCR division 4.5, chapter 11, Appendix XII(b)

Is drilling mud California code 521?

Code	When it fits
521	A drilling operation produced the mud and an applicable listing or characteristic makes it California hazardous waste.
No California hazardous waste code	An applicable exclusion is satisfied and no California listing or characteristic remains.

The federal drilling-waste exclusion doesn't cover every drilling job, such as ordinary construction that happens to make mud. Keep the source and classification evidence.

Which wastes take California code 521?

Waste	When it’s 521
Drilling mud	The fluid or residue came from a drilling operation

Which codes sit beside California code 521?

Code	What it is
511	Large pesticide container
512	Large non-pesticide container
513	Small hazardous-waste container
531	Chemical toilet waste
541	Photographic processing chemicals
551	Discarded laboratory chemicals
561	Discarded detergent or soap
571	Fly, bottom or retort ash