(1)

We categorize our treatment and disposal revenue as either “Base Business” or “Event Business” based on the underlying nature of the revenue source. We define Event Business as non-recurring projects that are expected to equal or exceed 1,000 tons, with Base Business defined as all other business not meeting the definition of Event Business. For the years ended December 31, 2021, 2020 and 2019, 24%, 27% and 22%, respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76%, 73% and 78% of our treatment and disposal revenue for the years ended December 31, 2021, 2020 and 2019, respectively.

(2)	Includes collection and transportation of non-hazardous and hazardous waste.

(3)	Includes industrial cleaning and maintenance for refineries, chemical plants, steel and automotive plants, marine terminals and refinery services such as tank cleaning and temporary storage.

(4)	Includes retail services, laboratory packing, less-then-truck-load service and household hazardous waste collection. Contracts for Small Quantity Generation may extend beyond one year and a portion of the transaction price can be fixed.

(5)

Through our TWM program, customers outsource the management of their waste compliance program to us, allowing us to organize and coordinate their waste management disposal activities and environmental compliance. TWM contracts may extend beyond one year and a portion of the transaction price can be fixed.

(6)	Includes site assessment, onsite treatment, project management and remedial action planning and execution. Contracts for Remediation may extend beyond one year and a portion of the transaction price can be fixed.

(7)

Includes services such as spill response, waste analysis and treatment and disposal planning as well as government-mandated, commercial standby oil spill compliance solutions and services that we provide to companies that store, transport, produce or handle petroleum and certain nonpetroleum oils on or near U.S. waters. Our standby services customers pay annual retainer fees under long-term or evergreen contracts for access to our regulatory certifications, specialized assets and highly trained personnel. When a customer with a retainer contract experiences a spill incident, we coordinate and manage the spill response, which results in incremental revenue for the services provided, in addition to the retainer fees.

(8)	Includes equipment rental and other miscellaneous services.

We provide services primarily in the United States, Canada and the EMEA region. The following table presents our revenue disaggregated by our reportable segments and geographic location where the underlying services were performed:


	2021
	Waste		Field		Energy
$s in thousands	Solutions		Services		Waste		Total
United States	$	374,414	$	450,276	$	36,565	$	861,255
Canada		76,835		3,785		—		80,620
EMEA		—		41,218		—		41,218
Other (1)		—		4,908		—		4,908
Total revenue	$	451,249	$	500,187	$	36,565	$	988,001


	2020
	Waste		Field		Energy
$s in thousands	Solutions		Services		Waste		Total
United States	$	355,226	$	445,405	$	34,687	$	835,318
Canada		70,187		3,064		—		73,251
EMEA		—		19,947		—		19,947
Other (1)		—		5,338		—		5,338
Total revenue	$	425,413	$	473,754	$	34,687	$	933,854


	2019
	Waste		Field		Energy
$s in thousands	Solutions		Services		Waste		Total
United States	$	354,625	$	221,942	$	12,560	$	589,127
Canada		85,922		2,577		—		88,499
EMEA		—		5,079		—		5,079
Other (1)		—		2,804		—		2,804
Total revenue	$	440,547	$	232,402	$	12,560	$	685,509

(1)	Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.