Assessment, Permitting and Response Revenues—Assessment, Permitting and Response revenues are generated from multidisciplinary environmental consulting services. The majority of the contracts are fixed-price or time and material based.

Measurement and Analysis Revenues—Measurement and Analysis revenues are generated from emissions sampling, testing and reporting services, leak detection services, ambient air monitoring services and laboratory testing services. The majority of the contracts are fixed-price or time-and-materials based.

Remediation and Reuse Revenues—Remediation and Reuse revenues are generated from engineering, design, implementation and operating and maintenance (“O&M”) services primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. Engineering, design and implementation contracts are predominantly fixed-fee and time-and-materials based. Services on the majority of O&M contracts are provided under long-term fixed-fee contracts.

Disaggregation of Revenue—The Company disaggregates revenue by its operating segments and geographic location. The Company believes disaggregating revenue into these categories achieves the disclosure objectives to depict how the nature, amount, and uncertainty of revenue and cash flows are affected by economic factors. Disaggregated revenue disclosures are provided in Note 18 - Segment Information and Geographic Location Information.

Contract Balances—The Company presents contract balances for unbilled receivables (contract assets), as well as customer advances, deposits and deferred revenue (contract liabilities) within contract assets and accounts payable and other accrued expenses, respectively, on the unaudited condensed consolidated statements of financial position. Amounts are generally billed at periodic intervals (e.g. weekly, bi-weekly or monthly) as work progresses in accordance with agreed-upon contractual terms. The Company utilizes the practical expedient to not adjust the promised amount of consideration for the effects of a significant financing component as the period between when the Company transfers services to a customer and when the customer pays for those services is one year or less. Amounts recorded as unbilled receivables are generally for services the Company is not entitled to bill based on the passage of time. Under certain contracts, billing occurs subsequent to revenue recognition, resulting in contract assets. The Company sometimes receives advances or deposits from customers before revenue is recognized, resulting in contract liabilities.

The following table presents the Company’s contract balances:


	March 31,		December 31,
	2024		2023
Contract assets	$	73,466	$	51,629
Contract liabilities		10,016		8,132

Contract assets acquired through business acquisitions were $0.3 million and $2.2 million as of March 31, 2024 and December 31, 2023, respectively. No material contract liabilities were acquired through business acquisitions as of March 31, 2024 and December 31, 2023.

Revenue recognized during the three months ended March 31, 2024, included in the contract liabilities balance at the beginning of the year was $4.5 million. The revenue recognized from the contract liabilities consisted of the Company satisfying performance obligations during the normal course of business.

Remaining Unsatisfied Performance Obligations—Remaining unsatisfied performance obligations represent the total dollar value of work to be performed on contracts awarded and in progress. The amount of remaining unsatisfied performance obligations increases with new contracts or additions to existing contracts and decreases as revenue is recognized on existing contracts. Contracts are included in the amount of remaining unsatisfied performance obligations when an enforceable agreement has been reached. As of March 31, 2024 and December 31, 2023, the estimated revenue expected to be recognized in the future related to unsatisfied performance obligations was approximately $83.8 million and $81.9 million, respectively. As of March 31, 2024, the Company expected to recognize approximately 70% of this amount as revenue within a year, and the remaining 30% to be recognized as revenue beyond one year.

Accounts Receivable, Net—The Company extends non-interest-bearing trade credit to its customers in the ordinary course of business. Accounts receivable, net consisted of the following:



	March 31, 2024			December 31, 2023
Accounts receivable, invoiced	$	106,870		$	115,064
Accounts receivable, other		483			20
Allowance for doubtful accounts		(2,619	)		(2,724	)
Accounts receivable, net	$	104,734		$	112,360

The Company did not have any customers that exceeded 10.0% of its gross receivables as of March 31, 2024 and December 31, 2023 and did not have any customers that exceed 10% of its revenue for the three months ended March 31, 2024 and 2023.

The allowance for doubtful accounts consisted of the following:


	Beginning Balance		Bad Debt (Recovery) Expense			Charged to Allowance			Ending Balance
Three months ended March 31, 2024	$	2,724	$	(886	)	$	781		$	2,619
Year ended December 31, 2023		1,915		3,142			(2,333	)		2,724