Note 2—Basis of Presentation

Interim consolidated financial statements — The interim condensed consolidated financial statements for the three and six month periods ended June 30, 2018 and 2017 have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). As such, certain disclosures, which would substantially duplicate the disclosures contained in our Annual Report on Form 10-K, filed on February 26, 2018, which contains our audited consolidated financial statements for the year ended December 31, 2017, have been omitted.

This Second Quarter 2018 Report on Form 10-Q should be read in concert with our most recent Annual Report on Form 10-K. The interim financial information is unaudited. In the opinion of management, the interim information includes all adjustments (consisting of normal recurring adjustments) necessary for the fair presentation of the interim financial information.

Reclassification — Certain previously reported amounts have been reclassified to conform to the current year presentation.

Restricted cash — Restricted cash consists of cash balances that are restricted as to withdrawal or usage. As a result of the Willbros acquisition, we acquired cash pledged to secure letters of credit, which is recorded as restricted cash at June 30, 2018. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheets to the totals of such amounts shown in the Condensed Consolidated Statements of Cash Flows (in thousands).


	June 30,		December 31,
	2018		2017
Cash and cash equivalents	$	139,404	$	170,385
Restricted cash		35,492		—
	$	174,896	$	170,385

Customer concentration — We operate in multiple industry segments encompassing the construction of commercial, industrial and public works infrastructure assets primarily throughout the United States. Typically, the top ten customers in any one calendar year generate revenue in excess of 50% of total revenue; however, the group that comprises the top ten customers varies from year to year.

During the three and six months ended June 30, 2018, revenue generated by the top ten customers were approximately $322.6 million and $581.6 million, respectively, which represented 50.4% and 49.7%, respectively, of total revenue during the applicable period. During the three and six months ended June 30, 2018, a state department of transportation customer represented 9.4% and 9.3% of total revenue, respectively, and a California utility customer represented 8.7% and 9.0% of total revenue, respectively.

During the three and six months ended June 30, 2017, revenues generated by the top ten customers were approximately $330.2 million and $713.5 million, respectively, which represented 52.3% and 59.8%, respectively, of total revenues during the applicable period. During the three and six months ended June 30, 2017, two large pipeline projects represented 11.0% and 19.2% of total revenues, respectively and a state department of transportation customer represented 10.6% and 10.5% of total revenues, respectively.

At June 30, 2018, approximately 6.5% of our accounts receivable were due from one customer, and that customer provided 8.8% our revenue for the six months ended June 30, 2018. In addition, of total accounts receivable, approximately 5.1% are from one customer with whom we are currently engaged in a dispute resolution. See Note 16 – “Commitments and Contingencies”.

At June 30, 2017, approximately 11.7% of our accounts receivable were due from one customer, and that customer provided 8.8% of our revenue for the six months ended June 30, 2017. In addition, approximately 11.0% of total accounts receivable at June 30, 2017 were from one customer with whom we are currently engaged in a dispute resolution.

Multiemployer plans — Various of our subsidiaries are signatories to collective bargaining agreements. These agreements require that we participate in and contribute to a number of multiemployer benefit plans for our union employees at rates determined by the agreements. The trustees for each multiemployer plan determine the eligibility and allocations of contributions and benefit amounts, determine the types of benefits, and administer the plan. To the extent that any plans are underfunded, the Employee Retirement Income Security Act of 1974, as amended by the Multi-Employer Pension Plan Amendments Act of 1980, requires that if we were to withdraw from an agreement or if a plan is terminated, we may incur a withdrawal obligation. The potential withdrawal obligation may be significant. In accordance with Generally Accepted Accounting Principles (“GAAP”), any withdrawal liability would be recorded when it is probable that a liability exists and can be reasonably estimated. In November 2011, we withdrew from the Central States Southeast and Southwest Areas Pension Fund multiemployer plan, as discussed in Note 16 — “Commitments and Contingencies”. We have no plans to withdraw from any other agreements.