11.

Construction Backlog

The following represents the backlog of signed construction and engineering contracts in existence at June 30, 2018 and December 31, 2017, which represents the amount of revenue the Company expects to realize from work to be performed on uncompleted contracts in progress and from contractual agreements in effect at June 30, 2018 and December 31, 2017, respectively, on which work has not yet begun:

	June 30, 2018			December 31, 2017
Balance – beginning of period	$	76,659,029		$	541,291
New contracts and change orders during the period		30,061,551			81,179,323
Subtotal		106,720,580			81,720,614
Less: contract revenue earned during the period		(3,849,325	)		(5,061,585	)
Balance – end of period	$	102,871,255		$	76,659,029

Backlog at June 30, 2018 includes two large contracts entered into by the Company during the third quarter of 2017 and one during the first quarter of 2018 in the amounts of approximately $55 million, $15 million and $27 million, respectively. The Company expects that all of this revenue will be realized by December 31, 2020.