(18) Related Party Transactions

Richard J. Heckmann, the Executive Chairman of the Company’s board of directors, and Mark D. Johnsrud, the Company’s Chief Executive Officer and Vice Chairman of the Company’s board of directors, are members of an entity that owns an aircraft used periodically by the Company for business-related travel. Reimbursements paid to the entity in exchange for use of the aircraft were $0.4 million, $1.2 million and $0.9 million for the years ended December 31, 2013, 2012 and 2011, respectively. Amounts payable to the entity were less than $0.1 million at December 31, 2013.

Mr. Johnsrud is the sole member of an entity that owns apartment buildings in North Dakota which are rented to certain of the Company’s employees at rates that are equal to or below market rates. Rent payments are collected from the employees by the Company through payroll deductions and remitted to the entity.

In connection with the Power Fuels Merger, assets received in exchange for the merger consideration excluded accounts receivable outstanding for more than ninety days as of November 30, 2012. Subsequent collections on these accounts receivable, which are recorded by the Company as restricted cash with an offsetting liability, are required to be periodically remitted to Mr. Johnsrud. Pursuant to the terms of this agreement, during the year ended December 31, 2013, the Company paid Mr. Johnsrud $3.6 million for such collections, net of a working capital adjustment of approximately $2.1 million. Amounts payable to Mr. Johnsrud at December 31, 2013 for accounts receivable collections totaled approximately $0.1 million.

The Company periodically purchases fresh water for resale to customers from a sole proprietorship owned by Mr. Johnsrud. Purchases made by the Company during the year ended December 31, 2013 amounted to $0.7 million. Purchases made by Power Fuels prior to its merger with the Company totaled approximately $2.2 million during the year ended December 31, 2012. No amounts were due to the sole proprietorship at December 31, 2013.

Mr. Johnsrud is the sole member of an entity that owns land in North Dakota on which five of the Company’s saltwater disposal wells are situated. The Company has agreed to pay the entity a per-barrel royalty fee in exchange for the use of the land, which is consistent with rates charged by non-affiliated third parties under similar arrangements. Royalties paid by the Company were approximately $0.1 million in each of the years ended December 31, 2013 and 2012, respectively. Royalties payable to the entity were less than $0.1 million at December 31, 2013 and 2012.

During 2009, the Company acquired an approximate 7% investment in Underground Solutions, Inc. (“UGSI”) a supplier of water infrastructure pipeline products, whose chief executive officer, Andrew D. Seidel, is a member of the Company’s board of directors. The Company’s total investment in UGSI was $7.2 million. During the quarter ended September 30, 2013, management performed an evaluation of various alternatives for this non-strategic investment, including its potential liquidation. As a result, the Company recorded a $3.8 million charge for the write-down of this investment to its estimated net realizable value. The Company’s interest in UGSI is accounted for as a cost method investment in the Company’s consolidated balance sheet as of December 31, 2013 and December 31, 2012, and is included in the Corporate/Other group for purposes of reportable segments (Note 19). The $3.8 million write-down was classified as a component of other expense, net in the consolidated statement of operations for the year ended December 31, 2013.