NOTE O—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at June 30, 2018 (in thousands):



Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	39,115	$	12,413
2019	73,080		21,037
2020	57,683		15,663
2021	38,639		8,008
2022	31,652		5,640
Thereafter	61,790		4,141
Total future lease and purchase commitments	$	301,959	$	66,902

Operating Leases

We are obligated under certain operating leases for railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. Certain operating lease agreements include options to purchase the equipment for fair market value at the end of the original lease term. In general, the above leases include renewal options and provide that we pay for all utilities, insurance, taxes and maintenance. Expense related to operating leases and rental agreements totaled approximately $24.9 million and $47.7 million for the three and six months ended June 30, 2018. Expense related to operating leases and rental agreements totaled approximately $15.8 million and $31.2 million for the three and six months ended June 30, 2017, respectively.

Minimum Purchase Commitments

We enter into service agreements with our transload service providers and transportation service providers. Some of these agreements require us to purchase a minimum amount of services over a specific period of time. Any inability to meet these minimum contract requirements requires us to pay a shortfall fee, which is based on the difference between the minimum amount contracted for and the actual amount purchased.

Contingent Liability on Royalty Agreement

On May 17, 2017, we purchased reserves in Crane County, Texas, for $94.4 million cash consideration plus contingent consideration. The contingent consideration is a royalty that is based on the tonnage shipped to third-parties. Because the contingent consideration is dependent on future tonnage sold, the amounts of which are uncertain, it is not currently possible to estimate the fair value of these future payments. The contingent consideration will be capitalized at the time a payment is probable and reasonably estimable, and the related depletion expense will be adjusted prospectively.

Other Commitments and Contingencies

Our operating subsidiary, U.S. Silica Company (“U.S. Silica”), has been named as a defendant in various product liability claims alleging silica exposure causing silicosis. During the six months ended June 30, 2018, one new claim was brought against U.S. Silica. As of June 30, 2018, there were 56 active silica-related products liability claims pending in which U.S. Silica is a defendant. Although the outcomes of these claims cannot be predicted with certainty, in the opinion of management, it is not reasonably possible that the ultimate resolution of these matters will have a material adverse effect on our financial position or results of operations that exceeds the accrual amounts.

We have recorded estimated liabilities for these claims in other long-term obligations as well as estimated recoveries under the indemnity agreement and an estimate of future recoveries under insurance in other assets on our condensed consolidated balance sheets. As of both June 30, 2018, and December 31, 2017 other non-current assets included zero for insurance for third-party products liability claims and other long-term obligations included $1.0 million for third-party products liability claims.