Commitments and Contingencies

Operating Ground Leases

Certain of our properties are subject to operating ground leases. Rental payments on these leases are adjusted periodically based on either the consumer price index or on a pre-determined schedule. Total rental property expense recorded for operating ground leases was $2.5 million, $2.5 million and $2.9 million for the years ended December 31, 2018, 2017 and 2016, respectively.

The following table sets forth our scheduled obligations for future minimum payments on operating ground leases at December 31, 2018:



Years Ending December 31,	Minimum Payments
2019	$	2,184
2020	2,223
2021	2,263
2022	2,305
2023	2,308
Thereafter	86,577
	$	97,860

Lease and Contractual Commitments

We have $484.8 million of lease and contractual commitments at December 31, 2018. Lease and contractual commitments represent commitments under signed leases and contracts for operating properties (excluding tenant-funded tenant improvements) and contracts for development/redevelopment projects, of which $60.4 million was recorded on our Consolidated Balance Sheets at December 31, 2018.

Contingent Consideration

We had $5.0 million at both December 31, 2018 and 2017 of contingent consideration related to certain parcels of acquired development land in Raleigh, Atlanta and Nashville. The contingent consideration for each is payable in cash to a third party if and to the extent future development milestones as outlined in the purchase agreements are met.

Environmental Matters

Substantially all of our in-service and development properties have been subjected to Phase I environmental assessments and, in certain instances, Phase II environmental assessments. Such assessments and/or updates have not revealed, nor are we aware of, any environmental liability that we believe would have a material adverse effect on our Consolidated Financial Statements.

Litigation, Claims and Assessments

We are from time to time a party to a variety of legal proceedings, claims and assessments arising in the ordinary course of our business. We regularly assess the liabilities and contingencies in connection with these matters based on the latest information available. For those matters where it is probable that we have incurred or will incur a loss and the loss or range of loss can be reasonably estimated, the estimated loss is accrued and charged to income in our Consolidated Financial Statements. In other instances, because of the uncertainties related to both the probable outcome and amount or range of loss, a reasonable estimate of liability, if any, cannot be made. Based on the current expected outcome of such matters, none of these proceedings, claims or assessments is expected to have a material effect on our business, financial condition, results of operations or cash flows.