We are the subject of, or party to, a number of pending or threatened legal actions and administrative proceedings arising in the ordinary course of our business including, but not limited to, royalty claims, contract claims and environmental claims. While many of these matters involve inherent uncertainty, we believe that the amount of the liability, if any, ultimately incurred with respect to proceedings or claims will not have a material adverse effect on our consolidated financial position as a whole or on our liquidity, capital resources or future annual results of operations.

When deemed necessary, we established reserves for certain legal proceedings. The establishment of a reserve is based on an estimation process that include the advice of legal counsel and subjective judgment of management. While management believes these reserves to be adequate, it is reasonably possible we could incur additional losses with respect to those matters in which reserves have been established. We will continue to evaluate our litigation on a quarterly basis and will establish and adjust any litigation reserves as appropriate to reflect our assessment of the then current status of litigation.

We have incurred and will continue to incur capital, operating and remediation expenditures as a result of environmental laws and regulations. As of December 31, 2019 and 2018, liabilities for remediation were not material. We are not aware of any environmental claims existing as of December 31, 2019 that have not been provided for or would otherwise have a material impact on our financial position or results of operations. Environmental liabilities normally involve estimates that are subject to revision until final resolution, settlement or remediation occurs.

The components of our total lease expense for the year ended December 31, 2019, the majority of which is included in general and administrative expense, are as follows (in thousands):

		Year Ended December 31,
		2019
Operating lease cost	$	15,536
Variable lease expense ⁽¹⁾		6,916
Short-term lease expense ⁽²⁾		2,965
Sublease income		(3,496	)
Total lease expense	$	21,921

Short-term lease costs ⁽³⁾	$	29,126

(1) Variable lease payments that are not dependent on an index or rate are not included in the lease liability or ROU assets.

(2) Short-term lease expense represents expense related to leases with a contract term of one year or less.

(3) These short-term lease costs are related to leases with a contract term of one year or less and the majority of which are related to drilling rigs and are capitalized as part of natural gas and oil properties on our consolidated balance sheets and may fluctuate based on the number of drilling rigs being utilized.

Supplemental cash flow information related to our operating leases is included in the table below (in thousands):

Year Ended

December 31,

2019

Cash paid for amounts included in the measurement of lease liabilities

18,700

ROU assets added in exchange for lease obligations (since adoption)

24,839

Supplemental balance sheet information related to our operating leases is included in the table below (in thousands):

		December 31, 2019
Operating lease ROU assets	$	62,053
Accrued liabilities – current	$	(27,856	)
Operating lease liabilities – long-term	$	(41,068	)

As part of our ongoing effort to reduce general and administrative expenses due to the lower commodity price environment, we announced the closing of our Houston office in fourth quarter 2019. We have recorded an impairment related to our Houston office lease ROU asset of $2.1 million which is included in impairment of proved property and other assets in our consolidated statements of operations for the year ended December 31, 2019.

Our weighted average remaining lease term and weighted average discount rate for our operating leases are as follows:

December 31,

2019

Weighted average remaining lease term

4.6 years

Weighted average discount rate

6.0%

Our lease liabilities with enforceable contract terms that are greater than one year mature as follows (in thousands):

		Operating Leases
2020	$	31,245
2021		14,252
2022		7,023
2023		6,500
2024		6,468
Thereafter		15,262
Total lease payments		80,750
Less effects of discounting		(11,826	)
Total lease liability	$	68,924

We have entered into firm transportation and gathering contracts with various pipeline carriers for the future transportation and gathering of natural gas, NGLs and oil production from our properties in Pennsylvania and North Louisiana. Under these contracts, we are obligated to transport, process or gather minimum daily natural gas volumes, or pay for any deficiencies at a specified reservation fee rate. In some cases, our production committed to these pipelines is expected to exceed the minimum daily volumes provided in the contracts. See Note 11 for additional information regarding deficiencies in North Louisiana. As of December 31, 2019, future minimum transportation, processing and gathering fees under our commitments are as follows (in thousands):

	Transportation, Gathering and Processing Contracts ^(a)
2020	$	945,392
2021		949,126
2022		905,920
2023		870,062
2024		853,457
Thereafter		5,154,987
	$	9,678,944

^(a) The amounts in this table represent the gross amounts that we are committed to pay; however, we will record in our financial statements our proportionate share of costs based on our working interest which can vary based on volumes produced.

In addition to the amounts included in the above table, we have entered into additional agreements which are contingent on certain pipeline modifications and/or construction for natural gas volumes of 25,000 mcf per day, which is expected to begin in 2022 and has a six-year term.

We have various volume delivery commitments that are related to our Marcellus Shale and North Louisiana areas. We expect to be able to fulfill our contractual obligations from our own production; however, we may purchase third-party volumes to satisfy our commitments or pay demand fees for commitment shortfalls, should they occur. As of December 31, 2019, our delivery commitments through 2031 were as follows:

Year Ending December 31,	Natural Gas (mmbtu per day)		Ethane and Propane (bbls per day)
2020		528,607	81,000
2021		491,313	65,932
2022		370,179	43,000
2023		167,970	35,000
2024-2028		100,000	35,000
2029		100,000	20,000
2030-2031		—	20,000

In addition to the amounts included in the above table, we have contracted with a pipeline company through 2035 to deliver ethane production volumes from our Marcellus Shale wells. These agreements and related fees, which are contingent upon pipeline construction and/or modification, are for 3,000 bbls per day starting in 2021 and increasing to 10,000 bbls per day through 2035. In addition, we have agreements in place to deliver natural gas volumes from our Marcellus Shale wells, which are also contingent upon pipeline construction and/or modification, for 35,000 mcf per day starting in late 2020, increasing to 50,000 mcf per day in late 2021 and decreasing to 15,000 mcf per day in 2025 through 2026.

We also have lease acreage that is generally subject to expiration if initial wells are not drilled within a specified period, generally between three and five years. We do not expect to lose significant lease acreage because of failure to drill due to inadequate capital, equipment or personnel. However, based on our evaluation of prospective economics, we have allowed acreage to expire and will allow additional acreage to expire in the future. To date, our expenditures to comply with environmental or safety regulations have not been a significant component of our cost structure and are not expected to be significant in the future. However, new regulations, enforcement policies, claims for damages or other events could result in significant future costs.