The Company acquired one property on March 9, 2022 that is subject to a non-cancelable, long-term ground lease where a third party owns the underlying land and has leased the land to the Company. Accordingly, the Company owns only a long-term leasehold in this property. This ground lease expires through the year 2084 including those options the Company deems probable of exercising. The ground lease expense is recognized on a straight-line basis over the term of the lease, including management's estimate of expected option renewal periods. Operating lease expense under the Company's ground lease was approximately $16,000 for the three months ended March 31, 2022. There are no variable lease expenses required to be paid by the Company as lessee per the lease terms. Cash paid for amounts included in the measurement of the Right of use liability, net was approximately $14,000 during the three months ended March 31, 2022.

The following table summarizes the undiscounted future cash flows by year attributable to the ground lease liability as of March 31, 2022 and provides a reconciliation to the Right of use liability included in the accompanying Consolidated Balance Sheet as of March 31, 2022.

	As of March 31, 2022
2022	$	188,913
2023		232,701
2024		244,077
2025		245,111
2026		245,111
Thereafter		22,065,755
Total undiscounted liability		23,221,668
Present value discount		16,907,714
Right of use liability		6,313,954
Discount rate		4.58	%
Term	62 years

For the three months ended March 31, 2022 and 2021 we had three and four tenants, respectively, that each account for more than 10% of our rental revenue as indicated below:

	2022	2021
Pratt and Whitney – Huntsville, AL property	14.5%	18.6%
General Services Administration – Walmer Ave. Norfolk, VA property	19.5%	24.0%
Maersk Shipping – Walmer Ave. Norfolk, VA property	Less than 10%	10.5%
PRA Holding – Corporate Blvd. Norfolk, VA property	16.1%	20.0%

The following table presents future minimum base rental cash payments due to the Company over the next five calendar years and thereafter as of March 31, 2022:

	Future Minimum Base Rent Payments
2022	$3,746,000
2023	4,629,000
2024	4,675,000
2025	4,547,000
2026	4,425,000
Thereafter	8,988,000
	$31,010,000