At June 30, 2022 and September 30, 2021, letters of credit totaled $4.5 million and $5.2 million, respectively, under our Revolving Credit Facility. As of June 30, 2022 and September 30, 2021, we had $1,145.5 million and $1,144.8 million, respectively, available under our Revolving Credit Facility.
2027 Senior Notes
On February 21, 2017, we completed a private placement offering of $1,000,000,000 aggregate principal amount of our unsecured 5.125% Senior Notes due 2027 (the “2027 Senior Notes”). On June 30, 2017, we completed an exchange offer to exchange the unregistered 2027 Senior Notes for registered notes, as well as related guarantees.
As of June 30, 2022, the estimated fair value of the 2027 Senior Notes was approximately $935.0 million. The fair value of the 2027 Senior Notes as of June 30, 2022 was derived by taking the mid-point of the trading prices from an observable market input (Level 2) in the secondary bond market and multiplying it by the outstanding balance of the 2027 Senior Notes. Interest is payable on the 2027 Senior Notes at a rate of 5.125% per annum. Interest on the 2027 Senior Notes is payable semi-annually on March 15 and September 15 of each year, commencing on September 15, 2017. The 2027 Senior Notes will mature on March 15, 2027.
At any time and from time to time prior to December 15, 2026, we may redeem all or part of the 2027 Senior Notes, at a redemption price equal to 100% of their principal amount, plus a “make whole” premium as of the redemption date, and accrued and unpaid interest to the redemption date. On or after December 15, 2026, we may redeem all or part of the 2027 Senior Notes at a redemption price equal to 100% of their principal amount, plus accrued and unpaid interest to the redemption date.
The indenture pursuant to which the 2027 Senior Notes were issued contains customary events of default, including, among other things, payment default, exchange default, failure to provide notices thereunder and provisions related to bankruptcy events. The indenture also contains customary negative covenants.
We were in compliance with the covenants relating to the 2027 Senior Notes as of June 30, 2022.
Other Debt
Other debt consists primarily of obligations under finance leases and loans and unsecured credit facilities.
Effective Interest Rate
Our average effective interest rate on our total debt, including the effects of the interest rate swap agreements, during the nine months ended June 30, 2022 and 2021 was 3.4% and 4.7%, respectively.
Interest expense in the consolidated statements of operations included amortization of deferred debt issuance costs for the three and nine months ended June 30, 2022 of $1.2 million and $3.7 million, respectively, and for the three and nine months ended June 30, 2021 of $4.6 million and $9.0 million, respectively.
Other Commitments
We enter into various joint venture arrangements to provide architectural, engineering, program management, construction management and operations and maintenance services. The ownership percentage of these joint ventures is typically representative of the work to be performed or the amount of risk assumed by each joint venture partner. Some of these joint ventures are considered variable interest entities. We have consolidated all joint ventures for which we have control. For all others, our portion of the earnings is recorded in equity in earnings of joint ventures. See Note 5, Joint Ventures and Variable Interest Entities, in the notes to our consolidated financial statements.
Other than normal property and equipment additions and replacements, expenditures to further the implementation of our various information technology systems, commitments under our incentive compensation programs, amounts we may expend to repurchase stock under our stock repurchase program and acquisitions from time to time and disposition costs, we currently do not have any significant capital expenditures or outlays planned except as described below. However, if we acquire additional businesses in the future or if we embark on other capital-intensive initiatives, additional working capital may be required.
Under our secured revolving credit facility and other facilities discussed in Other Debt and Other Items above, as of June 30, 2022, there was approximately $645.4 million, including both continuing and discontinued operations, outstanding under standby letters of credit primarily issued in connection with general and professional liability insurance programs and for contract performance