LONG-TERM DEBT

Our long-term debt consisted of the following (in thousands):



	March 31, 2016			December 31, 2015
SemGroup 7.50% senior unsecured notes due 2021	$	300,000		$	300,000
Unamortized debt issuance costs on SemGroup notes	(4,333		)	(4,540		)
SemGroup 7.50% senior unsecured notes due 2021, net	295,667			295,460

Rose Rock 5.625% senior unsecured notes due 2022	400,000			400,000
Unamortized debt issuance costs on Rose Rock 2022 notes	(6,709		)	(6,975		)
Rose Rock 5.625% senior unsecured notes due 2022, net	393,291			393,025

Rose Rock 5.625% senior unsecured notes due 2023	350,000			350,000
Unamortized discount on Rose Rock 2023 notes	(5,317		)	(5,455		)
Unamortized debt issuance costs on Rose Rock 2023 notes	(5,098		)	(5,266		)
Rose Rock 5.625% senior unsecured notes due 2023, net	339,585			339,279

SemGroup corporate revolving credit facility	70,000			30,000
Rose Rock revolving credit facility	24,000			—
SemMexico revolving credit facility	—			—
Capital leases	72			83
Total long-term debt, net	1,122,615			1,057,847
Less: current portion of long-term debt	27			31
Noncurrent portion of long-term debt, net	$	1,122,588		$	1,057,816

SemGroup senior unsecured notes due 2021

For the three months ended March 31, 2016 and 2015, we incurred $5.8 million and $5.8 million, respectively, of interest expense related to $300 million of 7.50% senior unsecured notes due 2021 (the "SemGroup Notes") including the amortization of debt issuance costs.

SemGroup corporate revolving credit facility

At March 31, 2016, we had $70.0 million of outstanding cash borrowings on our $500 million revolving credit facility of which $40.0 million incurred interest at the alternate base rate ("ABR") and $30.0 million incurred interest at the Eurodollar rate. The interest rate in effect at March 31, 2016 on ABR borrowings was 4.50%. The interest rate in effect at March 31, 2016 on Eurodollar rate borrowings was 2.62%.

At March 31, 2016, we had outstanding letters of credit under the facility of $5.3 million, for which the rate in effect was 2.0%.

We incurred interest expense related to the SemGroup revolving credit facility of $1.4 million and $1.0 million for the three months ended March 31, 2016 and 2015, respectively, including amortization of debt issuance costs.

Rose Rock senior unsecured notes due 2022

At March 31, 2016, Rose Rock had outstanding $400 million of 5.625% senior unsecured notes due 2022 (the "Rose Rock 2022 Notes"). For the three months ended March 31, 2016 and 2015, we incurred $5.9 million and $5.8 million, respectively, of interest expense related to the Rose Rock 2022 Notes including amortization of debt issuance costs.

Rose Rock senior unsecured notes due 2023

At March 31, 2016, Rose Rock had $350 million of 5.625% senior unsecured notes due 2023 (the “Rose Rock 2023 Notes”), which were issued on May 14, 2015. For the three months ended March 31, 2016, we incurred $5.2 million of interest expense related to the Rose Rock 2023 Notes including amortization of debt issuance costs.

Rose Rock revolving credit facility

At March 31, 2016, Rose Rock had $24.0 million of outstanding cash borrowings under the $585 million Rose Rock revolving credit facility, which incurred interest at the ABR rate. At March 31, 2016, the interest rate in effect on ABR borrowings was 5.0%.

At March 31, 2016, Rose Rock had $33.4 million in outstanding letters of credit, and the rate in effect was 2.50%.

Rose Rock had $33.5 million of secured bilateral letters of credit outstanding at March 31, 2016. The interest rate in effect was 1.75%. Secured bilateral letters of credit are external to the facility and do not reduce availability for borrowing on the revolving credit facility.

We incurred $1.5 million and $2.3 million of interest expense related to this facility during the three months ended March 31, 2016 and 2015, respectively, including letters of credit and amortization of debt issuance costs.

SemMexico revolving credit facility

At March 31, 2016, SemMexico had a $100 million Mexican pesos (U.S. $5.8 million at the March 31, 2016 exchange rate) revolving credit facility, which matures in May 2018. There were no outstanding borrowings on the facility at March 31, 2016. Borrowings are unsecured and bear interest at the bank prime rate in Mexico plus 1.50%.

At March 31, 2016, SemMexico had an outstanding letter of credit of $292.8 million Mexican pesos (U.S. $17.0 million at the March 31, 2016 exchange rate). The letter of credit was issued for a fee of 0.25%.

Capitalized interest

During the three months ended March 31, 2016 and 2015, we capitalized interest of $0.8 million and $0.3 million, respectively.

Fair value

We estimate the fair value of the SemGroup Notes, the Rose Rock 2022 Notes and the Rose Rock 2023 Notes to be $242 million, $270 million and $228 million, respectively, at March 31, 2016, based on unadjusted, transacted market prices near the measurement date, which are categorized as Level 2 measurements. We estimate that the fair value of our revolving long-term debt was not materially different than the reported values at March 31, 2016, and is categorized as a Level 2 measurement. It is our belief that neither the market interest rates nor our credit profile have changed significantly enough to have had a material impact on the fair value of our revolving debt outstanding at March 31, 2016.