7.	Long-Term Debt

Long-term debt consisted of the following:

		December 31, 2016					December 31, 2015
(In thousands)	Maturity Date	Amount Outstanding			Interest Rate		Amount Outstanding			Interest Rate
TDC
Senior secured notes - $25.0 million	December 30, 2020	$	17,500			8.50%	$	18,750			8.50%
SDTS
Senior secured notes - $60.0 million	June 20, 2018		60,000			5.04%		60,000			5.04%
Senior secured notes - $400.0 million	December 3, 2025		400,000			3.86%		400,000			3.86%
Senior secured notes - $100.0 million	January 14, 2026		100,000			3.86%		—		N/A
Senior secured notes - $53.5 million	December 30, 2029		42,600			7.25%		44,512			7.25%
Senior secured notes - $110.0 million	September 30, 2030		97,366			6.47%		101,627			6.47%
Total SDTS debt			699,966					606,139
Total long-term debt			717,466					624,889
Less unamortized deferred financing costs			(129	)				(161	)
Total long-term debt, less deferred financing costs			717,337					624,728
Less current portion of long-term debt			(7,849	)				(7,423	)
Debt classified as long-term debt, less deferred financing costs		$	709,488				$	617,305

In 2010, TDC issued $25.0 million aggregate principal amount of 8.50% per annum senior secured notes to The Prudential Insurance Company of America and affiliates (TDC Notes). Principal and interest on the TDC Notes are payable quarterly, and the TDC Notes are secured by the assets of, and InfraREIT LP’s equity interest in, TDC on materially the same basis as with lenders under InfraREIT LP’s revolving credit facility described above in Note 6, Borrowings Under Credit Facilities. In connection with the issuance of the TDC Notes, TDC incurred deferred financing costs which are shown as a reduction of the senior secured notes balance. The amount of unamortized deferred financing costs associated with the TDC Notes was $0.1 million and $0.2 million as of December 31, 2016 and 2015, respectively. These costs were reclassified from other assets to long-term debt, less deferred financing costs on the Consolidated Balance Sheets in accordance with new accounting guidance adopted January 1, 2016, see Note 1, Description of Business and Summary of Significant Accounting Policies.

In 2011, SPLLC entered into a construction term loan agreement and issued senior secured notes to The Prudential Insurance Company of America and affiliates (2011 Notes). The construction term loan was converted into a term loan with a balance of $407.0 million in 2014. After this conversion, interest accrued at LIBOR plus 2.25%. Interest under the term loan was payable the last day of the selected interest period for interest periods of three months or less, and every three months for interest periods greater than three months. Amortized principal amounts of the term loan were payable quarterly after the conversion. In 2015, the outstanding principal and interest on the term loan were paid in full with proceeds from the SDTS Series A Notes.

The 2011 Notes have a principal balance of $60.0 million which is due in full on June 20, 2018. Interest is payable quarterly at an interest rate of 5.04% per annum. The 2011 Notes do not provide for any principal payments until maturity. The 2011Notes were assumed by SDTS in connection with the SDTS Merger in 2015.

In December 2015, SDTS issued $400.0 million in 10 year senior secured notes, series A (Series A Notes), due December 3, 2025, and in January 2016 issued an additional $100.0 million in 10 year senior secured notes, series B (Series B Notes), due January 14, 2026. These senior secured notes were issued through a private placement conducted pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended (Securities Act) and bear interest at a rate of 3.86 % per annum, payable semi-annually. The Series A Notes are due at maturity with outstanding accrued interest payable each June and December. The Series B Notes are due at maturity with outstanding accrued interest payable each January and July.

In 2009, SDTS issued $53.5 million aggregate principal amount of 7.25% per annum senior secured notes to The Prudential Insurance Company of America and affiliates (2009 Notes). Principal and interest on these senior secured notes are payable quarterly.

In 2010, SDTS issued $110.0 million aggregate principal amount of 6.47% per annum senior secured notes to The Prudential Insurance Company of America (2010 Notes). Principal and interest on these senior secured notes are payable quarterly.

SDTS and TDC are entitled to prepay amounts outstanding under their senior secured notes, subject to a prepayment penalty equal to the excess of the discounted value of the remaining scheduled payments with respect to such notes over the amount of the prepaid notes.

The agreements governing the senior secured notes contain customary covenants, such as debt to capitalization ratios, debt service coverage ratios, limitation on liens, dispositions, mergers, entry into other lines of business, investments and the incurrence of additional indebtedness. The debt to capitalization ratios are calculated on a combined basis with Sharyland. SDTS’s Series A Notes and Series B Notes are not required to maintain a debt service coverage ratio. As of December 31, 2016 and 2015, SDTS and TDC were in compliance with all debt covenants under the applicable agreements.

SDTS’s Series A Notes, Series B Notes, 2009 Notes, 2010 Notes and 2011 Notes are secured by substantially all of SDTS’s T&D assets, the leases, certain accounts and TDC’s equity interests in SDTS on the same basis as SDTS’s revolving credit facility described above in Note 6, Borrowings Under Credit Facilities.

The senior secured notes of TDC and SDTS are subject to customary events of default. If an event of default occurs with respect to the notes and is continuing, the lenders may accelerate the applicable amounts due.

Future maturities of long-term debt are as follows for the years ending December 31:

(In thousands)	Total
2017	$	7,849
2018		68,305
2019		8,792
2020		21,813
2021		8,621
Thereafter		602,086
Total	$	717,466