	2018			2017
Revolving credit facility	$	11,500		$	95,000
Notes payable		—			13,296
8% senior notes		321,950			321,057
Subtotal		333,450			429,353

Current portion of revolving credit facility		(11,500	)		—
Current portion of notes payable		—			(1,212	)
Total	$	321,950		$	428,141

On December 30, 2016, the Company, Great Lakes Dredge & Dock Company, LLC, NASDI Holdings, LLC, Great Lakes Dredge & Dock Environmental, Inc., Great Lakes Environmental & Infrastructure Solutions, LLC and Great Lakes Environmental & Infrastructure, LLC (collectively, the “Credit Parties”) entered into a revolving credit and security agreement, as subsequently amended, (the “Credit Agreement”) with certain financial institutions from time to time party thereto as lenders, PNC Bank, National Association, as Agent, PNC Capital Markets, CIBC Bank USA, Suntrust Robinson Humphrey, Inc., Capital One, National Association and Bank of America, N.A., as Joint Lead Arrangers and Joint Bookrunners, Texas Capital Bank, National Association, as Syndication Agent and Woodforest National Bank, as Documentation Agent. The Credit Agreement, which replaced the Company’s former revolving credit agreement, provides for a senior secured revolving credit facility in an aggregate principal amount of up to $250,000, subfacilities for the issuance of standby letters of credit up to a $250,000 sublimit and swingline loans up to a $25,000 sublimit. The maximum borrowing capacity under the Credit Agreement is determined by a formula and may fluctuate depending on the value of the collateral included in such formula at the time of determination. The Credit Agreement also includes an increase option that will allow the Company to increase the senior secured revolving credit facility by an aggregate principal amount of up to $100,000. This increase is subject to lenders providing incremental commitments for such increase, the Credit Parties having adequate borrowing capacity and provided that no default or event of default exists both before and after giving effect to such incremental commitment increase.

The Credit Agreement also provides for certain actions contemplated in the plan of restructuring with respect to the Company’s 2017 and 2018 fiscal years including allowing up to an aggregate of $20 million of expenses related to the buy-out of operating leases and allowing capital expenditures planned but not incurred by all Credit Parties in fiscal year 2017 to be carried forward to fiscal year 2018; provided that, the aggregate amount of all capital expenditures incurred by all Credit Parties in fiscal years 2017 and 2018 does not exceed $135 million. Additionally, the Credit Agreement contains acknowledgments and agreements from the Agent and the required lenders with respect to certain EBITDA add-backs for fiscal years 2017 and 2018 described therein.

The Credit Agreement contains customary representations and affirmative and negative covenants, including a springing financial covenant that requires the Credit Parties to maintain a fixed charge coverage ratio (ratio of earnings before income taxes, depreciation and amortization, net interest expenses, non-cash charges and losses and certain other non-recurring charges, minus capital expenditures, income and franchise taxes, to net cash interest expense plus scheduled cash principal payments with respect to debt plus restricted payments paid in cash) of not more than 1.10 to 1.00. The Company is required to maintain this ratio if its availability under the Credit Agreement falls below $31,250 for five consecutive days or $25,000 for one day. The Credit Parties are also restricted in the amount of capital expenditures they may make in each of the next three fiscal years. The Credit Agreement also contains customary events of default (including non-payment of principal or interest on any material debt and breaches of covenants) as well as events of default relating to certain actions by the Company’s surety bonding providers. The obligations of the Credit Parties under the Credit Agreement will be unconditionally guaranteed, on a joint and several basis, by each existing and subsequently acquired or formed material direct and indirect domestic subsidiary of the Company. Borrowings under the Credit Agreement have been or will be used to refinance existing indebtedness under the Company’s former revolving credit agreement, refinance existing indebtedness under the Company’s former term loan agreement, pay fees and expenses related to the Credit Agreement, finance acquisitions permitted under the Credit Agreement, finance ongoing working capital and for other general corporate purposes. The Credit Agreement matures on December 30, 2019.

The obligations under the Credit Agreement are secured by substantially all of the assets of the Credit Parties. The outstanding obligations thereunder shall be secured by a valid first priority perfected lien on substantially all of the vessels of the Credit Parties and a valid perfected lien on all domestic accounts receivable and substantially all other assets of the Credit Parties, subject to the permitted liens and interests of other parties (including the Company’s surety bonding provider).

Interest on the senior secured revolving credit facility of the Credit Agreement is equal to either a Base Rate option or LIBOR option, at the Company’s election. The Base Rate option is (1) the base commercial lending rate of PNC Bank, National Association, as publically announced plus (2)(a) an interest margin of 2.0% or (b) after the date on which a borrowing base certificate is required to be delivered under Section 9.2 of the Credit Agreement (commencing with the fiscal quarter ending December 31, 2017, the “Adjustment Date”), an interest margin ranging between 1.5% and 2.0% depending on the quarterly average undrawn availability on the senior secured revolving credit facility. The LIBOR option is the sum of (1) LIBOR and (2) (a) an interest margin of 3.0% or (b) after the Adjustment Date, an interest rate margin ranging between 2.5% to 3.0% per annum depending on the quarterly average undrawn availability on the senior secured revolving credit facility. The Credit Agreement is subject to an unused fee ranging from 0.25% to 0.375% per annum depending on the amount of average daily outstandings under the senior secured revolving credit facility.

As of December 31, 2018, the Company had $11,500 of borrowings on the revolver and $37,749 of letters of credit outstanding, resulting in $174,555 of availability under the Credit Agreement. The availability under the Credit Agreement is suppressed by $26,196 as of December 31, 2018 as a result of certain limitations set forth in the Credit Agreement.

In conjunction with the Credit Agreement entered into on December 30, 2016, the senior revolving credit agreement with an aggregate principal amount of up to $199,000 and the senior secured term loan facility consisting of a term loan in an aggregate principal amount of $50,000 was paid in full. Depending on the Company’s consolidated leverage ratio, previous borrowings under the revolving credit facility bore interest at the option of the Company at either a LIBOR rate plus a margin of between 1.50% to 2.50% per annum or a base rate plus a margin of between 0.50% to 1.50% per annum. The previous borrowings under the term loan facility bore interest at a fixed rate of 4.655% per annum.

The Company has outstanding $325,000 of 8.000% senior notes (“8% Senior Notes”) due May 15, 2022. In May 2017, the Company issued the 8% Senior Notes at 100% of face value resulting in net proceeds of $321,653, net of underwriting fees. In connection with the issuance of the 8% Senior Notes, the Company retired all of its $275,000 of 7.375% senior notes due February 2019 for $282,638, which included a tender premium and accrued and unpaid interest. The Company used the remaining net proceeds from the debt offering to reduce the Company’s indebtedness under its Credit Agreement.

The Company’s obligations under these Senior Notes are guaranteed by certain of the Company’s 100% owned domestic subsidiaries. Such guarantees are full, unconditional and joint and several. The parent company issuer has no independent assets or operations and all non-guarantor subsidiaries have been determined to be minor.

The Company enters into note arrangements to finance certain vessels and ancillary equipment. In February 2018, the Company completed a sale-leaseback of a vessel yielding net proceeds of $4,500. Included in this transaction was the retirement of the asset and related equipment note, and the transaction resulted in a deferred gain.

The scheduled principal payments through the maturity date of the Company’s long-term debt, excluding equipment notes and capital leases, at December 31, 2018, are as follows:

Years Ending December 31,
2019	$	11,500
2020		—
2021		—
2022		325,000
2023		—
Thereafter		—
Total	$	336,500

The Company incurred amortization of deferred financing fees for its long term debt of $3,504, $3,280 and $2,438 for each of the years ended December 31, 2018, 2017 and 2016. Such amortization is recorded as a component of interest expense.