Lowell-based engineering, consulting and construction management services firm TRC Cos. has completed $15.5 million in private placement of convertible preferred stock.

TRC said it plans to use the gross proceeds of the private placement for general corporate purposes, reducing the use of its revolving debt facility for working capital, and to support capitalization and net-worth requirements necessary to secure project bonding capacity.

Eighteen months from the closing, and subject to prior shareholder approval, each of the 7,209 shares of preferred stock will automatically convert into 1,000 shares of common stock, the company said in a statement.

In addition, as part of the transaction, the maturity of the $5 million loan agreement with Federal Partners L.P., due to mature July 19, was extended until July 12, 2012 on its current terms, the firm said.

TRC said it also "added an amendment to its revolving credit agreement with Wells Fargo Foothill Inc. that revised several terms in the facility including borrowing rates and spreads, letter of credit issuance capacity, and EBITDA covenants as well as temporarily reducing the maximum revolver amount subject to WFF completing a syndication to replace a former additional lender."