Pasadena engineering firm Tetra Tech on Wednesday announced significantly lower net income despite higher revenue in the company’s third-quarter.

Net income was $20.6 million (33 cents per share), compared with $31.0 million (51 cents) in the third quarter of 2009. Revenue was $562 million, a 2 percent gain from last year’s $551 million.

Chairman Dan Batrack said in a statement the company’s performance was driven by strong demand for consulting and engineering services by the federal government.

In addition, Batrack announced Tetra Tech will acquire “a Canadian consulting and engineering firm with about $100 million in annual revenue.” He said the acquisition should close in August.

Prior to the announcement of the quarterly results, Tetra Tech’s stock closed at $18.96, down 2 percent or 46 cents for the day. In after hours trading, the stock gained 9 cents to trade at $19.05.