Tetra Tech Inc. on Tuesday said it has acquired a large Canadian scientific and engineering services firm for an undisclosed amount.

The Pasadena engineering company said that BPR, based in Quebec, has more than 1,600 employees and generated about $170 million in revenue in the last 12 months. BPR is expected to contribute 3 cents to 5 cents per share to Tetra Tech’s fiscal 2011 earnings.

The deal is Tetra Tech’s third major Canadian acquisition, following its purchases of EBA Engineering Consultants in August and Wardrop Engineering in January 2009. Tetra Tech now has about 3,500 employees working in Canada. An estimated 25 percent of the company’s fiscal 2011 net revenue is expected to be generated from international operations.

“Like Tetra Tech, BPR leads with science and focuses on complex water-related projects,” said Chief Executive Dan Batrack in a statement. “With the addition of BPR in eastern Canada, Tetra Tech now offers its Canadian clients complete coast-to-coast coverage.”

Shares were up 50 cents, or 2.4 percent, to $21.18 in midday trading on the Nasdaq.