Yes, it’s possible. However going from economics to engineering would be odd, and you may find yourself starting out way behind your classmates. Most engineering grad students are coming in with engineering degrees, or sometimes math or science degrees, and already have a strong background in math and science, as well as engineering courses. The typical environmental engineering bachelors would include 3-4 Calculus courses, physics, 2-3 chemistry courses, economics (lucky you), statistics, mechanics, and several courses specific to aspects of civil and environmental engineering. That’s your competition. If you don’t have a math/science background you may not get admitted, and also may end up spending your first year in remedial courses if you are admitted. Not to discourage you. It would be useful to contact the environmental engineering department at any colleges you are considering, and explain your situation, and find out what they would recommend.