Ken Bradbury (left) and Bob Nauta (right) at Big Spring in Fitchburg.

The GAC group looks into the spring-fed retention pond for the fish hatchery.

The GAC group at Big Spring. The light sandy areas underwater show where the springs well up to the surface.

Close up view of three spots where water is coming to the surface at different flow rates.

The group explores Nursery Spring, a larger spring than Big Spring with a flow of about one cubic foot per second.

Bob Nauta (center in blue) discusses features of Nursery Spring.

Closeup view of the flow out of Nursery Spring.