A detention basin is a dug out area designed to collect rainwater from roofs and parking lots and hold it for awhile after storms. Usually they are designed without thought to their potential as wildlife habitat, and are planted with high-maintenance turf. When located at a high school, it sounds like a place where water is told to go when it's been bad.
This basin was converted to a wetland, planted with native species and informally stocked with native frogs, fish and possibly a turtle. It is fed by an eternal spring, which is the romantic name I'm giving to the sump pump that sends groundwater from the school basement into the wetland every twenty minutes or so, year-round, rain or shine. The steady water supply allows a greater variety of native wetland species to prosper.
After two years and some t.l.c. from teacher Tim Anderson, his students, myself and others, the native plants have become well established. An early bloomer is the marsh marigold. This showy native species is difficult or impossible to find growing in the wild in Princeton, but flourishes in this constructed wetland. (Frequently mistaken for marsh marigold is the bright yellow flower that has colonized many local floodplains--an invasive exotic plant called Lesser Celandine--see April 27, 2007 post.)
The blooms of a species of willow planted in the ecolab wetland were a pleasant surprise. Though native, willow tends to be an aggressive grower that may need to be controlled to allow other species to coexist.
This spring, a pair of mallards showed up, and seemed to give serious consideration to breeding there.