MISSOULA – It’s one of Missoula’s largest urban forests you may not have noticed before — 100,000 hybrid poplar trees located on a 180-acre site just off Mullan Road near the wastewater treatment plant. …In a few years, they’ll be harvested and sold as sawlogs and then replanted. It’s a peaceful place that’s doing more than just providing habitat and a future source of income for the city. The trees are also helping to save the Clark Fork River by using what’s called effluent water to grow the trees. “We do this primarily to take nutrients: phosphorous and nitrogen out of the river and land apply it and grow trees. We’re taking 20-to-25 percent of our discharge to the river and putting it on our trees in the summer…when the algae season is and want to keep algae out of the Clark Fork River,” said wastewater plane supervisor Starr Sullivan.