From the Valley Courier (Guinevere Nelson):
The Willow Creek Reclamation Committee (WCRC) was created to find solutions to these problems. To change the effects of historic mining practices, the committee needed to know how these metals interacted with water. To solve these problems, the committee takes water samples twice a year, coinciding with seasonal high and low flows.
Water samples are taken in two methods; the first method involves taking water directly from the stream to the bottle, the second method involves forcing water through a small (0.45 micron) filter. The WCRC is interested what this second, filtered, method indicates. The filtered sample takes larger undissolved molecules out and reveals molecules that are hooked to water and thereby biologically available to whatever may be swimming around in the creek. Through examination the committee has considered pH and heavy metals, fish and zinc, and the creek’s hydrology.
More Colorado Water 2012 coverage here.