When it Rains it....
In older neighborhoods in Portland, OR, a series of pipes have been serving the residents by collecting both sewage and storm-water. The problem is that these pipes are designed to overflow when they have reached capacity. When this happens, as it does about 100 times each year, a mixture of sewage and storm-water flow straight into the Willamette River. With the completion of the 22ft wide, 6 mile long underground "Big Pipe" designed to collect overflow for treatment, things are looking better for the Willamette River. The number of yearly overflows should now be reduced to 5 times each year.
Portland is not unique in their struggle with sewage and storm water. As cities like Portland seek the economic benefits of increased urbanization, the increase in population density will also increase storm-water. A combination of infrastructural improvements and storm-water conscious architecture are necessary to make these cities sustainable.