The last major portion of a $1.4-billion CSO system, the East Side Willamette River Combined Sewer Overflow (CSO) Project will help reduce current sewer and stormwater flows into the Willamette River and Columbia Slough by more than 94 percent. The East Side CSO will convey captured flows from Southeast Portland under the East Side Industrial Area to a CSO pump station on Swan Island. A 30,000-foot long, 22-foot finished inside diameter tunnel, ranging in depth from 100 to 160 feet, will function as a storage and conveyance conduit for the captured flows. The tunnel alignment will intercept a series of gravity conduits and drop structures that connect to 13 existing combined sewer outfalls. Eight 84-inch inside diameter reinforced concrete pipe microtunnel drives, totaling 6,450 linear feet, will divert flows from the existing outfalls to the main tunnel.