This paper details the challenges associated with the design and construction of a “figure-eight” shaped, or dual cell shaft through soft ground and sedimentary rock for the Northeast Interceptor Sewer project in Los Angeles. The Humboldt Street Shaft was excavated as two cells, using a combination of both reinforced and un-reinforced concrete diaphragm walls. The Contractor chose to construct the diaphragm panels to full depth, using a Hydrofraise rather than sinking them only to the top of rock, thus eliminating the need for conventional rock support with shotcrete and ribs or dowels. This method of construction is unusual for sedimentary rock. The two cells varied in diameter and excavated depth, as each served a different purpose. The 21-m-diameter cell was excavated to a depth of 41 m to support tunneling operations and to allow construction of a junction drop structure and maintenance hole. The 12.5-m-diameter cell was only excavated to a depth of 19 m, allowing the construction of a stub-out connection to a future sewer. Other notable aspects of shaft construction included the use of rock anchors through the partition wall below the shallow cell and the use of weep holes through the shaft walls below the top of rock.