The Lake Oswego Interceptor Sewer’s buoyant sewer line is a prime example of state-of-the-art design and technology. AAC participated in both main phases of the LOIS Project. As the marine subcontractor on the Lake Down phase, AAC’s work included four design/build packages: a wind and wave anchor system; a free end pipe restraint system; tether bracket stand; and lowering the sewer pipe for barge crossings.
The wind wave anchors and free end restraint system included placing 3.4 million pounds of concrete anchor blocks in precise locations along the length of the lake. This system prevented movement of the buoyant interceptor during the 24-foot lake drawdown. The 15 tether brackets stands were designed and installed to prevent shallower sections of sewer pipe from grounding during the drawdown.
With the lake down and locations exposed, AAC cut and welded 300 pile caps where the interceptor transitions from water to land. AAC installed the pile long, in water, during the previous Lake Full phase. AAC also completed the final interceptor pipe survey and grading at all 428 pipe tethers.
· Second phase of LOIS Project.
· Marine support role.
· Marine welding package.
· Design/build wind and wave anchor package.
· Design/build tether bracket stands.
· Design/build pipe end restraints.
· Design/build lowered sewer pipe for barge crossing.
· GPS barge navigation and existing structure avoidance.
· Final buoyant pipe grading.