March 2015 - Technical investigation completed in two western drainage districts

The geotechnical investigation is completed in the two western drainage districts (Peninsula Drainage District #1 – PEN 1 – and Peninsula Drainage District #2 – PEN 2) and findings are presented to the Levee Ready Columbia partners. Findings include that:

• The railroad embankment on the western end of PEN 1, the location of the initial failure that led to the Vanport flood in 1948, remains an area of concern. Unfortunately, consultants were not able to collect soil samples or conduct analysis at this location because they were not permitted access to the land by the railroad. The information that is available indicates that the embankment does not meet modern soil stability or water seepage standards.
• There are two low spots on the PEN 1 cross levee near the I-5/Marine Drive interchange.
• The PEN 2 cross levee is too narrow, and the walls are too steep. The level of water in the canal is also too low, which can cause stability issues and result in erosion, which can cause failure.
• A low spot was also identified on vacant Port of Portland property in the northeastern part of PEN 2.

These finding represent an important first step in understanding the safety and resiliency of the levee system. A lot of work remains to be done.