As Council may recall, the 2001 Reclaimed Water System Expansion - Phase 2 Project included the extension of the City's reclaimed water system south to Gulf High School, sidewalk improvements, landscaping and the installation of four corner nodes at the Madison Street bridge. These four nodes were constructed as free standing structures, consisting of a gravel base, wall block, mortar, compacted soil and a concrete cap.
Subsequent to staffs inspection of the Madison Street Bridge, it was determined that several voids existed under the sidewalk area at the bridge nodes on the S.E., N.E., and N.W. corners. Further investigation identified vertical and horizontal gap enlargements between the bridge and free standing nodes. These types of defects suggested movement of the nodes caused by river tides and stormwater eroding the soil between the nodes and the bridge. The engineer's commendation for corrective action calls out for poly injection as to stabilize the soil by filling in the gaps and eliminating the possibility of stormwater erosion between the bridge and the nodes. This type of technology has been used to stabilize roadways, sewer lift stations, manholes, seawalls, building retaining walls, and building slabs. In this case the proposed repairs would be similar to a seawall repair where erosion has caused gaps behind the structure.