Title
Linn Avenue Sewer Moratorium Project Closeout
Body
RECOMMENDED ACTION (Motion):
Authorize the City Manager to execute contract amendment(s) for the Linn Avenue Sewer Improvements Project for an additional $78,533.13 establishing a final total contract amount of $632,796.13.
BACKGROUND
In September, 2016, the City entered into a $404,263 public improvement construction contract with Interlaken Construction to complete the Linn Avenue Sewer Improvements Project. This work included 1,055 lineal feet of trench excavation and new pipe, 4 manholes and 4 service lines along with all the other miscellaneous and associated sewer work. Construction of the work is complete and has sense eliminated building restrictions on this previously identified sanitary sewer moratorium flow-constrained area.
As previously reported, in early October 2016 the Contractor started encountering unanticipated ground conditions much different than articulated in our bid package which was based on four geotechnical borings. The main difference was several large (3-5 cubic yard) boulders found within the trench and manhole excavations at depths between three to twelve feet. The excavation work was further complicated by loose or soft surrounding soils, an unmapped, abandon and conflicting 12 inch water line, and the historic concrete panels that made up the old County Market Road. These unanticipated conditions resulted in a change of conditions beyond the contractor’s control. These differing trench conditions forced the City to direct the Contractor to close Linn Avenue, mobilize a larger excavator and a dedicated track mounted rock breaker. The conditions of the surrounding soil varied greatly, including very loose material which often gave way as boulders were removed, undermining the adjacent pavement and resulting in a much wider than anticipated trench. In a few cases, boulders fell from the trench sidewall and damaged exposed utility service lines.
Throughout the proje...
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