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MEMORANDUM
TO: Board of Directors, Lake County Sanitation District (LACOSAN)
FROM: Jan Coppinger, Special Districts Administrator
DATE: November 7, 2017
SUBJECT: (Sitting as the Lake County Sanitation District, Board of Directors) - Consideration of Change Order No. 1 for the Southeast Regional Wastewater Treatment Plant Headworks Improvement Project, Bid No. 15-08
EXECUTIVE SUMMARY: The plans specified a 10' diameter pre-cast structure for the grit chamber as part of the improvement at the headworks. The slab for this wet well structure was permitted in Addendum No. 2 to be a 13'-10" circular structure. However, when the contractor submitted shop drawings for the structure the design engineer required a square base for stability purposes. The design engineer further required the square base to be of one piece instead of a two piece design. This requirement was due to concerns about potential seepage through the joint line as well as an increased potential for differential settlement of the structure. The District in agreement with the design engineer decided against the two piece design and required a one piece, square slab for the structure to ensure the best water tight and stable structure for the project. This resulted in additional materials casting costs of $1,300, additional wide load trucking costs of $4,300 and additional crane costs of $5,400. To enhance the water-tightness of the precast structure the design engineer required that the wet well structure be coated with a two-part epoxy at a cost of $2,500. These measures resulted in an additional cost of $13,500 related to the wet well.
Plans and specifications allowed for the use of select native back fill around the wet well structure. During construction it was determined that the native backfill contained too high of a clay content and was potentially too expansive. The contractor was required to import 122 tons of Class 2 Aggregate Base at a cost of $2,424.14. Th...
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