IMCO General Construction 3/16/2020 Change Order 3

Project: WPCF Chlorination Building Upgrade Change Order No. 03 Change Order Effective Date: February 25,2020 New Added Item: New Item No. 12: Differing Site Conditions at Outfall Manhole. Create new item#12 entitled, "Differing Site Conditions at Outfall Manhole", in the agreed lump sum price of$200,317.43, resulting in a Contract price increase of$200,317.43. The net result of modifying the seven (7)each existing bid items and adding one(1)new item#12 results in a Contract price increase of$11,077.43. JUSTIFICATION: Bid Item No.01:At the outfall manhole,the per plan piling were not installed due to differing site conditions noted in new Bid Item No.12.The Contract documents called for a test pile to be installed at the outfall as well. Since the piling were not installed the test pile was not needed.This decreased the quantity of test piles needed for the project. Bid Item No.02 and No.03:The City's Geotechnical Engineer analyzed the data from the test piles installed under the future Chlorination Building and future generator pad. Because the piling achieved the required penetration resistance at a shallower depth than expected, our Engineer recommended shortening the length of the per plan piling.This decreased the quantity of 16%:" diameter piling needed for the project. Bid Item No.04 and No.05:The City's Geotechnical Engineer analyzed the data from the test piles installed under the future box culvert. Because the piling achieved the required penetration resistance at a shallower depth than expected, our Engineer recommended shortening the length of the per plan piling. At the outfall, the piling were not installed due to the differing site conditions. This decreased the quantity of 18" diameter piling needed for the project. Bid Item No.06 and No.07:The permanent sheet pile wall was extended approximately 9-feet on the west end of the wall.This was done to avoid having a sharp drop off adjacent to the west end of the wall.This increased the quantity of sheet piling needed for the project. New Item No.12:As part of the Chlorination Building Project a new outfall manhole was constructed adjacent to the Snohomish River. In order to shore the excavation for the manhole,the City's Contractor chose a shoring system that froze the ground around the excavation. The Contractor chose this shoring system based on the geotechnical report and borings provided by the City's design engineers.The report and borings indicated soils that were favorable for a freeze shoring system. During monitoring of the freeze shoring, it was observed the freeze wall was forming in the upper section of the future excavation but not the lower section.The freeze wall was not forming because groundwater from the Snohomish River was infiltrating the lower section of the Page 4 of 5