Agenda - Council - 01/27/2009 - Laserfiche WebLink

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CONSIDER CHANGE ORDER NO 1 AND PARTIAL PAY ESTIMATE NO 2 FOR ERMINE BOULEVARD CULVERT REPLACEMENT IP 06 -30 By: Steven J. Jankowski, City Engineer Background: The purpose of this project is twofold. It replaces a six foot diameter round concrete culvert which transmits flow from Trott Brook beneath Ermine Boulevard with a larger 6 foot by 14 foot box culvert. The existing culvert had open joints which was causing the loss of material from under the road bed. There were no culvert entrance or exit transitions which contributed to erosion, particularly downstream of the culvert. Secondly, the larger culvert will lower the upstream 100 year flood elevation. As a consequence a residence constructed in 1987 will no longer be within the floodplain. Since this project replaced an existing culvert it was anticipated that poor soils would have been removed when the existing culvert had been constructed in the early 1970's. However, organic soils unsuitable for a structural foundation were encountered up to eight feet below the bottom of the replacement culvert. As a result it was necessary to direct the Contractor, Dryden Excavating, to perform additional work to install this culvert. Change Order No 1 which is attached to this case is intended to compensate the contractor for this additional work. The major costs associated with this additional work included the removal of the unsuitable material and its replacement with good granular backfill beneath the base of the culvert. It was also necessary to dewater for this depth of excavation. Dewatering would not have been required for the original project which would have required only a two foot excavation beneath the bottom of the structure. Finally due to the wet fall preceding this project the flow through a temporary bypass culvert was greater than the 12 inch pipe specified could handle. As a result a larger 24 inch bypass pipe was needed. Staff has verified the quantities of fill and export material by reviewing trip tickets, hourly timesheets, and daily inspectors records. The cost of the larger pipe has been checked with material suppliers and the dewatering costs with local dewatering subcontractors. Financial Impact: This project is being financed through the storm water utility. The construction cost of this project had been estimated to be $153,000 prior to bidding. The construction cost of this contract including this change order revises the contract cost to $149,394.08, an B increase of$38,606. CASE # 3 —143—