8.1. SR 02-01-2021 - Laserfiche WebLink

Home Browse Search

\\wsbgvfiles01\projects\015125-000\Admin\Construction Admin\Additional Excavation01222021.docx 701 XENIA AVENUE S | SUITE 300 | MINNEAPOLIS, MN | 55416 | 763.541.4800 | WSBENG.COM Memorandum To: Brandon Wisner, City of Elk River From: Pete Willenbring, P.E., WSB Date: January 22, 2021 Re: Lake Orono Improvement Project WSB Project No. 015125-000 As provided for in the Plans and Specifications for the LORE project, a lake bottom survey was undertaken immediately prior to the commencement of dredging for the purpose of developing updated and jointly agreed upon pre-excavation elevations with the contractor that will be used to compute amount of material removed once the excavation is completed. This survey was undertaken as a collaborative effort with New Look Contracting in 2021. The recent survey found that lake bottom elevations were almost always within plus or minus 2 inches of the previous 2019 survey, however more elevations were found to be higher than lower. Given the soft conditions on the lake bottom and opportunity for more sediment to accumulate since the last survey, these elevations are well within survey tolerances, and to some extent an increase and or deviation from the previous survey was expected. The updated survey information was used to compute an updated estimated quantity of material that would need to be removed to achieve the water depths proposed in the plan. These computations indicate that because the lake bottom has more areas that are slightly higher than previously surveyed, approximately 5,000 yards of additional material will need to be removed in the various areas to meet desired water depths. This compares to a previous estimate of 125,000 yards. In addition, because the contractor’s equipment cannot excavate to an exact depth, and our specifications require a minimum depth excavation, it is possible the contractor may over- excavate a few inches, which could further increase the quantity of material removed. Based on the above, our best estimate is to now anticipate between 130,000 and 150,000 yards of material will be removed from the lake as part of the project, and unless other direction is provided to the contractor, estimate the total construction cost to come in between $2,175,000 and $2,400,000. If you have any questions, please feel free to contact me at 612.360.1288.