Agenda - Public Works Committee - 06/21/2011

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Public Works Committee 5. 3. Meeting Date: 06/21/2011 By: Tim Himmer, Engineering/Public Works Title: Consider Policy for Importing Material into the COR Background: In late 2010, the HRA authorized Landform to perform an extensive review of the grading, hydrology, and import policies for The COR. Over the last several years it has been assumed that the current site would require considerable fill to meet the proposed grades, and accordingly we have been accepting appropriate fill materials on -site in anticipation of that shortfall. The current development plan for The COR contemplates a considerable pond structure that will generate fill for the site, but it was unknown as to how much fill was necessary, and how much would be generated by this pond structure. Accordingly, the analysis needed to consider enough hydrological review to establish the pond volumes and determine the volume generated. It was the direction of the HRA to generate an import policy based on these design efforts, that would guide the procurement of import materials, testing, and placement. Notification: Observations: A mass grading concept design was completed based on Development Plan 5.02, and the hydrologic review of the subject site, as well as the anticipated inflow from outside the project borders. The grading contemplates a predominant commercial /retail use on the west side of the site, and accordingly provides pad elevations consistent with the proposed uses. With the exception of the proposed pond structure, there were no remarkable conditions encountered in the design. The design contemplates routing the majority of the remaining developable area through the new pond, then outletting to the existing system and eventually to the river. The attached cut/fill analysis was reviewed by the PW Committee on May 17, 2011, and like the HRA, staff was directed to develop a policy for accepting import material to execute the proposed final grading analysis. Based on the findings of the grading analysis, it appears that the proposed site will be approximately 100,000 cubic yards short of balancing. A deeper excavation of the new pond could offset that by approximately 50,000 yards which would still likely result in the need for additional material. Items to consider when developing this import policy include: • Pricing, which the Committee has stated should be free, but if we are unable to secure free clean fill we should have a process in place to consider acquiring material on a case -by -case basis. • Request a written proposal from anyone looking to provide material to the COR • Determine what City entity /governing body would be responsible to review and analyze such proposals • Request options for placement into a stockpile location and /or placed, compacted, etc. • Placement locations - where are the highest priority areas for development • Material types - do we accept all clean fill or limit it to existing site condition (primarily sand) • Are we interested in accepting topsoil, clays, peat, silts, etc.? • Testing • The City should be responsible for all compaction & placement testing services to ensure that the underlying soils are adequate to support the newly placed material (removal of buried organics, placed in appropriate lifts, acceptable densities, etc.) • The provider should be responsible to prove that the material is clean compactable fill, without restrictions