Review Mass Grading Concepts and Import Policy for The COR

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.  In addition, there has been considerable discussion about the characteristics of this pond as it relates to the expected features such as fountains, livestock, and other recreational uses.

Finally, 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, their testing, and placement on the site.

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. There were two forebays contemplated in the new pond that provide the required pre-treatment anticipated for the development, however, the possibility to do additional treatment at each location remains an option to be considered at each site plan review. This is consistent with the current review process in The COR.

The open discussion items for the committee include the following:

Depth of Lake Ramsey - it is currently anticipated that the proposed pond would have an average depth of approximately 15 feet. This is adequate to provide a considerable amount of fill to offset the shortfall, but could be further excavated to support livestock and generate additional material.

Policy for Import of Materials - Based on the findings of the grading analysis, it appears that the proposed site will be approximately 50,000 - 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.  Based on the direction of the committee, staff would like to develop a policy for the import of materials that includes direction on pricing, placement locations, materials, testing, access, and erosion control measures. A final fill placement plan would be prepared from this direction.

Funding for the Landform work to date, to complete the mass grading plan and cut/fill analysis, was funded through the HRA.  Funding to import material to the COR for the implementation of the mass grading plan will be discussed and developed as part of the policy discussion.

Staff recommends the committee consider the draft analysis prepared by Landform, and consider the items above.  Based on discussion, provide direction to staff to prepare a proposed policy on the import of materials and present to the committee at a future date.

Based upon discussion.