Approve Preparation and Submittal of Stormwater Management Plan for The COR

In October of 2004, the Polaris Group prepared and submitted a Stromwater Management Plan for Ramsey Town Center on behalf of the original developer.  This plan was ultimately approved by the city, and the LRRWMO and has been to working model for all stormwater facilities in and around The COR.  As the HRA is aware, there have been considerable changes to the plan since this approval. This study was based on previous plans prepared by the city's consultant that outlined a number of assumptions for areas outside The COR, but were routed through The COR effecting the stormwater design considerably.  There are a number of assumptions in these studies that have contributed dramatically to the oversizing of stormwater improvements in the area.  

In 2011, Landform prepared an earthwork analysis and preliminary stormwater design based on the new approved development plan.  In this effort, the concerns about off-site contributions and pipe sizing were raised, and the issue was identified for future resolution.

Essentially, the previous studies contemplated large areas of development north and northwest of The COR that would be developed at a very high percentage of impervious area (commercial or high density residential) with no stormwater management on-site to treat the run-off. The result was a dramatic increase in pipe sizes throughout The COR to carry this water, and a dramatic increase in the treatment facilities inside The COR to treat that runoff.  

This issue was again raised in the spring of 2012 when the North Commons area was designed.  The residential subdivision required approval from LRRWMO, and could not meet current Generation 3 plan requirements. The result of this effort was a solution that best addressed current requirements, with the existing infrastructure we were dealing with. We received approval on this project based on a modified set of requirements. Sarah Strommen, as the LRRWMO representative, presented the case to the WMO. 

In September of 2012 the Sunwood Retail Area was submitted to the WMO for approval.  The first round of comments back indicated they had an expectation that projects in The COR meet the current requirements, rather than the previous requirements approved with the original project.  In THIS instance, we were able to meet the current requirements with some relatively simple modifications, but the question was raised as to what the effect of the current plan requirements would be on the existing and future infrastructure in The COR.  Again, Sarah Strommen presented the HRA's case at WMO and indicated that we could meet the current requirements on this project, but that we would need to present a new overall study, based on the existing approved plan, and any new criteria we could easily incorporate.  We were given approval of the Sunwood Retail project, and we indicated we would present a new plan for their consideration in November.  Once approved, this plan would become the basis for all approvals in The COR going forward.

Based on the previous work completed as part of the overall grading plan and hydrology, and on the modifications to the assumptions for off-site contributions, a new drainage study needs to be completed and presented to the LRRWMO for approval. This study will identify all previous studies and designs, incorporate and document all assumptions, and provide direction as to the requirements for all future sites and public improvements in The COR.  This plan will be presented and ultimately approved by the LRRWMO, and will be their basis for their future reviews and approvals.

Attached to the case is a proposal for the fees necessary to complete the study and get WMO approval.

The development team recommends the HRA authorize the work necessary to complete the proposed stormwater management plan for The COR, and direct the development team to submit the plan for approval to the LRRWMO.

HRA Professional Services Budget & City Stormwater Utility Fund

Approve the proposal to prepare the stormwater management plan for The COR, and submit for approval at the LRRWMO at the next practical meeting.