Agenda - Planning Commission - 05/01/2003

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I I I I I I I I I I I I I I I I I I subject to all of the provisions 0f that program, including reducing the discharge of pollutants to the "maximum extent practicable" (MEP) through construction site runoff control. Any construction on the site will also be permitted through MPCA's NPDES general construction permit process. Prior to any earth moving in the south east corner of the site, Burlington Northern Santa Fe Railroad should be contacted in regards to arsenic contaminated soils. A more detailed description of contamination and contact information is included in Item 20. Elements of erosion protection will include: phased construction with minimized periods of bare soil exposure, rapid re-vegetation, slope/grade stabilization, use of mulch and fabric on exposed soils, temporary and permanent (if needed) sediment basins, properly installed and maintained silt fencing, and adoption of a regular maintenance and inspection schedule. Item 17 Mitigation element.' The conversion of agriCultUial land to Urban land ultimately increases the amount and rate of runoff leaving the land. Minimizing the impact of that increased runoff is the objective of this mitigation plan. It must be stressed that this portion of Ramsey does not have a natural outlet to the Mississippi River. The preliminary drainage system described within this AUAR assumes an outlet that takes advantage of publicly-owned, County land that extends from Highway 10 to the Mississippi River south of the RTC site. Preliminary discussions with the County on the use of this land have occurred, but resolution has not been agreed upon. Advantages of using this land extend beyond the RTC site, to the entire sub- watershed, including the eventual upgrade of Highway 10, which will also need a River outlet. If permission cannot be obtained from the County to use its land, an outlet option will need to be pursued to the southeast, along Highway 10. The small amount of water that now leaves the site, runs southeast along the highway, but infiltrates within a short distance. Mitigation Approach The quantity and quality approach laid-out earlier in this section describes an approach driven by the need to comply with runoff control rules of the LRRWMO and water quality requirements that are described in the next section. The runoff management system proposed in Figure 17.2 is done in a preliminary sense to allow the City and the developer to proceed with some knowledge of what design specifics will be needed. The City will assure that the developer(s) will design and build the final drainage and runoff management system within this overall framework, in compliance with the mandates of the LRRWMO. Implementation of BMt~s in Preliminary Design A system of BMPs can be initially proposed to meet the needs identified in the Item 12 and 17 discussions. The first aspect of this design is the handling of the large-scale (100- D-II- 43