07/29/2009 Env Bd Packet - Laserfiche WebLink

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• RCWD Permit Number 09 -048 16. HydroCAD Model Results dated 7 -1 -2009 and received 7 -2 -2009. 17. Upland Forest Floristic Assessment dated 7 -1 -2009 and received 7 -2 -2009. 18. Existing Conservation Easement Description dated 4 -23 -2004 and received 7 -2 -2009. 19. Existing Conservation Easement Map dated 6 -30 -2009 and received 7 -2 -2009. 20. Preliminary Plat for Eagle Brook Addition dated 10 -10 -2003 and received 7 -2 -2009. 21. Project Plan Set (Cover Sheet, Alignment Plan and Tabulation, Construction Plan, Grading and Strom Sewer Plan, Signing Striping and Lighting Plan, Construction Details (2 sheets), Planting Plan, Planting Details) dated 6 -12 -2009 and received 7 -2 -2009 22. Anoka County Conservation Easement Receipt of Recordings for Conservation Easement and Ponding and Flowage Easement dated 6-16 -2004 and received 7 -7 -2009. Findings: 1. Description — The 90± acre site is located in Lino Lakes. The applicant proposes to expand the existing parking facilities by 1.75± acres. The initial development of the site created 15± acres of impervious and was originally permitted in 2003. The site lies within RMP -3. 2. Stormwater — The project is located within RMP -3 and subject to the stormwater rules in Section 8. The rule requires the retention of runoff from a 2.3 -inch rainfall by infiltration practices if possible. If infiltration is not feasible the requirement must be met by bio- filtration or two -cell wetland treatment systems. RMP -3 also requires volume control for an additional 0.5- inches of runoff by measures specified by the following measures in 8(c): reestablishment of effectively drained wetlands and floodplain meadows, upland restoration /conservation, restoration of degraded wetlands, impervious disconnection, soil amendments /tilling. This requirement is subject to the conditions in RMP -3 9. The applicant proposes to provide an area of upland conservation located over an existing conservation easement in the southwest corner of the site. The existing conservation easement was voluntarily given to the RCWD in 2004 at the time of original site development to protect the natural resources and not to meet a requirement of the RCWD. According to RMP -3 9(b)(ii), upland restoration/conservation consists of high quality upland areas with a Natural Heritage ranking of "C" or better or restoration of Native Prairie, Woodlands or Forests. An assessment of the upland area Natural Heritage ranking provided by the applicant states that the proposed conservation area is a "C" ranking. According to Table in RMP -3, 0.85' of depth over the area will be given towards meeting the 0.5" volume requirement when using upland conservation. This results in a required conservation area of 1.05 acres. The applicant is proposing to convey 1.05 acres to upland conservation thereby meeting the requirements of RMP -3 8(c)b. The applicant proposes to treat the runoff from the new impervious area created under this permit by two new bio-filtration basins alongside the east and west side of the parking area, and by an existing bio - filtration basin adjacent to the new parking area. The new bio-filtration basins were designed to treat the volume from a 2.3 -inch rainfall meeting the requirements of RMP -3 b(i). Rules C.8(a)(1) and C.8(a)(2) require pretreatment and limit the drawdown time for infiltration basins respectively. The applicant is proposing bio - filtration as the form of treatment is not required to follow the design requirements in Rule C.8(a). However the bio - filtration basins will Houston Engineering Inc Page 3 of 4 7/16/2009