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Engineering Review Page 4 April 16, 2003 Century Farms North (1st -6th Additions) 3. Stormwater System - Plan Sheets 01, G2 and G1A through G1D: A. Stipulations set forth by the Rice Creek Watershed District (RCWD) permit application review /approval process shall be met, including wetland issues. It is our understanding that the Developer has submitted a review application to RCWD. It will be important for the Developer's Engineer to keep the Lino Lakes City Engineer updated as the review process with RCWD progresses. Ultimately, the City will review the approved RCWD permit to determine if the City's requirements are met. The Developer's Engineer has claimed through analysis that water levels in a wetland in Outlot C cannot support the delineated vegetation. They are requesting that the wetland area be reduced by fifty (50) percent. It is the LGU's (RCWD) responsibility to resolve this issue with the Developer's Engineer. Resolution of this issue could involve City Staff input. B. The overall routing of storm drainage from the development area must be in conformance with the City's Comprehensive Drainage Plan, and the Rice Creek Watershed District. The project area falls within the realm of the County Ditch 10 drainage sub - watershed system boundaries and ultimately drains to Marshan Lake. All drainage must continue to perpetuate from the site in accordance with the Comprehensive Drainage Plan. C. There are concerns regarding the proposed depths of the stormwater ponds in relation to groundwater elevations. The geotechnical evaluation provided indicated that the range of groundwater elevations is in the 891 to 893 range. Many of the proposed stormwater pond bottom elevations would be lower than the range of groundwater elevations. Thus, stormwater capacity will potentially be reduced significantly, and there would be other issues with regards to excavating below groundwater levels. D. In general, the City does not allow storm sewer pipes or inlets to be less than 15 inches in diameter. The Developer's Engineer should make the changes necessary to the proposed storm sewer conveyance system and inlet structures to comply with this City requirement. E. Proposed storm sewer outlet and inlet invert elevations are incomplete; elevations are shown in some locations but not others. The plans shall be updated with this information accordingly, and be further reviewed by RCWD as part of the Watershed application/review. F. Permanent easements with access availability will be required for all stormwater ponds and conveyance systems not located within the public right -of -ways. G. Drainage calculations have been submitted and the following comments are provided: 1. Existing drainage area and proposed drainage area maps need to be submitted. Drainage area maps should be labeled to match the model. 2. Pond outlet details area needed. This information is also needed to verify the pond information in the HydroCAD model.