07/11/2007 P&Z Packet - Laserfiche WebLink

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TKDA • ENGINEERS • ARCHITECTS • PLANNERS MEMORANDUM To: Thomas D. Prew, P.E. Reference: Moon Marsh 444 Cedar Street Suite 1500 Saint Paul, MN 55101 -2140 (651) 292-4400 (651) 292-0083 Fax www.tkda.com Copies To: James E. Studenski, P.E. Drainage Review City of Lino Lakes, Minnesota From: Connie J. Tail Ion, P.E. Proj. No.: 13810.002 Date: July 3, 2007 Routing: The following drainage review is based on these submittals: 1. Moon Marsh Preliminary Grading, Drainage, and Erosion Control Plans, and Storm Water Pollution Prevention Plan submitted by Hult & Associates, Inc., dated October 4, 2006. 2. Moon Marsh Drainage Report submitted by Hult & Associates, Inc., dated January 2007. New comments are in bold and identify items that need to be addressed. The following are significant issues that must be addressed prior to preliminary plat approval: 1. Submit a geotechnical report summarizing the seasonal high water mark which is identified as the mottled soils or highest anticipated waxer table. The lowest floor elevation is required to be 4 feet above the seasonal high waxer mark. It appears from the percolation report that mottled soils have been encountered in the test area between 12" to 20" below the ground surface. 06/19/07 The Geotechnical Report indicates that groundwater was found in the vicinity of 886± to 888.5 ±. The report goes on to state that `it is unlikely that this investigation has found groundwater at its highest leveL Most likely, maximum groundwater on the site is equivalent to the ordinary high water level (not short term flood level) of the vicinity wetland'. A seasonal high water mark has not been identified in the report and will need to be submitted. Based on the groundwater levels determined in the Geotechnical Report, Lots 1 and 2, Block 1, does not meet the City's minimum low floor requirement as stated in comment 1 above. 2. The filtration areas may not be feasible due to the presence of mottled soils near the surface which indicates high ground water levels. Groundwater could affect the efficiency of these systems. 3. Submit existing and proposed watershed maps and label each subwatershed so that the map corresponds with the HydroCAD model. 06/19/07 This item has been addressed. 4. Identify the location and elevation of the outlet and emergency overflow for all wetlands. Low openings are required to be a minimum of 1 foot above the emergency overflow elevation. 06/19/07 It appears that the emergency overflow for wetland No. 1, at the north end of the site, is located at the low point of the proposed road at station 19+00. The new overflow created by the construction of the road appears to be at a higher elevation than the overflow elevation for this wetland under existing conditions. Identify the overland emergency overflow