6.7. - 6.9. SR 09-20-1999 - Laserfiche WebLink

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. Mr. Scott Harlicker September 15, 1999 Page Three + The developers should verify whether or not a Corp of Engineers permit is necessary for any of the wetland issues on the project. C. Septic System Analysis . + City staff asked the developers to perform soil borings on selected lots to determine the suitability of the lots for septic systems. Ten lots were selected for this analysis. The developers hired Eco-Systems Engineers, Inc. of Elk River to perform this analysis. They performed soil borings on these 10 lots on September 1, 1999 and provided a written report summarizing the borings on September 2, 1999. The report indicates that 5 of the lots tested would require mound septic systems because of the seasonally high water table found on these lots. The report goes on to estimate that the area required for a mound drain field is approximately 3400 square feet. Therefore a primary and secondary location would require a total of 6800 square feet. There are several lots where it is questionable whether or not adequate space could be provided for the primary and secondary septic location assuming a mound system. We did a cursor review of the grading plan relative to this information and believe that it would be difficult to build two mound systems on Lot 8, Block 1 and also potentially on Lot 4, Block 3. Lot 7, Block 1 may also be difficult given the topography of the area available for septic systems proposed. On lots 10 and 11, Block 2 it will be virtually impossible to provide 6800 square feet for septic systems between the easement protecting the wetlands and the grading limits. Given this information, we would recommend that the developer go back and further analyze the lots to determine if there are any other ones requiring mound systems, then reevaluate the lot layout to ensure that the 6800 square feet can be provided on each lot requiring a mound system. This work should be done before any final plat is considered and these areas need to be identified and protected before any grading of the site has begun. + In lots where it is tight to provide two locations for a septic system the location of wells on the adjacent lots could also be an issue. The setback of a septic system from a deep well is required to be 50-feet. Well locations, where necessary, should be noted on the plans so that a well is not placed in a location which impacts the septic systems on an adjacent lot. D. Storm Drain Calculations + There are a number of storm sewer runs on the project which exceed the 1 a-feet per second maximum velocity. These would include: 1. CB 9 to CB 8 2. CB 8 to OL 1 3. CB 7 to OL 6 4. CB 25 to OL 26 These runs of storm sewer should be reevaluated to determine if the maximum velocity can be lowered to below 1 a-feet per second. . O:\PROJ\807640j\0240\640'1501.S~ward R. Green Company CONSULTING ENGINEERS