03-16-1992 Planning Packet - Laserfiche WebLink

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•. - f. Vfr. ^yA :« Zoning Pile #1721 March 12, 1992 Page 4 Septic m Please review Exhibit F. Weckman confirms that all septic systems meet the required setback from Tanager Lake (100' structure, 75* septic) and Browns Bay wetland (26* structure and 75' septic). Septic systems all test out for mound design. The 20' setback from proposed lot lines can be met by each of the sites. The City will require that the septic areas on Lots 3, 4 and 5 be staked prior to any lot grading or road construction activities. It shall be necessary to provide permanent staking and fencing for the septic areas on Lots 2 and 5. The private drives to each of the proposed residence sites will travel close to the septic areas. Because there is no other suitable area for septic sites on these lots, it will be necessary to protect the proposed test sites. . ^ _ The City will also ask that a swale be installed along the shared lot lines of 3 and 4 takes drainage to Tanager Lake. The swale will drain low seasonal retention area very close to the septic test site on Lot 3. r’. Gradinq/Drainaqe/Wetland •13, ^ V ■ All wetland areas shall be designated as drainage easements on the plat; Tanager Lake at 929.4, Browns Day wetland at 932.3, wetland to the north of Lot 1 ac the 932.3 and wetlands within Lots 2 and 3 at the 933.3. Drainage easement shall be taken over drainageway that extends from low retention area to Browns Bay wetland under proposed private roadbed. It is this wetland that shall retain the majority of run-off from developed lots and road hardcover. m ■ "■» ' ■■ -4! U‘ In early discussions with Ron Quanbeck of the Minnehaha Creek Watershed District, based on the hydraulic information and elevations taken on March 9th (since Cook report of 3/6/92), we have concurred that the 932.3 elevation is acceptable as the OHWL for the Browns Bay wetland. Review Exhibit H, the culvert under the railroad track, the outlet at the south side was found to be at 926.95. The invert at the north side was not detected but it is assumed there is no more than a foot of difference at approximately 927.94. The culvert is lower than the elevation of Lake Minnetonka at a 929.4 OHWL. Browns Bay wetland is directly Influenced by the lake level of Lake Minnetonka. Quanbeck says that the Lake level right now is at 930 and that the OHWL of the wetland would be approximated at 1' above tne lake level of Lake Minnetonka so the 932.3 is a very generous calling on the part of the applicant's engineer. It should also be noted that the original 933.8 elevation of the tracks of the railroad would not be the control elevation because the surveyor has also located a ditch that drains along the north side of the railroad to the west (Tanager Lake) at the 933 elevation. The Public Works Department has partially • I m kni. i '•m •■r .U ¥