02-17-26 City Council Meeting Packet

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Site Design and Development Standards The individual home sites appear to be able to meet residential home area, parking, and anticipate other applicable zoning requirements. The Developer proposes wastewater treatment through individual private septic systems. A minimum of 10,000 sq ft of suitable soils is required for primary/alternate drain field locations on the residential lots. The Developer has reviewed proposed sites with Washington County Public Health and Environment, including soil testing of the proposed areas and concluded that the lots appear to have at least 10,000 sq ft of suitable soil to support a SSTS on each lot. However, in order to ensure that each SSTS is designed and constructed for maximize service life to provide long-term sustainable wastewater management, the site layout for each lot must be required to maintain minimum vertical and horizontal separation from existing wetlands, and proposed stormwater BMPs and drainageways. Should premature SSTS failures occur, extension of public sanitary sewer to this proposed 18 lot subdivision will be cost prohibitive. • Both Washington County and Lake Elmo have standards that require SSTS systems to be a minimum of 75-feet from wetlands, 10-ft from property lines and 20-ft from building structures. Washinton County Standards also require the 75-foot separation from all other unclassified water bodies including ponds and drainageways, however that County has indicated that their definition of unclassified water bodies only applies to naturally occurring features, even though the standard definition does not make this distinction. • The City design standards require a minimum separation of 35-feet between stormwater BMPs and building foundations to avoid seepage into foundation drain tile systems. • The City and Minnesota Stormwater manual require infiltration basins to be a minimum of 35-feet from septic systems. It is strongly recommended that a 35-ft separation from all stormwater BMPs, including wet ponds, infiltration basins and drainage swales be established as a minimum separation with additional separation required as determined by the City Engineer on a case-by-case basis, in particular if the water body feature is at or above the SSTS soil absorption elevation. • The City Engineer also recommends that wet ponds should be lined using synthetic pond liners when the NWL and HWL pond elevations exceed adjacent lot elevations and building pads. • For the location of SSTS systems the developer must also incorporate minimum lot grading as part of the subdivision improvements to ensure that overland drainage is not allowed to encroach the SSTS locations and that the required drainage pattern changes to not impact adjacent properties. There are 5 stormwater ponds and two filtration basins for stormwater shown on the concept plan. Per City design standards , public owned and maintained stormwater BMPs must be located on Outlots which are deeded to the City of Lake Elmo. The stormwater management plan shown on the Concept will also require revisions to comply with City, State and VBWD design standards, Existing condition information showing off-site building low floor and low opening elevations and existing SSTS system locations will be required up to a distance of 150-feet from all subdivision boundaries (as required for preliminary plat submittal) to allow for City review of the grading and stormwater management plans. The developer has already initiated stormwater plan revisions which will continue through the development design as the application moves through the processes. For this particular site, there are specific concerns to be addressed regarding the stormwater basin outfall discharge locations and potential impacts to adjacent existing properties. Stormwater maintenance access will also need improvements prior to acceptance of the preliminary plat. Site Access and Transportation