1982-01-05 Septic System Design Report

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EX?N:0` iT _ _� TO: Jeanne A. Mabusth, Zoning Administrator FROM: Michael P. Gaffron, Septic System Inspector DATE: January 5, 1982 SUBJECT: Ringer Subdivision, North Willow Drive #615 Summary: All proposed lots were found to have high water tables, necessitating the use of mound systems. Percolation rates in the upper soil profile generally were suitable for :Hound systems, with slower rates found in deeper test holes. Slopes on them entire site are fairly level and suited for mound systems. This report will consist of: a) a short review of each lot of the proposed division and b) a discussion of mound systems,including how and why they work and their current and future use as part of Orono's land use management plan. The Ringer subdivision is perhaps the most extensive development in Orono to date that will require all mound systems. A. Ringer Subdivision A preliminary review of the Hennepin County Soil Survey indicated extensive areas of Cordova silty clay loam and Shorewood silty clay loam as well as Leseur loam would be found at this site. These soils all would be expected to have a seasonal water table or saturation zone between 1 and 3 feet bAlow the surface. During the course of the soils investigation, Imet with the site evaluator, Carl Borg, and r.ealtor Graydon McCulley on the site. We made a boring which definitely indicated these high water table soils were present. I Idter confirmed with Dr. James L. Anderson of the University of Minnesota Soils Extension Department that mound systems would be. appropriate for these soil types. These are much the same soils as found in the Medina-• Norningside area, which experience conventional trench septic system failures due to the soil conditions. In general, the loamy topsoil characteristics for the Ringer property are suitable for proper functioning of standard pressure -mound septic systems as per Orono's Code and Design Manual. For clarity's sake I have labeled the northern most tier cf seven lots as Block 1, the western group of six lots as Block 2, and the two lots to the southeast as Block 3. Lot 1, Block 1 Peres PB11 thru PB16. Borings BB11 thru BB13. Average perc rates for both primary and alternate sites are acceptable. Slopes are quite level. Saturation indications (mottling) started at 1.7 to 2.5 feet. Actual water table at 5-7' depth. A mound system should be used due to the presence of shallow saturation zones.