1982-01-05 Septic System Design Report

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EVDO ..iI,•'I.O L,T ._ TO: Jeanne A. Mabusth, Zoning Administrator FROM: Michael P. Gaffron, Septic 0 stem Inspector DATE: January 5, 1982 SUBJECT: Ringer Subdivision, North Willow Drive #615 su-mary: All proposed lots were found to have Nigh water tables, necessitating the use of mound systems. Percolation rates in the upper soil profile generally were suitable for mound systems, with slower rates found in deeper test holes. Slopes on tiv, entire site are fairly level and suited for mound systems. This report will consist of: a) a short review of each lot of the prcposed 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 rianage.,,ent plan. The Ringer subdivision is perhaps the most extensive development in Orono to da that will require all mound systems. A. Ringer Subdivision A preliminary review of the Hennepin County Soil Survey indicated Pxtersnive areas of Cordova silty clay loam and Shorewood silty clay loam as well as Leseur lo,m would be found at this site. Thesc soile all would be expected to have a seasonal water table or saturation zone between 1 and 3 i,:et below the surfar:. During the course of the soils investigation, Imet with the site evaluator, Carl Borg, and realtor Graydon McCulley on the site. We made a Loring which definitely indicated these high water table soils were present. I Ater confirmed with Dr. James L. Anderson of the University of ;-;innesota Soils Extension Department that mound systems would be.appropriate for these soil types. These are much the same soils as round in the McAina- florningside area, which experience conventic,.,al trench septic system failures duff to the so4l conditions. In cjoneral, the loamy topsoil characteristics for the Ringer property are suitable for proper functioning of ftandard preaszure-mound se,)t`_c systems as per Orono's Code and Dsr_sign Manual. For cl.arity's sake I nave la`3eled the northern m, st 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 PBll thru PS16. Borings BB11 thru BB13. -,-erage perc rates for both primary and alternate sites are acceptable. Slopes are quite level. Saturation indications (mottling) started at 1.7 ti 2.5 feet. Actual water rible at 5-7' depth. A mound system should be used due to th,: presence of shallow saturation zones.