HomeMy WebLinkAbout1982-01-05 Septic System Design ReportI
EXHIC31T
TO: Jeanne A. Mabusth, Zoning Administrator
I FROM: Michael P. Gaffron, Septic System Inspector
DATE: January 5, 1982
SUBJECT: Ringer Subdivision, North Will(jw 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 mound systems,
with slower rates found in deeper test holes. Slopes on tho 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,ineluding
how and why fihey 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 below the surface.
During the course of the soils investigation, I met with the site
evaluator, Carl Borg, and realtor.Graydon McCulley on the
site. We made a boring which definitely indicated these high
water table soils were present. I later 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-
Morningside 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 saturr 11
zones.