HomeMy WebLinkAbout1988-03-29 Septic System EvaluationTo: Street File - 888 Dakota Avenue oil
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From: Michael P. Gaffron, Asst Planning & Zoning Administrator
Date: March 29, 1988
Subject: Proposed Repairs to Septic System
This afternoon I met with Jerry Johnson, Steve Schirmers and property
owner Dave Woodward on the site to discuss the various possibilit-es for
repairing Mr. Woodwards's septic system, which is currently failing.
Because this is an extremely small lot, it is impossible to re -,lace the
existing system within the confines of minimum code requirements.
Schirmers has completed a site evaluation of the site, including
percolation tests and borings, and has indicated that due to a heavy clay
layer there is a high seasonal wat _ table ioL:ated at 18-24" as evidenced
by mottling.
Based on prior discussions with me and based on the existance of a
loam to sandy -loam layer underlying '_he clay loam, 3chirmers Proposed a
pressurized bed system which would remove the heavier clay layers and add
sand and rock, essentially being a mound system constructed below existing
grade level.
Septic system installer Jerry Johnson is proposing to constr•..ct a
normal, above grade mound sys"em in the same location, basing his pronosal
on the idea that there is a iairly deep layer of good loam top soil that
would accept effluent, and that although the mound system might be smaller
in size than would normally be required (due to the small lot area
-vailable), he feels that would be the most workable system.
Schirmers' proposal eliminates the concern about a clay pan layec that
.ffluent hp,,- to go through, but does not account for potential seasonal
water table problems that may exist below the clay layer but are not
confirmable, and does not account for any continuity of the sander layers
Below the clay pan that might outlet along the hillside to the :south and
..test. Schirmers' proposal also negates any future possibil=ty of a
secondary site for a mound to be located over the trenches, since tha soil
would be disturbed.
On the other hand, a mound system placed on the site and meeting at
least a minimum 5' setback from the lot line, 50' setback from neighboring
wells, and 10' setback from the house would .iot have the necessary 2,500
s.f. of basal area required to treat 600 gallons per day (for a 4 i.edroom
home), using the allowable loading rate of 0.24 gallons per day per s.f. as
shown in the P.C.A. Design Manual. Johnson's mound proposal would probably
have no more than 2,000 s.f. of basal area which would presumably handle
somewhat less than 500 gallons per day.
The other factor to take into account is that this is a 4 bedroom home
with only 4 occupants currently, although the design late is for 2 people
per bedroom or 8 people for this house, and 600 gallons er day, the actual
usage may be somewhat less in actuality.
888 Dakota Avenue
March 29, 1988
Page 2 of 2
Neither design technically meets all code requirements, and it is my
opinion that there is no system that can be designed for this site that
fully meet all requirem^nts. Given the acknowledgement by all parties
present on the site that there is a difference of opinion that would have
to be settled by the City inspector, it is my opinion that a mound system
was the most appropriate .' the two potential repair methods, from the
standpoint that the proposals seem to have an equal potential for success,
using a mound initially preserves the future possibility of installing a
trench or pressurized bed system later on if for some reason the mound
failed in the future. This would not be the case if the pressurized bed or
trench system was initially installed, which would disrupt the soil
structure and eliminate any future chance for a mound system.
This system was approved by me with the knowledge of all parties
present that the system will not technically meet all code standards but is
the best system under the circumstances. The property owner is advised to
remove the water softner from the system, and c»* down on water use as much
as is feasible.