HomeMy WebLinkAboutPermit Correspondence 1978-11-30Jack Q. Tomkins
Engineering Geologist
and
Soils Specialist
463O Larkwood Street
Eugene, Oregon 97405
(503) 343-5863
MEMORANDUM
TO:Mr. Dan Smith
City of Springfield
Public Works DePartment
346 Main Street
Springfield, Oregon 97477
SUBJECT:Water Seepag
River Hi1ls
Springfield,
e
Subdivision
Oregon
0n November 6, Lg78, I made f ield inspec-tion of p-ortion of footing excavation
for residence to be constrr"iua-on l,ot tlo. 118. HeIe- as welt as at other
sires in northern part of i;;;; *f,"i. cfiy lat;'.tt'a-U""o encountered' the
approved practice has beer-r to over-"*"tt'"|" f6oting trench to firm silt'
g;-avel or UeaiJ;k ;;a i"pf... maieriat e*ca.rated wlttr compacted pit run
E;;";i. No ,""prg" waters had been found'
This had been done during week of OctoPer 16' LgTS.without incident in case
of Lor Itro. 11g. Deprh to -.iii"-u"aio"r. ;";-ruo"r 4 feet. upon excava.ion
for cenrer posr foorings d#;;;;;;k-;i i;;;";ti so ' Ls78' seLpage developed
at clav-shale interface' Iftn6"-gf' seepage water.yl:,tot picked up in
earlier continuous footing i"''"6 excavaiion' reduction iir presg'1i" and
increase in permeability ,itt-fircement of pit run material could induce
flow from upslope when inside i'ost excavatibns were made'
Another factor is thaE Lot No. 11g is crose to east-west trending contact
rirre beEween ciay/shaie arld^'I iltTir"ar.r: -ii:-t is compe-retirzell'r fr:ee
draining ,or,.=!ii'ti;;-yryr; ;;;;' t; form a barrier to sround vrater move-
menr. Any "*Ilir.i;i,
;i"fol.;-Io i"t.,'f "oif change fiom clav to silt
would reduce barrier ot p.i-ned effect and encourage seepage'
similar footing excavations at rovrer-elevations to-Lot No. l1B encountered
no seepase. 'ilf;iI^;;;i;-i;ii".r.-1ack .;.;;;;"uiiit:' at ctavlshale contact
and supporr possibiliry "i-;;;;h.d grorrrd water on north flank of spur
knol1.
72r/
TO
Y " M^0 R A N D U r{Page 2
Mr. Dan SmithCity of SpringfieldPublic Works Department
Sowers, George B. and Sowers, George F.,
Introductory Soil- Mechanics & Founda.tions, 1970
Tomkins, J. Q., Engineering Geology and Soils Report,
River Hills, L977
!e9ga-ge water found at Lot No. f 18 though it appears to be perched orheld back from down-slope migration by Sgdv of'lfay, is p"rl-oi- locaffyderived and seasonally ieplenished ground water. Similai conditions willbe encountered at other hbme sites 5n north flank of spur knoll--ioh.r"elevation and soil type correspond.
RECOMMENDATIONS
Continued:
CONCLUSIONS
Perforated pipe and pea-gravel filler be placed in trench upslope toLot No. 1fB structure so as to intercept seepage vraters. -Depth shouldbe slightly below cLay/sha1e interface. Water should then be tarried bygravity in underground pipe to street location most feasible for catchbasin discharge into storm drain system.
Submitted: \ \ ,- { €.. .. ."/ t:
J*nz,i
a. Tomkins
REFEREI,ICES
cc:
cc:
John PickettE. H. Schaudt
O, TOil4KINS
OREGON
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Jack Q. Tomkins
Engineering Geologist
and
Soils Specidist
4630 Larl<utood Street
Eugene, Oregon 97405
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Mr. Dan SmithCity of Springfield
Public tJorks Department
346 Main StreetSpringfield, Oregon 97477
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