HomeMy WebLinkAbout1994.12.21 - Soil Assessment for Stormwater Infiltration Potential('^'. "
sw)
1i54 P4lrzzi,
203 Fourth Arc.
Suitc
city olE3tl,o#P'nd
DEC a,l 1994Mr. Michael Hildt
Gitli' of Port Townsend
540 Water Sireet
Port Townsend, WA 98368
Decoube.r 15-, L994
Report, File N_unbejr:M94-01-51 - -.- rt
,!Report Subject: Soil d,ssessment for stornw-ater infiltration pot-ential ahd-' : de'sign linitation-s :related to pto*imity t-o wetlands. ,,
-. \ .
LocaLion Llmnesfield ?uD-subdivision, i-.t the city of port. Torrrnsend,south of 49 street and west of san Juan rAvenue, sout-hwest of -
-the fair.grounds, locared wirhin rhe SE L/4'of Section 34, :
Township 31N, Range l-W.
soils infornation was collected on the site on NovemberPaIazzi,- (ARCPACS cerrified soil sp-ecialisE) for purposeinfiltration potential and site septic system design.
The purpose 'of this report is to first describe-on-site soil characteristicsfor stormwater facility desigir, but dlso to comment on the 'effect -of phaiing -
on the adjaient wetlands, ".r- whether any particular phasing sequence^would"beexpected to have less impact on the -wetland functions and valuei. Althoughthe two iss'ues are somevrhat related, they will be addressed separately b.iowto minimize confusion. section r sill.describe the on:site soilcharacteristics that will affect stornwater management. Section fI sillbriefly describe the expected. effects of lhasing-on the adjacent wbtlands
29, L994 by Lisa -
s-cif site. storryater
r. SToRI{TJATER FACTLITY .SOrL CHanecrunisTlcs '
A. Proposal Background
The property is about 20 acres and is locat-ed about L/2 nILe south of 49th .sEreet and about L/2 nile west of san'Juan Avenue, southwest of thefairgrounds in the city of Port Townsend. - The site is cur-rently pr_oposed tobe subdivided into a total of 70 single fanily lots and s-evpral nutrL-fanityunits in nine distinct phase-g, displayed on tire attached ?hase Map. Tte - "
development will start with Phase A: installation of the on"r"il stoimvaterretention/detention facilities -and infrastructure for rhe entire 1-00 uniipro'jecE. Phase-B -- the mul.ti-famiLy complex diiectly west of the qtormwater
Ref€rerrccD
S o il A-: s c s g rn8 nt fo r S to rm\/'l6 E r I nf iltt:atio nPotendal af|d D€eign Ltmltc.tlon RclaGd toProxirrrity to \F/etlands
$ rgCuosud by tha Clty of Fort Tos,ryl'gcnd,Ocbbrr 24, Lgg4
Page 1
facility .-- will be constructed next, followed by single fanily dwellings androads for'Phases G and c. phases H and D will U" Uniir .t""d,-lorpletinldeveloprnent of Holcornb Street dnd constructing the 40th Street connectfonbetween Holconb and Jackrnan. Finally, Phas6s E and F will be Uufit. -ii'-f,
expected that this phasing will proceed at a rate of about 7-10 units peryear.
the'propos'edi'stormtrater plan -ls'desigoed "to conduct excess'stcilnwater" runoff ,
llon th9 entiSe slte. via grpss-11ned:qwa1eg., to the stgrmr6t'er;;";;;;io;-.,;-; '
/detentiof_nona feciility rin,t(re gor.!,treast. corper. Th; grass-lined';ii; ,provlde filtratlon treatnent to the water as it:'drains dorn the'swale. -The 'z,
stormwater pond provides for additional suspended sedirnent setulfng and jtreatment, then allorrs the treated itormwater tot elther inflltratejir,to th.soils or drain to a nearby surface hrater system. The intent of this'pl"r i"to maintain pre-development trydrology as much as possible after aevelopment.
The background conditions that govern site-specific design details are,
-
-relatively silnle. Any post-development changes in sitb groundwater andsurface water hydrology are related to the raie of surfacE runoff "".^
:
infiltration, and direction of flow -- both surface and subsurface. iteintent of most stornsater Eanagenenr plans is to slow down "r;;;;'tlJw-r"t"",and to get the surface water back into.the ground as quickly as possfUfe-ina-within the same drainage basin.i Those '"r""! that wili u" iilp"r.,rious .(such as-, roads and rooftops) or somewhat'less pervious following deveiopment (such asgrassed areas) tttill not allow rainwater to drain into the soil'-as *""tty po"t-development as^was Possible,pre-development. This effect creates greatervolunes of surface runoff, which drains to the bottom of the basin fasteracross the soil surface than it would within the soil. However, when thisexcess surface water is infiltrated on site or at least *iaii" ot" ""r.
--
drainage basin, the overall effect on basin gro,rndwat.r ;il;;i.gt-i"-rinor inthat the water eventually ends up where ir wouta have anlnuay, "ileit ;.r"tit""slightly sooner. rf it is inpossible to infilrrare all sroinwater due ;;----natural soil limitations, the ltater can be released to a nearby surfac"-r""",system at a rate that rnimics a minor storm.
This procedure for- treating runoff, then releasing the water either tpgroundwater through infiltration or to surface.r"i",r through controlledoverland flow is a standard throughout the.Pacific Northwelt,'and.has beenProven very bffective both at maxinizing w6ter quality and at ninickingnatural surface and subsurface hydrology functions at a basin level aiter sitedevelopment. Howeiver, the best way to nanage,storuwaper.and r""rri"b:;;;r;ii-site lnfilrrarion potential and.rrater qualiiy ,is.tg maintain "" ^r"t ot,li"--surface as possible. in vegetation, co infiltiate roof rr.rnoff "t ;;;h t"r.t-ifpossible, and to niirinize soil compaction. These efforts will niiniri""-it.-volume of water that xrust be processed through the stormmrater system.
As proposed, this site has areas of vegetated open space and trails in
/
addition to the storwater facility open space area. These areas allcontribute greatly toward naintaining as uiich of the original hydroi"gi"fi.ulctions as possible. The proposed retention/detentlon faclfity is Iocatedon-site, so maximizes onsite lnfiltration of runoff . Any.'surfacl release,,ofthe treated nrnoff will drain to an adJace4t wetland "y"i"r, a snall pgnd just
Page 2.
7
a
<t
(
t
I
t
F
I
F
fj
west of the site. ft is assumed that all.water will eventually diain
subsurface to the. Townsend Meadows-wetland, which generally defines the bottom
of this basin and so is the eventual natural recipient of all surface and
subsurface lateral flow.
B- Happed Soil Series Descriotions: \. .
Accoi:ding to the Jefferson County soil survey, the fol-lowing soiL series'is
mapped on or near the site: the Clallam gravelly sandy lo+nn, 0-L5Z'slopes ,'(classified as a loarny-skeletal, mixed, mesic Entic Durochreptr);.the San
Juan.graveily sandy l-oam, 0-82 slopes (classifidd.as coarse-.loany over iandy
or sandy. skeletal, mixed, nesic,-P""ti" Xerunbrep?); and'the Agielt silt 16an(classilied as a fine-silty, mixed, mesic Typic Ochraqualft).'-
The CLallarn is napped across the western majority .of the site. These.soils
are generelly expected to have a.,shallow confining cemented glacial layer at
2-4 ieeX that will re-strict vertical percolation-of soil.water to sone degree.
The San Juan is napped in a narroer strip along the far eastern portion"of the
site. Ttrgsq soils are expected to be deep, loamy sand soils'with high.potential for moderately'rapid infi.ltration of'stormwater with no confining
layer within"5 feet of the soil.surface. The Agnew is napped Just of-fsite to
. the east in a strip paralleting the San Juan series. These soils are often
associated with wetlands and are expected to have a relatively finb-textured
-.- surface horizon overlying.hbrd.compact glacial till at about 3 feet. Please' refer to the attached SCS Soil Survey Map for nore details on mapped soil
areas
For your information, standard characterfstics of the napped soil series are
described in more detail in APPENDIX II. Please note that the SCS soil series
maps and descriptions charactbfize expected characteristics in only the top
60-L00 inches of soil. Furthermore, the rnaps units can have extensive
inclusions of other soil types, and in some cases, can be entirely in error.
Please refer to the individual pit descriptions in APPENDIX I for specifics on
observed site soil conditions.
I Loarsy-skeletal, mi.:red, oesic Entic Durochrept, generally oeanlng tbe soll has olnlnal horizon deve'lopenB
(ept and enLic), has-a pale-colored, low base satulatlon sulface bori,zon (ochi), has.an sillcate-ceoeated
subsurface layer (dur), has a oesic teop€latule regioe (mean anqual t€rlP€latule langEs f,roo 8" to 15'C (47' -,
59'F), has no.spscific olneralogic soulce (nLxed), bertu!€'of, the f,ine fraction 1s loam and coarse''f,ratment
coateng 13 gleater than 35I (loauy-skeletal)..
,"-ri,g rhe soil n"" ,'r,!'.1'o"il.t"iff" "oli,'"r".il?"."i;?i: ,i""t:':h'::i*#11,1i11"i:"HP;Tf '.Tff';:::
satulatlon (uobt), has developed under climate conditions of we! etint€rs and droughty sumels lxer),.and bas
adeep (greator than 50 cui), dark-colored, surfacehorizon (pachic), has amesic teoltelatur€regine(rneanannual
tenpelature lantes froo 8'to 15.C (47. - 59" F), no specific oJ.neraloglc source (nixed), has 15-501 sand, less
fhan 181 clay, and possibly g!€aLeE than 351 coalse fratEents (coarse-loaoy over sandy or sandy tkeletal).
("r.y'r to,:."on aad ,"".rll"ii#l"ri l'J"""t'"lli::.1:1ti"1"r",:"Tit&"3ili'ittii"""".tT":::"".1t11"f ,T"i:tl*i:
wLthin 18 lnches of the soil surface (aqu), has a pale-colored, low base satulation (les! tban 50!).surface
holizon (ochr), is otber:nlse typical (cyplc), has-a oesic teoperatut€ lsgioe (oean aturuaL teuleratqre ranges
froo 8'to 15'C (47".- 59'F), no speciflc oineralogic source (nixed), and is tr€ats! than 181 clay and lEss than
151 sand (or coarser) by weight (finc-silty).-
Page 3
C. Observed Site Geonorphology and 'Soils
Topography naps (provided ty-lhe clienrj indicate that overall site relief isabout 85 feet. The lowest elevati'on area is located in the northeast corner:-- where the stormwater facility is proposed, as is appropriaie to. t"t " ro"tadvantage of the site's natulal'slope and drainage potential. The highest-elevation area is located along a ridge in about the center of the weit.rlboundary. There are two minor ridges and three associated minor.swales.iLttrend across the site from west (high) ro east (lbw) to form thr-ee'"r-,b.b"sii" 'within the site, arl draining:roward rhe Towns""a u""ao*"-*;ti;"Jt.;-ii""";;i., ,fn general , Phases A,. B, C, G, and the northern part of D lie within-the -:-"t.:..
northern basin; Phase's'8, and H, rhe southern p.ii or D and the';;;;; parti -.of F lie within the rniddle basin; and phases I- and the southerri part of F 1iewithin the southern basin
-A total of 5 soil pits were assessed: one pit in the area proposed forstormwatfr facility, three pits in the neadow on the eastern iart of the sitb(two in swale bases and one on e ridge), and one in the ror" "t""ply sloped,heavily forested area on the weitet,"portrorr" oe the site
Soils in the area proposed for 'stornwatgr facility -ar'e Agnew seriJsr with -
evidence of regularly saturated conditions to witirin 17 fnch6s ofr the surfacelThat is not unexPected due to froximity ro and mininal elevation diff";;;;;--'from a nearby snall oPenwater wetland. tti" pit was excavated in an area.with an approxinate surface elevation of 20 feet'. The open warer pona -J!" r"surveyed at aPproxinately L5-L8 feet elevat,ion, abour_ l-00 feet to the ea;;:- :-
The soils in the neadow are upslope variations of the Agnew serie5 in thatthey have sone relatively pbrneable surface soils, but ire underlain with ,-
impermeable lakebed sedinents with evidence of water perching "rJ ar"iii",laterally across the tops of those layers. As a resglt, it.,Ls expected -thatnatural subsurface'stormwater flow across the meador-is primarily-Iateral atdepths of around 2 feet on the average. As would b.;;d;;"J,-.ir. "oii"-ir,-the base of the minor swales have evidence of slightiy "h"llo*"r ""a,rt"iioi.At no location was there evidence of log-tern saturation to the surface.
The soils in the steeper fordsted area to the west. are the Clallam series. Inthe area evaluated,, the substrata below 36 inches was still the o1d lakebed
_sediments, inplying that the more gravelly surface soils were eith'er laid downlater, or that the sediments, observed were the edge of the old lakebed iriththe hillside being the old lake bank. rn either casb, there nas a "trifi"r--cemented layer on toP of the lakebed sediments that is expected t" b;-;;;ewhatrestrictive to vertical flow of qrater through the soil. itt" surface soils '
above the cenented. zone are coarse-textured and expected to percolatelaterally at higher rates than the soils observed in the r""do* below. Itshould be noted that as a rule, ih" cemented layer found under tt"-iypt""iclallam soil is not expected to be conpletely imperneable. There is .evidenc-eof that situation in this pit which has no rltrf"a or gleyed areas that wouldindicate long-duration wetness.
D. Sgmary and RecomerrdatiorisStormater pond area: Because the soils are so fine textured and haveevidence of shallow seasonal water, we recornrnend designing the stormpond as a
Page 4
permanenE wet Pond system wlth a controlled surface water release to eitherthe wetland to the east, or via a constructed stream channel:to Townsend'
Meadows weEland t.o the southeasu. InfiLtration i3 naturally very slow, sowill only account for an insignificant water loss,from the pond. The winferwater elevation in the adjacent pond can be used'to imply the long-terngroundwater elevation across this area.for purposes of design
Heados Soils: These soils harie a relatively low lubsurface perneability due -
to fine textured, platy substrata. Uie of drywel-Ls to infiltrate,roof rirnpffat each lot will reduce the total required-storage volume at the. retention :-..
/detention facility. But the'shallow, fine textured soils make.effective '
drywell design difficult. If drywells are used, 'care should be taken to kdep
them as shallow as possible and to place thern downslope from the foundation tominimize potential of flooding in crawl spaces
During gefieral housing and road construction, care should be taken to niiinizesoil eonpaction and surface soll disturbance: The meadow soils are very proneto compaction and s-ealing if driven.on when wet.- The grass-lined swales alongthe roads will have very little indidental infiltration due to rhe finetextured, layered substrata. l
Forested, Steep Soils: These soils have a relatively low subsurfaceperneability due Eo a strongly to weakly cemented glacial till at about 2 feet'.depth. High gravel content in the surface soils however nake these soilsrelatively perneable above the cemented zones with wacer moving laterallyacross the cemented surface. Shallorir dryvells could be used to infiltrateroof runoff at each lot with sizing based on expected lateral flow rates(generafly taken to be'about 1,/3 of the vertical flow rare)
During construcEion, care should be taken to nininize soil compaction andsurface disturbance. These soils will be less prone to compaction and sealingthan the meadow soil due to a higher coarse fragnent content, but the steeperslopes make them rnore likely.to erode when disturbed.
II. EKPECTED PHASING EFFEGTS OII IJETIAIID FT]NCTIONS AND VALI]ES
As described above, nine development phases are proposed starting withstornltater infrastructure and progressing across the site more or tress fron.northwest to southeast. Fron a regulatory framework, as the site and anyproposed- construction is well outside the- Townsend Meadow wetland buffer,there is no regulatory guidance to suggest a rnethod to assess impactsHowever, as any phasing will tend Eo have the effect of easing the developmentinto the natural system over time, the phasing its-self appears more importantthan any particular phasing sequence. From an ecosystem standpoint, there areseveral factors to consider when evaluating inpacts.
First, in terms of hydrologic inpacts, the proposed stornwater syrstem isexpected to function well in nininizing water quality impacts of the
development on the wetland. It is, simply stated, the standard method usgd inthe Puget Sound Region to manage erater quality and quanticy on newdevelopnent. Due to havlng a high amount of open space and trails, as long as
rage i
t
T
t.
the soils are not severely compacted during constructlon, the,lwater suantl-tveffects are also expected to be mininal .".rl or",rerateJ,t;,-tiii"g-9ffi*.pulses thah io total volumes. As the stormwater system is to be devel.oped inthe first phase, the vegetation that herps so muctr in inptoving wate;-gr;ilii;in the system is expected to be-well developed and estauii.strea'by the.tine thewhole project is complete -- a facror rhar irearly reduc;;-;Fr;i.;l-; iiil"i"=potential.
'.'",
Second, 'in terrns of habitat impacts, there will be inevitable chanebs.in,' i
access to the wetlands iby terrestrial wlldlife .across the site .f;ffi-;";I tg ' '.east. But as there is a larle undeveloped tract to the south,-,it'ib '.anticipated that the wildlife will 'rnove rhat direcrion as the'a".,r.ilprerrt \phasing proceeds to the south. Displacement of some wildlife habitat isinevitable, but the- adjacent properiy "titt provides for a wildlife corridorto the wetland. Most.current signs-of deer'passage "r" "ro"g-il;-";;il;.edge of fhe site wherg,tt"="*i!tin-g,vegetation provides trorg cgver qcross:thd.open meadow. Aside forn that, theie i! "o
-r".ei
"i"g"r"r-rirJiife corridoracross the.site at this tine.from vest to east. : .;.--- . -----t;l
rrnpacts to wildfowl habitat are expected to be minimal due to.distar,"" y'ro*. lthe wetland as well as due to the ilan ro rerain itr" ""i"ii;; R;;;-"np.."tl"u"and miscett"tsorr-s b-rush along the eastern site boundary aal'afent to it" - .-wetland. That slrrubby vegetation'will provide " .r"trrr"l sight ""J-"o,r.,a -:barrier' rf desired during site landscaptng, some taller native shrubs ortrees could be pranted a{jacent to the "ii"Iiog Rosa hedg" .o pro.ri;;-;"-;"""greater barrier -in the futrtrg.
Due to the fact that the Townsend Meadoss wetland is an already disturbedurban system' ind is. closely suriounded by the high school properties on two.sides, ,its original habitat functions and vaLue" "r" somewhat-iiri;i"t"i'.'-irr.it still functions moderately well as migratory and possible ndsting habif.tfor some duck species, and as hunting ha6itat ior.r"iious raptor species. Andas the shrub and tree vegetation is ie-established over tine, the wetland isexpected to provide resting and feeding habitat for a resident deerpopulation.
Those functions are expected to continue to a great degree after developmentof this site' Due to being well outside of the regulatory wetrand buffer, anddue to plans to at least miintain_and possibly upgrade barrier vegetation, to- effeclively treat stormlrater runoff,'and to n;inlii., hyarololic continuit5r;this development- are not expected to have great. inpact on the current wetlanilhydrolofic or habirat ffncrions and valuesl ---- . ----"'"
The above described order of the phased developnent over tine is not expectedto have a significant impact on any of tt" i""iors l,isrea-;;;r". The phasi'ggenerally starts farthest away fron the wetland and gradually moves toward it.The _relarively fes homes p.r ye"r planned together wfrh rhe iradualdevelopnent of the site wlll irave the leasr Iiscernable inpaft;; will allowsoils-, hydrology and habitat Eo slowly adjust and equilibrate over time ratherthan, having the large initial disturbance norrnally associated jrithdeveloprnents of this size . '
'I
Page 5
e e
detalL
r_ hope this reporr prbvides enough lirformatloi to proceed wlth proJecrplanning. PLease call lf you have any questlons or requlre lddltionalor clarification on any of the'se issueC. -
Thank You, --l
LLsa Pal,azzi
ARCPACS cerrified soil specialist -,Certiflcatlon /133L3 . .
Page 7
(
Pte 1
florLz
A1
Azb
Bcw
Clcs
C2cs
PLZ 2
Eoriz
A
B1
BCcs
CcH
Dpth
o-t2
t2-L7
t7-24
24-3L
3 1-78
Co1
toYRz/2" 2/L" 4/t
" 6/2
" 6/2
Txt
LFS
L
SL
GrSL
GTSiCL
Struc
t{'G
!I,'SAB
MS
MS
SMAB
Struc
tt1F
IttsAS
MS
$.tPr
APPENDIX I
Perc'
2-6'
2-6'
.2-.6'. '
0-0. 060'd
.2-.6t
Mott
0
0
FI.ID
-- MFD
G.{F :
CF
10
.10
10
15
15
Roots Z9
<10
-<1015
15i
25
!M
6..
10
4
3
<3
cu.6-4-
3
<3
!,tF
CF
rF
FF
FF
San Juan cap ov€r Agnew stlis.. Tbe surface 12 inches ls disturbed-soll th6t burids the orl8inal surface.
The flne soil fraction (less than 2 m diameter) is soo€erhit coalse-gertured to 31 lirches, but changes.-
abruptly to a platy silty clay loan subitrata -- old glacial lakebbd deposlts. Sofl colori iDdicaee that
tbe so1l is salurated for lonS du:atlons to 24 inches depth wlth periodic f,luctuation up.--to,l7-inches --.--
probably for a few days following extended rainfall events. Due to tbe shallow water tible ind low
peroeabillty iu the substrata, very littte v€Etical lnfiltraiiba is expecled at tbis locatioa. Eowever,
there will be sooe lateral inflltlalion in pond sidewalls thaL will percolate downslope across the top of
the Clcs horizon.. fL is recomended to design this 3ysteo as a w€g-pond ttith a controlled surface butlet *
reteaslng'at a rate eguat. to the 2 year storo either !o the wetland to the €ast, or tbrough a consiructed -.
str66n channql to tbe Towasend Meadows vt€tland. I
t
(sqale plt)
Doth Col0-9 rovRz/29-1s " 4/315-19 " 6/219-53 " 5/2
'T*t
L
L
L
sicl-
CF
10
10
5
5
Perc
2-6r .-
o.6-2'
0-0 .060.d
.2-.6''
Mott
-00
!l1D
It{F
Roots &
18
22
25
IIF
cr
FF
FF
- Ihe profile matches the Agnew description, but without the.evidenbe of seasonal saturatlon'[o the su.rface.
There ig a strongly cemented lay€r.at 15-19 j.nches (the BCcs layer) that apPears to rostricg vertical
-? p€acolagion. If ls likely Bo have foroed as a resulL of, water.percbing and diss6lving 3oi1 sedioents above' lhe dense sil! loao layer that st,alts at 19 inches and exgends to the bottom of, thE pit at 53'iuohes (the
Ccs_layer). Because tlre Ccs has very strong structure, water caD-Epve! thrc:Slt it to some degree along ped
facei,. onc€ it g€ta through the less permeable BCcs above. Orerall expectation ls tbat without creating a
break ln the BCcs, Eost water wlll perch and drain a1on6 its surfaca. Wtrere ihere are breaks in the BCcs,
either by root channels, natural results of soil €xpaaslon aDd coatlaction, o! by hr:nan effects (sucb as
plowing), the percbed wate! will drain bhrough an{ into the Ccs, DoviDg thrdugh-cracks.-..Ab sooe depth, it
ir.rqr."ted thlu the Ccs layer will beccoe effectively iraperneable ihere the lakeb6d sedlmeats have uot.been
effected sufflciently by.surface rreathering plocesses to develop the cracks and channels observed i.n thE-
mote shallow sedioents. Grerall flow patterns rpill be lateral toratd gbe bottoE of'the basln.
Pib 3 (serale pit)
Eoriz Dp!b- Sg! gI Txt SLruc Perc Mott Roots Cl't - re.
A O-11 10YR4,/4 20 GrL lttE 2-6t 0 MF 6 25
81 11-16 " 4/3 10 SiCL $4AB 2-6'. FFF CF 3 .28
BZ L6-28 ".5/2 O SiCL S'lPr 0.2-0"6i'' MFP FF 3 28
c 28-84 " 5/2 0 SiCL MS 0 . 06-0 .2''' FFF 0 - <3 .28
Again, siollar to the Agnew descriptlon, but without the evidencE of seasonal 3atulation to- the surface.
this plt ls lackiry the strongly ceoented layer observed in the ptevious pit, but has the lakebed sedi-Dents
within 1,1 inches of bhe soil surface. Due to strong soil siructute, the soj.ls drain rather well down to 28
inches. Eowever, below tha! depth in the C-horizon, the solls are very fine-lexgurqd..aad-oassive,'e-Itect€d
to be eff,ectlvely iryervious. Agaia, waber Bov€Eent will be lateral.through th€ top.28 inches of the so-il.
. The! superscripL nuober replasents the estinated single-ditib percolation rate for that particular soi-1.
pit hotlzoD.
Page 8
PIt 4 (ridgctoP pit)
Eoriz Dpth eg! SE I& Struc perc Mo.qE Roots C[,t re. A O-9 10yR3/3 20 GrL ! G. 2-6' 0 Ur S Zs81 9-16 " 4/3 2:5 GTSiCL Sl.rSAB ?-6' O CF 4 30.BCcs 16-28 2.5Y6'/2 .20 GTSiCL SFSAB 0.2:0.6o.r FFF 'FF 3. 30Clcs 28-33 " 5/2 O SiCL MS O . 06-0 .21,. - FFF FF <3 30c2 33-38 " 5/C 0 LFS MS,/SG 2-6.; O 'FF <3 <10c3cs 3g-60 .. s/2...o sicl Msi - o-0.66n.- o o <3 'zs',.. c4 60-72 " 5/s., 40 v9:Ls lrSl.SG 6;20- o 0 I., <3 :10 .. . \
I'i.:';':
I-ransillonal to the Clallan aeriea. .The suriace golls are agaln siliy ciay loan froo 9 incles ddrndio sc i
lnfhes with evldeate-of reitrictions to vertical vater dnrnlge. Eor-ever,. {rorr .A; a;i;-ert"-;.ii- --
becooes lavered wlth loary iand lenseg rnd incro.-lint auounLi-of "o.r."-ii.gt*ir riil al;ti. -ih;-;;chg arthe base of the pit ar€ lrregulariy-shaped, large'chu3&,s of,;granite aad baaaltr-- lihely-i9 uii".i".i ', --
glacially deposlted. fhe value of the layers is ltoiEed by their lsolatlon between..fftier texturld lensesitheir oinioal thLckness (6 lncbes and 12 incheg), and a related pot€ntlal to b€ dls.j,ntinubuc aor*"i"p.. '
Dpf,h
0:3
3-L2
L2-24
^24-3636-4gr
Col CProtR2/t s0" 5/6 402.5t5i3 50
". 7/3. . .10" 6./3 o'
Pis 5
Eoriz
A
B1
82cw
Clci
C2cs
Txt Struc - Perc
VGISL -\ l.*G 2-6' -VbrSL tl4SAB 2-6,
. VGTLF$- l,lS, i.. . 6-20"
-.LFS ufl 0.06-0.20.'sil .. Ms 0-0.06'.-
.'. Mott
0.
0
-0.0'
0
Roots 'eU
MF r ,.. 155w/cc 4cE/64 3
rFl4r - 3d <e.
Transilional to the CIaIlan geries. The-base of the plt fs strongty ceoent,aa lroo 24 taches dilrn. Eowever,the-subsoils ate nog severely mttldd, and are not 6,1eyed, rndrcatrng d"g tfr.-r"tii ai"r"" off fast enoughacross the ceoented sulface thaL anaerobia condltions do aot develop. thA stireace soils. have a very htgh.natural infiltragion rate'enhanced by the high organic iatger conteirt-and hig,h grdirel content. the-horizondirectly above the ceoented layer has the hlghest gravel content and ls erpected tq percolabe, evenlaterally, at relalively high rates.
Page 9
AGNEIJ SERTES
The Agnew silt loams are nodefately deep, sqmewhat poorl-y-drained soiLs forrned
in, shlllow glaciolacustrine sediments overlying llninat.ed glacial till. fftllg
soils .are oit"r, associated with wetLands. bgner"lJ.y, the upper- soils are +!1t
loams grading tb silty clay loans with depth. Mottling is expected at 3 ;
inches depth and gleying "i ! inches depth -- evidence,of qeas-oqal water - .- -
"fr""a tolth" "uri"cl for extended periods... Below aPProx. 30 inches (in the C
horizon), gravel content increases abruptly'.fron (5Z.in the surface soil.s to
between l-0 and 502 in'the subsoils. The lower horizons are highly laninated
and very hard glacial till
Average "itl p"t"olation rates in the uPPer 9 inches aie expected to be -
rnoderire. (O.6--2 inches per hour), decreasing to noderately slow (0.2-0.6
in.t"" p"i ttorrt) below i inches depth. . ' rt-'
The Agnew solls ar. gen"ially sultable for song croPs and,.e1s!ure wittr ttre'
main limitarion beinl seaional wetness (a perched water table) at. L2' to 24' inches depth.
APPENDIX II
-'. The rnain lirnitations for onsite septic and stormwater treatment are related to
both the mininal depth to the hardpan and seasonal wetne-ss. Soil water
percolating through chese 3oi1s will rnove laterally in the soil rather than
down. The, seaso.rit tig't water table and/or the shalLovr till layer limits the
arnotint of soil available to effectively treat,storxmrater or septic efflueirt-
f
{r
tl.
CIAIIAI.I SERIES
The Clal1am gravelly sandy loams are- moderately deep, well-drained soils
formed in glacial tillt they are usually found on uplands, slopes ranging
from 0-302. Ttre surface soils are generaLLy grayish-brown to dark grayish-
brown gravelly sandy loams. They have a weakly cemented glacial till layer at
2O-4O inches depth that will restrict vertical soil percolation to some
degree
Average soil permeability is expected to be moderatg (0.6-2 inches per hour)
above the cemented till and very sldw (less _than 0.06 inches Per hour) in the
till layer. A seasonal perched water table is not expected; the till in these
areas rnlst be more fractured. However, the soil is eiipected to be saturated
periodically during the rainy season and the majori.ty of soil water will
percolate laterally.
The Glallan soils originally developed under a forest, but more than half of
the mapped acreage has beerr cleared and is now used for pasture, garders, --orcharis and homesites. The primary linitations are related to shallow.soil
depths. Stormwarer w111 perc;late intq the soi-l readily in undisturbed'areas,
bui will move laterally across the tilL layer, surfacing in adjacent drainages
and low-lying areas. Septic system design will be linited by minimal soil
depths and fluctuating seasonal high water.
Page L0
SAII JITAN SERIES
..] '
.
The San Juan graveLly sandy lbans are very deep, "or"*li"t excessively drainedsoils forned in glacial- outwash. The surface soils are generally dar:k-coloredgravelly sandy loams. Soil texture becomes coarser with depth, grading to :
gravelly loany coarse san6 anf gravelly coarse sand. .
i":1 ;: ,Average soiL perneability-is expected ro be.rapid (6-20 lnches-per houp)throughouE. o '' -.-i -,- ?.:. .,1)r, , :-.' i --. .. -,, -1..' ,- : ,.The San Juan.soils are is -used forfarniland, hayland,'paiture, woodLand orhomesites with few linitaiiions. The primary linitation Cor sgpFic drainfieldsor stortrwater facilities'are related to poor filtering capaciiyldue to'rapiapercolation rates and rblatively low suriace area in iandy soiis. If housingdensity ir rnoderate -to high, conrnirnity seivage systems or alternatl-ve sep,gig. ''
deslgns are -reconrnended to reduce potential of water supply contamination by
I
t
li
_ seePage.
.v"
Page l-l-
APPEilDIX III
DEFINIIIONS
Colurrr Eeadinss:
Bor1z - horizon: tAlt rord refers to the horlzontal bandr ol soi.l tha! foro a! variour. dePths froo tbo rurfiio--- ." a retulb of eigher a.ccunulallon of organlc roaterlals or leachlug of clays.and jalts by rater- "A"
horizons generally have an accrluulatlon of organic oatellalc. '8" horlzons gencrally -h1ve an accuuihglon
of clay! o! lalgs. !iC" horlzonc ari geacraLly elth.r undl,flercntlated paieo! matarial.o! ale belc'thei
zone of, naJor btologlcal actlvlly. A coall l6tler'tollc1'ng-lhe capltal'letior,Provld€s-lddttIonglI infomatlos. '"Br'deicrtbes a "caoblc" oi barcly developcd B horlion;'A "qr",'cl'l or'"cL:f attofla D oi
; ;;illb.s a horizon rttb rcat ccoentattJ', -""-t;; ;;:;-tti;, and lndutatlon'riapootrvely. An'r!'- ait-qf\
a B.o! C lndlcatec tbit th.-bollzon ls-dminabed by Japroiyte,' wiicb ls rottcn tb*--- 1.t.'ibck thlt li :
"o-a"iorpot"dtbatltirlt.mrtcoll.. An'R"alt€raClndicatesbhaLtheChorizoa'Ic'predootuanilyhtld;l .
tmdecooposed bedrb6k. A "2'lin lrciot of a B or C borizon thdlcates that thc cubcoili'have a dlffjasii! "r'''.pareng iaterial thau the'overlylng soils.
l.\
Dpth - depth: glves gh. dlrtanca fro the surface for tbe top and bottoo of each horlzctn.
Col'color: tive3 a tfunsell Book color ctrip code. ttre l,trmsell color codes.(eraople:10tlR-3/4) tive.infoilatlon
on the h1fi (1OYR), value (3), and chrooa (4) of the cotl. Sofl color caa be ussd to lnf,cr paient Ertdii.l,
pelcent organic congout, or roil drainage characterlstlcs.' For example, aotlc riih both lorr chhma and
ialue {exaruple: 10YR 2/21 ixc vcry dark-colored aad bend to baveblgh organic natte! conteltt; sotlr wlth
a l.trmsell chtooa code of 2 or lcrs (exinph:.' LOYR ?/2, oay be poorly dralnad. '..r' : ., _,i, '- ...: ..
Ttre f,olloring value/chroc 'coloi coder
'correrpond to th9 lofforfng goll color nmel, tor thc tro -oost
.comnly u""d EttE Pates lOtR.and 2.5Y:
1OIR EIIE
COIXR, f,AHE YALI'E,/CENcIIA
2.5I EI'E
@IIR trAHE VAII'E/CERCHA
whlte
lighl gray
traydark Brayveiy dark Bray
bl ack
very pale brown
litht brosttiish gray
grayish brown
dark trayish brown
very dark graylsh brown
very dark brown
yellow
pale brorn
brown
dark brownllght yellowish btown
brownish yellow
yellordsh brown
dark yellowlsh brornr
8/3,8/4,7/3,7/4
6/?,
5/2
4/2
3/2
2/2
8/6.
613
5/3
4/?,
5/4
6/6,,
5/4,
1/4,
8/8,7/6,7/8
3/3
6iB5/6,5/s
4/6,-.3/h, 316
8/L, 8/27/L,7/26/t, slL
4/L
3/L.
2/L
rhitelltb! gray
traydart, gray
very, dark gray . a
black
pale'yellow
Itght' bgowniih gray
traylsh brocta
dark graylrh brown
very dark grayish brown
ltghb browalsh graY
graylsh brown
dark graylsh brown
very darl grryish brown
pale yellor
light yellowlih brown
light olive brown
ollve brorynyellor ..ollve ydllor
N8/, 8/2
N7/, 7/2
'N6/, ils/ ,
.N4/
N3/- I'\2/
8/4,7/4.6/2 :
slz
4/2
3/2
8/2
5/2-
4/2
3/28/1,7/4
6/4
5/4,3/6
4/48/6, 8/8, 7/6, 7/8
6/6. 6/8
1tt - tertule: descrlbar ghe.rclailve doolnance ln,size of sotl partlcles soaller tban 2 in dlaoeber. Sand,
s1lb, and clay arc the thtee slze cfaases with.sand being largedt and clay belng loallesb. The tcxtural
nages ale appllod baged oa lhe vofu.rue pslcantlto of, sand (S), sllt (St), and ctsy (C). Thc field estlmat€
of percen! sand, all! and clay are.gLvea eith th. te:tural naoe.
Cf ' pelcent coalsa fragncnrbr. Coarse frapenta are deflned aa aay olneral fragnent in.the soll greaber ttian
2m diameter. If, nccded, coa!3e fragrneuts ars also d€rcitibed ln lormc of varl,ous clze clacceg -- Srdvel,
cobble, .st'one, €gc. Abbr€viatl.onc assocl,ated rlth CF peraenta8cs will be: Co ' cobbly (coarce lra8to€nti
>3,,dj.aeate!), Cn - concr.tlon! (roall, round pebble-llke fragments fomed by soll olnerals dlssolvlag and
then re-prectpitrtin8). If no'abbrevlat,lon ls lncludcd, a3su!!€ that the pelceng CF ls. desciibtng grqvel.r
(coarge iragrolngg >2m and <3" ln diameter).
If coalse fla8p€31t coirten! lr exprceaed ac 15-35 perc.rit, tbo flne f,laclion (soll particlea lesc. tban 2 m
dlaoeter) texgulal call ls oodlflcd and deltned as.gravolly (1.e. travelly loan or gra-velly sllty clay);
35-65 percent is very gravalty; treater than 65 p.rc6nt lc deflned as extrortrely gravelly.
Struc - ltructuto: describcs the ahapc and *lze o! !h€ natulal goll clods. Soil with stlongi strtrctur€'ls
AppIII-1
tener.lly consid€red to be rtable and rell developed. Sollt that are period].cally dtstdrbed generally hariepoor lBructure. Flnc tertured solls wiih weak .rbructu!€ ofte?r have poor periolatlon capabtllgi€s.
Cl'l - percent organt'c oatte!- In oinetal solls, org,anic oatt.! dccreases rrlth diltance f.rm Lhc rotl ruriace.Lorr p€rcentages (3l or less) at ihe surf,ace can tndlcate iroalon problos. Iucrcasod liercentagec below thecurface can lndlcrte r borled surfacc (tftl on the iurfaca), Organic oalter liiprove* atructqro and'fertj'llty. Surface Otf, in olneral aol1s raages trm 4 to 20t. Wfreu c1fZ lr greatd'r tian 2Ol,'t6r siff r"y -
be clasclfied as rn ortrtrlc racber than nLaerlt soll. Thtc lr generally lndicatlve of, laturtt.d and/or cplicoadltloas in the roil.
_ . ;. - 1 \, - . ,. ::
a-
Root - rootlrt depth:.can be usad to lbcatc laycri In.tbi soll,that oay'restrtc.t bronthioi ratcr,novedentl.j
Hott - mttleg: alc an ladtcallon that the soll goer lbrou8h alt€rilrbing p..roi" or: ert,endad satur-at1on-and:.1:-drYtns'
iPcrc - Percol.gion rat6' . tte P€lcol.allon rate is .rt es.limaie o! Inchee per hour ratci percolattonlibrough the 'soil. The range ln percolation iages as devised by tbe scS are as follows:
- cl re.llci-lnrlar{ rnafi-r,41'^..- -.
Very slow
Slorr
Mod;iitely lloqt
Mciderate
Moderately rapld
Rapid
Very rapid
lqrr thur 0-06
0.b6-0.2
-0.2-o:6
0.6-2.O
2.0-6.0
6 .0-20
nora thnn'z0
The field oltlDato ls oade based on soil texturd; porc€nt.-coa!se fragpents, and otbdr soll f,eaturel, rucbas.ihdlcaglon of coo€nting and the p!€sence of aottles. -;' -:
fyPe - soll type: as defiucd in Article IV, Rules. and Regulattons of lhe Thureton Courity ,Board of EealthGove-rning Dlsposal-'of Serage (saue as St-ate definltlon). Thesc grouplngs are being revlewed and revlsedrt the SBate I-evel. lhe revlsed lype deflntfl6ns are e4rectid to be-out by'lale 1993. The current sol.lLylre ttoupiugs ale as fo9ows:
Soil .f extural Ciasstftcatldns
-Coarse rands or coalsar
-t{edfi.nu rand t ' '; '
-Fiue sand, loaoy sand
-Saudy loao, loam ..t
-Porous, well-devbloped structure ia slLt and iilt loans-Oth3r ailt loams, allty clay loaos, and clay loans'
Slullat t'o soll percolatLon rat. estlnates, the field typlng estloite is based on incorpr.tation of effectg of,soil texture, percen! co.ase fragpents, and other goli features, sucb as indlcatlon of ceoentlng and thePtesence ot Dottles. In gcneral, soll type 1 is unsuited due to'too rapid percolation rates; soil typ€ Z crnbe used, oftsa rllh looe tJE. of sand filglr syst6ros; !ol1 type! 3 and 4 are lenerally preferred, "lttrough smetlrPe {'3 oay be lloited to s@e degree by slorr percolatlon; type 5 soils percolaLe very rlowly and are.generallyuntulted due to how easlly they are tr5zdraulically overloaded, but oormd or presrure dlrtributton.sy"t-s ".rrbe used 1a sos cases to c6ltea3aue for these lioiiatloas; type 6 solls aro on;trig.d due'to oln{nal percolation.
tC - Perccnt clay content ar estiDated usfng U;nd-t6rture techiques in the fteld: -
.
FIEI.D DATA ABBREVTATIOIS
Tcrtrrrc nadar Root s MaLi-l Sl-Friatrr?.
-. Soil troC
1
2
3
4
5
6
L - Loao(y)
St - Stlt(y)
S - Sand(y)
C - ClaY(6Y1*
F - Flne
Gr - Gravelly
V - V.ry
X - Extraoly
Co - Cobbly(t 9 tn front of
LS or SL stlDdsfor Coarse)
Flrst lcbter
M - Mrny
C - Comon
P - Ferr
Secoad lettcr
F - FiB€
M - Mcdtr:n
C - Coarse
PLrst letter
M - M6ny
C - ComonF-Felr
Secoud letter
F - FIn.ll - llodlun
L - Large1tl!d lettor
F - Faint
D - Dicttnct
P - Prooinent
SG - siDtle grained or loo!€,
no btruclure.
llIi - Masslve, oeanlng nbrtructuio, but uoB liltle 8!!iasd'Sirit lcttea represeatr the' ltlmttb of tbe ctdrctute
W - l{eal
M - Modcrate
S - ltront
Secood lctter rcPresmtr therlzc of thc ltructural untt
F - Flno,.
M - Mediun
AppIII-2
C'Coarac
llltd lettcr 6!ouP r.preteatr t'hc-
rhepe ol th. ttructural uD1t
SAB - rubantular blocky ;
63 - .lgular blocky'g r granilar
91 - platy
fbcse ar-e not lype L ox 2 raten,.but have Dod€rage to sltgbt ltsh. rildlife, or bunan use'- . values. -Ttrey lnclude lctneats of nrgulal wrters srd thelr assoclrted,r.tl..tids rhl,ch:
- (a) are g1E499C for dooestic u!6 by Dor. than 10 residentlal or-,caoptnt.unit3...;
(b) are used by. slgnllloaog luEbelB of .rtrdr@ur tlsh lor aparnJ.ng..roating o! mig:atloo,
sucb as tbose bavlng a deflncd cbarmel rtdth of, 5 leet or traat€r and a gradt.ent of leas
thaa 121 and uot upltr.ro of. a !.11s o! oora tban 10 vcrtlcal feet.
(c) a:e ulid by sltnlflcant, Dunbors o! r.sld€at 6ane fisb, such a! thoae havlng a defined
chaane!. ridth of 10 leet o! trasier, r 3u@er 1or flor o! tr.ater than 0.3CFS, and a '
gradieut o!'1e3s thrn 122, aua ponai cir iopoundnents wlth t!6ater than 0.5 acre of sutface
a!€a at ceasonal low water.(d) are hlgbly litnilicant for protection of downstr€an rater gualtty, such as trlbuta:les
that contlibu?€ Eole than 202 of the ftor to a lyp€ 1 or 2 wat€!...
these are not Type l, 2, or 3 waters, but are ooRsidered lulrortanr for protdction of dotrnltreao
water quality. Tbese alc aot f,Igh-bearint sgrorro!, but bave a dellned channel aad are either
iDg€r:nlrtEot drainagcs, or are perennial rlleaEs In qnrcachable poltloEs of a dralnat€.. ttese
raters contlnu€ uitsilaan unttl the channel becmes less than 2 f€cg ride.
Ttese arc not Type L, 2, q, o! 4 raters, but lncludc atreanr wl.th or ritboub *jrr-O"rrord
cbannels, arcag of.pereurial or ln!.rilltten! scipage,-ponds, uatural. ginks.and &ainageways
having short periods o! rprlag o! ltorm run off.
t-
Strei! IlPq : rtreao tlrpe: a. dellued.ln t{AC ?22-t6-O3,O, t{atcr typing.Syrtco. fhcle tylrlDt_were ertabllshbd' in cooperat!.on b€tre€n lba Dept.,'of llatu-ral.Besburcer, lhe Dopt. of Flsheiies,.the Dept.-
of Wlldlrf.: rhr Depi. ol Ecology, ana fh cbasultatloa ritb affected Indtin -!rlber, tte
!.su1gs are avatlabl. acroa!, the countrr .t-DNR Map and.Photo Sales.'-tlrc ciirrerig..ltteqi..j gypc deflal'tlons,ale as follorc (paraphrased fr6 the.WAC code dgrcgiptlorrt)! i-
-l .
,I. /
lvot-cal charactarLstlcs t
A11 shorellnes of the rtate, rs dcflned r:nder RCi{ 90 ,SS,.ritbiu tbeir ordina:y blglr waCcr mark,
ercepting.tbelr assoclated wetlands. Genarally, tbese laclude all riveis, lqler tloat€! tbaB
20 acres, and pereaaial str€aol dowristrelo o! the point oC tr€aBe! than 20 cfs flor. lbEre.
arc a,enerally conrLdcred Lo bc tlsh-bearlnt ratcrs. .-. ./.-
fhese .rc not Tyln 1 ratcrt, bub-do havr. btgh flsb, nildltle, or buoan uce val,ues. ltcy'
lnclude segn€rrt. o! natusal rqatera- and tbclr iqsoefatgd rrtlands vhfch:- -(., *l ai""rt.a for dmegtlc'uso by ibr.,i,l-t 100 nctdeattal ,or coplag uult'*.'.i
(b) are rttbln rny c&ryrttound rltb t!c.t.r thaa 30 caoping unlt!.r..; . :- . : I -.
Cc) are urcd by rubct.rttlal .nrrnberr of anadrmour .or rccidgnt troo tlrh for sparulng,
rearlng or alttation, luch ar/-thole havlng d defiaed cbarurel wldtb o! 20 fee! or greater
and a gradlmt o! lasr than 4t, or lalcs,.pondr 9r iulrcundnentr wltigrcalei than I aci6
of su:face 8!ca et searond!. lor watcr. r' (d) are used by ralmnid foi of,f-chann.l habttat, usually crltical loi'Juveni,le survlval,.
grrch as tJrorb qrear connected to a cl@trld bcaring stlean and accesslblc a! sooe tine of
th6 yea! and having !n accestr dralnage area wlth less than 5! gradlent.
Str.rm TvD€
z
1
3
4
5
AppIII-3
JEFFERSON COUN'TY AREA, WASHINGTON SHEET NUMBER 40
DE
oF
lw
ArFU
U NAJ
T
i
. -_-.!.^
JPrrtzo'l AuurT
S,t *,-/ ,"*l
(nL
5*A
413
9," fueuE/
9,/ szaet
U-///'a*
3d"* J-"*-Af^,
(-a-'y'ZUl 2z-4ez//wq/ 'o/5 /
t, :*.
(Joinr rheot 42)