HomeMy WebLinkAbout1992.11.02 - Evaluation of the Critical Drainage Corridor North of 49th Streetr- H—
n Lisa Palazzi, Principal
2W Fourth Ave. But
suite 416 " -
i (?IMpia. WA 9850?
205) 534.0346
Report Rile Number: E92 -0060 (EES42323.010).
Report'Subject:. Critical -drainage corridor north.,of 49th " Street. '
Location: The corridor evaluated runs approx. from the
intersection Hendricks and ,49th. St. east' to the
Chinese Gardens.:.-,
Client:; Port- Townsend- Public'Works `.
This- letter report Is provided. to •briefly describe findings of a recent
evaluation: of the -above defined drainage corridor. 'Various portions of •the _
site were wi_sitea on three separate - occasions'.'.. The i ntent was .to. deefine' at `-
least the cen- terli.ne of- the ,corridor,-' ;acid" i4 some areas:• to define - its."br. 6,id
extents-as rei.ting to already existing:City. street•- easements..•-.:
Field flagging :arid •evalua.tion 'was done by Li ga .PalazZi, -and Doug "Mason.
Initially ;_. -SCS soil -maps, 'Port `Townsend wetland. maps, .aerial: - photo's, 'and
to a limited'degree - topography maps were.consulted'to identify.• areas of-
concern on each site. Brief site visits were' used to: verify, -refute, or add
to existing' informition'.
No•soil pits were evaluated, so soils discussions are based solely on SCS
soil mapping of the areas evaluated
SOIL SERIES 'DESCRIPTIONS:
31ie following de'sc"riptiona are based on -the SCS soil.. mapping and expected
characteristics-, of the -:soil - '.series ,as mapped.'. Please- refer. to the-following
section ;`for- site:spec fic iTifnrmat .on.` according =to .the :Te£fe son •County = .
soil siiruey,.' three _ "soil "series=•'are ,_mapped'' alo g-_ the: d-corridor::
1) the A'6ew" iiji'•- xoam `aassified. _as • a fine =sil ty;= mixed, mesic
Oql raqualfi
Fine -sil mixed;" me sic. "'pic :Ochraqualf,': generallyty
meaning •the.: soil has'.Ian.
Ari '
i .lic . (clay): horizon: and greater than .-35x __base
sat at on,.'.(alf.),=
31-4 expected .to. hae. v a- seasonal' high water table within 18
2) the Clallam gravelly-sandy loam (classified as a loamy - skeletal, mixed,
mesic Entic Aurochrept')
3) the. San. Juan gravelly sandy loam . (cl'assified ' as coarse -loamy ..over sandy
or sandy skeletal; mixed, mesic: Pachic..Xe'rumbrept')
Additional soil -seri.es .such 'as the. Swantown,'.- Wapato, . and. Mukilteo_ -muck -are
mapped around .the' Chinese Gardens.:' .But since- they do not-affect the
majority of the drainage- corridor, -will, not•be-desdribed further.
AGM SERIES .',.
The Agnew si1t.-loams- are 'moderately.. deep, somewhat poorly- dtained: saii'sformed 'in. shallosd:'-glaciolacustrine . sediments: overlying laminated glacial
till.- .--"these' : soils.: are` often -associated with "wetlands.: - Generally.; _the_ uppersoilsare.silt loamy grading to_'silty clay loams with depth.':Mottl.ing is
expected ar'3 inches depth and gleying at 9 inches. depth -- .evidence of
seasonal water almost to :the surface for extended- periods. .'Below•approx. 30
inches (in the_ C :horizon),'. gravel content increases. abruptly, from <5% in the
surface, soils to". between 10'and'50% in the subsoils.. The. lower horizons are
highly laminated and 'very hard glacial. till..
Average soil percolation rates. iii the upper,9 :i.nches are expected to be
moderate .'(0.'672 inches per hour),. decreasing to moderately dour (6.2 -0.6
inches per hour) below 9.inches•depth.;: = .
The Agnew soils 'are'generally,suitable -for: some crops and pasture with the
main limitation being seasonal wetness (a:perched water.table) at 12 to 24.
inches .of. the 'soil. surface -. (aqu)•,'. has a pale -colored, low base .saturationthan50X), surface- horizon "(bchr) .' is otherwise: typical ..(typi.c) , has ''a" mesic _ -
temperature _regime. (mean annual temperature ranges from 8° to..15° C .(477 -.'590:k),
no.. specific' oe =-.(mixed), and -is greater than 18% slay -and less:"' minera1bgic s.urc
t;hav 15X sand (or coarser).._by weight (fine- silty)
Loamy - skeletal.; .mixed; .mesic Entic' Durochzept, generally meaning the soilhas-minimal horizon development (ept and erotic); has a pale- dolored,-low base-
saturation surface horizon (ochr), has an silicate- cemented subsurface. layer
Our), has:a mesic temperature regime- (mean annual temperature ranges from 80 to
15" C (470 '- .59° F), .has no specific mineralogic- source -(mixed), .texture of the.
fine fraction- is .loam and' coarse fragmerit- -.content is greater than 35X (loamy- Skeletal).-..
Coarse- loamy.`over: sandy or sandy skeletal_; mixed, .mesic•'.
Pachic Xerumbrept; :.generally meax i rig the. , soil.-ha' limited ' horizon'. development
ept)," has- :a'-dark colored ,sui'iace ;horizon'Aiith a =low base aatzirati~on {umbr) ;:.hasdevelopedunderciiniate- conditions..of.'wet wimters =aud droughty:summers- (xer) -, :and'. has a deep•:,rgFeater :than 50". cm)- dai:k =col tired;:. =sur €ace - horizon =(gachic), has a'
mesj.c temperature `.regime -meeant ;aririval .temperrature- =ranges'- from 8° to ' 15° -C "(47 -_
59 °.:F) .no':specific mineraiogic.saurc °(mi_xed).; -b"_."1.5-50% .sand; less than i.BX.
clay,.:aiid Rossbly gxeat.er' than 35X coarse £zagments -( coarse -loamy over sandy or . sandy skeletal)..' - - - -
inches depth.'.
The. main limitations for onsite'septic and'stormwater treatment are related toboththeminimaldepth :to 'the hardpan •and. seasonal .wetness. Sail waterpercolatingthroughthese 'soils "will modown; The' ve laterally in the soil rather thanseasonalrhighwater.table and /or the shallow .till layer limits theamountofsoil 'available :ta effectively treatt- stormwater or septic effluent.
CLALLAH• SERIES—` :
The :Clallam. gravelly sandy 16ams ar''e --oderatel • : - y.- deep,'..wel - drained .'soils. foried::in glacial ill. :: Th'ey 'are. usually. found -`6r uplands,.: 'slopes ranging
Y
from-0-30Z... ': The ,'surface soils -:are, generally grayish -brown to dark grayish- • ' brown• gravel] y 'saxidy .looms ._ = They• have a weakly- cemented •glacial till layer 'at _ 20 -40- inches :depth that will - restrict vertical' soil:' percolation to samedegree ; =: •. " .
Average soil permeability is - expected to moderate (0.6 =2 inches per hour) above the cemented "till and very, slow (less than 0.06 inches per hour)-in thetilllayer. t-A. seasonal.-perched water. table is not expected;: the till..in: theseareasmust -be more fractured. 'However, the- "soil is expected to be
satun:the
periodically• during the .rainy season "and the majority of '-soil water will ' percolate .;laterally,::' .
r
The : Glallam soils originally developed finder ' a' forest; .biit more than' half ofthemappedacreagehasbeencleared.and is now used for: "pasture,.'garderis," orchards and'hoinesites.'..The 'primary limitations are related- -to'shallow soil - depths. Storin_water will prcoae into soil.readily in. undisturbed areas; but will'. move laterally act -oss the-till layer, surfacing in adjacarit riraiiiageaand=low =lying areas: Septic'system desidepths •and•. fluctuatin .. will be Ii.mited. by minimal soil, g _seasonal high "water.
SAN`. JUAN
The San.J
S
uan
ERIES
sandy-- very de ep.,• somewhat exce_
ssivV
ely drainesoils• farmed in d` glacial. -The surface soils are "generally `dark- coloredgravellysandy'ioams.. Soil texture becomes coarser with-depth, gravelly loamy "coarse sand. and gravelly coarse sand.
p grading to
Average soil 'per'meability is "expected. to be rapid (6 -20 inches per hour) throughouut . ' - .
The San :Juan•`soUS are' i.s used for farmland -, hayland pasture; woodland or-. homesites _with few limitattions:. '.The "pri ry.'limitation .for se tic drainfields " or'`stormwater.: f c.i i ti-es are' "related to =poor.' filtering capacity due' to `rapidpercolationrates :and :rel'atively low surface" area in "saridy"soils.."'• If housingdensityis. moderate .=to` xiigh, =.=community: sewage. systems or alternative `septic . desigxis - are rec"onimended, to reduce- patential,-of: water sup} ily:,coi tami.z ation by
fir.. - '- _ • '. .
SITE •_SPECI' FIC :`CHARACTERISTICS _ - • _ - -
The western*' eh(' 'drainage' 'corridor ; initiates`'at • .• - Hendricks just north of theiitersectioiitaitli' 49th.'" "This cap'tuires'dfainage , from.the Lev ?nck ro er0. "the .west; The' ewe P. P ties"
t_ stern :end is:. undex•zairi with..the. San 'Juan series; a "deep "
3,,
sandy soil that can readily accept large volumes af. surface water. The soilsoffsiteto :the. west are much shallower, and as a result contribute asignificantamountofsurface .flow to this. area... However, because the soils.:, are so deep' and, 'coarse, -the stirface': flow- tends to be absorbed acid runsubsurface:.
xi titi a] y, ..the ..only.'evidence - of,'drainage.- :is :a 2--4% feet 4ide .ditch (human- made) initiating about -50 -100 feet north of an existing home facing on .Hendricks. The. centerline .pf 'th e drain 'was' flagged (A. on the map) _until i t..tdidens aboutOQ- 350`feet ao:the`• "northe ,: .
At that: point.'the_''corridoz bottonu'.became' cite :- q., flat and wide, supporting.anitnderstoyofsloughsedge , and _water parsley -with an overstory- of :cedar, blackcottonwood, ;and willows_ C j2).. ' This" .wetland raas .quite. extensive afeet.wide;'drainin a pprox.'100 . g pgrox. 400 -500 feet to the east where it narrows abruptlydownstreamof - ail old debris jam that appears to -have= dammed 'the drainage; causing the water -to back up. Both 'sides'of this- wetland. were flagged, luosely`:agplying x.989 delineation rules.•'A more detailed delineation shouldbedone 'in, the future as development plans. in:the - area are better defined..•
A Local. Improvement District (LID) "road (0) is-apparently proposed'to crosstheeasternhalfof .this'wetiand.. _fit appears: _that, the road will follow a' N/Sline .from the' - eastern property. boundary 'of •the four new houses. adjacent. ,'to49th. , _If ehe wetland is. to' be •crossed, new
will. be required to notify theACE; to delineate the wetl'and,.and'to. prepare a mitigation report and plaza:':
Downstream of the debris .jam, .the wetland. winds southeasterly in a marrow ' corridor toward the - :back'of...the developed properties .ad-jacent -to 49th :( .#4) The - coriridor °was'.flagged on the.centerli:ne-when- it eras. 4' feet or less wide, but on both .'sides :when, t widened out in'some. areas. :It possible ' °thathistoriaalIy,. the`di rainage flowed. through theJAevelo ed49th;' but at -this , time- :.it .'a
g P properties toward ,.
ppears ; "that "the'•pr ry channel -flows 'east-','; northeast: along the back and theii'north of: the' cleared,' developed properties. .
Some drain a ma _ : tigy.escape subsurface and flow in the ,'southeasterly; direction5), but- .-the primary channel draiiiing -to the northeast intersects withanotherchannelcoming 'in from upslope (JJ6) :. - --A large forested •wetland. complexhasformedattheconfluenceofthetwochannels. A short distance upslopefromthe 'confluen'ce
thaththat marks the.beginning of the Clallam soil map unit, indicating t the upslope sous to:.the- north'.and east are :expected to have ashallowsubsurfacetil.L. layer. ' ..The - effect of the till': layer is to, limit soilstorage,- 'xesu],txng :in- excess - surface Viand .soil' water draining downsl ope into ." the; deeper San': 3uazt soil s This ys111, catise: there'..to. be mare : saturated -soilsat,' the toeslgpe: on. this northeastern end .of -the .drainage, -. and..does appear tobe :reflected..:by:.ttifq jncxease:- in.iretlana area. we
If ,tile: tuna • p ;i-ywdra page _'Ewhich `drams :northe - dive ast fowaid_ the confluence).•weze: ted" °' fob -9W :,tie sautheasterl`'" clirect£oa bf flbw across ' 1ots,yi 'wosild:_ y'. :the back :of = the,' altrez ,the : hydrology:..of ':the dowristieam `wetlaiid to as unknowndegree,.:': Tii3.s -may xesi t -.ink better:::coiitrol of >stor&tvater, but:. wclearlydefaiiedandmtigatied. fQ otld have to -be
r'., 4'.
The forested wetland drains from the confluence almost due east toward thebackofthehomesonJackmanStreetbetween50thand51st. Only the southernside. of the wetland complex was- flagged.downstream of-the confluence. -But theupslopeboundarieswereapproximatedontheaerial- photo.
A recently - •cleared lot ( ii) behind a home• "facing on.. Jackman appears to be' atleast.-partially' :if -not all in. the - wetland. The vegetation directly .behind theberm-running along the -.western side 6 f -lot is spirea,. -black cottonwood, willoir, .and. - hawthorns all ;hyd rophytic .vegetation indicative of wetland ' status._, :Further more,--t ie..jvegefat on'.pattezns 'indicate. -that water. stands inthis-are- :a for extended : periods - =of .time during -the winter. . There is greatpotential:.for._ future "flooJing. on •the: lot - unless dikes' and •control devices .arewellengineered .and ma%ntai- ned. "`The',_future homeowner should be-notified that ' the back 'of their -property is'in the wetland and should be encouraged tomaintainavegetativebuffer'to•protect downstream water quality. They shouldalsobeencouragedtolocatetheirhomeasclosetotheeasternedgeaspossible.
The drainage •turns and tuns to the: south across possibly half. of the .cleared- lot and across the -backs of-several 'other lots along Jackman, Vegetation atthebackof" all these lots is primarily hydrophytic.:.They.appear to have beenbuilteitherin- the wetland or directly beside -the drainage -corridor'.• Thewetlanddrainagethenappearsto .spread across an open grassy area (0) northof49thandcrestofdseveral• 'homes-'fhat ate "located south of 50th. These homesMalmost•- certaizily are located in the middle ' of- the 'original - drainagechannel. Because the San,Juan'soi.ls are so porous and deep, tie majorityustseepdow -ofthewatermnslopesubsurface. 'But small drainage ditches 'around" the homes appear .to -•be designed to- convert surface flow-toward a.ditch:onJackman. '.that flows to" 49th. ....it -is- likely that -at least some of these' houseshavesubsurfacedrains" as well- to .divert seasonal' groundwater from their . foundations.. :.
The Agnew soil series. is mapped at the Jackman /49th Street- intersection withthegreatmajority•ag the "Agnew "map unit extending to the "south, under thefairgrounds. The Agnew is a hydric soil•,• and. -it is possible that prior todevelopmentandconstruction•of"the' road, excess drainage from the area' of 49th at least.- meandered through this low -lying area; possibly "subsurface' draining toward what is now Townsend Meadows rather than toward ChineseGardens. The Agnew is fine- textured;-typical of a flood deposit in a quietbackwater, and would not have formed without a source of upslope- sediment.
At 49th,.-the drainage flows into - a' 1.2 inch culvert. across ' Jackman' ( #l0) . We ' were: unable' to ,.fii-xd the other -end... of this cuivett, -. but there i' an 'obvious . ditch `runnixig' *long the•m'arth: •side. -of;49th from`the .east -side of. the - Jackman ' intersection ;`...'The ditch widens•-.out.again,-1- lowing northeast.-across. an_opengrassy :area :; (" 11) -, through : an .indised _ ."possibly - ditched drains a cuttin '' - g gbetiveen "two• - homes" - -on, Landis, " ; At 'that. -poi.nt., , the: soils are mapped as .changingfromtheSan- Juan to.'the•' Claliam 46ries.,•
rainage: is ctzlvetted•'under'- Landis, drains, east - northeast -across" afieldnorth.:of ahome on 50th,' then through_a culvert under•'Kuhn 'to -a ditch . running directly - X:nto Chinese : -Gardens - " .
5.
Since there. is evidence Of. a surface water' connection between all the wetlandsalongthedrainagecorridor, .they would be probably be regulated as a•single
wetland - complex- rather than a series of isolated wetlands. .Since. the wetland' is- a.-. relatively. pristine ' fores't.ed complex, it may be.'rated -as a Category 1, making mitigation and `replacement '.ratios very costly.. Impacts should .lie
avoided if possible -Aind minim zed. if 'it -is not. possible to- avoid.
As described :above far the.LID,.any• impact will : - require an ACE permit at theleast; in additxon.:to mitigati on plans .and wetland delineatidn in 'the area ofimpact.
SUMMARY
The'riatural 'drainage.corridor'•appeaxs . to meander back and forth. between the50thand51stStreeteasements;.- then. at Jackman drop south to 49th, -GrossJackmanin 'a culvert, then drain northeast again through a narrow but obviousdrainageto -the Chinese 'Gardens- ''The corridor is a series of -
jurisdictional wetlands connected by A surface channel. The surface water
connection means that they are,not "isolated wetlands" and would be tegulated . as a single jurisdictional- wetland system.
When the channel was -less than-4-feet wide,' only the centerline was _ flagged. Both' sides-.6f the corridor 'were .flagged west of the confluence :with theupslopedrainage.'.. *Only. the* south side of the'.corridor was flagged east of 'theconfluence, " :but the upper:side•was approximated` and marked on'the aerial
photo. - Arrows on the, serial photo: show the general direction of flowpatterns.
The Part Townsend ESA :requ_ ires'. that the. cent_ erline of .the . water co_ urse be
surveyed an-d thL- coriidor`-'and'centerlineI'be_ indicated on the Site ConstructionPlan.. The ESA'-does: not clearly. define 'the corridor other" to . -say_ that =it.:._..` is a "natural 'oz-.'parti.ail altered.*watercourse ' or ] ' -lying area that
contributes to 'water: quality and stormwater `'and erosion_ ' control .'" These- areas . are._ to ' be identified by 'the Dept.— of Public Works 'from - 'local -knowledge aoutregularflooding "_. -or "potential for - flooding if' existing, drainage is - modified."' :.
When -the surveying is completed, the City ESA wetland maps should be updated.
The soil mapped for the majority of the . drainage. corridor is the'deep,.porousSanJuan. It appears that characte'risties 'of the-San Juan soil-.have made.
this system very forgiving,'.al loving it- -to absorb ekcess .runoff .from upslopeshallowsoils, causing what: ' was surface ;runoff . upslope 'to run subsurface -'alongthe..:bottom slot some': time.: This ekfect gill buffer. the ,puls'e 'of .runoff -- following winter'storms,- thereby- reducing flood potential,• and -will inipzove_::- .:-;.'. water. '-quality. -
y. actiiiities = cti-- ectTy' impacts : the wetiaads'.'will.x'e airs ACE- :natifi.cation _
Permittitig, of 'the: actioii The, permit` will' be'=revi ewed'` by :_t he ACE' the -`: r fPA,r. =and various_ State ;Ageiicies`,for::compLiance' with other:wetlinds arid. -water,• quality statutes=: "-'Delineation: and a'a13 Ligation ,report may - tie red:
Depending -on `1- he activity;..: .the :City ",may also- require a- "wetlands report anddelineationsiroun. :.the .impacted areas . ;