HomeMy WebLinkAbout2004.04.20 - 20th Street Field Assessmenttt-\r..t. U. FruE
Olympic Wetland Resourees, Inc.
Dixie Llewellin, Principal Biologist
lhave'conducted a
Streets
wide gravel road to a hard
right of way).Private property will be purchased from Ross Markley to accommodate
this street widening between Howard Street and Rainier Street (part of Lots I and 26); the
remainder of the prpperfy needed for the street improvement is owned by the City.
History
The original evaluation for this vicinity was conducted by Polaris Engineering in May of
1997. At that time, surface saturation, inundation, and water in the soil test pits was
observed through out Basin 11 (Data Point #1, #3,#4, and #5 lWL2, WL 3). Along
with hydric soils, water tolerant plant communities were documented throughout the area.
The wetland edge, as mapped, is based on a limited number of observations, connecting
lines conforming to the available topographic maps. The evaluation was conducted
during ayear with above average rainfall (1997 had22.03"; average rainfall is 18.4").
Water was present during the 1997 evaluation, north of 20th Street(Lots24 and25 Phase
II Hamilton Heights). 'oThe wetland appears to extend north beyond the basin limits.
North of 20th Street, plastic flagging trung by others along an inundated area suggests
prior documentation of its extent." (Basin 11 Area Wetland Reconnaissance page 2).
For the past four years Port Townsend has experienced drought conditions (2004 is also
likely to be a drought yea.r), which have altered hydrology in many wetlands and drainage
corridors. This wetland/drainage corridor was dry during this evaluation. Included with
this letter is a rainfall graph compiled from information collected by Herb Henington,
Port Townsend Offrcial Weather Observer for the last 20 years.
Findings
Field findings show that wetland conditions appear sporadic on the south side of 20th
Street on the Markley property. The area did not have any standing water but vegetation
and soils do indicate the presence of a persistent water pattern in the low-lying swales.
Hydrophyic vegetation includes willows, spirea, and sedges
As indicated in Photo #1, the majority of the area south of 20th Street consists of an
upland plant community. The water pattern will need to be addressed when widening the
road in the swale associated with the lowest point in elevation along 20th Street. As
shown in Photo #2,thickets of willows and spirea are growing adjacent to a footpath that
lies near the undeveloped Rainer Street.
New roads are being constructed as part of Phase II of Hamilton Heights. A culvert,
which formerly ran under 20* Street east of St Helen Street and along Lots24 and,25,
Hamilton Heights, directing water from Basin 11 to the north, is no longer present. It
was altered during road construction, according to a conversation held withthe road
building crew. Field findings show that hydrophytic vegetation is dominant in much of
the area between St. Helen Street and Howard Street (Lots22,23,24,25,19 and 20) as
shown in Photos #3 and#4.
Recommendations
The construction along the southern edge of 20ft Street along the Markley property and
city property will cross a wetland/drainage corridor with minimal impacts if a culvert is
restored to allow the passage of water during high water periods.
Homes built on the southem parcels of Hamilton Heights between St. Helens Street and
Howard will experience problems due to natural drainage patterns. The functions and
values of the wetland at this location will be completely lost. It is not clear whether the
lots will be filled since they are below the grade of the new roads, as indicated in Photo
#5. The current road design directs water from impervious surfaces via ditches and pipes
to the man made stormwater pond but does not address water within the wetland.
High volume stormwater patterns should be evaluated. Remedies may include reducing
the density of the home sites at Hamilton Heights and enhancing the natural on site
wetland at this location by retaining the tree and shrub layer. The culvert should be
restored and awetland retention area on the south side of 20th Street could be constructed
when the road improvements are made.
If you have any question about this evaluation please feel free to call.
S
Dixie Llewellin
l.'
fide:Photographs
Hamilton Heights
2fth Street
0lyrnptu Yletlond Rmourar,
856fllthStreet
PorthwnmndIYA9S36S
3603${{fl
0'nil John McDonagh Planner II
Building and Community Development
lSl Quincy St, Suite 301
PortTownsend, WA98368
Shet \
#1
,/
April2004
Job#,2004 6758
Photo #l
Rood Widening to the South (right)
Plont Communily Consists of Solol ond Fir
Photo #2
Wetlond Vegetotion
Along Footpffi (Mokley Property)
Photo #5
20th Street Elevoted
Above Wetlqnd
Corner of 20th ond St Helerl Street
Looking Towords Homilton Heights
Sedges in Wetlond
ln Homilton Heights
lnchesPort Townsend Rainfall ig83 to 2003zottr,24232221201918171615't4131211I RAINFALL109o7o5AJ2101983 '1984 1985 19861988 1989 19911992 1993 1994 1995 .1996 1997*1 990Average Rainfall for Port Townsend 18.4"1998 1999 2000 2001 2002 20os-1987Source Herb HerringtonOfficial Weather Observer