HomeMy WebLinkAboutThayer Lake Hydropower Project Wetland Delineation Report - Jun 2016 - REF Grants 7040038, 7050825Wetland Delineation Report and Mapping for
the Proposed Thayer Creek Hydro Project -
Access Road, Penstock and Transmission Line,
Dam and Facilities
for Kootznoowoo, Inc.
Bosworth Botanical Consulting June 2016
Thayer Creek Hydro Project June 2016
Table of Contents
Introduction .............................................................................................................................................................. 3
Methods ...................................................................................................................................................................... 4
Project and Project Area Description ................................................................................................................. 8
Project Description .......................................................................................................................................... 8
Geology and Geomorphology........................................................................................................................ 9
Hydrology .......................................................................................................................................................... 10
Soils ..................................................................................................................................................................... 11
Vegetation ........................................................................................................................................................ 14
Results ..................................................................................................................................................................... 22
Conclusions ............................................................................................................................................................ 25
References ............................................................................................................................................................... 29
Appendix A - Scanned Sample Site Data Sheets ........................................................................................... 30
Thayer Creek Hydro Project June 2016
Introduction
Kootznoowoo Corporation Inc., the Angoon village corporation, in conjunction with Orenco
Hydropower, is investigating building a run-of-the-river style hydro project on Thayer Creek, a
small creek approximately 5.5 miles north of Angoon on the west side of Admiralty Island in SE
Alaska. This wetland delineation report and maps are in support of the US Army Corps of Engineers
wetland permit for development of this project.
Access to the site is via floatplane from Juneau or Sitka to Angoon and then a hired skiff ride the 5.5
miles up Chatham Strait to Thayer Creek.
Figure 1 - Location map for Thayer Creek Hydro Project
Thayer Creek Hydro Project June 2016
Methods
The area was visited first for wetland delineation in September 18-20, 2015. There had been light
rain and cool temperatures in the 40's and 50's °F during the 5 days before the the fall field work.
Two road access routes and dam site options were documented during that visit. During the winter
of 2015-16 a shorter and preferred access route was decided on. There is some overlap of the dam
site access route for 2015 and the 2016 transmission line route. As a result some of the 2015 data is
included this report.
The new project area was visited for delineation on May 12, 2016. After a very mild winter and
wetter than average April, there had been a trace of rainfall and temperatures in the 50's and 60's
°F in the three days before the field visit and temperatures in the 70's °F on the day of the field visit.
(The records below were obtained from the closest operating weather station, at Lena Point Lena
Point, though farther north and on the mainland, is in a similar geographic position to the mouth of
Thayer Creek)
Thayer Creek Hydro Project June 2016
After the second trip to the project area and documenting the presence of wetland on all of the
proposed staging area it was decided by project engineers that they would avoid impacting the
staging area wetlands by moving the staging area to an upland area approximately a quarter of a
mile along the access road. The new staging area is proposed to cover 1,292 sq. ft.. The original
it is the best professional judgment that all of the area is upland. The new stream length
amount for the new staging area is also an approximation.
Thayer Creek Hydro Project June 2016
Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987) as
supplemented by the, Regional Supplement to the Corps of Engineers Wetland Delineation Manual:
Alaska Region November 2007. Wetlands are required to have a prevalence of wetland hydrology,
hydric soils, and hydrophytic vegetation. Jurisdictional wetlands are determined when positive
indicators of all of these three criteria are present. The "routine determination delineation"
methodology was used. The wetland boundaries and classifications described herein represent best
professional opinion.
Maps of the proposed access road and facilities sites were provided and the routes flagged by
Kootznoowoo and Orenco. The transect width varied from 30 feet on the roadway to 60 feet on
road areas that had pullouts or more cut and fill. Sample points were done along the road and
transmission line alignment anywhere there were significant changes in vegetation, soils or
hydrology. At each sample point, the wetland status of that point was determined by observing
indicators of hydrophytic vegetation, hydric soil, and wetland hydrology. Once representative
sample points were done further wetland boundaries along the proposed route were flagged and
marked with a GPS waypoint.
Sample plot vegetation was divided into three strata; tree, shrub, and forb, and each layer was
classified using the prevalence index (a weighted-average wetland indicator status of all plant
species in the sample plot) and the dominance test (more than 50% of the dominant plant species
across all strata are rated obligate, facultative wet, or facultative). The 2012 U.S. Army Corps of
Engineers National Wetland Plant List Alaska Region was used to classify plants.
Hydrology was determined using two methods: (1) visually, if the water table is at or above the
surface, or (2) with a soil pit. The presence of standing water, depth to free water in the soil pit, and
depth to saturated soils was recorded. Other primary and secondary hydrology indicators were
recorded, such as presence of watermarks, sediment deposits, drift deposits, iron deposits,
hydrogen sulfide odor, geomorphic position, and drainage patterns in wetlands.
Wrack-lines and estuarine or salt-tolerant plants were used to determine the upper estuarine
boundary and then that line was checked with the Lidar data in the office.
Soil pits were dug to a depth of 12-16 inches, or to bedrock or glaciomarine sediment refusal, to
determine if indicators of hydric soils were present. Soil colors were determined from a moist
sample with the Munsell Soil Color Chart. Sample site data sheets are included in Appendix A.
Final delineation maps were done in GIS. The proposed routes, pullouts and cut and fill lines and
the 5 ft. contours, derived from the projects lidar data are also shown on the delineation maps.
Lidar point cloud transects were done across the staging area in both directions to show the
concave nature of this area and the scrubby nature of the trees.
Thayer Creek Hydro Project June 2016
The base map for the delineation map was 2014 Lidar imagery flown by Aerometrics, Inc. Polygon
acreages, route lengths, and stream lengths were calculated in GIS.
Thayer Creek Hydro Project June 2016
Project and Project Area Description
Project Description
During a field visit for wetland delineation in mid-September 2015 there were two options for the
dam and powerhouse site and as a result two access routes to those dams and powerhouses. A
shorter access road to the preferred dam and powerhouse sites, with significantly less wetland
impact and construction cost was initiated in the winter/spring of 2016. The 2016 access route
begins on the coast, approximately 0.8 miles north of the mouth of Thayer Creek. The dock site,
which is proposed to be built on sub-tidal and unvegetated intertidal, is not dealt with in this
document. The access road, as it leaves the dock site, and the buried transmission line, do traverse
short sections of vegetated intertidal those sections are included in this report as estuarine
intertidal.
Figure 2 - 2016 preferred access route, facilities and dam site for the Thayer Creek Hydro Project.
Thayer Creek Hydro Project June 2016
Geology and Geomorphology
The access route, buried transmission line, dam site and powerhouse location, are found primarily
on Devonian limestone or marble. Outcrops of Tertiary siltstone are also found along the beach at
the dock site and the mouth of Thayer Creek.
Figure 3 - Area geology map (from unpublished USGS Geology of SE Alaska - Wolfe, 1977)
Slopes were calculated along different sections of the access road and in the staging area:
staging area - 3%
wetland section of the road - 11%
steep drop from ridge to powerhouse site - 39%
Spur to dam site - 19%
Straight down into gorge from ridge top to dam site - 100%
Thayer Creek Hydro Project June 2016
Hydrology
Streams were categorized in the field into:
ephemeral - surface flows only after rain or snow-melt and has no distinct channel though
there is subsurface saturation/flow at all times.
seasonal or intermittent - flows during certain times of the year when smaller upstream
waters are flowing and when groundwater provides enough water for stream flow.
perennial streams - a stream that has continuous flow in parts of its stream bed all year
round during years of normal rainfall.
The Thayer Creek/Thayer Lake watershed is the primary watershed for the project area, though a
number of streams recorded along the 0.8 miles of access road drained directly into the ocean at
Chatham Strait.
Figure 4 - Thayer Creek - a perennial stream, just below the dam site.
Thayer Creek Hydro Project June 2016
Figure 5 - A seasonal stream at the north end of the access road.
Soils
The project area soils vary according to a geomorphic and hydrologic catena, from the
shallow-to-bedrock soils of the steep hillsides of the gorge to the deep, organic, saturated, soils in
the relatively flat areas of the project area. Following are the range of soils that are found within the
project area:
Subgroup-(Terric, Lithic and Dysic Typic) Cryosaprists - Deep, poorly-drained soils with
muck over beach deposits, bedrock, or glacial till.
Maybeso Series The Maybeso series consists of very poorly-drained soils of
nearly level to strongly sloping seepage areas, drainage ways and benches. These
soils are made up of mucky peat 16 to 50 inches over glacial till or uplifted intertidal
silts. This soil supports a forest of western hemlock, Sitka alder and skunk cabbage.
(Photo 7).
Subgroup- Typic Cryaquods
Wadleigh Series The Wadleigh series consists of somewhat poorly-drained soils
that occur on lower toe-slopes of hills and mountains. These soils are formed in very
gravelly loamy material underlain by uplifted intertidal or marine glacial silt
sediments (or firm glacial till) that impedes internal drainage. This soil supports a
forest of western hemlock and early blueberry.
Thayer Creek Hydro Project June 2016
Subgroup-Typic (Lithic) Humicryod - Well-drained, mineral soils found on slopes and
supports Sitka spruce and hemlock forests.
Figure 6 - Histic epipedon with five inches of saturated peat over bedrock at sample point 1.
Thayer Creek Hydro Project June 2016
Figure 7- A deep, saturated, mucky peat soil (Maybeso Series) with a water table at the surface at sample pt. #3.
Thayer Creek Hydro Project June 2016
Vegetation
Upland
The typical upland vegetation of the project area is a Sitka spruce (Picea sitchensis) and western hemlock
(Tsuga heterophylla) forest with a varied understory of one or more of the following species: early and
Alaska blueberry (Vaccinium ovalifolium and V. alaskaense),false azalea (Menziesia ferruginea)
salmonberry (Rubus spectabilis) spiny wood fern (Dryopteris dilatata) and/or dwarf dogwood (Cornus
canadensis). This is the most common vegetation type on the ridgeline above and below on the 40%+
slopes of the lower Thayer Creek gorge - more than half of the access road route.
The relatively flat, terraced upland riparian forest along Thayer Creek is an open-grown, large Sitka
spruce forest with an understory of devils club (Oplopanax horridus). The proposed transmission line
runs across this plant community type when it comes down from the powerhouse.
Figure 8 - Upland Sitka spruce and hemlock forest with blueberry and false azalea understory on the slopes of the
Thayer Creek gorge above the dam site.
Thayer Creek Hydro Project June 2016
Figure 9- Upland Sitka spruce and hemlock forest with well-grazed blueberry understory on the slopes of the
Thayer Creek gorge.
Figure 10 - Terraced floodplain deposits with upland open- grown Sitka spruce forest along Thayer Creek.
Thayer Creek Hydro Project June 2016
Figure 11 - View along access road to dam site. Upland Sitka spruce/western hemlock forest.
Figure 12 - Upland spruce forest just inside the beach and next to Thayer Creek. The buried transmission line
route comes through this plant community.
Thayer Creek Hydro Project June 2016
Forested Wetlands (PFO41)
Most of the wetland in the larger project area is forested wetland (PFO4 -palustrine forested needle-
leaved evergreen) and much of the forested wetland in the project area is a western hemlock forest with
an understory of early and Alaska blueberry (Vaccinium ovalifolium and alaskanse), false azalea
(Menziesia ferruginea) and skunk cabbage (Lysichiton americanum).
Figure 13 - A typical forested wetland along the proposed access road at sample point # with western hemlock,
false azalea, blueberry and skunk cabbage.
Estuarine Wetlands (E2EM1/E2SS1)
The estuarine intertidal emergent persistent/scrub-shrub broad-leaved deciduous wetland type is the
vegetated area of the intertidal up to the extreme high water-spring (which is approximately the
20.8 ft. tide line). Anything below the extreme high water line is considered wetland, whether it has
all three of the indicators or not. There were two very different estuarine vegetation types found
within the project area:
At the north end near the dock site there is a persistently wet, upper estuarine plant
community dominated at the upper end by Sitka alder (Alnus sinuata) and at the lower end
1 Cowardin wetland classification
Thayer Creek Hydro Project June 2016
by red fescue (Festuca rubra), Bering hair grass (Deschampsia beringensis) and beach
shooting star (Dodecatheon pulchellum). There's bedrock at 6 inches that perches the water
table and keeps this community wet.
At the south end of the project area near the mouth of Thayer Creek and along the
transmission line route there is a short section of upper estuarine beach rye (Leymus
mollis) -dominated dune. The sandy dune is well-drained.
Figure 14 - Alder, fescue, hairgrass, shooting star dominated estuarine vegetation type.
Thayer Creek Hydro Project June 2016
Figure 15 - Beach rye-dominated estuarine vegetation type.
Thayer Creek Hydro Project June 2016
Table 1 - Plant Species List (Lichvar, 2014)
Scientific name common name Indicator status2
Alnus sinuata Sitka alder FAC
Athyrium felix-femina lady fern FAC
Carex pauciflora few-flowered sedge OBL
Carex sitchensis Sitka sedge OBL
Circaea alpina enchanters nightshade FACW
Coptis asplenifolia goldthread FAC
Cornus canadensis dwarf dogwood FACU
Deschampsia beringensis Bering hairgrass FAC
Dodecatheon pulchellum beach shooting star FACW
Dryopteris dilatata spiny wood fern FACU
Equisetum arvense horsetail FACU
Festuca rubra red fescue FAC
Geum macrophyllum large- leaved avens FAC
Glyceria sp. manna grass OBL
Gymnocarpium dryopteris oak fern FACU
Heracleum maximum cow parsnip FACU
Juncus arcticus arctic rush OBL
Lathyrus japonicus beach pea FAC
Leymus mollis beach rye FAC
Lysichiton americanum skunk cabbage OBL
Menziesia ferruginea false azalea FACU
Oplopanax horridus devil's club FACU
Picea sitchensis Sitka spruce FACU
Potentilla anserina silverweed FACW
Ribes glandulosum skunk current FACU
Rubus pedatus trailing raspberry FAC
Rubus chamaemorus cloudberry FACW
Rubus spectabilis salmonberry FACU
Salix sitchensis sitka willow FAC
Sambucus racemosa elderberry FACU
Scirpus microcarpus small-flowered bulrush OBL
Streptopus amplexifolius twisted stalk FAC
Tiarella trifoliata foamflower FAC
Tsuga heterophylla western hemlock FAC
Tsuga mertensiana mountain hemlock FAC
Vaccinium ovalifolium early blueberry FAC
Veratrum viride American false hellebore FAC
Veronica americana speedwell OBL
Viola glabella yellow violet FACW
2 See Table 2 for abbreviation definitions
Thayer Creek Hydro Project June 2016
Table 2 - Indicator code table (Lichvar, 2012)
Indicator
Code Type Comment
OBL Obligate
Wetland
Almost always occur in wetlands. With few exceptions, these plants (herbaceous
or woody) are found in standing water or seasonally saturated soils (14 or more
consecutive days) near the surface.
FACW Facultative
Wetland
Usually occur in wetlands, but may occur in non-wetlands. These plants
predominately occur with hydric soils, often in geomorphic settings where
water saturates the soils or floods the soil surface at least seasonally.
FAC Facultative Occur in wetlands and non-wetlands. These plants can grow in hydric, mesic, or
xeric habitats. The occurrence of these plants in different habitats represents
responses to a variety of environmental variables other than just hydrology,
such as shade tolerance, soil pH, and elevation, and they have a wide tolerance
of soil moisture conditions.
FACU Facultative
Upland
Usually occur in non-wetlands, but may occur in wetlands. These plants
predominately occur on drier or more mesic sites in geomorphic settings where
water rarely saturates the soils or
floods the soil surface seasonally.
UPL Obligate
Upland
Almost never occur in wetlands. These plants occupy mesic to xeric non-wetland
habitats. They almost never occur in standing water or saturated soils. Typical
growth forms include herbaceous, shrubs, woody vines, and trees.
NI No indicator Insufficient information was available to determine an indicator status.
Thayer Creek Hydro Project June 2016
Results
Table 3 - Northern access roads, dam, facilities, penstock and transmission line
routes.
waypoint stream
type
stream
width and
depth
wetland
start/end
sample pt
& notes
mapped
wetland unit
area (sq.ft.)
Linear feet
of stream
impacted
(ft.)
WP1
Start wet
E2EM1/E2SS1
#1 - Access
road
WP2 End wet 3,899
WP3 seasonal 1.5"x4' 245
WP4
WP5 #2
WP6
Start wet
PFO4
WP7 wet
WP8 End wet 29,000
WP9 seasonal .5'x3"
Start wet
PFO4
39
WP10 End wet 5,932
WP11 seasonal .5'x1" 36
WP12 seasonal .5'x1" 39
WP13
Start wet
PFO4
WP14 #3
WP15 seasonal 3'x2" 31
WP16 End wet 10,808
WP17 seasonal 3'x1" 192
WP18 ephemeral .5'x1" 129
WP19
Start wet
PFO4
WP20 #4
WP21 End wet 2,931
WP22 ephemeral 10'x1" 33
WP23 perennial 4.5'x5" 262
WP24
power
house site 0
WP25 ephemeral 1'x1"
buried
transmission
line
9
WP26 perennial 4'x6" 9
WP27 Start E2EM1
WP28 End E2EM1 #5 124
Thayer Creek Hydro Project June 2016
Staging area
0
Powerhouse
site area 0
Dam site
Thayer Ck. 0 30
stream #
sub-totals
Wetland area
sub-totals
Stream
length sub-
totals
ephemeral
- 3
Estuarine
4,023
Ephemeral
171
seasonal -
7
Forested
38,671
Seasonal
582
perennial -
3
Perennial
301
Stream #
total - 13
Wetland area
total 42,694
Stream
length
total -1,054
Thayer Creek Hydro Project June 2016
Table 4 - Sample point table
Sample
point
Dominant vegetation/
Hydrology /
Geomorphology Cowardin Classification PJD3
Rationale for
PJD
1 Upper estuarine. High marsh
species - red fescue, Bering
hairgrass and shooting star. The
upper edge is dominated by
Sitka alder and transitions into
supra-tidal and then upland
Sitka spruce forest. Histic
epipedon - bedrock perches the
water table.
E2EM1/E2SS4 Yes Wetland on
ocean
2 Streamside opening in a sparse
hemlock/menziesia forest with
a skunk cabbage understory.
Water table at the surface.
Mucky histosol with layers of
streamside sand and gravel
mixed in.
PFO4 Yes Wetland on
RPW that flows
into ocean
3 Hummocky, sparse
hemlock/menziesia forest with
a skunk cabbage/lady fern
understory. Water table at the
surface. Deep peaty histosol
PFO4 Yes Wetland on
RPW that flows
into ocean
4 Flat toe-of-slope terrace.
Hemlock/blueberry/menziesia
forest with a depauperate
understory. Water table above
the surface in unusual pools.
Deep mucky histosol
PFO4 Yes Wetland on
RPW that flows
into ocean
5 Narrow band of estuarine on a
sandy shallow dune at the upper
end of the tidal influence. Beach
rye and beach pea dominate.
E2EM1 Yes Wetland on
ocean
3 PJD - Preliminary Jurisdictional Determination
Thayer Creek Hydro Project June 2016
Conclusions
Using GIS tools and wetland information gathered in the field, the square footage of wetlands along
the access roads, in the facility areas and along the penstock and transmission lines was calculated.
The access road routes, buried transmission line and facilities have a total of 42,694 square feet
(0.98 acres) of wetland - both PFO4 -38,671 sq.ft. and E2EM1 - 4,023 sq.ft. and 3 ephemeral, 7
seasonal and 3 perennial streams. Approximately 1054 linear feet of stream will be affected by the
project. When broken down into sections, the transmission line route has 124 square feet of
estuarine wetland and 1 ephemeral, and 1 perennial stream. The dam and penstock route has 0
square feet of wetland and affects 1 perennial stream (Thayer Ck. at the dam site). The access road
and staging area have .98 acres of wetland and 2 ephemeral, 7 seasonal and 1 perennial stream.
References
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Habitats of the United States. Office of Biological Services, USDI Fish and Wildlife Service.
Washington, D.C. FES/OBS-79-31. 131pp.
D'Amore, David V. 2010. personal communication. Wetland Soils of Northern Southeast Alaska.
D'Amore, David V., Warren C Lynn,. 2002. Classification of Forested Histosols in Southeast Alaska.
Soil Sci. Soc. Am. J. 2002 66: 554 562
Environmental Laboratory Technical Report Y-87-1. 1987 U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.
Hulten, E. 1968. Flora of Alaska and Neighboring Territories. Stanford University Press, Stanford,
California. 1008 pp.
Miller, R. 1975. Surficial geology map of the Juneau urban area and vicinity , Alaska. Miscellaneous
Investigations Series I-885.
National Wetlands Working Group/ edited by: B.G. Warner and C.D.A. Rubec, 1997. The Canadian
Wetland Classification System, Second Edition. Wetland Research Centre, University of Waterloo,
Waterloo, Ontario.
Lichvar, Robert W. and John T. Kartesz. 2012. North American Digital Flora: National Wetland Plant
List, version 2.4.0 (https://wetland_plants.usace.army.mil). U.S. Army Corps of Engineers, Engineer
Research and Development Center, Cold Regions Research and Engineering Laboratory, Hanover, NH,
and BONAP, Chapel Hill, NC.
Lichvar, R.W., M. Butterwick, N.C. Melvin, and W.N. Kirchner. 2014. State of Alaska - Wetland Plant
List - The National Wetland Plant List: 2014 Update of Wetland Ratings. Cold Region Research and
Engineering Lab. US Army Corps of Engineers. 1-42
Schoephorester, Dale B. and Clarence E. Furbush. June 1974. Soils of the Juneau Area, Alaska
U.S. Army Corps of Engineers, U.S. Army Corp of Engineers Wetlands Delineation Manual , USDA Soil
Conservation Service (NRCS).
U.S. Army Corps of Engineers. 1987. Corps of Engineers Wetland Delineation Manual. Technical
Report Y-87-1, US Army Waterways Experiment Station, Vicksburg, MS.
US Army Corps of Engineers, Oct. 2007. Regional Supplement to the Corps of Engineers Wetland
Delineation Manual: Alaska Region, Environmental Laboratory, ERDC/EL TR-06-x, US Army
Engineer Research and Development Center, Vicksburg, MS.
Thayer Creek Hydro Project June 2016
Appendix A - Scanned Sample Site Data Sheets