Wetland Analysis, Existing Situation and Proposed Future Situation
Harris Ranch
Prepared for:
LeNir LTD.
4940 E. Mill Station Dr., Suite 101-B
Boise, Idaho 83716
November 2006
Prepared by:
Karl Gebhardt, P.E., P.H.
Hydrologist/Environmental Engineer
Resource Systems, Inc.
10306 Harvester Dr.
Boise, Idaho 83709
Contents
Contents .......................................................................................................................................... 2
Introduction..................................................................................................................................... 3
Wetlands – Existing Situation......................................................................................................... 3
Methods....................................................................................................................................... 3
Hydrology ................................................................................................................................... 4
Vegetation ................................................................................................................................... 5
Soils............................................................................................................................................. 5
Table 1. Wetland Summary ...................................................................................................... 10
Proposed Situation and Mitigation................................................................................................ 11
References & Bibliography........................................................................................................... 12
2
Introduction
This report will present a concise summary of the existing situation and proposed mitigation for
wetland resources on the Harris Ranch Property. The term “wetland” as used in this report refers
to wetland that may be considered jurisdictional by the U.S. Army Corps of Engineers and would
likely require permitting under Section 404 of the Clean Water Act. The precise definition of
jurisdictional wetland is currently uncertain because of a recent U.S. Supreme Court ruling
(Rapanos v. United States, June 19, 2006) that will probably result in changes in the
jurisdictional definitions in the near future. This report will serve as a reasonable guide to what
wetlands are present on the site. This report is being prepared as a supplement to a much larger
overall submittal for the Harris Ranch Project and therefore will not contain particular
information on location, size, and other information that would be redundant to that provided in
the submittal.
Wetlands – Existing Situation
Wetland delineations have been prepared for the project area at least three times in the last 15
years or so. The latest wetland delineation is more than 5-years old and requires re-verification
and interpretation under the soon-to-be-released jurisdictional wetland definitions. The
information presented in this report utilizes the previous delineations. The initial delineation was
conducted in 1990 by Dr. Dana R. Sanders and Resource Systems, Inc. Dr. Sanders was a
principal author of the current Corps of Engineers wetland delineations guidance (Environmental
Laboratory, 1987). The areas of potential jurisdictional wetland are provided in Figure 1.
The project area has a number of important features significant to understanding the potential for
wetland development and for providing a point of reference. The project area is bisected by
Highway 21 and Eckert Road. The interior of the project area contains the bulk of potential
wetlands and is bounded by the Boise River on the south and west and the Penitentiary Canal on
the east and north. The project interior abuts the Boise Foothills to the north, which include the
watersheds of Warm Springs Creek and Squaw Creek. Land use on the project area is rangeland
in the foothills and irrigated pasture in the interior.
Methods
The routine determination described in Environmental Laboratory (1987) was followed in the
project area although many of the areas were considered to be atypical (man-induced) due to the
extensive flood irrigation and grazing on the property. The Ada County Soil Survey (Soil
Conservation Service 1980) was used to obtain general soil mapping boundaries. Pre-mapping
of the area was done according to the vegetation classification system used by the U.S. Fish &
Wildlife Service (Cowardin et.al. 1979) with assistance from the National Wetland Inventory
3
maps (USFWS 1982). Since much of the property has been under flood irrigation, sources of
water were carefully identified, along with the various ditches that convey the water. Historical
photos were located and analyzed to help assess the land use history of the property and flooding
characteristics of the Boise River. Weather records were obtained from the Soil Conservation
Service, State Climatologist, and National Weather Service to understand the potential natural
water supply for the property. Discharge of the Boise River was used to understand the flooding
recurrence of those areas influenced by the Boise River.
Site mapping and identification - Potential wetland sites were identified as follows:
Sites south of Warm Springs Avenue (HW21) and west of Eckert Road are shown as S-#; sites
north of HW21 are shown as N-#, and sites east of Eckert Road and south of HW21 are shown as
SE-#..
Hydrology
An area was determined to be a candidate for jurisdictional wetland if the area had a dominance
(> 50%) of obligate, facultative-wet, and/or facultative vegetation, had hydric soil indicators, and
wetland hydrology. The presence of wetland vegetation was generally not considered a definite
indication of a jurisdictional wetland since irrigation will produce such vegetation. Where
wetland vegetation was found to be dominant soil indicators and hydrology became the major
indicators. Since soil indicators are induced by hydrology, hydrology became the key indicator
used to determine if a jurisdictional wetland was likely present.
Waters of the United States were also considered those areas having water adjacent to and
supplied by the Boise River during the high flows of 1996, which were considered to be at the
jurisdictional mean high discharge (Boise River near 6500 cfs at Glenwood Bridge).
Modifications - A number of significant influences to the project area has occurred over the past
50 years that may influence the hydrology, soils, and wetland vegetation.
•
Lucky Peak reservoir has significantly altered the frequency of high flows that formed
many of the natural channel features on the property.
•
Much of the pasture area on the north side of HW21 has been altered to provide
irrigation. Some ditches have become filled between 1957 and present.
•
The Penitentiary Canal provides a significant source of water to the property and may be
responsible for much of the water emerging from the slopes above the Boise River floodplain to
the north containing wetland areas N2 – N7.
•
Warm Springs Creek had a number of routes to the Boise River but was straightened and
placed in a canal some time prior to 1939.
4
Vegetation
The project area contains several vegetation communities which can be described as:
•
Upland grasses - which are located on highly permeable soils or higher areas that do not
receive as much irrigation water as pasture; these are dominated by cheatgrass and medusahead
wildrye.
•
Irrigated pasture - containing mostly fescue, bluegrass, wheatgrass, and other pasture
grasses;
•
Irrigated pasture low areas - containing sedges, baltic rush, fescue;
•
Depressions/ponds - containing cattail, bulrush, sedges, rushes;
•
Cottonwood forest - cottonwood and willow.
Soils
The dominant soils in the project area are Moulton and Notus series. The Moulton series has a
moderately rapid permeability and is considered poorly drained. The series is not considered
hydric except in depressions. The Notus series has a moderately rapid permeability and is
considered somewhat poorly drained. The Notus series is not considered hydric. Both soils may
have inclusions of the Chance series, which is considered hydric and typically found in channels
and other depressions. The water table for the Chance series is generally within 10 inches of the
surface. Few areas showed true hydric characteristics indicating long-term reducing conditions
other than in some depressional areas having a high water table, found below 12 to 30 inches
below the surface. A number of areas had rust-colored mottles in the upper 6 inches or so,
indicating oxidizing conditions due to iron and water oxidation processes, likely resulting from
irrigation. The soil colors generally followed the soils series description closely.
S2
Delineation Status: Jurisdictional Wetland/Open Water
Acres: 0.98
This site is part of the Walling Ditch. It appears to be a modified side channel of the Boise River.
It normally flows some water all year even when the water level at the diversion is below the
mouth of the ditch (although the ditch is blocked at the upper end) . This is due to the
interception of ground water, irrigation, and sprinkling from the lumber operation. The dominant
vegetation depends on the position within the canal. The lowest vegetative position is generally
always inundated or saturated and consists of Typha latifolia, Scirpus acutus and other typical
emergent wetland plants. The position between this and the upper bank consists of willows and
cottonwood. It has some fishery potential that is presently limited by the poor quality of habitat
features and a lack of season-long flow.
5
S7
Delineation Status: Questionable Jurisdictional Wetland
Acres: 1.55
The S7 area is a depression believed to have been a flood channel or very old remnant of an
irrigation canal connected to the Boise River. It appears in photographs prior (1959, 1964) to the
construction of what now is the Producers Lumber site northeast of the northern bypass. It
appears as a portion of the PEM1a NWI inventory. The lumber yard appears to have cut off or
blocked ditches draining the area. Some pipe was found on the downstream end of this site that
could be connected to a drainage feature beneath the lumber yard. The area now serves as a
collection point for runoff and irrigation water from the north. The area is questionable because
it may lack a significant connection to the Boise River and it also may be ephemeral.
S 13
Delineation Status: Jurisdictional wetland/open water
Acres: 1.9
This area is a flood channel adjacent to the Boise River. The area is dominated by Juncus spp.
and Carex spp.. It is inundated during mean high discharge of the Boise River and would be
considered jurisdictional for that reason alone. The adjacent cottonwood site is not considered a
jurisdictional wetland as it would fail to meet inundation criteria and would not have sufficiently
high ground water for the coarse soil found at the site (mapped by the SCS as Notus but appears
too coarse).
S 15
Delineation Status: Jurisdictional Wetland/Open Water
Acres: 2.4
This site is on the far west point of the property and is adjacent to the Boise River. Dominant
vegetation is cottonwood and willow. The site is inundated at the normal high flow of the Boise
River.
S 16-17
Delineation Status: Isolate Wetland
Acres: .89
These are two areas whose wetland characteristics appear to be irrigation-induced. They are
dominated by sedges and rushes, but invasion of noxious and upland vegetation (mainly thistle)
is apparent. No water was found within 24 inches of the surface, but the soil did have mottles
and some gleying. After irrigation practices are halted on the property, characteristics will again
be checked for wetland criteria. In 2001, the Corps of Engineers determine wetland S-17 to be
isolated and exempt from permitting. Wetland area S-16 is expected to be similar.
6
SE 1
Delineation Status: Jurisdictional Wetland
Acres: 2.39
This area is a remnant side channel. It is inundated during mean high flow and is considered
Waters of the United States because of its adjacency. Dominant vegetation consists of Juncus
spp. and Carex spp..
SE 2
Delineation Status: Jurisdictional Wetland
Acres: 0.04
This area appears to be an old flood channel and functions as a depression capturing runoff and,
more importantly, appears to be supplied by a local ground water system. Dominant vegetation
include Juncus spp., Carex spp. and rabbit-grass. Soil in this site is very dark, indicative of longterm saturation.
SE 3-5
Delineation Status: Jurisdictional Wetland
Acres: 4.69
These areas appear to be remnants of an old mill pond since wood chips were found in the soil.
It is also adjacent to a railroad (spur) base that was probably used to move logs from Barber
Pond further downstream. There is evidence of a subsurface water. Dominant vegetation is
Juncus spp., Carex spp., Festuca rubra, and rabbit-grass. Artesian conditions are known to be
present just east of this area. These conditions are probably the result of Barber Dam. The
jurisdictional determination should be checked with the latest definitions since there may be a
nexus issue at these sites.
SE 6-8
Delineation Status: Questionable Jurisdictional Wetland
Acres: 6.1
This area changed character considerably from spring to summer. In April of 1996 the area
dominated by Typha and was inundated with 1-2 inches of water. By late summer, when it was
field checked, it was almost exclusively growing smartweed, and there was no water at the
surface. It may be substantially supplied by subsurface sources, as the water supply to these
areas appears to originate adjacent to the east side of SE 8, but it does not appear to be a
permanent source of water. The area has changed substantially since the removal of irrigation.
These wetlands may also lack a suitable nexus to the Boise River.
N3
Delineation Status: Probable Jurisdictional Wetland
7
Acres:
This area appears to have been the outside of a progressive meander of the Boise River many,
many years ago. The soils are mapped as Bissel loam and Moulton fine sandy loam although the
soil is very clayey to a depth of about a foot and then turns to fine sand. The soils did not have
convincing hydric indicators. The site was mapped by the NWI as PEM1f. N3 has a dominance
of wetland vegetation consisting of purple loosestrife and hardstem bulrush. The site was
inundated with irrigation return flow during field examination and is supplied continuously by
irrigation water for its wetland indicators. The site appears to have a suitable connection with
the Boise River.
N 4a-f
Delineation Status: Questionable Jurisdictional Wetland
Acres:
These areas appear to have been developed prior to 1957 (photo date) as a conveyance for
irrigation. All of the sites were connected with a ditch that is clearly evident in photography as
late as 1964. These sites probably developed from long-term flood irrigation with vegetation
establishing at the spill points. Over the years the ditch and spill points have filled with very
fine-grained soil and created very suitable conditions for maintaining wetland vegetation. These
areas would likely dry up with the removal of irrigation and the Penitentiary Canal, but are
included as jurisdictional at this time until monitoring proves otherwise.
N 5, 6, 7
Delineation Status: Questionable Jurisdictional Wetland
Sites N 7a and b are identified by the NWI as PEM1a. All of the sites contain hydric vegetation
consisting of Typha spp., Juncus spp. and Carex spp.. These sites are on a relatively high slope
for emergent wetlands and therefore must be supplied by a large and consistent amount of water
during the growing season. The hydrology is explained in Appendix 2 and describes the sources
and possible development of the areas. When examined by Dr. Sanders in 1990 he stated “My
onsite investigation revealed that soils of the areas lack colors associated with hydric soils,
indicating that these soils did not develop under anaerobic soil conditions”. Some of our study,
however, did find hydric soil indicators near the surface (chromas of 1), but not at depth (16
inches) in the profile. We believe, as does Dr. Sanders, that these areas would disappear upon
the removal of irrigation water.
N 8 (also continues into S)
Delineation Status: Jurisdictional Wetland
Acres: 1.65
This area is Warm Springs Creek and is considered a tributary to the Boise River. The channel
and immediate banks are included as jurisdictional wetland and/or open waters of the United
8
States. The wetland communities are more indicative of a struggling riparian zone, but without
grazing pressure, the stream may produce viable wetland characteristics, albeit marginal.
The foothill drainages contain ephemeral drainages that could be regulated for fill. Each of these
areas should be examined if a fill is proposed.
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Table 1. Wetland Summary
Map
Unit
N3
N4a
N4b
N4c
N4d
N4e
N4f
N5
N6
N7
N8
S2
S7a
S13
S16
S17
SE1
SE2
SE3
SE4
SE5
SE6
SE7
SE8
Total
Acres
2.86
0.11
0.09
0.40
0.10
0.22
0.16
0.26
0.56
6.81
1.65
0.98
1.55
1.92
0.53
0.36
2.39
0.04
0.23
3.08
1.38
2.43
0.54
3.13
31.80
Proposed Situation and Mitigation
The proposed flood mitigation would substantially alter the north floodplain of the Boise River
adjacent to the river (Figure 2). Most of this area is non-wetland and rarely, if ever, flooded. The
proposed grading would lower this area to make it much closer to ground water and also would
become part of the active floodplain of the Boise River, becoming flooded or very wet at normal
bankfull flows. This area is expected to create approximately 30 acres of wetland and enhance 2 – 6
acres, producing a complex of emergent, scrub-shrub and forested habitats along the Boise River and
Walling Ditch.
Warm Springs Creek would be realigned to eliminate potential flooding of the Idaho Power
Transmission line tower footings and to eliminate the ditch feature between Warm Spring Avenue and
the Boise River. The realignment would also accommodate Squaw Creek allow both waters to move
through wetland prior to their discharge into the Boise River. At least one sedimentation detention
pond would be located above Harris Ranch Road to protect downstream residents. The flood channel
would resemble a large swale with a safety factor of at least 1.4, meaning that it will convey 40 percent
more than the 100-year flood. Squaw Creek would be combined with Warm Springs Creek above
Warm Springs Avenue. The flood channel would eventually return to the right bank of the Boise River
via a constructed wetland to remove as much sediment as possible. This will be a large improvement
in sediment delivered to the Boise River from Warm Springs Creek compared to existing conditions.
The channel footprint would be approximately 80 feet wide with side slopes of about .10 - .17 feet/foot
(10:1, 6:1).
Fill is proposed for the wetland areas as shown on Figure 2 and on the table below.
Table 2. Wetland Impacts
Map
Unit
N3
N4a
N4b
N4c
N4d
N4e
N4f
N5
N6
N7
N8
S7a
S16
S17
Total
Acres
2.86
0.11
0.09
0.40
0.10
0.22
0.16
0.26
0.56
6.81
1.65
1.55
0.53
0.36
15.66
Proposed
Fill
0.93
0.11
0.09
0.40
0.10
0.22
0.16
0.36
0.56
6.81
1.65
1.55
0.53
0.36
13.83
Wetland Created
& Enhanced
Created Areas
Mitigation Area
Warm Springs
Total Created
Acres
24.00
6.00
30.00
Enhancement
S2
S13
Total Enhanced
1.50
1.92
3.42
Net Increase
19.59
11
The proposed project would fill most of the areas north of Warm Springs Avenue which are considered
to have low function and value when compared to wetland adjacent to the Boise River. Wetland
suspected as being non-jurisdictional (S16 and S17) would be filled. Warm Springs Creek would be
relocated and its length increased by about 1,900 feet with an estimated increase in functional wetland
by at least 2 acres.
Walling Ditch
The mitigation area is being designed to have the potential to carry a small creek along the north bank
eventually connecting to the Walling Ditch which has been proposed for restoration for many years.
This feature, if constructed, would significantly benefit the Boise River fishery and would provide
additional habitat currently not in existence.
Summary
The project would fill nearly 14 acres of areas that may be jurisdictional wetland. Most of the wetland
proposed for fill are relatively isolated parcels and not associated with the Boise River. The project
proposed to create or enhance between 25 and 30 acres of wetland that would be adjacent the Boise
River and directly contribute to connectivity and habitat values. The wetlands created would have
potential for developing forested and shrub habitat. The habitat would be created to allow the
connection of a side-channel creek to the Walling Ditch potentially improving the Boise River fishery.
The project intends to create truly functional Class-A habitat in an area that currently has little, if any,
functional, high-value habitat.
References & Bibliography
ASCE. 1989. Water use by naturally occurring vegetation: An annotated bibliography. American
Society of Civil Engineers, New York.
Cowardin, L.M., V. Carter, F. C. Golet, E. T. LaRoe. 1979. Classification of wetlands and deepwater
habitats of the United States. USFWS/OBS-79/31
Dion, N.P. 1972. Some effects of land-use changes on the shallow ground-water system in the BoiseNampa area, Idaho. Idaho Department of Water Administration, Water information Bulletin No. 26.
47 p.
Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual, Technical
Report Y-87-1, US Army Engineer Waterways Experiment Station, Vicksburg, Miss.
Mundorff, M.J., E.G. Crosthwaite, and C. Kilburn. 1960. Ground Water for irrigation in the Snake
River Basin in Idaho. USGS open-file report. J.S. Geological Survey, Boise, Idaho.
Nace, R.L.. S. W. West. and R.@. Mower. 1957. Feasibility of ground-water features of the alternate
plan for the Mountain Home project, Idaho: U.S. Geol. Survey Water Supply Paper 1376, 121 p.
12
Sanders, D.R. 1990. Preliminary Draft Identification and delineation of “Waters of the United States”
on Harris Ranch, Ada County, Idaho. Prepared for Wilsey & Ham Pacific, Inc., Boise, Idaho.
Savage, C.N.. 1958. Geology and mineral resources of Ada and Canyon Counties: Idaho Bur. Mines
and Geology County Report no. 3, 94 p.
U.S. Army, Corp of Engineers, 1977. Boise valley regional water management study, background
information appendix.
U.S- Soil Conservation Service, 1980, Soil survey of Ada county. SCS, Boise, Idaho.
13