HomeMy WebLinkAboutWetland Mitigation 001284006
Final Wetland Mitigation Report
Proposed Hangar Project and A TF Mitigation
Jefferson County International Airport
Jefferson County, Washington
Corps Reference No: 200500715
December 27, 2006
Addendum to: Wetland Delineation and Conceptual Mitigation Report
Dated June 16, 2006
RECEIVED
FEB 2 1 2008
Prepared for:
Port of Port Townsend
Point Hudson Marina
P.O. Box 1180
Port Townsend, WA 98368
JHfERSON tDUNT1 Den
TII=~ TOUCHSTONE
L~ ECOSERVICES
125 North 168th Street
Shoreline, WA 98133
(206) 801-7154
TABLE OF CONTENTS
Page
1.0 INTRODUCTION 1
2.0 REVISIONS TO THE CONCEPTUAL MITIGATION APPROACH 2
2.1 REVISED WATER DISPERSAL SYSTEM 3
2.2 REVISED MITIGATION RATIOS AND AREA 4
3.0 PROPOSED MITIGATION AREA EXISTING CONDITIONS 4
3.1 VEGETATION 5
3.1.1 Adjacent Vegetative Communities 6
3.2 SOILS 6
3.3 HYDROLOGY 7
4.0 PROPOSED MITIGATION DESIGN 8
4.1 GRADING PLAN 9
4.2 WATER REGIME 10
4.3 SOILS 10
4.4 PLANTING PLAN 11
5.0 GOALS, OBJECTIVES, AND PERFORMANCE STANDARDS 13
6.0 FIVE-YEAR MONITORING PLAN 15
6.1 WETLAND ENHANCEMENT/CREATION AREA AND BUFFER ENHANCEMENT 16
6.2 TEMPORARILY AFFECTED WETLAND AREAS 16
6.2 WETLAND A HYDROLOGY 17
7.0 MAINTENANCE AND CONTINGENCY PLANS 17
8.0 MITIGATION IMPLEMENTATION TIMELINE 18
9.0 USE OF TIllS REPORT 19
10.0 REFERENCES 20
LIST OF TABLES
1
2
3
4
5
Revised unavoidable impacts, ATF museum mitigation and hangar development
Revised Impact Analysis by HGMlCowardin Classification
Revised Proposed Mitigation Area
Seeding Mixes
Mitigation Plant Schedule
4
4
8
10
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LIST OF FIGURES
1 Vicinity Map
2 Proposed Hangar Design & Water Dispersal System
3 Dispersion System Details
4 Proposed Mitigation Area
5 Proposed Mitigation Grading Plan
6 - 8 Proposed Mitigation Planting Plan
9 Monitoring and Photo Stations at the Wetland Enhancement/Creation Area
10 Hydrologic Monitoring Stations at Wetland A
LIST OF APPENDICES
A Mitigation Area Photographs (2006)
B Wetland Mitigation Installation Specifications
C Scots Broom Control by Cutting and Mowing
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1.0 Introduction
This fmal mitigation plan is an addendum to the Wetland Delineation and Conceptual Mitigation
Report (TES 2006) and addresses wetland impacts and mitigation for the proposed development of new
hangars and taxilanes and the after-the-fact compensation for wetland impacts incurred during
construction of the museum project at the Jefferson County International Airport near the city of Port
Townsend in Jefferson County, Washington (Figure 1). These projects are located in close proximity to
each other near the helicopter landing apron. They will result in 0.15 acre of permanent wetland impacts
and 0.07 acre of temporary wetland impacts (see Figure 2).
The proposed compensation for permanent wetland impacts includes wetland creation and
enhancement at the northeast end of the airport, located in a similar hydrogeopmorphic position in the
landscape as the affected wetland area. Proposed compensation for temporary impacts will be located in
situ. Also, a new gravity-run, groundwater dispersal system will be placed to deliver groundwater to
Wetland A. Impacts due to this system are included in the wetland impact analysis.
A complete JARPA application was submitted to the u.s. Army Corps of Engineers (Corps) on
July 5, 2006. The Wetland Delineation and Conceptual Mitigation Report (TES 2006) was included in
that submittal and provided information on:
. responsible parties
. proposed development project and after-the-fact action
. description of the development site
. assessment of impacts at the development site
. mitigation approach
. proposed mitigation site
. existing conditions at the proposed mitigation area
. conceptual mitigation design
Following the public review and comment period, the Corps provided the comments regarding
the wetland mitigation plan on October 18, 2006 (U.S. Army Corps of Engineers 2006). These
comments are summarized below:
Mitigation Approach:
. The wetland impact analysis and mitigation approach is acceptable, however the mitigation ratios
need to be increased from recommended ratios in the joint agency guidance document, Wetland
Mitigation in Washington State (Washington State Department of Ecology et al. 2006) to address
temporal impacts from unauthorized activities. That is, a 1.5:1 plus 3:1 mitigation ratio for
wetland creation and enhancemen, respectively.
. Revise Table 3 in the conceptual mitigation report to reflect the new ratios based on impacts area.
. Review the proposed water dispersal system in Wetland A; and revise or explain why the pipe is
buried through the western portion of Wetland A.
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· Changes to the wetland mitigation area configuration and the water dispersal system require the
submittal of revised project drawings for the JARP A.
Proposed Mitigation Site
· Provide an assessment of the baseline conditions of the proposed mitigation site, including a
description of the existing species and aerial coverage of the invasive/non-native plants and color
photographs.
· Describe the presence and density of invasive/non-native plant species in adjacent areas that
could provide a seed source to colonize the proposed mitigation site.
Proposed Mitigation Site Plan/Design
· The mitigation plan must include plan views of the existing conditions and wetland boundaries,
the proposed wetland mitigation area, any buffer restoration areas, and the planting plan; and a
section view of the mitigation change in grade in the mitigation area.
· Indicate the depth of the hardpan layer in the grading cross-section.
· Show locations of fencing or signage to protect the mitigation area on the plan drawing.
· Provide a plant legend that includes the species list, planting densities, and number of plants.
· Provide goals, objectives, and performance standards. Particularly, performance standards for
minimum wetland hydrology and maximum invasive species cover.
Monitoring Plan
· An As-Built drawing needs to be submitted the year of construction as the Year 0 conditions.
· Monitoring is required each year for five years, preferably in the spring to assess, at a minimum,
wetland hydrology, plant survival and growth, and the presence of invasive/non-native species.
· Include designated photo stations along monitoring plots/transect lines and a panoramic photo of
the entire mitigation site.
· Include hydrologic monitoring along the west portion of Wetland A where the wetland impacts
occurred. Designate the sample plots on a plan view drawing.
Maintenance and Contingency Measures
· Include maintenance and contingency measures in the mitigation plan.
Implementation Schedule
· Provide a proposed implementation schedule for mitigation construction.
This fmal mitigation plan provides information on the revised mitigation plan. Appendix A includes
photographs of the wetland areas to be affected (Photos I through 3) and the northwest portion of
Wetland A (Photo 4).
2.0 Revisions to the Conceptual Mitigation Approach
Revisions have been made to the initial conceptual mitigation plan as specified by the Corps'
comments and include revisions to the water dispersal system in Wetland A and mitigation ratios. Each
of these elements is described below.
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2.1 Revised Water Dispersal System
The existing drainage system consists of a 12-inch perforated pipe (curtain drain) that captures
groundwater along the north and east retaining wall by the museum. The manhole rim in the northeast
comer of the new parking lot is at an elevation of 119.44 ft. and approximately 9 ft. below existing
ground surface at that point. The 12-inch perforated pipe has an invert elevation of 113.86. The
perforated pipe continues collecting water along the east side of the museum building to the south to 10ft.
beyond the south side of the museum building. From there, the pipe is tightlined at 111.7 ft elevation to
the existing pipe outlet in the unauthorized trench and daylights at 111.4 ft. elevation (approximately 3.2
ft. below ground surface).
The conceptual pipe dispersal system design tightlined water 310ft. to the east of the existing
pipe outlet and delivered water at the ground surface in the middle portion of Wetland A. The new design
uses perforated pipe to distribute groundwater into Wetland A to both the east and east of the existing
pipe outlet as described below (see Figures 2 and 3).
The revised gravity-drain dispersal system is designed to disperse the usual low volume flow to
the west and high volumes expected from large storm events to both the east and west of the existing pipe
outlet. While the new design is developed with the intent to bring water as close to ground surface as
possible, it is imperative to avoid impacting the museum foundation. Thus, all overflow elevations in the
revised design are set so that water does not back up into the curtain drain along the museum.
A catch basin will still be placed at the pipe outlet as in the original design. The revised design
now uses perforated pipe to disperse water underground to the west and east at elevations of 111.1 ft. and
111.3 ft., respectively. The western perforated pipe, 80 ft. in length, will be placed to nearly the western
boundary of the wetland and will be slightly lower in elevation to allow as much water as possible to
drain to the western end of the wetland. The eastern perforated pipe, 470 ft. in length, will be set at a
slight grade to allow water to drain along the system. The easternmost 200 ft. of the pipe will come
within 12 inches of the ground surface. To accommodate large storm events a series of ten 6-inch
standpipes will be placed from the pipe to ground surface along the last 200 ft. of the eastern perforated
pipe to release high flows from large storm events that may not infiltrate. In addition, a 6-inch standpipe
elevated 2 ft. above the ground surface will be placed at the end of the pipe. This standpipe will have
perforations every 6 inches along its length and is intended to serve as an indicator of the need to clean
out the buried perforated pipe or standpipe orifices when water backs up into the higher holes on the last
standpipe (that starts at elevation 111.7 ft.). The standpipe will also serve as a marker showing the
position of the perforated pipe and will allow for ease in maintaining the stand pipes at ground surface.
This new design reduces the permanent impacts by 0.01 acre since the 310 feet of half pipe at
ground elevation is no longer part of the design. Additionally, the new design increases the temporary
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impacts by 0.01 acre with the longer trench for the perforated pipe. The new impact analysis is shown in
Table 1 and impacts by landscape position and habitat classification are shown in Table 2.
Table 1.* Revised unavoidable impacts, ATF museum mitigation and hangar development
Permanent Temporary
Proposed Development Affected Area Impact Impact
(acre) (acre)
A TF Museum wetland impact Northwest lobe of Wetland A 0.1
A TF Trenching Southwest lobe of Wetland A 0.05
Catch basin and standpipes at surface Southwest lobe of Wetland A 0.0003
Perforated pipe - buried Western end of Wetland A 0.02
Hangar taxiway 2 access Wetland Y 0.05
Hangar taxilanes 1 & 2 access Jurisdictional ditch 0.004
Total imnacts: 0.15 acre 0.07 acre
* Revisions to Table 1 in Wetland Delineation and Conceptual Mitigation Report (TES 2006)
Table 2. * Revised Impact Analysis by HGM/Cowardin Classification**
Slope Depressional Ditch Total
Impact Type Impact
(acre) (acre) (acre) (acre)
PFO PSS PEM PFO PSS PEM
Permanent Impacts 0.02 0.04 0.03 0.05 0.004 0.15
Temporary Impacts 0.07 0.07
Total by Habitat type 0.02 0.04 0.1 0 0 0.05 0.004
* Revisions to Table 2 in Wetland Delineation and Conceptual Mitigation Report (TES 2006)
** Cowardin classification legend: PFO = palustrine (freshwater) forest, PSS = palustrine scrub-shrub,
PEM = palustrine emergent (grasses and forbs).
2.2 Revised Mitigation Ratios and Area
For permanent impacts, the Corps is requiring a 50 percent increase to the typical mitigation ratios
recommended in the Wetland Mitigation in Washington State (Washington State Department of Ecology
et al. 2006). The recommended ratios for creation and enhancement are 1:1 PLUS 2:1, respectively, for
a total ratio of 3: 1. With the 50 percent increase, the total mitigation ratio for permanent impacts will be
4.5:1; thus, for the 0.15 acre of permanent impacts, at least 0.68 acre of compensatory mitigation will be
completed. See Section 4.0 for a discussion of the revisions to the proposed mitigation design.
3.0 Proposed Mitigation Area Existing Conditions
Existing conditions where the in-situ restoration of temporary impacts are proposed consist of
slope, palustrine emergent habitat (see Photo 3 in Appendix A) and are described in the Wetland
Delineation and Conceptual Mitigation Report (TES 2006).
The compensatory mitigation area proposed for wetland creation, wetland enhancement, and
buffer restoration has been increased to comply with the increased mitigation ratio. This area is located
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immediately east of State Route (SR) 20 and immediately north of the emergency access road in the
northwest portion of the airport. The western third of the mitigation area includes the disturbed, northwest
portion of Wetland C with the remaining area comprised of upland habitat (see Figure 4). Existing
conditions for vegetation, soils, and hydrology are described below. The vegetation discussion also
includes a description of vegetation communities located adjacent to the mitigation area. In addition to
the site's physical characteristics described below, wildlife species observed in and near this area during
field visits include song sparrow, winter wren, bushtit, a flycatcher species, and Swainsons thrush.
3.1 Vegetation
The area proposed for wetland enhancement is comprised of the northwest portion of Wetland C
located immediately east of SR-20 and north of the airport's emergency access road. Wetland C is a
Category N wetland. The area of the wetland proposed for enhancement supports 95 percent cover of
vegetation comprised of a mosaic of palustrine scrub-shrub (PSS) and palustrine emergent (PEM) habitats
with PSS comprising approximately 55 percent ofthis area (see Photo 5 in Appendix A). The PSS habitat
is dominated by Nootka rose (Rosa nutkana, F AC-), with patches of Douglas spirea (Spiraea douglasii,
F ACW), black cottonwood (Populus balsamifera, F AC) saplings, and Sitka willow (Salix sitchensis,
FACW) saplings, Pacific willow (Salix lucida, FACW+) saplings, and red-osier dogwood (Cornus
sericea, F ACW), with infrequently occurring snowberry (Symphoricarpos albus, F ACU) and black
hawthorn (Crataegus douglasii, F AC).
The PEM habitat is dominated by creeping bentgrass (Agrostis stolonifera, F AC) and tall fescue
(F estuca arundinacea, F AC-). Numerous wetland emergent species occur throughout the PEM habitat in
patches including common velvetgrass (Holcus lanatus, F AC), field horsetail (Equisetum arvense, F AC),
soft rush (Juncus effusus, FACW), slender rush (J. tenuis, FACW-), daggerleaf rush (J. ensifolius,
FACW), tapertip rush (J. acuminatus, OBL), creeping spikerush (Eleocharis palustris, OBL), marsh
speedwell (Veronica scutellata, OBL), tall buttercup (Ranunculus acris, FACW-), centaury (Centaurium
erythraea, FAC), Engish plantain (Plantago lanceolata, FAC), and Watson willowherb (Epilobium
ciliatum, FACW-) (see Photo 6 in Appendix A).
Scattered patches of invasive species occur throughout the proposed enhancement area in
Wetland C, including Scots broom (Cytisus scoparius, NI), Canada thistle (Cirsium arvense, FAC-), and
Himalayan blackberry (Rubus armeniacus, F ACU). Overall, invasive species comprise approximately
30 percent cover in this wetland area. The enhancement area that connects Wetland C and Wetland I is
comprised of 100 percent cover of Himalayan blackberry.
The proposed wetland creation and buffer restoration areas abut the eastern edge of Wetland C
and continue east nearly to the eastern lobe of Wetland I. This area is bordered by the emergency access
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road to the south and the forested buffer along Wetland I to the north. Upland habitat in this area supports
100 percent cover of vegetation and is dominated by shrub habitat with small mosaic pockets of
herbaceous habitat occurring primarily at the eastern end ofthis area (see Photo 7 in Appendix A). Shrub
habitat is dominated by Scot's broom, snowbeny, and Nootka rose intermixed with each other. Tall
Oregon grape (Mahonia aquifolium, NI) and Himalayan blackbeny also occur infrequently in this area.
A narrow band of nearly monotypic snowbeny is dominant along most of the northern edge of this area
with infrequently occurring tall Oregon grape and red alder (Alnus rubra, F AC) saplings. Invasive
species in this area have approximately 50 percent cover.
Herbaceous habitat is dominated by bentgrass species, with less frequently occurring trailing
blackberry (Rubus ursin us, F ACU), orchardgrass (Dactylis glomerata, F ACU), scouring-rush (Equisetum
hyemale, FACW), cleavers bedstraw (Galium aparine, FACU), and bracken fern (Pteridium aquilinum,
F ACU).
3.1.1 Adjacent Vegetative Communities
Vegetation communities located adjacent to the proposed mitigation area vary greatly. To the
north is a band of upland forest habitat that abuts the south edge of Wetland I (see Photo 7, Appendix A).
The forest is dominated by red alder, black cottonwood, and Sitka willow with less frequently occurring
western red cedar (Thuja plicata, F AC), Douglas fir (Psuedotsuga menziesii, F ACU), Sitka spruce (Picea
sitchensis, FAC), and Pacific willow (Salix lucida, FACW+). The relatively open understory is a mosaic
of salal (Gaultheria shallon, FACU), Nootka rose, beaked hazelnut (Corylus cornuta, FACU), tall
Oregon grape, and Himalayan blackbeny. Patches of stinging nettle (Urtica dioica, FAC+) occur in the
nearly bare ground layer.
Upland habitat continues to the east of the proposed mitigation area with nearly equal cover of
upland herbaceous and shrub habitat and the same species as described in section 3.1.
To the south of the proposed mitigation area is the emergency access road with upland shrub
habitat to the south of the road. The shrub habitat is dominated by Scots broom with approximately 50
percent cover. The understory is 100 percent vegetated with bentgrass species and orchardgrass.
3.2 Soils
Soils in the proposed mitigation area are identified as Swantown gravelly sandy loam, 0-8 percent
slopes (NRCS 2006a). A typical profile consists of 0-3 inch organic layer of leaves, twigs, and needles.
From 3 to 8 inches BGS it is a very dark grayish brown (lOYR 3/2) to grayish brown (10YR 5/2) very
gravelly sandy loam. From 8 to 16 inches BGS, it is a brown (10YR 5/3) to very pale brown (10YR 7/3)
very gravelly sandy loam with common medium distinct strong brown (10YR 5/6) mottles. And from 16
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to 25 inches BGS, it is a gray (10YR 5/1) very gravelly sandy loam with mottles (NRCS 2006b). Formed
in glacial till on till plains, it has a cemented till layer that begins at approximately 25 inches BGS with a
thickness varying from one to two feet. Runoff is slow with moderately rapid permeability (2 to 6 inches
per hour) in the surface layer, very slow permeability (less than 0.06 inches per hour) in the cemented
layer, and somewhat poorly drained in between. A perched water table as high as 6 inches to 2 feet can
occur during the rainy season.
Repres~ntative soil plots in the Wetland C enhancement area showed soils comprised of a surface
layer of black (10YR 2/1) sandy loam with no mottles ranging in depth from 3 to 6 inches below ground
surface (BGS). Below that, to a depth of 5 to 18 inches, the soils are a very dark grayish brown (lOYR
3/2) sand with distinct mottles. Below that layer and extending to about 22 inches BGS, soils are a dark
gray (10YR 4/1) sand, with similar mottling as described in the layer above it.
Representative soil plots in the wetland creation area showed soils comprised of a surface layer of
black (lOYR 2/1) sandy loam with no mottles to a depth of approximately 12 inches BGS. Below that, to
a depth of 14 to 17 inches BGS, soils range from a very dark gray (10YR 3/1) to a black (lOYR 2/1)
sandy silt loam with distinct mottles. Below that layer to a depth of 20 inches BGS, soils are a dark
grayish brown to a very dark grayish brown (1 OYR 3/2 and lOYR 4/2, respectively) sand with mottling.
Soil samples collected on December 4, 2006 were analyzed for pH, potassium, phosphorus, and
nitrate-nitrogen by Twiss Analytical. Samples were taken from the wetland creation area and, as a control
comparison, from the relatively undisturbed Wetland I habitat to the north. Samples in the creation area
were taken just below the planned fmished substrate elevation (approximately 16-18 inches BGS). Test
results determined that the pH, nitrogen, and potassium in both areas are similar and potassium is higher
in the wetland creation area. The one different is the amount of organic content in the soils; greater than
10 percent in Wetland I and approximately 2 percent in the wetland creation area. Based on this
information, soils in the created wetland will be amended with compost to increase the organic content.
3.3 Hydrology
The Swantown soil series typically has a perched water table as high as 6 inches to 2 feet during
the rainy season (NRCS 2006b). Hydrology observations at the proposed mitigation area were
documented during site visits conducted on March 1997 (pRSW 1998), May 2002 (LA! 2005), July 2006
and December 2006.
During the March 1997 wetland delineation, groundwater was observed within 3 inches of the
soil surface in Wetland C. During the May 2002 wetland verification, groundwater was observed at
approximately 12 inches BGS in the wetland enhancement area. At that time, soils in the adjacent,
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upslope Wetland I were saturated to the soil surface with pockets of standing water several inches deep in
the central portion of this bowl-shaped wetland.
In July 2006, no groundwater or saturated soils were observed in the wetland enhancement and
creation areas. Soils were dry to approximately 6 inches BGS, with soils becoming moist at the 6 to 18
inch BGS soil horizon. At the subsequent December 2006 site visit, soils in the proposed mitigation area
were beginning to rehydrate. No groundwater or saturated soils were observed. However, soils were very
moist at 12 inches BGS in both the wetland enhancement and wetland creation areas. At that time, soils
in Wetland I were saturated at 3 inches BGS with standing water at 8 inches BGS.
Wetland C appears to receive water from precipitation and groundwater perched near the ground
surface as evidenced by the F ACW to OBL ground layer plant species growing throughout this wetland.
4.0 Proposed Mitigation Design
The mitigation design will compensate for temporary and permanent impacts to wetland acreage
and functions. Compensation will be comprised of restoring 0.07 acre of temporary wetland impacts (at
Wetland A), delivering groundwater to Wetland A, and compensating for permanent loss of wetland area
and functions (at Wetlands A and Y and the jurisdictional ditch). Temporary impacts will be restored by
replacing the removed soil in the trenched areas to existing grade and seeding all bare ground with a seed
mix of native wetland grasses (see Section 4.3). Delivering groundwater to Wetland A is described in
detail in Section 2.1 in this report.
Compensation for permanent impacts will consist of a combination of wetland
enhancement/creation and buffer enhancement (Figure 4). Table 3 shows the proposed mitigation area by
compensation type.
Table 3. * Revised Proposed Mitigation Area
Proposed Mitigation Area Mitigation Area
Compensation Type Habitat Type (acre) Needed**
(acre)
Wetland Enhancement PSS 0.34
Wetland Creation PSS 0.34 0.68
Total Wetland Mitigation Area 0.68
Buffer Restoration SS 0.26
* Revisions to Table 3 in Wetland Delineation and Conceptual Mitigation Report (illS 2006).
** Compensation for 0.15 acre of permanent wetland impacts at a ratio of 4.5:1.
The northwest portion of Wetland C is proposed for enhancement for the purpose of changing
the growth stage of vegetation present in this area. This area, located under and adjacent to the power
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lines, had been cleared in the past. Currently, the plant community is comprised of a mosaic of emergent
and scrub-shrub wetland habitat, and invasive species. The reference wetland area to the northeast is
comprised of scrub-shrub and mixed forest habitat. This mitigation plan proposes to control invasive
species and enhance the existing plant community by adding additional native wetland shrub species.
Because of the proximity of this area to the utility lines and the runway, a limited number of trees will be
added to this plant community.
Wetland creation is proposed immediately adjacent to the eastern edge of the enhanced wetland
area and down slope from the nearby Wetland I. Wetland creation will be achieved through grading
down to intercept the groundwater table and establishing native, woody, wetland vegetation.
In addition, upland buffer surrounding the new wetland area that is affected by grading will be
enhanced with native upland plantings. Buffer enhancement will serve to protect the new wetland area
and discourage invasive species establishment.
Elements for this proposed mitigation are described in detail in the sections that follow.
Appendix B provides the installation specifications for grading, soil amendments, planting, and
maintenance at the mitigation area.
4.1 Grading Plan
No grading will occur in the Wetland C enhancement area. The grading plan for the created
wetland area is based on the recent topography survey completed by Clark Land Office in summer 2006
and on Reid Middleton's hydrologic analysis of the site soils and groundwater information collected by
Touchstone EcoServices.
The wetland creation area will be graded down to bring the bottom elevation of the wetland to
within 12 inches or less of the groundwater table (see Figure 5). The finished grade at the west end ofthe
wetland creation area, at approximately 106.0 ft., will match the elevation of Wetland C. The newly
created wetland will have a 0.5 percent gradient rise with a bottom elevation of 107.5 ft. at the northwest
end of the wetland to make sure that the new wetland does not drain water from Wetland C. The new
wetland will be slightly bowl-shaped with 3: 1 side slopes (maximum).
Best Management Practices will be used to protect Wetland C during grading activities. Prior to
any grading activities, sediment fencing will be placed along the limits of grading and clearing on the
north, west, and east sides of the wetland creation area. Fencing will be inspected by a wetland biologist
prior to the beginning of earth moving. All removed material will be placed on airport property to the
east ofthe mitigation area on an already disturbed upland area.
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4.2 Water Regime
The grading plan is designed to avoid significant changes to the water regime in Wetland C.
Because the FAA is concerned about attracting waterfowl near the runway, the water regime at the
created wetland is not intended to be inundated for any length of time. Instead, the wetland creation area
will be graded to an elevation at which saturated soils and/or groundwater will be present within 12
inches of the ground surface for at least 12.5% of the growing season. The growing season for the
Swantown series in Jefferson County is about 220 days (NRCS 2006), thus wetland hydrology as defmed
above will be present at the mitigation site for at least 28 consecutive days between March 1 and October
31 each calendar year.
4.3 Soils
Organic material will be added to the existing sandy soils in the graded wetland creation area to
facilitate capillary action and provide beneficial nutrients for new plantings. Soils will be amended by
tilling 3 inches of compost into the wetland substrate to a depth of 6 to 8 inches. In addition, exposed
disturbed soils due to invasive species removal in the wetland enhancement and buffer enhancement areas
will also be amended with compost.
Grading in the mitigation area will occur in fall 2007. Exposed soils in the wetland creation and
buffer enhancement areas will be seeded at a rate of 1.5 lbs per 1,000 sq ft using the following seed
mixes. Both mixes will provide excellent erosion protection and the wetland seed mix performs well in
developing wetlands and in sites that seasonally dry out.
Table 4: Seeding Mixes, Jefferson County International Airport
Wetland Seed mix:
Common Name Scientific Name Percent of Mix
Water foxtail Alopecurus geniculatus 20
Creeping bentgrass Agrostis stolonifera 30
Native red fescue F estuca rubra v. rubra 30
Tall mannagrass Glyceria elata 20
Wetland Buffer Seed Mix:
Common Name Scientific Name Percent of Mix
Native red fescue F estuca rubra v. rubra 40
Annual ryegrass Lo/ium multiflorum 40
Fowl bluegrass Poa palustris 20
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This plan assumes that soils will not be prepared for seeding until the beginning of October when
the summer drought is over and fall rains begin. Moisture from the fall rain will be necessary for
germination of the seed mix.
4.4 Planting Plan
A planting plan prepared for the wetland creation/enhancement and wetland buffer areas is
shown in Figures 6 to 8. Based on the vegetative composition ofthe relatively undisturbed wetland area
in Wetland I and the northwestern fringe of Wetland A, this mitigation plan calls for planting native
scrub-shrub habitat with scattered wetland trees. The entire wetland creation area will be planted. The
wetland enhancement area, which currently has approximately 55 percent cover of native wetland species,
will be planted at approximately 45 percent with plantings placed between patches of existing native
scrub-shrub species.
Buffer plantings will consist of native shrubs and tree species that occur in the project vicinity
and are drought tolerant species. Due to the constraint of the power utility lines along the emergency
access road, only low-growing shrubs will be planted under or in close proximity to the power lines.
Prior to planting, all invasive species will be removed from the mitigation area. Invasive plants in
the wetland creation area will be removed during grading, as will most of the invasive plants in the
wetland buffer. Plants will be removed by hand in Wetland C using a weed wrench or similar tool. The
dense blackberry patch in the northern enhancement area will be grubbed out with a backhoe. This area
will be accessed from the wetland creation area to avoid impacts to Wetland C. In addition, all Scot's
broom plants located south of the emergency road, within 100 feet of the restored buffer area will be
mowed or cut down (see Appendix C).
Nine native wetland shrub and trees species will be planted in the wetland creation and
enhancement areas and 8 native upland shrubs and trees will be planted in the buffer enhancement area, as
specified in Table 4. The overall planting density for the wetland enhancement/creation and buffer
enhancement plantings will be approximately 695 plants per acre.
Plantings will be placed as appropriate for water regime and sun/shade preferences for each
species. Woody and herbaceous species from adjacent habitats are expected to reseed within the wetland
creation area and the buffer enhancement area, augmenting the suite of planted species. Expected
desirable colonizing wetland species include Douglas spirea, red alder, black cottonwood, soft rush,
slender rush, daggedeaf rush, tapertip rush, creeping spikerush, marsh speedwell, and tall buttercup.
Expected desirable upland buffer species include beaked hazelnut, western red cedar, and salal.
Shrubs and trees will be planted in the winter of 2007 when soils are wetter and the plants are
dormant. This will allow the plants time to establish their roots systems over the winter and spring
Mit Rpt Addendum
11
Touchstone EcoServices
seasons before the dry summer weather season. During construction, a wetland biologist will verify that
plants are placed in the appropriate locations. When the plant installation is complete, the biologist will
conduct an inspection within 1 month and will provide detailed notes on any changes to the final
mitigation plan. This "as-built" will be submitted to the Corps and will include information on the fmal
grade and plant installation.
Table 4: Miti2ation Plant Schedule, Jefferson County International Airport
Species Spacing Size
Number of plants Scientific Name English Name (on-center)
CR* EN* BU*
5 Abies grandis Grand ftr 25-ft 2 gal. or 24"
bareroot
57 40 Cornus sericea Red-twig dogwood 6-ft 18" bareroot
or 1 gal
10 18 Crataegus douglasii Black hawthorn 10-ft 18" bareroot
or 1 gal
25 Holodiscus discolor oceanspray 10- ft 18" bareroot
or 1 gal
55 36 11 Lonicera involucrata Black twinberry 6-ft 18" bareroot
or 1 gal
35 Mahonia aquifolia Tall Oregon grape 6-ft 1 gal.
12 17 Malus fusca Western crabapple 10-ft 18" bareroot
or 1 ~al
8 Philadelphus lewisii Mock orange 10-ft 18" bareroot
or 1 ~al
7 4 Picea sitchensis Sitka spruce 25-ft 2 gal. or 24"
bareroot
32 18 Rhamnus purshiana Cascara 10- ft 18" bareroot
or 1 ~al
94 12 Rosa nutkana Nootka Rose 6-ft 18" bareroot
or 1 ~al
44 20 Salix sitchensis Sitka willow 6-ft Live stake or
18" bareroot
9 Sambucus racemosa Red elderberry lO-ft 18" bareroot
or 1 gal
76 Symphoricarpos albus snowberry 6-ft 18" bareroot
or 1 gal
9 Thuja plicata Western red cedar 25-ft 2 gal. or 24"
bareroot
311 162 181 Total plants per area
* CR = wetland creation area, EN = wetland enhancement area, BU = buffer restoration area.
Mitigation plantings will need to be watered during the fIrst two summer seasons after
installation. A temporary irrigation system will be installed with raised, 2-ft. tall sprinkler heads spaced
Mil Rpl Addendum
12
Touchstone EcoServices
at approximately 20 ft. on-center throughout the wetland creation and buffer enhancement areas to
provide head-to-head irrigation coverage. A water truck will be used to pump water into the system at the
rate specified in Appendix B.
A split rail fence and/or a row of untreated logs will mark the outside edge of the wetland buffer
along the emergency access road; this simplistic barrier will demarcate the outer edge of the buffer where
equipment and machinery will be prohibited from entering after mitigation activities are complete. A
locked gate on the emergency access road prevents public access to the mitigation area.
5.0 Goals, Objectives, and Performance Standards
Goals are broad statements that generally defme the intent or purpose of the proposed mitigation.
Objectives identify specific elements to be undertaken to meet the mitigation goals. Objectives are
subdivided into specific performance standards, which are measurable criteria of specific attributes that
provide a gauge for measuring the success of the mitigation. Site specific goals, objectives, and
performance standards are described below:
GOAL #1: Compensate for 0.15 acre of permanent wetland impacts by enhancing and creating 0.68
acre of wetland habitat.
OBJECTIVE lA.
Vegetative
Year 1
Year 4
Standard lAl Planted woody material within the wetland enhancement/creation area
will have a 100 percent survival rate. Native, woody volunteer species
less than 18" tall may NOT be counted toward this performance
standard. Dead or missing planted tree/shrub stock will be replaced to
maintain 100 ercent survival rate.
Standard lA2 Planted woody material within the wetland enhancement/creation area
will have an 80 percent survival rate or at least 20% aerial cover of
native woody species. Appropriate woody volunteer native species (as
approved by the Corps ) MAY be counted toward this performance
standard.
Standard lA3 Planted woody material within the wetland enhancement/creation area
will have an 80 percent survival rate or at least 30% aerial cover of
native woody species; Appropriate woody volunteer native species (as
approved by the Corps) MAY be counted toward this performance
standard.
Standard lA4 Planted woody material within the wetland enhancement/creation area
will have an 80 percent survival rate or at least 40% aerial cover of
native woody species. Appropriate woody volunteer native species (as
approved by the Corps) MAY be counted toward this performance
standard.
Year 2
Year 3
Mil Rpl Addendum
13
Touchstone EcoServices
GOAL #1. Continued:
Year 5 Standard lA4
Year 5
Standard lA5
Planted woody material within the wetland enhancement/creation area
will have an 80 percent survival rate or at least 50% aerial cover of
native woody species. Appropriate woody volunteer native species (as
approved by the Corps ) MAY be counted toward this performance
standard.
At the end of Year 5, native wetland scrub-shrub habitat will be
established in the 0.68-acre enhancement/creation mitigation area with a
minimum of 5 native scrub-shrub species and 2 native tree species
throu out.
Years 1-5
Standard lA 7
The wetland creation area will have saturated soils within 12 inches of
the surface for a minimum of 28 consecutive days during the growing
season in years of normal preci itation.
OBJECTNE IB. Enhance 0.26 acre of wetland buffer habitat through invasive species control and
native species establishment.
Year 1
Standard IBI
Year 2
Standard IB2
Year 3
Standard IB3
Year 4
Standard IB4
Year 5
Standard IB4
Year 5
Standard IB5
Planted woody material within the buffer enhancement area will have a
100 percent survival rate, or if 100 percent survival of planted stock is
not achieved, appropriate species of native volunteer plants (as
a roved by the Co s will be counted for each dead or missin lant.
Planted woody material within the buffer enhancement area will have
an 80 percent survival rate or at least 20% aerial cover of native woody
species. Appropriate volunteer native species (as approved by the
Co s) will be counted toward this erformance standard.
Planted woody material within the buffer enhancement area will have
an 80 percent survival rate or at least 30% aerial cover of native woody
species. Appropriate volunteer native species (as approved by the
Co s) will be counted toward this performance standard.
Planted woody material within the buffer enhancement area will have
an 80 percent survival rate or at least 40% aerial cover of native woody
species. Appropriate volunteer native species (as approved by the
Corps) will be counted toward this erformance standard.
Planted woody material within the buffer enhancement area will have
an 80 percent survival rate or at least 50% aerial cover of native woody
species. Appropriate volunteer native species (as approved by the
Co s) will be counted toward this erformance standard.
At the end of Year 5, there will be a minimum of 6 native woody
s ecies throu out the buffer.
Years 1-5
StandardlB6
Mil Rpt Addendum
Invasive plants (Himalayan blackberry, evergreen blackberry, Scots
broom, thistle, etc.) will have less than 10 percent cover in the enhanced
buffer area.
14
Touchstone EcoServices
GOAL #2: Compensate for 0.07 acre of temporary wetland impacts at a 1:1 ratio
OBJECTIVE 2A. Restore wetland grade and wetland vegetation to all areas in Wetland A affected
temporarily by trenching.
Year 0
Year 1
Standard 2AI Grades within the temporarily affected wetland areas will match the
existin s of surroundin wetland habitat.
Years 2-5
Standard 2A2 Seed germination within the temporarily affected wetland areas will be
high enough to provide at least 90 percent cover of wetland grass
species, or if 90 percent cover is not achieved, appropriate species of
native volunteer herbaceous plants (as approved by the Corps) will be
counted toward this erformance standard.
Standard 2A3 Herbaceous wetland vegetation within the temporarily affected wetland
areas will have 100 ercent.
Years 1-5
Invasive plants (Himalayan blackberry, evergreen blackberry, Scots
broom, thistle, etc.) will have less than 10 percent cover in the
tem oraril affected wetland areas.
Goal #3: Monitor hydrology in the northwest portion of Wetland A.
OBJECTNE 3A. Document the presence of continued wetland hydrology in Wetland A adjacent to the
museum development.
YearO-5
Standard 3Al
The northwest portion of Wetland A will have saturated soils within 12
inches of the surface for a minimum of 28 consecutive days during the
growin season in ears of normal precipitation.
6.0 Five-Year Monitoring Plan
Monitoring will consist of field observation and documentation of site conditions in the three
areas addressed in the mitigation goals; 1) the creation/enhancement area, 2) the temporarily affected
wetland areas, and 3) the northwest portion of Wetland A. Wetland mitigation areas will be monitored
for a period of 5 years as required by the Corps.
The monitoring plan for each of these areas is described briefly below. Monitoring reports will
be prepared each year in compliance with the Corps' Regulatory Guidance Letter (RGL) 06-03 and will
document site conditions and success in meeting performance standards. If performance standards are not
met, contingency plans will also be included in the monitoring report. The annual reports will be
submitted to the Corps and County no later than October 15th each year.
Mil Rpl Addendum
15
Touchstone EcoServices
6.1 Wetland Enhancement/Creation Area and Buffer Enhancement
Permanent monitoring and photo stations, locations shown in Figure 9, will be established within
the wetland and buffer areas. Vegetative data will be collected within 5-meter (~16-ft.) plots for shrubs
and IO-meter (~33 ft.) plots for trees at each monitoring station. Hydrologic data will be collected at
monitoring stations within the created wetland. Photographs will be taken annually at each photo station
to provide clear visual documentation of mitigation conditions.
Vegetative conditions will be monitored twice each year. A site visit will be conducted annually
in the spring between April 1 and May 15 to assess general site and invasive species conditions. If
necessary, the project proponent will take immediate steps to address invasive species as recommended
by the monitoring biologist. A second site visit will be conducted in the late growing season between
July 1 and August 1 to assess invasive species conditions and document plant cover by species, vigor, and
mortality.
Hydrologic conditions will be monitored between March 1 and June 1 each year. The depth of
saturated soils and/or free standing groundwater will be documented at permanent monitoring stations in
the wetland creation area. Monitoring will be done on a bi-weekly (defmed as once every two weeks)
basis until the hydrologic performance standard is met, that is, when wetland hydrology has been
documented for 28 consecutive days.
Formal monitoring of native vegetative survival and percent will be conducted for 5 years unless
the vegetative performance standards are exceeded for Year 3. If Year 3 standards are exceeded, then
photographs will be used to informally document native plant cover conditions in Year 4. Formal
monitoring of native vegetation will be conducted in Year 5 in all cases. Hydrologic monitoring and
invasive species control monitoring and contingencies will be conducted for all 5 years.
6.2 Temporarily Affected Wetland Areas
Due to the linear and narrow configuration of the temporarily affected wetland areas, no
monitoring stations will be placed in these areas. Instead, the entirety of each temporarily trenched area
will be visually assessed for percent cover of herbaceous vegetation and invasive species, and photos will
be taken at each end of the re-seeded areas.
Vegetative conditions will be monitored twice each year for all 5 years of the monitoring period.
A site visit will be conducted annually in the spring between April 1 and May 15 to assess general site
and invasive species conditions. If necessary, the project proponent will take immediate steps to address
invasive species as recommended by the monitoring biologist. A second site visit will be conducted in
Mil Rpl Addendum
16
Touchstone EcoServices
the late growing season between July 1 and August 1 to assess invasive species conditions and document
plant cover by species and plant vigor.
6.2 Wetland A Hydrology
Permanent monitoring, locations shown in Figure 10, will be established within the northwest
portion of Wetland A adjacent to the disturbance from the museum development. Hydrologic data will
be collected at the monitoring stations and photographs will be taken of the monitored area from the south
end of each transect to provide clear visual documentation of wetland conditions.
Hydrologic conditions will be monitored between March 1 and June 1 all 5 years of the
monitoring period. The depth of saturated soils and/or free standing groundwater will be documented at
each monitoring station. Monitoring will be done on a bi-weekly basis until the hydrologic performance
standard is met, that is, when wetland hydrology has been documented for 28 consecutive days.
7.0 Maintenance and Contingency Plans
The mitigation area will be maintained on a regular basis throughout the monitoring period.
Maintenance will include actions required to maintain plants free of insects and disease, eliminate
competition with grasses and weeds, protect plantings from browsing, and provide beneficial growing
conditions. During the first year after plant installation, the mitigation area will be maintained by the
landscape contractor as specified in Appendix B (Part 10). Following the one-year maintenance period by
the landscape contractor, the Port of Port Townsend's maintenance department will continue to maintain
the mitigation area with guidance from the wetland biologist. In addition, any problems observed by the
wetland biologist during monitoring visits will be conveyed in writing to the Port to explain the problem,
the solution, and timeline for addressing the problem.
If there is a significant problem with the mitigation achieving the performance standards specified
for any given year, the cause of the problem will be determined and a contingency plan will be developed.
The Corps will be informed of proposed contingency plans, which can include but are not limited to:
additional plant installation, substitution of a plant species more suited to site conditions, increased
management of invasive and/or competitive species, erosion control, adjustments to the temporary
irrigation plan, modification to hydrology, and herbivory protection such as rodent collars or fencing.
Mil Rpl Addendum
17
Touchstone EcoServices
8.0 Mitigation Implementation Timeline
Mitigation plans as discussed previously in this document will be implemented on the following
timeline and each element will be completed in the order given below:
April 1, 2007 - October 31,2007
1. Construct the stormwater pond next to State Route 19.
2. Grade the development area for the hangars and taxilanes. Install utilities, drainage/stormwater
system and pave taxilanes. This includes wetland impacts to the jurisdictional ditch and Wetland
Y for construction of taxiway access.
3. Install the groundwater dispersal system in Wetland A as specified in engineering drawings as
soon as the drainage/stormwater system for the hangars and taxilanes is in place and functioning.
The groundwater dispersal system will be complete no later than September 30th.
4. Re-fill temporary trenches in Wetland A using the removed native soils and seed exposed soils
with specified seed mix. Exposed soils will be seeded no later than October 7th.
5. By April 30, stake and flag the limits of clearing in the wetland creation area. Then clear invasive
species within the limits of clearing, in the southern buffer enhancement area, and the area south
of the emergency access road by mowing or cutting to avoid soil disturbance. Whether plants are
mowed or manually cutting back, the ideal time is May through mid-June. Follow specifications
in Appendices B and C.
6. Concurrent with installation of the groundwater dispersal system in Wetland A, silt fencing and
finished grade stakes will be placed as specified in the wetland creation area. Wetland biologist
will inspect these items prior to grading.
7. Grade wetland creation area as specified in grading plan and installation specifications.
8. Remove invasive species from the wetland enhancement areas as specified in installation
specifications.
9. As soon as grading and invasive species removal is complete in the wetland
enhancement/creation and buffer enhancement areas, amend all exposed soils with compost as
specified in installation specifications and seed all exposed soils with specified seed mix.
Exposed soils will be seeded no later than October 7th.
10. Wetland biologist to complete the interim as-built inspection immediately after the earthwork,
invasive species removal, and seeding has been completed. Take panoramic photographs of the
as-built mitigation work outlined in items 3-7 above and submit photos to the Corps and County
no later than October 31,2007.
December 15,2007 to February 15,2008
1. Install plantings in enhancement and creation areas, wetland and buffer, as specified in the
mitigation planting plan and installation specifications. Date of installation depends on
availability of bare roots plant stock. Plant installation to be supervised and/or inspected by a
wetland biologist. Spot over-seeding may be necessary in specific locations where soil
disturbance during plant installations has disrupted the previously-seeded ground surface.
2. Wetland biologist to complete the as-built inspection immediately after the planting work has
been completed. Take panoramic photographs of the restoration work outlined in item 1 above
and submit photographs to the Corps and County no later than March 1, 2008.
Mit Rpt Addendum
18
Touchstone EcoServices
2008 - 2012
1. On an annual basis, a wetland biologist will monitor the wetland and wetland buffer mitigation
areas at the proposed designated monitoring plots, identified in this mitigation plan report, to
determine wetland hydrology, vegetation survival and cover, and invasive species control.
Monitoring will occur twice a year through 2012, once during the early growing season (early
April to mid-May) to document hydrologic conditions and once in the summer (July through
August) to document vegetative conditions.
2. Prepare and submit a yearly Monitoring Report to the Corps and County no later than October
15th each year during the monitoring period. The report will include photographs of all mitigation
areas.
9.0 Use of this report
This wetland mitigation report was prepared for the exclusive use of the Port of Port Townsend
for the specific application to the proposed North Hangar and A TF museum project. The use by others, or
for purposes other than intended, is at the user's sole risk. The reuse of information, conclusions, and
specifications provided herein for extensions of the project or for any other project, without review and
recommendations by Touchstone EcoServices, shall be at the user's sole risk. The findings presented
herein are based on our understanding of the Corps of Engineers written communications with the Port of
Port Townsend and phone conversations with representatives of the Corps, the topographic survey of the
site, and evaluation of site hydrology by Reid Middleton. Within the limitations of scope, schedule, and
budget, the findings presented in this report were prepared in accordance with generally accepted
sensitive area investigation principles and practices in this locality at the time the report was prepared.
Touchstone EcoServices makes no other warranty, either express or implied.
Mit Rpt Addendum
19
Touchstone EcoServices
10.0 References
LA!. 2005. Revised Wetland Delineation Report for Jefferson County International Airport. Prepared for
the Port of Port Townsend. Landau Associates, Inc. Edmonds, WA. June 15.
NRCS. 2006a. Natural Resources Conservation Service Web Soil Map. Website:
http://websoilsurvey.nrcs.usda.gov/app/ checked May 5,2006.
NRCS. 2006b. National Cooperative Soil Survey - Official Soil Series Description. Website:
http://www2.ftw.nrcs.usda.gov/osd/dat/S/SWANTOWN.html checked December 10,2006.
PRSW. 1998. Final Jefferson County Airport Wetland Delineation Report, File Number M98-0050.
Prepared for the Port of Port Townsend. Pacific Rim Soil & Water, Inc. Olympia, Washington.
December 30.
Touchstone EcoServices. June 2006. Wetland Delineation and Conceptual Mitigation Report for the
Proposed Hangar Project and ATF Mitigation at Jefferson County International Airport. Prepared for
the Port of Port Townsend. Shoreline, W A.
U.S. Army Corps of Engineers. August 3, 2006. Regulatory Guidance Letter 06-03: Mitigation
Monitoring Report Format. U.S. Army Corps of Engineers Seattle District. Seattle, WA.
U.S. Army Corps of Engineers. October 18, 2006. Memorandum for the Record (MFR): Wetland
Mitigation Review for the Port of Port Townsend, Reference Number: 200500715. U.S. Army Corps
of Engineers Seattle District. Seattle, W A.
Washington State Department of Ecology, U.S. Army Corps of Engineers Seattle District, and U.S.
Environmental Protection Agency Region 10. March 2006. Wetland Mitigation in Washington State
- Part 2: Developing Mitigation Plans (Version 1). Washington State Department of Ecology
Publication #06-06-011 b. Olympia, W A.
Mil Rpl Addendum
20
Touchstone EcoServices
OLYMPIC
NATIONAL
PARK
FIGURE 1
~
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~ 425 741-3800
SCALE: NONE
DATE: 12/15/06
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JEFFERSON COUNTY
INTERNATIONAL AIRPORT
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JEFFERSON COUNTY
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PROPOSED HANGAR DESIGN &
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FIGURE 3
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97 @ Comus seticea Red-twig dogwood 6-ft. 18" bareroot or 1 gal. "~ Picea sitchensis Silka spruce 250ft. 2 gal. or 24- bareroot
28 0 CrataegtJ8 dougfasii Black hawthorn 1D-ft, 18. bareroot or 1 gal. 50 0 Rhamnus purshlana Cascara 1D-ft. is'' bareroot or 1 gal.
25 0 Holodiscus discolor Oceanspray 10ft. is'' bareroot or 1 gal. 106~ Rosa nutkana Nootka Rose 6-ft. 18" bareroot or 1 gal. N
102 C0 Lon/cera involucrata Black twinberry 6-ft. 18" bareroDt or 1 gal. 64 0 5a1b< sitchensis Sitka wiDow 6-fl. Live stake or 18" bareroot
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0 30
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Approx. Scale in Feet
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9 Thuja plicata Western red cedar 25-ft. 2 gal. Dr 24" bareroot
TES JEFFERSON COUNTY INTERNATIONAL AIRPORT Figure
TOUCHSTONE Proposed Mitigation Planting Plan 6
ECOSERVICES
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TES
TOUCHSTONE
ECOSERVICES
JEFFERSON COUNTY INTERNATIONAL AIRPORT
Proposed Mitigation Planting Plan
Figure
7
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TES
TOUCHSTONE
ECOSERVICES
JEFFERSON COUNTY INTERNATIONAL AIRPORT
Proposed Mitigation Planting Plan
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TES
TOUCHSTONE
ECOSERVICES
JEFFERSON COUNTY INTERNATIONAL AIRPORT
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TES
TOUCHSTONE
ECOSERVICES
JEFFERSON COUNTY INTERNATIONAL AIRPORT
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Source: Reid Middleton
Figure
10
APPENDIX A
Mitigation Area Photographs
(taken June and September 2006)
Photo 1: Jurisdictional ditch (looking north from the south end of the ditch where it empties into
Wetland Y) is to be crossed in two places to provide access from the new hangars and taxilanes to the
existing Taxiway B.
Photo 2: Wetland Y (looking east from the west end ofthe wetland) to be crossed in one place using a
span bridge to provide access to Taxiway A.
A-I
Photo 3: Palustine emergent habitat in the area of temporary wetland disturbance during placement of
the groundwater delivery system for Wetland A. (Looking north toward the southeast comer of the
museum).
Photo 4: Northwest portion of Wetland A, looking east from the clearing line.
A-2
Photo 5: Wetland C - typical palustrine scrub-shrub habitat. looking northeast toward the
area immediately west of the proposed wetland creation area. (Rosa nutkana, Spiraea
douglasii, Salix sp. saplings, Populus balsamifera)
Photo 6 : Wetland C - typical pocket of palustrine emergent habitat. Cytisus scoparius be-
ginning to invade native plant community of Juncus effusus, J tenuis, J, ensifolius, J
acuminatus, Holcus lanatus, Agrostis alba, Epilobium ciliatum, and Salix sp. seedlings.
A-3
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Appendix B
Wetland Mitigation Installation Specifications
PART 1- GRADING SPECIFICATION
Grading Schedule
All earthwork within the mitigation area shall be completed by October 31 st to ensure
adequate seed establishment prior to the wet season. All exposed ground shall be seeded
immediately upon completion of grading and temporary irrigation system installation.
General Site Conditions
Contractor shall give the Wetland Specialist a minimum of 10 days notice prior to
intention to proceed with construction. The approved plans and specifications shall be
reviewed by the Contractor and Wetland Specialist prior to construction work to allow
parties involved to understand the intent and specific details related to the construction
documents, specifications, and site constraints.
Locations of existing utilities have been established by field surveyor obtained from
available records and should be considered approximate only and not necessarily
complete. It is the sole responsibility of the Contractor to: 1) independently verify the
accuracy of utility locations and 2) discover and avoid any utilities within the mitigation
area not shown which may be affected by implementation of this plan. Such areas are to
be clearly marked in the field. Owner's Representative shall resolve any conflicts with
the approved grading plan prior to start of construction.
Construction must be performed in accordance with Agency standards, codes, permit
conditions, and other applicable ordinances and policies. The. applicant is responsible for
obtaining any other related or required permits prior to the start of construction.
A copy of the approved plans, specifications, permits, and agency approvals must be on
site whenever construction is in progress and shall remain on site until project
completion. A qualified wetland consultant shall be on site, as necessary, to monitor
construction and approve minor revisions to the plan.
Topographic elevations represented on the mitigation plans are based upon a topographic
survey by Clarks Land Office and grading plans by Reid Middleton, Inc. Final elevations
may vary depending on site specific conditions. It is the responsibility of the Contractor
to verify pre-construction topographic elevations, the adjacent wetland boundary, and
existing vegetation locations for accuracy prior to grading. Contractor shall notify
Wetland Specialist immediately if any modifications to the plans may be necessary due to
inaccuracies of the original survey.
Survey/Stake/Flag Limits of Clearing/Grading
Prior to any construction, limits of clearing and grading shall be staked and flagged. The
Wetland Specialist shall review and approve flagging of clearing limits prior to any
vegetation removal. No significant trees (>6" diameter at breast height) shall be removed
from the mitigation area without written authorization from Wetland Specialist.
Contractor shall be responsible for avoiding disturbance to existing vegetation outside the
limits of clearing and grading. No removal of any vegetation shall occur without prior
approval of the Wetland Specialist. Areas outside clearing limits that area degraded or
accidentally cleared shall be replanted consistent with other mitigation planting occurring
as a part of this contract, at no extra cost to the Owner. Plant species and quantities to be
approved by Wetland Specialist prior to installation.
Erosion Control Measures
Construct erosion control measures before beginning any other work. Silt fences and
other BMPs must be installed prior to any disturbance activity within or adjacent to
wetland areas. Contractor shall install silt fencing at the downslope side of grading or
clearing limits through the mitigation area.
Vegetation to Remain
Any living woody plant that is damaged during construction shall be treated within 24
hours of occurrence. Wound shaping treatment shall be done. Wound shaping includes,
but is not limited to evenly cutting broken branches, exposed roots, and damaged tree
bark. Injured plants shall be thoroughly watered and additional measures taken, as
appropriate, to aid in plant survivability.
Clear and Grub
Clearing Contractor shall clear and grub areas within the clearing limits of the wetland
creation and buffer enhancement areas. No grading is to occur in the existing wetland
(Wetland C enhancement) areas. In the western wetland enhancement area, Clearing
Contractor shall removed blackberry and Scots broom by hand with minimal disturbance
to the existing vegetation. In the northern wetland enhancement area, blackberry thickets
may be removed by grubbing, this area is to be accessed via the graded wetland creation
area only. No herbicides will be sprayed. Cleared and grubbed vegetation shall be
bagged and exported from the site. Particular care must be given to ensure complete
removal of the tops and roots (to a depth of 18") of invasive species. Invasive species to
be removed in the mitigation area are Scots broom, Himalayan and evergreen blackberry,
and thistle.
Survev/Stake/Flag: Proposed Grades
Contractor shall contract a licensed surveyor to survey, stake and flag proposed fInish
grades within the mitigation area following clearing and grubbing. Surveyor shall supply
grade stakes at a minimum of 40' O.C. spacing. Wetland Specialist shall approve grade
staking prior to excavation and shall monitor during construction. Maintain grade stakes
through excavation process. If grad stakes are removed prior to grading sign-off, the
Contractor shall supply as-built grade staking without additional cost to Owner.
B-2
Mitigation Area Excavation
Contractor shall excavate the wetland creation area per the approved grading plan.
Excavated soils shall be removed immediately to airport location provided by Owner.
Minor adjustments to grading plant shall be made only by obtaining prior approval of
Wetland Specialist.
PART 2 - FINISH GRADING, COMPO STING, IRRIGATION INSTALLATION, AND
SEEDING
Compost Incorporation
Wetland Specialist shall approve earthwork in the mitigation area prior to incorporation
of compost. In all graded areas, 3' of weed-free, vegetative compost shall be placed over
grade. Compost shall be thoroughly tilled into the existing grade to a depth of 6".
Amended soil shall be lightly track-walked on sloped areas to prevent erosion rilling.
After compost incorporation, no heavy or large equipment shall be allowed into the
mitigation area.
Compost shall also be tilled in to soils exposed due to removal of invasive species in the
wetland enhancement and wetland buffer areas. Compost will be added to the same
specifications as above.
Irrigation
A temporary irrigation system shall be designed and installed by Contractor prior to
inatllation plantings within the mitigation area. Irrigation system shall have raised 2'
sprinklers. All enhanced and created mitigation areas shall receive head-to-head
irrigation coverage. Irrigation system is to be used in conjunction with a water truck.
Irrigation is required within the mitigation area for at least two growing seasons flowing
planting to ensure adequate establishment of plant material. The mitigation area shall be
irrigated to allow for expected Puget Sound lowland precipitation and adjusted to
according to changes in weather patterns seasonally. Typical irrigation rates are W' of
precipitation 2 times per week between April 15th and October 18t of the first year after
planting; and W' once weekly between June 18t and October 18t in the second year after
planting,. If planting occurs between May and October, then irrigation shall be extended
to three growing seasons.
Contractor is responsible for ensuring proper function of the irrigation system and to
'winterize' installed irrigation system prior to October 31 st. It is the Contractor's
responsibility to maintain the irrigation system for the duration of the two years (or three)
in which it is required. At the end of the irrigation period, and if plant establishment is
successful as determined by Wetland Specialist, the Contractor shall remove the
irrigation system.
Seeding
After irrigation system installation and prior to seeding, Contractor shall water
thoroughly all exposed soils.
B-3
Seeding operations shall be conducted immediately following grading operations,
incorporation of compost and irrigation system installation; and no later than October 7.
Fine rake entire area to provide even, smooth grades. Scarify the soil to 1/2" depth. Seed
mixes specified in the planting schedule shall be applied at the rate of 1.51bs. per 1,000
square feet. Seed using hydroseeding method to fully cover all planting areas as
incorporating the hydromulch, emulsifier, and tackifier.
Maintain adequate moisture immediately following seeding and until grass has
germinated.
Coverage after one growing season: Contractor shall warrant growth and coverage of
hydro seed planting to the effect of a minimum of 98% of the area planted shall be
covered with grass. No bare spots shall exist greater than four square feet. Additional
seeding may be required in the spring following plant installation. For small areas, hand
seeding is recommended; for larger areas, mechanical or hydro seeding will be required.
Hydroseeded areas exhibiting conditions unacceptable shall be repaired/and or replaced
at no additional cost to the Owner.
PART 3 - CONTRUCTION REVIEW
Posting-Grading Evaluation
Wetland Specialist shall approve grading work, compost incorporation, irrigation
installation, and seeding prior to plant installation to confirm that the mitigation plans
were properly implemented. If items are to be corrected, Wetland Specialist shall prepare
a punch list and submit it to the Contractor for completion. After punch list items have
been completed, Wetland Specialist shall review the project for fmal internal acceptance
of grading plan implementation and planting may proceed.
PART 4 - CONSTRUCTION DELAYS
Soil Stabilization
If there is a delay in construction for any reason, Contractor, unless otherwise stated in
writing, shall be responsible for maintenance of erosion control measures and temporary
irrigation during construction delay period.
Disturbed land areas in which construction activities may be suspended for 30 days or
more shall be immediately seeded with the mixes specified in the plant schedule. Seeded
areas shall be irrigated with a water truck if irrigation system has not been installed and
maintained until acceptable seed germination has been achieved (98 percent coverage).
Upon construction completion, Contractor shall re-seed all exposed ground (second hand
seed application) with the seed mixes specified in the plant schedule.
B-4
PART 5- WARRANTY
Contractor shall ensure that construction related activities do not damage off site features
or adjacent vegetation. Wetland Specialist shall be notified immediately if accidental
damage occurs (see plant replacement requirements in clearing section).
Contractor shall ensure that adjacent roads are maintained and clear of soil and/or other
debris at times during construction, including the emergency access road. Contractor
shall make himself aware of and comply with County codes regarding street
maintenance/cleaning/traffic control during construction.
Any changes or modifications to this plan must receive prior approval from the Wetland
Specialist.
Part 6 - PLANTS
Planting Schedule
Planting may not occur until the irrigation system is installed and operating. Planting
may occur only during the cool season months (October 1 to March 1). If planting
commences after March 31 st, expect a higher rate of mortality; and a third year of
irrigation will be necessary.
General Conditions
Prior to plant installation, Contractor shall remove invasive species as specified the Clear
and Grub section (Part 1). Contractor shall verify that plant installation conditions are
suitable within the mitigation area. Any unsuitable conditions shall be corrected prior to
the start of work. When conditions detrimental to plant growth are encountered, such as
rubble, fill, adverse drainage conditions, or obstructions, Contractor shall notify Wetland
Specialist prior to planting. Beginning of work constitutes acceptance of conditions as
satisfactory.
Plant Material Standards
Within 30 days of award of the landscape contract, Contractor shall submit
documentation that specified plant materials have been ordered and secured. A list of
supplier names, addresses, phone numbers and the storage/growing location of the
materials shall be submitted to Wetland Specialist.
Plant material shall meet the requirements of State and F ederallaws with respect plant
disease and infestations. Inspection certificates, required by law, shall accompany each
and every shipment and shall be submitted to Wetland Specialist upon contractor's
receipt of plant materiaL
Plants shall be nursery grown, well-rooted, of normal growth and habit, and free from
disease or infestation. Plant materials shall be locally grown (western Washington,
western Oregon, or western British Columbia), healthy, bushy, in vigorous growing
B-5
conditions, and be guaranteed true to size, name, and variety. Container stock shall be
fully rooted but not root bound.
Deciduous trees shall have uniform branching, single straight trunks and the central
leader intact and undamaged.
Coniferous trees shall be full and bushy with uniform branching and a natural, non-
sheared form. Original central leader shall be healthy and undamaged. Maximum gap
between branching shall not exceed 9", and length ofleader shall not exceed 12".
Shrubs shall be a minimum height of 18 inches. Single stemmed or thin plants will not
be accepted. Side branches shall be generous, well-twigged, and the plant as a whole
well-bushed to the ground. Plants shall be in a moist, vigorous condition, free from dead
wood, bruises, or other root or branch injuries.
Substitutions
Substitutions of plant species or sizes may be permitted based on plant availability, but
only with prior written approval by Wetland Specialist.
Locate/StakeN erify Planting Areas
Contractor shall field locate, stake, and verify planting areas and configurations prior to
planting. Wetland Specialist shall review and approve locations prior to planting.
Wetland Specialist reserves the right to adjust the locations of the landscape elements
during the installation period as appropriate to the job.
If obstructions are encountered that are not shown on the drawings, do not proceed with
planting operations until alternate plant locations have been selected. Tree locations shall
be adjusted to clear all overhead lines and structures.
Planting locations shown on planting plans are approximate, based on anticipated site
conditions. Actual planting locations may vary from those shown due to final site
conditions and locations of existing vegetation. Nevertheless, any variations from the
planting plan will require approval by Wetland Specialist.
Plant spacing for species listed is random (naturalistic), and not in a regular grid pattern.
On-center spacing indicated on plant list shows average spacing. For example, when the
plan calls for 6' O.C., spacing shall vary from 4' to 7' O.c., with an average spacing of 6'
O.C.
Proposed locations of trees and shrubs shall be staked and identified with an approved
coding system or by placement of the actual plant material. For large groupings of a
single species, Contractor may stake the planting boundaries.
Wetland Specialist shall review and approve all planting locations prior to planting.
B-6
Verify Nursery Stock Condition
Wetland Specialist shall inspect plant material at the job site for compliance with
required standards for plant size, and quality prior to planting. This includes, but is not
limited to: size and condition of root systems, presence of insects, latent injuries and
defects. Trees must be untied and separated for inspection. Wetland Specialist reserves
the right to require replacement or substitution of any plants deemed unsuitable any time
prior to final acceptance if it is determined that such material does not meet the
specifications as described above. Rejected material shall be immediately removed from
the site and replaced with like material that meets the required standards.
Storage Site and Method
Store plants in the manner necessary to accommodate their horticultural requirements.
Protect plant material stored on site from weather damage, construction ac ctivity, and the
public. Keep plants moist (wetland species saturated) and shaded until the actual time of
installation. Ifbare-root materials are specified, soak roots in water 1 hour minimum
prior to planting. Before planting, immediately saturate soils in the planting area to
prevent capillary stress.
PART 7 -PLANT INSTALLATION
Planting Specs
Planting shall be performed only by experienced workers familiar with native plant
installation procedures under the supervision of a qualified supervisor
Trees and shrubs shall be pit planted. Excavate circular plant pits with vertical sides.
Scarify the bottom and sides of the pit to a depth of 4 inches. Place 6 inches minimum
lightly compacted layer of planting soil under root system of each tree and shrub. For
trees, excavate the hole l' beyond the edge of the roots on all sides.
Set plant material in the planting pit to proper grade and alignment. Set plants upright,
plumb, and faced to give the best appearance or relationship to each other or adjacent
structure. Set root collar flush to the finish grade. No filling will be permitted around
trunks or stems.
Backfill the pit with native material. Do not use frozen or muddy mixtures for backfilling.
No fertilizers shall be utilized in the wetland or wetland creation areas. Amend backfill in
all planting pits with a hydrated soil moisture retention agent (polymer). Follow
manufacturer's specifications for directions for use and application rates.
Form a ring of soil 3 inches high around the edge of each shrub planting pit and 6 inches
high around the edge of each tree planting pit.
Water all plantings within the first 24 hours of initial planting. Irrigation shall continue
for the first two growing seasons in upland buffer situations, and within the wetland
zones if adequate hydrology is not established.
B-7
Staking: Only stake trees 6 feet or greater in height per planting. Plant ties should be
loosely placed, and must be composed of biodegradable material (no wire, plastic, or
nylon cords).
In zones where herbivores are expected, wrap all woody trunks with thin plastic mesh
rodent protection to reduce cambian damage by rodents. Assure that the gauge of
protective wrap is such that tree growth will split the material if it is not physically
removed.
Plant material which settles from an upright position during the construction and
guarantee period shall be repositioned or replanted as required.
Landscape Contractor shall securely, but loosely, tie a 2' piece of pink flagging to the top
portion of all planted vegetation.
Mulch
Place 6-8 inches of woodchip mulch around the base of each new tree (24" diameter ring)
and shrub plantings (18" diameter ring) for erosion, weed control, and moisture retention.
Mulch shall be comprised of medium soft wood, weed-free mulch, or organic compost.
Keep mulch or woodchip material at least 3 inches away from the stem/trunk, do not
allow mulch/woodchips to touch the stem of woody plants inorder to avoid mildew
and/or fungus growth.
Fencing
Fencing, split rail fencing, or untreated logs, will be placed along the north edge of the
emergency access road by contractor after plant installation.
Clean Up
Perform cleaning daily during installation and upon completion of the work. Remove
from site all excess materials, soil, debris, and equipment. Repair damage resulting from
planting operations.
Perform off-site street sweeping as required by jurisdiction.
No storage of toxic materials (including fuel or lubricants) shall occur onsite unless they
are stored within a secured and contained storage locker or facility.
Contractor shall be responsible for the removal of construction materials and debris on
the site following installation of plant materials and fence placement.
PART8-PLANTWARRANTY
This warranty shall include replacement of plants (same size and species as shown in
planting plans) that prove either to be mislocated or unsuitable as to plant material
B-8
standards. Except for loss due to excessively severe climatological conditions
(substantiated by lO-year recorded weather charts), installed plant materials are required
to be guaranteed for one year against defects and unsatisfactory growth, except for cases
of neglect by Owner or abuse/damage by others. Plants replaced shall be reinitiated
under plant guarantee conditions.
Part 9 - FINAL ACCEPTANCE
Upon completion of the planting, the Landscape Contractor shall provide Owner's
Representative with a set of clearly marked prints designating the actual locations and
quantities of plantings within the mitigation areas. Landscape Contractor shall keep a
complete set of prints at the job site during construction for the purpose of "red-lining"
changes or modifications to the approved plans and shall update said information on a
daily basis.
Inspection to determine acceptance of planted areas shall be made by Wetland Specialist
upon Contractor's request. Provide notification at least 5 working days before requested
final observation date. Provisional acceptance of the planted areas shall occur at the end
of installation. Provisional acceptance shall be granted provided the plant material has
been installed correctly, site clearing has been completed, and watering requirements, if
necessary, have been satisfactorily addressed.
Wetland Specialist shall approve planting locations. If items are to be corrected, a punch
list shall be prepared by Wetland Specialist and submitted to the Landscape Contractor
for completion. After punch list items have been completed, Wetland Specialist shall
review the project for final acceptance of plan implementation. The maintenance period
begins immediately following final acceptance and the beginning of the one year
warranty period, and lasts for a period of one year.
After final acceptance has been obtained, Landscape Contractor shall provide as-built
drawings to Wetland Specialist of planted material.
Final observation shall occur at the end of the one year warranty period. Final
acceptance shall be granted provided all requirements, including required maintenance,
have been complied with an plant materials are alive and in a healthy, vigorous condition.
Part 10 - ONE-YEAR MAINTENANCE
Landscape Contractor shall review landscape maintenance recommendations with the
Owner's Representative who is familiar with the stated goals and objectives of the
mitigation plan. Maintenance is to be provided throughout construction and for one year
following construction beginning at fmal acceptance.
Maintenance shall include all actions required to maintain plants free of insects and
Disease, eliminate competition with grasses and weeds, and die-back or mortality due to
inadequate soil moisture.
B-9
Landscape Contractor shall maintain trees and shrubs as required to maintain healthy
growth and habitat diversity. This may include tightening and repair of tree stakes,
resetting plants to proper grade and upright position, grass and invasive species control.
Removal of grass and/or invasives shall be done by hand, with hand-pulling of all weeds
within the drip ring of any installed woody plant. NO weed-whipping will be allowed
between woody plants, unless woody stems have been equipped with rodent barriers.
Landscape Contractor shall be responsible for consistent and adequate water application
throughout the growing season. Landscape Contractor shall winterize and reinstate
system in spring, including tune-up and repairs during the one-year maintenance period.
Irrigation is required within the wetland mitigation area for at least two growing seasons
following planting to ensure adequate establishment. At the end of that time, the
Landscape Contractor shall remove the irrigation system.
Landscape Contractor shall remove silt fencing at the end of the maintenance period or
when grass reaches 1 foot in height. Restore disturbed soils in the fence area by hand
seeding all bare areas greater than 1 square foot between April 1 st and October 15th.
General Maintenance Items
Correct defective work as soon as possible after deficiencies become apparent and
weather and season permit.
Tree Stake Removal- Any installed tree stakes should be removed after the first growing
season to prevent girdling of staked plant material.
Debris Removal - The Landscape Contractor shall remove all trash and other debris on a
regular basis. Contractor shall leave all dead plant material and other organic debris (i.e.,
leaf matter, fallen branches, etc.) except pest-infested vegetation.
Foraging and Browsing - The Maintenance Contractor shall implement measures to
prevent damage of plant material by browsing (e.g., rabbits, mice, voles, etc.).
Maintenance of Trees and Shrubs - Routine maintenance of trees and shrubs shall be
performed. Tall grasses shall be weeded at the base ofthe plantings. Weed control
should be performed by hand removal and/or installation of weed barrier cloth.
Pruning of Woody Plants - Woody plants shall only be pruned to remove pest
infestations.
Contractor, under the direction of the Owner, shall correct erosion and drainage problems
as specified in the annual monitoring report throughout the maintenance period.
B-10
Appendix C
Scots Broom Control through Cutting and Mowing
Scots broom can be effectively controlled through hand cutting and mechanical
mowing. It is important to keep soil disturbance to a minimum during these control
activities as bare soils and mixing of the surface soils encourages germination of the
existing seed bank of this and other invasive species. In addition, long-term management
will be needed to exhaust the seed bank and prevent re-colonization in cleared areas.
Manual Removal
Hand clearing permits the removal of weeds without damage to surrounding
native vegetation. Young plants up to 3 ft. in height growing in moist soil can be easily
pulled out by hand, roots and all. Root removal is important as young plants tend to re-
sprout from roots left in the ground. Larger plants can be pulled from the ground using
weed wrenches, root jacks, and pulaskis.
The best timing for hand pulling is in the late spring (May in the Pacific
Northwest) just before the plants go to flower. To prevent germination ofthe existing
seed bank where bare ground is left from pulling plants, mulch should be placed over any
exposed soil to a depth of 6 inches.
Scots broom can also be cut back as an effective control measure. Plants should
be cut below the basal node (that is, near or below the ground level) where the stem is
more yellow than green. Old plants in dry soil have a nearly zero re-growth rate if cut
correctly. About half of young plants that have been cut back will re-sprout. For this
reason, two to four passes through the area to be cleared should be done in May and June
before seed set to make sure all flowering plants have been removed; with a follow-up
visit in July to cut down any plants that were missed and have gone to seed. All plants
with seeds must be bagged and removed from the site.
Mechanical Removal
Mechanize equipment can be used to remove Scots broom using a tractor-
mounted mower on relatively even ground. Because these cuts are higher than the
recommended basal cuts, the plants have a greater tendency to re-sprout. Using this
method, broom plants typically require several cuttings before individual plants die. The
best time for the first cutting is when the plants begin to flower (late May-June) when
root reserves are lowest and new seeds haven't been produced. Follow-up mowing on a
regular basis throughout the summer is necessary to remove re-sprouted plants. All
plants with seeds must be bagged and removed from the site.
Whatever control method is used, maintenance will need to be conducted on a
regular basis throughout the monitoring period (and ideally, continuing beyond the
monitoring period) to avoid the establishment of any new broom plants in the control
area.
Information in this Appendix is from the article: Controlling Scotch (Scots) Broom
(Cytisus scoparius) in the Pacific Northwest, prepared by the Nature Conservancy and
based on information http://tncweeds . ucdavis. edulmoredocsl cytscoO 1. pdf
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