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  • Blackjack Creek Mitigation Site

    Restoration and Management Plan

    Wildlands of Washington, Inc.

    June 2006

    Note from the author:

    This document was prepared for Wildlands of Washington, Inc., a mitigation banking

    company based in western Washington State.

    Preparation included:

    Site research into the existing site conditions (soils, vegetation, topography);

    Preparation of the proposed mitigation design;

    Close communication with the client to properly capture project intent;

    Several iterations of draft submittals and incorporation of revisions based on client

    comments;

    Preparation of supporting tables (figures and appendices provided by others); and

    Finalization of document for submittal to state and federal agencies (e.g. U.S.

    Army Corps of Engineers, WA Department of Ecology).

    Because of this documents proprietary nature, the full table of contents is shown, but only

    select sections are provided.

    Janice Cessna

  • June 16, 2006 Blackjack Creek Mitigation Site

    Wildlands of Washington, Inc. Restoration and Management Plan

    1

    Table of Contents

    Executive Summary ...3

    Project Purpose4

    Mitigation Approach...4

    Mitigation Site Goals and Objectives...5

    Mitigation Site Description5

    Site Details .5

    Site Selection Rationale ...6

    Constraints of the Site ..5

    Existing/Baseline Conditions .6

    Site Plan and Design ...11

    Description .5

    Water Regime 6

    Grading Plans ...5

    Planting Plans ...6

    Wetland Functions Comparison.4

    Mitigation Acreages and Perimeter Buffer 5

    Performance Standards ..15

    Monitoring Plan ...18

    Monitoring Schedule...18

    Monitoring Methods20

    Maintenance, Monitoring and Contingency Plans ..21

    Financial Assurances and Site Protection..21

    References ..22

  • June 16, 2006 Blackjack Creek Mitigation Site

    Wildlands of Washington, Inc. Restoration and Management Plan

    2

    List of Tables Table 1 Proposed Mitigation Acreage without Perimeter Buffer XX

    Table 2 Proposed Mitigation Acreage with Perimeter Buffer ....XX

    Table 3 Monitoring Schedule for Blackjack Creek Mitigation Site .19

    List of Figures Figure 1 - Vicinity Map

    Figure 2 - Site Overview Map

    Figure 3 Zoning Map

    Figure 4 - Wetland Delineation

    Figure 5 - Groundwater Well Locations

    Figure 6 - Natural Resource Conservation Service Soils

    Figure 7 - FEMA Floodplains

    List of Appendices Appendix A Existing Conditions map

    Appendix B Cultural Resources Report by Landau Associates

    Appendix C Phase I Environmental Site Assessment by Landau Associates

    Appendix D Wetland Delineation Report by Landau Associates

    Appendix E Blackjack Creek Mitigation Site groundwater data

    Appendix F Grading Plan, Planting Plan, and Details sheets

    Appendix G Wetland Rating Form: Blackjack Creek Mitigation Site After Implementation

  • June 16, 2006 Blackjack Creek Mitigation Site

    Wildlands of Washington, Inc. Restoration and Management Plan

    3

    Water Regime The proposed Mitigation Site will experience the same flooding frequency and duration that

    occurs now. Groundwater will remain the primary year-round water source with surface flow

    from Blackjack Creek contributing a significant portion only in the winter season. Therefore, no

    water rights are needed. No mass grading, culvert installation, or water control structures are

    proposed in the project design.

    As described earlier in the existing conditions, the dredged creek spoils currently serve as a

    physical barrier to initial floodwaters within Blackjack Creek. By removing the spoils, the creek

    will have an entirely open connection to its floodplain within the project site. Some spoils,

    however, will be left in place as upland islands for greater habitat diversity. These will be

    approximately twenty-five square feet (approx. 5 by 5) or less and scattered intermittently

    along the creek length with approximately several hundred feet between each.

    Removal of drain tiles and plugging of drainage ditches will restore the natural hydrologic cycle

    within the site by discontinuing the current expedited drainage routes. The groundwater table

    will likely rise closer to the ground surface, becoming more readily available throughout the year

    and sustaining a saturated perennial wetland system. Existing herbaceous species dominated by

    facultative grasses will transition to domination by obligate sedges and rushes.

    Because no volume or flow analysis has been conducted on Blackjack Creek, a quantification of

    the potential water table rise is not presented. However, the review of the existing conditions

    within the southeast forested wetland as discussed earlier in the existing conditions section offers

    a glimpse of the future habitat. In this area, saturation is at or within a few inches of the ground

    surface year-round, as demonstrated in Landau Associates wetland delineation report.

    Additionally, small pockets of water ponds in low spots during the winter months.

    The groundwater monitoring wells will be kept in place and maintained during the

    implementation of this Restoration and Management Plan, as well as through the duration of the

    monitoring and maintenance periods. The wells will likely be preserved and occasionally

    monitored for a time after final project acceptance by responsible agencies.

    Grading Plans Proposed grading will be limited to the removal existing spoils along Blackjack Creek and

    removal of the existing site access road east of the creek bridge. Both areas will supply fill

    material for use on-site as ditch plugs and upland hummocks. This process involves

    approximately 2000 cubic yards of material. Because the volume of available spoil material will

    not be sufficient to facilitate filling of all on-site ditches, plugs will only be placed at key

    intersections with Blackjack Creek, thereby blocking site drainage and impounding water within

    the site interior. However, the southwest ditch and the long perimeter ditch running along the

    south and east boundary, will remain intact since impacting their function would have significant

    impacts to neighboring properties. In the future, should Wildlands succeed in acquiring the

    adjacent parcels, these ditches will be abandoned.

  • June 16, 2006 Blackjack Creek Mitigation Site

    Wildlands of Washington, Inc. Restoration and Management Plan

    4

    Remaining spoil material will be used to create hummocks of varying dimensions across the

    rehabilitated wetland. Proposed locations and approximate dimensions are depicted on the

    Grading Plan and Details (Appendix F). Also depicted is the removal of all culverts and concrete

    slab bridges. The existing bridge crossing Blackjack Creek will remain for site access purposes.

    All extracted items will be disposed of offsite. No major invasive vegetation removal is planned

    during construction. Any incidental invasive species material removed during project

    implementation will be removed from the site.

    After the grading and demolition work is completed, removal of the drain tiles will occur.

    Unfortunately, the tiles precise locations are not known. In order to find and successfully

    remove these, a small dozer or similar machine with ripping tines will make passes parallel to

    Blackjack Creek on both sides. No equipment or surface disturbance will occur within ten feet of

    the top of bank.

    Focusing the ripping area to this vicinity will limit large-scale disturbance to the site by limiting

    the ripping to an area already disturbed by grading activities. While the tiles will remain across

    the remaining Mitigation Site, their function will be halted through this localized disruption and

    removal. Any tiles brought to the surface will be collected and disposed offsite.

    Planting Plans Care will be taken during implementation of the grading plan elements to minimize existing

    vegetation disturbance. There will be no or very limited impacts to existing scrub-shrub or

    forested communities. However, disturbance to herbaceous vegetation will occur during the spoil

    relocation described above. Any healthy wetland herbaceous species that can be reasonably

    salvaged will be removed from the excavation area and either returned after grading is complete,

    or transplanted to a similarly disturbed location elsewhere on site.

    Aside from replacing salvaged material, Wildlands will also plant native species that are known

    to occur in the area and are appropriate for the site. Herbaceous emergent wetland and grass

    species will be installed for immediate post-construction erosion control and wetland habitat

    while woody vegetation matures. Species include Slough sedge (Carex obnupta), Tufted

    hairgrass (Deschampsia caespitosa), and Scirpus lacustris (Softstem bulrush).

    As for woody species, the existing scrub-shrub and forested wetland communities on site and

    within the surrounding landscape indicates a mosaic of similar vegetation would be appropriate.

    Existing topography and groundwater have created wetter areas in th