Atach_10_-_Riparian_Mitigation_Planting_Guidelines.pdf

Draft Restoration Guidelines for Dry Creek Bridge Replacement Project

Chadwick McCready

Center for the Environmental Management of Military Lands

Cooperative Agreement W9126G-18-2-0045, Task 3.3

Introduction

The following is a list of guidelines to be used for restoration and mitigation of temporary and permanent impacts to riparian habitat and wetlands from construction activities along the Dry Creek riparian corridor at Beale Air Force Base (AFB). The guidelines presented were adapted from the Restoration Plan for the Dry Creek Riparian Area (River Partners 2011) and the Conceptual Stream Mitigation and Monitoring Plan (HDR 2016), and can be referenced for additional information. Additionally, oak tree replacement has been modified to address losses of mature valley oaks within the project boundaries and reflects the 3-to-1 replacement ratio given by the Integrated Natural Resources Management Plan (2018). These guidelines will be incorporated into design plans for the removal and replacement of the 4 bridges project and will be used to mitigate losses of riparian forest and streambank habitat due to the project footprint/activities. The ultimate goal of the mitigation is to restore and enhance the vegetation community within and adjacent to the site, while preventing erosion and degradation of the site and resulting in no net loss of habitat or deterioration of water quality due to erosion.

Site Conditions and Restoration

The proposed area to be impacted by bridge replacement is composed primarily of Great Valley Oak Riparian Forest and associated in-stream aquatic habitat. Mitigation areas will consist of the disturbed banks and adjacent upland areas of the project. The mitigation sites will be located in an area adjacent to the project location, or in areas of the project where temporary impacts have been completed. Upland areas will be planted with a mix of plants in the Great Valley Oak Riparian Forest assembly (Table 1 & 2), in the ratios given, with a minimum of 300 container plants per acre, while streambanks and transitions will be seeded and planted with riparian plants (Tables 3 & 4). All disturbed areas at the site that are not replanted are to be hydroseeded with a native seed mix that is approved by the Natural Resource Manager.

Plant Selection

All container plants and seed will be procured from local (i.e. Northern/Central California) sources familiar with restoration projects. All valley oak shall be 15-gallon containers (INRMP 2018). All other container plants shall be at least 1-gallon size. All willow cuttings or stakes shall be locally collected. All native seed mix used should be certified weed free and purchased as Pure Live Seed (PLS). All seed/plant sources must be approved by the Natural Resources Manager before purchase and installation.

Riparian Forest Site Preparation

Site preparation includes the various tasks necessary for restoration on a typical site. The entire planting site (unit) should be disked to bury the crop stubble and weed mulch. If the site has an abundance of nonnative and invasive plants, the site may require herbicide treatment in order to reduce competition for soil moisture and light. Where the soil-profile is compacted, preparation of planting sites sometimes requires ripping (fracturing soil profile) or auguring (homogenizing the soil profile) to facilitate root growth. Transitions to slopes that have been altered during construction shall be graded to prevent erosion and restore natural flood processes to the site. More information on site preparation can be found in the Restoration Plan for the Dry Creek Riparian Area (River Partners 2011). Disturbed sites are known to impact native plant survival due to damage to the soil microbial community. If the mitigation site is known to have had the soil disturbed, or is to be disturbed during project activities or site preparation, the site shall be inoculated using topsoil from nearby undisturbed plant communities (e.g. shrublands and other undisturbed perennial communities). Soil will be collected during the dry season, with care given not to disturb the roots of the donor plant community (Vic Classen PhD, personal communication).

Field Layout

The layout of planting rows for the riparian mitigation plantings will be designed to allow flood flow conveyance to pass through the restoration site without raising water elevations while also accommodating equipment needs, such as the width of the mower that will control weeds in the aisles. All plants shall be selected from the composition table (Table 1) at a rate of 300 plants per acre, at the proportions listed. All woody trees and shrubs will be planted in rows that will be oriented parallel to flood flows, roughly north to south. Planting rows should be spaced approximately twenty feet apart, while plants within each row should be planted at approximately 6-foot spacing. Plant placement should reflect a natural situation, with no suggestion of a landscaped appearance or separation of plants by species. In addition to the tree and shrub installation, the planting rows will be filled in with native grass seed and perennial plugs to suppress weed growth and control erosion (Table 2).

Table 1: Composition of Great Valley Oak Riparian Forest for Beale AFB. 275 total plants per acre should be planted.

Species Name Form Plants per Acre Valley oak (Quercus lobata) Tree 75 Buckeye (Aesculus californicus) Tree 20 Oregon ash (Fraxinus latifolia) Tree 20 Mulefat (Baccharis salicifolia) Shrub 20 Coyote bush (Baccharis pilularis) Shrub 30 Coffeeberry (Rhamnus californica) Shrub 40 Blue elderberry (Sambucus mexicanus) Shrub 20 Toyon (Heteromeles arbutifolia) Shrub 30 Ceanothus (Ceanothus cuneatus) Shrub 20

Table 2: Composition of riparian restoration understory for Beale AFB.

Species Name Form Pounds PLS Per Acre

Plugs/Bulbs per Acre

Squirrel tail (Elymus elymoides) Grass 5 - Purple needlegrass (Stipa pulchra) Grass 5 - Blue rye (Elymus glaucus) Grass 5 -

Creeping rye (Elymus triticoides) Grass 5 - Mule’s ear (Wyethia angustifolia) Perennial 1 - Elegant brodiaea (Brodiaea elegans) Perennial - 200 bulbs Mugwort (Artemisia douglasiana) Perennial 1 50 plugs Narrow-leaf milkweed (Asclepias fascicularis)

Perennial 1 50 plugs

Gumplant (Grindelia camporum) Perennial 1 50 plugs

In-Stream/Stream Bank Restoration

In-stream restoration design will require a qualified landscape designer or stream hydrologist with experience in restoring streambanks. All streambank restoration and design will adapt recommendations from the Conceptual Stream Mitigation and Monitoring Plan (HDR 2016). Planting along the stream bank shall consist of the planting of container stock and/or cuttings and application of seed to disturbed/altered streambanks (see Table 3 and 4 for suggested). The restoration design shall improve age structure and structural diversity by mixing plant species and sizes (e.g. cuttings/stakes and container plantings). The actual arrangement and composition is dependent on the amount of streambank disturbed by the project and the landscape architect. Plant placement should reflect a natural situation, with no suggestion of a landscaped appearance. Proper erosion control best management practices, including but not limited to straw wattles, jute netting, and hydroseeding will also be used to prevent stream bank erosion while plants are establishing.

Table 3: Suggested Streambank Container Plants

Species Name Size Form # Plants per acre Streambank

Arroyo willow (Salix lasiolepis) Cutting/ 1 gallon

Tree 200

Narrow-leaf willow (Salix exigua) 1 gallon Shrub 100

Blue Elderberry(Sambucus mexicanus) 1 gallon Shrub 50

Mulefat (Baccharis salicifolia) Cutting/1 gallon

Shrub 250

Button willow (Cephalanthus occidentalis)

Cutting/1 gallon

Shrub 50

Table 4: Suggested Creek Slope Seed Mix

Species Name Form Pounds PLS Seed per Acre

Plugs/Bulbs per Acre

Purple needlegrass (Stipa pulchra) Grass 6 - California Buckwheat (Eriogonum fasciculatum)

Shrub 6 -

Coyote bush (Baccharis pilularis) Shrub 6 - Mugwort (Artemisia douglasiana) Perennial 6 -

Great Valley Gumplant (Grindelia camporum) Perennial 6 - Creeping wildrye (Leymus triticoides) Grass 6 - Narrow-leaf milkweed (Asclepias fascicularis) Perennial 1 50

Plant Protectors

Plant protectors (one-quart milk cartons and stakes) shall be installed around the seedlings or cuttings at the time of planting in the field with about 3 inches of wood mulch (natural pine, oak, redwood mulch only) applied around the base (approx. 3 ft diameter) of each plant to hold soil moisture and minimize weed growth. Plant protectors shall be installed below the surface of the mulch to prevent herbivory. For small plants and plugs, milk cartons are recommended because they are cheap, biodegradable, and effective for protection from herbicide drift, herbivory, and desiccation. For larger trees and shrubs, plastic treeshelters should be installed to protect the plants from herbivory. Additionally, fencing shall be installed around larger tress to prevent deer herbivory.

Irrigation

The planting rows should be watered for the first year once every ten days using drip line, or preferably a sprinkler line. Watering should be conducted in the early morning or evening to reduce evaporation.

Watering events will be prolonged to increase the depth of soil moisture and promote deep rooting of the mitigation plants. All irrigation designs must be approved by the Natural Resources Manager.

Follow-up Maintenance

The goal is self-sustaining riparian communities. This means that at the end of the maintenance period the trees and shrubs are large enough to persist through summer droughts on their own, through inherent drought-tolerance or by having grown roots into the surface of the water table. Careful monitoring will reveal the success of achieving this goal by the end of the maintenance period. Maintenance and monitoring of the site will be conducted for two years after plant installation. Watering in the first year will be weekly, with second year watering reduced to deep watering once every three to four weeks.

Monitoring will consist of survival monitoring for three years following installation, and should be reported at the end of each growing season (fall/winter). Survival at the end of the monitoring period shall be at least 80% of the original plant numbers. Any plants lost below that threshold shall be replaced.

Table 5 shows the proposed implementation timeline for the mitigation project.

Table 5: Proposed Implementation Timeline for Mitigation Activities and Maintenance

Task Year 1 Year 2 Year 3

Win Spr Sum Fal Win Spr Sum Fal Win Spr Sum Fal

1. Assess Site

2. Develop Restoration Plan

3. Prepare Areas for Restoration

4. Establish Layout for Restoration

5. Install Irrigation System

6. Plant Riparian Vegetation

7. Maintain Riparian Plantings

8. Monitor and Report Results

References

HDR 2016. Conceptual Stream Mitigation Plan, Beale Air Force Base, California. March 2016

INRMP 2018. Integrated Natural Resources Management Plan (INRMP) for Beale Air Force Base, California, 2018.

River Partners 2011. Restoration Plan for the Dry Creek Riparian Area, Beale Air Force Base. September 2011.