A.07.23._Attachment_5_Example_Levee.pdf

LEVEE VEGETATION MAINTENANCE

MILL CREEK FLOOD CONTROL PROJECT

WALLA WALLA, WASHINGTON

ENVIRONMENTAL ASSESSMENT

PM-EC 2012-0099

July 2015 i

TABLE OF CONTENTS

SECTION 1 - INTRODUCTION

1.1 Introduction

1.2 Background Information

1.2.1 Description of the Proposed Action Area

1.3 Purpose and Need

1.4 HQUSACE Levee Vegetation Guidance and Policy

1.5 Mill Creek Project Habitat Improvements

SECTION 2 - ALTERNATIVES

2.1 Introduction/Screening

2.2 Alternatives

2.2.1 Alternative 1 - No Action (Current Practice)

2.2.2 Alternative 2 – Levee Vegetation Removal Phases I and II (Proposed Action)

2.2.2.1 Vegetation Removal

2.2.2.2 Levee Vegetation Maintenance in the Future

2.2.2.3 Alternative 3 – Levee Vegetation Removal on the Levee Structure Only (Variance)

2.2.3 Alternative 4 – Setback Levee

2.3 Alternatives Carried Forward

SECTION 3 - AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES

3.1 Introduction

3.2 Aesthetics/Visual Resources

3.2.1 Affected Environment

3.2.2 Environmental Consequences

3.2.2.1 Alternative 1: No Action

3.2.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.3 Aquatic Resources

3.3.1 Affected Environment

3.3.2 Environmental Consequences

3.3.2.1 Alternative 1: No Action

3.3.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.4 Terrestrial Resources/Wildlife

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3.4.1 Affected Environment

3.4.2 Environmental Consequences

3.4.2.1 1 Alternative 1: No Action

3.4.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.5 Threatened and Endangered Species

3.5.1 Affected Environment

3.5.1.1 Listed species under the ESA for Walla Walla County, Washington:

3.5.2 Environmental Consequences

3.5.2.1 Alternative 1: No Action

3.5.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.6 Vegetation

3.6.1 Affected Environment

3.6.2 Environmental Consequences

3.6.2.1 Alternative 1: No Action

3.6.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.7 Cultural Resources

3.7.1 Affected Environment

3.7.2 Environmental Consequences

3.7.2.1 Alternative 1: No Action/No Change

3.7.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.8 Recreation

3.8.1 Affected Environment

3.8.2 Environmental Consequences

3.8.2.1 Alternative 1: No Action

3.8.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.9 Noise

3.9.1 Affected Environment

3.9.2 Environmental Consequences

3.9.2.1 Alternative 1: No Action

3.9.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.10 Climate Change

3.10.1 Affected Environment

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3.10.2 Environmental Consequences

3.10.2.1 Alternative 1: No Action

3.10.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.11 Socioeconomics

3.11.1 Affected Environment

3.11.2 Environmental Consequences

3.11.2.1 Alternative 1: No Action

3.11.2.2 Alternative2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.12 Environmental Justice

3.12.1 Affected Environment

3.12.2 Environmental Consequences

3.12.2.1 Alternative 1: No Action

3.12.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

3.13 Cumulative Effects

3.13.1 Resources Considered

3.13.2 Geographic and Temporal Scope of Cumulative Effects Analysis

3.13.3 Past, Present, and Reasonably Foreseeable Future Actions and Implications for Resources

3.13.3.1 Past Actions

3.13.3.2 Effects of Past Actions on Resources

3.13.3.3 Present Actions

3.13.3.4 Effects of Present Actions on Resources

3.13.3.5 Reasonably Foreseeable Future Actions

3.13.3.6 Effects of Reasonably Foreseeable Future Actions on

Resources

3.13.4 Summary of Cumulative Effects of Past, Present, and Reasonably Foreseeable Future Actions on Resources

SECTION 4 - COMPLIANCE WITH APPLICABLE ENVIRONMENTAL LAWS AND

REGULATIONS

4.1 National Environmental Policy Act

4.2 Endangered Species Act

4.3 National Historic Preservation Act

4.4 Native American Graves Protection and Repatriation Act

4.5 Clean Water Act

4.6 Migratory Bird Treaty Act

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4.7 Watershed Protection and Floodplain Management Act

4.8 Executive Order 11988, Floodplain Management

4.9 Executive Order 11990, Protection of Wetlands

SECTION 5 - COORDINATION, CONSULTATION, AND PUBLIC INVOLVEMENT

5.1 Agency Consultation

5.1.1 Endangered Species Act

5.2 Public Involvement

SECTION 6 - REFERENCES

Tables

Table 1-1: Recent Planting Activities at the Mill Creek Project Table 2-1: Screening Process Table 3-1: Geographic and Temporal Boundaries of Cumulative Effects Area

Figures

Figure 1-1. Federally-Owned Portion of the Mill Creek Flood Control Project Figure 1-2: Aerial View of the Federally-Owned Portion of the Mill Creek Flood

Control Project Near Walla Walla, Washington Figure 1-3: Proposed Project Footprint Area Figure 1-4: Minimum Vegetation-Free Zone Required for a Basic Levee Structure Figure 2-1: Vegetation Removal Area Figure 2-2: Proposed Disposal Sites for Tree and Vegetation Debris and Wood Chips .. 11 Figure 2-3: North Levee Turn-Around Site Figure 2-4: South Levee Turn-Around Site Figure 2-5: Horse Trailer Parking Area to Be Used as a Contractor Staging Area Figure 2-6: Rooks Park Parking Lot to Be Used as a Contractor Staging Area Figure 3-1: Levee Failure Inundation Map

Photos

Photo 1-1: A Portion of the Federally-Owned Mill Creek Flood Control Project, Lined with Levees and In-Water Concrete Sills (Viewing West Northwest) Photo 2-1: Vegetation Control Using Goats Photo 3-1: Vegetation Growing on the North Levee Structure at Rooks Park

(Viewing West)

SECTION 1 - INTRODUCTION

1.1 Introduction

The U.S. Army Corps of Engineers, Walla Walla District (District) proposes to remove woody vegetation from the landward side of the levees along the federally owned portion of the Mill Creek Flood Control Channel in Walla Walla, Washington (Figure 1-1). This maintenance is being proposed in order to meet flood risk reduction maintenance requirements in accordance with U.S. Army Corps of Engineers Headquarters (HQUSACE) regulations and policies.

HQUSACE policy on levee vegetation mandates that a corridor (vegetation-free zone) remain free of all woody vegetation. The vegetation-free zone includes the levee structure plus 15 feet from the landward and riverward levee toes (or the federal property boundary, whichever is less). The levee toe or toe line, is the line of intersection formed where the sloped surface of the levee and the surrounding grades meet, forming what resembles a crease in the ground surface.

This vegetation-free zone is to provide access to and along the levee for surveillance, inspection, maintenance, monitoring and flood-fighting. Root systems within the levee structure compromise the integrity of the levee creating safety concerns during high water events. Vegetation clearing of this type would continue as routine operation and maintenance of the levees in the future. The proposed action does not include any vegetation removal on the riverward side of the levees as currently only grasses and small shrubs exist there. This Environmental Assessment (EA) considers the potential environmental effects from the proposed action and any reasonable alternatives.

This EA was prepared in accordance with Engineer Regulation (ER) 200-2-2, Procedures for Implementing NEPA, and the Council on Environmental Quality (CEQ) Regulations for Implementing the Procedural Provisions of the National Environmental Policy Act (NEPA), Title 40 Code of Federal Regulations (CFR), Part 1500-1508. The objective of the EA is to evaluate potential environmental effects of the proposed levee maintenance project. If such effects are relatively minor, a Finding of No Significant Impact (FONSI) will be issued and the District will proceed with the federal action. If the environmental effects are determined to be significant, an Environmental Impact Statement (EIS) will be prepared before a decision is reached on whether to implement the proposed action. Applicable laws under which these effects will be evaluated include but are not limited to, NEPA, the Endangered Species Act, the Clean Water Act, the Clean Air Act, and the National Historic Preservation Act.

The National Environmental Policy Act is a full disclosure law, providing for public involvement in the NEPA process. All persons and organizations that have a potential interest in this proposed action – including the public, other federal agencies, state and local agencies, Native American tribes, and interested stakeholders – are encouraged to participate in the NEPA process.

Figure 1-1. Federally-Owned Portion of the Mill Creek Flood Control Project

1.2 Background Information

1.2.1 Description of the Proposed Action Area

Mill Creek is located in southeastern Washington State and flows through the City of Walla Walla (Figure 1-1). Mill Creek is 37 miles long. It flows for 15 miles in a relatively deep and narrow canyon, through mountainous terrain and enters an alluvial fan a few miles east of Walla Walla. Elevations range from 5,500 feet in the headwaters to about 590 feet at its confluence with the Walla Walla River. Mill Creek drains a basin of 165 square miles.

The Mill Creek Flood Control Project (MCFCP) was authorized in 1938, under Public Law 75-761.

The federally-owned portion of the MCFCP is located between river mile (RM) 10.4 and 11.5 on Mill Creek (Figure 1-2). The lower six miles of the MCFCP (RM 4.5 to approximately RM 10.4) are owned and managed by the Mill Creek Flood Control Zone District (MCFCZD), and levee vegetation maintenance on that portion is not part of the proposed action evaluated in this EA.

The federal project (Mill Creek Project) is composed of two major units: 1) Mill Creek Channel;

and 2) the off-channel reservoir, Virgil B. Bennington Lake (Bennington Lake).

The channel has been highly altered and includes two dams; the Bennington Lake Diversion Dam and the Mill Creek Division Works Dam (Figure 1-2). The original purpose of the Diversion Dam was to create a backwater during high flows, making it possible to divert part of the floodwater to Bennington Lake, reducing the flow through Walla Walla.

Just below the Diversion Dam, the channel is lined with earth-embankment levees and is stabilized by 84 full-span, concrete sills spaced 75 feet apart across the width of the channel

(Photo 1-1). Near the western edge of the federal boundary is the Mill Creek Division Works Dam; a two-foot-high dam that creates enough backwater to divert a portion of the flows into Yellowhawk and Garrison Creeks. However, only a maximum flow of about 50 cubic feet per second (cfs) is diverted, because of residential development and other encroachments downstream. During low flows, the division works are operated by District personnel at the direction of the State of Washington, Department of Ecology (Ecology), as necessary to benefit fish and fish habitat.

Figure 1-2: Aerial View of the Federally-Owned Portion of the Mill Creek Flood Control Project Near Walla Walla, Washington

Photo 1-1: A Portion of the Federally-Owned Mill Creek Flood Control Project, Lined with Levees and In-Water Concrete Sills (Viewing West Northwest)

The Mill Creek levees are constructed of well-compacted earthen materials. The levees have 1V:2H slopes, and crests that vary from 12 to 20 feet in width. The riverward slope is protected with riprap overlaying wire and rock revetment, and the slope protection toe extends three feet below the channel invert. Following initial construction, both the riverward and landward side slopes were seeded with native grasses, but were left clear of woody vegetation. The south bank levee crest consists of angular gravel surfacing (top course) for vehicle access. There is a paved bike path along the north bank levee crest and a pedestrian bridge near Rooks Park.

Within the channel, boulders have been placed to enhance fish habitat. In addition, occasional patches of grasses and other herbaceous vegetation exist in the channel.

The riverward slope has a well established stand of dryland grasses and small shrubs. No mature trees exist on the riverward slope or within 15 feet of the riverward toe at this time, however guidelines require this area be kept clear of all woody vegetation as well so clearing may be performed in the future.

Woody and non-woody vegetation is growing on the landward shoulder and slope, and within 15 feet of the levee landward toe. This vegetation is mature and consists of grasses, shrubs, and trees (cottonwood is dominant, but locust is common in this area too) of varying height and girth. Some of the cottonwood trees are close to 100 feet tall; however, based on the District

Forester’s analyses, many are considered hazardous because they are estimated at approximately 60 to 70 years of age and nearing the end of their lifespan.

For the purposes of this EA, the footprint for the effects analysis includes the section between Bennington Lake Diversion Dam and the western most edge of the federal boundary just downstream of the Mill Creek Division Works Dam (Figure 1-3). This reach is roughly one mile long.

Figure 1-3: Proposed Project Footprint Area

1.3 Purpose and Need

The District proposes to remove all woody vegetation from the landward side of the levees in an approximate one mile stretch from the Bennington Lake Diversion Dam to the western most federal boundary (Figure 1-3) on the federally-owned portion of the Mill Creek Flood Control Project, in accordance with HQUSACE regulations and guidelines for managing levee vegetation.

The vegetation removal zone includes the levee structure itself and 15 feet beyond the levee toe. This type of vegetation removal would continue as routine maintenance in the future. The purpose of the proposed action is to maintain flood risk reduction for the City of Walla Walla and surrounding area communities by managing vegetation on the levees. The action is needed because vegetation on the levees is overgrown to the point of obstructing visual inspections and access for maintenance, which compromises public safety during high water events.

Alternatives considered must: (1) maintain required flood risk reduction for Walla Walla and surrounding communities, (2) comply with HQUSACE regulations and guidance, (3) be technically feasible, and (4) be environmentally acceptable.

1.4 HQUSACE Levee Vegetation Guidance and Policy

Levee vegetation management is considered routine maintenance, and must be in compliance with HQUSACE policies. The District is required to follow all applicable Engineering Regulations, policies, etc., established for the management of levee vegetation. Levee vegetation must be maintained in accordance with Engineering Technical Letter (ETL) 1110-2-583, Engineering and Design: Guidelines for Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtenant Structures, dated 30 April 2014 and expiring 30 April 2019 (www.publications.usace.army.mil). This document is the governing standard applying to vegetation on all flood risk reduction projects for which the Corps of Engineers has design, operation, maintenance, inspection, or certification responsibility. According to this current HQUSACE policy on vegetation, the levee prism (structure) and 15 feet from the levee toe (or property boundary, whichever is less) must remain free of shrubs, brush, and trees. The minimum vegetation-free zone is a three-dimensional corridor surrounding the levee. This vegetation-free zone applies to all vegetation except grass. Grass species are permitted for the purpose of erosion control. All roots within 15 feet from the levee toe must be completely removed. Voids created by vegetation removal must be free of organic debris, and compacted according to original soil and compaction specifications.

The primary purpose of the vegetation-free zone is to provide a reliable corridor of access to, and along, the levee. This corridor must be free of obstructions to assure adequate access by personnel and equipment for surveillance, inspection, maintenance, monitoring, and flood fighting. In addition, levee vegetation maintenance assures safety, structural integrity and functionality. The vegetation-free zone also serves a secondary purpose by providing distance between root systems and levees. This helps to moderate reliability risks associated with potential piping and seepage due to root penetration and structural damage (a hole in the ground surrounded by an area of disturbed earth) resulting from a tree overturning.

In the case of flood fighting, this access corridor must also provide the unobstructed space needed for the construction of temporary flood control structures. Access is typically by four-wheel drive vehicle, but for some purposes, such as maintenance and flood fighting, access is required for larger equipment, such as tractors, bulldozers, dump trucks, and helicopters.

Accessibility is essential to the reliability of flood damage reduction systems. The minimum height of the corridor must be eight feet, measured vertically from any point on the ground.

The minimum width of the corridor will be the width of the levee plus 15 feet on each side, measured from the outside edge of the outermost critical structure. No vegetation other than approved grasses may be planted in the vegetation-free zone.

http://www.publications.usace.army.mil/

Figure 1-4: Minimum Vegetation-Free Zone Required for a Basic Levee Structure

The purpose of the guidelines (ETL 1110-2-583) is “to provide guidelines to assure that landscape planting and vegetation management provide aesthetic and environmental benefits without compromising the reliability of levees, floodwalls, embankment dams and appurtenant structures”. However, to further enhance environmental values or to meet state or federal laws and/or regulations, District offices of the Corps of Engineers may request a variance from HQUSACE from the standard vegetation guidelines set forth in the ETL. A draft Policy Guidance Letter (PGL), “Process for Requesting a Variance from Vegetation Standards for Levees and Floodwalls” was published in the Federal Register on 17 February 2012 (https://federalregister.gov/a/2012-3701) with comments requested on or before 17 April 2012. In order for a variance to be approved by HQUSACE, it must be shown to be necessary, and the only feasible means to (1) preserve, protect, and enhance natural resources, and/or (2) protect the rights of Native Americans, pursuant to treaty and statute. Although not yet final, HQUSACE evaluates variance requests in accordance with the draft guidance, until final guidance is issued.

1.5 Mill Creek Project Habitat Improvements

Planting efforts throughout the history of the Mill Creek Project have improved habitat, and are in support of the Mill Creek Master Plan (Corps, 1993). Volunteers and staff plant several acres of selected vegetation within the project boundaries on an annual basis. As part of the proposed action, the District would plant approximately 20 to 30 cottonwood trees over 8 feet tall in the Bennington Lake Diversion Dam forebay. In addition, District staff have identified four areas within the Mill Creek Project for future planting work: 1) the Bennington Lake Diversion Dam forebay; 2) Bennington Lake; 3) Russell Creek; and 4) Lower Snake River Fish and https://federalregister.gov/a/2012-3701

Wildlife Compensation Plan (LSRFWCP) lands. Specific locations within the four areas have been mapped as potential sites, based on slope, aspect, presence of existing vegetation, and District staff input. All areas identified would provide quality habitat that appears natural in design. The Mill Creek Project has identified planting strategies over the next five years.

The following, is a list of recent planting activities carried out by District staff and volunteers in the last three years:

Table 1-2: Recent Planting Activities at the Mill Creek Project

Location Tree Species Approximate Acreage Units

Diversion Dam Forebay Cottonwoods 5 300 Rook’s Park Sycamores, Oaks, Maples 5 20 LSRFWCP Comp Land Ponderosa Pines 2 300 LSRFWCP Comp Land Various Pines 2 200 East Intake Canal Hawthorne, Cottonwoods, Cherry 1.5 100 Project Office Various Landscaping Plantings 2 500

SECTION 2 - ALTERNATIVES

2.1 Introduction/Screening

The National Environmental Policy Act (NEPA) and 33 CFR Part 230 Procedures for Implementing NEPA require a reasonable range of alternatives be considered during the planning process.

Alternatives considered under NEPA must include, at least, the proposed action and the “No Action” Alternative, which provides a baseline from which to compare other alternatives. The alternatives identified below were evaluated to determine if they satisfy the purpose and need of the proposed action (Section 1.3):

(1) The No Action Alternative

(2) The Proposed Action (Levee Vegetation Removal Phases I and II)

(3) Levee Vegetation Removal on the Levee Structure Only (Variance)

(4) Setback Levees.

However, in order for any alternative to be acceptable for further evaluation it must meet certain objectives, or screening criteria. Screening criteria help eliminate those alternatives that could not reasonably or practically meet the project purpose and need. In this case, alternatives must: (1) maintain required flood risk reduction for Walla Walla and surrounding communities, (2) comply with HQUSACE levee vegetation regulations and guidance, (3) be technically feasible, and (4) be environmentally acceptable (see Table 2-1 on page 16 for the screening process).

2.2 Alternatives

2.2.1 Alternative 1 - No Action (Current Practice)

Under Alternative 1, the No Action Alternative, no vegetation would be removed from the levees except what is already removed under routine maintenance activities. This includes occasional mowing and the annual use of goats to keep grasses down on the riverward side of the north and south levees.

The No Action Alternative does not meet the project purpose and need; however, it is carried forward to Section 3 for comparative purposes as required by NEPA.

2.2.2 Alternative 2 – Levee Vegetation Removal Phases I and II (Proposed Action)

Under Alternative 2, the proposed action, the District would remove all existing woody vegetation from the landward slope of the levee structure and 15 feet beyond the toe along a one-mile stretch of the federally-owned portion of the Mill Creek Flood Control Channel from the Bennington Lake Diversion Dam to the western most federal boundary (Figure 2-1; see Appendix A for a detailed set of Google Earth Images). The vegetation removal zone on the landward side of the levees includes the levee structure itself and 15 feet beyond the levee toe.

It is important to note that significant portions of the landward side levee slopes are currently sloped more gradually than the original design specified. The toe line adjacent to overly gradual slopes intersects the surrounding grades farther away from the levee crown than the originally designed cross section requires. Therefore, the location of the toe line for the originally designed levee slope (1V:2H) was calculated and surveyed in March 2015 to correctly determine the limits of the vegetation-free zone and minimize the area from which vegetation would be removed. Elevation variations in the surrounding grades cause the horizontal distance from the levee crown to the toe line to vary, as such, the outer bound of the vegetation-free zone varies with it.

Figure 2-1: Vegetation Removal Area

Implementation of this alternative would be conducted in two phases. Phase I, scheduled for the fall of 2015 involves cutting the trees and vegetation to ground level. During Phase I, approximately 308 trees would be cut down (211 from the north levee, and 97 from the south levee) in addition to the understory (grasses, shrubs and plants under the trees). It is probable that the debris would be removed and transported to an approved off-site location; however, some or all of the debris could be stored on-site for potential future habitat improvement projects. Two potential disposal sites have been identified in Figure 2-2. Phase II, scheduled for the fall of 2016, involves excavating the remaining stumps and root balls from the ground (clearing and grubbing). Phase I in 2015 and Phase II in 2016 would be complete no later than January 30th of the following year.

2.2.2.1 Vegetation Removal

During tree cutting activities, all or portions of the trail on the side of Mill Creek where work is being performed would be closed to the public. Trees would be cut down with chainsaws.

Other heavy equipment on site would be a wood chipper, dump trucks and possibly an excavator or crane. Trees and shrubs may be processed (chipped) on site or hauled to another location before being processed. Trees would not be allowed to fall into the creek. Any damage to the levee trail surface would be repaired once all of the trees have been cut down and removed.

Figure 2-2: Proposed Disposal Sites for Tree and Vegetation Debris and Wood Chips

During Phase II of the project, all stumps, roots and root balls would be removed using an excavator, a bull dozer equipped with a ripper, or similar equipment. Any fill material used to fill the voids created by the stump/root ball removal would be free of organic debris and compacted according to original soil and compaction specifications. Some material may be brought in from an approved commercial source to rebuild sections to the original design dimensions. All disturbed soils would be re-compacted using the bull dozer.

During Phase I and Phase II, large dump trucks would be used to transport debris. Due to the limited area available to the large equipment on the levees, two locations have been identified as “turn-around sites” for these vehicles. The north levee turn-around site would be located just north of the Mill Creek Division Works Dam (Figure 2-3) and the south levee turn-around site would be located approximately 3/10th of a mile south of the Diversion Dam (Figure 2-4).

Levee Vegetation Disposal Sites

Figure 2-3: North Levee Turn-Around Site

Figure 2-4: South Levee Turn-Around Site

Some stumps and root balls may be temporarily stored on-site for future off-site beneficial use such as stream restoration efforts carried out by the Tribes, other agencies or environmental restoration groups.

Heavy equipment would be staged in designated areas away from Mill Creek. The horse trailer parking area on the south side of the creek near the Mill Creek Project office would be used as well as the Rooks Park parking lot on the north side of the creek (Figure 2-5 and Figure 2-6).

Figure 2-5: Horse Trailer Parking Area To be Used as a Contractor Staging Area

Figure 2-6: Rooks Park Parking Lot To be Used as a Contractor Staging Area

2.2.2.2 Levee Vegetation Maintenance in the Future

When levee vegetation removal and repairs are complete, approved perennial grasses would be seeded along the levee structure and within the 15 foot vegetation-free zone. In accordance with HQUSACE’s ETL 1110-2-583, Engineering and Design: Guidelines for Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtenant Structures, the only acceptable levee vegetation is perennial grass. As ground cover in a system designed to reduce flood damage, the primary purpose of grasses is to prevent erosion. The grasses have adapted to the soils and climate of eastern Washington and will grow successfully with little maintenance. Grasses generally germinate and establish readily from seed, grow rapidly, and form a good ground cover with a fibrous root mass. These characteristics make perennial grasses highly valuable for erosion control. Selected species would tolerate mowing and grazing each year.

Grasses typically do not compromise levees and only become an issue when they grow large enough to hinder visual inspection of the levees. Stable grass or sod cover provides a certain level of protection from local runoff. If necessary, grasses on the levees may be mowed prior to high flows and routine inspections.

The following list designates the types of grasses that are considered acceptable vegetation on Corps flood control levees:

• Indian Ricegrass (Achnatherum hymenoides)

• Blue Grama (Bouteloua gracilis)

• Idaho Fescue (Festuca idahoensis)

• Sheep Fescue (Festuca ovina)

• Bluebunch Wheatgrass (Pseudoroegneria spicata)

• Streambank Wheatgrass (Elymus Ianceolatus)

In the future, it would be necessary to perform annual vegetation maintenance (removal) and levee inspections along the Mill Creek Flood Control Project levees. Maintenance would include vegetation removal from the entire levee prism or structure, plus the additional 15-foot vegetation-free zone measured from the landward and riverward toe. No woody vegetation would be permitted. Annual vegetation maintenance would be scheduled to coincide with the levee inspections to reduce the need for repeated maintenance activities. The channel and levees would first be visually inspected for excess vegetation. Excess vegetation would then be cut and removed using hand tools or power tools such as a mower, a hedge trimmer and/or weed eater.

The District may also control excess vegetation using herbicides. A licensed applicator would apply herbicides approved for use near water by both the Environmental Protection Agency (EPA) and Washington Department of Ecology (Ecology). Herbicide application would normally be done in May or June (sometimes as late as September), and only on an “as-needed” basis.

All chemical applications would be handled in accordance with the District’s Integrated Pest Management Plan (Corps, 2013) http://www.nww.usace.army.mil/Missions/Projects/PestManagement.aspx.

Using goats to graze down excess vegetation is another way the District has in the past and would in the future, limit vegetation growth on the levees. In summer 2013, a large herd of goats was put on the north levee for several days to graze on grasses and blackberry bushes.

This experiment proved highly successful and the herd was brought in to graze on the south levee (Photo 2-1) in late spring 2014. This method would continue to be used for future vegetation maintenance.

http://www.nww.usace.army.mil/Missions/Projects/PestManagement.aspx

Photo 2-1: Vegetation Control Using Goats

2.2.2.3 Alternative 3 – Levee Vegetation Removal on the Levee Structure Only (Variance)

Under Alternative 3, the District would need to apply for and receive approval for a variance from HQUSACE regulations and guidance for levee vegetation maintenance. If approved, all woody vegetation from the landward side of the levees along the one mile stretch of the federally-owned portion of the Mill Creek Channel from the Bennington Lake Diversion Dam to the western most federal boundary would be removed. This alternative would not include the 15 foot area adjacent to the levee toe. Rather, vegetation removal would occur only on the levee structure itself. This would be a “variance” from the standard vegetation guidelines set forth in ETL 1110-2-583. Vegetation variances for either federal or non-federal flood damage reduction systems may be permitted, however there are two criteria requirements that must be met, pursuant to HQUSACE guidance: The variance must be shown to be necessary, and the only feasible means to (1) preserve, protect, and enhance natural resources, and/or (2) protect the rights of Native Americans, pursuant to treaty and statute.

This alternative was removed from further evaluation due to the fact that the vegetation variance criteria as set forth above is not satisfied, as there are other feasible means (i.e., other vegetation plantings) that could offset removal of levee vegetation. For example, see reference to the Mill Creek Project’s habitat improvement planting strategy as described in Section 1.5.

2.2.3 Alternative 4 – Setback Levee

The Setback Levee concept would move the levee landward to allow the Mill Creek channel more conveyance through the project reach and not require vegetation maintenance on existing levees. This alternative would require the acquisition of privately-owned land, as current federal land is extremely limited, and would also require hydraulic and geotechnical modeling studies to show the technical feasibility of the setback levees and eventual channel modification.

This alternative was removed from further evaluation as not technically feasible. District managed federal land near the Mill Creek channel is extremely limited. Setback levees would require acquisition of additional land from adjacent private landowners, which would require authorization from Congress, and construction of new levees (as compared to maintaining existing levees) would be cost prohibitive.

2.3 Alternatives Carried Forward

Table 2-1 lists the four alternatives in the far left column, the four mandatory screening criteria across the top row and whether each alternative meets or does not meet these criteria.

Alternative 1 (No Action) and Alternative 2 (Proposed Action) are carried forward for detailed evaluation in Section 3.

Table 2-1: Screening Process

Alternatives

Maintains required flood risk reduction for WW and area?

Complies with HQUSACE Levee

Vegetation Regulations and

Guidance?

Technically Feasible?

Environmentally Acceptable?

1: No Action No No Yes No 2: Proposed

Action: Levee Vegetation

Removal (Phases I and II)

Yes Yes Yes Yes

3: Levee Vegetation

Removal on the Levee Structure Only (Variance)

No No Yes Yes

4: Setback Levee

Yes Yes No Yes

SECTION 3 - AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES

3.1 Introduction

Alternatives that satisfy the project’s purpose and need have been developed. This section discusses the existing environmental conditions of the project study area, as well as effects anticipated to occur for the proposed action over a wide range of environmental and social elements. In addition, the No Action Alternative is evaluated, which provides a comparison to the proposed action. For the purposes of this EA, the project study area is the Mill Creek channel and adjacent levees from the Bennington Lake Diversion Dam to the western most federal boundary, just downstream of the Mill Creek Division Dam. Two separate material disposal areas are also included in the study area. Descriptions of the biological, physical, cultural, and socioeconomic resources serve as a basis for evaluation and comparison of the anticipated effects of the alternatives.

3.2 Aesthetics/Visual Resources

3.2.1 Affected Environment

Aesthetic or visual resources are the natural and cultural features of the landscape that can be seen and that contribute to the public’s appreciative enjoyment of the environment. The aesthetic quality of an area is a subjective factor to quantify. It is a measure of one’s perception of how pleasing an area is. Many people visit the Mill Creek Project because of its aesthetic value and visitors enjoy high visual resources through a variety of landforms, wildlife, fisheries, recreation and vegetation. Some even enjoy the man-made built environment of the concrete channels and dams and earth-embankment levees.

3.2.2 Environmental Consequences

3.2.2.1 Alternative 1: No Action

Under the No Action Alternative, visual resources would either evolve from the existing condition in a natural process or by routine operation and maintenance activities performed by Mill Creek staff members. However, these maintenance activities would have minor or no effects to aesthetics by implementing Best Management Practices (BMP’s). BMP’s would be used to eliminate or significantly reduce potential adverse effects such as vegetation overgrowth, soil disturbance, turbidity, etc.

If the levees failed due to lack of vegetation maintenance in the proposed action area, aesthetics would be negatively affected. Some of the adverse effects: Vegetation and trees could be uprooted and displaced, and possibly carried downstream by high water. Oftentimes, large vegetation lodges under the bridges, clogging them up and in turn creating more flooding.

Turbid water would fill the channel and possibly over top the levees creating a flooded environment in Rooks Park and in other areas. Following the recession of flood waters, mud and silt would be left behind requiring extensive clean-up efforts.

3.2.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

Implementation of Alternative 2 means that all of the existing woody vegetation along the levees (as previously described) would be removed. While it is true that the landward slope of the levees and the 15-foot vegetation-free zone would look different than it does now, the affected area only amounts to one percent of the federally owned lands at Mill Creek Project.

Because elevation variations in the surrounding grades cause the horizontal distance from the levee crown to the toe line to vary, the outer bound of the vegetation-free zone varies too.

Therefore, an undulating or soft, wavy border would be created along the line of vegetation removal lessening the negative aesthetic impact. In addition, there are trees and vegetation outside of the vegetation-free zone that would remain. The aesthetics of the overall project area (Bennington Lake trails, portions of Rooks Park and the forebay above the Diversion Dam) would not be impacted. Upon completion of the vegetation removal, native perennial grasses would be planted on the levees and consistently maintained in the future. In addition, the District has a planting strategy in place and many trees already have been and many would be planted on the Mill Creek Project grounds. Implementation of the proposed action would not result in significant effects to aesthetics and visual resources.

3.3 Aquatic Resources

3.3.1 Affected Environment

Fish species presently in the project area of Mill Creek include rainbow trout/steelhead, bull trout, Chinook salmon, mountain whitefish, bridgelip sucker, redside shiner, freshwater sculpin, dace, and brook lamprey. Amphibians typically found in the area are Pacific tree frogs, leopard frogs, and bullfrogs. Common aquatic insects in the creek are mayflies, caddisflies, dragonflies, and stoneflies.

3.3.2 Environmental Consequences

3.3.2.1 Alternative 1: No Action

Under the No Action Alternative, nothing would change to the aquatic resources environment unless the levees were breached or overtopped during high flows. If the levees did fail due to lack of vegetation management in the proposed action area, aquatic resources could be negatively affected. Fish could be carried out of the channel and get stranded when flows recede.

3.3.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

Under Alternative 2, there would be no direct impact on aquatic resources. No in-water work would occur. Indirectly however, removal of riparian trees would cause a slight decrease in the amount of shade on the creek. The percentage of shade would decrease from 2.5% coverage to 0% coverage. This minimal change is not likely to cause a measureable increase in stream temperature and is not likely to negatively affect aquatic resources.

There would also be an indirect effect on some fish which depend on terrestrial insects as part of their diet. Aquatic insects would also be affected by the reduction of leaves falling into the river and becoming substrate for bacteria to colonize which is in turn used by the insect larvae as food.

No in-water work would be conducted so the effects from the proposed action on aquatic resources would be indirect and very minor. Mill Creek’s east/west orientation along with its wide and shallow cross section does not provide for any substantial shade from the riparian vegetation. Habitat conditions for aquatic resources are marginal and would continue to be marginal in the future. Implementation of the proposed action would not result in significant effects to aquatic resources.

3.4 Terrestrial Resources/Wildlife

3.4.1 Affected Environment

Various forms of wildlife are generally abundant close to riparian corridors. Many species of mammals, birds, amphibians, and reptiles inhabit riparian corridors during different parts of the year. Mammals common to the area include white-tailed deer, coyote, raccoon, mink, muskrat, beaver, river otter, striped skunk, bats, and a variety of small rodents. Occasionally, bobcat, black bear, and even cougar and moose have been seen in the area. Common birds include wild turkey, belted kingfisher, California quail, ring-necked pheasant, swallows, sparrows, woodpeckers, various other songbirds, ducks, hawks, osprey, and many different owls. On occasion, bald eagles can be seen as well, mostly during winter. The area immediately adjacent to the creek provides limited wildlife habitat quality. Although some wildlife can be found around the project area, the large number of people recreating in the area keeps wildlife numbers down.

3.4.2 Environmental Consequences

3.4.2.1 1 Alternative 1: No Action

There would be no direct positive or negative effects on terrestrial resources/wildlife under the No Action Alternative. If the levees did fail due to lack of vegetation maintenance, overland flooding could displace some wildlife temporarily. There would be no measureable impact to any species population. However, trees (wildlife habitat) would age and die and begin to decay, eventually falling. They would then likely be removed from the area if they dislocate the levee surface. The existing trees have a diverse age class so replacement trees are already present.

3.4.2.2 Alternative 2: Levee Vegetation Removal Phases I and II (Proposed Action)

Alternative 2 would produce moderately negative effects on terrestrial wildlife resources through a reduction of riparian habitat. Some of the now varied-age trees closest to the creek would be removed and replaced with grass. Better wildlife habitat exists upstream from the levees and would not be affected.

A few bird species would be specifically affected. Belted kingfishers perch within the branches close to the creek where they hunt for minnows and other small fish. Osprey also use the tree branches for hunting perches. In addition there are two or more great blue heron nests close to the vegetation-free zone. These nests may not be removed with the trees, but they would become more open to the elements and may become unsuitable for use in future years.

Only six acres of terrestrial wildlife habitat would be affected by the proposed action. This is less than one percent of the Mill Creek Project lands and a much smaller fraction of the amount of riparian habitat available upstream. The first year after the trees are cut, some birds would have to seek alternate nesting locations. In the second year the local population would have adjusted to the available habitat and there would likely be no noticeable change to bird populations at the watershed scale. There would be no significant effect to any terrestrial species population.

3.5 Threatened and Endangered Species

3.5.1 Affected Environment

3.5.1.1 Listed species under the ESA for Walla Walla County, Washington:

There are five ESA-listed species and one candidate species in Walla Walla County, Washington.

Following are these species and a brief description.

Threatened: Canada lynx (Lynx canadensis) Steelhead (Oncorhynchus mykiss) Bull trout (Salvelinus confluentus) Ute Ladies’-tresses (Spiranthes diluvialis) Yellow-billed cuckoo (Coccyzus americanus)

Candidate: Washington Ground Squirrel (Urocitellus washingtoni)

Two of these species, mid-Columbia steelhead and Columbia Basin bull trout, are found in Mill Creek in the proposed project impact area. Canada lynx, Ute Ladies’-tresses, and Washington ground squirrel are not found near the proposed project. Yellow-billed cuckoo is not known to occur in the area and may be extirpated as a breeder from Washington.

• Canada lynx

Canada lynx were listed as threatened under the ESA in March 2000. Critical Habitat was designated in November 2006. The designation was revised in March 2009 and revised again in September 2014. In Washington, areas above 4,000 feet elevation in the north Cascades are included in the designation. The area around the proposed project is not included in the designation. The elevation is approximately 1,240 feet. Canada lynx are not known to occur near the proposed project area.

• Steelhead

Mid-Columbia River steelhead were listed as threatened under the ESA in August 1999. Critical Habitat was originally designated in March 2000, was later vacated, and has since been re-designated. Mill Creek is designated as Critical Habitat for mid-Columbia River steelhead.

Steelhead are an anadromous salmonid, and adults return to their natal streams from December through April to spawn. After spending one or two years rearing in the area, juveniles begin their outmigration to the ocean in April and May, when flows are usually higher than average. Periodic low flows, flood control measures, irrigation diversions, and habitat destruction can limit both adult and juvenile steelhead.

Steelhead utilize the project area for migration and rearing habitat. A survey for the USFWS in 2009 (Gallion and Anglin 2009) estimated there were fewer than 600 salmonids in Mill Creek between the Diversion Dam and the Mill Creek Division Works Dam over the summer. No spawning is known to occur in this section of Mill Creek. There could be limited spawning in Yellowhawk Creek. However, the substrate in Yellowhawk Creek is mostly fine silt due to the highly controlled hydrology of the creek (no high flows to flush out the silt).

• Bull trout

The USFWS listed Columbia Basin bull trout as threatened on July 10, 1998. Critical Habitat was designated for bull trout in 2010, and Mill Creek was included in the designation. Bull trout are a wide-ranging species that formerly inhabited most of the cold lakes, rivers, and streams throughout the western United States and British Columbia. They are piscivorous, and require an abundant supply of forage fish for vigorous populations. Resident bull trout spend their entire life-cycle in the same (or nearby) streams where they were hatched. They display a high degree of sensitivity at all life stages to environmental disturbance. Bull trout growth, survival, and long-term population persistence depends on the availability of quality habitat.

The U.S. Forest Service has conducted radio-tracking studies on bull trout in Mill Creek, which have shown that adults move to the upper reaches of the watershed between mid-May and mid-August. Spawning takes place between mid-August and mid-October. There are five monitoring sites set up on Mill Creek that utilize Passive Integrated Transponder (PIT) tags to track tagged fish as they move through the system. In a 2009 survey by Gallion and Anglin occurring in June, July and August, two sub-adult bull trout were captured in sampled sections between the Diversion Dam and the Division Works Dam in July. They were not able to estimate bull trout abundance from this limited data.

• Ute Ladies’-tresses

Ute ladies’-tresses, an orchid known to inhabit wetland and riparian areas, was listed under the ESA in January 1992. It has been found at about 1,500 feet elevation, at a site in Okanogan County, in the northeastern part of Washington State. In other parts of its range, it is found up to about 7,000 feet. It is usually found in moist areas of open shrub or grassland. The proposed project location is at about 1,240 feet elevation in the southeastern part of the state.

Habitat that supports Ute ladies’-tresses is not present in the area likely to be impacted by the proposed project, nor has it been identified or documented at the site.

• Yellow-billed Cuckoo

Yellow-billed cuckoo, in the western portion of North America, were listed as threatened on October 3, 2014. Critical habitat has been proposed, though Washington is not included in the proposal. This bird prefers open woodlands with clearings and a dense shrub layer. They are often found in woodlands near streams, rivers, or lakes, but yellow-billed cuckoos occur most frequently and consistently in cottonwood forests with thick understory (Talyor 2000). In winter, yellow-billed cuckoos can be found in tropical habitats with similar structure, such as scrub forest and mangroves. Individuals may be on breeding grounds between May and August.

There are no known occurrences of yellow-billed cuckoo in the proposed action area. Removal of the trees would occur after the migratory bird nesting season (April 1 to August 15) and none of these birds should be present when the work is being conducted. Critical Habitat is not proposed in Washington State. However, the riparian forest habitat along the Mill Creek levees could be suitable for yellow-billed cuckoos.

• Washington Ground Squirrel

The Washington ground squirrel is listed as a candidate species. It spends much of its time underground. Adults emerge from hibernation between January and early March, depending on elevation and microhabitat conditions, with males emerging before females. Their active time is spent in reproduction and fattening for their six-month or longer dormancy.

Washington ground squirrels occur in dry grassland or in patches of grass and other herbaceous plants within low open sagebrush. They prefer deep, loose soil, which they need for digging burrows. The greater part of its current range is uncultivated steppe in Walla Walla, Franklin, Adams, Lincoln, and Grant Counties.

No suitable ground squirrel habitat exists in the proposed project area. The disposal areas are also not suitable habitat for ground squirrels.

3.5.2 Environmental Consequences

3.5.2.1 Alternative 1: No Action

Under the No Action Alternative, nothing would change with respect to ESA-listed species. Only minor reductions in riparian canopy would occur when trees or branches are removed for public safety. Trees would be removed from the area if they fall into the creek, over the trail, or onto private property. There would be no significant effects from this alternative.