Appendix J - 404(b)(1).pdf

Ten Year Operations and Maintenance Plan for the Glendale Narrows Reach of the Los Angeles River

Programmatic Environmental Assessment

Appendix J

404(B)(1) Analysis i

Los Angeles District®

Environmental Resources Branch/Planning Division

Final Clean Water Act 404(B)(1) Evaluation

September 2023

1.0 CLEAN WATER ACT SECTION 404(B)(1) REGULATORY BACKGROUND

Section 404 of the Clean Water Act (CWA) governs the discharge of dredged or fill material into waters of the U.S. Although the USACE does not process and issue permits for its own activities, the USACE authorizes its own discharges of dredged or fill material by applying all applicable substantive legal requirements, including application of the Section 404(b)(1) Guidelines. 33 C.F.R. 336.1(a).

Under the Section 404(b)(1) Guidelines, an analysis of practicable alternatives is the primary tool used to determine whether a proposed discharge is prohibited. The Section 404(b)(1) Guidelines prohibit discharges of dredged or fill material into waters of the US if a practicable alternative to the proposed discharge exists that would have less adverse impacts on the aquatic ecosystem, including wetlands, as long as the alternative does not have other significant adverse environmental impacts (40 C.F.R. 230.10(a)). An alternative is considered practicable if it is available and capable of being implemented after considering cost, existing technology, and logistics in light of the overall project purpose (40 C.F.R. 230.10(a)(2)). The Section 404(b)(1) Guidelines follow a sequential approach to project planning that considers mitigation measures only after the project proponent shows no practicable alternatives are available to achieve the overall project purpose with less environmental impacts. Once it is determined that no practicable alternatives are available, the guidelines then require that appropriate and practicable steps be taken to minimize potential adverse effects on the aquatic ecosystem (40 C.F.R.

230.10(d)). Such steps may include actions controlling discharge location, material to be discharged, the fate of material after discharge or method of dispersion, and actions related to technology, plant and animal populations, or human use (40 C.F.R. 230.70-230.77).

Beyond the requirement for demonstrating that no practicable alternatives to the proposed discharge exist, the Section 404(b)(1) Guidelines also require the USACE to compile findings related to the environmental impacts of discharge of dredged or fill material. The USACE must make findings concerning the anticipated changes caused by the discharge to the physical and chemical substrate and to the biological and human use characteristics of the discharge site.

These guidelines also indicate that the level of effort associated with the preparation of the alternatives analysis be commensurate with the significance of the impact and/or discharge activity. 40 C.F.R. 230.6(b).

2.0 BASIC AND OVERALL PROJECT PURPOSE

2.1 Basic Project Purpose

Where the activity associated with a discharge which is proposed for a special aquatic site (e.g., wetland, riffle pool, tidal marsh, etc.) does not require access or proximity to or siting within the special aquatic site in question to fulfill its basic purpose (i.e., is not “water dependent”), practicable alternatives that do not involve special aquatic sites are presumed to be available, unless clearly demonstrated otherwise. In addition, where a discharge is proposed for a special aquatic site, all practicable alternatives to the proposed discharge which do not involve a discharge into a special aquatic site are presumed to have less adverse impact on the aquatic ecosystem, unless clearly demonstrated otherwise. The basic project purpose comprises the fundamental, essential, or irreducible purpose of the proposed project. For purposes of this evaluation, the basic project purpose is maintenance of an engineered river channel, which is water dependent. Although special aquatic sites (wetlands) occur within the Proposed Project Area, the rebuttable presumption that all practicable alternatives to the proposed discharge which do not involve a discharge into a special aquatic site are presumed to have less adverse impact on the aquatic ecosystem does not apply because the wetlands are located atop the engineered river channel where maintenance is needed.

2.2 Overall Project Purpose

The overall project purpose serves as the basis for the USACE’s section 404(b)(1) alternatives analysis and is determined by further defining the basic project purpose in a manner that more specifically describes the goals and accounts for logistical considerations for the project, and which allows a reasonable range of alternatives to be analyzed. It is critical that the overall project purpose be defined to provide for a meaningful evaluation of alternatives. It should not be so narrowly defined as to give undue deference to the preferred alternative, thereby unreasonably limiting the consideration of alternatives. Conversely, it should not be so broadly defined as to render the evaluation unreasonable and meaningless. The overall project purpose is:

1. Improve conveyance capacity to reduce risk of flooding.

2. Reducing potential for breakout flows at bridge locations.

3. Establishing a VFZ and VMZ throughout the Glendale Narrows.

4. Removing trash and foreign debris from the LAR channel.

3.0 PROPOSED PROJECT AREA

The Proposed Project Area encompasses an approximately 7.4 mile section of the LAR channel through Glendale Narrows. Approximately 5.6 miles of the 7.4-mile-long reach is permeable and lined with derrick stones. The remaining sections are lined with concrete. The Proposed Project Area encompasses the 5.6-mile-long, derrick stoned-lined section. The upstream terminus is near Bette Davis Park where the river makes a sharp southerly turn. The downstream terminus is near Dodger Stadium, just upstream of the Interstate 5 (I-5) Freeway bridge near Taylor Yard.

This reach of the LAR channel is adjacent to Griffith Park and traverses near the Los Angeles city communities of Elysian Valley, Atwater Park, Frog Town, and Los Feliz.

Laterally, the Proposed Project Area encompasses the LAR channel and embankments on both sides of the LAR channel. Also included are staging areas located on the left embankment facing downstream).1 As shown in Figure 1of the EA, the Proposed Project Area is segmented into five reaches starting with Reach 2.2

1 The terms “left embankment” and “right embankment” are designated with the observer looking downstream. The right embankment is adjacent to Griffith Park and the Interstate 5 Freeway. The left embankment is adjacent to Bette Davis Park, Glendale Riverwalk, Los Feliz Golf Course and Taylor Yard.

2 This EA uses the reach classifications from the Los Angeles River Ecosystem Restoration Integrated Feasibility Report. Reach 1, which is not within the Proposed Project Area, begins near Buena Vista Park on the left bank and ends at the midpoint of Bette Davis Park.

For this evaluation in general, the scope of analysis includes the 5.6-mile section. Laterally, the scope of analysis extends to the ordinary high water mark (OHWM), which is approximately half-way up the embankment.

4.0 JURISDICTIONAL DETERMINATION OF WATERS OF THE US

The discussion of jurisdiction under the Clean Water Act herein is for planning purposes. For purposes of this analysis, the USACE has assumed the LAR is a waters of the U.S. based on the 2010 U.S. Environmental Protection Agency’s Special Case Evaluation Regarding Status of the LAR which documented the historical and current navigability of the LAR and deemed the LAR to be a Traditional Navigable Water (TNW), a water of the U.S. pursuant to 33 C.F.R.

328.3(a)(1).

In the absence of adjacent wetlands, jurisdictional limits in non-tidal waters of the U.S. extend to the OHWM. When adjacent wetlands are present, jurisdiction extends beyond the OHWM to the limit of the adjacent wetlands. No adjacent wetlands were identified in the Proposed Project Area. Wetlands within the non-concrete bottom portions of the LAR are located on sand banks and are variable, prone to changes in size and location depending on the severity of storm flows.

4.1 Waters of the U.S.

OHWM within the LAR was established by examining debris lines deposited on the trapezoidal embankments during and after storm flows. Based on a conservative interpretation of physical evidence, the OHWM is halfway up the embankment. Based on this lateral extent of jurisdiction, the total acreage of waters of the US within the LAR channel from Reach 2 through Reach 6 is approximately 234 acres.

4.2 Wetlands

Most native riparian vegetation within the LAR channel indicative of wetlands. For example, black willow (Salix nigra) is an obligate wetland species, i.e., plants that are found only within wetlands. Arroyo willow (Salix lasiolepis) is recognized as facultative wetland plant, i.e., plants that predominantly occur within wetlands. Mule fat (Baccharis salicifolia) is recognized as a facultative species, i.e., species that are likely to occur in wetlands and non-wetlands. Based on the above, wetlands are presumed to be present where native vegetation are present. Vegetation surveys in 2013 indicate the following acreages of native vegetation.

Reach Percent Native Vegetation in LAR (Acres)

0-25 25-50 50-75 75-100 Total

Reach 2 0 0 0 2.97 2.97

Reach 3 0 0 0.86 0 0.86

Reach 4 0 0 0 12.88 12.88

Reach 5 0.13 0.86 0.17 9.08 10.24

Reach 6 3.5 10.89 1.39 12.01 27.79

Total 3.63 11.75 2.42 36.94 54.74

Based on the above, there are approximately 54.74 acres of potential wetlands within the LAR channel through Glendale Narrows. Wetlands within the LAR channel are located on sand banks and are variable, prone to changes in size and location depending on the severity of storm flows.

4.3 Exemption From Regulation Under Section 404 of the Clean Water Act

To be exempt from regulation under section 404 of the Clean Water Act, the activity must be exempt under one of the provisions in section 404(f)(1) and must not be subject to “recapture” under section 404(f)(2) of the CWA. Section 404(f)(1)(B) exempts the discharge of dredged or fill material for the purpose of maintenance of currently serviceable structures. The proposed activity is required to maintain flow conveyance, and does not change the character, scope, or size of the structure’s permitted original fill design in accordance with 33 CFR 323.4(a)(2). The channel is currently serviceable. The activity would not convert an area of the waters of the United States into a use to which it was not previously subject and the flow or circulation of waters of the United States would be improved. Therefore, portions of the action where sediment and vegetation would be removed from atop engineered structures are exempt from regulation pursuant to CWA Section 404(f)(l)(B).

5.0 ALTERNATIVES

For clarity and brevity, the alternatives are described with respect to discharges of dredged or fill material. See Section 2 of the EA for a detailed description of the alternatives.

The project involves maintenance of the LAR channel through Glendale Narrows. Thus, all alternatives including the No Action Alternative entail removal of sediment and vegetation. All alternatives would also entail hauling operations – staging areas, access routes, etc. All hauling operations are located in the uplands outside the LAR channel and would not result in discharges of fill within waters of the U.S.

Accumulated sediment, in the form of sandbars, is present throughout the Glendale Narrows.

Sandbars may be vegetated or unvegetated. Removal of sediment and vegetation would result in use of loaders and excavators on the channel bed resulting in discharges of dredged material.

Examples include bulldozer sidecast and temporary stockpiles.

There would be temporary discharges of fill material during water diversion operations when k-rails or cofferdams or similar structures are placed in the river bottom. These structures would be removed upon completion of work. There would be no permanent discharges of fill material such as concrete under the alternatives.

There would also be temporary discharges of earthen fill associated with the construction up to four temporary earthen access ramps upstream and downstream of Fletcher Drive at Reach 5 and

Taylor Yard Bridge at Reach 6. The temporary access ramps would be located on the slope of the left embankment. A typical ramp would be approximately120 foot-long by 15 foot-wide by 2 foot-high. The earthen ramps would be removed upon completion of work at each reach or at the end of the annual work window. In the event of forecasted storm flows, the earthen ramps would be removed and reconstructed after storm flows have abated.

The only distinctions between the alternatives are the volumes of sediment that would be removed and acreage of vegetation within the waters of the US, including wetlands, affected.

5.1 Alternative 1: No Action Alternative

Under the No Action Alternative, there would be no comprehensive sediment and vegetation management program through the Glendale Narrows. Instead, site-specific sediment removal and vegetation management projects would continue to be implemented in critical areas as needs arise and to levels commensurate with available funding and resources, as has been standard practice in the past. The primary purpose would be to maintain the existing level of flood conveyance. The location and size of future site-specific sediment removal operations are unknown.

5.2 Alternative 2: Fifty Percent Sediment Removal & Vegetation Management

Alternative (Preferred Alternative)

Under Alternative 2, up to 50% of total accumulated sediment within Glendale Narrows, approximately 168,860 cy, would be incrementally removed over a 10-year period generally proceeding from downstream to upstream reaches. Work within Reach 6 where vegetation is densest and where the least Bell’s vireo has been found in surveys from 2016 and 2018, work would be phased in order to minimize impact to the habitat. In the area between the VMZs, native trees would be preserved. For native trees, sediment removal would be limited to no closer than 5 ft from tree canopy dripline to ensure survivorship of trees. Approximately 38.74 acres of riparian/wetland vegetation would be enhanced through removal of non-native species.

Native and non-native vegetation would be removed from upstream and downstream of nine bridge crossings.

Subsequent to vegetation removal, wetland vegetation that can flex and bend during storm flows such as native understory vegetation (e.g., mulefat scrubs, willow scrubs, etc.) or emergent freshwater marsh vegetation (e.g., cattails, bulrush, etc.) would be allowed to grow throughout the channel including the VMZs.

All sediment and vegetation would be disposed at landfills. Sediment testing results will determine the appropriate landfill classes for disposal.

5.3 Alternative 3: Full Sediment Removal Alternative

Under Alternative 3, up to 100% of total accumulated sediment within Glendale Narrows, approximately 337,719 cy, would be incrementally removed over a 10-year period generally proceeding from downstream to upstream reaches. As part of the process approximately 54.74 acres of riparian/wetland vegetation would be removed. Native trees would be avoided to the extent practicable.

6.0 ALTERNATIVES ANALYSIS

6.1 Restrictions on Discharge

The 404(b)(1) Guidelines prohibit the discharge of dredged or fill material into waters of the U.S. if there is a practicable alternative to the proposed discharge which would have less adverse impact on the aquatic ecosystem, so long as the alternative does not have other significant adverse environmental consequences. 40 C.F.R. 230.10(a). To be “practicable,” an alternative must be “available and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall project purposes.” 40 C.F.R. 230.10(a)(2).

6.2 Overall Project Purpose

With the exception of the No Action Alternative all action alternatives meet the overall project purpose. The No Action Alternative does not meet the overall project purpose because it would not improve the flood conveyance capacity of the LAR within Glendale Narrows. Thus, it is not carried forward consideration in the 404(b)(1) evaluation.

6.3 Practicability (Technology)

All action alternatives can be constructed with existing technology. All action alternatives would utilize conventional construction techniques and conventional construction equipment.

6.4 Practicability (Logistics)

All action alternatives are practicable with respect to logistics. The active maintenance footprint for both action alternatives would be located within the LACDA project lands. Both alternatives would use the same trucking routes. The trucking routes would mostly be located atop existing access roads. Some staging areas would be sited on lands owned by the city of Los Angeles (Rigali Ave. staging area and Taylor Yard) and the state of California (Bowtie Parcel).

Temporary easements would be required for use of these properties.

6.5 Practicability (Cost)

Both alternatives are considered practicable in terms of cost.

Alternatives

Practicability Test

Impacts to waters of the

US

Meets Overall Project

Purpose? Cost Logistics Technology Temporary (Acres)

Permanent (Acres)

Fill for Temp.

Access Ramp

(cubic feet) Alternative 1 (No Action) n/a n/a n/a n/a 0 n/a No

Alternative 2 (50% Cut) Yes Yes Yes 102* 0 7,200# Yes

Alternative 3 (100% Cut) Yes Yes Yes 102* 0 7,200# Yes

∗ 102 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎= 5.6 𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑎𝑎× 5280 𝑓𝑓𝑓𝑓 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚

× 150 𝑓𝑓𝑓𝑓. 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑎𝑎ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑚𝑚 𝑤𝑤𝑚𝑚𝑤𝑤𝑓𝑓ℎ.× 𝑎𝑎𝑎𝑎𝑎𝑎𝑚𝑚 43 ,560 𝑓𝑓𝑓𝑓2

# 120 𝑓𝑓𝑓𝑓.× 15 𝑓𝑓𝑓𝑓.× 2 𝑓𝑓𝑓𝑓.= 3,600 𝑎𝑎𝑐𝑐𝑐𝑐𝑚𝑚𝑎𝑎 𝑓𝑓𝑎𝑎𝑎𝑎𝑓𝑓.𝑜𝑜𝑓𝑓 𝑤𝑤ℎ𝑚𝑚𝑎𝑎ℎ1 𝑚𝑚𝑎𝑎 𝑐𝑐𝑎𝑎𝑚𝑚𝑜𝑜𝑤𝑤 𝑓𝑓ℎ𝑎𝑎 𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂= 1,800 𝑎𝑎𝑐𝑐𝑐𝑐𝑚𝑚𝑎𝑎 𝑓𝑓𝑎𝑎𝑎𝑎𝑓𝑓 × 4 𝑎𝑎𝑎𝑎𝑚𝑚𝑟𝑟𝑎𝑎.

6.6 Impacts to waters of the U.S.

In the LAR channel through Glendale Narrows, approximately 5.6 miles of the channel bed is permeable and lined with derrick stones. On the average the channel width from toe-to-toe of the levees is approximately 150 ft. Thus, there are approximately 102 acres of permeable, derrick stone-lined riverbed through the Glendale Narrows. Of the 102 acres, approximately 54.74 acres are vegetated according to surveys performed in 2023.

Under Alternative 2, vegetation would be removed from VFZs, VMZs, and the upstream and downstream approaches to bridge crossings resulting in removal of 16 acres of vegetation, leaving approximately 38.74 acres of vegetation in the remaining areas. Under Alternative 2, non-native vegetation from the remaining 38.74 acres would be removed. Impact acreage associated with non-native removal in the remaining 38.74 acres would vary according to conditions at the time of work. Conditions include but are not limited to: location, shape, and volume of sandbars; and location, density, and acreage of vegetation. Thus, the minimum impact acreage to vegetation would be larger than 16 acres and the maximum acreage to vegetation would be less than 38.74 acres.

Under Alternative 3, vegetation would be removed from VFZs, VMZs, and the upstream and downstream approaches to bridge crossings resulting in removal of 16 acres of vegetation, leaving approximately 38.74 acres of vegetation in the remaining areas. With the goal of removing most excess sediment in the channel, it is possible that much of the vegetation within the 38.74 acres of vegetation remaining in the channel would be removed. Thus, the minimum impact acreage to vegetation would be larger than 16 acres and the maximum acreage to vegetation would be close to 54.74 acres.

Under both alternatives construction of up to four temporary access ramps would result in the temporary discharge of earthen fill along the slope of the left embankment. Each ramp would discharge approximately 1,800 cubic feet of fill below the OHWM. Thus, in total up to approximately 7,200 cubic feet of fill could be temporarily discharged below the OHWM. The earthen ramps would be removed upon completion of work at each reach or at the end of the annual work window. In the event of forecasted storm flows, the earthen ramps would be removed and reconstructed after storm flows have abated.

Impacts would be temporary as there would be no permanent loss of waters of the U.S.

7.0 ENVIRONMENTAL EFFECTS

In accordance with the Section 404(b)(1) Guidelines, the potential short-term or long-term effects of a proposed discharge of dredged or fill material on the physical, chemical, and biological components of the aquatic environment must be determined. With the exception of the No Action Alternative both the Full Sediment Removal Alternative and the Fifty Percent Sediment Removal & Vegetation Management Alternative (Preferred Alternative) would entail temporary discharges of dredged or fill material into waters of the US. The following discussion evaluates impacts of both alternatives on environmental resources identified in Subpart C through Subpart F of the Section 404(b)(1) Guidelines.

7.1 Potential Direct and Secondary (Indirect) Impacts on Physical and Chemical

Characteristics of the Aquatic Ecosystem (Subpart C)

7.1.1 Substrate

Due to a shallow groundwater table, the channel bed of the LAR channel through Glendale Narrows was not lined with concrete. To let groundwater percolate and at the same time to stabilize the invert, large derrick stones were placed in the invert. The increased channel roughness and decrease in flow velocity across the derrick stone bed results in sediment accumulation which in turn reduces flow volume through the Glendale Narrows. The 2022 flood conveyance assessment estimated the amount of sediment that has accumulated in the channel above the as-built condition. In total, there are approximately 337,719 cubic yards (cy) of accumulated sediment in the form of sandbars present throughout the Glendale Narrows.

Unvegetated Sandbars Per previous sediment analysis of sandbars in Reach 5C, cobbles and boulders make up a substantial portion of the material and range from 55 to 90% (by volume) of the material. The largest of the boulders exceeded approximately 3 feet in diameter and typical clast size was estimated as a large cobble on the order of 9 inches in diameter. The remaining soil matrix in the interstitial space consists primarily of granular material ranging from poorly graded sand with silt and gravel to poorly graded gravel with sand. The percentage of fines (particles smaller than 0.075mm) varies between 2.5% and 7.3% with more silt than clay particles. The specific gravity of the soils tested varies between 2.65 and 2.69.

Vegetated Sandbars The base of vegetated sandbars is similar to those of unvegetated sandbars with gravels, cobbles and boulders comprising the base material. However, atop the base are mounds of loamy sand trapped by vegetation. By volume, vegetated sandbars likely have more loamy sand than cobbles and rocks.

7.1.1.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation Management Alternative (Preferred Alternative)

Direct Impacts: Up to 50% of total accumulated sediment within Glendale Narrows, approximately 168,860 cy, would be incrementally removed resulting in disturbance of the upper stratum of native substrate. However, the composition of the accumulated material is homogeneous. Thus, removal of the accumulated material would mostly expose additional boulders and cobbles. Sediment remaining in the interstitial space would be composed of gravel, rough sand, and fines. The exposed surface would continue to remain exposed to water.

Boulders and cobbles would not be subject to movement from wind action. Movement of top soils composed of fines and sand is expected. The temporary absence of vegetation from the newly exposed surface would increase potential for erosion during high energy storm flows.

However, sediment would be replenished since channel roughness and low velocity baseline flows would cause sediment to settle out of the water column. Sediment equilibrium within the water column would determine sedimentation or erosion rates.

Up to four temporary access ramps would be constructed along the slope of the left embankment.

Because the fill would be mostly located atop the concrete structure and would be removed upon completion of work or forecasted inclement weather, it would have no effect on changes to sedimentation or erosion rates.

Indirect Impacts: Vegetation is expected to naturally reestablish in the area due to the perennial flows and existing seed bank. In particular, native understory vegetation (e.g., mulefat scrubs, willow scrubs, etc.) or emergent freshwater marsh vegetation (e.g., cattails, bulrush, etc.) would be allowed to grow throughout the channel including the VMZs. Vegetation growth would increase sedimentation.

There would be no un-replenishable loss of substrate from the LAR channel.

7.1.1.2 Alternative 3: Full Sediment Removal Alternative

Direct Impacts: All accumulated sediment, approximately 337,719 cy in total, would be removed. Direct impacts to substrate would be similar to Alternative 2.

Indirect Impacts: In the short-term, subsequent to sediment removal operations, erosion rates would be greater than Alternative 2 because sediment would be removed over a greater area.

However, the long-term impacts would be the same as those characterized for Alternative 2:

channel roughness would recapture sediment; existing seedbank would result in regrowth of vegetation; scrubs and marsh vegetation would be retained further increasing sedimentation.

There would be no un-replenishable loss of substrate from the LAR channel.

7.1.2 Suspended Particulates and Turbidity

The major sources of water at Glendale Narrows are storm flows; nuisance flows from urban areas that enter the LAR through major storm outfalls; and treated wastewater from the Tillman Water Reclamation Plant and the Glendale Water Reclamation Plant. The flow through this reach is perennial due to the discharge of approximately 30 million gallons per day from the two water reclamation plants.

Discharge of treated wastewater primarily constitute dry weather flows. The flows are not visibly turbid because the releases are low energy and the water column is primarily in contact with concrete surfaces prior to reaching Glendale Narrows. Storm flows are high energy and are visibly turbid because they convey sediment from the Santa Monica Mountains, Santa Susana Mountains, Verdugo Hills as well as fines from urban areas.

7.1.2.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation

Direct Impacts: Prior to the sediment removal work, work areas would be isolated from flows with water diversion structures such as k-rails or coffer dams. Movement of vehicles across earthen substrate during placement and removal of water diversion structures would temporarily elevate turbidity in the water column. When fully isolated from surrounding flows, work within the LAR would not increase turbidity.

If storm flows are anticipated, all water diversion structures would be removed outside the LAR channel.

Access ramps would be constructed along the slope of the left embankment. The fill would be mostly located atop the concrete structure and would be removed upon completion of work or forecasted inclement weather, it would have no effect turbidity.

Indirect Impacts: Sediment remaining in the channel after construction would be susceptible to water erosion during high energy storm flows Increased turbidity can cause slight elevation in water temperature and affect fish. However, stormflows tend to be turbid in general throughout the LAR. Given the sediment load entering the LAR from the larger watershed, contributions to turbidity from the Glendale Narrows would be minimal. During normal flows, notable increase in turbidity is not expected. As stated above, the sandbars where excess sediment accumulates is primarily composed of rocks, cobbles and sand.

Vegetation is expected to naturally reestablish in the area due to the perennial flows and existing seed bank. In particular, native understory vegetation (e.g., mulefat scrubs, willow scrubs, etc.)

or emergent freshwater marsh vegetation (e.g., cattails, bulrush, etc.) would be allowed to grow throughout the channel including the VMZs. Vegetation growth would stabilize loose soils and minimize potential for downstream turbidity. Turbidity within the VMZs would not be notable.

As stated above, the sandbars where excess sediment accumulates is primarily composed of rocks, cobbles and sand.

7.1.2.2 Alternative 3: Full Sediment Removal Alternative

Direct Impacts: Impacts would be similar to those characterized for Alternative 2: When fully isolated from surrounding flows, work within the LAR would not increase turbidity.

Indirect Impacts: With removal of all accumulated sediment over a larger area, the potential for erosion during high energy storm flows would be greater than Alternative 2, because the unvegetated surface area exposed to storm flows would be larger. Increased turbidity can cause slight elevation in water temperature and affect fish. However, stormflows tend to be turbid in general throughout the LAR. Given the sediment load entering the LAR from the larger watershed, contributions to turbidity from the Glendale Narrows would be minimal. During normal flows, notable increase in turbidity is not expected. As stated above, the sandbars where excess sediment accumulates is primarily composed of rocks, cobbles and sand.

Vegetation is expected to naturally reestablish in the area due to the perennial flows and existing seed bank. In particular, native understory vegetation (e.g., mulefat scrubs, willow scrubs, etc.)

or emergent freshwater marsh vegetation (e.g., cattails, bulrush, etc.) would be allowed to grow throughout the channel including the VMZs. Vegetation growth would stabilize loose soils and minimize potential for downstream turbidity.

7.1.3 Contaminants

Nuisance flows and storm flows that enter the LAR through storm outfalls convey pollutants associated with the urban environment into the water column: fecal coliform bacteria, pesticides;

metals (e.g., copper, chromium, lead); nutrients (nitrogenous and phosphorus compounds);

petroleum-based oils and solvents; and trash. Thus, the LAR through Glendale Narrows is listed as an impaired water pursuant to Section 303(d) of the Clean Water Act.

Results from a comprehensive water quality test during the 2018 Reach 4D toe repair project did not find detectable levels for most organic chemicals tested. Where organic chemicals were detected, their levels were substantially below the regulatory thresholds. However, levels for several metals exceeded regulatory thresholds in the LARWQCB Basin Plan. The results are consistent with the LARWQCB’s Section 303(d) listing of this reach of the LAR for presence of metals.

Comparison of Water Quality Testing Results to LARWQCB Regulatory Limits

Metals Reach 4D

Baseline Water Quality Testing Results

(mg/L)1

LARWQC Basin Plan Limits

(mg/L)2

Chromium 0.15 0.05 Nickel 0.5 0.1 Cadmium 0.006 0.005 Beryllium 0.011 0.004 Mercury 0.003 0.002 Chromium 0.15 0.05

7.1.3.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation

Prior to the sediment removal work, work areas would be isolated from flows with water diversion structures such as k-rails or coffer dams. These fill materials would be chemically inert, and would not leach contaminants into the water column. The water diversion structures would be removed upon completion of construction. If storm flows are anticipated, all water diversion structures and equipment would be removed outside the LAR channel.

Use of construction vehicles increases the potential for accidental release of fuels, solvents, or other petroleum-based contaminants. However, potential for contact with water would be minimal because flows would be diverted around the work area.

Sediment removal would disturb the upper strata of native substrate. After removal, initial inundation from incoming flows would cause unconsolidated sediment to enter the water column and resuspend contaminants. However, potential for sediment resuspension would be limited.

As stated above, the sandbars where excess sediment accumulates is primarily composed of rocks, cobbles and sand. Furthermore, resuspension would not introduce new contaminants not already present within the existing substrate. Moreover, resuspension of contaminants is unlikely to notably increase their concentration in the water column. Sediment would be tested and all refueling would occur in the uplands, outside the LAR channel.

Water infiltration would also cause loose soils to settle and reconsolidate. Regrowth of vegetation over time would further trap and consolidate soils. Thus, impacts from resuspension would be temporary and decrease over time.

Temporary access ramps would be constructed along the slope of the left embankment. Ramps would be constructed of clean earthen fill. Because the fill would be mostly located atop the concrete structure and would be removed upon completion of work or forecasted inclement weather, it would not introduce contaminants into the water column.

Indirect Impacts: Temporary resuspension of contaminants would make additional contaminants available for ingestion for wildlife that consume river water or aquatic species.

However, resuspension would not introduce new contaminants not already present within the existing substrate. Furthermore, resuspension of contaminants is unlikely to notably increase their concentration in the water column. Furthermore, the existing CWA 401 Water Quality Certification (WQC) for the proposed discharges requires water quality monitoring. Based on the above and with implementation of the terms and conditions of the 401 WQC, impacts would be de minimis.

7.1.3.2 Alternative 3: Full Sediment Removal Alternative

Direct impacts would be similar to those characterized for Alternative 2. Likewise, avoidance and minimization measures – sediment testing, refueling in the uplands, sediment testing, and water quality monitoring – impacts would be de minimis.

Indirect Impacts: With removal of all accumulated sediment over a larger area, the potential for resuspension of contaminants would be greater than Alternative 2. However larger the difference may be, indirect impacts would be similar to those characterized for Alternative 2.

7.1.4 Water Flow

Sediment and vegetation in the river have reduced conveyance capacity throughout the Glendale Narrows section of the LAR. Furthermore, sandbars also concentrate currents against the toe of levees. The currents cause erosion, displace ballast rocks, and undermine the engineered structure. Sandbars also block flows in some locations resulting in stagnant backwaters creating odors and vector control issues.

7.1.4.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation

Prior to the sediment removal work, work areas would be isolated from flows with water diversion structures such as k-rails or coffer dams. Thus, low flows would remain unchanged during construction. If storm flows are anticipated, all water diversion structures would be removed outside the LAR channel. With removal of sediment and vegetation, design flood conveyance capacity would be partially restored. Potential for breakout flows around bridge crossing would also be minimized. Removal of sandbars would also remove blockages and restore positive drainage throughout all reaches of Glendale Narrows.

Temporary access ramps would be constructed along the slope of the left embankment. Because the fill would be mostly located atop the concrete structure. Thus, it would not affect flows through the channel. The ramps would be removed upon completion of work or forecasted inclement weather. Thus, they would have no effect on storm flows.

Indirect Impacts: With removal of accumulated material that force low flows against the embankment, low flows may sheet flow across the cleared area. Furthermore, blockages and backwaters would be cleared, thereby reducing odors and reducing potential for vector control issues.

However, the bend at Reach 5C and Reach 6A coupled with hydraulics and the existing channel roughness would continue to promote the process of sedimentation. Thus, a sandbar is expected to reform over time at the location, pushing low flows to the right embankment.

7.1.4.2 Alternative 3: Full Sediment Removal Alternative

Direct impacts would be similar to those characterized for Alternative 2. With removal of all accumulated sediment over a larger area, flood conveyance capacity would be partially restored to design condition over a larger portion of the Glendale Narrows compared to Alternative 2.

Indirect Impacts: With removal of all accumulated sediment over a larger area, the potential for restoring linear flows would be greater. However, the bend at Reach 5C and Reach 6A coupled with hydraulics and the existing channel roughness would continue to promote the process of sedimentation. Thus, a sandbar is expected to reform over time at the location, pushing low flows to the right embankment.

7.1.5 Cumulative Impacts

The Glendale Narrows reach of the LAR is an approximately 5.6-mile long, rock-lined permeable, trapezoidal channel that traverses Elysian Valley. Prior to construction of the LAR channel, the river meandered through the valley leaving minimal room for development. By 1928, segments of the LAR through the Glendale Narrows had been contained by vegetated earthen embankments to protect adjacent development. It was an earthen trapezoidal channel, and the river bottom was primarily composed of sand. The flow regime was ephemeral.

Accordingly, there were no riparian forests or wetlands in the middle of the river.

Construction of the LAR channel through Glendale Narrows and increasing development drastically changed the flow regime and sedimentation process. Construction of the channel resulted in discharge of rocks in the river bottom, increasing channel roughness. Development has also changed the flow regime of Glendale Narrows from ephemeral to perennial. The Glendale Narrows reach is now a perennial water body that conveys approximately 30 million gallons per day discharged from the Tillman Water Reclamation Plant, and the Glendale Water Reclamation Plant. Perennial flows and increased channel roughness resulted in the presence of vegetated sandbars. The increase in the size and scope of the vegetated sandbars resulted in decreased conveyance capacity.

Increased development in the uplands has resulted in long-term water quality impairments.

Nuisance flows and storm flows that enter the LAR through major storm outfalls convey pollutants associated with the urban environment into the water column: fecal coliform bacteria, pesticides; metals (e.g., copper, chromium, lead); nutrients (nitrogenous and phosphorus compounds); petroleum-based oils and solvents; and trash. Thus, the LAR at Glendale Narrows is consistently listed as an impaired water pursuant to Section 303(d) of the Clean Water Act.

As development increased, the LAR channel through Glendale Narrows was further modified for bridge crossings, utility crossings, and construction of storm drain outfalls. In addition, maintenance activities were conducted. These modifications and maintenance activities resulted in the discharge of concrete structural fill below the OHWM. However, the rock-lined river bottom and perennial flow regime remain unchanged. Discharges of fill associated with these activities also did not change the design conveyance capacity of the LAR channel.

Future projects in the uplands within the Proposed Project Area would likely entail redevelopment or conversion of existing land uses. Minor modifications to the LAR channel associated with construction, modifications, and maintenance of existing and future infrastructure such as bridges and utilities are anticipated.

Regionally, there is an increasing awareness of the recreational, economic and environmental importance of the LAR to the social milieu of the city as the dense urban environment has highlighted the need to connect people to the river and facilitate access to green spaces.

Furthermore, with the exception of the 2.4-mile-long reach transecting the Sepulveda Basin, Glendale Narrows is the only substantial segment of the LAR resembling a natural river system.

Thus, this reach of the LAR has increasingly become the focal point for revitalization and restoration efforts. As discussed in Recreational Resources, regional parks, pocket parks, river walks, and bicycle paths are presently adjacent to the LAR channel through Glendale Narrows.

In addition, organizations such as the Friends of the Los Angeles River and the MRCA among others have implemented recreation programs along the Glendale Narrows.

Programmatically, the Los Angeles River Master Revitalization Plan (LARMRP) and the LARER project would further implement projects designed to create access and facilitate interaction with the LAR and green spaces. To that end, the North Atwater Bridge which forms the architectural centerpiece of the revitalization was completed in 2019. In 2023, the USACE completed design of Phase IA of the LARER project, located immediately upstream of Reach 2A. Phase IA is scheduled for construction in 2024.

Changes to the hydraulic characteristics (e.g., velocity, and water surface elevations) would be mitigated as appropriate for actions requiring Rivers and Harbors Act Section 408, 33 U.S.C.

408, approvals and reviews. Impacts to water quality would be temporary and would be attenuated through CWA Section 401 and Section 404 and Section 408 permitting requirements.

Both action alternatives, similar to past, present, and foreseeably future actions would entail minor temporary impacts to the physical and chemical characteristics of the aquatic ecosystem.

However, the fundamental physical and chemical characteristics of the river – the perennial flow regime, channel roughness, and pollutants from nuisance and storm flows – would remain intact.

Therefore, proposed action would not result in substantial cumulative changes to the physical and chemical characteristics of the aquatic ecosystem.

7.2 Potential Direct and Secondary Impacts on Biological Characteristics of the Aquatic

Ecosystem (Subpart D)

7.2.1 Endangered Species

Based on existing protocol-level survey data, only the federally endangered Least Bell’s Vireo (Vireo bellii pusillus, LBVI) occurs within the Proposed Project Area. Although protocol surveys in 2023 did not indicate presence of nesting LBVI, surveys in 2018 and 2016 did indicate presence of 2-3 individuals in the Reach 6 where vegetation is most dense.

7.2.1.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation

Direct Impacts: Sediment and vegetation management would potentially affect the LBVI due to a long-term reduction in potential habitat including an approximate 29% reduction in native vegetation (see Table 15 of the EA). Sediment removal and vegetation management activities would occur outside the migratory bird and LBVI breeding season to avoid direct and adverse effect on nesting individuals.

Compared to other Glendale Narrows Reaches, Reach 6 has the highest acreage of non-native plant cover. Within this reach, approximately 23% of native vegetation would be removed while the remaining 77% of native vegetation would be enhanced through non-native vegetation removal (Table 15 of EA). In Reach 6, overall habitat quality in expected to improve and benefit the species in the long-term. Due to the limited number of individuals detected and the habitat enhancement benefits of non-native vegetation removal, the remaining habitat in Reach 6 would likely continue to support at least two LBVI.

Temporary access ramps would be constructed along the slope of the left embankment. Because the fill would be mostly located atop the concrete structure, the ramps would have minimal affect on vegetation or LBVI habitat.

Indirect Impacts: There would be no secondary impacts.

7.2.1.2 Alternative 3: Full Sediment Removal Alternative

Direct Impacts: Native trees would be avoided to the extent practicable. However, because most trees are rooted in sandbars, removal of all accumulated sediment would result in a notable decrease in native trees. Reduction in native trees, especially in Reach 6, would render the LAR channel less viable for the 2 LBVI individuals that have been detected in past surveys. The impact would be adverse not for the species in the southern California region but for the limited number of individuals that may be habituated to nesting within Reach 6. Loss of habitat for the few LBVI would not by itself be significant. However, in combination with the transformation of habitat from a riparian corridor to one dominated by emergent freshwater marsh vegetation, impacts would be significant.

Indirect Impacts: There would be no secondary impacts.

7.2.2 Other Wildlife (Reptiles, Birds, and Mammals)

The wildlife species expected to occur in the Proposed Project Area are those species most adapted to and tolerant of human managed landscapes. These include common reptiles such as the western fence lizard (Sceloporus occidentalis) and the common side blotch lizard (Uta stansburiana), as well as mammals such as opossums, skunks, rats, California ground squirrels (Otospermophilus beecheyi). Birds are the most diverse taxa present within the LAR. A table of all known and possibly present species can be found in Appendix D. No fish species native to the LAR watershed are expected to occur within the Proposed Project Area. Past surveys upstream of and within the Proposed Project Area (LADWP 2004; FoLAR 2008) have only collected non-native fish species such as fathead minnow (Pimephales promelas), carp (Cyprinus carpio), black bullhead (Ameiurus melas), Amazon sailfin catfish (Pteroplichthys pardalis), green sunfish (Lepomis cyanellus), bluegill (Lepomis macrochirus), mosquito fish (Gambusia affinis), tilapia (Oreochromis spp.), and largemouth bass (Micropterus salmoides).

7.2.2.1 Alternative 2: Fifty Percent Sediment Removal & Vegetation

Noise and vibration would temporarily scatter wildlife present within the channel during sediment and vegetation management activities. Likewise, daily ingress and egress of equipment from some staging areas such as Bette Davis Park or Taylor Yard would result in the same.

However, most general wildlife present in the Glendale Narrows are urban-adapted and mobile.

Less mobile invertebrates, amphibians, and reptiles could be buried or crushed by construction equipment. However, loss of individuals would be limited to those located within the construction footprint. Individuals outside the construction footprint would be unaffected.

Upon completion of sediment removal, affected areas would be available for wildlife use.

Within the VFZ and VMZs all vegetation, native and non-native, would be removed. In the approaches leading to and from bridge crossings, native and non-native vegetation would be removed. Elsewhere in the channel native vegetation would be preserved to the extent practicable, providing functions and services associated with the vegetation such as foraging, nesting, or predation avoidance. There would not be a substantial decline of general wildlife population.

Wildlife movement throughout the Glendale Narrows would not be constrained. Staging areas would be limited to highly disturbed urban areas: USACE’s rights-of-ways atop the levee, access roads, and access ramps; small areas adjacent to Bette Davis Park and the Los Feliz Golf Course;

and small areas are sited in the Bowtie Parcel and Taylor Yard. Terrestrial wildlife inhabiting the general area such as rats, racoons, opossums and squirrels are urban-adapted species capable of traversing through and around staging areas. In-water sediment and vegetation management work would not require impoundment of flows. Thus, riverine passages through the Glendale Narrows would remain unobstructed for aquatic species. Last, passage for avian species would remain viable since approximately 71% of native vegetation would remain in the Glendale Narrows.

Temporary access ramps would be constructed along the slope of the left embankment. Because the fill would be mostly located atop the concrete structure, the ramps would not affect wildlife.

Indirect Impacts: Removal of non-natives would allow for growth and expansion of native vegetation. Furthermore, native grasses and emergent freshwater vegetation would further augment the diversity and complexity of native riparian vegetation.

7.2.2.2 Alternative 3: Full Sediment Removal Alternative

Direct Impacts: Temporary construction impacts would be similar to those characterized for Alternative 2.

Indirect Impacts: In the long-term, transformation of vegetation from heterogenous riparian corridor to a mono-stratum vegetation community composed of native grasses and freshwater wetland vegetation such as cattails or bulrushes growing throughout the channel including the VMZs would affect movement of birds through the river. With a notable decrease in trees, the LAR channel would be less viable for birds. There would be an absence of nesting habitat and protection from predation for nesting birds. Their movement up and down the river would be less efficient because they would need to utilize tree cover atop the embankments. Thus, avian movement in the river within Glendale Narrows would be more hampered relative to Alternative 2.

Terrestrial wildlife inhabiting the general area such as rats, racoons, opossums and squirrels and similar urban-adapted species would be less affected because they would still be able to utilize in-river vegetation for movement.

7.2.3 Fish, Crustaceans, Mollusks and other Aquatic Organisms in the Food Web

No fish native to the LAR watershed are expected to occur in open water areas within the Proposed Project Area.