B08_Attachment_08_GLCA_Hite_FWSOF_DRAFT.pdf

National Park Service

Glen Canyon Recreation Area Low-Water Ramp at Hite, Hite, Utah

GLCRA-318744

Statement of Findings for Director’s Order #77-1: Wetland Protection and Director’s Order #77-2: Floodplain

Management Draft

August 2025

Prepared by:

Jacobs Government Services Company

Denver, CO

Contract No. 140P2023D0006

Task Order No. 140P2024F0242

U.S. Department of the Interior

Glen Canyon Recreation Area Low-Water Ramp at Hite, Hite, Utah

GLCRA-318744

Statement of Findings for Director’s Order #77-1: Wetland Protection and

Director’s Order #77-2: Floodplain Management, Draft August 2025

Draft Statement of Findings for

Protection of Wetlands (Executive Order 11990) and

Floodplain Management (Executive Order 11988)

Low Water Ramp at Hite

March 2025

Glen Canyon Recreation Area

Recommended: ______________________________________________

Superintendent Date

Certification of Technical Adequacy and Servicewide Consistency:

Acting Chief, NPS Water Resources Division Date

Approved: _____________________________________________________

Acting Regional Director Date

Table of Contents Page i

Table of Contents

Acronyms and Abbreviations ........................................................................................... iii

Chapter 1 – Introduction ............................................................................................... 1-1

1.01 Floodplains ............................................................................................. 1-1

1.02 Wetlands ................................................................................................. 1-2

Chapter 2 – Project Description ................................................................................... 2-1

2.01 Project Location ...................................................................................... 2-1

2.02 Purpose and Need .................................................................................. 2-1

2.03 Proposed Action ..................................................................................... 2-2

Chapter 3 – Site Description ........................................................................................ 3-1

3.01 Existing Conditions ................................................................................. 3-1

Chapter 4 – Wetlands in the Project Area .................................................................... 4-1

4.01 Survey Methods ...................................................................................... 4-1

4.02 Riverine Features ................................................................................... 4-3

4.03 Lacustrine Features ................................................................................ 4-4

4.04 Wetland Functions and Values Assessment ........................................... 4-5

4.05 Impacts of the Proposed Action .............................................................. 4-9

4.06 Other Alternatives Considered .............................................................. 4-11

4.07 Justification for the Use of Wetlands ..................................................... 4-12

4.08 Impact Avoidance and Minimization ..................................................... 4-12

Chapter 5 – Floodplains ............................................................................................... 5-1

5.01 Floodplains ............................................................................................. 5-1

5.02 Justification for Use of the Floodplain ..................................................... 5-4

5.03 Detailed Flood Hazard and Flood Risk Analysis ..................................... 5-4

5.04 Floodplain Impact Mitigation Measures................................................... 5-8

Chapter 6 – Conclusions .............................................................................................. 6-1

Chapter 7 – Preparers .................................................................................................. 7-1

Chapter 8 – References ............................................................................................... 8-1

Table of Contents Page ii

List of Figures

Figure 5-1. Existing Condition Floodplain (100-year flood plus 2 feet) Extents for Both Low- and High-lake Levels in Lake Powell ........................................................ 5-2

Figure 5-2. Existing Condition Floodplain (100-year flood plus 2 feet) Elevations for Low-lake Level Scenario ................................................................................... 5-3

Figure 5-3. Existing Condition Floodplain (100-year flood plus 2 feet) Elevations for High-lake Level Scenario ................................................................................... 5-4

Figure 5-5. Existing and Proposed Floodplain (100-year plus 2 feet) Extent for the Low-lake Level Scenario ................................................................................... 5-6

Figure 5-6. Existing and Proposed Floodplain (100-year plus 2 feet) Extent for the High-lake Level Scenario ................................................................................... 5-7

List of Tables

Table 1. Location Information ....................................................................................... 2-1

Table 2. Anticipated Construction Timeline .................................................................. 2-3

Table 3. Soil Series Mapped within the Study Area ..................................................... 3-2

Table 4. Summary of Aquatic Resources Investigated in the Project Area .................. 4-2

Table 5. Summary of the Wetland Functional Assessment .......................................... 4-6

Table 6. Riverine Wetland Impacts ............................................................................ 4-10

Table 7. Lacustrine Wetland Impacts ......................................................................... 4-10

List of Appendices

Appendix A – Photo Log

Appendix B – Wetland Determination Data Forms

Appendix C – Wetland Function and Value Data Sheets

Acronyms and Abbreviations Page iii

Acronyms and Abbreviations

Acronym Definition

°F degree(s) Fahrenheit amsl above mean sea level

BMP Best management practice

EO Executive Order fps feet per second

GLCA Glen Canyon National Recreation Area

HUC Hydrologic Unit Code

ID identifier

LiDAR light detection and ranging

NEPA National Environmental Policy Act

NHD National Hydrography Dataset

NPS National Park Service

NRCS Natural Resources Conservation Service

NWI National Wetlands Inventory

OHWM Ordinary High Water Mark

SOF Statement of Findings

USACE U.S. Army Corps of Engineers

USGS U.S. Geological Survey

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Chapter 1 – Introduction Page 1-1

Chapter 1 – Introduction

The National Park Service (NPS) is proposing to construct a new ramp to provide river and lake access at lower water levels in the Hite District of Glen Canyon National Recreation Area (GLCA). Currently, access to the river at the existing Hite Ramp on the river left (south/east) bank is no longer possible due to low water levels and the presence of unconsolidated reservoir sediments. This proposed ramp will replace an existing ramp that is inaccessible at current and anticipated future lake levels due to its grade. GLCA is initiating this project to provide ongoing water access at the Hite District.

1.01 Floodplains

Executive Order (EO) 11988, “Floodplain Management,” requires NPS and other federal agencies to evaluate the likely impacts of actions in floodplains. The objective of EO 11988 is to avoid, to the extent possible, the long-term and short-term adverse impacts associated with occupancy, modification, or destruction of floodplains and to avoid indirect support of development and new construction in such areas wherever there is a practicable alternative. NPS administers floodplain policy through Director’s Order 77-2:

Floodplain Management (DO 77-2) and Procedural Manual 77-2 Floodplain Management (PM 77-2).

It is NPS policy to preserve floodplain functions and values and minimize potentially hazardous conditions associated with flooding, including threats to human health/life, risk to capital investment, and impacts on natural and beneficial floodplain values. If a proposed action is found to be in an applicable regulatory floodplain with associated impacts and relocating the action to a non-floodplain site is considered not to be a practicable alternative, then a formal floodplain “Statement of Findings” must be prepared. The “Statement of Findings” must:

(a) Quantify flood conditions and associated hazards as a basis for management decision making

(b) Describe the rationale for selection of a floodplain site

(c) Disclose the resources and amount of risk associated with the chosen site

(d) Explain flood mitigation plans

This Floodplains and Wetlands Statement of Findings (SOF) provides:

1. A detailed justification for selecting a proposed action that would adversely impact the Federal Flood Risk Management Standard (FFRMS) floodplain.

2. A detailed and comprehensive description of the flood hazard and risk associated with implementation of the proposed action.

Chapter 1 – Introduction Page 1-2

3. A thorough description of mitigation measures chosen to eliminate, to the extent possible, adverse floodplain impacts associated with the proposed action(s).

1.02 Wetlands

EO 11990, “Protection of Wetlands,” directs all federal agencies to avoid to the maximum extent possible the long- and short-term adverse impacts associated with the occupancy, destruction, or modification of wetlands and to avoid direct or indirect support of new construction in wetlands wherever there is a practicable alternative. In the absence of such alternatives, parks must modify actions to preserve and enhance wetland values and minimize degradation.

To comply with EO 11990, NPS has developed a set of policies and procedures found in Director’s Order (DO) #77-1 Wetland Protection and Procedural Manual #77-1:

Wetland Protection (2025). These policies and procedures emphasize:

1) Exploring all practical alternatives to building on, or otherwise adversely affecting, wetlands;

2) Reducing impacts to wetlands whenever possible; and

3) Providing direct compensation for any unavoidable wetland impacts by restoring degraded or destroyed wetlands on other NPS properties.

If a Preferred Alternative would have adverse impacts on wetlands, an SOF must be prepared that documents these steps and presents the rationale for choosing an alternative that would have adverse impacts on wetlands.

DO #77-1 allows for positive wetland identification based on two attributes (hydrophytic vegetation and wetland hydrology or hydric soil and wetland hydrology) or one attribute (wetland hydrology). The Federal Geographic Data Committee Wetlands Classification Standard encompasses more aquatic habitat types than the U.S. Army Corps of Engineers (USACE) definition (33 CFR § 328.3) and delineation manual used by the USACE for identifying wetlands subject to Section 404 of the CWA.

Pursuant to DO #77-1, a wetland must have one or more of the following three attributes:

1. At least periodically, the land supports predominantly hydrophytes (wetland vegetation).

2. The substrate is predominantly undrained hydric soil.

Chapter 1 – Introduction Page 1-3

3. The substrate is non-soil and is saturated with water or covered by shallow water during the growing season of each year.

This Wetlands SOF:

• Presents the rationale for implementation of the project with regards to wetlands and documents the anticipated effects on wetland resources.

• Describes the effects on wetland values associated with the Proposed Action.

• Provides a description of mitigation measures.

• Ensures “no net loss” of wetland functions and values.

Chapter 2 – Project Description Page 2-1

Chapter 2 – Project Description

2.01 Project Location

The 107.33-acre project area is situated between the Hite Crossing Bridge and Hite Marina Campground, and is within San Juan County, Utah (Figure 1). Table 1 includes additional location information for the project area.

Table 1. Location Information

Main Water bodies Lake Powell (Colorado River) (Traditional Navigable Waterway)

Tributary to and Downstream Water body

Gulf of California

Watershed Hydrologic Unit Code (HUC) and Name

Upper Lake Powell (14070001)

Central Latitude and Longitude (DD) 37.886523, -110.380379

Township, Range, Section Township 33S, Range 14E, Sections 21, 22, 27, 28

USGS Quadrangles Hite North and Sewing Machine

HUC = Hydrologic Unit Code TNW = traditional navigable waters USGS = U.S. Geological Survey

2.02 Purpose and Need

Lake Powell is formed by the impounded waters of the Colorado River above the Glen Canyon Dam and is the second-largest reservoir in the nation. The lake is considered a premier watersports destination and recreation area. When Lake Powell is full (at a water elevation of 3,700 feet above mean sea level [amsl]), it accounts for 13 percent of GLCA’s geographic area and is a major draw for the approximately 4 million visitors annually. However, persistent droughts are contributing to unprecedented low-water conditions. Water levels fluctuate throughout the year, with recent levels in the lake dropping to a low of 3,522 feet amsl in April 2022. In October 2024 water levels were at 3,577 feet amsl. The U.S. Bureau of Reclamation determined that under a Probable Minimum Scenario, Lake Powell’s physical elevation was projected to be 3,571.63 feet by December 31, 2024 (USBR 2022).

These lower water levels in Lake Powell have exposed reservoir sediments. In upper reaches of the river no longer influenced by the downstream control of Glen Canyon Dam, the transition from a reservoir to river conditions has caused dynamic changes in riverbed elevation and stability and associated riverbank stability.

Chapter 2 – Project Description Page 2-2

In the Hite District, the Colorado River is actively adjusting to abundant sediment supply from the Dirty Devil tributary and change in base level (local control on elevation of the riverbed) resulting from reservoir declines. The alignment of the river has also changed compared to pre-dam conditions.

Currently, access to the river at the existing Hite Ramp on the river left (south/east) bank is no longer possible due to the presence of unconsolidated reservoir sediments, creating conditions causing trucks and trailers to get stuck. On the river right (north) bank, an unmaintained informal access (known as North Wash) leads to the river located downstream of the Dirty Devil River confluence. The access route is loose and steep, and river conditions are dynamic (depicted on Figure 1). Together, these factors create inconsistent and challenging access to the water at this location. The GLCA is initiating this project to provide ongoing water access at the Hite District.

The purpose of this project is to provide reliable, sustainable, and safe access to the Colorado River near Hite, located at the downstream end of Cataract Canyon located approximately 4.75 miles to the east. The park was created to provide recreational opportunities, including water recreation. With the Hite boat ramp closed, some boaters currently use the North Wash access described above as a take-out and primitive launch area. However, this area is problematic due to its location on an exterior bend of the river channel. Natural hydrological forces continually wash away and destabilize the shoreline at this location, rendering it unsafe for boaters and rafters. The purpose of this project is to provide stable, safe, continuous water access to levels as low as 3,450 feet amsl in the far northern part of Lake Powell while protecting natural and cultural resources.

The project is needed to:

• Ensure Glen Canyon can continue to meet the direction to maintain public recreation access for the foreseeable future.

• Provide safe, reliable, and operational access to the northern end of Lake Powell.

• Protect natural and cultural resources by providing designated ingress and egress to and from the water.

2.03 Proposed Action

2.03.1 Construction

Construction is anticipated to begin in May of 2027 and be completed by January 2028.

Construction would last approximately 8 months (Table 2).

Chapter 2 – Project Description Page 2-3

Table 2. Anticipated Construction Timeline

Construction Estimated Time Frame

Mobilization, install erosion control, clearing and grubbing June 2027

Roadway and parking earthwork June through January 2028

Blasting (ramp work) June through August 2027; after September 1 if within 0.5 mile of MSO habitat

Concrete placement (ramp work) December through January 2028

Roadway surface aggregate January 2028

Parking surface aggregate January 2028

Construction completion February 2028

Access Road. The proposed access road would be approximately 18 feet wide by 5,295 feet long (1mile). While primarily designed for one-way traffic, the width would accommodate two vehicles passing. The road would follow the alignment of an existing primitive road from its intersection with the Hite Marina Road for approximately 2,433 feet and be extended by 4,134 feet. The new portion of the access road would extend northwest, curve to the north and then to the northeast, coming down off the plateau to a terrace where the access road runs parallel to the river, and finally curves north again where the boat ramp would be constructed up to the river’s edge. Culverts would be installed under the access road to facilitate effective stormwater runoff within ephemeral drainages during precipitation events. Riprap/erosion control materials are planned to be used during construction activities. Gravel and fill materials may be generated from onsite construction activities (such as rock blasting), sourced from a commercial supplier, or generated from an offsite quarry. If gravel materials are imported, all materials would be inspected for noxious weeds or would be commercially certified weed-free before being incorporated into the project.

Launch Ramp. The boat ramp would consist of concrete surfacing and would service lake water level elevations ranging from 3,650 to an ultimate depth of 3,495 feet amsl.

However, the interim construction ramp will only reach 3,529 feet amsl. The launch ramp would be approximately 35 feet wide by 1,000 feet long. In-water work may include, but is not limited to, grading, blasting, dredging, cofferdam, gravel placement, dewatering, and installation of concrete slabs. The parking area and launch ramp may also accommodate locations for materials processing, including crushing for aggregate used for road fill and surfacing. If road materials are imported, all materials would be sourced from a local commercial supplier and would be certified weed-free.

Rock Blasting. The proposed project may require up to 276,000 cubic yards of rock blasting. Rock blasting would be performed to facilitate adequate ramp grade to the

Chapter 2 – Project Description Page 2-4 water, and much of the remaining debris would be used as fill under the road, parking lot, and ramp.

Staging Areas. There would be staging/spoil location areas within the project area boundary. Areas would include the proposed parking lot at the top of the ramp. All staging and stockpiling of equipment and materials would be located outside of waterways. All areas not needed for continued operation of the launch ramp and access road would be reclaimed and returned to their preexisting contours after construction is complete.

2.03.2 Operation

The launch ramp would be operated year-round. On average, there are approximately 1,800 small vessel craft retrieved annually, with the majority of use occurring seasonally between June and August/September. Approximately 1,100 of these retrievals are specific to the 20 or so Canyonland rafting concessioners that are floating down the Cataract Canyon. Retrieval activities require trucks of varying size and capacities, with trailers (CHM 2022).

2.03.3 Maintenance

General maintenance activities for the access road include the following:

• Regular inspection of road surface

General maintenance for the concrete boat launch ramp includes the following:

• Regular inspection of concrete pavement surface and edges

• Regular repair of cracks to prevent further separation or faulting development

• Joint sealant application to minimize water intrusion and protect against water-related spalling, softening, corrosion, pavement joint blow-ups, and/or materials related distress

• High friction surface treatments

• Partial depth repair (e.g. spalling, popouts, surface issues)

• Full depth repair (panel replacement)

2.03.4 Post-construction Reclamation

All construction areas not needed for operation would be recontoured and reseeded using an NPS-approved native seed mix as soon as reasonably possible after completion of phased construction.

Chapter 3 – Project Description Page 3-1

Chapter 3 – Site Description

3.01 Existing Conditions

3.01.1 Regional Setting

The study area is within the Colorado Plateau Level III Ecoregion and the Arid Canyonlands Level IV Ecoregion (Woods et al. 2001). The Arid Canyonlands Ecoregion consists of arid narrow chasms, cliffs, valley floors, floodplains, structural benches, mesas, and cuestas where the terrain has been deeply eroded by major rivers and their tributaries (Woods et al. 2001). Elevations within this arid ecoregion range from approximately 3,200 to 5,000 feet.

3.01.2 Topography

Topography within the study area varies drastically and ranges from gently sloping terraces to vertical cliff faces with the natural gradient generally sloping downward from south to north. Several watercourses flow through the site and eventually drain to Lake Powell, which is located in the northern portion of the study area. Elevations in the study area range from approximately 4,035 feet amsl near Hite Marina Road in the southern portion of the study area to approximately 3,550 feet amsl within Lake Powell in the northern portion of the study area.

3.01.3 Climate

Climate within the study area is characterized by mild winters and hot, dry summers, with average high temperatures of up to 100 degrees Fahrenheit (°F) in July to 48°F in January. Annual precipitation in the Arid Canyonlands Ecoregion ranges between 5 and 8 inches, with precipitation values being lower in deeper canyons (Woods et al. 2001).

3.01.4 Hydrology

The project area is located within the Upper Lake Powell (Hydrologic Unit Code [HUC] 14070001) watershed within the Colorado River basin. Persistent drought conditions within the Colorado River basin over the past 2 decades have resulted in reduced flows into Lake Powell as well as a significant decrease in water surface elevation. Flood conditions are controlled by both natural and anthropogenic actions. Regional-scale snowmelt and precipitation in the Rocky Mountains are the main drivers of inflow rates and volumes. Snowpack-depth, timing of snow melt, and precipitation patterns heavily influence seasonal inflows and flooding. The magnitude of flooding can be attenuated by the system of dams upstream of the Project Area.

Named surface water features in the study area include the Colorado River, which is discussed in this document primarily as Lake Powell; however, the terms can be used interchangeably. It is important to note that due to persistent drought conditions, the site is in a dynamic period where fluctuating water elevation results in a free-flowing river

Chapter 3 – Project Description Page 3-2 during certain portions of the year and lake conditions in other portions of the year due to backwatering from the Glen Canyon Dam. For decades, the study area was significantly more influenced by backwater from Lake Powell; however, in recent years the site has fluctuated between riverine and lacustrine conditions. Given that gage data from the U.S. Geological Survey (USGS) indicates that the river at Hite still receives backwater from the Glen Canyon Dam at certain times of the year, the term Lake Powell is used as part of this assessment. The study area also includes several unnamed watercourses that appear to only flow in response to wet season precipitation and runoff.

Figure 2 shows aquatic resources in the study area identified by the National Wetlands Inventory (NWI) (USFWS 2024) and the National Hydrography Dataset (NHD) (USGS 2024a). The NWI identifies Lake Powell as lacustrine, limnetic, unconsolidated bottom, permanently flooded, diked/impounded (L1UBHh). One tributary to Lake Powell is identified as riverine, intermittent, streambed, seasonally flooded (R4SBC). These features were mapped using color infrared imagery from 1986, and since their mapping in the NWI, the extent and water level of Lake Powell has significantly reduced (USFWS 2024). The NHD also displays Lake Powell (Colorado River) and the same intermittent drainage as the NWI (USGS 2024a).

3.01.5 Soils

Soils in the study area have been mapped by the Natural Resources Conservation Service (NRCS) and are described in the Soil Survey of San Juan Area, Utah (NRCS 2024a and SCS 1962). Soil series mapped within the study area are summarized in Table 3 and shown on Figure 3. In addition to the soil types mapped within the site, the northern portion of the study area associated with Lake Powell is mapped as water.

Table 3. Soil Series Mapped within the Study Area

Type or Series

Texture Landscape Position and Parent

Material Drainage and Permeability

NRCS

Hydric Rating

Myton Extremely boulder loam

Deep soils on steep to very steep hillslopes and mountain slopes.

Formed in colluvium derived from sandstone and shale.

Well drained; high runoff; moderately rapid permeability

No

Needle Fine sand Shallow to very shallow soils on hills with soil derived from eolian and alluvial deposits. Includes sand sheets on structural benches and rolling plateaus.

Excessively drained;

slow to medium runoff; rapid permeability

No

Sources: NRCS 2024a and 2024b

Chapter 3 – Project Description Page 3-3

3.01.6 Land Cover and Vegetation Communities

Biotic communities in the study area mapped by the U.S. Geological Survey (USGS) Southwest Regional Gap Analysis Project consist of mostly unvegetated Colorado Plateau Mixed Bedrock Canyon and Tableland as well as Colorado Plateau Blackbrush- Mormon Tea Shrubland (USGS 2005). Colorado Plateau Mixed Bedrock Canyon and Tableland consists of barren to sparsely vegetated landscapes over steep cliff faces, narrow canyons, and open tablelands that occur on substrates derived predominantly from sedimentary rocks, such as sandstone, shale, and limestone (USGS 2005).

Colorado Plateau Blackbrush-Mormon Tea Shrubland occurs on benches, colluvial slopes, and bajadas that generally have shallow sandy or gravelly substrates derived from sedimentary rock. Blackbrush-Mormon Tea Shrubland can also occur in deeper soils on sandy plains and is characterized by extensive open shrublands with sparse herbaceous cover (USGS 2005). A lesser amount of Inter-Mountain Basins Mixed Salt Desert Scrub is present, along with small pockets of Invasive Annual Grassland and Inter-Mountain Basins Active and Stabilized Dune communities.

Dominant vegetation species observed throughout the study area include:

• Blackbrush (Coleogyne ramosissima)

• Mormon tea (Ephedra sp.)

• Shadscale saltbush (Atriplex confertifolia)

Other plant species observed in the study area include:

• Broom snakeweed (Gutierrezia sarothrae)

• Fragrant sumac (Rhus aromatica)

• Singleleaf ash (Fraxinus anomala)

• Stansbury cliffrose (Purshia stansburiana)

• Soaptree yucca (Yucca elata)

• Plains prickly pear (Opuntia polyacantha)

• Mojave hedgehog cactus (Echinocereus mojavensis)

• Desert trumpet (Eriogonum inflatum)

• Invasive species detected included Russian thistle (Salsola tragus) and saltlover (Halogeton glomeratus).

Chapter 4 – Weltalnds in the Project Area Page 4-1

Chapter 4 – Wetlands in the Project Area

4.01 Survey Methods

4.01.1 Pre-field Investigation

Resources relevant to site conditions and aquatic resources were collected and reviewed as part of the delineation. The following materials were included in this data review:

• Bing satellite imagery (Bing 2024)

• NRCS soil maps and descriptions (NRCS 2024b)

• NHD maps (USGS 2024a)

• NWI (USFWS 2024)

• Lake Powell, Arizona and Utah Topographic Lidar Technical Data Report (NV5 Geospatial, Inc. 2022)

• Hite North and Sewing Machine USGS topographic maps (USGS 2024b)

4.01.2 Field Survey

Jacobs Government Services Company wetland scientists Greg Davis and Sabra McNeish conducted the aquatic resources field survey on October 2 and 3, 2024.

The field survey was limited to the project area.

The delineation method was routine and conducted in accordance with the Corps of Engineers Wetland Delineation Manual (Environmental Laboratory 1987), the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region (Version 2.0) (USACE 2008), the National Ordinary High Water Mark Field Delineation Manual for Rivers and Streams (Interim Version) (USACE 2022), and the NPS Procedural Manual #77-1: Wetland Protection (D.O. #77-1) (NPS 2025).

Aquatic resources within the survey area were mapped in ArcGIS Field Maps using an Apple iOS device paired with a Juniper Geode global navigation satellite system that provided submeter accuracy. Aerial imagery of the survey area was used to identify locations with potential wetland signature for field investigation and mapping (Bing 2024).

Steep cliffs prohibited safe access and data collection at the lake shore. Additionally, persistent drought conditions have contributed to a lowered Ordinary High Water Mark (OHWM) throughout Lake Powell. Perched locations on the terraces above Lake Powell were used as vantage points for observation of OHWM indicators. The OHWM was mapped using a combination of recent gage data, aerial imagery, and field observations.

Chapter 4 – Weltalnds in the Project Area Page 4-2

4.01.3 Results

Figure 4 shows the aquatic resources delineated in the project area. Appendix A provides representative photographs of features within the project area. Table 4 summarizes results of the aquatic resource delineation.

Table 4. Summary of Aquatic Resources Investigated in the Project Area

Aquatic Resource

ID[a]

Cowardin Code[b]

Latitude Longitude

OHWM

Width (feet)

Area (Acres)

Length (linear feet)

Other Waters

Riverine Features

EDR-1 R6 37.8806006 -110.36902332 2 <0.01 78

EDR-2 R6 37.88059034 -110.3693721 2 to 15 0.04 286

EDR-3 R6 37.88094707 -110.36976242 2 to 10 0.02 221

EDR-4 R6 37.88084116 -110.37033376 2 to 30 0.17 580

EDR-5 R6 37.88142524 -110.37102082 2 to 45 0.29 638

EDR-6 R6 37.88229795 -110.37191981 2 to 25 0.12 400

EDR-7 R6 37.88196807 -110.37184328 2 to 25 0.22 680

EDR-8 R6 37.88312386 -110.37351531 2 to 60 0.63 1,906

EDR-9 R6 37.88370008 -110.37513084 2 0.01 180

EDR-10 R6 37.88457993 -110.37490243 2 to 35 0.22 400

EDR-11 R6 37.88560554 -110.37622342 2 to 4 0.01 213

EDR-12 R6 37.88592953 -110.37661102 2 to 35 0.10 579

EDR-13 R6 37.88611555 -110.37849447 3 to 22 0.11 420

EDR-14 R6 37.88485548 -110.38040274 2 to 4 0.06 460

EDR-15 R6 37.88484975 -110.37931432 2 to 5 0.18 1,532

EDR-16 R6 37.88714358 -110.37995296 2 to 30 0.32 1,236

EDR-17 R6 37.88920805 -110.37273018 3 to 5 0.03 261

IDR-1 R4SB 37.88985144 -110.37206943 5 to 20 0.07 306

Riverine Features Total 2.60 10,376

Chapter 4 – Weltalnds in the Project Area Page 4-3

Aquatic Resource

ID[a]

Cowardin Code[b]

Latitude Longitude

OHWM

Width (feet)

Area (Acres)

Length (linear feet)

Lacustrine Features

LP-1 L2US 37.89023702 -110.37564741 N/A 3.61 N/A

OW-1 L1UB 37.89050757 -110.37425695 N/A 3.08 N/A

Lacustrine Features Total 6.69 N/A

Total Other Waters 9.29 10,376

[a] EDR = ephemeral watercourse; IDR = intermittent watercourse; LP = Lake Powell; OW = open water [b] Source: Cowardin et al. 1979. L1UB = lacustrine, limnetic, unconsolidated bottom; L2US = lacustrine, littoral, unconsolidated shore; R4SB = riverine, intermittent, streambed; R6 = riverine, ephemeral < = less than ID = identifier

4.02 Riverine Features

Riverine features delineated within the study area include 17 ephemeral watercourses (2.53 acres, 10,070 linear feet) and one intermittent watercourse (0.07 acre, 306 linear feet). Ephemeral waters are those that flow only briefly after precipitation events, while intermittent waters seasonally flow during wet seasons. The following chapter discusses these features (Figure 4). Appendix A provides representative photographs of these features.

4.02.1 Ephemeral Watercourses

Seventeen ephemeral watercourses, features EDR-1–17, were delineated within the study area. These ephemeral features consisted of broad washes and incised drainages that were mostly barren to sparsely vegetated with upland herbaceous and shrub species. Shrub species observed along the banks of the ephemeral watercourses varied but included species such as:

• Four-wing saltbush (Atriplex canescens)

• Shadscale (Atriplex confertifolia)

• Fremont barberry (Berberis fremontii)

• Yellow rabbitbrush (Chrysothamnus viscidiflorus)

• Rubber rabbitbrush (Ericameria nauseosa)

• Stansbury cliffrose (Purshia stansburiana)

• Singleleaf ash (Fraxinus anomala)

Chapter 4 – Weltalnds in the Project Area Page 4-4

Occasionally, scattered individuals of these shrubs were observed within the channels of the ephemeral watercourses. These species are not listed in the Arid West Wetland Plant List and therefore are considered to be upland plants (USACE 2020).

Five of these ephemeral watercourses, EDR-4, EDR-5, EDR-7, EDR-8, and EDR-12, cross the existing dirt access road. A slight berm is present along the outboard edge of the road surface in some areas and other sections of the road are sloped towards the inboard edge of the road. This has caused several portions of these ephemeral features to divert seasonal flow down the road before exiting at a low point (Photos 5 and 10 in Appendix A).

Several watercourses within the study area, EDR-10 and EDR-13 through EDR-17, are partially conveyed over rock outcrops. These features convey seasonal flow via broad sheet flow over relatively flat rock outcrops (Photo 8, Map 2 of Figure 4) and by well-defined bedrock channels (Photo 11, Map 3 of Figure 4). One of these drainages, EDR- 16, flows through a steep bedrock canyon and transitions into an incised channel on the bench above Lake Powell at the base of a cliff (Photo 15, Maps 4 and 5 of Figure 4).

Another drainage, EDR-17, flows down to a cliff edge where the channel dissipates within the rock outcrops and infiltrates the ground on the terrace below (Photos 22 and 23, Map 6 of Figure 4). These watercourses are not shown on USGS topographic maps as blue line features and are not documented by the NWI and NHD datasets as drainages (Figure 2).

4.02.2 Intermittent Watercourse

One intermittent watercourse, feature IDR-1, was delineated within the study area. This intermittent watercourse flows through a bedrock canyon in the northeastern portion of the study area and drops down a steep cliff face to an inaccessible terrace above Lake Powell (Photo 23, Map 6 of Figure 4). IDR-1 is conveyed through an incised channel into Lake Powell, where hydrophytic shrubs such as mule fat (Baccharis salicifolia) and tamarisk (Tamarix sp.), as well as other emergent herbaceous species, are present along the channel and margins of the lake. This feature is shown on USGS topographic maps as a blue line feature and is also documented by the NWI and NHD datasets as an intermittent drainage (Figure 2).

4.03 Lacustrine Features

Lacustrine features delineated within the study area include Lake Powell (3.61 acres) and open water (3.08 acres). These features are additionally discussed in the following paragraphs and are depicted on Figure 4.

4.03.1 Lake Powell

Approximately 3.61 acres of Lake Powell, feature LP-1, were delineated within the study area. The boundaries of LP-1 were mapped between the open water of Lake Powell up to the OHWM. Within the study area, LP-1 consisted of vertical cliff faces and shoreline

Chapter 4 – Weltalnds in the Project Area Page 4-5 that has started to revegetate due to receding water elevation (Photos 18 to 21, Maps 5 and 6 of Figure 4). Observed field indicators of the OHWM of Lake Powell included break in slope, shelving, change in vegetation type and density, and water staining (Photos 18 and 21). Water staining was evident on the opposite side of Lake Powell (north bank) and is visible as a white band that corresponds with the delineated OHWM (Photos 18-21). Additionally, portions of the shoreline had incised rivulets extending from the OHWM to OW-1 are indicative of receding water. Supplemental data used to confirm field observations of the OHWM included data from the USGS Colorado River AB Dirty Devil NR Hite, UT stream gage (09328990), aerial imagery, and light detection and ranging (LiDAR). The extent of this lacustrine littoral wetland extends from the OHWM down to lacustrine limnetic wetland boundary, which is where the water depth reaches 8.2 feet (2.5 meters) at low water.

4.03.2 Open Water

Approximately 3.08 acres of open water (also referred to as deepwater habitat) associated with Lake Powell, feature OW-1, were delineated within the study area. The open water boundary delineated during the survey is represented by the current low-flow extent of Lake Powell where water is more than 8.2 feet (2.5 meters) deep below low water. The low-flow water elevation at Lake Powell, as measured by the USGS Colorado River AB Dirty Devil NR Hite, UT stream gage (09328990), was approximately 3,571 feet amsl in 2024.

4.04 Wetland Functions and Values Assessment

The functional wetland assessment was conducted with reference to the Wetlands Functions and Values: A Descriptive Approach as described in the September 1999 Supplement to The Highway Methodology Workbook (Supplement) by USACE (1999).

This method uses a descriptive approach to characterize functions and values of wetlands and is typically used for National Environmental Policy Act (NEPA) projects.

This method is based on qualitative descriptions of the wetlands primarily based upon best professional judgment. The method is designed to provide a flexible approach that incorporates wetland science along with human judgment regarding more subjective values and benefits.

Wetland functions are ecosystem properties that are present without regard to any subjective human values as a result of the biologic, geologic, hydrologic, biogeochemical and/or physical processes that occur within a wetland (USACE 1999).

The existing wetlands were evaluated based on wetland functions and values described in NPS Procedural Manual #77-1: Wetland Protection (NPS 2025) and the Supplement (USACE 1999). Functions attributed to wetlands include the following:

• Groundwater Recharge/Discharge

• Floodflow Alteration

• Fish and Shellfish Habitat

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• Sediment/Toxicant/Pathogen Retention

• Nutrient Removal/Retention/Transformation

• Production (Nutrient) Export

• Sediment/Shoreline Stabilization

• Wildlife Habitat

Wetland values are the perceived benefits to society that can be derived from the ecosystem functions and/or other characteristics of a wetland (USACE 1999). These values may depend on considerations such as location of the wetland, accessibility, human disturbance or pressures, economics, surrounding land uses, and cultural or historic information. Values attributed to wetlands include the following:

• Recreation

• Education/Scientific Value

• Uniqueness/Heritage

• Visual Quality/Aesthetics

• Threatened or Endangered Species Habitat

The wetland features are organized in this function and value assessment and grouped based on their close similarities and Cowardin codes. Table 5 summarizes the wetland functional assessment.

Table 5. Summary of the Wetland Functional Assessment

FUNCTIONAL VALUE

PARAMETER

WETLAND

EDR-1 to

EDR-17

IDR-1 LP-1 OW-1

Groundwater Recharge/Discharge X X X

Floodflow Alteration X X X X

Fish and Shellfish Habitat X X

Sediment/Toxicant/Pathogen Retention

X X X

Nutrient Removal/Retention/Transformation

X X X

Production Export X X

Sediment/Shoreline Stabilization X

Wildlife Habitat X X X

Recreation X X

Educational/Scientific Value

Uniqueness/Heritage

Visual Quality/Aesthetics X X

Endangered Species Habitat

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4.04.1 Riverine Ephemeral Watercourses

The 17 riverine ephemeral features classified in the Cowardin system as R6 (riverine, ephemeral) (EDR-1 through EDR-17) range between 2 to 60 feet wide. The functions and values of the riverine ephemeral features within the study area as noted in Table 5 are low quality for the following reasons:

• The features convey seasonal flows and do not contribute to groundwater recharge or discharge within the study area.

• The features receive and convey overland sheet flow from runoff from surrounding uplands, which provides limited floodflow alteration.

• The features do not provide suitable habitat to shellfish or fish due to their ephemeral flow regime.

• The features provide minimal sediment, toxicant, pathogen, nutrient retention and removal or export due to their ephemeral flow regime.

• The features do not offer any production export due to their lack of vegetation, fish or shellfish, or other commercially used products.

• The features primarily flow during stormwater runoff events and are subject to high amounts of erosion, scour, and channelization.

• There is no wildlife habitat unique from the surrounding terrain and no endangered species habitat associated with the features.

• The features are not used for recreation and sustain minimal education/scientific and uniqueness/heritage value in the area.

• Due to the prevalence of similar ephemeral riverine features in the area, these features contribute minimally to the visual quality/aesthetics of the surrounding landscape.

4.04.2 Riverine Intermittent Watercourse

IDR-1, an intermittent watercourse, is classified in the Cowardin system as R4SB

(riverine, intermittent, streambed) and is 5 to 20 feet wide. The functions and values of

IDR-1 within the study area as noted in Table 5 are low to moderate quality for the following reasons:

• IDR-1 is an intermittent watercourse that flows into Lake Powell, which may contribute to groundwater recharge.

• IDR-1 receives and conveys overland sheet flow from runoff from surrounding uplands, which provides limited floodflow alteration.

• IDR-1 does not provide consistent habitat to shellfish or fish due to its intermittent flow regime.

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• The hydrophytic shrubs and emergent herbaceous species present along IDR-1’s channel banks can trap sediments, toxicants, pathogens, and nutrients before entering Lake Powell. This vegetation can also stabilize Lake Powell’s streambanks and shorelines against erosion.

• IDR-1 does not offer any production export due to its lack of fish or shellfish or other commercially used products.

• There is no wildlife habitat unique from the surrounding terrain and no endangered species habitat associated with IDR-1.

• IDR-1 is not used for recreation and sustains minimal education/scientific and uniqueness/heritage value in the area.

• IDR-1 contributes minimally to the visual quality/aesthetics of the surrounding landscape.

4.04.3 Lake Powell

Lake Powell, referred to as LP-1, is classified in the Cowardin system as a lacustrine littoral wetland (L2US) and consists of vertical cliff faces and the shoreline that has started to revegetate due to receding water elevation. The functions and values of LP-1 within the study area as noted in Table 5 are moderate quality for the following reasons:

• LP-1 receives flows from IDR-1 and is associated with Lake Powell, a perennial water, which contributes to groundwater recharge.

• LP-1 is sustained by input from upgradient watersheds and river systems and can retain inputs, which provides floodflow alteration.

• LP-1 provides fish and shellfish habitat; however, LP-1 within the study area is not suitable habitat for any endangered species. Fish and shellfish inhabitants promote nutrient cycling and provide potential food sources within the area, which contributes to LP-1’s production export value.

• LP-1 receives sediment, nutrient, toxicants, and pathogens from upgradient systems and adjacent lands during precipitation runoff events.

• LP-1’s sparse vegetation provides minimal stabilization for Lake Powell’s streambanks and shorelines against erosion.

• LP-1 is used for recreation activities, such as fishing and boating; however, LP-1 provides minimal education/scientific or uniqueness/heritage value.

• The canyon walls and undeveloped land surrounding LP-1 provide for high visual quality and overall aesthetics.

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4.04.4 Open Water

The open water, also referred to as deepwater habitat, associated with Lake Powell (OW-1) is classified in the Cowardin system as L1UB (lacustrine, limnetic, unconsolidated bottom). The functions and values of LP-1 within the study area as noted in Table 5 are moderate quality for the following reasons:

• OW-1 receives flows from IDR-1 and LP-1 and is associated with Lake Powell, a perennial water, which contributes to groundwater recharge.

• OW-1 is sustained by input from upgradient watersheds and river systems and can retain inputs, which provides floodflow alteration.

• OW-1 provides fish and shellfish habitat; however, OW-1 within the study area is not suitable habitat for any endangered species. Fish and shellfish inhabitants promote nutrient cycling and provide potential food sources within the area, which contributes to OW-1’s production export value.

• OW-1 receives sediment, nutrient, toxicants, and pathogens from upgradient systems and adjacent lands during precipitation runoff events.

• OW-1 is used for recreation activities, such as fishing and boating; however, OW- 1 provides minimal education/scientific or uniqueness/heritage value.

• The canyon walls and undeveloped land surrounding OW-1 provide for high visual quality and overall aesthetics.

4.05 Impacts of the Proposed Action

Although the project’s design is still being developed, to facilitate timely project planning and permitting, and to meet the NPS legislative mandate to provide continued access to Lake

Powell, all aquatic resources within the project area that meet the NPS definition of a wetland per the National Park Service Procedural Manual #77-1 Wetland Protection are being evaluated in this SOF and are included in the impact analysis, acreage totals, and mitigation plan. Actual impacts would likely be significantly less than those assumed in this SOF. Tables 6 and 7 outline the potential impacts to the wetland features identified in the project area.

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Table 6. Riverine Wetland Impacts

Wetland Cowardin Code OHWM Width

(feet)

Approx. Length (feet)[a]

Impact Area

(acres)[b]

EDR-1 R6 2 to 10 0 0

EDR-2 R6 2 to 30 0 0

EDR-3 R6 2 to 45 >1 <0.01

EDR-4 R6 2 to 25 200 0.04

EDR-5 R6 2 to 25 330 0.10

EDR-6 R6 2 to 60 350 0.09

EDR-7 R6 2 700 0.13

EDR-8 R6 2 to 35 775 0.34

EDR-9 R6 2 to 4 0 0

EDR-10 R6 2 to 35 175 0.12

EDR-11 R6 3 to 22 70 <0.01

EDR-12 R6 2 to 4 400 0.05

EDR-13 R6 2 to 5 540 0.11

EDR-14 R6 2 to 30 0 0

EDR-15 R6 3 to 5 0 0

EDR-16 R6 5 to 20 1,250 0.24

EDR-17 R6 2 to 10 0 0

IDR-1 R4SB 2 to 30 0 0

Total Acres: 1.21

[a] Approximate length refers to the full length of the mapped features within the disturbance limits.

[b] Area refers to total acreage within the OHWM for each water body within the disturbance limits.

> = greater than

Table 7. Lacustrine Wetland Impacts

Wetland Cowardin Code Area (acres)

LP-1 L2US 0.074

OW-1 L1UB 0.121

Total Acres: 0.195

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EDR-1, EDR-2, EDR-9, EDR-14, EDR-15, EDR-17, IDR-1 – No construction would occur within the OHWM of these washes. The project would avoid impacts on these aquatic resources.

EDR-3, EDR-4, EDR-5, EDR-6, EDR-7, EDR-8, EDR-10, EDR-11, EDR-12, EDR-13,

and EDR-16 – Proposed impacts to these ephemeral washes would occur during construction of the proposed 18-foot-wide access road. Impacts to wetlands resulting from construction would be permanent. Potential impacts to the wetlands would result from grading, placement of fill and roadway surface aggregate, erosion control measures, and installation of culverts. Culverts would be installed under the access road at each wetland crossing to sustain flow and manage stormwater runoff. Potential impacts to wetland functions and values from the construction activities include stream channelization within the culvert features resulting in potential increases in erosion downstream due to increased flow velocities, as well as potential increases in sedimentation and turbidity following ground disturbance activities. Best management practices (BMPs) would be used to control erosion and sediment and would minimize runoff and sediment discharges from the project area.

LP-1 and OW-1 – Proposed impacts to LP-1 and OW-1 would occur during construction of the proposed 35-foot-wide boat ramp. Impacts wetlands resulting from construction would be permanent. Potential impacts to the wetlands would result from grading, blasting, dredging, installation of a cofferdam, gravel placement, dewatering, and installation of precast concrete slabs. Functions and values that have the potential to be affected within the permanent impact area include direct loss of fish and shellfish habitat from the construction activities, loss of sediment / toxicant / pathogen retention and removal, nutrient removal / retention / transformation function, and loss of production export from destruction of aquatic plants resulting from added fill to the wetland feature.

The visual quality/aesthetic of the wetland would be impacted due to the development of the ramp and the increase in human use, though recreation value would benefit from increased access to the lake.

4.06 Other Alternatives Considered

The Preferred Alternative was selected based on a Value Analysis Study completed for the project (NPS 2023).