Proactive Dust Control Plan - Salton Sea · This 2017/2018 Proactive Dust Control Plan (PDCP) was prepared for the Imperial Irrigation District (IID) as a requirement of the Salton

Proactive Dust Control Plan 2017/2018 Annual Plan

Prepared for: Imperial Irrigation District

in coordination with the County of Imperial

Prepared by: Formation Environmental, LLC

Air Sciences Inc. PlanTierra LLC

APRIL, 2018

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TABLE OF CONTENTS List of Abbreviations ..................................................................................................................................................... vi

Executive Summary ............................................................................................................................................... 1

Plot-Based Dust Control Measure Pilot Studies ........................................................................................................ 4

Surface Roughening................................................................................................................................................... 4

Vegetation Enhancement .......................................................................................................................................... 6

Field Scale Dust Control Measure Pilot Study Planning ............................................................................................ 8

1 Introduction ................................................................................................................................................ 10

2 Findings of the 2015-2017 Plot Studies ........................................................................................................ 11

2.1 Surface Roughening....................................................................................................................................... 11

2.1.1 Near Surface Wind Speed Reduction ................................................................................................. 11

2.1.2 Tillage Implements and Roughness Configuration ............................................................................ 13

2.1.3 Soil Conditions ................................................................................................................................... 14

2.1.4 Vegetation Establishment .................................................................................................................. 15

2.1.5 Performance Monitoring of Roughness Elements ............................................................................. 17

2.2 Vegetation Enhancement .............................................................................................................................. 18

2.2.1 Plants and Seed Collection ................................................................................................................. 18

2.2.2 Germination ....................................................................................................................................... 20

2.2.3 Seedling Growth ................................................................................................................................ 22

2.2.4 Relationship of Groundwater Depth and Quality to Vegetation Establishment................................ 23

2.2.5 Performance Monitoring ................................................................................................................... 23

2.3 Results Relevant to Field Studies................................................................................................................... 25

3 Planning Process for 2017/2018 Field Studies .............................................................................................. 26

3.1 Playa Prioritized for Field Studies .................................................................................................................. 27

3.1.1 Portable In-Situ Wind Erosion Lab Sampling...................................................................................... 27

3.1.2 Surface Survey and Source Delineation ............................................................................................. 27

3.2 Site Characterization ..................................................................................................................................... 31

3.2.1 Topographic Survey ........................................................................................................................... 31

3.2.2 Soil Survey .......................................................................................................................................... 33

3.2.3 Groundwater ...................................................................................................................................... 41

3.2.4 Wind Direction ................................................................................................................................... 41

3.3 Dust Control Modeling .................................................................................................................................. 43

3.3.1 SWEEP Automation ............................................................................................................................ 44

3.3.2 SWEEP Parameterization ................................................................................................................... 44

Salton Sea Air Quality Mitigation Program 2017/2018 Proactive Dust Control Plan

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3.3.2.1 Topsoil Variables ........................................................................................................................... 45

3.3.2.2 Surface Roughened Variables ....................................................................................................... 47

3.3.2.3 Twenty-Four Hour Wind Speed Time Series ................................................................................. 47

3.3.3 Normalized Saltation Flux .................................................................................................................. 48

3.3.4 SWEEP Results and Trends ................................................................................................................. 49

3.3.4.1 Wind Speeds Required to Initiate Saltation .................................................................................. 49

3.3.4.2 Saltation on Roughened versus Non-roughened Surfaces............................................................ 50

3.4 Field Study Specifications .............................................................................................................................. 51

3.4.1 Dust Control Measure Selection ........................................................................................................ 52

3.4.2 Dust Control Measure Orientation .................................................................................................... 52

3.4.3 Dust Control Measure Specifications ................................................................................................. 53

3.4.3.1 Surface Roughening ...................................................................................................................... 53

3.4.3.2 Vegetation Establishment ............................................................................................................. 54

3.4.4 Site Layout ......................................................................................................................................... 56

3.5 Dust Control Performance Monitoring ......................................................................................................... 56

3.5.1 Roughness Elements .......................................................................................................................... 57

3.5.2 Aerometric Monitors ......................................................................................................................... 60

4 Proposed 2017/2018 Field Studies............................................................................................................... 60

4.1 Alamo South Field Study ............................................................................................................................... 60

4.1.1 Site Characterization .......................................................................................................................... 63

4.1.2 Dust Control Modeling ....................................................................................................................... 64

4.1.3 Specifications ..................................................................................................................................... 65

4.1.3.1 Surface Roughening Dust Control Measure .................................................................................. 67

4.1.3.2 Vegetation Establishment Dust Control Measure ......................................................................... 67

4.2 Coachella Playa Field Study ........................................................................................................................... 68



4.2.3 Specifications ..................................................................................................................................... 73



4.3 New River West Field Study .......................................................................................................................... 76



4.3.3 Specifications ..................................................................................................................................... 80



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4.3.4 Species Conservation Habitat – New River West ............................................................................... 82

5 Proposed Future Studies .............................................................................................................................. 83

5.1 Salton City Wash and Clubhouse Field Studies and Groundwater Investigation .......................................... 83

5.2 Vail Drain Field Study .................................................................................................................................... 85

5.3 San Felipe Creek North .................................................................................................................................. 85

5.4 Surface Stabilizer Plot Study .......................................................................................................................... 85

6 Conclusion ................................................................................................................................................... 85

7 References ................................................................................................................................................... 90

Tables

Table 1: Summary of November 2016 Local Seed Availability and Plot Study Sowing Rate ....................................... 20

Table 2: Key Findings from the Plot Studies used in Development of the 2017/2018 Field Studies ........................... 25

Table 3: SWEEP Modeled Conditions .......................................................................................................................... 45

Table 4: SWEEP Model Value Selection ....................................................................................................................... 47

Table 5: 2017 Vegetated Barrier Seed Mix .................................................................................................................. 55

Table 6: Current and Future Plot and Field Studies ..................................................................................................... 83

Table 7. Existing and Proposed Dust Control Projects and Their Contribution to Yearly Playa Emissions ................. 87

Figures

Figure 1: Near Surface Wind Speed Reduction within Surface Roughened Area ........................................................ 12

Figure 2: Wind Speed Assumed to Initiate Saltation Outside and Inside Surface Roughening ................................... 13

Figure 3: Oriented Roughness Coupled with Interrow Random Roughness ............................................................... 14

Figure 4: Example Ridge Height versus Soil Texture Relationship ............................................................................... 15

Figure 5: Photo of Vegetation Establishment in a Sandy Bull Plow Furrow ................................................................ 16

Figure 6: Alamo North Vegetated Furrow Plant Height Monitoring Summary .......................................................... 16

Figure 7: Comparison of Methods of Determining Roughened Ground Surface Level ............................................... 17

Figure 8: Example Plot Study Layout for the Bombay Beach Site ................................................................................ 19

Figure 9: Germination Results by Site and Treatment ................................................................................................. 21

Figure 10: Seedling Density versus Soil Salinity ........................................................................................................... 22

Figure 11: Allenrolfea occidentalis (ALOC) Seedling Height by Treatment.................................................................. 23

Figure 12: Vegetation Presence and Vegetated Barrier Continuity from UAS Multispectral Images.......................... 24

Figure 13: Planning Timeline for Proactive Dust Control Plans ................................................................................... 27


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Figure 14: Nearshore Alamo North PI-SWERL Transect .............................................................................................. 28

Figure 15: PM10 Flux Versus Loose Sand Coverage ...................................................................................................... 29

Figure 16: PM10 Flux Versus the Presence of Wind Erosion Features ......................................................................... 29

Figure 17: Example Source Delineation (New River West) .......................................................................................... 30

Figure 18: Example of Digital Elevation Model to Characterize Site Topography (Coachella Playa) ........................... 32

Figure 19: Photo of the DUELEM-421 Sampling Soil Apparent Electrical Conductivity ............................................... 33

Figure 20: Example Soil Apparent Electrical Conductivity Dataset .............................................................................. 34

Figure 21: Classification of Soil Apparent Electrical Conductivity ............................................................................... 34

Figure 22: Example Soil Core Sampling Scheme Based on Conductivity Classes (Alamo South) ................................. 35

Figure 23: Photos of the #5-TS Direct Push (left) and a Minimally Disturbed Soil Core (right) ................................... 36

Figure 24: Photos of Soil Lab Processing ..................................................................................................................... 38

Figure 25: Sand Regression Model .............................................................................................................................. 39

Figure 26: Clay Regression Model................................................................................................................................ 39

Figure 27: Example Soil Map (Alamo South) ............................................................................................................... 40

Figure 28: Example Depth to Groundwater (Poe Road) .............................................................................................. 41

Figure 29: Meteorological Station Locations around the Salton Sea........................................................................... 42

Figure 30: Example 10m Wind Record from Salton City Meteorological Station ........................................................ 43

Figure 31: Histogram of Percent Sand and SWEEP Value Selection ............................................................................ 46

Figure 32: Histogram of Surface Crust Thickness and SWEEP Value Selection............................................................ 46

Figure 33: Scale of Maximum 24hr Wind Speed Time series at 10m Above Ground Surface ..................................... 48

Figure 34: Example of Normalized Saltation Flux ........................................................................................................ 49

Figure 35: SWEEP Modeling Results of Wind Speeds Required to Initiate Saltation ................................................... 50

Figure 36: SWEEP Modeling Results for Saltation on Roughened versus Non-roughened Surfaces ........................... 51

Figure 37: Saturated Hydraulic Conductivity Versus Percent Fines ............................................................................. 52

Figure 38: Example Wind Rose and Roughness Orientation ...................................................................................... 53

Figure 39: Oriented Roughness Terminology .............................................................................................................. 54

Figure 40: Sand Abrasion Induced Plant Mortality ...................................................................................................... 55

Figure 41: Monthly Average Precipitation and Reference Evapotranspiration at Westmoreland .............................. 56

Figure 42: Experimental Ridge Height Measurements Made with High Density LiDAR .............................................. 58

Figure 43: Experimental Random Roughness Measurements Made with High Density LiDAR ................................... 59

Figure 44: Alamo South Characterization .................................................................................................................... 62

Figure 45: Wind Speed Versus Wind Direction at Sonny Bono Meteorological Station .............................................. 63

Figure 46: Normalized Saltation Flux Versus Vegetated Barrier Spacing at Alamo South ........................................... 64

Figure 47: Normalized Saltation Flux Versus Ridge Spacing By Ridge Height at Alamo South .................................... 65

Figure 48: Site Layout for the Alamo South Field Study .............................................................................................. 66


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Figure 49: Windrose with Roughness Orientation at Alamo South ............................................................................. 67

Figure 50: Cross Section of a Shallow Sloped Furrow as a Planting Bed ..................................................................... 68

Figure 51: Coachella Playa Characterization ................................................................................................................ 70

Figure 52: Depth to Groundwater Time series at Coachella Playa .............................................................................. 71

Figure 53: Wind Speed Versus Wind Direction at the 1001 Meteorological Station (2016) ....................................... 71

Figure 54: Normalized Saltation Flux Versus Vegetated Barrier Spacing at Coachella Playa ...................................... 72

Figure 55: Normalized Saltation Flux Versus Ridge Spacing By Ridge Height at Coachella ......................................... 73

Figure 56: Windrose at 1001 Meteorological Station.................................................................................................. 74

Figure 57: Site Layout for the Coachella Playa Field Study .......................................................................................... 75

Figure 58: Cross Section of a Constructed Beach Ridge .............................................................................................. 76

Figure 59: New River West Characterization ............................................................................................................... 77

Figure 60: Depth to Groundwater Time series at New River West ............................................................................. 79

Figure 61: Normalized Saltation Flux Versus Vegetated Barrier Spacing at New River West ...................................... 79

Figure 62: Normalized Saltation Flux Versus Ridge Spacing by Ridge Height at New River West ............................... 80

Figure 63: Site Layout at the New River West Field Study........................................................................................... 81

Figure 64: 2016 Hydrograph of the Trifolium 12 Drain ............................................................................................... 82

Figure 65: Salton City Wash and Clubhouse Field Studies ........................................................................................... 84

Figure 66: Vail Drain Field Study .................................................................................................................................. 88

Figure 67: San Felipe Creek North ............................................................................................................................... 89

Figure A-1: Histogram of Percent Clay and SWEEP Value Selection ............................................................................ 93

Appendices

Appendix A. SWEEP Parameterization


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LIST OF ABBREVIATIONS CFS Cubic Feet Per Second

cm Centimeters

DCM Dust Control Measure

DEM Digital Elevation Model

dS/m deciSiemens per meter

GPM Gallons Per Minute

ICAPCD Imperial County Air Pollution Control District

IID Imperial Irrigation District

LiDAR Light Detection and Ranging

m Meters

mm Millimeters

m/s Meters Per Second

NSF Normalized Saltation Flux

OHV Off-Highway Vehicle

PDCP Proactive Dust Control Plan

PI-SWERL Portable In-Situ Wind Erosion Laboratory

PLS Percent Live Seed

PM10 Particulate Matter Less Than 10 Microns in Aerodynamic Diameter

QSA Quantification Settlement Agreement

SCH Species Conservation Habitat

SS AQM Program Salton Sea Air Quality Mitigation Program

SSMP Salton Sea Management Plan

SWEEP Single-event Wind Erosion Evaluation Program

UAS Unmanned Aerial System

UAV Unmanned Aerial Vehicle


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EXECUTIVE SUMMARY This 2017/2018 Proactive Dust Control Plan (PDCP) was prepared for the Imperial Irrigation District (IID) as a requirement of the Salton Sea Air Quality Mitigation Program (SS AQM Program). The SS AQM Program was developed in 2016 for IID, in cooperation with the Imperial County Air Pollution Control District (ICAPCD). It has three main components: 1) an annual Emissions Monitoring Program to estimate emissions and to identify high priority areas of exposed playa for proactive dust control, 2) an annual Proactive Dust Control Plan (PDCP) with recommendations and design for site-specific dust control measures (DCMs) and 3) implementation of DCMs (e.g., surface roughening and vegetation establishment) to prevent potential PM10

1 dust source areas from becoming significant sources of dust emissions. The annual Emissions Monitoring Program is designed to work hand-in-hand with the development of the annual PDCP and subsequent implementation of dust control measures.

The overall goal of the SS AQM Program is keep playa emissions at low levels, even as playa exposure accelerates, through implementation of targeted, proactive dust control measures on priority playa areas. To this this end, the plot and field studies described in this PDCP will cover over 3, 600 acres of high priority playa. These areas account for nearly 38% of the total yearly emissions (115 of the 306 tons/year) (Table ES 1) (Figure ES-1) identified in the 2016/2017 Annual Emissions Monitoring Report (IID, 2018). When considered together with projects planned by other stakeholders, the acreage increases to nearly 4,950 acres of dust control measures. This prioritized/targeted acreage accounts for over 51% of the total yearly playa emissions (~158 of the 306 tons), yet is only 29% of the exposed playa surface. Future annual emission estimates will use results from this PDCP to benchmark progress and report reductions in emissions due to implementation of the IID Salton Sea AQM Program.

This first annual PDCP presents summary findings from a series of plot-based pilot studies (plot studies) used to identify playa conditions and settings suitable for surface roughening and vegetation-based DCMs. Based on annual emissions monitoring data and the suitability criteria developed from the plot studies, the PDCP presents site-specific planning and dust control measure design for three field-scale pilot studies (field studies) (Figure ES-1). Surface roughening is recommended for suitable playa and soil conditions within the footprint of the field studies. This DCM is effective, waterless and can be quickly implemented. A combination of surface roughening and vegetation establishment is recommended for all areas where surface roughening alone may not be suitable or sufficient for long-term dust control.

Implementation of the multipurpose field studies presented in this PDCP proactively accomplish the following objectives identified in the SS AQM Program:

• Provide cost-effective dust control for the majority of priority playa areas that are not currentlyincorporated into existing IID pilot projects, projects by stakeholders or the Salton SeaManagement Plan (SSMP).

• Facilitate evaluation of dust control effectiveness and implementability using a combination ofdust control techniques at a larger scale.

1 Particulate matter less than 10 microns in aerodynamic diameter.


2

• Refine dust control performance monitoring techniques and identify appropriate criteria fortriggering management, augmentation or replacement of DCMs implemented on high priorityplaya.

• Refine the proactive dust control planning and design process used in this PDCP based onfindings from implementation of the field studies.

TABLE ES-1: EXISTING AND PLANNED DUST CONTROL PLOT AND FIELD STUDIES.

THIS TABLE PROVIDES AN OVERVIEW OF THE EXISTING AND PLANNED PLOT AND FIELD STUDIES AS WELL AS THEIR ANNUAL EMISSIONS PRIOR TO CONSTRUCTIONS (PRE-CONTROL)

Project Name Purpose Acres

Total Annual Emission (tons)

Prior to Construction

% Contribution

to Total Playa

Emission

Construction Phase as of January 2018

Identified Site Characterization Design Construction Construction

Finished

Alamo North Established Plot Study 204 13.3 4.3 x x x x x

Poe Road Established Plot Study 400 11.3 3.7 x x x x x

Bombay Beach

Established Plot Study 33 0.1 0.0 x x x x x

Alamo South 2017/2018 PDCP 261 9.0 2.9 x x x x x

Coachella Playa

2017/2018 PDCP 246 0.0 0.0 x x x x

New River West

2017/2018 PDCP 350 0.7 0.2 x x x

Salton Wash 2018/2019 PDCP 276 8.5 2.8 x x

Vail Drain 2018/2019 PDCP 498 16.5 5.4 x x

Club House 2018/2019 PDCP 580 15.4 5.0 x

San Felipe Creek North

2018/2019 PDCP 782 41.2 13.4 x

Subtotal IID Projects 3,630 115.9 37.9 Red Hill Bay Habitat Project

US Fish and Wildlife Service 618 30.6 10.0 x x x x

Species Conservation Habitat

State of California 699 11.4 3.7 x x x

Subtotal Other Projects 1317 42 13.7

Total for all Projects 4,947 157.9 51.6


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DATE: FEB 14, 2018

Emissions InventoryFigure ES-1. Annual Emissions

for the Playa and DustControl Measure Pilot Studies

New River Delta

Alamo RiverDelta

EasternDry Washes

San Felipe Fan

Tule Fan

Naval Test BaseSand Dunes

NorthwesternDry Washes

±0 2 4 6 81Miles

Coachella Playa(Surface Roughening andVegetation Enhancement)

Clubhouse(Physical Barriers andVegetation Establishment)

Bombay Beach(Vegetation

Enhancement)

Alamo South(Surface Roughening and

Vegetation Establishment)

Alamo North(Surface Roughening and


Vail Drain(Surface Rougheningand VegetationEstablishment)Poe Road

(Surface Roughening andVegetation Enhancement)

New River West(Surface Roughening

and SurfaceSurfactants)

San Felipe Creek North(TBD)

Salton Wash(Physical Barriers and


LegendAnnual PM10 Emissions on Playa(Tons/km2)

0

0.001 - 0.267

0.268 - 2.14

2.15 - 7.22

7.23 - 11.8

11.9 - 15.8

15.9 - 21.4

21.5 - 27.3

27.4 - 31.8

31.9 - 68.2

SS AQMP Projects

Existing StudiesAlamo North

Bombay Beach

Poe Road

2017/2018 PDCPAlamo South

Coachella Playa

New River West

2018/2019 PDCPClub House

Salton Wash


Vail Drain

Other Stakeholder ProjectsState of CA Red Hill Bay Habitat Project

State of CA Species Conservation Habitat Project

Other FeaturesBase Shoreline

Heavily Vegetated Playa

2016/2017 IID Annual Emissions Estimate (IID, 2018) Existing and Planned Dust Control Studies and Stakeholder Projects

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Implementation of the field studies is subject to funding authorized by the QSA Joint Powers Authority. In addition, the field studies may be refined to accommodate anticipated projects by stakeholders or the SSMP. The field studies will be adaptively managed based on performance monitoring data. Future PDCPs will draw on the results of these field studies, and additional plot studies, to plan and manage suitable combinations of DCMs on high priority areas identified in the ongoing annual Emissions Monitoring Program.

PLOT-BASED DUST CONTROL MEASURE PILOT STUDIES A series of plot studies were implemented during the 2015/2016 and 2016/2017 dust seasons at two locations totaling approximately 550 acres at Alamo River North and Poe Road. These plot studies are designed to generate data regarding site-specific factors controlling DCM effectiveness, implementability, operations, maintenance and cost. Results and knowledge gained from these plot studies were used to inform the design of the field studies described herein. Each plot study is summarized below.

SURFACE ROUGHENING

Surface roughening is recognized around the world as an effective DCM on exposed surfaces. It provides quick, waterless and effective control on exposed playa by decreasing the wind velocity at the surface and by physically trapping soil particles from upwind sources. These plot studies were designed to evaluate the relative effectiveness and durability of surface roughness on different soil types roughened with various types of tillage implements (Figure ES-2). Detailed information on these plot studies can be found in the Imperial Irrigation District – Surface Roughening Pilot Study (Salton Sea Air Quality Team, 2015).

Key findings informed the field study planning procedure on soil suitability criteria, surface roughness configurations and the combination of tillage implements best suited for creating and maintaining large, durable ridges that confer dust control. Plot study results demonstrated that, in sandier soils, bull plow furrows support quick vegetation establishment when irrigated and seeded. This vegetation augments the surface roughness by creating more durable, longer-term dust control elements and physically trapping saltating soil particles. Key findings are highlighted in Table ES-1.


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FIGURE ES-2: SURFACE ROUGHENING PLOT STUDY

TABLE ES-2: KEY FINDINGS FROM SURFACE ROUGHENING PLOT STUDY

Parameter Key Finding

Wind Speed Roughness reduced wind speeds near the surface by 50% (on average) during high wind events compared to adjacent non-roughened playa.

Tillage Implement and Roughening Configuration

Directional roughness created using the bull plow combined with interrow random roughness created using a switch plow created a protective configuration, protecting the surface from high winds in the primary and non-dominant wind directions.

Soil Condition Roughening of fine textured soils with adequate soil moisture conferred the largest, most durable ridges and armoring clods. Roughness of sandy, dry soils degraded more quickly and required maintenance to sustain the target roughness. However, native vegetation passively established in some sandy furrows with low salinity and high internal drainage. Active seeding, reclamation and irrigation of furrows improved germination and vegetation establishment.

Performance Monitoring Technique

Elevation data captured through UAV-based (Unmanned Aerial Vehicle) high density LiDAR (Light Detection and Ranging) (as compared to manual point measurements and UAS photogrammetry) provided the most robust, accurate and cost efficient data collection method to quantitatively monitor ridge height, ridge spacing and inter-row random roughness over time.


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VEGETATION ENHANCEMENT As the Salton Sea recedes, existing plant communities along the shoreline are naturally expanding onto the playa. This occurs most often on historical linear “beach ridges” formed by wave action. Similar to surface roughening, vegetated beach ridges provide effective dust control on exposed playa by decreasing the wind velocity at the surface and by physically trapping soil particles from upwind sources. The central concept of these plot studies was to understand these natural processes and then determine the best practices for enhancing and constructing vegetated beach ridges (Figure ES-3). Conditions under evaluation in these plot studies include the effect of proximity to the shoreline, groundwater depth and quality, the diversity of native species seeded, agronomic characteristics of the soil and amendments needed to enhance vegetation establishment on the playa.

Results from these plot studies informed the field studies in this PDCP by establishing important guidelines on seeding and germination, soil reclamation, soil amendments and groundwater depth needed for successful vegetation establishment on the playa. Key findings are highlighted in Table ES-2.

FIGURE ES-3: VEGETATION ENHANCEMENT PLOT STUDY


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TABLE ES-2: KEY FINDINGS FROM VEGETATION ENHANCEMENT PLOT STUDY

Parameter Key Finding

Plants and Seed Collection

Natural beach ridges around the playa generally have 10 vegetative species, mostly dominated by iodine bush (Allenrolfea occidentalis) and big saltbush (Atriplex lentiformis). Seed from these 10 native species were collected locally, dried and tested to determine Percent Live Seed. Results inform future seeding rates.

Seeding and Germination

After seeding, 9 of the 10 species germinated at all sites. Germination was highest on constructed beach ridges that included irrigation and all soil amendments.

Soil Reclamation Soil sampling and seedling density measurements demonstrate that seed bed soils must be reclaimed to less than 30 deciSiemens per meter (dS/m) for maximum germination.

Soil Amendments Treatment comparisons demonstrate that constructed beach ridges with compost reclaimed more quickly, had highest germination density and produced larger seedlings compared to natural beach ridges.

Groundwater Depth At all treatment sites, the greatest germination density was at the medium groundwater depth interval, while the lowest density was at the deep groundwater depth interval.


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FIELD SCALE DUST CONTROL MEASURE PILOT STUDY PLANNING The purpose of the field studies is to gain experience scaling, adapting and combining DCMs (e.g., surface roughness and vegetation) to efficiently achieve proactive dust control at a larger scale. Field studies are proposed on approximately 800 acres2 of diverse soil and surface conditions at different settings around the Sea. Field study sites include Alamo South, Coachella Playa and New River West (Figure ES-1). These sites were selected based on high emissions potential areas identified during the 2015/2016 and 2016/2017 dust season in the Emission Monitoring Program (documentation in progress). Quantitative site characterization data were used to guide recommendations on DCM type, intensity and configuration. In general, surface roughening is prescribed on finer texture soils, and a combination of surface roughening and vegetation establishment is prescribed on coarser textured, well-drained soils. The Single-event Wind Erosion Evaluation Program (SWEEP), developed and used by the Agricultural Research Service (ARS) for specification of dust control measures, was parameterized with site-specific soil and surface characteristics and used to determine the vegetation spacing, ridge spacing/ridge height relationships, and random roughness needed to reduce saltation at each site.

After construction of each site, performance characteristics will be monitored, including the ridge height, random roughness, meteorological data, sand motion monitoring and vegetation characteristics. Monitoring will be similar for all field studies and will occur quarterly through remote sensing techniques. As-built survey data collected after construction will be used to site meteorological stations, video surveillance, sand motion monitoring equipment (e.g., Sensits and sand catchers) and upwind/downwind PM10 monitors.3 Performance monitoring data will be used to verify dust control performance relative to the dust control design criteria. Performance monitoring data will also be used to identify and define performance criteria for maintenance (e.g., scale, timing and method) needed to sustain a stabilized surface. Results and findings from implementation and monitoring of the field studies will be used to improve and refine the dust control planning approach described in this PDCP. Each field study is summarized in Table ES-3.

2 The extent of the field studies may be refined based on landowner permission to implement a study or to accommodate anticipated projects by stakeholders or the SSMP. For example, approximately 100 acres of the New River West site is owned by the Bureau of Land Management. In addition, the State’s Species Conservation Habitat is proposed for this area. 3 Upwind/downwind portable BGI PM10 monitors will be installed prior to forecast high wind events and then removed after each event. Portable monitors will be rotated to each site, and it is anticipated that each site will be monitored during at least one high wind event per year; however, this is dependent on the number of high wind events that actually occur.


9

TABLE ES-3. SUMMARY OF PROPOSED 2017/2018 FIELD STUDIES

Site Site Characteristics Dust Control Measure Specifications Design Features

Alam

o So

uth

Approximate Size: 270 acres

Emissions: 65% of the site mapped as a high or medium priority.

Soils: 78% of the site characterized as fine texture soils suitable for surface roughening. 22% of the site characterized as sandy texture soils suitable for vegetation establishment.

Surface roughness specifications derived from SWEEP modeling to achieve greater than 95% reduction in sand motion include: • Ridge height: greater than 35 centimeters (cm)• Ridge spacing: less than 3.5 meters (m)• Interrow random roughness: greater than 20 millimeters (mm)Vegetation enhancement specifications derived from SWEEP modelingto achieve 95%+ reduction in sand motion include:• Vegetated barrier spacing: less than 50m

Irrigation: Vegetated furrows will be slightly off contour and will be pre-graded to facilitate flood irrigation. Irrigation water will be supplied from the Alamo River using a pump and sand filter system for removal of tamarisk seed.

Coac

hella

Pla

ya


Emissions: 50% of the site mapped as high or medium priority.


Surface roughness specifications derived from SWEEP modeling to achieve greater than 95% reduction in sand motion include: • Ridge height: greater than 30 cm• Ridge spacing: less than 7 m• Interrow random roughness: greater than 20 mmVegetation enhancement specifications derived from SWEEP modelingto achieve greater than 95% reduction in sand motion include:• Vegetated barrier spacing: less than 60m

Irrigation: Subsurface drip irrigation will be used. Irrigation water will be supplied from the Whitewater River, Torres Martinez wetland well or municipal sources.

New

Riv

er W

est


Emissions: 70% of the site mapped as high or medium priority.


Surface roughness specifications derived from SWEEP modeling to achieve greater than 95% reduction in sand motion include: • Ridge height: greater than 35 cm• Ridge spacing: less than 3.5 m• Interrow random roughness: greater than 20 mmVegetation enhancement specifications derived from SWEEP modelingto achieve greater than 95% reduction in sand motion include:• Vegetated barrier spacing: less than 50m

Irrigation: Vegetated furrows will be slightly off contour and will be pre-graded to facilitate flood irrigation. Irrigation water may be supplied from the Trifolium 12 drain through a gravity fed system.


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1 INTRODUCTION This 2017/2018 Proactive Dust Control Plan (PDCP) was prepared for the Imperial Irrigation District (IID) as a requirement of the Salton Sea Air Quality Mitigation Program (SS AQM Program). One key component of the SS AQM Program is to proactively implement dust control measures (DCMs) to prevent evolving playa areas from becoming a significant source of dust emissions. The annual Emission Monitoring Program identifies exposed playa and prioritizes areas (based on multiple lines of scientific evidence) for proactive dust control. Lines of evidence include mapping exposed playa, monitoring surface characteristics, mapping soil properties, delineating dust source areas, documenting dust plumes and estimating high wind event emissions. The SS AQM Program specifies that the annual PDCP will recommend implementation of dust control measures (type, intensity, and configuration) for priority playa areas identified in the Emission Monitoring Program. This first annual PDCP recommends implementation of multipurpose field scale pilot studies (field studies) to accomplish the following objectives:

• Provide cost-effective dust control for the majority of priority playa areas are not currentlyincorporated into existing IID pilot projects, projects by stakeholders or the Salton SeaManagement Plan (SSMP).

• Facilitate evaluation of dust control effectiveness and implementability using a combinations ofdust control techniques at a larger scale.

• Refine dust control performance monitoring techniques and identify appropriate criteria fortriggering management, augmentation or replacement of DCMs implemented on high priorityplaya.

• Refine the proactive dust control planning and design process used in this PDCP based onfindings from implementation of the field studies.

Implementation of the field scale pilot studies is subject to funding authorized by the Quantification Settlement Agreement Joint Powers Authority. The field scale pilot studies described herein may be refined to accommodate anticipated projects by stakeholders or the SSMP.

This PDCP incorporates summary findings from a series of plot-based pilot studies (plot studies) used to identify playa conditions and settings suitable for surface roughening and vegetation-based DCMs in the field scale planning process. Surface roughening is recommended for all suitable playa areas within the footprint of the field studies. This DCM is effective, waterless, and can be quickly implemented. A combination of surface roughening and vegetation establishment is recommended for all areas where surface roughening alone may not be suitable or sufficient for long-term dust control. Future PDCPs will draw on the results of these field studies, and additional plot studies, to refine the dust control planning process and efficiently recommend suitable combinations of DCMs on high priority areas identified in the ongoing annual Emissions Monitoring Program.

This PDCP includes the following sections:


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• Section 2, Findings of the 2015-2017 Plot Studies, describes the key findings, knowledge gained andsuitability criteria developed from implementation of a series of intensive plot studies performedfrom 2015 through 2017.

• Section 3, Planning Process for 2017/2018 Field Studies, describes general planning and designapproach used to develop dust control measures for the 2017/2018 field studies.

• Section 4, Proposed 2017/2018 Field Studies, describes the site-specific planning used at AlamoSouth, Coachella Playa, and New River West.

• Section 5, Proposed Future Studies, describes preliminary planning information for known plot andfield studies planned for the 2018/2019 dust season.

Relevant data generated for the plot and field studies are available through the SS AQM Program Data Portal (www.saltonseaprogram.com).

2 FINDINGS OF THE 2015-2017 PLOT STUDIES Plot studies are focused on evaluating the effectiveness and suitability of individual DCMs on the diverse conditions of Salton Sea playa. A series of plot studies were implemented during the 2015/2016 and 2016/2017 dust seasons on approximately 550 acres (Figure ES-1). These plot studies were located in areas of exposed playa that have high emissions potential, on IID-owned land and were designed to generate data regarding site-specific factors that affect individual DCM effectiveness, feasibility, operations and cost. The finding of these plot studies were used to develop suitability criteria for surface roughening and vegetation DCMs used in the 2017/2018 field studies. Each plot study and relevant findings are summarized below.

2.1 SURFACE ROUGHENING Surface roughening is recognized around the world as an effective DCM on exposed surfaces (Bielders et al., 2000). Surface roughening provides quick, waterless, and effective control on exposed playa by decreasing the wind velocity at the surface and by physically trapping soil particles from upwind sources. The central concept of these plot studies was to evaluate the relative effectiveness and durability of surface roughness on different soil types roughened with various configurations of surface roughening (e.g., ridge height, ridge spacing and random roughness) imposed by different tillage implements (Salton Sea Air Quality Team, 2015). Surface roughening was completed using a switch plow and bull plow combination at the Alamo North and Poe Road sites totaling approximately 600 acres. The following sections describe key findings related to the near surface wind speed reduction (Section 2.1.1), roughness configuration (Section 2.1.2), soil conditions (Section 2.1.3), vegetation establishment (2.1.4) and performance monitoring (Section 2.1.5).

2.1.1 NEAR SURFACE WIND SPEED REDUCTION As noted above, surface roughening confers dust control by reducing the wind speed at the surface. The wind speed at 10m above the ground surface is typically used for planning purposes because it is a


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common monitoring height. To evaluate the effect of surface roughening on near surface wind speeds, two temporary meteorological stations were installed at Alamo North: one inside surface roughening and one outside surface roughening. Anemometers were placed at 15cm, 2m and 6m above the ground surface. Results demonstrate that surface roughening dramatically reduces the near surface wind speed at the meteorological station placed within the surface roughening compared to the meteorological station placed outside the surface roughening (Figure 1). Specifically, within surface roughened areas, the 15cm wind speed was reduced by approximately 45%, the 2m wind speed was reduced by approximately 24% and the 6m wind speed was reduced by approximately 15%. These results indicate that the minimum wind speed at 10m required to initiate the process of saltation is increased by approximately 75% within surface roughened areas as compared to non-roughened areas (Figure 2).

FIGURE 1: NEAR SURFACE WIND SPEED REDUCTION WITHIN SURFACE ROUGHENED AREA

Linear models were fit to the data for each anemometer height. Results suggest that surface roughening significantly reduces the near surface wind speed.


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FIGURE 2: WIND SPEED ASSUMED TO INITIATE SALTATION OUTSIDE AND INSIDE SURFACE ROUGHENING

A 12m/s wind speed at 10m above bare ground was pulled from literature (Gillette et al., 1980 &Shao, 2008). Using the wind profile power law, the 15cm wind speed assumed to initiate saltation outside surface roughening was estimated. The 15cm linear relationship shown in Figure 1 was used to estimate the 15cm wind speed required to initiate saltation inside surface roughening. The wind profile power law was used again to estimate the 10m wind speed that initiates saltation in surface roughened areas.

2.1.2 TILLAGE IMPLEMENTS AND ROUGHNESS CONFIGURATION The dust control effectiveness of surface roughness is dependent on the geometric characteristics of ridges and random roughness. Tillage implements impose surface roughness (e.g., ridge height, ridge spacing and random roughness). Commonly used tillage implements are a deep plow (i.e., bull plow) and moldboard plows (i.e., a modified switch plow). The bull plow is generally used to produce oriented roughness and the modified switch plow is generally used to produce interrow random roughness. Oriented roughness coupled with interrow random roughness was observed at Alamo North and Poe Road to create a surface protected from high winds in the dominant and non-dominant directions (Figure 3). This surface protection was also verified and quantified through dust control modeling (Section 3.3).


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FIGURE 3: ORIENTED ROUGHNESS COUPLED WITH INTERROW RANDOM ROUGHNESS

2.1.3 SOIL CONDITIONS Soil texture and moisture affect important surface roughness features, including the durability and longevity of ridges. Soil conditions at each site were quantified by soil coring to a depth of 1.5 m. Each soil core was characterized using laboratory and spectroradiometer procedures (Waiser et al., 2007 & Cheng-Wen et al., 2001) for soil texture, soil carbon and soil moisture. Data to date suggest that soil texture and soil moisture in the top 60cm are the primary factors influencing ridge height and durability. Specifically, moist fine textured soils with greater than 35% clay and silt produced ridge heights greater than 35cm through the first year (Figure 4). Conversely, sandy soils with less than 35% silt and clay degraded more quickly and required a maintenance event within 9 months of installation. Bull plow furrows in sandy soils appear to be suitable for vegetation establishment due to adequate drainage and low surface salinities. These results were used to set the soil suitability criteria for the field studies in this PDCP. Results from the field studies, which will occur on more diverse soil conditions, will be used to further understand this relationship and refine the soil suitability criteria.


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FIGURE 4: EXAMPLE RIDGE HEIGHT VERSUS SOIL TEXTURE RELATIONSHIP

An operational target ridge height range was set to 35cm to 45cm based on what is feasibly imposed with a bull plow and what was observed at the Alamo River North site. The sum of percent silt and percent clay is summarized as percent fines along the x axis. These data are coarser than the average soil texture observed around the Salton Sea.

2.1.4 VEGETATION ESTABLISHMENT Surface roughening on soils with greater than 65% sand in the top 60cm at the Alamo North site showed signs of early degradation from sand motion during the first dust season after DCM installation. During December 2016, Morton Bay, which bounds Alamo North to the east, rose and flooded portions of the site. Furrows along the periphery of the site were converted into head ditch conveyance features. Flood waters were used to irrigate individual furrows and test the feasibility of establishing vegetation. The furrows were treated with either: irrigation and seed, irrigation without seed or no irrigation without seed. Vegetation establishment within the bull plow furrows was achieved (Figure 5). Vegetation monitoring was performed 4 months after seeding along the length of the treated furrows (Figure 6). For direct comparison between treatments, the total furrow distances were normalized. The monitoring results suggest a clear trend of increased vegetation establishment with irrigation and seed. Many irrigated furrows that were not seeded also had significant vegetation establishment likely due to the large seed bank in the irrigation water supply. A sandy bull plow furrow flooded for 6 hours successfully established a continuous vegetated barrier. This was the minimum amount of irrigation and reclamation completed during the test. This observation, in part, was used to help specify the proposed irrigation system and operations at Alamo South and New River West field studies.

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FIGURE 5: PHOTO OF VEGETATION ESTABLISHMENT IN A SANDY BULL PLOW FURROW

A continuous band of Atriplex lentiformis established within a bull plow furrow on a coarse textured soil. This bull plow furrow received seed and irrigation. The irrigation was a single pulse of water within the bull plow furrow maintained for 6 hours.

FIGURE 6: ALAMO NORTH VEGETATED FURROW PLANT HEIGHT MONITORING SUMMARY

Furrow distances were normalized by the total distance of furrows sampled within each treatment class. Over 5 kilometers of furrows were sampled.


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2.1.5 PERFORMANCE MONITORING OF ROUGHNESS ELEMENTS Quantitative characterization of surface roughening performance (i.e., durability and longevity of roughness) is essential for defining performance criteria to ensure dust control effectiveness over time. Methods for monitoring roughness elements (ridge height, spacing, and durability) using remote sensing were developed and assessed at the plot study sites. This included collection and analysis of high resolution topographic data from an Unmanned Aerial System (UAS) at Alamo North and Poe Road plot study sites. One UAS was equipped with a RGB camera for image and photogrammetry analysis, while the other was equipped with a high-density light detection and ranging (LiDAR) sensor. The high-density LiDAR and photogrammetry methods were benchmarked against a ground-based Trimble R10 Real-time Kinematic (RTK) GPS survey. This provided known reference data for the comparison.

Data from the remotely sensed topographic survey comparison suggest that elevation data collected using LiDAR from an UAS provided a robust, accurate and cost-efficient data collection method (Figure 7). Average accuracies of the LiDAR were +/- 2.5cm when compared to the ground-based survey method. In addition, the LiDAR system collected data more quickly, in low light situations, and required less post processing than the photogrammetry method.

Automated analysis routines were also developed to extract important attributes of the surface roughening array from the high-density LiDAR. These include ridge height, ridge spacing, inter-row spacing and inter-row random roughness. Monitoring of attributes over time will be used to report performance and refine performance criteria associated with operations and maintenance.

FIGURE 7: COMPARISON OF METHODS OF DETERMINING ROUGHENED GROUND SURFACE LEVEL


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2.2 VEGETATION ENHANCEMENT As the Salton Sea recedes, existing plant communities along the shoreline are naturally expanding onto the playa. This occurs most often on historical linear “beach ridges” formed by wave action. Similar to surface roughening, vegetated beach ridges provide effective dust control on exposed playa by decreasing the wind velocity at the surface and by physically trapping soil particles from upwind sources. The central concept of this plot study is to understand these natural processes of establishment and to determine the best practices for enhancing and creating vegetated beach ridges as proactive dust control.

Vegetated beach ridges were created at three study sites (Bombay Beach, Poe Road and Coachella playa). These sites were chosen to represent the range of playa conditions where vegetation may be implemented as dust control. Successful proactive vegetation enhancement requires sowing and establishment soon after the Sea recedes. To study the effect of proximity to the shoreline, depth to groundwater and surface salinity, three laterals each with shallow, medium and deep depths to groundwater were established at each plot study site (Figure 8). The laterals represent a gradient of groundwater depth from the playa toward the shoreline. Along each lateral, nine treatments were replicated four times. Conditions under evaluation (quantitatively and qualitatively) include the effect of proximity to the shoreline, groundwater depth and quality, the diversity of native species seeded, vegetative cover characteristics, agronomic characteristics of the soil, soil amendments needed, playa surface and subsurface conditions, and beach ridge orientation and composition. Additional information on the plot study design is documented in the Vegetation Enhancement Pilot Study at the Salton Sea (Salton Sea Air Quality Team, 2016b). The Vegetation Enhancement Pilot Project 2017 Brochure (Salton Sea Air Quality Team, 2017) documents the initial germination and establishment results after implementation. A technical memorandum summarizing vegetation growth and characteristics after the first full growing season will be completed in Fall 2017. The following sections summarize pertinent information and current findings relevant to the design of the field studies in this PDCP.

2.2.1 PLANTS AND SEED COLLECTION Allenrolfea occidentalis and Atriplex lentiformis are the main species observed on recently exposed beach ridges around the Sea. Over time, many other species will likely establish in these areas. To achieve similar diversity and to enhance the rate of succession, seed from 10 locally adapted, native species was collected from numerous locations around the Sea during three separate seed collection events. This included Spring 2016, Fall 2016, and Spring 2017. Approximately 330 pounds of bulk seed were collected during the first two events in 2016 and over 330 pounds during the Spring 2017 event. The seed was dried and tested to determine Percent Live Seed (PLS), which informs the amount of applied seed necessary to vegetate the beach ridges. PLS varied significantly by species, ranging from 1% for Isocoma to over 40% for Typha. Results from the PLS analysis were used to develop a field study sowing rate for vegetation establishment locations within this PDCP (Table 1).


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FIGURE 8: EXAMPLE PLOT STUDY LAYOUT FOR THE BOMBAY BEACH SITE

The inset shows the three laterals (shallow, medium and deep depths to groundwater). Individual, replicated treatment and constructed beach ridges are also shown.


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TABLE 1: SUMMARY OF NOVEMBER 2016 LOCAL SEED AVAILABILITY AND PLOT STUDY SOWING RATE

Summary of November 2016 total seed available and Percent Live Seed (PLS) Average

Species Name Total Bulk Seed Available Nov 2016 (lb)

Weighted Average PLS%

Field Study Sowing Rate (PLS lb/ac)

Allenrolfea occidentalis 122.22 13.2 1

Atriplex canescens var. macilenta 3.6 25.9 0.33

Atriplex hymenelytra 8.04 15.8 0.5

Atriplex lentiformis 50.99 52 2.5

Atriplex polycarpa 14.76 7.5 0.25

Bolboschoenus maritimus ssp. paludosus

27.84 24 1

Isocoma acradenia var. eremophila 32.47 1 0.075

Sesuvium verrucosum 7.36 11.2 0.25

Suaeda nigra 17.84 6.3 0.5

Typha domingensis 46.24 40.1 0.05

2.2.2 GERMINATION Upon sowing, nine of the 10 species germinated at all sites. The majority of the germination occurred 55 days after sowing, with 95% of the germinated seedlings consisting of four species: Atriplex lentiformis, Suaeda nigra, Allenrolfea occidentalis, and Atriplex canescens. Germination density for all plot study sites was highest on the constructed ridges with all soil amendments, but was also very high on the natural beach ridges with all soil amendments (Figure 9). Overall, treatment comparisons show that constructed beach ridges with compost reclaimed (i.e., reduced the surface salinity) more quickly, had the highest germination density and produced larger seedlings than natural beach ridges with no amendments.


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The native plant species used in this plot study are exceptionally tolerant of salinity after establishment, but high soil salinity can significantly reduce germination. Results from soil sampling and seedling density measurements show that the seed bed soil should be reclaimed to less than 30 dS/m for acceptable germination (Figure 10). Poe Road had the slowest germination rate compared to the other sites, likely due to high initial soil salinity and slow reclamation to the 30 dS/m ECe (electrical conductivity) threshold. Treatment comparisons also demonstrated that pre- and post-sowing reclamation efforts are equally effective for germination.

FIGURE 9: GERMINATION RESULTS BY SITE AND TREATMENT

Overall, treatment comparisons show that constructed ridges with all soil amendments had the highest germination rates.

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FIGURE 10: SEEDLING DENSITY VERSUS SOIL SALINITY

Seedling density versus soil salinity (ECe) indicates a clear visual threshold of roughly 30 dS/m. Above this threshold, seedling densities decrease dramatically.

2.2.3 SEEDLING GROWTH Similar to germination density, the largest seedlings of the four most abundant species were observed on constructed ridges with all amendments during the February and March monitoring periods. In particular, Allenrolfea occidentalis seedling height increased substantially from February to March 2017 (Figure 11). March seedling height was largest on constructed ridges with all amendments, but was similar for natural ridges with compost. The strength and significance of the trend will be verified during subsequent monitoring events throughout the next year and reported in the Fall of 2017.

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FIGURE 11: ALLENROLFEA OCCIDENTALIS (ALOC) SEEDLING HEIGHT BY TREATMENT

2.2.4 RELATIONSHIP OF GROUNDWATER DEPTH AND QUALITY TO VEGETATION ESTABLISHMENT Understanding groundwater depth and quality across the gradient of successional plant communities is essential to vegetation establishment. At all treatment sites, the greatest germination density and seedling growth was at the medium groundwater depth lateral. Groundwater depth and quality will continue to be monitored to understand the factors conducive to successful establishment of beach ridge species and how those species utilize the groundwater resource.

2.2.5 PERFORMANCE MONITORING Quantitative characterization of vegetated roughness elements (i.e., size, continuity and stress) is essential to managing vegetation establishment. A brief study was performed on the vegetation enhancement pilot study to assess vegetated barrier continuity using remote sensing methods. High-resolution multispectral data was used to measure vegetated barrier continuity. A UAS with a multispectral sensor (Parrot Sequoia) captured imagery from which the Normalized Difference Vegetative Index (NDVI) was derived. NDVI is commonly used to determine the presence and absence of vegetation and assess vegetation health. Each pixel with an NDVI value greater than a threshold value was classified as vegetation and used to generate a high-resolution map of vegetation presence. All the pixels that intercepted the centerline of the vegetated barrier were summed. The ratio of the vegetated pixels to the total number of pixels along the centerline represents hedge row continuity (Figure 12).

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As shown in Figure 12, this approach produces a lot of noise in the results, which could introduce error in interpretation. More appropriate methods to derive vegetated barrier continuity and barrier height from high-density, full waveform, multiple return UAS LiDAR are under development for the field studies.

2.3 RESULTS RELEVANT TO FIELD STUDIES The plot based pilot studies performed from 2015 through 2017 provided findings relevant to the 2017/2018 field studies (Table 2). Findings informed the placement of dust control measures based on the soil suitability criteria, construction methods, agronomic inputs for vegetation establishment and performance monitoring methods.

TABLE 2: KEY FINDINGS FROM THE PLOT STUDIES USED IN DEVELOPMENT OF THE 2017/2018 FIELD STUDIES

Study Parameter Key Finding

Surf

ace

Roug

hnes

s

Wind Speed Surface roughness reduced wind speeds at the surface by 50% (on average) during high wind events compared to adjacent non-roughened playa.

Tillage Implement and Roughening Configuration

Directional roughness created using the bull plow combined with interrow random roughness created using a switch plow created a configuration that protected the surface from high winds in the primary and non-dominant wind directions.

Soil Condition Roughening of fine textured soils with adequate soil moisture conferred the largest, most durable ridges and armoring clods. Roughness of sandy, dry soils degraded more quickly and required maintenance to sustain the target roughness. However, native vegetation passively established in some sandy furrows with low salinity and high internal drainage. Active seeding, reclamation and irrigation of furrows improved germination and vegetation establishment.

Performance Monitoring Technique

Elevation data captured through UAV-based (Unmanned Aerial Vehicle) high density LiDAR (Light Detection and Ranging) (as compared to manual point measurements and UAS photogrammetry) provided the most robust, accurate and cost efficient data collection method to quantitatively monitor ridge height, ridge spacing and inter-row random roughness over time.

Vege

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Plants and Seed Collection

Natural beach ridges around the playa generally have 10 vegetative species, mostly dominated by Allenrolfea occidentalis and Atriplex lentiformis. Seed from these 10 native species were collected locally, dried and tested to determine Percent Live Seed (PLS). PLS results inform future seeding rates.

Seeding and Germination

After seeding, 9 of the 10 species germinated at all sites. Germination was highest on constructed beach ridges that included irrigation and all soil amendments.

Soil Reclamation Soil sampling and seedling density measurements demonstrate that seed bed soils must be reclaimed to less than 30 deciSiemens per meter (dS/m) for maximum germination.


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Study Parameter Key Finding Soil Amendments Treatment comparisons demonstrate that constructed beach ridges with

compost reclaimed more quickly, had highest germination density and produced larger seedlings compared to natural beach ridges.

Groundwater Depth

At all treatment sites, the highest germination density was at the medium groundwater depth interval and the lowest density was at the deep groundwater depth interval.

3 PLANNING PROCESS FOR 2017/2018 FIELD STUDIES The purpose of the field studies in this PDCP is to gain experience scaling, adapting and combining DCMs (e.g., surface roughness and vegetation) to efficiently achieve proactive dust control at a large scale. In addition, implementation of the field studies and subsequent monitoring results will be used to refine the planning approach. The proposed field study sites were selected based on several lines of evidence produced from the annual Emission Monitoring Program activities. Specifics regarding the emissions potential at each site and other areas around the playa will be documented in the 2016/2017 annual Emission Monitoring Program report. It is anticipated that this report will be completed during the fourth quarter of 2017. However, several lines of evidence are available and were used to select the field study sites based on dust source delineations, measured emissions potential and plume observations during the 2015/2016 and 2016/2017 dust seasons.

This section describes the overall process used to develop plans for designing and implementing field studies. A brief summary of emissions potential by site is provided in Section 3.1. The critical steps in developing dust control plans include: site characterization (Section 3.2), dust control modeling (Section 3.3), dust control design (Section 3.4) and performance monitoring (Section 3.5). The overall planning timeline to develop and implement PDCPs is illustrated in Figure 13.


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FIGURE 13: PLANNING TIMELINE FOR PROACTIVE DUST CONTROL PLANS

3.1 PLAYA PRIORITIZED FOR FIELD STUDIES The annual Emission Monitoring Program identifies exposed playa and prioritizes areas for proactive dust control based on multiple lines of evidence. Lines of evidence include mapping exposed playa, monitoring surface characteristics, mapping soil properties, delineating dust source areas, documenting dust plumes and estimating high wind event emissions. Data gathered throughout the 2016/2017 dust season were used to identify priority playa areas for the field studies. A summary of the specific lines of evidence used to prioritize playa at each field study site is provided in the remainder of this section. Summaries of site specific information are provided in Section 4.0. The first annual 2017 Emission Monitoring Program report will be available in the fourth quarter of 2017.

3.1.1 PORTABLE IN-SITU WIND EROSION LAB SAMPLING The PI-SWERL provides a quantitative measure of dust emission potential. The PI-SWERL exerts a known friction velocity upon the playa surface and measures the resulting PM10 and saltation flux. PI-SWERL data are an integral line of evidence used to quantify playa emissions potential and confirm dust source delineations. As an example, PI-SWERL transect data from Alamo North show the emissions potential for various surface conditions and the relationship to the distance from the shoreline (i.e., duration of exposure) (Figure 14). Results demonstrate that emission potential increases with distance from the current shore.

3.1.2 SURFACE SURVEY AND SOURCE DELINEATION Ground-based surface surveys and source delineations are performed during the dust season to estimate the emissions potential of playa surfaces across large areas. Surface surveys characterize the crust type and hardness, surface texture, loose sand percentage and features of wind erosion. Surface surveys coupled with PI-SWERL data are used to inform dust source delineations. As shown in Figure 15,


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the amount of PM10 flux is dependent on the presence of loose sand and the friction velocity applied by the PI-SWERL. Areas with loose sand present have larger PM10 flux. A similar relationship is displayed in Figure 16 for the presence of features of wind erosion, such as scouring or buffing. An example source delineation based on these techniques is shown in Figure 17.

FIGURE 14: NEARSHORE ALAMO NORTH PI-SWERL TRANSECT

The black dashed line represents the height of the ground surface relative to the average 2016 Salton Sea level. The surface moisture status changes from moist to dry at 3ft above the elevation of the Salton Sea level and 1200ft from the shoreline. The PM10 flux becomes greater than one at a similar height above the Salton Sea level and distance from shoreline.


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FIGURE 15: PM10 FLUX VERSUS LOOSE SAND COVERAGE

The five step PI-SWERL test applies five known friction velocities on the surface denoted in the legend. Loose sand coverage was assessed within a square meter at each PI-SWERL sampling location. Each zero value of PM10 flux was replaced with a one value to allow plotting on a log axis.

FIGURE 16: PM10 FLUX VERSUS THE PRESENCE OF WIND EROSION FEATURES

The five step PI-SWERL test applies five known friction velocities on the surface denoted in the legend. The presence of features of wind erosion was assessed within a square meter at each PI-SWERL sampling location. Each zero value of PM10 flux was replaced with a one value to allow plotting on a log axis.


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LegendNew River West

Source Delineation PriorityHigh

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3.2 SITE CHARACTERIZATION After site identification, site-specific data are collected for surface topography (Section 3.2.1), soil texture (Section 3.2.2), groundwater depth (Section 3.2.3) and wind direction (Section 3.2.4). Each is described below.

3.2.1 TOPOGRAPHIC SURVEY Digital elevation models (DEMs) were generated using photogrammetry methods to characterize site topography for each field study location. The DEMs provide important information for DCM design, including information for the design of water conveyance infrastructure. As an example, the photogrammetric DEM for Coachella Playa is shown in Figure 18. A brief outline of the methodology used to generate DEMs for the field studies is provided below:

• Data Acquisition. High resolution imagery was acquired for each site using the eBee RTK surveygrade UAS. The eBee was flown at 200 feet above the ground surface with image overlap set at85% forelap and 75% sidelap. These settings were chosen to capture images with enoughoverlap to produce an accurate photogrammetric DEM and produce an orthophoto with aspatial resolution of approximately 1.5 cm. Ground control reference data for “visual targets”were collected across the site using a Trimble R10 Real-time Kinematic (RTK) GPS survey.

• Data Processing. The data acquired were processed using the Agisoft Photoscan Professionalsoftware suite. This photogrammetric processing includes algorithms which align photos usingtheir geolocation and matching common features within adjacent photos. Based on theresulting geometric model, the software calculates depth information for visual features fromeach camera generating a single dense point cloud. A DEM was then generated by rasterizingthe dense point cloud. During the photogrammetric process, the photos were stitched togetherbased on the geometric model results to create a seamless orthoimage. An orthoimage is animage which presents every pixel in a down-looking (on-nadir) view.

• Final Data Products. Final data products included a high resolution orthophoto in .jpg format aswell as a DEM with a vertical error of +/- 5 cm as compared to the ground control referencedata. All final geospatial products are available on the SS AQM Program Data Portal(www.saltonprogram.com).


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Site Topography(Coachella Playa)

LegendCoachella Playa Digital Elevation Model

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3.2.2 SOIL SURVEY Soil properties (e.g., soil texture, hydraulic conductivity and soil cohesion) are important considerations for DCM selection (e.g., drainage for vegetation, durability of ridges). Soil survey data for recently exposed playa surfaces around the Salton Sea do not exist. Accordingly, a soil core sampling scheme was implemented to map soil texture by depth, from which hydraulic conductivity and soil cohesion could be inferred. In addition, soil chemistry and agronomic data with depth were also collected from select soil cores to assess vegetation suitability and reclamation requirements. Soil cores for each dust control area were analyzed to develop site-specific soil maps. The sampling scheme and laboratory analysis methods facilitate precise and cost-effective collection of soil data for large areas.

The soil core sampling scheme was stratified by soil apparent electrical conductivity. Soil electrical conductivity was mapped vertically and horizontally using a DUALEM-421 meter (DUALEM). The DUALEM uses bobbin-wound coils for its transmitter and receiver. It transmits a primary magnetic field from its transmitter that induces an electrical current in the subsurface. A secondary magnetic field is created in the subsurface by the current and detected by the instrument’s receiver. The amplitude and phase of the secondary magnetic field at the receiver is then normalized to that of the primary field to determine the conductivity of the subsurface. A secondary magnetic field with a phase and amplitude that vary little from that of the primary field signifies a more conductive material. The resulting data provide conductivity profiles from 0.5m to 6.4m in 20cm depth increments with overlap between the profiles. Position data were collected continuously with the DUALEM using a Trimble Ag GPS and StarPal software (Figure 19).

FIGURE 19: PHOTO OF THE DUELEM-421 SAMPLING SOIL APPARENT ELECTRICAL CONDUCTIVITY


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Results from the survey were used to infer static soil properties (soil texture) and dynamic soil properties (salinity, moisture, etc.) through apparent electrical conductance by depth (Figure 20). The vertical variation in soil apparent electrical conductance was classified into 11 classes (Figure 21) for each 20cm depth increment to 1.5m. The number of different classes with depth per sample location were counted and then spatially interpolated to inform the sampling scheme (Figure 22). Soil core locations were then stratified by the count of the number classes representing vertical variations in soil apparent electrical conductivity. This type of soil core sampling schemes was developed for each site.

FIGURE 20: EXAMPLE SOIL APPARENT ELECTRICAL CONDUCTIVITY DATASET

FIGURE 21: CLASSIFICATION OF SOIL APPARENT ELECTRICAL CONDUCTIVITY

For each value of soil apparent electrical conductivity with a range, a conductivity class was assigned.


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Soil cores were collected for each sampling location at each field study site (250 total cores). Minimally disturbed soil cores were collected to a depth of 1.5m (5ft) with #5-TS Direct Push by Giddings Machine Company Inc. (Figure 23). Cores were collected in a 2.5in soil tube with view slots and immediately placed in a PVC tray and wrapped with plastic (Figure 23) to aid in moisture retention and to prevent salt precipitation and oxidation, which would alter the soil’s characteristics. Soil cores were then immediately transported to the laboratory for further processing.

FIGURE 23: PHOTOS OF THE #5-TS DIRECT PUSH (LEFT) AND A MINIMALLY DISTURBED SOIL CORE (RIGHT)

Soil core laboratory analysis included the following steps:

1. Photo documentation. Soil cores were split down the length of the core to expose the soilstructure and color. A high resolution photo was taken using a custom-built photogrammetryworkbench (Figure 24b). Visual, to-scale records of soil cores facilitate direct comparison tolaboratory data, depth distributions of soil texture, and QC/verification of measurements afterthe core has been discarded (Figure 24c). The photogrammetry workbench included a custom-built, automated station that uses a step motor, connected to a camera, and a Raspberry Picomputer to take pictures every 5cm along the length of the core. Individual photos were thenstitched together to create a continuous, high-resolution reference soil core photo (Figure 24a).

2. Soil Texture Estimation. Spectroradiometer readings were collected at 5cm intervals todetermine soil texture by depth. Spectral measurements were captured on the open flat


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surface of the soil core on a 5cm interval along the length of the core. At each interval, the measurement was conducted twice with a 90° rotation of the contact probe (Figure 24d). By utilizing this methodology, each of the soil cores was scanned vertically and horizontally. Each of the individual measurements was the average of 20 instantaneous readings to reduce noise and increase accuracy. These spectral measurements were then processed and correlated with a subset of soil samples analyzed for particle size distribution using a standardized methodology (Hydrometer, ASTM D7928). Regression models between the spectroradiometer and hydrometer estimates of particle size class were generated to infer particle size classes from the spectroradiometer readings (Figure 25 and Figure 26). This instrument and approach has been used in many previous studies to map different soil properties (e.g., mineral content) around the world including the Salton Sea area (Waiser et al., 2007 & Cheng-Wen et al., 2001). The limited precision and accuracy of the hydrometer method used in this study is not ideal for the calibration of the spectroradiometer measurements. It is recommended that future sampling efforts use a laboratory that can implement a more accurate and precise pipette method for soil particle size analysis (Natural Resources Conservation Service, 2007).

3. Soil Description. Following photo documentation and soil texture estimation, each core wasdescribed using standard soil survey methods (Schoeneberger et al., 2012). This includeddescriptions with depth of soil horizons, soil color, structure, and oxidation status. Followingdescriptions, sub-samples were taken and sent to Stanworth Laboratory for one or more of thefollowing analysis: particle size, soil fertility and salinity.

4. Soil Mapping. All data generated in steps 1 through 3, above, were mapped to the specific GPSlocation and depth increment and made available in the SS AQM Program Data Portal(www.saltonprogram.com). Depth distributions of soil texture from step 2 were furtheranalyzed to create spatial predictions of soil texture by depth using a radial-based functioninterpolation method (ArcMap 10.9 by ESRI Inc.) (Figure 27). The percent fines suitabilitycriteria from the surface roughening plot study were then applied to each field study site todetermine soil suitable for surface roughening and which soils required a combination of surfaceroughening and vegetation enhancement. In general, surface roughening is prescribed on finertextured cohesive soils and a combination of surface roughening and vegetation enhancement isprescribed on coarser textured well drained soils.


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FIGURE 24: PHOTOS OF SOIL LAB PROCESSING

A full-scale high-resolution soil core (A), a photo of the photogrammetry work station (B), a section of a high-resolution soil core (C), and a spectroradiometer (D).


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FIGURE 25: SAND REGRESSION MODEL

The blue line is a linear regression line. The equation of the line is y = 0.73x + 15.8. The R2 is 0.73.

The blue line is a linear regression line. The equation of the line is y = 0.63x + 4.9. The R2 is 0.61.

FIGURE 26: CLAY REGRESSION MODEL


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Figure 27: Example Soil Map (Alamo South)

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3.2.3 GROUNDWATER

Groundwater depth and quality are important considerations for vegetation establishment. Near-surface groundwater depth affects salt crust development and root zone connectivity to groundwater on exposed playa (Rosen, 1994). Groundwater access tubes were used to assess the suitability of shallow groundwater as a water source for vegetation after initial establishment with irrigation. Groundwater access tubes slotted over the upper water bearing zone were placed along transects perpendicular to the shoreline around the Salton Sea. Submersible pressure transducers and a collocated barometric pressure transducer were installed to observe the position of the water table (Figure 28). Groundwater quality variables, including redox potential, electrical conductivity and nitrate concentration, were analyzed at each access tube.

FIGURE 28: EXAMPLE DEPTH TO GROUNDWATER (POE ROAD)

Transducer measurements are continuous and validated using manual measurements. The depth of groundwater is measured below ground surface.

3.2.4 WIND DIRECTION DCMs are typically oriented perpendicular to the dominant wind direction because it confers the most dust control. Since 2010, a series of meteorological stations have been collecting wind speed and wind direction data around the Salton Sea shoreline (Figure 29). Data from the meteorological stations are used to determine the dominant wind direction for each field study site. The selection of the meteorological station is based on proximity to the site and similarity in landscape position. The dominant wind direction is determined by the mean wind direction of wind records faster than a threshold 10m wind speed assumed to initiate saltation. Using circular statistics, one standard deviation is calculated from the mean wind direction of 10m wind records faster than the threshold wind speed. An example wind record displaying the mean (i.e., dominant) wind direction and one standard deviation of the data above the threshold 10m wind speed is provided (Figure 30).


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FIGURE 30: EXAMPLE 10M WIND RECORD FROM SALTON CITY METEOROLOGICAL STATION

The mean wind direction of the 10m wind records with speeds faster than 12 meters per second (m/s) was computed (dash). One standard deviation from the mean wind direction of the 10m wind records with speeds faster than 12m/s was determined (dash dot).

3.3 DUST CONTROL MODELING Dust control planning was completed using was the Single-event Wind Erosion Evaluation Program (SWEEP). SWEEP is a module of the Wind Erosion Prediction System (WEPS), a physically based model developed by the United Stated Department of Agriculture (USDA), Agricultural Research Service (ARS) to assess soil erosion and the effectiveness of control measures in reducing PM10 emissions. WEPS is used to evaluate annual erosion potentials for specific combinations of soils, surfaces, crops, climate and roughness. SWEEP applies the same soil and erosion modules from WEPS to simulate the erosion and PM10 emission potential over a 24-hour wind event. Although SWEEP originates from an agricultural context, it has been successfully applied in the design of pilot studies for dust control measures on disturbed lands (Tatarko et.al., 2016) and playa surfaces (Schreuder & Schaaf, 2014b). Examples of dust control measures that can be evaluated with SWEEP include surface roughening and vegetation establishment.

As a design tool, SWEEP facilitates the physical investigation of different combinations of roughness elements (i.e., vegetated barrier spacing, ridge height and ridge spacing). SWEEP accepts input parameters related to field dimensions, wind barriers, soil characteristics, surface characteristics and wind conditions. Throughout this PDCP, site specific soil, surface and wind conditions were used to select values for SWEEP input parameters in a data driven approach (Section 3.3.2). To facilitate evaluation of multiple DCM scenarios, an automated modeling process was developed (Section 3.3.1).


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As described in this section, SWEEP was used to 1) evaluate the range of 10m wind speeds that can start the process of saltation for a range of surface conditions and 2) determine the wind speed and direction that starts the process of saltation after surface roughening is installed as compared to a non-roughened condition. This section describes the automation and parameterization of SWEEP, including the summarization and use of SWEEP output. Final SWEEP modeling results used to design DCMs for the field studies are provided in Section 4.

3.3.1 SWEEP AUTOMATION The SWEEP modeling process was automated to improve efficiency. The automated process is categorized into four stages, as described below:

1. In the first stage, a series of SWEEP input files, one for each model run, is modified andgenerated based on various scenarios. The range and increment of the input parameters to bevaried are specified, and the parameters to be held constant are set.

2. The second stage is to execute the SWEEP program in batch mode using the command linewindow on each input file that was created in the first stage. The method of using thecommand line window provides flexibility to execute millions of runs without manually runningeach input file through SWEEP’s graphical user interface.

3. In the third stage, a process is scripted to pull a single vector of saltation flux oriented in theupwind-to-downwind direction out of the output file. The vectors of saltation flux for eachmodel run are summarized as normalized saltation flux values.

4. The fourth stage is visualization of the result. A data table of normalized saltation flux and thevaried input variables from the first stage are generated and pulled into R statistical software fordisplay and evaluation.

3.3.2 SWEEP PARAMETERIZATION SWEEP was parameterized using data collected on exposed playa for over 10 of the more sensitive SWEEP input parameters, including wind speed, soil texture and crust stability. When available data related to a SWEEP input parameter were limited, the model input value was conservatively adjusted to over predict saltation. If no data were available, then reasonable values from similar environments (i.e., Owens Lake) were selected. Data gaps will be addressed to support continued model parameterization.

A “book-end” modeling approach was used to evaluate the range of 10m wind speeds that can start the process of saltation for a range of surface conditions, with the objective of determining realistic ends of the range. Specifically, model parameterization included the following:

• To bound the lower-end of 10m wind speeds that could start the process of saltation, a coarsenon-crusted surface was parameterized using data by selecting the 10th percentile forparameters that decrease the saltation flux and the 90th percentile for parameters that increasethe saltation flux.


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• To bound the upper-end 10m wind speeds that could initiate the process of saltation, a finecrusted surface was parameterized using data by selecting the 90th percentile for parametersthat decrease the saltation flux and the 10th percentile for parameters that increase thesaltation flux.

A “before-and-after” modeling approach was used to determine the wind speed and direction that starts the process of saltation after surface roughening is installed as compared to a non-roughened condition. Specifically, model parameterization included the following:

• For parameters unaffected by surface roughening, such as soil texture, the mean values wereselected and held constant for both the non-roughened and roughened conditions.

• For crust-related parameters adversely affected by surface roughening, such as crust thicknessand surface crust fraction, the mean value was used for the non-roughened condition and the10th percentile was used for the roughened condition.

• For parameters intentionally increased by surface roughening, such as ridge height and randomroughness, reliable values were selected for the non-roughened condition and the mean of datareflecting surface roughened surfaces was used for the roughened condition.

Additional parameters are described in the following sections, including 24-hour wind speeds, soil layers, soil surface and surface roughened variables.

3.3.2.1 TOPSOIL VARIABLES

The objective of this section is to demonstrate the data used to select modeled values for the topsoil variables. Over 10,000 hyperspectral measurements of soil texture and over 250 field estimates of surface characteristics on exposed playa were collected and analyzed. Two cases for each modeling approach were parameterized (Table 3). Histograms of percent sand (Figure 31) and surface crust thickness (Figure 32) overlain by the value selected per modeled condition are included to visualize topsoil parameterization.

TABLE 3: SWEEP MODELED CONDITIONS

Modeled Condition Modeling Approach Objective Fine Book-end of wind speeds that

could start the process of saltation

Parameterize a saltation-resistant surface

Coarse Book-end of wind speeds that could start the process of saltation

Parameterize a surface susceptible to saltation

Non-roughened Before and after of roughened vs. non-roughened

Parameterize a common surface before surface roughening is performed

Roughened Before and after of roughened vs. non-roughened

Parameterize a common surface after surface roughening is performed


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FIGURE 31: HISTOGRAM OF PERCENT SAND AND SWEEP VALUE SELECTION

The total number of observations used to generate the histogram was 10,678. The vertical lines represent the percent of sand used in each modeled condition.

FIGURE 32: HISTOGRAM OF SURFACE CRUST THICKNESS AND SWEEP VALUE SELECTION

Surface crust thickness data were collected by averaging three crust thickness measurements at sampling locations. The total number of observations used to generate the histogram was 254. The vertical lines represent the surface crust thickness used in each modeled condition. The roughened condition was adjusted down from the non-roughened condition due to crust disturbance induced during surface roughening.


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3.3.2.2 SURFACE ROUGHENED VARIABLES

Experimental surface roughening performance monitoring data (i.e., high-density LiDAR) were collected. Over 2,000 surface roughening elements (i.e., ridge height and random roughness) were extracted from the high-density LiDAR (Section 3.5.1). Due to the underlying uncertainty in feature extraction, values were conservatively adjusted from the mean. The remainder of the data-driven SWEEP parameterization values are provided in Table 4 and can be visualized in Appendix A.

TABLE 4: SWEEP MODEL VALUE SELECTION

Parameter

Value Modeled Condition

Units Coarse Fine Non-

Roughened Roughened Percent Clay 4 25 14 14 (%) Percent Silt 8 49 36 36 (%)

Surface Crust Fraction 0.03 0.75 0.4 0.03 (m2/m2)

Loose Material on Crust 1 0.03 0.11 0.11 (m2/m2) Crust Stability 0 2 1 0.5 ln(J/kg)

Allmaras Random Roughness 3 5 5 30 (mm) Ridge Height 0 0 0 350 (mm)

3.3.2.3 TWENTY-FOUR HOUR WIND SPEED TIME SERIES

The SWEEP model requires an hourly time series of wind speeds observed at the 10m anemometer height. A scale of maximum 24-hour wind speed time series observed at 10m was modeled using a cosine function (Figure 33). This scale of maximum 24hr wind speed time series was used to stress the soil system until it saltated for each modeled condition. The magnitude of saltation was considered and summarized as normalized saltation flux.


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FIGURE 33: SCALE OF MAXIMUM 24HR WIND SPEED TIME SERIES AT 10M ABOVE GROUND SURFACE

The boxplots are generated from 219,311 validated hourly wind records from meteorological stations placed around the Salton Sea from 2010 through 2014. The light blue dots above the top whiskers are outliers defined as greater than the third quantile plus 150% of the inter-quantile range. The scale of modeled maximum 24hr wind speed time series at 10m are displayed as lines.

3.3.3 NORMALIZED SALTATION FLUX Normalized saltation flux is proportional to the field scale PM10 flux (Ravi et al., 2011). Summarizing SWEEP model results as normalized saltation flux (NSF) is useful because it facilitates the comparison of saltation flux between model results using only one value. SWEEP produces an estimated saltation flux for each grid cell in the modeling domain. An upwind-downwind line is drawn along the modeled wind direction, starting from where the wind enters the modeling domain to where it exits the modeling domain. A value was extracted for each raster cell that intersects the upwind-downwind line and assigned to a data vector generating a downwind saltation flux profile. The data vector containing the downwind saltation flux profile is summed, generating a cumulative saltation flux value. To compare two modeling results, each cumulative saltation flux is divided by the larger of the two, producing values ranging from 0 to 1. NSF is the magnitude of saltation flux relative to another condition. An NSF value of 0 should be interpreted as “no saltation occurred.” An example is provided in Figure 34.


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FIGURE 34: EXAMPLE OF NORMALIZED SALTATION FLUX

Two model conditions are shown by row. The left column of plots contains 2-D summaries of saltation flux within the SWEEP modeling domain. The center column of plots contains 1-D summaries of downwind saltation flux profiles. The right column is a workspace where the cumulative saltation fluxes are summarized as NSF.

3.3.4 SWEEP RESULTS AND TRENDS This section describes SWEEP results and trends for wind speeds required to initiate saltation on a range of surface conditions and for wind speeds required to initiate saltation on roughened versus non-roughened surfaces.

3.3.4.1 WIND SPEEDS REQUIRED TO INITIATE SALTATION

As described in Section 3.3.2, a series of models was generated and analyzed to evaluate the range of 10m wind speeds that can start the process of saltation for a range of surface conditions. A “bookend” modeling approach was used to explore the ends of a reasonable range of expected responses. A scale of maximum 24hr wind speeds observed at 10m was used to stress each modeled condition to saltate. Each model result was normalized by the coarse soil at the fastest time series of wind speeds (i.e., 22 m/s wind speed time series observed at 10m) (Figure 35).


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The modeling results suggest that the range of 10m wind speeds required to initiate the process of saltation is approximately 9 to 14m/s. The 10m wind speed required to initiate saltation for a bare, coarse, non-crusted surface is approximately 9m/s. The 10m wind speed required to initiate saltation for a bare, fine-crusted surface is approximately 14m/s.

FIGURE 35: SWEEP MODELING RESULTS OF WIND SPEEDS REQUIRED TO INITIATE SALTATION

Values for inputs parameters for the coarse non-crusted and fine-crusted modeled conditions are described in Sections 3.3.2.1 and 3.3.2.3. The 10m wind speeds required to initiate saltation were determined by reading the fastest 24hr wind speed time series at 10m with a normalized saltation flux value of 0.

3.3.4.2 SALTATION ON ROUGHENED VERSUS NON-ROUGHENED SURFACES

As described in Section 3.3.2, a series of models was generated and analyzed to determine the wind speed and direction that starts the process of saltation after surface roughening is installed as compared to non-roughened conditions. A scale of maximum 24hr wind speeds time series at 10m was used to stress each modeled condition to saltate. Each model result was normalized by the NSF value for a non-roughened condition at the fastest time series of wind speeds (Figure 36).

The modeling results suggest that the 10m wind speed required to initiate the process of saltation is increased for the roughened condition when compared to a non-roughened condition. The 10m wind speed required to initiate saltation for the worst case wind direction a wind event oriented 90 degrees off of the dominate wind direction was increased from to 10m/s to 17m/s. The 10m wind speed required to initiate saltation for a wind event from the dominate wind direction was increased from 10m/s to 20m/s.


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FIGURE 36: SWEEP MODELING RESULTS FOR SALTATION ON ROUGHENED VERSUS NON-ROUGHENED SURFACES

Values for input parameters for non-roughened and roughened modeled conditions are described in Sections 3.3.2.1 and 3.3.2.3. The 10m wind speeds required to initiate saltation were determined by reading the fastest 24hr wind speed time series at 10m with an normalized saltation flux value of 0.

3.4 FIELD STUDY SPECIFICATIONS The purpose of the field studies in this PDCP is to gain experience scaling, adapting and combining a combination of DCMs (e.g., surface roughness and vegetation) to efficiently achieve proactive dust control at a larger scale. This section describes the selection of DCMs based on soil texture, orientation to the wind direction, specifications for implementation and the layout of associated site features, such as access routes and irrigation conveyance.


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3.4.1 DUST CONTROL MEASURE SELECTION

The top 60cm is considered an adequate depth for DCM planning because it is the maximum depth of tillage implements used for surface roughening. Soil cohesion and hydraulic conductivity are inferred from soil texture within the top 60cm. In general, surface roughening is prescribed on finer textured, cohesive soils (with greater than 35% fines) that produce erosion resistant clods. A combination of surface roughening and vegetation enhancement is prescribed on coarser textured, well drained soils (with less than 35% fines). Well drained soils are identified by hydraulic conductivity (Natural Resources Conservation Service, 2016) (Figure 37).

FIGURE 37: SATURATED HYDRAULIC CONDUCTIVITY VERSUS PERCENT FINES

The soil texture threshold of 35% fines in the top 60cm is used to prescribe the mosaic of site-specific DCMs. Soils with less than 35% fines demonstrate fast hydraulic conductivity. Soils greater than 35% fines demonstrate slow hydraulic conductivity. Results of hydraulic conductivity were modeled using Rosette Lite.

3.4.2 DUST CONTROL MEASURE ORIENTATION The dominant wind direction informs the orientation of DCMs (e.g., direction of ridge roughness and vegetated barriers). The threshold 10m wind speed assumed to initiate the process of saltation for the example dataset was set to 12m/s (Figure 35). Wind direction data below the threshold wind speed were removed to isolate wind direction above the threshold (Figure 30). The optimal orientation is perpendicular to the mean wind direction for hourly wind events above the threshold 10m wind speed. In field conditions where DCM orientation cannot be directly perpendicular, then a range of acceptable orientation is used. The range of acceptable roughness orientation is set perpendicular to the mean wind direction to +/- one standard deviation for the data above the threshold 10m wind speed as displayed in Figure 38.


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FIGURE 38: EXAMPLE WIND ROSE AND ROUGHNESS ORIENTATION

This windrose plot includes the dominant (i.e., mean) wind direction (black dash) and +/- one standard deviation from the mean wind direction (black dash dot). The optimal roughness orientation (purple dash) is drawn perpendicular to the dominant wind direction. The range of acceptable roughness orientations (purple dash dot) is drawn perpendicular to the wind direction +/- one standard deviation from the mean.

3.4.3 DUST CONTROL MEASURE SPECIFICATIONS DCMs recommended for the field studies are surface roughening and surface roughening with vegetation. Specifications for each are described below.

3.4.3.1 SURFACE ROUGHENING

Surface roughening provides dust control on exposed playa by decreasing the wind velocity at the surface and by physically trapping windblown sand in furrows. Dust control effectiveness is dependent on the geometric characteristics of ridges, including ridge spacing, furrow depth, interrow spacing and ridge height (Figure 39). Total displacement, ridge height and ridge spacing are produced by the tillage implement. Commonly used tillage implements are the deep moldboard plow (i.e., bull plow) and a series of shallow moldboard plows (i.e., a modified switch plow). The bull plow is generally used to produce oriented roughness and the modified switch plow is generally used to produce random roughness.


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FIGURE 39: ORIENTED ROUGHNESS TERMINOLOGY

Ridge height is defined at one half of total displacement. For oriented roughness with irregular ridge spacing, ridge spacing is defined as the average ridge spacing.

The pattern of roughening is specified at oriented roughness coupled with interrow random roughness (Figure 3). The oriented roughness is designed to protect against large wind events from the predominant wind direction (Section 3.3). For all sites, the target ridge height is set to 45cm and the maximum ridge spacing is set to 3m. The interrow random roughness is designed to protect against a large wind event from any wind direction (Allmaras et al., 1966; Chu et al., 2012; Woodruff & Siddoway, 1965). The ridge spacing required for effective dust control is determined from site-specific SWEEP modeling.

3.4.3.2 VEGETATION ESTABLISHMENT

Vegetated barriers are continuous, linear strips of vegetation that act as porous barriers to protect exposed playa from erosion. Vegetated barriers can be established in furrows or on constructed beach ridges. The effectiveness of this DCM is based on the vegetated barrier continuity, aerodynamic porosity, barrier height and barrier spacing (Woodruff & Siddoway, 1965). Field study sites are designed for maximum vegetated barrier continuity. Aerodynamic porosity is dependent on the species. Allenrolfea occidentalis is the target species for this DCM and has a mean aerodynamic porosity of 12%, which is adequate to reduce the near surface wind speed (Cornelis & Gabriels, 2005). Barrier height is also dependent on the species. The barrier height is set to greater than 110cm, which is the mean height of mature Allenrolfea occidentalis observed around the Salton Sea (Salton Sea Air Quality Team, 2016b). Barrier spacing is site-specific and depends on surface soil characteristics and nearby wind records.


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Sand abrasion is a plant stressor and, in some cases, appears to cause plant mortality in juvenile plants (Figure 40). Coupling bull plow furrows with vegetated barriers minimizes sand motion within the DCM, thus protecting vegetation barriers until establishment.

FIGURE 40: SAND ABRASION INDUCED PLANT MORTALITY

Notice the recently deceased Suaeda nigra underlain by nearly a foot of aeolian sand deposition.

Agronomic inputs are required for successful vegetation establishment. Seeding, reclamation (desalinating soil), irrigation, fertilizer and compost should be supplied to achieve maximum seedling germination, plant growth and vegetated barrier continuity across a variety of soil textures and groundwater depths, as described in Section 2.2. The 2017 Vegetated Barrier Seed Mix includes 8 locally collected—and thus locally adapted—native species tolerant of drought and salinity (Table 5). The dominant species is iodine bush (Allenrolfea occidentalis). Irrigation and reclamation rates are dependent upon site-specific topography and water supply quality and quantity. Irrigation for vegetation establishment should commence in late fall, when the difference between precipitation and reference evapotranspiration is decreasing (Figure 41). Compost and fertilizer are applied as a band along the centerline of the vegetated barrier. The compost is an aged manure applied at a rate of 0.04 m3/m. The fertilizer is APEX 22-6-8 NPK PLUS applied at the rate of 0.1 kg/m (Salton Sea Air Quality Team, 2016b).

TABLE 5: 2017 VEGETATED BARRIER SEED MIX

Species Seeding Rate (live seed/ft2)

Allenrolfea occidentalis 19.8 Atriplex canescens var. macilenta 0.1 Atriplex hymenelytra 0.1 Atriplex lentiformis 2.4 Atriplex polycarpa 0.6 Bolboschoenus maritimus ssp. paludosus 0.4 Sesuvium verrucosum 1.1 Suaeda nigra 1.4


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FIGURE 41: MONTHLY AVERAGE PRECIPITATION AND REFERENCE EVAPOTRANSPIRATION AT WESTMORELAND

Developed from California Irrigation Management Information System (CIMIS) station #41, Calipatria/Mulberry, from 1983 to 2017. ETo refers to reference evapotranspiration.

3.4.4 SITE LAYOUT

Additional considerations for site layout include irrigation and water supply infrastructure and site access routes. Irrigation and water supply infrastructure are site-specific. Access routes are minimized to those required for site implementation and maintenance. Access routes are typically mulched to reduce wind erosion. Roughness is oriented perpendicular to the dominate wind direction or within the range of acceptable roughness orientations. Two additional bull plow furrows are implemented parallel to the access routes to prevent vehicle access within the dust control measures. Culverts may be installed for irrigation conveyance. Dust control area layouts for the proposed field studies are provided in Section 4.

3.5 DUST CONTROL PERFORMANCE MONITORING After construction of each site, performance characteristics will be monitored including roughness elements and aerometric monitors (e.g., wind speed, sand motion, upwind [PM10] and downwind [PM10]). Monitoring will be similar for all field studies. As-built survey data collected after construction will be used to site meteorological stations, video surveillance, sand motion monitoring equipment (e.g., Sensits and sand catch) and upwind/downwind PM10 monitors. Data from these instruments will be used to verify dust control performance relative to the design criteria. Performance monitoring data will also be used to define triggers for maintenance (e.g., scale, timing, and method) necessary to maintain a stabilized surface.


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3.5.1 ROUGHNESS ELEMENTS Routine quantitative characterization of roughness elements using topographic data is essential for accurately mapping, classifying and evaluating performance of the field studies over time. Accurate topographic data in the form of a LiDAR point cloud or raster-based DEMs will be used in combination with terrain analysis techniques to quantify roughness elements features (e.g., ridge height, ridge spacing, random roughness, furrow depth) (Figure 39) for each field study. Once LiDAR point cloud data are acquired, quantifying the morphological attributes of roughness elements is attainable in any standard GIS and statistical software package. The methodology used to routinely quantify geomorphometric roughness elements includes the following steps:

1. Acquire Topographic Data. The first step is to acquire topographic elevation data with sufficientresolution, accuracy and precision to capture fine scale variability of the roughening elements.An UAS will be used to capture elevation data with a LiDAR sensor. Specifically, the pulseaerospace Vapor 55 survey grade UAS with a Reigel VUX1 LiDAR sensor will be used to capturehigh resolution topographical data. UAS LiDAR systems were chosen based on findings from thesurface roughening plot study. This study demonstrated that the UAS based LiDAR was moreaccurate, reliable and repeatable than low altitude photogrammetric methods. LiDAR canprovide ridge height monitoring results similar to ground-based survey methods (Section 2.1.5).In addition, full waveform, multiple return LiDAR also provides quantification of vegetationbased roughness, including vegetation height, width, density and continuity.

2. Identify and Characterize Roughness Elements. Surface roughening and vegetation roughnesselements will be identified, quantified and extracted from the LiDAR data. This includes (but isnot limited to): ridge height, ridge spacing, vegetation height, vegetation continuity, furrowdepth, inter-row spacing and inter-row random roughness. Automated classification of theseelements will be accomplished using object-based image analysis software to extract featuresfrom the LiDAR data and attribute them to small polygons, enabling time series comparison andmapping. Examples of initial quantification and mapping of ridge height and random roughnessare provided (Figure 42 and Figure 43).

3. Reporting. A reporting grid will be determined for each site to provide feedback on the surfaceroughening and vegetation conditions over time. Standard summary statistics (minimum,maximum, mean, median, range and standard deviation) will be summarized for all roughnesselements. The frequency of monitoring will be bi-monthly for the first 6 months. After the firstsix months, the monitoring frequency may be reduced to a quarterly or bi-annual basis for theduration of the study.


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3.5.2 AEROMETRIC MONITORS Sand motion monitoring equipment (i.e., Sensits and Cox Sand Catchers) provides quantitative measurements of horizontal saltation flux. Sand motion monitoring equipment will be sited based on as-built survey data collected after construction. The sand motion monitoring equipment will be distributed throughout the site to evaluate DCM performance relative to the design criteria. In addition, the horizontal saltation flux monitoring data can be used to validate SWEEP results of modeled saltation flux (Wagner, 2013).

Portable PM10 BGI monitors (obtained through a California Air Resources Board grant) will be installed upwind and downwind prior to forecasted high wind events and then removed after each event. The portable PM10 monitors will be rotated among each site. Each site will be monitored during at least one high wind event per year; however, this data collection is dependent on the number of high wind events that occur.

4 PROPOSED 2017/2018 FIELD STUDIES Field studies integrate the individual concepts and knowledge gained in the plot studies into a combination of DCMs designed to meet dust control objectives cost effectively at a large scale. In preparation for the 2017/2018 dust season, three priority dust source areas were identified for field studies. The proposed field studies are Alamo South, Coachella Playa, and New River West. Implementation of the field studies is subject to funding authorized by the QSA Joint Powers Authority. In addition, the field scale pilot studies may be refined based on landowner input, to accommodate anticipated projects by stakeholders or the SSMP, or based on field conditions at the time of construction.

Section 3 described the general planning process for field study site characterization, modeling, specification and monitoring. Site-specific characterization, modeling and specification for each field study is described in the following sections. Surface roughening and vegetation establishment dust control measures are prescribed for all three sites.

4.1 ALAMO SOUTH FIELD STUDY Alamo South dust control area is approximately 270 acres located partially on the Alamo River Delta south of Alamo River. Transect based PI-SWERL measurements consistently demonstrated high emissions potential at this site, particularly in areas exposed for 2 or more years. Erosional source delineations completed during 2015/2016 and 2016/2017 dust seasons mapped 105 acres as severely eroded. This area is delineated as high priority and consists of a long, stranded shoreline oriented north to south, composed of sandy soil with free sand on the surface (Figure 44a). Approximately 70 acres were delineated as medium priority, characterized by features of wind erosion and a soft friable crust. The remaining 95 acres at the site were delineated as low priority due to periodic inundation by the Salton Sea during westerly wind events. This area had no noticeable features of wind erosion, but is included in the field study footprint due to an anticipated high emissions potential as the Salton Sea


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continues to recede. Surface roughening is prescribed for 210 acres and vegetation establishment is prescribed for 60 acres.


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4.1.1 SITE CHARACTERIZATION Site characterization is primarily based on topographic survey, soil survey, groundwater depth and wind records. Figure 44 shows the relative location of the site to meteorological stations, a high-resolution DEM and a soil map of average percent fines in the top 60cm. Groundwater depth was inferred based on observations at the New River West site, which has similar landscape positions and proximity to fresh water recharge boundaries. Observations of depth to groundwater at New River West suggest a shallow water table (1-3m below ground surface level) that remains at a nearly constant depth throughout the year.

The Sonny Bono meteorological station was selected to identify the dominant wind direction (Figure 45). It is important to note that Obsidian Butte is positioned west-southwest of the Sonny Bono meteorological station, which may slow the wind speeds recorded at the station. The mean (i.e., dominant) wind direction for wind events greater than 12m/s is 265 degrees. The standard deviation of observations of wind direction above 12m/s is 12 degrees.

FIGURE 45: WIND SPEED VERSUS WIND DIRECTION AT SONNY BONO METEOROLOGICAL STATION

The data displayed is from 5-year validated wind record (2010-2014) observed at 10m above the ground surface level.


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4.1.2 DUST CONTROL MODELING The SWEEP model was used to evaluate the effectiveness of vegetated barrier spacing of mature Allenrolfea occidentalis and ridge spacing at Alamo South by using site-specific soil texture and wind speed data. The vegetated barrier height was set to 1.1m, which is the mean of mature Allenrolfea occidentalis on the playa observed as a part of the vegetation enhancement plot study. The 99.99th percentile of the hourly 10m wind speed observed at the Sonny Bono meteorological station was used to identify the 24hr wind speed time series (e.g., 20m/s) for input into SWEEP (Figure 33). The soil texture values selected from data collected at Alamo South are analogous to the methods described in Section 3.3.2. The vegetated barrier spacing required to achieve a normalized saltation flux of less than 0.05 was 50m, however, a conservative planning approach was taken and a 30m spacing is specified (Figure 46). The ridge spacing is specified as less than 3.5m to achieve a normalized saltation flux less than 0.05 (Figure 47).

FIGURE 46: NORMALIZED SALTATION FLUX VERSUS VEGETATED BARRIER SPACING AT ALAMO SOUTH

These SWEEP modeling results indicate that a vegetated barrier spacing of 60m will reduce saltation to 5% of the saltation that occurs from a coarse non-roughened surface. The black dashed line represents the target normalized saltation flux value of 0.05.


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FIGURE 47: NORMALIZED SALTATION FLUX VERSUS RIDGE SPACING BY RIDGE HEIGHT AT ALAMO SOUTH

These SWEEP modeling results indicate that a ridge spacing of less than 3.5m will reduce saltation to less than 5% of the saltation that occurs from a surface roughened at a ridge spacing of 10m. The black dashed line represents the target normalized saltation flux value of 0.05.

4.1.3 SPECIFICATIONS The following sections describe the specifications of surface roughening and vegetation establishment at Alamo South. The southern 50 acres are excluded from the design due to a potential land use conflict with the Red Hill Bay shallow flood project. The site layout is shown on Figure 48.


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4.1.3.1 SURFACE ROUGHENING DUST CONTROL MEASURE

Surface roughening was prescribed for approximately 160 acres, consistent with the dust control design criteria described in Section 3.4. The optimal roughness orientation was set perpendicular to the mean dominant wind direction at 355 degrees. The range of acceptable roughness orientation was set to +/- one standard deviation of the optimal roughness orientation (i.e., 343-367 degrees) (Figure 49).

FIGURE 49: WINDROSE WITH ROUGHNESS ORIENTATION AT ALAMO SOUTH

This windrose displays all the validated data for wind speeds greater than 12m/s from the Sonny Bono meteorological station during the period of 2010-2014. This windrose plot includes the dominant (i.e., mean) wind direction (black dash) and +/- one standard deviation from the mean wind direction (black dash dot). The optimal roughness orientation (purple dash) is drawn perpendicular to the dominant wind direction. The range of acceptable roughness orientations (purple dash dot) are drawn perpendicular to the wind direction +/- one standard deviation from the mean.

4.1.3.2 VEGETATION ESTABLISHMENT DUST CONTROL MEASURE

Vegetation establishment is prescribed for approximately 40 acres, consistent with the general dust control design criteria described in Section 3.4.1. Site-specific considerations are described below.

The planting bed will be a shallow sloped bull plow furrow to allow for in-furrow vegetation establishment and irrigation (Figure 50). A native seed drill will be used to sow seed along a 3ft planting width.


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FIGURE 50: CROSS SECTION OF A SHALLOW SLOPED FURROW AS A PLANTING BED

The Alamo River is the irrigation water supply. A pump and sand filter will be placed at the diversion point (an unimproved boat launch at the northern end of the site). The sand filter is specified to remove suspended particles greater than 0.15 mm and tamarisk seed. Active (i.e., pumped) furrow irrigation will be implemented. The bull plow furrows will be 60cm deep with blocked ends and slightly off contour. The furrow heads will be located on the upslope end and will be pre-graded to a near constant slope fit to topography.

At the Alamo North plot study, it was observed that a single large pulse of water down a hand-seeded sandy textured bull plow furrow was sufficient to establish a continuous hedge row. An unsteady flow hydraulic model (WinSRFR by USDA-ARS; Bautista et al., 2009) was used to evaluate furrow length (500m), inflow rate (160 gallons per minute for a single furrow) and cutoff time (6 hours) to achieve this initial pulse. An initial pulse of at least 30cm deep water along the entire length of the furrow is prescribed. The optimal irrigation schedule for successful vegetation establishment in bull plow furrows across different soil types and groundwater depths will be refined over time.

Once the initial irrigation schedule was determined, the pump requirements were specified. The pump needs to produce at least 640 GPM with a major friction loss of 14ft of water through a 10” aluminum pipe. There is a 2ft elevation increase from the water source to the pump location. The elevation difference between pumping location and the highest discharge point is negligible, while the elevation drop from the pumping location to the lowest discharge point is roughly 3ft. The number of furrows grouped together to receive irrigation water at the same time is 4, which will reduce the operation time while remaining below a discharge rate specified for commercially available portable water filtration products. Subsequent pulses will be triggered by irrigation and vegetation monitoring.

4.2 COACHELLA PLAYA FIELD STUDY The Coachella Playa dust control area is approximately 250 acres located on the northern edge of the Salton Sea near the Whitewater River Delta and west of the Whitewater River. Approximately 80 acres were identified as high priority and have been exposed for over 10 years (Figure 51a). This highly


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eroded area consists of a sandy soil with free sand on the surface that transitions to an efflorescent salt crust with a thick, unconsolidated high sub crust to the Northwest. Large dust plumes during high wind events have been observed originating from this area. Approximately 52 acres were delineated as medium priority, characterized by intermittent features of wind erosion and a soft friable efflorescent crust that formed after precipitation or flood events. The remaining 118 acres at the site were delineated as low priority due to periodic inundation by the Salton Sea as well as shallow groundwater maintaining moist conditions near the surface. This area had no noticeable features of wind erosion, but is included in the field study footprint due to anticipated high emissions potential of these soil conditions as the Salton Sea continues to recede. Surface roughening is prescribed for 230 acres and vegetation establishment is prescribed for 20 acres.

4.2.1 SITE CHARACTERIZATION The relative location of the site to meteorological stations, the relative location of the groundwater access tubes to the site, a high-resolution DEM and a soil map of average percent fines in the top 60cm are shown in Figure 51.

Groundwater access tubes were installed in a transect perpendicular to the shoreline to evaluate groundwater depth to assess the shallow aquifer’s ability to support vegetation establishment (Figure 52). Groundwater depths observed on the furthest upslope access tube (AT-13A) are 4.3ft deep on average and oscillated between 3.2ft in the winter and 5.3ft in the summer. The depth to groundwater at AT-11A appears to be affected by the transient position of the shoreline. During the dry period (e.g., May through November) the timing of sharp groundwater depth changes correlates with wind events coming from 135 to 140 degrees (data not shown). Due to wind pushing the Sea inland during southeasterly wind events, an ephemeral recharge boundary can be located on top of AT-11A. The presence of this ephemeral recharge boundary has implications for the expected salinity of the shallow aquifer and the placement of furrows near the shoreline.

The 1001 meteorological station and Torres Martinez meteorological station were evaluated for this site. The 1001 meteorological station was selected because it is located within the site boundary on exposed playa. The wind records used to generate the design roughness orientation at Coachella Playa included the 2016 wind record observed at 6m above ground surface (Figure 53). Only one wind record exceeded 12 m/s at both the Torrez Martinez and 1001 meteorological stations; therefore, the threshold wind speed was reduced to 8.5m/s to capture the top percentile of the data, which is enough data to identify a mean wind direction. The dominant wind direction for wind events greater than 8.5 m/s was set to 314 degrees


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FIGURE 52: DEPTH TO GROUNDWATER TIME SERIES AT COACHELLA PLAYA

Transducer measurements are continuous and validated using manual measurements. The depth of groundwater is measured below ground surface.

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FIGURE 53: WIND SPEED VERSUS WIND DIRECTION AT THE 1001 METEOROLOGICAL STATION (2016)

The anemometer height is 6m above the ground surface. Due to the lack of wind speed data above 12m/s, the threshold wind speed (P) was set to the 99th percentile of the data, a value of 8.5m/s.


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4.2.2 DUST CONTROL MODELING The SWEEP model was used to evaluate the effectiveness of vegetated barrier spacing of mature Allenrolfea occidentalis and ridge spacing at Coachella Playa by using site-specific soil texture and wind speed data. The 99.99th percentile of the hourly 10m wind speed record observed at the Torrez Martinez meteorological station was used to identify the 24hr wind speed time series (e.g., 17m/s) used to stress the soil system (Figure 33). The soil texture values selected from data collected at Coachella Playa are analogous to the methods described in Section 3.3.2. The vegetated barrier spacing was set to 50m to achieve a normalized saltation flux less than 0.05 (Figure 54). The ridge spacing was set to less than 7m to achieve a saltation flux less than 0.05 (Figure 55).

FIGURE 54: NORMALIZED SALTATION FLUX VERSUS VEGETATED BARRIER SPACING AT COACHELLA PLAYA



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FIGURE 55: NORMALIZED SALTATION FLUX VERSUS RIDGE SPACING BY RIDGE HEIGHT AT COACHELLA

These SWEEP modeling results indicate that a ridge spacing of less than 5m will reduce saltation to less than 5% of the saltation that occurs from a surface roughened with a ridge height of 35cm at a ridge spacing of 10m. The black dashed line represents the target normalized saltation flux value of 0.05.

4.2.3 SPECIFICATIONS The following sections describe the specifications of surface roughening and vegetation establishment at Coachella Playa. Surface roughening is prescribed for approximately 230 acres and vegetation establishment is prescribed for approximately 20 acres. The site layout is shown on Figure 57.


Surface roughening is prescribed for approximately 230 acres, consistent with the dust control design criteria described in Section 3.4. The optimal roughness orientation was set to 224 degrees, perpendicular to the dominant wind direction (Figure 56). There was insufficient data above the threshold wind speed to support a statistically based range of acceptable roughness orientation.


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FIGURE 56: WINDROSE AT 1001 METEOROLOGICAL STATION

This windrose displays all the validated data for wind speeds greater than 8.5m/s from the 1001 meteorological station during the 2016 calendar year. This windrose plot includes the dominant (i.e., mean) wind direction (black dash). The optimal roughness orientation (purple dash) is drawn perpendicular to the dominant wind direction.


Vegetation establishment is prescribed for approximately 20 acres, consistent with the general dust control design criteria described in Section 3.4. Site-specific considerations are described below.

Natural vegetation establishment on exposed playa typically occurs on beach ridges (Salton Sea Air Quality Team, 2016b). To replicate these conditions, the planting bed will be a constructed beach ridge 125m in length. The beach ridge is constructed by removing the upper saline soil and building a ridge from the underlying soil (Figure 58).

Drip irrigation from a water tank is the identified water source because there is not a readily accessible surface water source. Subsurface drip is identified as the most efficient irrigation method. The drip irrigation will have pressure-compensating emitters spaced at 20cm with a flow rate of 1 L/hour. The system will include a single pump designed to deliver 35 gallons per minute and maintain a head in the range of 60-90ft. The 12 laterals will be irrigated simultaneously. Each irrigation event will require approximately 1,000 gallons.


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Figure 57: Site Layout for the Coachella Playa Field Study

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FIGURE 58: CROSS SECTION OF A CONSTRUCTED BEACH RIDGE

The irrigation tank will be at the northern end of the site. A water conveyance line will connect the tank to the heads of the laterals. The irrigation schedule will begin in late fall. It will include three irrigation events per week during germination (approximately two months), two irrigation events per week through establishment (approximately four months) and one irrigation event per week for the last six months to sustain vegetation through the first summer.

Vehicle access routes will parallel bull plow furrows to restrict off-highway vehicle (OHV) traffic in the site. A walking path is located next to the conveyance line to provide irrigator access to the lateral heads.

4.3 NEW RIVER WEST FIELD STUDY The New River West dust control area is approximately 350 acres4 located on the New River Delta west of New River (Figure 59). The site is bordered by the Trifolium 12 drain to the south. Approximately 60 acres of the site were delineated as high priority during the 2015/2016 and 2017/2018 dust seasons (Figure 59a). This highly eroded feature consists of a long, stranded shoreline oriented north to south, composed of sandy soil with free sand on the surface that transitions to a friable salt crust on the edges. Approximately 170 acres were identified as medium priority, characterized by intermittent features of wind erosion and a soft friable efflorescent crust that consistently formed after precipitation events or inundation periods. This condition was unique to the New River West and resulted in very soft friable efflorescent salt crusts immediately after precipitation events. Emissions potential measured by the

4 The extent of this field study may be refined based on landowner permission to implement the study or to accommodate the State’s Species Conservation Habitat Project at New River West.


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PI-SWERL demonstrated that these surfaces had high emissions potential at much lower wind speeds as compared to other salt crust types around the Sea. The remaining 120 acres of the site were delineated as low priority due to periodic inundation by the Salton Sea during westerly wind events. This area had no noticeable features of wind erosion, but is included in the field study footprint due to anticipated high emissions potential as the Salton Sea continues to recede.

Approximately 100 acres of this proposed site is owned by the Bureau of Land Management and IID does not currently have permission to implement this field study on the BLM-owned land. In addition, the State’s Species Conservation Habitat (SCH) – New River West Project is planned for this area (Section 4.3.4). Accordingly, this field study may be significantly refined or not implemented as described below.

4.3.1 SITE CHARACTERIZATION The relative location of the site to meteorological stations, the relative location of the groundwater access tubes to the site, a high-resolution DEM and a soil map of average percent fines in the top 60cm are shown in Figure 59.

The New River provides a freshwater recharge boundary along the eastern edge of the site. The groundwater access tube transect is located near the mouth of the New River. Analogous to the Coachella Playa site, the access tube record most proximal to the Salton Sea recorded sharp recharge events likely caused by inundation due to westerly wind events. The central and distal groundwater access tubes demonstrate a water table between 5ft and 6ft below ground surface with an annual fluctuation of less than 1ft (Figure 60). This record suggests that the near surface aquifer is connected to a nearby recharge boundary that should provide enough water to support vegetation establishment at the site.

New River West is positioned between the abandoned Naval Salton Sea Test Base and Sonny Bono meteorological stations, both of which contain 5-year validated datasets. The Sonny Bono meteorological dataset was selected due to the similar landscape position between the site and the location of the station. The dominant wind direction for wind events greater than 12 m/s was set to a mean of 265 degrees. The standard deviation of observations of wind direction above 12 m/s was 12 degrees (Figure 45).

4.3.2 DUST CONTROL MODELING The SWEEP model was used to evaluate the effectiveness of vegetated barrier spacing of mature Allenrolfea occidentalis and ridge spacing at New River West by using site-specific soil texture and wind speed data. The 99.99th percentile of the hourly 10m wind speed record observed at the Sonny Bono meteorological station (Figure 45) was used to identify the 24hr wind speed time series (e.g., 20m/s) used to stress the soil system (Figure 33). The soil texture values selected from data collected at New River West are analogous to the methods described in Section 3.3.2. The vegetated barrier spacing was specified at 30m to achieve a normalized saltation flux of less than 0.05 (Figure 61). The ridge spacing


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was specified as less than 3.5m and ridge height set to 35cm to achieve a normalized saltation flux less than 0.05 (Figure 62).

FIGURE 60: DEPTH TO GROUNDWATER TIME SERIES AT NEW RIVER WEST

The depth to groundwater is measured relative to ground surface. The AT-18 and AT-19 transducers became unsubmerged during the time period displayed in this plot.

FIGURE 61: NORMALIZED SALTATION FLUX VERSUS VEGETATED BARRIER SPACING AT NEW RIVER WEST



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FIGURE 62: NORMALIZED SALTATION FLUX VERSUS RIDGE SPACING BY RIDGE HEIGHT AT NEW RIVER WEST

These SWEEP modeling results indicate that a ridge spacing of less than 3.5m will reduce saltation to less than 5% of the saltation that occurs from a surface roughened with a ridge height of 35cm and a ridge spacing of 9.5m. The black dashed line represents the target normalized saltation flux value of 0.05.

4.3.3 SPECIFICATIONS The following sections describe the specifications for surface roughening and vegetation establishment at New River West. A clear transition between soil properties occurs near a contour located at -228 feet above mean sea level. Surface roughening is prescribed upslope of this contour and vegetation establishment is prescribed below. The site layout is shown on Figure 63.


Surface roughening is prescribed for approximately 190 acres, consistent with the dust control design criteria described in Section 3.4. The optimal roughness orientation was set perpendicular to the mean dominant wind direction at 355 degrees. The range of acceptable roughness orientation was set to +/- one standard deviation of the optimal roughness orientation (i.e., 343-367 degrees) (Figure 49).


Vegetation establishment is prescribed for approximately 160 acres, consistent with the general design criteria described in Section 3.4. Site-specific considerations are described below.

The planting bed will be a shallow sloped bull plow furrow (Figure 50). WinSRFR was used to determine the vegetated furrow length and the number of furrows that can be irrigated simultaneously based on site-specific topography, soils and water availability. The vegetated furrow length is 1000m and the irrigation set size is four furrows.


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The Trifolium 12 drain may be used to provide irrigation through a gravity fed system.5 The Trifolium 12 drain meets the grade of the playa at -228ft above mean sea level, which is a higher elevation than the vegetation establishment area. The proposed diversion point is shown on Figure 63. Figure 64 shows the 2016 hydrograph of Trifolium 12 drain discharge to the Sea. Discharge varies daily based on irrigation supply. A partial diversion will divert 3 cubic feet per second (CFS) during late fall when the daily flow is greater than 6 CFS. The diversion will be scheduled with irrigation water deliveries that affect drain discharge to ensure adequate supply.

FIGURE 64: 2016 HYDROGRAPH OF THE TRIFOLIUM 12 DRAIN

The points are daily discharge values near the end of the drain. The line is a smoothed function fit to the data, and the shaded region is the pointwise confidence interval.

The optimal irrigation schedule for successful vegetation establishment in bull plow furrows across different soil types and groundwater depths will be refined over time. An initial pulse of at least 30cm deep water along the entire length of the furrow, maintained for 24 hours, is prescribed.

Vehicle access routes will parallel bull plow furrows to restrict OHV traffic in the site. A vehicle access route will be placed on the -228 AMSL contour line for water conveyance.

4.3.4 SPECIES CONSERVATION HABITAT – NEW RIVER WEST The State’s Species Conservation Habitat (SCH) construction is also planned for the New River West field study site. This field study was designed assuming that SCH construction would commence in 2023, thereby providing six years of interim dust control in this high priority area. The State’s current schedule is to perform site design for the SCH from July 2017 to 2018. SCH construction may commence as early

5 The irrigation water supply may change from the Trifolium 12 drain to an alternative source.


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as 2019, but this remains uncertain. In a best-case scenario, interim dust control is still necessary for the 2017/2018 dust season and likely for the 2018/2019 dust season.

The field study is still necessary to provide interim dust control until SCH construction begins. If it was certain that SCH construction would commence prior to the 2019/2020 dust season, then it may be reasonable to alter the design of the field study to include only surface roughening. Surface roughening without vegetation on sandy soils should not be expected to maintain performance for more than two dust seasons. As noted, the SCH construction schedule is uncertain; therefore, the New River West field study should proceed as currently designed. The field study can readily be incorporated and/or regraded prior to SCH construction.

5 PROPOSED FUTURE STUDIES Several proposed studies are planned for the 2018/2019 dust season. Proposed studies are summarized in Table 6 and described in this section.

TABLE 6: CURRENT AND FUTURE PLOT AND FIELD STUDIES

Site Size (acres) Land Ownership

Salton City Wash Field Study ~280 Bureau of Reclamation

Clubhouse Field Study ~580 USA and IID

Vail Drain Field Study ~500 IID

San Felipe Creek North ~782 USA and IID

Surface Stabilizer Plot Study Unknown IID

5.1 SALTON CITY WASH AND CLUBHOUSE FIELD STUDIES AND GROUNDWATER INVESTIGATION

Off-Sea sand migration from upwind sources, like dunes, dry washes and alluvial fans along the western side of the Salton Sea, represent a large risk to current and future emission potential of exposed playa. Migrating sand from off-Sea sources significantly increases the emissions potential of the exposed playa (by over 20X) compared to adjacent, non-disturbed playa surfaces (IID, 2018)

The Salton City Wash (280 acres) and Clubhouse (580 acres) field studies will investigate water efficient vegetation, waterless physical wind barriers and surface stabilization techniques on sand sheets migrating onto the exposed playa (Figure 65). Water resources are limited along the western side of the Salton Sea, with no current method of getting agricultural return flows for irrigation and vegetation establishment. A groundwater investigation and pilot pumping program will be completed to assess the feasibility of groundwater use for water efficient vegetation establishment at these pilot study sites as well as other areas along the western side.


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5.2 VAIL DRAIN FIELD STUDY This field study will evaluate the dust control effectiveness of a combination of surface roughening and vegetation establishment on approximately 500 acres of highly diverse soil conditions between the New River and Vail Drain (Figure 66). This deltaic site is characterized by a series of linear beach ridge dunes that start at the mouth of the New River and run parallel along the shoreline of the Salton Sea. The beach ridge dunes and the inter-dune areas have been delineated as a high priority, with areas of severely eroded playa. Performance monitoring will be conducted to evaluate the effectiveness and operational aspects of the field study design and implementation.

5.3 SAN FELIPE CREEK NORTH Off-Sea sand migration from upwind sources, like dunes, dry washes and alluvial fans along the western side of the Salton Sea, represent a large risk to current and future emission potential of exposed playa. Migrating sand from off-Sea sources significantly increases the emissions potential of the exposed playa (by over 20X) compared to adjacent, non-disturbed playa surfaces (IID, 2018)

The San Felipe Creek North field study (780 acres) will investigate the use of water efficient vegetation, waterless physical wind barriers and surface stabilization techniques on the San Felipe alluvial fan. This area has increased dust emissions due to migrating sand from alluvial fluvial (water) and aeolian (wind blow) sand from upwind dunes. In this area, sand is deposited on the exposed playa during rain events and then reworked during high wind events where it continues to migrate further east and disturb playa (making it more emissive). As with other areas on the western portion of the playa, water resources are limited. This study will be designed (to the extent feasible) to take advantage of natural flows from the alluvial fan and dry wash to passively irrigate and establish vegetation proactively. If needed, a groundwater investigation will be completed to provide a longer-term, more reliable water source for proactive dust control in this region.

5.4 SURFACE STABILIZER PLOT STUDY This plot study will evaluate the use of surface stabilizers as a dust suppressant. Surface stabilizers could provide interim dust control in isolated areas prone to dust emissions or in areas that require minimal dust control infrastructure due to existing operational uses (e.g., geothermal development). Surface stabilizers are usually applied topically and can include water, salts and brines, organic non-petroleum products, synthetic polymers, organic petroleum products, or mulch and fiber mixtures. The dust control effectiveness of surface stabilizers will be evaluated in a randomized block design to evaluate the effectiveness by product type, soil type, surface sand percentage, and application rate. Routine PI-SWERL sampling will assess emissions potential over time. The locations for the surface stabilizer plot studies have not been identified but will include up to three diverse sites around the Salton Sea.

6 CONCLUSION The primary focus of this 2017/2018 PDCP was to demonstrate the methods used to develop plans for implementation of three proposed field studies in the Fall of 2017. Key findings from the plot studies


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performed from 2015 through 2017 informed the planning process used in this PDCP. The soil suitability criteria, in conjunction with fine resolution soil mapping, provided the information required to place the surface roughening and vegetation establishment dust control measures. Meteorological datasets (i.e., wind direction and wind speed) from meteorological stations near field study locations were used to orient roughness perpendicular to the dominate wind direction. Findings from the 2015-2017 plot studies and physically-based modeling were used to specify site-specific dust control measures. Site layouts and associated specifications were provided for the proposed field studies at Alamo South, Coachella Playa, and New River West. Implementation and monitoring of these field studies will provide important feedback to improve the dust control planning process for future dust control at the Salton Sea.

As mentioned previously, the annual Emissions Monitoring Program is designed to work hand-in-hand with the development of the annual PDCP and subsequent implementation of dust control measures to prevent the playa from becoming a significant source of PM10. Results from the 2016/2017 Annual Emissions Monitoring Program (IID, 2018) demonstrate that the playa is currently a minor source of PM10 emissions compared to sources identified in the ICAPCD 2009 SIP, as well as the nearby desert sources. The overall goal of the SS AQM Program is keep playa emissions at low levels, even as playa exposure accelerates, through implementation of targeted, proactive dust control measures. To that end, existing and planned dust control pilot projects described in this PDCP will cover over 3,600 acres of playa that account for nearly 38% of the total yearly playa emissions (115 of the 306 tons/year) (Table 7). When considered together with projects planned by other stakeholders, the acreage increases to nearly 4,950 acres. This prioritized acreage account for over 51% of the total yearly playa emissions (~158 of the 306 tons), yet is only 29% of the exposed playa extent. Future annual emission estimates will use results from implementation of this PDCP to benchmark progress and report reductions in emissions due to implementation of the IID Salton Sea AQM Program.


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TABLE 7. EXISTING AND PROPOSED DUST CONTROL PROJECTS AND THEIR CONTRIBUTION TO YEARLY PLAYA EMISSIONS

Project Name Purpose Acres

Total Annual Emission (tons)

Prior to Construction

% Contribution

to Total Playa

Emission

Construction Phase as of January 2018

Identified Site Characterization Design Construction Construction

Finished

Alamo North Established Plot Study 204 13.3 4.3 x x x x x

Poe Road Established Plot Study 400 11.3 3.7 x x x x x

Bombay Beach

Established Plot Study 33 0.1 0.0 x x x x x

Alamo South 2017/2018 PDCP 261 9.0 2.9 x x x x x

Coachella Playa

2017/2018 PDCP 246 0.0 0.0 x x x x

New River West

2017/2018 PDCP 350 0.7 0.2 x x x

Salton Wash 2018/2019 PDCP 276 8.5 2.8 x x

Vail Drain 2018/2019 PDCP 498 16.5 5.4 x x

Club House 2018/2019 PDCP 580 15.4 5.0 x


2018/2019 PDCP 782 41.2 13.4 x

Subtotal IID Projects 3,630 115.9 37.9 Red Hill Bay Habitat Project

US Fish and Wildlife Service 618 30.6 10.0 X x x x

Species Conservation Habitat

State of California 699 11.4 3.7 X x x

Subtotal Other Projects 1317 42 13.7

Total for all Projects 4,947 157.9 51.6


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the interrow zone as influenced by tillage. USDA Conserv. Res. Rep, 7(7), 1–22.

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Bielders, C. L., Michels, K., & Rajot, J. (2000). On-Farm Evaluation of Ridging and Residue Management Practices to Reduce Wind Erosion in Niger, 64(October), 1776–1785.

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Cheng, H., Liu, C., Li, J., Zou, X., Liu, B., Kang, L., & Fang, Y. (2017). Wind erosion mass variability with sand bed in a wind tunnel. Soil and Tillage Research, 165(19), 181–189. https://doi.org/10.1016/j.still.2016.08.013

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Gillette, D. (2004). A combined modeling and measurement technique for estimating windblown dust emissions at Owens (dry) Lake, California. Journal of Geophysical Research, 109(F1), 1–23. https://doi.org/10.1029/2003JF000025

Gillette, D., Adams, J., Endo, A., Smith, D., & Kihl, R. (1980). Threshold Velocities for Input of Soil Particles Into the Air by Desert Soils. Journal of Geophysical Research, 85(NO. C10), 5621–5630.

Hagen, L. J., & Armbrust, D. V. (1992). Aerodynamic roughness and saltation trapping efficiency of tillage ridges. Trans. ASAE, 35(August), 1179–1184.

Halliwell, D. J., Barlow, K. M., & Nash, D. M. (2001). A review of the effects of wastewater sodium on soil physical properties and their implications for irrigation systems. Australian Journal of Soil Research, 39(6), 1259–1267. https://doi.org/10.1071/SR00047

Ishizuka, M., Mikami, M., Leys, J. F., Shao, Y., Yamada, Y., & Heidenreich, S. (2014). Power law relation between size-resolved vertical dust flux and friction velocity measured in a fallow wheat field. Aeolian Research, 12, 87–99. https://doi.org/10.1016/j.aeolia.2013.11.002

Imperial Irrigation District. (2018, In Review). Salton Sea Emission Monitoring Program Annual Report and Emissions Estimate for 2016/2017. Prepared by the Salton Sea Air Quality Team

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Macpherson, T., Nickling, W. G., Gillies, J. A., & Etyemezian, V. (2008). Dust emissions from undisturbed and disturbed supply-limited desert surfaces. Journal of Geophysical Research: Earth Surface, 113(2). https://doi.org/10.1029/2007JF000800

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Natural Resources Conservation Service, S. (2017). Nation Soil Survey Handbook, title 430-VI. Retrieved from http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_054242

Ravi, S., Odorico, P. D., Breshears, D. D., Field, J. P., Goudie, A. S., Huxman, T. E., … Zobeck, T. M. (2011). Aeolian Processes and the Biosphere, (2010), 1–45. https://doi.org/10.1029/2010RG000328.1.INTRODUCTION

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Schreuder, M., & Schaaf, M. (2014a). Quantifying Potential Fugitive Dust Emissions from Open Area Sources in the Southwestern United States Using the Portable In-Situ Wind Erosion Lab (PI-SWERL). In Geological Society of America.

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and STANMOD Software Packages and Related Codes. Vadose Zone Journal, 7(2), 587. https://doi.org/10.2136/vzj2007.0077

Sweeney, M., Etyemezian, V., Macpherson, T., Nickling, W., Gillies, J., Nikolich, G., & McDonald, E. (2008). Comparison of PI-SWERL with dust emission measurements from a straight-line field wind tunnel. Journal of Geophysical Research: Earth Surface, 113(1), 1–12. https://doi.org/10.1029/2007JF000830

Tatarko, J., Donk, S. J. Van, Ii, J. C. A., & Walker, D. G. (2016). Application of the WEPS and SWEEP models to non- agricultural disturbed lands. Heliyon, (November), e00215. https://doi.org/10.1016/j.heliyon.2016.e00215

Wagner, L. E. (2013). A history of Wind Erosion Prediction Models in the United States Department of Agriculture: The Wind Erosion Prediction System (WEPS). Aeolian Research, 10, 9–24. https://doi.org/10.1016/j.aeolia.2012.10.001

Waiser, T. H., Morgan, C. L. S., Brown, D. J., & Hallmark, C. T. (2007). In Situ Characterization of Soil Clay Content with Visible Near-Infrared Diffuse Reflectance Spectroscopy. Soil Science Society of America Journal, 71, 389. https://doi.org/10.2136/sssaj2006.0211

Woodruff, N. P., & Siddoway, F. H. (1965). A Wind Erosion Equation. Soil Sci. Soc. Am. J., 29(5), 602–608. https://doi.org/10.2136/sssaj1965.03615995002900050035x

(Allmaras et al., 1966; Bautista et al., 2009; Brenner, 2011; Buck, King, & Etyemezian, 2011; Cheng et al., 2017; Chu et al., 2012; Gillette, 2004; Hagen & Armbrust, 1992; Halliwell, Barlow, & Nash, 2001; Ishizuka et al., 2014; King, Etyemezian, Sweeney, Buck, & Nikolich, 2011; Lyon & Smith, 1992; Macpherson, Nickling, Gillies, & Etyemezian, 2008; Natural Resources Conservation Service, 2016, 2017; Ravi et al., 2011; Saleh & Fryrear, 1999; Salton Sea Air Quality Team, 2015, 2016a, 2016b, 2017, Schreuder & Schaaf, 2014a, 2014b; Šimůnek, van Genuchten, & Šejna, 2008; Sweeney et al., 2008; Wagner, 2013; Woodruff & Siddoway, 1965)


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APPENDIX A. SWEEP PARAMETERIZATION

The purpose of this appendix is to provide histograms of data used to select SWEEP model input parameters used to 1) evaluate the range of 10m wind speeds that can start the process of saltation for a range of surface conditions and 2) determine the wind speed and direction that starts the process of saltation after surface roughening is installed as compared to a non-roughened condition, for the variables in Table 4. Figures A-1 through A-7 demonstrate the histogram and model value selection by modeled condition (Section 3.3.2) for the topsoil variables of percent clay, percent silt, surface crust fraction, loose material on crust, crust stability, random roughness and ridge height.

FIGURE A-168: HISTOGRAM OF PERCENT CLAY AND SWEEP VALUE SELECTION

The total number of observations used to generate the histogram was 10,678. The vertical lines represent the percent clay value used in each modeled condition.


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FIGURE A-2: HISTOGRAM OF PERCENT SILT AND SWEEP VALUE SELECTION

The total number of observations used to generate the histogram was 10,678. The vertical lines represent the percent silt value used in each modeled condition.

FIGURE A-3: BAR CHART OF GLOBAL SURFACE CRUST FRACTION AND SWEEP VALUE SELECTION

Surface crust fraction data were collected by visually estimating the surface crust fraction at sample locations. Due to the uncertainty in the method of measurement, the SWEEP value selections were conservatively adjusted. The total number of observations used to generate the histogram was 254. The vertical lines represent the surface crust fraction value used in each modeled condition.


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FIGURE A-4: BAR CHART OF GLOBAL LOOSE MATERIAL ON CRUST AND SWEEP VALUE SELECTION

Loose material on crust data were collected visually estimating loose material at sample locations. The total number of observations used to generate the histogram was 254. The vertical lines represent the loose material on crust value used in each modeled condition.

FIGURE A-5: HISTOGRAM OF GLOBAL CRUST STABILITY AND SWEEP VALUE SELECTION

Crust stability data were collected by averaging three crust stability measurements made with a pocket penetrometer at sample locations. Due to the lack of sensitivity to the lower range of crust stabilities of the pocket penetrometer, values in the range from 0 to 2 ln(J/kg) were detected as 0. The total number of observations used to generate the histogram was 254. The vertical lines represent the crust stability value used in each modeled condition.


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FIGURE A-6: HISTOGRAM RANDOM ROUGHNESS OBSERVED AT POE ROAD AND SWEEP VALUE SELECTION

The total number of observations used to generate the histogram was 4,470. The vertical lines represent random roughness value used in each modeled condition.

FIGURE A-7: HISTOGRAM RIDGE HEIGHT OBSERVED AT POE ROAD AND SWEEP VALUE SELECTION

The total number of observations used to generate the histogram was 2,235. The vertical lines represent ridge height value used in each modeled condition.


Proactive Dust Control Plan - Salton Sea · This 2017/2018 Proactive Dust Control Plan (PDCP) was prepared for the Imperial Irrigation District (IID) as a requirement of the Salton

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