DRAFT OFF-SITE SAMPLING PLAN

August 2021

DRAFT OFF-SITE SAMPLING PLAN Near the Former PureGro Facility Site

Brawley, California

prepared by:

Department of Toxic Substances ControlSite Mitigation and Restoration Program

James Wilkinson, P.G., Engineering GeologistDaniel Cordero, Senior HSE, Project Manager

Shukla Roy-Semmen, Ph.D., Senior Toxicologist5796 Corporate Avenue

Cypress, California 90630714.484.5300

James Wilkinson, P.G.

Engineering Geologist

Daniel Cordero

Project Manager

D R A F T O F F - S I T E S A M P L I N G P L A NP U R E G R O E V A L U A T I O N

Table of Contents

August 2021 Page i

Section Page

1. INTRODUCTION ............................................................................................................. 11.1 PURPOSE ............................................................................................................................................. 11.2 OSP OBJECTIVES ............................................................................................................................. 11.3 RESPONSIBLE AGENCY, SUPPORTING AGENCIES, AND PARTICIPATING

ENTITIES ............................................................................................................................................. 21.4 PROJECT ORGANIZATION .......................................................................................................... 2

2. PROJECT HISTORY AND BACKGROUND.................................................................... 32.1 GEOLOGICAL AND HYDROGEOLOGICAL INFORMATION ....................................... 32.2 AERIAL PHOTO STUDY ................................................................................................................ 62.3 HISTORICAL ON-SITE AND OFF-SITE INVESTIGATIONS AND ACTIONS ............ 62.4 DEVELOPMENT OF SITE CONCEPTUAL MODEL ............................................................ 9

3. DATA QUALITY OBJECTIVES ..................................................................................... 123.1 DATA QUALITY OBJECTIVES ................................................................................................... 123.2 DATA REVIEW AND MANAGEMENT ................................................................................... 16

4. SOIL SAMPLING ................................................................................................................. 164.1 DESIGN AND RATIONALE ...................................................................................................... 164.2 FIELD EQUIPMENT ..................................................................................................................... 174.3 METHODS AND PROCEDURES .............................................................................................. 174.4 LABORATORY ANALYSIS .......................................................................................................... 184.5 SAMPLE CONTAINERS, PACKAGING AND SHIPPING ................................................. 194.6 DISPOSAL OF RESIDUAL MATERIALS ................................................................................ 194.7 SAMPLE DOCUMENTATION ................................................................................................... 204.8 FIELD QUALITY CONTROL SAMPLES ................................................................................. 224.9 FIELD VARIANCES ....................................................................................................................... 224.10 FIELD HAZARD APPRAISAL AND RECOGNITION PLAN .......................................... 224.11 DATA EVALUATION AND REPORTING .............................................................................. 22

5. REFERENCES ................................................................................................................... 23


Table of Contents

Page ii Department of Toxic Substances Control

Figures

Figure 1 Site Location Map

Figure 2 Former PureGro Site and Neighborhood Area

Figure 3 Off-Site Sampling Areas

Figure 4 Previous Off-Site Sampling Locations

Tables

Table 1 Analytical Methods and Sample Number

Table 2 List of Samples and Identification/Location

Table 3 Soil Screening Levels/Detection Limits

Table 4 Field Equipment Inventory Form

APPENDICES

Appendix A CARB Air Dispersion Modeling Results

Appendix B Hazard Appraisal and Recognition Plan

Appendix C Environmental Records Search Report (Aerial Photos)

.


August 2021 Page 1

1. Introduction

1.1 PURPOSE

This document presents the Off-Site Sampling Plan (OSP) for the off-site investigation near the

former PureGro Facility Site (Site), located at 1025 River Drive, Brawley, California (Figures 1 and

2). The OSP presents the scope of sampling to determine if contaminated particles from the Site

have migrated and deposited off-site via wind-blown dust. On December 10, 2018, the Department

of Toxic Substances Control (DTSC) held a public meeting for the Site’s proposed Remedial Action

Plan (RAP). During this meeting, community members expressed concern about the spreading of

contaminants to off-site areas. This OSP has been developed by DTSC to address community

concerns and assess off-site migration of contaminants from the PureGro Site.

1.2 OSP OBJECTIVES

The primary objectives of the OSP are:

· To evaluate soil samples collected from areas outside the PureGro facility (off-site) to

determine:

Ø If contaminants, identified as risk-drivers at the former PureGro Facility, have migrated

off-site.

Ø If contaminants detected in the off-site soil samples, are present at concentrations above

residential risk-based screening levels per DTSC’s Human Health Risk Assessment

(HHRA) Note 3.

Ø To determine whether areas identified as dust settlement areas per the Air Dispersion

Model presented by the California Air Resources Board (CARB), have been affected by

contamination from PureGro.

Constituents to be evaluated will include four contaminants identified as risk drivers for onsite

receptors in the 2010 Human Health Risk Assessment: disulfoton, phorate,

pentachloronitrobenzene and dieldrin.


Page 2 Department of Toxic Substances Control

The OSP presents proposed sample locations for the off-site screening evaluation. The sampling

protocols and methods outlined in the OSP will be used for any future sampling efforts if deemed

necessary.

Rights of Entry (ROE) will be required to enter off-site properties, therefore, sample locations

depicted in this OSP are approximate. Final locations will be determined once ROEs are obtained

and will be reflected in the subsequent Report. Samples will be collected from unpaved and

undisturbed areas of soft scape.

1.3 RESPONSIBLE AGENCY, SUPPORTING AGENCIES, AND PARTICIPATING ENTITIES

DTSC is the agency providing oversight of this sampling investigation. CARB has provided support

by assisting DTSC in developing air dispersion modeling maps to help guide the scope of work for

this investigation.

1.4 PROJECT ORGANIZATION

The following table presents the list of key project personnel, their contact information and

responsibilities.

Key Project Personnel Contact Information and Responsibilities

Title Name Phone

Number

Responsibilities

DTSC Project Manager Daniel Cordero (714) 484-5428 Coordinates, organizes, and plans

for sample collection activities.

DTSC Geologist/Field Team

Leader

James Wilkinson (714) 484-5407 Sample collection, documentation,

packaging and shipment.

DTSC Toxicologist Shukla Roy-

Semmen

(714) 484-5448 Develops decision inputs for risk

assessment, when appropriate.


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2. PROJECT HISTORY AND BACKGROUND

The Site (Figure 2) was used to formulate, store, and distribute agricultural products (e.g., fertilizers

and pesticides) from the 1940’s to 2000. Pacific Guano Company operated the facility from the

1940’s until it was acquired by Unocal in 1961 (it was renamed PureGro Company in 1967). The

Unocal subsidiary operated the Site from 1961 through 1993 when Crop Production Services (doing

business as Western Farm Services) purchased the facility. In 2000, property ownership was

transferred from Crop Production Services back to PureGro Company. In 2005, Chevron acquired

Unocal and its assets, including previously closed legacy operations such as this site. During its

operational history, the Site contained features such as a warehouse, lime sulfur plant, sulfur sludge

pond, reactor areas, metal machine shop, hazardous waste storage area, grease pit, wash/rinse areas,

liquid emulsion plant, underground and aboveground storage tanks, and an evaporation pond.

Facility operations were discontinued in December 2000, and the majority of site improvements

including buildings, tanks, and concrete pads were demolished in 2001. The Site consists of two

parcels that total 11.66 acres in size. The Site is currently a vacant, fenced, relatively flat lot with

three concrete slabs.

2.1 GEOLOGICAL AND HYDROGEOLOGICAL INFORMATION

Regional Geology

The site is located south of the Salton Sea within the Imperial Valley area of southern California and

within the Colorado Basin geomorphic province. The Imperial Valley is part of the Salton Trough, a

deep basin that represents the structural extension of the Gulf of California into North America.

The Salton Trough also represents the transition zone between the North American and Pacific

plates. The San Andreas Fault Zone is the most prominent feature along this boundary and extends

southeast to northwest approximately 13 miles northeast of the site. Other significant faults near the

site include the Imperial Fault, Superstition Hills Fault, and Superstition Mountain Fault (Alles

2011). The San Andreas, Imperial, and Superstition Hills faults are defined as "sufficiently active and

well-defined faults" according to the Alquist-Priolo Earthquake Zoning Act of 1972. The Brawley

fault zone and the Brawley seismic zone constitute the principal transfer zone accommodating strain

between the San Andreas and Imperial faults (Meltzner et al. 2006). Sediment in the basin is greater

than 1,200 feet thick based on wells drilled in the Hayfield Planning Area, which lies to the north-



northeast of the Imperial Valley Planning area, as discussed in the Water Quality Control Plan for

the Colorado River Basin (RWQCB 2006).

Site Geology

Subsurface investigations indicate that the site is underlain primarily by lacustrine deposits generally

consisting of silt and clay, with interbedded lenses of sand and gravel, between 1 and 55 feet below

ground surface (bgs), which is the maximum depth of investigation. Gravel backfill/base material

was also encountered in the upper 1 to 2 feet in areas of former buildings and above ground storage

tanks.

Regional Hydrogeology

The site lies within the Imperial Valley Groundwater Basin, in the southern part of the Colorado

River Hydrologic Region. According to California’s Groundwater Bulletin 118, the Imperial Valley

Groundwater basin is bounded by the Sand Hills on the east, and the bedrock of Fish Creek and the

Coyote Mountains on the west. The basin is bounded by the Salton Sea to the north, which is the

final discharge point for groundwater in the basin, and by the international border with Mexico to

the south (although the basin actually extends across the border into Baja California) (DWR 2004).

Groundwater within the Imperial Valley Groundwater Basin generally flows toward the axis of the

Imperial Valley and then northwestward toward the Salton Sea (Montgomery Watson, Inc. 1995).

Groundwater in the Brawley area generally flows to the north. Based on surface elevation data the

average surficial gradient from the site to the New River in a northerly direction is approximately

0.005 ft/ft. Groundwater elevations in the upper aquifer are relatively shallow, especially in the

northern portion of the basin near the Salton Sea. Water movement through the valley floor is

impeded by the fine-grained lacustrine sediment, which promotes accumulation of saline water at

the surface (RWQCB 2006). Groundwater elevation contours from United States Geological Survey

(USGS) regional maps indicate that both the New River and Alamo River are groundwater discharge

points for the basin (i.e., they are gaining streams) (USGS 2009). However, the quantity of natural

groundwater input is very small (i.e., few tens of thousands of acre-feet per year) compared to the

estimated seepage from the All-American Canal and Alamo Canal, and from irrigation return flow

from the drainage network which is on the order of hundreds of thousands acre-feet per year

(Loeltz et al. 1975). The Water Quality Control Plan for the Colorado River Basin also supports that

the fine-grained lake sediment in the central portion of Imperial Valley inhibits groundwater


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movement. (RWQCB 2006). The results of the 2008 and 2013 well surveys and conversations with

representatives from the City of Brawley indicate that there is no evidence of domestic, municipal,

or industrial uses of groundwater within 1 mile of the site, and no evidence of agricultural pumping

has been encountered to date. The nearest well is located approximately 18 miles from the Site.

Significant water quality variations are observed throughout the basin. In general, groundwater

within the basin is described as generally saline (RWQCB 2006) and is unsuitable for domestic and

irrigation purposes without treatment. The predominant source of agricultural irrigation water in the

region is the All-American Canal (RWQCB 2006) which transports water from the Colorado River

to the Imperial Valley. The site is located within the Imperial Hydrologic Unit (723.00) of the

Imperial Valley Planning Area (RWQCB 2006). Designated beneficial uses of groundwater within

the Imperial Hydrologic Unit include municipal and industrial process supply; however, the

beneficial use designations only indicate that "at least one of the aquifers within that unit currently

supports a municipal beneficial use...and the actual municipal usage of the Imperial Hydrologic Unit

is limited only to a small portion of that groundwater unit” (RWQCB 2006).

Site Hydrogeology

Groundwater at the site has been encountered between approximately 18 and 29 feet below ground

surface (bgs) from 2008 to 2018 and does not discharge to the surface on or near the site. The

average calculated groundwater flow velocity at the site is approximately 10 feet per year. Previous

groundwater data indicate a groundwater flow direction generally to the north-northeast in the

direction of the New River (which is over a mile away from the site).

During the most recent groundwater monitoring event, groundwater flow direction was to the east-

northeast with a horizontal hydraulic gradient of 0.0042 feet per foot (ft/ft) in the southern portion

of the site. This gradient was approximately 0.009 ft/ft in the northern portion of the site; 0.007

ft/ft in the central portion of the site; and 0.006 ft/ft in the southern portion of the site (ARCADIS

2014).

Two site monitoring wells are located within 50 feet of the Stanley Canal. Total Dissolved Solids

(TDS) concentrations in these wells are similar to TDS concentrations in Colorado River water,

whereas TDS concentrations in other monitoring wells at the site are generally higher with

increasing distance from the canal. Thus, groundwater at these two wells appears to have been

affected by input from a freshwater source(s) and is not considered to be indicative of the

background quality of site groundwater. However, based on constituent concentrations collected



from downgradient monitoring locations, any increase in hydraulic gradient due to such freshwater

input has not resulted in a significant effect on migration of these constituents at the site.

For more in-depth geological and hydrogeological information related to the Site, please refer to the

Remedial Investigation Report, dated August 13, 2014.

2.2 AERIAL PHOTO STUDY

DTSC reviewed historical aerial photos of the Site and surrounding area provided by Environmental

Record Search (Appendix C). The photos covered the timeframe of 1948 to 2016. The results of

the study indicate that the immediate area to the east of the Site has been utilized as an agricultural

field from at least 1948 to 2002. This area has been vacant since 2002 and is reportedly to be re-

zoned to residential. The area to the south of the Site (across River Drive) contained water ponds

associated with the California Electric Power Company, Ice Plant Division, Ice Plant Number 3; the

ponds were present in 1937 prior to the establishment of Pacific Guano Company in 1955 north of

River Drive (Arcadis, May 21, 2021). The Historical Aerial Photos (Appendix C) indicate that the

ponds were still in operation up to approximately 1981.

2.3 HISTORICAL ON-SITE AND OFF-SITE INVESTIGATIONS AND ACTIONS

Investigations and Activities Conducted Prior to DTSC Involvement (1992-1994)

In 1992, a phosphoric acid spill of approximately 8,200 gallons occurred in the north-central part of

the site. The acid spill was contained, and impacted soil was approved for treatment on site.

Approximately 450 cubic yards (cy) of impacted soil (from onsite and off-site) and stockpiles were

placed in a bermed area in the northern portion of the site. On-site and off-site confirmation soil

samples were collected after excavating the acid-affected areas, and the samples were analyzed for

pH. In December 1992, the stockpiled soil from the phosphoric acid spill was sampled for waste

disposal characterization, and pesticides were identified (Sierra-Pacific Groundwater Consultants,

Inc. [Sierra-Pacific] 1995). In 1994, the PureGro Company elected to treat the soil on-site using

thermal desorption oxidation technology. Post-treatment analytical results demonstrated that

stockpiled soil did not contain organochlorine pesticides (OCPs), organophosphorus pesticides

(OPPs), or metals at concentrations exceeding hazardous waste classification criteria (Sierra-Pacific


August 2021 Page 7

1995). The treated soil was stockpiled in the northeast corner of the Site. Based on post-treatment

pesticide concentrations, Sierra-Pacific recommended "redistributing and grading the soil to the

surface at the north end of the Site." Documentation for the final disposition of the thermally

treated soil from the Site was not available.

Between 1992 and 1995 limited investigations were conducted by various parties as part of real

estate transactions. Additional investigations were conducted between 1996 and 2001 as part of the

Site’s Decommissioning and Demolition activities upon closure of the PureGro Facility operations.

Additional details about past investigations and activities prior to DTSC involvement can be found

in the Remedial Investigation Report for the Site, dated August 13, 2014.

Investigations and Activities During DTSC Oversight (2003-2013)

On March 20 & 21, 2003, DTSC responded to a complaint regarding a potential release of pesticides

at the Site. DTSC representatives collected 10 on-site and three off-site soil samples in response to

this complaint (DTSC 2004a). At the time, DTSC determined that the Site was contaminated with

OCPs above hazardous waste levels, and on March 30, 2004, DTSC issued an Imminent and

Substantial Endangerment Determination and Consent Order requiring the property owner to

characterize the Site.

Between 2003 and 2005, Geosyntec Consultants and Leighton Group, on behalf of the property

owner, conducted on-site soil, soil vapor, and groundwater evaluations. Samples were analyzed for

OCPs, OPPs, total petroleum hydrocarbons (TPH), volatile organic compounds (VOCs), polycyclic

aromatic hydrocarbons (PAHs), metals, perchlorate, and general chemistry. Groundwater was

evaluated for OCPs, VOCs, TPH, metals, perchlorate, and general chemistry.

From 2008 to 2010, additional assessment of on-site soils and groundwater was conducted to

characterize the extent of contaminants remaining at the Site. A total of 512 soils samples from 163

locations, and 169 groundwater samples were collected from 43 locations across the site by various

contractors. Sampling defined the lateral and vertical extent (to approximately 20 feet bgs) of

contamination and determined that groundwater had been impacted but did not appear to be

migrating off site.

Groundwater was monitored and sampled on a quarterly basis beginning in mid-2013 until 2017, as

a result of identifying Site contaminants in groundwater during the previous investigations.



Off-Site Investigation

In May 2004, soil sampling was performed on the adjoining properties north and east of the site to

further evaluate the potential presence of constituents above comparison criteria in off-site soil

(Leighton Consulting, Inc. 2004). A total of 85 off-site soil samples were collected and analyzed for

OCPs, metals, and/or pH (Figure 4). OCPs were detected at concentrations exceeding United States

Environmental Protection Agency (U.S. EPA) residential Preliminary Remediation Goals (PRGs)

(ARCADIS 2014). In 2006, a Remedial Action Workplan was approved by DTSC and, as a result,

15,000 cubic yards of soil were excavated from the adjoining eastern property and stockpiled in the

northeastern area of the Site. The stockpile was staged on a low permeability geosynthetic

membrane and placed within a second internal fenced enclosure.

A full summary of historical sampling efforts and associated data are reflected in the 2014 Remedial

Investigation Report for the Site.

Human Health Risk Assessment Findings

In 2010, DTSC approved a HHRA for the Site. Results of over 500 soil samples collected between

2005 to 2008 were used to evaluate cancer risks and non-cancer hazards to potential future receptors

at the site. These included a commercial/industrial worker, a construction worker, a trespasser and

an off-site resident. The primary risk drivers at the Site were determined to be disulfoton, phorate,

pentachloronitrobenzene and dieldrin. The analytical sampling suite proposed in this OSP has been

specifically designed to focus on these four chemicals.

Remedial Action Plan (2018-2020)

DTSC public noticed the first Draft Remedial Action Plan (DRAP) which proposed the spreading of

the stockpile soil over the site; the construction of a cap to prevent the infiltration of water; the

installation of ground water monitoring wells; and the long-term monitoring of these wells. On June

21, 2018, DTSC issued a responsiveness summary to over 100 public comments received. The

majority of public comments did not approve of the remedy chosen in the DRAP, and requests for

off-site sampling were received. In response to public input, on June 20, 2018 DTSC requested that

a revised Remedial Action Plan be submitted.


August 2021 Page 9

In an effort to provide an avenue through which the public could provide input on the revised DRAP,

the Center for Creative Land Recycling (CCLR) was brought in to help establish constructive

communication between the community, DTSC, and Chevron; this was accomplished by identifying

key concerns and constraints of all involved in the Cleanup process. CCLR also helped identify

possible end uses and requirements to reach each end use of the Site.

A revised DRAP was public noticed from November 13, 2019 to December 17, 2019 with a

community meeting held on December 5, 2019 at the American Citizen Club. The revised DRAP

proposed the removal of the soil stockpile; hotspot soil excavation; construction of a cover;

installation of groundwater wells for the purpose of long-term monitoring; cleanup of buffer zones

on the eastern and southern edges of site to residential standards; construction of a block wall on the

eastern property boundary; and landscaping along the northern side of River Drive. Approximately

100 comments were received. DTSC issued a responsiveness summary on May 29, 2020 and requests

for off-site sampling were again received. DTSC approved the revised DRAP on June 1, 2020.

Stockpile Removal

The first phase of the approved DRAP comprised the removal of the stockpile from the Site. DTSC

approved stockpile removal and dust control work plans on September 2, 2020 and September 8,

2020, respectively. Between September and December 2020, 15,000 cubic yards (more than 100

truckloads) of stockpile soil were removed and disposed of at an approved, out-of-state facility.

2.4 DEVELOPMENT OF SITE CONCEPTUAL MODEL

The initial step in developing the OSP included establishing a site-specific conceptual site model

(CSM). Factors considered in defining the parameters of the CSM include, but are not limited to:

· Time of operation of the Former PureGro Facility.

· Wind direction and dispersion rates – movement of particles via wind.

· Types of contaminants to be considered in the evaluation.



2.4.1 PARTNERSHIP WITH CALIFORNIA AIR RESOURCES BOARD

In an effort to develop an appropriate CSM for the OSP, DTSC requested the assistance of the

California Air Resources Board (CARB). On December 23, 2019, DTSC and CARB initiated

discussions regarding developing an Air Dispersion Model (ADM) for the Brawley area. The ADM

would provide data to support and define the probable study area, sampling locations, and the extent

of sampling efforts for the OSP. As a result, CARB’s Modeling and Meteorology Branch assigned

staff specialized in air modeling to assist DTSC with this effort.

2.4.2 AIR DISPERSION MODELING

Air modeling is a mathematical simulation of how air dust/pollutants disperse in the atmosphere. It

is performed with computer programs that solve the mathematical equations and algorithms which

simulate the dust/pollutant dispersion.

The AERMOD model was used to calculate and project potential dust deposition via wind-blown

particulates. The AERMOD model is recommended by the U.S. EPA for regulatory usage. It has

been extensively evaluated and well documented and has been widely used in various applications.

The ADM Report can be found in Appendix A. Surface meteorology and precipitation

measurements from the El Centro (Imperial County) Airport, along with upper air radiosonde data

in San Diego, were used to generate model-ready meteorological data sets. San Diego is the closest

radiosonde site to the study area with a complete dataset for the entire modeling period (47 years).

Figures 1 and 2 in Appendix A show the wind rose and wind speed distribution, respectively.

Data presenting the wind speed and direction are the most critical factors in predicting how much

dust is emitted from the site and the probable location for dust particles to be transported and

ultimately deposited. Based on the ADM, high wind events occurred regularly over the past 47 years,

which indicates the potential for windblown dust emissions and transport. Calm winds do not affect

the modeling results because there is no windblown dust emitted when the wind is calm (i.e., less

than 0.5 m/s). AERMET is AERMOD’s meteorological pre-processor that generates all

meteorological parameters needed by AERMOD. The meteorological field for AERMOD is

horizontally uniform but vertically variable to reflect the vertical variations in meteorology such as

wind shear.


August 2021 Page 11

A series of data inputs as well as conditions and assumptions were developed to provide a

conservative estimation of the amount of dust and particulates blown off-site via wind and the

distance in which those particulates could deposit. The Air Modeling data inputs, conditions and

assumptions can be found in Appendix A.

2.4.3 AIR DISPERSION MODELING RESULTS The ADM Report results depict the areas around the Site predicted to have the highest

concentration of dust (Appendix A -Figures 4 and 5) and is being used as the CSM for the OSP.

Based on the ADM, it is expected that the area predicted to have the highest concentration of dust is

the primary estimated dust settlement area. The second highest concentration of dust is expected to

be found in the secondary estimated dust settlement area. The lowest concentrations of dust are

expected to be found in the tertiary estimated dust settlement area. The ADM results are based on

wind direction and speed to determine the areas with the highest concentration of dust and is a

qualitative map. This investigation has been designed to confirm if contaminants followed the

pattern of dispersion shown in the ADM. Based on the results of this investigation, the CSM will be

updated, and additional samples collected as needed.

Based on the results of the air dust dispersion modeling, sampling will be conducted to the east and

south of the Site to define contaminant concentrations identified as primary risk drivers (disulfoton,

phorate, pentachloronitrobenzene and dieldrin) in soils that may have migrated off site. For the

purposes of this OSP, sampling will be carried out in the primary and secondary dust settlement

areas.



3. DATA QUALITY OBJECTIVES

3.1 DATA QUALITY OBJECTIVES

The data collection activities are premised on the data quality objectives that were developed for the

project. The U.S. EPA initially developed the Data Quality Objectives (DQO) process in 1994, and

the development of these project-specific DQOs is consistent with the “Guidance on Systematic

Planning using the Data Quality Objectives Process” (EPA, 2006). The DQO-based approach

ensures that the information being collected, and that the quality and quantity of the samples meet

the objectives of off-site evaluation.

The DQO process consists of seven steps and each step defines the criteria that will be used to

develop the sampling design. The seven steps are:

1) State the Problem

2) Identify the Goal of the Study

3) Identify Information Inputs

4) Define Study Boundaries

5) Develop the Analytical Approach

6) Specify Performance or Acceptance Criteria

7) Develop the Plan for Obtaining Data/Data Review and Management

The goal of this investigation is to collect data that can support a determination as to whether

contaminated particles from the Site have migrated and been deposited off-site via wind-blown dust.

The DQO process used in the development of this OSP is listed in the subsequent sub-sections.

3.1.1 STEP 1: STATE THE PROBLEM

Residents living adjacent to the Site expressed concern about the potential for Site contaminants

having migrated off-site during the many years of operation of the Site. Data from the remedial

investigation indicates that off-site contamination above residential screening levels were identified

and removed during the 2006 off-site soil removal conducted immediately east of the Site.


August 2021 Page 13

Residents remained concerned that Site contaminants migrated beyond the boundaries of the 2006

off-site soil removal. This OSP is designed to address this concern.

In the effort to begin forming the OSP scope, development of a CSM was initiated with the assistance

of CARB to develop the ADM Report; this report summarizes the historical wind-dispersion data to

help direct sampling efforts for the OSP, as described in Section 2 above.

3.1.2 STEP 2: IDENTIFY THE GOALS OF THE STUDY

The second step of the DQO process identifies the goal of the investigation and possible actions

and decisions that may result from the data collected.

The goal of the OSP is to determine if Site contaminants have migrated to adjacent properties via

wind-borne particulates.

Study Question: Were Site contaminants from PureGro deposited off-site due to wind

dispersion?

Additionally, two questions stem from the main problem statement:

a. If soils migrated off the PureGro property via wind dispersion, where would the soil or dust

deposit?

b. If soil or dust from the PureGro property migrated off-site, were the soils contaminated?

And if so, were the concentrations above the residential screening levels?

3.1.3 STEP 3: IDENTIFY INFORMATION INPUTS

· Evaluation Areas: Results of the air dust dispersion modeling conducted by CARB use the

ADM to guide soil sample locations. The model establishes the primary, secondary, and

tertiary dust dispersion areas where the predicted concentration of dust, possibly containing

Site contaminants, may have been deposited. Based on the model, soil samples will be

collected from open space downwind to the south and east, proximate to the Site in the

primary and secondary dust settlement areas.



· Sample Locations: Where possible, soils from the unpaved areas within the primary and

secondary dust settlement areas will be sampled. Unpaved areas have the highest probability

to be affected by wind-blown dust and contaminant deposition.

· Prior to initiating sampling on properties, DTSC will request consent from property owners

to access their property for sampling. During the consent process, property owners will be

interviewed regarding known past use of pesticides and fertilizers, or other chemicals on the

property.

· Analyte List: Results of several investigations at PureGro demonstrated that OCPs and

OPPs have been identified as the key chemicals of potential concern, in the HHRA.

Therefore, the soil samples taken will be analyzed for the primary risk drivers: disulfoton,

phorate, pentachloronitrobenzene and dieldrin.

· Analytical DQOs: Laboratory requirements for precision, accuracy, representativeness,

completeness, and comparability (PARCC) will be determined with the analytical laboratory.

PARCC are criteria established to assess the quality and usability of the data.

· Exposure Pathways: Potential exposure routes include ingestion, dermal contact, and

inhalation of contaminated dust.

3.1.4 STEP 4: DEFINE STUDY BOUNDARIES

The lateral boundaries of the sampling activities include areas identified by the ADM, as discussed in

Section 2 and Appendix A. The ADM results depict the area around the Site predicted to have the

two highest concentrations of dust (Figure 3). The area predicted to have the highest concentration

of dust is known as the primary estimated dust settlement area. The area predicted to have the next

highest concentration of dust is known as the secondary estimated dust settlement area. Based on

the results of the ADM, sampling will be conducted to the east and south of the Site in the primary

and secondary estimated dust settlement areas.

The number of samples and locations may vary depending on access and availability. The vertical

boundaries of the sampling activities will be from the ground surface to a depth of 6 inches (0-6

inches bgs).


August 2021 Page 15

3.1.5 STEP 5: DEVELOP THE ANALYTIC APPROACH

This step identifies the action level and the dataset parameters that will be used to support the

decision-making process.

Decision Rules/Actions:

1) No further action if chosen Site contaminants are not detected.

2) If chosen Site contaminants are detected, then compare contaminant concentrations to

established residential soil screening levels1. Screening levels are included in Table 3.

a. Determine whether elevated concentrations are the result of past agricultural

use or if pesticides were used by the owner of the property. An assessment of

past activities should be conducted at each property considered for sampling.

The assessment should include an interview of the property owner.

b. If the contaminant concentration of each constituent is below the established

residential soil screening levels, then no further action.

c. If the contaminant concentration of any of the constituents is above its

established residential soil screening level, then additional evaluation may be

required.

3.1.6 STEP 6: SPECIFY LIMITS ON DECISION ERRORS

Decisions are usually based by performing a statistical hypothesis test on the collected data, i.e., the

error rates of the data collection. However, the scope of the data collection activities is limited to

the collection of a fixed number of samples rather than on a statistically based sampling design.

Therefore, this step in the DQO process discusses the following uncertainties associated with the

sampling design:

1 Screening levels for residential soil will be based on U.S. EPA Region 9 Regional Screening Levels.



• Uncertainties in the air dust modeling results influence the uncertainties in the proposed

sampling locations.

• Collecting a limited number of samples off-site could potentially underestimate or overestimate

the magnitude of exposures.

3.1.7 STEP 7: DEVELOP THE PLAN FOR OBTAINING DATA

The sampling approach discussed in the following sections is based on the project-specific DQOs

discussed in this section.

3.2 DATA REVIEW AND MANAGEMENT

Data review will be performed by DTSC’s Environmental Chemistry Laboratory (ECL), or contract

laboratory, using qualifiers on the analytical data, if necessary. The ECL will place qualifiers on the

data based on the Instrument Detection Limits, Method Detection Limits, Reporting Limits,

Laboratory Control Samples, and possible matrix interference. The ECL will indicate in the

laboratory case narrative any corrective actions applied which could include rejection of data, re-

analysis or recommendations for resampling. The Practical Quantitation Limits should meet risk-

based criteria.

The Field Team Leader will ensure that data are transferred accurately from collection to analysis to

reporting. Use of field notes and photographs will be used to record and review the data collection

processes.

4. Soil Sampling

4.1 DESIGN AND RATIONALE

The position of each sampling location will be determined in advance by consulting the property

owner(s) to gain access. A Consent for Access to Property will be provided to each property owner

for review and signature prior to sample collection. Sampling will target unpaved and undisturbed

areas of soft scape. The collection of samples and locations may vary depending on access and


August 2021 Page 17

availability. For each proposed field and residential sampling point, one sample will be collected, per

lot, at the surface (0 to 6 inches). All samples collected will be screened against residential screening

values.

4.2 FIELD EQUIPMENT

A list of equipment that will be used in the field to collect samples, including decontamination

equipment, is included in Table 4.

4.3 METHODS AND PROCEDURES

Soil samples will be collected within 6 inches of the ground surface. If available, single use,

individually wrapped and sealed hand trowels/scoops will be used to collect the surface samples and

then transfer samples to the appropriate containers. Otherwise, field equipment will be

decontaminated after each use. Care will be taken to ensure that any surface debris such as leaves,

rocks, twigs, lawn cuttings, etc. will be excluded from the sampling containers.

The exact soil sampling locations will be determined in the field. The criteria that will be used to

determine sampling locations will include accessibility and input from property owners. Soil sample

locations will be recorded in the field logbook as sampling is completed. A sketch of the sample

location will be entered into the logbook and any physical reference points will be labeled. If

possible, measured distances to the reference points will be given. Additionally, a photograph of

each sample location will be taken and logged for documentation.

Surface soil samples will be collected as grab samples (independent, discrete samples) from a depth

of 0 to 6 inches bgs. Sample containers will be filled to the top, taking care to prevent soil from

remaining in the lid threads prior to being closed to prevent potential contaminant migration to or

from the sample. Holes will be filled to grade with materials similar to the surrounding area.

Duplicate samples will be collected at a rate of 10 percent.



Each sample container will be labeled and sealed with tamperproof custody tape (Section 4.7).

Section 4.7 describes sample documentation and chain-of-custody procedures. Personnel involved

in sampling must wear clean, disposable gloves of the appropriate type specified in the approved

“Hazard Appraisal and Recognition Plan” (Appendix B).

If available, dedicated sampling equipment will be utilized for the surface sample collection to limit

the need for decontamination. Disposable equipment intended for one-time use will be packaged

for appropriate disposal. Each non-disposable sampling tool will be washed prior to use in a 5-

gallon plastic bucket using powdered detergent and water followed by two additional rinses with

clean water. Each non-disposable sampling tool will be inspected after cleaning to ensure all visible

soil is removed prior to use (Note: If dedicated sampling equipment is not available, full decontamination

procedures will be followed after each sample collection). The U.S. EPA, Region 4, Laboratory Services and

Applied Science Division guidance titled “Field Equipment Cleaning and Decontamination”, with

the effective date of June 22, 20202, will be followed for decontamination procedures.

4.4 LABORATORY ANALYSIS

All samples will be analyzed for Pesticides by DTSC’s Environmental Chemistry Laboratory (ECL),

or their contract laboratory, utilizing U.S. EPA Method 8270E to analyze the organochlorine

pesticides pentachloronitrobenzene and dieldrin; and to analyze the organophosphate pesticides

disulfton and phorate. A standard turnaround time will be requested for these analyses. Each

sample will be placed into cleaned and certified glass jars. No preservatives are required for Method

8270E other than maintaining the samples at 4° Celsius (+/- 2°) during shipment and pending

analysis. The laboratory holding time after sample extraction is 40 days.

For the purposes of laboratory quality assurance and quality control (QA/QC), the analytical

laboratory will utilize matrix spike (MS) and matrix spike duplicate (MSD) samples by spiking known

quantities of pesticides at the laboratory. The analytes used as spiking compounds will depend upon

the analytical method used. MS and MSD samples are a form of QA/QC used for determining

matrix effects and the reliability of the analytical processes and equipment. The matrix effect is a

condition in which sample composition interferes with the analysis of the desired analyte. Spiked

sample recovery supplies percentage recovery information so that the laboratory can evaluate its

measurement accuracy. MS and MSD samples are equal portions of a single initial sample that has

2 Guidance can be found at: https://www.epa.gov/sites/production/files/2016- 01/documents/field_equipment_cleaning_and_decontamination205_af.r3.pdf

https://www.epa.gov/sites/production/files/2016- 01/documents/field_equipment_cleaning_and_decontamination205_af.r3.pdf

https://www.epa.gov/sites/production/files/2016- 01/documents/field_equipment_cleaning_and_decontamination205_af.r3.pdf


August 2021 Page 19

been spiked in the laboratory with specific analytes in known quantities; the analytical results must

meet laboratory requirements to be acceptable.

4.5 SAMPLE CONTAINERS, PACKAGING AND SHIPPING

Soil samples will be homogenized and transferred from the sample-dedicated homogenization pail

or bucket into pre-cleaned and certified glass jars. The samples will be placed into an ice chest

chilled to 4 degrees Celsius immediately upon collection.

All sample containers will be placed in a strong-outside shipping container (a cooler). The following

packaging procedures will be followed:

· Wet ice will be packed in Ziploc®, double plastic bags. The drain plug of the cooler will be

sealed with tape to prevent melting ice from leaking out of the cooler.

· The bottom of the cooler will be lined with bubble wrap to prevent container breakage

during shipment.

· All screw caps will be checked for tightness prior to sealing the cooler for shipment.

· All container tops will be secured with custody seals.

· Sample labels will be affixed onto each container.

· All sample containers will be wrapped in bubble wrap to prevent breakage.

· All sample containers will be placed into heavy duty plastic Ziploc® bags. Sample numbers

will be written on the outside of each plastic bag with indelible ink.

· Appropriate chain-of-custody documentation will be placed in a Ziploc® plastic bag affixed

to the underside of the cooler lid.

· Empty space in the cooler will be filled with bubble wrap or Styrofoam peanuts to prevent

movement and breakage during shipment.

· Each ice chest will be securely taped shut, and custody seals will be affixed to the front, right

and back of each cooler.

4.6 DISPOSAL OF RESIDUAL MATERIALS

In the process of collecting samples, different types of potentially contaminated Investigation

Derived Waste (IDW) will be generated that include the following:



· Used personal protective equipment (PPE)

· Disposable sampling equipment

· Decontamination water

Used PPE and disposable equipment will be double bagged and placed in a municipal refuse

dumpster. These wastes are not considered hazardous and can be sent to a municipal landfill. Any

PPE and disposable equipment that is to be disposed of which could potentially be reused will be

rendered inoperable before disposal in the refuse dumpster. The decontamination water will be

tested and managed appropriately.

4.7 SAMPLE DOCUMENTATION

Detailed record keeping will be made in the field. These records will include field logbook(s) and

photographs.

Field logbooks will be used to document where, when, how, and from whom any vital project

information was obtained. Logbook entries will be sufficiently complete and accurate to permit

reconstruction of field activities. Logbooks will have consecutively numbered pages. All entries

should be legible, written in black ink, and signed by the individual making the entries. At a

minimum, the following information will be recorded during the collection of each sample:

· Sample location and description, including a sketch showing sample location and measured

distances

· Sampler's name(s), date and time of sample collection, type of sampling equipment used

· Designation of sample as composite or grab, type of sample (i.e., soil), preliminary sample

descriptions (e.g., for soils: silty sand, dry)

· Field observations and details related to analysis or integrity of samples (e.g., weather

conditions, noticeable odors, colors, etc.)

· Lot numbers of the sample containers, sample identification numbers and any explanatory

codes, and chain-of-custody form numbers

· Shipping arrangements (overnight air bill number), name of recipient laboratory

In addition to the sampling information, the following specific information will also be recorded in

the field logbook for each day of sampling:


August 2021 Page 21

· Team members and their responsibilities, levels of safety protection, other personnel on site,

time of arrival/entry on site and time of site departure, summary of any meetings or

discussions with others, changes in personnel and responsibilities with reasons for the

changes

· Deviations from sampling plans, site safety plans, and Quality Assurance Project Plan

procedures

Photographs will be taken at the sampling locations and at other areas of interest on site or sampling

area. They will serve to verify information entered in the field logbook. For each photograph taken,

the following information will be written in the logbook or recorded in a separate field photography

log:

· Time, date, location, and weather conditions, description of the subject photographed, name

of person taking the photograph

All samples collected will be labeled in a clear and precise way for proper identification in the field

and for tracking in the laboratory. The samples will have pre-assigned, identifiable, and unique

numbers. At a minimum, the sample labels will contain the following information: location, date of

collection, and analytical parameter. Every sample will be assigned a unique sample number.

All sample shipments for analyses will be accompanied by a chain-of-custody record. Form(s) will

be completed and sent with the samples for each shipment (i.e., each day). If multiple coolers are

sent to a single laboratory on a single day, form(s) will be completed and sent with the samples for

each cooler.

The chain-of-custody form will identify the contents of each shipment and maintain the custodial

integrity of the samples. Generally, a sample is considered to be in someone's custody if it is either

in someone’s physical possession, in someone's view, locked up, or kept in a secured area that is

restricted to authorized personnel. Until the samples are shipped, the custody of the samples will be

the responsibility of DTSC. The sampling team leader or designee will sign the chain-of-custody

form in the “relinquished by” box and note date, time, and air bill number.

A self-adhesive custody seal will be placed across the lid of each sample container. The shipping

containers in which samples are stored (usually a sturdy ice chest) will be sealed with self-adhesive



custody seals any time they are not in someone’s possession or view before shipping. All custody

seals will be signed and dated.

4.8 FIELD QUALITY CONTROL SAMPLES

Field quality control samples will include field duplicates and equipment blanks. Field duplicates will

be collected and analyzed in the same manner as the initial samples to evaluate variability in

heterogeneity, sample collection, and analysis. Equipment blanks will be collected to evaluate the

effectiveness of the decontamination procedures. The equipment blanks will be collected after

decontamination by pouring clean water over the non-disposable sampling tool and allowing the

water to collect in a glass jar for analysis of Site contaminants. The rate of collection for both field

duplicates and equipment blanks will be 10 percent.

4.9 FIELD VARIANCES

As conditions in the field may vary, it may become necessary to implement minor modifications to

sampling as presented in this plan. Modifications to the approved plan will be documented in the

sampling project report.

4.10 FIELD HAZARD APPRAISAL AND RECOGNITION PLAN

DTSC’s project-specific health and safety procedures will be followed in the field, including safety

equipment and clothing that may be required, explanation of potential hazards that may be

encountered, and location and route to the nearest hospital or medical treatment facility. A copy of

the approved “Hazard Appraisal and Recognition Plan” is included as Appendix B.

4.11 DATA EVALUATION AND REPORTING

Following sample collection and laboratory analysis, the results will be compiled and evaluated for

chemicals of concern. Data collected will be evaluated against residential screening levels. Data

evaluation and decisions for future actions will follow the decision rationale outlined in Section 3.1.5

above. If additional sampling is warranted, this OSP will be used as a basis for further assessment.


August 2021 Page 23

5. ReferencesDavid L. Alles, Geology of the Salton Trough, October 28, 2011.

Aron J. Meltzner, Recent and Long-Term Behaviour of the Brawley Fault Zone, May 17, 2006.

California Regional Water Quality Control Board. 2006. Water Quality Control Plan, Colorado River

Basin - Region 7. California Regional Water Quality Control Board and State Water Resources Control

Board. Includes amendments through June 2006.

California Department of Water Resources. 1975. California’s Groundwater, Bulletin 118, Hydrologic

Region Colorado River, Imperial Valley Groundwater Basin (7-30). Original 1975, Updated February

27, 2004.

Loeltz, O.J. et.al, 1975, Geohydrologic Reconnaissance of the Imperial Valley, California, U.S.

Geological Survey Professional paper 486-K.

U.S. Geological Survey. 2009. Ground Water Atlas of the United States – Segment 1 California

Nevada. Accessed online at: http://pubs.usgs.gov/ha/730b/report.pdf

ARCADIS U.S., Inc. 2014. Quarterly Groundwater Monitoring Results Report, Third Quarter 2013,

Former PureGro Facility, 1025 River Drive, Brawley, California. January 27.

Imperial Irrigation District. 2014. Water Use, Title 22 Reports, Central Main Canal 2012, Online at:

http://www.iid.com/index.aspx?page=183. January.

California Department of Toxic Substances Control. 2004a. Imminent and Substantial Endangerment

Determination and Consent Order. Docket No. I&SE-CO 03/04- 009. March 30.

Leighton Consulting, Inc. 2004. Data Report for Offsite Sampling, Former PureGro Company

Facility, 1025 River Drive, Brawley, California 92227. July 2.

EnviroStor, https://www.envirostor.dtsc.ca.gov/public/profile_report?global_id=13070097

Arcadis, Fourth Quarter 2020 Groundwater Gauging Results Summary, November 2020.

Arcadis, Annual Groundwater Monitoring Report, Second Quarter 2020, November 5, 2020.

CARB\MMB, Air Dispersion Modeling Results for DTSC PureGro Project, March 30, 2020.

Arcadis, Stockpile Sampling Report, March 29, 2020.



Arcadis, Revised Draft Remedial Action Plan, September 27, 2019.

Guidance on Systematic Planning using the Data Quality Objectives Process, U.S.EPA, 2006.

Arcadis, Site and Vicinity Land Use Memorandum, May 21, 2021.


August 2021 Page 25

Figures

Next 4 pages have been intentionally left blank – placeholder for pdf figures



Arrow Connector 53

FIGURE 1

SITE LOCATION MAP

FIGURE 1 - SITE LOCATION MAP

OFF-SITE SAMPLING PLAN

AUGUST 2021

SITE LOCATION

1000 feet

Source:National Geospacial Program US Topo

Product Standard, 2011. Brawley Quadrangle

California – Imperial County

7.5-Minute Series


August 2021 Page 27

FIGURE 2

FORMER PUREGRO SITE AND NEIGHBORHOOD AREA

FIGURE 2 - FORMER PUREGRO SITE AND

NEIGHBORHOOD AREA


AUGUST 2021

200 feet

Source:

https://earth.google.com/web/@32.98898597,-115.52436002,-

36.68315286a,1747.47158073d,35y,0h,0t,0r

FORMER PUREGRO SITE



* Based on CARB AERMOD Air Dispersion Model**Residential sample locations will be determined upon receipt of access agreements. Specific sample location disclosure will be subject to agreement by the property owner. Each home will include 1 soil sample at the surface (0-6inch).

FLD-E01 FLD-E02

Residential Study area South

Samples to be labelled RES-S

FLD-S04FLD-S03

FLD-E04

Residential Study Area East

Samples to be labelled RES-E

Legend: Residential lot sample locations** Southern Field sample locations Eastern Field sample locations

Number of actual samples (field and residential locations) will be determined upon right-of-entry, access, and coordination with property owner(s).

Former PureGro Site (Source Area)

Primary dust settlement area*

Secondary dust settlement area*

Primary Estimated Dust Settlement Area

Secondary Estimated Dust Settlement Area

Tertiary Estimated Dust Settlement Area

FLD-E03

FLD-S01 FLD-S02

FIGURE 3 – OFF-SITE SAMPLING LOCATIONS


AUGUST 2021

FIGURE 3

OFF-SITE SAMPLING LOCATIONS

200 feet

Source:

Dust Air Dispersion Modeling Results for DTSC’s PureGro Project (CARB/MMB, 7/10/2020)

FLD-E09

FLD-E06FLD-E07

FLD-E10

FLD-E08

FLD-E05


August 2021 Page 29

FIGURE 4

OFFSITE SAMPLE LOCATIONS FROM 2006 REMOVAL ACTION WORKPLAN

Source:GeoSyntec Consultants, Removal Action Workplan – Offsite Area, February 2006 (Figure dated August 2004)

FIGURE 4 – OFFSITE SAMPLE LOCATIONS

FROM 2006 REMOVAL ACTION WORKPLAN


AUGUST 2021



Tables


August 2021 Page 31

Table 1Analytical Methods and Numbers of Samples

Constituent of Concern Analytical Method

Number of Samples and Type

Disulfoton 8270E ·14 Field sample locations between facility and homes (4 south, 10 east). One depth per field sample location.

· Residential properties to the South and East (1 sample per residential lot) at one depth per sample location

Note: number of residential samples to be determined based on access agreements received

Phorate 8270EPentachloronitrobenzene 8270EDieldrin 8270E


August 2021 Page 33

Table 2List of Samples and Identification/Location

Sample Type Sample ID Depths LocationField Soil FLD-E01 0.5 0-6”, East of PuregroField Soil FLD-E02 0.5 0-6”, East of PuregroField Soil FLD-E03 0.5 0-6”, East of PuregroField Soil FLD-E04 0.5 0-6”, East of PuregroField Soil FLD-E05 0.5 0-6”, East of PuregroField Soil FLD-E06 0.5 0-6”, East of PuregroField Soil FLD-E07 0.5 0-6”, East of PuregroField Soil FLD-E08 0.5 0-6”, East of PuregroField Soil FLD-E09 0.5 0-6”, East of PuregroField Soil FLD-E10 0.5 0-6”, East of PuregroField Soil FLD-S01.05 0-6”, South of PuregroField Soil FLD-S02 0.5 0-6”, South of PuregroField Soil FLD-S03 0.5 0-6”, South of PuregroField Soil FLD-S04 0.5 0-6”, South of Puregro

Residential Soil, 1 location per residential lot

RES-S01 0.5To

RES-S018 0.5 0-6” South of Puregro

Residential Soil, 1 location per residential lot

RES-E01 0.5To

RES-E046 0.5 0-6” East of Puregro



Table 3

Soil Screening Levels/Detection Limits

Risk Driver Soil Screening Level* Detection Limits

Disulfoton 2.5 mg/kg** 5 µg/kg***Phorate 13 mg/kg 5 µg/kgPentachloronitrobenzene 2.3 mg/kg 5 µg/kgDieldrin 0.034 mg/kg 25 µg/kg

*Soil Screening Level based on U.S.EPA Region 9 Regional Screening Values for residential soils.**mg/kg – milligrams per kilogram***µg/kg – micrograms per kilogram


August 2021 Page 35

Table 4

Field Equipment Form




August 2021 Page 37

Appendices


Appendix A


Appendix A

CARB Air Dispersion Modeling Results

D R A F T O F F - S I T E S A M P L I N G P L A N P U R E G R O E V A L U A T I O N

August 2021 Page A-1

Appendix A CARB Air Dispersion Modeling Results Dust Air Dispersion Modeling Results for DTSC’s PureGro Project

(CARB/MMB, 7/10/2020) Objective The objective of this modeling exercise is to assist the Department of Toxic Substances Control (DTSC) in identifying locations within communities near the PureGro Facility (Site) where windblown dust, would have concentrated in the soil. This is achieved by investigating the modeled distribution of dust deposition within the nearby communities. Air Dispersion Modeling Approach Air dispersion modeling was conducted to estimate the relative distribution of cumulative dust deposition over the past 47 years (1973-2019). The period of 1955-1972 (time period of pesticide production) was also requested for consideration by DTSC, but no meteorological data exists for this time period. The air dispersion model - AERMOD (version 19191) was used to estimate dust deposition. AERMOD is recommended by the U.S. EPA for regulatory use. It has been extensively evaluated and widely used in various applications. Two types of meteorological data: (1) surface data, and (2) upper air data, are usually required to drive an air quality dispersion model. Surface data are meteorological data that are measured at the earth’s surface (technically, somewhere between the ground level and 10 meters above ground level). This data contains physical parameters that are measured directly by instrumentation, such as temperature, dew point, wind direction, wind speed, cloud cover, cloud layer(s), ceiling height, visibility, current weather, and precipitation amount. Surface data are reported by the National Weather Service for each hour. Upper air data are meteorological data that are measured for upper-air conditions such as atmospheric pressure, temperature and humidity, wind speed and direction in the vertical layers of the atmosphere. Upper air data are usually measured by twice daily radionsonde soundings, taken at 00 and 12Z (Greenwich time). The surface and upper air data are processed as an input to air dispersion models. In this study, surface meteorology and precipitation measurements from the El Centro (Imperial County) Airport, along with upper air radiosonde data in San Diego, were used to generate model-ready meteorological data sets. San Diego is the closest radiosonde site to the study area with a complete dataset for the entire modeling period (47 years). Figures 1 and 2 show the wind rose and wind speed distribution, respectively.


Page A-2 Department of Toxic Substances Control

Figure 1. Wind rose based on surface wind observations at El Centro Airport (1973-2019). The circular format of the wind rose shows the direction the winds blew from and the length of each "spoke" around the circle shows how often the wind blew from that direction. For example, the wind rose above shows that during the 1973-2019 sampling period the wind blew from the west 6.5% of the time, and from the southeast 3% of the time, etc. The different colors of each spoke provide details on the speed of the wind from each direction.



Figure 2. Wind speed distribution based on surface wind observations at El Centro Airport (1973-2019). This bar chart shows the wind speed and percentage of time wind was measured at a speed range over the 1973-2019 time period. For example, the bar chart shows that wind speeds from .50-2.10 meters per second were observed for 11.5 % of the time from 1973-2019. Wind speed and direction are the most critical factors that control how much dust is emitted and where the dust is transported and ultimately deposits. Figures 1 and 2 show that high wind events occurred regularly over the past 47 years, which indicates the potential for windblown dust emissions and transport. Calm winds (less than 0.5 meters per second (m/s)) do not create windblown dust and do not affect the modeling results.



AERMET is AERMOD’s meteorological pre-processor that generates all meteorological parameters needed by AERMOD. The meteorological field for AERMOD is horizontally uniform but vertically variable to reflect the vertical variations in meteorology such as wind shear. Air Modeling Conditions and Assumptions The following are conditions and assumptions made for this modeling exercise;

1. Potential emission sources to be modeled. Emissions are emitted uniformly within the facility fence line boundary as shown in figure 3 below.

2. The emissions are only generated by high winds during dusting storms. The model will utilize an empirical relationship of wind speed and dust generation rate from the literature, which has been used for the other projects for DTSC. It is assumed for the 2 time periods shown that 1) there have not been any preventive measures, such as vegetation, trees, structures or other materials covering the surface of the sites, 2) the activities within the sources (described above) take place uniformly, i.e., no activities/emission gradient, and activities generated by people’s walking and/or vehicles’ moving, or other activities will be ignored.

3. The time periods for the activities/emissions are assumed to be from 1973 to 2019 for Figure 4 and

1973 to 2010 for Figure 5. The model considers hourly activity/emission for the 47 years (1973-2019) for Figure 4 and 38 years for Figure 5. The time for Figure 5 is shorter to reflect the number of years that Soil Sement (dust preventative) was applied to the Site. The period of 1955 to 1972 (Time period of Pesticide production) was also requested to be considered by DTSC, but no meteorology data covering the period exists, and therefore was not included in the modeling activity.

4. The meteorology from El Centro (Imperial County) Airport covering 1973-2019 will be used as

surface conditions, while the sounding data from San Diego covering the same time period will be used as upper air conditions (please see page 1).



Assumptions Made for Site contaminants • Once the hourly TSP emission rate is calculated, Site contaminant emission rates can be obtained by

multiplying the TSP emission rate by Site contaminant concentrations in the TSP. Unfortunately, Site contaminant concentrations in the TSP can change substantially depending on the original emission locations. Based on what is known about the facility and emitting areas, two time periods were studied.

• The first period (Figure 4, 1973-2019) assumes that the emissions are emitted uniformly within the facility fence line boundary.

• The second period (Figure 5, 1973-2010) assumes that the emissions are emitted uniformly within the facility fence line boundary, but this time reflects the number of years that Soil Sement (dust preventative) was applied to the Site.

• If the two time periods give the same or similar locations where the deposited dust are the highest (relative basis), then those areas are the areas where soil sampling should take place. Figure 3 shows the spatial layout of emission sources.

Potential Emissions Since Site contaminants are emitted predominantly by soil erosion within the facility, it is reasonable to assume that the mechanism of Site contaminants emission generation is the same as that for total suspended particulates (TSP). However, there is a noticeable difference between Site contaminants and TSP emissions since Site contaminants emissions vary with Site contaminants concentrations in the soil, while TSP emissions are approximately uniform throughout the facility. Considering the assumptions used to develop the study, it is presumed that the results will present an overestimation of TSP emissions for the following reasons: 1) the Site had concrete slab buildings on site; 2) the stockpile has been covered since being created (2006); and 3) for the time period 1973-2019 on-site soils had been treated with Soil Sement (dust suppressant) since 2003 (annual application since 2013). How TSP Emissions are Determined TSP emissions are determined by friction velocity, a micrometeorological parameter affected primarily by wind speed and secondarily by the vertical variation of temperature, and precipitation. For any hour with a measurable amount of precipitation (not less than 0.01 inch) recorded at the El Centro Airport, the TSP emission rate for that hour and the following five hours are set to zero. For all other hours, hourly TSP emissions were calculated following Macpherson et al. (2008, Journal of Geophysical Research, Vol. 113, F02S04) with a formula derived from wind tunnel soil dust measurements (Equation 1): 𝐸𝐸 = 5.64 × 10−12𝑢𝑢∗1.9744 [𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢 𝑎𝑎𝑎𝑎𝑎𝑎:

𝑔𝑔𝑐𝑐𝑐𝑐2𝑢𝑢

] Equation (1)

where 𝑢𝑢∗ is the friction velocity in cm/s.. This formula, which is valid for an undisturbed surface, was derived from a 2008 Maricopa Co. PM10 Emission Inventory (Macpherson et al. 2008, Journal of Geophysical Research, Vol. 113, F02S04)). A scaling factor of 100/52.3 has been applied to the formula so that the formula is valid for TSP rather than PM10, where 52.3 is the percentage of PM10 in TSP for road and



soil dust (US EPA, 1997, Guidance For Network Design and Optimum Site Exposure For PM2.5 And PM10, EPA-454/R-99-022). It should be noted that existing methods for calculating an annual emission rate are not used here because they can’t take the temporal variation of emissions into consideration. Examples of these methods include the US EPA’s AP-42 (https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors) and the ARB’s method of estimating windblown dust from agricultural lands (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwj79L-LjcPoAhX9HjQIHUhaD74QFjAAegQIAhAB&url=https%3A%2F%2Fwww.arb.ca.gov%2Fei%2Fareasrc%2Ffullpdf%2Ffull7-12.pdf&usg=AOvVaw3vme6yGG-1SofphJtCoDrB)

Figure 3. Layout of the PureGro Facility.

MW-14MW-15

PZ-1

MW-11

MW-3MW-12MW-10

MW-2MW-9

MW-1

MW-6

MW-8

MW-7

NW5

B-34

W1

B-53

MW-5

MW-13

https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors

https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwj79L-LjcPoAhX9HjQIHUhaD74QFjAAegQIAhAB&url=https%3A%2F%2Fwww.arb.ca.gov%2Fei%2Fareasrc%2Ffullpdf%2Ffull7-12.pdf&usg=AOvVaw3vme6yGG-1SofphJtCoDrB





Modeling Results Air modeling that considers the assumptions stated above suggests that the highest concentrations of dust could have been dispersed and deposited to the neighborhood area located to the south of the Site and in the open area to the east. Figures 4 and 5 show the same southern location within the primary estimated dust settlement area. While the community to the east falls into the tertiary dust settlement areas. Figures 4 and 5 show that both emission periods give a similar dust deposition area to the east and south. Therefore, soil samples should be concentrated to the south and east in the primary estimated dust settlement areas.

Figure 4. Contour plot of total dust deposition for Period 1 (1973-2019).

Primary es�mated dust se�lement

Secondary es�mated dust se�lement

Ter�ary es�mated dust se�lement

Assumed Source




1973 -2019



Figure 5. Contour plot of total dust deposition for Period 2 (1973-2010).

1973 -2010




Assumed Source





August 2021 Page 39

Appendix B

Hazard Appraisal and Recognition Plan


August 2021 Page B-1

HAZARD APPRAISAL AND RECOGNITION PLAN (HARP) FORM TO BE COMPLETED AND INSERTED UPON FINALIZATION OF WORKPLAN



Appendix C

Aerial Photographs

Aerial Photograph Research

Report Results for: Nicholas Bui Department of Toxic Substances Control 5796 Corporate Avenue Cypress, CA 90630 2104712775 AO

Site Information: 1025 River Drive Brawley, CA 92227

August 6, 2019

ENVIRONMENTAL RECORD SEARCH

©2017

(800) 377-2430 | www.reccheck.com

Subject Site: ERS Order #:

Client’s Project #: 2104712775 AO Address: 1025 River Drive City, State Zip: Brawley, CA 92227

Prepared For: Date:

Name: Nicholas Bui August 6, 2019 Company: Department of Toxic Substances

Control Prepared By:

Address: 5796 Corporate Avenue Name: Phuc Tran City, State Zip: Cypress, CA 90630 Phone #: (714) 669-8096

Ext. 1003

Enclosed are the results of our…..

Aerial Photograph Research. Thank you for selecting Environmental Record Search!

To aid you in locating your site on the imagery provided, we have placed a box over/surrounding your site. Note: This box is not representative of your site boundaries. It is simply a tool to assist you with the location of your site within the image. The box has been placed in the same location on each image to help you locate your site easily from year to year. If you have any problems locating your site, please call us. We are here to help.

Aerial photo years available:

2016 2010 2002 1996 1981 1972 1969 1953 1948


©2017


Historical Aerial Photo

Year 2016

1025 River Drive Brawley, CA

Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 2010


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 2002


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1996


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1981


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1972


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1969


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1953


Target Site: 32.986758, -115.524935 Job #: 2104712775


©2017



Year 1948


Target Site: 32.986758, -115.524935 Job #: 2104712775

Documents

DRAFT OFF-SITE SAMPLING PLAN