RMC_2008_Final_Crownpoint_SI_07-15-09_(1)_0002.pdf

Prepared for:

Bureau of Indian Affairs Navajo Regional Office 301 West Hill Road P.O. Box 1060 Gallup, New Mexico

Provided by:

RMC Consultants, Inc.

12345 W. Alameda Parkway, Suite 205 Lakewood, CO 80228 303-980-4101

Final Site Investigation, Exposure Assessment, and

Engineering Evaluation/Cost Analysis Crownpoint Community School

Crownpoint, New Mexico

Final Site Investigation Report, Exposure Assessment, and Engineering Evaluation/Cost Analysis Crownpoint Community School, New Mexico

RMC Consultants, Inc.

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FINAL

SITE INVESTIGATION REPORT,

EXPOSURE ASSESSMENT, AND

ENGINEERING EVALUATION/COST ANALYSIS

CROWNPOINT COMMUNITY SCHOOL

CROWNPOINT, NEW MEXICO

Prepared for:

Bureau of Indian Affairs Navajo Regional Office

301 West Hill P.O. Box 1060

Gallup, New Mexico Contract Number: CMN00070028

Prepared by:

RMC Consultants, Inc.

12345 West Alameda Parkway, Suite 205

Lakewood, CO 80228

July 2009

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TABLE OF CONTENTS

1.0 INTRODUCTION......................................................................................................... 1-1

1.1 PURPOSE AND SCOPE.......................................................................................... 1-1

1.2 REPORT ORGANIZATION..................................................................................... 1-1

2.0 SITE HISTORY ............................................................................................................ 2-1

2.1 SITE DESCRIPTION AND HISTORY....................................................................... 2-1

2.2 PREVIOUS INVESTIGATIONS ............................................................................... 2-1

2.3 ENVIRONMENTAL SETTING ................................................................................ 2-4

2.3.1 Regional and Site Geology.................................................................... 2-4

2.3.2 Regional Hydrology .............................................................................. 2-4

3.0 SITE INVESTIGATION ACTIVITIES...................................................................... 3-1

3.1 DIRECT-PUSH SOIL SAMPLING ........................................................................... 3-1

3.2 SOIL CHEMICAL ANALYSIS ................................................................................ 3-1

3.3 SOIL ANALYTICAL RESULTS .............................................................................. 3-2

3.3.1 Building 3002 (Tank #2) ....................................................................... 3-2

3.3.2 Building 3010 (Tank #3) ....................................................................... 3-2

3.3.3 Building 3008 (Tank #4) ....................................................................... 3-3

3.3.4 Building 3009 (Tank #5) ....................................................................... 3-3

3.3.5 Building 3004 (Tank #7) ....................................................................... 3-4

3.3.6 Building 3001 (Tank #8 and #9) ........................................................... 3-4

3.4 SOIL GEOTECHNICAL ANALYSIS ........................................................................ 3-5

3.5 SOIL GEOTECHNICAL RESULTS .......................................................................... 3-5

3.6 INVESTIGATION DERIVED WASTE MANAGEMENT AND DISPOSAL .................... 3-5

4.0 EXPOSURE ASSESSMENT........................................................................................ 4-1

4.1 HUMAN HEALTH RISK ASSESSMENT.................................................................. 4-1

4.2 NATURE AND EXTENT OF CONTAMINATION ...................................................... 4-2

4.2.1 Building 3002 (Tank#2) ........................................................................ 4-2

4.2.2 Building 3010 (Tank #3) ....................................................................... 4-2

4.2.3 Building 3008 (Tank #4) ....................................................................... 4-3

4.2.4 Building 3009 (Tank #5) ....................................................................... 4-3

4.2.5 Building 3004 (Tank #7) ....................................................................... 4-4

4.2.6 Building 3001 (Tank #8) ....................................................................... 4-4

4.2.7 Building 3001 (Tank #9) ....................................................................... 4-4

4.3 DATA ADEQUACY............................................................................................... 4-5

4.4 POTENTIAL RECEPTORS AND PATHWAYS OF EXPOSURE ................................... 4-5

4.4.1 Potential Receptors................................................................................ 4-5

4.4.2 Potentially Complete Exposure Pathways............................................. 4-6

4.4.2.1 Surficial Soil Ingestion or Dermal Contact .............................. 4-6

4.4.2.2 Surface Water Ingestion or Dermal Contact ............................ 4-6

4.4.2.3 Groundwater Ingestion or Dermal Contact .............................. 4-6

4.4.2.4 Inhalation of Volatiles and Particulates in Air ......................... 4-6

4.4.2.5 Food Chain Exposure/Contamination ...................................... 4-8

4.4.3 Exposure Point Concentrations ............................................................. 4-9

4.5 TOXICITY ASSESSMENT...................................................................................... 4-9

4.6 SITE SPECIFIC RISK CHARACTERIZATION .......................................................... 4-9

4.6.1 Building 3002 (Tank #2) ..................................................................... 4-10

4.6.2 Building 3010 Tank #3) ...................................................................... 4-10

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4.6.3 Building 3008 (Tank #4) ..................................................................... 4-10

4.6.4 Building 3009 (Tank #5) ..................................................................... 4-11

4.6.5 Building 3004 (Tank #7) ..................................................................... 4-12

4.6.6 Building 3001 (Tank #8 and #9) ......................................................... 4-12

4.7 ECOLOGICAL RISK ASSESSMENT...................................................................... 4-12

4.8 UNCERTAINTY ANALYSIS................................................................................. 4-13

4.9 CONCLUSIONS AND RECOMMENDATIONS ........................................................ 4-13

5.0 ENGINEERING EVALUATION/COST ANALYSIS............................................... 5-1

5.1 PURPOSE AND SCOPE.......................................................................................... 5-1

5.2 IDENTIFICATION OF ALTERNATIVES................................................................... 5-1

5.3 IDENTIFICATION OF ARARS............................................................................... 5-2

5.4 ANALYSIS OF ALTERNATIVES ............................................................................ 5-4

5.5 COMPARATIVE ANALYSIS OF ALTERNATIVES.................................................... 5-5

5.6 RECOMMENDED ALTERNATIVES ........................................................................ 5-5

6.0 CONCLUSIONS AND RECOMMENDATIONS ...................................................... 6-1

7.0 REFERENCES .............................................................................................................. 7-1

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LIST OF TABLES

Table 3-1 Summary of Soil Analytical Results for Building 3002 (Tank #2) Table 3-2 Summary of Soil Analytical Results for Building 3010 (Tank #3) Table 3-3 Summary of Soil Analytical Results for Building 3008 (Tank #4) Table 3-4 Summary of Soil Analytical Results for Building 3009 (Tank #5) Table 3-5 Summary of Soil Analytical Results for Building 3004 (Tank #7) Table 3-6 Summary of Soil Analytical Results for Building 3001 (Tank #8 and #9) Table 4-1 Summary of Applicable and Relevant Soil Screening Values Table 4-2 Summary of Building 3002 Exposure Point Concentration and Risk Ratios Table 4-3 Summary of Building 3010 Exposure Point Concentration and Risk Ratios Table 4-4 Summary of Building 3010 Indoor Air Cancer Risk and Risk Ratios Table 4-5 Summary of Building 3008 Exposure Point Concentration and Risk Ratios Table 4-6 Summary of Building 3009 Exposure Point Concentration and Risk Ratios Table 4-7 Summary of Building 3009 Indoor Air Cancer Risk and Risk Ratios Table 4-8 Summary of Building 3004 Exposure Point Concentration and Risk Ratios Table 4-9 Summary of Building 3001 Exposure Point Concentration and Risk Ratios Table 5-1 Summary of Potential ARARs for Remedial Actions at Former UST Sites Table 5-2 Summary of Comparative Analysis of Alternatives

LIST OF FIGURES

Figure 1-1 Site Location Map Figure 2-1 Crownpoint Community School – Campus Layout Map Figure 3-1 Direct-push Soil Sample Location and Results Map- Building 3002 (Tank#2) Figure 3-2 Direct-push Soil Sample Location and Results Map- Building 3010 (Tank#3) Figure 3-3 Direct-push Soil Sample Location and Results Map- Building 3008 (Tank#4) Figure 3-4 Direct-push Soil Sample Location and Results Map- Building 3009 (Tank#5) Figure 3-5 Direct-push Soil Sample Location and Results Map- Building 3004 (Tank#7) Figure 3-6 Direct-push Soil Sample Location and Results Map- Building 3001 (Tank#8) Figure 3-7 Direct-push Soil Sample Location and Results Map- Building 3001 (Tank#9) Figure 4-1 Conceptual Site Model for Crownpoint Community School

APPENDICES

Appendix A Completed Field Forms Appendix B Photographic Logs Appendix C Analytical Data Sheets Appendix D Geotechnical Data Sheets and Engineering Cost Sheets

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LIST OF ACRONYMS

AASHTO American Association of State

Highway and Transportation Officials ARARS Applicable, Relevant and

Appropriate Requirements AST Aboveground Storage Tank ASTM American Society for Testing and

Materials ASTS ASTS Incorporated bgs below ground surface BIA Bureau of Indian Affairs

CERCLA Comprehensive Environmental

Response, Compensation, and Liability Act CWA Clean Water Act

DAF Dilution Attenuation Factor DRO Diesel Range Organics

EE/CA Engineering Evaluation/Cost

Analysis EPA U.S. Environmental Protection

Agency EPC Exposure point concentration foc fraction organic carbon g/cm3 grams per cubic centimeter

HHRA Human Health Risk Assessment HQ hazard quotient

IDW Investigation Derived Waste IRIS Integrated Risk Information

System

MCL Maximum Contaminant Level MEK methyl ethyl ketone or 2-butanone MRL method reporting limit MTG migration to groundwater mg/kg milligram per kilogram mL milliliter

NCP National Contingency Plan NMED New Mexico Environmental

Department

NNEPA Navajo Nation Environmental Protection Agency

PAH Polynuclear Aromatic

Hydrocarbons Pcf pounds per cubic foot PID Photoionization Detector PPE Personal Protective Equipment PRGs Preliminary Remedial Goals ppm parts per million

RA Risk Assessment RCRA Resource Conservation and

Recovery Act RMC RMC Consultants, Inc.

RL reporting limit

SCS Soil Conservation Service SDWA Safe Drinking Water Act SI Site Investigation SSL Soil Screening Level SVs Screening Values

TBC to be considered TPH Total Petroleum Hydrocarbons ug/kg micrograms per kilogram USCS Unified Soil Classification System UST Underground Storage Tank

VOA Volatile Organic Analysis VOC Volatile Organic Compound

WP Work Plan ºC degree Celsius

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1.0 INTRODUCTION

This Site Investigation (SI) report documents the field activities completed in January of 2009 at the Crownpoint Community School located in Gallup, New Mexico. A site location map is provided as Figure 1-1. Additionally, this report presents a exposure assessment / risk assessment (RA) and a completed Engineering Evaluation/Cost Analysis (EE/CA) based on the SI findings. This combined SI, RA, and EE/CA report was prepared by RMC Consultants Inc. (RMC) under Contract No. CMN00070028 with the Bureau of Indian Affairs (BIA). This document describes the work performed pursuant to the approved Work Plan (WP) (RMC, 2008).

1.1 Purpose and Scope

Under the applicable BIA Contract, RMC was tasked to further delineate soil contamination, perform a RA, and identify potential remedial action alternatives for the heating oil contaminated soil at the Crownpoint Community School. This SI was initiated as a result of Petroleum contaminated soil being discovered at the site in 2004 during underground storage tank (UST) closure activities performed by ASTS, Inc.

(ASTS).

The primary purpose of this SI was to gather additional site data necessary to complete an RA and an EE/CA. More specifically, the intent of the SI is to achieve the following objectives:

• Advance direct-push probeholes and collect soil samples to determine the vertical and horizontal extent of petroleum soil contamination.

• Complete a RA using data obtained from the soil samples to evaluate the potential threat to human health and/or the environment.

• Complete an EE/CA and identify a minimum of six remedial action alternatives, including the no action alternative, and provide associated cost estimates to mitigate soil contaminated by heating oil released at the site.

This SI report presents the procedures utilized and data obtained to assess and recommend appropriate actions for the Crownpoint Community School.

1.2 Report Organization

This WP is divided into seven sections. Section 1 provides introductory information and site history. Section 2 provides a description of the site history. Section 3 summarizes the SI procedures and results. The assessment of risk to human health and the environment is provided in Section 4. Section 5 describes the EE/CA. Conclusions and recommendations are presented in Section 6. References cited are provided in Section 7.

Referenced tables and figures are included in separate sections following the text.

Supporting data are included in Appendix A through D.

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2.0 SITE HISTORY

2.1 Site Description and History

The Crownpoint Community School is a BIA operated facility located in northwestern New Mexico within the Navajo Nation. The school is located approximately one mile east of the village of Crownpoint in McKinley County, New Mexico near the intersection of U.S. Highway 371 and Navajo Route 9. A Site Location Map is included as Figure 1- 1.

The school, which has been in operation since the 1950’s, has nine major structures on the main campus that contain active classrooms and dormitories for students. These structures are Building 3000 (classrooms and administrative offices), Building 3001 (Social Services), Building 3002 (multi-purpose and gymnasium), Building 3003 (Career Development and Adult Education), Building 3004 (Criminal Investigations and Land Offices), Building 3008 (kitchen and cafeteria), Building 3009 (girls dormitory), Building 3010 (student center), and Building 3012 (coed dormitory). A site map illustrating the layout of the school campus is provided as Figure 2-1.

Ten USTs supplied heating oil fuel to the boilers used to heat the buildings on the main campus. Two of the ten USTs were located at Building 3001. Buildings 3000, 3002, 3003, 3004, 3008, 3009, 3010, and 3012 each had one UST located adjacent to their respective boiler rooms. The USTs were installed in 1953 and used until the summer of 2000, when they were replaced by above ground storage tanks (ASTs) currently in use at the school.

The Navajo Nation Environmental Protection Agency (NNEPA) was notified of a release from the abandoned USTs via correspondence dated March 31, 2004. The removal of ten USTs and associated pipe systems at the school occurred in the spring of 2004 during the tank closure activities performed by ASTS (see Section 2.2).

Residual contamination, above the NNEPA UST regulatory limit of 500 parts per million (ppm) for Total Petroleum Hydrocarbons (TPH), remains in place at the former UST locations at Buildings 3001, 3002, 3004, 3005, 3008 and 3009. In addition, residual contamination above 100 ppm remains in place at the remote fill locations associated with Building 3004, 3009 and 3010. In the 2004 closure report, further investigations of these locations to completely delineate the extent of the petroleum-contaminated soil was recommended (ASTS, 2004).

2.2 Previous Investigations

UST closure activities were documented in the Closure Report of Underground Storage Tanks, Volume I: Report, Crownpoint (T’iists’oozi’) Community School (August 9, 2004).

The facility had not been previously investigated for a hydrocarbon release prior to the UST closure activities.

A total of 1,498 cubic yards of petroleum-contaminated soil was removed from the campus during the 2004 closure activities. The largest occurrence and highest concentration of contaminated soils were detected at Building 3001, which contained two

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USTs. ASTS recommended closure for tanks 1, 6, and 10, which were associated with Buildings 3000, 3003, and 3012, respectively. Further investigation was recommended for soils adjacent to Buildings 3001, 3002, 3004, 3008, 3009, and 3010 after TPH concentrations collected from the furthest extent of the UST/remote fill excavations exceeded the then NNEPA regulatory limit of 100 ppm in soil samples (ASTS, 2004).

Key findings from the 2004 tank closure activities are presented below beneath the corresponding building and UST tank numbers.

Tank #2 (Building 3002)

Petroleum-contaminated soil, likely the result of overfilling, was encountered at the tank and remote fill location. The removal of the tank revealed an accumulation of free product along the bottom of the excavation at a depth of approximately 12 feet below ground surface (bgs). The final dimensions of the tank excavation were 30 feet along the axis by 22 feet wide by 17 feet in depth. A well-cemented sandstone bench was encountered during excavation at 17 feet bgs.

One of seven soil samples collected for laboratory analysis from the tank and associated fill line excavations exceeded the 100 ppm limit for TPH. A concentration of 250 ppm was reported for sample CNPT-T2-N, which was collected from the north end of the tank at a depth of 13 feet bgs. Petroflag samples collected from the east and west walls of the excavation produced estimated concentrations of 1,227 and >2,000 ppm, respectively.

Following excavation of contaminated soils, soil samples collected for laboratory analysis from the supply line and remote fill, were all below the regulatory limit.

Tank #3 (Building 3010)

Contaminated soil, the result of perforations in Tank #3, was encountered at Building 3010. Contaminated soil was encountered at the remote fill for this UST as well.

Excavation of the remote fill preceded to a depth of 6.5 feet bgs, but ceased at this depth due to the presence of a six-inch transite water pipeline and a propane gas pipeline.

Excavation of this UST resulted in the removal of approximately 10 cubic yards of soil.

A concentration of 1,700 ppm (TPH) was recorded for sample CNPT-T3-R+160 collected at the remote fill for Tank #3. Samples CNPT-T3-N and CNPT-T3-S were collected from the north and south end of the UST footprint, respectively, at depths of 9 feet bgs. The samples both exceeded the TPH limit at 21,000 ppm and 940 ppm, respectively. Petroflag results from the north, east, and south walls of the excavation all produced estimated TPH concentration in excess of 2,270 ppm. A Petroflag result for the west wall was not reported.

Tank #4 (Building 3008)

Petroflag analysis conducted beneath Tank #4 indicated petroleum contamination in excess of 600 ppm TPH. Further excavation was prohibited by the presence of a 10-inch thick slab of concrete. The slab dimensions are eight feet wide by 16 feet long. An analytical sample was obtained from the top of the slab with a result of 650 ppm.

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However, the concrete slab is believed to have prohibited further vertical migration of the petroleum contamination. Fuel was not present in the tank, which was free of perforations. Petroflag samples from the east and west walls exceeded the TPH limit at 167 ppm (11.5 feet bgs) and 1,287 ppm (8.0 feet bgs), respectively.

The remote fill concrete structure was removed prior to the UST excavation as part of a pavement resurfacing project at the school. The closure report states that approximately 60 feet of remote fill pipe remained in place and samples were not collected from the former remote fill location. However, Gilbert Gruber, with the Crownpoint Community School maintenance department, stated the line was removed during the 2004 tank closure.

Tank #5 (Building 3009)

Laboratory samples CNPT-T5-N and CNPT-T5-S were obtained from the bottom of the excavation (12 feet bgs) from the north and south end of the tank footprint, respectively.

These samples yielded concentrations of 8,000 ppm and 920 ppm TPH, respectively.

Petroflag samples taken from each of the four tank excavation walls (12 feet bgs) all exceeded the TPH limit at concentrations greater than 2,500 ppm. Inspection of the excavated tank revealed three perforations ranging in size from 0.25 to 0.50 inches.

In addition, laboratory sample CNPT-T5-R-120 was obtained at 5.4 feet bgs beneath the remote fill line with a result of 190 ppm. Further excavation along this section of fill pipe was prohibited by the presence of a liquid petroleum (LP) gas line in close proximity. As part of this SI, this section of the remote fill pipe will be further investigated to determine the extent of the petroleum contamination.

Tank #7 (Building 3004)

An inspection of Tank #7 following its removal revealed three perforations ranging in size from 0.5 to 1.5 inches in diameter. Laboratory sample CNPT-T7-N was collected at 12 feet bgs from the north end of the tank footprint and yielded a TPH concentration of 24,000 ppm. A four-inch water line was encountered just nine inches to the north of the tank. Four Petroflag samples obtained from each of the four excavations walls at eight feet bgs were all below the TPH limit of 100 ppm.

Laboratory sample CNPT-T7-R-120 was collected at 4.5 feet bgs from the remote fill location and yielded a TPH concentration of 30,000 ppm. Further excavation was not performed at this location and no explanation was provided by ASTS in the closure report.

Sample CNPT-T7-l+27 was collected at the foundation of Building 3004 at 2.2 feet bgs where the return and supply lines from the UST enter the building. This laboratory sample resulted in a TPH concentration of 120 ppm. RMC will attempt further investigation at this location assuming the location of utilities allows adequate clearance for safe advancement.

Tank #8 (Building 3001)

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Tank #8 was located next to the Explorer Loop perimeter road and therefore did not require a remote fill. There was no concrete pad associated with this 4,000 gallon fiberglass tank. Fuel was observed leaking from a suspected hairline fracture in the tank during removal. Laboratory samples CNPT-T8-E and CNPT-T8-W were collected from the east and west ends of the tank footprint at depths of 12 and 8 feet bgs, respectively.

Analytical results for both samples exceeded the TPH limit at 380 and 360 ppm, respectively.

A Petroflag sample obtained from each of the four excavations walls and all the supply line laboratory samples (6) were below the TPH limit of 100 ppm.

Tank #9 (Building 3001)

Tank #9 contained 44 inches of heating oil, which was removed prior to excavation. The initial excavation of Tank #9 revealed nine separate utility lines and AST vaulted fuel lines located between the building and the long axis of the tank. Inspection of the tank revealed a minimum of 13 perforations ranging in size from 0.5 to 1.5 inches in diameter.

Laboratory sample CNPT-T9-S was collected from the south end of the tank footprint at a depth of 12 feet bgs and yielded a TPH concentration of 340 ppm. All four Petroflag samples, one from each of the four excavation walls, and all the supply line laboratory samples (6) were below the TPH limit of 100 ppm.

2.3 Environmental Setting

2.3.1 Regional and Site Geology

Crownpoint, New Mexico is located on the Mesozoic formations of the Colorado Plateau.

More precisely, the school is situated within the Gallup Sag. This structure is a depression consisting of a broad area of low ridges and alluvial valleys between the Zuni Uplift and Defiance Plateau. The school is situated on sedimentary rocks that dip gently to the north and east away from the uplifted areas (ASTS, 2004).

According to the UST closure report, the majority of soils encountered during the UST excavations were silty-sands with some occurrences of clayey-sands and silty-clays.

Additionally, a one-foot coal seam associated with the Gibson Coal Member of the Crevasse Canyon Formation was encountered at a depth between four to seven feet bgs throughout the school campus. The soil section ranged from six to thirteen feet before encountering consolidated rock (ASTS, 2004).

In each tank hold area, excavation revealed occurrences of beds of partially consolidated carbonaceous shale, siltstone, and claystone, interbedded with thin discontinuous coal seams. These seams overlay pale yellowish-gray to white, very fine to medium grained, poorly sorted sandstone beds from 1.5 to 4.0 feet in thickness (ASTS, 2004).

2.3.2 Regional Hydrology

Four potable water wells owned and operated by the Navajo Tribal Utility Authority are located within a 1.5 mile radius of the Crownpoint Community School. The closest well, RMC Consultants, Inc.

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CRWNPT-PM6, is located approximately 0.25 miles west of the school campus. It has a reported static water level of 350 feet bgs and a total depth of 2,500 feet bgs. The average depth to water for the three remaining wells, which are located three-quarter of a mile or more from the school, is 381 feet bgs. The wells were completed in intervals of Jurassic and older rock formations. There are no known shallow aquifers or surface water bodies and/or wetlands in the vicinity of the school.

The annual average precipitation at Crownpoint is 9.52 inches. Rainfall is fairly evenly distributed throughout the year. The wettest month of the year is August with an average rainfall of 1.36 inches (www.idcide.com/weather/nm/crownpoint.htm).

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3.0 SITE INVESTIGATION ACTIVITIES

The field data collection actions associated with the approved WP (RMC, 2008) are detailed in the following sections. The objective was to obtain sufficient information to determine the vertical and horizontal extent of soil contamination at the former UST and associated remote fill sites. Prior to implementing the field data collection actions, work and schedules were coordinated with personnel from the Crownpoint Community School.

SI work tasks commenced on January 12 and concluded on January 17, 2009.

3.1 Direct-Push Soil Sampling

Prior to commencing direct-push soil sampling activities at the site, Hydro Physics out of Albuquerque, New Mexico was contracted to locate underground utilities within the proposed sampling areas. Additionally, to ensure the safety of personnel and minimize the possibility of damage to underground utilities, the initial four feet of each proposed direct-push location was advanced using a hand auger. Soil probeholes were advanced at buildings 3001, 3002, 3004, 3008, 3009, and 3010 using a truck-mounted GeoProbe® operated by Drill Pro Services located in Denver, Colorado. During all direct-push activities orange snow fence was placed around the perimeter of the work area to isolate the activity from school personnel and children.

Soil probeholes were advanced and continuously sampled using a GeoProbe stainless steel Macro-Core sampler with disposable acetate liners. During sampling all locations were logged using the Unified Soil Classification System (USCS) for unconsolidated materials and field screened for volatile organic compounds (VOCs) using a MiniRae 2000 photo-ionization detector (PID). Details of the individual probehole logs are included in Appendix A. A total of 84 soil samples (two samples per probehole) and 9 duplicate samples were obtained at depths ranging from six to 15.5 feet bgs. A total of 42 probeholes were advanced as follows: nine probeholes at building 3001, six probeholes at building 3002, seven probeholes at building 3004, four probeholes at building 3008, nine probeholes at building 3009, and seven probeholes at building 3010.

Probeholes progressed from known areas of contamination and progressed laterally away from the contamination in an effort to assess the lateral extent of contamination. The locations of the soil direct-push locations are illustrated on Figures 3-1 through 3-7.

Following completion of direct-push activities at each location, the probeholes were properly abandoned by backfilling each hole with hydrated bentonite pellets. The surface areas were then restored to pre-activity conditions with like material (i.e., asphalt paving, cement, landscape material, or native soil).

Upon completion of all sampling activities, the horizontal location of each probehole was measured in relation to each respective building.

3.2 Soil Chemical Analysis

All soil samples were analyzed in accordance with the approved WP and SW-846 Method 8260B for VOCs, and 8015B for TPH/diesel range organics (DRO). One soil sample, exhibiting the maximum headspace PID reading, at each former tank site was

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TPH/DRO and PAH samples were collected in clean air-tight laboratory supplied jars.

VOC soil samples were collected in methanol and bisulfate preserved 40 milliliter (mL) volatile organic analysis (VOA) vials. All samples were stored in ice-packed sample coolers until shipment to Pace Analytical Laboratories in Lenexa, Kansas at the end of the project.

3.3 Soil Analytical Results

Soil analytical results for VOCs and PAHs were compared to the United States Environmental Protection Agency (EPA) Region 3, 6 and 9 Residential Soil Screening Levels (SSLs). EPA currently has no regulatory standards for TPH; therefore concentrations were compared to the 500 mg/kg level as recommended by the NNEPA.

The following subsections discuss the results from the six building locations.

3.3.1 Building 3002 (Tank #2)

Four probehole locations were advanced around the former location of Tank #2 and two probehole locations were advanced adjacent to the former remote fill location at Building 3002. Twelve samples were analyzed for TPH and one sample was analyzed for PAH at the site. TPH and PAH compounds were all reported below the laboratory reporting limit (RL) or non-detect at building 3002. Acetone and 2-butanone (or methyl ethyl ketone [MEK]) were the only VOCs detected above the laboratory RL. Acetone was present in seven of the 12 samples at a maximum concentration of 234 ug/kg. 2-Butanone (MEK) was detected in samples B3002-BH2-RF-4' and B3002-BH2-T2-6.5' at concentrations of

10.1 ug/kg and 42.9 ug/kg, respectively. All field PID screened soil results were also measured at zero ppm.

A summary of soil analytical concentrations for Building 3002 are presented in Table 3-

1. Results from the current and previous investigations are presented graphically on Figure 3-1.

3.3.2 Building 3010 (Tank #3)

Seven probehole locations were advanced around the former location of Tank #3. TPH was detected in six of the 14 samples collected at building 3010, however only four of the samples exceeded 100 mg/kg. Sample B3010-BH1-T3-10' reported the highest TPH concentration of 14,000 mg/kg. Other TPH concentrations exceeding 100 mg/kg included B3010-BH4-T3-11.5' (3,660 mg/kg), B3010-BH5-T3-10.5' (1,940 mg/kg), and B3010-BH3-T3-9.5' (1,210 mg/kg). Diesel range organics (DRO) was also detected in sample B3010-BH2-T3-12' at a concentration of 1,330 mg/kg.

VOCs were detected in nine of the 14 soil samples for building 3010. PAH was analyzed for in sample B3010-BH4-T3-11.5’. The following constituents were detected above the laboratory RL in the sample: acenaphthene (750 ug/kg), acenaphthylene (322 ug/kg), benzo(b)fluoranthene (87.2 ug/kg), fluorene (2,190 ug/kg), naphthalene (402 ug/kg), and pyrene (102 ug/kg). Field PID screened soil results were generally zero until the 10 to 13 foot depth range, where headspace readings ranged from 57.8 to 281 ppm.

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A summary of soil analytical concentrations for building 3010 are presented in Table 3-2.

Results from the current and previous investigations are presented graphically on Figure 3-2.

3.3.3 Building 3008 (Tank #4)

Four probehole locations were advanced around the former location of Tank #4 at Building 3008. TPH was detected in two of the eight samples collected at building 3008.

TPH was detected in samples B3008-BH1-T4-10.5' at a concentration of 7,490 mg/kg, and sample B3008-BH4-T4-11.5' at a concentration of 404 mg/kg. Both TPH concentrations exceed 500 mg/kg.

VOCs were detected in all eight of the soil samples for Building 3008. In particular, acetone was present in seven of the eight samples at a maximum concentration of 120 ug/kg. Additional VOCs were detected in five of the eight samples, including sample B3008-BH1-T4-10.5' which contained a naphthalene concentration of 9,860 ug/kg. None of the other detected VOCs were above EPA residential SSLs.

PAH was analyzed for in sample B3008-BH2-T4-11.5'. The following constituent was detected in the sample: benzo(b)fluoranthene (14 ug/kg). Field PID screened soil results were generally zero until the 11 to 12 foot depth range, where headspace readings ranged from 0 to 108 ppm.

A summary of soil analytical concentrations for building 3008 are presented in Table 3-3.

Results from the current and previous investigations are presented graphically on Figure 3-3.

3.3.4 Building 3009 (Tank #5)

Nine probehole locations were advanced around the former location of Tank #5 at Building 3009. TPH was detected in 12 of the 18 samples collected at Building 3009, including 11 of the 12 which exceeded 500 mg/kg. Sample B3009-BH4-T5-8' contained the highest TPH concentration of 36,200 mg/kg. Other TPH concentrations exceeding 500 mg/kg included B3009-BH2-T5-8' (25,000 mg/kg), B3009-BH7-T5-11' (24,300 mg/kg), B3009-BH3-T5-11.5' (21,600 mg/kg), B3009-BH5-T5-10' (20,000 mg/kg), B3009-BH5-T5-12.5'(19,800 mg/kg), B3009-BH2-T5-11.5' (18,400 mg/kg), B3009- BH6-T5-11.5 (16,500 mg/kg), B3009-BH7-T5-12.5' (13,300 mg/kg), B3009-BH4-T5- 11.5' (5,070 mg/kg), and B3009-BH1-T5-12' (789 mg/kg).

VOCs were detected in seven of the 18 samples collected. Naphthalene was detected in samples B3009-BH3-T5-11.5’ (30,800 ug/kg), B3009-BH4-T5-8’ (19,700 ug/kg), B3009-BH6-T5-11.5’ (16,500 ug/kg), B3009-BH7-T5-11’ (14,200 ug/kg), and B3009- BH7-T5-12.5’ (4,220 ug/kg). Ethylbenzene was detected in samples B3009-BH2-T5- 11.5’ (16,700 ug/kg) and B3009-BH3-T5-11.5’ (12,500 ug/kg). Three other VOCs including 1,1,2,2,-tetrachlorethane (1,460 ug/kg), 1,2,3-trichloropropoane (1,180 ug/kg), and 1,2-dibromo-3-chloropropane (1,870 ug/kg) were detected in sample B3009-BH2- T5-11.5’.

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PAHs were analyzed in sample B3009-BH2-T5-11.5'. The following constituents were detected in the sample: acenaphthylene (2,090 ug/kg), benzo(a)anthracene (62.8 ug/kg), benzo(b)fluoranthene (101 ug/kg), chrysene (304 ug/kg), fluoranthene (688 ug/kg), naphthalene (13,700 ug/kg), and pyrene (132 ug/kg). Field PID screened soil results were generally zero until the 11 to 13 foot depth range, where headspace readings ranged from 0.1 to 624 ppm.

A summary of soil analytical concentrations for Building 3009 are presented in Table 3-

4. Results from the current and previous investigations are presented graphically on Figure 3-4.

3.3.5 Building 3004 (Tank #7)

Four probehole locations were advanced around the former location of Tank #7 and three probehole locations were advanced adjacent to the former remote fill location at Building 3004. TPH and PAH were not detected in any of the samples at Building 3004. Acetone and 2-Butanone (MEK) were the only VOCs detected. Acetone was present in two of the 14 samples at a maximum concentration of 261 ug/kg. 2-Butanone (MEK) was detected in samples B3004-BH1-RF-4', B3004-BH1-T7-10.5', and B3004-BH2-RF-7.5' at concentrations of 12.5 ug/kg, 30.8 ug/kg, and 21.2 ug/kg, respectively. Of the detected constituents none of the results were above EPA residential SSLs. Field PID screened soil results were all zero ppm.

A summary of soil analytical concentrations for building 3004 are presented in Table 3-5.

Results from the current and previous investigations are presented graphically on Figure 3-5.

3.3.6 Building 3001 (Tank #8 and #9)

Five probehole locations were advanced around the former location of Tank #8 and four probehole locations were advanced around the former location of Tank #9 at Building 3001. TPH was detected in three of the 18 samples collected at Building 3001. Of the three boreholes where TPH was detected only sample B3001-BH3-T8-8' contained a concentration exceeding 500 mg/kg (3,270 mg/kg).

VOCs were detected in 14 of the 18 soil samples for building 3001. Acetone was present in all 14 of the samples at a maximum concentration of 291 ug/kg. Additional VOCs were only detected in samples B3001-BH2-T8-6' and B3001-BH3-T8-8'.

PAHs were analyzed in samples B3001-BH2-T9-8.5' and B3001-BH3-T8-8'. Sample B3001-BH2-T9-8.5’ only contained benzo(b)fluoranthene at a concentration of 14.1 ug/kg. Sample B3001-BH3-T8-8' contained the following constituents: acenaphthylene (1,330 ug/kg), anthracene (337 ug/kg), fluoranthene (814 ug/kg), naphthalene (1,230 ug/kg), phenanthrene (5,630 ug/kg), and pyrene (264 ug/kg). Field PID screened soil results from probeholes around Tank #8 were generally zero with the exception of probehole 2 and 3. At these two locations, PID values ranged from 97 to 121 ppm at 6 and 9 feet bgs, respectively. PID values from the probeholes located around Tank #9 were all zero.

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A summary of soil analytical concentrations for building 3001 are presented in Table 3-6.

Results from the current and previous investigations are presented graphically on Figures 3-6 and 3-7.

3.4 Soil Geotechnical Analysis

Four soil samples were collected for geotechnical analysis. The samples were tested in accordance with either American Society for Testing and Materials (ASTM) standards or American Association of State Highway and Transportation Officials (AASHTO) standards. Geotechnical analysis consisted of the following; sieve size (ASTM D 422), percent moisture (ASTM D2216), effective porosity, specific gravity (AASHTO T 100), bulk density (AASHTO T 233), and organic content (ASTM 2974). The geotechnical samples were analyzed by CTL Thompson in Pueblo, Colorado.

3.5 Soil Geotechnical Results

Core samples were obtained during drilling activities from four distinct soil horizons which were encountered during subsurface exploration. Laboratory test results for the four core samples analyzed for the physical properties discussed above are presented in the results table provided by CTL (Appendix D). Due to the general loose nature of the material, the soil bulk density, effective porosity, and specific gravity could not be calculated for samples CP-1 and CP-4.

Sample CP-1 was classified as sandy, slightly gravelly silt or clay. The soil contained an organic content of 1.8 percent and a moisture content of 9.8 percent.

Sample CP-2 was classified as sandy claystone. This soil contained an organic content of

1.8 percent and a moisture content of 17.3 percent. Soil bulk density was calculated at 105 pounds per cubic foot (pcf) which is typical for a sandy soil. Soil bulk density is defined as the ratio of the mass of dry solids to the bulk volume of the soil occupied by those dry solids. Specific gravity was calculated at 2.691 while effective porosity was determined to be 0.374. Porosity is the percentage of pore volume or void space, or that volume within a matrix that can contain fluids. The bulk density of soil is inversely related to the porosity of the same soil. The more pore space in a soil the lower the value for bulk density

Sample CP-3 was classified as sandy clay. The soil contained an organic content of 2.4 percent and a moisture content of 15.6 percent. Soil bulk density was calculated at 108 pcf which is typical for a sandy soil. Specific gravity was calculated at 2.698 while effective porosity was determined to be 0.359.

Sample CP-4 was classified as silty or clayey sand. The soil contained an organic content of 0.7 percent and a moisture content of 15.2 percent.

3.6 Investigation Derived Waste Management and Disposal

The primary investigation derived waste (IDW) consisted of discarded soil cuttings left over from the direct-push activities. After logging each borehole and collecting the necessary soil samples for chemical and/or geotechnical analysis, the remaining soil was

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3-6 consolidated into a single 55-gallon drum. The drum of soil was disposed of on January 20, 2009 at the Envirotech Landfarm Facility located in Hilltop, New Mexico. Analytical data from previous investigations at Crownpoint Community School was utilized to characterize the soil as non-hazardous waste prior to disposal.

Miscellaneous disposable personal protective equipment (PPE), acetate liners, and other SI debris were generated and collected in plastic bags for disposal in a Resource Conservation and Recovery Act (RCRA) Subtitle D Landfill for non-hazardous waste.

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4.0 EXPOSURE ASSESSMENT

The NNEPA Draft UST Tank Act requires the owners of leaking UST’s to complete an exposure assessment to determine the extent of exposure, or potential exposure, to petroleum substances from a release from a UST. The purpose of the exposure assessment is to evaluate the data and determine the potential for adverse effects to human health or the environment as a result of any potential future exposure to residual materials from the former USTs. The exposure assessment was conducted according to currently accepted methods by the USEPA, the New Mexico Environment Department (NMED), and the NNEPA as follows:

• USEPA, 1989 – Risk Assessment Guidance for Superfund Risk Assessment Guidance for Superfund. Volume I. Human Health Evaluation Manual Volume I. Part A. Interim Final. December 1989.

• USEPA. 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments. Interim Final. Office of Solid Waste and Emergency Response. June 1997. EPA 540-R-97-006

• NMED. 2006a. Technical Background Document for Development of Soil Screening Levels, Revision 4.0. Hazardous Waste Bureau and Ground water Quality Bureau, Voluntary Remediation Program. June, 2006.

(http://www.nmenv.state.nm.us/gwb/New_Pages/ros_files/vrp_new/vrp_stat_rules_guid.htm)

• NMED. 2006b. New Mexico Environment Department TPH Screening Guidelines. Hazardous Waste Bureau and Ground water Quality Bureau, Voluntary Remediation Program. October, 2006 (http://www.nmenv.state.nm.us/gwb/New_Pages/ros_files/vrp_new/vrp_stat_rules_guid.htm)

• Navajo Nation. In Draft, No Date. Navajo Nation UST Act.

(http://www.navajonationepa.org/laws&regulations.html)

4.1 Human Health Risk Assessment

This risk evaluation is consistent with current EPA guidance for human health risk assessments (EPA, 1989; EPA, 2008a). The initial evaluation follows a screening-level approach, designed to be implemented where data are limited. Conservative assumptions inherent in the screening-level process assure that risk estimates are overestimated (i.e., risk results are biased high). Thus, analytes that are less than the screening values (SVs) are unlikely to present a risk. Analytes above the SVs possibly present a risk, and if additional data were collected and further risk analysis pursued, may or may not be found to pose a threat of an adverse effect on human health and the environment. A summary of applicable and relevant soil screening values used in this evaluation is presented in Table 4-1. The magnitude of the hazard quotients or risk ratios (i.e., the measured media concentration divided by the SV) is typically not a direct correlation to the amount of risk. However, analytes with measured concentrations much higher than their SVs are likely to continue to produce excess risk in a full baseline risk assessment unless additional site-specific data are collected or they were found to be below natural background.

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The Human Health Risk Assessment (HHRA) presents the methods and results of a screening level risk assessment (Tier I) for the residual contamination left in place as a result of the USTs removal efforts completed at the Crownpoint Community School.

4.2 Nature and Extent of Contamination

The following sections describe the nature and extent of petroleum contamination identified during the recent SI at the Community School.

4.2.1 Building 3002 (Tank#2)

Four probeholes were advanced to a refusal depth of between six and 16 feet bgs around the former UST tank hold area. Two probeholes were advanced to a refusal depth of between six and eight feet bgs at the former remote fill location (see Figure 3-1). Prior sampling results (ASTS, 2004) around the former tank hold location indicated TPH results between 250 to greater than 2000 ppm at a depth of between 13 to 17 feet bgs.

Our sampling depths were shallower due to direct-push sampling refusal; however, our analytical results indicated no results for TPH or PAH above the laboratory method RL.

Acetone and 2-butanone were detected above the method reporting limit (MRL) in three of the locations at concentrations ranging from 28.7 to 234 ug/kg (acetone) and 42.9 ug/kg (2-butanone). These are common laboratory solvents, and are also used in other industrial applications.

Prior sampling results from five to eight feet bgs for TPH around the former remote fill location were below 26 ppm (ASTS, 2004). Our analytical results for TPH from comparable sample depths were all below the MRL. Acetone was detected at both remote fill sampling locations at concentrations ranging from 19.8 to 99.8 ug/kg. 2- Butanone was detected at one location at the remote fill area at a concentration of 10.1 ug/kg. A site map illustrating the sampling locations and detected analytical results is provided as Figure 3-1.

4.2.2 Building 3010 (Tank #3)

Seven probeholes were advanced to a refusal depth of between 10 and 13 feet bgs around the former UST tank hold area (see Figure 3-2). Prior sampling results (ASTS, 2004) around the former tank location indicated TPH results between 940 to greater than 2,500 ppm from a depth of nine feet bgs. Our sampling depths were comparable (i.e., eight to

12.5 feet bgs) to the 2004 data, with current TPH results ranging from 1,210 to 14,000 ppm The extent of petroleum contaminants above 500 ppm is defined on the western side of the former tank location however, the building foundation and underground utilities on the east and south side of the tank area precluded further delineation in those directions. Additionally, the northern most probehole (BH5) sample results at 10.5 feet bgs indicated a TPH results of 1,940 ppm. The field screening PID results for that interval only indicated 115 ppm total volatiles. No additional step-out location on the northern side was deemed necessary due to the low PID headspace value. From the seven probehole locations advanced at the site, petroleum contamination is present in a soft clay with some fine sand at a depth of between 9.5 to 12 feet bgs. The aerial extent of TPH above 500 ppm is estimated to be 65 feet in the north-south direction and 50 feet in an east-west direction. The thickness of contaminated soil is believed to be

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4-3 approximately 1.5 feet. This results in a contaminant volume of approximately 181 cubic yards of soil.

4.2.3 Building 3008 (Tank #4)

Four probeholes were advanced to a refusal depth of between 11 to12 feet bgs around the former UST tank hold area (see Figure 3-3). Prior sampling results (ASTS, 2004) around the former tank location indicated TPH results between 480 to greater than 2,000 ppm from a depth of seven to nine feet bgs. Our sampling depths were comparable (i.e., 11 to 12 feet bgs), and TPH results ranged from less than the MRL (11 ppm) to 7,490 ppm.

The extent of petroleum contaminants above 500 ppm is defined on the north, west, and east sides of the former tank location; however, the building foundation and underground utilities on the south side of the tank area precluded further delineation in that direction.

From the four probehole locations advanced at the site, petroleum contamination is present in soft clay with some fine sand at a depth of between 11 to 12 feet bgs. The aerial extent of TPH above 500 ppm is estimated to be 40 feet in the north-south direction and 17 feet in an east-west direction. The thickness of contaminated soil is believed to be approximately one-foot. This results in a contaminant volume of approximately 25 cubic yards of soil.

4.2.4 Building 3009 (Tank #5)

Nine probeholes were advanced to a refusal depth of between 12 to 14 feet bgs around the former UST tank hold area (Figure 3-4). Prior sampling results (ASTS, 2004) around the former tank location indicated elevated TPH results between 920 to 8,000 ppm from a depth of 12 feet bgs. Our sampling depths were comparable (i.e., 12 to 14 feet bgs), with TPH results ranging from less than the MRL (11 ppm) to 36,200 ppm. Seven of the nine probehole locations indicated TPH results above 500 ppm.

VOCs were detected in seven of the 18 samples collected. Naphthalene was detected in samples BH3 at 11.5’ (30,800 ug/kg), BH4 at 8’ (19,700 ug/kg), BH6 at 11.5’ (16,500 ug/kg), BH7 at 11’ (14,200 ug/kg), and BH7 at 12.5’ (4,220 ug/kg). Ethylbenzene was detected in samples BH2 at 11.5’ (16,700 ug/kg) and BH3 at 11.5’ (12,500 ug/kg).