iinaba_-_Tuba_City_Fourth_Semi-Annual_Monitoring_Well_Sampling_Report_12-2022_FINAL_-_Copy_0002.pdf

FOURTH SEMI-ANNUAL GROUNDWATER MONITORING AND

SAMPLING EVENT

BUREAU OF INDIAN AFFAIRS OPERABLE UNITS OU-1, OU-2,

AND OU-3

TUBA CITY, COCONINO COUNTY, ARIZONA

DECEMBER 2022

Prepared for: Prepared by:

Navajo Region Office 1812 Schofield Lane 301 West Hill Ave., Rm. 324 Farmington, NM 87401 Gallup, NM 87301 Phone: (505) 327-1072 Phone: (505) 863-8226 Fax: (505) 327-1517 iiná bá Project No.: 21-008-03 BIA Contract No.: 140A0921P0006

TOC-1

FOURTH SEMI-ANNUAL GROUNDWATER MONITORING AND SAMPLING EVENT

BUREAU OF INDIAN AFFAIRS OPERABLE UNITS OU-1, OU-2, AND OU-3

TUBA CITY, COCONINO COUNTY, ARIZONA

TABLE OF CONTENTS

TITLE PAGE

EXECUTIVE SUMMARY……………………………………………………………….. ES-1

LIST OF ACRONYMS…………………………………………………………………..LOA - 1

1.0 INTRODUCTION………………………………………………………………

1.1 Purpose and Intent………………………………………………………. 1

1.2 Site History………………….…………………………………………….. 1

1.3 Current Site Characteristics…………………………………………….. 4

1.4 Site Geology and Hydrogeology………………………………………...5

1.5 Clearances, Notifications and Permits………………………………… 5

2.0 SUMMARY OF SITE ASSESSMENT ACTIVITIES………………………….. 7

2.1 Groundwater Monitoring Well Gauging and Sampling..………………7

2.2 Monitoring Well Field Data and Laboratory Groundwater Grab

Analytical Sample Results Summary……………………………………8

2.2.1 Discussion of Operable Unit OU-1………………………………10

2.2.2 Discussion of Operable Unit OU-2………………………………10

2.2.3 Discussion of Operable Unit OU-3………………………………10

2.3 Discussion of Augmentation Parameter Results……………………… 10

2.3.1 Ammonia………………………………………………………….. 10

2.3.2 Nitrate……………………………………………………………… 11

2.3.3 Nitrite………………………………………………………………. 11

2.3.4 Sulfate………………………………………………………………11

2.3.5 Iron………………………………………………………………….11

2.3.6 Manganese……………………………………………………….. 12

2.4 Discussion of Observed Site Conditions………………………………. 12

3.0 SUMMARY OF SITE ASSESSMENT FINDINGS………….………………….13

4.0 CONCLUSIONS…………………

5.0 RECOMMENDATIONS…………………………………………………………..15

TOC-2

APPENDICES

APPENDIX 1 FIGURES

Figure 1 – Site Location Map Figure 2 – Site Layout Map Figure 3 – Groundwater Flow Map (November 2022) Figure 4 – Dissolved BTEX in Groundwater (November 2022)

Figure 5 – Dissolved Naphthalene in Groundwater (November 2022) Figure 6 – Dissolved TPH-DRO in Groundwater (November 2022) Figure 7 – BTEX Trends Figure 8 – DRO Trends Figure 9 – Naphthalene Trends

APPENDIX 2 TABLES

Table 1 – Summary of Groundwater Monitoring Data Table 2 – Summary of Groundwater Monitoring and Sample Parameter Data Table 3 – Summary of Groundwater Analytical Sample Data Table 4 – Summary of Groundwater Analytical Sample Data – Natural Attenuation Parameters

APPENDIX 3 LABORATORY ANALYTICAL REPORT

APPENDIX 4 SUPPORTING DOCUMENTATION

Notification of Site Work

Jobsite Safety Meeting Forms (4) Well Sampling Forms (67) Standard Operating Procedure: IBI-MWG Standard Operating Procedure: IBI-VOLUME Standard Operating Procedure: IBI-LFGWS Standard Operating Procedure: IBI-MWFPM Standard Operating Procedure: IBI-LABEL Standard Operating Procedure: IBI-COC Standard Operating Procedure: IBI-SHIP Standard Operating Procedure: IBI-DECON Standard Operating Procedure: IBI-WTE

ES-1

EXECUTIVE SUMMARY

The Bureau of Indian Affairs (BIA) Navajo Region Office has requested, under Contract

No. 140A0921P0006, the performance of semi-annual groundwater monitoring and sampling at the Operable Units OU-1 through OU-3 located in Tuba City, Arizona in accordance with the Work Plan and Health and Safety Plan dated April 2, 2021. The following summarizes the conclusions and recommendations regarding this effort:

Impacts to groundwater across the subject site occur within OU-2 and OU- 3, with a minor, single-well occurrence within or near OU-1;

Impacts above the NNEPA Water Cleanup Standards are limited to five

(5) naphthalene exceedances;

TPH-GRO detections are scarce and isolated due to the nature of the petroleum release (heating oil/fuel oil);

TPH-DRO detections are scattered across the subject site, but there is currently no NNEPA Water Cleanup Standard for this gross petroleum analytical screening method;

None of the PAH compounds previously analyzed for (with the exception of naphthalene) were reported at concentrations exceeding the NNEPA Water Cleanup Standards;

Remedial actions performed within OU-2 show some decline in contaminant concentrations, especially the lighter volatile compounds

(BTEX);

There are no significant changes in plume position or concentration across the subject site since the previous sampling event;

Continue with the semi-annual groundwater monitoring and sampling events for the remaining two (2) periods in 2023 per the existing contract;

ES-2

The removal of the NAPL layer on groundwater at monitoring wells MW- 227 and MW-20 should be performed to eliminate this condition as a source of possible dissolved-phase impacts to local groundwater;

Begin to consider reducing the footprint of the existing, long-term groundwater monitoring well network by initially plugging and abandoning those groundwater monitoring wells with a history of being dry to eliminate these locations from being a liability (direct conduit to the water table) and then further reduce the number of monitoring wells no longer needed to monitor plume migration, reduction, or degradation; and, All remaining flush-mount groundwater monitoring wells along Oak Street and First Street should be evaluated for existing conditions and markers or barricades of some sort need to be erected to prevent any more wells from becoming damaged or destroyed. All monitoring wells should have general routine maintenance performed to maintain their integrity including, locks for security and painting of protective covers/housings.

LOA-1

BUREAU OF INDIAN AFFIARS OPERABLE UNITS OU-1, OU-2, AND OU-3

LIST OF ACRONYMS

ADEQ Arizona Department of Environmental Quality ASTs aboveground storage tanks

BIA Bureau of Indian Affairs blg below ground surface BTEX benzene, toluene, ethylbenzene, total xylenes

CES Contract Environmental Services COC Chain-of-Custody CRC Cherokee Remediation Company CY cubic yard

DO dissolved oxygen e.g. for example EPA Environmental Protection Agency etc. etcetera

GEC Geotechnical and Environmental Consultants, Inc.

GRO gasoline-range organics

IBI iiná bá, Inc.

i.e., that is Inc. Incorporated

LHC liquid-phase hydrocarbon LNAPL light non-aqueous phase liquid

MCL Maximum Contaminant Limit MDL method detection limit µS/cm micro-Siemens per centimeter mV millivolts

LOA-2

MTBE methyl tertiary-butyl ether MW monitoring well

NNEPA Navajo Nation Environmental Protection Agency

ORP oxidation-reduction potential OU Operable Unit

PCS petroleum contaminated soil

RSL Regional Screening Level

SOP Standard Operating Procedures su Standard Units

TEA terminal electron acceptor TPH total petroleum hydrocarbons

U.S. United States UST underground storage tank USEPA United States Environmental Protection Agency

VOC Volatile Organic Compounds

1.0 INTRODUCTION

The Bureau of Indian Affairs (BIA) Navajo Region Office has requested, under Contract

No. 140A0921P0006, the performance of semi-annual groundwater monitoring and sampling at the Operable Units OU-1 through OU-3 located in Tuba City, Arizona in accordance with the Work Plan and Health and Safety Plan dated April 2, 2021.

1.1 Purpose and Intent

The purpose of this effort was to:

Monitor depth to groundwater and the presence or absence of free-phase petroleum hydrocarbons in existing monitoring and remediation wells. A total of 65 wells were evaluated for this effort; and, Obtain representative samples of groundwater from the subject monitoring and remediation wells for analysis of petroleum-related hydrocarbons and select natural attenuation monitoring parameters.

After completing the activities referenced above, the intent of the contract effort was to:

Evaluate any changes in contaminant plume concentration in monitoring and remediation well locations based on previous analytical data; and, Make recommendations regarding the need to perform additional remedial actions.

1.2 Site History

According to available background information, including a Feasibility Study report dated September 8, 2000 by Geotechnical and Environmental Consultants, Inc. (GEC), a heating plant facility formerly located within OU-2, utilized heating oil (e.g., diesel) as a fuel source. The oil was stored in two (2) 50,000-gallon above ground storage tanks

(ASTs) that were located immediately southeast of the boiler building.

In 1999, a boiler explosion occurred at the heating plant. This incident was identified as the expected cause of damage to the underground boiler system oil supply lines and the resulting release of an unknown amount of heating oil to the subsurface. Immediate and initial site characterization efforts included the installation of 39 groundwater monitoring wells and 11 extraction wells. The initial site characterization efforts focused on OU-2 area, but later expanded to OU-1 due to the related historical presence of an underground storage tank (UST) associated with the former Tuba City Motors facility and the finding of petroleum hydrocarbons in groundwater samples obtained from monitoring wells upgradient of OU-2.

Area OU-3 was also investigated as the area is located downgradient of both OU-1 and

OU-2 and due to potential releases associated with the exterior storage of drums containing used petroleum products and ASTs.

The identified potential release sources, including the USTs at OU-1, the two ASTs, and subsurface piping at OU-2 have since been removed. The ASTs and drums of motor oil in OU-3 had been previously removed. In OU-3, during May through June 2018, Envirotech, Inc. (Envirotech) of Farmington, New Mexico, was contracted by Cherokee

CRC, LLC (CCRC) to excavate petroleum hydrocarbon contaminated soil (PCS) from the subsurface of the OU-2 and OU-3 facilities; design and install a horizontal injection well network. Envirotech completed the excavation and stockpiling of approximately

6,440 cubic yards (CY) of over burden soil (0 to 9 feet below ground surface [bgs]) at the OU-3 facility and the excavation and disposal of approximately 2,808 cubic yards of

PCS from OU-3 facility from approximate depths of 9 to 12 feet bgs. The PCS was transported by Envirotech and disposed at Contract Environmental Services (CES) land farm near Aneth, Utah, and Envirotech’s soil remediation facility, Landform #3, located near Hilltop, New Mexico. During the remedial excavation, asbestos-containing materials were identified and a cease work order was initiated by BIA. Within the base of the excavation, a bio-remediation injection piping system was installed for planned future use. The piping system was backfilled with approximately 360 tons of ¾-inch crushed gravel. The remaining excavation was left unfilled. This area remained as an open excavation at the time of the fall 2019 sampling event and has since been backfilled to grade. Several monitoring wells located within the excavation area (e.g., MW-209 through MW-213) were not abandoned or replaced. During the fall 2020 sampling, well MW-210 was found to be dry, having been filled with several feet of soil relative to its expected depth apparently due to backfilling of this area.

Approximately 7,000 gallons of liquid-phase hydrocarbons (LHC), or heating oil, and dissolved-phase liquids were reportedly recovered during the remedial actions at OU-2.

A groundwater monitoring report, prepared by TerraNext, Inc. (TerraNext) in 2011, indicated that LHC (0.1-foot apparent thickness) was present in monitoring well MW-20, located southeast and directly downgradient from OU-2. Groundwater monitoring results also indicated petroleum constituents were present in groundwater at OU-3 to the east.

The site-wide results suggested multiple petroleum releases November-December 2018 have occurred at locations within OU-1, OU-2, and OU-3.

Concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) were slightly above U.S. Environmental Protection Agency (EPA) Preliminary Remediation Goals

(PRGs), now called Regional Screening Levels (RSLs), for groundwater ingestion

(TerraNext, 2011). In 2016, approximately 1,760 CY of petroleum-impacted soil was excavated from OU-1 and shipped off-site for disposal by Rock Gap Construction under contract to the BIA with Wells monitoring and oversight. The majority of the impacted soils in OU-1 were encountered at depths of 5-10 feet bgs and extended to the bedrock interface. The base of the excavation was also backfilled with processed gravel, which was subsequently covered with the non-impacted shallow site soils and other imported soils. Residual soil impacts remained at the base of the excavation (bedrock interface), as well as in some perimeter and inaccessible areas including below a water supply line and the adjacent building. This work has been further described in Wells’ Soil

Excavation Report (Wells, 2017d).

In 2015 and 2016, approximately 7,500 cubic yards (CY) of petroleum-impacted soils were excavated from OU-2 and shipped off-site for disposal by Rock Gap Construction under contract to the BIA with Wells monitoring and oversight. Most of the petroleum-impacted soils were encountered at depths of five (5) feet or more below ground surface

(bgs). The impacted soils were excavated down to the bedrock interface (typically 10 to

12 feet bgs). The base of the excavation was backfilled with an approximate 2-foot bed of processed gravel. Several lengths of perforated pipes were lain on the gravel to provide for optional future injections of bioamendment fluids.

Residual petroleum-impacted soils remained at the base of the excavation (bedrock interface), as well as in some perimeter and inaccessible areas, such as below a sewer line and shed. The excavation area above the gravel was filled with the original overburden non-impacted shallow site soils and soils imported from off site. This work has been further described in Wells’ Soil Excavation Report (Wells, 2017d).

In April and October 2017, Wells conducted injection events at OU-1 and OU-2, utilizing subsurface piping systems installed in the excavations in 2016 and 2017. The injected materials consisted of a Custom Blend Nitrate (CBN) fertilizer mixed with water, a surfactant and hydrocarbon-degrading consortium. A total of 9,000 pounds of CBN, 160 gallons of surfactant and 80 gallons of consortium we mixed with approximately 20,000 gallons of water were injected into OU-2, while 6,000 pounds of CBN, 80 gallons of surfactant and 40 gallons of consortium were injected at OU-1. The report discussing the injection methods, volumes, flow rates and other details is included in a report entitled “Bio-injection Program at Operable Units OU-1 and OU-2, Tuba City, Arizona”, dated December 2017 (Wells, 2017b).

1.3 Current Site Characteristics

The Tuba City site is located near the northwestern corner of the intersection of Oak

Street and Edgewater Drive, and is bordered by Birch Avenue to the north, Edgewater

Drive to the south, and encompasses both sides of Oak and Pine Streets (see

Figures 1 and 2 in Appendix A). Oak Street bisects the OUs from north to south, as does Pine Street. The site is at an approximate elevation of 4,950 feet above mean sea level (msl). The site’s topography slopes gently toward the southeast. The nearest naturally-occurring surface water is Pasture Canyon Reservoir located approximately one (1) mile to the east.

1.4 Site Geology and Hydrogeology

Surficial soils consist of windblown aeolian sand and silt. Dune features are common, and surficial aeolian deposits are more permeable than the underlying bedrock

(Petersen et.al., 1979). The geology at the site consists of primarily overburden soils comprised of sandy silts and clayey silts, which are transitional both laterally and vertically in various locations, with lenses of silty fine sands. These soils extend to depths of between approximately 10 to 15 feet below ground, at which point bedrock is present. Bedrock has been identified by previous consultants as silty sandstones and mudstones of the Moenkopi Formation. TerraNext indicated that the site geology likely consists of surficial aeolian (wind-blown) deposits of fine clays, silts and sands overlying the Navajo Sandstone bedrock, which is relatively more impermeable that the overlying material (TerraNext 2011).

The principal aquifer beneath Tuba City, Arizona is a weakly cemented and variably permeable Navajo Sandstone which is often referred to as the N-aquifer. Near Tuba

City, groundwater springs emerge along the contact between the Navajo Sandstone and underlying Kayenta Formation in Pasture Canyon and Moenkopi Wash. The Navajo

Sandstone and Kayenta Formation interfinger; thus, the mapped geologic contact between these formations is not considered precise. The transition zone between the

Navajo and Kayenta formations consists of alternating mudstone, siltstone, and sandstone, which likely has a local influence on shallow groundwater flow paths.

1.5 Clearances, Notifications, and Permits

Prior to the performance of site activities, the following was conducted:

Notified the Bureau of Indian Affairs of the proposed sampling schedule.

A copy of the notification is attached to Appendix 4.

All site work was conducted in accordance with the April 2, 2021 Health and Safety Plan

(with Work Plan) issued to the BIA on April 2, 2021. A Daily Job Site Safety Meeting

Form was completed during all phases of field work. Copies of these forms is included in Appendix 4.

2.0 SUMMARY OF SITE ASSESSMENT ACTIVITIES

2.1 Groundwater Monitoring Well Gauging and Sampling

Groundwater grab samples were collected from each viable monitoring well or remediation well location between Monday, November 14, 2022 and Thursday, November 17, 2022 using a Geotech™ peristaltic pump. Polyethylene tubing was lowered to near the bottom of each well and was connected to the pump using surgical tubing. A flow-through cell was connected to the discharge side of the pump for measuring field parameters using a YSI Multi-meter. During the purging process, measurements of pH, temperature, specific conductance (SC), dissolved oxygen (DO), and oxygen-reduction potential (ORP) were obtained and recorded on Well Sampling

Forms (see Appendix 4). The discharge tubing attached to the pump was utilized to obtain representative groundwater grab samples for analysis by United States

Environmental Protection Agency (USEPA) Method 8260B for Volatile Organic

Compounds (VOCs) including the compounds benzene, toluene, ethylbenzene, and total xylenes (BTEX), methyl tertiary-butyl ether (MTBE), naphthalene, 1,2,4- and 1,3,5-trimethylbenzene, and 1,2-Dichloroethane (DCA); by EPA Method 8015B for Gasoline

Range Organics (GRO) and Diesel Range/Oil Range Organics (DRO/ORO), and by various natural attenuation (nutrient) methods for Ammonia, Nitrate, Nitrite, Sulfate, Phosphate, Potassium, Manganese, Iron, and Magnesium. All samples were submitted under appropriate Chain-of-Custody Procedures (utilizing standard IBI Operating

Procedures) to Green Analytical Laboratories in Durango, Colorado via Fed Ex®.

Groundwater monitoring wells MW-206, MW-210 and MW-234 were found to be dry or nearly dry, and MW-34, RMW-MW-1, RMF-MW-2, MW-201, MW-210, MW-212, MW-

213, MW-216, MW-218, MW-219, MW-220, MW-227, MW-233, MW-236, MW-303,

MW-308, and MW-312 were found to either be covered (unlocatable), damaged or destroyed. IBI noticed the maintenance yard doing some grading and cleanup work along the fence line to OU-3 during the sampling event. More wells along the roadway on the east and west side of OU-3 were found damaged or missing (see Photographs in

Appendix 4). IBI spoke to a BIA Facility Maintenance employee during sampling and he indicated that motor grader work along the roadway has damaged several wells in the recent past. Finally, groundwater monitoring wells MW-20 and MW-227 were not sampled due to the presence of a floating layer of fuel oil.

2.2 Monitoring Well Field Data and Laboratory Groundwater Grab Analytical Sample Results Summary

Static water level readings ranged from 5.64 feet to 12.27 feet below the top of well casings;

Most wells sampled contained an adequate quantity of groundwater for sampling, with the exception of those wells that went dry prior to sampling all of the target parameters;

A floating layer of fuel oil was noted on groundwater in monitoring wells MW-20 and MW-227;

Benzene concentrations across all OUs were below the NNEPA Water Cleanup Standard of 5.0 micrograms per liter (µg/L);

Toluene concentrations across all OUs were below the NNEPA Water Cleanup Standard of 1,000 µg/L;

Ethylbenzene concentrations across all OUs were below the NNEPA Water Cleanup Standard of 700 µg/L;

Total xylene concentrations across all OUs were below the NNEPA Water Cleanup Standard of 10,000 µg/L;

Methyl tertiary-butyl ether (MTBE) concentrations cross all OUs were below the NNEPA Water Cleanup Standard of 2.6 µg/L;

Naphthalene concentrations detected in groundwater monitoring wells MW-1, MW-224, MW-235, MW-239, MW-302, and MW-307 exceed the NNEPA Water Cleanup Standard of 6.2 µg/L; and, No PAH compounds were reported with detections exceeding the NNEPA Water Cleanup Standards.

In order to better understand the distribution of dissolved petroleum hydrocarbons in groundwater, the concentrations of BTEX, TPH-DRO, and Naphthalene were illustrated on Figures 3, 4, and 5 in Appendix 1, respectively. In addition, concentration trends for BTEX, naphthalene, and TPH-DRO concentrations in select impacted wells (MW-

223, MW-227, MW-236, MW-237, MW-302, and MW-307) are also included in

Appendix 1 to evaluate any trends in concentration over time (since 2017).

2.2.1 Discussion of Operable Unit OU-1

The only detection of petroleum in groundwater at or near this OU remains to be in monitoring well MW-302 along Oak Street off the eastern side of the subject area. The minor impacts appear to be more gasoline like than fuel oil like, with none of the analytical parameters exceeding the NNEPA Water Cleanup Standards.

2.2.2 Discussion of Operable Unit OU-2

This unit still contains a plume that is oriented from the northwest to the southeast along the prevailing groundwater flow direction. The plume is centered around the east-central portion of the unit. The plume crosses Oak Street and is present within the western limits of OU-3 near its southern boundary. There are isolated occurrences of impact along the southern boundary as well as two (2) occurrences of NAPL (very southeastern corner at MW-227 and offsite south of OU-3 at MW-20).

2.2.3 Discussion of Operable Unit OU-3

Besides the naphthalene emanating upgradient from OU-2 along the southwestern limits, there is a small naphthalene plume along the eastern limits of this unit that slightly crosses First Street.

2.3 Discussion of Augmentation Parameter Results

The following discusses the significance of the “nutrient” parameter data obtained from a select number of groundwater monitoring wells across the OU areas.

2.3.1 Ammonia

Excluding manmade sources (e.g., wastewater discharges, agricultural activity), the presence of ammonia can be the result of nitrogen fixation by microbes (bacteria) feeding off a source of organic matter in groundwater (e.g., residual fuel oil). Most groundwater has a natural ammonia concentration of about 0.20 milligrams per liter

(mg/L) or less. Concentrations in the 15 targeted wells sampled ranged from <0.10 mg/L to 33.8 mg/L (MW-307).

2.3.2 Nitrate

Nitrate is a preferred Terminal Electron Acceptor (TEA) after all of the viable oxygen dissolved in groundwater is used up by microbial activity (anaerobic). This occurs as denitrification of organic carbon. Measurable concentrations of nitrite in groundwater is an indication of nitrate reduction. In an area of a contaminant plume acting as a source of organic carbon, the reduction of nitrate and the reduction of dissolved contaminants with an measurable increase of nitrate signifies denitrification. Wells with elevated or measurable nitrate concentrations do not exhibit any appreciable nitrite concentrations.

So, nitrate reduction is not likely occurring onsite.

2.3.3 Nitrite

As indicated above, measurable concentrations of nitrite in groundwater, coupled with nitrate reduction and plume concentration reductions is evidence of denitrification as a dominant biodegradation mechanism. Again, this is not evident in the data collected from this sampling event.

2.3.4 Sulfate

Sulfate can also be used as a TEA under anaerobic conditions after available oxygen, nitrate, and ferric iron have been depleted. Sulfate is very soluble in groundwater.

Under sulfate-reducing conditions, sulfate demand will be high and sulfate concentrations will be depleted relative to concentrations upgradient of the contaminant plume. Sulfate concentrations reportedly range from 10.0 mg/L (MW-223) to 305 mg/L

(MW-310). The concentrations appear randomly across the subject site and have no apparent relationship between being upgradient, within, or downgradient of any identifiable contaminant plume.

2.3.5 Iron

Iron, typically as ferric iron (Fe3+), is insoluble in groundwater unless reduced to its soluble form, ferrous iron (Fe2+). This reduction process can occur when microbes use ferric iron as a TEA. As a result, you expect to see increases in ferrous iron concentrations where plume concentrations are reducing under anaerobic biodegradation. Since the previous scope only evaluated dissolved iron and did not distinguish between ferric and ferrous concentrations onsite, it can only be speculated by the general lack or very low concentrations of dissolved iron analyzed that iron is not being utilized as a TEA for this biodegradation effort.

2.3.6 Manganese

Manganese (Mn4+), much like ferric iron, is insoluble in groundwater unless reduced to its soluble form, Mn2+ during anaerobic degradation. Since it is interchangeable with ferric iron in nature, it depends on which metal is dominant in the aquifer material when determining which one will become a TEA. The same relationship holds true for manganese; increase in dissolved manganese coupled with decrease in contaminant plume concentration under anaerobic conditions. Since the previous scope only evaluated total manganese and did not determine dissolved manganese concentrations onsite, an evaluation on whether the biodegradation effort is utilizing manganese as a

TEA cannot be made at this time.

2.4 Discussion of Observed Site Conditions

The following is summary of some observed site conditions pertaining to the wells included in the monitoring and sampling plan.

Many of the existing groundwater monitoring wells do not exhibit any detectable concentration of petroleum impact and are therefore not providing any useful data to evaluate the extent of any contaminant plume or plume migration (stability);

A several more groundwater monitoring wells along the shoulders of Oak Street and First Street were found damaged or missing. There was evidence of active blading of the shoulder with pieces of well collars and concrete pads nearby (see photographs in Appendix 4);

There is still a measurable, black floating layer of old fuel oil on groundwater in monitoring well MW-227 (see photograph in Appendix 4) and recently discovered in monitoring well MW-20. The presence of this layer (or ability to create a layer once groundwater is withdrawn from a well) will contribute to release the more soluble components of this fuel to the dissolved phase unless it is effectively removed.

3.0 SUMMARY OF SITE ASSESSMENT FINDINGS

Based on a review of all site-specific data collected at the Tuba City OU areas, the following summarizes the results of the Fourth Semi-Annual Groundwater Monitoring and Sampling Event:

There are a considerable number of groundwater monitoring wells within the existing network that do not contain any analytical evidence of impact to groundwater at their location;

Gasoline-grade petroleum compounds (BTEX) are nearly absent across the subject site with none of the current concentrations exceeding the NNEPA Cleanup Standards;

There are only five (5) detections of naphthalene in groundwater across the entire site that exceed the NNEPA Cleanup Standards;

The presence of PAH compounds continues to be insignificant across all OU sites due to their low solubility in groundwater;

A floating layer of fuel oil is present on groundwater at MW-227 and MW-20;

While no NNEPA Cleanup Standard exists for TPH-DRO, there are several exceedances in the Tapwater cleanup level published by the USEPA in the Regional Screening Levels (RSL) across the subject site; and, An evaluation of concentration trends in the selected wells for this period indicates a slight increase in BTEX at MW-302, which may be temporal. This appears to be true for the previous spike in TPH-DRO at MW-302 and MW- 307 which now have returned to earlier concentrations. Naphthalene concentrations were erratic in MW-223, but have been declining over time and have remained low for the past year and a half. A similar trend has been occurring in MW-302, MW-307, and to a lesser extent MW-237. Overall, trends appear to be either steady or declining, with no suggestion of any significant rebounding of concentrations.

4.0 CONCLUSIONS

Based on the results from the groundwater monitoring efforts and the current sampling event, the following conclusions were drawn:

Impacts to groundwater across the subject site occur within OU-2 and OU- 3, with a minor, single-well occurrence within or near OU-1;

Impacts above the NNEPA Water Cleanup Standards are limited to five

(5) naphthalene exceedances;

TPH-GRO detections are scarce and isolated due to the nature of the petroleum release (heating oil/fuel oil);

TPH-DRO detections are scattered across the subject site, but there is currently no NNEPA Water Cleanup Standard for this gross petroleum analytical screening method;

None of the PAH compounds previously analyzed for (with the exception of naphthalene) were reported at concentrations exceeding the NNEPA Water Cleanup Standards;

Remedial actions performed within OU-2 show some decline in contaminant concentrations, especially the lighter volatile compounds (BTEX); and, There are no significant changes in plume position or concentration across the subject site since the previous sampling event.

5.0 RECOMMENDATIONS

Based on the conclusions provided above, iiná bá offers the following recommendations with regards to the Bureau of Indian Affairs Operable Unit site located in Tuba City, Coconino County, Arizona:

Continue with the semi-annual groundwater monitoring and sampling events for the remaining two (2) periods in 2023 per the existing contract;

The removal of the NAPL layer on groundwater at monitoring wells MW-227 and MW-20 should be performed to eliminate this condition as a source of possible dissolved-phase impacts to local groundwater;

Begin to consider reducing the footprint of the existing, long-term groundwater monitoring well network by initially plugging and abandoning those groundwater monitoring wells with a history of being dry to eliminate these locations from being a liability (direct conduit to the water table) and then further reduce the number of monitoring wells no longer needed to monitor plume migration, reduction, or degradation; and, All remaining flush-mount groundwater monitoring wells along Oak Street and First Street should be evaluated for existing conditions and markers or barricades of some sort need to be erected to prevent any more wells from becoming damaged or destroyed. All monitoring wells should have general routine maintenance performed to maintain their integrity including, locks for security and painting of protective covers/housings.

APPENDIX 1 — FIGURES

CONTRACT NO. 140A0921P0006

WaterWastewaterSolid WasteRoadsStormwaterSubdivisionsSurveyingGIS

HydrologyAir QualityESASoil InvestigationsSPCCWater RightsLUST

PREPARED FOR:

BUREAU OF INDIAN AFFAIRS NAVAJO REGION OFFICE

DIVISION OF ENVIRONMENTAL AND CULTURAL RESOURCE MANAGEMENT

301 WEST HILL AVENUE, ROOM 324

GALLUP, NEW MEXICO 87301

PREPARED BY:

IINÁ BÁ, INC.

1812 SCHOFIELD LANE

FARMINGTON, NM 87401

www.iinábá.com

PHONE: (505) 327-1072

FAX: (505) 327-1517

DECEMBER 2022

SOURCE: 7.5-MINUTE USGS TOPOGRAPHIC MAP – TUBA CITY, AZ

DATE: 1969

0 985 1,970 FEET

SCALE: 1 INCH ≅ 985 FEET

BIA Contract No.: 140A0921P0006

EXPLANATION

LIMITS OF STUDY AREA

FIGURE 1: SITE LOCATION MAP

BUREAU OF INDIAN AFFAIRS THIRD SEMI-ANNUAL

GROUNDWATER MONITORING AND SAMPLING EVENT

OPERABLE UNITS (OU) 1, 2, AND 3

N

FIGURE 2: GROUNDWATER MONITOIRNG WELLS

BUREAU OF INDIAN AFFAIRS THIRD SEMI-ANNUAL

GROUNDWATER MONITORING AND SAMPLING EVENT

OPERABLE UNITS (OU) 1, 2, AND 3

TUBA CITY, COCONINO COUNTY, ARIZONA

SOURCE: GOOGLE EARTH IMAGE – TUBA CITY, AZ

AERIAL PHOTO DATE: 6/2017

0 200 400 FEET

SCALE: 1 INCH ≅ 200 FEET

BIA Contract No.: 140A0921P0006

N

LIMITS OF OPERABLE UNIT

GROUNDWATER MONITORING WELL WITH ID

OU1 – TUBA CITY MOTOR COMPANY

OU2 – BIA HEATING PLANT

OU3 – BIA ROAD MAINTENANCE FACILITY

RMF-MW-2

RMF-MW-5

MW-26 MW-19

MW-305

RMF-MW-4 MW-205

MW-206

MW-218

MW-12

MW-15

MW-311

MW-302

MW-216

MW-28

MW-301

MW-203

MW-202

MW-1

MW-8

MW-233

MW-227

MW-226

MW-204

MW-307

MW-308

MW-309

MW-230

MW-229

MW-228

MW-20

MW-34

MW-215

MW-235

MW-236

MW-214

MW-238

RMF-MW-7

MW-239

MW-33

MW-212

MW-306

MW-303

MW-32

MW-208

MW-223

MW-304

MW-225

MW-207

MW-24

MW-232

MW-231

MW-312

MW-224

MW-220

MW-222

OU1

OU2

OU3

MW-210

MW-213

MW-310

NEW WELL

MW-234

MW-219

MW-201

MW-209

MW-211

RMF-MW-1

MW-237

FIGURE 3: GROUNDWATER FLOW DIRECTION

(November 2022)

BUREAU OF INDIAN AFFAIRS

OPERABLE UNITS (OU) 1, 2, AND 3

TUBA CITY, COCONINO COUNTY, ARIZONA

BIA Contract No.: 140A0921P0006

N

RMF-MW-2

RMF-MW-5

MW-26

MW-305

RMF-MW-4 MW-205

MW-206

MW-218

MW-15

MW-302

MW-28

MW-301

MW-203

MW-202

MW-233

MW-227

MW-226

MW-204 MW-309

MW-230

MW-229

MW-228

MW-20

MW-34

MW-215

MW-235

MW-236

MW-214

MW-238

MW-237

RMF-MW-7

MW-239

MW-33

MW-212

MW-306

MW-32

MW-208

MW-223

MW-304

MW-225

MW-207

MW-24

MW-232

MW-224

MW-222

OU2

MW-210

MW-213

MW-310

4,934.93

NA 4,931.28

4,934.49

4,931.22

4,931.54

4,935.19

4,934.21

NA

4,931.95

4,933.36

NA

NA

4,935.83

4,935.90

4,935.80

4,935.76

4,935.73

4,934.40

NA

DRY

4,933.04

4,932.93

NA

NA

NA

NA

4,934.28

4,934.53

4,934.27 4,934.22

NA

4,933.59

NA

4,932.31

4,934.99 4,933.79

NA

4,933.79

NA

NA

4,931.92

4,933.08

4,936.53

NA

4,933.72

4,934.62

NA

4,934.45

MW-220

4,934.45

NA

MW-234 4,933.62

MW-219

NA

MW-211 NA

MW-209

MW-201

NA

4,932.34

4,938.55

4,938.00

4,935.00 OU1

MW-311

4,937.82

4,937.00

MW-303

4,935.61

MW-12

4,935.58

MW-308

4,934.48

MW-307

4,936.00

4,932.00

MW-1

MW-8

MW-312

4,929.94

OU3

MW-231

MW-19

4,935.00

4,937.00

MW-216

4,936.09

4,935.31

4,936.57

4,933.00

4,938.00

FOOTNOTES:

CONTOUR INTERVAL = 1.0 FOOT

NA – NOT AVAILABLE, WELL NOT LOCATED

NA

4,936.00

4,933.00

GROUNDWATER ELEVATION IN FEET AMSL

WATER TABLE POTENTIOMETEIC CONTOUR

INFERRED GROUNDWATER FLOW DIRECTION

RMF-MW-1 NA

NEW WELL

NA

4,932.00

4,934.00

4,934.00

BTEX CONCENTRATION IN UG/L

BTEX ISOCONCENTRATION CONTOUR

VALUES WITH RED BOXES INDICATE

DETECTIONS ABOVE THE REPORTING LIMIT.

WELL IDS IN RED INDICATE WELL DAMAGED

OR DESTROYED.

FIGURE 4: DISSOLVED BTEX IN GROUNDWATER

BUREAU OF INDIAN AFFAIRS FOURTH SEMI-ANNUAL

GROUNDWATER SAMPLING EVENT

OPERABLE UNITS (OU) 1, 2, AND 3

TUBA CITY, COCONINO COUNTY, ARIZONA

BIA Contract No.: 140A0921P0006

N

RMF-MW-5

MW-26

MW-305

MW-28

MW-233 MW-226

MW-309

MW-230

MW-229

MW-228

MW-215

MW-214

MW-238

MW-237

RMF-MW-7

MW-33

MW-212

MW-207

MW-24

MW-232

MW-222

OU2

MW-210

MW-310

1.0

NA

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

NA

NA

<1.0

<1.0

<1.0

NA

<1.0

DRY

<1.0

<1.0

NA

NA

NA

0.8

<1.0

<1.0

<1.0

<1.0

NA

NA

NA

<1.0

<1.0

NA

<1.0

<1.0

<1.0

NA

MW-234

<1.0

MW-219

NA

MW-211 NA

MW-209

MW-201

NA

<1.0

OU1

MW-311

<1.0

MW-303

MW-12

<1.0

MW-308

MW-8

MW-312

<1.0

OU3

MW-19

MW-216

93.6

FOOTNOTES:

LESS THAN SYMBOL (<) INDICATES COMPOUNDS ANALYZED FOR BUT NOT DETECTED

AT INDICATED QUANTIFICATIION LIMIT.

NAPL – NON-AQUEOUS PHASE LIQUID (FUEL OIL)

MW-32

MW-202

MW-204

NA

MW-213

<1.0

MW-301

MW-302

1.0

MW-236

MW-223

MW-235

<1.0

NAPL

MW-20

MW-205

NAPL

MW-227

MW-206

RMF-MW-4

RMF-MW-1 NA

RMF-MW-2

MW-1

MW-307

MW-203

NA NA

MW-34 MW-224

<1.0

NA

NEW WELL

NA

MW-208

<1.0 <1.0

MW-225

<1.0

MW-306

2.0

MW-239

<1.0

MW-231

MW-218

MW-304 <1.0

MW-220

0.9

0.6

MW-15

0.6

NAPHTHALENE CONCENTRATION (UG/L)

NAPHTHALENE ISOCONCENTRATION CONTOUR

VALUES WITH RED BOXES INDICATE DETECTIONS

ABOVE THE REPORTING LIMIT.

CONCENTRATIONS WITH RED SHADE INDICATE

EXCEEDENCE IN MCL.

FIGURE 4: DISSOLVED NAPHTHALENE IN GROUNDWATER

BUREAU OF INDIAN AFFAIRS FOURTH SEMI-ANNUAL

GROUNDWATER SAMPLING EVENT

OPERABLE UNITS (OU) 1, 2, AND 3

TUBA CITY, COCONINO COUNTY, ARIZONA

BIA Contract No.: 140A0921P0006

N

RMF-MW-5

MW-26

MW-305

RMF-MW-4

MW-206

MW-218

MW-15

MW-28

MW-301

MW-203

MW-226

MW-309

MW-230

MW-229

MW-228

MW-214

RMF-MW-7

MW-239

MW-33

MW-212

MW-223

MW-304

MW-207

MW-24

MW-232

MW-222

MW-210

MW-310

8.0

<0.5

<0.5

<0.5

<0.5

<0.5

NAPL

<0.5

<0.5

NA

NA

<0.5

NA

<0.5

DRY

<0.5

NA

NA

NA

NA

3.0

<1.0

<0.5

<0.5

<0.5

NA

NA

NA

10.0

<0.5

<0.5

MW-220

<0.5

NA

MW-234 <0.5

MW-219

NA

MW-211 NA

MW-209

NA

5.1

<0.5

OU1

MW-311

<0.5

<0.5

MW-12

<0.5

MW-308

MW-312

<0.5

OU3

MW-19

MW-216

18.0

<0.5

<0.5

FOOTNOTES:

MW-204

NA

MW-302

MW-213

RMF-MW-2

MW-237

MW-238 3.0

MW-307

MW-202

MW-224

MW-236

NA

MW-233

MW-20

<0.5

<0.5

MW-227 NAPL

MW-235

<0.5

MW-215

<0.5

MW-201 OU2

0.7 NEW WELL

NA

RMF-MW-1

MW-34

NA

MW-208

0.6

NA

NA

MW-231

<0.5

MW-8

15.0

MW-306

MW-1

0.6

MW-225

<0.5

MW-205

3.0

NA MW-303

1.0

FIGURE 6: DISSOLVED TPH-DRO IN GROUNDWATER

BUREAU OF INDIAN AFFAIRS FOURTH SEMI-ANNUAL

GROUNDWATER SAMPLING EVENT

OPERABLE UNITS (OU) 1, 2, AND 3

TUBA CITY, COCONINO COUNTY, ARIZONA

BIA Contract No.: 140A0921P0006

N

RMF-MW-5

MW-26

MW-305

RMF-MW-4 MW-205

MW-206

MW-218

MW-15

MW-302

MW-28

MW-301

MW-226

MW-309

MW-230

MW-229

MW-228

MW-214

RMF-MW-7

MW-33

MW-306

MW-304

MW-24

MW-232

MW-222

OU2

MW-210

MW-213

MW-310

<1.0

<1.0

<1.0 <1.0

<1.0

<1.0

3.9

<1.0

<1.0

NA

NA

<1.0

<1.0

NA

DRY

<1.0

NA

NA

NA

NA

1.7

<1.0

NAPL

<1.0

<1.0

<1.0

<1.0 <1.0

NA

NA

NA

<1.0

<1.0

NA

<1.0

<1.0

<1.0

MW-220

<1.0

NA

MW-234 <1.0

MW-219

NA

MW-211 NA

MW-209

MW-201

NA

4.1

<1.0

OU1

MW-311

<1.0

MW-303

<1.0

MW-12

<1.0

MW-308

MW-1

MW-8

MW-312

<1.0

OU3

MW-231

MW-19

MW-216

<1.0

<1.0

<1.0

FOOTNOTES:

MW-202

MW-204

NA

<1.0

MW-239

MW-212

NA MW-237

MW-238

MW-34

MW-236

MW-223 MW-307

5.76

MW-227

MW-233

MW-20

MW-215

<1.0

TPH-DRO CONCENTRATION (MG/L)

TPH-DRO ESTIMATED EXTENT CONTOUR

VALUES IN RED BOXES INDICATED DETECTIONS

ABOVE THE REPORTING LIMIT

NA

MW-224

<1.0

MW-235

2.66

RMF-MW-2

NA

NEW WELL NA

MW-203

<1.0

MW-208

1.23 1.22

MW-225

<1.0

1.12 MW-207

4/1/2017 10/1/2017 4/1/2018 10/1/2018 4/1/2019 10/1/2019 4/1/2020 10/1/2020 4/1/2021 10/1/2021 4/1/2022 10/1/2022

BT

EX

C O N

CE

N

TR

AT

IO

N (U

G /L

SAMPLE DATE

BIA TUBA CITY OPERABLE UNITS ‐ BTEX TRENDS

MW‐223 MW‐227 MW‐236 MW‐237 MW‐302 MW‐307

FIGURE 7: BTEX CONCENTRATION

TRENDS

4/1/2017 10/1/2017 4/1/2018 10/1/2018 4/1/2019 10/1/2019 4/1/2020 10/1/2020 4/1/2021 10/1/2021 4/1/2022 10/1/2022

M

TB

E

CO

N

CE

N

TR

AT

IO

N (M

G /L

SAMPLE DATE

BIA TUBA CITY OPERABLE UNITS ‐ TPH‐DRO TRENDS

MW‐223 MW‐227 MW‐236 MW‐237 MW‐302 MW‐307

FIGURE 8: TPH-DRO CONCENTRATION

4/1/2017 10/1/2017 4/1/2018 10/1/2018 4/1/2019 10/1/2019 4/1/2020 10/1/2020 4/1/2021 10/1/2021 4/1/2022 10/1/2022

N

AP

H

TH

AL

EN

E

CO

N

CE

N

TR

AT

IO

N (U

G /L

SAMPLE DATE

BIA TUBA CITY OPERABLE UNITS ‐ NAPHTHALENE

TRENDS

MW‐223 MW‐227 MW‐236 MW‐237 MW‐302 MW‐307

FIGURE 9: NAPHTHALENE CONCENTRATION

APPENDIX 2 — TABLES

CONTRACT NO. 140A0921P0006

WaterWastewaterSolid WasteRoadsStormwaterSubdivisionsSurveyingGIS

HydrologyAir QualityESASoil InvestigationsSPCCWater RightsLUST

PREPARED FOR:

BUREAU OF INDIAN AFFAIRS NAVAJO REGION OFFICE

DIVISION OF ENVIRONMENTAL AND CULTURAL RESOURCE MANAGEMENT

301 WEST HILL AVENUE, ROOM 324

GALLUP, NEW MEXICO 87301

PREPARED BY:

IINÁ BÁ, INC.

1812 SCHOFIELD LANE

FARMINGTON, NM 87401

www.iinábá.com

PHONE: (505) 327-1072

FAX: (505) 327-1517

DECEMBER 2022

TABLE 1: SUMMARY OF GROUNDWATER MONITORING DATA

Tuba City, Coconino County, Arizona

BIA Contract No. 140A0921P0006 iiná bá, Inc. Project No. – 21-008-03

Well No. Well

Depth (ft bTOC)

Casing Elevation (ft AMSL)

DTW

(4/2021)

WTE

(4/2021)

DTW

(10/2021)

WTE

(10/2021)

DTW

(5/2022)

WTE

(5/2022)

DTW

(11/2022)

WTE

(11/2022)

MW-1 9.12 4,942.82 7.89 4,934.93 NM NA 7.38 4,935.44 7.89 4,934.93

RMF-MW-1 14.77 4,941.62 NM NA NM NA 11.65 4,929.97 NM* NA

RMF-MW-2 13.29 4,941.62 7.77 4,933.85 NM NA 7.40 4,934.22 NM* NA

RMF-MW-4 14.15 4,940.31 8.97 4,931.34 NM NA 8.55 4,931.76 9.03 4,931.28

RMF-MW-5 12.42 4,942.80 7.96 4,934.84 NM NA 7.61 4,935.19 8.31 4,934.49

RMF-MW-7 13.21 4,941.46 10.22 4,931.24 NM NA 9.90 4,931.56 10.24 4,931.22

MW-8 9.11 4,939.58 7.92 4,931.66 NM NA 7.45 4,932.13 8.04 4,931.54

MW-12 9.61 4,943.22 7.40 4,935.82 NM NA 7.13 4,936.09 8.03 4,935.19

MW-15 9.67 4,944.24 8.67 4,935.57 NM NA 8.07 4,936.17 8.93 4,935.31

MW-19 14.94 4,943.13 8.61 4,934.52 NM NA 8.15 4,934.98 8.92 4,934.21

MW-20 7.83 4,939.40 6.53 4,932.87 NM* NA NM* NA NM* NA

MW-24 12.36 4,940.43 8.47 4,931.96 NM NA 8.19 4,932.24 8.48 4,931.95

MW-26 14.61 4,943.36 9.46 4,933.90 NM NA 9.10 4,934.26 10.00 4,933.36

MW-28 10.30 4,946.67 8.40 4,938.27 NM NA 7.91 4,938.76 8.85 4,937.82

MW-32 9.92 4,946.75 7.74 4,939.01 NM NA 7.30 4,939.45 8.20 4,938.55

MW-33 14.19 4,941.08 7.81 4,933.27 NM NA 7.45 4,933.63 NM* NA

MW-34 NM 4,939.91 NA NA NM* NA NM* NA NM* NA

MW-201 NM 4,942.90 NA NA NM NA 5.16 4,937.74 NM NA

MW-202 10.52 4,943.16 7.20 4,935.96 NM NA 6.70 4,936.46 7.33 4,935.83

MW-203 11.63 4,942.15 6.23 4,935.92 NM NA 6.25 4,935.90 6.25 4,935.90

MW-204 10.66 4,942.30 6.86 4,935.44 NM NA 5.61 4,936.69 6.72 4,935.58

(ft bTOC)

Casing Elevation (ft AMSL)

DTW

(4/2021)

WTE

(4/2021)

DTW

(10/2021)

WTE

(10/2021)

DTW

(5/2022)

WTE

(5/2022)

DTW

(11/2022)

WTE

(11/2022)

MW-205 10.52 4,942.63 6.65 4,935.98 NM NA 6.18 4,936.45 6.83 4,935.80

MW-206 10.68 4,942.18 6.30 4,95.88 NM NA 5.68 4,936.50 6.42 4,935.76

MW-207 10.54 4,942.82 6.92 4,935.90 NM NA 6.28 4,936.54 7.09 4,935.73

MW-208 10.18 4,942.55 8.22 4,934.33 NM NA 7.67 4,934.88 8.15 4,934.40

MW-209 23.06 4,941.54 11.42 4,930.12 NM NA 11.04 4,930.50 11.60 4,929.94

MW-210 6.59 4,941.57 Dry NA Dry NA Dry NA Dry NA

MW-211 17.71 4,941.38 9.77 4,931.61 NM NA 7.56 4,933.82 NM* NA

MW-212 22.78 4,941.33 11.40 4,929.93 NM* NA NM* NA NM* NA

MW-213* NM 4,941.64 NM NA NM NA NM NA NM NA

MW-214* NA 4,940.49 NA NA NM NA NM NA 7.56 4,932.93

MW-215 12.96 4,940.20 7.19 4,933.01 NM NA 6.83 4,933.37 7.16 4,933.04

MW-216* NM 4,940.49 NA NA NM NA NM NA NM NA

MW-218* NM 4,942.07 NA NA NM NA NM NA NM NA

MW-219* NM 4,941.41 NA NA NM NA NM NA NM NA

MW-220 12.29 4,939.03 4.92 4,934.11 NM NA 4.44 4,934.59 NM NA

MW-222 11.50 4,938.76 4.85 4,933.91 NM NA 5.50 4,933.26 NM NA

MW-223 11.30 4,942.89 8.61 4,934.28 NM NA 8.03 4,934.86 8.61 4,934.28

MW-224 14.66 4,945.68 11.08 4,934.60 NM NA 10.55 4,935.13 11.15 4,934.53

MW-225 14.05 4,945.87 11.41 4,934.46 NM NA 11.11 4,934.76 11.60 4,934.27

MW-226 16.81 4,944.76 10.64 4,934.12 NM NA 10.09 4,934.67 10.54 4,934.22

MW-227 14.11 4,944.43 10.53** 4,933.90 NM NA NM NA NM NA

(ft bTOC)

Casing Elevation (ft AMSL)

DTW

(4/2021)

WTE

(4/2021)

DTW

(10/2021)

WTE

(10/2021)

DTW

(5/2022)

WTE

(5/2022)

DTW

(11/2022)

WTE

(11/2022)

MW-228 11.41 4,939.23 5.66 4,933.57 NM NA 5.19 4,934.04 5.64 4,933.59

MW-229 7.75 NA 6.27 NA NM NA 5.85 NA 6.25 NA

MW-230 14.93 4,942.60 10.26 4,932.34 NM NA 9.89 4,932.71 10.29 4,932.31

MW-231 19.68 4,947.26 12.05 4,935.21 NM NA 11.51 4,935.75 12.27 4,934.99

MW-232 18.06 4,945.86 11.61 4,934.25 NM NA 11.27 4,934.59 12.07 4,933.79

MW-233 11.00 NA 5.80 NA NM NA 5.38 NA NM NA

MW-234 6.70 4,939.49 Dry NA NM NA Dry NA 5.87 4,933.62

MW-235 6.52 4,940.82 5.87 4,934.95 NM NA 6.69 4,934.13 7.03 4,933.79

MW-236 11.22 4,940.76 7.05 4,933.71 NM NA NM* NA NM* NA

MW-237 12.77 4,940.38 7.84 4,932.54 NM NA 7.42 4,932.96 NM* NA

MW-238 13.00 4,939.85 7.92 4,931.93 NM* NA NM* NA 7.93 4,931.92

MW-239 11.28 4,941.33 8.12 4,933.21 NM NA 7.75 4,933.58 8.25 4,933.08

MW-301 12.28 4,945.26 8.34 4,936.92 NM NA 7.71 4,937.55 8.73 4,936.53

MW-302 11.78 4,943.76 7.32 4,936.44 NM NA 6.70 4,937.06 7.67 4,936.09

MW-303 12.23 4,945.20 9.15 4,936.05 NM NA 8.55 4,936.65 NM NA

MW-304 14.56 4,942.99 6.97 4,936.02 NM NA 6.35 4,936.64 7.38 4,935.61

MW-305 12.58 4,942.79 8.98 4,933.81 NM NA 8.56 4,934.23 9.07 4,933.72

MW-306 13.16 4,941.85 7.18 4,934.67 NM NA 6.76 4,935.09 7.23 4,934.62

MW-307 10.21 4,941.85 7.41 4,934.44 NM NA 6.83 4,935.02 7.37 4,934.48

MW-308* NM 4,941.90 NA NA NM NA NM NA NM NA

MW-309 11.93 4,941.00 6.59 4,934.41 NM NA 6.02 4,934.98 6.55 4,934.45

(ft bTOC)

Casing Elevation (ft AMSL)

DTW

(4/2021)

WTE

(4/2021)

DTW

(10/2021)

WTE

(10/2021)

DTW

(5/2022)

WTE

(5/2022)

DTW

(11/2022)

WTE

(11/2022)

MW-310 12.72 4,940.84 6.40 4,934.44 NM NA 5.82 4,935.02 6.39 4,934.45

MW-311 13.70 4,944.82 7.88 4,936.94 NM NA 7.25 4,937.57 8.25 4,936.57

MW-312 12.02 4,941.47 6.39 4,935.08 NM NA NM* NA NM* NA

NEW WELL 10.39 NA 6.76 NA NM* NA 6.31 NA NM* NA

Footnotes:

All depths are in feet below top of casing.

DTW – depth to water.

ft – feet.

WTE – water table elevation.

bTOC – below top of casing.

NA – Not available.

NM – Not measured, damaged water tape.

*Well damaged or obstructed, could not sample.

TABLE 2: SUMMARY OF GROUNDWATER MONITORING AND SAMPLE PARAMETER DATA

Sample No. Depth

(ft bgs) Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

MW-1 9.12 4/20/2021 09:37 7.89 6.95 60.69 3,794 0.47 -116.3 NM

10/26/2021 12:48 NM 7.35 67.39 3,522 3.38 -84.3 NM

5/2/2022 16:28 7.38 7.22 62.96 3,407 0.60 -152.1 NM

11/14/2022 13:10 8.04 7.82 65.10 2,744 0.56 -231.1 NM

MW-8 9.11 4/20/2021 09:14 7.92 6.82 59.36 2,924 0.91 +52.3 NM

10/26/2021 11:58 NM 7.30 68.56 3,169 4.87 -85.0 NM

5/2/2022 16:03 7.45 7.79 60.62 3,152 0.67 -147 NM

11/15/2022 16:02 7.89 7.94 63.20 3,144 0.61 -213.9 NM

MW-12 9.61 4/19/2021 15:04 7.40 6.20 62.24 721 1.32 -64.2 NM

10/25/2021 16:18 NM 6.78 71.08 851 0.67 -49.6 NM

5/2/2022 14:10 7.13 7.07 62.24 848 0.55 -170.6 NM

11/14/2022 14:37 8.03 7.46 67.00 1,028 0.89 -235.3 NM

MW-15 9.67 4/19/2021 14:18 8.67 8.81 61.41 1,197 2.76 +139.1 NM

10/25/2021 15:08 NM 7.35 73.76 1,300 5.87 +104.4 NM

5/2/2022 13:25 8.07 7.90 61.88 1,174 1.56 -143.9 NM

11/14/2022 14:08 8.93 7.63 66.90 1,148 2.80 -179.8 NM

MW-19 14.94 4/22/2021 13:28 8.61 6.51 62.55 2,302 0.90 +60.7 NM

10/28/2021 16:24 NM 6.81 73.24 2,268 0.59 +55.6 NM

Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

MW-19 14.94 5/4/2022 10:27 8.15 7.06 60.98 1,986 2.90 -44.9 NM

11/16/2022 11:32 8.92 7.65 67.80 1,600 0.59 -110.2 NM

MW-20 7.83 4/21/2021 11:29 6.53 6.82 62.13 1,872 0.20 -92.4 NM

10/27/2021 14:07 NM 6.99 73.02 1,325 2.23 -22.4 NM

5/3/2022 NA NM NM NM NM NM NM NM

11/15/2022 NA NM NM NM NM NM NM NM

MW-24 12.26 4/22/2021 09:51 8.47 6.79 59.56 1,053 0.33 +56.4 NM

10/28/2021 11:38 NM 7.57 68.79 1,974 0.53 +65.6 NM

5/5/2022 09:43 8.19 7.32 60.62 1,628 2.85 -64.2 NM

11/17/2022 10:14 8.48 7.17 64.20 1,150 0.74 -192.4 NM

MW-26 14.61 4/22/2021 13:43 9.46 6.40 61.43 1,159 0.22 +81.8 NM

10/28/2021 17:08 NM 7.17 73.65 569 0.67 +72.8 NM

5/4/2022 10:45 9.10 7.07 60.62 373 4.77 -69.8 NM

11/16/2022 11:54 10.00 7.09 68.90 393 0.58 -104.3 NM

MW-28 10.30 4/19/2021 10:03 8.40 5.96 60.26 246 8.61 +200.7 NM

10/25/2021 11:42 NM 7.03 71.13 336 2.07 +157.7 NM

5/2/2022 12:08 7.91 7.93 60.98 386 3.76 -99 NM

11/14/2022 12:27 8.85 7.79 67.70 348 1.75 -32.5 NM

Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

MW-32 9.92 4/19/2021 10:31 7.74 6.35 59.31 390 2.10 +172.2 NM

10/25/2021 11:06 NM 7.05 67.46 339 2.79 +164.8 NM

5/2/2022 12:32 7.30 7.74 59.54 280 3.86 -97.5 NM

11/14/2022 12:49 8.20 7.83 64.80 294 2.61 -11.8 NM

MW-33 14.19 4/23/2021 08:38 7.81 6.32 61.29 2,166 0.29 -12.8 NM

10/29/2021 09:18 NM 6.89 70.48 2,480 0.70 -70.9 NM

5/4/2022 12:02 7.45 7.82 62.06 1,442 4.34 -104.5 NM

MW-34 NM 4/23/2021 Damaged Well Collar

10/29/2021 Damaged Well Collar

5/5/2022 Damaged Well Collar

11/15/2022 Damaged Well Collar

RMF-MW-1 14.77 4/22/2021 11:08 12.05 6.98 61.92 1,972 0.40 -57.8 NM

10/28/2021 12:28 NM 7.21 70.43 1,877 0.40 -46.8 NM

5/5/2022 10:40 11.65 7.86 61.88 1,824 3.24 -64.6 NM

11/17/2022 NM Well Missing, Damaged By Grader

RMF-MW-2 13.29 4/23/2021 08:58 7.77 6.58 61.64 2,051 0.38 -170.3 NM

10/29/2021 09:58 NM 7.35 70.95 2,012 0.60 -260.7 NM

5/4/2022 12:31 7.40 7.77 61.70 1,752 4.02 -283.5 NM

Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

RMF-MW-2 13.29 11/16/2022 NM Well Missing, Damaged By Grader

RMF-MW-4 14.15 4/22/2021 12:31 8.97 6.64 62.89 1,485 0.20 -101.7 NM

10/28/2021 14:20 NM 7.27 72.91 1,494 0.38 -175.7 NM

5/5/2022 08:55 8.55 7.07 61.70 1,304 3.16 -108.1 NM

11/17/2022 11:46 9.03 7.08 66.60 1,241 0.45 -242.5 NM

RMF-MW-5 12.42 4/23/2021 08:08 7.96 6.51 60.33 1,186 0.63 +6.8 NM

10/29/2021 08:28 NM 6.95 70.57 896 1.29 -2.6 NM

5/4/2022 11:26 7.61 7.80 60.44 572 5.07 -65.6 NM

11/16/2022 12:39 8.31 7.89 66.60 773 0.57 -56.6 NM

RMF-MW-7 13.21 4/23/2021 10:23 10.22 6.44 61.11 2,159 0.56 +29.2 NM

10/29/2021 11:08 NM 7.21 69.08 2,182 1.02 -46.7 NM

5/4/2022 13:17 9.90 7.90 59.54 2,495 6.69 -99.9 NM

08:42 10.24 7.03 63.90 2,171 0.90 -41.0 NM

MW-201 NM 4/20/2021 Well not located

10/26/2021 14:55 NM 7.37 70.65 2,147 0.40 -91.3 NM

5/2/2022 15:36 5.16 7.97 62.42 730 1.38 -175.9 NM

11/15/2022 NM Well Not Located, Buried

Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

MW-202 10.52 4/20/2021 11:07 7.20 6.93 62.60 1,878 0.39 +25.7 NM

10/26/2021 15:31 NM 7.45 69.82 1,950 1.17 -52.9 NM

5/3/2022 09:12 6.70 7.32 63.32 1,745 1.54 -59.6 NM

11/15/2022 10:32 7.33 7.32 67.20 1,624 0.55 -206.0 NM

MW-203 11.63 4/20/2021 12:38 6.23 7.26 59.92 1,095 7.10 +106.2 NM

10/26/2021 16:06 NM 7.72 70.03 987 5.78 +24.9 NM

5/3/2022 09:49 6.25 7.49 59.90 1,944 2.95 -52.4 NM

11/15/2022 11:05 6.25 7.60 64.80 560 4.67 -134.0 NM

MW-204 10.66 4/20/2021 12:55 6.86 6.99 59.86 1,985 4.16 +120.7 NM

10/26/2021 16:36 NM 7.70 68.74 969 3.91 -29.7 NM

5/3/2022 09:36 5.61 7.07 60.62 821 3.99 -60.6 NM

11/15/2022 11:23 6.72 7.32 64.50 1,844 0.92 -139.6 NM

MW-205 10.52 4/20/2021 08:53 6.65 6.35 57.49 1,020 1.90 +53.2 NM

10/26/2021 10:20 NM 7.01 67.86 945 0.78 -44.6 NM

5/2/2022 15:09 6.18 7.09 58.10 1,477 0.41 -207.6 NM

11/14/2022 15:42 6.83 7.92 62.80 1,013 0.58 -252.9 NM

MW-206 10.68 4/20/2021 08:36 6.30 6.71 60.19 1,170 0.97 -88.1 NM

10/28/2021 09:50 NM 7.41 68.74 1,210 4.87 -41.9 NM

Sample

Date Sample

Time Depth to Water

(ft bgs) pH (su)

Temp* (⁰F)

SC

(µS/cm)

DO

(mg/L)

ORP

(mV)

Turbidity

(NTU)

MW-206 10.68 5/2/2022 14:47 5.68 7.34 61.34 1,263 0.43 -230.2 NM

11/14/2022 NA 6.42 Muddy Water, Insufficient to Sample

MW-207 10.54 4/20/2021 08:10 6.92 6.47 60.44 1,114 0.97 -211.4 NM

10/26/2021 09:11 NM 7.24 70.63 1,209 0.25 -108.7 NM

5/2/2022 14:28 6.28 7.43 61.88 1,172 0.34 -217.3 NM

11/14/2022 15:00 7.09 7.78 66.80 1,302 0.46 -264.8 NM

MW-208 10.18 4/21/2021 09:17 8.22 6.90 60.24 2,219 0.89 -91.0 NM

10/27/2021 11:14 NM 7.39 70.99 2,076 0.44 -135.0 NM

5/3/2022 13:32 7.67 7.14 61.34 1,849 3.42 -123.2 NM

11/15/2022 09:18 8.15 7.08 64.60 2,335 0.57 -263 NM

MW-209 23.06 4/22/2021…