C05b_ATT4_Pre-CERCLA_1284LM26Q4001_P0001.pdf

Pre-CERCLA Screening Checklist/Decision Document

Rabbit Ears Manganese, Jackson County, Colorado

August 12th, 2025

EPA Region 8

Site Assessment Program

1595 Wynkoop Street

Denver, CO 80202

Pre-CERCLA Screening – Rabbit Ears Manganese

Pre-CERCLA1 Screening (PCS) and sampling was conducted at the Rabbit Ears Manganese site on August 12th, 2025 by the Region 8 Environmental Protection Agency (EPA) Site

Assessment Program and other federal and state members of the Colorado Mixed-Ownership Team. Sampling and

Analysis were completed in accordance with the EPA/USFS/CDPHE-approved 2025 Sampling of Abandoned

Mine Lands Throughout Colorado Sampling and Analysis Plan/Quality Assurance Project plan.

The PCS Checklist/Decision Document, as required by EPA Pre-CERCLA Guidance (Office of Land and Emergency

Management (OLEM)) Directive # 9200.3-107, is included as Attachment A. A summary of soil and water analytical results as reported by the EPA-approved contractor, TechLaw, is included in Attachment B.

1 – Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)

Attachment A

Rabbit Ears Manganese Pre-CERCLA Screening Decision Form

Pre-CERCLA Screening Checklist/Decision Form

This form is used in conjunction with a site map and any additional information required by the EPA Region to document completion of a Pre-CERCLA Screening (PCS). The form includes a decision on whether a site should be added to the Superfund program’s active site inventory for further investigation.

EPA Region: 8 State: Colorado

EPA ID No. (If Available): Not Applicable

Site Category: Draining Mines

Select a Site Name (Primary): Rabbit Ears Manganese Site

Site Number: Not Applicable Date of Site Visit: August 12, 2025 Time of Site Visit: 11:11

Checklist Preparer

Title: Site Assessment/Project Manager

Name: Brittany Lease

Organization: EPA

Street Address: 1595 Wynkoop St

City: Denver

State: Colorado Zip Code: 80202

Phone: (720) 965-7653

Email: Lease.Brittany@epa.gov

Site Contact

Title: Nathan Williams

Name: Environmental Engineer

Organization: United States Forest Service

Street Address: 1617 Cole Blvd. Bldg 17

City: Lakewood

State: CO Zip Code: 80226

Phone: 720-689-7151

Email: Nathan.williams3@usda.gov

Site Information - Preliminary

Site Name (Alternate 1): Rabbit Ears Manganese

Site Name (Alternate 2): N/A

Region: 8

State: Colorado County: Jackson

Congressional District:

Township & Range:

Section:

Section (1/4):

Section (1/16):

Spatial Location

Latitude: 40.40357

Longitude: -106.60953

Collection Method: Desktop Location

Horizontal Accuracy in Meters:

Site Description (of this Spatial Location):

Approximate Center of Site

Preliminary Assessment - Historical Data

CERCLA 105d Petition for Preliminary Assessment: No

Petition Date: Not Applicable

RCRA Subtitle C Site Status: Not Applicable Is site in RCRA Info?: No

RCRAInfo Handler ID #: Not Applicable

Additional RCRAInfo ID #: Not Applicable

State ID: None

Ownership Type: USFS

Site Type: Abandoned Mine Site

Site Sub-Type: Hard Rock Mining

Federal Facility: No

Federal Facility Owner: Not Applicable

Federal Facility Operator: Not Applicable

Formerly Used Defense Site (FUDS): No

Federal Facility Docket: No

Federal Facility Docket Listing Date: Not Applicable

Federal Facility Docket Reporting Mechanism: Not Applicable

Native American Interest: Unknown

Tribe: Not Applicable

Additional Tribe: Not Applicable

Other ID: None

Site Description - Physical Setting

Abandoned Mine Site: Yes

Buildings: Buildings Not Present

Mill or Milling Equipment or Tailing Present: Yes

Steep Waste Piles: Yes

Safety Hazards Present: Yes

Safety Hazards: Dangerous slide potential or steep vertical face/wall/cliff (caused by mining operations), Hazardous abandoned equipment or facilities, Miscellaneous Debris, Pits/Trenches, Steep Vertical Inclines

Accessibility (provide details with regard to ability to access the site): Trail

Time it takes to reach this site (Hours: Minutes): ~ 30 minutes from Steamboat Springs, CO

Detailed description of how the site was accessed: From Steamboat Springs, head South on US 40 for about 20 miles. Take a left onto Buffalo Park Trail/USFS Rd 315.1. Take a right onto USFS Rd 315.1/CR 199. Continue on USFS Rd 315 for about 0.70 miles and then the site is located on the left.

Adjacent to Resident(s): No

Adjacent Residential Features: Not Applicable

Mountainous Steep Terrain: Yes

Vegetation Present: Yes

Vegetation Density: Moderate/Interspersed

Surface Water Body on or Adjacent to the Site: Yes

Open Fields: Yes

Waste Pile Erosion Observed: Yes

Describe Waste Pile Run Off: The waste pile on the northern end of middle pond is adjacent to it. The pile is eroding into the middle pond.

Tailings Erosion Observed: Yes, within the flatter waste area near the ore chute.

Describe Tailings Run Off: Natural erosion/disturbance throughout the tailings.

Draining Adits or Seeps Discharge from the Site: No

Adits Flow Rate from Site: Not Applicable

Describe Adit Flow from Site: Not Applicable

Draining Adits or Seeps Discharge Across Waste Piles: No

Draining Adits or Seeps Discharge to Adjacent Habitat: No

Adit Flows into what habitat: Not Applicable

Habitat Name: Not Applicable

Physical Setting and Access Features: Regularly used for public recreation (e.g., roads, trails, camping, etc.)

Physical Setting (Field Notes - provide a brief summary of physical setting including notable safety concerns, waste types, human uses/exposures to wastes, runoff/drainage, and notable habitat/ecological use): The site is accessible from USFS Road 315/CR 199 and surrounded by USFS forest land and open fields, there are also 3 ponds on site that appear to drain into one another and eventually lead to Grizzly Creek. 3 noticeable waste areas were observed; 1 steep pile in between the upper and middle ponds, 1 flat waste area where camping occurs, and 1 flatter area near an ore chute in between the middle and lower ponds where camping also likely occurs. Several steep trenches were observed in the northern area of the site and appear to be associated with historic mining operations.

Site Description - Land Use

Observed/likely fishing/consumption of fish/aquatic organisms at the mine site or within ¼ miles downstream:

Unknown

Are there other observed sensitive environments on-site or downstream of the waste area(s) within ¼ mile?

Unknown

Other Sensitive Environments:

Land Use (Field Notes – provide a brief summary of human/ecological type of use and use level (e.g., heavily used for biking and camping; observed camp fire rings and picnic tables at the site immediately adjacent to the waste runoff; narrow foot trail with difficult steep access to the waste areas and minimal use of the area, etc.):

The Site is used frequently for recreational purposes and within USFS land. Hiking/biking trails and several areas for camping are located throughout the site. Camping areas with fire rings were observed near the northern waste pile area just north of the middle pond as well as near the ore chute just south of the middle pond. Individuals camping out of their vehicles were also spotted closer to the hiking trail near USFS Road 315/CR 199 during the PCS visit.

Road/Trail Type: 4-Wheel Track/Trail

Human Activity Type: Moderate

Residential Density: Not Applicable

Recreational Density: Heavy

Camping Frequency: Moderate

Fishing Frequency: Not Applicable

Hiking Frequency: Moderate

Biking Frequency: Moderate

Picnicking Frequency: Not Applicable

Ecological Activity: Heavy

Roads/Trails: Yes

Human Activity: Yes

Residential: No

Recreational Use: Yes

Camping: Yes

Fishing: Unknown

Hiking: Yes

Biking: Yes

Picnicking: Unknown

Ecological Activity: Yes

Site Surface Description

Draining Adit: No

Waste Piles: Yes

Airborne Release of Fine Material/Dust: Potential

Surface Water on or Immediately Adjacent: Yes

Wetlands on or Adjacent to Site: Yes

Forested on or Adjacent to the Site: Yes

Site Surface (Field Notes): Drainage from the ponds lead to Grizzly Creek; trail leads to open fields and forested area and the waste piles/areas are easily accessible to recreational users.

Site Description - Other

Groundwater Seeps Observed: Yes

Primary Drainage Name: Ponds, especially below the upper retention pond area.

Groundwater Seeps (Field Notes): The upper pond was isolated, but some drainage appeared to surface south of it and drained towards the middle larger pond.

Previous Investigations: No

Investigation Type: Not Applicable

Who Completed Investigations at this Site: Not Applicable

Cleanup Activities: No Cleanup Type:Not Applicable

Site Description Cleanup Field Notes: Not Applicable

Who Completed Cleanup Activities at this Site: Not Applicable

Previous Regulatory Actions (Permitting and Enforcement): No

Previous Regulatory Type: Not Applicable

Site Feature Name(s): Not Applicable

Field Note(s): Not Applicable

Who Completed Regulatory Actions at this Site: Not Applicable

Institutional Controls: No Institutional Control Type: Not Applicable

Institutional Controls (indicate name/entity on signs/controls): No Institutional Controls

Community Interest: Unknown Community Interest Type: Not Applicable

Community Interest (Indicate watershed group or other interest group): Not Applicable

Draining Adit Type: Not Applicable

Number of Waste Piles: 3 areas of mine waste

Water Body Name: 3 Ponds, which drain to Grizzly Creek

Riparian on or Adjacent to the Site: Yes

Survey Form

1. An initial search for the site in EPA's Superfund active, archive and non-site inventories should be performed prior to starting a PCS. Is this a new site that does not already exist in these site inventories?

Yes

2. Is there evidence of an actual release or a potential to release?

Evidence of Potential Release:

Waste pile material observed in water body or other surrounding environment, Evidence of waste pile runoff/erosion (channels, rills, run off)

3. Are there possible targets that could be impacted by a release of contamination at the site?

4. Is there documentation indicating that a target has been exposed to a hazardous substance released from the site?

No

5. Is the release of a naturally occurring substance in its unaltered form, or is it altered solely through naturally occurring processes or phenomena, from a location where it is naturally found?

6. Is the release from products which are part of the structure of, and result in exposure within, residential buildings or business or community structures?

7. If there has been a release into a public or private drinking water supply, is it due to deterioration of the system through ordinary use?

8. Are the hazardous substances possibly released at the site, or is the release itself, excluded from being addressed under CERCLA?

9. Is the site being addressed under RCRA corrective action or by the Nuclear Regulatory Commission?

10. Is another federal, state, tribe or local government environmental cleanup program other than site assessment actively involved with the site (e.g., state voluntary cleanup program)?

11. Is there sufficient documentation or evidence that demonstrates there is no likelihood of a significant release that could cause adverse environmental or human health impacts?

12. Are there OTHER site-specific situations or factors that warrant further CERCLA remedial/integrated assessment or response?

US EPA Pre-CERCLA Checklist/Decision Form OLEM 9355.1-119, February 2018.

Current version of the PCS checklist and additional information is available at:

https://www.epa.gov/superfund/pre-cercla-screening.

https://www.epa.gov/superfund/pre-cercla-screening

Preparer’s Recommendation

Preparer's Recommendation: Do not add to the Superfund active site inventory.

Please explain recommendation below: The Rabbit Ears Manganese site (Site) is located on USFS land and was once used for historic mining operations, most notably for manganese. The Site has heavy recreational use, including hiking trails, biking trails, and camping, and there are no institutional controls for the mine waste and old mining remains throughout the Site. During the PCS event, 3 areas of mine waste were observed and XRF screening showed some extent of heavy metal contamination throughout all areas. One area included a steep pile in between the upper and middle ponds, another area included a flatter waste area slightly south of the steep pile, and one flatter area near an ore chute and collapsed building workings in between the middle and lower ponds. Both flatter waste areas were observed to have had previous camping activity. The Site also has 3 retention ponds, referred to as the upper, middle, and lower ponds, which appear to have drainage that connects them and eventually flows into Grizzly Creek. The middle retention pond has old pipes entering it that were observed from the surface and are likely from historic mining operations.

Surface water (SW) samples were collected from all three retention ponds as well as Grizzly Creek. SW results for Grizzly Creek were below EPA Regional Screening Levels (RSLs), but the lower retention pond showed elevated manganese concentrations (862 ug/L) which are above upstream SW concentrations and the EPA RSLS. Co-located sediment samples were also collected at 4 locations, including each retention pond and from Grizzly Creek downstream where the retention ponds drainage enters Grizzly Creek. The middle and lower retention ponds showed elevated manganese levels (1,250 mg/kg and 1,050 mg/kg, respectively) which are above EPA freshwater sediment screening benchmarks.

Soil samples were collected from each mine waste area and showed elevated concentrations of a range of heavy metals, most notably being manganese and arsenic. Manganese reached 28,000 mg/kg and arsenic reached 120 mg/kg, both which exceed site background levels and EPA RSLs. Aluminum, cobalt, thallium, and vanadium levels also exceeded background concentrations and EPA RSLs.

The site is not recommended to be added to EPA’s Superfund active site inventory. However, the Site is being referred to our partners at the USFS for consideration due to being on USFS land. It is recommended that the USFS install institutional controls, such as warning signs or physical barriers to certain waste areas, to help limit recreational exposure to the heavy metal contamination at the Site.

Site Assessor's Name: Brittany Lease

Site Assessor's Signature:

Date: February, 20th, 2026

EPA Regional Review and Pre-CERCLA Screening Decision

EPAs Recommendation: Do not add to the Superfund active site inventory.

Add site to the Superfund active site inventory for completion of a:

☐ Standard/full preliminary assessment (PA)

☐ Abbreviated preliminary assessment (APA)

☐ Combined Preliminary Assessment/Site Inspection (PA/SI)

☐ Integrated Removal Assessment and Preliminary Assessment

☐ Integrated Removal Assessment and Combined PA/SI

☐ Other Description

Do not add site to the Superfund active site inventory. Site is:

☐ Not a valid site or incident

☐ Refer to/being addressed by EPA’s Removal Program

☐ Refer to/being addressed by a State cleanup program

☐ Refer to/being addressed by Tribal cleanup program

☐ Refer to/being addressed under Resource Conservation and Recovery Act (RCRA)

☐ Refer to/being addressed by the Nuclear Regulatory Commission (NRC)

☐ Other Description: Do not add to the Superfund active site inventory. Refer to USFS for implementation of institutional controls (i.e. signage placement, barriers near potential camping areas) and further consideration.

EPA Region 8 Reviewer’s Name: Brittany Lease

EPA Region 8 Reviewer’s Signature:

Date: February 20th, 2026

Site Location

(Approximate center of Site)

Photographs

View of Upper Pond, Looking North

View of Middle Pond from Open Field, Looking South

Waste Pile Area In Between Upper and Middle Ponds (REM-SO-MP01-02), Looking North

Old Pipe in the Northern Area of the Middle Retention Pond, Likely Part of Historic Mining Operations

Camp Fire Ring in Flat Waste Area (REM-SO-CS01-01) Just South of Waste Pile, Looking Southwest

2nd Flat Waste/Camping Area near Ore Chute In Between Middle and Lower Ponds (REM-SO-MP02-01), Looking North

Abandoned Car near 2nd Flat Waste/Camping Area, Shows Human Interference with Site(REM-SO-MP02-01), Looking North

Ore Chute/Eastern Pile Area of REM-SO-MP02-01, Looking East

Bottom of Ore Chute, Possible Old Mill Area (REM-SO-MP02-01), Looking Northeast

Mine Operations Equipment Near Open Fields, Looking South

Attachment B

Pre-CERCLA Screening Sampling and Analysis Summary

Site Name Matrix Sampled Location ID Latitude Longitude Sample Location Description

REM-SW-GRZ-UPS-01 40.4082688 -106.6110378 Collected from Grizzly Creek upstream of the mining activity.

REM-SW-TRIB-01 40.4019383 -106.6066790

Collected from drainage coming from retention ponds before it enters Grizzly Creek.

REM-SW-A02-01 40.4018112 -106.6064877

Collected from Grizzly Creek about 50 meters downstream of the confluence with the ponds drainage.

REM-SW-GRZ-DNS-01 40.3966900 -106.6007700 Collected from Grizzly Creek downstream of the mining activity.

REM-SW-URP-01 40.4053800 -106.6101500 Collected from the upper retention pond.

REM-SW-MRP-01 40.4036110 -106.6094440 Collected from the middle/larger retention pond.

REM-SW-LRP-01 40.4026800 -106.6086700 Collected from the lower retention pond.

REM-SD-URP-01 40.4053800 -106.6101500 Collected from the upper retention pond.

REM-SD-MRP-01 40.4036110 -106.6094440 Collected from the middle/larger retention pond.

REM-SD-LRP-01 40.4026800 -106.6086700 Collected from the lower retention pond.

REM-SD-A02-01 40.4018112 -106.6064877

Collected from Grizzly Creek about 50 meters downstream of the confluence with the ponds drainage.

REM-SO-MP01-02 40.4043900 -106.6097900

Composite of mine waste pile adjacent and north of middle retention pond.

REM-SO-CS01-01 40.4039300 -106.6096200

Composite of camping area adjacent to middle retention pond.

REM-SO-MP02-01 40.4032940 -106.6089771 Composite of old mill area in between middle and lower retention ponds.

REM-SO-Grab-01

40.4044006 -106.6097289

Grab sample from mine waste pile adjacent and north of middle retention pond.

REM-SO-Grab-02 40.4038394 -106.6096154 Grab sample from the camping area adjacent to the middle retention pond.

REM-SO-Grab-03 40.4033265 -106.6089191 Grab sample from the old mill area in between middle and lower retention ponds.

Background Soil Sample

REM-SO-BKG-01 40.4025748 -106.610977

Composite sample of soil from a naturally wooded area about 320 feet southeast of the middle retention pond.

Sampling Locations

Rabbit Ears Manganese

Surface Water from Grizzly

Creek

Surface Water from Retention

Ponds

Sediment from Retention Ponds

Soil from Mine Waste Areas

Surface Water Analytical Results

Aluminum Antimony Arsenic Barium Beryllium Cadmium Calcium Chromium Cobalt Copper Iron Lead Magnesium Manganese Mercury Molybdenum Nickel Potassium Selenium Silica (SiO2) Silver Sodium Thallium Uranium Vanadium Zinc Hardness ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L mg/L

TRM 102 J 3.19 J 5.00 U 25.0 U 2.00 U 0.750 U 7270 7.50 U 0.500 U 2.50 U 150 U 1.00 U 2090 10.3 J 0.0350 UJ 5.00 UJ 2.50 U 502 7.50 U 24700 1.50 U 2350 2.50 U 0.500 U 15.0 U 17.9 J N/A DM 50.0 U 3.07 1.04 J 13.9 2.00 U 0.150 U 7090 1.71 J 0.100 U 0.500 U 150 U 0.200 U 2020 10.0 U N/A 1.00 UJ 0.500 U 464 J 1.50 U 24000 0.300 UJ 2310 0.500 U 0.100 U 3.00 U 15.0 U 26 TRM 64.8 J 3.28 J 5.00 U 25.0 U 2.00 U 0.750 U 11700 7.50 U 0.500 U 2.50 U 650 1.00 U 3790 87.2 0.0350 UJ 5.00 UJ 2.50 U 1160 7.50 U 14400 1.50 U 2960 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 4.11 1.00 U 13.7 2.00 U 0.150 U 11600 1.50 U 0.100 U 0.626 J 322 0.200 U 3740 10.0 U N/A 1.00 UJ 1.32 1050 1.50 U 14100 0.300 UJ 2930 0.500 U 0.100 U 3.00 U 20.0 J 44 TRM 50.0 U 2.54 J 5.00 U 25.0 U 2.00 U 0.750 U 7200 7.50 U 0.500 U 2.50 U 150 U 1.00 U 2060 10.0 U 0.0350 UJ 5.00 U 2.50 U 417 J 7.50 U 23600 1.50 U 2340 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 2.92 1.14 J 14.9 2.00 U 0.150 U 7070 1.56 J 0.100 U 0.544 J 150 U 0.200 U 2030 10.0 U N/A 1.00 UJ 0.500 U 379 J 1.50 U 23400 0.300 UJ 2300 0.500 U 0.100 U 3.00 U 15.0 U 26 TRM 50.0 U 3.05 J 5.00 U 25.0 U 2.00 U 0.750 U 7630 7.50 U 0.500 U 2.50 U 150 U 1.00 U 2200 10.0 U 0.0350 UJ 5.00 UJ 2.50 U 429 J 7.50 U 23500 1.50 U 2380 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 3.08 1.00 U 15.1 2.00 U 0.150 U 7400 1.50 U 0.100 U 0.500 U 150 U 0.200 U 2150 10.0 U N/A 1.00 UJ 0.500 U 360 J 1.50 U 22700 0.300 UJ 2310 0.500 U 0.100 U 3.00 U 15.0 U 27 TRM 50.0 U 4.08 J 5.00 U 25.0 U 2.00 U 0.750 U 2920 7.50 U 0.500 U 2.50 U 150 U 1.00 U 722 18.7 J 0.0350 UJ 5.00 UJ 2.50 U 986 7.50 U 409 1.50 U 1180 2.50 U 0.500 U 15.0 U 17.7 J N/A DM 50.0 U 4.44 1.00 U 10.9 2.00 U 0.150 U 2890 1.50 U 0.100 U 0.758 J 150 U 0.200 U 688 10.0 U N/A 1.00 UJ 0.500 U 928 1.50 U 353 0.300 UJ 1120 0.500 U 0.100 U 3.00 U 15.0 U 10 TRM 70.6 J 4.97 J 5.00 U 25.0 U 2.00 U 0.750 U 2900 7.50 U 0.500 U 2.50 U 150 U 1.00 U 706 28.4 0.0350 UJ 5.00 UJ 2.50 U 917 7.50 U 478 1.50 U 1160 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 5.22 1.00 U 10.8 2.00 U 0.150 U 2830 1.50 U 0.100 U 0.774 J 150 U 0.200 U 677 10.0 U N/A 1.00 UJ 0.500 U 875 1.50 U 346 0.300 UJ 1140 0.500 U 0.100 U 3.00 U 15.0 U 10 TRM 106 J 3.69 J 5.00 U 25.0 U 2.00 U 0.750 U 8810 7.50 U 0.500 U 2.50 U 321 1.00 U 3150 48.2 0.0350 UJ 5.00 UJ 2.50 U 883 7.50 U 17000 1.50 U 2960 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 3.08 1.50 J 18.6 2.00 U 0.150 U 8760 1.50 U 0.166 J 0.534 J 150 U 0.200 U 3090 17.0 J N/A 1.00 UJ 0.849 J 860 1.50 U 16700 0.300 UJ 2920 0.500 U 0.100 U 3.00 U 15.0 U 35 TRM 105 J 3.95 J 5.00 U 39.0 J 2.00 U 0.750 U 5970 7.50 U 1.32 2.50 U 1740 1.00 U 1980 862 0.0350 UJ 5.00 UJ 2.62 J 1630 7.50 U 10100 1.50 U 2890 2.50 U 0.500 U 15.0 U 15.0 U N/A DM 50.0 U 4.93 1.25 J 16.6 2.00 U 0.150 U 5750 1.50 U 0.460 0.711 J 338 0.200 U 1880 208 N/A 1.00 UJ 1.76 1450 1.50 U 9440 0.300 UJ 2870 0.500 U 0.100 U 3.00 U 15.0 U 22

Location ID Analysis Matrix Date Time pH Temp. (°C)

Dissolved Oxygen (mg/L)

Conductivity (uS/cm) Flow

Flow Measurement

Equipment

REM-SW-GRZ-UPS-01 In Situ Measurement

Surface Water 8/12/2025 16:40 7.97 10.04 8.13 64.5 0.771 Flow Tracker

REM-SW-TRIB-01 In Situ Measurement

Surface Water 8/12/2025 14:55 7.91 10.52 7.9 103.5 0.0041

1-inch Baski Flume

REM-SW-A02-01 In Situ Measurement

Surface Water 8/12/2025 14:00 7.95 11.14 7.89 64.7 0.6185 Flow Tracker

REM-SW-GRZ-DNS-01 In Situ Measurement

Surface Water 8/12/2025 11:45 7.66 9.79 8.29 67.2 0.8071 Flow Tracker

REM-SW-URP-01 In Situ Measurement

Surface Water 8/12/2025 12:50 6.86 13.5 7.08 28 N/C* N/A

REM-SW-MRP-01 In Situ Measurement

Surface Water 8/12/2025 11:45 6.57 17.2 4.56 86.6 N/C* N/A

REM-SW-LRP-01 In Situ Measurement

Surface Water 8/12/2025 11:10 6.8 15.6 5.05 64.8 N/C* N/A

Bromide Chloride Fluoride Nitrate/Nitrite

(Nitrogen) Sulfate (SO4) Total

Alkalinity mg/L mg/L mg/L mg/L mg/L mg CaCO3/L

REM-SW-GRZ-UPS-01 Wet Chemistry

Surface Water 8/12/2025 16:40 0.2 U 0.5 U 0.1 U 0.5 UJ 1.7 J 33.3

REM-SW-TRIB-01 Wet Chemistry

Surface Water 8/12/2025 14:55 0.2 U 0.5 U 0.1 J 0.5 UJ 4.1 J 51.3

REM-SW-A02-01 Wet Chemistry

Surface Water 8/12/2025 14:00 0.2 U 0.5 U 0.1 U 0.5 UJ 1.8 J 33.2

REM-SW-GRZ-DNS-01 Wet Chemistry

Surface Water 8/12/2025 11:45 0.2 U 0.5 U 0.1 U 0.5 UJ 1.9 J 34.7

REM-SW-URP-01 Wet Chemistry

Surface Water 8/12/2025 12:50 0.2 U 0.5 U 0.1 U 0.5 UJ 1.2 U 13.7

REM-SW-URP-01-DUP Wet Chemistry

Surface Water 8/12/2025 12:50 0.2 U 0.5 U 0.1 U 0.5 UJ 1.2 U 13.7

REM-SW-MRP-01 Wet Chemistry

Surface Water 8/12/2025 11:45 0.2 U 0.5 U 0.1 J 0.5 UJ 1.6 J 43.7

REM-SW-LRP-01 Wet Chemistry

Surface Water 8/12/2025 11:10 0.2 U 0.16 J 0.1 U 0.5 UJ 2.4 J 29.5

Sediment Analytical Results

Aluminum :

TRM

Antimony :

TRM

Arsenic :

TRM Barium : TRM

Beryllium :

TRM

Cadmium :

TRM Calcium : TRM

Chromium

: TRM

Cobalt :

TRM

Copper :

TRM Iron : TRM

Lead :

TRM

Magnesium

: TRM

Manganese :

TRM

Mercury :

TRM

Molybdenu m : TRM Nickel : TRM

Potassium :

TRM

Selenium :

TRM

Silica (SiO2) : TRM Silver : TRM

Sodium :

TRM

Thallium :

TRM

Uranium :

TRM

Vanadium :

TRM Zinc : TRM mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

REM-SD-URP-01 Sediment Composite

8/12/2025 12:50 11400 0.492 U 2.63 151 0.984 U 0.189 J 2130 28.4 2.6 6.76 9310 10.7 1680 169 0.04 J 0.984 U 10.3 1190 1.48 U 4450 0.295 U 135 0.492 U 0.612 24.1 42.5

REM-SD-URP-01-DUP Sediment Composite

8/12/2025 12:50 11500 0.491 U 2.72 145 0.982 U 0.318 2070 28 2.73 7.65 9360 9.53 1710 158 0.04 J 0.982 11 1100 1.47 U 3250 0.295 U 125 0.491 U 0.612 26.3 52.1

REM-SD-MRP-01 Sediment Composite

8/12/2025 11:45 13400 0.997 U 24.1 208 1.54 J 0.391 J 4310 36.7 16.1 22.1 32700 13.7 2980 1250 0.04 U 1.99 U 30 1700 2.99 U 4570 0.598 U 181 0.997 U 2.52 37.8 82.4

REM-SD-LRP-01 Sediment Composite

8/12/2025 11:20 12000 0.495 U 8.71 228 1.29 J 1.03 3870 28.2 19.6 13.3 19200 15.6 2170 1050 0.04 J 0.99 U 21.9 1520 1.48 U 3610 0.297 U 93.4 J 0.495 U 1.52 25.8 112

REM-SD-A02-01 Sediment Composite

8/12/2025 14:10 12200 0.498 UJ 13.1 156 1.57 J 0.532 5390 33.4 J 8.73 J 13.2 J 23000 13.4 J 3110 J 930 0.04 U 1.14 J 23.3 J 1550 J 1.49 U 5580 0.299 U 147 0.505 J 1.78 30.1 J 72.6

J: The result is an estimated value; the associated numerical value is the approximate concentration of the analyte in the sample.

U: The analyte was not detected above the method detection limit; the method detection limit is reported as the value for these analytes.

REM-SW-LRP-01 Surface Water

8/12/2025 11:10

J: The result is an estimated value; the associated numerical value is the approximate concentration of the analyte in the sample.

U: The analyte was not detected above the method detection limit; the method detection limit is reported as the value for these analytes.

Field-Measured Water Quality Parameters

N/C: Not Collected, N/A: Not Applicable *Flow was not collected from the retention ponds due to there being no actively flowing water.

Anions/Alkalinity Wet Chemistry Analytical Results

Location ID Matrix

J: The result is an estimated value; the associated numerical value is the approximate concentration of the analyte in the sample.

U: The analyte was not detected above the method detection limit; the method detection limit is reported a the value for these analytes.

Location ID Matrix/Metho Date Time

TRM: Total Recoverable Metals, mg/kg: Milligrams per kilograms, RSL: Residential Screening Levels, N/A: Not Available

Date Time

REM-SW-URP-01 Surface Water

8/12/2025 12:50

REM-SW-URP-01-DUP Surface Water

REM-SW-MRP-01 Surface Water

8/12/2025 11:45

8/12/2025 12:50

Analysis

TRM: Total Recoverable Metals, DM: Total Dissolved Metals, ug/L: Microgram per Liter, N/A: Not Available

REM-SW-A02-01 Surface Water

8/12/2025 14:00

REM-SW-GRZ-DNS-01 Surface Water

8/12/2025 11:45

REM-SW-GRZ-UPS-01 Surface Water

8/12/2025 16:40

REM-SW-TRIB-01 Surface Water

8/12/2025 14:55

Surface Water Total Recoverable (TRM) and Total Dissolved (DM) Metals Analytical Chemistry Results

Location ID Analysis Matrix Date Time

Soil Results

Aluminum :

TRM

Antimony :

TRM

Arsenic :

TRM

Barium :

TRM

Beryllium :

TRM

Cadmium :

TRM

Calcium :

TRM

Chromium :

TRM

Cobalt :

TRM

Copper :

TRM

Iron : TRM Lead : TRM Magnesium

: TRM

Manganese

: TRM

Mercury :

TRM

Molybdenum

: TRM

Nickel :

TRM

Potassium :

TRM

Selenium :

TRM

Silica (SiO2)

: TRM

Silver :

TRM

Sodium :

TRM

Thallium :

TRM

Uranium :

TRM

mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg REM-SO-BKG-01 Soil Composite 8/12/2025 16:25 18900 1.01 UJ 12.2 J 162 1.34 J 0.412 J 4690 14.7 7.51 15.2 26600 18.1 2870 448 0.04 J 2.02 UJ 16 3230 3.03 U 35900 0.606 U 85.9 J 1.01 U 1.53

REM-SO-MP01-02 Soil Composite 8/12/2025 13:20 16100 0.995 U 68.5 J 585 2.34 J 0.531 J 5150 52.1 63.1 29.7 48200 18.1 3700 4600 0.04 U 5.09 72.1 2010 2.99 U 7590 0.597 U 215 3.24 2.27 REM-SO-CS01-01 Soil Composite 8/12/2025 13:40 19000 0.997 U 57.2 J 439 2.89 J 0.583 J 5890 70.7 52.5 28.8 55000 13.9 3810 2640 0.04 U 2.83 J 72.6 1570 2.99 U 11900 0.598 U 326 1.95 J 2.55 REM-SO-MP02-01 Soil Composite 8/12/2025 15:24 21400 1 U 18.5 J 426 2.92 J 0.692 4620 48 48.8 22.6 39900 11.6 4930 2360 0.04 U 2.01 U 64.8 2130 3.01 U 8790 0.602 U 240 1.47 J 1.59 REM-SO-Grab-01 Soil Grab 8/12/2025 13:20 19800 0.996 U 30.6 J 818 4.38 J 0.567 J 5600 50.1 96.7 28.9 46600 12.7 5210 5770 0.04 U 3.09 J 85.7 1540 2.99 U 10600 0.597 U 307 3.39 2.26 REM-SO-Grab-02 Soil Grab 8/12/2025 13:58 18000 0.986 U 80.7 J 804 4.08 J 0.719 7310 86.5 100 32.6 68900 9.74 3980 5830 0.04 U 3.62 J 103 1810 2.96 U 10500 0.592 U 383 3.63 2.28 REM-SO-Grab-03 Soil Grab 8/12/2025 16:03 8730 0.997 U 120 J 3560 4.12 J 1.26 4880 103 304 103 72800 8.99 3820 28000 0.04 U 32.4 144 2160 2.99 U 8280 0.598 U 222 35.1 2.95

Aluminum :

SPLP

Antimony :

SPLP

Arsenic :

SPLP

Barium :

SPLP

Beryllium :

SPLP

Cadmium :

SPLP

Calcium :

SPLP

Chromium :

SPLP

Cobalt :

SPLP

Copper :

SPLP Iron : SPLP Lead : SPLP

Magnesium

: SPLP

Manganese

: SPLP

Mercury :

SPLP Nickel : SPLP

Potassium :

SPLP

Selenium :

SPLP

Silver :

SPLP

Sodium :

SPLP

Thallium :

SPLP

Vanadium :

SPLP Zinc : SPLP ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L REM-SO-MP02-01 Soil Composite 8/12/2025 15:24 23000 14 U 27 330 1.2 J 0.69 U 6,400 36 29 J 23 J 31000 23 3700 J 1500 0.15 J 44 3600 J 17 U 2.6 U 17000 J 7.6 U 52 79

Location ID Matrix Date Time

SPLP: Synthetic Precipitation Leaching Procedure, ug/L: Micrograms per Liter J: The result is an estimated value; the associated numerical value is the approximate concentration of the analyte in the sample.

U: The analyte was not detected above the method detection limit; the method detection limit is reported a the value for these analytes.

Location ID Matrix/Method Date Time

TRM: Total Recoverable Metals, mg/kg: Milligrams per kilograms, N/A: Not Available

J: The result is an estimated value; the associated numerical value is the approximate concentration of the analyte in the sample.

U: The analyte was not detected above the method detection limit; the method detection limit is reported a the value for these analytes.

X-Ray Fluorescence (XRF) Spectrometry Soil Survey Results* Location XRF Sample ID Latitude Longitude Date Time Units Ti Ti +/- Cr Cr +/- Mn Mn +/- Fe Fe +/- Co Co +/- Ni Ni +/- Cu Cu +/- Zn Zn +/- As As +/- Se Se +/- Rb Rb +/- Sr Sr +/- Zr Zr +/- Mo Mo +/- Ag Ag +/- Cd Cd +/- Sn Sn +/- Sb Sb +/- Ba Ba +/- Hg Hg +/- Pb Pb +/-

Rabbit Ears Manganese REM-SO-MP01-02-X001 40.4041604 -106.6095501 8/12/2025 12:32 mg/kg 4349 644 <LOD 173 1277 115 28355 515 <LOD 274 <LOD 78 <LOD 41 79 10 <LOD 14 <LOD 5 93 4 301 8 234 7 <LOD 13 <LOD 53 <LOD 62 <LOD 101 <LOD 109 <LOD 831 <LOD 16 27 6

Rabbit Ears Manganese REM-SO-MP01-02-X002 40.4046493 -106.6099569 8/12/2025 12:38 mg/kg 2617 383 <LOD 119 884 66 21332 272 <LOD 159 <LOD 47 <LOD 27 51 6 <LOD 7 <LOD 3 73 3 231 5 159 4 12 3 <LOD 35 <LOD 42 <LOD 67 <LOD 73 544 174 <LOD 11 10 3

Rabbit Ears Manganese REM-SO-MP01-02-X003 40.4045787 -106.6098725 8/12/2025 12:41 mg/kg 3195 443 <LOD 140 655 69 31616 397 281 68 <LOD 54 <LOD 28 58 6 18 3 <LOD 4 72 3 329 6 222 5 10 3 <LOD 37 <LOD 44 <LOD 70 <LOD 77 721 201 <LOD 12 15 4

Rabbit Ears Manganese REM-SO-MP01-02-X004 40.4044616 -106.6098295 8/12/2025 12:44 mg/kg 4868 514 <LOD 152 1205 85 38904 484 <LOD 227 <LOD 60 <LOD 30 71 7 <LOD 10 <LOD 4 69 3 537 9 196 5 <LOD 9 <LOD 38 <LOD 45 75 24 <LOD 81 948 228 <LOD 11 29 4

Rabbit Ears Manganese REM-SO-MP01-02-X005 40.4044335 -106.6097795 8/12/2025 12:46 mg/kg 6374 577 230 61 1837 104 50961 631 445 91 <LOD 66 47 11 82 7 19 3 <LOD 4 51 2 533 9 249 5 <LOD 10 <LOD 39 <LOD 47 <LOD 75 <LOD 82 920 251 <LOD 14 16 4

Rabbit Ears Manganese REM-SO-MP01-02-X006 40.4044006 -106.6097289 8/12/2025 12:48 mg/kg 7472 599 <LOD 178 3253 131 54416 687 <LOD 281 <LOD 68 <LOD 32 80 7 21 4 <LOD 4 44 2 569 9 228 5 12 3 <LOD 40 <LOD 47 <LOD 76 <LOD 84 <LOD 750 <LOD 13 23 4

Rabbit Ears Manganese REM-SO-MP01-02-X007 40.4044598 -106.6096723 8/12/2025 12:50 mg/kg 6564 583 <LOD 176 2216 113 51441 648 416 92 <LOD 69 <LOD 32 93 8 17 3 <LOD 4 44 2 592 10 223 5 <LOD 10 <LOD 40 <LOD 47 <LOD 75 <LOD 82 <LOD 752 <LOD 14 <LOD 11

Rabbit Ears Manganese REM-SO-MP01-02-X008 40.4044913 -106.6097268 8/12/2025 12:52 mg/kg 6482 561 <LOD 165 3133 126 47119 596 <LOD 261 <LOD 67 <LOD 31 78 7 22 3 <LOD 4 58 3 487 8 255 5 13 3 <LOD 39 <LOD 47 <LOD 74 <LOD 81 <LOD 710 <LOD 14 <LOD 12

Rabbit Ears Manganese REM-SO-MP01-02-X009 40.4046781 -106.6098264 8/12/2025 12:55 mg/kg 3401 416 <LOD 129 413 59 26065 324 228 60 <LOD 51 <LOD 27 56 6 9 3 <LOD 3 77 3 292 5 184 4 9 3 <LOD 36 <LOD 43 <LOD 68 <LOD 75 569 185 <LOD 11 17 4

Rabbit Ears Manganese REM-SO-MP01-02-X010 40.4046084 -106.6096896 8/12/2025 12:57 mg/kg 7940 631 <LOD 176 678 84 50822 647 426 93 <LOD 69 38 11 89 8 14 3 <LOD 4 47 2 470 8 249 5 <LOD 10 <LOD 40 <LOD 48 <LOD 77 <LOD 84 1114 269 <LOD 14 14 4

Rabbit Ears Manganese REM-SO-MP01-02-X011 40.4045239 -106.6096060 8/12/2025 13:00 mg/kg 1757 430 <LOD 156 305 66 24396 369 <LOD 208 <LOD 58 <LOD 29 42 6 24 4 <LOD 4 77 3 313 7 234 6 <LOD 11 <LOD 43 <LOD 50 <LOD 82 <LOD 90 <LOD 597 <LOD 14 <LOD 12

Rabbit Ears Manganese REM-SO-MP01-02-X012 40.4045707 -106.6095756 8/12/2025 13:01 mg/kg 1624 354 <LOD 118 829 64 21822 273 <LOD 157 <LOD 46 <LOD 25 46 5 18 3 <LOD 4 81 3 325 6 243 5 <LOD 9 <LOD 35 <LOD 42 <LOD 68 <LOD 75 530 167 <LOD 11 26 4

Rabbit Ears Manganese REM-SO-MP01-02-X013 40.4045192 -106.6094336 8/12/2025 13:03 mg/kg 1967 358 <LOD 124 416 59 32480 376 329 65 <LOD 48 <LOD 25 99 7 11 3 <LOD 3 78 3 188 4 124 3 15 3 <LOD 34 <LOD 40 <LOD 63 <LOD 68 <LOD 492 <LOD 10 18 3

Rabbit Ears Manganese REM-SO-MP01-02-X014 40.4043930 -106.6095725 8/12/2025 13:06 mg/kg 3987 693 <LOD 214 1437 126 48097 788 749 119 <LOD 83 <LOD 42 70 9 33 5 <LOD 5 47 3 561 12 222 7 <LOD 13 <LOD 51 <LOD 61 <LOD 96 <LOD 106 1105 318 <LOD 16 18 5

Rabbit Ears Manganese REM-SO-MP01-02-X015 40.4042869 -106.6095343 8/12/2025 13:08 mg/kg 6191 579 <LOD 171 1604 102 55162 681 367 94 <LOD 70 54 11 91 8 16 3 <LOD 4 48 2 544 9 204 5 <LOD 10 <LOD 39 <LOD 46 <LOD 75 <LOD 82 903 253 <LOD 12 17 4

Rabbit Ears Manganese REM-SO-CS01-01-X001 40.4039227 -106.6095561 8/12/2025 13:40 mg/kg 5182 636 <LOD 209 4221 161 75151 981 <LOD 351 <LOD 79 <LOD 35 109 9 73 5 <LOD 5 45 3 535 10 174 5 <LOD 11 <LOD 43 <LOD 50 <LOD 81 <LOD 89 1013 287 <LOD 14 17 4

Rabbit Ears Manganese REM-SO-CS01-01-X002 40.4036983 -106.6094809 8/12/2025 13:43 mg/kg 2755 349 <LOD 111 380 52 20602 253 167 50 <LOD 45 <LOD 23 52 5 12 3 <LOD 4 72 2 162 4 163 4 11 3 <LOD 34 <LOD 40 <LOD 63 <LOD 69 <LOD 457 <LOD 10 40 4

Rabbit Ears Manganese REM-SO-CS01-01-X003 40.4038390 -106.6096162 8/12/2025 13:45 mg/kg 4570 638 <LOD 201 3605 146 69785 892 505 111 <LOD 76 <LOD 33 83 8 44 4 <LOD 4 45 3 570 10 190 5 11 3 <LOD 42 <LOD 49 <LOD 79 <LOD 87 1935 300 <LOD 14 18 4

Rabbit Ears Manganese REM-SO-CS01-01-X004 40.4039300 -106.6096300 8/12/2025 13:48 mg/kg 6092 633 <LOD 206 2272 125 71343 908 482 112 <LOD 78 <LOD 33 90 8 39 4 <LOD 4 47 3 517 9 226 5 14 4 <LOD 42 <LOD 49 <LOD 79 <LOD 87 996 280 <LOD 13 17 4

Rabbit Ears Manganese REM-SO-CS01-01-X005 40.4038970 -106.6094900 8/12/2025 13:50 mg/kg 4669 609 206 68 2125 119 71741 887 522 110 <LOD 74 36 11 91 8 51 4 <LOD 4 39 2 630 10 183 5 <LOD 10 <LOD 40 <LOD 48 <LOD 76 <LOD 84 1562 282 <LOD 13 18 4

Rabbit Ears Manganese REM-SO-MP02-01-X001 40.4032913 -106.6089879 8/12/2025 15:24 mg/kg 1766 408 <LOD 138 600 69 20472 307 211 62 <LOD 53 <LOD 31 102 8 13 4 <LOD 4 105 4 122 4 157 4 12 3 <LOD 41 <LOD 49 <LOD 78 <LOD 87 <LOD 566 <LOD 12 34 5

Rabbit Ears Manganese REM-SO-MP02-01-X002 40.4032983 -106.6089797 8/12/2025 15:26 mg/kg 2477 373 <LOD 125 168 52 25392 317 185 59 <LOD 47 <LOD 27 101 7 12 4 <LOD 4 101 3 104 3 162 4 <LOD 9 <LOD 36 <LOD 42 <LOD 68 <LOD 74 <LOD 500 <LOD 11 69 5

Rabbit Ears Manganese REM-SO-MP02-01-X003 40.4031635 -106.6091097 8/12/2025 15:29 mg/kg 1900 402 <LOD 131 <LOD 176 41139 489 436 77 <LOD 52 <LOD 28 56 6 10 3 <LOD 4 93 3 91 3 144 4 11 3 <LOD 37 <LOD 44 <LOD 71 <LOD 77 <LOD 563 <LOD 12 28 4

Rabbit Ears Manganese REM-SO-MP02-01-X004 40.4029911 -106.6088667 8/12/2025 15:32 mg/kg 5485 554 <LOD 169 937 88 51650 638 532 92 <LOD 69 <LOD 31 76 7 15 3 <LOD 4 51 2 590 9 170 5 13 3 <LOD 39 <LOD 47 <LOD 75 <LOD 83 861 244 <LOD 11 16 4

Rabbit Ears Manganese REM-SO-MP02-01-X005 40.4030559 -106.6086945 8/12/2025 15:34 mg/kg 2685 422 <LOD 136 858 74 35218 431 383 72 <LOD 55 <LOD 26 87 7 10 3 <LOD 4 103 3 225 5 155 4 9 3 <LOD 37 <LOD 44 <LOD 71 <LOD 77 <LOD 579 <LOD 10 24 4

Rabbit Ears Manganese REM-SO-MP02-01-X006 40.4031645 -106.6085969 8/12/2025 15:37 mg/kg 6615 684 274 78 2920 143 101791 1253 418 131 <LOD 87 56 12 101 8 32 4 <LOD 5 27 2 741 12 149 5 18 3 <LOD 41 <LOD 48 <LOD 78 <LOD 85 1237 307 <LOD 14 21 5

Rabbit Ears Manganese REM-SO-MP02-01-X007 40.4031831 -106.6085251 8/12/2025 15:39 mg/kg 3166 386 <LOD 127 526 62 29770 360 265 63 <LOD 50 <LOD 26 103 7 <LOD 9 <LOD 4 124 3 101 3 139 3 <LOD 9 <LOD 36 <LOD 42 <LOD 68 <LOD 74 <LOD 501 <LOD 12 23 4

Rabbit Ears Manganese REM-SO-MP02-01-X008 40.4034023 -106.6086576 8/12/2025 15:41 mg/kg 7866 815 <LOD 276 14091 316 136313 1764 757 163 <LOD 101 <LOD 39 100 9 236 9 <LOD 5 23 2 648 11 139 5 15 4 <LOD 44 <LOD 52 <LOD 83 <LOD 91 1641 369 <LOD 16 28 5

Rabbit Ears Manganese REM-SO-MP02-01-X009 40.4034723 -106.6085992 8/12/2025 15:45 mg/kg 2710 506 <LOD 168 8228 200 42646 551 322 84 <LOD 63 40 11 87 8 29 4 <LOD 4 79 3 397 7 162 4 17 3 <LOD 40 <LOD 47 <LOD 75 <LOD 82 1178 240 <LOD 14 24 4

Rabbit Ears Manganese REM-SO-MP02-01-X010 40.4034723 -106.6085379 8/12/2025 15:47 mg/kg 3744 422 <LOD 126 1208 78 31940 386 343 67 <LOD 54 <LOD 28 73 6 16 3 <LOD 4 98 3 233 5 183 4 17 3 <LOD 36 <LOD 43 <LOD 68 <LOD 75 <LOD 551 <LOD 12 32 4

Rabbit Ears Manganese REM-SO-MP02-01-X011 40.4035882 -106.6085346 8/12/2025 15:49 mg/kg 4923 541 <LOD 174 1624 105 60666 750 445 100 <LOD 67 <LOD 31 73 7 70 5 <LOD 4 62 3 429 8 216 5 <LOD 10 <LOD 40 <LOD 48 <LOD 76 <LOD 83 <LOD 710 <LOD 14 17 4

Rabbit Ears Manganese REM-SO-MP02-01-X012 40.4036089 -106.6084588 8/12/2025 15:51 mg/kg 4118 498 <LOD 162 1393 93 46333 571 351 85 <LOD 63 31 10 65 7 43 4 <LOD 4 69 3 427 7 224 5 12 3 <LOD 38 <LOD 46 <LOD 74 <LOD 80 <LOD 667 <LOD 11 16 4

Rabbit Ears Manganese REM-SO-MP02-01-X013 40.4033312 -106.6086769 8/12/2025 15:54 mg/kg 7251 679 <LOD 220 12692 274 72143 926 456 114 <LOD 77 <LOD 34 115 9 40 4 <LOD 5 29 2 734 12 157 5 20 4 <LOD 42 <LOD 48 91 26 <LOD 85 1239 300 <LOD 14 20 4

Rabbit Ears Manganese REM-SO-MP02-01-X014 40.4033310 -106.6087287 8/12/2025 15:56 mg/kg 2089 335 <LOD 105 620 56 17471 223 201 47 <LOD 44 <LOD 24 87 6 10 3 <LOD 3 119 3 112 3 173 4 <LOD 8 <LOD 34 <LOD 40 <LOD 65 <LOD 70 <LOD 454 <LOD 10 20 3

Rabbit Ears Manganese REM-SO-MP02-01-X015 40.4033205 -106.6088794 8/12/2025 15:58 mg/kg 4817 914 492 128 26544 601 144083 2353 <LOD 620 <LOD 123 105 18 119 12 58 6 <LOD 6 43 3 385 10 117 5 56 5 <LOD 56 <LOD 65 <LOD 104 <LOD 114 <LOD 1263 <LOD 21 29 7

LOD: Level of Detection, mg/kg: milligram per kilogram, Ti: Titanium, Cr: Chromium, Mn: Manganese, Fe: Iron, Co: Cobalt, Ni: Nickel, Cu: Copper, Zn: Zinc, As: Arsenic, Se: Selenium, Rb: Rubidium, Sr: Strontium, Zr: Zirconium, Mo: Molybdenum, Ag: Silver, Cd: Cadmium, Sn: Tin, Sb: Antimony, Ba: Barium, Hg: Mercury, Pb: Lead *The XRF reading locations are consistent with the collection spots for the composite samples MP01-02, CS01-01, and MP02-01

Rabbit Ears Manganese

REM-SW-A02-01

08/12/2025

Aluminum = <50 Arsenic = 1.14

Cadmium = <0.15 Copper = 0.544

Iron = <150 Lead = <0.2

Manganese = <10 Nickel = <0.5 Zinc = <15

Hardness = 26 pH = 7.95

Flow = 0.6185

REM-SW-GRZ-DNS-01

08/12/2025

Aluminum = <50 Arsenic = <1

Cadmium = <0.15 Copper = <0.5 Iron = <150 Lead = <0.2

Manganese = <10 Nickel = <0.5 Zinc = <15

Hardness = 27 pH = 7.66

Flow = 0.8071

REM-SW-GRZ-UPS-01

08/12/2025

Aluminum = 102 Arsenic = 1.04

Cadmium = <0.15 Copper = <0.5 Iron = <150 Lead = <0.2

Manganese = <10 Nickel = <0.5 Zinc = <15

Hardness = 26 pH = 7.97

Flow = 0.771

REM-SW-LRP-01

08/12/2025

Aluminum = 105 Arsenic = 1.25

Cadmium = <0.15 Copper = 0.711

Iron = 338 Lead = <0.2

Manganese = 208 Nickel = 1.76 Zinc = <15

Hardness = 22 pH = 6.8

Flow = NA

REM-SW-MRP-01

08/12/2025

Aluminum = 106 Arsenic = 1.5

Cadmium = <0.15 Copper = 0.534

Iron = <150 Lead = <0.2

Manganese = 17 Nickel = 0.849

Zinc = <15 Hardness = 35 pH = 6.57 Flow = NA

REM-SW-TRIB-01

08/12/2025

Aluminum = 64.8 Arsenic = <1

Cadmium = <0.15 Copper = 0.626

Iron = 322 Lead = <0.2

Manganese = <10 Nickel = 1.32

Zinc = 20 Hardness = 44 pH = 7.91 Flow = 0.0041

REM-SW-URP-01

08/12/2025

Aluminum = <50 Arsenic = <1

Cadmium = <0.15 Copper = 0.758

Iron = <150 Lead = <0.2

Manganese = <10 Nickel = <0.5 Zinc = <15

Hardness = 10 pH = 6.86 Flow = NA

G rizzly C reek

Rabbit Ears Manganese

\\tt.local\GIS\US\EMI\R08_STARTV\AMLMixedOwnershipMinesSAR2024\AMLMixedOwnershipMinesSAR2025_COLORADO_Samples.aprx\Figure A.5 Rabbit Ears Manganese 2025 Pre-CERCLA Screening Surface Water Sample Locations and Results

Date:

2/12/2026

Contract:

68HE0820D0001

TO/TD:

2361-2401-09

Sources:

Background: Google Aerial Imagery Sample/Mine Locations: EPA Region 8 Streams: USGS National Hydrography Dataset Roads: ESRI from U.S. Census Bureau (USCB) Spatial Reference: WGS 1984 Web Mercator Auxiliary Sphere Coordinate System

Analyst: M. Caldwell

2025 Pre-CERCLA Screening Water Sampling

Locations/Key Results* Sampling Date: August 12, 2025

Upper Grizzly Creek Subwatershed Jackson County, Colorado

Figure A.5 Rabbit Ears Manganese

*Red font indicates an exceedance of hardness-based CO Department of Public Health and Environment (CDPHE) Regulation 31 Chronic Water Quality Standard.

Red BOLD font indicates an exceedance of hardness-based CDPHE Regulation 31 Chronic and Acute Water Quality Standard.

CDPHE Reg 31: https://www.coloradosos.gov/CCR/GenerateRulePdf.do?

ruleVersionId=11749&fileName=5%20CCR%201002-31

Total Recoverable Metals: units = 𝜇g/L Dissolved Metals: units = 𝜇g/L Flow: units = cubic feet/second pH: units = standard units Hardness: units = mg of CaCO3/L

0 500 1,000250

Feet

Water Sample Locations

Creeks

Roads

Mine Locations https://www.coloradosos.gov/CCR/GenerateRulePdf.do?ruleVersionId=11749&fileName=5%20CCR%201002-31

Rabbit Ears Manganese

REM-SD-A02-01

08/12/2025

Arsenic = 13 Cadmium = 0.532

Copper = 13 Iron = 23,000

Lead = 13 Manganese = 930

Zinc = 72.6

REM-SD-LRP-01

08/12/2025

Arsenic = 8 Cadmium = 1 Copper = 13

Iron = 19,200 Lead = 15

Manganese = 1,050 Zinc = 112

REM-SD-MRP-01

08/12/2025

Arsenic = 24 Cadmium = 0.391

Copper = 22 Iron = 32,700

Lead = 13 Manganese = 1,250

Zinc = 82.4

REM-SD-URP-01

08/12/2025 Arsenic = 2

Cadmium = 0.189 Copper = 6

Iron = 9,310 Lead = 10

Manganese = 169 Zinc = 42.5

REM-SO-BKG-01

08/12/2025

Arsenic = 12 Cadmium = 0.412

Copper = 15 Iron = 26,600

Lead = 18 Manganese = 448

Zinc = 70.5

REM-SO-CS01-01

08/12/2025

Arsenic = 57 Cadmium = 0.583

Copper = 28 Iron = 55,000

Lead = 13 Manganese = 2,640

Zinc = 74.8

REM-SO-Grab-01 08/12/2025

Arsenic = 30 Cadmium = 0.567

Copper = 28 Iron = 46,600

Lead = 12 Manganese = 5,770

Zinc = 92.4REM-SO-Grab-02 08/12/2025

Arsenic = 80 Cadmium = 0.719

Copper = 32 Iron = 68,900

Lead = 9 Manganese = 5,830

Zinc = 101

REM-SO-Grab-03 08/12/2025

Arsenic = 120 Cadmium = 1 Copper = 103 Iron = 72,800

Lead = 8 Manganese = 28,000

Zinc = 134

REM-SO-MP01-02

08/12/2025

Arsenic = 68 Cadmium = 0.531

Copper = 29 Iron = 48,200

Lead = 18 Manganese = 4,600

Zinc = 89.5

REM-SO-MP02-01

08/12/2025

Arsenic = 18 Cadmium = 0.692

Copper = 22 Iron = 39,900

Lead = 11 Manganese = 2,360

Zinc = 66.1

G rizzly C reek Rabbit Ears Manganese

\\tt.local\GIS\US\EMI\R08_STARTV\AMLMixedOwnershipMinesSAR2024\AMLMixedOwnershipMinesSAR2025_COLORADO_Samples.aprx\Figure A.6 Rabbit Ears Manganese 2025 Pre-CERCLA Screening Mine Waste Soil and Sediment Sample Locations and Results

Date:

2/12/2026

Contract:

68HE0820D0001

TO/TD:

2361-2401-09

Sources:

Background: Google Aerial Imagery Sample/Mine Locations: EPA Region 8 Streams: USGS National Hydrography Dataset Roads: ESRI from U.S. Census Bureau (USCB) Spatial Reference: WGS 1984 Web Mercator Auxiliary Sphere Coordinate System

Analyst: M. Caldwell

*Red indicates an exceedance of EPA Residential Regional Soil Screening Levels (RSLs).

Red BOLD indicates an exceedance to Residential and Industrial Screening Levels.

https://www.epa.gov/risk/regional-screening-levels-rsls

2025 Pre-CERCLA Screening Mine Waste/Surface Soil Sampling

Locations/Key Results* Sampling Date: August 12, 2025

All results in mg/kg

Upper Grizzly Creek Subwatershed Jackson County, Colorado

Figure A.6 Rabbit Ears Manganese

EPA Regional Screening Levels (mg/kg) Screening Level Arsenic Cadmium Copper Iron Lead Manganese Zinc

Residential 0.68 7.10 3,100 55,000 200 1,800 23,000

Industrial 3.00 100 47,000 820,000 800 26,000 350,000

0 150 30075

Feet

Background Composite

Mine Waste Composite

Mine Waste Grab

Sediment

Creeks

Roads

Mine Locations https://www.epa.gov/risk/regional-screening-levels-rsls

Rabbit Ears Manganese Deposits ")Æ

REM-SO-MP02-01-X003

REM-SO-MP02-01-X002

REM-SO-MP01-02-X011

REM-SO-CS01-01-X002

REM-SO-MP01-02-X009

REM-SO-MP01-02-X013

REM-SO-MP02-01-X007

REM-SO-MP02-01-X001

REM-SO-MP02-01-X014

REM-SO-MP01-02-X003

REM-SO-MP01-02-X010

REM-SO-MP01-02-X012

REM-SO-MP02-01-X005

REM-SO-MP01-02-X002

REM-SO-MP02-01-X004

REM-SO-MP01-02-X004

REM-SO-MP02-01-X010

REM-SO-MP01-02-X001

REM-SO-MP02-01-X012

REM-SO-MP01-02-X014

REM-SO-MP01-02-X015

REM-SO-MP02-01-X011

REM-SO-MP01-02-X005

REM-SO-CS01-01-X005

REM-SO-MP01-02-X007

REM-SO-CS01-01-X004

REM-SO-MP02-01-X006

REM-SO-MP01-02-X008

REM-SO-MP01-02-X006

REM-SO-CS01-01-X003

REM-SO-CS01-01-X001

REM-SO-MP02-01-X009

REM-SO-MP02-01-X013

REM-SO-MP02-01-X008

REM-SO-MP02-01-X015

Path: Y:\R08_STARTV\AMLMixedOwnershipMinesSAR2024\AMLMixedOwnershipMinesSAR2025_CO_XRF_As\AMLMixedOwnershipMinesSAR2025_CO_XRF_As.aprx\Figure A.7 2025 Pre-CERCLA Screening Rabbit Ears Manganese XRF Survey - Manganese Results

Date:

10/14/2025

Contract:

68HE0820D0001

TO/TD:

2361-2401-09

Sources:

Background: NAIP Imagery Sample/Mine Locations: EPA Region 8 Streams: USGS National Hydrography Dataset Roads: ESRI from U.S. Census Bureau (USCB)

Spatial Reference: WGS 1984 Web Mercator Auxiliary Sphere Coordinate System

Analyst: S. DeNeice

0 75 15037.5

Feet

Manganese Residential Screening Level = 1,800 mg/kg Manganese Industrial Screening Level = 26,000 mg/kg Manganese Residential Soil Removal Management Level = 5,500 mg/kg Manganese Industrial Soil Removal Management Level = 77,000 mg/kg

Non-Detect

< Residential RSL

> Residential RSL

> Residential RML

> Industrial RSL

Local Roads

Creeks

")Æ Mine Features

Figure A.7 Rabbit Ears Manganese Deposits Upper Grizzly Creek Subwatershed

Jackson County, Colorado

2025 Pre-CERCLA Screening XRF Survey - Manganese Results (mg/kg)

Survey Date: August 20, 2025