Attch_4_-_2019_M_M_Summary_Report_(Lab_Data_Package_Omitted).pdf

September 11, 2019

Alaska Department of Environmental Conservation Attn: Anne Marie Palmieri 410 Willoughby Ave, Suite 303 P.O. Box 111800 Juneau, Alaska 99811-1800

U.S. Environmental Protection Agency Attn: Matt Wilkening 950 W Bannock St, Suite 900 Boise, ID 83702

RE: BLM Contaminated Soil Landspread Area Red Devil Mine, Red Devil, Alaska

Subj: 2019 Maintenance and Monitoring Report

This report presents Environmental Management, Inc.’s (EMI) 2017 monitoring of the petroleum contaminated soils being treated in the land spread area. EMI followed the procedures set forth in Weston Solutions’ approved Maintenance and Monitoring Plan for Petroleum Contaminated Soil Treatment, March 2011 (M&M Plan) and our 2019 sampling plan. This report was prepared by EMI under contract with the U.S. Bureau of Land Management (BLM).

BACKGROUND

The site is an active Alaska Department of Environmental Conservation (ADEC) Contaminated Site identified as the BLM Red Devil Mine site, Alaska Department of Environmental Conservation (ADEC) file No. 2442.38.001, and is in the U.S. Environmental Protection Agency’s (EPA) Superfund Enterprise Management System (SEMS) database as USDOI Red Devil Mine ID number AKD980495618. The Property is known to U.S. Bureau of Land Management (BLM) as the Red Devil Mine (RDM). The RDM is an abandoned cinnabar mine and mercury retorting operation at a remote location near the village of Red Devil, Alaska. In 1987, mercury and arsenic was present in tailings piles, and free mercury was present in site soils associated with a large mercury processing operation that ceased in the early 1970’s. Petroleum hydrocarbon was present in various locations associated with fuel storage tanks and distribution to housing and maintenance shops. Other contaminants associated with mercury mining were also present. The site is approximately 10 acres and owned by BLM.

During 2010 a petroleum contaminated soil treatment facility was established at the RDM. The facility consists of six 100’ x 100’ Decision Units (DU). Three DUs (DU 4 through DU 6) currently hold diesel fuel contaminated soil undergoing landspread treatment. Soil in the other DUs have completed treatment and will not be further monitored. The soil in each DU to be monitored is 0.5 to

1.5 feet deep.

The RDM site is located on the south bank of the Kuskokwim River approximately two miles upstream from Red Devil Village. Access to the RDM and the landspread area is along approximately two miles of pioneer road from the airstrip, or by boat to the mouth of Red Devil Creek. Legal description of the property is: Township 10N, Range 44W, southeast quarter of Section 6, Sleetmute D-4 Quadrangle, Seward Meridian, Alaska. GPS coordinates for the approximate center of the 200’ x 300’ landspread facility are Latitude 61°45'40.78"N and Longitude 157°18'52.53"W.

FIELD ACTIVITIES

Field activities were conducted on July 3, 2019. Andy Coulson and Hannah Deeney of EMI were accompanied by Larry Beck and Crystal Smith of the BLM. Mr. Coulson and Ms. Deeney are both Qualified Environmental Professionals according to 18 AAC 75.325.

Thirty-six increments were collected from each DU. Increments were evenly spaced on a 14.3 foot grid using pre-marked 100-foot strings and marked with pin flags. Increments were collected from 6 inches below ground surface with a stainless steel spoon.

Multi-increment samples were collected from DUs 4, 5, and 6. A duplicate sample was collected from DU4 by offsetting increment locations 4 feet to the west, and a triplicate sample was collected from DU 4 by offsetting increment locations 4 feet to the north. A clean dedicated stainless steel spoon was used for each multi-increment sample. Samples were stored in Ziploc bags and were submitted to SGS Anchorage for multi-increment processing and analysis for DRO by method AK 102.

RESULTS

The sample from Decision Unit 6 (17987-DU6) contained 200 milligrams per kilogram (mg/Kg) DRO. The sample from Decision Unit 5 (17987-DU5) contained 877 mg/Kg DRO. The sample from Decision Unit 4 (17987-DU4) contained 373 mg/Kg DRO, its duplicate (17987-DU7) contained 362 mg/Kg, and its triplicate (17987-DU8) contained 476 mg/Kg.

The mean DRO concentration of samples from Decision Unit 4 was 404 mg/Kg, with a standard deviation of 62.9 mg/Kg; the relative standard deviation was 15.6 %. The 95% upper confidence limit (UCL) of DRO concentrations in Decision Unit 4 was 562 mg/Kg.

Assuming the variation is similar in DU5 and DU6 the estimated 95% UCL of the mean level of DRO for DU5 is 1280 mg/kg and for DU6 is 292 mg/kg. Complete results are presented in Table 1 and the attached laboratory report. The ADEC laboratory data review checklist was completed and is included with the attached laboratory report; no discrepancies were noted.

DISCUSSION

The levels of DRO in the treatment areas continues to decrease. DU4 and DU5 need further treatment before they will be below the MTG cleanup levels. We do not have enough data to say with 95% confidence that the mean level of DRO in DU6 is below the MTG cleanup level. If the variations were similar to what was found in DU5 in 2017, we could be 95% confident that the mean level is below 250 mg/kg, but based on the variation found in 2019 samples we cannot.

CONCLUSIONS

DRO concentrations in Decisions Units 4 and 5 remain above the MTG cleanup level of 250 mg/Kg (18 AAC 75). Decision Unit 6 is likely below the ADEC Migration to Groundwater (MTG) cleanup level, but we do not have enough data to be 95% confident that is the case.

Continuing active landspread treatment is recommended for Decision Units 4 and 5. No further active landspread treatment is likely needed for Decision Unit 6. Monitoring should continue for all three Decision Units.

If you have any questions or wish to discuss this project further please do not hesitate to contact the undersigned at (907) 272-9336.

Respectfully, Environmental Management, Inc.

Andy Coulson Environmental Scientist

Encl: Table 1 – Analytical Results

Figure 1 – Vicinity Map Google Earth Image Figure 2 – Decision Units Google Earth Image Photo Log Field Notes 3 July 2019

SGS Laboratory Report 1193604 and ADEC Laboratory Data Review Checklist

Table 1 Analytical results and 95% Upper Confidence Limit for multi-increment samples collected from the Red Devil Mine Landspread

Analysis Analyte

MTG

Cleanup Level

Unit

AK102 Diesel Range Organics 250 mg/Kg 200 877 373 362 476 AK102 DRO 95% UCL 250 mg/Kg 292 1,280 562

Notes MTG Cleanup Level 18 AAC 75 Table B1, Method Two, Under 40

Inch Zone Migration to Groundwater Soil Cleanup Level.

mg/KG Milligrams per kilogram.

200 DRO was detected at 200 mg/Kg, less than the

ADEC MTG cleanup level.

292 The result exceeds the ADEC MTG cleanup level.

t_95 2.92 for n:3, where n is the number of samples

95% UCL Average concentration * ((t_95*Std.Dev)/ SquareRoot(n))

UCL Upper Confidence Limit

Decision Unit 4

(Triplicate)

Sample ID 17987-DU617987-DU517987-DU4 17987-DU7 17987-DU8 Location

Decision Unit 6

Decision Unit 5

Decision Unit 4

Decision Unit 4

(Duplicate)

DATE:

REVIEWED:

DRAWN:

EMI JOB:

VICINITY MAP

RED DEVIL LAND SPREAD,

RED DEVIL, ALASKA

FIGURE

9/9/19

AVC

HJD

17987

F I G

U R

E

S

O U

R C

E

U

S

B

L M

DATE:

REVIEWED:

DRAWN:

EMI JOB:

SITE MAP

RED DEVIL LAND SPREAD,

RED DEVIL, ALASKA

FIGURE

9/9/19

AVC

HJD

17987

F I G

U R

E

S

O U

R C

E

U

S

B

L M

Photo Log

Photo page 1

Photo 1: Decision Unit 6. Facing northeast, 3 July 2019.

Photo 2: Decision Unit 5. Facing north, 3 July 2019.

Photo Log

Photo page 2

Photo 3: Sample collection in Decision Unit 4. Facing south, 3 July 2019.