Churchill County legal - 21467

Public Notice: Five-Year Review

Sierra Army Depot, Herlong, California

The U.S. Army Corps of Engineers, Los Angeles District, has completed

the Sixth Five-Year Review for the Sierra Army Depot located in

Herlong, California. This statutory Five-Year Review was conducted in

accordance with the Comprehensive Environmental Response, Compensation,

and Liability Act Section 121, consistent with the National

Contingency Plan. The purpose of a Five-Year Review is to evaluate the

implementation and performance of a remedy in order to determine if

the remedy is or will be protective of human health and the environment.

Five-Year Reviews also identify issues found during the review, if any,

and provide recommendations to address them. The Five-Year Review

has been prepared because hazardous substances, pollutants, or contaminants

remain at the site above levels that allow for unlimited use and

unrestricted exposure.

This Five-Year Review evaluated the following six Installation Restoration

Program sites:

SIAD-001 (Trinitrotoluene Leaching Beds Area & Paint Shop subsite):

The remedy at SIAD-001 currently protects human health and the

environment because source removal actions were completed and Institutional

Controls (soil/groundwater restrictions, dig permits, and development

restrictions) prevent inadvertent exposure to contamination in soil

and groundwater. However, for the remedy to be protective in the long

term, the following actions need to be taken to ensure protectiveness:

• Re-evaluate the progress of the remedy component of monitored

natural attenuation, enhanced with the implementation of the

n-Situ Reactive Zone Demonstration Program, for treatment of

volatile organic compound contaminants of concern.

• Add hexavalent chromium, cis-1,2-dichloroethene, vinyl chloride,

2-amino-4,6-dinitrotoluene, and 4-amino-2,6-dinitrotoluene to the

list of groundwater contaminants of concern, identify appropriate

Protective Water Quality Objectives, and evaluate if the current

remedial approach will address the impact from these contaminants

at SIAD-001.

• Evaluate nitrate as a potential contaminant of concern and determine

whether additional action is required at SIAD-001 or if the

current remedial approach will address nitrate impacts.

• Conduct additional investigations to delineate the volatile organic

compound plume boundaries west of SIAD-001, near the Paint

Shop Subsite.

SIAD-002 (Defense Reutilization & Marketing Office Trench Area):

The remedy at SIAD-002 currently protects human health and the environment

because source removal actions were completed, and Institutional

Controls (soil/groundwater restrictions, dig permits, and development

restrictions) prevent inadvertent exposure to contamination in soil

and groundwater. However, for the remedy to be protective in the long

term, the following actions need to be taken to ensure protectiveness:

• Add cis-1,2-dichloroethene, vinyl chloride, and perchlorate to the

list of groundwater contaminants of concern, identify appropriate

Protective Water Quality Objectives, and evaluate if the current

remedial approach will address cis-1,2- dichloroethene, vinyl

chloride, nitrate, and perchlorate impacts at SIAD-002.

• Evaluate nitrate as a potential contaminant of concern and determine

whether additional action is required at SIAD-002 or if the

current remedial approach will address nitrate impacts.

• Complete the Enhanced Reductive Dechlorination rebound

evaluation initiated in 2019 to determine if monitored natural

attenuation will achieve the Remedial Action Objective of limiting

contaminant migration and degradation rates to within acceptable

ranges to the State of California and the Army.

• Conduct additional investigations to delineate the trichloroethene

plume boundary south- and northwest of SIAD-002 where

boundary wells DMO-06-MWA and DMO-07-MWA exhibit TCE

exceedances and an increasing trend at DMO-07-MWA.

SIAD-003 (Abandoned Landfill/Southern Sites Area): The remedy at

SIAD-003 currently protects human health and the environment because

land use controls (soil/groundwater restrictions, dig permits, and development

restrictions) prevent inadvertent exposure to contamination in

soil and groundwater.

However, for the remedy to be protective in the long term, the following

actions need to be taken to ensure protectiveness:

• Add cis-1,2-dichloroethene and vinyl chloride to the list of

groundwater contaminants of concern, identify appropriate

cleanup levels, and evaluate if the current remedial approach

will address cis-1,2- dichloroethene and vinyl chloride impacts at

SIAD-003.

• Delineate the Southern Sites Area western plume boundary

near groundwater monitoring well MPA-03-MWA and implement

appropriate contingency measures per the 2018 Final Monitored

Natural Attenuation Letter Work Plan.

• Conduct additional investigations to delineate the Southern Sites

Area southern plume boundary near groundwater monitoring well

SSA-01-MWA and potable supply well PSW-08 and implement

appropriate contingency measures per the 2018 Final Monitored

Natural Attenuation Letter Work Plan.

• Conduct additional investigations to delineate the Abandoned

Landfill plume boundary near groundwater monitoring well CCB-

01-MWA and implement appropriate contingency measures per

the 2018 Final Monitored Natural Attenuation Letter Work Plan.

• Expand the SIAD-003 Land Use Control boundary to include

all wells with detected trichloroethene and prohibit use of and

exposure to contaminated groundwater.

• Evaluate nitrate as a potential contaminant of concern and determine

whether additional action is required at SIAD-003 or if the

SIAD-010 (Upper Burning Ground Area): The remedy at SIAD-010

is protective of human health and the environment. Surface ordnance

and explosives/unexploded ordnance and scrap metal clearance, soil

excavation, and placement of contaminated soil in the Corrective Action

Management Unit was completed in 2006. Post removal action soil

confirmation sampling indicated that cleanup levels were met. Groundwater

samples collected from Upper Burning Ground Corrective Action

Management Unit wells indicate that no metal contaminants are being

released from the Corrective Action Management Unit and all contaminant

of concern concentrations in groundwater remain below Maximum

Contaminant Levels. Quarterly Corrective Action Management Unit

inspections confirm the dense graded aggregate layer and drainage

controls are in good working condition with only minor maintenance

required. Land Use Controls, including fencing, signs, dig permits, and

annual inspections, continue to restrict site use/access and mitigate

the risks to human health resulting from potential direct contact with

contaminated soil.

SIAD-014 (Building 210 Area): The remedy at SIAD-014 currently

protects human health and the environment because land use controls

(soil/groundwater restrictions, dig permits, and development restrictions)

prevent inadvertent exposure to contamination in soil and groundwater.

However, for the remedy to be protective in the long term, the following

actions need to be taken to ensure protectiveness:

• Add cis-1,2-dichloroethene and vinyl chloride to the list of

groundwater contaminants of concern, identify appropriate

cleanup levels, and evaluate if the current remedial approach

will address cis-1,2-dichloroethene and vinyl chloride impacts at

SIAD-014.

• Conduct additional investigations to delineate the trichloroethene

plume boundary east of the Building 210 Area, near the

Doyle Wildlife Area.

• Evaluate the effectiveness of the on-site treatment of trichloroethene

impacted groundwater via Enhanced Reductive

Dechlorination injections at the Building 210 Area. Additional

site characterization may be necessary to determine if residual

sources are contributing to TCE concentrations, rebounds, and

migration.

• Evaluate nitrate as a potential contaminant of concern and

determine whether additional action is required at SIAD-014 or if

the current remedial approach will address nitrate impacts.

SIAD-022 (Old Popping Furnace Area): The remedy at SIAD-022 is

protective of human health and the environment. Surface ordnance and

explosives/unexploded ordnance clearance, excavation, and consolidation

of the contaminated soil with placement of an engineered Corrective

Action Management Unit cover continue to reduce the potential for

windborne movement of surface soil containing antimony, arsenic, or

lead above their respective cleanup levels. Corrective Action Management

Unit groundwater monitoring continues to satisfy the Applicable

or Relevant and Appropriate Requirements, including the requirements

of Title 22 CCR § 66264.97. Administrative and engineered land use

controls (fencing, signs, dig permits, annual inspections) continue to

mitigate the risks to human health and the environment from potential

direct contact with soil containing antimony, arsenic, or lead at concentrations

exceeding their respective cleanup levels. Routine inspection

and maintenance activities and groundwater monitoring ensure longterm

protection of groundwater resources

This Five-Year Review evaluated the following seven Military Munitions

Response Program sites:

SIAD-006-R-01 (.50 Caliber Firing Range), SIAD-007-R-01 (1960

Demolition Area), SIAD-009-R-01 (Hazard Classification Test Site),

SIAD-010-R-01 (Honey Lake Demolition Range), SIAD-012-R-01

(Lower Burning Ground), SIAD-014-R-01 (Upper Burning Ground),

SIAD-015-R-01 (Bureau of Land Management – Administered

Land): The remedy for the Military Munitions Response Program Seven

Sites is protective of human health and the environment. Land Use

Controls (fencing, dig permits, annual inspections) are in place to prohibit

use of and restrict exposure to potential explosive hazards at the

Military Munitions Response Program Seven Sites. Annual Land Use

Control inspections occurred between 2016 and 2020 without lapse. All

Land Use Control inspections concluded that fences and signage were

in good condition and signage was spaced at approximately 600-foot

intervals.

The Sixth Sierra Army Depot Five-Year Review Report was signed on

January 21, 2022 and is available at the following information repositories:

Herlong Library

California Street, Building 2067

Herlong, California 96113

Susanville Library

1618 Main Street

Susanville, California 96130

Sierra Army Depot

74 Currant St., Building 63

Herlong, California 96113

Should members of the community have questions or comments about

the Sierra Army Depot Five-Year Review or are interested in additional

site information, please contact Cortney Carrier at (530) 827- 4612 or

via email at cortney.a.carrier.civ@army.mil.

Pub Date: February 17, 2022

Ad #21467