# Presentation: 810980

## Remedy Analysis for Sierra Army Depot, Building 210 Area

**Remedy Analysis for Sierra Army Depot, Building 210 Area**
**Herlong, California**

- Desert Remedial Action Technologies Workshop
- Phoenix, Arizona
- Jackie Saling, PE

## Outline

- Site Background
- Historical Investigations
- Interim Remedial Activity
- Pilot Tests
- Conceptual Site Model
- Enhanced Reductive Dechlorination
- Soil Vapor Extraction
- Conceptual Site Model- Revisited
- Moving Forward

## Site Location and Historical Operations

- 1942 – storage of supplies and inert materials
- 1950s – explosives, guided missiles, and fuels
- Current – storage of war reserves and munitions
- Activities at the Site fluctuate

**Building 210 Area**

**Notes:**
Located XX miles north of Reno, NV in the ????? Desert
Located adjacent to Honey Lake
Surrounded by the ??? Mountians
Activities included vehicle maintenance, sand blasting, spray painting, steam cleaning, and tank engine fogging
Irrigation wells operate near the site
How do site feature effect the hydrogeology of the site

## Site Location and Surrounding Features

- Surrounded by Mountains
- Honey Lake Valley
- Arid Climate
- Annual precipitation less than 5”

- Fort Sage Mountains

- Amedee Mountains

- Diamond Mountains

- Honey Lake

**Building 210 Area**

## Regional Geology

- Block faulted mountains
- Alluvial fans- poorly sorted coarse grained
- Fine grained lake deposits

**Notes:**
Honey Lake Valley is a 2400 square mile drainage basin. The streamflow comes from the mountains inflitrates ath land surface to become groundwater and , in the driest years accumulate in to Honey

The whole depot cover 54 square miles

## Regional Hydrogeology

- Honey Lake

- Regional groundwater flow toward Honey Lake
- Closed hydrologic basin
- Intermittent streams
- Surface area of Honey Lake fluctuates
- Horizontal K:Vertical K 100:1

## Building 210 Area

- Vehicle Maintenance
- Popping furnace
- Sand blasting, spray painting, steam cleaning, engine fogging
- Degreasing solvents, oils, sludge

## Potential Source Areas

**Potential Source Areas**

- TCE and TCA degreaser tanks

- Possible dumping in ditches behind buildings

- TCE degreaser tanks

- Solvent recovery activities

- Waste discharged to shallow ditch

## Site Investigation Timeline

## Investigation Findings – Soil and Soil Gas

- Soil gas isocontours developed from 1992 investigation

- Unsaturated zone consists of interbedded silty sand and poorly-graded sands and gravel
- Depth to groundwater 95 ft
- Lower permeability silt zones were encountered from approximately 105 to 155 feet bgs
- No soil impacts observed
- TCE in soil gas

## Investigation Findings - Groundwater

- Hydraulic conductivity 8 x 10-3 to 3.22 x 10-2 cm/s in shallow groundwater
- TCE in groundwater near or below criteria in intermediate groundwater (160-170’bgs)

**Investigation Findings - Groundwater**

- 50

- 500

- Building 210

- 5

## Pump and Treat System Layout

- 50

- 24-EX

- 23-EX

- 21-EX

- 500

- 50

- 5

- 5

- Building 210

**Reinjection Trenches**

## Interim Remedial Activity- Pump and Treat

**Notes:**
Initially a 2 year interim measure.
Composed of 3 groundwater extraction wells, air stripper for treatment, 
discharged to recharge trenches

## Pump and Treat Performance Data

## Pump and Treat Issues

- Fouling decreased efficiency of groundwater recovery

**HRC Area, 2000**

**ZVI PRB Area, 2003**

**Follow Up HRC Area, 2002**

**ZVI Injection Area, 2001**

**ERD Injection Area, 2004**

**Building 210**

**SVE Area, 2006**

## Pilot Test – Hydrogen Release Compound®

- Injection of HRC® into injection wells surrounded by monitoring wells in 2000, follow up 2002
- Limited TCE degradation was observed, release rate of hydrogen was not high enough to overcome aerobic conditions

## Pilot Test – Zero Valent Iron Injection

- Conducted in October 2001
- Injection of micro-scale into 9 injection points surrounded by monitoring wells
- TCE concentrations decreased initially, but have rebounded

## Pilot Test - Zero Valent Iron PRB

- Implemented in May 2003
- Construction of a micro-scale permeable reactive barrier with 5 injection points

- B21-73-PZ

## Conceptual Site Model

- Virtually no groundwater movement
- No connection observed between possible source areas and groundwater impacts identified
- No recharge to transport contaminants vertically from potential source to groundwater
- Heavy TCE vapor travel through vadose zone and spread out on top of the groundwater table creating a broad thin groundwater plume
- Vapor migration transports TCE, no transport in groundwater
- Significant mass in vadose zone

## Site Conditions

- Current Groundwater Plume Figure

## Pilot Test – Enhanced Reductive Dechlorination

- Monthly injections began July 2004, 30% molasses
- Decreased frequency of injections and molasses concentration over time
- ERD injections are ongoing

## Enhanced Reductive Dechlorination – Operational Data

- Decreased to 10% molasses

- Decreased to 1% molasses, increased injection volume to 1500 gal/well

- Monitoring Well 77-PZ

**Enhanced Reductive Dechlorination – Operational Data**

## Enhanced Reductive Dechlorination – Operational Data

- Monitoring Well 77-PZ

## Enhanced Reductive Dechlorination – Operational Data

**Enhanced Reductive Dechlorination – Operational Data**

- Monitoring Well 77-PZ

## Best results with low concentration, high volume injections
Long time before reductive conditions were established
Effective in decreasing TCE concentrations in groundwater after reductive conditions are established
Small injection well ROIs due to the flat gradient, full scale application would require many injection wells and possible groundwater recirculation system
Will not address significant mass in the soil vapor

- Long time before reductive conditions were established
- Effective in decreasing TCE concentrations in groundwater after reductive conditions are established
- Small injection well ROIs due to the flat gradient, full scale application would require many injection wells and possible groundwater recirculation system
- Will not address significant mass in the soil vapor

**Enhanced Reductive Dechlorination – Results**

## Pilot Test – Soil Vapor Extraction

- One extraction well
- Six monitoring points
- Two passive vents
- 85 cfm, 50 in H2O at the blower
- Pilot test ongoing

- Passive Vent

- Monitoring Well

- Extraction Well

## Soil Vapor Extraction System - Operation

## Soil Vapor Extraction – Vacuum Distribution

- 60

- 61

- 56

- 120

- 100

- 80

- 140

- 60

- 40

- 20

- 0

- 20

- 40

- 60

- 80

**SVE Well**

- East-West Cross Section

## Soil Vapor Extraction – Operational Data

## Soil Vapor Extraction Groundwater Impact

**1,500**

- May 2007

## Soil Vapor Extraction Groundwater Impact

**1,500**

- 0

- 10

- 20

- 30

- 40

- 50

- SVE Well

**500**

**1,000**

**1,000**

**1,000**

- July 2007

## Soil Vapor Extraction Summary 

- Successful in removing mass from vadose zone and groundwater, 2.1 to 9 pounds TCE removed per month from one extraction well
- No operational issues, runs 24-7
- Vacuum propagation is further to the north and west due to subsurface heterogeneity
- Ability to reduce TCE concentrations below surface of the water table will be diffusion limited
- May not be able to reduce groundwater concentrations to regulatory standards

## Conceptual Site Model - Revisited

- ORIGINAL: Virtually no groundwater movement
**REVISED: Groundwater moving in the SE direction,**

**observed groundwater velocity 0.5 ft/day**

## ORIGINAL: Vapor migration transports TCE, no transport in groundwater

REVISED: Updated groundwater model and better understanding of hydrogeology indicates that vapor AND groundwater are transporting TCE. Updated groundwater model shows plume is stable. 

**REVISED: Updated groundwater model and better understanding of hydrogeology indicates that vapor AND groundwater are transporting TCE. Updated groundwater model shows plume is stable. **

**Conceptual Site Model - Revisited**

## ORIGINAL: Heavy vapors travel through vadose zone and spread out on top of the water table creating a broad, thin plume

REVISED: Plume is not as thin as initially thought due to diffusion of TCE in the groundwater over time

**REVISED: Plume is not as thin as initially thought due to diffusion of TCE in the groundwater over time**

**Conceptual Site Model - Revisited**

## No connection observed between possible source areas and groundwater impacts identified
No recharge to transport contaminants vertically from potential source to groundwater
Significant mass in vadose zone

- No recharge to transport contaminants vertically from potential source to groundwater
- Significant mass in vadose zone

**Conceptual Site Model - Revisited**

## Moving Forward

- Groundwater flow direction?
- Pumping operation on property to the SE?
- Recharge onsite?
- Building 210 operations?
- Geological feature?
- Full scale soil vapor extraction implementation

## Moving Forward

- Proposed full scale SVE system layout

## Conclusion

- Numerous technologies tested at the site
- SVE and ERD are both viable technologies to use at the site
- SVE- proven technology
- Best mass removal
- Low cost
- Consider and evaluate options to overcome diffusion limitations associated with soil vapor extraction