1. Remedy Analysis for Sierra Army Depot, Building 210 Area
Herlong, California
Desert Remedial Action Technologies Workshop
Phoenix, Arizona
Jackie Saling, PE

2. 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

3. 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
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
Building 210 Area

4. Site Location and Surrounding Features
Amedee Mountains
Surrounded by Mountains
Honey Lake Valley
Arid Climate
Annual precipitation less than 5”
Honey Lake
Building 210 Area
Diamond Mountains
Fort Sage Mountains

5. Regional Geology Block faulted mountains
Diamond Mountains
Fort Sage Mountains
Amedee Mountains
Honey Lake
Regional Geology
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
Block faulted mountains
Alluvial fans- poorly sorted coarse grained
Fine grained lake deposits

6. Regional Hydrogeology
Regional groundwater flow toward Honey Lake
Closed hydrologic basin
Intermittent streams
Surface area of Honey Lake fluctuates
Horizontal K:Vertical K 100:1
3982
3984
3986
3988
Building 210 Area
Honey Lake

7. Building 210 Area Vehicle Maintenance Popping furnace
Sand blasting, spray painting, steam cleaning, engine fogging
Degreasing solvents, oils, sludge

8. 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

9. Site Investigation Timeline
1994
1983
1992
1995
2002
1997
Surface Soil (6 samples)
Subsurface Soil (5 borings)
Background Soil
Subsurface Soil (52 samples)
Soil Gas (294 samples)
Groundwater (20 samples)
Geophysics
Hydraulic Testing
Groundwater Investigation
Plume Delineation
Additional Hydraulic Testing
Groundwater Treatment Analysis
CP Testing (20 locations)
Soil Gas (20 samples)

10. Investigation Findings – Soil and Soil Gas
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 10 1
100
Soil gas isocontours developed from 1992 investigation

11. Investigation Findings - Groundwater
TCE in groundwater detected up to 5,000 mg/L in shallow groundwater (95-115’ bgs)
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 ( ’bgs) 5
500
Building 210 50

12. Pump and Treat System Layout
Building 210 50
24-EX 5
Reinjection Trenches
23-EX 5
21-EX
500 50

13. Interim Remedial Activity- Pump and Treat
Initially a 2 year interim measure.
Composed of 3 groundwater extraction wells, air stripper for treatment,
discharged to recharge trenches

14. Pump and Treat Performance Data

15. Pump and Treat Issues
Fouling decreased efficiency of groundwater recovery

16. ERD Injection Area, 2004
Follow Up HRC Area, 2002
ZVI Injection Area, 2001
SVE Area, 2006
HRC Area, 2000
Building 210
ZVI PRB Area, 2003

17. 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

18. 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

19. 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

20. 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

21. Site Conditions
Building 210
Current Groundwater Plume Figure

22. 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

23. Enhanced Reductive Dechlorination – Operational Data
Monitoring Well 77-PZ
Decreased to 1% molasses, increased injection volume to 1500 gal/well
Decreased to 10% molasses

24. Enhanced Reductive Dechlorination – Operational Data
Monitoring Well 77-PZ
Began injection of NaOH

25. Enhanced Reductive Dechlorination – Operational Data
Monitoring Well 77-PZ

26. Enhanced Reductive Dechlorination – Results
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

27. 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

28. Soil Vapor Extraction System - Operation
Vacuum extracted air
Atmospheric vent

29. Soil Vapor Extraction – Vacuum Distribution56
SVE Well 60 61
East-West Cross Section
140
120
100 80 60 40 20 20 40 60 80

30. Soil Vapor Extraction – Operational Data

31. Soil Vapor Extraction Groundwater Impact10 20 30 40 50
SVE Well
500
1,000
Monitoring Well
May 2007
1,500

32. Soil Vapor Extraction Groundwater Impact
July 2007
SVE Well
1,000
1,000
500
1,000
1,500 10 20 30 40 50

33. 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

34. Conceptual Site Model - Revisited
ORIGINAL: Virtually no groundwater movement
REVISED: Groundwater moving in the SE direction,
observed groundwater velocity 0.5 ft/day

35. Conceptual Site Model - Revisited
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.

36. 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

37. 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

38. 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

39. Moving Forward Proposed full scale SVE system layout Extraction Well
Extraction Well/Passive Vent

40. 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