Post on 24-Dec-2015
Remedy Analysis for Sierra Army Depot, Building 210 AreaHerlong, California
Desert Remedial Action Technologies WorkshopPhoenix, 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
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
Diamond MountainsDiamond Mountains
Fort Sage MountainsFort Sage Mountains
Amedee MountainsAmedee MountainsHoney LakeHoney Lake
Block faulted mountains Alluvial fans- poorly sorted coarse
grained Fine grained lake deposits
Regional Hydrogeology
Honey Lake
398239843986
3988
3988
3988
Building 210 Area
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 AreasTCE and TCA
degreaser tanks
Possible dumping in ditches behind
buildings
TCE degreaser tanks
Solvent recovery activities
Waste discharged to shallow ditch
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)
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
10
1
100
TCE in groundwater detected up to 5,000 g/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 (160-170’bgs)
Investigation Findings - Groundwater
B21EX
B23EX
B24EX
0 1000 2000
50
500
Building 210
5
Pump and Treat System Layout
5024-EX
23-EX
21-EX
500
50
5
5
Building 210
Reinjection Trenches
Interim Remedial Activity- Pump and Treat
Pump and Treat Performance Data
0
5
10
15
20
25
30
1999 2000 2001 2002 2003 2004 2005 2006Year
Ave
rag
e T
CE
Rem
ova
l R
ate
(lb
s/m
o)
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
180,000
Averag
e Daily F
low
(gp
d)
Monthly TCE Removal Rate Average Daily Flow
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
0
500
1,000
1,500
2,000
2,500
Jul-02 Jun-03 Jun-04 Jun-05 Jun-06 Jun-07
TC
E C
on
ce
ntr
ati
on
(u
g/L
)
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
Building 210
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
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
Jul-04 Dec-04 Jun-05 Dec-05 Jun-06 Dec-06 Jun-07
TO
C (
mg
/L)
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
0
1
2
3
4
5
6
7
8
Jul-04 Dec-04 Jul-05 Dec-05 Jun-06 Dec-06 Jun-07
pH (
SU
)
Began injection of NaOH
Monitoring Well 77-PZ
0
5,000
10,000
15,000
20,000
25,000
30,000
Jul-04 Dec-04 Jun-05 Dec-05 Jun-06 Dec-06 Jun-07
Meth
an
e C
on
cen
trati
on
(u
g/L
)
0
2
4
6
8
10
12
14
16
Jul-04 Dec-04 Jun-05 Dec-05 Jun-06 Dec-06 Jun-07
Co
nce
ntr
atio
n (
um
ol/
L)
TCE c-DCE VC Ethene
Enhanced Reductive Dechlorination – Operational DataMonitoring 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
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 - OperationVacuum extracted
airAtmospheric
ventAtmospheric
vent
Soil Vapor Extraction – Vacuum Distribution
0
10
20
30
40
50
60
0 10 20 30 40 50 60
Distance from Extraction Well (ft)
Vac
uu
m (
inch
es o
f w
ater
)
60 6156
120 100 80140 60 40 20 0 20 40 60 80
SVE Well
East-West Cross Section
Soil Vapor Extraction – Operational Data
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
Aug-06 Oct-06 Dec-06 Feb-07 Apr-07 Jun-07 Aug-07 Oct-07
TC
E R
emo
val
Rat
e (l
bs/
mo
)
Soil Vapor Extraction Groundwater Impact
1,500
0 10 20 30 40 50
SVE Well
500
1,00
0
Monitoring Well
Monitoring Well
Monitoring Well
May 2007
Soil Vapor Extraction Groundwater Impact
1,500
0 10 20 30 40 50
SVE Well
500
1,00
01,000
1,00
0
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.
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
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
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
Extraction WellExtraction Well/Passive Vent
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